Simulation study on the effects of charge stratification on HCCI combustion

Controlling the combustion phasing and extending the operating range are still tough works for HCCI combustion mode. Previous studies revealed that charge stratification had the ability to change combustion events. Numerical study with an improved auto-ignition model is performed to better understand its effects on the HCCI combustion. First of all, anew chemical kinetic mechanism for gasoline is developed to modify the existing auto-ignition model and then validated by combining CFD code Chemkin and GT-power. After that, integration of ECFM3Z turbulence model and modified autoignition model is confirmed to be reasonable to correctly reproduce the HCCI combustion. And finally, mixture stratification is introduced with intend by adjusting the timing of Start of Injection (SOI) managed by ECU in real time. Simulation study employs previous modified auto-ignition andECFM3Z model to investigate the effects of stratification on the start of combustion and burn duration under series of operating points. Conclusions come to that modified autoignition model is suitable for HCCI combustion simulation. Charge stratification is capable to change the combustion phasing and extend the combustion duration.