Experimental Study on Combustion and Emission Characteristics of Gasoline Compression Ignition Engines Under Cooperative Control of Operating Parameters

This study investigated the effects of cooperative-control of the start of injection (SOI), excess air ratio (lambda), internal exhaust gas recirculation (I-EGR), and intake air temperature (IAT) on the combustion and emission characteristics of gasoline compression ignition (GCI) engines, especially regards to the combustion stability and knock characteristics. And optimizing the GCI engine combustion and emissions through the cooperative control of multiple parameters is the innovation of this research. The results showed that advancing the SOI and increasing the I-EGR ratio can significantly expand the low-load limit, but the heating effect of 20% I-EGR only worked when the SOI was earlier. An appropriate increase of lambda could increase the maximum brake thermal efficiency (BTE) to 40.06%, but resulted in high-knock probability and high NOx emissions. Rising the IAT was more effective than advancing the SOI in improving combustion fluctuations, but the knock probability and knock intensity were more sensitive to the early SOI. When the SOI varied from 26 degrees CA BTDC to 30 degrees CA BTDC, lambda was 1-1.5, the I-EGR ratio was 5%-20%, and the IAT was 40-50 degrees C; the GCI engine can obtain the balance among high thermal efficiency, high combustion stability, low knock probability, and low emissions.