Abstract
This paper presents an efficient three-dimensional (3D) structural model for bump-type gas foil bearings (GFBs) developed by considering friction. The foil structures are modeled with a 3D shell finite element model. Using the bump foil mechanical characteristics, the Guyan reduction and component mode synthesis methods are adopted to improve computational efficiency while guaranteeing accurate static responses. A contact model that includes friction and separation behaviors is presented to model the interactions of the bump foil with the top foil and bearing sleeve. The proposed structural model was validated with published analytical and experimental results. The coupled elastohydrodynamics model of GFBs was established by integration of the proposed structural model with data on hydrodynamic films, and it was validated by comparisons with existing experimental results. The performance of a bearing with an angular misalignment was studied numerically, revealing that the reaction torques of the misaligned bearing predicted by GFB models with 2D and 3D foil structure models are quite different. The 3D foil structure model should be used to study GFB misalignment.
Highlights
Gas foil bearings (GFBs) have been applied to high speed and high performance rotating machinery in many industrial fields because of their low frictional losses and oil-free operation [1, 2]
The complex geometry and nonlinear friction behavior lead to challenges in analyzing its mechanical characteristics
Efficient shell elements are used to model the foil structure, the finite element (FE) model still has a large number of degrees of freedom (DOF) when one considers the actual 3D geometry of the bump foil
Summary
Gas foil bearings (GFBs) have been applied to high speed and high performance rotating machinery in many industrial fields because of their low frictional losses and oil-free operation [1, 2]. Advanced and comprehensive foil models were developed to obtain a more accurate structural stiffness of the bump foil by considering the actual geometry, the interactions between bumps, and the frictional forces. The third generation GFB [5], whose bump stiffness changes in more than one direction, has a better bearing load carrying capacity Another example is that the bump foil removed from the region of minimum film thickness improves the steady behavior of a GFB rotor system with a large unbalance [33]. GFBs misalignment will lead to asymmetric hydrodynamic pressure distributions and foil deflections along the bearing axial direction [35] In this case, the model of the foil structure should have the ability to represent the 3D effect accurately.
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