Analysis of Gas Lubricated Compliant Thrust Bearings

Abstract

This work is concerned with an evaluation of the performance of a gas thrust bearing using what amounts to a spring supported compliant foil as the bearing surface. To enhance the load capacity of such a device, the leading portion of the foil is given an appropriate converging geometry. The paper offers an analytical investigation of the elastohydrodynamics of the compliant foil bearing, and the effects that the various structural and operational variables have on bearing behavior. Following the solution of the relevant differential equation, the geometry of the thrust sector is first optimized, then solutions are provided for a range of relevant geometrical and operational parameters. The parametric study shows that the optimum geometry for a bearing with the common OD to ID ratio of 2 is β = 45 deg, b = 0.5, h1 > 10 In addition to the geometric parameters, there are also the structural parameters of the foil. The load capacity is shown to increase as the compliance of the bearing rises. While at moderate Λ’s high values of compliance yield the highest load capacity, at high Λ, the optimum compliance is some intermediate value, in our case, α* = 1. Since the stiffness of the bearing is a function of both the structural and hydrodynamic film stiffnesses, high loads tend to flatten the values of K for the softer bearings, leaving essentially the structural stiffness as the dominating spring constant.