HEAT-LOSSES DURING KNOCKING IN A 4-STROKE GASOLINE-ENGINE

Knocking in internal combustion engines causes various problems such a s increase in thermal loads, abnormal wear and the deterioration of pe rformance. Even the mechanism of thermal loads alone has not been clar ified yet. In this study, therefore, instantaneous temperatures on pis ton top surfaces of a four-stroke gasoline engine during knocking, cau sed by changing the spark timing and octane number, have been measured using highly accurate thin-film thermocouples. Conditions of heat los ses dependent on the knock intensity have been clarified from the inst antaneous heat fluxes and coefficients of heat transfer determined fro m measurements.