1988-09-01

Study Of Influences Of Inlet Valve Timings On In-Cylinder Flow, Gas Temperature And Combustion in Spark Ignition Engines 885093

Combustion in spark ignition engines is strongly affected by characteristics of in-cylinder flow. The role of in-cylinder flow on combustion becomes more important under lower temperature conditions which are made by, for example, Millor cycle engines whose power is controlled by inlet valve open and close timings (1)*.In this study, influences of early and late Inlet valve close timings have been investigated by means of an engine simulation model which is based on the entrainment model, and by means of in-cylinder flow measurements using the Hot Wire Method.Inlet valve open and close timings can be varied from 150°BBDC to 170°ABDC (in case of close timings), changing a phase between a cam shaft and a crank shaft through a gear. An early close and a late close cycles are then gotten.In case of early or late valve closed timings, decreases of magnitude of gas flow velocity and temperature have been made sure by measurements as well as by calculations.The vortex scale, however, becomes smaller under non-throttle condition. A deteriorate of thermal efficiency under early or late close timings condition, can be considerably resolved by an increase of swirl and turbulence.

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