Stiffness Prediction for Various Compliant Bump Structures Used in Gas Foil Bearings

Gas foil bearings (GFB) have been successfully used in various high-speed turbomachinery such as turboexpanders, turbocompressors, high-speed spindles, etc. Gas foil bearings have been proven to provide higher load-carrying capacity with higher reliability under various adverse operating conditions. A gas foil bearing consists of three components- a bearing base, a compliant/spring-like structure, and a thin, smooth top foil. The thickness of the thin compliant structure is in the order of 100–150 µm. The structural stiffness of the thin foils in a gas foil bearing is one of the major constraints for its use in high-speed machinery, where high stiffness is essential for its vibrational behaviour. Current research focuses on the design of various types of compliant structures, which are used beneath the smooth thin top foil of the foil bearings. Compliant bump structures included in the studies are bump Foil with Stiffeners, Elliptical Bump Foil, and Elliptical Bump Foil with Stiffeners, etc. The numerical simulation of these GFB is performed in Ansys® software. For these foil structure models, the variation in bump deflection is evaluated under the uniform pressure distribution. Further, the stiffness and equivalent stresses are predicted at various bump indexes. Finally, a detailed comparison is made to understand the various advantages and disadvantages of the above-mentioned compliant bump structure.