Thermohydrodynamic analysis of turbulent flow in journal bearings running under different steady conditions

Abstract

In this study, the thermohydrodynamic (THD) characteristics of journal bearings with turbulent lubricant flow are determined using computational fluid dynamic techniques. The bearing has infinite length and operates under incompressible and steady conditions. The numerical solution of two-dimensional 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 is carried out. The AKN low- Re k–ε turbulence model is employed for computation of turbulence fluctuations. Because of the complex physical geometry, the governing equations are transformed for use in the computational domain such that the relation between computational and physical domains is obtained by conformal mapping. Discretized forms of the transformed equations are obtained by the control volume method and solved by the SIMPLE algorithm. 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 homogeneous mixture with equivalent property is assumed and the governing equations still apply in the cavitated domain. In this study, the effects of Reynolds number, clearance ratio, and eccentricity ratio on THD behaviour of journal bearings are examined. Comparison between the present numerical results and experiment shows good agreement.