Heat Losses during Knocking in a Four-Stroke Gasoline Engine

Abstract

Knocking in internal combustion engines causes various problems such as increase in thermal loads, abnormal wear and the deterioration of performance. Even the mechanism of thermal loads alone has not been clarified yet. In this study, therefore, instantaneous temperatures on piston top surfaces of a four-stroke gasoline engine during knocking, caused by changing the spark timing and octane number, have been measured using highly accurate thin-film thermocouples. Conditions of heat losses dependent on the knock intensity have been clarified from the instantaneous heat fluxes and coefficients of heat transfer determined from measurements.