Experimental and computational results regarding turbulent mixing of passage
flow and the coolant from a high-pressure turbine blade trailing edge cooling
scheme are documented. Special interest is devoted to gaining a fundamental
understanding of the thermal protection provided by the cooling scheme.
The trailing edge cooling scheme is a scaled version of a generic scheme, tested
in a suction type wind tunnel. The scaled model is three-dimensional with
rectangular ribs. Three different lip geometries (square, single round, and double
round) are tested. The freestream Reynolds number, based upon the lip
thickness, is fixed at 10,200. Primarily, three blowing ratios, M=1.5, M=1.0, and
M=0.5 are documented. A hot-wire sensor and a thermocouple are placed inside
the slot and detailed measurements of velocities, turbulence intensities, and
temperatures are acquired. Values of adiabatic effectiveness obtained on the
model surface quantify thermal protection.
Spectral analysis of the hot-wire signal is performed at various locations in the
flow field. Spectra indicate a coherent mechanism of mixing. This clear
unsteadiness is attributed to vortex shedding from the lip. It is shown that
effectiveness increases as the blowing ratio increases. This document suggests
also that lip geometry is an influential parameter for this cooling scheme.
Effectiveness is greatly increased when a rounded lip is utilized. In one case,
additional blowing ratios (M=0.75 and M=1.25) were tested. Experiments concluded that above M=1.25, effectiveness is insensitive to blowing ratio.
Two-dimensional simulations are presented for M=1.5, M=1.0 and M=0.5. They
use various Reynolds Averaged Navier Stokes turbulence closure models. The
frequencies of unsteadiness are well modeled but, in general, effectiveness is
over-predicted. Furthermore, general features of the flow and thermal fields are
modeled well, but surface heat transfer characteristics are not.
University of Minnesota M.S. thesis. November 2010. Major: Mechanical Engineering. Advisor: Dr. Terrence W. Simon. 1 computer file (PDF); xii, 126 pages, appendix p. 121-126. Ill. (some col.)
Boomsma, Aaron Anno.
A fundamental study of high pressure turbine blade trailing edge cooling: an experimental and numerical approach..
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