{"http:\/\/dx.doi.org\/10.14288\/1.0105938":{"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool":[{"value":"Applied Science, Faculty of","type":"literal","lang":"en"},{"value":"Mechanical Engineering, Department of","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider":[{"value":"DSpace","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#degreeCampus":[{"value":"UBCV","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/creator":[{"value":"Fandrich, Helmut Edward","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/issued":[{"value":"2011-12-09T22:59:59Z","type":"literal","lang":"en"},{"value":"1962","type":"literal","lang":"en"}],"http:\/\/vivoweb.org\/ontology\/core#relatedDegree":[{"value":"Master of Applied Science - MASc","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#degreeGrantor":[{"value":"University of British Columbia","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/description":[{"value":"The high speed 2-stroke cycle engine designed for high power-to-weight ratio is relatively inefficient at part throttle. It would be advantageous to incorporate a simple method of allowing extra air to enter the cylinder prior to the fresh mixture, thus stratifying the charge and increasing the proportion of the air-fuel mixture retained in the cylinder at part loads while not deleteriously affecting the maximum power at full throttle. A series of tests, on an engine fitted with a reed valve connecting the atmosphere to the passageway leading to intake ports, were carried out with varying amounts of extra air, the results showed that power, speed, thermal efficiency, and fuel trapping efficiency gave increases at nearly all settings, but with a large excess of extra air, the air-fuel ratio through the carburetor had to be decreased to maintain stable operation.","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO":[{"value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/39619?expand=metadata","type":"literal","lang":"en"}],"http:\/\/www.w3.org\/2009\/08\/skos-reference\/skos.html#note":[{"value":"STRATIFIED CHARGE SCAVENGING OF A TWO-STROKE ENGINE AT PART THROTTLE by. HELMUT EDWARD FANDRICH B . A . S c , U n i v e r s i t y o f B r i t i s h Columbia , i960 \u2022A THESIS SUBMITTED IN PARTIAL.FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF ' MASTER OF APPLIED SCIENCE . \u2022 i n . t h e Department o f M e c h a n i c a l E n g i n e e r i n g We accept t h i s t h e s i s as conforming t o the r e q u i r e d s tandard THE UNIVERSITY OF BRITISH COLUMBIA September, 1962 \u2022 In. presenting: this thesis.in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes\u2022may be granted'by the Head of my Department\u2022or by his representative. It . is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Mechanical Engineering, The University of British Columbia, Vancouver 8,' B.C.., Canada. September, 1962. ABSTRACT The high speed 2-stroke cycle engine designed for-high power-tovweight ratio is relatively inefficient at part throttle. It would be advantageous to incorporate a simple method of allowing extra air to enter the cylinder prior to the fresh mixture, thus stratifying the charge and increasing the proportion of the air-fuel mixture retained in the cylinder at part loads while not deleteriously affecting.the maximum power at fu l l throttle. .A series of tests, on an engine fitted with a reed valve connecting the atmosphere to the passageway leading to intake ports, were carried out with varying amounts of extra air; the results showed that power, spped, thermal efficiency, and fuel trapping efficiency gave increases at nearly a l l settings, but with a large excess of extra air,.the air-fuel ratio through the carburetor had to be decreased to maintain stable operation. vi ACKNOWLEDGEMENT The experimental work, described in.this report was carried out in the Mechanical Engineering Laboratory at the University of British Columbia and the calculations performed at the University Computing Centre. The use of these facil it ies is gratefully acknowledged. To a l l the people who made this project possible,.the author would like to express-his thanks. Particular thanks are due to the following: Professor W.O. Richmond for his valuable guidance and assistance during a l l phases of the project and for the use of the facil it ies of the Mechanical Engineering Department; Professor J . Young for his direction during the in i t ia l stages of this project; Power Machinery Limited of Vancouver, and Mr. Jack Stainsby in particular for their co-operation and for supplying the engine and spare parts, and fabricating special parts; Consolidated Mining and Smelting Company of Trail for making this project financially possible through the Cominco Fellowship and Grant. i i i TABLE OF CONTENTS' CHAPTER PAGE I. Introduction 1 II. Previous Work . 1 5 III. Details of Test. Arrangement 2 3 IV. Details of Test Procedure 3 3 V. Discussion and Results 3 7 VI. Summary and Conclusions 1 3 2 :APPENDIX I. Glossary 1 3 6 II. Symbols I 3 8 III. Efficiency Derivation 142 IV. Tables of Observed Results 149 V. Tables of Calculated Results 1 5 6 BIBLIOGRAPHY 163 iv LIST OF FIGURES Number Page 1= Schematic view of a 2-cycle engine with a reed valve 2 positioned 2. Theoretical relationships between scavenging efficiency 8 and trapping efficiency and scavenging ratio 0 3- Theoretical realtionsips between scavenging efficiency, 11 trapping efficiency, and scavenging ratio for stratified charge operation .4. Theoretical relationships between trapping efficiency, 13 and scavenging ratio for stratified charge-operation at part throttle \u20225. Russian \"Jet Ignition\" engine lo 6. I.F.P. engine modified for heterogeneous carburetion 17 .7\u00b0' Combustion chamber for Broderson method of stratification 18 8. Ricardo system of stratification in a 2-stroke engine 19 9- Stephenson method of stratification in a 2-stroke engine 20 10. . A crossrsection of the scavenging air valve 23 11. A photograph of the scavenging air valve arrangement 24 12. General view of engine on test bed 1 25 13. View of instrumented engine 26 14. Readout instruments 29 15- Sample photograph of peak combustion pressures 32 16- 20. Performance curves with TP 50$, Jet ,20\/l6, NS 4700, from 41 sheet 20 21^26. Performance curves with TP' 50$, Jetl6\/l6, NS 4500, from kQ sheet 17 27-32. Performance curves with TP 50$, J e t -lk\/l6, NS 4900, from 55 sheet 15 33-38. Performance curves with TP 60$, Jet F\/A, NS ,$000, from 62 sheet 21 LIST OF FIGURES (cori't) Number Page 3 9 - 2 + 3 . Performance curves with TP 85$, \u2022 Jet 1 7 \/ l 6 , NS 5300, 6 9 from sheet 19\u2022 . 44-48. Performance curves with TP 100$, Jet l 4 \/ l 6 , 75 NS 2700, from sheet 14 49-54. Performance curves with TP 70$, Jet F\/A, NS. 4300, \u20228l from sheet 22 55-62. Performance curves with TP 30$, Jet F\/A, from 88 sheet 23 63-7O. .Performance curves with VP 100$, Jet. F\/A, from 98 sheet 24 \u2022 , 71-78. Performance curves with VP 100$, Jet F\/A, NS 4500, 108 from sheet 25 79^85. Speed and sfc curves 117 86-92. Exhaust and spark plug temperature curves 125 I Chapter I . INTRODUCTION Chapter a. INTRODUCTION 1-Scavenging, the process of replacing the exhaust gases in the cylinder with a fresh charge, is inefficient in the 2-stroke engine because some exhaust gases are not displaced, thereby reducing the quantity of fresh charge available for combustion. Some mixing between the exhaust gases and fresh charge always takes place so that.some fresh charge escapes with the exhaust. If this fresh charge contains gasoline vapours, raw fuel flows through the engine unburned, and unutilized. Throttling, the process of restricting the entry of the fresh charge into the engine, reduces, the brake horse power. At thepstart of compression, the volume of fresh charge retained in the cylinder together with the volume of exhaust gas remaining, constitute a constant cylinder volume. Thus throttling, by restricting the fresh charge entry, indirectly increases the proportion of the exhaust gases in the combustion mixture, resulting in reduced efficiency, rel iabil i ty, and durability. The effect of the - disadvantages of the two processes may be reduced by admitting air into the cylinder prior to the:?fresh air-fuel charge, that is , by stratifying the charge. This stratified charge scavenges the exhaust gases and reduces the loss of fuel-air mixture through the exhaust ports. In the system under investigation, the stratification of the charge is accomplished by admitting air through an auxilliary valve into the passage-ways between the crankcase and ports as close to the ports as possible as shown in figure 1. Figure 1. Schematic view of a 2-cycle engine with a reed valve positioned. The upward movement of the piston creates a partial vacuum in the crankcase and passageway drawing a mixture of air and fuel through the carburetor Into the crankcase, and a separate quantity of air through the auxilliary scavenging air valve into the passageway. Downward movement of the piston precempresses the charge. As the air is ^head of the air-fuel mixture, i t is the f irst to enter the cylinder when the intake port is uncovered; ,in so doing it.experts .\u2022 most .of the exhaust gases leaving an atmosphere of air in the cylinder. .The fuel-air mixture from the main crankcase follows the entrance of kthe air, scavenging the air-exhaust mixture, leaving an atmosphere: of air and air-fuel mixture. The scavenging air serves both to scavenge the exhaust almost completely and to supply an excess of oxygen for more efficient combustion. The chemical equation for combustion gives a stoichiometric ratio of 15 lb of air per lb of gasoline in order to supply the amount of oxygen 3-required to burn the fuel completely. For complete combustion in an actual engine, there must be an excess of air and thorough mixing of fuel and air. There is a limit however to the air-fuel ratio for satisfactory combustion. Maximum efficiencies are usually obtained when the air-fuel ratio is some-where between 15 and 16. Specific fuel, comsumption increases as the air-fuel ratio increases above l6 due to slower burning and\/or incomplete combustion. \u2022Cyclic irregularity also increases because in some cycles the combustion velocity has decreased to such an extent that combustion is not completed by the time the exhaust ports open. The increase in cyclic irregularity eventually produces missing, limiting the upper air-fuel ratio of homogeneous mixtures to about 18. In the other direction, greater power is obtained by supplying more fuel than can be burned with the air available. The hydrogen in the fuel has a greater affinity for oxygen than has the carbon so that in a shortage of oxygen, the hydrogen reacts with more oxygen reducing the amount available for the reaction with carbon. During the reaction of hydrogen with oxygen to form water a greater amount of energy is released than in the reaction of carbon with oxygen to form carbon monoxide or carbon dioxide. Thus more energy is released in the combustion of a mixture with excess fuel. Also the probability of a l l the oxygen combining with the hydrocarbons in the fuel is increased i f the hydrocarbons in the fuel.are increased duetto.\"aylower air...fuel ratio.,.:;..;. The engine will.run cooler at low air-fuel ratios. This is due to an increase in the specific heat.of the gases. To increase the upper cr i t ica l air-fuel ratio two conditions must be met: (1) the mixture must remain ignitable, and (2) a sufficiently rapid rate of combustion must be maintained. These requirements necessitate an increase in.the ignition energy, achieved in practice either by means of a precombustion chamber, or by a stratified charge. In both of these practices a small,. easily ignited portion of the charge initiates and sustains combustion of the main charge. IF a prechamber is employed with homogeneous mixtures, its walls are maintained at ,a high temperature to impart the required energy to the combustible mixture. The burning gases issuing from the prechamber into the main combustion chamber act as a torch to ignite the main charge. Conditions approaching those of pre-ignition would be desirous to assist rapid and complete combustion. For \"satisfactory combustion to occur in a stratified charge with or without a ^prechamber, a volume of the correct or slightly rich air-fuel ratio is directed to surround the spark.plug. The expansion of the burning gases and temperature increase of this burning mixture raises the pressure and temperature of the remaining lean charge to its ignition point. To facilitate rapid and complete combustion the cylinder head and prechamber must be designed to ensure turbulence and mixing of the \"burning gases with the main charge. Engine knock is greatly reduced as the air-fuel ratio is increased. Detonation lias been explained as being due to the rapid combustion of the fuel-air mixture in the unburned portion preceding the flame. A flame front radiating outwardly from the point of ignition^.compresses.and heats the yet unburned gases in advance of i t to such a degree that self-ignition takes;:.>place. Flame propagation is slower in leaner mixtures so that in a high air-fuel ratio mixture,!the temperature and pressure of the unburned portion of the cylinder volume does not reach self rrignition conditions before the piston has expanded the gases and reduced the temperature and. pressure. As the energy requirements for ignition increases with the air-\u20225-fuel ratio, leaner mixtures require -higher temperatures before self-ignition wil l take place. The completeness of combustion\u2022is one of the factors which affects the specific heat of a working substance. The value of C v which determines k, depends on thettemperature of the mixture as well as on the air-fuel ratio. Table I gives the value of C v at several different air temperatures and air-fuel mixture ratios. C v CONDITIONS 0.1715 Air.\u00ae' 540\u00b0R 0.185 . Air @ 1200\u00b0R 0.235 Air-@ 5000\u00b0R 0,282 Fuel and air during lean mixture combustion O.296 Fuel and air during correct mixture combustion O.3U7 Fuel and air during rich mixture combustion Table I. Specific Heat (Cy-) at Constant Volume. \u2022 (l) * '\/\u2022..The apparent increase in C v with decreasing air-fuel ratios or increasing temperature is due to dissociation, the mechanism which tends to reverse the Initial chemical reaction of combustion or to form new Intermediate compounds such as nitric oxides. Because the chemical reaction partially reverses or does not go to completion, not a l l of the potential chemical, energy of the fuel is released in the process of burning. Because the value of k varies with the completeness .of combustion i t is possible to predict a change in the thermal efficiency as the air-fuel ratio Is varied by considering the.ideal Otto cycle efficiency equation. It may beqstated as: * Numbers in parenthesis refer to Bibliography at end of report. 