Date of Award

12-9-2009

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Paul I. King, PhD

Abstract

A flow visualization study was conducted on a model of a film-cooled turbine blade leading edge in a closed-loop water channel at ReD = 30k. The model consisted of an 8.89 cm diameter half-cylinder with flat afterbody joined at the ninety degree point. A single radial coolant hole (dc / D = 0.054) drilled 21.5° from the stagnation line, angled 20° to the surface and 90° to the flow direction generated a coolant jet transverse to the freestream. Water channel testing assessed the hydrodynamic effects of 16 passive flow control features, to include a variety of dimples upstream and downstream of the coolant hole and transverse trenches milled directly over the coolant hole. Compared to an unmodified coolant hole, a single row of small cylindrical or spherical dimples (d / dc = 0.79, h / d = 0.2) upstream of the coolant hole steadies the coolant jet at blowing ratios up to M = 0.75. Medium (d / dc = 1.59, h / d = 0.2) and large (d / dc = 2.38, h / d = 0.2) spherical dimples downstream of the coolant hole also have a calming effect on the coolant jet up to M = 0.75. None of the dimple geometries studied affect the coolant jet at M ≥ 0.75. A single-depth, square-edged transverse trench (w / dc = 1, h / w = 0.5) spreads the coolant, increasing spanwise coverage of a single coolant hole more than two times. This trench suffers from coolant blow-out above M = 0.50, but a deeper, tapered-depth trench (w / dc = 1, h / w = 1 at coolant hole tapered to h / w = 0.5 at end) provides very effective film cooling at blowing ratios above M = 0.50. It spreads the coolant in the spanwise direction, prevents coolant jet liftoff, and was the only geometry studied that holds the coolant tighter to the surface than an unmodified coolant hole.

AFIT Designator

AFIT-GAE-ENY-09-D01

DTIC Accession Number

ADA513856

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