Research on Vibration Characteristic Analysis of Magnetic Suspended Dual-Rotor System with Fixed-Point Rubbing

Due to the elimination of wear and lubrication system and effective solution to the vibration control issue, magnetic suspended dual-rotor system (MSDS) offers the possibility to significantly enhance the performance of aero-engines. However, research on MSDS vibration characteristics under fixed-point rubbing with the consideration of nonlinear support characteristics of active magnetic bearing (AMB) has rarely been addressed. In this research, an improved EF model of AMB is proposed by equivalent magnetic circuit method and verified by finite element model. Then, the Lankarani-Nikravesh model is employed to describe the impact force during rubbing process. On this basis, the rubbing dynamic model is established by finite element method and verified by comparing with the experimental results in literature. Finally, the MSDS vibration characteristics are explored, and some interesting phenomena are found. Fixed-point rubbing will cause abundant frequency components equally spaced around the combined frequency components of rotor rotational speeds at different frequency intervals. Due to the stimulation of the AMB nonlinear EF, the fractional frequency component of MSDS second-order critical speed emerges in a certain speed range and implies potential instability of the system, and the rotational speed corresponding to the initial appearance of this frequency component will decrease when fixed-point rubbing occurs. With the decrease of proportional coefficient and the increase of differential coefficient, the maximum normal impact force in the rubbing process decreases.