6. e = 1 - (i)*\" 1 \u2022 . r \u2022 where r - compression ratioy and n \u2022 k = ratio of specific heate = _\u00a3. G v As an example the average value,of k is;1.3 for a correct carburetted mixture and equal to 1-h for pure air. Using these values, of k and a compression ratio of 10, the ideal Otto cycle efficiencies are 50$ for correct air-fuel, mixtures and 60$ for pure air. Further calculations of the possible theoretical gains relative to the efficiency with a correct air-fuel ration give a gain of 8$ for an air-fuel ratio increase from 15 to 20, and a gain of 12$ for an air-fuel ratio increase from 15. to 27 (2). These calculations predict that .if an engine could \"be run eatisfactorily on a lean air-fuel mixture higher\u2022efficiencies. would be the result. To reduce the power produced by an engine at a constant speed, the quantity of heat liberated in the cylinder per cycle must be reduced. In the ordinary carburetted 2-stroke cycle engines, throttling of the intake charge produces the desired result by restricting the quantity of fuel and air mixture entering the crankcase. The consequential lowering of the precompression pressure results in less charge entering the cylinder\u2022during intake so its partial pressure is reduced. For the total pressure in the cylinder to remain approximately constant at the start of compression, the partial pressure of the exhaust gases must increase which is brought about by more\" of the exhaust gases remaining in the cylinder. The residue gases dilute the fresh mixture. The exhaust gases prevent rapid and complete mixing of the combustible gases by:'isolating the oxygen and fuel. With less oxygen available for combustion and the overall air-fuel ratio increased, combustion is incomplete. The lack of oxygen is partially compensated for by the high 7-temperature exhaust gases increasing the energy of. ignition and velocity of the flame front in the exhaust-fresh charge mixture. Nevertheless to maintain smooth and reliable firing at part loads, the overall mixture strength should be kept above stiochiometric by enriching the fresh charge. With the stratified charge scavenging system, the reduction of the heat liberated and consequently the power output, is accomplished by admitting more air through the scavenging air valve instead of. restricting the air-fuel mixture. The reduction in partial pressure of. the air-fuel mixture is achieved by increasing the partial pressure of the air entering through the scavenging air valve so that the exhaust partial pressure remains approximately constant. The result is that.as the power requirements drop, more air is admitted through the scavenging air valve thereby reducing the amount of fresh air-fuel mixture entering through the carburetor while retaining approximately the same amount of residual gases. At part.load the stratified charge scavenging system wil l result in supplying the fuel with an excess amount of air instead of an excess of exhaust gases as is the case in the conventional engine. With conventional scavenging, three hypothetical relationships exist between the scavenging efficiency defined as the ratio of the mass of charge retained to the ideal mass that the piston displaces, trapping efficiency defined as the ratio of mass of charge retained to the mass supplied, and scavenging ratio defined as the ratio of mass supplied to the ideal mass that the piston displaces. These relationships are shown in figure 2. , Although these representations are hypothetical, they do permit an approximate analysis of a scavenging system to be undertaken. 8. Figure 2. Theoretical relationships between scavenging efficiency (SE)  trapping efficiency (TE) and scavenging ratio (R) according to Taylor (3); (a) SE. with perfect scavenging (b) SE with perfect mixing (c) TE with perfect mixing, and (d) SE with complete short circuiting. In the case of perfect scavenging the fresh charge is assumed to replace the exhaust gases completely without mixing or\u2022short circuiting. This means that for a given volume of fresh charge entering the intake ports, an equal volume of undiluted exhaust gases leave by way of the exhaust ports. Under this assumption, the scavenging efficiency is equal to the scavenging ratio at a l l points and the trapping efficiency is equal to unity. The second and most important representation, because i t approximates the actual conditions best, assumes that the volume of fresh charge mixes completely with the residual gases as soon as i t enters the cylinder and that an equal volume of the resultant mixture leaves the cylinder. To get a simple relationship, i t is necessary to assume that the residual exhaust gases are at the same temperature and have the same molecular weight as the fresh charge, and that the piston remains at 'bottom dead center during the scavenging process. The resultant equations, derived by Taylor (3) are: SE = 1..- e\"R where SE = scavenging efficiency, T E - 1 \" 6 \" T E = T R A P P L N S efficiency, R R = scavenging ratio. As more mixture enters the cylinder at constant speed so that the scavenging ratio increases, the amount retained wi l l increase and the proportion of amount retained to amount supplied wi l l decrease. The third possibility is that the fresh charge flows through the cylinder in a separate stream without mixing with the residual gases or pushing them out. This process is called short.circuiting and results in very l i t t l e fresh charge retention. In an actual engine the above three processes occur together. In the scavenging process some of the exhaust is pushed out without mixing, some of the fresh charge mixes with the exhaust and both flow out, and some of the fresh charge flows out without mixing. Studies conducted by Taylor at Massachusetts Ifistitute of Technology (ref.3) reveal that the actual curve of the scavenging ratio versus scavenging,efficiency has the same general shape as the curve for perfect mixing. This fact, together with some high-speed motion picture of the scavenging process in a large 2-cycle engine made .'by Boyer et al . (k) indicate that there is much mixing and l i t t l e \"piston\" action in the actual scavenging process. The actual, curves of the scavenging efficiency versus scavenging ratio as determined experimentally by Taylor, generally l ie below the curves for perfect mixing indicating considerable short circuiting. Because the actual curve has the same general shape as.the curve for . 1 0 . perfect mixing, and because for the purposes of this investigation the variation of the scavenging efficiency and trapping efficiency are more important than their magnitude, the following analysis assumes, that perfect mixing takes place in the scavenging process. The process of throttling the fresh charge in a conventional, scavenging system increases the restriction to the air flow which results in a smaller quantity, of mixture entering the cylinder. The reduction in the mass decreases the scavenging ratio which corresponds,to the line A-B in figure 2 moving to the lefty say to A?-B'. The result is a decrease in the scavenging efficiency and an increase in the trapping efficiency as the figure also shows. An increase in the trapping efficiency means that a greater proportion of the charge remains in.the cylinder and a smaller proportion escapes with the exhaust gases out the exhaust ports. A new set of equations are necessary to describe the efficiencies resulting from scavenging the exhaust gases with a stratified charge. The relationships as derived by Taylor niay s t i l l be used to approximate the scavenging and trapping efficiencies of the total charge of air entering through the scavenging\u2022air valve and the air-fuel, mixture entering through the carburetor, butrnew definitions were-necessary to estimate the retained proportion of the carburetted air-fuel mixture. The ideal equation for fuel scavenging efficiency, defined as the ratio of mass of fuel-air mixture inspired through carburetor to ideal mass that the piston displaces, and the fuel trapping efficiency, defined as the ratio of the mass.of carburetted fuel-air mixture retained to the mass supplied,.are derived in appendix III, employing similar assumptions to those used by Taylor in his derivation of the charge scavenging and - trapping .efficiencies. \u2022\u2022- The .resultant relationships assuming perfect mixing are: 11. FSE = 1 - e - ^ 1 - ^ ) 1 _ e-R(l-SAR) FTE = (i-SAR)R. where FSE = fuel scavenging efficiency, PTE = fuel trapping efficiency, SAR = scavenging air ratio, R = scavenging ratio. These efficiency equations are represented in graphical form in figure 3. Figure 3- Theoretical relationships between scavenging efficiency^  trapping efficiency, and scavenging ratio for stratified charge operation  assuming perfect mixing. When the scavenging air valve is closed so that the charge is \"homogenous , the fuel trapping efficiency is equal to the charge trapping efficiency and the fuel scavenging efficiency is equal to the charge scavenging efficiency and the scavenging air ratio is equal to zero as shown by the fu l l lines in figure 3- When the scavenging air valve is opened to allow .a- small quantity, of' scavehgihglairv.to enter: cylinder prior 12. to the a i r - f u e l mixture, ( w i t h the engine running at f u l l t h r o t t l e ) , the scavenging: .air\\;ratf or.i\"S'mo.';:lo)n;ger.,zero,,s6v.:that: the f u e l I t r a p p i h g o e f f i c i e n c y a h d . f u e l scavenging e f f i c i e n c y are d i f f e r e n t from the charge t r a p p i n g and scavenging e f f i c i e n c y r e s p e c t i v e l y . These e f f i c i e n c y equations are given i n g r a p h i c a l form by the dotted l i n e s i n f i g u r e 3' The shape o f the curves are independent of the scavenging a i r r a t i o as the only change t h a t occurs i s t h a t the o r i g i n s o f the fuel, t r a p p i n g e f f i c i e n c y and f u e l scavenging e f f i c i e n c y curves are - d i s p l a c e d to the r i g h t by an amount equal to the value of (R)X(SAR). The charge e f f i c i e n c y r e l a t i o n s h i p s are not a l t e r e d so they can s t i l l be represented by the s o l i d l i n e s i n f i g u r e 3- T o t a l a i r consumption increases only to a small extent because the amount of the a i r - f u e l mixture e n t e r i n g the c a r b u r e t o r reduces w i t h an increase i n the amount of a i r e n t e r i n g through the v a l v e . Because the t o t a l a i r consumption change i s Bmall the value of the scavenging r a t i o remains approximately constant. I f , f o r a p a r t i c u l a r speed, the value of the scavenging r a t i o i s R]_ the f u e l scavenging e f f i c i e n c y w i l l drop from F S E Q t o FSE]_ , and the f u e l t r a p p i n g e f f i c i e n c y w i l l increase from F T E Q to FTE-j_, as the scavenging a i r v a l v e i s opened t o give the scavenging a i r r a t i o a value pf SAR-^ . The f u e l scavenging e f f i c i e n c y decrease means, t h a t the \u2022 amount of a i r - f u e l mixture r e t a i n e d t o i d e a l mass d i s p l a c e d decreases but t h i s decrease i s the r e s u l t of a smaller q u a n t i t y of a i r - f u e l mixture b e i n g s u p p l i e d . The a i r - f u e l mixture i s reduced by an amount. approximately equal to. ( R ) ( S A R ) . The increase i n the f u e l t r a p p i n g e f f i c i e n c y i n d i c a t e s t h a t more of the a i r - f u e l mixture being s u p p l i e d by the ca r b u r e t o r i s r e t a i n e d i n the c y l i n d e r . When,.the scavenging a i r valve i s opened w i t h the engine running at p a r t t h r o t t l e , a d d i t i o n a l a i r enters the crankcase accompanied by a r e d u c t i o n - i n the amount of a i r f l o w i n g through the carburetor. The r e s u l t 13. of the reduced restrictions to air flow due to the additional path, made available for the air through the \u2022 scavenging air' valve,, is that.the total air consumption increases. The speed also increases, due to combustion efficiency increase and the reduction.in the crankcase vacuum. The effect of the air consumption increase is to increase the scavenging ratio which is partially offset by the speed increase so the resultant scavenging ratio is R-j_, figure k. But as scavenging air ratio Is now a positive number the 0 ( S A R K R ^ RO H 1 R > Figure 4. Theoretical relationship between trapping efficiency and  scavenging ratio for stratified charge operation at part throttle, (a) fuel trapping efficiency with scavenging air valve open> (b) fuel trapping efficiency with scavenging air valve closed, or trapping efficiency with scavenging air valve open or closed. origin of the fuel trapping efficiency wi l l be to the right. The overall result is thattifche fuel trapping efficiency wil l increase from FTEQ to FTE-^  and the charge trapping efficiency wi l l decrease from .TEQ to RE^. By stratifying the charge for purposes of exhaust scavenging the proportion of lh. the total air. retained to total amount supplied is reduced and. the proportion of the air-fuel mixture retained to amount supplied is increased. The increase in the amount of fresh air in the exhaust and a decrease in the amount of fuel wasted in scavenging,. wi l l increase the thermal efficiency of the engine as wil l as decrease the exhaust temperatures for lower specific fuel consumption and a more durable engine. In this investigation the stratified charge scavenging system was tested on a powerful, high-speed, lightweight engine, piston ported through-out. The requirement of simplicity ruled out any modifications requiring fuel injection or elaborate precombustion chambers but did not negate reed valves. Even then in future designs i t should be possible to simpliBy the. system even more by controlling the scavenging air entrance with the piston as is done at the present time with the control of the air-fuel mixture. It is also a simple matter to revert back to ordinary scavenging,with no deterent effects on performance at maximum power i f conditions warrant it., The intake ports must deflect the rich mixture to the spark plug so that at, top dead center the spark wi l l cause ignition of the volume surrounding the plug,.which in turn\u2022will Ignite the\u2022remaining charge. The degree to which the overall fuel air ratio may be reduced with this system while maintaining satisfactory combustion, would depend on how well the stratification could be controlled by the intake 3.port deflections, and on the scavenging air temperature. Chapter II. PREVIOUS WORK 16. Various methods of burning a stratified charge in a 4-stroke engine have been investigated throughout the -world. One method considered at the Institut Francais du Petrole and reported by Baudry (2) is to inject a small amount of fuel, roughly corresponding to the idle requirements of the engine, into a precombustion chamber and to aspirate a lean mixture through the carburetor. This procedure involves a number of difficulties. The presence of a prechamber always entails a reduction of thermal efficiency and the requirement of fuel injection pumps and nozzles greatly increases expenses as well as involving a l l the drawbacks of fuel injection. Experimental results have been published by Nilov in Russia (.5) whereby aspiration of a carburetted mixture has been substituted for fuel injection as shown in Figure 5. During the induction period, the engine; inspires a lean mixture through the main carburetor and a rich mixture through the prechamber inlet valve. The rich mixture is ignited by the spark plug located in the prechamber and the lean mixture is ignited, by the torch effect of the preehamber. This system has the disadvantage that Prechamber engine Figure 5. Russian \"Jet\" Ignition engine (5) 17-the thermal losses produced by the prechamber lowers the peak engine output. It is possible to accomplish stratification without using a prechamber by direct injection of the: fuel into the vicinity of the spark plug. However cost and complexity are increased as stratification by injection is practical only when used in conjunction with a special combustion chamber as revealed by experiments at the Citroen works in France, (U.S.A. patent no. 2,929,250), and by Texaco in the United States (6). Barber and his associates at Texaco eliminated engine knock by means of stratification. Their system is characterized as one involving injection near top dead center and a non-homogeneous charge. \u2022 ; A system for heterogeneous mixture formation in the cylinder without a prechamber was developed at the Institut Francais du Petrole by Baudry (2). The carburetted mixture was divided into two separate streams of completely different fuel-air mixtures as shown in Figure 6. The rich mixture is delivered into.the vicinity of the spark plug by a supplementary Hoke rich mixture Figure 6. I.F.P. engine modified for heterogeneous carburetion. carburetor through a heater. The standard intake pipe supplies either pure air or a lean mixture to the remaining cylinder volume as determined by power requirements. 