Suppression of self-excited vibration caused by oil film bearing using bearingless motor

Abstract

Oil film bearings have high load capacity and large damping. However, at high rotational speeds, fluid forces in the bearings, such as oil whip or oil whirl, can induce self-excited vibrations in the rotor. A hybrid system consisting of oil film bearings and a bearingless motor (BLM) is one of the possible ways in which a heavy rotor can be supported and rotated at high speed without inducing self-excited vibrations. In this study, first, in order to evaluate the effectiveness of this hybrid system, a compact rotor system supported by a pair of oil film bearings, and rotated and radially controlled by a bearingless motor (BLM) is designed. Secondly, the torque, the radial force of the BLM and the eigenvalues of the rotor-oil film bearing system are numerically calculated. Finally, the rotor vibration with and without the designed BLM is simulated to evaluate the feasibility of the proposed hybrid system.