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Research Papers

Film-Cooling Performance of a Turbine Vane Suction Side: The Showerhead Effect on Film-Cooling Hole Placement for Cylindrical and Fan-Shaped Holes

[+] Author and Article Information
Hossein Nadali Najafabadi

Department of Management and Engineering,
Linköping University,
Linköping 581 83, Sweden
e-mail: hossein.nadali.najafabadi@liu.se

Matts Karlsson

Department of Management and Engineering,
Linköping University,
Linköping 581 83, Sweden

Mats Kinell, Esa Utriainen

Siemens Industrial Turbomachinery AB,
Finspång 612 83, Sweden

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 1, 2014; final manuscript received March 3, 2015; published online March 17, 2015. Assoc. Editor: Kenichiro Takeishi.

J. Turbomach 137(9), 091005 (Sep 01, 2015) (11 pages) Paper No: TURBO-14-1224; doi: 10.1115/1.4029966 History: Received September 01, 2014; Revised March 03, 2015; Online March 17, 2015

In this paper, the transient IR-thermography method is used to investigate the effect of showerhead cooling on the film-cooling performance of the suction side of a turbine guide vane working under engine-representative conditions. The resulting adiabatic film effectiveness, heat transfer coefficient (HTC) augmentation, and net heat flux reduction (NHFR) due to insertion of rows of cooling holes at two different locations in the presence and absence of the showerhead cooling are presented. One row of cooling holes is located in the relatively high convex surface curvature region, while the other is situated closer to the maximum throat velocity. In the latter case, a double staggered row of fan-shaped cooling holes has been considered for cross-comparison with the single row at the same position. Both cylindrical and fan-shaped holes have been examined, where the characteristics of fan-shaped holes are based on design constraints for medium size gas turbines. The blowing rates tested are 0.6, 0.9, and 1.2 for single and double cooling rows, whereas the showerhead blowing is maintained at constant nominal blowing rate. The adiabatic film effectiveness results indicate that most noticable effects from the showerhead can be seen for the cooling row located on the higher convex surface curvature. This observation holds for both cylindrical and fan-shaped holes. These findings suggest that while the showerhead blowing does not have much impact on this cooling row from HTC enhancement perspective, it is influential in determination of the HTC augmentation for the cooling row close to the maximum throat velocity. The double-row fan-shaped cooling seems to be less affected by an upstream showerhead blowing when considering HTC enhancement, but it makes a major contribution in defining adiabatic film effectiveness. The NHFR results highlight the fact that cylindrical holes are not significantly affected by the showerhead cooling regardless of their position, but showerhead blowing can play an important role in determining the overall film-cooling performance of fan-shaped holes (for both the cooling row located on the higher convex surface curvature and the cooling row close to the maximum throat velocity), for both the single and the double row cases.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

Experimental setup indicating the bypass valve denoted as P, pneumatic actuator, and test section with corresponding dimensions

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Fig. 2

The prototype vane with showerhead cooling, positions, and numbering of the film-cooling rows. The cavities supplying cooled air are marked C1–C3. The surface length S is defined such that S = 0 indicates the position of stagnation point. Accordingly, S  >  0 and S  <  0 denote the suction and pressure sides, respectively.

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Fig. 3

Fan-shaped cooling hole detailed geometry, to the left, cylindrical hole parameters and radial angle for showerhead cooling holes, to the right

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Fig. 4

Nondimensional pressure distribution Cp

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Fig. 5

Nondimensional freestream and surface temperature as function of Fourier number (nondimensional time). The freestream temperature represents the step change in the main-flow temperature after the bypassed time (indicated by dashed line) in which the valve is opened and the heated air is entered into the test section.

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Fig. 6

Comparison of raw data and smoothed data for cooling row #1, fan-shaped without showerhead cooling: (a) laterally averaged film-cooling effectiveness (η) and (b) laterally averaged Nusselt number (Nu)

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Fig. 7

Comparison of laterally averaged adiabatic film effectiveness for cooling row #1 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole

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Fig. 8

Comparison of laterally averaged adiabatic film effectiveness for cooling row #3 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole. For legend, see Fig. 7.

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Fig. 9

The superposition effect for laterally averaged adiabatic film effectiveness for M = 0.6 (a) cooling row #1 and (b) cooling row #3

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Fig. 10

Comparison of laterally averaged adiabatic film effectiveness for double staggered row cooling (rows #2 and #3) with and without showerhead cooling for fan-shaped holes. Note, S/D = 0 indicates the cooling hole center of row #3. For legend, see Fig. 7.

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Fig. 11

Laterally averaged Nu of uncooled (smooth) vane and showerhead cooling on the suction side. Position of the showerhead cooling as well as cooling rows #1 and #3 is denoted by vertical dashed lines.

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Fig. 12

Comparison of laterally averaged HTC augmentation for cooling row #1 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole. For legend, see Fig. 7.

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Fig. 13

Comparison of laterally averaged HTC augmentation for cooling row #3 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole. For legend, see Fig. 7.

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Fig. 14

Comparison of laterally averaged HTC augmentation for double-row cooling (rows #2 and #3) with and without showerhead cooling for fan-shaped holes: (a) cylindrical hole and (b) fan-shaped hole. Note, S/D = 0 indicates the cooling hole center of row #3. For legend, see Fig. 7.

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Fig. 15

Comparison of laterally averaged NHFR for cooling row #1 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole. For legend, see Fig. 7.

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Fig. 16

Comparison of laterally averaged NHFR for cooling row #3 with and without showerhead cooling: (a) cylindrical hole and (b) fan-shaped hole. For legend, see Fig. 7.

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Fig. 17

Comparison of laterally averaged NHFR for double-row cooling (rows #2 and #3) with and without showerhead cooling for fan-shaped hole. Note, S/D = 0 indicates the cooling hole center of row #3. For legend, see Fig. 7.

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