Accession Number : ADA330090

Title :   Laser Anemometer Measurements of the Flow Field in a 4:1 Pressure Ratio Centrifugal Impeller.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Skoch, G. J. ; Prahst, P. S. ; Wernet, M. P. ; Wood, J. R. ; Strazisar, A. J.

PDF Url : ADA330090

Report Date : AUG 1997

Pagination or Media Count : 15

Abstract : A laser-doppler anemometer was used to obtain flow-field velocity measurements in a 4:1 pressure ratio, 4.54 kg/s (10 lbm/s), centrifugal impeller, with splitter blades and backsweep, which was configured with a vaneless diffuser. Measured through-flow velocities are reported for ten quasi-orthogonal survey planes at locations ranging from 1% to 99% of main blade chord. Measured through-flow velocities are compared to those predicted by a 3-D viscous steady flow analysis (Dawes) code. The measurements show the development and progression through the impeller and vaneless diffuser of a through-flow velocity deficit which results from the tip clearance flow and accumulation of low momentum fluid centrifuged from the blade and hub surfaces. Flow traces from the CFD analysis show the origin of this deficit which begins to grow in the inlet region of the impeller where it is first detected near the suction surface side of the passage. It then moves toward the pressure side of the channel, due to the movement of tip clearance flow across the impeller passage, where it is cut by the splitter blade leading edge. As blade loading increases toward the rear of the channel the deficit region is driven back toward the suction surface by the cross-passage pressure gradient. There is no evidence of a large wake region that might result from flow separation and the impeller efficiency is relatively high. The flow field in this impeller is quite similar to that documented previously by NASA Lewis in a large low-speed backswept impeller.

Descriptors :   *CENTRIFUGAL FIELDS, *IMPELLERS, VELOCITY, MEASUREMENT, EFFICIENCY, COMPUTATIONAL FLUID DYNAMICS, FLOW FIELDS, FLOW RATE, PRESSURE, FLOW SEPARATION, FLUID FLOW, LASER ANEMOMETERS, DIFFUSERS.

Subject Categories : Hydraulic and Pneumatic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE