Cavitating Flow within an Injector-Like Geometry and the Subsequent Spray 2019-01-0284

Cavitation plays a significant role in the spray characteristics and the subsequent mixing and combustion process in engines. Cavitation has beneficial effects on the development of the fuel sprays by improving injection velocity and promoting primary break-up. On the other hand, intense pressure peaks induced by the vapor collapse may lead to erosion damage and severe degradation of the injector performance. In the present paper, the transient cavitating flow in the injector-like geometry was investigated using the modified turbulence model and cavitation criterion. A local density correction was used in the Reynolds-averaged Navier-Stokes turbulence model to reduce the turbulent viscosity, which facilitates the cavitation development. The turbulent stress was also considered in the cavitation inception stage. The modified model is capable of reproducing the cavitating flow with an affordable computational cost. For a better understanding of the cavitation and turbulence induced breakup, the Kelvin-Helmholtz wave, Aerodynamic, Cavitation, and Turbulence induced breakup model with the improved velocity coupling method of liquid-gas was used for spray simulation. The simulation results of the internal flow were used to determine the model coefficients in the improved breakup up model. Compared with the breakup model induced by Kelvin-Helmholtz wave and Rayleigh-Taylor instabilities, the improved model predicted a more dispersed spray with the shorter tip penetration. Various spray characteristics resulting from the different internal flow results indicated that the reliable reproduction of the cavitation characteristics is the prerequisite for the accurate simulation of the spray process.