Rub-Impact Dynamics of Offset Disc Rotor with Imbalance and Loosening Pedestal

Abstract

It is easy for rotating machinery to produce looseness at the pedestal after long-term operation. The looseness of the pedestal causes the sudden increase of the vibration for the rotor, which leads to the rub-impact between the rotor and the stator. Compared with the middle disc rotor, the offset disc rotor in actual engineering is more universal; the gyro effect of the rotor is often neglected in the study of complicated systems, but the effect generates deflecting torque and affects the vibration characteristics, stability, maneuverability, and life of the system. Considering the disc offset and gyro effects of the rotor, the rub-impact dynamic characteristics of an unbalanced rotor system with pedestal looseness are investigated in this paper. This work is novel and more general in comparison with the traditional research on the imbalance-looseness-rubbing rotor system. The piecewise linear stiffness and damping of the support are used to describe the pedestal looseness, and Coulomb friction is applied to simulate the friction of the rub-impact. Based on the Lagrange equation, the equation of motion for the system is developed, and the Runge-Kutta method of the fourth-fifth order variable step is employed to solve the equation. The influence mechanism of the key parameters on the dynamics of the system is studied. The results show that the rotating speed, disc offset, loosening mass, and the rub-impact stiffness have vital effects on the dynamic responses of the system; the dynamic characteristics of only loosening fault and the coupling faults of the looseness and the rub-impact are obtained; there exists an optimal the rub-impact clearance value between the rotor and the stator for the efficiency and the stability of the machinery.