Topological structures of vibration responses for dual-rotor aeroengine

Many advanced aeroengines are typically designed with coaxial coupling dual-rotor structures. As a result, the vibration responses of the rotor system are characterized by complex multifrequency oscillations. In the paper, the topological structures of the nonlinear vibration responses of the dual-rotor system are revealed, providing a better understanding of the complex structural dynamics of many advanced aeroengines. A nonlinear dynamic model of the structural system of a dual-rotor-aeroengine experimental rig is established using the finite element (FE) method. This model takes into the blade-casing rubbing, misalignment, and the nonlinearities of the supporting rolling element bearings. The component mode synthesis (CMS) method is used to reduce the order of the dynamic model with high-degrees of freedom (DOFs) in order to enhance the computational efficiency. We first discover that long periodic structures exist in the multiharmonic vibration responses of the dual-rotor system. The structures of Poincare mappings and bifurcation diagrams provide clearer and more concise information when obtained through long periodic sampling. The numerical periodic vibration response structures matched the measurements. These results help uncover the inherent structural characteristics of the complex nonlinear vibrations of a dual-rotor aeroengine.