Effects of Wake Passing on Stagnation Region Heat Transfer

[+] Author and Article Information
J. E. O’Brien

NASA Lewis Research Center, Cleveland, OH 44135

J. Turbomach 112(3), 522-530 (Jul 01, 1990) (9 pages) doi:10.1115/1.2927690 History: Received March 01, 1988; Online June 09, 2008


An experimental study is described in which both time-averaged and time-resolved effects of wake passing were measured in a cylinder stagnation region. The experiments were carried out in an annular-flow wind tunnel, which was fitted with a spoked-wheel wake generator. The cylindrical spokes produce wakes that simulate those shed from a turbine inlet guide vane. Time-averaged heat transfer results indicate an asymmetric distribution of heat transfer coefficient about the stagnation line, with higher heat transfer coefficients on the windward side (with respect to the bar-passing direction), which corresponds to the suction side of a turbine blade. This asymmetry is also reflected in the time-resolved heat transfer results, which were obtained using a test cylinder instrumented with platinum thin-film gages. Unsteady heat flux records reveal very large positive excursions (as much as a factor of three) in instantaneous heat flux during wake passing on the windward side of the cylinder and much smaller effects on the leeward side. Hot-film records in the cylinder stagnation region were also obtained by operating the thin-film gages in the constant-temperature mode. Spectra of these hot-film records indicate that vortex shedding is a major contributor to the unsteady buffeting of the test-cylinder boundary layer at circumferential stations located at both + 60 deg and − 60 deg from the stagnation line, but makes a very small contribution on the stagnation line itself.

Copyright © 1990 by The American Society of Mechanical Engineers
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