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Research Papers

Geometrical Parameter Effects on Film-Cooling Effectiveness of Rectangular Diffusion Holes

[+] Author and Article Information
Bai-Tao An

Industrial Gas Turbine Laboratory,
Institute of Engineering Thermophysics,
Chinese Academy of Sciences,
Beijing 100190, China
e-mail: anbt@mail.etp.ac.cn

Jian-Jun Liu, Si-Jing Zhou

Industrial Gas Turbine Laboratory,
Institute of Engineering Thermophysics,
Chinese Academy of Sciences,
Beijing 100190, China

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 17, 2016; final manuscript received February 9, 2017; published online April 4, 2017. Assoc. Editor: Dr. David G. Bogard.

J. Turbomach 139(8), 081010 (Apr 04, 2017) (15 pages) Paper No: TURBO-16-1244; doi: 10.1115/1.4036007 History: Received September 17, 2016; Revised February 09, 2017

This paper presents an experimental investigation of the rectangular diffusion hole. The effects of rectangular aspect ratio and lateral diffusion angle on film-cooling effectiveness were studied at a low-speed flat-plate experimental facility. The pressure-sensitive paint (PSP) measurement technique was employed to determine the adiabatic effectiveness. The experiments were performed at a density ratio of DR = 1.38 and a mainstream turbulence intensity of Tu = 3.5%. The blowing ratio was varied from M = 0.5 to M = 2.5. Three aspect ratios and three lateral diffusion angles were chosen to match the semicircle and straight-line sidewall shape of the rectangular cross section. A comparative investigation was performed among a typical fan-shaped hole and ten rectangular diffusion holes. The experimental results exhibited diversified film distribution patterns of the rectangular diffusion hole, including single-, bi-, and tripeak patterns. The overall cooling effectiveness increased with the increase of rectangular aspect ratio. The improved magnitude was amplified as blowing ratio increased. The holes with semicircle sidewall were shown to be more suitable for high blowing ratio conditions. The maximum increase of cooling effectiveness was over 70% compared to the fan-shaped hole. The reduction of the lateral diffusion angle affected the film distribution pattern significantly, thereby influencing the cooling effectiveness. To obtain a fixed coverage ratio of film hole row, the rectangular diffusion hole with a larger cross-sectional aspect ratio and a slightly smaller lateral diffusion angle is a preferred scheme.

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Figures

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Fig. 1

Schematic diagram of experimental facilities

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Fig. 2

Geometries of the test section

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Fig. 3

Geometries of the test flat plate and hole: (a) coordinate system and geometries of the 3D-printed flat plate and (b) close-up photo of 3D-printed film hole

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Fig. 4

PSP calibration curves

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Fig. 5

Geometrical configuration of the typical fan-shaped hole

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Fig. 6

Adiabatic film cooling effectiveness distribution of fan-shaped hole on whole PSP painted plane under blowing ratio M = 1.5

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Fig. 7

Laterally averaged effectiveness comparison of typical fan-shaped hole between previous and present experimental results at blowing ratio M = 1.5

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Fig. 8

The cross-sectional aspect ratio schemes of the rectangular diffusion hole: (a) AS3.5-Gamma14-Cir, (b) AS5.0-Gamma14-Cir, (c) AS6.7-Gamma14-Cir, (d) AS3.5-Gamma14-Str, (e) AS5.0-Gamma14-Str, and (f) AS6.7-Gamma14-Str

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Fig. 9

The width and height variation of the rectangular cross section

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Fig. 10

The lateral diffusion angle schemes of the rectangular diffusion hole: (a) AS5.0-Gamma12-Cir, (b) AS5.0-Gamma12-Str, (c) AS6.7-Gamma10-Cir, and (d) AS6.7-Gamma10-Str

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Fig. 11

Adiabatic film cooling effectiveness distribution of the holes with semicircle sidewall under different rectangular aspect ratios and same lateral diffusion angle: (a) AS3.5-Gamma14-Cir, (b) AS5.0-Gamma14-Cir, and (c) AS6.7-Gamma14-Cir

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Fig. 12

Adiabatic film cooling effectiveness contours of the holes with straight-line sidewall under different rectangular aspect ratios and same lateral diffusion angle: (a) AS3.5-Gamma14-Str, (b) AS5.0-Gamma14-Str, and (c) AS6.7-Gamma14-Str

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Fig. 13

Schematic diagram of the downstream vortices structure: (a) fan-shaped hole, (b) rectangular diffusion hole with semicircle sidewall, and (c) rectangular diffusion hole with straight-line sidewall

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Fig. 14

Comparison of spatially averaged effectiveness among three aspect ratio schemes: (a) semicircle sidewall and (b) straight-line sidewall

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Fig. 15

Comparison of spatially averaged effectiveness between the holes with different sidewall shapes

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Fig. 16

Comparison of local film cooling effectiveness among six aspect ratio schemes at x/D = 10 under blowing ratio M = 2.5

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Fig. 17

Comparison of laterally averaged cooling effectiveness among three different rectangular aspect ratios under different blowing ratios: (a) M = 1.5 and (b) M = 2.5

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Fig. 18

Comparison of laterally averaged effectiveness between rectangular diffusion hole and mesh-fed slot [27]

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Fig. 19

Adiabatic film cooling effectiveness contours of the holes with semicircle sidewall under different rectangular aspect ratios and lateral diffusion angles: (a) AS5.0-Gamma12-Cir and (b) AS6.7-Gamma10-Cir

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Fig. 20

Adiabatic film cooling effectiveness contours of the holes with straight-line sidewall under different rectangular aspect ratios and lateral diffusion angles: (a) AS5.0-Gamma12-Str and (b) AS6.7-Gamma10-Str

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Fig. 21

Comparison of local film cooling effectiveness among different lateral diffusion angle schemes at x/D = 10 under blowing ratio M = 2.5: (a) semicircle sidewall and (b) straight-line sidewall

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Fig. 22

Comparison of spatially averaged effectiveness between the holes with different lateral diffusion angles: (a) semicircle sidewall and (b) straight-line sidewall

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Fig. 23

Comparison of laterally averaged effectiveness between two lateral diffusion angle schemes for aspect ratio AS ≈ 5.0: (a) semicircle sidewall and (b) straight-line sidewall

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Fig. 24

Comparison of laterally averaged effectiveness between two lateral diffusion angle schemes for aspect ratio AS ≈ 6.7: (a) semicircle sidewall and (b) straight-line sidewall

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Fig. 25

Comparison of spatially averaged effectiveness among the holes with different aspect ratios and lateral diffusion angles

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