Heat Losses on Occurrence of Knock in a Four-Stroke Gasoline Engine.

Abstract

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