Analysis of the Rotor Supported by Gas Foil Bearings Considering the Assembly Preload and Hardening Effect

This article discusses a new method for modelling elastic deformations of a foil bearing's structure, taking into account key phenomena influencing its characteristics. Special attention was paid to the assembly preload, which has an impact on the stiffness of the supporting system and thus also on the static and dynamic properties of the rotor. There has been proposed the method which allows for the inclusion of a selected preload into the bearing model. A new FEM model of the foil bearing's structure has been described. This model was coupled with an in-house developed flow model of the bearing and the entire rotating system. Computations were made for several assembly preload values, taking into account changes in the bearing structure stiffness as the load increases. The changes in stiffness associated with the load changes were due to the nonlinear geometry of the foils, and also due to the contact phenomena, including friction between components. The applied calculation algorithm allowed to take into account all these phenomena. The results obtained using the developed model confirm the very high influence of the foil bearing's pre-clamp and the progressive stiffness on the properties of the rotating system. Numerical models of this type can pave the way for a further development of foil bearings and for their wider use in modern high-speed fluid-flow machines.