Theoretical Analysis and Optimum Design of High Speed Air Film Thrust Bearings (Application to Optimum Design Problem)

Abstract

Hydrodynamic air film thrust bearings are widely used for very high speed, lightly loaded rotating machinery such as gas expander, compressor, gyroscope and business machines, etc. In the design of hydrodynamic air film thrust bearings, it is of cardinal importance to enhance the friction and stability capacities of air films for keeping the minimum friction loss within a particular level and for minimizing the vibration due to external excitations. Among various types of hydrodynamic air film thrust bearings, spiral and herring bone types of grooved bearings have an advantage of high stability and load carrying capacity, but the characteristics of the bearings depend on many design parameters. Therefore, when these parameters are designed suitably, it is expected to improve considerably the friction and stability characteristics of the bearings. In this paper, the optimum design methodology is presented to minimize the friction torque and also to maximize the stiffness of air film for spiral and herring bone types of grooved air film thrust bearings, and the applicability of the methodology is verified experimentally.