The combustion and particle emission characteristics of a gasoline engine were investigated in a port fuel injection gasoline engine using different exhaust gas recirculation (EGR)methods.The results indicate that the range of EGR ratio of the engine with stable combustion is wider in the case of admiting exhaust gas to one of the two intake ports (stratified EGR) than that in the case of introducing exhaust gas into the intake manifold before throttle (manifold EGR).Meanwhile,the indicated thermal efficiency of the former is higher than that of the latter.The individual indicated mean effective pressure in the consecutive cycles of the stratified EGR case is more concentrated than that of the manifold EGR at the same load,indicating much more stable combustion of the engine in the former case.The particle number and surface area of nuclei mode particles per cubic centimeter decrease with the increase of EGR rate,and it is higher in the case of stratified EGR than that in the case of manifold EGR at the same EGR ratios.The particle number and surface area of accumulation mode particles per cubic centimeter decrease firstly and then increases with the increase of EGR ratio.However,it is lower in the case of stratified EGR than that in the case of manifold EGR at the same EGR ratios.%研究了不同废气再循环(EGR)方式下,汽油机的燃烧与颗粒排放特性.结果表明,由进气道引入废气的分层废气再循环(分层EGR)方式与由节气门前引入废气再循环(总管EGR)方式相比,汽油机稳定燃烧的EGR率范围大,而且前者比后者的汽油机指示热效率高.在相同负荷下,分层EGR方式下汽油机连续循环中各个循环的指示平均有效压力比总管EGR方式下的更加集中,前者的燃烧更稳定.两种EGR方式下汽油机排气中单位体积内的核态颗粒物和表面积数随着EGR率的增加而降低,而且在相同EGR率下,分层EGR方式下的值比总管EGR下的值高.单位体积内积聚态颗粒物数和总表面积随着EGR率的增加,先减少后增加,但在相同EGR率下,分层EGR方式下的值要比总管EGR下的值低.
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