Theoretical Analysis And Experimental Investigations Of Novel Gas Bearings

Gas foil bearings(GFBs)are considered as the key technology of high speed rational machinery which use ambient air or process gas as lubricants.Because they have lots of advantages such as high speed,maintenance-free,high reliability and high temperature resistance thus this kind of bearings have been widely applied.Micro/meso scale gas foil bearings(MGFBs)have been widely used in micro turbine machines and micro electro mechanical system(MEMS).However,lots of study are focused on theory and ignored the effects of slip flow which generated by the micro scale clearance.Thus the results exist some errors.Theoretical research of normal scale gas foil bearings are becoming mature,yet there are still some defects on structure innovation and dynamic parameter analysis at high speed.In view of these points,the main research contents of this thesis are as follows:A stiffness model of the novel elastic foundation was carried out and a test rig was built to test the stiffness of the elastic layer and the test results confirmed the predictions.Static and dynamic performance of the bearing was predicted by coupling the stiffness model of the elastic foundation.Establish the Reynolds equation which considering first order slip flow and use the finite difference method(FDM)solve the equation.Found that the eccentricity ratio increase and the thickness of film decrease under the influence of slip flow.On basis of static equation's solution,perturbation method was used to solve the dynamic equation.The test results show that dynamic stiffness coefficients decrease under the influence of slip flow but dynamic damping coefficients show opposite trend.What's more,the dynamic parameters' variation trend under effect of excitation frequency ratio.The structure parameter of elastic foundation are also studied which can be the guidance of the following research.The results indicate that eccentricity ratio together with the dynamic stiffness increase whereas dynamic damping coefficients show opposite trend with the increase of the thickness and number of the elastic foundation.A novel nested spring gas foil bearing was made and its performance are analysis in detail.Form the manufacture of bearing,the stability of bearing are test through the take off experiment.In order to ensure the clearance between the three bearings which have nested spring number.The cyclic loading test was carried out to ensure the coherence of the three bearings.Use the hammering method and excitation method to test bearing's dynamic parameters.Not only the static and dynamic stiffness and damping of the three different NSFB are study,but also the do's and don'ts of the install are mentioned in detail.In addition,matters need attention about the assemble and sensors of the test rig of excitation experiment are illustrated.The results of stiffness and damping verified the feasibility of this method.