Impact-rubbing Dynamic Behavior Of Magnetic-liquid Double Suspension Bearing Under Electromagnetic Fault

Magnetic-liquid double suspension bearing(MLDSB)is a new type of suspension bearing with electromagnetic suspension as the main part and hydrostatic supporting as the auxiliary part.In the actual operation process,once the corrosion of the electromagnetic coil and the fault of the power amplifier circuit occur,the electromagnetic system will fail,resulting in the impact-rubbing phenomenon between the rotor and the stator.In serious cases,the coating of magnetic guide sleeve and magnetic pole will crack and fall off,greatly reducing the operational reliability and stability of MLDSB.Therefore,in this paper,the impact-rubbing dynamics behavior of MLDSB is investigated.Then,the similarities and differences between the hydrostatic support in MLDSB system and the protection device in AMB(Active Magnetic Bearings)system are compared.The main research contents of this paper are as follows:(1)Aiming at the impact-rubbing problem of MLDSB in the electromagnetic fault mode,the mathematical model of single degree of freedom MLDSB supporting system is established.Then,considering the electromagnetic fault modes,the impact-rubbing dynamic equation of the system is derived based on the single degree of freedom supporting mathematical model.(2)Based on the impact-rubbing dynamic equation of the single degree of freedom system,the rotor displacement,the impact-rubbing force and the variation law of each supporting characteristics are numerically simulated.The "clearance-rubbing" internal mechanism of MLDSB under electromagnetic fault mode is revealed.(3)The impact-rubbing dynamic equation of three degrees of freedom system with radial MLDSB’s rotor under electromagnetic fault mode is established.The influence of unbalance and rotational speed on the impact-rubbing dynamic behavior of MLDSB system is simulated,and the changes of rotor axis trajectory,rotor displacement,impact-rubbing force and each supporting characteristics are extracted for comparative analysis.The "clearance-rubbing" motion mechanism of MLDSB under three degrees of freedom electromagnetic fault mode is revealed.(4)The impact-rubbing dynamic equation of rotor on three kinds of protective devices under electromagnetic fault mode is established.The rotor’s axial center trajectory and motion law are numerically simulated,and the impact-rubbing dynamic behavior characteristics of the rotor in three kinds of protection devices are compared and analyzed.The similarities and differences of rotor impact-rubbing dynamic behavior between the static pressure system and the traditional protective bearing devices is investigated when electromagnetic fault occurred.(5)The dynamic behavior of the single degree of freedom system under electromagnetic fault is experimentally studied,and the accuracy of the numerical simulation of the impact-rubbing dynamic behavior of the single degree of freedom system is verified.