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Performance of a dual-fuel prechamber diesel engine with natural gas Song, Seaho 1984

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PERFORMANCE OF A DUAL-FUEL PRECHAMBER DIESEL ENGINE WITH NATURAL GAS BY SEAHO (SONG U n i v e r s i t y of B r i t i s h C o l u m b i a , 1 SUBMITTED IN PARTIAL FULFILLMENT REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n THE FACULTY OF GRADUATE STUDIES THE DEPARTMENT OF MECHANICAL ENGINEERING We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d .Sc., The A THESIS THE THE UNIVERSITY OF BRITISH May 1984 © S e a h o Song, 1984 COLUMBIA In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I f u r t h e r agree that p e r m i s i i o n for extensive copying of t h i s t h e s i s for s c h o l a r l y purposes may be granted by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of Mechanical Engineering The U n i v e r s i t y of B r i t i s h Columbia 2324 Main M a l l Vancouver, Canada V6T 1W5 Date: June 1984 i i ABSTRACT The f e a s i b i l i t y of d u a l - f u e l operation with n a t u r a l gas i n a prechamber d i e s e l engine was studi e d with s p e c i a l emphasis on f u e l consumption and c y l i n d e r pressure development. The e f f e c t s of a i r r e s t r i c t i o n , p i l o t d i e s e l flow rate and i n j e c t i o n t iming were a l s o s t u d i e d . D u a l - f u e l operation showed poor p a r t - l o a d f u e l consumption; near f u l l load the f u e l consumption was c l o s e to that of s t r a i g h t d i e s e l o p e r a t i o n . In the absence of i n j e c t i o n t iming adjustment the maximum power output of dua l -f u e l operation was severely l i m i t e d by the maximum c y l i n d e r pressure. Retarding the i n j e c t i o n t iming was e f f e c t i v e i n reducing the maximum c y l i n d e r pressure to a safe l e v e l . The a n a l y s i s of apparent energy release i n d i c a t e s the d i f f e r e n c e s i n combustion mechanism between a u t o - i g n i t i o n of d i e s e l f u e l i n s t r a i g h t d i e s e l operation and propagation of flame f r o n t s i n d u a l - f u e l o peration. i i i Table of Contents Abstract i i L i s t of Tables i v L i s t of Figures y Acknowledgements v i i i Nomenclature i x I. INTRODUCTION 1 1 .1 Background - 1 1.2 Present Study 7 I I . REVIEW OF LITERATURE 10 2.1 H i s t o r y of Dual-Fuel D i e s e l Engine 10 2.2 Review of Research 12 I I I . APPARATUS AND INSTRUMENTATION ... 26 3.1 Engine and Test Bed • 26 3.2 Instrumentation 38 3.3 Fuel 43 3.4 Data Process 45 IV. EXPERIMENTAL RESULTS 47 4.1 Fuel Consumption 47 4.1.1 Fuel Consumption with Unmodified Engine .. 47 4.1.2 E f f e c t of R e s t r i c t i n g Intake A i r 55 4.1.3 E f f e c t of Varying I n j e c t i o n Timing 56 4.2 Cy l i n d e r Pressure 63 4.2.1 Cyl i n d e r Pressure i n Unmodified Engine ... 63 4.2.2 E f f e c t of R e s t r i c t i n g Intake A i r 74 • 4.2.3 E f f e c t of Varying I n j e c t i o n Timing 79 V. ANALYSIS OF APPARENT ENERGY RELEASE 84 5.1 General 84 5.2 Method of C a l c u l a t i o n 85 5.2.1 D e f i n i t i o n s , Equations, and Assumptions .. 85 5.2.2 Computation Procedure 98 5.3 A n a l y s i s 107 5.3.1 Operation with Unmodified Engine 107 5.3.2 E f f e c t of R e s t r i c t i n g Intake A i r 124 5.3.3 E f f e c t of Varying I n j e c t i o n Timing ....... 130 VI. CONCLUSIONS AND RECOMMENDATIONS 135 6.1 Conclusions 135 6.2 Recommendations 138 BIBLIOGRAPHY 139 APPENDIX A - CALIBRATION CURVES 142 APPENDIX B - COMPUTATION OF INDICATED MEAN EFFECTIVE PRESSURE 146 APPENDIX C - COMPUTER PROGRAM FOR DATA ACQUISITION .... 148 APPENDIX D - COMPUTER PROGRAM FOR DATA PROCESS 157 APPENDIX E - COMPUTER PROGRAM FOR APPARENT ENERGY RELEASE 162 i v L i s t of Tables 2.1 Summary of Past Experimental Work 13 3.1 Engine S p e c i f i c a t i o n 29 3.2 T y p i c a l composition of the Natural Gas Used 44 3.3 T y p i c a l Output of Computer Program for Data Processing 46 5.1 Comparison of A c t u a l and Computed Fuel Energy Consumed . . 105 5.2 E f f e c t of Intake A i r R e s t r i c t i o n on Mixture Temperature at Top Dead Center 126 V L i s t of Figures 1.1 Combustion Chambers o f . D i r e c t - I n j e c t i o n and Prechamber Engines 5 2.1 E f f e c t of Gas-Air Mixture Strength on I g n i t i o n delay 17 2.2 T y p i c a l Pressure-Time Trace of Non-Knocking and Knocking Operation . . w • 21 2.3 V a r i a t i o n of Power Output with the O v e r a l l Mixture Strength f o r D i f f e r e n t Intake Tempertures 22 2.4 T y p i c a l Thermal E f f i c i e n c i e s of Dual-Fuel and S t r a i g h t D i e s e l Operation 25 3.1 Apparatus and Instrumentation 27 3.2 Flow of A i r , F u e l , and Exhaust Gas 28 3.3 Shape of Combustion Chambers 30 3.4 Sleeve Metering Fuel System 32 3.5 Fuel I n j e c t i o n Pump and Housing 32 3.6 Seqence of I n j e c t i o n Events 33 3.7 Governor Components of Sleeve Metering 33 3.8 Fuel I n j e c t i o n Nozzle 34 3.9 Turbocharger Cutaway View 36 3.10 Gas Mixer 37 3.11 Mounting of Cyl i n d e r Pressure Transducer 39 4.1 E f f e c t of P i l o t D i e s e l Flow Rate on Brake Thermal E f f i c i e n c y 48 4.2 Fuel Consumption at i d l i n g Operation 50 4.3 E f f e c t of p i l o t D i e s e l Flow Rate on Indicated Thermal E f f i c i e n c y 52 4.4 Comparison of Brake Thermal e f f i c i e n c i e s f or Dual-Fuel and S t r a i g h t D i e s e l Operation 54 4.5 E f f e c t of Intake A i r R e s t r i c t i o n on Brake Thermal E f f i c i e n c y 57 4.6 T y p i c a l C y l i n d e r Pressure Trace and Apparent Point of I g n i t i o n S t a r t 58 4.7 Apparent Point of I g n i t i o n S t a r t at Various Loads 59 4.8 E f f e c t of Varying I n j e c t i o n Timing on Brake Thermal E f f i c i e n c y 61 4.9 P-V Diagram of S t r a i g h t D i e s e l Operation 64 4.10 Ln P-V Diagram of S t r a i g h t D i e s e l Operation 66 4.11 Comparison of P-V Diagrams f o r Dual-Fuel and S t r a i g h t D i e s e l Operation 67 4.12 Comparison of Ln P-V Diagrams f o r Dual-Fuel and S t r a i g h t D i e s e l Operation 69 4.13 Comparison of Maximum C y l i n d e r Pressures f o r Dual-Fuel and S t r a i g h t D i e s e l Operation 70 4.14 Maximum C y l i n d e r Pressure at Various Loads 71 vi 4.15 Comparison of Maximum Rate of Cy l i n d e r Pressure Rise for Dual-Fuel and S t r a i g h t D i e s e l Operation 72 4.16 Maximum Rate of Cyl i n d e r Pressure Rise at Various Loads 73 4.17 E f f e c t of Intake A i r R e s t r i c t i o n on Maximum Cyl i n d e r Pressure 75 4.18 E f f e c t of Intake A i r R e s t r i c t i o n Pressure P r i o r to Combustion 76 4.19 E f f e c t of Intake A i r R e s t r i c t i o n on Maximum Rate of C y l i n d e r Pressure Rise 78 4.20 E f f e c t of Varying I n j e c t i o n Timing on Maximum c y l i n d e r Pressure and Rate of Pressure Rise 80 4.21 E f f e c t of Varying I n j e c t i o n Timing on Pressure P r i o r to Combustion and Point of I g n i t i o n S t a r t .. 81 4.22 E f f e c t of Varying I n j e c t i o n Timing on P-V Diagram 82 5.1 Control Volume for Apparent Energy Release A n a l y s i s 86 5.2 Apparent Heat Transfer Rate and Heat Transfer Model 91 5.3 E f f e c t of Heat Transfer Model on Apparent Rate of Energy Release 93 5.4 E f f e c t of E q u i l i b r i u m C a l c u l a t i o n on Apparent Rate of Energy Release 97 5.5 E f f e c t of Smoothing Pressure Data on Apparent rate of Energy Release 101 5.6 Flowchart of Computer Program f o r Apparent Energy Release 103 5.7 T y p i c a l Output of Computer Program for Apparent Energy Release A n a l y s i s 104 5.8 Rate of Energy Release of S t r a i g h t D i e s e l Operation at Various Loads 108 5.9 Cumulative Energy Release of S t r a i g h t D i e s e l Operation at Various Loads 109 5.10 E f f e c t of A i r - F u e l Ratio on Maximum Rate of Energy Release i n S t r a i g h t D i e s e l Operation 111 5.11 Rate of Energy Release of Dual-Fuel Operation at Various Loads 112 5.12 E f f e c t of Gas-Air Mixture Strength on Maximum Rate of Energy Release i n Dual-Fuel Operation .... 113 5.13 Cumulative Energy Relese of Dual-Fuel Operation at Various Loads 115 5.14 Comparison of Rate of Energy Release f o r S t r a i g h t D i e s e l and Dual-Fuel Operation 116 5.15 Comparison of Cumulative Energy Release f o r S t r a i g h t D i e s e l and Dual-Fuel Operation 117 5.16 Rate of Energy Release of Dual-Fuel Operation at Various P i l o t D i e s e l Flow Rates 118 v i i 5.17 Cumulative Energy Release of Dual-Fuel Operation at Various P i l o t D i e s e l Flow Rats 120 5.18 F r a c t i o n of Fuel Burnt i n Low Load Dual-Fuel Operation 121 5.19 Rate of Energy Release of Dual-Fuel Operation at Various P i l o t D i e s e l Flow Rates 122 5.20 Cumulative Energy Release of Dual-Fuel Operation at Various P i l o t D i e s e l Flow Rates 123 5.21 E f f e c t of R e s t r i c t i n g Intake A i r on Rate of Energy Release 125 5.22 E f f e c t of R e s t r i c t i n g Intake A i r on Cumulative Energy Release 127 5.23 E f f e c t of R e s t r i c t i n g Intake A i r on Rate of Energy Release 128 5.24 E f f e c t of R e s t r i c t i n g Intake A i r on Cumulative Energy Release 129 5.25 E f f e c t of Advancing I n j e c t i o n Timing on Rate of Energy Release 131 5.26 E f f e c t of Advancing I n j e c t i o n Timing on Cumulative Energy Release 132 5.27 E f f e c t of Retarding I n j e c t i o n Timing on Rate of Energy Release 133 5.28 E f f e c t of Retarding I n j e c t i o n Timing on Cumulative Energy Release 134 \ vi i i Acknowledgement The author wishes to acknowledge a sincere g r a t i t u d e to Dr. P.G. H i l l f or h i s advice and encouragement. Numerous d i s c u s s i o n s with Dr. Roger Milane have and w i l l remain valuable to the author. Thanks are a l s o due to Messrs Stan Mah, Shu Osaka, and John Hoar for t e c h n i c a l advice and a s s i s t a n c e i n s e t t i n g up the equipments. Stan Mah was responsible for the i n s t a l l a t i o n of the engine, and for development of the instrumentation before the p r o j e c t commenced. P r o v i s i o n of t e c h n i c a l information and a s s i s t a n c e by Mr. Jim Bare of Finnings T r a c t o r s i s g r e a t l y appreciated. Further thanks are due to the members of the t h e s i s committee, Dr. B. Ahlborn, Dr. B. Evans and Dr. E.G. Hauptmann. This work was f i n a n c i a l l y supported by the Federal Department of Energy Mines and Resources. ix Nomenclature A area m2 ATDC after top dead center BMEP brake mean e f f e c t i v e pressure kPa BTDC before top dead center CA crank angle CE chemical energy kJ D bore mm E energy kJ e c internal energy of combustion kJ/kg K equilibrium constant k thermal conductivity kW/(irt' C) m^  mass of fuel kg N number of moles kmole P pressure MPa Q heat transfer kJ q heat transfer rate kW R Reynolds Number T temperture C U internal energy kJ V volume m3 V mean veloci t y m/s W work kJ V equilibrium composition v v i s c o s i t y kg/m-s p density kg/m3 $ equivalence r a t i o X inverse of equivalence r a t i o Subscripts: 9 i gas state 1 CH.I I n t r o d u c t i o n  1 .1 Background Dual-Fuel D i e s e l Engines with Natural Gas Du a l - f u e l d i e s e l engines are here defined as those which burn e i t h e r gaseous f u e l s or d i e s e l , or both at the same time. The mode of operation i s defined as s t r a i g h t d i e s e l i f only d i e s e l f u e l i s used, and d u a l - f u e l i f two f u e l s are used at the same time. In d u a l - f u e l operation the gaseous f u e l i s mixed with a i r at lean g a s - a i r r a t i o and the mixture i s then compressed during the compression stroke. Near the end of the compression s t r o k e , d i e s e l f u e l i s i n j e c t e d and a u t o - i g n i t e s , i n i t i a t i n g the combustion of the ga s - a i r mixture. Because of i t s f u n c t i o n to i n i t i a t e the combustion the d i e s e l i n d u a l - f u e l operation i s often r e f e r r e d to as p i l o t d i e s e l . The changeover of the mode of operation, e i t h e r from d u a l - f u e l to s t r a i g h t d i e s e l or s t r a i g h t d i e s e l to d u a l - f u e l can take place while the engine operates. Combustion c h a r a c t e r i s t i c s of d u a l - f u e l operation d i f f e r from those of s t r a i g h t d i e s e l o p e ration. In d i e s e l operation the combustion takes places w i t h i n small zones where the f u e l -a i r r a t i o i s s u i t a b l e for combustion. As a stream of d i e s e l f u e l i s i n j e c t e d i n t o the c y l i n d e r , i t i s mixed with a i r to be d i s i n t e g r a t e d i n t o f i n e d r o p l e t s which i n turn vapourize and 2 a u t o - i g n i t e due to the high temperature of the compressed a i r . The time p e r i o d during which l i q u i d d i e s e l i s mixed with a i r and vapourized i s r e f e r r e d to as ' p h y s i c a l delay' and the time taken from then to the point j u s t p r i o r to i g n i t i o n i s r e f e r r e d to as 'chemical delay'. These two delay periods are combined and commonly termed ' i g n i t i o n delay'. Combustion i n d u a l - f u e l operation, i n c o n t r a s t , occurs i n a nearly homogeneous f u e l - a i r mixture. During the intake s t r o k e , a nearly uniform mixture of gas and a i r i s drawn i n t o the c y l i n d e r , then compressed by p i s t o n movement to high temperature and pressure but not high enough to e l i c i t a u t o - i g n i t i o n . A small amount of d i e s e l f u e l i s i n j e c t e d i n t o the homogeneous ga s - a i r mixture near the end of the compression strok e . The i n j e c t e d p i l o t d i e s e l subsequently goes through the i g n i t i o n delay before i t d i s i n t e g r a t e s i n t o d i e s e l ' vapour to i n i t i a t e flame f r o n t s which propagate through the g a s - a i r mixture. The propagation of flame f r o n t s i s l a r g e l y responsible for subsequent combustion of the remaining g a s - a i r mixture. I t i s i n t h i s regard that the combustion process of d u a l - f u e l operation d i f f e r s from that of s t r a i g h t d i e s e l o peration. The combustion i n s t r a i g h t d i e s e l operation i s l a r g e l y due to a u t o - i g n i t i o n of d i e s e l f u e l , whereas that of d u a l - f u e l operation depends h e a v i l y on both the a u t o - i g n i t i o n c h a r a c t e r i s t i c s of p i l o t d i e s e l and the propagation of flame f r o n t s . The gaseous f u e l we are concerned with here i s n a t u r a l gas. Natural gas i s a v a i l a b l e i n most l o c a l i t i e s , and i s i n many places more abundant than other kinds of f u e l . The temperature at which the n a t u r a l gas a u t o - i g n i t e s i s higher than that of 3 o t h e r a v a i l a b l e g a s e o u s f u e l s . B e c a u s e of t h e h i g h a u t o -i g n i t i o n t e m p e r a t u r e t h e g a s - a i r m i x t u r e c a n be c o m p r e s s e d t o h i g h c o m p r e s s i o n r a t i o w i t h o u t a u t o - i g n i t i o n . T h i s , w i t h th e low c o s t of n a t u r a l g a s , makes d u a l - f u e l d i e s e l o p e r a t i o n w i t h n a t u r a l gas an a t t r a c t i v e means f o r power p r o d u c t i o n , e s p e c i a l l y i n p l a c e s where t h e gas s u p p l y may p o s s i b l y be i n t e r r u p t e d . D u a l - f u e l d i e s e l e n g i n e s w i t h n a t u r a l gas have been employed e x t e n s i v e l y i n power g e n e r a t i n g s t a t i o n s where e n g i n e s o p e r a t e c o n s t a n t l y a t n e a r f u l l l o a d . The f u e l c o n s u m p t i o n r a t e of d u a l - f u e l d i e s e l o p e r a t i o n w i t h n a t u r a l gas a t f u l l l o a d has been shown t o be as good as or sometimes b e t t e r t h a n t h a t of s t r a i g h t d i e s e l o p e r a t i o n . T y p i c a l l y , t h e amount of p i l o t d i e s e l used i n t h e p a s t has c o n s i s t e d of l e s s t h a n 10% of t o t a l e n e r g y i n p u t . In a p p l i c a t i o n s s u c h as p i p e l i n e i n d u s t r i e s , where t h e r e q u i r e d power i s n e a r l y c o n s t a n t , d u a l - f u e l d i e s e l o p e r a t i o n has been shown t o be s a t i s f a c t o r y . The maximum power of d u a l - f u e l d i e s e l o p e r a t i o n i s l i m i t e d by t h e o c c u r r e n c e of knock w i t h i t s h i g h r a t e o f c y l i n d e r p r e s s u r e r i s e . Knock i n d u a l - f u e l e n g i n e s i s b e l i e v e d t o be t h e same t y p e as i n s p a r k - i g n i t i o n e n g i n e . I f t h e d u a l - f u e l e n g i n e has t o o p e r a t e o v e r a r a n g e o f l o a d , t h e economic a d v a n t a g e of d u a l - f u e l d i e s e l o p e r a t i o n a t f u l l l o a d may be o f f s e t by poor c o m b u s t i o n c h a r a c t e r i s t i c s a t low l o a d , w h i c h r e s u l t i n poor f u e l c o n s u m p t i o n r a t e . A t low l o a d s i g n i f i c a n t amounts of n a t u r a l gas s u r v i v e c o m b u s t i o n and e s c a p e t h r o u g h t h e e x h a u s t b e c a u s e of l e a n g a s - a i r m i x t u r e s t r e n g t h . Low l o a d f u e l c o n s u m p t i o n r a t e c a n be i m p r o v e d by r e s t r i c t i n g i n t a k e a i r , 4 which e f f e c t i v e l y increases g a s - a i r mixture s t r e n g t h , or by i n c r e a s i n g the p i l o t d i e s e l flow r a t e . Other p o s s i b l e methods which improve low load f u e l consumption rate are preheating the intake charge and advancing the i n j e c t i o n timing of p i l o t d i e s e l . Preheating the intake charge r e s u l t s i n higher mixture temperature and thus a s s i s t s the o x i d a t i o n r e a c t i o n of the gaseous f u e l . Advancing the i n j e c t i o n timing provides longer time fo r the gaseous f u e l to react subsequent to the i n i t i a l r e a c t i o n of the p i l o t d i e s e l . Prechamber D i e s e l Engine D i e s e l engines can be c l a s s i f i e d i n t o two types: d i r e c t -i n j e c t i o n or i n d i r e c t - i n j e c t i o n types depending on whether the combustion involves one or two chambers. A prechamber d i e s e l engine i s an i n d i r e c t - i n j e c t i o n engine c o n s i s t i n g of two chambers, prechamber and main chamber. F i g . 1 . 1 shows the t y p i c a l shape of the combustion chambers for d i r e c t - i n j e c t i o n and prechamber d i e s e l engines. The volume of the prechamber i s t y p i c a l l y 20 to 30 percent of the clearance volume. The main o b j e c t i v e of the prechamber design i s to burn a small f r a c t i o n of the i n j e c t e d f u e l i n the prechamber so that the r e s u l t i n g pressure, r i s e w i l l d r i v e the mixture of p a r t i a l l y burnt and unburned f u e l i n t o the main chamber as a high speed j e t whose turbulence w i l l promote r a p i d and complete combustion. The advantages of the prechamber d i e s e l engine compared to the d i r e c t - i n j e c t i o n type are b e t t e r emission c h a r a c t e r i s t i c s Figure 1 .1 - Combustion Chambers of D i r e c t - I n j e c t i o n and Prechamber Engines 6 and l e s s tendency to knock. Because of the b e t t e r emmision c h a r a c t e r i s t i c s the prechamber engines are p r e f e r r e d for higher speed operations. The disadvantages are mainly a s s o c i a t e d with higher surface-to-volume r a t i o which enhances heat l o s s and t h r o t t l i n g between prechamber and main chamber. These r e s u l t i n higher f u e l consumption r a t e . The type of d i e s e l engine used i n d u a l - f u e l operation with n a t u r a l gas has been almost e x c l u s i v e l y d i r e c t - i n j e c t i o n , so that the behaviour of a prechamber d i e s e l engine with d u a l -f u e l l i n g over a range of load appears to be v i r t u a l l y unknown. 7 1.2 Present Study  Object ives The primary o b j e c t i v e of t h i s study was to determine the f e a s i b i l i t y of d u a l - f u e l operation with n a t u r a l gas i n a prechamber d i e s e l engine. Observations were made of f u e l consumption and c y l i n d e r pressure development which may c r i t i c a l l y a f f e c t engine d u r a b i l i t y . The e f f e c t s on f u e l consumption and c y l i n d e r pressure of the f o l l o w i n g v a r i a b l e s were studied: a. flow rate of p i l o t d i e s e l b. g a s - a i r mixture strength c. i n j e c t i o n timing of p i l o t d i e s e l Computer a n a l y s i s of apparent energy release was employed to study the combustion c h a r a c t e r i s t i c s , f i r s t f or s t r a i g h t d i e s e l operation and then with regard to the above three operating v a r i a b l e s . Past experience with d i r e c t - i n j e c t i o n engines was considered i n a n t i c i p a t i n g p o s s i b l e operating d i f f i c u l t i e s and in a n a l y z i n g the observed combustion c h a r a c t e r i s t i c s . Experimental Work A C a t e r p i l l a r 3304, f o u r - c y l i n d e r prechamber marine engine, with turbocharger was used i n the course of the study. The experimental study was done at constant engine speed because load changes rather than speed changes were considered to be of 8 c h i e f concern i n examining the f e a s i b i l i t y of d u a l - f u e l operation. Throughout the experiments measurments were taken to produce f u e l consumption and c y l i n d e r pressure data. The f i r s t phase of t e s t s was performed w i t h v a r i o u s loads and p i l o t d i e s e l f u e l r a t e s . I t was found that the f u e l consumption rate of d u a l - f u e l operation i s considerably higher than that of s t r a i g h t d i e s e l operation at loads much lower than the ' f u l l load' s p e c i f i e d by the engine manufacturer. As the load was increased to near f u l l load the f u e l consumption rate approached that of s t r a i g h t d i e s e l operation. I t was observed that at some point beyond f u l l load the f u e l consumption rate of the d u a l - f u e l operation would become lower than that of s t r a i g h t d i e s e l o p eration. The flow rate of p i l o t d i e s e l was shown to g r e a t l y a f f e c t the f u e l consumption rate at low loads. As the load was increased the e f f e c t of p i l o t d i e s e l flow rate became smaller. The maximum c y l i n d e r pressure and pressure r i s e were observed to increase r a p i d l y with increase i n load. .The maximum power output was severely ' l i m i t e d •by the maximum c y l i n d e r pressure. I t was found that when the flow rate of p i l o t d i e s e l was below a c e r t a i n l i m i t the operation became e r r a t i c with m i s f i r i n g s . For a range of loads and p i l o t d i e s e l flow r a t e s , a region of unstable operation due to i n s u f f i c i e n t p i l o t d i e s e l flow r a t e was e s t a b l i s h e d . The second phase of the experiments was intended for study of the e f f e c t of intake a i r r e s t r i c t i o n . During the i n i t i a l stage of the experiments i t was n o t i c e d that excessive a i r r e s t r i c t i o n can cause surge of the compressor i n the 9 turbocharger. Since surge can e a s i l y cause mechanical damage of the turbocharger the intake a i r r e s t r i c t i o n had to be l i m i t e d to a small range of a i r flow red u c t i o n . In the l a s t stage of experiments the e f f e c t of i n j e c t i o n timing was studi e d p r i m a r i l y because of concern over maximum pressures a s s o c i a t e d with d u a l - f u e l l i n g and normal i n j e c t i o n t i m i n g . I t was found that r e t a r d i n g the i n j e c t i o n timing r e s u l t s in s i g n i f i c a n t reduction i n both the maximum c y l i n d e r pressure and pressure r i s e . The change in f u e l consumption rate due to the retarded i n j e c t i o n was found to be sma l l . Computer A n a l y s i s of Apparent Energy Release A computer program which computes apparent energy release due to combustion was developed in order to study the combustion c h a r a c t e r i s t i c s . The c y l i n d e r pressure data obtained during the course of above three phases of experiments were used in the a n a l y s i s . The a n a l y s i s showed that the excessive maximum c y l i n d e r pressure was mainly a s s o c i a t e d with high rate of combustion energy r e l e a s e . The r e s u l t s of the a n a l y s i s are co n s i s t e n t with d i f f e r e n t mechanisms of combustion: auto-i g n i t i o n of d i e s e l i n s t r a i g h t d i e s e l operation and propagation of flame f r o n t s i n d u a l - f u e l o p eration. 