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Research Papers

Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade

[+] Author and Article Information
Shakeel Nasir1

Trey Bolchoz, Wing-Fai Ng

Mechanical Engineering Department,  Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Luzeng J. Zhang, Hee Koo Moon

Heat Transfer Department,  Solar Turbines Inc., San Diego, CA 92186

Richard J. Anthony

Propulsion DirectorateAir Force Research Laboratory, Wright-Patterson AFB, OH 45433

1

Corresponding author.

J. Turbomach 134(5), 051021 (May 11, 2012) (11 pages) doi:10.1115/1.4004200 History: Received March 22, 2011; Revised April 30, 2011; Published May 11, 2012; Online May 11, 2012

This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex  = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105 , 1.1 × 106 and 1.5 × 106 , respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx /P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Virginia Tech transonic cascade wind tunnel

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Figure 2

Profile view of showerhead film cooled vane

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Figure 3

Section view of the stagnation row of holes

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Figure 4

Cascade diagram showing the vanes and the axis orientation for measurements with the traverse

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Figure 5

Gauges and thermocouples mounted on the vane

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Figure 6

Determination of h and η

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Figure 7

Local Mach number distribution

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Figure 8

Acceleration parameter distribution

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Figure 9

Effect of BR on Nu at Mex  = 0.57

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Figure 10

Effect of BR on Nu at Mex  = 0.76

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Figure 11

Effect of BR on Nu at Mex  = 1.0

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Figure 12

Effect of BR on η at Mex  = 0.57

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Figure 13

Effect of BR on η at Mex  = 0.76

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Figure 14

Effect of BR on η at Mex  = 1.0

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Figure 15

Effect of BR on NHFR at Mex  = 0.57

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Figure 16

Effect of BR on NHFR at Mex  = 0.76

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Figure 17

Effect of BR on NHFR at Mex  = 1.0

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Figure 18

Effect of Re/Mach # on Nu at BR = 1.5

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Figure 19

Effect of Re/Mach # on Nu at BR = 2.0

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Figure 20

Effect of Re/Mach # on Nu at BR = 2.5

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Figure 21

Effect of Re/Mach # on η at BR = 1.5

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Figure 22

Effect of Re/Mach # on η at BR = 2.0

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Figure 23

Effect of Re/Mach # on η at BR = 2.5

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