Dynamic Characteristics And Stability Domain Analysis Of Porous Aerostatic Bearings Under Working Conditions

Due to its special throttling mode,the porous gas hydrostatic bearing has higher bearing capacity and rigidity than the traditional small-hole throttling gas bearing,and has good stability,which shows great development prospects.At present,the research on the static bearing capacity and static stiffness design of porous gas bearings has been basically mature,but the research on its dynamic characteristics under normal working conditions is still relatively rare.Therefore,this paper has the experience and lack of experimental verification for the dynamic performance of porous gas bearings.The theoretical analysis and numerical simulation of the dynamic stiffness and damping coefficient of the dynamic characteristics of porous hydrostatic bearings are carried out.In order to further compensate the problem that the traditional linear constant bearing-rotor system model can not accurately reflect the performance of the bearing under normal working conditions,a nonlinear viscous bearing-rotor model system is established,and the bearing working condition is calculated.The vibration response and stability domain provide design basis and technical support for the realization of ultra-precision,high-performance porous gas hydrostatic bearings.The main research contents of this paper are as follows:(1)Based on the steady-state lubrication calculation model of the porous gas static pressure bearing film,a simulation calculation model of the bearing is established.According to the three law of conservation of gas flow in the bearing,combined with the fluid control equation in the gas film gap,the steady-state lubrication equation of the gas film under normal disturbance is obtained by theoretical calculation.Dynamic grid technology is used to solve the problem of mesh distortion in bearing motion,and the dynamic characteristics of porous gas hydrostatic bearing are simulated by finite volume method(FVM method).(2)The influence of gas static pressure bearing on the dynamic stiffness and damping of gas film under different structural parameters and working conditions is studied.The dynamic disturbance model of porous gas static pressure bearing film was established,and the influence of external disturbance amplitude,permeability of porous material,gas gap and gas supply pressure on dynamic stiffness and damping characteristics of gas film was analyzed.The gas static bearing has good static performance,establishes a dynamic simulation model of the local porous gas hydrostatic bearing,and coMpares the dynamic stiffness and damping of the gas film with the porous gas hydrostatic bearing to obtain a partial porous gas static.Pressure bearings have good dynamic stiffness and damping characteristics.(3)The vibration response characteristics and stability domain analysis of the gas hydrostatic bearing were carried out.The viscoelastic Maxwell gas film equivalent vibration model is established.The influence of supply pressure,bearing load and air gap on the amplitude-frequency characteristics of the bearing-rotor system is analyzed.The dynamic model of the porous gas hydrostatic bearing under working conditions is established.The critical speed of the bearing steady state is obtained,and coMpared with the local porous gas static bearing stability domain.Finally,the test experiment of the bearing platform on the vibration response of the bearing-rotor system is established,and the equivalent vibration of the gas film established in this paper is verified.The rationality and accuracy of the model.