Abstract: A concept of lean dilution combustion (LDC) was proposed for gasoline direct injection (GDI) engines with combining lean dilution burn and exhaust gas dilution to reduce pumping loss and to improve brake thermal efficiency. The influential factors of LDC were investigated by experiments on a GDI engine at partload to measure the fuel economy (fuel energy distribution), the combustion characteristics, and the emission characteristics of the engine. The results show that the fuel economy is improved 4%—6% more at the engine brake mean effective pressure of 200—600 kPa, without too much NOx emissions by employing LDC. Fuel energy distribution indicates that the LDC reduces the engine loss of heat transfer and pumping, and the LDC mode is proved to be feasible.

Key words: gasoline engine gasoline direct injection (GDI), lean dilution combustion exhaust gas dilution air dilutiofuel consumption