Effects of Exhaust Gas Recirculation on Knock Intensity of a Downsized Gasoline Spark Ignition Engine

Exhaust gas recirculation (EGR) has gained prominence as a significant method to control port fuel injection engine knock caused by high compression ratio and high intake pressure (IP). In this paper, the effect of EGR on knock intensity was investigated under various conditions which included different compression ratios (9:1, 10:1, 11:1), IPs (1.0 bar, 1.2 bar, 1.4 bar) and intake temperatures (ITs, 20 degrees C, 40 degrees C, 60 degrees C). The torque output being a crucial variant was also considered. The results showed that EGR effectively reduced the maximum amplitude of pressure oscillations (MAPO) and knock intensity factor (KI20). The effect of EGR on knock resistance was more significant at higher compression ratio, IP, and IT. The output torque of the engine reached a peak value with a suitable EGR ratio which also controlled the intensity of knock under different conditions.