Abstract
Homogeneous Charge Compression Ignition (HCCI) engines are being widely researched today, having attracted considerable interest for their low emissions and high efficiency. However, HCCI engines have a narrow range of stable operation owing to the occurrence of extremely rapid combustion at high loads and misfiring at low loads. The results of previous studies have shown that the application of exhaust gas recirculation (EGR) has the effect of moderating the combustion process by suppressing the occurrence of rapid combustion. The present study examined the effects of the engine speed and the EGR rate on HCCI combustion. The results revealed that the scavenging temperature rose and the ignition timing advanced with increasing engine speed. As a result, rapid combustion tended to occur because of a higher maximum pressure rise rate (dP/dt_<max>). It was also observed that when EGR was applied to moderate combustion, the rapidity of combustion did not increase even when the engine speed was raised.
