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Research Papers

The Combined Effects of an Upstream Ramp and Swirling Coolant Flow on Film Cooling Characteristics

[+] Author and Article Information
Wenshuo Yang

Department of Thermal Science
and Energy Engineering,
University of Science and Technology of China,
Jinzhai Road 96,
Hefei 230027, China
e-mail: wenshuo@mail.ustc.edu.cn

Jian Pu

Department of Thermal Science
and Energy Engineering,
University of Science and Technology of China,
Jinzhai Road 96,
Hefei 230027, China
e-mail: jianpu@mail.ustc.edu.cn

Jianhua Wang

Department of Thermal Science
and Energy Engineering,
University of Science and Technology of China,
Jinzhai Road 96,
Hefei 230027, China
e-mail: jhwang@ustc.edu.cn

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received March 2, 2016; final manuscript received March 29, 2016; published online May 17, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(11), 111008 (May 17, 2016) (10 pages) Paper No: TURBO-16-1059; doi: 10.1115/1.4033292 History: Received March 02, 2016; Revised March 29, 2016

This paper presents an experimental investigation on the performances of a new film cooling structure design, in which a ramp is placed upstream of a cylindrical film hole and a cylindrical cavity with two diagonal impingement holes is set at the inlet of the film hole to generate a swirling coolant flow entering the film hole. The experiments are carried out by two undisturbed measurement techniques, planar laser induced fluorescence (PLIF) and time-resolved particle image velocimetry (TR-PIV) in a water tunnel. The effects of the upstream ramp angle, blowing ratio (BR), and coolant impingement angle on the film cooling performances of a flat plate are studied at three ramp angles (0 deg, 15 deg, and 25 deg), two coolant swirling directions (clockwise and counterclockwise), two impingement angles (15 deg and 30 deg), and three BRs (0.6, 1.0, and 1.4). The experimental results show that at high BRs, the combination structures of the upstream ramp with the swirling coolant flow generated by the impingement angles can significantly improve film cooling performances; the best combination is at a 30 deg impingement angle and a 25 deg ramp angle. This can be explained by the fact that the swirling flow is significantly pressed on to the wall by means of the upstream ramp. Using the analogous analysis of heat and mass transfer, the adiabatic film effectiveness averaged over a cross section is obtained; the analysis indicates that at high BRs, the combined effect of a ramp with a large angle of 25 deg with 30 deg impingement angle can increase the film effectiveness up to 30% when compared to the test case without a ramp at the exit of the film hole. The images captured by PLIF exhibit an interesting phenomenon, i.e., the swirling of the coolant in different directions can influence the counter vortex pair (CVP) in rotating layers, and the coolant swirling in a clockwise direction enhances the right mixing of the CVP with coolant ejection, whereas the coolant swirling in a counterclockwise direction enhances the left-mixing of the CVP with coolant ejection.

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References

Figures

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Fig. 1

Geometries of the film hole and the ramp

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Fig. 2

Structure of the swirling flow

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Fig. 3

Schematic diagram of the experimental system

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Fig. 4

Transient images of PLIF

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Fig. 5

Dimensionless concentration distribution at x/d = 0 in clockwise and counterclockwise swirling directions (R0S15 and R0S-15)

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Fig. 6

Dimensionless concentration distribution at the centerline BR = 1.0 (R0NS, R0S15, and R0S30 without ramp)

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Fig. 7

Dimensionless concentration distribution at the centerline, BR = 2.0 (R15NS and R25NS)

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Fig. 8

Dimensionless concentration distributions at the centerline in the test cases of R0S30, R15S30, and R25S30. (a) BR = 1.4 and (b) BR = 1.0.

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Fig. 9

Lateral-averaged film effectiveness from x/d = 0 to x/d = 3 (R0S30, R15S30, and R25S30). (a) BR = 1.4, (b) BR = 1.0, and (c) BR = 0.6.

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Fig. 10

Lateral-averaged film effectiveness versus BR (R15S30 and R25S30). (a) x/d = 0 and (b) x/d = 1.

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Fig. 11

Lateral-averaged film effectiveness from x/d = 0 to x/d = 3 (R0S15, R15S15, and R25S15). (a) BR = 1.4, (b) BR = 1.0, and (c) BR = 0.6.

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Fig. 12

Line-averaged film effectiveness versus BR (R15S15 and R25S15). (a) x/d = 0 and (b) x/d = 1.

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Fig. 13

Dimensionless concentration distribution at cross sections BR = 1.4 (R0S30 and R25S30)

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Fig. 14

Vorticity distribution of cross section at x/d = 0, BR = 1.4 (R0S30 and R25S30)

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Fig. 15

Dimensionless concentration distribution at the centerline (R0S15, R15S15, and R25S15). (a) BR = 1.4 and (b) BR = 1.0.

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Fig. 16

Dimensionless concentration distribution at BR = 1.4 (R0S15 and R15S15)

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Fig. 17

Lateral-averaged vorticity distribution at BR = 1.4 (R0S15 and R15S15)

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Fig. 18

The dimensionless concentration averaged over bottom plane from x/d = 0 to x/d = 3 versus BR (R0S15, R15S15, R25S15, R0S30, R15S30, and R25S30)

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