Study On Spray Characteristics In Two Stroke Disi Engines Based On CFD

Improving fuel economy and reducing emissions are the great challenges to the internal combustion engine industry because of the increasingly serious energy and environment problems. As for the traditional two-stroke gasoline engines, the short-circuiting of the fresh charge during the scavenging process results in the poor fuel economy and high emission level. The development of gasoline direct injection (GDI) technology provides an effective way to solve the problem mentioned above,meanwhile, the well-atomized spray is required. Pressure-swirl injector is widely used in GDI injection system due to its advantages of good atomization quality, moderate penetration and so on.Based on the research of the atomization mechanism, the spray characteristics of two-stroke direct injection engine are studied by CFD technology.Firstly,the physical model and mathematical model of the pressure-swirl internal flow field are established and used to analyze the effects of working parameters and internal geometry on the flow characteristics with three-dimensional numerical simulation. Secondly, the suitable models for GDI spray are established and validated. Finally, based on the spray models validated and the results of the internal flow simulation, AVL FIRE is applied to simulate the spray from a pressure-swirl injector in a constant volume, and the influences of injection pressure, ambient pressure and internal geometry on the spray characteristics are studied. The research provides the theoretical reference and technical reserve for the optimization design of the fuel injection system in GDI engines.