Nonlinear dynamic behavior of a dual-rotor bearing system with coupling misalignment and rubbing faults

Abstract Taking the dual-rotor system in an aero-engine as a research object, the vibration behaviors of a dual-rotor bearing system that is fault-free or has misalignment, rub-impact or misalignment rub-impact coupling faults are studied, respectively. First, the three-dimensional model of the dual rotor bearing system is established, and then the first six modes and critical speeds of the dual rotor bearing system are obtained by the finite element method. Then, the dynamic equations of the dual rotor bearing system with and without faults are derived based on the Lagrange method. The Runge–Kutta method is used to solve the dynamic equation, and the nonlinear dynamic response of the system is obtained. The vibrational behaviors of the dual rotor system with misalignment, rub-impact and misalignment rub-impact coupling faults are analyzed and discussed through the time history, phase diagram and frequency spectrum of the rotor. The vibrational behaviors of the first six modes of the dual rotor system with and without faults are analyzed, respectively. The results provide theoretical guidance for the structural optimization design of an aero-engine rotor system and the prior decision information for misalignment and rub-impact coupling fault diagnosis.