Theoretical design, manufacturing, and numerical prediction of a novel multileaf foil journal gas bearing for PowerMEMs

Abstract

Mesoscale gas bearing is widely used in micro-turbine machineries and auxiliary power units due to their certain advantages of low drag friction, good stability, and high tolerance to shaft misalignment. A novel mesoscale multileaf foil bearing, fabricated with UV lithography technology, is proposed and analyzed in this study. The multileaf foil bearing is designed with piecewise stiffness, which can achieve low stiffness during start or stop and high load capacity during operation. Moreover, the increasing contacting surface leads to large bearing damping. Equation governing the hydrodynamics of the fluid film is coupled with equations describing the elastic deformation of the cantilevered curved foil to determine the static and dynamic characteristics. The governing deformation equation is derived using Castigliano’s theorem and verified with commercial finite element software. A power microelectromechanical systems supported on mesoscale multileaf foil bearings is proposed, and rotordynamic performance is predicted using the calculated bearing coefficients. Predictions show that the load capacity of a multileaf bearing whose cantilevered foil has contact at the free end is larger than that of a bearing whose cantilevered foil has no contact at the free end. The novel multileaf bearing with a lager reserved clearance Cr has superior stability characteristic than the bearing with smaller reserved clearance.