Hydrodynamic Lubrication of Finite Length Rough Gas Journal Bearings

Abstract

Surface roughness effects on the hydrodynamic lubrication characteristics of finite length gas journal bearings has been studied by numerically solving the ensemble averaged compressible Reynolds equation. Analysis is based on the premise that the ensemble averaged Reynolds equation with film thickness averages using incompressible lubrication assumptions is valid for compressible lubrication at moderate compressibility numbers (Λ≤100). Film thickness averages are derived for a roughness distribution given by a polynomial fit of a Gaussian distribution. Load capacities and viscous friction losses for finite length gas journal bearings with longitudinal and transverse roughness patterns are compared with smooth bearings for varying eccentricity ratios, LID ratios and compressibility numbers. The finite length time dependent Reynolds equation for rough bearings is solved using a semi-implicit scheme and compared with smooth bearing results. As an illustration, the nonlinear transient unbalance response of a...