Applicability of Volume of Fluid Method to Two-Phase Flow Turbomachinery Application

Hydrodynamic bearings, based on lubrication oil, are commonly used in turbomachinery. The understanding and modeling of the air-oil two-phase flows in the bearing casing, piping and drain are important during the design phase. Given the limitations of the analytical methods and experiments, the use of robust and fast numerical methods, which can aid the engineers to assess various designs, is significant. In this paper, the use of VOF method for the air-oil flows for turbomachinery is reviewed. The paper first scrutinizes the use of VOF method for certain flow regimes from the perspective of the underlying VOF numerical method. Then, based on a detailed investigation using test rig observation of the bearing casing of a radial bearing of a turbocharger, the corresponding two-phase flow simulations using VOF are presented. Sensitivity studies are carried-out to understand the role of the key parameters and determine an appropriate CFD model. With the proper numerical setup, the CFD results are in good agreement with the test rig. The numerical setup is further applied to a common use case of air-oil two-phase flows of turbomachinery, namely the oil drain. The CFD model of the oil drain leads to realistic results and illustrates the applicability of the VOF method.