Investigation on the Transient Lateral Vibration of a Flexible Rotor System with Substantial Unbalance

Substantial unbalance is a possible condition usually induced by large blade off or bird strike during operation of aero-engine, and related dynamics are very crucial to the safety design of aero-engine. The main purpose of this paper is to get insight into the nonlinear transient lateral vibration of a flexible rotor with considering the nonlinearity of substantial unbalance. A new nonlinear rotor dynamic model with substantial unbalance is first built based on Lagrange method and finite element method. Then the effects of substantial unbalance on rotor’s modal and stability characteristics are analyzed. Finally, the transient vibration responses during rotor decelerating process are discussed. The results show that there exist multiple modal coupling regions. In those regions, some vibration modes are instable, which may lead to the divergence of steady-state response or lead to several new resonance peaks. The rotation speed variation has a significant effect on rotor’s transient response. Obvious amplitude oscillation phenomenon can be observed, and it becomes more intense with the increase of decelerating time. Improving system damping can effectively reduce the nonlinear effect caused by substantial unbalance.