Abstract
A reduction in heat losses is an important factor of improving thermal efficiency of internal combustion engines. This study developed a two-zone combustion model considering autoignition in the unburned gas zone, coupled with an instantaneous heat transfer model on the combustion chamber wall. These models made it possible to discuss the interaction of the heat losses and knock occurrence and to optimize the spark ignition timing. The specific purpose of the present study is to explore the fundamental characteristics of wall surface temperature swings and the effect of applying a low thermal conductivity and low specific heat material to the combustion chamber wall on thermal efficiency and then to indicate the possibility of improving thermal efficiency and its mechanisms.
