Effect of Compression Ratio on the Intake Characteristics of a Hybrid Gasoline Engine
The effects of different compression ratios on intake,in-cylinder turbulent kinetic energy,roll-off ratio,and in-cylinder flow are investigated for a 1.5 L naturally aspirated hybrid dedicated gasoline engine.A three-dimensional computational fluid dynamics(CFD)simulation software is used to design six different compression ratios(13.1-16.9)to study and analyze with the rest of the parameters unchanged.The following conclusions can be drawn from the data:the in-cylinder air intake decreases with increasing compression ratio,and the degree of change is very small,only within 0.5%,which is negligible.However,an increase in the compression ratio has a significant impact on the turbulent kinetic energy within the cylinder.The maximum reduction in turbulent kinetic energy within the cylinder at the upper stop of compression is nearly 24%compared to the minimum compression ratio.This is unfavorable to the flame propagation within the cylinder.The same result can be obtained through the velocity cloud diagram within the cylinder.Moreover,the variation in the compression ratio also results in a certain degree of fluctuation in the in-cylinder tumbling ratio.
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