Influence of tilting rotor on characteristics of fluid-induced vibration for labyrinth seals

Abstract

Labyrinth seal is a key component for the safe and reliable operation of a turbine unit. This paper sets up a three-dimensional numerical model of a labyrinth seal with a tilting rotor based on a compressor eye seal which was studied by Computational Fluid Dynamics method and a test labyrinth seal. The influence of the tilting rotor on the static and dynamic characteristics of labyrinth seals was investigated. Numerical results demonstrated a good agreement with the published article. Both the radial and tangential fluid-induced forces show an obvious increase when the rotor is in tilting conditions. From an efficiency viewpoint, a bigger tilt angle of the rotor is desirable. And eccentricity existence is not beneficial to the seal performance. The results based on the test seal show the whirl frequency ratio increases with the increasing eccentricity ratio. In case of tilting conditions (δ= 0.05 mm, θ= 0.8 deg), the whirl frequency ratio decreases with the increasing rotational speed. The higher rotational speed will be beneficial to the stability improvement when the rotor is in tilting conditions. The whirl frequency ratio also shows a decrease with the increasing inlet pressure. The higher inlet pressure tends to improve the stability when the rotor is in tilting conditions. All the stiffness coefficients and damping coefficients increase as the tilt angle increases. The whirl frequency ratio also shows an increase with the increasing tilt angle. The tilting rotor tends to reduce the stability when the rotor is in eccentric conditions.