The relationship between energy separation and base drag in turbine blade wakes

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Proceedings titleProceedings of the ASME Turbo Expo
ConferenceASME Turbo Expo 2013: Turbine Technical Conference and Exposition, GT 2013, 3 June 2013 through 7 June 2013, San Antonio, Tx
Volume6:00 AM
SubjectAggressive designs; Annular cascades; Energy re distributions; Energy separations; Peak of energies; Planar cascades; Temperature probes; Total temperatures; Exhibitions; Gas turbines; Nozzle design; Nozzles; Separation; Subsonic aerodynamics; Vortex shedding; Wakes
AbstractDuring annular cascade testing of a highly-loaded turbine stage of aggressive design, the nozzle blading experienced a redistribution of the downstream total temperature field. In this ostensibly adiabatic arrangement, the central regions of the vane wakes exhibited a significant decrease in total temperature and their edges showed an unexpected increase. To resolve these anomalous results and obtain detailed information over the Mach number range, the mid-span section of the nozzle was tested in a large scale transonic planar cascade. At high subsonic speeds, vortex shedding created energy redistribution in the wake. This was measured using an 80 kHz bandwidth temperature probe, making it possible to investigate wake total temperature fluctuations in addition to fluctuations in total pressure, and hence entropy. 'Hot spots' of increased total temperature were found to be located at the edge of the wake and 'cold spots' of decreased total temperature were located close to the wake center line. The results from the turbine cascade were consistent with the phenomenon of energy separation behind bluff bodies. High base pressure losses were observed and were also related to the vortex shedding. The blade had a thick trailing edge and the high base pressure loss condition coincided with the peak of energy separation in the wake. The analysis indicates that in the subsonic speed range the phenomena of energy separation and of base pressure deficit are inextricably linked to, and are caused by, vortex shedding. A strategy for minimizing the related adverse impacts on performance is outlined. Copyright © 2013 by ASME.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21270971
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Record identifier26564ba5-3727-4b97-95cc-ae6b49c59879
Record created2014-02-18
Record modified2016-05-09
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