18. In the United States, Conta and Durbetaki at the University of Rochester employed the Broderson method to achieve stratification (7)\u00b0 This is characterized by injection of fuel near bottom dead center into a throat betweentthe prechamber and the main combustion chamber as shown in figure 7\u2022 Figure 7- Combustion chamber for Broderson method of stratification Proper stratification of the fuel is insured by simultaneously controlling the quantity of fuel injected and the time injection begins. Early injection whentthe intake valve is s t i l l open and air is flowing into the main chamber draws fuel into the main chamber; injection after the valve is closed and piston is compressing air into the auxilliary chamber restricts fuel to the prechamber. Harry Ricardo of London, England, ran a 2-cycle engine on a stratified charge system in 1905* (8). The system he used required a prechamber into which the rich mixture was inspired through a separate intake valve and carburetor. But he was unable to obtain more than one-half or two-thirds of the maximum power obtainable from a similar engine burning a homogeneous mixture. Later Ricardo experimented with two separate fuel injections through one injector to f u l f i l l the need for very thorough mixing of the fuel and 19-air.before ignition. The injector was placed vertically in the head of the cyli.ider and the injection was in the form of a hollow cone directed to meet the air as i t entered through the inlet ports in the sleeve valve as shown in figure 8. Additional fuel was injected after the end of normal 45* A.B DC 60* A B DC. Main fuel injection Secondary low-pres: ure fuel injection Figure 8. Ricardo system of stratification in a 2-stroke engine  injection period, in order to provide, locally, a mixture sufficiently rich to be ignited by the spark plugs even though the mixture in the main cylinder was too lean for ignition from a spark, though not too lean for ignition by a flame Issuing from a prechamber. However, in this system a gap existed between .15 and 40$ fu l l torque where ignition was irregular and uncertain. Below 15$ of full-load torque, combustion took place in the prechamber alone; from 35-40$ fu l l torque and upwards combustion took place in the prechamber and main chamber. But between 15$ and 40$ the mixture in the main combustion chamber was too weak to be ignited from the 20. prechamber. In 1911 a patent was granted by the U.S. - Patent Office to William \u2022Stephenson, (No. 1,012, 288); the patent was. to increase the efficiency \u2022and speed of the then slow turning 2-stroke engine by allowing air to enter the pre-compression chamber independently of the mixed charge through a spring loaded poppet valve as shown in Figure 9-Figure 9. Stephenson method of stratification in a 2-stroke engine At the University of British Columbia in 1958 Peter. Koch installed a reed valve to admit extra air into the crankcase of two outboard motors. A limited number of tests indicated an increase in power and a decrease in .the specific fuel comsumption. Apparently the normally rich mixture was being diluted by the.air in the crankcase giving a combustible mixture 21. which approaches the stoichiometric ratio, thus increasing the power and decreasing the specific fuel consumption. The present principle of using a reed valve to allow extra air to enter the cylinder prior to the main charge is similar to the principle Koch employed in his outboard motors. The method of stratification under investigation in this report is similar to Stephenson's method but a reed valve is used in place of a poppet valve. Stephenson's method was for a slow speed engine whereas the present system is for high-speed, low specific weight engines where the scavenging ratio is below one as the time for scavenging is very short. His engine had valves whereas, the engine presently used is piston-ported throughout. Ricardo's system reduced the maximum power whereas the present system has no deterrent effects at fu l l power and throttle. Fuel injection is completely impractical for the size of engine being considered. No experimental results on the effects that stratifying the charge has on the scavenging and throttling of a two-cycle engine have been located, although W. Seaver made an analytical investigation of stratified charging of an internal combustion engine for his Master's degree thesis at Yale School of Engineering (9). Chapter III. DETAILS OF TEST .ARRANGEMENT Chapter III. DETAILS OF TEST ARKA*?GFiffiNT 2 3 . The engine used for this test was a model 2 7 0 Canadian chain saw engine made in Vancouver by Power Machinery7Ltd. It had the following specifications: Bore - . 2 5 \/ 1 6 in. Stroke - 1 3 \/ 8 in. Capacity - 5 - 8 cubic in. Compression ratio - 1 0 . Fuel-oil mixture - 1 6 : 1 Carburetor - Tillotson diaphragm Ports - piston ported throughout Recommended carburetor setting - main jet 3 \/ 4 - 1 turn open The outside walls of the passageway were built up with weld material as shown in figures 1 0 and 1 1 . A hole was drilled and tapped to take a Figure 1 0 . A cross-section of the scavenging air valve 2k. Figure 11. A photograph of the scavenging air valve arrangement 25-threaded copper tube. The tube projected into the passageway and served as a seat for the high carbon steel reed valve. The valve itself was fastened by two screws in the passageway machined flat to permit the valve to seat properly. On the other end of the copper tube an Imperial cock valve was fastened; the hole of the valve had been opened up to allow as much air as possible to enter when the valve was fu l l open. The engine was mounted on a small engine test bed in the Mechanical Engineering Laboratory, and coupled to a Froude hydraulic dynamometer, absorbing a maximum of 30 hp at 10,000 rpm. A photograph of the setup is shown in figure 12. The engine was bolted to an adjustable mount but separated from it by a wooden plate to absorb some of the engine vibration. Figure 12. General view of engine on test bed The engine was instrumented as shown in figure 13, so that the following quantities could be' determined: 26. Figure 13. Viev of instrumented engine (1) a i r consumption, (2) f u e l consumption, (3) speed and power, engine temperatures (5) exhaust gas constituents, (6) combustion pressures. From 'these quantities the operating cha r a c t e r i s t i c s of the engine were determined. ( l ) A i r Consumption The a i r inspired through the carburetor was drawn from a 45 gallon drum f i t t e d with bypass valves and several different size nozzles. The nozzle used was machined according to VDI standard dimensions (inside diameter .4000 inches), with the standard nozzle c o e f f i c i e n t s being read from published graphs (10). The average reading of two water manometers connected across the nozzle was taken as the nozzle pressure drop. The pressure i n the straight pipe leading to the nozzle (inside diameter..58 inches), was read on another water manometer. A b i - m e t a l l i c thermometer projecting into the surge tank was read f o r the a i r temperature. The pressure drop across the nozzle varies with the square of the mass flow. Thus i f the pressure upstream.of the nozzle i s at atmospheric pressure, the pressure downstream w i l l be below the barometric reading and w i l l vary as the mass flow varies. A high flow rate w i l l r e s u l t i n a large pressure drop across the nozzle so that the difference between the carburetor intake pressure which is\u2022downstream of the nozzle and the barometric pressure w i l l be great. \u2022 This condition i s analogous to operating the engine with the choke p a r t l y closed. The effect of varying the a i r flow would be si m i l a r to varying the choke setting. A vacuum cleaner blower was used to boost the nozzle upstream 28. -pressure to above atmospheric pressure so that the pressure downstream of the nozzle could he maintained at atmospheric conditions. The quantity of air flowing through the nozzle was controlled with by-pass valves so that the desired downstream pressure could be maintained. The nozzle and blower were1 employed only when the nozzle pressure drop reading was required; at other times the\u2022auxilliary valves leading to the surge tank were opened and the air allowed to by-pass the nozzle. The quantity of air flowing through the scavenging air valve was measured by a gas flow meter. . Saturated conditions were assumed to prevail downstream of the meter. (2) Fuel Consumption The fuel consumption was measured by weighing the fuel in.the tank from which fuel was being drawn, or by drawing the fuel from a graduated pipette. The former method gave the weight consumption over the complete test whereas the latter method gave the volume of fuel consumed for only a short time, usually one or two minutes. The fuel weighing method was generally used and consisted of.-'weighing the fuel and the tank at the start\" of a test.,,..and whenever readings were required. The fuel tank was connected to the fuel lines leading to engine, with flexible tubing which had a negligible effect on the weight readings. The tank was positioned on a balancing scale calibrated in grams. . As the fuel was consumed, the weight of fuel in the tank decreased A pipette calibrated in cubic centimeters, could be f i l l ed with fuel and then allowed to drain to the^engine as i t required the fuel. The number of cubic centimeters of fuel used per minute could thus be determined. A l l fuel flowed through a Dwyer variable area flowmeter to indicate instantaneous fuel consumption. This reading was of value in determining .flow fluctuations. ( 3 ) Speed and Power 2 9 > A Be r k e l y e l e c t r o n i c counter w i t h a maximum counting a b i l i t y o f 6000 counts per minute was adapted t o count the number o f r e v o l u t i o n s . The counter i s shown i n f i g u r e 14. The t r i p p i n g switch was connected to the Figure l U . Readout instruments tachometer d r i v e s h a f t which has a d r i v e reduction of 10,000 to 1.8l8., Two copper set screws served double purposes i n p o s i t i o n i n g a b a k e l i t e wheel on the d r i v e s h a f t and a c t i n g as a conductor f o r the t r i p p i n g c i r c u i t . A f l a t s p r i n g made contact w i t h the b a k e l i t e wheel, c l o s i n g the c i r c u i t whenever the s p r i n g touched a set screw. The e l e c t r o n i c counter r e g i s t e r e d the number of times the c i r c u i t was clo s e d . The tachometer on the dynamometer was used to check the v a r i a t i o n i n speed and i n d i c a t e a nominal operating speed. 30. The torque produced by the engine was measured by the Froude hydraulic dynamometer. (4) .Engine temperatures Two copper-constantin . \"megopak\" thermocouples indicated the temperature of the mixture in each of the passageways leading to the ports. . As these unshielded thermocouples were located between hot walls, the readings were probably a few degrees too high due to radiation, but as the variation in I temperature was more important than.the correct temperature they were assumed to give readings of sufficient accuracy. Two copper-constantin thermocouples were installed in the cooling air stream downstream of the engine,.another was silver-soldered to a washer placed under a cylinder head nut, and a iron-constantin .thermocouple was silver-soldered to a copper ring placed under the spark plug. A copper-constantin and iron-constantin thermocouple indicated carburetor intake temperatures and valve intake temperatures respectively. Two iron-constantin thermocouples were fitted into steel probes and screwed into the exhaust pipe and exhaust muffler. The thermocouple; in the pipe was in the direct path of exhaust issuing from the exhaust ports so was completely surrounded by hot exhaust gases. The thermocouple; in the muffler was not in a direct exhaust flow path so was in somewhat stagnant exhaust gases. The reference junctions of a l l thermocouples were individually placed in an ice-bath with the cold junctions placed in glass tubes f i l l ed with kerosene. . A vacuum tube voltmeter was connected across the thermocouples via a rotary switch. This instrument was used to read the potentials for the lower temperatures as well as indicate when the exhaust temperature had become steady. A potentiometer was connected in parallel with the vacuum tube voltmeter to read the higher temperatures more accurately. These instruments are shown in figure 14. 