Measurements of Compressibility Effects in Stepped Thrust Gas Film Bearings

Hydrodynamic gas film bearings are used for supporting high-speed, lightly loaded rotating machinery. Stepped-type gas film bearings are often used for such machinery because of theïr simple structure, high stability and load carrying capacity. This paper describes the measurements of compressibility effects on the static and dynamic characteristics of stepped thrust gas film bearings. In the experiments, the minimum film thickness, friction torque on the bearing surface and stiffness and damping coefficients of gas films are measured for a range of rotational speed from 10,000 rpm to 20,000 rpm under a constant stator mass and a fixed step height. The measured data are compared with the theoretical results and the gas film compressibility effects on the static and dynamic characteristics of the bearings are discussed. The experimental results agree well with the predicted results based on the compressible lubrication theory.