Simultaneous Heat Flux and Velocity Measurements in a Transonic Turbine Cascade

[+] Author and Article Information
D. G. Holmberg

 Building Environment Division, BFRL, NIST, Gaithersburg, MD 208 99-8631

T. E. Diller

 Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061-0238

J. Turbomach 127(3), 502-506 (Aug 17, 2004) (5 pages) doi:10.1115/1.1860576 History: Received July 08, 2004; Revised August 17, 2004

The gas turbine engine combustor generates turbulence that increases heat transfer on downstream turbine blades, but the mechanisms of that heat transfer are not fully understood. In this work, simultaneous time-resolved surface heat flux and velocity measurements have been made at three locations on the pressure surface of a high-turning transonic airfoil. Grids were used upstream of the linear turbine cascade to produce free-stream turbulence with two different inlet length scales, but the same turbulence intensity. High-frequency response instrumentation was used to obtain both steady and unsteady measurements. Results show that the time-averaged heat transfer is larger for the flow with the smaller integral length scale. Frequency-domain analysis demonstrates coherence between the fluctuations of heat flux and velocity over a broad range of frequencies. This is a direct indication that free-stream turbulent eddies penetrate completely through the boundary layer to the surface.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Heat flux sensor and hot-wire measurement locations on the blade. Arrows indicate flow direction at inlet and exit of blade row.

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Figure 2

Velocity energy spectra of flow above PS1 comparing grid turbulence

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Figure 3

Surface heat flux spectra (normalized by Taw−Ts) at PS1 for three grid conditions (no hot-wire present)

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Figure 4

Coherence magnitude for velocity and heat flux spectra at PS1

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Figure 5

Coherence magnitude for velocity and heat flux spectra at PS2

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Figure 6

Phase shift of heat flux response lagging velocity turbulence at PS1




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