Static characteristics of small aerodynamic foil thrust bearings operated up to 350,000 r/min

Foil bearings have been attracting considerable attention for their application in achieving low power consumption in small-sized turbo machines, excellent stability at high speeds, and durability at high temperature. Foil bearings with bump foils are one of the most suitable candidates for these applications as indicated in recent studies. However, it was reported that current small foil thrust bearings had insufficient load capacity to support thrust forces in practical high-speed turbo machines, and were needed to improve the load capacity at high speeds. As a first step in improving the load capacity of small foil thrust bearings, the load capacity and rotational torque of this type of foil thrust bearings that operate at up to 350,000 r/min were investigated experimentally and numerically in this paper. In the numerical calculation, the Reynolds and elasticity equations for the top foil were solved simultaneously by using the finite difference and the finite element method, respectively. It was experimentally and numerically found that the foil thrust bearings treated in this paper have the load capacity coefficient of 5.36 × 10⁻⁶N/(mm)³ kr/min, which was comparable to that of the second-generation foil thrust bearings.