Collision Mechanism and Dynamic Response of Rotor System With Pedestal Looseness

Abstract

Abstract In the structural design of aeroengine multi fulcrum flexible rotor, due to the limitation of assembly conditions and working load environment, there is a certain fit clearance between the bearing outer ring and the bearing pedestal, which is called pedestal looseness. When the response amplitude is high, the outer ring and pedestal collide, which affects the dynamic characteristics of the rotor system. Previous research often characterize the collision caused by pedestal looseness on the rotor as a nonlinear stiffness term in the rotor dynamics model, which can not directly reflect the real collision mechanism of the rotor. In this paper, the mechanical model of flexible rotor system with pedestal looseness was established. The motion variation process of rotor when collision occurred and subjected to radial impact was analyzed, which is characterized as the collision force of rotor, and the dynamic response is obtained. The results showed that when the response amplitude is large, rotor and bearing pedestal collided periodically, and various combination frequencies of rotation frequency and collision characteristic frequencies appeared in dynamic response; the combination frequencies may be equal to the modal frequency of the rotor system at the non critical speed point, so that the rotor may still have a large response amplitude when the speed is far from the critical speed.