Turbulence Measurements of High Shear Flow Fields in a Turbomachine Seal Configuration

SUMMARYTheflowfieldinsideanannularsealwhirlingatawhirlratio of 1 and an eccentricity ratio of 0.50 has been measured using a 3-D laser Doppler anemometer system. Reynolds numbers of 12,000 and 24,000 were investigated while the Taylor number was heldconstant at 6,600. The flow structure, as evidenced by the velocity and turbulence distributions in the whirling annular seal proved tobe far different than in a statically eccentric seal otherwise operating at the same conditions. Prominent features included a peak axialvelocity that began in the pressure section of the clearance at the inlet and rotated around Io the suction side of the clearance at the exit,avena contracta on the pressure side of the rotor, and no significant increase in tangential velocity with whirling rotor motion whencompared to statically eccentric seals.The axial flow profiles for both the high and low Reynolds number cases have similarities but also display substantialdifferences. In both the profiles, the peak axial velocity rotates from the pressure to the suction side of the clearance. In the lowReynolds number case, this started at 60* with a magnitude of 2.4U,,, over the inlet. By midplane the profile spreads uniformly acrossmost of the clearance. This rotates around the clearance, and at Z/L=0.77 the peak reaches the final circumferential position of 300*.Downstream of this position, the peak continues to grow, increasing to 1.9U,, at the exit of the seal.The mean velocity field reveals a highly three dimensio,ml flow with large radial velocities near the inlet of the seal. Thenormalized axial momentum near the inlet on the pressure side of the rotor is higher in the low Reynolds number case due to an axialrecirculation zone that occurs on the suction side of the rotor at the inlet. Another recirculation zone exists on the rotor surface on thepressure side of the inlet at both Reynolds numbers. This recirculation zone extends from 20* to 200* in the tangential direction, andis one third of a clearance wide radially (not apparent in the contour plots). The high Reynolds number recirculation zone is 1.5 meanclearances long, while the low Reynolds number zone extends 2 mean clearances downstream. When compared to previous non-whirlingflow studies (Johnson (1989)) at similar flow parameters, the tangential momentum does not significantly increase with the onset of whirl.Areas of high tangential momentum occur in regions of the clearance where the axial momentum is low. Average exit plane tangentialvelocities in the low Reynolds number case are 1.5 times greater than those in the high Reynolds number case.NOMENCLATUREA