Modified Single-Fluid Cavitation Model for Pure Diesel and Biodiesel Fuels in Direct Injection Fuel Injectors

A cavitation model has been developed for the internal two-phase flow of diesel and biodiesel fuels in fuel injectors under high injection pressure conditions. The model is based on the single-fluid mixture approach with newly derived expressions for the phase change rate and local mean effective pressure—the two key components of the model. The effects of the turbulence, compressibility, and wall roughness are accounted for in the present model and model validation is carried out by comparing the model predictions of probable cavitation regions, velocity distribution, and fuel mass flow rate with the experimental measurement available in literature. It is found that cavitation inception for biodiesel occurs at a higher injection pressure, compared to diesel, due to its higher viscosity. However, supercavitation occurs for both diesel and biodiesel at high injection pressures. The renormalization group (RNG) $k-ɛ$ model for turbulence modeling is reasonable by comparing its performance with the realizable $k-ɛ$ and the shear stress transport (SST) $k-ω$ models. The effect of liquid phase compressibility becomes considerable for high injection pressures. Wall roughness is not an important factor for cavitation in fuel injectors.