Analytical Dynamic Model of Statically Indeterminate Rotor System and Misalignment

For the statically indeterminate rotor structure of low-pressure rotor system in aero-engine, mechanics features of bearing deformation and rotor structure were analyzed, combined with the principle of virtual work, and the global stiffness matrix of the rotor system was deduced. According to the Lagrange method, the analytical dynamic model of statically indeterminate rotor system with three flexible supports based on the flexibility analysis was built. An analytical dynamic model of intermediate supporting misalignment was established on the basis of the model. The natural characteristic and unbalance response of aligned and misaligned statically indeterminate rotor system were obtained through the analytical solution, and the experimental verification was conducted. These findings indicate that intermediate bearing misalignment of statically indeterminate rotor system can not only produce the 2X component, but also make the 1X component change. The experimental results are essentially in agreement with the calculated ones. The study laid the foundations for model basis and experimental reference of the statically indeterminate rotor system design, dynamic modeling and vibration control.