1 0 CH.II Review of L i t e r a t u r e 2.1 H i s t o r y of the Dual-Fuel D i e s e l Engine The e a r l i e s t p r a c t i c a l use of gas as an engine f u e l dates back to the end of the 19th century. S p a r k - i g n i t e d engines c a l l e d 'gas engines' operated i n much the same way as modern gas engines. In these e a r l y engines the gas- a i r mixtures were nearly s t o i c h i o m e t r i c and the compression r a t i o s were about 6:1. Commercial production of engines of various s i z e s began i n about the year 1900. Jones(l944) s t a t e s that by 1920 in B r i t a i n engines with maximum power ranging from 5 to 2000 horse power (4 to 1500 kW) were manufactured for use mainly on waste gases, p a r t i c u l a r l y b l a s t furnace gas. The f i r s t attempt to burn gas in a compression i g n i t i o n engine appears to have been made by the C.&G. Cooper Company in 1927. According to Boyer and Crooks(1951), the f i r s t t e s t c o n s i s t e d of i n j e c t i n g n a t u r a l gas alone at high pressure at the end of the compression s t r o k e . This r e s u l t e d i n i r r e g u l a r f i r i n g of the gas. In the next t e s t a small p o r t i o n of d i e s e l was i n j e c t e d i n a d d i t i o n to the gas. This was the b i r t h of the so c a l l e d ' g a s - d i e s e l ' engine, i n which the gaseous f u e l was i n j e c t e d i n t o the c y l i n d e r at high pressure (about 1000 p s i or 7 MPa). The f i r s t commercial i n s t a l l a t i o n of such engine was achieved by the Nordberg Company i n 1935. A 1,665 horse power (1,241 kW) engine was i n s t a l l e d at Lubbock, Texas, and the operation was s u c c e s s f u l ; at f u l l load the s p e c i f i c f u e l 11 consumption was as low as that of d i e s e l operation. The high pressure gas i n j e c t i o n equipment needed for the ' g a s - d i e s e l ' engines gave r i s e to problems: the equipment was c o s t l y and thus l i m i t e d to use on large engines, and i t was rather d i f f i c u l t to maintain. In 1938 the N a t i o n a l Gas and O i l Company developed an 8-cylinder 440 horse power engine, which used town gas. In t h i s engine the gas was admitted to the c y l i n d e r at low pressure through a separate passage from the a i r i n l e t . The operation was s u c c e s s f u l and l e d to the conversion of e x i s t i n g engines at the C o l e s h i l l Works of the Birmingham Tame and Rea D i s t r i c t Drainage Board. An a l t e r n a t i v e means of a d m i t t i n g the gas at low pressure became commonly used. M i t c h e l l and Whitehouse(1954) described one such scheme developed by the E n g l i s h E l e c t r i c Company to provide b e t t e r g a s - a i r mixing. Instead of being d i r e c t l y admitted i n t o the c y l i n d e r , gas was mixed with a i r i n the intake manifold a f t e r upstream i n j e c t i o n through a ' f l u t t e r ' v a l v e . This f l u t t e r valve acted as non-return valve to prevent pressure p u l s a t i o n s or explosions passing back i n t o the gas supply pipes. The l i t e r a t u r e of the 1950's reveals some fundamental studies of d u a l - f u e l operation on d i r e c t - i n j e c t i o n d i e s e l engines. These are discussed in d e t a i l i n the f o l l o w i n g s e c t i o n . 12 2.2 Review of Research An extensive summary of the r e s u l t s of d u a l - f u e l d i e s e l combustion research i s provided i n review papers by Karim(l980) and Karim(l982). Both research r e s u l t s and a p p l i c a t i o n s have been reviewed by 0'Neal(1982). The l i t e r a t u r e contains a considerable amount of information concerning the operating experience and combustion processes of d u a l - f u e l d i e s e l operation though t h i s i s r e s t r i c t e d to d i r e c t - i n j e c t i o n engines only. The research experiences are discussed i n t h i s section in c h r o n o l o g i c a l order as i n d i c a t e d in Table 2.1 which mentions the main features of each p r o j e c t . The review here i s r e s t r i c t e d to s t u d i e s which involve methane-based gases. The importance of g a s - a i r mixture strength i n d u a l - f u e l operation was studied by E l l i o t t & D a v i s ( l 9 5 l ) . In t h e i r experiments with a CFR" d i e s e l engine at a compression r a t i o of 21:1, s e l e c t e d p i l o t d i e s e l rates were held constant to determine the e f f e c t of the concentration of n a t u r a l gas (88.9% methane, 10.6% other hydrocarbons) i n the i n t a k e . Their experiments showed that when the g a s - a i r mixture strength was below a c e r t a i n l i m i t , the proportion of gas r e a c t i n g increased with d i e s e l f u e l - a i r r a t i o and gas-air mixture strength. They found that i f the concentration of gas i s below the lower l i m i t of f l a m m a b i l i t y (which i s commonly defined as the concentration *CFR (Cooperative Fuel Research) engine: s i n g l e - c y l i n d e r engine, with 3.25 i n . (82.5 mm) bore and 4.5 i n . (114 mm) s t r o k e , manufactured by the Waukeska Engine Co. of Waukeska, Wis., the standard engine used for detonation measurement and g e n e r a l l y f o r detonation research. AUTHOR DATE ENGINE GASEOUS FUEL MAIN FINDINGS E l l i o t & D a v i s 1951 CFR d i e s e l c r . 16: 1, 21: 1 n a t u r a l gas methane 88.9% o t h e r h y d r o c a r b o n 10.6% lowe r l i m i t of f lammab i 1 i ty, dependence of amount of gas r e a c t e d on g a s - a i r m i x t u r e s t r e n g t h and d i e s e l f u e l -a i r r a t i o . L e w i s 1954 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n c r . 14.7:1 bo r e 105mm s t r o k e 152mm s l u d g e gas me thane 8 6.8% n i t r g e n 4.5% c a r b o n d i o x i d e 5.5% e f f e c t of i n t a k e a i r r e -s t r i c t i o n and i n t a k e a i r p r e h e a t i n g on e f f i c i e n c y . S imons on 1954 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n c r . 14.7:1 me thane e f f e c t of i n t a k e a i r p r e -h e a t i n g on r e a c t i o n s of gaseous c h a r g e . S imons on 1955 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n c r . 14.7:1 bore 105mm s t r o k e 152mm methane e f f e c t of i n t a k e a i r p r e -h e a t i n g , i n t a k e a i r r e s t r i -c t i o n , and v a r y i n g i n j e c t -i o n t i m i n g on e f f i c i e n c y . Moore & M i t c h e l l 1955 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n b o re 105mm s t r o k e 152mm me thane e f f e c t of i n t a k e a i r p r e -h e a t i n g , i n t a k e a i r r e s t r -i c t i o n , and v a r y i n g i n j e c t -i o n t i m i n g on e f f i c i e n c y . Mi t c h e l l & Wh i t ehous e 1955 f o u r - c y l i n d e r d i r e c t - i n j e c t i o n c r . 13.5:1 bore 254mm s t r o k e 30 5mm s l u d g e gas methane 87.9% n i t r o g e n 4.4% ca r b o n d i o x i d e 5.5% e f f e c t of i n t a k e a i r r e -s t r i c t i o n on e f f i c i e n c y F e l t & S t e e l e 1962 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n c r . 16.2:1 n a t u r a l gas me thane 8 7.1% n i t r o g e n 7 . 1% o t h e r h y d r o c a r b o n 5.1% pr o b l e m s w i t h l o s s of com-b u s t i o n c o n t r o l , e f f e c t of a d d i t i v e s on k n o c k - l i m i t e d power. Kar im, K l a t , & Moore 1966/67 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n c r . 14.2:1 bore 108mm s t r o k e 152mm me thane 9 7.8% d e t e r m i n a t i o n of knock-l i m i t e d powe r . Kar im & Kahn 1968 s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n b o r e 105mm s t r o k e 152mm me thane h e a t r e l e a s e a n a l y s i s , two-phased c o m b u s t i o n . * gas c o m p o s i t i o n based on volume T a b l e 2.1 - Summary o f P a s t E x p e r i m e n t a l Work 15 of gaseous f u e l in the intake a i r at which the minimum l i q u i d f u e l - a i r r a t i o y i e l d s c o n s i s t e n t and close-to-complete combustion) the gas does not.react completely with oxygen unless i t i s i n , or immediately adjacent t o , an inflamed or high temperature region. In the absence of p i l o t d i e s e l , a s t o i c h i o m e t r i c g a s - a i r mixture does not appear to react to a s i g n i f i c a n t extent; the exhaust gas a n a l y s i s shows no sign of the presence of carbon d i o x i d e , carbon monoxide, or aldehydes. Therefore, unless the n a t u r a l gas i s i n a comparatively high temperature region, i t i s u n l i k e l y that the gas would react when i t s c o ncentration i s lower than the lower l i m i t c o n c e n t r a t i o n . The t e s t s of E l l i o t and Davis in sev e r a l d i e s e l engines showed that the lower l i m i t of f l a m m a b i l i t y of n a t u r a l gas i n a i r under c o n d i t i o n s e x i s t i n g at the end of compression i s approximately 4 to 5 percent by volume. The corresponding r a t i o for the s t o i c h i o m e t r i c mixture stre n g t h was 9.1% by volume. The experiments by Lewis(l954) were focused mainly on operations with weak g a s - a i r mixture strength (below 8% by volume). Lewis used sludge gas(86.6% methane, 5.45% carbon d i o x i d e , 4.5% nitrogen by volume) i n a s i n g l e c y l i n d e r d i r e c t -i n j e c t i o n engine with compression r a t i o of 14.7:1 and engine speed of 1000 rpm. The lower l i m i t of f l a m m a b i l i t y in h i s work was shown to be about 6.2% by volume. This i s somewhat higher than the r e s u l t of e a r l i e r work by E l l i o t and D a v i s ( l 9 5 l ) , and may be due to the high concentration of carbon d i o x i d e and nitrogen i n the sludge gas used by Lewis. The experiments by Lewis showed that when the g a s - a i r mixture strength i s below the f l a m m a b i l i t y l i m i t , r e s t r i c t i n g intake a i r r e s u l t s i n 16 s i g n i f i c a n t increase i n the amount of gas reacted and i n increase i n i g n i t i o n delay. Preheating of intake a i r was a l s o found to increase the amount of gas reacted, but r e s u l t e d i n decreased i g n i t i o n delay. With preheating of the intake charge to 225 deg.C s u b s t a n t i a l l y complete combustion was achieved (95% of gas reacted at 4.5% gas-air mixture strength ,and 70% at 1.0% mixture s t r e n g t h ) . The i g n i t i o n delay of p i l o t d i e s e l i n r e l a t i o n to g a s - a i r mixture s t r e n g t h was a l s o s t u d i e d . The i g n i t i o n point was i d e n t i f i e d from the pressure-time trace as the point of s i g n i f i c a n t pressure r i s e due to combustion. Figure 2.1 shows the r e s u l t s obtained at constant p i l o t d i e s e l rate of 0.415 lb/h (0.188 kg/h, 10% of the s t r a i g h t d i e s e l f u l l load f u e l r a t e ) . Increase in g a s - a i r mixture strength r e s u l t e d i n i t i a l l y i n longer i g n i t i o n delay of p i l o t d i e s e l . Beyond the g a s - a i r mixture strength of about 4% by volume, f u r t h e r increase in mixture strength showed sharp reduction i n the i g n i t i o n delay. The v a r i a t i o n i n i g n i t i o n delay for the range of mixture strength of 0 to 8% by volume was about 3 deg. C A . The e f f e c t on combustion c h a r a c t e r i s t i c s of g a s - a i r mixture strength and intake charge temperature of a motored-engine was studied by Simonson(1954). His experiments were performed with methane i n a d i r e c t - i n j e c t i o n s i n g l e - c y l i n d e r engine for intake charge temperatures ranging from 241 to 325 deg.C and g a s - a i r mixture strength ranging from 0 to 5% by volume. The r e s u l t s from exhaust a n a l y s i s of constant-speed motored t e s t s revealed that increase i n intake charge temperature r e s u l t s i n more favourable c o n d i t i o n s for flame propagation. 13 < O 12 o LU Q 11 >-< _J LU Q O 10 8 7 0 speed 1000 rpm pilot diesel 0.415 Ib/hr gas methane 2 GAS IN 3 4 5 6 7 8 (%) ENGINE I N T A K E BY VOLUME ( L e w i s , 1954) F i g u r e 2 . 1 - E f f e c t of G a s - A i r M i x t u r e S t r e n g t h on I g n i t i o n Delay 18 Further work by Simonson(1955), with f i r e d - e n g i n e operation included s t u d i e s of the e f f e c t s of a i r r e s t r i c t i o n , and changes in p i l o t d i e s e l rate and i n j e c t i o n t i m i n g . A d i r e c t - i n j e c t i o n engine (the same engine as the one used by Lewis(1954)) with compression r a t i o of 14.7:1 was used with methane at the speed of 1000 rpm. Preheating of intake charge to 157 deg.C showed improvements of 20 to 30% i n f u e l consumption at part loads (10-60 p s i or 70-410 kPa i n brake mean e f f e c t i v e pressure) with p i l o t d i e s e l rate c o n s i s t i n g 8.5% of d i e s e l rate of s t r a i g h t d i e s e l f u l l load operation. With the same p i l o t d i e s e l r a t e , advancing of i n j e c t i o n timing by 6 deg. C A . r e s u l t e d in improvement of f u e l consumption by 10 to 17% in the same part load range. Both intake a i r r e s t r i c t i o n and increase in p i l o t d i e s e l rate gave s i g n i f i c a n t improvements i n f u e l consumption. Maximum c y l i n d e r pressure was observed to increase with advanced i n j e c t i o n t i m i n g . Tests at brake mean e f f e c t i v e pressure of 115 p s i (793 kPa) revealed that advancing the i n j e c t i o n timing by 8 deg. C A . increased the maximum c y l i n d e r pressure from 1000 to 1250psi (7 to 8.7 MPa). E a r l y i g n i t i o n and r a p i d rates of pressure r i s e were reported to set a l i m i t to the extent to which improved performance can be obtained by advancing the i n j e c t i o n t i m i n g . With a p i l o t d i e s e l i n j e c t i o n rate of 0.8 lb/h (0.36 kg/h, 16% of s t r a i g h t d i e s e l f u l l load f u e l rate) at 24 deg BTDC (10 deg advance) combustion was rough even at the brake mean e f f e c t i v e pressure of 30 p s i (210 kPa). Experiments leading to improvement i n p a r t - l o a d f u e l consumption were done by Moore and M i t c h e l l ( 1 9 5 5 ) . A s i n g l e -c y l i n d e r d i r e c t - i n j e c t i o n engine with 4.125 i n (105.4 mm) bore 19 and 6.00 i n (152 mm) stroke was used at the speed of 1000 rpm. Tests c a r r i e d out with sludge gas on the e f f e c t s of a i r r e s t r i c t i o n , intake charge preheating, and advancing i n j e c t i o n timing showed r e s u l t s s i m i l a r to those of the experiments by Simonson (1 955) . As much as 20% improvement i n f u e l consumpti'on was reported i n each separate t e s t of the above methods. In reviewing past work they concluded that r a i s i n g the intake temperature i s the only p r a c t i c a l way of extending the lower l i m i t of f l a m m a b i l i t y . Work on a large engine was described by M i t c h e l l and Whitehouse (1955 ). A f o u r - c y l i n d e r d i r e c t - i n j e c t i o n engine of 10 i n (254 mm) bore and 12 i n (305 mm) stroke with compression r a t i o of 13.5:1 was used at the speed of 600 rpm to determine the optimum c o n d i t i o n s for r e l i a b i l i t y and e f f i c i e n c y . The gaseous f u e l used was sludge gas (87.9% methane, 5.5% carbon d i o x i d e , 4.4% n i t r o g e n ) . The p i l o t d i e s e l rate was a constant 6% of s t r a i g h t d i e s e l f u l l load f u e l r a t e . Tests on the e f f e c t of a i r r e s t r i c t i o n showed a considerable improvement i n f u e l consumption: 46% improvement was reported at the brake mean e f f e c t i v e pressure of 20 p s i (140 kPa, 26% of f u l l l o a d ) . I t was a l s o found that with optimum a i r r e s t r i c t i o n the exhaust temperature remained approximately constant ( w i t h i n ± 50 deg.F or 30 deg.C) at a l l loads. Experiments made by F e l t and Steele(1962) showed that k n o c k - l i m i t e d maximum power i s d i r e c t l y r e l a t e d to the a n t i -knock q u a l i t y of the primary f u e l . A t h r e e - c y l i n d e r d i r e c t -i n j e c t i o n engine with compression r a t i o of 16.2:1 was used with 20 p i l o t d i e s e l rate of 1.65 l b / h (0.74 kg/h, 12.8% of s t r a i g h t d i e s e l f u l l load f u e l r a t e ) . Lead a l k y l anti-knock compounds were found to be q u i t e e f f e c t i v e i n enhancing the anti-knock q u a l i t y of the primary f u e l . A mixture c o n s i s t i n g of 95% propane and 5% tetramethyllead was bled i n t o the intake a i r stream. With a d d i t i o n of 5.5-6.0 gm of lead per therm (100,000 Btu or 106,000 kJ) of n a t u r a l gas, i t was p o s s i b l e to enhance the maximum power of d u a l - f u e l operation with n a t u r a l gas (87.1% methane, 5.1% other hydrocarbons, 7.1% nitrogen) by 28 percent without knock. The knock was described as 'audible high-frequency combustion l o s s ' , which was v i s i b l e on the pressure-time t r a c e . The knock was described from the observation of the shape of the pressure-time trace as 'end-gas knock': the knock a r i s i n g from the a u t o i g n i t i o n of the end-gas ahead of the flame f r o n t . I t i s the type of knock which may occur in s p a r k - i g n i t i o n engines. The i n f l u e n c e s o f f u e l - a i r mixture strength, p i l o t d i e s e l rate and intake a i r temperature on knock-limited power were studied i n d e t a i l by Karim et al.(1966/67) with a s i n g l e -c y l i n d e r d i r e c t i n j e c t i o n engine with compression r a t i o of 14.2:1 and 97.8% methane as the gaseous f u e l . The knock was observed to be a s s o c i a t e d with a sharp change i n the running regime of the engine and accompanied by lou d l y audible sound. The t y p i c a l shape of the pressure diagram i s shown i n Figure 2.2. The knock-limited power, which i s shown i n Figure 2.3, was observed to decrease with increase i n the intake a i r temperature and/or p i l o t q u a n t i t y . I t was found that the knocking occured only i n a c e r t a i n range of mixture strength; i f 21 - 6 0 - 3 0 T D C 3 0 6 0 (Karim et al.,1966/67) Figure 2.2 - T y p i c a l Pressure-Time Trace of Non-knocking and Knocking Operation with Methane as Gaseous Fuel Figure 2.3 - V a r i a t i o n of Power Output with the O v e r a l l Mixture Strength for D i f f e r e n t Intake Temperatures 23 the engine was operated on e i t h e r side of that range of mixture s t r e n g t h , knock could be avoided. The region of knocking was on the lean side of s t o i c h i o m e t r i c mixture s t r e n g t h . The e f f e c t of the cetane number of the p i l o t d i e s e l on the onset of knock was found to be sma l l . Karim and Kahn(l968) employed heat release a n a l y s i s i n an attempt to i n t e r p r e t the combustion processes. From the a n a l y s i s with a s i n g l e - c y l i n d e r d i r e c t - i n j e c t i o n engine and methane as the gaseous f u e l , they concluded that d u a l - f u e l combustion g e n e r a l l y undergoes two d i s t i n c t phases. The f i r s t i s mainly a s s o c i a t e d with the consumption of the p i l o t f u e l together with part of the gaseous f u e l . The second i s ass o c i a t e d mainly with the gaseous f u e l and depends on i t s concentration and q u a l i t y . The heat release a n a l y s i s of very lean operation supported previous experimental evidences that poor combustion at low load operation i s due mainly to the i n a b i l i t y of the gaseous charge to supplement e f f e c t i v e l y the heat release of the f i r s t phase. The a n a l y s i s of the operation with knock i n d i c a t e d that the knock was mainly a s s o c i a t e d with r a p i d simultaneous burning of the p i l o t d i e s e l together with a s u b s t a n t i a l f r a c t i o n of the gaseous charge. Study of kno c k - l i m i t e d maximum power i n r e l a t i o n to compression r a t i o and engine speed i s included i n the review paper by 0'Neal(1982). The kn o c k - l i m i t e d power increases very r a p i d l y as the compression r a t i o i s reduced. The trend for the kno c k - l i m i t e d bmep i s to increase with engine speed. As engine speed i n c r e a s e s , l e s s time i s a v a i l a b l e for the end-gas to reach 24 the temperature f o r a u t o i g n i t i o n , and thus the onset of knock i s suppressed. In summary, the l i t e r a t u r e reveals that considerable research has been done on d u a l - f u e l operation with the d i r e c t -i n j e c t i o n type of d i e s e l engine. At low loads, combustion s u f f e r s from weak gas- a i r mixture strength r e s u l t i n g i n unburned gas escaping with the exhaust. F i g . 