3 1 . (5) Exhaust gas constituents. A Republic continuous CCvj recorder drew in a continuous sample of the exhaust and analyse! i t . The results from this instrument showed a continuous variation in the CCv, content of the exhaust. An orsat analyser, shown in figure 14, indicated the percentage CCvj, 0\u00a3 and CO at one particular, time and not an average over the run. (6) Combustion pressures The pressure in the cylinder was displayed on an oscilloscope by means of a Kistler transducer system. Any number of cycles from one to eleven on one scope were possible by adjusting the sweep synchronizing control through which the triggering signal passed. The cylinder pressure acted on a P2-14 SLM quartz pickup which .changed the pressures into an electrostatic charge, through a hole in a specially fabricated spark plug. The piezo-calibrator in turn amplified the electrostatic charge and produced a voltage signal which was proportional to the pressure. The voltage was displayed on the cathode ray oscilloscope. The calibrator allowed various ranges of pressure to be displayed, not only as the primary trace, but also as a means of calibrating the pressure signal on the scope. The x axis was on a time base triggered by an electro-magnetic signal, iriitiatedby' the dynamometer shaft. The triggering signal f irst of a l l passed through a sweep-synchronizing control which regulated the number of pulses the oscilloscope received so that a constant number of cycles would be displayed on the scope, independently of speed. The number of cycles desired was set on the sweep-synchronizing control. The apparatus is shown in figure 12. Five or six of the eleven cycle displays were photographed side by side on a single frame, with a calibration pressure superimposed, usually 400 psi , as. shown in figure 15- The peak cylinder pressures were measured by 3 2 . Figure 15. Sample photograph of peak combustion pressures p r o j e c t i n g the frame on to graph paper w i t h an enlarger. From the values of the peak combustion pressures the average peak combustion pressure and average v a r i a t i o n were determined. A v e r t i c a l water manometer, connected to the exhaust p i p e , measured the average exhaust pressure over the whole c y c l e . Chapter IV. DETAILS OF TEST PROCEDURE Chapter IV. DETAILS OF TEST PROCEDURE 3^. The procedure g e n e r a l l y f o l l o w e d i n making a t e s t i s described i n the f o l l o w i n g paragraphs;, v a r i a t i o n s t o t h i s are des c r i b e d w i t h the r e s u l t s . Before the t e s t was s t a r t e d and w h i l e the engine was s t i l l warming up w i t h the scavenging a i r v a l v e c l o s e d , the blower was switched on and the v a l v e s adjusted t o d e l i v e r the amount of a i r r e q u i r e d by the engine and yet maintain the c a r b u r e t o r i n t a k e pressure the same as when the surge tank and nozzle are bypassed. A f t e r the adjustments were completed, the a i r was allowed t o bypass the surge tank, n o z z l e , and blower through an a d d i t i o n a l v a l v e , and the blower was stopped. When the exhaust temperature had become steady, the t e s t was commenced by s t a r t i n g the r e v o l u t i o n counter and counter stopwatch simultaneously, s t a r t i n g the f u e l f l o w stopwatch when the:.fuel weighing s c a l e was balanced, and s t a r t i n g the scavenging a i r f l o w stopwatch at an even flowmeter reading. The blower was then again s t a r t e d and the nozzle pressure drop> the nozzle i n t a k e p ressure, and c a r b u r e t o r Intake pressure noted when a l l the a i r was being drawn i n through the no z z l e . When the readings were completed the a i r was d i v e r t e d and blower stopped. A complete set of a l l pressure and temperature readings was then taken. A f t e r the readings were completed, about 10 minutes a f t e r the t e s t was s t a r t e d , the r e v o l u t i o n counter and time were noted simultaneously) the f u e l weighing s c a l e was adjusted t o read s l i g h t l y under-weight so when i t balanced the time and sc a l e reading noted,and the a i r fl o w meter read on an even minute; The pressure drop across the nozzle and dynamometer reading were again noted, the two exhaust temperatures read on the potentiometer, and the passageway temperature read on the voltmeter. Twenty-five or. t h i r t y minutes a f t e r the t e s t was commenced, the procedure f o r a complete set o f readings was repeated. The scavenging a i r valve was then f u l l y opened and the whole t e s t procedure repeated. The f u l l open 35-scavenging air valve position was followed by several tests with intermediate openings\u2022 Results of both sets of readings were reduced on the IBM 1620 computer but.the 10 minute reading results were used only as a check on the results of the second set of readings. The nozzle pressure drop and dynamometer readings varied during a test as did the exhaust temperature and passageway temperature so these important readings were averaged over the duration of the test and used in the second set of calculations. Chapter V. DISCUSSION AND RESULTS Chapter V. DISCUSSION AND RESULTS 37-The main objective of the tests was to compare the normal operating characteristics of the engine on the conventional scavenging ; system with the operation on the stratified charge scavenging system. For these tests the only adjustment made was that the scavenging air valve was changed to various positions. The second objective was to see what effect throttling has on the performance of an engine with stratified charge scavenging. For one set of these tests, the only adjustment made was that the throttle was changed to various positions; for the other set of tests, the throttle was adjusted and then the dynamometer setting changed to bring the speed back.to its original value. 33. The r e s u l t s o f the t e s t s on the engine o p e r a t i n g on the s t r a t i f i e d charge scavenging system are i n c l u d e d on the pages t h a t f o l l o w . An a n a l y s i s of the r e s u l t s f o l l o w s the s e t , o f graphs f o r the p a r t i c u l a r t e s t . Each t e s t i s i d e n t i f i e d by the t h r o t t l e p o s i t i o n , j e t adjustment, nominal speed,. and the sheet number on which the data was recorded during the a c t u a l run. The sheet number i s c r o s s - r e f e r e n c e d w i t h the t a b l e s of observed r e s u l t s t r a n s c r i b e d from the data sheets and i n c l u d e d i n appendix IV, and the t a b l e s of c a l c u l a t e d r e s u l t s t r a n s c r i b e d from computor r e s u l t s and i n c l u d e d i n appendix V. The f i r s t few t e s t s , sheets Ik, 15,-17> 19* 20 and 21, were w i t h a constant t h r o t t l e s e t t i n g , constant dynamometer s e t t i n g and wide open choke. The engine was run w i t h a v a l v e p o s i t i o n v a r y i n g from f u l l c l o s e d to f u l l open* Tests recorded on sheets 22 and 23 were s i m i l a r to the above except the choke was adjusted when necessary t o give s t a b l e engine operation. Sheet 2k shows the r e s u l t s o f t e s t s w i t h the valve f u l l open, constant dynamometer s e t t i n g , and a t h r o t t l e p o s i t i o n v a r y i n g from i d l e to f u l l open. The choke was adjusted as r e q u i r e d . The r e s u l t s on sheet .25 were taken from runs w i t h speed constant, the v a l v e f u l l open, the t h r o t t l e v a r i e d and the dynamometer adjusted t o o b t a i n the d e s i r e d speed. A comparison of the r e s u l t s o f the conventional scavenging and the s t r a t i f i e d charge scavenging i s made from a l l the r e s u l t s p l o t t i n g them on a bhp base i n s t e a d of the u s u a l scavenging a i r r a t i o base. F i g u r e s 16-P0 w i t h TP J e t - 2 0 \/ 1 6 . NS 14-700. from sheet 20 The f u e l weighing method was used f o r f u e l consumption and gave s a t i s f a c t o r y r e s u l t s . The surge tank was kept connected during the run but the a u x i l l i a r y n o zzles were openedf.when the pressure drop was not b e i n g read. The vacuum i n the surge tank remained at about ..0k inches of water. 39. Analysis of figure 16 reveals that the speed, torque and power did not increase until the scavenging air ratio was greater than 5$- Nevertheless the specific fuel consumption decreased up to a ratio of 10$ when i t increased. From these curves i t appears that the best scavenging air ratio would be 10$. The reason for the power not increasing as would have been indicated by a speed increase, may be explained with the aid of figure 19- The power increase due to a decrease in the specific fuel consumption was offset by a reduction in the fuel consumption due to a decrease in the- quantity of air flowing through the carburetor. With a further increase in the scavenging air ratio, the fuel consumption increased as the air-fuel ratio through carburetor decreased, but as the overall air-fuel ratio was increasing, the thermal efficiency also increased so that the net result was a power increase. With a further increase in the scavenging air ratio,, the air-fuel ratio in the carburetor s t i l l decreased, but the air flow through carburetor increased) so that the overall air-fuel ratio decreased, reducing the thermal efficiency. Comparing the fuel scavenging efficiency, figure 17.with the specific fuel consumption) figure 16, the curves seem to be of the same general form. Because of the similarity, the decrease in the specific fuel consumption seems to be the result of a larger proportion of fuel remaining in the cylinder. The approximately\"linear relationship between the air-fuel ratio and the weight of air flow through carburetor breaks down above a ratio of 10 which means that the fuel flow fluctuated independently of the air flow through the carburetor, possible due to fuel control valve sticking,- or to changes in air or fuel densities, or to fuel flow restrictions. It should be mentioned that the first test was with a scavenging air ratio of 11,5$ and the last test, two hours later,..was with a ratio of 10.0$. Comparing the average combustion pressure, figure 20, fuel trapping efficiency, figure 17, and the overall air fuel ratio, figure 19,. i t appears 40 c that the peak combustion pressure varies with the amount of fuel-air mixture trapped. The exhaust temperature, figure l 8 , and the exhaust pressure drop, figure 20, vary inversely with the average combustion pressure. These relationships indicate that when the combustion pressure is', high, more useful energy is removed from the cylinder. This increase in combustion pressure is probably the result of a more rapid rate of burning so that the combustion is completed earlier. With the peak combustion pressure occuring shortly after top dead centre, i t has a longer time to act on the piston so more energy is. removed, lowering the exhaust temperature. The exhaust pressure varies with the total air consumption as well as with the combustion pressure. Combustion would also be more complete i f rapid combustion occured so thatrlthe amount of after-burning in the exhaust would reduce. 41. 3.0 2.8 2.6 SH 43 I o. 43 u &. 43 rH 2.4 o m 2.2 p. 43 43 +\u00bb I 43 2.0 l c 8 Q) cr o EH 1.6 1 .4 1.2 IcO SPEED TORQUE. 10 15 20 Scavenging a i r r a t i o (\"\/ 25 30' Figure 16. Performance curves with TP 50%, Jet 20\/16, NS 4700, f rom sheet 20. Figure 17. Efficiency curves with TP 50%, Jet 20\/16, US 4700, from sheet 20. 44. 3 .90 cu c o f o 8 0 oo a o o \u00a7 o 7 0 e cu cu.60 o cu CD c o o u \u2022H 50 o 4 0 22 M 43 I cu \u2022 \u00b0 1 8 CD CU jo H O CO 1 4 10 WPTC TAC 1 0 1 5 2 0 S c a v e n g i n g a i r r a t i o (%) 2 5 1 6 15 1 4 13 12 o 1 1 % U io is \u2022a! 8 3 0 F i g u r e 19. A i r & f u e l consumption curves w i t h TP 50$, J e t 20\/16, NS 4700, from sheet 20. 45o 50 \u2022rt CO P. w 4 5 P. <D 6 -40 a. 35 o td \u2022H > T3 S30 to 03 CD P. \u00a7 2 5 ro e o \u00b020 Q U \u00a3 1 5 CO ? O CS s l l l O \u2022 GO CO OJ f-f P. co ^ a) ( >\u2022 < BMEP ^ J, <~~- 1 ACPD V h\u2014 1 EPD 440 420 400 380 360 300 280 260 \u2022rt to P. 0) u m CO a> U P. 340 a o \u2022rt +> CO a 320 8 Q> bD a3 U > 10 15 20 S c a v e n g i n g a i r r a t i o 25 30 240 Figure 20. Pressure curves with TP 50%, Jet 20\/16, US 4700 from sheet 20, ii-6. (2) Figures 21-26 vith TP 50$, Jet l 6 \/ l 6 , HS U5OO, from sheet 17 This test was with the throttle half open,, the main jet one complete turn open, and with a nominal speed of ij-500 rpm. During the tests, the engine suddenly slowed down to about two-thirds speed and then gradually crept back up to operating speed again. This phenomenon occured twice with scavenging air valve closed, once when the valve was 70$ open,.and once when i t was 100$ open, but not at a l l when:the valve was 40$ open. The sudden drop in speed seemed inexplicable but i t may have been caused by carburetor malfunction or slugs of o i l in the gas. Fuel consumption was measured by drawing the fuel from the pipette for one minute during each test. Carburetor air was drawn from surge tank through auxilliary nozzles except when the pressure drop across the nozzle was being measured. The carburetor intake pressure was thus below atmospheric pressure. The cylinder head temperatures could not be read as the thermocouple to the nut had broken off. Generally the temperatures were quite constant during a test. The specific fuel consumption versus scavenging air ratio is not a straight line as the other main operating characteristics seem to be, as indicated on figure 21. As the fuel consumption drops off at scavenging air ratio of 3?5$> figure 25, one could suspect that the fuel consumption measurement over the one minute interval was not representative of the average consumption over the whole time. But the exhaust temperature dropped and the left port; temperature increased probably due to the valve intake temperature increase so that, due to rapid combustion in a greater amount of air, more energy was removed before the exhaust was discharged. This could explain why the fuel consumption decreased yet the power continued to increase* The total air consumption, figure 25, increased beyond proportion at this scavenging air ratio so that the air-fuel ratio curve also was not a straight line. hi. As the brake mean effective pressure and the average peak combustion pressure are proportional, figure 2 6 , the increased effective pressure was the result, of higher pressures acting ;for longer periods as the combustion was completed sooner. . With higher overall pressures, the overall temperature should also be higher; this.is. born out by the spark plug temperature in figure 2k. Speed and power increase, figure 2 1 , is probably the result of more fuel being retained and more efficient combustion in a greater proportion.of air. The valve intake temperature was high,, figure 2k, so when the scavenging air valve was opened and the hot scavenging air entered the crankcase, the passageway temperature increased. As more air flowed past the hot scavenging valve where i t picked up its heat,- its temperature reduced, thus decreasing the passageway temperature until the increasing temperature of the passageway walls and crankcase counteracted the valve intake temperature decrease. The hot scavenging air has a high ignition energy so i t is not very surprising to notice that the brake thermal efficiency was high, figure 2 3 , the exhaust temperature low, figure 2k,- and the exhaust pressure drop low, figure 2 6 , when the valve intake temperature was high at a scavenging air ratio of 3 - 5 $ . The exhaust temperature and pressure are low because more energy is removed from the cylinder when combustion is faster, leaving a smaller amount in the exhaust gases, as well as reducing the amount of afterburning in the exhaust pipe. The exhaust pressure also depends on the quantity of air being discharged, which is confirmed by comparing these quantities on figure 25 and 2 6 . Nevertheless the average peak cylinder pressure deviation increased rapidly indicating greater cyclic irregularity. 