Research Papers

Overall Effectiveness and Flowfield Measurements for an Endwall With Nonaxisymmetric Contouring

[+] Author and Article Information
Amy Mensch

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: amy.mensch@nist.gov

Karen A. Thole

Department of Mechanical
and Nuclear Engineering,
The Pennsylvania State University,
University Park, PA 16802
e-mail: kthole@psu.edu

1Corresponding author.

2Present address: National Institute of Standards and Technology, Gaithersburg, MD 20899.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 7, 2015; final manuscript received October 21, 2015; published online December 22, 2015. Editor: Kenneth C. Hall.

J. Turbomach 138(3), 031007 (Dec 22, 2015) (10 pages) Paper No: TURBO-15-1220; doi: 10.1115/1.4031962 History: Received October 07, 2015; Revised October 21, 2015

Endwall contouring is a technique used to reduce the strength and development of three-dimensional secondary flows in a turbine vane or blade passage in a gas turbine. The secondary flows locally affect the external heat transfer, particularly on the endwall surface. The combination of external and internal convective heat transfer, along with solid conduction, determines component temperatures, which affect the service life of turbine components. A conjugate heat transfer model is used to measure the nondimensional external surface temperature, known as overall effectiveness, of an endwall with nonaxisymmetric contouring. The endwall cooling methods include internal impingement cooling and external film cooling. Measured values of overall effectiveness show that endwall contouring reduces the effectiveness of impingement alone, but increases the effectiveness of film cooling alone. Given the combined case of both impingement and film cooling, the laterally averaged overall effectiveness is not significantly changed between the flat and the contoured endwalls. Flowfield measurements indicate that the size and location of the passage vortex changes as film cooling is added and as the blowing ratio increases. Because endwall contouring can produce local effects on internal cooling and film cooling performance, the implications for heat transfer should be considered in endwall contour designs.

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Fig. 1

Heat transfer measurements for the Pack-B cascade at Reexit of 2 × 105 (Ref. [16]): (a) Nusselt number contours for the flat endwall and (b) heat transfer augmentation contours due to endwall contouring with box for area-averaging

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Fig. 2

One-dimensional conjugate model of a conducting endwall with impingement and film cooling

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Fig. 3

Depiction of (a) the large-scale low-speed wind tunnel, (b) the test section containing the Pack-B linear blade cascade and conjugate endwall, and (c) the side view of the plenum and impingement channel for the flat endwall

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Fig. 4

Pack-B cascade static pressure distribution at the blade midspan compared to CFD predictions

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Fig. 5

Comparison of oil flow visualization of endwall streaklines [16] with film cooling hole inlet and outlet locations for the (a) flat and (b) contoured endwalls, and (c) qualitative representation of the contoured endwall height

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Fig. 6

Depiction of (a) the computational domain and boundary conditions and (b) the prism layer volume grid in the holes and impingement channel

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Fig. 7

Planes measured with PIV (a) shown from above and (b) shown from the view of plane C overlaid with flat endwall CFD tke contours for Mavg = 2.0

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Fig. 8

Contoured endwall overall effectiveness for (a) Mavg = 1.0 measured, (b) Mavg = 1.0 predicted, (c) Mavg = 2.0 measured, and (d) Mavg = 2.0 predicted

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Fig. 9

Measured endwall overall effectiveness for the flat endwall [15] at (a) Mavg = 0.6, (b) 1.0, and (c) 2.0, and for the contoured endwall at (d) Mavg = 0.6, (e) 1.0, and (f) 2.0

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Fig. 10

Laterally averaged overall effectiveness for (a) film and impingement, (b) film cooling only, and (c) impingement only, measured for the flat and contoured endwalls

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Fig. 11

In-plane time-averaged streamlines measured with PIV, with contours of magnitude for the contoured endwall for (a)–(c) no film cooling, (d)–(f) Mavg = 1.0, and (g)–(i) Mavg = 2.0

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Fig. 12

Turbulent kinetic energy measured with PIV for the contoured endwall for (a)–(c) no film cooling, (d)–(f) Mavg = 1.0, and (g)–(i) Mavg = 2.0




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