GDI发动机冷怠速工况缸内混合气形成模拟研究  

Simulation of Mixture Formation in Cylinder for Gasoline Direct Injection Engine at Cold Idle

作　　者：朱航[1] 刘国庆[1] 杨俊伟[1] 刘义克[1] 

机构地区：[1]奇瑞汽车股份有限公司发动机工程研究院,芜湖241009

出　　处：《内燃机工程》2014年第5期69-76,共8页Chinese Internal Combustion Engine Engineering

基　　金：国家"八六三"高技术研究发展计划项目(2012AA111702)

摘　　要：采用三维CFD仿真建立了缸内直喷发动机冷怠速工况缸内混合气形成过程仿真模型,并与光学发动机台架测量结果进行了对比,验证了仿真模型的准确性。基于仿真模型研究了冷怠速工况两次喷油正时与喷射比率对缸内混合气形成、燃油碰壁的影响。研究结果表明:进气行程喷油过早会导致活塞顶油膜增加,过晚喷射则会导致缸套壁面油膜增加,进气行程喷油正时对缸内混合气分布有一定的影响,但压缩上止点附近火花塞附近浓区形成与保持主要由压缩行程喷射来实现;压缩行程喷油过早,在点火时刻缸内会形成相对均质的混合气分布,过迟则会导致活塞顶油膜量急剧增加;两次燃油喷射量比率对火花塞附近浓区的形成影响相对较小,但压缩行程喷射量过多会导致活塞顶油膜量明显增加。A CFD simulation model of in-cylinder mixture formation process for GDI engine at cold idle was established and verified by comparison with the results from an optical engine experiment. Based on the simulation model, the effect of injection timing and injection rate on in-cylinder mixture formation and fuel impingement at cold idle were studied. The results show that too early intake injection will increase fuel film at piston top, and too later injection will increase fuel film on cylinder wall. Intake injection timing has some influence on mixture distribution in cylinder, but the formation and maintenance of stable concentrated mixture around spark plug near top dead center is achieved by injection at compression stroke. Too early compression injection will lead to relatively homogeneous mixture formation at ignition, and too later compression injection will increase fuel film at piston top quickly. The fuel split ratio of double injection have rela- tively small impact on the formation of concentrated mixture near spark plug, but too much injection at com- pression stroke will increase fuel film at piston top obviously.

关 键 词：内燃机 缸内直喷汽油机 冷怠速 混合气形成 模拟 

分 类 号：TK411.2[动力工程及工程热物理—动力机械及工程]