Thermohydrodynamic Characteristics of Journal Bearings Running under Turbulent Condition

Abstract

A thermohydrodynamic (THD) analysis of turbulent flow in journal bearings is presented based on the computational fluid dynamic (CFD) techniques. The bearing has infinite length and operates under incompressible and steady conditions. In this analysis, the numerical solution of Navier-Stokes equations with the equations governing the kinetic energy of turbulence and the dissipation rate, coupled with the energy equation in the lubricant flow and the heat conduction equation in the bearing are obtained. The AKN Low-Re k-ε turbulence model is used to simulate the mean turbulent flow field. Considering the complexity of the physical geometry, conformal mapping is used to generate an orthogonal grid and the governing equations are transformed to the computational domain. Discretized forms of transformed equations are obtained by the control volume method and solved by the SIMPLE algorithm. In this study, cavitation effects are also considered by using an appropriate cavitation model. The liquid fraction in the cavitated region is computed based on the continuity requirements and rather than the two-phase flow of lubricant in this region, a homogenous mixture with equivalent properties is assumed and the governing equations still apply in the cavitated region. From this method, the lubricant velocity, pressure and temperature distributions in the circumferential and cross film directions are obtained without any approximation. The numerical results are compared with experimental data and good agreement is found.