冷启动下米勒循环对缸内直喷汽油机混合气形成影响研究  

Research on the Influence of Miller Cycle on Mixture Formation in GDI Engine under Cold Start

作　　者：魏胜利[1] 倪士栋 丁统元 张绍邦 张志成 WEI Shengli;NI Shidong;DING Tongyuan;ZHANG Shaobang;ZHANG Zhicheng(School of Automotive and Traffic Engineering,Jiangsu University,Zhenjiang,Jiangsu 212013,China;GRC Automotive Technology(Suzhou)Co.,Ltd.,Suzhou,Jiangsu 215100,China)

机构地区：[1]江苏大学汽车与交通工程学院,江苏镇江212013 [2]吉孚汽车技术(苏州)有限公司,江苏苏州215100

出　　处：《西安交通大学学报》2022年第8期122-130,共9页Journal of Xi'an Jiaotong University

基　　金：国家重点研发计划资助项目(2017YFB0103402)。

摘　　要：以一台缸内直喷(GDI)汽油机为研究对象,进行发动机台架试验与一维仿真工作,为三维仿真模拟的冷启动工况提供可靠的边界与初始条件,并进行了相关验证。设计了进气门早关(EIVC)米勒循环气门升程型线,构建了米勒循环发动机模型,探究了米勒循环对缸内低温环境下的附壁油膜发展、喷雾场形成质量的影响。结果表明:米勒循环发动机在进气冲程后期缸内附壁油膜的质量均高于原机;在整个进气与压缩过程中,大部分的油膜以及厚油膜区域均集中在活塞凹坑。EIVC75米勒循环活塞顶部油膜铺展面积显著增大,凹坑周围油膜厚度明显降低;在压缩冲程中后期,由于缸内湍动能耗散较慢,促进了其附壁燃油蒸发;在点火时刻,EIVC60与EIVC75米勒循环较原机附壁燃油质量分别下降了28%、48%,可以有效避免“池火”现象,与此同时,原机的浓度场分布与EIVC60、EIVC75米勒循环相比具有较大差异,原机火花塞附近的当量比在0.8左右,而米勒循环发动机火花塞附近则形成了当量比为1.1~1.2的适宜点火的可燃混合气。In this paper,a gasoline direct injection(GDI)engine is selected for bench test and one-dimensional simulation to provide reliable boundary and initial conditions for the 3D simulation.Miller cycle valve lift lines for early intake valve closing(EIVC)is designed,and the Miller cycle engine model is established and verified to examine the influence of the Miller cycle on the development of wall film and the formation quality of spray field in low temperature environment.Research shows that the mass of the wall film in the Miller cycle engine is greater than that of the original engine at the end of the intake stroke.During the entire intake and compression strokes,most fuel film including the thick fuel film was concentrated in the piston pit.The spreading area of the fuel film on the top of the piston in the EIVC75 Miller cycle increased significantly,and the thickness of the fuel film around the pit decreased clearly.In the middle-late stage of the compression stroke,due to the slow dissipation of turbulent kinetic energy in the cylinder,the evaporation of the fuel wall film is promoted.At the time of ignition,the wall film mass of EIVC60 and EIVC75 decreased by 28% and 48% respectively,which can effectively avoid the‘pool fire’phenomenon.Moreover,the concentration field of the original engine is greatly different from that of EIVC60 and EIVC75.The equivalence ratio near the original engine spark plug is about 0.8,while that of a mixture suitable for ignition near the spark plug of the Miller cycle engine is 1.1-1.2。

关 键 词：缸内直喷汽油机 冷启动 附壁油膜 米勒循环 

分 类 号：TK411[动力工程及工程热物理—动力机械及工程]