Numerical Study on Characteristics of Spray under Air Flow in Gasoline Engine 2019-32-0616

The air flow affects the spray feature and mixture significantly in gasoline engine. The effects of air flow with atmosphere and pressurized ambient pressure were investigated experimentally in the previous work, the gasoline spray characteristics and air flow are analyzed using CFD method in this study. By polishing the model of droplet breakup according to the experimental results, the simulations are taken with various air flow conditions. Modeling of spray injected under typical condition of crossflow is employed to compare the numerical results with experimental results, using the corrected model the more calculation are carried out simulating the real conditions. With changing the injection and air flow conditions, the spray feature, droplet size, droplet movement, and droplet distribution are calculated by a commercial software. The effects of air flow on spray are clearer by numerical method than that in experimental measurements, the bended spray outline is varied with changing air flow speed, ambient pressure and injection angle, the penetration decreases when the cross-flow speed is increased and better second droplet breakup; Droplet size increases when the ambient pressure is increased, the tiny droplets appears in the area downstream the air flow even after the spray column near nozzle, the coalescence between droplets happens, which case large droplets appear downstream air flow; the small droplets are easy to be mingled with air flow, which is distinct in bottom of spray, the air flow field is also changed by the spray, turbulence appears downstream flow after spray; air flow most enhance the distribution of spray when the spray angle is 90°, decreasing or increasing the spray angle case the more weaken distribution of spray. The numerical results agree with the experimental measurement, it is meaningful to optimize the air flow parameters during design and control.