Effect of Tooth Bending Damage on the Leakage of Straight-Through Labyrinth Seals

Unavoidable rotordynamic impacting on labyrinth seal teeth sometimes occurs when centrifugal compressors, for example, undergo transients. Consequently, the labyrinth seal teeth are damaged or disfigured in various ways when the surface opposite to the teeth is non-abradable. Thus far, no quantitative information concerning the effect on seal leakage is available. The present work focuses on the effect of seal leakage due to such permanently bent labyrinth seal teeth. The investigation was done numerically by solving the 2-D, axisymmetric RANS equations with a finite-volume algorithm. The high-Reynolds number k-ε turbulence model was used with standard wall functions. A broad variety of tooth seal bending was studied by varying the bending curvature and the length of bending, as well as the after-bend tooth radial clearance. The results show that the bending damage drastically affects the leakage as well as the flow pattern. This is due largely to the altered clearance caused by the bending. However, other bending factors, such as the bending curvature and the percentage of tooth length that is bent, also contribute to the change of leakage and flow pattern.