The effects of injection timing on the combustion process and particle emission were investigated by ex-periment on a turbocharged gasoline direct injection engine by using the combustion analyzer and DMS500 fast par-ticulate spectrometer. The results show that with the continous delay of injection timing, the peak values of cylinder pressure, instantaneous heat release rate and cylinder mean temperature increase at first, then decrease, and their locations postpone after the first advance. The flame development duration and rapid burning duration decrease gradually first and then increase. In this process, optimal injection timing brings the minimum cycle-to-cycle varia-tions. The exhausted particles from the gasoline direct injection ( GDI) engine exhibited a bimodal size distribution of the nucleation mode and accumulation mode particles. With the delay of injection timing, the peak number con-centration of accumulation mode particles decreases and then increases, but for the nucleation mode it shows an op-posite trend. However, the peak size of accumulation mode particles gets smaller and smaller, while the peak size of nucleation mode changes a little. The total particle number concentration and the number density in accumulation mode decrease gradually firstly and then increase with the delay of injection timing. There is the optimal injection timing value between 280 ~ 310℃A BTDC at each operating condition.%利用燃烧分析仪和快速微粒光谱仪开展了喷油定时对增压直喷汽油机燃烧和微粒排放特性影响的实验研究.结果表明:随着喷油定时的不断推迟,缸内压力、瞬时放热率和缸内平均温度峰值均先增大后减小,峰值位置先提前后推迟;火焰发展期和快速燃烧期先缩短后增大,存在最佳喷油定时使得循环波动最小. 缸内直喷汽油机微粒排放呈现核态和积聚态的双峰值. 随着喷油定时的延后,积聚态的微粒峰值数量浓度先降低后增加,核态微粒则呈现相反的变化趋势;积聚态微粒峰值粒径逐渐减小,而喷油定时对核态微粒峰值粒径影响很小;微粒总数量浓度和积聚态微粒数量浓度均呈现先降低后增加的趋势,且不同工况点的喷油定时均存在最佳值,在280~310℃A BTDC.
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