Anisotropic Vibration Characteristics Analysis of Steam Turbine Rotor Influenced by Steam Flow Excited Force Coupling Thermal and Dynamic Loads

In order to reveal the influence of thermal and dynamic loads coupling on the vibration characteristic of steam turbine rotor, the high-pressure cylinder anisotropic rotor of a 1000-MW ultra-supercritical steam turbine was modeled by the lumped mass method. The steam flow excited force of the front eight stages obtained through the numerical simulation before and after the coupling was converted to the equivalent gas bearing and added on the rotor, and the influence of steam flow excited force on rotor vibration characteristics was obtained by the Riccati transfer matrix method. The results show that, considering the thermal and dynamic loads, the two ends of the ellipse trajectory are smaller and the middle is larger. Before and after coupling thermal and dynamic loads, the azimuth of ellipse trajectory increases with the increase of load and nodes. The greater the load, the greater the changing range of azimuth. As the load increases, the first-order natural speed of the rotor increases and the second-order natural speed decreases, but the natural speed after the coupling is noticeably lower than that before the coupling. The changing scope of the first-order amplitude shrinks with the load increasing. The first-order logarithmic decrement rate can be increased under the relatively higher load by coupling thermal and dynamic loads, but the stability margin of rotor is insufficient, which causes the instability.