Research on the dynamic characteristics of rotor-bearing-seal system with breathing cracks under steam flow excited force

Abstract

In order to reveal the influence of breathing-type straight cracks on the motion characteristics and stability of a turbine rotor-bearing-seal system. The study examines the motion characteristic of a cracked rotor system under different loads with different crack depths, the coupled thermal and dynamic loads. The research derives motion differential equations for the cracked system, considering nonlinear dynamic properties such as nonlinear stiffness and damping. The equations incorporate the nonlinear steam flow excited force obtained from numerical simulations. The resulting motion equations are solved using the Runge-Kutta method, and the accuracy of the investigation of nonlinear dynamic characteristics is validated through experimental comparisons. Based on these findings, the motion characteristics and stability of the cracked rotor system under different conditions are analyzed. The results indicate that the motion characteristics of the rotor are progressively altered by the crack depth, and at a certain depth, the motion deviates from the established pattern. The influence of cracks on rotor stability is predominantly notable in the 34–58% THA region and under high load conditions. Moreover, the chaotic characteristics of rotor motion is more significant after applied the coupled thermal and dynamic loads, and the stability of the 34–58% THA region is significantly worse.