Identifier

etd-08222007-143725

Degree

Doctor of Philosophy (PhD)

Department

Engineering Science (Interdepartmental Program)

Document Type

Dissertation

Abstract

Film cooling is one of the cooling systems investigated for the application to gas turbine blades. Gas turbines use film cooling in addition to turbulated internal cooling to protect the blades outer surface from hot gases. The present study concentrates on the experimental and numerical investigation of film cooling performance for a row of cylindrical holes in a modern turbine blade. The adiabatic film effectiveness and the heat transfer coefficient are determined experimentally on a flat plate downstream of a row of inclined different geometries hole exit by using a single test transient IR thermography technique. The focus of this investigation is to investigate advanced cooling hole geometries on film cooling heat transfer and cooling effectiveness over flat and turbine airfoil surfaces. Four test designs, crescent and converging slot, trench and cratered hole exits, are tested. Variations of these configurations are tested under two different test rigs. Results show that both the crescent and slot exits reduce the jet momentum at exit and also provide significantly higher film effectiveness with some increases in heat transfer coefficients. The trench where in the jets come in and spread evenly into a slot before exiting. An optimum trench depth exists at 0.75D as shallower and deeper trenches show worse performance. The cratered holes increase film effectiveness over the baseline case by about 50%. However, they do not provide significant lateral spreading as seen for trenched holes. Meanwhile, film cooling predictions are used to understand the mechanisms of the jets that exit these trenched holes and crater holes. The present work employs RSM (Reynolds stress transport model) for simulation of turbulent flows in film cooling and the simulation was run using FLUENT computer code. Comparisons are made with experimental data for the film effectiveness distributions. Results show that the film cooling jet exiting the trenched hole is more two-dimensional than the typical cylindrical holes and crater holes. Detailed flow structure visualization shows that the trench design counteracts the detrimental vorticity of the round hole flow, allowing it to remain attached to the surface.

Date

2007

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Srinath V. Ekkad

DOI

10.31390/gradschool_dissertations.344

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