混合动力汽车发动机起动要快速，其瞬态程度更高，势必造成起动过程排放控制困难。为了研究不同起动瞬态变化条件下的发动机燃烧和排放特性，基于自行搭建的单轴并联混合动力试验平台，分别用24 V原机起动和800 r/min，1 000 r/min及1 200 r/min转速拖动发动机起动。研究结果表明：随着拖动转速升高，起动过程中的缸内压力峰值、平均有效压力和燃烧持续期均减小，但减少幅度会降低，800 r/min拖动起动时，燃烧波动较大；发动机起动过程中的CO，NO_x和Soot排放均随着拖动转速的升高而减少；原机24 V起动和800 r/min拖动起动时燃烧和排放特性随循环或时间的变化趋势一致，1 000 r/min和1 200 r/min拖动起动时的燃烧和排放特性变化趋势一致；以800~1 000 r/min拖动起动是较好的快速起动策略，但是需要重新标定起动时的喷油策略。

The high transient requirement of rapid start for a hybrid electric vehicle engine will inevitably make it difficult to control emission during the starting process. In order to study the engine combustion and emission characteristics under different starting transient conditions, different start methods were conducted including 24 V motor start and drag start at 800 r/min, 1 000 r/min and 1 200 r/min respectively based on a selfbuilt single-shaft parallel hybrid test platform. The research results show that the incylinder pressure peak, the mean effective pressure and the combustion duration all decrease and the reduction becomes small with the increase of the drag speed during the starting process. Besides, CO, NO_x and soot emissions also reduce. However, the combustion fluctuation is relatively high at the drag speed of 800 r/min. The combustion and emission characteristics between 24 V motor start and 800 r/min drag start have the same trend with cycle or time and the changes of them between 1 000 r/min and 1 200 r/min drag starts are the same. Generally, 800-1 000 r/min drag start is a better rapid start strategy, but the fuel injection mass at start time needs to be recalibrated.