Due to increasingly strict emission regulations, lean combustion is one of the essential directions in internal combustion engine design. However, lean combustion leads to high cycle-to-cycle variation, which indicates combustion instability and affects engine performance. Therefore, understanding the reasons for cycle-to-cycle variation is crucial for the internal combustion design. This paper investigates the causes of cycle-to-cycle variation of a spark-ignition engine through the large eddy simulations done by CONVERGE v3.0. The analysis focus on the mechanism and consequences of intake tumble flow variation. It is found that the tumble ratio varies from cycle to cycle and causes the turbulence kinetic energy variation. Moreover, the tumble variation is due to the random secondary flow in a specific area between the cylinder head and intake flow. Reducing the size of this area e.g., by changing cylinder head geometry or delaying intake valve opening, contributes to the smaller tumble variation.
Session:
ZERO-IMPACT-EMISSIONS I
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| 14:30 - 15:00