Numerical Study on the Influence of Gas Foil Thrust Bearings on the Vibrational Behavior

Abstract

Gas Foil Bearings (GFBs) have a promising future in high-speed turbomachinery such as air cycle machines and turbochargers. To achieve complete oil-free operation of the rotor support structure Gas Foil Thrust Bearings (GFTBs) can be used in combination with Gas Foil Journal Bearings (GFJBs). The present study numerically investigates the influence of GFTBs on the rotordynamic behaviour. In a first step the perturbation method is used to calculate linearized stiffness and damping coefficients. The perturbation approach used in this study is widely used in GFJBs resulting in uncoupled first-order equations to calculate the stiffness and damping parameters. Previously published approaches for GFTBs were relying either on coupled first order equations or were independent of excitation frequency. The calculated bearing parameters are validated against numerically calculated data published in the available literature. Linear stability analysis for a rigid rotor supported by GFTBs is performed and later extended for a rotor supported by both GFTBs and GFJBs.