Analysis of Externally Pressurized Gas Porous Bearings

Abstract

An analytical solution is presented to predict the performance of an externally pressurized porous gas thrust bearing. When the wall thickness of the pad is small compared to its radius, the expressions for the bearing characteristics can be given in a closed form. The bearing number Λ—a dimensionless design variable—can adequately describe the performance of the bearing. The load capacity and mass flow rate progressively increase with the bearing number; the static stiffness increases with the bearing number up to Λ ∼ 4.0 and then gradually decreases. The decisive influence of permeability of the pad material in controlling the performance of the bearing is discussed and the interesting behaviour of the static stiffness as the film thickness is reduced is pointed out. It is found that there is near perfect agreement between the predicted performance of the bearing and the one experimentally evaluated. The characteristics are plotted over a wide range for the bearing number (.01 ≤ Λ ≤ 2500) in such a way that the information is of direct use to designers and applications engineers. Also, the results are given in tabular form to facilitate interpolation of the values as required.