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RESEARCH PAPERS

Wake–Boundary Layer Interactions in an Axial Flow Turbine Rotor at Off-Design Conditions

[+] Author and Article Information
H. P. Hodson, J. S. Addison

Whittle Laboratory, Cambridge University, Cambridge, United Kingdom

J. Turbomach 111(2), 181-192 (Apr 01, 1989) (12 pages) doi:10.1115/1.3262254 History: Received January 13, 1988; Online November 09, 2009

Abstract

A series of experimental investigations has been undertaken in a single-stage low-speed turbine. The measurements involved rotor blade surface flow visualization, surface-mounted hot-film anemometry, and exit pitot traverses. The effects of varying the flow coefficient and Reynolds number upon the performance of the rotor blade at midspan are described. At the design flow coefficient (φ = 0.495), the rotor pressure surface flow may be regarded as laminar, while on the suction surface, laminar flow gives way to unsteady stator wake-induced transition and then to turbulent flow. Over the range of Reynolds numbers investigated (1.8×105 –3.3×105 ), the rotor midspan performance is dominated by the suction surface transition process; suction surface separation is prevented and the rotor midspan loss coefficient remains approximately constant throughout the range. At positive incidence, suction surface leading edge separation and transition are caused by a velocity overspeed. Reattachment occurs as the flow begins to accelerate toward the throat. The loss associated with the separation becomes significant with increasing incidence. At negative incidence, a velocity overspeed causes leading edge separation of the pressure side boundary layers. Reattachment generally occurs without full transition. The suction surface flow is virtually unaffected. Therefore, the rotor midspan profile loss remains unchanged from the zero incidence value until pressure side stall occurs.

Copyright © 1989 by ASME
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