2.4 shows t y p i c a l thermal e f f i c i e n c i e s of d u a l - f u e l operation with d i r e c t - i n j e c t i o n d i e s e l engines. R e s t r i c t i n g or preheating intake a i r , i n c r e a s i n g p i l o t d i e s e l flow r a t e , and advancing the i n j e c t i o n timing have been shown to be e f f e c t i v e for improving the f u e l consumption at low loads. Maximum power output of high load operation i s l i m i t e d by the occurence of knock, which appears to be of the same kind as i n s p a r k - i g n i t i o n engines. Adding lead a l k y l anti-knock compounds or c o o l i n g the intake a i r were shown to be e f f e c t i v e in improving knock-limited maximum power. The l i t e r a t u r e , however, seems s i l e n t on d u a l - f u e l d i e s e l operation with the prechamber type of d i e s e l engine. o Brake Mean E f f e c t i v e P r e s s u r e (kPa) F i g u r e 2.4 - T y p i c a l T h e r m a l E f f i c i e n c i e s o f D u a l - F u e l and S t r a i g h t D i e s e l O p e r a t i o n 26 CH.III Apparatus and Instrumentation The arrangement of apparatus and instruments i s shown i n F i g . 3.1. The engine was coupled to an electromagnetic dynamometer. The s i g n a l s from the c y l i n d e r pressure transducer were c o l l e c t e d by a NEFF/620 data a q u i s i t i o n u n i t . The data obtained from various instruments were processed with a PDP 11/34 computer. The flow diagram of a i r , n a t u r a l gas, and exhaust gas i s provided i n F i g . 3.2. Natural gas i s mixed with a i r p r i o r to entering the turbocharger. The g a s - a i r mixture e x i t i n g from the turbocharger enters the c y l i n d e r during the intake s t r o k e . The exhaust gas from the c y l i n d e r passes through the t u r b i n e side of the turbocharger, and then enters a muffler before d i s c h a r g i n g to open a i r . 3.1 Engine and Test Bed Engine A c a t e r p i l l a r 3304 f o u r - c y l i n d e r engine coupled with an electromagnetic dynamometer was used i n t h i s p r o j e c t . The engine speed was adjusted to 1600 rpm throughout the experiments. F u l l load at t h i s speed was s p e c i f i e d by the manufacturer as 124 p s i (856 kPa) i n brake mean e f f e c t i v e pressure. The engine i s of prechamber type and i s equipped with a turbocharger. The s p e c i f i c a t i o n of the engine i s provided i n diesel load control = C 3 T 1 diesel flow rate^ dynamometer loaa cell intake pressure^ 7 C A T . 3 3 0 4 TT •pressure transducer [toothed wheel turbocharger •I gas flow rate^A gas valve —^  gas mixer air. . ,. restriction ^-optical pickup t exhaust T air air flow rate 1 charge amp. NEFF data acqufeit unit PDP 11 minicomputer terminal printer Figure 3 . 1 - Layout of Apparatus and Instrumentation exhaust Figure 3.2 - Flow Diagram of A i r , F u e l , and Exhaust Gas 2 9 BORE 1 2 . 1 cm ( 4 . 7 5 i n . ) STROKE 1 5 . 2 cm ( 6 . 0 in.) DISPLACEMENT 6 9 7 0 c m 3 ( 4 2 5 cu.in.) COMPRESSION RATIO 1 7 . 5 : 1 NUMBER OF CYLINDERS 4 MAXIMUM POWER 9 3 . 2 kW ( 1 2 5 hp) at 2 0 0 0 rpm TYPE prechamber ASPIRATION turbo-charged Table 3 . 1 - Engine S p e c i f i c a t i o n 30 SCALE 2.5:1 A - PRECHAMBER B - MAIN CHAMBER F i g u r e 3.3 - Shape of C o m b u s t i o n Chambers 3 1 Table 3.1. The volume of the prechamber i s 27 percent of the t o t a l volume when the p i s t o n i s at the top dead center. The c r o s s - s e c t i o n of prechamber and main chamber i s shown i n F i g . 3.3. D i e s e l I n j e c t i o n System The engine was equipped with a sleeve metering type of f u e l system. F i g . 3.4 shows the layout of the system. The main components of the sleeve metering d i e s e l - i n j e c t i o n pump are shown i n F i g . 3.5. The plunger i s moved up and down i n s i d e the b a r r e l by the a c t i o n of the pump camshaft. F i g . 3.6 shows the e f f e c t i v e stroke of the plunger and the sequence of the i n j e c t i o n events. The sleeve metering system uses c e n t r i f u g a l governor f l y w e i g h t s (shown in F i g . 3.7) i n order to prevent any change i n engine speed due to the v a r i a t i o n i n load. Thus once the governor c o n t r o l i s set at c e r t a i n p o s i t i o n in the rack s e t t i n g , the engine speed i s maintained constant regardless of p o s s i b l e change i n load. F i g . 3.8 shows the s i n g l e hole d i e s e l -i n j e c t i o n nozzle used i n the engine. The i n j e c t i o n timing was adjusted to d e s i r e d angle according to the s e r v i c e manual(NO.SER7053-01, pp80). 32 Figure 3.4 - Sleeve Metering Fuel System Roller Follower Figure 3.5 - Fuel I n j e c t i o n Pump and Housing 33 PORT 1 — H L L I N l * EFFECTIVE STROKE J-BEC::. INJECTION 3 • CO*.7;SJE INJECTION SPILL PORT Figure 3.6 - Sequence of I n j e c t i o n Events BELLCRANK SHAFT • ELLCRANK-CARRIER SPRING SEATS THRUST GOVERNOR COLLAR SPRING GOVERNOR DRIVE GOVERNOR COVER OF SHAFT FLYWEIGHTS GOVERNOR FLYWEIGHTS GOVERNOR CONTROL SHAFT GOVERNOR CONTROL LEVER Figure 3.7 - Governor Components of Sleeve Metering F i g u r e 3.8 - F u e l I n j e c t i o n N o z z l e 35 Turbocharger The engine was equipped with a T1210 model turbocharger manufactured by AiResearch. A cutaway view of the turbocharger i s shown i n F i g . 3.9. Dynamometer The engine was coupled to an electromagnetic dynamometer (General E l e c t r i c , model 1G136). The absorption c a p a c i t y of the dynamometer was 200 horse power (150 kW). Gas-mixer In order to introduce the n a t u r a l gas, a simple gas-mixer was i n s t a l l e d on upstream of the i n l e t to the turbocharger. F i g . 3.10 shows the gas-mixer. Intake A i r R e s t r i c t i o n A simple ' b u t t e r f l y ' type of valve was i n s t a l l e d near the gas-mixer to c o n t r o l the amount of a i r intake. F i g u r e 3.9 - T u r b o c h a r g e r Cutaway View 37 38 3.2 Instrumentation  Torque The torque a p p l i e d by the engine shaft to dynamometer was obtained by p l a c i n g a s t r a i n gage load c e l l ( I n t e r f a c e Inc., model 1420-4F) on the dynamometer housing. The maximum allowable load s p e c i f i e d by the manufacturer was 500 l b . A bridge a m p l i f i e r meter ( E l l i s A s s o c i a t e s , model BAM-1) was used to amplify the response from the load c e l l . The load c e l l was c a l i b r a t e d by p l a c i n g various weights on the arm of the dynamometer housing and reading the voltage from the bridge a m p l i f i e r meter. The c a l i b r a t i o n curve for the load c e l l i s provided i n Appendix A. The r e l a t i o n between, the response of the load c e l l and the a p p l i e d weight was very nearly l i n e a r . C y l i n d e r Pressure The no. 1 c y l i n d e r was instrumented with an AVL piezo-e l e c t r i c pressure transducer (model 8QP500c). The transducer was cooled with water and mounted i n a s t e e l sleeve through the c y l i n d e r head. F i g . 3.11 shows the l o c a t i o n of the mounted transducer. The s i g n a l from the transducer was tr a n s m i t t e d by a low noise cable to a charge a m p l i f i e r ( K i s t l e r , model 5004) and then to a data a c q u i s i t i o n system. The system c o n s i s t e d of a NEFF, System 620, analogue to d i g i t a l converter which was connected to a PDP 11/34 minicomputer. A computer program was S C A L E 1 . 7 : 1 Figure 3 .11 - Mounting of Cylinder Pressure Transducer 40 w r i t t e n (see Appendix C) to sample the pressure s i g n a l at i n t e r v a l s of one degree crank angle, along with a bottom dead center s i g n a l , drawn from an o p t i c a l sensor mounted on the toothed wheel at the front of the engine. The program computed an ensemble-averaged value of pressure c o l l e c t e d over 30 to 50 c y c l e s for each degree of crank angle. The averaged values were then used to compute i n d i c a t e d mean e f f e c t i v e pressure and to analyze apparent energy r e l e a s e . The pressure transducer was c a l i b r a t e d using a dead-weight t e s t e r for a pressure range of 0 to 2000 p s i (14 MPa). The c a l i b r a t i o n curve i s provided in Appendix A. A i r Flow Rate A laminar flow element (Meriam Instrument, model 50MC2-4F, range 0-400SCFM) was used to measure the a i r flow r a t e . I t was mounted between the a i r f i l t e r and turbocharger. The pressure drop• across the element was read i n inches of water on a water-f i l l e d U-tube manometer and t r a n s l a t e d to volumetric flow r a t e . The c a l i b r a t i o n curve provided by the element manufacturer i s shown in Appendix A. Gas Flow Rate The n a t u r a l gas was drawn i n from the mains supply at a pressure of 5 p s i . The gas was then passed through a pressure r e g u l a t o r which reduced the pressure to a pressure a few inches 41 of water higher than atmospheric pressure. A l a m i n a r f l o w element (Meriam Instrument, model 50MH10-1.25NT, r a n g e 0-15SCFM) was mounted to measure the flow r a t e . The p r e s s u r e d r o p a c r o s s the element was read in inches of water on a w a t e r - f i l l e d U - t u b e manometer and t r a n s l a t e d to volumetric f l o w r a t e . The f l o w r a t e was then c o r r e c t e d for n a t u r a l gas by m u l t i p l y i n g t h e r a t i o o f v i s c o s i t i e s for a i r and n a t u r a l gas. The amount o f gas a d m i t t e d to intake was c o n t r o l l e d manually with a tapered t y p e of gas valve. The c a l i b r a t i o n curve provided by t h e e l e m e n t manufacturer i s shown i n Appendix A. D i e s e l Flow Rate A p o s i t i v e displacement type of flow m e t e r (American Meter, model 1A, range 0.05-5GPH) which m e a s u r e s c u m u l a t e d f l o w r a t e was used with a stop watch for a time p e r i o d o f 10 t o 20 minutes to obtain the volumetric flow rate of d i e s e l . The accuracy o f the flow meter was confirmed by using a g r a d u a t e d c y l i n d e r . Turbocharger I n l e t Pressure As a precaution to prevent the p o s s i b i l i t y o f turbocharger surge due to excessive a i r r e s t r i c t i o n , the a i r p r e s s u r e at the i n l e t of compressor side of the turbocharger was measured for each change of a i r flow r a t e . A w a t e r - f i l l e d U - t u b e manometer was used. The l i m i t i n g measure of the compressor i n l e t pressure s p e c i f i e d by the engine manufacturer was 24 inches of water 42 below the atmospheric pressure. Intake A i r Pressure In order to measure the intake a i r pressure a f t e r the turbocharger, a bourdon-tube type of pressure gage (Marquette, model 41-123, range 30 inches of water vaccuam to 15 p s i above atmospheric pressure) was mounted on the intake manifold near no. 4 c y l i n d e r . Engine Speed The engine speed was measured by a hand d i g i t a l tachometer (Shimpo, model DT-205) which sends out a continuous l i g h t beam and counts the pulses r e f l e c t e d o f f a piece of r e f l e c t i v e tape attached on the engine s h a f t . 43 3.3 Fuel  D i e s e l The d i e s e l f u e l used throughout the experiments had the f o l l o w i n g t y p i c a l p r o p e r t i e s : API g r a v i t y - 31 s p e c i f i c g r a v i t y - 0.871 lower heating value - 45,263 kj/kg In the a n a l y s i s of energy release and computation of s t o i c h i o m e t r i c f u e l - a i r r a t i o dodecane (C iaH^) was assumed to be the representing hydrocarbon for the d i e s e l f u e l . Natural Gas The n a t u r a l gas used in the experiments had the f o l l o w i n g propert i e s : d e n s i t y - 0.766 kg/m3 at 101.3 kPa, 25 deg. C v i s c o s i t y - 108.96 micropoise at 21.1 deg. C lower heating value - 48,558 kJ/kg A t y p i c a l composition of the n a t u r a l gas used here i s given i n Table 3.2. 44 COMPOSITION RELATIVE VOLUME (%) methane 94.00 ethane 3.30 propane 1 .00 i so-butane 0.15 n-butane 0.20 i so-pentane 0.02 n-pentane 0.02 ni trogen 1 .00 carbon di o x i d e 0.30 hexane 0.01 Table 3.2 - T y p i c a l Composition of the Natural Gas Used 45 3.4 D a t a P r o c e s s The m e a s u r e m e n t s o b t a i n e d f r o m v a r i o u s i n s t r u m e n t s f o r e a c h e x p e r i m e n t w e r e f e d i n t o t h e PDP 11/34 c o m p u t e r f o r c o m p u t a t i o n o f t h e f o l l o w i n g : . p o w e r o u t p u t . t h e r m a l e f f i c i e n c y . v o l u m e t r i c e f f i c i e n c y . p r o p o r t i o n o f d i e s e l t o t o t a l f u e l i n p u t b a s e d on h e a t i n g v a l u e s . g a s - a i r , d i e s e l - a i r , t o t a l f u e l - a i r r a t i o A t y p i c a l o u t p u t f r o m t h e d a t a p r o c e s s i s shown i n T a b l e 3.3. A l i s t i n g o f t h e c o m p u t e r p r o g r a m u s e d f o r t h e c o m p u t a t i o n s i s i n c l u d e d i n A p p e n d i x I I . 46 engine speed 1 601 rpm a i r flow rate 170 c u.f t/m i n d i e s e l flow rate 1 .82 1/hr gas flow rate 6.32 c u.f t/m i n f u e l consumption rate 11,683 BTU/hr-hp power output 35.6 hp brake mean e f f e c t i v e pressure 4 1.4 ps i thermal e f f i c i e n c y 21.8 % volumetric e f f i c i e n c y 86.3 % d i e s e l input p r o p o r t i o n 15.5 % g a s - a i r equivalence r a t i o 0.365 d i e s e l - a i r equivalence r a t i o 0.068 f u e l - a i r equivalence r a t i o ( t o t a l f u e l ) 0.433 Table 3.3 - T y p i c a l Output of Computer Program for Data Processing 47 CH. IV. Experimental R e s u l t s  4.1 Fuel Consumption 4.1.1 Fuel Consumption with Unmodified Engine Tests were c a r r i e d out to study the change i n f u e l consumption r a t e with v a r i a t i o n i n load and p i l o t d i e s e l flow r a t e . The engine speed was set at 1600 rpm for a l l the experiments. The i n j e c t i o n timing of the d i e s e l f u e l remained constant at 12.3 degrees before top dead centre. Tests always s t a r t e d from s t r a i g h t d i e s e l o p e ration. While the engine was running on 100 percent d i e s e l f u e l , the speed was adjusted with the d i e s e l f u e l governor rack s e t t i n g to 1600 rpm, and the load to the predetermined s e t t i n g . The gas was then g r a d u a l l y added by opening the gas c o n t r o l v a l v e . As the amount of gas was increased, the flow of d i e s e l f u e l was reduced to maintain the speed at 1600 rpm. In F i g . 4.1, brake thermal e f f i c i e n c i e s based on lower heating value are p l o t t e d against the f r a c t i o n a l d i e s e l energy input, which i s here define d as the r a t i o of d i e s e l to t o t a l energy in p u t . The shaded area on the l e f t corresponds to the region where s t a b l e operation i s not p o s s i b l e because of i n s u f f i c i e n t p i l o t d i e s e l flow r a t e . In t h i s region, the operation was e r r a t i c w i t h m i s f i r e d c y c l e s observed on the c y l i n d e r pressure-time t r a c e on the o s c i l l o s c o p e . The i n t e r p o l a t e d paths of constant p i l o t d i e s e l operation are Brake Thermal Efficiency (%) 8fr 49 i n d i c a t e d by the dotted l i n e s . As p r e v i o u s l y described i n Chapter I I I , the d i e s e l i n j e c t i o n rate of the engine was c o n t r o l l e d by two mechanisms - the governor rack s e t t i n g , which i s adjusted manually, and the c e n t r i f u g a l governor f l y w e i g h t s , which respond to any small change i n a p p l i e d load i n order to maintain a constant speed. Thus even though the rack s e t t i n g i s held f i x e d , a d d i t i o n of gas i n the intake would r e s u l t i n change in d i e s e l i n j e c t i o n r a t e . For t h i s reason i t was not p o s s i b l e to c a r r y out t e s t s for constant p i l o t d i e s e l flow r a t e . I t i s seen from F i g . 4.1 that the decrease of thermal e f f i c i e n c y due to reduction of of p i l o t d i e s e l flow rate becomes smaller as the load increases. At the brake mean e f f e c t i v e pressure of 714 kPa (84 % of f u l l l o a d ) , the change i n thermal e f f i c i e n c y i s l e s s than 1 percent over the range of f r a c t i o n a l d i e s e l energy input of 7 to 100 percent. The extent to which the f u e l consumption rate depends on the p i l o t d i e s e l flow rate for i d l i n g operation i s seen i n F i g . 4.2. The i d l i n g operation with the f r a c t i o n a l d i e s e l energy input of 15 percent r e q u i r e s nearly twice as much energy input than that of s t r a i g h t d i e s e l operation. To obtain another p i c t u r e of the r o l e of p i l o t d i e s e l flow rate i n d u a l - f u e l operation, c a l c u l a t i o n s were made of i n d i c a t e d thermal e f f i c i e n c i e s . The i n d i c a t e d thermal e f f i c i e n c y , being based on t o t a l power produced ( i n c l u d i n g the power used to overcome the f r i c t i o n a l and pumping l o s s e s ) , should be more c l o s e l y c o r r e l a t e d with the e f f e c t i v e n e s s of the combustion process than the engine e f f i c i e n c y based on shaft power output. OS 51 This assumption i s c o n s i s t e n t with the work of Simonson (1955) i n which the measured values of i n d i c a t e d thermal e f f i c i e n c y and the proportion of gaseous f u e l reacted showed q u a l i t a t i v e l y s i m i l a r trends. Appendix B includes a d e s c r i p t i o n of the method used in present work to obtain i n d i c a t e d mean e f f e c t i v e pressure. The i n d i c a t e d thermal e f f i c i e n c i e s were i n t e r p o l a t e d and p l o t t e d i n F i g . 4.3. The e f f i c i e n c i e s are shown as a f u n c t i o n of the flow rate of p i l o t d i e s e l at constant g a s - a i r mixture strength. . The equivalence r a t i o 4>g of the gas was computed as the r a t i o of the mass of the s t o i c h i o m e t r i c amount of a i r required for combustion of the gas alone to the mass of the a c t u a l amount of a i r drawn i n : i . e . 4>g = s t o i c h i o m e t r i c a i r mass flow rate a c t u a l a i r mass flow rate I t can be seen from F i g . 4.3 that the p i l o t d i e s e l flow rate has a very s i g n i f i c a n t e f f e c t on the thermal e f f i c i e n c y at low gas-a i r mixture s t r e n g t h . As the g a s - a i r mixture strength becomes r i c h e r , the thermal e f f i c i e n c y becomes l e s s s e n s i t i v e to the change i n p i l o t d i e s e l flow r a t e . With gas equivalence r a t i o of 0.6, an increase of p i l o t d i e s e l flow rate from 1.4 to 3.5 kg/h r e s u l t s i n l e s s than 1 percent improvement i n i n d i c a t e d thermal e f f i c i e n c y . I f i t i s assumed that the measured values of the i n d i c a t e d thermal e f f i c i e n c i e s are l a r g e l y a f u n c t i o n of the amount of gas burned, then the g a s - a i r equivalence r a t i o of 0.6 would be a good approximation f o r the lower l i m i t of f l a m m a b i l i t y for t h i s p a r t i c u l a r type of engine. The gas 53 equivalence r a t i o of 0.6 corresponds to the g a s - a i r volumetric r a t i o of about 4 percent. This approximate value i s cl o s e to the lower i n f l a m m a b i l i t y l i m i t of 4 to 5 percent suggested by E l l i o t t and D a v i s ( l 9 5 l ) for a d i r e c t - i n j e c t i o n d i e s e l engine. The dotted l i n e s i n F i g . 4.3 i n d i c a t e the paths of constant load operation with v a r i a t i o n i n p i l o t d i e s e l r a t e . The l i n e at the bottom traces the operation at i d l i n g , and the one at the top the operation at about 84 percent of f u l l l oad. Operating with a constant p i l o t d i e s e l rate of 3.4 kg/h would correspond to 100 percent d i e s e l f u e l l i n g at i d l i n g and 20 percent d i e s e l f u e l l i n g at 85 percent of f u l l l oad. The shaded area on the l e f t i s the region of unstable operation due to m i s f i r i n g . F i g . 4.4 shows brake thermal e f f i c i e n c y for s t r a i g h t d i e s e l and d u a l - f u e l operations. The s t r a i g h t d i e s e l operation shows the f u e l consumption c h a r a c t e r i s t i c s t y p i c a l of compression i g n i t i o n engines. As the load i s increased from i d l i n g , the e f f i c i e n c y improves because of the increase i n power output while the f r i c t i o n a l l o s s of the engine remains r e l a t i v e l y constant f o r a f i x e d speed. At the brake mean e f f e c t i v e pressure of about 700 kPa, the thermal e f f i c i e n c y reaches a peak. With f u r t h e r increase i n load, the curve s t a r t s to d e c l i n e , presumably due to the decreased access of f u e l to oxygen. One of the d u a l - f u e l e f f i c i e n c y curves corresponds to operation with the minimum p i l o t d i e s e l flow rate needed to assure s t a b l e operation without m i s f i r i n g . This curve i s obtained from F i g . 4.1 by i n t e r p o l a t i o n . The thermal e f f i c i e n c y of the d u a l - f u e l operation at part load i s s u b s t a n t i a l l y lower o CD . F i g u r e 4 .4 - Comparison of Brake T h e r m a l E f f i c i e n c i e s f o r D u a l - F u e l and S t r a i g h t D i e s e l O p e r a t i o n 55 than that of s t r a i g h t d i e s e l operation. At the brake mean e f f e c t i v e pressure of 850 kPa, which i s about the rated f u l l load at 1600 rpm, the thermal e f f i c i e n c i e s of both operations are same. E x t r a p o l a t i o n of the d u a l - f u e l operation curve to higher loads suggests the trend of the thermal e f f i c i e n c y surpassing that of s t r a i g h t d i e s e l operation. This trend may be due to the homogeneous nature of g a s - a i r mixture i n d u a l - f u e l o p e r a t i o n , which allows better access of f u e l to oxygen. 4 . 1 . 