增程式电动汽车用二冲程LPG直喷发动机混合气形成过程的数值解析

Numerical simulation of mixture formation and selection for two-stroke LPG direct injection engine for range-extended electric vehicle

利用LPG携带和存储方便、易于蒸发汽化的燃料特性,选定二冲程LPG直喷发动机作为轻型电动汽车在增程模式下发电机组的动力源。在验证计算方法的可行性后,使用Fire V2011软件,优化不同工况时燃料的喷射开始时刻,并进一步数值解析在选定的不同LPG喷射开始时刻、不同转角时的缸内混合气速度场和浓度场。结果表明:无论是启动、暖机工况(2 000 r/min),还是发电机组工况(4 800、6 000 r/min),在排气口关闭(73℃A ABDC)时,新鲜混合气被锁定在气缸内,并且在相应的火花塞点火时刻,缸内都会形成较理想的均质理论混合气。

Liquefied Petroleum Gas （LPG）, as a fuel, is easy to evaporate and also is convenient to be stored and carried. In this study, LPG is selected as the fuel of a two-stroke direct injection engine which is used as the power source of a light electric vehicle. The mixture formation process of the engine is numerically calculated using a CFD software Fire V2011. The injection timings at different running conditions are optimized at the first, then the evolution of the velocity and concentration fields during the process of mixture formation under typical conditions are analyzed. The results show that the fuel can be locked in cylinder at the timings of intake port closing（73 ~CA ABDC）and finally homogenous theoretical mixture can be formed at spark timings for all the calculated cases,including beth warming condition （2 000 r/m in） and electricity generation conditions （4 800 and 6 000r/m in）.