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Research Papers: Forced Convection

Film Cooling of Cylindrical Hole With a Downstream Short Crescent-Shaped Block

[+] Author and Article Information
Baitao An

e-mail: anbt@mail.etp.ac.cn

Sijing Zhou

Institute of Engineering Thermophysics,
Chinese Academy of Sciences,
Beijing 100190, China

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received December 12, 2011; final manuscript received September 6, 2012; published online February 8, 2013. Assoc. Editor: Frank Cunha.

J. Heat Transfer 135(3), 031702 (Feb 08, 2013) (9 pages) Paper No: HT-11-1560; doi: 10.1115/1.4007879 History: Received December 12, 2011; Revised September 06, 2012

This paper presents a method to improve the film-cooling effectiveness of cylindrical holes. A short crescent-shaped block is placed at the downstream of a cylindrical cooling hole. The block shape is defined by a number of geometric parameters including block height, length and width, etc. The single row hole on a flat plate with inclination angle of 30 deg, pitch ratio of 3, and length-diameter ratio of 6.25 was chosen as the baseline test case. Film-cooling effectiveness for the cylindrical hole with or without the downstream short crescent-shaped block was measured by using the pressure sensitive paint (PSP) technique. The density ratio of coolant (argon) to mainstream air is 1.38. The blowing ratios vary from 0.5 to 1.25. The results showed that the lateral averaged cooling effectiveness is increased remarkably when the downstream block is present. The downstream short block allows the main body of the coolant jet to pass over the block top and to form a new down-wash vortex pair, which increases the coolant spread in the lateral direction. The effects of each geometrical parameter of the block on the film-cooling effectiveness were studied in detail.

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Figures

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Fig. 2

PSP calibration curves

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Fig. 1

Schematic of the test facilities

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Fig. 8

Comparison of centerline cooling effectiveness under different blowing ratios

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Fig. 3

Geometry of downstream short crescent-shaped block: (a) top view and (b) side view

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Fig. 7

Local distributions of adiabatic film-cooling effectiveness: (a) ORI case and (b) BSL case

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Fig. 4

Schematic of tested flat plate with film-cooling holes

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Fig. 5

Top views of different block geometries: (a) with/without the block, (b) W variation, (c) δ variation, (d) B variation, (e) H variation, and (f) λ variation

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Fig. 17

Lateral averaged effectiveness distributions for varied block H/D

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Fig. 18

Lateral averaged effectiveness distributions for varied block λ/D

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Fig. 6

Comparison of adiabatic effectiveness of cylindrical hole with published data: (a) centerline cooling effectiveness and (b) lateral averaged cooling effectiveness

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Fig. 9

Comparison of lateral cooling effectiveness distributions: (a) x/D = 5 and (b) x/D = 10

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Fig. 10

Illustration of cylindrical hole jet with downstream crescent-shaped block

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Fig. 11

Comparison of lateral averaged effectiveness distributions under different blowing ratios

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Fig. 12

Schematic of coolant flow at the centerline: (a) without the block and (b) with the block

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Fig. 13

Comparison of area averaged cooling effectiveness under different blowing ratios

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Fig. 14

Lateral averaged effectiveness distributions for varied block W/D

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Fig. 15

Lateral averaged effectiveness distributions for varied block δ/B

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Fig. 16

Lateral averaged effectiveness distributions for varied block B/D

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