Nonlinear Vibration Responses of a Rigid–Flexible Coupled Dual-Rotor System Under Coexisting Unbalance, Misalignment, and Rub-Impact Faults: Numerical Simulation and Experimental Validation

Aero-engine dual-rotor systems commonly suffer from simultaneous unbalance, support misalignment, and rotor–stator rub−impact, triggering complex coupled nonlinear vibrations, aliased fault features and dynamic instability. Most prior research concentrates on single-fault cases using linear superposition, neglecting nonlinear interactions among multiple faults. This study constructs a rigid–flexible coupled dual-rotor dynamic model incorporating inter-shaft bearing effects, rub-impact constraints, and misalignment-induced torque. Numerical simulations and parameter analyses are conducted to explore vibration behaviors under single and coupled faults. Results show unbalance and misalignment dominate low-speed vibration and suppress rub-impact, while rub-impact effects are enhanced at medium–high speeds. Misalignment worsens rubbing and unbalance magnifies resonance, exhibiting multi-fault amplification. Triple-fault coupling produces noise bands, distorted orbits, and periodic–chaotic alternation. Dual-rotor test-rig experiments validate the simulation findings: unbalance excites fundamental components, misalignment amplifies 2N1 harmonics, rub-impact generates combined frequencies, and coupled faults cause feature aliasing and amplitude modulation. This work reveals multi-fault vibration mutation mechanisms and supports fault decoupling, diagnosis, and vibration control for aero-engine dual-rotor systems.