48. TORQ 10 15 20 Scavenging a i r r a t i o 25 30' Figure 21. Performance curves with TP 50%>, Jet 16\/16, NS 4500, from sheet 17. 49. J 0 5 10 15 20 25 30 S c a v e n g i n g a i r r a t i o (%) Figure 22. Efficiency curves with TP 50$, Jet 16\/16, NS 4500, from sheet 17. Figure 23. Efficiency curves with TP 50%, Jet 16\/16, NS 4500, from sheet 17. 51. Figure 26. Pressure curves with TP 50%, Jet 16\/16, US 4500, from sheet 17. 5 4 . ( 3 ) Figure . 2 7 - 3 2 with TP 5 0 $ , Jet lk\/l6, NS 4 9 0 0 , from sheet 1 5 The test was conducted at 5 0 $ fu l l open throttle, jet open 7\/8 f u l l turn, and a nominal speed of 4-9QO. When not being measured, the air entered the surge tank through auxilliary nozzles so the pressure in the surge tank varied between .04 and . 0 6 in. of water. The maximum amount of air that could be admitted through the f u l l open valve was only 5 $ of total air consumption. Power, spee.d> and brake mean effective pressure, figures 2 7 and 3 2 , dropped at f irst as air was admitted through the savenging air valve. \u2022 This is probably due to the peak combustion pressure decreasing at f irst , and then increasing. The probability of this being the cause is quite high as the pressure in the cylinder did actually drop and then rise again, figure 3 2 - The spark plug temperature did similarly, figure 3 0 , suggesting that combustion was slower at a scavenging air ratio of 2 . 5 $ and then becoming faster. The higher exhaust temperature indicated that more energy was lost through the exhaust gases. The reason why the exhaust pressure varied inversely with the exhaust temperature instead of directly> as wouldMiave been expected with an increase in the exhaust energy, is that the total air consumption decreased and then increased, the curve being similar in form to the exhaust pressure curve. From the increase in the fuel trapping efficiency, figure 2 8 , one would expect that the brake '.thermal efficiency would increase, but this is not the case; the efficiency remains constant up to 2 . 5 $ and then drops. But in figure 3 1 , the air-fuel ratio is shown to decrease continually, so that, ejv:en though more of the mixture remains in the cylinder, combustion, is slower due to a shortage of oxygen. 55. 3.0 2; 8 2.6 xt i P. xi x i 0) ft X) H 2.4 o CO P. X! x> 4 S I X) 2.2 2o0 lo8 ID 3 o 1.6 1.4 1.2 1.0 \u2022 < s j) & TORQ j BHP t 3 SFC 5200 5000 4800 4600 4400 4200 4000 3800 3600 3400 10 15 20 S c a v e n g i n g a i r r a t i o (%) 25 30 3200 Figure 27. Performance curves with TP 50$, Jet 14\/16, NS 4900, from.sheet 15. 78 77 43 n-j \u2022 \u2022 \u2022 \u2022 \u2022 \u2022 0 5 10 15 20 25 30 Scavenging a i r ratio (%) F i g u r e 28. E f f i c i e n c y curves w i t h TP 50%, J e t 14\/16, NS 4900, from sheet 15. 57. 80 75 70 65 60 o C (4) \u2022H 55 o *H <M 50 45 40 35 30 ( 0. D R \\ W 1 BTE 20 18 16 14 12 fl 0) 10 o \u2022rt <H W 8 5 10 15 20 25 S c a v e n g i n g a i r r a t i o ($) 30 F i g u r e 29- E f f i c i e n c y c u r v e s w i t h TP 50$, J e t 14\/16, MS 4900, f rom s h e e t 15. 5 8 . 1 J ' SpT * ** ) ET c > j & \u2014 e r ) LPT c 7 CAT \\ r - J i T Z E A - V1T I ( * E T I M 4 1 0 390 290 2 8 0 1 8 0 1 6 0 1 4 0 1 2 0 1 0 0 1 0 1 5 2 0 S c a v e n g i n g a i r r a t i o (%) 2 5 3 0 Figure 3 0 . Temperature curves with TP 5 0 $ , Jet 1 4 \/ 1 6 , NS 4 9 0 0 , from sheet 1 5 . 59. o c v f?v~ D T A C V 1 5 P C 3 \u00b0 A P \\ g A P C I S A 1 ^  S A C 16 15 14 13 12 11 10 8 10 15 20 S c a v e n g i n g a i r r a t i o 25 30 F i g u r e 3 1 . A i r and f u e l c o n s u m p t i o n c u r v e s w i t h T P 50$, J e t 14\/16, N S 4900, f r o m s h e e t 15. 60. 50 CO '45 P. co S jo -40 CO a. c o \u00a3 3 5 cd \u2022 r l S> CU S30 CQ CQ CO U P. \u00a725 \u2022H - P CQ 42 e o \u00b020 \u00a3 1 5 03 <H O \u2022 CQ CO CO rH O. 4 3 5 CQ 0 cd X! K 0 \u2014 o \u2014 ) BMSP ) ACPD ] ACP \\ \\ EPD 440 420 400 380 \u2022H CO 360 \u00bb CQ 03 a> u (X 340 o * +\u00bb CO 4S 320 8 CD bO oS CP > 300 280 10 15 20 S c a v e n g i n g a i r r a t i o 25 30 260 240 F i g u r e 32 . P r e s s u r e curves w i t h TP 50$, J e t 14\/16, NS 4900. ' from sheet 15. 6 l . (h) Figures 33-38 with TP 60$, Jet F\/A, NS 5000, from sheet 21 This test at a throttle position 60$ open and nominal speed 5000 rpm, was with a new carburetor adjusted at the factory. But as the instrumented engine had greater restrictions to the carburetor air flow than an uninstrumented one at the factory would have, the fuel flow in carburetor would not be ;the same in both eases. Nevertheless the engine ran relatively smooth during the test but i t did not seem to be running under optimum conditions: when choked or when the carburetor intake : pressure was increased, the engine would speed up. The resultant operating characteristics were far from normal, e.g. specific fuel consumption was 4.0 lbs per bhp-hr. The air-fuel ratio in the carburetor dropped but the overall air-fuel ratio increased slightly> as \/shown in figure 37-The air-flow restrictions were reduced so that the volumetric efficiency increased. As the ratio of the\u2022exhaust temperature to the total air consumption is nearly constant, the amount of heat lost by the exhaust gases depends on the total air consumption and independent .of the combustion variation. Thus the only major gain in efficiency is due to an increase in the trapping efficiency. 62. 4.5 4.0 u 43 I P. 43 42 SH CD P. 43 rH 3.5 o CO 3.0 1.1 P, 43 43 \u00b08 1.0 I 43 rH CD a< U o 1 ( \/ SPEED 1 \/ SPC ^ T O R Q S3 ' 5100 5000 4900 P. 13 CD CD CX 4800 4700 10 . .- \u2022 15 20 S c a v e n g i n g a i r r a t i o 25 30 Figure 33. Performance curves with TP .60$, Jet PA, US 5000 from sheet 21. < i \u2014 , \/ ( \u00ae \u2014 * BTE 20 18 16 14 12 10 o \u2022H W 8 10 15 20 Scavenging a ir ratio ($) 25 30 Figure 55. Efficiency curves with TP 60$, Jet FA, NS 5000, from sheet 21. 6.5. S c a v e n g i n g a i r r a t i o ($) Figure 56. Temperature curves with TP 60$, Jet FA, NS 5000, from sheet 21. 66. Figure 37. Air & fuel consumption curves with TP 60$, Jet FA, NS 5000, from sheet 21. 67. 50 CQ (X '45 (X CD s x> <* -40 co fl o \u00a3 3 5 cd \u2022 H > CD S30 CO CO CD U cu \u00a7 2 5 \u2022 H -P CO 43 e o \u00b0 2 0 o u \u00a3 1 5 cd is O C j H a o CQ CO CD u a CO cd 43 X 'ACP 440 420 400 380 CO p. 360 jo u 2 CO CO CD u cu 340 c o -r4 -p CO 43 a 320 8 CD fao cd U CD 1> < 300 280 260 0 10 15 20 25 S c a v e n g i n g a i r r a t i o (%) 30 240 Figure 38. Pressure curves with TP \u202260$. Jet FA. NS 5000, from sheet 21. 68. (5) Figures 39-^3 with TP 85$, Jet Yj\/lG, , NS- 5300 from sheet 19 The jet.was set at 1 l \/ l 6 turns open at the start pf this test to give the maximum power with the throttle 85$ open and a nominal speed of 5300 rpm. When the scavenging air valve was openedu, the fresh charge hacked out through the valve and meter instead of ai r being drawn in. The result i s a decrease in the specific fuel consumption - even though approximately 2$ of the fuel vapour escaped through the valve uriburned;. the vapour could be seen issuing from the meter. The reversing of the air flow could have been the result of poor reed valve sealing with the pressure difference between the inside [ of the valve and the outside of the valve not as great as when the throttle i s closed further which stopped the leakage and resulted in normal entrance of the scavenging air. The force to keep the valve on i t s seat against the vibrating forces would not be sufficient to seal the valve, thus allowing the charge to leak out on pre-compression. 69. 3 . 0 2 . 8 2 . 6 u Xi I Q, Xi x> u a> (X 2 o 4 V l co Xi \u2022 \u00b0 2 o 0 l o 8 CD U o EH 1 . 6 1 . 4 1 . 2 1 = 0 Ail i TORQ > BHP SPC 3 -2 0 1 0 1 5 2 0 Scavenging a i r r a t i o 2 5 3 0 ' Figure 39. Performance, curves with TP 85$, Jet 17\/16, NS 5300, from sheet 19. 7 0 . 80 75 70 65 60 u C CO 55 <t-l 50 45 40 35 30 ) VE j BTE > 20 18 16 14 12 d co 10 o \u2022H < H pa 8 - 2 0 10 15 20 S c a v e n g i n g a i r r a t i o 25 30 Figure 40. Efficiency curves with TP 85$, Jet 17\/16, NS 5300, from sheet 19. 71. 900 860 820 780 ^ 7 4 0 co \u00a9 u +\u00bb d5 \u00a3 7 0 0 6 0) +> +\u00bb CD a 660 620 580 540 500 s ) ET j_ SPT \/ > GHT \\ RPT LPT ) ETIM -2 10 15 20 Scavenging a i r r a t i o (%) 25 30 Figure 41. Temperature curves with TP 85$, Jet 17\/16, NS 5500, from sheet 19. 7 2 . e-90 c o \u2022 H f .80 co 0 O o S\u00ab70 B ex.60 c o 03 c o o rt \u2022 H 50 40 22 rl X! I o. X! \u2022\u00b0 18 \u2022H 03 P . X i . r H O a) CO 14 10 - 2 5 TAC > 0AP 3 FC 1 S A C 16 15 14 13 12 11 * 0) V I io i ; 8 10 15 20 S c a v e n g i n g a i r r a t i o (%) 25 30 Figure 42 . Air & fuel consumption curves with TP 85$, Jet 17\/16, NS 5300, from sheet 19. 73. 50 CQ P. '45 P. a> s 43 -40 CQ CH 35 fl o \u2022 H -P cd \u2022 H CD \u00a3 3 0 3 CQ CO CD U P. \u00a7 2 5 \u2022 H -P co 43 e o \u00b0 2 0 o \u00a3 1 5 cd S V l o fl ^ 1 0 CO CO CD p, +1 5 co v cd 43 \u00ab Q\u2014 < BMEP ) 5 EPD -2 440 420 400 380 CD P. 360 \u00ab u CO CO CD P. 340 c o \u2022 H +> CO 43 320 8 CD t*0 cd u CD !> < 300 280 260 0 10 15 20 S c a v e n g i n g a i r r a t i o {%) 25 30 240 F i g u r e 43. P r e s s u r e curves w i t h TP 85$, J e t 17\/16, US 5300, from sheet 19. 7^. Figures hk-kQ, with TP'100$, Jet lk\/lS, NS 2700, from sheet lh Fuel measurements for these tests were taken over two minute intervals with the graduated pipette. As the air flow through carburetor was small, Reynolds number for the nozzle was below the lower limit.of the graphs from which the nozzle flow coefficients were read. It was necessary to extrapolate, the curve for these coefficients. , At the fu l l open position of the valve the power and specific fuel consumption was 3-Ower than i t was at the closed valve position, figure hh. The low specific fuel consumption was probably due to the higher overall air-fuel ratio and the higher fuel trapping efficiency,. figure 45 and hj. Even though the overall air-fuel ratio was above the stoichiometric ratio the actual air-fuel ratio in.the engine cylinder was lower as some air, but l i t t l e fuel, esc ape devout the exhaust ports. The reduced restrictions to air flow and the decrease in speed resulted in the specific air consumption increasing even though the total air consumption remained approximately constant. The spark plug and cooling a i r temperatures dropped indicating a reduced combustion temperatures, figure h6. The constant exhaust temperature indicates that the energy lost in the exhaust remained Approximately constant. Figure 44. Performance curves with TP 100$, Jet 14\/16, NS 2700, from sheet 14. 76. 77. Figure 4 6 . Temperature curves with T P 1 0 0 $ , Jet 1 4 \/ 1 6 , N S 2 7 0 0 from sheet 1 4 . 78. Figure 47. Air and fuel consumption curves with TP 100$, Jet 14\/16, NS 2700, from sheet 14. 79. 50 \u2022H CO Q. '45 a. CD s -40 CO OH fl o a) \u2022H > a> S30 ca CQ CD u a. \u00a7 2 5 \u2022 H - P CO 3 43 s O \u00b0 2 0 o < u \u00a3 1 5 CC) \u00abM O fl c t i o CQ CQ CD rl a. 4 3 5 CQ 3 cd 43 X W ( BMEP ) <i \u2014(7) BPD 3\u2014 10 '2'0 -30 440 420 400 380 \u2022rt CO D, 360 \u00bb M 3-CO CO CD U (X 340 c o i-i - P co 3 43 e 320 8 CD (50 cd rl CD > 300 280 260 40 Scavenging a i r r a t i o (%) 50-60 240 F i g u r e 48. P r e s s u r e curves w i t h TP 100$, J e t 14\/16, NS 2700, from sheet 14. \/ 80. Figure 4 9 - 5 4 with TP 70$, Jet F .A. , HS 4300, from sheet 22. Tests were conducted with the above settings, f irst with the scavenging air valve closed, then 5 5 $ open, and finally with i t wide open; the jet adjustment on the new carburetor remained as i t had been received from the factory. During the second test, the engine speed suddenly dropped approxim-ately 500 rpm and then picked up again; this fluctuation occured 4 times during the test. The speed dropped approximately 15OO rpm twice just after the valve was opened 100$, but remained steady during the test. From figure 4 9 i t appears that the power dropped slightly for low scavenging air ratios and then increased for higher ratios while the fuel consumption dropped more rapidly at f irst and then increased again, figure 53. Thus the specific fuel consumption decreased rapidly and then increased again as the scavenging air ratio increased, figure 49- The fuel trapping efficiency, figure 5 0 , increased continuously so that less fuel was wasted. As the charge trapping efficiency decreased, more of the air was lost in .the exhaust which cooled the exhaust. Figure 52 shows that the exhaust temperature remained nearly constant even though the overall combustion temperature had increased as indicated by the spark plug and cylinder head temperatures. The valve inlet air temperature affected the right passageway temperature. With less restriction to air flow, the total air consumption and volumetric efficiency increased although the f irst increase in the weight of air flowing through valve was compensated for by the corresponding reduction in the weight of air flowing through carburetor, figure 53-81. 3 . 0 Zi 8 ^ 2 .6 u J3 I P. J3 n 2.4 cu o 2 . 2 (0 X! \u2022\u00b0 2 . 0 -p V l 1 .8 03 c u o 6H 1.6 1 . 4 1.2 1 .0 ,\u2014TORQUE ( >.\u2014__ (-\"SPEED BHP I r r 0 10 15 20 Scavenging a i r r a t i o 25 3 0 ' F i g u r e 4 9 . P e r f o r m a n c e c u r v e s w i t h TP 7 0 $ , J e t F A , IS 4500, f rom s h e e t 2 2 . .82. Figure 50. Efficiency curves with TP 70$, Jet FA, NS 4300. from sheet 22. 0 5 10 15 20 25 30 S c a v e n g i n g a i r r a t i o ($) F i g u r e 51. E f f i c i e n c y curves w i t h TP 70$, J e t FA, HS 4300. from sheet 22. 84. 10 15 20 S c a v e n g i n g a i r r a t i o 25 30 Figure 52. Temperature curves with TP 70$, Jet FA, NS 4300, from sheet 22. 85. F i g u r e 53. A i r and f u e l consumption curves w i t h TP 70$, J e t PA, MS 4300, from sheet 22. 86. 