Performance Predictions On Novel Journal And Thrust Gas Foil Bearings

Gas foil bearings(GFBs)have been widely applied in high-speed rotating machinery such as air compressor and air circulation machine because of many advantages,including high rotational speed,high efficiency,oil free,no scheduled maintenance and so on.GFBs are divided into two branches of journal bearings and thrust bearings,which are mainly composed of housing,top foil and elastic support foil.In order to broaden the application and application fields of the GFBs,it is necessary to make continuous innovation on the structure,stability and processing technology of the bearing.In this dissertation,the theoretical models are proposed for the novel gas foil journal bearing and gas foil thrust bearing,and the structural characteristics,static and dynamic performances and thermohydrodynamic performance are analyzed.The main research works and achievements are as follows:According to the structure characteristics of the novel three-pad gas foil journal bearing(TGFJB),the support foil was modeled as two rigid links and a horizontal spring.Then the equivalent vertical stiffness of support foil was solved according to the force analysis and energy method.The two-dimension shell element model of top foil was established.The Reynolds equation for compressible gas and foil deformation equation were coupled to calculate the gas pressure distribution,and then the static and dynamic performances of TGFJB would be researched.Through the comparison and analysis of the results,the performance differences of TGFJB and the equal size rigid bearing were studied.The influence of bearing preload and bearing installation angle on the static and dynamic performances of TGFJB was analyzed,providing reference and guidance for the design and application of TGFJB in the later.Besides,the change of bearing dynamic performances with rotating speed was studied.Subsequently,it could be used as the input of rotor dynamic model to get dynamic characteristics.A beam model was established for the novel laminated gas foil thrust bearing(LGFTB)to calculate the equivalent vertical stiffness of the laminated support foils.The Reynolds equation suitable for LGFTB was derived,and then the static and dynamic performances of LGFTB were obtained by using the finite difference method(FDM)and the perturbation method.According to the calculation results,the distribution of the stiffness of the support foil was analyzed,the second wedge effect and the double peaks phenomenon of gas pressure were explained.The relationship between the minimum thickness of gas film and the static and dynamic performances was discussed.The influence of different wedge height on the bearing capacity,friction moment,dynamic stiffness and damping was investigated,and the determination of this important parameter in design was guided from the theoretical level.Considering the shear dissipation energy of LGFTB,a nonisothermal Reynolds equation and energy equation of LGFTB were established.After analyzing the heat transfer in LGFTB,a thermal resistance model was also built.The temperature of each point position in gas film was obtained by numerical simulation.The effect of bearing load and speed on the temperature of bearing components was studied,and the influence of the cooling air flow on the bearing temperature was analyzed.