Experiment Research On Extending The Operation Range Of Gasoline HCCI Combustion

HCCI (Homogeneous Charge Compression Ignition)gasoline engines have been received a lot of attention from the world-wide automotive field due to their ultra-low NOx emissions and high thermal efficiency. However, they are confronted with the problems in operation range extension. In this paper, for extending the HCCI operation range, the HCCI combustion characters of a gasoline engine on borderline using exhaust re-compression strategies was investigated in detail by experiment. \ Whereafter, the studies of the combustion-related factors and theirs effects on the combustion progress are carried out to find the key factor limiting the HCCI combustion operation range. Using spark assistant / external EGR / supercharge extents the operation range of HCCI combustion. The experimental results show:Spark assistant HCCI combustion could increase the combustion duration, make the combustion intension weaker, make the boundary of HCCI extended around 0.6 bar towards the big load. Correspondingly it could make the CO and HC emissions better to a degree.Leading the external EGR to the HCCI combustion using the internal EGR re-compression strategy, could increase the combustion duration, postpone the ignition timing, avoid the knocking availably, make NOx emission decreased. It could break through the knocking limit, make the operation range extent about 0.8 bar. But due to too late ignition, misfire limits the operation range farther large.Using the supercharge, make the load large with the same internal exhaust gas recirculation fraction, but due to lack enough dilution, knocking limits the operation range all the same.