50 CO P. '45 P. CD s XI \u202240 CO P. 35 c o \u2022H +> a) \u2022rl > OJ ^30 CO CO a> U a. \u00a7 2 5 \u2022H +? CO 3 X i e o \u00b0 2 0 o \u00a3 1 5 a) O a \u2022110 CQ 03 0) U P, +\u00bb m 3 a] 43 ir -\u00ae-BMBP ACPD ACP EPD 440 420 400 380 \u2022H CO P. 360 \u00ae u 3 CO CO cu rl P. 340 53 O \u2022H +> co 3 X i 6 320 8 v a) rl CO > 300 280 260 0 5 10 15 20 Scavenging a i r r a t i o 25 30 240 Figure 54. Pressure curves with TP 70$, Jet FA, NS 4300, from sheet 22, 8 7. Figure 55-62 with TP 30$, Jet F .A. , from sheet 23 With the scavenging air valve wide open resulting in a scavenging air ratio of 5h^>, the engine would run smoothly for ^0-h0 seconds and then suddenly drop down from 4@00 rpm to 3000 rpm, gradually pick up speed, and then remain constant for the ^0-k0 seconds before repeating the cycle. The engine seemed to be running put of fuel. Thus,the tests at the valve setting were limited in length to 30 seconds. Several readings were taken when the engine was running steady and then the readings were averaged. For the next test, the only adjustment made was to choke the engine so that the speed would not drop more than several hundred rpm; this adjustment increased the scavenging air ratio to 56$. During the last test with the scavenging air ratio 48.4$, speed fluctuated between 4900 rpm and 4600 rpm and the temperature fluctuated. During the test, the engine slowed down by 1000 rpm once. The. engine exhibited severe vibrations between 3800-4000 rpm so that no tests were run with speeds in this range. Figure 6 l shows that the fuel consumption remained approximately constant as the scavenging air ratio increased but made a sudden jump when the cr i t ica l vibration speed was exceeded. Nevertheless the specific fuel consumption decreased approximately linearly, figure 55. The lowest specific fuel consumption obtained was .91 lb per bhp-hr., but to maintain steady speed operation, choking was necessary whijih increased the specific fuel consumption to 1.06 lb per bhp-hr. Choking reduced the power and speed and the air fuel ratios, figure 60. Figure 56 shows that the ideal fuel trapping efficiency increased continually with the scavenging air ratio, while the ideal trapping efficiency remained approximately constant until the scavenging air ratio exceeded 3 0 $ \u2022 The decrease, in the specific fuel consumption is the result of an increase in the fuel trapping efficiency and an increase in the air-fuel ratio made possible by stratifying the charge. 3 3 . 89. 0 10 20 30 40 50 60 S c a v e n g i n g a i r r a t i o ($) Figure 57. Efficiency curves with TP 30$, Jet FA, from sheet 25. 700 0 10 20 30 40 50 60 Scavenging a i r ratio (%) Figure 58. Bxhaust temperature curves with TP 30$, Jet FA, from sheet 23. 92. 9 3 . 94. Figure 61. Air and fuel consumption curves with TP 30%, Jet FA, from sheet 23. 95. 96. Figures 63-TO with VPI00$, Jet F .A. , from sheet 2k The purpose of this series of tests was to determine the performance of the engine; at a constant scavenging air valve position with varying throttle positions which would change the scavenging air ratio. The f irst test was with the valve closed and the rest of the tests were with the valve wide open. The choke was adjusted as required to give steady speed operation. The inaccurate choke adjustment and fluctuations in air-fuel ratio in carburetor wi l l account for the variation in the air-fuel ratios and fuel consumption, figures 68 and 69. . After the tests with the scavenging air valve open were completed and the valve closed, the speed could not be brought up to the in i t ia l value so that the test was conducted at the maximum speed obtainable. The results are plotted as isolated points at a scavenging air ratio equal to zero. The other series of isolated points at a scavenging air ratio equal to 3-4 $ resulted from a test with conditions identical to those which gave results at scavenging air ratio equal to 8.1$ except that the choke was fully opened. The fuel trapping efficiency and charge trapping efficiency both increased so.that more air and more fuel were trapped in the cylinder. As the quantity of air consumed was reduced, the volumetric efficiency decreased. Neverthe-less the specific air consumption and specific fuel consumption remained nearly constant up to a scavenging air ratio of 50$, figures 68 and 69. The-exhaust temperature dropped continuously while the cylinder head and spark plug temperatures gradually increased up to 50$ scavenging air ratio, figure 66. and 67, although these latter temperatures fluctuated with the overall air-fuel ratio, figure 68. A peak in the specific fuel consumption at a scavenging air ratio of 12$ was probably due to excessive choking. If a carburetor, was. designed to supply the required mixture strength at .all throttle settings, the specific fuel 97* consumption f l u c t u a t i o n s would not be as great. The shape of the average combustion pressure curve, f i g u r e JO, i s analogous t o the shape of the o v e r a l l a i r - f u e l r a t i o curve, f i g u r e 68, and the brake thermal e f f i c i e n c y curve, f i g u r e 65. Although the average combustion pressure d e v i a t i o n v a r i e s c o n s i d e r a b l y , i t l i k e w i s e f o l l o w s the general t r e n d o f the o v e r a l l a i r - f u e l r a t i o , . a l t h o u g h i t does not drop o f f at the maximum scavenging a i r r a t i o . The exhaust pressure drop v a r i e s w i t h the t o t a l a i r consumption although i t does increase at maximum scavenging a i r r a t i o . The increase at t h i s r a t i o may be due to slow burning as i n d i c a t e d by the low combustion pressures and the drop i n the spark p l u g and c y l i n d e r head temperatures. I f the peak combustion temperature and pressure occured much a f t e r top dead c e n t r e , the exhaust temperature would increase as l e s s energy i s removed from the c y l i n d e r as power. However the t r a p p i n g e f f i c i e n c y l e v e l l e d o f f whereas the f u e l t r a p p i n g e f f i c i e n c y d i d not, f i g u r e 6k, so th a t a l a r g e r p r o p o r t i o n of the c o o l scavenging a i r went out the p o r t s w i t h the.exhaust gases. The c o o l a i r i n the exhaust negated some of the exhaust temperature increase due t o delayed combustion. 98. 99. J 1 _ L 1 1 1 L o 0 12 2.4; 36; 48 60 72 S c a v e n g i n g a i r r a t i o ($) \u00a3ure_64. Efficiency curves with TP 100$, Jet FA. from sheet 24. 100. 0 12 24 36, 48 60 72 S c a v e n g i n g a i r r a t i o ($) Figure 65. Efficiency curves with VP 100$, Jet FA. from sheet 24. 101. Scavenging a i r r a t i o (%) Figure 66. Temperature curves with VP 100%, Jet FA, from sheet 24. 102. 104. 1 0 5 . 106. Figures 71-78 with VP 0$ or 100$, Jet F .A. , NS 4500, from sheet 25 The purpose of this series of tests was to compare the performance of the engine at constant speed on the basis of power produced. The scavenging air valve was kept wide open and the throttle varied to obtain several different torque readings with the stratified charge scavenging system; the valve was then closed and several more tests taken to obtain the torque readings with conventional scavenging. The f irst few tests were performed with the valve fu l l open and the throttle varied from f u l l open to a minimum setting which s t i l l allowed the engine speed to be kept at 4500 rpm. The choke was adjusted as required to maintain smooth operation.. Engine exhaust produced excessive smoke during most of the::tests. Over the duration of each of the tests, the engine \u2022 slowed down.5\u00a9 - 250 rpm. When the valve was closed after the tests with the open valve were finished, the speed could not be brought up to the desired value of 4-500 rpm, so that a test was conducted at maximum speed obtainable. The performance at this setting is plotted as the points at .92 bhp. These points wi l l not be considered representative of normal engine performance, as the exhaust ports were found to be almost completely closed with carbon when the engine was stopped. The carbon was removed and several days later the tests were continued with the valve closed^at several throttle positions. As in a l l the tests, the speed was brought up to 4500 rpm by adjusting the dynamometer after the throttle had been set. Figure 71 indicates a definite reduction in the specific fuel consumption with the stratified charge scavenging system. But the temperatures, figure 75 and 76, indicate that the engine ran hotter when the scavenging was done with a stratified charge. The exhaust temperature as well as the spark plug and cylinder head temperatures were a l l generally higher. The reason.for this 107-may be explained with reference to the air-fuel ratio, figure 77- As the low air-fuel ratio approaches the stiochiometric ratio, as a result of stratifying the charge> combustion is more efficient as explained in chapter 1. The result is an increase in the combustion temperatures. The specific fuel consumption, figure \"jQ, is higher as extra air is admitted to cylinder which also generally increases the volumetric efficiency, figure jk. The fuel trapping efficiency is increased, figure 72, indicating that more of the fuel remains in the cylinder. Due to the few points for conventional scavenging the shape of the curve may be closer to the trapping efficiency with stratified charge scavenging than the curve that is drawn would indicate. Similar observations maybe made about the scavenging efficiencies as shown in figure 73-108. D Conventional scavenging 0 Stratified charge sc. \/ \\ SPEED \/ \/ 1 n 7 SPEED V 1 1 SFC \\ \\ SPC \\ 5200 5000 4800 4600 4400 4200 4000 3800 3600 3400 3200 0 1.0 15 20 Brake horse power 25 3.0 'ilM\u00a3SjJLk' Performance curves with VP 100$, Jet FA, ITS 4500, from sheet 25. 109. Figure 72. Trapping efficiency curves with VP 100$, IS 4500, from sheet 25. Figure 75. Scavenging efficiency curves with VP 100$, Jet FA, NS 4300, from sheet 25. 111. 80 75 70 65 60 8? A CD \u2022H 55 O <M W 50 45 40 35 30 \u2022 C o n v e n t i o n a l sc O S t r a t i f i e d char a v e n g i n g ge s c . \/ YE O - ( SAB 1.0 13 2JD Brake horse pov\/ar 2.5 3<P Figure 74. Efficiency and air ratio curves v\/ith VP 100$, Jet FA, NS 4500, from sheet 25. F i g u r e 75. Temperature curves w i t h VP 100%, J e t FA, US 4500, from sheet 25. Figure 76. Temperature curves with VP 100$, Jet FA r NS 4500, from sheet 25. 114. O Conve O Strat ntional s if ied cha cavenging rge s c. p AFC\/ AFC & OAF 1 1 OAF^p j 16 14 13 12 3 Vi I U -H < 8 7 0 .5 1.0 15 2J0 25 3.0 Brake horse power Figure 77. Air-fuel ratio curves with VP 100$, Jet FA, US 4500, from sheet 25. U 5 . 90 ,80 70 S P. P..60 fl o -p P. co fl o o \u2022H < 50 40 D Conventional scavenging O S t r a t i f i e d charge sc. > TAC \/ TAC V J \/r \/ SAC\"\"-~ SAC \u2014\u00ab\u2014 50 XI I P. X! \u2022\u00b020 u CD P. O co-co 10 V> 15 2.0 Brake, horse power 2.5 3P F i g u r e 78. A i r consumption curves w i t h VP 100$, J e t FA, NS 4500, from sheet 25. 116. Figures 79-85 Speed and specific fuel consumption curves The specific fuel consumption and speed for each series of tests were plotted on a brake horse power base to enable a comparison to be made at a particular brake horse power. In most cases interpolation of the curves was necessary. The specific fuel consumption was generally lower when the engine was running on the stratified charge scavenging system, although in several cases the consumption was the same for both the new and the conventional system and in one case the consumption was higher. The unreliable inter-polation of the line from only two points may account.for the exception in the latter case. There is very l i t t l e difference between the speeds for the two scavenging methods as the power absorbed by the dynamometer varies with th6 speed of the engine. Figure 85 may be taken as representing the results as thesei:cufves were plotted from the results obtained from tests performed with the throttle position varying from f u l l open to 2 3 $ open. The curve indicates a very definite decrease in the specific fuel consumption especially at the lower end of the horse power scale. 117. 3 . 0 2 . 8 2 .6 u X ) I p, A X t u CD P -2 . 4 co 2 . 0 1.8 1.6 1.4 1 .2 1 .0 VConven O Strati tional sc fied char avenging ge sc. -\u00a9 0\u2014 ID SPEED a SPC 5200 5000 4800 4600 4400 s 4200 -a a> <u p. co 4000 3800 3600 3400 >00 Brake horse, power Figure 79. Speed & sfc curves with T P 50$, 4900, from sheet 15. 113. \u2022 Conventional scavenging 0 Stratified charge sc. SPEED \u20141 \"W B c \u2022>,., _\/?>\u2014\u2014\" <\u2022 . S P C 5200 5000 4800 4600 4400 4200 4000 3800 3600 3400 3200 1.0 1.1 1.2 1.3 1.4 B r a k e h o r s e power 1.5 1.6 Figure 80. Speed and sfc curves with TP 50$, NS 4500, from sheet 17 119. 3.0 2^ 8 ^  2\u00b0 6 u XJ I ft XI X i u 2o4 cu ft x> r H o 2.2 CO 2.0 1.8 1.6 1.4 1.2 1.0 D Conven O Strati tional sc fied char avenging ge sc. !3 -\u00a9 SPC SPEED 0.9 1.0 1.1 1.2 1.3 Brake horse power 1.4 1.5 Figure 81. Speed and sfc curves with TP 50$. US 4700. from sheet 20. 120. u xi i a, xi Xi cu a-\u00a3 4 . 2 co 4.0 3.8 J.O: 3.4; 3.2 3.0 a Conven O Strati: \u2014 ' 1 tional sc fied char avenging ge sc. SPEED B V SPC 5200 5000 4800 4600 4400 B 4200 CO CO p. CO 4000 3800 3600 3400 0 .7 0.0 0.9 1\/0 I . l Brake .horse power ... li.2 I . 7? 200 Figure 82. Speed & sfc curves with TP 60$, NS 5000, from sheet 21. 121. 3.0 2.8 u S3 I Q. si Si u 2.4 (a P. o2.2 V i CO 2.0 1.8 1.6 1.4 1.2 1.0 O Conven O Strati 1 tional sc fied char avenging ge sc. SPEED ' SPC \/ \u2022 V 1 . 4 4 1 . 4 3 1 . 5 2 1 . 5 6 1 . 6 0 .: Brake horse power 1 . 6 4 5200 5000 4800 4600 4400 6 4200 T3 Ct) 0) P. ra 4000 3800 3600 3400 >00 Figure 85. Speed & sfc curves with TP 70$, ITS 4300. from sheet 2 2 . 122. 5400 J J 1 \u2022 I I 11400 0 0.3 0.5 0.9 1.2 1V5 1.8 B r a k e h o r s e power F i g u r e 84. Speed & s f c curves w i t h TP 30$, from sheet 23. 123. 3.0 2.8 2.6 u Xi i ft Xi Xi u CD Cu 43 H 2o4 o m 2.2 2.0 1.8 1.6 lc4 1.2 1.0 O Conven O Strati tional sc fied char avenging ge sc. SPEED \/ [ 1 \/ \/ \/ . SPC fl 5200 5000 4800 4600 4400 s 4200 T3 CD CD Cu CQ 4000 3800 3600 3400 0.4 0.8 1.2 1.6, Drake horse power 3200 2.0 2.4 Figure 85. Speed & sfc curves with VP 100%, from sheet 24. 124, Figures 86-92j\" Experimental curves of exhaust and spark plug temperatures The exhaust and spark plug temperatures were plotted on a brake horse and power base, to enable a\"icomparison to be made on the basis of a particular brake horse power. The exhaust temperatures are generally lower for stratified charge although in three tests i t was slightly higher. The spark plug temperature was sometimes higher, and sometimes lower. Figure 92 can be taken as representing the tests generally as the points for this curve were drawn from tests conducted at a constant valve position for purposes.of determining the performance of the engine as the incoming charge was throttled. The curves show that the exhaust temperature is lower and the spark plug temperature is higher for the stratified charge scavenging system; The higher spark plug temperaturenindicates more efficient combustion as the overall combustion temperature is higher. The lower exhaust temperature indicates that more energy is removed from the,exhaust gases before being discarded. The lower temperature may also be due to an increase in the quantity of cool air present.in the exhaust pipe which had escaped from the cylinder through the exhaust ports. 125. b Conv O Stra | 1 entional t i f ied cr 1 scavengin large sc. \u2014 \u00ae ET 0 \/ SPT Q r B 480 0> r-i 460 g a> P. a CD EH 440 420 400 380 1.-80 .1.-85 1V90 1.95 2.00, Brake horse power 2.05 360 2.10 Figure 86. Spark plug & exhaust temperature curves with TP 50$, NS 4900.' from sheet 15. 126. 900 860 820 780 \u2014740 CO CD u cd 2700 P. s co +> 4> CO cd 660 xl X n 620 580 540 500 \u2022 Conventional scavenging 0 Stratif ied charge sc. ET \u2014 \u00ae ~ ~ ^ > SPT \u2014 \u2022-(*)\u2014\u2014^ m \/ 1.0 1.1 1.2 1.3 1.4, Brake horse power 1.5 1.6 Figure 87. Exhaust and spark plug temperature curves with TP 50\/fa, US 4500, from sheet 17. 127. 