Rigid–Flexible Coupled Dynamic Modelling, Fault Simulation, and Experimental Validation for an Aeroengine Dual-Rotor System

Complex multi-rotor aeroengine systems exhibit intricate dynamic behaviours governed by mass distribution, rotor stiffness, bearing flexibility, and assembly coaxiality errors. Establishing accurate and physically representative dynamic models is essential to interpret their vibration characteristics. Taking a turbofan aeroengine dual-rotor configuration as the research object, this paper constructs a rigid–flexible coupled dynamic model within a multi-body dynamics framework. In this model, the fan and high-pressure rotors are simplified as rigid bodies, while squirrel-cage elastic supports and the slender low-pressure turbine shaft are defined as flexible components to improve modelling fidelity. Modal validation against prototype measured data shows that the developed rigid–flexible coupled model yields a maximum natural-frequency relative error of 11.31%, while the fully-rigid model suffers from severe prediction deviation with the maximum relative error reaching 102.37%. Three typical rotor faults, namely multi-disc random multi-phase unbalance, support misalignment, and stator–rotor rub-impact behaviour, are numerically simulated to extract fault-related vibration signatures. Further experimental investigations are carried out on a dual-rotor test rig: critical-speed identification, unbalance-driven vibration, support-misalignment, and fixed-point rub-impact tests. Measured vibration responses under different fault conditions qualitatively corroborate the key simulation predictions, which further validates the reliability and practicability of the rigid–flexible coupled modelling strategy. This work provides a high-precision modelling framework for dual-rotor assemblies and supplies experimental-supported fault-vibration datasets, offering technical references for vibration monitoring and intelligent fault diagnosis of aeroengine rotor systems.