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Handbook of Turbomachinery Second Edition Revised - Ventech!

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Figure 15 Miniature heat flux gauges.<br />

or both sides <strong>of</strong> a thin plastic film. Because the testing is <strong>of</strong> short duration,<br />

the surface on which they are mounted may be assumed to be that <strong>of</strong> a semiinfinite<br />

body. Then the gauge-measured heating rate at the surface can be<br />

transformed into a heat-flux history using the Laplace transform technique<br />

(see [40]).<br />

The literature also describes examples <strong>of</strong> several other types <strong>of</strong> highfrequency<br />

pressure and temperature gauges and the challenges involved in<br />

their use. For a representative example, see Dunn and Haldeman [39], where<br />

surface pressure and temperature fluctuations on a rotor blade surface from<br />

upstream wake passing were measured on a rotor blade surface revolving at<br />

20,000 rpm.<br />

Figures 16 and 17 present time-resolved, midspan heat-flux data from<br />

a moving blade in the MIT turbine blow-down turbine rig by Abhari et al.<br />

[41]. The plots are scaled heat-flux versus blade passing period (about two<br />

and a half passings in each case) at various positions on the blade for two<br />

different incidence angles, 08 (14a) and 10 (14b). As the figure shows, the<br />

heat flux is highly variable and depends primarily on the location on the<br />

Copyright © 2003 Marcel Dekker, Inc.

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