Effects of Two Film Rupture Models on the Thermal Analysis of a Journal Bearing

Abstract

A model for the thermal behavior of lubricant in the cavitated regions of a journal bearing is presented. The model assumes a bubbly mixture of liquid and air and includes the calculation of local mixture properties for the fluid film. Temperature in the film is calculated by a first order approximate energy equation that includes heat transfer between the film and its boundaries. A second order profile is assumed to represent the temperature distribution across the film. The classical Reynolds equation is applied, using a viscosity that does not vary across the film. Results of calculations are compared with published experimental results and with a prior theory that uses an effective length calculation in the cavitation zone. Results are found to be in good agreement with experiment at two different speeds, predicting the peak temperature of the bearing wall within 10 to 20 percent of the total temperature rise. The model predicts the temperature in the cavitated zone with much greater accuracy than the effective length model, with all theoretical values within 2 C of the measured values.