Design Approach for Large Foil Bearings Considering Rotordynamics

Abstract

In recent years, gas foil bearings have gained increased attention due to potential applications in aerospace systems. Research and development efforts have been focused towards simplifying design and analysis methods or experimentally demonstrating stable bearing performance under various operating conditions. Many researchers have proposed design guidelines for parameters such as load capacity, stiffness, and damping etc., for extending the state of the art based on experimental data available in existing literature. The authors previously presented scaling laws for radial clearance and support structure stiffness of radial foil bearings. In that study, the criteria for selecting radial clearance and support structure stiffness for scale up or scale down of an existing bearing design was presented. In addition, the results from that paper showed that a hydrodynamic film could be sustained for large bearings (up to 300 mm diameter) demonstrating that the bearings would have adequate load capacity. However, the rotordynamic effects for the various bearing sizes were not considered in that study. This paper serves as an extension of the paper on scaling laws by the same authors. The subject of this paper is a four degree of freedom (4-DOF) rotordynamic analysis performed for turbomachinery systems that employ bearings designed using the scaling laws for radial clearance and support structure stiffness. Further, case studies to show feasibility of foil bearings for applications in Mega Watt range turbo blowers and turbo compressors is presented.