Research On Static Characteristics Of Bump Foil Gas Bearing Based On The 3D Shell Model

As the self-acting hydrodynamic devices,bump type foil bearings have been successfully applied to wide range of high-speed rotating machinery at abroad such as air cycle machines of aircrafts,auxiliary power units,and cryogenic turbo-compressors.This type of bearing offers several advantages over a conventional gas bearing including lower power loss,better stability,environmental durability,and operation at high and low temperatures.However,there are some problems such as complex structure and difficult to manufacture for the bearings,and still not have successful commercial applications in the domestic.The design of bump type foil bearing is a multi-disciplinary problem.Researchers at home and abroad mainly focus on the foil deformation.And thus far,all of models have simplified the foil structure without consideration of its 3D shape.The experiments are concerned on the static and dynamic characteristics of the first generation bearing and the surface coating materials.In the dissertation,a new practical and theoretical 3D foil model is built up to calculate the stiffness of bump foil and the static characteristics of bearing.And the manufacturing process of one and two generation bearing is studied.A finite element foil structural model that considers the three-dimensional foil shape is developed.Using this model,the stiffness effects of the segments between bumps and the load distributions along axis direction is analyzed.The friction between bumps and their mating surfaces exerts great effects on the load capacity and stability of the bearing.From this point of view,a curve beam model and 3D elastic shell model is put forward considering the effects of Coulomb friction.And the results indicates that the load distribution along circumference and friction have great influence on the bump stiffness.Fluid lubrication Reynolds equation is discretized by using the Galerkin method,Newton Simpson method and finite difference method.The developed model was integrated into the bearing prediction Matlab programming to investigate the static performance of the bearing,such as: load capacity,minimum film thickness and attitude angle.In this paper,the fabrication process and static characteristics of the bearing are studied.The bearing sleeve,bump molds,bump foil forming and heat treatment of the two generation bearings have been described in detail.And a bearing test rig is set up to analysis the static performance of the bearings.A number of bearings with different parameters are assembled individually,and the parametric influences on the bearing performance are studied using the test data.