Research Papers

Comparison of Film Effectiveness and Cooling Uniformity of Conical and Cylindrical-Shaped Film Hole With Coolant-Exit Temperature Correction

[+] Author and Article Information
Cuong Q. Nguyen1

 Center for Advanced Turbines and Energy Research (CATER), Department of Mechanical, Material and Aerospace Engineering, University of Central Florida, Orlando, FL 32816cuong.quoc.nguyen@knights.ucf.edu

Perry L. Johnson, Bryan C. Bernier, Son H. Ho, Jayanta S. Kapat

 Center for Advanced Turbines and Energy Research (CATER), Department of Mechanical, Material and Aerospace Engineering, University of Central Florida, Orlando, FL 32816


Corresponding author.

J. Thermal Sci. Eng. Appl 3(3), 031011 (Sep 13, 2011) (10 pages) doi:10.1115/1.4003886 History: Received August 14, 2010; Revised February 03, 2011; Accepted February 07, 2011; Published September 13, 2011; Online September 13, 2011

Data from conical-shaped film cooling holes are extremely sparse in open literature, especially the cooling uniformity characteristic, an important criterion for evaluating any film cooling design. The authors will compare the performance of conical-shaped holes to cylindrical-shaped holes. Cylindrical-shaped holes are often considered a baseline in terms of film cooling effectiveness and cooling uniformity coefficient. The authors will study two coupons with conical-shaped holes, which have 3° and 6° diffusion angles, named CON3 and CON6, respectively. A conjugate heat transfer computational fluid dynamics model and an experimental wind tunnel will be used to study these coupons. The three configurations: cylindrical baseline, CON3, and CON6, have a single row of holes with an inlet metering diameter of 3 mm, length-to-nominal diameter of 4.3, and an injection angle of 30°. In this study, the authors will also take into account the heat transfer into the coolant flow from the coolant channel. In other words, the coolant temperature at the exit of the coolant hole will be different than that measured at the inlet, and the conjugate heat transfer model will be used to correct for this difference. For the numerical model, the realizable k-ɛ turbulent model will be applied with a second order of discretization and an enhanced wall treatment to provide the highest accuracy available. Grid independent studies for both cylindrical-shaped film cooling holes and conical-shaped holes will be performed, and the results will be compared to data in open literature as well as in-house experimental data. Results show that conical-shaped holes considerably outperform cylindrical-shaped holes in film cooling effectiveness at all blowing ratios. In terms of cooling uniformity, conical-shaped holes perform better than cylindrical-shaped holes for low- and midrange blowing ratios, but not at higher levels.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 2

Schematic of a subsonic wind tunnel (a) overall view of the subsonic wind tunnel, (b) close-up view of the test-section and (c) blow-up view of the balsa wood test surface painted with TSP

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Figure 3

Demonstration of the TSP technique: (a) test setup and (b) temperature image (adapted from Rodriguez [11])

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Figure 4

Experiment Cd curves of CYL, CON3, and CON6

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Figure 5

Experimental FCE data at BR = 1.0 (left) and BR = 1.5 (right) for (a) CYL, (b) CON3, and (c) CON6

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Figure 6

The CHT 3D numerical model

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Figure 7

Grid structure of the CHT model (CON3 is selected to show): (a) overall view and (b) close-up view

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Figure 8

Two turbulent schemes versus experimental data (adapted from Rodriguez [11])

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Figure 9

Grid independent study for the 3D numerical model: temperature monitored at three set points x/D = 0, 30, and 50 for (a) CYL and (b) CON3

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Figure 10

Traditional CFD versus CHT CFD comparison for cylindrical and conical-shaped film hole

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Figure 11

Cd comparison between numerical (CON3), experimental (CON3) and literature

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Figure 12

Numerical versus experimental comparison on local FCE: (a) CYL (BR = 1.0) and (b) CON3 (BR = 0.5)

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Figure 13

Conical versus cylindrical on centerline FCE

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Figure 14

Conical versus cylindrical on: (a) laterally averaged FCE and (b) spatially averaged FCE

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Figure 15

Conical versus cylindrical on: (a) laterally averaged CUC and (b) spatially averaged CUC

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Figure 1

Coupons used in the experiment: (a) cylindrical-shaped hole and (b) conical-shaped hole




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