An Analysis of Gas-Lubricated, Multileaf Foil Journal Bearings With Backing Springs

Abstract

This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. The surface of these bearings is made up of preformed, leaf-type, compliant foils that are anchored to the bearing housing by spacer keys. Each leaf overlaps an adjacent leaf. Beneath each foil and attached to the inside of the bearing housing is a strip of backing spring. The stiffnesses of various foil bearing structures are modeled and presented as influence coefficients. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. The solutions include values of bearing stiffness coefficients due to both structural and hydrodynamic stiffnesses. The analysis, which is conducted for multileaf configurations by varying the number of leaves, uncovers the effects that the various structural, geometric, and operational variables have on bearing behavior. Also discussed are design guidelines with regard to the number of leaves, the degree of compliance, and bearing operational parameters.