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Research Papers

Effect of Blowing Ratio on the Internal Heat Transfer of a Cooled Nozzle Guide Vane in a Linear Cascade

[+] Author and Article Information
Arun Kumar Pujari

Thermal Turbomachines Laboratory,
Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: akp327@gmail.com

B. V. S. S. S. Prasad

Thermal Turbomachines Laboratory,
Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: prasad@iitm.ac.in

Nekkanti Sitaram

Thermal Turbomachines Laboratory,
Department of Mechanical Engineering,
Indian Institute of Technology Madras,
Chennai 600036, India
e-mail: nsitaram.iitm@gmail.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received September 5, 2015; final manuscript received May 30, 2016; published online July 27, 2016. Assoc. Editor: Ting Wang.

J. Thermal Sci. Eng. Appl 8(4), 041004 (Jul 27, 2016) (15 pages) Paper No: TSEA-15-1253; doi: 10.1115/1.4034057 History: Received September 05, 2015; Revised May 30, 2016

Experimental and computational heat transfer investigations are reported on the interior side of a nozzle guide vane (NGV) subjected to combined impingement and film cooling. The domain of study is a two-dimensional five-vane cascade having a space chord ratio of 0.88. The vane internal surface is cooled by dry air, supplied through the two impingement inserts: the front and the aft. The blowing ratio (ρcVcmVm) is varied systematically by varying the coolant mass flow through the impingement chamber and also by changing the mainstream Reynolds number, but by keeping a fixed spacing (H) to jet diameter (d) ratio of 1.2. The surface temperature distributions, at certain locations of the vane interior surface, are measured by pasting strips of liquid crystal sheets. The vane interior surface temperature distribution is also obtained by the computations carried out by using shear stress transport (SST) k–ω turbulence model in the flow solver ansys fluent-14. The computational data are in good agreement with the measured values of temperature. The internal heat transfer coefficients are thence determined from the computational data. The results show that, when the blowing ratio is increased by increasing the coolant flow rate, the average internal surface temperature decreases. However, when the blowing ratio is varied by increasing the mainstream Reynolds number, the internal surface temperature increases. Further, the temperature variations are different all along the internal surface from the leading edge to the trailing edge and are largely dependent on the coolant flow distributions on the internal as well as the external sides.

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References

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Figures

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Fig. 1

Schematic diagram of the experimental setup: (a) front view, (b) top view, (c) cascade, and (d) schematic of coolant and mainstream flow path

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Fig. 2

Vane assembly with coolant supply tubes

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Fig. 3

Geometrical details of NGV: (a) NGV with film hole location and (b) impingement hole location with NGV inner surface

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Fig. 4

(a) Schematic of copper sheet instrumented with thermocouple and (b) TLC sheets pasted on the suction surface of the vane

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Fig. 5

(a) Different camera positions for calibration and (b) calibration curves of TLC for (i) pressure surface, (ii) leading edge, and (iii) suction surface

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Fig. 6

(a) TLC image, (b) cropped parts of the image, and (c) processed image

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Fig. 7

Cascade flow domain

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Fig. 8

Cascade domain meshing: (a) flow domain meshing and (b) boundary layer mesh

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Fig. 9

Grid independency study

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Fig. 10

Comparison of Nusselt number of the present study with Katti and Prabhu [28]

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Fig. 11

Nondimensional velocity distributions at cascade exit: (a) Re1 = 1.44 × 105 and (b) Re1 = 3.38 × 105

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Fig. 12

Coefficient of static pressure (Cp) distribution around the vane at different Reynolds numbers

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Fig. 13

Experimental results: (a) local temperature distribution along the line-Le1, (b) effect of coolant flow rate at Re1 = 1.44 × 105, (c) effect of coolant flow rate at Re2 = 2.4 × 105, and (d) effect of coolant flow rate at Re3 = 3.38 × 105

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Fig. 14

Computational results: effect of coolant mass flow variation on vane interior surface—(a) Re1 = 1.44 × 105, (b) Re2 = 2.40 × 105, and (c) Re3 = 3.38 × 105

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Fig. 15

Computational results: effect of mainstream Reynolds number variation on vane interior surface: (a) Mmin, (b) Mmod, and (c) Mmax

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Fig. 16

Film thickness reduction with increase in mainstream Reynolds number: (a) Mmin Re1, (b) Mmin Re2, and (c) Mmin Re3

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Fig. 17

Effect of mainstream Reynolds number on internal coolant flow structure along the jet row PSIH6

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Fig. 18

Effect of conductivity on nondimensional surface temperature distribution

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Fig. 19

Comparison of computational static pressure results with experimental data

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Fig. 20

Comparison of experimental and computational results for Mmin Re1

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Fig. 21

Computational results: effect of coolant flow rate on average Nusselt number distribution—(a) Re1 = 1.44 × 105, (b) Re2 = 2.40 × 105, and (c) Re3 = 3.38 × 105

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Fig. 22

Computational results: effect of mainstream Reynolds number on Nusselt number distributions—(a) Mmin, (b) Mmod, and (c) Mmax

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Fig. 23

(a) Flow structure along the chord of the vane, (b) flow structure along the span (jet row PSIH9), and (c) local Nusselt number variations along the jet row PSIH9

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