Finite Element Analysis Of Rotor Dynamics With Magnetic-liquid Double Suspension Bearing

As a new composite bearing,Magnetic-Liquid Double Suspension Bearing(MLDSB)is designed by introducing hydrostatic supporting theory into Active Magnetic Bearing(AMB).MLDSB is composed of electromagnetic suspension and hydrostatic system,and has the advantages of strong bearing capacity,large stiffness and damping,excellent cooling performance,high stability and reliability.It is suitable for medium speed and heavy load,large bearing capacity,long service life,high stability and reliability of the occasions.Because the liquid film thickness of MLDSB is only about 1/10 of air-gap of AMB,and the protective bearing is cancelled,higher requirements are put forward for the supporting characteristics of MLDSB and the dynamic characteristics of rotor.Based on this,the excellent dynamic characteristics of rotor can be obtained through parameterization analysis of MLDSB to avoid the crash between rotor and stator.In addition,aiming at the status of crash,the transient dynamic characteristics of rotor are studied in depth,so as to reduce the damage.The main research work in this paper is as follows:(1)The supporting mechanism of MLDSB is introduced,and the mathematical model of the Single DOF system is built on the basis of Maxwell's electromagnetic and hydrostatic theory.Based on Lagrange equation,the dynamics equation of rotor with5-DOF is deduced.It provides theory and calculation basis for the finite element analysis subsequently.(2)By linearizing the mathematical model of the Single DOF system,the relationship between MLDSB parameters such as the magnetic-liquid proportional coefficient K,flow q₀,liquid film thickness h₀and the equivalent stiffness k_n,equivalent damping c_nis obtained.Then the relationship between the k_n,c_nand the natural frequency,response amplitude of rotor is obtained by the modal analysis and harmonic response analysis.Finally,the law between the K,q₀,h₀and the natural frequency,response amplitude is obtained by analysis.(3)The relationship between the two-parameter of MLDSB and the equivalent stiffness k_n,equivalent damping c_nis calculated.The law between the two-parameter of MLDSB and the natural frequency,response amplitude is obtained by the modal analysis and harmonic response analysis.(4)The displacement response,shaft centerline orbit and stress distribution are obtained by the transient dynamics analysis.The law between the peak value of radial excitation,number of radial excitation and the transient dynamic characteristics of rotor is obtained.(5)The natural frequency and response amplitude of each parameter of MLDSB are measured by the piezoelectric acceleration sensor system,and the results were compared with the simulation results.