2 E f f e c t of R e s t r i c t i n g Intake A i r Tests to determined the e f f e c t on thermal e f f i c i e n c y of r e s t r i c t i n g intake a i r were performed for seve r a l load s e t t i n g s ranging from i d l i n g to about 50 percent of f u l l load. For each load s e t t i n g , the rate of gas flow was c o n t r o l l e d so that the flow rate of p i l o t d i e s e l would remain approximately constant. The a i r r e s t r i c t i o n was l i m i t e d by the minimum allowable pressure of the a i r at the i n l e t of the turbocharger. Excessive r e s t r i c t i o n of a i r beyond the l i m i t r e s u l t e d i n surging of the turbocharger, which i n turn caused v i o l e n t unsteadiness of the engine. Because of t h i s , the a i r - g a s flow r a t i o reduction had to be confined to about 10 percent. S u f f i c i e n t reduction of a i r , e i t h e r by using gating or e l i m i n a t i n g the turbocharger, would have increased the mixture s t r e n g t h to near the lower l i m i t of f l a m m a b i l i t y . Such an increase i n the mixture strength may have l e d to much improved f u e l consumption. 56 F i g . 4.5 shows- the e f f e c t of a i r r e s t r i c t i o n on brake thermal e f f i c i e n c y at various load s e t t i n g s . The g a s - a i r mixture strength i s represented by the equivalence r a t i o based on the gas alone. The t e s t s for a l l the load s e t t i n g s e x h i b i t improvements when a i r r e s r i c t i o n i s imposed. The increase i n brake thermal e f f i c i e n c y however was for a l l cases l e s s than 1 percent for about 10 percent a i r r e d u c t i o n . 4.1.3 E f f e c t of Varying I n j e c t i o n Timing The i g n i t i o n delay of p i l o t d i e s e l was studied by observing the averaged c y l i n d e r pressure vs crank angle t r a c e . In determining the point of the s t a r t of i g n i t i o n (the point at which combustion has proceeded far enough to a f f e c t the pressure n o t i c e a b l y ) , the e a r l i e s t s i g n i f i c a n t d e v i a t i o n of pressure from the expected compression curve near top dead centre was sought by c l o s e examination. In most cases t h i s method allowed i d e n t i f i c a t i o n of the point without d i f f i c u l t y . F i g . 4.6 shows a t y p i c a l pressure trace and i d e n t i f i c a t i o n of the apparent po i n t of i g n i t i o n . With the i n j e c t i o n timing f i x e d at 12.3 degree BTDC, the change in i g n i t i o n delay of p i l o t d i e s e l with a d d i t i o n of gas was i n v e s t i g a t e d at a range of load s e t t i n g s . F i g . 4.7 shows the crank angle at the s t a r t of i g n i t i o n with the p i l o t d i e s e l rate varying from 10-20 to 100 percent of t o t a l energy input. For s t r a i g h t d i e s e l operation at low load, the i g n i t i o n does not p CD* IT) CD u QJ IT) CN UJ <=» CM '—I ro QJ in a ro — CD 1/5 1.5 kg/h 571 kPa -o 278 kPQ cn b^ep o CO i — i — i — i — r i—i—r i—r i — i — r 0.2 0.24 0.28 0.32 0.36 0.4 0.44 0.48 0.52 0.56 0.6 0.64 Gas-Rir Mixture Strength (equivalence r a t i o based on gasJ 0.6B Figure 4.5 - E f f e c t of Intake A i r R e s t r i c t i o n on Brake Thermal E f f i c i e n c y 58 F i g u r e 4.6 - T y p i c a l C y l i n d e r P r e s s u r e Trace and Apparent P o i n t of I g n i t i o n S t a r t F i g u r e 4 . 7 - A p p a r e n t P o i n t o f I g n i t i o n S t a r t a t V a r i o u s L o a d s 60 s t a r t u n t i l 2 degrees a f t e r top dead centre. As the load i s r a i s e d to h a l f of f u l l load, the i g n i t i o n point i s advanced by a degree probably due to the increased end-gas temperature. The pressure vs crank angle trace reveals the increase i n end-gas pressure of about 50 kPa f o r the above load increase. The a d d i t i o n of gas extends the i g n i t i o n delay by 1 to 2 degrees. The corresponding r e s u l t obtained by Moore and M i t c h e l l (1955) i n a d i r e c t i n j e c t i o n engine was about 2 degrees and by Karim (1980) a l s o i n a d i r e c t i n j e c t i o n engine about 1.5 degrees. These agreements i n magnitude of the extended i g n i t i o n delay seems to suggest that the higher l e v e l of turbulence p r i o r to the i g n i t i o n of p i l o t d i e s e l in prechamber engine does not have a s i g n i f i c a n t e f f e c t on i g n i t i o n delay of the p i l o t d i e s e l . In the absence of a i r r e s t r i c t i o n , the point of i g n i t i o n i s no l a t e r than 3 degrees ATDC f o r a l l the loads and p i l o t d i e s e l flow rates t e s t e d . To study the e f f e c t on thermal e f f i c i e n c y of varying i n j e c t i o n t i m i n g , the timing was advanced by 5 and 10 degrees for two load s e t t i n g s , 143 and 278 kPa i n brake mean e f f e c t i v e pressure. The flow rate of p i l o t d i e s e l was c o n t r o l l e d to be about 20 percent of t o t a l energy input. The lower graph of F i g . 4.8 shows that advancing the i n j e c t i o n t iming by 5 degrees advances the point of i g n i t i o n to top dead center for both of the load c o n d i t i o n s . The improvement i n brake thermal e f f i c i e n c y f or the corresponding change i n i n j e c t i o n t iming i s very l i t t l e , as shown by the upper graph. Further advance of the timing by 5 degrees r e s u l t s i n advancement of the apparent point of i g n i t i o n s t a r t to 4 degrees BTDC. The thermal 61 CN C3 CD . CM a CM OJ ro LO OJ ~~ ro J- cr, , bmep 278 kPa 143 kPa T r i 1 — i — r i i i r i — i — i — r -1—1 V-1 — I •Is I ro -CZl c£ T1-i n . i ~i i r~ i—i—i—i—i—i—i—r 8.0 10.0 12.0 14.0 16.0 18.0 Injection Timing 20.0 22.0 24.0 (deg BTDC) 26.0 F i g u r e 4.8 - E f f e c t o f V a r y i n g I n j e c t i o n T i m i n g on B r a k e T h e r m a l E f f i c i e n c y and A p p a r e n t P o n i t o f I g n i t i o n S t a r t 62 e f f i c i e n c y of the low l o a d o p e r a t i o n of 143 kPa i n brake mean e f f e c t i v e p r e s s u r e shows no improvement, w h i l e t h a t of the o p e r a t i o n of 278 kPa i n brake mean e f f e c t i v e p r e s s u r e e x h i b i t s a t r e n d t o d e t e r i o r a t e . The t e s t s f o r h i g h e r l o a d c o n d i t i o n s were a v o i d e d i n f e a r of e x c e s s i v e i n c r e a s e i n maximum c y l i n d e r p r e s s u r e . 63 4.2 Cy l i n d e r Pressure 4.2.1 C y l i n d e r pressure i n Unmodified Engine For each randomly s e l e c t e d c y c l e c y l i n d e r pressure was measured at every crank angle. The pressure values at each angle were than averaged over 30-50 c y c l e s . The engine speed and the i n j e c t i o n timing were f i x e d at 1600 rpm and 12.3 degree BTDC r e s p e c t i v e l y . F i g . 4.9 shows the P-V diagrams for s t r a i g h t d i e s e l operation with various load s e t t i n g s ranging from i d l i n g to f u l l load. The low load operations reveal the delay u n t i l a f t e r the top dead centre of s i g n i f i c a n t r i s e i n pressure due to combustion. The maximum c y l i n d e r pressure reached at f u l l load operation i s about 7870 kPa (1140 p s i ) . The - c y l i n d e r pressure and volume of compression and expansion processes i n i n t e r n a l combustion engines can be approximately r e l a t e d by f o l l o w i n g r e l a t i o n s h i p s : n P V = const or Ln(P) = n Ln(V) + const The exponent 'n' would be e x a c t l y the r a t i o of s p e c i f i c heats i f the working f l u i d was an i d e a l gas with constant p r o p e r t i e s , and the compression or expansion process was a d i a b a t i c and f r i c t i o n l e s s . For a mixture of r e a l gases at combustion pressures, the i d e a l gas i s a good approximation and for small 65 f r i c t i o n a l e f f e c t , small heat t r a n s f e r to the w a l l s , slowly changing p r o p e r t i e s the above r e l a t i o n s h i p i s v a l i d with nearly constant value of 'n'. The l n ( P ) - l n ( V ) p l o t thus provides an approximate but convenient means to i d e n t i f y the p o i n t s of the beginning and the end of the combustion. F i g . 4.10 shows the l n ( P ) - l n ( V ) p l o t of the s t r a i g h t d i e s e l operation. The f i g u r e i n d i c a t e s the separate prechamber and main-chamber stages of combustion through t h e i r e f f e c t s on the pressure development. At f u l l l oad, the i n i t i a l combustion s t a r t s near top dead centre. A short period of expansion which i s recognized by a short s t r a i g h t l i n e near the ln(volume r a t i o ) of 0.65. The subsequent stage of combustion i s i d e n t i f i e d by the d e v i a t i o n of pressure from a s t r a i g h t l i n e . This c h a r a c t e r i s t i c i s l e s s d i s t i n c t i v e at lower loads. The i d l i n g operation shows no sign of the 2-stage combustion c h a r a c t e r i s t i c . I t seems that the combustion i n the f i r s t stage corresponds to the i n i t i a l incomplete combustion i n the prechamber. The short period of •expansion process f o l l o w i n g the f i r s t stage i s no doubt as s o c i a t e d with the escape from the prechamber of the hot p a r t i a l l y burned d i e s e l - a i r mixture and mixing with a i r which has resided i n the main chamber. The second stage combustion then takes place i n the main chamber. As the load i s reduced to i d l i n g , the flow rate of d i e s e l f u e l i s reduced to a small amount and the combustion i n the prechamber i s probably nearly complete, r e q u i r i n g l i t t l e f u r t h e r combustion i n the main chamber. F i g . 4.11 compares t y p i c a l i n d i c a t o r diagrams of d u a l - f u e l and s t r a i g h t d i e s e l operations. The d u a l - f u e l operation Log C y L Volume R a t i o (V/VbdcJ F i g u r e 4 . 1 0 Ln P - V D i a g r a m o f S t r a i g h t D i e s e l O p e r a t i o n 68 e x h i b i t s a much slimmer P-V diagram, with much of the combustion t a k i n g place within, a narrow range of c y l i n d e r volume. The l n ( P ) - l n ( V ) diagrams i n Fig.' 4.12 shows the very d i f f e r e n t combustion c h a r a c t e r i s t i c s of d u a l - f u e l and s t r a i g h t d i e s e l operations. The l n ( P ) - l n ( V ) diagram of d u a l - f u e l operation shows no obvious intermediate expansion period which i s q u i t e d i s t i n c t i v e l y recognized i n s t r a i g h t d i e s e l operation. The e f f e c t i s p a r t i c u l a r l y n o t i c e a b l e at high load where the combustion duration of d u a l - f u e l operation i s much shorter than that of s t r a i g h t d i e s e l operation. This would be c o n s i s t e n t with r a p i d propagation of flame f r o n t s i n the g a s - a i r mixture, i n c o ntrast to the slower combustion i n s t r a i g h t d i e s e l operat i o n . F i g . 4.13 shows the change i n maximum c y l i n d e r pressure with load v a r i a t i o n for s t r a i g h t d i e s e l and d u a l - f u e l operation with p i l o t d i e s e l c o n s i s t i n g 20 percent of t o t a l energy input. At high load the maximum c y l i n d e r pressure of d u a l - f u e l operation i s very much higher than that of s t r a i g h t d i e s e l operation. At brake mean e f f e c t i v e pressure of 714 kPa, which corresponds to 84 percent of f u l l l o a d , the maximum pressure of d u a l - f u e l operation i s about 35 percent higher than that of the s t r a i g h t d i e s e l o p e r a t i o n . The maximum c y l i n d e r pressures of d u a l - f u e l operation at vari o u s loads and p i l o t d i e s e l rates are shown i n F i g . 4.14. F i g 4.15 shows the comparison of maximum rat e of c y l i n d e r pressure r i s e at var i o u s load s e t t i n g s . F i g . 4.16 shows the maximum rate of pressure r i s e at va r i o u s p i l o t d i e s e l r a t e s . 1 1 1 — I — I I I I I 1 1 1 — I — I I I I 1 30 3 5 1 lO" 1 3 5 1 )Q 4 Log C y l . Volume R a t i o (V/VbdcJ F i g u r e 4.12 - C o m p a r i s o n o f Ln P-V Diagrams, f o r D u a l - F u e l and S t r a i g h t D i e s e l O p e r a t i o n o Comparison of Maximum Cylinder Pressures for Dual-Fuel and S t r a i g h t D i e s e l Operation Figure 4.14 - Maximum Cylinder Pressure at Various Loads < o co _ 10 CL O o X o o i n j e c t i o n t i m i n g 12.3 deg. b t d c 100 200 ~ r 300 T T 400 500 600 700 Brake Mean Effective Pressure 800 (kPa) 900 Figure 4.15 - Comparison of Maximum Rate of Cy l i n d e r Pressure Rise for Dual-Fuel and S t r a i g h t D i e s e l Operation ez 74 One of the most se r i o u s features of d u a l - f u e l operation with n a t u r a l i s the very l a r g e increase i n mechanical loading of the engine, unless the p i l o t d i e s e l i n j e c t i o n i s retarded. In se c t i o n 4.2.3, i t w i l l be shown how peak pressures and maximum rates of pressure r i s e can be g r e a t l y reduced by r e t a r d i n g the i n j e c t i o n t i m i n g . 4.2.2 E f f e c t of R e s t r i c t i n g Intake A i r The e f f e c t on maximum c y l i n d e r pressure of r e s t r i c t i n g intake a i r was considered f or two load c o n d i t i o n s , 428 kPa (50 percent of f u l l load) and 571 kPa (67 percent of f u l l load) in brake mean e f f e c t i v e pressure. The flow rate of p i l o t d i e s e l was 15 percent of t o t a l energy input. F i g . 4.17 shows the change i n maximum c y l i n d e r pressure with r e s t r i c t i o n of intake a i r . As mentioned before the maximum amount of allowable a i r r e s t r i c t i o n was l i m i t e d by the turbocharger surging c h a r a c t e r i s t i c s . S u b s t a n t i a l reduction i n maximum c y l i n d e r pressure was achieved without exceeding the t h r o t t l i n g l i m i t a t i o n . With maximum a i r r e s t r i c t i o n when the load i s below 67 percent of f u l l load the maximum c y l i n d e r pressure does not exceed that of s t r a i g h t d i e s e l operation at f u l l l o a d , which i s about 8000 kPa. F i g . 4.18 shows the change i n pressure j u s t before combustion with reduction of manifold pressure due to t h r o t t l i n g . The pressure j u s t p r i o r to combustion was obtained F i g u r e 4.17 - E f f e c t of I n t a k e A i r R e s t r i c t i o n on Maximum C y l i n d e r P r e s s u r e 9Z 77 from the c y l i n d e r pressure vs crank angle trace as the point j u s t p r i o r to the s i g n i f i c a n t pressure r i s e due to combustion. For both of the load c o n d i t i o n s the change i n maximum c y l i n d e r pressure i s of the same order of the change i n the pressure p r i o r to combustion. At the brake mean e f f e c t i v e pressure of 428 kPa the reduction of a i r flow rate from 4.9 to 4.3 m3/min r e s u l t e d i n the drop i n the pressure p r i o r to combustion of 400 kPa and i n maximum c y l i n d e r pressure of 500 kPa. At the brake mean e f f e c t i v e pressure of 571 kPa the reduction i s 450 kPa f o r the pressure p r i o r to combustion and 500 kPa f o r the maximum c y l i n d e r pressure when the a i r flow i s r e s t r i c t e d to 4.38 from 5.01 m3/min. This seems to suggest that the reduction of maximum c y l i n d e r pressure when the intake a i r i s r e s t r i c t e d i s due mainly to the decreased pressure p r i o r to combustion (due to reduction in manifold pressure). The e f f e c t on the maximum rate of c y l i n d e r pressure r i s e of intake a i r r e s t r i c t i o n i s shown i n F i g . 4.19. The r e s t r i c t i o n of intake a i r seems to r e s u l t i n higher maximum rate of c y l i n d e r pressure r i s e . This trend i s be l i e v e d to be the consequence of the increased g a s - a i r mixture strength which favours flame propagation. F i g u r e 4.19 - E f f e c t of I n t a k e A i r R e s t r i c t i o n on Maximum Rate of C y l i n d e r P r e s s u r e R i s e 79 4.2.3 E f f e c t of V a r y i n g I n j e c t i o n Timing The e f f e c t on maximum c y l i n d e r p r e s s u r e of r e t a r d i n g i n j e c t i o n t i m i n g was c o n s i d e r e d f o r a brake mean e f f e c t i v e p r e s s u r e of 571 kPa. The f l o w r a t e of p i l o t d i e s e l used was 10 p e r c e n t of t o t a l energy i n p u t . The reduced maximum c y l i n d e r p r e s s u r e as a r e s u l t of i n j e c t i o n t i m i n g r e t a r d a t i o n by 2 and 4 degrees CA are shown i n F i g . 4.20. R e t a r d a t i o n of merely 4 degrees reduced the maximum p r e s s u r e by 1850 kPa. The change i n the p r e s s u r e p r i o r t o combustion f o r the c o r r e s p o n d i n g r e t a r d a t i o n was 460 kPa as shown i n F i g . 4.21. F i g . 4.22 shows the P-V diagram f o r d i f f e r e n t i n j e c t i o n t i m i n g s . As the i n j e c t i o n t i m i n g i s r e t a r d e d the p o i n t of the s i g n i f i c a n t p r e s s u r e r i s e i s r e t a r d e d f u r t h e r from the top dead c e n t r e e x h i b i t i n g l e s s s t e e p and wider t r a c e . The maximum r a t e of p r e s s u r e r i s e was a l s o reduced as shown i n F i g . 4.20. The change i n t h e r m a l e f f i c i e n c y due t o i n j e c t i o n t i m i n g r e t a r d a t i o n was l e s s than 0.5 p e r c e n t . Test a t h i g h e r l o a d , a t a brake mean e f f e c t i v e p r e s s u r e of 714 kPa (83% of f u l l l o a d ) , w i t h 10 p e r c e n t f r a c t i o n a l d i e s e l energy i n p u t and 4 degrees r e t a r d a t i o n showed r e d u c t i o n of peak p r e s s u r e from 10.2 t o 7.7 MPa and maximum r a t e of p r e s s u r e r i s e from 2.1 t o 1.4 MPa/deg. The l o s s i n brake t h e r m a l e f f i c i e n c y due t o the i n j e c t i o n r e t a r d a t i o n was about 1 p e r c e n t . I t i s e s t i m a t e d t h a t s a f e f u l l - l o a d d u a l - f u e l o p e r a t i o n would r e q u i r e 4 t o 6 degrees of i n j e c t i o n t i m i n g r e t a r d a t i o n and t h i s would r e s u l t i n l o s s of t h e r m a l e f f i c i e n c y of 1 t o 80 o l o n i i i i i i i i i — i — i — i — i — i — i — i — | — i — | — i — | — | — | — i — | — | — i — | — , — r 0.0 0.04 0.08 0.12 0.16 0.2 0.24 0.28 0.32 0.36 0.4 0.44 0.48 0.52 0.56 0.6 C y l i n d e r Volume R a t i o (V/Vbdc) F i g u r e 4.22 - E f f e c t of V a r y i n g I n j e c t i o n T i m i n g on P-V D i a g r a m 83 2 percent. At loads beyond f u l l load, since i t i s expected that the thermal e f f i c i e n c y of d u a l - f u e l operation without i n j e c t i o n r e t a r d a t i o n would surpass that of s t r a i g h t d i e s e l operation (see s e c t i o n 4.1.1), the d u a l - f u e l operation witn s u f f i c i e n t i n j e c t i o n r e t a r d a t i o n to assure safe l e v e l of peak pressure would s t i l l r e s u l t i n thermal e f f i c i e n c y c l o s e to that of s t r a i g h t d i e s e l o p e ration. Retarding i n j e c t i o n timing seems to be a p r a c t i c a l , and necessary means of ensuring the safe dual-f u e l operation at high load. 84 CH.V A n a l y s i s of Apparent Energy Release 5.1 General One of the most e f f e c t i v e means of i n t e r p r e t i n g the combustion processes i n i n t e r n a l combustion engines i s the est i m a t i o n of the rate of chemical energy r e l e a s e , or burning r a t e , from the measured pressure d i s t r i b u t i o n . The combustion energy released a f f e c t s the i n t e r n a l energy of the gas mixtures i n s i d e the c y l i n d e r , the heat t r a n s f e r through the c y l i n d e r w a l l s , and the work done on the p i s t o n head. By appropriate es t i m a t i o n of heat t r a n s f e r and thermodynamic p r o p e r t i e s of gas mixtures, the apparent energy release due to combustion can be estimated from measured values of c y l i n d e r pressure and change i n c y l i n d e r volume. The a n a l y s i s provides a q u a l i t a t i v e p i c t u r e of the combustion processes of d u a l - f u e l and s t r a i g h t d i e s e l operation. 85 5.2 Method of c a l c u l a t i o n 5.2.1 D e f i n i t i o n s , Equations, and Assumptions When both the intake and exhaust valves are c l o s e d the mixtures of a i r and burned and unburned f u e l s can be considered as a system undergoing a change of s t a t e , which i s bounded by c y l i n d e r w a l l s and p i s t o n head (see F i g . 5.1). The f i r s t law of thermodynamics then can be a p p l i e d to the system for a small time change 6t: f i r s t law 6Q = dE + 5W where Q - heat t r a n s f e r to the system E energy of the system W - work done by the system Since the only s i g n i f i c a n t energies of the system involved here are the i n t e r n a l and chemical energy, the energy of the system can be assumed to c o n s i s t of the f o l l o w i n g : E = U + CE where U - i n t e r n a l energy of the system CE - chemical energy of the system F i g u r e 5.1 - C o n t r o l Volume f o r A p p a r e n t E n e r g y R e l e a s e A n a l y s i s 87 Then the corresponding f i r s t law becomes: 6Q = dU +dCE + 6W For a f i n i t e change of time, At, with the system undergoing a change from stat e / to st a t e the f i r s t law can be in t e g r a t e d to y i e l d the f o l l o w i n g : • Q . = AU + ACE + .W. . 1^ 1+1 1 i+1 where AU = U i + 1 - U. ACE = CE.., " CE. 1 + 1 l If P i s defined to be the average pressure of the system : l i+1 I i+1 then the work done on the system can be approximated as: •W. - • P • , , (V. J.1 - V. ) i i + 1 i i + 1 i + 1 I where - c y l i n d e r volume at i f c ^ s t a t e The change i n chemical energy of the system can be estimated as: ACE jm f j U c j 88 where m^j - mass of j t n f u e l burned d u r i n g i f c ^ s t a t e , ( j = 1 f o r d i e s e l , j = 2 f o r n a t u r a l gas) u c j - i n t e r n a l energy of combustion of j t h f u e l Now a f i n i t e d i f f e r e n c e form of the f i r s t law may be w r i t t e n as: f m f j U c j - i Q i + l " A U " i P i + 1 A V (Eqn 5 . 1 ) c h e m i c a l heat i n t e r n a l work energy t r a n s f e r energy change change E v a l u a t i o n of t h e s e terms w i l l be d i s c u s s e d i n subsequent s e c t i o n s . Assumpt i o n s In d e v e l o p i n g the method of c o m p u t a t i o n s e v e r a l assumptions were made, namely: 1 . The c o n s t i t u e n t s of the m i x t u r e i n the c y l i n d e r behave as i d e a l gases w i t h temperature-dependent thermodynamic p r o p e r t i e s . 2 . The gaseous c o n s t i t u e n t s of the m i x t u r e a r e c o n s i d e r e d t o be homogeneous and u n i f o r m i n thermodynamic s t a t e : s p a t i a l n o n - u n i f o r m i t y i n t h e r a t e of c h e m i c a l energy r e l e a s e i s i g n o r e d . 