900 860 820 780 \u2014 7 4 0 ca CD U 3 - P a J a> 700 P. e <D +\u00bb \u2022 P CO 3 eg 660 \u00bb 620 580 540 500 1 D Convert 0 Strati: tional sc t?ied char avenging ge sc. ET \\ y \\ SPT 370 CD U 3 -P a) U CD a, a CD EH bO 360 3 .. p. U ni a, co 350 340 330 1.0 1.1 1.2 1.3 1,4 Si.. . Brake horse,.power 1.5 320 1.6 Figure 88. Exhaust & spark plug temperature curves with TP 50%>, NS 4700, from sheet 20. 128. Figure 89. Exhaust and spark plug temperature curves with TP 60$, US 5000, from sheet 21. 129. 900 860 OConventional scavenging OStrat i f ied charge sc. 820 780 \u2014740 CO CO u 3 -p g70Q s -p -p CO ca 660 xt x w 620 580 540 500 0 ET SPT OJ f-i 3 400 g co p. a CO EH 380 360 340 320 300 1. 40 1.50 ' 1.55 1.60 1-.65 1*70 Brake horse power Figure 90. Exhaust & spark plug temperature curves with TP 70$, NS 4300, from sheet 22. 1 3 0 c Figure 91. Exhaust & spark plug temperature curves with TP 3 0 $ , from sheet 2 3 . 1 3 1 . 900 860 820 780 \u2014 7 4 0 CO CO u 3 cd | 700 P. e CD -P +> m cd 660 xi K W '620 580 540 500 \u2022 Conven O Strati: tional sc fied char avenging ge sc. \u2014 H - , \u00ae ET I \u2022 \u00a9 \/ \/ ro SPT I 0 CD 3 -p cd CD cu s CD <50 3 i~l Cu cd a cn 360 340 320 1.0 1,2 1.4 1.6 l.,8,, Brake horse' power 300 2.0 2.2 Figure 92. Temperature curves with VP 100$, from sheet 24. Chapter VI. SUMMARY AND CONCLUSIONS 1 3 3 -Chapter VI. SUMMARY AND CONCLUSIONS From the results of the tests described, i t is obvious that there are great fluctuations, in the operating characteristics of the engine. For a small high-speed 2-stroke cycle engine operating at part throttle, this is to be expected. The conclusions which can be drawn from experiments on such an engine can only be generalizations and may not hold true in a l l cases. The greatest problem to consistent.results seemed to be the variation in the air-fuel ratio through the carburetor. The continuous C O 2 recorder showed fluctuations of about +_ 1 - 2 $ C O 2 during a l l of the tests. Average C O 2 content was usually around 6 $ . As the results of the tests show, the air-fuel ratio through the carburetor was not always consistent even when the intake was not choked.. A contributing factor to this may have been the variation in the momentum of the air mass entering the carburetor from a straight pipe. In the tests minimum specific fuel consumption was usually obtained at maximum overall air-fuel ratio as the ratio was generally below the stoichiometric ratio at part throttle. In the stratified charge scavenging system> the additional air entering through the scavenging air valve increases the overall air-fuel ratio. As the air-fuel mixture enters the cylinder after the scavenging air, more of the mixture is trapped in the cylinder. These two factors increase the brake 'thermal efficiency. As the charge trapping efficiency decreases, more air escapes with the exhaust gases so that the exhaust is codler and as the fuel trapping efficiency increases, less fuel is available for afterburning in the exhaust pipe. The higher overall air-fuel ratio results in more efficient combustion raising the overall combustion temperature and negating the cooling effect of the excess 13^ -air in the exhaust gases. It is quite satisfactory to keep the valve at a constant position and vary the throttle setting to change the power produced, as is done in the conventional throttling system. But as the throttle is closed, the scavenging air flow increases, so that i t is necessary to limit- the scavenge ing.air ratio to obtain efficient operation at low power requirements. On the other hand the scavenging air valve is closed when maximum power is required with no deterrent effects to peak engine output. Generally the stratified charge scavenging system shows definite reductions in the specific fuel consumption, especially at low power requirements. The specific fuel consumption decreased 10.6$ at 2.1 hp and 34.8$ at 1.2 hp during one test. The normal decrease was between 5 and 15$. The temperatures are not as consistent although the exhaust temperatures are generally lower, and the cylinder head and spark plug temperatures generally higher. Nevertheless much work is s t i l l required to adapt the principle of stratified charge scavenging to a practical, trouble-free, consistent system. The following l i s t contains some of the work s t i l l to be done on similar engines to obtain more detailed information about the effects of stratifying the charge for more efficient combustion at part throttle. (1) comparison of the performance with a scavenging air valve in each of the two passageways instead of only one; (2) comparison of the performance at various valve intake temperatures by preheating the air entering the valve by means of a heat exchanger from the exhaust gases or by an external heat source; (3) compare the actual scavenging and trapping efficiency with the theoretical..This would require a method of determining the amount of air and fuel which has escaped into the exhaust pipe; 135-(U) method of determining the degree of mixing between the scavenging air and the carburetted air-fuel mixture, and the degree of mixing of the exhaust gases with the fresh charge. This may require studies in models; (5) more tests with the present system with a carburetor that allows closer control of the air-fuel ratio. Appendix I. GLOSSARY 137-GLOSSARY (1) Scavenging a i r v a l v e , (SAV): valve arrangement of reed valve and cock c o n t r o l valve t h a t allows a d d i t i o n a l a i r to enter passageway to p o r t s ; (2) Scavenging a i r : a i r t h a t enters through the scavenging a i r v a l v e ; (;\/ (3) (Carburetted) a i r - f u e l mixture: mixture of f u e l and a i r t h a t enters crankcase through the carb u r e t o r ; (U) .'.'Charge: Fresh gases e n t e r i n g the engine or c y l i n d e r and made up of scavenging a i r and c a r b u r e t t e d a i r - f u e l mixture; (5) Scavenging a i r r a t i o , (SAR): d e f i n e d as the mass r a t i o of scavenging a i r s u p p l i e d to t o t a l charge s u p p l i e d ; (6) ^Scavenging e f f i c i e n c y , (SE): d e f i n e d as the mass r a t i o of charge r e t a i n e d t o the i d e a l mass r e t a i n e d ; (7) Scavenging r a t i o , (R): de f i n e d as the r a t i o of mass of charge s u p p l i e d to i d e a l mass; (8) ^Trapping e f f i c i e n c y , (TE): defined as mass r a t i o of charge r e t a i n e d t o charge s u p p l i e d ; (9) * F u e l scavenging e f f i c i e n c y , (FSE): defined as the r a t i o of mass of c a r b u r e t t e d a i r - f u e l mixture r e t a i n e d t o i d e a l mass th a t the c y l i n d e r should have retaixied; (10) F u e l scavenging r a t i o , (FR): de f i n e d as the mass r a t i o of ca r b u r e t t e d a i r - f u e l mixture s u p p l i e d to i d e a l mass that the c y l i n d e r should r e t a i n ; (11) * F u e l t r a p p i n g e f f i c i e n c y , (FTE): d e f i n e d as mass r a t i o of ca r b u r e t t e d a i r - f u e l mixture r e t a i n e d to c a r b u r e t t e d a i r - f u e l mixture supplied. *NOTE: For i d e a l e f f i c i e n c i e s , p e r f e c t mixing i s assumed. Appendix II. SYMBOLS, ABBREVIATIONS AND UNITS SYMBOLS,. ABBREVIATIONS ;AND UNITS The following is a l i s t of symbols and abbreviations used throughout the text. A symbol not listed is defined on introduction. The units refer to the values as specified in the tables of data and results in Appendix TV and Appendix V. ACP - average of peak combustion pressures (psi); ACPD - average deviation of peak combustion pressures from ACP (psi AF - overall air-fuel ratio; AFC air-fuel ratio of mixture inspired through carburetor; BARO - barometric pressure (in. of Hg); . BHP - brake horse power; BMEP - brake mean effective pressure;(pei); BTE - brake thermal efficiency ($); CAT cooling air temperature (?F); CHT - cylinder head temperature (\u00b0F); CIT - carburetor intake temperature ( ? F ) ; CIPD - carburetor intake pressure drop (in. of water); COUNT - number of counts of revolution counter in time TS; DBT - dry bulb temperature (\u00b0F); DYNA - dynamometer torque reading ET - exhaust temperature in pipe ( F); ETIM - exhaust temperature in muffler ( F); EPD - exhaust pressure drop (in. of water); FC - fuel consumption (ppm); FR - fuel scavenging ratio; FSE - fuel, scavenging efficiency ($>); FTE - fuel trapping efficiency ($); IFSE - ideal fuel scavenging efficiency ($); IFTE _ ideal fuel trapping efficiency ($); i.kd. ISE - ideal charge scavenging efficiency ($); ITE - ideal charge trapping efficiency ($); JET - 16 times fraction of one turn that.jet.is open; MIT - flowmeter inlet temperature (\u00b0F); NS - nominal speed from tachometer (rpm); OAF - overall air-fuel ratio; IOD - nozzle (orifice) inlet density (lh per cubic f t . ) ; OIT - nozzle (orifice) inlet.temperature (\u00b0F); OIPR - nozzle (orifice) intake pressure (rise) above\"BARO (in. Hg); OPD - nozzle (orifice) pressure drop (in. of water); PT. - passageway air temperature (\u00b0F); (RPT - right and LPT - left); QM - volume reading of flowmeter in time TM (cubic f t . ) ; R - scavenging ratio; RT - room temperature (\u00b0F); REYN - Reynolds, number; S - speed (rpm); SAC - specific air consumption (lb per bhp-hr.); SAR - scavenging air ratio; SFC - specific fuel consumption (lb per bhp-hr.); SPT - spark plug temperature (\u00b0F); SP GR - specific gravity; TAC \u2022- total mass air\u2022consumption (ppm); TF - time for WF lb fuel flow (min); TM - time for QM cubic ft air flow through meter (min); TORQ - torque (lb-ft.); TP - throttle position - ratio to f u l l open ($); TRIAL - reference to data sheets taken during the tests; TS - time for COUNT counts on rev. counter (min.); 141. VDT - Verein Deutscher Ingenieure - nozzle standards; VE - volumetric efficiency ($>); VIPD - valve intake pressure drop (in. of Hg); VIT - valve intake air temperature (\u00b0F); VP - valve position - ratio to fu l l open ($); WBT - vet bulb temperature (\u00b0F); WF - fuel.consumed in time TF (Kilogram or cubic centimeters); WFTC - weight air flow through carburetor (ppm); WFTV - weight air flow through scavenging air valve (ppm); Appendix III. EFFICIENCY DERIVATIONS WITH PERFECT MIXING EFFICIENCY DERIVATIONS WITH PERFECT MIXING J \" Derivation of the relationships between scavenging efficiency, trapping efficiency, and scavenging ratio with perfecij mixing requires the following asEumptions: (1) Scavenging air and the carburetted air-fuel mixture do not mix prior to cylinder entry; (2) the scavenging air mixes completely with the exhaust gases as. soon as the air enters, and then the carburetted air-fuel mixture mixes completely with the resultant air-exhaust mixture as soon as the fuel-air mixture enters the cylinder; (3) the exhaust, air, and air-fuel mixture are at the temperature of the mixture in the passageway; (k) the exhaust and air-fuel mixture have the samei?molecular weight as air; (5) the pressure is assumed constant and equal to the average exhaust pressure. For an homongeneous charge Let: y\u2022= volumetric fraction of charge in the cylinder at any instant to total volume of cylinder, v = volume of mixture that has flowed into cylinder, V = cylinder volume. The volumetric increase in the mixture is equal to the volume of fresh charge which has flowed in, minus the volume of the.fresh charge which has escaped. In mathematical terms this relationship may becSexpressed as: Vdy = dv - ydv dy = (l-y)dv V Integration yields: \u2022\u2022 u y = 1 - e\" V (1) Ikk. By d e f i n i t i o n s : TAC R = (PID)(S)(V) (2) WFTC , , m = (piD)(a)(y) (3) = f (4) FSE FTE = \u2014 ( 5) WFTV SftR: = TAG\" (6) For an homogeneous mixture: WFTC = TAC SAR = 0 y = SE = FSE U \u2122 TAC V = R = F R = (PID)(S)(V) S u b s t i t u t i n g these values i n t o equations 1, h and 5 g i v e s : y = SE = 1 - e~ R (7) FSE = 1 - e\" R (8) TE = 1 ~ e \" R (9) R 1 - e- R , ^ FTE = ^ (10) For a s t r a t i f i e d charge - symmetrical admission i n t o c y l i n d e r The i d e a l i z e d equations 7 and 9 s t i l l h o l d f o r t h e . t o t a l amount of scavenging a i r and ca r b u r e t t e d a i r - f u e l mixture (charge) s u p p l i e d . To determine the equations f o r scavenging e f f i c i e n c y and tr a p p i n g e f f i c i e n c y of only the c a r b u r e t t e d a i r - f u e l mixture v and y must be defined as f o l l o w s : 145-y = volumetric fraction.of the carburetted air-fuel mixture in the Cylinder to total cylinder volume, v = volume of the carburetted air-fuel mixture that has flowed in up to time \"t\". With these definitions y = FSE Z = FR V Equation 1 becomes FSE = 1 - e\"FR ( l l ) \u2122 , FSR 1 - e~m , . and FTE = = fl?) FR FR v ' To determine the value of FR, consider v = total volume of. charge flowed in per cycle minus the volume of scavenging air flowed in during the same cycle TAC WFTV \" (PID)(S) \" (PID)(S) 1 V 1 - x (TAC - WFTV) = (PID)(S) . Then ^ \" (V)(PID)(S) (TAC -WFTV) (13) By equation 6, WFTV = (SAR)(TAC) Substituting into equation 13 yields: v = 1 V = (V)(PID)(S) ( T A C ^ T A C ) ( S A R ) ) T A C ' 1 - SAR (V)(PID)(S) Using equation 2, H = R (1 - SAR) (lk) 146. Substituting into equation 11 and 12 , - R ( I - S A R ) . . F S E = 1 - e > ' (15) 1 _ -R(l-SAR) F T E = R ( l - S A R ) < L 6 > For stratified charge - non symmetrical charge admission If a l l of the scavenging air enters one scavenging air valve and the . assumption is made that this air enters the cylinder through only one port (in a symmetrical 2-ported engine), say the right one, then equations 15 and 16 mustbbe modified although equations 7 and 9 are s t i l l valid. Consider that the charge entering the left port.is separated from the charge entering the right port, that is , divide the cylinder into, two equal volumes and analyse them separately. The equations for perfect mixing for the left port with no scavenging air, wi l l be the same.as for ordinary scavenging, that is, equations 15 and 16 cancel down to equations 8 and 10, as SAR is zero. For left volume: TAC (FR) = R = (S)(PID)V (FSL)L.= 1 - e\"R ( F T E ) L = 1 - e\"R The efficiencies for the right volume containing a l l the scavenging air, can be expressed by modified forms of equation 15 and l 6 . For right volume; (SAR)R = \u2122 R (WFTV + WFTC) \u00a3 2(WFTV) TAC = 2(SAR) (17) , s fTAC - WFTV) (F H ) R = (S)(PID)(V) i But WFTV = TAC(SAR) Therefore . . (TAC - TAC(SAR)) 2 R = ~ (S)(PID)(V) (S)(PID)(V) 2 = R ( l - 2 (SAR)) (18) Equation 1 checks w i t h equation 15 i f the SAR i n equation 15 i s taken as (SAR) R . S u b s t i t u t i n g equation 18 i n t o equation 11 and 12 ( F S E ) R = 1 - e ^ 1 \" 2 (^AR)) (PTE) = j _ e - ^ 1 - 2 ( SAR)) R ( l - 2 (SAR)). For the o v e r a l l e f f e c t of both volumes of the c y l i n d e r , the e f f i c i e n c i e s must be averaged ( F S E ) t + ( F S E ) R FSE = L K 2 - R ( l - 2 (SAR)) -R FSE = 1.T.