Two-phase lubrication characteristics of journal bearing in refrigerant-oil system under high-pressure environment considering gaseous cavitation.

• Gaseous cavitation occurs due to change of refrigerant solubility in bearing. • Load-carrying capacity in high eccentricity is increased due to cavitation. • Negative pressure zone occurs in bearing at pressurized refrigerant environments. • Reversed flow from ambient should be addressed in bearing design and simulation. The journal-bearing system is crucial for the reliability of refrigerant compressors that operate under high-ambient-pressure environments. The pressure changes rapidly, which hereby results in the variation in solubility of refrigerant in oil, and causes gaseous cavitation of the refrigerant-oil mixture in the bearing. However, the cavitation mechanism under high-pressure environments is not well understood, and its impact on lubrication characteristics has been rarely discussed. In this paper, a numerical model is developed to simultaneously solve the gaseous cavitation and two-phase lubrication problems. The first systematic comparison of lubrication characteristics for constant-eccentricity journal bearings, in such a special environment, between the classical Reynolds boundary and gaseous cavitation boundary is presented. Results indicate the load-carrying capacity is reduced by about 3% at a lower eccentricity of 0.3, but is greatly enhanced by about 21% at a higher eccentricity of 0.9 due to the gaseous cavitation. Meanwhile, the 'reverse' flow rate is found to reach -0.057 at the end side of the bearing owing to sub-ambient pressure up to -1 MPa at the eccentricity of 0.8. The cavitation-induced sub-ambient pressure should be addressed for the design of the bearing operating in such pressurized refrigerant environments as ambient gas might be sucked into the bearing. [ABSTRACT FROM AUTHOR]