Thermohydrodynamic behavior of journal bearings running under different steady conditions



In most previous investigations, journal bearing performance characteristics have been analyzed using different simplified assumptions. The purpose of this study is to eliminate most of those assumptions, using computational fluid dynamics (CFD) techniques to solve the exact governing equations. The bearing has a finite length and operates under incompressible laminar flow and steady conditions. Numerical solutions of the full three-dimensional Navier-Stokes equations, coupled with the energy equation in the lubricant field and the heat conduction equations in the bearing and the shaft are obtained. Considering the complexity of the physical geometry, conformal mapping is used to generate an orthogonal grid and the governing equations are transformed for use in the computational domain. Discretized forms of the transformed equations are obtained by control volume method and solved by SIMPLE algorithm. Cavitation effects are also considered by introducing an appropriate three-dimensional cavitation model. In order to study the effect of main parameters on thermohydrodynamic behavior of journal bearings, solutions are obtained for different values of the eccentricity and radial clearance and also for different values of the rotational speed of the shaft. To validate the computational results, comparison with the experimental data of other investigators is made, and reasonable agreement is obtained.