89 3. The composition of the combustion products corresponds to e q u i l i b r i u m d i s s o c i a t i o n . 4. The continuous v a r i a t i o n of thermodynamic p r o p e r t i e s with time can be adequately represented by stepwise v a r i a t i o n over a small time i n t e r v a l corresponding to 1 degree crank angle. 5. Presence of r e s i d u a l gas during the intake i s neglected. 6. Overlap of intake and exhaust valve i s ignored. 7. At any given i n s t a n t the burned f r a c t i o n s of the n a t u r a l gas and d i e s e l f u e l s are the same. Heat Transfer In order to account for the heat t r a n s f e r between the gas mixture and the c y l i n d e r w a l l s , both convective and r a d i a t i v e modes were considered, f o l l o w i n g the procedure of Annand(l963) whose equation i s : q/A = a(k/D)(R) b(T - T w a l l > + c(T« - T ^ ^ ) -where q - heat t r a n s f e r rate A - surface area of c y l i n d e r w a l l s k - thermal c o n d u c t i v i t y of the mixture D - bore R - Reynolds number defined as pVD//x where p - d e n s i t y of the mixture 90 "V - mean p i s t o n v e l o c i t y n - v i s c o s i t y of the mixture T - mixture temperature T w a l l ~ c y ^ ^ n c ^ e r w a l l temperature a ,b,c - constants The f i r s t term with the f i r s t order of temperature accounts for the convective heat t r a n s f e r and the second term with the fo u r t h order temperature for the r a d i a t i v e . The constants 'a' and 'b' for the convective term were s e l e c t e d to y i e l d a f i t with l e a s t - s q u a r e - e r r o r s to the apparent heat t r a n s f e r during the compression strok e . A nonlinear l e a s t - s q u a r e s - f i t technique was adopted i n o p t i m i z i n g the two constants f o r a large set of apparent heat t r a n s f e r data obtained (from equation 5.1 and measured pressures with no combustion and known c o n s t i t u e n t s of the mixture) for d u a l - f u e l and s t r a i g h t d i e s e l operation over a range of loads. F i g . 5.2 shows the f i t t e d curve and data for s t r a i g h t d i e s e l operation at brake mean e f f e c t i v e pressure of 571 kPa. The optimized values for the dimensionless constants 'a' and 'b' were 0.47 and 0.7 r e s p e c t i v e l y . The values suggested by Annand(l963) for 'a' was 0.35-0.8 and for 'b' was 0.7. The constant 'c' f o r the r a d i a t i o n term was taken to be 3.3 x 10" 1 1 kJ/K* as suggested by Annand for d i e s e l engines. This value would correspond to the product of the Stefan-Boltzmann constant a and an e m i s s i v i t y of 0.58, appropriate to grey body r a d i a t i o n . v. a' o ~t ~I QJ te X ) m CL im — ro o CO CD I —I ' CD cn cn i C J CD CO CD Heat T r a n s f e r (k J/sec ) 50 0 -30 0 -10.0 1 0 . 0 3 0 . 0 5 0 . 0 7 0 . 0 . 9 0 . 0 1 1 0 . 0 1 3 0 . 0 1 I I I I I I I I I I I ! I I I 1 I— cn CD CL ro a 55 CD ro cn -to. CD X I X x * I x I 3 *l X X IX X . ^ X 1 l x X X X I i * i X < X x # , X ^ \ X V \ in cr 10 01 •o 3 Q Q. "CJ i ght <—r o CL cn o cn ~o CMc 3 o 10 o 5T CL IJ 3 Q operation a TJ T3 a TJ 3 o a Q 1 6 92 I t was assumed that the temperature of the w a l l , at a given load, stays constant throughout the c y c l e , and v a r i e s l i n e a r l y with the a p p l i e d load. The measurements of wa l l temperature made by Kamel and Watson(l979) on an i n d i r e c t - i n j e c t i o n Ricardo s w i r l engine showed that the change i n w a l l temperature throughout the cy c l e at f u l l load was l e s s than 10 percent of the mean temperature. Their data a l s o suggested that the w a l l temperature of both prechamber and main chamber v a r i e d nearly l i n e a r l y with a p p l i e d load. In the present work the w a l l temperature was c a l c u l a t e d from 0.071(bmep) + 540 bmep i n kPa T ,, i n K w a l l The numbers obtained from t h i s formula f o r T ^ are w e l l w i t h i n 10 percent of those measured by Kamel and Watson at the same engine speed. F i g . 5.3 shows a t y p i c a l c a l c u l a t i o n of the apparent rate of energy release with and without the adopted heat t r a n s f e r model; the computation procedure i s presented l a t e r . D i s s o c i a t i o n In computing the c o n s t i t u e n t s of the combustion products e q u i l i b r i u m d i s s o c i a t i o n was assumed. The d i s s o c i a t i o n r e a c t i o n s considered are as f o l l o w s : T w a l l " OJ T J , QJ in ro UJ cn QJ o ' £"\ Q J ^ " •f-» ro CH cn o with heat transfer model without heat transfer model straight diesel operation bmep - 571 kPa speed - 1600 rpm v. V, v. I0.O 1 1— 30. D Crank Angle T -la.o tdc 50.0 (deg flTDC) 7D:0 F i g u r e 5 . 3 - E f f e c t o f Heat T r a n s f e r M odel on A p p a r e n t Rate o f E n e r g y R e l e a s e 94 a. C0 2 < > CO + 1/2 0 2 b. H 20 < > 1/2 H 2 + OH c. H 20 < > H 2 + 1/2 0 2 d. 1/2 N 2 + 1/2 0 2 < > NO I t may be noted that i n h i s engine mixture d i s s o c i a t i o n c a l c u l a t i o n s , Campbell(1977) considered the above d i s s o c i a t i o n s , and i n a d d i t i o n the d i s s o c i a t i o n of 0 2, H 2, and OH. As w i l l be shown the degree of d i s s o c i a t i o n i s small at the r e l a t i v e l y high pressures and low temperatures of compression i g n i t i o n engines. Hence only 4 d i s s o c i a t i o n processes were considered i n the e q u i l i b r i u m c a l c u l a t i o n . For each step of incremental time At and given pressure and temperature of the mixture, the f o l l o w i n g set of nonlinear equations were solved for the number of moles of combustion products: Y CO 0, v Y c o 2 = K.(P'/P) or (N c o+A)[N Q +1/2(A+C-D)] 2 < N co 2 " A ) 2 (\otyH " V P V P ) ^ Y ' 2 Y X H ? OH i = KR(P°/P)'2 Y YH 20 or u (N H +1/2B+C) 2(N Q H+B) ( NH 20- B- C^ ( N t o t ) " " 2 - K B(P°/P) : 95 Y Y H 2 ° 2 Y K C ( P 7 P ) 1 H 2 0 o r ( N H + l / 2 B + C ) [ ( N Q + l / 2 ( A + C - D ) ] "2 1 : " ^ t o t y k = ( N H 2 0 " B " C ) K C [ P ° / P ) : Y NO _ V  N 2 ° 2 D o r < N NO+ D ) (NXI - l / 2 D ) 4 [ N N + l / 2 ( A + C - D ) ] J 5 N t o t = I N i + 1 / 2 ( A + B + C) w h e r e K ^ , K g , K ^ , K ^ a r e e q u i l i b r i u m c o n s t a n t s f o r r e a c t i o n s a , b , c , d . ^CO'^NO' E T C a r e e c l u i l i D r i - u m c o m p o s i t i o n s . Nfjo'^NO' e t C a r e t ^ i e n u m ^ e r °^ m 0 ^ e s o f c o n s t i t u e n t s p r e s e n t p r i o r t o t h e c u r r e n t s t e p o f c o m b u s t i o n . A , B , C , % D a r e n u m b e r s o f m o l e s o f C O , , H 2 0 , H 2 0 , K ' 2 o r 0 2 d i s s o c i a t e d i n r e a c t i o n s a , b , c , d , r e s p e c t i v e l y . P° i s a t m o s p h e r i c p r e s s u r e , 1 0 1 . 3 k P a . P i s t h e gas m i x t u r e p r e s s u r e . «. i s t h e t o t a l n u m b e r o f m o l e s o f t o t t h e m i x t u r e . 96 G i v e n t h e p r e s s u r e and t e m p e r a t u r e of t h e m i x t u r e , t h e f i v e e q u a t i o n s were s i m u l t a n e o u s l y s o l v e d f o r A, B, C, D, and N t o t u s i n g a m o d i f i e d Newton's method. The v a l u e s o f t h e e q u i l i b r i u m c o n s t a n t s , w h i c h a r e f u n c t i o n s o f t e m p e r a t u r e , were c a l c u l a t e d f r o m f i t t e d c u r v e s b a s e d on thermodynamic d a t a g i v e n i n t h e JANAF Thermodynamics T a b l e s . F i g . 5.4 shows a t y p i c a l c a l c u l a t i o n o f t h e a p p a r e n t r a t e of e n e r g y r e l e a s e computed w i t h and w i t h o u t d i s s o c i a t i o n . F i g u r e 5.4 - E f f e c t o f E q u i l i b r i u m D i s s o c i a t i o n C a l c u l a t i o n on A p p a r e n t R a t e o f E n e r g y R e l e a s e 98 5,2.2 Computation Procedure The apparent energy release i s obtained by s o l v i n g the equations of mass and energy conservation for the mixture temperature and the f r a c t i o n of f u e l burned. The work done on the p i s t o n i s computed from the smoothed pressure data and change i n c y l i n d e r volume. The rate of heat t r a n s f e r i s estimated as described i n s e c t i o n 5.2.1. The composition of the mixture i s computed with the e q u i l i b r i u m d i s s o c i a t i o n assumption, and with the equations provided i n the previous s e c t i o n . Consider a small step i n the c a l c u l a t i o n during which the s t a t e of the mixture changes from s t a t e / to s t a t e The c a l c u l a t i o n s f o r s t a t e (i+1) s t a r t with complete knowledge of s t a t e /; the f o l l o w i n g c o n d i t i o n s are given: T i ' P i ' ( n C H . ) i ' ( n C 1 2 H 2 6 > i { n j h where the n^'s are the numbers of moles of CH 4, C, 2H 2 6, N 2, 0 2, H 20, C0 2, CO, H 2, OH, NO. The c a l c u l a t i o n procedure i s as f o l l o w s : 1. Assume T..1f ( f r ) . . ( f r a c t i o n of f u e l burned i n one 1+1 I to 1+1 s t e p ) . 2. Obtain the composition molar f r a c t i o n s ( n j ) ^ + 1 which would e x i s t i n s t a t e (i+1) were there no d i s s o c i a t i o n . 99 With the assumed T^ + 1 and the measured pressure P^ + 1 perform e q u i l i b r i u m d i s s o c i a t i o n c a l c u l a t i o n s to obtain the values of ^ n j ^ i + i which s a t i s f y the d i s s o c i a t i o n r e l a t i o n s h i p s i n sect ion 5.2.1. For each species c a l c u l a t e the change i n the number of moles An.= ( n . ) . . , - ( n . ) . 3 3 1+1 j 1 Compute the changes i n chemical energy ACE and i n t e r n a l energy AU as ACE = ?An . ( u 0 . • + Au .) j 3 l3 3 where u°£j = i n t e r n a l energy of formation at 298 K A U j = U j ( T i + 1 ) - Uj(298K) AU = ?(n.).(u.(T.,.) - u.(T.)) j 3 1 3 1+> 3 1 where U j - i n t e r n a l energy of j * " * 1 c o n s t i t u e n t of gas mixture 6. Compute ^Q^+1 and i w j + 1 7. Check the f o l l o w i n g two conservation equations: ACE = .Q.+1 + AU + .W.+1 P i + 1 V i + 1 = ^ ^ j ^ - H I > R T i + 1 8. I f the above two equations are s a t i s f i e d then computation i s completed. If not, repeat from 1. 100 C y l i n d e r Pressure Data The c y l i n d e r pressure was recorded at every degree of crank angle. The measured values were then averaged over 30-50 randomly s e l e c t e d c y c l e s . I t required 20-30 minutes to obtain an averaged pressure trace of 30 c y c l e s with the NEFF data a q u i s i t i o n u n i t and the PDP/11 computer. Because of l a r g e c y c l e - t o - c y c l e v a r i a t i o n s , the r e s u l t i n g pressure-crank angle curves were not smooth enough to provide a smooth c a l c u l a t e d curve of rate of energy r e l e a s e . The pressure-crank angle curves were smoothed by f i t t i n g a curve between the obtained data. The technique involved f i t t i n g a piece-wise cubic polynomial (continuous to the second d e r i v a t i v e ) between the pressure measurements over a crank angle range of 180 degrees with minimization i n square e r r o r s . The inverse of the v a r i a t i o n i n the slope of the pressure trace for four neighbouring p o i n t s were used i n p r o v i d i n g the weight for the least-squares f i t . F i g . 5.5 shows the rate of energy release c a l c u l a t e d from unsmoothed and smoothed pressure-crank angle curves. The smoothed pressure curve showed very small v i s u a l l y d e t e c t a b l e change, except i n the region near the peak of the combustion pressure. Computer Program f o r Apparent Energy Release The main f u n c t i o n of the computer program was to execute the computation procedure described i n the previous s e c t i o n . The program i n i t i a l l y read i n the c y l i n d e r pressure data and flow cn _ cd" CD OJ -o CD OJ cn ro " OJ —H (O QJ o ' " 1 _ UJ 0 J d ro CC C3 " CD" smoothed not smoothed straight diesel operation bmep - 571 kPa speed - 1600 rpm 1 10.0 30.0 Crank Angle -1D.0 t d c 50.0 (deg.RTDC) 70.0 F i g u r e 5.5 - E f f e c t o f S m o o t h i n g P r e s s u r e Data on A p p a r e n t R a t e o f E n e r g y R e l e a s e 102 rates of a i r and f u e l s along with data for operating c o n d i t i o n s . The pressure data were then smoothed-and volumes of the c y l i n d e r f o r a l l crank angles were computed. Subsequently, for each degree of crank angle, equations for energy and mass conservation were simultaneously and i t e r a t i v e l y solved for the temperature and the f r a c t i o n of f u e l burned. A modified Newton's method was used i n s o l v i n g the system of nonlinear equations. The program assumed that combustion may take place at anytime a f t e r the i n j e c t i o n of d i e s e l f u e l . Before the d i e s e l i n j e c t i o n p o i n t , the program took an a l t e r n a t e route and merely computed the mixture temperature d i r e c t l y from i d e a l gas law. F i g . 5.6 shows the flowchart of the procedures adopted i n the computer program. A l i s t i n g of the computer program i s provided i n Appendix E. F i g . 5.7 shows a t y p i c a l output of the program. Check of Computation In order to confirm q u a n t i t a t i v e l y the correctness of the method used, the computed amount of consumed f u e l energy per averaged c y c l e from the computer output was compared with a c t u a l amount of f u e l energy input. Because the computed rate of chemical energy release i s e s s e n t i a l l y zero except f o r the crank angle i n t e r v a l of -10 to +90 degrees a f t e r top dead center, i t was necessary to i n t e g r a t e the energy release only i n t h i s range. Table 5.1 shows the r a t i o s of the computed to a c t u a l energy consumed f o r various operations. From a l l the r a t i o s shown i n the t a b l e , i t i s seen that the agreements between the computed and 103 r e a d i n f l o w r a t e of d i e s e l , g as, a i r P ( 0 ) , C.A. a t i g n i t i o n , i n j e c t i o n r e a d i n p r o p e r t i e s of d i e s e l , g as, a i r , c o m b u s t i o n p r o d u c t s comp u te V(0) r e p e a t f o r 0 = -89 to 9JJ smooth P(O) u p d a t e number of moles of r e a c t a n t s compute T from i d e a l gas law compute h e a t t r a n s f e r s e t e n e r g y r e l e a s e = 0 p r i n t P, T, h e a t t r a n s f e r , e n e r gy r e l e a s e s e t 0 = 0 + 1 guess amount o f f u e l b u r n t , T compute s t o i c h i o m e t r i c c o m b u s t i o n p r o d u c t s a c c o u n t f o r d i s s o c i a t i o n compute h e a t t r a n s f e r yes a r e mass and e n e r g y c o n s e r v e d ? Figure 5.6 - Flowchart o f Computer Program f o r Apparent Energy Release A n a l y s i s 104 F i g u r e 5 . 7 - T y p i c a l O u t p u t o f Computer Program f o r A p p a r e n t E n e r g y R e l e a s e A n a l y s i s LOAD (kPa) MODE OF OPERATION FRACTIONAL DIESEL ENERGY INPUT (%) ACTUAL ENERGY CONSUMED (kJ) COMPUTED ENERGY CONSUMED (kJ ) RATIO OF COMPUTED TO ACTUAL ENERGY CONSUMED 0 s t r a i g h t d i e s e l - 0 .79 0.83 1.06 279 s t r a i g h t d i e s e l - 1 . 74 1.67 0.96 571 s t r a i g h t d i e s e l - 3 .05 2.84 0.93 713 s t r a i g h t d i e s e l - 3 . 75 3.48 0.93 856 s t r a i g h t d i e s e l - 4 . 58 4.26 0.93 571 d u a l - f u e l 20 . 9 3.17 3.01 0 .95 571 d u a l - f u e l 10 . 2 3.14 2 .95 0 .94 T a b l e 5.1 - Comparison of A c t u a l and Computed F u e l Energy Consumed 106 a c t u a l energy consumed are q u i t e good. The small disagreements are probably due to the v a r i a t i o n i n heating values of f u e l s , inadequacy of heat t r a n s f e r model, unburned f u e l , and various assumptions made during the course of method development. I t should be noted that the amount of unburned gas escaping the c y l i n d e r was not subtracted from the a c t u a l amount of f u e l energy input. 107 5.3 A n a l y s i s 5.3.1 Operations with Unmodified Engine The c a l c u l a t e d rate of energy release for s t r a i g h t d i e s e l operation with loads ranging from i d l i n g to f u l l load i s shown i n F i g . 5.8. At i d l i n g near the top dead center the curve d e c l i n e s to negative values p r i o r to the peak. This may be the r e s u l t of the inadequacy of the heat t r a n s f e r model. At low loads the model seems to underestimate the rate of heat t r a n s f e r , r e s u l t i n g i n negative values for the apparent rate of energy r e l e a s e . The roughness of the curves during and towards the end of combustion i s due to roughness i n the pressure data. The roughness could have been reduced by f u r t h e r smoothing the pressure data. At f u l l load(bmep = 856 kPa) the rate of energy release r e v e a l s two stages of combustion. The f i r s t stage l a s t s u n t i l 12 to 14 degrees a f t e r top dead c e n t r e . As the load decreases the second stage combustion becomes l e s s d i s t i n c t i v e . I t seems that the f i r s t peak corresponds to combustion i n the prechamber and the second to combustion i n the main chamber. The c a l c u l a t e d cumulative energy release i n F i g . 5.9 f u r t h e r supports t h i s view. Near 13 degree C.A. a f t e r the top dead c e n t r e , which i s approximately the point separating the two stages of combustion, the cumulative energy r e l e a s e for the loads other than i d l e i s nearly the same at about 1.3 kJ. This i s about 30% of the t o t a l cumulative energy release at f u l l l o a d . The volumetric r a t i o of prechamber to the t o t a l volume at F i g u r e 5.8 Rate o f E n e r g y R e l e a s e o f S t r a i g h t D i e s e l O p e r s t i o n a t V a r i o u s L o a d s F i g u r e 5.9 Cumulative E n e r g y R e l e a s e o f S t r a i g h t D i e s e l O p e r a t i o n a t V a r i o u s Loads 110 the top dead centre i s about 25 percent. Thus the a n a l y s i s suggests that the combustion in s t r a i g h t d i e s e l operation of prechamber engine c o n s i s t s of two d i s t i n c t and subsequent stages-prechamber and main chamber. From F i g . 5.9 i t can be seen that the time period during which the combustion takes place increases with the increase i n load. The maximum rate of energy release i s the smallest at f u l l load and increases as the load i s decreased. At very low loads the rate of energy release r i s e s very r a p i d l y although the maximum rate of energy release i s l i m i t e d by the t o t a l d i e s e l energy input. F i g . 5.10 shows the dependence on a i r - f u e l r a t i o of the maximum rate of energy r e l e a s e . I t i s seen that the r a p i d i t y of the combustion i n s t r a i g h t d i e s e l operation increases nearly l i n e a r l y with a i r -f u e l r a t i o . •* F i g . 5.11 shows the rate of energy release with d u a l - f u e l operation i n which p i l o t d i e s e l f u e l accounts f o r about 20 percent of the t o t a l energy input, and when no change has been made i n d i e s e l i n j e c t i o n t i m i n g . The most noteworthy feature i s the nearly twofold increase i n the maximum rate of energy r e l e a s e . I t i s observed from the f i g u r e that the change i n combustion du r a t i o n with v a r y i n g load i s r e l a t i v e l y small when compared to that of s t r a i g h t d i e s e l o p e r a t i o n . The shapes of the rate of energy release curves e x h i b i t very l i t t l e of the two-staged combustion c h a r a c t e r i s t i c which i s observed i n s t r a i g h t d i e s e l o p e r a t i o n . The r a p i d i t y of r i s e of the rate of energy release increases with the increase i n loa d . F i g . 5.12 shows the maximum rate of energy release p l o t t e d against the g a s - a i r mixture s t r e n g t h . The f i g u r e • i n d i c a t e s strong I l l n 1 1 1 1 1 1 1 r~ - m n tdc 10.0 30.0 50.0 70.0 Crank Rngle (derj PTDC1 F i g u r e 5 . 1 1 - Rate o f E n e r g y R e l e a s e o f D u a l - F u e l O p e r a t i o n a t V a r i o u s L o a d s ^ O r _ actual gas-air mass ratio g stoichiometric gas-air mass ratio F i g u r e 5.12 - E f f e c t o f G a s - A i r M i x t u r e S t r e n g t h on Maximum Rate o f E n e r g y R e l e a s e i n D u a l - F u e l O p e r a t i o n i 114 dependence of the r a p i d i t y of combustion on the gas-a i r mixture strength. The cumulative energy release of d u a l - f u e l operation corresponding to the curves i n F i g . 5.11 i s shown i n F i g . 5.13. F i g . 5.14 and F i g . 5.15 compare s t r a i g h t d i e s e l and du a l -f u e l operation at 85 and 33 percent of• f u l l load. From F i g . 5.14 i t i s seen that for high load operation the combustion duration of the d u a l - f u e l operation i s much shorter than that of the s t r a i g h t d i e s e l operation, and the maximum rate of energy release i s about 3.7 times higher. The remarkable d i f f e r e n c e i n the shape of the rate of energy release f or the two modes of operations supports the view mentioned i n s e c t i o n 4.2.1 that the mechanisms of combustion are d i f f e r e n t . E v i d e n t l y the combustion i n d u a l - f u e l operation i s mainly c a r r i e d out by flame propagation through' the premixed gas - a i r mixture, i g n i t e d by the burning d i e s e l spray which penetrates the main chamber as a hot j e t . In s t r a i g h t d i e s e l o p e r a t i o n , combustion occurs i n the f u e l - a i r mixture adjacent to evaporating f u e l drops rather than propagating as a turbulent flame through the e n t i r e mixture. Since most of the f u e l does not req u i r e evaporation i n the former case i t i s reasonable that t h i s mode of combustion should be f a s t e r . F i g . 5.16 shows the rat e of energy release f o r a low load operation (brake mean e f f e c t i v e pressure of 279 kPa) with various flow rates of p i l o t d i e s e l . The apparent i g n i t i o n p o i n t s , which may be i d e n t i f i e d as the p o i n t s where the curves s t a r t r i s i n g , agree q u i t e w e l l with those observed from the pressure-crank angle t r a c e . The i g n i t i o n delay i s increased as 9TI LP TO . T O l o QJ " a ^ to QJ LO c-) ro QJ QJ cr CO Oi CO LU o* QJ — t-1 a ro co o a I -IU.O Straight diesel operation dual-fuel operation bmep - 279kPa bmep-279kPa 714 kPa (21% diesel) 714kPa (18% diesel) -<^^.