Leakage reduction by optimization of hole-pattern damping seal with inclined hole cavity

Abstract

The hole-pattern damping seal (HPDS) is one of the most typical sealing solutions used in gas turbines. Structural innovation and geometrical optimization of hole cavity shape of hole-pattern damping seal are effective ways to reduce leakage rate during operation. A novel hole-pattern damping seal with inclined holes, the central axis of which at an angle with the axis of a rotating shaft, is proposed by introducing a parameter of axial inclined angle. The 3D flow field and pressure distribution of hole-pattern damping seal with different hole cavity geometries were simulated with RNG k-ε turbulent model utilizing Fluent software. The leakage characteristics of hole-pattern damping seal and labyrinth seal (LS) with a straight or inclined hole cavity were compared numerically and experimentally. A velocity field with three-speed zones was proposed to reveal the leakage reduction mechanism for windward inclined hole-pattern damping seal. The influence of operation condition and key geometrical parameters on the leakage rate of windward inclined hole-pattern damping seal were investigated. The results show that the leakage rate of windward inclined hole-pattern damping seal is expected to be reduced remarkably compared to that of both straight hole-pattern damping seal and slanted-tooth labyrinth seal, the maximum leakage reduction ratio of which reaches up to 25%. The low-speed zone formed adjacent to both sides of the hole cavity outlet and the fully developed turbulent vortex inside the cavity are the main reasons contribute to leakage reduction of windward inclined hole-pattern damping seal. Moreover, the leakage reduction capability of windward inclined hole-pattern damping seal depends greatly on the proper match of parameter values such as seal clearance, hole diameter and axial inclined angle. The hole with a larger diameter is suitable for the larger seal clearance condition, while the hole with a smaller diameter is suitable for the smaller seal clearance condition.