中文摘要：

采用三维CFD数值模拟的方法,对试验发动机冷机起动倒拖时的缸内燃油喷射雾化过程进行了仿真计算分析。研究结果表明：在燃油喷雾过程中,由于燃油蒸发吸热,导致缸内温度明显下降,与不喷油时相比下降了32K;缸内喷雾过程出现大量的燃油附壁,附壁量占总喷油量的70%左右;喷雾过程结束时形成的混合气浓度场和温度场呈极不均匀的分层分布,浓度较高的区域温度较低,且分布于靠近活塞壁面的薄层,不利于焰前反应的进行。这些因素均对冷起动过程缸内混合气的着火燃烧产生关键性的影响。此外,研究结果还表明,喷油油束速度是冷起动条件下影响缸内油滴蒸发过程的重要因素。

英文摘要：

Fuel spray in direct injection diesel engine during cold start cranking was investigated using 3D CFD simulation method. Investigation shows that during fuel atomization in-cylinder temperature decreases obviously resulted from fuel evaporation, temperature decrease reaches about 32 K compared with the cycle without fuel injection. Large amount of fuel, about 70% of total fuel injected is attaches to cylinder wall. After fuel injection, the in-cylinder mixture and temperature exhibits extremely inhomogeneous stratified distribution. In the location of higher fuel vapor concentration, temperature is lower, and most of the fuel vapor spreads near the piston wall, thus unfavorable to pre-flame reaction progress. These factors have significant effect on mixture ignition during engine cold start. Furthermore, it is also suggested that fuel evaporation in cold start condition is obviously affected by fuel spray speed.