Experimental and numerical evaluation of the damping properties of a foil bearing structure taking into account the static and kinetic dry friction

Abstract

Over the past decades, experimental and theoretical studies on gas foil bearings have been conducted extensively. The essence of the operation of these bearings lies in the use of a unique underlying support mechanism, whose properties adapt to current operating conditions. The static and dynamic characteristics of the foil bearing structure depend not only on the geometry of the supporting structure but also on foil material, surface topology, the velocity of contact surfaces, load, etc. While the concept of stiffness is more intuitive and well described in the literature, the evaluation of the damping in foil bearings is not as obvious. The goal of this paper is to improve the understanding of the damping mechanism of the bump-type foil bearing structure under dynamic loads. At the beginning of the paper, the experimental studies of the foil bearing structure in a wide frequency range are discussed. Then, the experimental conditions were reproduced using an advanced numerical model that took into account the geometry of the top and bump foil, contact phenomena and dry friction. A new solution, unprecedented in the existing literature, is the inclusion of static and kinetic friction in the numerical model of the foil bearing structure. The developed numerical model made it possible to determine the system characteristics, including the evaluation of stiffness and damping. An important contribution of this work is the comparison of the results of calculations obtained with the use of an advanced numerical model with the results of experimental research. The paper gives clear guidelines for the experimental and numerical determination of dynamic characteristics for the bump-type foil bearing structure. The presented results of the experimental research can also be used to verify other numerical models.