Analysis On Natural Vibration Of Superconducting Generator Rotor

Compared with traditional generators, superconducting generators have many advantages, such as smaller synchronous, higher efficiency, smaller volume, lighter quality, easier maintenance and lower noise, and so on. Consequently, they have a big potential in the fields such as military vessels, merchant ships and maglev trains, and so on. The main difference of the structure between superconducting generators and traditional generators was that the superconducting generator rotor was a high-speed rotating cryostat with multilayer cylindrical shell. Therefore, this paper adopts the theoretical analysis and finite element simulation to research the natural vibration characteristics of the superconducting generator rotor.Firstly, the thick shell model of superconducting generator rotor is established. Based on the theory of thick shell, considering the influence of rotary inertia, transverse shear deformation and transverse normal extrusion in shells, the expressions of geometric, physical equations and energy of rotor are obtained. The equations of motion of rotor are derived by using Hamilton principle.Secondly, ignoring the influence of circumferential variable, simplifying the motion equations of thick shell rotor, the axially symmetric natural vibration characteristics of the superconducting generator rotor are presented. Considering the boundary restraint conditions of the inner rotor and outer rotor of generator, the mode functions satisfied the displacement boundary conditions are established. The natural vibration differential equations of the rotors are obtained by using the Galerkin integral method, and their natural frequencies are derived. Extending this method to analyze the non-axially symmetric natural vibration characteristics of the superconducting generator rotor, the analytical solutions of the natural vibration of superconducting generator rotor are obtained, and the law of their natural frequencies are analyzed.Finally, modal analysis of the inner rotor, outer rotor and the whole double-decked structure rotor of superconducting generator are executed by using the ANSYS software of finite element. Considering the influence of flexible support in the inner rotor, using thetwo different boundary constraints to simulate bearing, that is, regarding them as rigid and flexible constrains, the natural frequencies and the vibration-mode vectors of the first 10 orders are obtained. The influence of the bearing stiffness on the natural vibration characteristics are discussed by using the analysis of the result, and the natural vibration characteristics of the double-decked rotor structure are studied.