Analysis of a new analytical law of heat release rate (HRR) for homogenous charge compression ignition (HCCI) combustion mode versus analytical parameters

Homogeneous charge compression ignition (HCCI) engines produce very low NOx and soot emissions and alsoimprove engine efficiency when compare to conventional spark ignition engines. The combustion process bases on the self-ignition of a homogenous air-fuel mixture without an external ignition source. The gas temperature is very important to initiate the combustion and to promote the appropriate chemical kinetics. As a result, the heat release rate and heat transfer inside the combustion chamber play a significant role in the HCCI combustion mode. The high relevance of gas temperature on this combustion mode means that heat transferis considered through a dedicated heat transfer model. In this system the forced convection from hot gases to the combustion chamber walls is the dominant heat transfer mechanism. This paper focuses on the relationship between HRR in HCCI combustion mode and the four parameters that are required for an analytical function to model this heat release rate. More specifically, the influences of the fuel-air equivalence ratio, engine speed and EGR on the four parameters that control HRR are examined. The analytical HRR law is validated over a wide range of operating conditions in HCCI combustion mode and shows that these four parameters are directly related to any load condition, including engine speed, fuel rate and EGR. These parameters can therefore be used to characterize this combustion mode.