^-^V- ~T C7>^p^ t d c -I 1 1 1— I0.Q 30.0 Crank Rngle 50.0 f d e g flTDCJ F i g u r e 5.14 - C o m p a r i s o n o f Rate o f E n e r g y R e l e a s e f o r S t r a i g h t D i e s e l and D u a l - F u e l O p e r a t i o n F i g u r e 5.15 - C o m p a r i s o n o f Cumulative E n e r g y R e l e a s e f o r S t r a i g h t D i e s e l and D u a l - F u e l O p e r a t i o n bmep - 279kPa (33% full load) 13.5 V. diesel 20.6% diesel 32.0% diesel 1 0 0 % diesel OJ R-) _ ir, CD •o ,1 I I I I I I I I 1 -10 0 t d c 10-° 30.0 5 0-° 7 0 0 Crank Angle (deg RTDC) F i g u r e 5.16 - Rate o f E n e r g y R e l e a s e o f D u a l - F u e l O p e r a t i o n a t V a r i o u s P i l o t D i e s e l Flow R a t e s to CD oo . -=r cn CD QJ \ rr, 119 much as 2 degree C A . as the flow rate of p i l o t d i e s e l i s decreased from 100 to 13.5 percent of t o t a l energy input. The f i r s t stage of combustion i n s t r a i g h t d i e s e l operation consumes about 70 percent of the d i e s e l energy input (see F i g . 5.17). A reduction of p i l o t d i e s e l to 32 percent of t o t a l energy input r e s u l t s i n a higher peak f o r rate of energy release with no i n d i c a t i o n of the two-staged conbustion. Further reduction of p i l o t d i e s e l r e s u l t s i n lower and wider peaks. F i g . 5.18 shows the f r a c t i o n of f u e l burned at d i f f e r e n t p i l o t q u a n t i t i e s . The operation with low p i l o t d i e s e l flow rate shows a large amount of unburned f u e l . The amount of unburned f u e l decreases as the flow rate of p i l o t d i e s e l i s increased. F i g . 5.19 shows the rate of energy release f o r a high load operation (brake mean e f f e c t i v e pressure of 571 kPa). Reduction of p i l o t d i e s e l flow rate appears to increase i g n i t i o n delay and decrease the maximum rate of energy r e l e a s e . The cumulative energy release shown i n F i g . 5.20 i n d i c a t e s that at t h i s load combustion occurs i n two stages at a l l p i l o t d i e s e l energy r a t i o s . The small second-stage combustion i n high load d u a l -f u e l operation seems to be the consumption, i n the main chamber, of the unburned and/or p a r t i a l l y burned f u e l remaining from the flame propagation i n the f i r s t stage. bmep - 279kPa ( 3 3 % full load) T3.5% diesel 20.6% diesel 32.0% diesel 1 0 0 % diesel ro o " I 70.0 1 1 50.0 (deg RTQC) CD LO CO .—. cn ^ CO CD (/) ro CD "ai ai in CM' a i a> CN m _ cu > +-> rd 3 LP c6 CD LP CD •10.0 t d c 10.0 30.0 Crank Angle F i g u r e 5.17 - Cumulative E n e r g y R e l e a s e o f D u a l - F u e l O p e r a t i o n a t V a r i o u s P i l o t D i e s e l F l o w R a t e s F i g u r e 5.18 - F r a c t i o n o f F u e l B u r n t i n Low Load D u a l - F u e l O p e r a t i o n ZZI CD LO CO CD LP -10.0 tdc 10.0 30.0 50.0 70 0 Crank Angle (deg FITDC) F i g u r e 5.20 - Cumulative E n e r g y R e l e a s e o f D u a l - F u e l O p e r a t i o n a t V a r i o u s P i D i e s e l F l o w R a t e s 124 5.3.2 E f f e c t of R e s t r i c t i n g Intake A i r F i g . 5.21 shows the rate of energy release for low load operation with and without a i r r e s t r i c t i o n . I t i n d i c a t e s that r e s t r i c t i o n of intake a i r lengthens i g n i t i o n delay by 1-2 degrees. Table 5.2 i l l u s t r a t e s the temperature and pressure of mixture at top dead centre with and without r e s t r i c t i o n of a i r . When the intake a i r i s r e s t r i c t e d a drop i n the pressure at top dead centre i s n o t i c e d . A rather s u p r i s i n g phenomenon i s that there appears from the c a l c u l a t i o n to be an increase i n temperature. This i s contrary to the assumption that the temperature would drop as the pressure drops, which was the basis used by Lewis(l953) i n e x p l a i n i n g the increase i n i g n i t i o n delay when the r e s t r i c t i o n of a i r i s imposed. I t seems that the increase i n i g n i t i o n delay i s not the r e s u l t of the change i n chemical delay since the-chemical delay would be shortened i f the temperature i s increased. This would suggest that the change i n i g n i t i o n delay i s probably more s e n s i t i v e to the change i n p h y s i c a l delay. F i g . 5.22 shows the cumulative energy release f o r the corresponding operations. The e f f e c t of a i r r e s t r i c t i o n f o r high load operation i s shown i n F i g 5.23 and F i g . 5.24. The operation at the brake mean e f f e c t i v e pressure of 571 kPa (67% f u l l load) e x h i b i t s a r a d i c a l increase i n maximum rat e of energy release when the intake a i r i s r e s t r i c t e d . The g a s - a i r mixture s t r e n g t h for the corresponding operation i s 0.606 i n equivalence r a t i o . This value i s s l i g h t l y above the p r e v i o u s l y mentioned value for the lower l i m i t of f l a m m a b i l i t y . Thus the sudden increase i n the CO co . . cm a QJ \ 1 0 • \ ro _ crj ~ J QJ ^ . LO <=> ro QJ >~ CJ) CU CD c ;. UJ <=> U-o QJ ~. . +-> CD ro cc co CD CO CD I bmep - 279 kPa, a i r r e s t r i c t e d (5 = 0. 400) , 14.5% d i e s e l g bmep - 279 kTa, a i r u n r e s t r i c t e d (d 13.5% d i e s e l 9 = 0.364) , bmep - 143 kPa, a i r r e s t r i c t e d (c5 = 0. 308) , 20.9% d i e s e l g bmep - 143 kPa, a i r u n r e s t r i c t e d (<E 19.5% d i e s e l g 0.279), CD I -10.0 tdc 10.0 Crank 30.0-Angle 50.0 (deg flTD-C) 70.0 F i g u r e 5.21 E f f e c t o f R e s t r i c t i n g I n t a k e A i r on Rate o f E n e r g y R e l e a s e LOAD (kP a ) AIR RESTRICTION FRACTIONAL DIESEL ENERGY INPUT (%) * g a s T t d c ™ P t d c (kPa) # OF MOLES OF INTAKE MIXTURE 143 u n r e s t r i c t e d 19.5 0. 279 968 4810 0.0631 143 r e s t r i c t e d 20.9 0.308 999 4 370 0.0555 279 u n r e s t r i c t e d 13.5 0.364 951 4860 0.064 8 279 r e s t r i c t e d 14 .5 0.400 1010 44 70 0.0564 4 29 u n r e s t r i c t e d 15 .0 0.437 944 5000 0.0673 429 r e s t r i c t e d 15 . 3 0.483 1010 4680 0.0586 571 u n r e s t r i c t e d 10.2 0.526 955 5210 0.0692 571 r e s t r i c t e d 10 . 7 0.606 1010 4 7 8.0 0.06 01 T a b l e 5.2 - E f f e c t o f I n t a k e A i r R e s t r i c t i o n on M i x t u r e T e m p e r a t u r e a t Top Dead C e n t e r CD LO CO 3 CO CO ^ </> CM OJ CO cc s-co c CD CM' LO CO > •r-+J I— CD 3 —' E o LO CD bmep - 279 k P a , a i r r e s t r i c t e d (cD = 0 . 4 0 0 ) , 14.5% d i e s e l g bmep - 279 k P a , a i r u n r e s t r i c t e d (cB = 0 . 3 6 4 ) , 13.5% d i e s e l g bmep - 143 k P a , a i r r e s t r i c t e d (<5 = 0 . 308) , 20.9% d i e s e l g bmep - 143 k P a , a i r u n r e s t r i c t e d (cB 0 . 2 7 9 ) , 1 9 . 5 % d i e s e l g CD CD CD 1 1 30.0 Crank Ang le •10.0 t d c 10.0 50.0 fdeg flTDC) 70.0 F i g u r e 5.22 - E f f e c t o f R e s t r i c t i n g I n t a k e A i r on Cumulative E n e r g y R e l e a s e Rate of Energy Release (kJ / aeg) -0.1 -0.G3 0.03 0.1 0.16 0.23 0.3 0.36 0.43 0.5 _] I I I I I I I i I I I I 1 L_ C u — | o CD O •J ID n i n Gj • CD ro a a ZD •V---iD — CD nf If tf If i cn I "3 I CO $ 5 5 QJ QJ QJ Q) u - i Q) O P-• 1-1 CP i-( Ch cn £' R" tn p-rb o t ( QJ O P-• f< M o'P C a R P- fD a) cn ifl rr P> OJ Ul p-• f-( ui <#> i-i CD Oi cn ft cn P-n> o i — i QJ In p-• t-l o o'P C ^ a P- CD (D cn cn n-CD H< -3 -r-:ted P" P-O ft P1 p-o ff 9* el I et il II cQ o II o n cn o .J> O o • 00 • CO -—' NJ ' CO 821 o Ln CD CO LO CM* 01 (O * CD cn c — > •r- CD +-> —' UJ E 3 O LO CD CD 429 kPa, a i r u n r e s t r i c t e d (c6 =0 . 4 3 7 ) , 1 5 . 0 % d i e s e l g 429 kPa, a i r r e s t r i c t e d (« = 0 . 4 8 3 ) , 1 5 . 3 % d i e s e l g 571 kPa, a i r u n r e s t r i c t e d (ffi = 0 . 5 2 6 ) , 1 0 . 2 % d i e s e l g 571 kPa, a i r r e s t r i c t e d (I> = 0 . 6 0 6 ) , 1 0 . 7 % d i e s e l g i n CD •10.0 t d c 10.0 30.0 Crank Ang le 1 — 50.0 (deg ATDC) 70.0 F i g u r e 5.24 - E f f e c t o f I n t a k e A i r R e s t r i c t i o n on Cumulative E n e r g y R e l e a s e 130 maximum rate of energy release seems to be the r e s u l t of f u e l -a i r r a t i o on propagation of a flame through a premixed g a s - a i r mixture. 5.3.3 E f f e c t of Varying I n j e c t i o n Timing F i g . 5.25 and F i g . 5.26 show the e f f e c t of advancing the i n j e c t i o n timing at low load. Advancing the i n j e c t i o n timing by 10 degree C A . r e s u l t s i n the maximum rate of energy release occuring at top dead center. For t h i s timing the second stage combustion i s more d i s t i n c t . For the operations with i n j e c t i o n t i ming of 12.3 and 17.3 degree C A . BTDC the combustion i s ta k i n g place only a f t e r the p i s t o n has s t a r t e d moving downwards, thus a s s i s t i n g the flow of mixture from prechamber to the main chamber. For the operation with i n j e c t i o n timing of 22.3 degree C A . BTDC, the combustion takes place when the p i s t o n i s nearly motionless, and the second stage combustion would be more d i s t i n c t i v e . The e f f e c t of r e t a r d i n g i n j e c t i o n timing at high load i s shown i n F i g 5.27 and F i g . 5.28. S i g n i f i c a n t reduction i n the maximum rate of energy release i s observed when the timing i s retarded. Again the two-staged combustion c h a r a c t e r i s t i c s become l e s s d i s t i n c t i v e as the timing i s retarded. LTJ CD bmep - 279 kPa, 20% d i e s e l i n j e c t i o n a t 12.3 BTDC 17.3 BTDC 22.3 BTDC j _l , ( , , r — , , r— -10.0 tdc 10.0 30.0 50.0 70.0 Crank Angle (deg ATDCJ CO . . "3 QJ - a . CD \ CO F i g u r e 5.25 - E f f e c t o f A d v a n c i n g I n j e c t i o n T i m i n g on Rate o f E n e r g y R e l e a s e Cumulative Energy Release (kJ) -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 _ l I I I I I l i i i I I I I ' i i CD O n CD CD o QJ ID rj . to co i , a CL 70 a 3D ' a g —1 a 1 tr 1 3 1 fD ! i 1 TI 1 i 1 h j . M "'3 -J i_ J. <£> ? ] r t 13 H -0 ^ 3 0) O rt <#> M h-1 M a to • • . ro CO CO CO cn (D h-1 CD 03 UJ i-3 t-3 t-3 a a a o n n ZEI LO C3 CO tzn b QJ "TZJ CD -I QJ ° ? . LO CD ro QJ >. P cn to c —. -LU <=) QJ —; •M CD ro CO CD OO CD I -10.0 brep - 571 kPa, 10% diesel i n j e c t i o n a t 12.3 BTDC 10.3 BTDC 8.3 BTDC CO OO tdc 10.0 30.0 Crank Ang le 50.0 (deg flTDC) 70.0 F i g u r e 5.27 - E f f e c t o f R e t a r d i n g I n j e c t i o n T i m i n g on Rate o f E n e r g y R e l e a CD LD CO CD L P -10.0 t d c 10.0 30.0 50.0 70.0 Crank Ang l e (deg flTDC) F i g u r e 5.28 - E f f e c t o f R e t a r d i n g I n j e c t i o n T i m i n g on Cumulative E n e r g y R e l e a s e 135 CH.VI Conclusions and Recommendations 6.1 Conclusions Safe operation of a prechamber d i e s e l engine with d u a l -f u e l l i n g with n a t u r a l gas i s severely l i m i t e d by maximum c y l i n d e r pressure. Even at h a l f load the maximum c y l i n d e r pressure of d u a l - f u e l operation i s as high as that of s t r a i g h t d i e s e l operation at f u l l l oad. The excessive maximum c y l i n d e r pressure i s ass o c i a t e d with the high r a t e of energy release by combustion which takes place w i t h i n a nearly homogeneous g a s - a i r mixture. The maximum c y l i n d e r pressure, as w e l l as the rate of c y l i n d e r pressure r i s e , can be reduced to a safe l e v e l by r e t a r d i n g the i n j e c t i o n timing by about 4 to 6 degrees of crank angle. The change i n thermal e f f i c i e n c y due to the r e t a r d a t i o n i s small ( l e s s than 0.5 percent with 4 degree r e t a r d a t i o n at 67 percent of f u l l l o a d ) . R e s t r i c t i n g the intake a i r can reduce a l s o the maximum c y l i n d e r pressure, but t h i s r e s u l t s i n higher maximum rate of c y l i n d e r pressure r i s e . Stable d u a l - f u e l operation r e q u i r e s s u f f i c i e n t flow rate of p i l o t d i e s e l f u e l ; i n s u f f i c i e n t amount, of p i l o t d i e s e l f u e l r e s u l t s i n e r r a t i c operation with m i s f i r e d c y c l e s . The minimum p i l o t d i e s e l f u e l required i n order to ensure a s t a b l e operation i s t y p i c a l l y 8 to 15 percent of the t o t a l energy input, depending on engine load. 136 D u a l - f u e l operation at part load showed g e n e r a l l y higher f u e l consumption than that of s t r a i g h t d i e s e l operation. The apparent energy release a n a l y s i s revealed that the higher f u e l consumption rate i s mainly due to gas s u r v i v i n g unburned through the. combustion chamber. The main cause of t h i s poor combustion i s weak gas- a i r mixture strength. Increase i n p i l o t d i e s e l flow r a t e s reduces the amount of unburned gas and thus improves the f u e l consumption r a t e . The dependence of t o t a l f u e l consumption rate on p i l o t d i e s e l flow rate i s l e s s with higher g a s - a i r mixture c o n c e n t r a t i o n . With r e s t r i c t i o n on turbocharger i n l e t pressure (to prevent surge) l e s s than about 10 percent a i r r e s t r i c t i o n was p o s s i b l e i n the t e s t s conducted; t h i s showed some improvement (perhaps one percent) on f u e l consumption r a t e . Advancing i n j e c t i o n timing showed no s i g n i f i c a n t e f f e c t on f u e l consumption r a t e . The f u e l consumption rate during d u a l - f u e l operation near f u l l load approached that of s t r a i g h t d i e s e l o p e r a t i o n . E x t r a p o l a t e d beyond f u l l load d i e s e l o p e r a t i o n , the f u e l consumption rate of d u a l - f u e l operation would become lower than that of s t r a i g h t d i e s e l operation. The combustion c h a r a c t e r i s t i c s of s t r a i g h t d i e s e l and d u a l -f u e l operation d i f f e r i n that i n the former the combustion c o n s i s t s mainly of a u t o - i g n i t i o n of d i e s e l f u e l , whereas i n the l a t t e r the combustion i s c a r r i e d out by the propagation of flame f r o n t s . This d i s t i n c t i o n was c l e a r l y e x h i b i t e d i n the a n a l y s i s of apparent energy r e l e a s e , where s t r a i g h t d i e s e l operation showed a two-staged combustion and d u a l - f u e l operation a 137 s h o r t e r , s i n g l e - s t a g e d combustion. 138 6.2 Recommendations • Without d i f f i c u l t m o d i f i c a t i o n s the current engine can be converted i n t o a d i r e c t - i n j e c t i o n engine. Further t e s t s on t h i s converted engine would lead to comparative study between prechamber and d i r e c t - i n j e c t i o n engines. • Further s t u d i e s at d i f f e r e n t engine speeds are requ i r e d . • Further study of the e f f e c t of r e s t r i c t i n g a i r intake without the turbocharger may show some improvement i n f u e l consumption at low loads. • Exhaust gas a n a l y s i s would provide some important information such as the lower l i m i t of f l a m m a b i l i t y . 139 BIBLIOGRAPHY 1. ANNAND, W.J.D., Heat Transfer i n the C y l i n d e r s of  R e c i p r o c a t i n g I n t e r n a l Combustion Engines", Proc. I n s t . of Mech. Eng., V o l . 177,No. 36, 1963. 2. AUSTEN,A.E.W.,LYN,W.T., " R e l a t i o n between Fuel I n j e c t i o n  and Heat Release i n a D i r e c t - I n j e c t i o n Engine and the Nature of  Combustion Processes", Proc. Auto. Div. I n s t , of Mech. Eng. No.1,1960-61 3. 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G., "Operating Problems of the Dual-Fuel Engine", Power E n g i n e r r i n g , March, 1953. 39. TAYLOR, C.F., "The I n t e r n a l Combustion Engine in Theory  and P r a c t i c e " , V o l . 1 & 2, M.I.T. Press, 1982. 40. VAN WYLEN, G.J., SONTAG, R.E., Fundamental of C l a s s i c a l  Thermodynamics", 2nd ED., John Wiley & Sons, 1978. 41. WATSON, N.,KAMEL, M., "Thermodynamic E f f e c i e n c e e v a l u a t i o n  of an I n d i r e c t I n j e c t i o n D i e s e l Engine", SAE Paper No. 790039, Feb-Mar 1979. 42. WHITEHOUSE, N.D., STOTTER, A., GOUDIE, G.D., PRENTICE, B.W., "Method of P r e d i c t i n g Some Aspects of Performance of a Di e s e l Engine Using a D i g i t a l Computer", Proc. I n s t . of Mech. Eng., V o l . 176, No, 9, 1962. 43. WHITEHOUSE, N.D., WAY, R., Rate of Heat Release in D i e s e l  Engines and I t ' s C o r r e l a t i o n with Fuel I n j e c t i o n Data", Proc. I n s t . Mech. Eng., V o l . 184, Pt. 3J, ppl7, 1969/70. 142 APPENDIX A - CALIBRATION CURVES Load S e n s o r o o" o o' o o o' 00 o o' T3 O •J O V o l t a g e (mV) * s l o p e - 2 2 . 2 N/mV 143 A i r Flow E l e m e n t 144 Gas Flow E l e m e n t D i f f e r e n t i a l P r e s s u r e (kPa) 145 146 APPENDIX B - COMPUTATION OF INDICATED MEAN EFFECTIVE PRESSURE  D e f i n i t i o n An i n d i c a t e d mean e f f e c t i v e p r e s s u r e , imep, i s d e f i n e d as t h a t t h e o r e t i c a l c o n s t a n t p r e s s u r e w h i c h can be i m a g i n e d e x e r t e d d u r i n g each power s t r o k e of the e n g i n e to p r o d u c e work e q u a l to the i n d i c a t e d work: J V l P dV = P. „ AV i n d where P - c y l i n d e r p r e s s u r e P. , - i n d i c a t e d mean e f f e c t i v e i n d - p r e s s u r e , imep V - c y l i n d e r volume V^ - V a t the b e g i n n i n g of the c y c l e - V at the end of the c y c l e bdc t d c I n d i c a t e d mean e f f e c t i v e p r e s s u r e , i n t h i s p r o j e c t , was computed a c c o r d i n g to the f o l l o w i n g : (P. + P.,,) 1 + 1 ( V . „ - V.) 2 i+1 r ^ i n d ( V b d c V t d c ) where P^, a r e c y l i n d e r p r e s s u r e and volume a t i t ^ 1 s t a g e , and each s t a g e c o r r e s p o n d s to a d e g r e e of c r a n k a n g l e t h r o u g h o u t a c y c l e . 147 148 APPENDIX C - COMPUTER PROGRAM FOR CYLINDER PRESSURE DATA  ACQUISITION 1 4 9 L i s t i n g of APP.PR0G2 at 22:10:05 on APR 11, 1984 for CCid=AFPH 1 2 C C Acquires data from D i e s e l Engine 3 C 4 EXTERNAL QTQIO 5 EXTERNAL GETADR 6 EXTERNAL ASNLUN 7 C e INTEGER LISTC3002), IDAT(3002), 1PARM(6) 9 INTEGER YES, NO, ANS, IPARR(5), IBDC(3) 10 REAL LOAD, PMEAN(721), VOLUME*5) 1 1 C 12 YES = 1 1 3 NO = 0 1 4 SCALE = -32768.0 1 5 NPOINT = 3001 1 6 NPCYC = 720 1 7 NPCYCE = 750 18 NPCYCS = 700 19 NPCY2 = 360 20 STROKE = 6.0 21 ARM = 3.0 22 ROD = 9.595 23 VCLEAR = 6.444 24 PTAREA = 3.1416* ( 4 . 7 5 / 2 . 0 ) * * 2 25 NPC1 = 721 26 FNPC1 - FLOAT(NPC1) 27 NPCY3 = NPCY2 + 50 28 RDPDEG = 0.0174533 29 PTHR = 400.0 30 PMINRF = 14.7 31 STHR = 0.6 32 C 33 DO 5 1 = 1 ,3002 34 IDAT(I) = 0 35 5 CONTINUE 36 C 37 DO 6 1=1,NPC1 38 PMEAN(I) = 0.0 39 6 CONTINUE 40 CALL ASNLUN(3, 'NI', 0) 4 1 CALL ASSIGN*1, 'PAR2.DAT') 42 C 43 READ(1,100) CLOCK 44 DWELL = 1. / CLOCK 45 HERTZ =1. / XRATE(DWELL, I RATE, IPRSET, 1) 46 CALL CLOCKB(I RATE, IPRSET, 1, IND, 1) 47 DELT = 1. / HERTZ 48 WRITE(5,200) IND, HERTZ 49 C 50 READ(1,101) NCHAN 51 READ(1,102) NDPCH 52 C 53 c 54 NDTOT = NPOINT 55 ISTRT = 1 56 I LAST = NDTOT + 1 57 c read in port address 58 READ(1,103) LIST(1) ISTAT(2) 150 L i s t i n g of APP.PROG2 at 22:10:05 on APR 1 1 , 1 984 for CCid=AFPH 59 c read in scan i n s t r u c t i o n s 60 DO 10 I=2,NCHAN+1 61 READ(1,103) L1STU) 62 1 0 CONTINUE 63 c f i l l the rest of scan l i s t by repeating 64 DO 11 I=NCHAN+2,ILAST 65 LIST(I)"= LIST(I-NCHAN) 66 11 CONTINUE 67 c reset s e r i e s 500 BUS 6B IPARMC2) = 2 69 CALL GETADR(IPARM(1), IDAT) 70 CALL WTQ10("1002,3,10,1,1 STAT,IPARM,IDS) 71 WRITE(5,201) 72 WRITE(5,202) ISTAT(I), ISTAT(2), IDS 73 c 74 IRSA = 1 75 c write scan l i s t to RAM, read back and c h e c k 76 IPARM(2) = (ILAST-ISTRT+1) * 2 77 IPARM(3) = IRSA 78 CALL GETADR(IPARM(1),LI ST(1 START)) 79 CALL WTQIO("400,3, 10, 1 ,I STAT,IPARM,IDS) 80 c read back 81 CALL • GETADR(IPARM(1), I DAT(ISTRT)) 82 CALL WTQIO("1000,3,10,1,1 STAT,IPARM,IDS) 83 c p r i n t any discre p a n c i e s 84 I ERR = 0 85 DO 20 1 = 1STRT,I LAST 86 IF (IDAT(I) .EQ. LIST(I)) GO TO 20 87 I ERR = I ERR + 1 88 WRITE(5,203) LI ST(I ),I DAT(I) 89 20 CONTINUE 90 WRITE(5,204 ) I ERR 91 WRITE(5,202) ISTAT ( l ) , ISTAT(2), IDS 92 IF (I ERR .GT. 0) GO TO 999 93 c acquire data 94 IWCT = NDTOT + 1 95 CALL I DATE(ID 1 , ID2, ID3) 96 WR1TE(5,205) ID1, ID2, ID3 97 c 98 c c a l i b r a t i o n of Pressure Measurement 99 c 100 PCPPSI = 0.830 101 CHMUPV = 1000.0 1 02 PCPMU = 1.415 103 GAIN = 1 . 