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Research Papers

Heat Transfer Measurements Downstream of Trenched Film Cooling Holes Using a Novel Optical Two-Layer Measurement Technique

[+] Author and Article Information
Peter Schreivogel

Institut für Thermodynamik,
Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: peter.schreivogel@unibw.de

Michael Pfitzner

Professor
Institut für Thermodynamik,
Fakultät für Luft- und Raumfahrttechnik,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: michael.pfitzner@unibw.de

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 29, 2015; final manuscript received October 15, 2015; published online November 24, 2015. Editor: Kenneth C. Hall.

J. Turbomach 138(3), 031003 (Nov 24, 2015) (9 pages) Paper No: TURBO-15-1211; doi: 10.1115/1.4031919 History: Received September 29, 2015; Revised October 15, 2015; Accepted October 19, 2015

A new approach for steady-state heat transfer measurements is proposed. Temperature distributions are measured at the surface and a defined depth inside the wall to provide boundary conditions for a three-dimensional heat flux calculation. The practical application of the technique is demonstrated by employing a superposition method to measure heat transfer and film cooling effectiveness downstream of two different 0.75D deep narrow trench geometries and cylindrical holes. Compared to the cylindrical holes, both trench geometries lead to an augmentation of the heat transfer coefficient supposedly caused by the highly turbulent attached cooling film emanating from the trenches. Areas of high heat transfer are visible, where recirculation bubbles or large amounts of coolant are expected. Increasing the density ratio from 1.33 to 1.60 led to a slight reduction of the heat transfer coefficient and an increased cooling effectiveness. Both trenches provide a net heat flux reduction (NHFR) superior to that of cylindrical holes, especially at the highest momentum flux ratios.

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Figures

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Fig. 1

Wind tunnel test section

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Fig. 2

Schematic of test plate composition (dimensions in mm)

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Fig. 3

Average phosphor calibration curve

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Fig. 4

Cooling hole configurations

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Fig. 5

Laterally averaged heat transfer coefficients for three different wall temperatures (T, DR = 1.6, I = 8)

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Fig. 6

Centerline cooling effectiveness downstream a cylindrical hole [5,27] (C, DR = 1.6, M = 1)

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Fig. 7

Comparison of laterally averaged heat transfer coefficients of the cylindrical holes (C) and straight trench (T) to literature data [4,28]

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Fig. 8

Trench adiabatic cooling effectiveness, DR = 1.33

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Fig. 9

Trench laterally averaged cooling effectiveness for DR = 1.33 and 1.60

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Fig. 10

Heat transfer coefficient augmentation, DR = 1.33

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Fig. 11

Trench laterally averaged heat transfer coefficient augmentation for DR = 1.33 and 1.60

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Fig. 12

CFD simulation of the trench flow field, DR = 1.33, I = 8

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Fig. 13

Spatially averaged NHFR (C-cylindrical hole, T-straight trench, S-segmented trench)

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