Numerical investigation of the effect of working fluid on cavitating throttled flows

• A 3D CFD model is developed in ANSYS Fluent to simulate throttled cavitating flow in a rectangular micro-channel. • The model uses the mixture approach for two-phase flow, LES (WALE) for turbulence, and two cavitation models. • Simulations with Diesel are validated against published experimental and numerical data, showing good overall agreement. • Methanol and ethanol cases exhibit higher vapor generation, and lower mass flow rates compared to Diesel. • Erosion risk indicators reveal more cavitation-prone zones for methanol and ethanol, indicating higher damage potential. In the present work, a three-dimensional CFD model is developed in ANSYS Fluent to simulate the cavitating flow through a square orifice. The simulations are carried out using Fluent’s compressible solver to account for the pressure-dependent liquid density, while the two-phase flow (liquid and vapor) is modeled using the mixture model. Turbulence is resolved using the WALE large eddy simulation (LES) model, and cavitation mass transfer is computed using two cavitation models: Zwart–Gerber–Belamri (ZGB) and Schnerr–Sauer (SNS). The model is first validated using Diesel fuel under high-pressure conditions (P in = 300 bar, P out = 120 bar), demonstrating good agreement with published experimental and numerical data. Specifically, the predicted mass flow rate differs by less than 1 %, the velocity profiles within the channel show a maximum deviation of 9.2 % at the center (y = 1.5 mm), and the predicted vapor volume fraction distribution in the middle plane closely matches the reference data. Minor discrepancies are observed in the location of the boundary layer reattachment point, corresponding to the extent of the cavitation cloud, and in the velocity profiles near the channel midpoint. The ZGB model is selected as the reference cavitation model, as it shows better agreement with the published data, particularly in capturing the vapor volume fraction distribution within the channel. Following validation, the simulations are extended to methanol and ethanol, two promising alternative fuels, under the same operating conditions. The results reveal increased vapor generation in the channel for methanol and ethanol compared to Diesel, leading to slightly higher velocities: 4.3 % at x = 0.5 mm and 6.7 % at x = 0.8 mm, and a 3 % reduction in mass flow rate. Finally, selected cavitation erosion risk indicators (ERIs), based on key derivatives such as those of pressure and vapor volume fraction, are evaluated to identify regions most susceptible to cavitation erosion.