3-D laser doppler velocimeter measurements of eccentric annular and labyrinth seals

Abstract

A 3-D laser doppler velocimeter was used to measure the flow field inside a whirling annular and labyrinth seal. The data was collected and phase averaged with the seals operating at a Reynolds number of 24,000 and a Taylor number of 6,600. The annular seal has an outside diameter of 164 mm, is 37.3 mm long and has a clearance of 1.27 mm. The labyrinth seal was of a straight through design with seven cavities. The seal has an outer diameter of 164 mm, is 33.5 mm long and has a clearance of 1.27 mm. The eccentricity ratios of the annular and labyrinth seals were 0.10 and 0.50 respectively. The whirl ratio for both seals were 1.00. For both seals the maximum axial velocity is not located at the maximum clearance over the length of the seals as would be expected. Instead the maximum a)axial velocities are seen on the pressure side of the seals at the inlet but migrates to the suction side of the seal at the exit. The magnitude of this migration is dependent upon the seal eccentricity. The labyrinth seal exhibits an axial recirculation zone at the seal inlet due to its larger eccentricity. The radial velocity profiles are generally dependent on the seal eccentricity as well. Tangential velocities are seen to develop in inverse proportion to the axial velocity. For the annular seal the flow exhibits an uniform tangential velocity distribution by a location of ZAL = 0.10. The labyrinth seal displays a similarly uniform distribution for the tangential component by the third cavity(Z/L = 0.36). The exit magnitudes of the azimuthal velocity is about 0.4WSh indicating that the azimuthal velocity is not significantly altered by altering the whirl ratio. Turbulence generation is dominant over the first third of the seal after which there is a sharp decrease in the turbulence levels.