Effect of CO_2 dilution on combustion and emissions of a GDI engine under the peak NO_x generation mixture

摘要

In this paper, CO2 was introduced to intake charge, the combustion and emissions behaviors between added CO2 and added EGR (exhaust gas recirculation) in a gasoline direct injection (GDI) engine under the peak NOX generation mixture and at low and medium loads were analyzed and compared in order to assess the role of CO2 in the intake charge of engine. Experimental results show that the combustion performances for added CO2 was better than that of added EGR. The effect of added CO2 on the combustion parameters at low loads was greater than that at medium loads. The coefficient of variation of indicated mean effective pressure almost did not change with increasing percentage of CO2 under only added CO2 and medium load. The effect of added CO2 on combustion parameters was much less than added EGR. At a fixed CO2, CO and HC emissions for added CO2 were lower significantly than those of added EGR at medium load, and vice versa on low load. Increasing CO2, the NOX emissions decreased significantly for added EGR and added CO2 at any engine loads. At a fixed CO2, the NOX emissions for added CO2 was higher obviously than that of added EGR at any engine loads. The soot emission was decreased slightly as increasing percentage of CO2.