Refrigerant foil bearing behavior—A Thermo-HydroDynamic study: (Application to rigid bearings)

Internal experiments at Liebherr-Aerospace FRANCE (LTS) on new refrigerant-lubricated compressor designs have shown that under specific operating conditions, a mixture of vapor and liquid appears in the compressor, instead of a single-phase vapor flow. Therefore, refrigerant-lubricated foil bearings behavior is studied, including the likelihood of two-phase flow in the lubricant. In this paper, we focus on the lubricant behavior only, in the operating conditions of foil bearings. The coupling with structural behavior is a complex process and will be the topic of another paper. The Thermo-HydroDynamic approach describes lubricant characteristics such as pressure, density, viscosity, and temperature. It involves the use of a Generalized Reynolds Equation for turbulent flow, a nonlinear cubic Equation of State for two-phase flow and a 3D turbulent thin-film energy equation. Journal bearing global parameters are calculated for steady-state conditions.