不同类型微火源对复合燃烧作用机制的辨识

缸内喷射少量二甲醚(DME)形成微火源引燃汽油复合燃烧,可以拓展汽油稀释燃烧的界限,进一步提高发动机的经济性.基于三维计算流体动力学(CFD)结合化学反应动力学模拟,分析了不同微引燃燃料缸内分布作用下初始自燃点的产生机制,为集聚型和离散型微火源的类型判定提供辨识依据.结果表明:微火源的形成受到局部温度和DME浓度的共同...

Identification of Different Mechanisms of Micro Flame on Hybrid Combustion

The boundary of gasoline dilute combustion can be expanded by micro flame induced by a small amount of high activity fuel of dimethyl ether(DME).The generation mechanism of initial auto-ignition points on different timing of micro flame fuel injection was studied based on three-dimensional computational fluid dynamics(CFD)numerical simulation platform combined with chemical kinetic mechanism,which provides the basis for the discrete and congregate micro flame.Results indicate that the spontaneous combustion of the micro flame source is affected by local DME concentration and temperature.The discrete micro flame is mainly influenced by the local temperature,while the congregate micro flame is influenced by the local DME concentration.The discrete micro flame can enhance the global reactive activity and the flame speed of dilute mixture,and the congregate micro flame can ignite the high dilute mixture.The net generation rate of formaldehyde,as an important intermediate,can be used to identify different kinds of micro flame.The basis are that the variation of formaldehyde is less than 10%of maximum mass during the transitional process with multiple zero point in the derivative,which indicates that the formaldehyde is generated in the concentrated DME position and is consumed in the area of low temperature.