Dynamic Stability of Staggered Labyrinth Seals with Supercritical Carbon Dioxide

Numerical analysis model of the staggered labyrinth seal with supercritical CO₂ as working fluid was established. The dynamic and static characteristics of the staggered labyrinth seal for different width of rotor convex plate, clearance of seal and compared with the conventional labyrinth seal were studied based on infinitesimal theory. Results showed that the cross-coupled complex dynamic stiffness of staggered labyrinth seals had little effect on the effective damping coefficient, and the main damping had a major influence on it. At low whirling frequency (<160 Hz), the conventional labyrinth seal had better dynamic stability. When the whirling frequency was higher than 160 Hz, the effective damping coefficient of the staggered labyrinth seal was about 105% to 113% of the conventional labyrinth seal. The optimal value of the convex plate width to make the sealing system the best stability was 5.13 mm in this paper. With the decrease of seal clearance, the effective damping coefficient increased and the frequency dependence increased. The leakage flow rate of staggered labyrinth seal was 45.5% lower than that of conventional labyrinth seal. Compared with the original model (b=4 mm, c₂=0.5 mm), the leakage flow rate of 5.13 mm convex plate width and 0.4 mm seal clearance was reduced by about 5% and 19%, respectively. The leakage flow rate of staggered labyrinth seal decreased with decreasing of seal clearance.