-| e + e (19) (FTE) T + (F T E ) n PTE F T E 2 \u00b1 _ e - R ( l - 2 (SAR)) 1 _ e \" R 2 ( R ) ( l - 2 (SAR)) + ^ R T \" ( 2 0 ) Charge e f f i c i e n c y equations 7 a n < l 9. s t i l l h o l d : SE = 1 - e \" R ( 7 ) 148. Where R and SAR are as previously defined, i . e . , TAC R = (PID)(S)(V) ( 2) WFTV SAR = TAG- (6) Equations 19, 20, 7> 9> 2, and 6 are the ones used for approximating the scavenging efficiency and trapping efficiency of the 2-stroke engine stratified charge scavenging system. Appendix IV. TABLES OF OBSERVED RESULTS TABLE II . OBSERVED EXPERIMENTAL DATA TRIAL JET NS TP BARO VP ACP ACPD COUNT TS DYNA WP TP OPD CIPD 15-2 14 4900 50 29.67 0 316.0 18.90 59756 35 1.64 31.3c c 1.00 4.46 .06 5 100 307.0 21.97 55600 33 1.65 31.4c c\"1;00 3.87 .04 8 50 303.2 21.57 60648 36 1.63 30.4c c 1.00 3.94 .04 17-2 16 4500 50 29.94 0 271.3 17.38 53599 35 1.16 22.5cc 1.00 2.15 .02 5 70 292.1 24.54 48810 31 1.29 23.3cc 1.00 1.88 .02 7 100 303.0 28.78 57809 31 1.37 23.8cc 1.00 ' 1.83 .02 11 40 279.7 24.30 51067 33 1.24 2i.5cc 1.00 2.02 .02 19-2 17 5300 82 29.90 0 - \u2022 - 54860 30 2.11 .760 31.00 6.24 .07 5 100 - - 58259 32 2.09 .740 31.05 6.05 .06 20-2 20 4500 50 29.94 100 275.2 \"18.77 70928 44 1.33 1.240 49.64 3.00 .04 \u2022 5 0 268.0 15.21 62458 40 1.23 .980 39.52 3.37 .03 7 50 277.6 19.87 32800 21 1.22 .420 17.70 2.98 .03 11 70 278.2 18.17 48171 30 1.35 .710 29.70 2.88 .02 21-2 P.A. 5000 60 30.02 0 251.2 12.14 56714 33 .69 .800 32.62 3.18 ' .04 4 100 260.2 9.98 29150 16 .86 .390 14.92 2.68 .03 5 100 254.8 10.61 76450 42 .86 .980 37.90 2.68 ,03 TABLE I I . (Con't) TRIAL JET NS TP BARO VP ACP ACPD COUNT TS DYNA WP TP OPD CIPD 21-8 F.A. 5000 60 30.02 70 -249.8 9.65 53953 30 .84 .669 26.22 2.74 .03 -11 50 248.9 10.20 54667 31 .74 .64 25.66 2.88' .03 22-1 P. A. 4300 70 29.84 0 258.0 16.30 26340 18 1.57 .30 17.43 2.31 .01 -5 . 55 279.2 21,46 51350 35 1.53 .54 34.45 1.89 .01 - 8 100 292\u201e6 18.12 72150 48 1.55 .73 . 42.88 1.69 .01 , 23-2 P,A. . 2800 : 30 29.81 0 189o7 11.98 33482 36 .33 .23 27.01 .36 .00 -5 - 40 190.2 7.96 24513 25 .35 .16 20.38 .27 .00 -7 55 193 c 7 . 6.42 24060 21 .49 .10 11.87 .23 .00 . - 9 100 298.2 16.26 1706 \u2022 1 1.39 .10 8.87 .36 .00 -12 100 244.2 27.10 57269 34 1.25 .35 30.10 .30 .00 ' -15 80 - - 50499 31 1.06 .'19 16.45 .36 .00 24-2 5200 100 29.80 0 263.3 18.26 53229 30 1.70 .58 25.38 4.04 .02 -5 100 100 287.4 24.72 57019 32 1.71 .58 26 c 50 3.75 .02 - 8 70 100 246.6 19.12 53110 31 1.48 .62 28.03 3.05 .02 -11 70 100 280.1 23.42 53512 30 1.70 .57 27.71 3.71 .02 -14 60 100 239.0 14.31 53399 32 1.36 .64 29.30 2.63 .02 TABLE II . (Gon't) TRIAL JET NS TP BARO VP ACP ACPD COUNT TS DYNA WF TF OPD CIPD 24-17 F.A. 5200 50 29.80 100 241.6 18.62 40194 25 .1.30 .40 24.00 1.57 .01 -20 40' 225.0 14.70 31986 21 1.21 .31 22.60 .81\" .01' -23 30 29.87 248.8 20.18 48720 34 1.10 .33 30.77 .40 .01 -26 23 197.3 19.31 27295 29 .33 .28 24.12 .06 .01 . -29 50 0 - 29990 20 1.17 .39 20.30 2.46 .01 2 5-2 P . A . 4500 100 29.86 100 - \u2014 52772. 34 1.65 -\u00b057 33.01 2.36 .02 -5 70 - - 35020 23 1.43 .36 20.25 2.09 .02 - 8 - 65 - - 44116 29 1.17 .46 24.35 2.03 . .02 -11 50 - - 38517 25 .96 = 33 21.15 1.08 .01 -14 40 \u2022 - - 41950 28 .73 .25 23.71 .40 .00 \" -17 100 0 - - 20540 14 .92 .15 12.15 1.47 .01 ' 14-8 14 4700 - 100 29.73 0 - - 32550 40 1.12 22.Ice 2.00 .88 .00 \"-12 100 100 - - 30630 34 1.11 20.6cc .2.00 .38 .00 25-20 F.A. 4500 100 29.80 0 -. - 42483 27 1.98 .43 22.95 4.02 .01 -23 60 0 - - 40851 26 1.65 .54 25.80 3.02 .01 -26 50 0 - - 25464 17 1.04 .32 18.52 1.70 .01 TABLE III . OBSERVED EXPERIMENTAL DATA TRIAL QH TM OIPB YIPD EPD CAT CIT CUT SPT VIT ET ETIM R'PT LPT OIT MIT DBT WBT 15-2 0 0 4.46 0 6.2 199 84 121 391 163 . 815 568 278 - 82 . 76 75 64 1 5 11.93 30 3.87 1.3 5.5 202 83 125 404 136 829 581 288 - 82 76 . 8 6.99 38 4.00 .9 5.4 201 83 125 390 183 831 584 288 - 82 76 17-2 0 0 2.15. .0 \u20222.5 202 75 108 370 156 788 568 307 - 74 69 68 60 5 16o49 2 5 1.88 .8 2.6 205 76 113 383 127 787 571 313 - 74 69 7 33.66 31 1.83 1.2 ' 3.1 206 76 113 386 112 798 57.8 316 - 74 69 11 5.99 32 2.02 .2 2.3 205 77 108 373 179 766 565 .316 - 75 70\" 19-2 0 0 6.25 0 6.6 142 79 362 461 160 896 614 294 301 78.. 74 ' 71 '60 5 -4.34 27 6.07 .9 5.4 141 80 358 457 230 900 617 299 307 78 ,74 20-2 35.22 43 3.1 .10 3.3 126 72 294 351 100 791 553 282 281 \u2022 72 68 66 58 5 0 0 3.6 0 2.5 124 72 282 334 146 770 545 270 270 \u202272 68 5.26 16 ' 3.1 .03 2.3 124 72 284 337 139 759 541 277 276 72 68 11 20.69 30 2.9 .06 2.5 124 72 288 347 108 770 545 275 279 72 68 21-2 0 0 3.3 0 2.4 140 73 252 228 149 726 505 249 244 72 67 \u2022 .68 59 \u20224 - 1-5.93 14 2.7 .14 2.5 143 74 259 232 93 796 543 254 252 73 67\" 5 35.97 34 2.7 .14 2.9 143 74 259 226 94 798 546 254 252 72 67 TABLE III. (Con't) TRIAL QM TM OIPR VIPD EPD CAT CIT CHT SPT VIT ET ETIM HET i p r OIT MIT DBT WBT 21-8 20.03 23 2 .74 .12 3 .5 142 73 257 209 97 789 539 253 251 72 67 68 59 \" - 11 13 = 08 29 2 .95 .07 3 .0 141 . 72 251 198 124 757 5 1 ? 251 247 72 67 22-1 oOO 0. 2 .40 .00 2 . 9 134 75 307 316 163 727 522 295 284 72 71 69 62 - 5 14 .27 30 1.91 .05 2 .9 137 75 316 342 134 726 519 305 295 74 71 -8 44 .70 38 1.72 .15 3 .2 136 75 316 346 100 738 523 303 282 74 71 23-2 .00 0 .36 .00 1.5 111 70 210 201 127 372 303 227 228 69 68 68 60 - 5 7 .67 24 .29 .04 1.6 114 70 220 206 120 388 319 245 240 69 68 - 7 15 .91 22 .26 .07 1.4. 122 72 242 223 111 485 391 282 264 71 68 - 9 2 .49 1 .37 .47 3 .9 126 73 305 343 85 654 480 314 280 71 68 -12 79 .55 32 .30 .46 3 .5 130 74 306 353 86 643 468 326 286 ' 72 68 -15 60 .18 30 .37 .31 3 .4 153 73 283 317 84 656 468 316 286 72 69 24-2 .00 00 4 .15 .00 5.7 182 68 300 329 145 817 553 262. 265 68 66 65 59 - 5 . 7 .14 29 3 .81 .04 5-9 186 68 307 343 135 821 556 274 277 70 67 -8 1.5.61- 28 3 = 12 .02 5 = 3 178 68 282 329 105 796 546 270 271 ' 70 67 - 1 1 . - . 7 . 3 8 30 3 = 84 .04 . 5 = 9 198 69 322 406 133 807 553 275 282 71 67 -14 24 = 66 33 2 .69 .09 4 = 4 179 68 275 333 98 776 542 271 2.69 71 67 TABLE III. (Con't) TRIAL QM TM OIPR VIPD EPD GAT CIT CHT SPT VIT ET ETIM H P T : L P T OIT MIT DBT WBT 2 4 - 1 7 2 8 . 9 6 27 i ; ' 5 9 . 1 4 3 . 1 188 67 286 352 89 749 531 296 280 71 67 69 65 - 2 0 3 5 , 4 6 25 . 8 6 . 1 9 2 . 3 186 66 283 3 4 1 83 696 505 309 275 ' 70 67 . - 2 3 6 1 . 0 9 35 . .41 . 2 6 1 .7 195 71 294 359 85 632 465 3 1 7 276 70 6 7 - 2 6 53 = 86 26 . 0 7 . 3 4 2 . 4 151 72 212 243 8 0 418 329 2 2 9 199 71\" 67 - 2 9 . 0 0 00 2 . 4 8 . 0 0 3 . 1 182 74 268 325 135 724 529 2 6 9 263 72 6 9 25-.2 2 2 . 4 6 3 1 2 . 4 1 . 0 9 3 . 4 164 72 333 430 1.10 738 541 294 291 72 68 69 61 - 5 1 7 . 1 3 22 2 . 2 0 . 0 9 3 . 1 152 72 299 370 103 742 540 294 283 73 6 9 - 8 2 0 . 2 5 27 2 . 0 9 . 0 9 3 . 1 143 73 280 335 103 722 532 283 275 74 70 - 1 1 2 5 . 7 1 25 1 . 1 0 . 1 2 2 . 1 143 71 283 345 92 670 - 296 274 74 \" 71 - 1 4 3 3 . 2 0 25 . 4 1 . 1 7 1 .1 146 70 286 346 85 530 - - 300 279 ' \"74 71 - 1 7 . 0 0 0 0 1 . 5 0 . 0 0 1 .1 148 69 288 352 131 563 = 286 280 74 73 1 4 - 8 . 0 0 00 . 9 2 . 0 0 2 . 6 232 85 382 167 591 439 292 - 80 75 74 64 - 1 2 4 5 . 1 6 34 . 4 0 . 0 0 2 . 9 226 87 134 354 111 591 444 303 - 79 75 2 5 - 2 0 0 0 4 . 3 0 . 0 1 4 . 8 186 76 366 420 154 747 531 300 307 74 71 69 62 '-23. 0 0 3 . 18 . 0 1 3 . 7 158 77 302 344 146 742 510 284 283 74 71 - 2 6 0 0 1=90 . 0 1 2 . 5 1.46 77 266 319 139 680 474 288 285 74 7 1 Appendix V. TABLES OF CALCULATED RESULTS TABLE IV. REDUCED EXPERIMENTAL RESULTS TRIAL BHP SPC SAR TAC IFTE BMEP TORQ VE BTE ISE SAC ITE APC OAP PC 15-2 1.95\" 1.55 .0 .565 75.1 28.5 2.18 66.9 8.10 45.2 17.4 75.1 11.2 11.2 .0503 5 1.91 1.58 '5.1 .556 75.9 28.3 2.17 67.5 7.93 45.5 17.5 74.9 . 10. 5 11.0 .0504 8 1.89 1.55 2.4 .544 75.8 27.9 2.14 66.1 8.10 44.8 17.3 75.3 10.9 11.1 .0438 17-2 1.22\" 1.77 .0 .395 79.2 19.9 1.52 53.9 7.06 38.4 19.4 79.2 10.9: 10.9 .0361 5 1.40 1.60 11.7 .418 79.8 22.1 1.69 56.0 7.82 39.6 v 17.9 78.5 9.9 11.2 .0373 7 \u20221.53 1.50 16.0 .437 81.1 23.8 1.82 57.7 8.38 40.5 17.1 78.0 9.6 11.4 .0382 11 1.32 1.58 3.5 .396 79.7 21.3 \u2022 1.63 54.2 7.97 38.6 18.0 79.1 11.0 11.4 .0346 19-2 2.65 .1.22 .0 .679 72.4- 36.2 2.77 76.0' 10.27 49.6 15.4 72.4 12.6 12.6 .0540 5 2.62 1.20 -1.8 .657 35.8 2.74 74.6 10.42 48.9 15.1 . . 12.7 \u2014-\u2014 .0525 20-2 1.47 2.24 11.5 .530 77.9' 22.8 1.75 66.3 5.60 44.9 21.6 75.3 8.5 9.6 .0550 5 1.33 2.46. .0 .498 76.2 21.3 - 1.63 63.5 5.09 43.5 22.5 .76.2 9.1 9.1 .0546 . 7 1.32 2.38 5.0 .491 77.4 21.1 1.61 63.2 5.28 43.4 22.3 76.2 8. 92 9.4 .0523 11 1.49 2.12 10.1 . 511 . 78.1 23.1 1.77 63.9 5.92 43.7 20.6 76.0 8.7 9.7 . .0527 21-2 .82 3.98 .0 .484 . 79.1 \"11.8 .90 54.1 3.15 38.6 35.6 79.1 8.9 8.9 .0540 4 . 1.09 3.17 16.2 .527 81.7 14.9 1.14 56.1 3.95 39.6 29.0 78. 5 \u2022 7.6 9.1 .0576 5 1.08 3.18 15.1 .523 81.6 14.7 1.13 55.6 3.95 39.5 29.1 78.7 7.8 .9.2 .0570 TABLE IV. (Con't) TRIAL BHP SPC SAR TAC IPTE BMEP TORQ VE BTE ISE SAC ITE APC OAP PC 21-8 1.05\" 3.21 12.7 .514 81.2 14.6 1.12 55.1 3.91 39.1 29.3 78.8 8.0 9.1 .0561 -11 .90 3.68 6.8 .494 80.4 12.7 .97 54.0 3.41 38.5 33.0 79.2 8.4 9.0 .0549 22-1 1.58 1.44 .0 .410 78.1 26.9 2.06 57.4 8.71 40.3' 15.5 78.1 10.8 10.8 .0379 -5 1.54\" 1.34 ' 8.7 .404 79.8 26.2 2.00 57.2 9.35 40.3 1.5.7 78.1 10.7 11.7 .0345 -8 1.60 1.40 20.0 .435 77.4 26.6 2.04 59.5 8.93 41.5 16.3 77.4 9.3 11.6 .0375 23-2 \u2022 -21 5.34 .0 .159 86.8 5.7 .43 32.3 2.34 25.2 45.2 86.8 8.5 '8.5 .0187 -5 .24 4.40 14.7 .161 88.8 6.0 .46 31.6 2.85 24.8 41.0 87.0 7.9 9.3 .0173 -7 .39 2.89 29.8 .180 90.7 8.4 .64 31.6 4.35 24.8 28.0 87.0 6.8 9.7 .0185 _9 1.63 .91 53.8 .344 92.4 23.8 : 1.83 41.6 13.73 31.2 12.6 \u2022 83.4 6.4 13.8 .0248 -12 1.45 1.06 . 56.1 .329 93.0 21.4 1.64 40.9 11.82 30.8 13.6 83.7 5.6 12.8 .0256 -15 1.19 1.29 48.4 .307 91.8 18.2 1.39 39.2 9.76 29.7 15.5 84.3 6.2 12.0 .0254 24-2 2.07 1.46 .0 .547 77.0 29.1 2.23 60.7 8.61 42.1 15.8 77.0 10.9 10.9 .0503 -5 2.09 1.38 3.4 .545 77.6 29.3 2.24 61.1 9.10 42.3 15.6 76.9 10.9 11c3 .0482 -8 1.74 1.68 8.1 .514 79.0 ' 25.4 1.94 59.6 7.48 41.5 17.7 77.4 9.7 10.5 .0487 -11 2.08 1.30 3.4 .541 77.7 29.1 2.23 60 = 8 9.62 42.1 15.6 77.0 11.5 11.9 .0453 . -14 1.56 1.85 11.3 .493 . 79.8 23.3 2.23 58.9 6.78 41.1 19.0 '77 = 6. 9.1 10.2 .0481 TABLE IV. (Con't) TRIAL BHP SPC SAR TAC IFTE BMEP TORQ VE BTE ISE SAC ITE APC OAP PC 24-17 1.44\" 1.53 19.2 .416 83.1 22.3 1.71 53.0 8.18 37.9 17.4 79.5 9.1 11.3!\" .0367 -20 1.27 1.43 30.3 .349 86.8 20.7 1.59 47.2 8.77 34.6 16.5 81.5 8.0 11.5 .0302 -23 1.08 1.31 43.7 .298 90.2 18.9 1.44 43.4 9.59 32.3 16.5 82.8 7.1 \u2022 12.6 .0236 -26 .21 7.19 70.7 .218 95.7 5.6 .43 42.7 1.74 31.9 61.2 83.0 2.5 8.5 .0255 -29 1.21 2.11 .0 .423 78.6 20.1 1.54 56.0 5.96 39.6 21.0 78.5: 10.0 10.0 .0423 25-2 1.76 1.30 11.5 .468 79.0 28.3 2.17 62.0 9.68 42.7 15.9 76.6 10.9 12.3 .0380 -5 1. 50 1.57 12.9 .447 79.9 24.5 1.87 59.9 7.99 41.7 17.9 77.3 9.9 11.4 .0391 -8 1.22 2.04 12.7 .438 80.3 20.1 1.'54 58.1 6.15 40.7 21.5 77.8 9.2 10.5 .0416 -11 1.02 2.03 21.5 .353 85.3 16.5 1.26 46.8 6.18 34.4. 20.8 81.6. 8.1 10.3 .0343 -14 .75 1.85 37.0 .265 90.5 ' 12.5 .96 36.4 6.77 28.0 21.2 85.5 ' 7.2 11.4 .0232 -17 .93 1.76 .0 .325 82.2 15.8 1.21 45.1 7.13 33.4 21.0 82.2 11.9 11.9 .0272 14-8 . .71 1.50 .0 .240 79.4 19.0 1.46 53.4 8.34 38.1 20.3 79.4 13.5 13.5 .0177 -12.' .69 1.43 37.4 .259 85.3 19.2 1.47 60.1 8.75 41.8 22.4 77.2' 9.75 15.5 .0166 2 5-20 , 2.14 1.16 0 .543 73.7 33.9 2.60 71.7; 10.85 47.6 15.2 73.7 13.1 13.1 .0413 -23 1.78 1. 55 0 .469 77.1 28.3 2.17 60.6 8.08 42.0 15.8 77.1 10.2 10.2 .0461 -26 : 1.07 2.13 0 .349 81.3 17.8 1.36 47.7 5.88 3.4.9 19.6 81,3 9.2 9.2 .0380 TABLE V. REDUCED EXPERIMENTAL RESULTS TRIAL CHOKE R IPSE SPEED 15-2 0 .602 45.2 4695 -5 0 .608 43 .8 4633 -8 0 .595 .44 .1 4633 17-2 0 .485 38 .4 4211 - 5 \"o .504 35 .8 4330 , - 7 0 .519 35-1 4400 ' - 11 0 .488 37.6 4256 19-2 0 .684 49.6 5029. - 5 0 .671 - 5007 20-2 ' 0 .597 41 .0 4433 - 5 0 .571 43 .5 4294 - 7 0 .569 41 .8 4295 -11 0 .572 40.3 4416 21-2 0 .487 38.6 4726 - 4 0 .504 34 .2 5010 -5 0 .\u2022500 34 .4 5006 TABLE V. (Con't) TBIAL CHOKE R IPSE SPEED 21-8 0 .496 35.0 4946 -11 0 .486 36.4 4849 22-1 0 .517 40.3 4024 -5 0 .515 37.5 4035 -8 0 .536 34.5 4134 23-2 0 .291 25.2 2557 -5 0 .285 21.5 2696 -7 0 .285 17.8 : 3151 -9 0 _ .374- 14.2 4691 -12 30\/70 .368 13.1\" 4632 -15 30\/70 .353 15.4 4480 24-2 48\/70 .546 42.1 4879 -5 48\/70 \u2022 .550 41.2 4900 -8 48\/70 .537 38.9 4711 -11 45\/70 .547 41.0 4905 -14 0 .530 37.4 4589 m A T ) T - n IT Y n . 1 4 . ^ TRIAL CHOKE R IPSE SPEED 24-17 \u2022 5\/70 .477 31.7 4421 -20 27\/70 .425 25.0 ' 4189 -23 20\/70 .390 18.6 3940 -26 13\/70 .385 7.3 2 588 -29 0 .504 39.6 4124 25-2 20\/70 .558 38.8 4268 -5 16\/70 .539 \" 37.3 4187 -8 0 .523 36.5 4183 -11 10\/70 . 421 27.8 4237 -14 18\/70 .328 18.1 4120 -17 18\/70 .406 33.4 4035 14-8 0 . 480 38.1 2559 -12 0 .541 27.3 2477 25-20 17\/70 .646 47.6 4327 -23 0 .545 42 o 2 4321 -26 12\/70 .429 34.9 4119 BIBLIOGRAPHY 153\u00bb Cleveland, A . E . , & Bishop, I.N., \"Fuel Economy,\" SAE Jornal Volume 6 8 , No.8, August i 9 6 0 , page 26. Baudry, Jean, \"A new IFF Process for Engine Combustion: A Variable Air-fuel Ratio C I . . Engine>\" SAE Paper no. 3 8 O F , Summer 1 9 6 1 . Taylor> O . F . . , . \"The Internal Combustion Engine in Theory and Practice,\" Vol. 1> John Wiley & Sons, New York, and Technology Press of M.I .T. , i 9 6 0 , pages 2 1 1 - 2 6 5 . Boyer et al . \"A Photographic Study of Events in a lk in Two-cycle Engine Cylinder,\" Transactions ASME 76, 1 9 5 4 , page.97. Nilov,. \"Special Features of Carburetor Engines with Jet Ignition,\" Avtomobilnaya Promyshlennost, 1 9 5 8 > No.8, from OTS Abstract S O V - 1 1 3 - 5 8 - 8 - 8 \/ 2 1 . Barber, E.M., Reynolds, B. , and Tierney, S.W., \"Texaco Combustion Process Gives Knock-free Operation,\" SAE Journal, v o l.58, September 1 9 5 0 , pages 5 1 - 5 7 \u00b0 Conta, L.D.> and Durbetaki, P.\"Research on Charge Stratification of S.I. Engines,\" ASME Paper no.60-WA-3l4, October i 9 6 0 , Ricardo, H.R., \"The High Speed Internal Combustion Engine\/' Blackie and Son Limited, London, 1 9 5 3 > pages 3 6 6 - 3 6 9 -Seaver, W.B., \"An Analytical Investigation of Stratified Charging of an Internal Combustion Engine,\" Thesis for Master of Science, Yale School of Engineering, 1940. Streeter, V . L . , \"Fluid Mechanics,\" McGraw-Hill-, New York, \u2022 1 9 5 8 , . page 3 1 8 ","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/hasType":[{"value":"Thesis\/Dissertation","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/isShownAt":[{"value":"10.14288\/1.0105938","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/language":[{"value":"eng","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#degreeDiscipline":[{"value":"Mechanical Engineering","type":"literal","lang":"en"}],"http:\/\/www.europeana.eu\/schemas\/edm\/provider":[{"value":"Vancouver : University of British Columbia Library","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/publisher":[{"value":"University of British Columbia","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/rights":[{"value":"For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https:\/\/open.library.ubc.ca\/terms_of_use.","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#scholarLevel":[{"value":"Graduate","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/title":[{"value":"Stratified charge scavenging of a two-stroke engine at part throttle","type":"literal","lang":"en"}],"http:\/\/purl.org\/dc\/terms\/type":[{"value":"Text","type":"literal","lang":"en"}],"https:\/\/open.library.ubc.ca\/terms#identifierURI":[{"value":"http:\/\/hdl.handle.net\/2429\/39619","type":"literal","lang":"en"}]}}