The limiting static and dynamic performance of foil bearings

Abstract

Foil bearings have attracted considerable attention in small-sized turbomachines with its excellent stability, high compliance, and temperature durability. However, as the foil bearing is applied to turbine machinery with higher load and impact, the evaluation of its limiting performance becomes more important. Thus, a simple analytical method is proposed for predicting the limiting performance of the journal and thrust foil bearings. The analytical model is verified by comparing it with the full numerical algorithm. The results indicate that with the increase of rotating speed, the pressure distribution of both journal and thrust foil bearing approach to the analytical model but can never reach due to the boundary conditions. When the rotating speed tends to infinity, the principal stiffness Kxx, Kyy, Kzz converge to a certain value, while the cross stiffness Kxy and Kyx approach to infinity and 0, respectively. The static and dynamic performance are evaluated with foil compliance, rotor eccentricity, and film thickness as independent variables to provide further reference for system design.