Effects of Spark Ignition on Smoothness of Ethanol SI/HCCI Combustion Mode Transition

The spark ignition(SI) and homogeneous charge compression ignition(HCCI) have been realized in a modified single cylinder engine.The operation regions of the two combustion modes have been defined,and SI/HCCI combustion mode transitions under different operation conditions have been performed.The effects of spark on the combustion mode transition have been investigated in order to improve the smoothness of the transition.The results show that HCCI combustion stability has been improved greatly and the combustion cycle-by-cycle variations decrease when the spark is utilized in the critical temperature operation conditions.During the transition process,the utilization of spark is equivalent to adding extra energy into the cylinder to ignite the mixture,hence,the smoothness of the combustion mode transition has been enhenced.