中文摘要：

在不同转速和负荷下,用快速微粒光谱仪（DMS500）对PFI汽油机排气微粒的数浓度和粒径分布进行了测量。结果表明：在中低负荷下,PFI汽油机产生的微粒几乎全部为纳米级核模态粒子,随着负荷的增加,微粒数浓度单调增加,并且峰值粒径向粒径增大方向迁移;微粒的几何平均直径（GMD）和中位直径（CMD）都是随着负荷的增加而逐渐增加;在高负荷工况区开始生成大量的聚集态微粒;随着发动机转速的升高,微粒数浓度大体上单调增加;在中低转速下,PFI汽油机排放的微粒绝大多数为核模态粒子;与柴油机一样,PFI汽油机排气微粒中核模态粒子占有较大的数量百分比,聚集模态粒子占有较大的体积百分比。

英文摘要：

At different speeds and loads,the exhaust particle number concentration and size distribution were measured in a PFI gasoline engine by DMS500 fast particulate spectrometer.The results show that the exhaust particles were almost nano-scale nucleation modal particles at medium and low loads.With the increase of load,the particle number concentration increases monotonically and the peak size increases.The geometric mean diameter（GMD） and count median diameter（CMD） of exhaust particle also increase gradually.At high loads,massive accumulated modal particles generates.With the increase of engine speed,the exhaust particulate number concentration increases monotonically.At medium and low speeds,most of particulates emitted by PFI gasoline engine are nuclear modal particles.Being the same as diesel engine,the nuclear modal particles of PFI gasoline engine take the larger number fraction and its accumulated modal particles take the larger volume fraction.