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On the Physics of Flow Separation Along a Low Pressure Turbine Blade Under Unsteady Flow ConditionsThe present study, which is the first of a series of investigations dealing with specific issues of low pressure turbine (LPT) boundary layer aerodynamics, is aimed at providing detailed unsteady boundary flow information to understand the underlying physics of the inception, onset, and extent of the separation zone. A detailed experimental study on the behavior of the separation zone on the suction surface of a highly loaded LPT-blade under periodic unsteady wake flow is presented. Experimental investigations were performed at Texas A&M Turbomachinery Performance and Flow Research Laboratory using a large-scale unsteady turbine cascade research facility with an integrated wake generator and test section unit. To account for a high flow deflection of LPT-cascades at design and off-design operating points, the entire wake generator and test section unit including the traversing system is designed to allow a precise angle adjustment of the cascade relative to the incoming flow. This is done by a hydraulic platform, which simultaneously lifts and rotates the wake generator and test section unit. The unit is then attached to the tunnel exit nozzle with an angular accuracy of better than 0.05 , which is measured electronically. Utilizing a Reynolds number of 110,000 based on the blade suction surface length and the exit velocity, one steady and two different unsteady inlet flowconditions with the corresponding passing frequencies, wake velocities and turbulence intensities are investigated using hot-wire anemometry. In addition to the unsteady boundary layer measurements, blade surface pressure measurements were performed at Re=50,000, 75,000, 100,000, and 125,000 at one steady and two periodic unsteady inlet flow conditions. Detailed unsteady boundary layer measurement identifies the onset and extent of the separation zone as well as its behavior under unsteady wake flow. The results presented in ensemble-averaged and contour plot forms contribute to understanding the physics of the separation phenomenon under periodic unsteady wake flow. Several physical mechanisms are discussed.
Document ID
20030062126
Acquisition Source
Glenn Research Center
Document Type
Technical Memorandum (TM)
Authors
Schobeiri, Meinhard T. (Texas A&M Univ. College Station, TX, United States)
Ozturk, Burak (Texas A&M Univ. College Station, TX, United States)
Ashpis, David E. (NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
September 7, 2013
Publication Date
June 1, 2003
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
E-13852
GT-2003-38917
NASA/TM-2003-212290
NAS 1.15:212290
Meeting Information
Meeting: Turbo Expo 2003
Location: Atlanta, GA
Country: United States
Start Date: June 16, 2003
End Date: June 19, 2003
Sponsors: American Society of Mechanical Engineers, International Gas Turbine
Funding Number(s)
WBS: WBS 22-708-28-07
CONTRACT_GRANT: NCC3-793
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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