EXPERIMENTAL-STUDY OF THE FLOW-FIELD INSIDE A WHIRLING ANNULAR SEAL

The flow field inside a whirling annular seal has been measured using a 3-D Laser Doppler Anemometer (LDA) system. The seal investigated has a clearance of 1.27 mm, a length of 37.3 mm and is mounted on a drive shaft with a 50 percent eccentricity ratio. This results in the rotor whirling at the same speed as the shaft rotation (whirl ratio = 1.0). The seal is operated at a Reynolds number of 12000 and a Taylor numbe r of 6300 (3600 rpm). The 3-D LDA system is equipped with a rotary enc oding system which is used to produce phase averaged measurements of t he entire mean velocity vector field and Reynolds stress tensor field from 0.13 mm upstream to 0.13 mm downstream of the seal. The mean velo city field reveals a highly three-dimensional flow field with large ra dial velocities near the inlet of the seal as well as a recirculation zone on the rotor surface. The location of maximum mean axial velocity migrates from the pressure side of the rotor at the inlet to the suct ion side at the exit. Turbulence production is a maximum near the seal inlet as indicated by the rapid increase of the turbulence kinetic en ergy (kappa). However, turbulence production and dissipation attain eq uilibrium fairly quickly with K remaining relatively constant over the last half of the seal.