Development of Aerodynamic Foil Bearing for Micro Gas Turbine

Abstract

A new type of aerodynamic foil bearing is proposed here in order to develop the high performance air bearing applicable to the super-high-speed turbo machineries such as a micro gas turbine. The aerodynamic foil bearings with the different dimensions, namely with the different foil stiffness and the different bearing clearances, were designed and were manufactured, and then the rotation tests were carried out for the purpose of clarifying the bearing performances and obtaining the design criteria. From the experimental results, the following facts were clarified. The foil stiffness had the strong effects on the bearing performances. The stability of the rotor was improved as the foil stiffness increased. On the other hand, as the foil stiffness decreased, the load-carrying capacity increased and the movement to the condition of the fluid film lubrication became faster. After the movement to the condition of the fluid film lubrication, the friction torque was kept low and almost constant. The dynamic bearing stiffness was higher than the static foil stiffness except the case of very low foil stiffness. Finally, it was clarified that the excellent performances were achieved by the choice of the adequate foil stiffness and bearing clearance, and the stable rotation up to 100000 rpm, which is one of the main objectives in the present tests, was achieved.