Abstract:  Aiming at the prominent problem of unbalanced coupled vibration of the cantilever coaxial dual-rotor system, the coupled mechanism of the cantilever dual-rotor system was theoretically derived, simulated, and experimentally studied by taking the dual-rotor system of an open rotor engine as the research object. Firstly, the equivalent dynamic model and coupled dynamic equation of the dual-rotor system were established by finite element method(FEM), and the coupled vibration mechanism of the cantilever coaxial dual-rotor system was analyzed. Then, the mode analysis, critical speed analysis, and unbalanced response analysis of the dual-rotors system were conducted by finite element software. The concept of the self-sensitivity coefficient was established to quantitatively evaluate the sensitivity of the system to unbalanced vibration and coupled state. Finally, according to the actual structure, a cantilever coaxial dual-rotor test platform was designed to perform the unbalanced vibration suppression experiment under different speed ratios, and the simulation results were verified by the experimental results. The research results show that the self-sensitivity coefficient proposed by the simulation can be used as the theoretical basis for the actual vibration measuring point arrangement and unbalanced vibration suppression strategy of the dual-rotor system. The unbalanced vibration reduction of the dual-rotor system can be reduced by more than 80% by applying the multi-step vibration suppression strategy of balancing the inner rotor first and then the outer rotor. This study has certain guiding significance for the layout of sensor measurement points and the coupled vibration suppression of the system in the dual-rotor system.
Key words:  mechanical vibration; coupled vibration mechanism; finite element method (FEM); dynamical equation; dynamic characteristic; steady state response analysis; unbalanced; modal analysis