Date of Award

12-2002

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Paul I. King, PhD

Abstract

Flow separation on a low pressure turbine blade is explored at Reynolds numbers of 25k, 45k and 100k. Experimental data is collected in a low-speed, draw-down wind tunnel using a cascade of eight Pak-B blades. Flow is examined from measurements of blade surface pressures, boundary layer parameters, exit velocities, and total pressure losses across the blade. Two recessed dimple shapes are assessed for suppressing flow separation and associated losses. One dimple is spherical, and the second is asymmetric, formed from a full dimple spanwise half-filled. A single row of each dimple shape is tested at 50%, 55% and 65% axial chord. Symmetric dimples reduce separation losses by as much as 28%, while asymmetric dimples reduce losses by as much as 23%. A complementary three-dimensional computational study is conducted to visualize local flow structure. Computational analysis uses Gridgen v13.3 as a mesh generator, Fluent® v6.0 as a flow solver and FIELDVIEW© v8.0 for graphic display and analysis. Computational results for Pak-B blades at a Reynolds number of 25k indicate that both dimple shapes cause a span-wise vortex to rollup within the dimple and provide a localized pressure drop.

AFIT Designator

AFIT-GAE-ENY-02-13

DTIC Accession Number

ADA409462

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