高/低压EGR对汽油机和增压器影响的试验研究

在一款涡轮增压汽油缸内直喷(gasoline direct injection,GDI)汽油机上进行了高压(HP)废气再循环(exhaust gas recirculation,EGR)和低压(LP)EGR对发动机和增压器性能影响的试验研究。分别对比了HP EGR和LP EGR系统在外特性和部分负荷工况对发动机燃烧、油耗、进排气的影响及增压器相应的工况变化,并分析了出现这些变化的原因。结果表明,汽油机EGR系统能够优化缸内燃烧,减少泵气损失,从而降低油耗。低压EGR系统在部分负荷工况热效率比高压EGR更高,主要原因为低压EGR系统的涡轮增压器可利用的尾气能量更多,且进入发动机的废气温度较低,能进一步优化缸内燃烧。

Investigation on Effects of Low and High Pressure EGR on GDI Engine and Its Turbocharger

The investigation was performed by testing into the effects of low pressure(LP) exhaust gas recirculation(EGR) or high pressure(HP) EGR on a gasoline direct injection(GDI) engine and its turbocharger. The behavior changes of the engine and turbocharger with LP EGR or HP EGR were compared at full and partial loads. The reasons of the changes were analyzed through some variations, including combustion, fuel consumption, as well as intake and exhaust. The results indicate that EGR can optimize the combustion of a turbocharged GDI engine, reduce the pumping mean effective pressure and lower the fuel consumption. At partial load, the thermal efficiency with LP EGR is higher than that with HP EGR. The mean reason is that with LP EGR more exhaust energy is applied to turbocharger and the temperature of exhaust gas entering cylinder is lower, thus optimizing combustion.