通过改变EGR率，在一台GDI汽油机上进行了EGR对燃烧和排放特性影响的试验．结果表明：加入EGR后，燃烧持续期增大；且随EGR率增加，着火时刻先提前后延迟；放热率曲线峰值逐渐降低且后移，放热过程迟缓，缸内压力和缸内温度逐渐降低，压力峰值前移．此外，EGR率增加导致NOx排放逐渐降低，最高降低比例达80％以上，THC和CO排放逐渐增加，最大增加比例分别约为25％和7％．GDI汽油机排气颗粒物呈核态和积聚态的双峰分布；积聚态颗粒物峰值数密度随EGR率升高逐渐降低，核态颗粒物峰值数密度和颗粒物总数量浓度在加入EGR后均明显增加，核态和积聚态颗粒物峰值粒径受EGR的影响较小．%The effects of EGR on the combustion and emission characteristics were investigated experi- mentally in a gasoline direct-injection （GDI） engine. Results show that the introduction of EGR leads to an increase in combustion duration. With the increase of EGR rate, ignition timing shows an advance and then delay behavior, and the peak value of heat release rate gradually decreases and moves away from TDC, inducing a slow heat release process. Cylinder pressure and temperature gradually decrease, and the peak pressure moves to TDC. With the increase of EGR rate, NOx emissions decrease gradually with maximum reduction rate of 80%, whereas THC and CO emissions increase gradually with maximum in- crement rate of 25% and 7% respectively. Moreover, exhaust particles from GDI engine exhibit a bimodal size distribution consisting of nucleation mode and accumulation mode. Peak value of accumulation mode particle number density decreases gradually with the increase of EGR rate. Adoption of EGR leads to a significant increase in peak value of nucleation mode particle number density and total particle number concentration. But EGR has a slight influence on peak size of nucleation mode and accumulation mode particles.
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