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The relative effects of intake and compression generated turbulence on I.C. engine combustion duration

University of British Columbia

A Rapid Intake and Compression Machine was designed and built, which makes it possible to simulate the piston motion of a reciprocating internal combustion engine at 1000 rpm. The compression stroke can be run by itself or following the intake stroke. Hot Wire Anemometer measurements were made at several locations inside the combustion chamber during intake and compression stroke and during the compression stroke by itself. Under similar operating conditions a combustible mixture was drawn in and ignited with varying ignition times after simulating the intake and compression stroke together and after simulating the compression stroke by itself. The mass fraction burned curves versus time were calculated from the pressure trace. The velocity measurements were compared to the combustion test results and the one stroke results were compared to the results found from the two stroke tests. It was found that the compression stroke run by itself generates very little flow motion in a flat disk combustion chamber without swirl, compared to the intake and compression stroke run together. The ignition delay period as well as the main combustion duration were considerably shorter after the intake and compression stroke compared to the compression stroke by itself. In the case of intake and compression stroke more advanced ignition timing reduced the ignition delay period as well as the main combustion duration. It is concluded that under the present engine conditions the compression stroke generates practically no turbulence. Thus the contribution of the compression stroke to the flow conditions around ignition time is limited to counteracting the decay of intake generated turbulence through compression effects.

Text

2010-07-10

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http://hdl.handle.net/2429/26284

Mechanical Engineering

University of British Columbia

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