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 assembly clearance between the bearing outer ring and the bearing pedestal,&nbsp;which is called pedestal looseness. This will affect the dynamic characteristics of the rotor system in two aspects: on the one hand, the support stiffness is nonlinear and uncertain, which will affect the modal characteristics of the rotor system; on the other hand, when the vibration response amplitude of the rotor under the excitation of various loads is large, the rotor will collide with the bearing seat, and the self-excited vibration will appear due to the impact from the bearing pedestal. The vibration of the rotor may be unstable.In this paper, a mechanical model of a flexible rotor system with pedestal looseness was established. The modal characteristics of the rotor system were analyzed by the improved harmonic balance method. The vibration response characteristics and stability of the rotor system were obtained by numerical integration method.The results showed that the modal frequencies of each order were interval distributed, and increased as the amplitude of the pedestal ascended; in a certain speed range, the harmonic vibration caused by the nonlinear stiffness of the support and the self-excited vibration caused by the impact effect occured simultaneously, and the self-excited vibration might be unstable.This paper will provide a theoretical method for dynamic optimization of multi fulcrum flexible rotor system, which is helpful to realize the reliability and safety design of aeroengine.

Dynamic Characteristics Analysis of Flexible Rotor System With Pedestal Looseness

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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