Numerical investigations on passive control of vibration induced by bolted-joint rotor suspended by AMBs

Rotor-Active magnetic bearing (rotor-AMB) systems offer significant advantages in power consumption and are increasingly being applied in turbomachinery. However, in such machinery, the impeller and the rotor are commonly connected by bolted-joint. We observed once a certain pre-tightening torque is applied to the bolted connection and the interface contact between the rotor and the impeller is formed, the bending mode vibration will be excited when the rotor is levitated. The conventional active control method is limited in this vibration suppression and it is essential to increase the damping at bending mode to inhibit vibration. This research presents a novel passive control method to suppress this vibration by using the eddy current damping. Numerical simulations were carried out based on the rotor-AMBs system model considering bolted-joint interface contact model and analytical eddy-current damping model. Results obtained show that when decreasing the axial clearance between permanent magnet and the impeller, the eddy-current damping is increased exponentially, which will lead to the suppression of the bending mode response and reduce the vibration amplitude by 99.5%.