0 104 C1P = CHMUPV * PCPMU / PCPPSI / SCALE * GAIN 1 05 c 106 DO 600 1600=1,100 107 WRITE(5,270) 108 READ(5,170) SPEED 109 FREQRQ = SPEED / 60.0 / 2.0 * FLOAD(NPCYC) * 2 1 1 0 DWELL = 1. / FREQRQ 1 1 1 HERTZ = 1. / XRATE(DWELL, I RATE, IPRSET, 1) 1 12 CALL CLOCKBCIRATE, IPRSET, 1, IND, 1) 1 1 3 DELT = 1. / HERTZ * 2 1 14 DTPDEG = DELT 1 15 WRITE(5,200) IND, HERTZ 1 16 NCYCLE = 1 0 151 L i s t i n g of APP.PROG2 at 22:10:05 on APR 11, 1984 for CCid=AFPH 1 7 WRITE(5,271) NCYCLE 1 8 READ(5,171) NCYCLE 1 9 IPMAX = 0 20 FNCYC = FLOAT(NCYCLE) 2 1 NSET = 1 22 DO 610 1610=1,NPC1 23 PMEAN(1610) = 0.0 24 610 CONTINUE 25 PMAX0 = 0.0 26 DPDTM0 = 0.0 27 RPMIN0 = 0.0 28 RIMEP0 = 0.0 29 SUMRP = 0.0 30 SUM2RP = 0.0 31 SUMIM = 0.0 32 SUM2IM = 0.0 33 SUMPX = 0.0 34 SUM2PX = 0.0 35 SUMPN = 0.0 36 SUM2PN = 0.0 37 SUMDN = 0.0 38 SUM2DN = 0.0 39 WRITE(5,269) 40 READ(5,170) PINTAK 41 PINTAK >= PINTAK + 14.7 42 WRITE(5,210) 43 READ(5,110) CR 44 DO 650 M650=1,500 45 IF (NSET .GT. NCYCLE) GO TO 651 46 C 47 CALL GETADR(I PARK(1 ) , I DAT) 46 IPARM(2) = IWCT *2 49 IPARM(3) = IRSA 50 CALL WTQIOC3001 ,3,1 0, 1 ,I STAT,IPARM,IDS) 51 C 52 MB = 3 53 MF =751 54 DO 680 M680=1 ,2 55 DO 661 M=MB,MF,2 56 S = IDAT(M) 57 S = ABS(S/SCALE) 58 IF (S .LT. STHR) GO TO 681 59 P = IDAT(M+359) 60 P = P * C1P 61 IF (P .LT. PTHR) GO TO 68 2 62 IBDC(1) = M 63 GO TO 683 64 682 CONTINUE 65 MB = M + 680 66 MF = MB + 80 67 GO TO 680 66 681 CONTINUE 69 680 CONTINUE 70 GO TO 650 7 1 663 CONTINUE 72 INDXBD = 2 73 MB = IBDC(1) + 680 74 MF = MB + 80 152 L i s t i n g of APP.PR0G2 at 22: 10:05 on APR 1 1, 1984 for CCi d=AFPH 175 DO 685 M685=1,2 176 DO 686 M=MB,MF,2 177 S = 1DAT(M) 178 S = ABS(S/SCALE) 179 IF (S .LT. STHR) GOTO 686 180 IBDC(INDXBD) = M 181 MB = M + 680 182 MF = MB + 80 183 INDXBD = INDXBD + 1 184 GO TO 685 185 686 CONTINUE 186 GO TO 650 187 685 CONTINUE 188 IDIFFA = IBDC(2) - IBDC(1) 189 IDIFFB = IBDC(3) - IBDC(2) 190 MB = IBDC(2) + 681 191 MF = MF + 80 192 PMIN = 0.0 193 621 CONTINUE 194 IDIFF = IDIFFA + IDIFFB 195 RPMIND = 60.0 / (FLOAT(IDIFF) * DELT) * 4.0 196 MM = IBDC(3) - 81 197 DO 625 M= 1 ,40 198 PM = I DAT(MM) 199 PMIN = PMIN + PM 200 MM = MM + 2 201 625 CONTINUE 202 PMIN = PMIN / 40.0 *C1P 203 626 CONTINUE 204 IBDC1P = IBDC(1) - 1 205 IBDC3P = IBDC(3) - 1 206 PMAX = 0.0 207 DPDTMX=0.0 208 RIMEP =0.0 209 THETA =-180.0 210 DTHETA = 720. / FLOAT(IDIFF) * 2.0 211 DO 632 J1=IBDC1P,1BDC3P,2 212 PJ1P1 = IDAT(J1+2) 213 PJ1 IDAT(J1) 214 PJ1P1 - PJ1P1 * C1P - PMIN + PINTAK 215 PJ1 = PJ1 * C 1 P - PMIN + PINTAK 216 DPDT = ABS((PJ1P1-PJ1) / DELT) * DTPDEG 217 IF (DPDT .GT. DPDTMX) DPDTMX = DPDT 218 RAD1 = THETA * RDPDEG 219 RAD2 = (THETA + DTHETA) * RDPDEG 220 X1 = -ARM * COS(RADI) 221 1 SQRT(ROD*ROD - (ARM * SIN(RADI)) ** 2) 222 X2 = -ARM * COS(RAD2) 223 1 ~ SQRT(ROD*ROD - (ARM * SIN(RAD2)) ** 2) 224 PAVER = (PJ1 + PJ1P1) / 2.0 225 RIMEP = RIMEP + PAVER / STROKE * (X2 - X1) 226 IF (PJ1 .GT. PMAX) PMAX = PJ1 227 THETA = THETA + DTHETA 228 632 CONTINUE 229 WRITE(5,914) IBDC1P, IBDC3P 230 914 FORMAT*' Cycle l i e s between ',15,' < > ',15,' degrees ') 231 WRITE(5,272) NSET, ID1FF, RPMIND 232 WRITE(5,273) 153 L i s t i n g of APP.PROG2 at 22:10:05 on APR 11, 1984 for CCid=AFPH 233 WRITE(5,274) PMAX, PINTAK, RIMEP, DPDTMX 234 C 235 WRITE(5,279) 236 READ(5,120) ANS 237 IF (ANS .EQ. NO) GO TO 650 2 38 FI BDC 1 «= FLOAT(IBDCIP) 239 DO 637 JI=1,721 240 FJJ1 - FLOAT(JI-l) / DTHETA * 2.0 + FIBDC1 241 INDX - (FJJ1 / 2.0) 242 INDX - INDX * 2 243 RINDX = (FJJ1 - FLOAT(INDX)) / 2.0 244 PINDX = IDAT(INDX) 245 PINDX1 = IDAT(INDX+2) 246 PINDX = PINDX *C1P - PMIN + PINTAK 247 PINDX1 = PINDX1 * C1P - PMIN + P.1NTAK 248 P = PINDX * RINDX * (PINDX1 - PINDX) 249 PMEAN(J1) = PMEAN(J1) + P / FNCYC 250 637 CONTINUE 251 PMAX0 = PMAX0 + PMAX 252 RIMEP0 = RIMEP0 + RIMEP 253 DPDTM0 = DPDTM0 + DPDTMX 2 54 RPMIN0 = RPMIN0 + RPMIND 2 55 SUMRP = SUMRP + RPMIND 256 SUM2RP « SUM2RP + RPMIND*RPMIND 257 SUMIM « SUMIM + RIMEP 258 SUM2IM = SUM2IM + RIMEP*RIMEP 259 SUMPX n SUMPX • PMAX 260 SUM2PX - SUM2PX + PMAX*PMAX 261 SUMPN • SUMPN + PMIN 262 SUM2PN = SUM2PN + PMIN*PMIN 263 SUMDP = SUMDP + DPDTMX 264 SUM2DP = SUM2DP + DPDTMX*DPDTMX 265 NSET = NSET + 1 266 650 CONTINUE 267 WRITE(5,299) 268 GO TO 652 269 651 CONTINUE 270 PMAX0 = PMAX0 / FNCYC 271 DPDTM0 ' DPDTMO / FNCYC 272 RPMIN0 « RPMINO / FNCYC 273 RIMEPO « RIMEPO / FNCYC 274 FNCYC1 = FNCYC - 1 275 IF (FNCYC1 .EQ. 0) FNCYC1=1 276 SDIMEP = SQRT((SUM2IM-SUMIM*SUMIM/FNCYC)/FNCYC1) 277 SDPMAX •= SQRT((SUM2PX-SUMPX*SUMPX/FNCYC)/FNCYC1) 278 SDPMIN «= SQRT( (SUM2PN-SUMPX*SUMPN/FNCYC )/FNCYC 1 ) 279 SDDPDT = SQRT((SUM2DP-SUMDP*SUMDP/FNCYC)/FNCYC1) 280 SDRPM = SQRT((SUM2RP-SUMRP*SUMRP/FNCYC)/FNCYC1) 281 WR1TE(5,275) 282 WRITE(5,276) NCYCLE, SPEED, HERTZ 283 WRITE(5,277) 284 WRITE(5,27B) RPMINO, PMAXO, PINTAK, RIMEPO, DPDTMO 2B5 WRITE(5,286) SDRPM, SDPMAX, SDPMIN, SDIMEP, SDDPDT 286 C 287 652 CONTINUE 288 WRITE(5,290) 289 READ(5,120) ANS 290 IF (ANS .EQ. NO) GO TO 998 154 L i s t i n g of APP.PROG2 at 22:10:05 on APR 1 1, 1984 for CCi d = AFPH 291 600 CONTINUE 292 C 293 C 294 998 CONTINUE 295 WRITE(5,29l) 296 READ(5,120) ANS 297 IF (ANS •EQ. NO) GO TO 999 298 CALL ASSIGN(2, 'P.DAT') 299 WRITE(5,292) 300 READ(5,192) NDEG 301 IPVDGM = NO 302 INTERD = NDEG / 180 303 IF (IPVDGM .EQ. YES) INTERD = INTERD * 2 304 NDAT = NDEG / INTERD + 1 305 NDEG2 = NDEG / 2 306 ITDC = 181 307 IPBEG = ITDC - NDEG2 3 08 IPEND = ITDC + NDEG2 309 IF '(NEG .EQ. 720) IPBEG = 1 310 IF (NEG .EQ. 720) IPEND = 721 311 WRITE(2,700) 312 PMAX = 0.0 313 NSKIP = 5 * INTERD 314 DO 660 1660=IPBEG,IPEND,NSKIP 315 JB = 1660 316 JF - 1660 + NSKIP -1 317 JL = 1 318 DO 661 J=JB,JF,INTERD 3 19 P = PMEAN(J) 320 IPARR(JL) = P 321 JL = JL + 1 322 661 CONTINUE 323 JLM1 = JL -1 324 WRITE(2,70l) (IPARR(LL), LL=1,JLM1) 325 660 CONTINUE 326 MINX = IPBEG - 181 327 MAXX = IPEND - 181 328 WRITE(2,702) 329 IF (IPVDGM .EQ. YES)- GO TO 670 330 WRITE(2,703) NDAT, MINX, INTERD 331 WRITE(2,704) MINX, MAXX 332 WRITE(2,705) 333 WRITE(2,706) RPMIN0 334 WRITE(2,707) 335 GO TO 674 336 670 CONTINUE 337 WRITE(2,710) 338 THETA = MINX 339 FINTER = FLOAT(INTERD) 34 0 THETA = THETA - FINTER •34 1 DO 662 I 662 = IPBEG,IPEND,NSKIP 342 JB = 1662 343 JF = 1662 + NSKIP -1 344 JL = 1 345 DO 663 J=JB,JF,INTERD 34 6 THETA = THETA + FINTER 34 7 RAD = THETA * RDPDEG 348 X «= ROD + ARM - ARM * COS(RAD) 155 L i s t i n g of APP.PROG2 at 22: 10:05 on APR 1 1 , 1964 for CCid = AFPH 349 1 - SQRT(ROD * ROD - (ARM * SIN(RAD)) ** 2) 3 50 VOLUME(JL) = X * PTAREA + VCLEAR 351 JL = JL + 1 352 663 CONTINUE 353 JLM1 = JL - 1 354 WRITE(2,711) (VOLUME(LL), LL=1,JLM1) 355 662 CONTINUE 356 WRITE(2,702) 357 WRITE(2,714) 356 WRITE(2,715) 359 WRITE(2,706) RPMINO 360 WRITE(2,717) 361 674 CONTINUE 362 WRITE(2,708) 363 WRITE(2,709) 364 999 CONTINUE 365 STOP 366 C 367 C 366 100 FORMAT(1X,F16.5) 369 101 FORMAT(1X,I 2) 370 102 FORMAT(1X,I 4) 371 103 FORMAT(05) 372 110 FORMAT(A5) 373 120 FORMAT(11) 374 150 FORMAT(F12.4) 375 170 FORMAT(F7.2) 376 17 1 FORMAT(I 2) 377 180 FORMAT(F5.1,1X.F5.3,IX,F5.1) 378 192 FORMAT(13,1X,I 2) 379 195 FORMAT(II) 380 C 381 C 382 200 FORMAT(IX,' IND CODE = ', 13,', Frequency = ' , F 8 . 1 , ' Hz') 383 201 FORMAT(1X,' SERIES 500 BUS RESET!!!',/) 384 202 FORMAT(1X,' DRIVER COMPLETION CODE =',06,' (OCTAL)',/ 385 1, 1X,' LAST RESPONSE =',06,' (OCTAL)',/ 386 2, 1X,' DIRECTIVE STATUS =',06,' (OCTAL)',/) 387 203 FORMAT(IX,'XXXX RAM ERRORXXXXXXXXXXXXXXXXXXXXXXXXXX',/ 388 1, 1X,' OUTPUT = ',05,' ; READ BACK = ',05,/) 389 204 FORMAT(1X,' WRITE TO RAM AND READBACK COMPLETE*,I 3,' ERRORS', 390 205 FORMAT(//,IX,' date:', I 3,1X,I 2,IX,I 2,//) 391 210 FORMAT(IX,'?? To s t a r t scaning, enter RETURN!',$) 392 225 FORMAT(1X,I5,2X,E14.6) 393 269 FORMAT(IX,' >> > Enter Intake Pressure in (p s i ) : ' , $ ) 394 270 FORMAT(IX," >> > Enter Engine Speed in RPM:',$) 395 271 FORMAT(1X,' Ideal * of Cycles i s ',12,', Enter desired * 12 ', 396 272 FORMAT(10X,' # of data points in ',13,'th c y c l e i s ',14,/, 397 1 10X,' Indicated Engine Speed i s ',F6.1,' rpm') 398 273 FORMAT(IX,' P max (psi) P intake IMEP dpdt max ( p s i / d e g 399 274 FORMAT(1X,3(2X,FB.3),4X,F11.2) 400 275 F0RMAT(15X,' # of Cycles Engine Speed Data aqusit Freq',/, 401 1 15X,' (c y c l e s ) (rpm) (Hz) ') 402 276 FORMAT(15X,BX,I 2,3X,5X,F6.1,4X,7X,F8.1) 403 277 FORMAT(IX,' Mean: Indicated Speed P max P intake IMEP 404 1 ' dPdt max ') 405 278 FORMAT(IX,1IX,F8.3,5X,5(F11.2)) 406 279 FORMAT(IX,' Do you want to s e l e c t t h i s c y c l e ? (1/0):',$) 156 L i s t i n g o f A P P .PP0G2 a t 2 2 : 1 0 : 05 on APR 1 1 , 1984 f o r C C i d = A F P H 407 2 8 0 FORMAT( 1X,' >> > E n t e r M.U. p e r V , p C p e r M.U., G a i n : ' , ? ) 4 0 8 ~ 8 u F O R M A T * I X , ' S t a n d . D e v L ' , F8 . 3 , 5X , 5 ( F 1 1 . 3 ) ) 4 0 9 2 5 0 F O R M A T ( / / , 1 ? ? ? ? ? ? To R e r u n e n t e r l o r 0 ' , S ) 4 1 0 2 9 : F O R M A T ( 1 X , ' T o s a v e d a t a f o r p l o t , E n t e r 1 o r 0 : ' , S ) 411 ? 9 2 F O R M A T ! 1 X , ' E n t e r C r a n k A n g l e R a n g e 1 3 : ' , $ ) 4 1 2 7 9 5 F O R M A T * I X . ' D o y o u w a n t a P-V d i a g r a m ? E n t e r l o r 0 : ' , S ) 4 1 3 2 9 9 FORMAT*' <======> C y c l e NOT f o u n d . <======> ') 414 7 00 F O R M A T ( 1 X , ' E N P R E S f ) 4 15 7 1 0 F O R M A T * I X , ' E N VOL &') 4 16 701 FORMAT*IX,5(15,IX),'I') 4 1 7 7 11 F O R M A T * 1 X , 5 ( F 5 . 1 , 1 X ) , ' ' ) 4 1 8 7 02 F O R M A T ( I X , ' ; ' ) 4 19 "i*3 FORMAT ( I X , ' EN ANGL SHOR ' , 1 3 , I X , 1 4 , I X , 1 2 ) 4 2 0 7;.4 FORMAT ( 1X , ' GR ANGL PRES ; YR - 2 0 0 1 6 0 0 ; X R ' , I 4 , 1X , I 3 , ' ; £ ' ) 421 7 U FORMAT ( I X , ' GR VOL PRES ; YR - 2 0 0 1 6 0 0 ; X R 5 1 1 5 ; i ' ) 4 2 2 705 FORMAT ( l X , ' T I ' ' C y l i n d e r p r e s s u r e v s C r a n k A n g l e ' ';(,') 4 2 3 7 •, 5 FORMAT ( l X , ' T I ' ' C y l i n d e r p r e s s u r e v s V o l u m e ' ' ; i ' ) 424 706 FORMAT*IX,'DA ' ' ' , F 6 . l , ' rpm'';&') 4 2 5 707 FORMAT ( I X , ' X T I T ' ' C r a n k A n g l e ( d e g ) '';(>') 42 6 7-.7 FORMAT* I X , ' X T I T ' ' V o l u m e ( c u . i n . )'';&') 427 "0= FORMAT*ix,'YTIT ' ' P r e s s u r e p s i '';&') 4 28 709 FORMAT*IX,'YG;XG') 4 2 9 END 157 APPENDIX D - COMPUTER PROGRAM FOR DATA PROCESSING 158 L i s t i n g of APP.PROG 1 at 22:58:59 on APR 6, 1984 for CCid = AFPH 1 2 C C 3 C This program processes data from d i e s e l engine 4 C 5 C 6 EXTERNAL WTQIO 7 EXTERNAL GETADR 8 EXTERNAL ASNLUN 9 C 10 1 1 INTEGER LISTC200), IDATC200), IPARM(6), I STAT(2) INTEGER YES, NO, ANS, IACTIV(2) 12 REAL LOAD 13 c 1 4 YES = 1 1 5 NO = 0 16 SCALE = 32768.0 1 7 c 18 c c a l i b r a t i o n constants for gas flow 19 c 20 C1GAS = 2 . 22 21 C2GAS = -0.0194 22 c 23 CALL PERFRM(VOLDSL,VOLGAS,VOLAIR,SPEED,LOAD,QINPPW,BM; 24 1 POWER,THRMEF,VOLEFF,PERDSL,RAF,RAD,RAG,0) 25 c 26 WRITE(5,248) 27 READ(5,150) VLOAD 28 LOAD = 5.0 * VLOAD 29 WRITE(5,249) 30 READ(5,150) SPEED 31 WRITE(5,247) 32 READ(5,150) DPQAIR 33 VOLAIR = 2.173 + 0.221 * DPQAIR 34 WRITE(5,245) 35 READ(5,150) DPQGAS 36 c convert pascal to in water 37 VOLGAS = DPQGAS / 248.8 38 VOLGAS = CI GAS * VOLGAS + C2GAS * VOLGAS * VOLGAS 39 WRITE(5,246) 40 READ(5,150) VOLDSL 41 VOLDSL = VOLDSL * 60.0 42 CALL PERFRM(VOLDSL,VOLGAS,VOLAIR,SPEED,LOAD,QINPPW,BMEP 43 1 POWER,THRMEF,VOLEFF,PERDSL,RAF,RAD,RAG,1) 44 WRITE(5,250) 45 WRITE(5,251) SPEED, LOAD, VOLAIR, VOLDSL 46 WRITE(5,254) 47 WRITE(5,255) QINPPW, POWER, BMEP, THRMEF, VOLEFF 48 WRITE(5,256) 49 WRITE(5,257) VOLGAS, PERDSL 50 WRITE(5,258) 51 WRITE(5,259) RAF, RAD, RAG 52 c save data in a f i l e ? 53 WRITE(5,224) 54 READ(5,120) ANS 55 IF (ANS .EQ. NO) GO TO 70 56 IF (L .EQ. 1) CALL ASSIGN(2, 'OUT.DAT') 57 WRITE(2,250) 58 WRITE(2,251) SPEED, LOAD, VOLAIR, VOLDSL 159 L i s t i n g of APP.PROG 1 at 22:58: 59 on APR 6, 1984 for CCid = AFPH 59 WRITE(2,252) 60 WRITE(2,253) DPTURB, DPCOMP, T1TURB, T2TURB, T1COMP, T2COMP 61 WRITE(2,254) 62 WRITE(2,255) QINPPW, POWER, BMEP, THRMEF, VOLEFF 63 WRITE(2,256) 64 WRITE(2,257) VOLGAS, PERDSL 65 WRITE(2,258) 66 WRITE(2,259) RAF, RAD, RAG 67 C 68 70 CONTINUE 69 WRITE(5,226) 70 READ(5,120) ANS 71 IF (ANS .EQ. NO) GO TO 999 72 500 CONTINUE 73 C 74 C 75 999 CONTINUE 7 6 STOP 77 C 78 100 FORMAT(1X,F16.5) 79 101 FORMAT(1X, I 2) 80 1 02 FORMAT(IX, 12) 81 103 FORMAT(05) 82 110 FORMAT(A5) 83 120 FORMAT(II) 84 150 FORMAT(F12.4) 85 C 86 C 87 224 FORMAT(IX,' ???? Enter 1 or 0 to save data!',$) 88 225 FORMAT(1X,I 5,2X,E14.6) 89 226 FORMAT(//,'???? To rerun enter 1-or 0',$) 90 245 FORMAT(IX,' >> > Enter Gas Flow in Pascal :',$) 91 246 FORMAT(IX,' >> > Enter D i e s e l Flow in l i t r e / m i n : ' , $ ) 92 247 FORMAT(IX,' >> > Enter A i r Flow in Pascal:',$) 93 248 FORMAT(1X,' >> > Enter Load in Voltage:',$) 94 249 FORMAT(IX,' >> > Enter Engine Speed in rpm:',?) 95 250 FORMAT(1X,' Speed (rpm) Load (lb) A i r Flow (ft3/min) ', 96 1 ' D i e s e l Flow ( l t r / h r ) ' ) 97 251 FORMAT(3X,F7.2,7X,F7.3,7X,F10.3,5X,F10.4) 98 253 FORMAT(1X,6(F8.2,2X)) 99 254 FORMAT(5X,'Heat cons Power out BMEP Therm e f f Vol e f f ', 100 1 5X,'(BTU/hr-hp) (hp) ( p s i ) (%) (%) 101 255 FORMAT(1X,F15.2,2X,F8.3,2X,F8.3,2X,F8.4,2X,F8.4) 102 256 FORMAT(10X,'Gas Flow d i e s e l input proportion (heat)',/, 103 1 10X,'(ft3/min) (percent t o t a l heat) ') 104 257 FORMAT(1 OX,F12.3,5X,F8.2,' %') 105 258 FORMAT(10X,' LAMDA (tot) LAMDA (dsl) LAMDA (gas)') 106 259 FORMAT(1 OX, 3F16.2) 107 END 108 C 109 C 110 C 111 SUBROUTINE PERFRM(VOLDSL,VOLGAS,VOLAIR,SPEED,LOAD,QINPPW, 112 1 BMEP,POWER,THRMEF,VOLEFF,PERDSL,RAF,RAD,RAG,INDEX) 113 C 114 C computes performance c h a r a c t e r i s t i c s 115 C 116 REAL LOAD,LHVDSL,LHVGAS 160 ; t i n g o f APP. PROG 1 a t 22:58:59 on APR 6, 1984 f o r CC id=AFPH 1 17 C 1 IB I F (INDEX .NE. 0) GO TO 10 1 19 C 1 20 C i n i t i a l i z e c o n s t v a l u e s 121 C 1 22 V1SCAG = 1.669 123 DENDSL = 0.8697 * 62.27 124 DENGAS = 0.044386 125 DENAIR = 0.07541 126 STCDSL = 15.0 127 HHVDSL = 1058288.4 128 STCGAS •= 16.7 129 LHVDSL = 1002560.0 1 30 HHVGAS = 1024.7 131 LHVGAS = 926.0 132 DSPLMT = 425.04 133 ARMLEN = 17.5 / 12.0 1 34 C 135 C c o n v . f a c t o r s 136 C 137 F3PLTR = 0.03531 138 HPPFPM = 1 . 0 / 33000. 1 39 BTUPHP = 2544.433 / 1.01387 / 0.986315 140 PI = 3.1415 141 C 142 RETURN 143 C 144 10 CONTINUE 145 c 146 c p r o c e s s d a t a 147 c 148 TQDYNO • LOAD * ARMLEN 149 POWER = TQDYNO * SPEED * 2.0 * PI * HPPFPM 1 50 VSWEPT = DSPLMT * SPEED / 2.0 151 BMEP = (POWER / HPPFPM * 12.0) / VSWEPT 152 DSLFLW = VOLDSL * F3PLTR 153 GASFLW = VOLGAS * V1SCAG 154 FMAIR = DENAIR * VOLAIR 155 FMDSL = DENDSL * DSLFLW / 60.0 156 FMGAS = DENGAS * GASFLW 157 RAD = FMAIR / (STCDSL * FMDSL) 158 RAG = 0.0 159 I F (FMGAS .GT. 0.0) RAG = FMAIR / (STCGAS * FMGAS) 160 RAF = FMAIR / (STCDSL * FMDSL + STCGAS * FMGAS) 161 VOLEFF = VOLAIR / (VSWEPT / 12.0 / 12.0 / 12.0) * 100. 0 162 PERDSL = LHVDSL*DSLFLW / (LHVDSL*DSLFLW+LHVGAS*GASFLW* 60 163 PERDSL •= PERDSL * 100.0 164 G 165 C b r a n c h i ou t n o - l o a d i e . i d l i n g 166 C 167 IF (ABS(LOAD) .LT. 0.00001) G O T O 11 168 QINPPW = (LHVDSL*DSLFLW + LHVGAS*GASFLW* 60. 0 ) / POWER 169 THRMEF = BTUPHP / QINPPW * 100.0 170 RETURN 171 C 172 1 1 CONTINUE 173 c 174 QINPPW = 0.0 161 L i s t i n g o f APP.PROG 1 a t 2 2 : 5 8 : 5 9 on APR 6, 1984 f o r C C i d = AFPH 175 THEMEF = 0 .0 176 C 177 RETURN 178 END 162 APPENDIX E - COMPUTER PROGRAM FOR APPARENT ENERGY RELEASE 163 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 1 1 2 C C 3 C 4 C . Rate of Heat Release A n a l y s i s Program 5 c 6 c written by : Seaho Song 7 c Dec / 1983 8 c 9 c 10 c 1 1 c 12 c This program reads in the c y l i n d e r pressure data 13 c to compute the rate of heat release for every C A . 1 4 c 15 c 16 c 17 c 18 c 19 c 20 Cmmmnmmmmmmmmmmmnmmmnunmmmmmm 21 Cm m 22 Cm Main Routine m 23 Cm m 24 CiTunmmmmmmmrnmmmnimnunmmmmmmmmmmmmmnuninmrnrnmmmmmmmmrnmmnirnmmminrnmrn 25 C 26 C 27 IMPLICIT REAL*8(A-H,0-Z) 28 REAL*8 CYLVOL(180) 29 REAL* 8 GAS (10), GASNEWOO), P(180) 30 REAL*8 HEATRT(180),ANGLE(180), GASNE0(10),DH01(10), 31 REAL*8 F(2),DFDX(2,2),X(2),DX(2),FEP(2),XEP(2), 32 1 WORKAR(2,2) 33 REAL*8 NTOT, SAVGAS(180,10) 34 INTEGER I PERM(4) 35 COMMON / GEOM / ARM, ROD, BORE, STROKE, VCLEAR 36 COMMON / EXPMT/ SPEED, BMEP 37 COMMON / PROP 1/ DENAIR, DENDSL, DENNG, WTDSL, WTNG, 38 1 WTAIR 39 COMMON /THDYPR/ H0F(10), R0, WT(10), NGAS 40 c 41 c 42 c s p e c i f y c y l i n d e r geometry in inches, then convert 43 c i n t o metric. 44 c 45 CONVF1 = 0.0254 46 ARM =3.0 * CONVF1 47 ROD = 9.595 * CONVF1 48 BORE =4.75 * CONVF1 49 STROKE =6.0 * CONVF1 50 VCLEAR = 6.444 * CONVF1**3 51 c 52 c To smoothen pressure data SET I SOOT = 1 53 c To use heat t r a n s f e r model SET IHTRSF = 1 54 c To consider d i s s o c i a t i o n SET IDSSOC = 1 55 c To obtain output appropriate 56 c for p l o t t i n g SET IPLOT = 1 57 c 58 c S e t t i n g ISMOOT = 0; IHTRSF = 0; IDSSOC'= 0 w i l l 164 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 2 59 C assume unsmoothed, a d i a b a t i c with no d i s s o c i a t i o n . 60 C 61 ISMOOT = 1 62 IHTRSF = 1 63 IDSSOC = 1 64 I PLOT = 1 65 c 66 EPSIL = 0.1E-1 67 c 68 c compute c y l i n d e r volume at every C A . 69 c 70 CALL GEOMTR(CYLVOL, ANGLE) 71 c 72 c assign c o e f f i c i e n t s f or thermodynamic 73 c p r o p e r t i e s of various gases. 74 c 75 CALL READPR 76 c 77 c read in c y l i n d e r pressure data, i n j e c t e d d i e s e l 78 c amount, CH4 amount, and i n j e c t i o n & i g n i t i o n 79 c c h a r a c t e r i s t i c s . 80 c 81 CALL DATAIN(GAS,P,DSLAMT,INJBEG,INJEND,IGNBEG) 82 c 83 c write out the mode of operation and bmep in kPa 84 c 85 BMEPKP = BMEP * 6.8 95D0 B6 IF (GAS(2) .LT. 0.1D-12) 87 1 WRITE(6,210) SPEED, BMEPKP 88 IF (GAS(2) .GE. 0.1D-12) 89 2 WRITE(6,211) SPEED, BMEPKP 90 c 91 c smooth the P data 92 c 93 IF (ISMOOT .NE. 1) GO TO 10 94 c 95 CALL SMOOTP(P, ANGLE, IGNBEG, IPOK) 96 IF (IPOK .EQ. 0) WRITE(6,914) 97 IF (IPOK .EQ. 0) STOP 98 c 99 10 CONTINUE 100 c 101 c set up for i n i t i a l stage 102 c 103 c FRREM keeps track of f r a c t i o n of f u e l remaining. 1 04 c FRBURN .. .. burnt. 1 05 c 1 06 c The s u b s c r i p t 1 r e f e r s to the previous step 107 c 2 .. present 108 c 109 FRREM = 1.0 110 FRBURN = 0.0 1 1 1 QCACCM = 0.0 112 PI . = P(1) 1 13 V1 = CYLVOL(1) 1 14 Tl = P1 * VI / R0 115 c 116 c .TOTMAS - t o t a l mass of gases present 165 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 1 17 C NTOT - t o t a l number of Kmoles of gases present 118 c 119 c GASM-10) - # of Kmoles of each gas present 120 c GASNEW(I-IO) - used to update GAS(I-IO) 121 c 122 TOTMAS = 0.D0 123 NTOT = 0.D0 124 DO 29 J=1,NGAS 125 GASNEW(J) = GAS(J) 126 TOTMAS = TOTMAS + GAS(J) * WT(J) 127 NTOT = NTOT + GAS(J) 128 29 CONTINUE 129 C 130 C DH0TOT - Enthalpy at T1 minus the Enthalpy at 25 131 C for the t o t a l gas 132 C 133 CALL DH0FN(T1,DH01) 1 34 DH0TOT = 0.0 135 DO 31 1=1,NGAS 136 DH0TOT = DH0TOT + GASNEW(I) * DH01(I) 137 31 CONTINUE 138 U2 = DH0TOT - NTOT * R0 * T1 139 C 140 C write headings for the output 141 c 1 42 WRITE(6,200) 143 c 144 c c a l c u l a t i o n of rate of heat release i s c a r r i e d 145 c out for each C A . degree. 146 c 147 DO 50 ITH=2,180 148 P2 = P(ITH) 1 49 V2 = CYLVOL(ITH) 150 c 151 c update the number of Kmoles of d i e s e l 152 c i n j e c t e d . 153 c 1 54 IF (ITH .EQ. INJBEG) 1 55 1 GAS(1) = GAS(1) + DSLAMT 156 IF (ITH .NE. INJBEG) GOTO 750 157 c 158 TOTMAS = 0.D0 159 NTOT = 0.D0 160 DO 732 J=1,NGAS 161 TOTMAS = TOTMAS + GAS(J)*WT(J) 162 NTOT = NTOT + GAS(J) 163 732 CONTINUE 164 750 CONTINUE 165 IF (ITH .GE. INJBEG) GO TO 55 166 C 167 c no combustion. 168 c. processes compression stroke. 169 c 170 25 CONTINUE 171 FRAC = 0.0 172 RN = NTOT * R0 173 T2 = P2 * V2 / RN 174 C 166 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page compute rate of heat t r a n s f e r , i n t e r n a l energy. CALL UPROD(P1,P2,T1,T2,V1,V2,GAS,GASNEW,DHO1,FRAC, 1 DHO,NTOT,TOTMAS,U2RES,QC,QHT,0,1HTRSF) GO TO 58 combustion i s taking place, processes combustion and expansion stroke. 55 CONTINUE assign i n i t i a l guess values for f r a c t i o n of fu e l burnt and the gas mixture temperature. 175 C 176 C 177 178 179 180 C 181 C 182 C 183 C 184 c 185 C 186 c 187 c 188 c 189 190 191 192 c 1 93 c 1 94 c 195 c 196 c 197 c 198 c 199 c 200 c 201 c 202 c 203 c 204 c 205 c 206 c 207 c 208 c 209 c 210 c 21 1 c 212 213 c 214 c 215 c 216 217 218 c 219 c 220 c 221 222 223 c 224 c 225 c 226 c 227 c 228 c 229 c 230 c 231 c 232 c IF (FRAC .LT.0.1D-20) FRAC X(1) = FRAC X(2) = P2 * V2 / R0 / NTOT 0.1D-6 useing modified Newton's method, the following two are c a l c u l a t e d i t e r a t i v e l y : FRAC - f r a c t i o n of f u e l burnt T2 - gas mixture temperature the f o l l o w i n g system of two nomlinear eqations are solved for X P - (nRT/V) 2 2 U - U + work - Qhtr 2 1 1 2 1 2 FRAC T2 DO 650 L650=1,50 given X, compute F CALL GETF(X;F,GAS,T1,P1,P2,V1,V2,NTOT, GASNEW,QHT,QC,TOTMAS,DH 01,DH 0,1HTRSF,IDS SOC) i f s o l u t i o n i s found, terminate the i t e r a t i o n . IF ((DABS(F(1)).LT.1.0).AND.(DABS(F(2)).LT.0.1E-4)) GO TO 59 formulate the Jacobian matrix of F as: dF/dX dF / dX dF / dX 1 1 1 2 dF / dX 2 1 dF / dX 2 2 1 6 7 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page - 5 233 C 234 DO 651 LJ=1,2 235 DO 652 LI=1,2 XEP(LI) = X(LI) 236 237 652 CONTINUE 238 XEP(LJ) = XEP(LJ) + EPSIL 239 CALL GETF(XEP,FEP,GAS,T1,P1,P2,V1,V2,NTOT, GASNEW,QHT,QC,TOTMAS,DH01,DH0,IHTRSF,IDSSOC) 240 1 241 DO 653 LI=1,2 242 DFDX(LI,LJ) = (FEP(LI)-F(LI)) / E P S I L 243 653 CONTINUE 244 651 CONTINUE 245 C 246 C the i t e r a t i o n scheme i s as fol l o w s : 247 C 248 C X = X + DX 249 C i + 1 i 250, c 251 c DX i s obtained by s o l v i n g 252 c (dFdX) DX = -F 253 c 254 c i i 255 c 256 c 257 F(1) = -F( 1 ) 258 F(2) = -F(2) 259 c 260 c the routine SLE i a a UBC L i b r a r y subroutine 261 c which solves a system of l i n e a r equations. 262 c 263 CALL SLE(2,2,DFDX,1,2,F,DX,I PERM,2,WORKAR, DET,JEXP) 264 1 265 c 266 DO 654 LI=1,2 267 X(LI) = X(LI) + DX(LI) 268 654 CONTINUE 269 650 CONTINUE 270 66 CONTINUE 271 C 272 C i t e r a t i o n f a i l e d , terminate the execution. 273 C 274 WRITE(6,913) L650, X(1), X(2) 275 GO TO 850 276 c 277 c s o l u t i o n found 278 c 279 59 CONTINUE 280 FRAC = X(1) 281 T2 = X(2) 282 58 CONTINUE 263 C 284 C compute the accumulated heatrelease, 285 C accumulated f r a c t i o n of f u e l burnt. 286 C 287 QCACCM = QCACCM + QC 288 IANGLE = ITH - 90 289 FRBURN = FRBURN + FRAC * FRREM 290 FRREM = 1 . 0 - FRBURN 168 L i s t i n g of DIG.HEAT.K at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 6 291 C 292 C write out the s o l u t i o n for the current C A . 293 C 294 WRITE(6,201) IANGLE, P2, T2, QHT, QC, QCACCM, 295 1 FRAC, FRBURN, V2 296 C 297 C s h i f t index for next C A . computation. 298 C 299 T1 = T2 300 P1 = P2 301 V1 = V2 302 DO 71 1=1,NGAS 303 DH01(I) = DHO(I) 304 71 CONTINUE 305 IF (ITH .LT. 80) GO TO 851 306 IF (ITH .GT. 170) GO TO 851 307 C 308 C write out the s o l u t i o n for p l o t t i n g purpose. 309 C 310 IF (IPLOT .NE. 1) GO TO 851 311 WRITE(1,205) ANGLE(ITH), P2 312 WRITE(2,205) ANGLE(ITH), T2 313 WR1TE(3,205) ANGLE(ITH), QCACCM 314 WRITE(4,205) ANGLE(ITH), QC 315 851 CONTINUE 316 C 317 C save the instantaneous gas mixture composition 318 C to write out at the end of the rate of heat release 319 C output. 320 C 321 IF (ITH .LT. (INJBEG -1) ) GO TO 50 322 DO 61 J=1,NGAS 323 GAS(J) = GASNEW(J) 324 SAVGAS(ITH,J) = GAS(J) 325 61 CONTINUE 326 C 327 C t h i s i s the end of the process for one C.A.. 328 C C A . i s incremented end the process proceeds 329 C to the next C A . . 330 C 331 50 CONTINUE 332 850 CONTINUE 333 C 334 C end of a l l the processese. 335 C write out the gas mixture composition for each C A . 336 C from the C A . just p r i o r to the d i e s e l i n j e c t i o n . 337 C 338 WRITE(6,202) 339 INJBM1 = INJBEG - 1 340 DO 72 ITH=INJBM1,180 341 IANGLE = ITH - 90 342 WRITE(6,203) IANGLE, (SAVGAS(ITH,J), J=1,NGAS) 343 72 CONTINUE 344 STOP 345 200 FORMAT('- CA P kPa T deg K, Q h t r . ( k J ) , Q r' 346 1 'elease , Q accum Frac Frac cum Vol') 347 201 FORMAT (IX,15,1 OEM.5) 348 202 FORMAT( 1IGas Comp(Kmol) Dsl CH4 N2 02 169 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 7 349 1 ' C02 H20 H2 OH CO 350 2 NO ' ) 351 203 FORMAT(1X,I 3,7X,10E10.4) 352 205 FORMAT(1X,2E14.6) 353 210 FORMATCl S-D Operation Speed = ',F6.1,' rpm, ', 1 ' bmep = ',F5.1,' kPa ') 354 355 211 FORMATCl D-F Operation Speed = ',F6.1,' rpm, ', 1 ' bmep = *,F5.1,' kPa ' ) 356 357 913 FORMATC- NO Conv in fr&T L, f r , T = ',I5,2E14.5) 358 914 FORMATC- F a i l e d to Smooth P data ') 359 END 360 C 361 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 362 c s 363 SUBROUTINE READPR 364 c s 365 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 366 c s 367 c This routine assigns valuse, for various gases, s 368 c density, molecular weight, enthalpy of formation, s 369 c number of d i f f e r e n t kind of gases considered, s 370 c i d e a l gas constant. s 371 c s 372 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 373 c 374 c 375 IMPLICIT REAL*8(A-H,0-2) 376 COMMON /PROP 1/ DENAIR,DENDSL,DENNG,WTDSL,WTNG,WTAIR 377 COMMON /THDYPR/ H0F(10),RO,WT(10),NGAS 378 c 379 c density 380 c 381 DENAIR = 0.337600E-01 382 DENDSL = 0.848900E+00 383 DENNG = 0.1B5760E-01 384 c 385 c molecular weight of intake gases 386 c 387 WTDSL = 0.170000E+03 388 WTNG = 0.160000E+02 389 WTAIR = 0.137280E+03 390 c 391 c number of d i f f e r e n t kind of gases considered, and 392 c the i d e a l gas constant. 