Unbalance response of a magnetic suspended dual-rotor system

The magnetic suspended dual-rotor system applied in more electric aero-engine can eliminate the wear and lubrication system of mechanical bearings and solve the vibration control issue of system effectively, which provides the possibility to improve the performance of aero-engine significantly. This research focuses on the unbalance response of the magnetic suspended dual-rotor system. First, a structure of dual-rotor system supported by two active magnetic bearings and two permanent magnetic bearings is presented. With proportional derivative (PD) control adopted, the bearing characteristics of active magnetic bearings are modeled as the equivalent stiffness and equivalent damping, and the permanent magnetic bearings are modeled as elastic support. Then, the Riccati transfer matrix method with good numerical stability is used to establish the model of the magnetic suspended dual-rotor system unbalance response. Subsequently, the validity of the present formulation has been tested against some known results available in literature and the simulation results obtained by finite element method (FEM). Finally, the dynamic characteristics of the unbalance response are investigated. The results reveal that the influence of the inner rotor imbalance excitation on the magnetic suspended dual-rotor system unbalance response is much larger than that of the outer rotor imbalance excitation. In addition, the critical speeds increase with the proportional coefficient, and the derivative coefficient can affect the amplitudes of the unbalance response, but not critical speeds. From the perspectives of the maximum bearing capacity and maximum displacement of active magnetic bearing-rotor system, the possibility of the magnetic suspended dual-rotor system safely crossing the critical speeds of the first three orders is investigated.