分层扫气二冲程汽油机的数值模拟

Numerical simulation of stratified scavenging two-stroke gasoline engine

为研究分层扫气发动机的扫气特性和工作机理,建立了分层扫气发动机三维模型,并利用三维CFD仿真软件Fluent在额定转速下分别对有无分层扫气系统的发动机流场进行仿真与分析,计算所需的边界条件通过对发动机进行一维模拟计算得到。结果表明:分层扫气发动机在工作过程中利用纯空气在新鲜混合气和废气之间形成分层,并由纯空气承担一部分扫气损失,使得未燃碳氢化合物的排放减少了15%,提高了发动机的燃油经济性;有无分层扫气发动机扫气效率都是75%,分层扫气系统对发动机扫气效率没有较大影响,研究结果可以为分层扫气发动机的设计提供参考。

A three-dimensional model of stratified scavenging engine was established to study the scavenging characteristics and working mechanism of stratified scavenging engine,then three-dimensional CFD software Fluent was used to simulate and analyze the fluid structure with or without stratified scavenging system at rated speed,and the boundary conditions required for its calculation were obtained by one-dimensional simulation calculation of the engine.Results showed that,the stratified scavenging engine used pure air to form a stratification between the fresh mixture and the exhaust gas during operation,apart of the scavenging loss was taken by the pure air,which reduced 15%of unburned hydrocarbon and improved the fuel economy of the engine;the stratified scavenging engine and the non-stratified scavenging engine had a scavenging efficiency of 75%,without significant effect on the scavenging efficiency.The results of the research can provide reference for the design of stratified scavenging engines.