Numerical study on the cavitation flow characteristics of high-pressure fuel in injector orifices based on compressible non-isothermal model

Abstract

The flow inside the orifices in diesel injector largely determines the injection characteristics, which further affects the performance of the diesel engine. In this paper, numerical simulation is conducted to characterize the fuel flow with characteristics of two-phase cavitation, high speed, high pressure, high turbulence intensity, and high viscosity in two crucial orifice locations. The OZ orifice is selected as a benchmark to select the appropriate turbulence model and cavitation model. The simulation results from different turbulence and cavitation models are analyzed, and the combination of the realizable k–ɛ turbulence model and the Zwart–Gerber–Belamri cavitation model proves to be superior. Then, based on the validated models, the compressibility and non-isothermal characteristics of the fuel and two geometric parameters of the nozzles in an injector are emphatically discussed to depict the cavitation flow. The results suggest that the compressibility and non-isothermal characteristics of fuel affect the mass flow rate, fuel flow velocity, and cavitation extent within the orifices with a maximum deviation of the mass flow rate of 7.1%. However, their influence on the orifice flow coefficient is relatively minor with a maximum deviation of 0.8%. The mass flow rate and flow coefficient are both positively correlated with the rounded edge radius and taper coefficient. A greater rounded edge radius and taper coefficient can lead to a better fuel flow capacity in the nozzle orifice.