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Research Papers: Gas Turbines: Heat Transfer

Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

[+] Author and Article Information
Amy Mensch

e-mail: aem277@psu.edu

Karen A. Thole

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

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 29, 2013; final manuscript received October 22, 2013; published online November 14, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(3), 031901 (Nov 14, 2013) (10 pages) Paper No: GTP-13-1331; doi: 10.1115/1.4025835 History: Received August 29, 2013; Revised October 22, 2013

Ever-increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven-blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine-relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film-cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified, one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.

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References

Figures

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Fig. 1

Depiction of the (a) large-scale, low-speed wind tunnel, with a corner test section housing the Pack-B cascade, and (b) the coolant loop with auxiliary cooling capability and the inlet flow development section

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Fig. 2

Schematic of the Pack-B linear blade cascade with blade and passage numbering and top view of the conjugate endwall

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Fig. 3

Pack-B cascade static pressure distribution at the blade midspan compared to a CFD prediction [20]

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Fig. 4

Schematic of internal and external cooling scheme from the side view (a) and the top view (b)

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Fig. 5

Discharge coefficient measured as a function of pressure ratio compared to Refs. [36] and [37]

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Fig. 6

Coolant and wall temperatures of the conjugate wall with film and impingement cooling

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Fig. 7

Contours of ϕf for blowing ratios: (a) Mavg = 0.6, (b) Mavg = 1.0, (c) Mavg = 2.0, with 30 deg inclined holes and plenum boundaries overlaid, and (d) pitchwise, laterally averaged ϕf plotted as a function of axial distance

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Fig. 8

Contours of ϕo for blowing ratios: (a) Mavg = 0.6, (b) Mavg = 1.0, (c) Mavg = 2.0, with 90 deg impingement holes and plenum boundaries overlaid, and (d) pitchwise, laterally averaged ϕo plotted as a function of axial distance

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Fig. 9

Contours of ϕ for blowing ratios: (a) Mavg = 0.6, (b) Mavg = 1.0, (c) Mavg = 2.0, with 30 deg inclined film holes, 90 deg impingement holes, and plenum boundaries overlaid, and (d) pitchwise, laterally averaged ϕ plotted as a function of axial distance

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Fig. 10

Area-averaged ϕ (using area outlined in Fig. 4) plotted as a function of blowing ratio for all three cooling configurations

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Fig. 11

Pitchwise, laterally averaged ϕ plotted as a function of axial distance for the three cooling configurations at Mavg = 1.0

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Fig. 12

Overall effectiveness of all cooling configurations at Mavg = 0.6 plotted as a function of y/p at x/Cax = 0.22

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Fig. 13

Overall effectiveness of all cooling configurations at Mavg = 1.0 plotted as a function of y/p at x/Cax = 0.22

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Fig. 14

Overall effectiveness of all cooling configurations at Mavg = 2.0 plotted as a function of y/p at x/Cax = 0.22

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Fig. 15

Coolant and wall temperatures of the conjugate wall with film cooling only

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Fig. 17

Comparison of laterally averaged ϕcalc and ϕmeas plotted as function of axial distance for all three blowing ratios

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Fig. 16

Coolant and wall temperatures of the conjugate wall with impingement cooling only

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