Effect of Ethanol on the HCCI Combustion

Bio-ethanol is one of the most promising alternative fuels for vehicles. It is important for the spread of bio-ethanol to investigate its ignition quality and its optimum combustion procedure. It is particularly important for the application of bio-ethanol to a homogeneous-charge compression ignition (HCCI) engine to investigate the HCCI combustion characteristics of ethanol. In this study, the inhibiting effects of ethanol on the HCCI combustion of heptane were investigated by using a rapid compression machine (RCM) under various conditions. The results indicate that ethanol effectively retarded the hot ignition period of HCCI combustion due to its effective retardation of the cool flame period. The hot ignition peak period for 30 wt% ethanol/70 wt% heptane was more delayed than that of PRF having an octane number of 60 under the ϕ=0.4 condition. In addition, the hot ignition peak period for 50 wt% ethanol/50 wt% heptane was more delayed than that of PRF having an octane number of 80. Furthermore, the effects of diethyl ether, which can be produced from ethanol, on HCCI combustion were investigated by using RCM. Diethyl ether had significantly high ignition quality, suggesting that HCCI combustion control with ethanol and diethyl ether would be effective.