DESIGN METHOD OF CRITICAL SPEED DISTRIBUTION FOR DUAL-ROTOR SYSTEM WITH INTER-SHAFT BEARING BASED ON MODAL STRAIN ENERGY ANALYSIS

Aiming to solve the critical speeds design problem of the dual rotor system with Inter-shaft bearing, a design method based on modal strain energy analysis and the evaluation parameters of mode shape is proposed. This method classifies the hazardous critical speeds by mode shape evaluation parameters and analyzes the modal strain energy distribution to determine the key structural characteristic parameters. Through the analysis of the influence law of the characteristic parameters and their comprehensive adjustment, the distribution of critical speeds of the dual-rotor system is optimized. The results show that the safety margin improvement of the critical speeds of rigid mode shape can be achieved easily by adjusting the support stiffness, while the safety margin improvement of the critical speed of bending mode shape with mode coupling characteristics depends on the full use of gyroscopic effect and the comprehensive adjustment of several structural characteristic parameters related to the rotor stiffness. After optimization, the margin of hazardous critical speeds is significantly improved, among which the margin of coupled bending mode shape critical speed is increased from 4.4% to 17%, which verifies the effectiveness of the method in this paper.