Numerical Simulation of Cavitation and FlashBoiling in GDI Nozzle and Spray

This work aims at using Computational Fluid Dynamics (CFD) method to establish a gasoline direct injection (GDI) engine nozzle and combustion chamber model to simulate cavitation and flash boiling phenomena and analyze how these phenomena affect the engine performance. FLUENT 15.0 is used to simulate the flow of fuel. The cavitation phenomenon in GDI nozzle was simulated comprehensively, and the influences of parameter values such as inlet pressure and outlet pressure on cavitation were studied in this work. The results show that high injection pressure can promote the occurrence of cavitation and high outlet pressure has an inhibitory effect on cavitation. However, the effect of cavitation on atomization cannot be seen intuitively only through the simulation of the internal nozzle. The two-dimensional inter nozzle model established in this work is a foundation for the establishment of external nozzle model. It can provide specific boundary conditions at nozzle outlet. In addition, a three-dimensional external nozzle model was established to simulate the flash boiling spray in the combustion chamber. Based on the mechanism, it can be found that flash boiling spray improves the atomization quality. After verifying the simulation results with relevant experiments, these models could bring great convenience to the study of cavitation and flash boiling with sufficient reliability in further study.