393 c 394 NGAS = 10 395 R0 = 0.831425E+01 396 c 397 c enthalpy of formation at standard c o n d i t i o n . 398 c 399 H0F(1) = -.290871E+06 400 H0F(2) = -.748730E+05 401 H0F(3) = 0.000000E+00 402 H0F(4) = 0.000000E+00 403 H0F(5) = -.393522E+06 404 H0F(6) = -.241827E+06 405 H0F(7) = 0.000000E+00 406 H0F(8) = 0.394630E+05 170 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 8 407 408 409 410 41 1 412 413 414 4 1 5 416 417 418 4 1 9 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 C C C H0FC9) = -.110529E+06 H0F(10)= 0.905920E+05 molecular weight C C WT( 1) WT(2) WT(3) WT(4) WT(5) WT(6) WT(7) WT(8) WT(9) WT(10) RETURN END 0. 170000E+03 0.160400E+02 0.280130E+02 0.319990E+02 0.440100E+02 0.180150E+02 0.201600E+01 0.170070E+02 0.280100E+02 0.460000E+02 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s C s SUBROUTINE GEOMTR(CYLVOL, ANGLE) C s C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s C s C This routine assigns valuse for the engine geometry s C and computes c y l i n d e r volume at each C A . s C s C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s c IMPLICIT REAL*8(A-H,0-Z) c c c c c COMMON / GEOM / ARM, ROD, BORE, STROKE, VCLEAR REAL*B CYLVOLO80), ANGLE(180) Computes V, ANGLE for Theta=-90,89 (Crank Angle) XAREA ARMSQ RODSQ RADPDG in cu. meter 3.14* BORE * BORE / 4.0 ARM * ARM ROD * ROD 3.14 / 180.0 100 compute c y l i n d e r volume ITH1 = -89 ITH2 = 90 DO 100 ITH=ITH1,ITH2 TH = DFLOAT(ITH) RD = TH * RADPDG X = ROD+ARM*(1.O-DCOS(RD))-DSQRT(RODSQ-ARMSQ*DSIN(RD)**2) CYLVOL(ITH+90) = XAREA * X + VCLEAR ANGLE(ITH+90) = TH CONTINUE C C 171 L i s t i n g of DIG.HEAT.N at 20:4B:34 on MAY 28, 1984 for CCid=AFPH Page _ 9 465 RETURN 466 END 467 C 468 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 5 s s s s s s s s s s s s s s s s s s s 469 c S 470 SUBROUTINE DATAIN(GAS, P, DSLAMT,INJBEG,INJEND,IGNBEG) 471 c s 472 C S S S S S S S S S 5 S S S S S S S S S S S S S S S S S S S S S S S S S S S S S 5 S S S S S S S S S S S S S S S S S 5 S S 473 c S 474 c This routine reads in the data for i n j e c t i o n and s 475 c i g n i t i o n c h a r a c t e r i s t i c s , c y l i n d e r pressure, engine s 476 c speed, BMEP, flow rates of a i r , gas, d i e s e l . s 477 c The flow rates are converted to number of Kmoles s 478 c per c y c l e r . s 479 c s 480 C S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S 5 S S 5 481 c 482 IMPLICIT REAL*8(A-H,0-Z) 483 c 484 COMMON / EXPMT / SPEED, BMEP 485 COMMON / PROP 1 / DENAIR, DENDSL, DENNG, WTDSL, 486 1 VJTNG, WTAIR 487 REAL*8 GAS(10), P(180) 488 c 489 c Reads in from Log Unit 10 490 c 491 c SPEED - engine speed in rpm 492 c BMEP - load in p s i 493 c 494 c QAIR - a i r flow in ft3/min 495 c QDSL - d i e s e l flow i n l t r / h r 496 c QNG - nat gas flow in ft3/min 497 c 498 c INJBEG - beginning of d i e s l i n j in deg C A . 499 c INJEND - end of d i e s e l i n j in deg C A . 500 c IGNBEG - beginning of i g n i t i o n in deg C A . 501 c " 502 c P(1-180) - c y l i n d e r pressure in p s i 503 c 504 c 505 READ(10,100) SPEED, BMEP 506 READ(10,101) QAIR, QDSL, QNG 507 READ(10,102) INJBEG,INJEND,IGNBEG 508 c 509 JA = 1 510 DO 10 L=1,36 51 1 JB = JA + 4 512 READ(10,103) (P(J), J=JA,JB) 513 JA = L * 5 + 1 514 10 CONTINUE 515 c 516 c convert pressure data from p s i to kPa 517 c 518 DO 20 J=1,180 519 P(J) = P(J) * 6.895 520 20 CONTINUE 521 c 522 c compute # of moles per c y c l e : 172 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 10 523 C 524 C GAS(2) - nat gas 525 c (3) - N2 526 c (4) - 02 527 c 528 DO 30 L=1,20 529 GAS(L) = 0.0 530 30 CONTINUE 531 c 532 c making sure of # of c y l i n d e r = 4 533 c 534 GAS(2) = QNG * DENNG / SPEED * 2.0 / WTNG / 4.0 535 AIRMOL = QAIR * DENAIR / SPEED * 2.0 / WTAIR 536 GAS(3) = 3.76 * AIRMOL / 4.0 537 GAS(4) = AIRMOL /4.0 538 c 539 c compute amount of d i e s e l i n j e c t e d i n kmoles 540 c 541 DSLAMT = QDSL / 60.0 * DENDSL / SPEED * 2.0 / WTDSL / 4.1 542 c 543 c 544 RETURN 545 100 FORMAT(1X, F6.1, 1X, F5.1) 546 101 FORMAT(IX, F5.1, 1X, F5.2, 1X, F5.2) 547 102 FORMAT(IX,3(13,IX)) 548 103 FORMAT(IX, 5(F6.1,1X)) 549 END 550 c 551 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 552 c s 553 SUBROUTINE UPROD(P1,P2,T1,T2,V1,V2,GAS,GASNEW,DHO1,FRAC, 554 1 DHO,NTOT,TOTMAS,U2RES,QC,QHT,ICOMB,IHTRSF) 555 c s 556 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 557 c s 558 c This routine checks out whether the f i r s t law i s met. s 559 c The deviance from the f i r s t law i s designated by U2RES.S 560 c s 561 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 562 c 563 IMPLICIT REAL*8(A-H,0-Z) 564 c 565 REAL*8 GAS(10),GASNEW(10),R1(10),DH01(10),DH0(10),NTOT 566 COMMON /THDYPR/ H0F(10), R0, WT(10), NGAS 567 c 568 WORK = 0.5D0 * (PI + P2) * <V2 - V1) 569 c 570 CALL DH0FN(T2,DH0) 571 c 572 IF (ICOMB .EQ. 0) GOTO 5 573 c 574 c compute the heat release due to combustion during 575 c the current C A . i n t e r v a l . 576 c 577 QC = O.ODO 578 DO 20 1=1,NGAS 579 QC = QC + (GASNEW(I) - GAS(I)) 580 1 * (H0F(I) + DH0(I) - R0 * T2) 173 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 11 581 20 CONTINUE 582 C 583 QC = -QC 584 C 585 5 CONTINUE 586 IF (I COMB .EQ. 0) QC = 0.0 587 C 588 C 589 DU = 0.D0 590 R0DT = R0 * (T2 - T l ) 591 DO 30 1=1,NGAS 592 DU = DU + GAS(I) * (DHO(I) - DHO1(1) - R0DT) 593 30 CONTINUE 594 C 595 C comput heat t r a s f e r . 596 C i f IHTRSF i s set to 0, a d i a b a t i c processe i s 597 C assumed. 59B C 599 QHT = 0.D0 600 IF (IHTRSF .NE. 1) GO TO 10 601 QHT = QHTRSF(T2,V2,GASNEW,TOTMAS) 602 C 603 10 CONTINUE 604 U2RES = DU + WORK - QC - QHT 605 c 606 RETURN 607 END 608 c 609 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 610 c s 61 1 SUBROUTINE STCHPD(GAS,FRAC,GASNEW) 612 c s 613 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 614 c s 615 c T h i s routine computes the number of Kmoles of s 616 c s t o i c h i o m e t r i c combustion product, and y i e l d the s 617 c updated composition of the gas mixture in the s 618 c c y l i n d e r . s 619 c s 620 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 621 c 622 IMPLICIT REAL*8(A-H,0-2) 623 c 624 COMMON /THDYPR/ HOF(lO), R0, WT(10), NGAS 625 REAL*8 GAS(10), GASNEW(lO), N, M 626 c 627 c M - number of moles of d i e s e l burnt at current C A . 628 c N - .. CH4 629 c 630 M = GAS(1) * FRAC 631 N = GAS(2) * FRAC 632 c 633 GASNEW(1) = GAS(1) - M 634 GASNEW(2) = GAS(2) - N 635 GASNEW(3) = GAS(3) 636 GASNEW(4) = GAS(4) - 18.5*M - 2.0*N 637 GASNEW(5) = GAS(5) + 12.0*M + N 638 GASNEW(6) = GAS(6) + 13.0*M + 2.0*N 174 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 12 639 DO 10 1=7,NGAS 640 GASNEW(I) = GAS(I) 641 10 CONTINUE 642 C 64 3 RETURN 644 END 645 C 646 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 647 C s 648 SUBROUTINE SMOOTP(P, ANGLE, IGNBEG, IPOK) 649 C s 650 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 651 C s 652 C This routine uses Cubic-Spline-Least-Squares-Fit s 653 C to smooth the c y l i n d e r pressure data. s 654 C The rate of pressure r i s e i s numerically computed s 655 C from the UNSMOOTHED data, and t h i s i s used in s 656 C weight to c o n t r o l the degree of l o c a l smoothness. s 657 C The weighting i s based on scatterness the of slop ofs 658 C of the pressure data. s 659 C s 660 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 661 C 662 IMPLICIT REAL*8(A-H,0-Z) 663 C 664 REAL* 8 P(180), DPDTHO80), TOL(lBO), ANGLE ( 1 80) 665 REAL*8 PDl(lBO), PD2(180) 666 REAL*8 W(2000) 667 C 668 C compute dp/dTheta by f i t t i n g a quadratic through 669 C 3 points 670 C 671 DO 5 J=2,179 672 DPDTH(J) = (P(J+1) - P ( J - l ) ) / 2.DO 67 3 5 CONTINUE 674 DPDTH(1) = (4.D0*P(2) -3.D0*P(1) -P(3)) /2.D0 675 DPDTHC180) = (3.D0*P(180)-4.D0*P(179)+P(17B))/2.DO 676 C 677 C TOL0 c o n t r o l s the l o c a l smoothness. 678 C SVAL .. the gl o b a l 679 C 680 TOL0 = 1.0 681 SVAL = 1000.0 682 IPOK = 1 683 DO 10 1=4,177 684 JS = I - 3 685 JF = I + 2 686 AV = 0.0 687 DO 11 J=JS,JF 688 AV = AV + DPDTH(J) 689 11 CONTINUE 690 AV = AV / 10.0 691 C 692 C SD i s a measure of scatterness in the slop of 693 C of the pressure data. This i s computed by 694 C co n s i d e r i n g 4 adjacent p o i n t s . 695 C 696 SD = 0.0 175 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 13 697 DO 12 J=JS,JF 698 SD = SD + DABS(DPDTH(J) - AV)**2 699 12 CONTINUE 700 TOL(I) = TOL0 * DABS(SD / AV / AV) 701 C 702 C The degree of smoothness i s l e s s forced for 703 C the points befor the s t a r t of i g n i t i o n . 704 C 705 IF (DABS(DFLOATCI-IGNBEG)).LT.5.0) TOL(I)=TOL(I)/10 706 10 CONTINUE 707 DO 20 1=1,3 708 TOL(I) = TOL(4) 709 20 CONTINUE 7 1 0 DO 30 1=178,180 71 1 TOL(I) = TOL(177) 712 30 CONTINUE 713 C 714 C The routines DSPLFT and DSPLN are UBC L i b r a r y 715 C subroutines, which performs Least-Squares-Fit 716 C with Cubic-Spline as basis f u n c t i o n s . 717 C 718 CALL DSPLFT (ANGLE, P, TOL, SVAL, 180,W,5,613) 719 CALL DSPLN (ANGLE, P,PD1 ,PD2, 180,5.61 3) 720 RETURN 721 c 722 613 CONTINUE 723 c 724 c The f i t has f a i l e d 725 c 726 IPOK = 0 727 RETURN 728 END 729 c 730 C S S S S S S S S 5 S S S S 5 S S 5 S S S S S S S S S S S S S S S S S S S S S S S 5 S S S S S S S S S S S S S S S 5 731 c s 732 SUBROUTINE VISCST(T,GAS,VISC) 733 c s 734 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 735 c s 736 c computes mean v i s c o u s i t y of gas mixtures. s 737 c s 738 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 739 c 740 IMPLICIT REAL*8(A-H,0-Z) 741 c 742 REAL*8 GAS(10) 743 COMMON /THDYPR/ H0F(10),R0,WT(10),NGAS 744 c 745 TM = T**0.645 746 VISC = GASO) * WT(1) * 1.33 747 VISC = VISC + GAS(2) * WT(2) * 3.35 748 VISC = VISC + GASO) * WT(3) * 4.57 749 VISC = VISC + GAS(4) * WT(4) * 5.09 750 VISC = VISC + GAS(5) * WT(5) * 3.71 751 VISC = VISC + GAS(6) * WT(6) * 3.26 752 c 753 TOTW = GAS(1)*WT(1)+GAS(2)*WT(2)+GAS(3)*WT(3) 754 1 + GAS(4)*WT(4)+GAS(5)*WT(5)+GAS(6)*WT(6) 176 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCicUAFPH Page 14 755 C 756 VISC = VISC / TOTW * 10.**(-7) * TM 757 RETURN 758 END 759 C 760 C 761 C 762 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 763 c f 764 DOUBLE PRECISION FUNCTION QHTRSF(T2,V2,GASNEW,TOTMAS) 765 c f 766 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 767 c f 768 c This routine computes the heat t r a n s f e r at current f 769 c Annand's model i s used. f 770 c f 771 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 772 c 773 IMPLICIT REAL*8(A-H,0-Z) 774 c 775 COMMON / GEOM / ARM,ROD,BORE,STROKE,VCLEAR 776 COMMON /EXPMT / SPEED, BMEP 777 REAL*8 GASNEW(10) 778 c 779 c This routine employees Annand's model to 780 c compute the rate of heat t r a n s f e r . 781 c 782 A = 0.47D0 783 C = 1.6D-12 784 CP = CP0VAL(T2,GASNEW) / TOTMAS 785 30 CONTINUE 786 PISVEL = SPEED * STROKE / 30.0 787 CALL VISCST(T2,GASNEW,VISC) 788 DENTOT = TOTMAS / V2 789 RENUM = DENTOT * PISVEL * BORE / VISC 790 REKD = CP * VISC / 0.7 / BORE * RENUM**(0.7) 791 c 792 c The wall temperature i s assumed to be pr o p o r t i o n a l 793 c to the a p p l i e d load. 794 c 795 TW = 0.484 * BMEP + 540.0 796 c 797 c The suface are of the c y l i n d e r 798 c 799 SURFA = (V2 - VCLEAR) * 4.DO / BORE + 0.0304D0 800 QCONVC = A * SURFA * REKD* (T2 - TW) 801 QRAD = (1.6E-12)*(10.76)*C*SURFA*(T2**4-TW**4) 802 c 803 c 804 QHTRSF = -(QCONVC + QRAD) * (60./SPEED/360.) 805 c 806 c 807 c 808 RETURN 809 END 810 c 811 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 812 C S 177 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 15 813 SUBROUTINE DSSOCN(P,T,GAS1,GAS2,NTOT) 814 C S B15 C S 5 S S S S S S S S S S S S S S S S S S 5 S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S 5 816 c s 817 c This routine computes the e q u i l i b r i u m d i s s o c i a t i o n s 818 c products. The t h e o r e t i c a l d e t a i l s i n c l u d i n g the s 819 c numerical methods are described i n the extern a l s 820 c documentation. s 821 c s 822 c The reactions considered are: s 823 c s 824 c 1. CO <==> CO + 1/2 0 s 825 c 2 2 s 826 c s 827 c 2. H O <==> 1/2 H + OH s 828 c 2 2 s 829 c 5 830 c 3. H O <==> H + 1/2 O s 831 c 2 2 2 s 832 c s 833 c 4. 1/2 N + 1 / 2 0 <==> NO s 834 c 2 2 s 835 c 5 836 C S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S S 5 837 c 838 IMPLICIT REAL*8(A~H,O-Z) 839 c 840 COMMON /THDYPR/ HOF(10),R0,WT(10),NGAS 841 REAL*8 GAS1(10), GAS2O0), NTOT 842 REAL*8 K(4), F(5), FEP(5),KPOP(4), DX(5), X(5), XEP(5) 843 REAL*8 WORKDB(5,5), DXDBL(5), FDBL(5),DFDXDB(5,5),DETDBL 844 INTEGER I PERM(10) 845 c 846 SUMN = 0.0 847 DO 5 1=1,NGAS GAS2(I) = GAS 1(I) 848 849 SUMN = SUMN + GAS 1(I) 850 5 CONTINUE 851 c 852 IF (GAS1(5) .GE. 0.1E-20) GO TO 500 853 NTOT = SUMN 854 RETURN 855 c 856 c 857 500 CONTINUE 858 c 859 c compute the e q u i l i b r i u m constants for the given 860 c temperature. 861 c 862 K(1) = DEXP(DLOG(T)**(-7.4721)*(-0.65549E+8)+10.53) 863 K(2) = DEXP(DLOG(T)**(-7.0457)*(-0.30372E+8)+l0.159) 864 K(3) = DEXP(DLOG(T)**(-6.8674)*(-0.18879E+8)+8.7095) 865 K(4) = DEXP(DLOG(T)**(-7.3355)*(-0.16593E+8)+1.80127) 866 c 867 POP = 101.325DO/P 868 KP0P(1) = K(1) * K(1)*P0P 869 KP0P(2) = K(2) * K(2)*P0P 870 KP0P(3) = K(3) * K(3)*P0P 178 L i s t i n g of DIG.HEAT.N at.20:48:34 on MAY 28, 1984 for CCid=AFPH Page 871 KPOPU) = K(4) * K(4) 872 C 873 C i f the reactions are i n s i g n i f i c a n t , then s k i p . 674 C B75 RMK =0.0 876 DO 10 1=1,4 IF (DABS(KP0P(I ) ) .GT. RMK) RMK = DABSCKPOPdi 677 878 10 CONTINUE 879 IF (RMK .GT. 0.1E-5) GO TO 20 880 NTOT = SUMN 881 RETURN 882 c 883 c 884 20 CONTINUE 885 C 886 C i n i t i a l guess 887 C . 888 X(1) = K(1)*DSQRT(P0P/SUMN/GAS1(4))*GAS1(5) 889 X(1) = X(1) - GAS 1(9) / SUMN 890 X(3) = K(3)*DSQRT(P0P/SUMN/GAS1(4))*GAS1(6) 891 X(3) = X(3) - GAS 1(7) / SUMN 892 X(2) = K(2)*DSQRT(P0P/SUMN)*GAS1(6) 893 X(2) = X(2)/DSQRT(DABS(GAS1(7)+X(3)*SUMN)) 894 X(2) = X(2) - GAS1(8)/SUMN 895 X(4) = K(4)*DSQRT(GAS1(3)*GAS1(4))/SUMN 896 X(4) = X(4) - GAS 1 (10)/SUMN 897 X(5) = SUMN 898 40 CONTINUE 899 C 900 c Solve for X using modified Newton's method. 901 c The method i s p r e c i s e l y the same as that in 902 c the main routine, and the notaions are a l s o 903 c nearly the same. 904 c 905 TOL = DABS (KPOPU) ) * 0.1 D-4 906 DO 50 L=1,100 . 907 CALL EVALF(X,GAS2,KP0P,SUMN,F) 908 c 909 c I t i s s u f f i c i e n t to check only the F(4 ) , 910 c since i t i s the most slowly converging term. 91 1 c 912 IF (DABS(F(4)) .LT. TOL) GOTO 300 913 c 914 DO 51 LJ=1,5 915 EPSIL = DSQRT(0.1D-12+0.1D0*DABS(X(LJ))) 916 DO 52 LI=1,5 917 XEP(LI) = X(LI) 918 52 CONTINUE 919 XEP(LJ) = XEP(LJ) + EPSIL 920 CALL EVALF(XEP,GAS2,KP0P,SUMN,FEP) 921 DO 53 LI=1,5 922 DFDXDB(LI,LJ) = (FEP(LI)-F(LI)) / EPSIL 923 53 CONTINUE 924 51 CONTINUE 925 c 926 DO 55 LI=1,5 FDBL(LI) = -F(LI) 927 928 55 CONTINUE 179 L i s t i n g of DIG.HEAT.K at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 17 929 C 930 C Again, SLE i s a UBC L i b r a r y subroutine, which 931 C solves a system of l i n e a r equations. 932 C In s o l v i n g the systems of equations, the routine 933 C r e t a i n s the decomposed matrix. 934 C 935 CALL SLE(5,5,DFDXDB,1,5,FDBL,DXDBL,I PERM,5,WORKDB, 936 1 DETDBL,JEXB) 937 C 938 DO 54 LI=1,5 939 X(LI) = X(LI) + DXDBL(LI) 940 54 CONTINUE 94 1 NTOT = X(5) 942 A = X(1) * NTOT 94 3 B = X(2) * NTOT 944 C = X(3) * NTOT 94 5 D = X(4) * NTOT 946 GAS2(3) = DABS(GAS1(3) - 0.5*D) 947 GAS2(4) = DABS(GAS1(4) + 0.5MA+C-D)) 948 GAS2(5) = DABS(GAS1(5) - A) 949 GAS2(6) = DABS(GAS1(6) - B - C) 950 GAS2(7) = DABS(GAS1(7) + 0.5*B + C) 951 GAS2(8) = DABS(GAS1(8) + B) 952 GAS2(9) = DABS(GAS1(9) + A) 953 GAS2O0) = DABS (GAS 1(10) + D) 954 C 955 C Here, once a Jacobian matrix i s formed for F, 956 C i t i s used for 3-4 i t e r a t i o n s , thus reducing 957 C the cos t . 958 C 959 DO 70 J70=1,3 960 CALL EVALF(X,GAS2,KP0P,SUMN,F) 961 DO 71 LI=1,5 962 FDBL(LI) = -F(LI) 963 71 CONTINUE 964 C 965 C The routine DBS i s a l s o a UBC L i b r a r y r o u t i n e . 966 C The routine uses the decomposed matrix by the 967 C routine SLE to very economically compute new 968 C s o l u t i o n with newly given FDBL 969 C 970 CALL DBS(5,1,5,FDBL,DXDBL,I PERM,5,WORKDB) 971 DO 73 LI=1,5 972 X(LI) = X(LI) + DXDBL(LI) 97 3 73 CONTINUE 974 C 975 C update the composition of the gas mixture. 976 C 977 NTOT = X(5) 978 A = X(1) * NTOT 979 B = X(2) * NTOT 980 C = X(3) * NTOT 981 D = X(4) * NTOT 982 GAS2(3) = DABS(GAS1(3) - 0.5*D) 983 GAS2(4) = DABS(GAS 1(4) + 0.5*(A+C-D)) 984 GAS2(5) = DABS(GAS1(5) - A) 985 GAS2(6) = DABS(GAS1(6) - B - C) 986 GAS2(7) = DABS(GAS1(7) + 0.5*B + C) 180 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 18 987 GAS2(8) = DABS(GAS1(8) + B) 988 GAS2(9) = DABS(GAS1(9) + A) 989 GAS2O0) = DABS (GAS 1(10) + D) 990 70 CONTINUE 991 50 CONTINUE 992 C 993 C I t e r a t i o n has f a i l e d . The execution w i l l terminate 994 c with a proper e r r o r message. 995 c 996 WRITE(6,213) 997 STOP 998 c 999 c mission completed. E x i t . 1 000 c 1001 300 CONTINUE 1002 RETURN 1003 213 FORMATC- xXxXxXxXxX F a i l to Converge in Dssocn xXxXxX 1 004 END 1005 c 1006 c 1007 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 1008 c s 1009 SUBROUTINE EVALF(X,N,KP0P,SUMN,F) 1010 c S 1011 C S S S S S S S S S S S S S S S S S S S S S S 5 S S S S S S S S S S S S S S S S S S S S S S S S 5 S S S S S 1012 c s 1013 c This routine checks the appropriateness of s 1014 c the given p o s s i b l e s o l u t i o n for the s 1015 c e q u i l i b r i u m d i s s o c i a t i o n . The d e v i a t i o n i s s. 1016 c designated by the vector F. s 1017 c s 1018 C S S S S S S S S S 5 S S S S S S S S S S S S S S S S S S S S S S S S S S S 5 S S S S S S S S S S S S S S S 1019 c 1020 IMPLICIT REAL*8(A-H,0-Z) 1021 c 1022 REAL*8 X(5), N(10), KP0P(4), F(5), NTOT 1 023 c 1024 NTOT = X(5) 1025 c 1026 TERM1 = N(4)/NTOT+0.5*(X(1)+X(3)-X(4)) 1027 TERM2 = (N(7)/NTOT + 0.5*X(2) + X(3)) 1 028 TERM3 = (N(3)/NTOT-0.5*X(4))*(N(4)/NTOT 1029 1 +0.5*(X(1)+X(3)-X(4))) 1030 c 1031 F(1) = (N(9)/NTOT+X(1))**2*TERM1/(N(5)/NTOT-X(1))**2 1032 1 - KP0P(1) 1033 F(2) = TERM2*(N(B)/NTOT+X(2))**2/(N(6)/NTOT-X(2)-X(3)) 1034 1 - KP0P(2) 1035 F(3) = TERM2**2 * TERM1 1036 1 /(N(6)/NTOT-X(2)-X(3))**2 - KP0P(3) 1037 F(4) = (N(10)/NTOT+X(4))**2/TERM3 1038 1 -KP0P(4) 1039 F(5)- = (SUMN-NTOT)-0.5D0*(X(1)+X(2)+X(3))*NTOT 1 040 c 1041 c 1042 RETURN 1043 END 1044 c 181 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 19 1045 C 1046 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 1047 c s 1048 SUBROUTINE GETF(X,F,GAS,T1,P1,P2,V1,V2,NTOT, 1049 1 GASNEW,QHT,QC,TOTMAS,DHO1,DHO,IHTRSF,IDSSOC) 1050 c s 1051 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 1052 c s 1053 c This routine checks the appropriateness of the given s 1054 c p o s s i b l e s o l u t i o n s for the requrements for the f i r s t s 1055 c law and the i d e a l gas law. Th i s routine i s used in s 1056 c the main routine for computing the f r a c t i o n of f u e l s 1057 c burnt and T2. s 1058 c s 1059 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 1060 c 1061 IMPLICIT REAL*8(A-H,0-Z) 1062 c 1063 REAL*8 X(2),F(2),GAS(10),GASNEW(10),DH0(10) ,DH01 (10) 1 064 REAL*8 NTOT,GASNE0(20) 1065 COMMON /THDYPR/ H0F(10),R0,WT(10),NGAS 1 066 c 1067 FRAC = X(1) 1068 T2 = X(2) 1069 c 1 070 IF (IDSSOC .EQ. 0) GO TO 50 1071 CALL STCHPD(GAS,FRAC,GASNE0) 1072 CALL DSSOCN(P2,T2,GASNE0,GASNEW,NTOT) 1073 GO TO 51 1 074 50 CONTINUE 1075 CALL STCHPD(GAS,FRAC,GASNEW) 1076 51 CONTINUE 1 077 CALL UPROD(P1,P2,T1,T2,V1,V2,GAS.GASNEW,DHO1,FRAC, 1078 1 DHO,NTOT,TOTMAS,U2RES,QC,QHT,1,IHTRSF) 1 079 c 1 080 F(1) = P2 - NTOT * R0 * T2 / V2 1 081 F(2) = U2RES 1082 c 1083 c 1 084 RETURN 1085 END 1086 c 1087 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 1088 c f 1089 DOUBLE PRECISION FUNCTION CP0VAL(T,GAS) 1090 c f 1091 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 1092 c f 1093 c T h i s routine computes the mean value of the s p e c i f i c f 1094 c heat Cp. f 1095 c f 1096 C f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f f 1097 c 1098 IMPLICIT REAL*8(A-H,0-Z) 1099 c 1 100 COMMON /THDYPR/ H 0 F(10), R0, WT(10),NGAS 1101 REAL*8 GAS(10), C P 0(10), NTOT 1 102 c 182 L i s t i n g of DIG.HEAT.N at 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 20 103 C 104 TH = T / 100.0 105 TH2 = TH * TH 106 TQ = TH**(0.25) 107 TQ2 = TQ * TQ 108 TQ2 = TQ * TQ * TQ 109 TQ6 = TQ3*TQ3 110 C 1 1 1 CP0C1) = 104.18 + 465.5 * (T / 1000.0) 1 12 CP0(2) = -672.87 + 439.74*TQ - 24.875*TQ3 + 323.88/TQ2 1 13 CP0(3) = 39.06-512.79/TQ6+1072.7/TH2-820.4/(TH**3) CP0(4) = 37.432 + 0.020102*TQ6-178.57/TQ6+236.88/TH2 1 14 115 CP0(5) = -3.7357+30.529*TQ2-4.1034*TH+0.024198*TH2 1 16 CP0(6) = 143.05-183.54*TQ+82.751*TQ2-3.6989*TH 1 17 CP0(7) = 56.505-702.74/TQ3+1165.O/TH-560.7/TQ6 118 CP0(8) = 81.546-59.35*TQ+17.329*TQ3-4.266*TH 1 19 CP0(9) = 69.145-0.70463*TQ3-200.77/TQ2+l76.76/TQ3 120 CP0(10)= 46.045+216.1/TQ2-363.66/TQ3+232.55/TH2 121 C 122 CPOVAL = 0.0 123 C DO 20 1=1,NGAS 124 DO 20 I=2,NGAS 125 CPOVAL = CPOVAL + CP0(I) * GAS(I) 126 20 CONTINUE 1 27 C 1 28 C 1 29 RETURN 1 30 END 131 C 132 C 133 C 134 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 135 c 5 136 SUBROUTINE DH0FN(T,DH0) 137 c s 138 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 1 39 c s 140 c This routine computes the change in enthalpy s 141 c between the given temperature and 298 deg K. s 142 c s 143 c The unit f or DH0O-10) i s kJ/Kmol-K s 144 c s 145 C s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s s 146 c 147 IMPLICIT REAL*8(A-H,0-Z) 148 c 149 REAL*8 DH0(10) 1 50 c 151 T2 = T*T 152 T3 = T*T*T 153 TQ2 = DSQRT(T) 154 TQ = DSQRT(TQ2) 1 155 TQ3 = TQ * TQ2 1156 TQ5 = T * TQ 1 157 TQ6 = T * TQ2 1 158 TQ7 = T * TQ3 1 159 c 1 160 DH0(1) = 104.18*T+0.23276*T2-51714.3 183 L i s t i n g of 161 162 163 1 64 165 166 167 1 68 169 170 171 172 173 174 175 176 1 77 178 179 180 181 182 183 1 84 185 186 187 188 189 1 90 191 DIG.HEAT.N at C DHO(2) = C DH0(3) = C DH0(4) = DHO(5) = DHO(6) • DH0(7) = DHO(8) -DHO(9) = DHO(10)= C C 20:48:34 on MAY 28, 1984 for CCid=AFPH Page 21 -672.B7*T+111.25*TQ5-0.449495*TQ7+6477.6*TQ2 -39442.6 39.06*T+0.102558D7/TQ2-0.10727D8/T+0.4102D9/T2 -39672.7 37.432*T+0.0080408D-3*T2*TQ2+0.35714D6/TQ2 -0.23688D7/T - 23906.6 -3.7357*T+2.0353*TQ6-2.0517D-2*T2 +0.008066D-4*T3 - 7556.3 143.05*T-46.432*TQ5+5.51667*TQ6-0.0184 94 5*T2 - 11876.4 56.505*T-0.8889D5*TQ+0.1165D6*DLOG(T) + 0.11214D7/TQ2 - 376187.0 81.546*T-15.0144*T5+0.313137*TQ7-0.0213 3*T2 -10509.4 69.145*T-0.0127328*TQ7-0.40154D4*TQ2 +0.223586D5*TQ - 43912.9 59.283*T-0.11397 3*T6-0.141226D4*TQ2 - 0.149778D6/TQ2 + 15975.8 RETURN END 

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