Miniature aerodynamic elastic foil gas bearing for palm-sized high speed turboexpander

To meet the operation requirement of miniature high speed turbo-machinery, a new type of compliant aerodynamic foil gas bearing manufactured by conventionally precise machining is developed, where the foil configuration is composed of smooth top foil and elastic bump foil with series of hemispherical convex dots. This kind of bump foil contains one layer or multilayer structure. For multilayer structure, the convex dots on the first layer are set on the middle of span of second layer convex dots. This foil bearing is firstly applied to a palm-sized high speed turboexpander with shaft diameter of 6 mm, and an experiment on a high speed gas bearing turboexpander test rig is conducted to examine the vibration characteristic and stability. It indicates that the proposed foil bearing is endowed with fine damping performance to restrain unstable whirling. The hemispherical convex dots on the foil are able to adjust foil stiffness and damping by the self-deformation. The maximum rotational speed of the tested palm-sized turboexpander reaches 360000 r/min.