Dynamic characteristics of an aeroengine dual-rotor system with inter-shaft rub-impact

Inter-shaft rub-impact, i.e., the rub-impact between two rotors, may occur in an aeroengine dual-rotor system. This paper represents the first attempt to investigate the nonlinear dynamics of a dual-rotor system with inter-shaft rub-impact. The dynamic model of a complex dual-rotor system is built using the 3D finite solid element method by considering the inter-shaft rubbing forces. An analysis strategy combining the component mode synthesis method and numerical integration method is developed to overcome the problem of solving the large-DOF model. The modes and vibration responses of the dual-rotor system under the effect of inter-shaft rub-impact are clarified. The results show that the inter-shaft rub-impact leads to vibration coupling between LP and HP rotors, leading to the appearance of novel resonance peaks in the vibration response. Three kinds of rubbing types, i.e., continuous rub-impact, intermittent rub-impact and self-excited vibration may be excited when inter-shaft rub-impact occurs in a dual-rotor system. The characteristics and mechanisms of these rubbing motions are examined using the orbit, time and frequency curves as well as the rubbing force and relative velocity curves. By reducing the rubbing stiffness and friction coefficient, the dangerous self-excited rubbing vibrations can be eliminated. Moreover, by comparing the rubbing responses under constant and variable speeds, the key effects of the initial conditions on the inter-shaft rubbing responses are highlighted. Finally, the results of inter-shaft rubbing experiments conducted using a real aeroengine dual-rotor system are discussed and used to verify the correctness of the theoretical results.