Three-dimensional thermohydrodynamic analysis of axially grooved journal bearings

Abstract

A thermohydrodynamic analysis of an axially grooved fluid film journal bearing, based on computational fluid dynamics (CFD) techniques is presented. The bearing has a finite length and operates under incompressible laminar flow and steady conditions. This analysis is based on the numerical solution of the full three-dimensional Navier-Stokes equation, coupled with the energy equation in the lubricant flow and the heat conduction equations in the bearing and the shaft. Considering the complexity of the physical geometry, conformal mapping is used to generate an orthogonal grid and the governing equations are transformed in the computational domain. Discretized forms of the transformed equations are obtained by the control volume method and solved by the semi-implicit method for pressure-linked equations (SIMPLE algorithm). In this study, cavitation effects are also considered by introducing an appropriate three-dimensional cavitation model. The liquid fraction in the cavitated region is computed on the basis of continuity requirements and, rather than the flow of gas and liquid in this region, a homogeneous mixture with equivalent properties is assumed and the governing equations still apply. From this method, the lubricant velocity, pressure and temperature distributions in the circumferential, cross-film and axial directions are obtained without any approximation. Also, a comparison is made between two-dimensional and three-dimensional analyses and the effect of bearing length on performance is studied. The numerical results are compared with several experimental data sets and good agreement is found.