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Research Papers

Endwall Boundary Layer Development in an Engine Representative Four-Stage Low Pressure Turbine Rig

[+] Author and Article Information
Maria Vera1

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UK

Elena de la Rosa Blanco2

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UK

Howard Hodson

Whittle Laboratory, University of Cambridge, Cambridge CB3 0DY, UK

Raul Vazquez

 Industria de Turbopropulsores, Madrid 28830, Spain

1

Present address: Institute for Aviation and the Environment, University of Cambridge, Cambridge CB2 1PX, UK.

2

Present address: Aerodyne Research Inc., Billerica, MA 01821.

J. Turbomach 131(1), 011017 (Nov 06, 2008) (9 pages) doi:10.1115/1.2952382 History: Received November 20, 2007; Revised November 29, 2007; Published November 06, 2008

Research by de la Rosa Blanco (“Influence of the State of the Inlet Endwall Boundary Layer on the Interaction Between the Pressure Surface Separation and the Endwall Flows  ,” Proc. Inst. Mech. Eng., Part A, 217, pp. 433–441) in a linear cascade of low pressure turbine (LPT) blades has shown that the position and strength of the vortices forming the endwall flows depend on the state of the inlet endwall boundary layer, i.e., whether it is laminar or turbulent. This determines, amongst other effects, the location where the inlet boundary layer rolls up into a passage vortex, the amount of fluid that is entrained into the passage vortex, and the interaction of the vortex with the pressure side separation bubble. As a consequence, the mass-averaged stagnation pressure loss and therefore the design of a LPT depend on the state of the inlet endwall boundary layer. Unfortunately, the state of the boundary layer along the hub and casing under realistic engine conditions is not known. The results presented in this paper are taken from hot-film measurements performed on the casing of the fourth stage of the nozzle guide vanes of the cold flow affordable near term low emission (ANTLE) LPT rig. These results are compared with those from a low speed linear cascade of similar LPT blades. In the four-stage LPT rig, a transitional boundary layer has been found on the platforms upstream of the leading edge of the blades. The boundary layer is more turbulent near the leading edge of the blade and for higher Reynolds numbers. Within the passage, for both the cold flow four-stage rig and the low speed linear cascade, the new inlet boundary layer formed behind the pressure leg of the horseshoe vortex is a transitional boundary layer. The transition process progresses from the pressure to the suction surface of the passage in the direction of the secondary flow.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

General assembly of the fourth stage ANTLE LPT rig

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Figure 2

Hot-film sensors on the tip passage of an NGV4 blade

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Figure 3

Flow visualization experiments on the endwall of the low speed linear cascade; Re=232,000

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Figure 4

Raw shear stress traces on the endwall of the low speed linear cascade; Re=232,000

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Figure 5

Hot-film sensors on the tip inlet platform of an NGV4 blade

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Figure 6

Raw (gray) and ensemble averaged (black) shear stress on the tip inlet platform of an NGV4 blade; Re=86,000

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Figure 7

Raw (gray) and ensemble averaged (black) shear stress on the tip inlet platform of an NGV4 blade; Re=86,000

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Figure 8

Nondimensional rms (gray) and ensemble averaged (black) shear stress on the tip inlet platform of an NGV4 blade; Re=86,000

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Figure 9

Raw (gray) and ensemble averaged (black) shear stress on selected sensors on the tip inlet platform of an NGV4 blade at different Reynolds numbers

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Figure 10

Raw (gray) and ensemble averaged (black) shear stress on the passage of the NGV4 tip; Pressure side; Re=69,000

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Figure 11

Raw (gray) and ensemble averaged (black) shear stress on selected sensors on the passage of the NGV4 tip at different Reynolds numbers; Pressure side

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Figure 12

Raw (gray) and ensemble averaged (black) shear stress on the passage of the NGV4 tip; Suction side; Re=69,000

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Figure 13

Raw (gray) and ensemble averaged (black) shear stress on selected sensors on the passage of the NGV4 tip at different Reynolds numbers; Suction side

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