中文摘要：

在缸内直喷汽油机上进行了燃用纯甲醇和甲醇／汽油混合燃料的微粒排放特性研究，分析了点火定时、喷油定时和过量空气系数对微粒排放的影响规律。试验结果表明：在选定的发动机典型常用运行工况下，燃用纯甲醇燃料（M100）时，缸内直喷汽油机几乎不产生微粒排放；燃用甲醇／汽油混合燃料时（M20或M25），排气微粒数浓度主要集中在核态微粒区域，微粒质量浓度主要集中在积聚态微粒区域，其中M25燃料的微粒排放性要优于M20燃料；随着点火定时的提前，排气微粒数浓度和质量浓度均有所升高；随着喷油定时的提前，排气微粒数浓度降低，微粒质量浓度升高。

英文摘要：

Effects of ignition timing, injection timing and excess air ratio ,t on particulate matter （PM） emission from a gasoline direct injection （GDI） engine fueled with pure methanol and gasoline-methanol blends was investigated experimentally. Results show that there is almost no PM emission when fueled with pure methanol; for gasoline-methanol blends M25 and M20, particulate number concentration mainly concentrates in the nucleation mode zone, and particulate mass concentration mainly concentrates accumulation mode zone. PM emission for M25 is generally lower than M20. As spark timing advance, PM number concentration and mass concentration increase, and as injection timing advance, PM number concentration decreases and PM mass concentration increases.