Nonlinear vibration of dual-rotor system with surface waviness in inter-shaft bearing

Considering the effect of dual-rotor model with surface waviness in inter-shaft bearing, the motion equations of a dual-rotor system were formulated by employing rotor dynamics and Langrange equations. The nonlinear vibration responses of the system were derived through numerical calculations. Accordingly, the dynamic behaviors of the system influenced respectively by rotation speed, maximum surface waviness amplitude, surface waviness order and the initial surface waviness amplitude were analyzed. The results showed that the effects of the surface waviness on the high pressure rotor and the low pressure rotor were almost the same. With the increase of the rotation speed, both of high pressure and low pressure rotors showed an alternative variation of periodic motion and non-periodic motion. In particular, the quasi-periodic and even chaotic motions may occur within a relatively low rotation speed region. With the increase of maximum surface waviness amplitude, the dynamic behavior of the system may turn from periodic motion into periodic 2 motion, quasi-periodic motion and periodic 4 motion against the safety and stability of the vibration system. When the surface waviness order was integer multiples of the number of rollers, the motion of the system would might be non-periodic, e.g. quasi-periodic or chaotic. With the increase of the initial surface waviness amplitude, the system showed an alternative variation of quasi-periodic motion and chaotic motion. Nevertheless, for a larger initial surface waviness amplitude, the vibration amplitude of system was even smaller.