A nonlinear model of flow-structure interaction between steam leakage through labyrinth seal and the whirling rotor

A nonlinear model of flow-structure interaction between steam leakage through labyrinth seal and the whirling rotor was presented. The particular concern was placed on incorporating thermal properties of the steam fluid into the mathematical model. To see the influence of the steam fluid on the whirling rotor, two sets of thermal parameters of the steam fluid, e.g., temperature and pressure drop in each seal cavity, were selected from the typical 1000 MW supercritical and 300 MW subcritical power units in China. The interlocking seal widely employed in practical situations was chosen for study. The rotor-seal system was modeled as a Jeffcott rotor subject to shear stress and pressure force associated with the steam leakage. Spatio-temporal variation of the steam forcing on the rotor surface in the coverage of the seal clearance and the cavity volume was specifically delineated by using the Muzynska model and the perturbation analysis, respectively. The governing equation of rotor dynamics including the influence of the steam leakage was solved by using the fourth-order Runge-Kutta method, resulting in the orbit of the whirling rotor. Stability of the rotor was inspected by using Liapunov’s first method. The results showed that the destabilization speed of the rotor was significantly influenced by the steam leakage.