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Research Papers

Detailed Heat Transfer Distributions of Narrow Impingement Channels for Cast-In Turbine Airfoils

[+] Author and Article Information
Alexandros Terzis

Group of Thermal Turbomachinery (GTT),
École Polytechnique Fédérale
de Lausanne (EPFL),
Lausanne CH-1015, Switzerland
e-mail: alexandros.terzis@me.com

Peter Ott

Group of Thermal Turbomachinery (GTT),
École Polytechnique Fédérale
de Lausanne (EPFL),
Lausanne CH-1015, Switzerland

Jens von Wolfersdorf, Bernhard Weigand

Institute of Aerospace Thermodynamics (ITLR),
University of Stuttgart,
Stuttgart D-70569, Germany

Magali Cochet

Alstom Power,
Baden CH-5401, Switzerland

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 7, 2013; final manuscript received May 5, 2014; published online June 3, 2014. Assoc. Editor: Ardeshir Riahi.

J. Turbomach 136(9), 091011 (Jun 03, 2014) (9 pages) Paper No: TURBO-13-1228; doi: 10.1115/1.4027679 History: Received October 07, 2013; Revised May 05, 2014

The current capabilities of the foundry industry allow the production of integrally cast turbine airfoils. Impingement cooling effectiveness can be then further increased due to the manufacturing feasibility of narrow impingement cavities in a double-wall configuration. This study examines experimentally, using the transient liquid crystal technique, the cooling performance of narrow cavities consisting of a single row of five impingement holes. Heat transfer coefficient distributions are obtained for all channel interior surfaces over a range of engine realistic Reynolds numbers varying between 10,900 and 85,900. Effects of streamwise jet-to-jet spacing (X/D), channel width (Y/D), jet-to-target plate distance (Z/D), and jet offset position (Δy∕D) from the channel centerline are investigated composing a test matrix of 22 different geometries. Additionally, the target plate and sidewalls heat transfer rates are successfully correlated within the experimental uncertainties providing an empirical heat transfer model for narrow impingement channels. The results indicate similarities with multijet impingement configurations; however, the achievable heat transfer level is about 20% lower compared to periodic multijet impingement correlations found in open literature.

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References

Figures

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Fig. 1

Cast-in cooling channels in a turbine vane. (Reprinted with permission [3].)

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Fig. 2

Impingement cooling test facility

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Fig. 3

Schematic representation of the test models

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Fig. 4

Jet-plate discharge coefficient (Cd) for various channels over a range of ReD. X/D = 5.

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Fig. 5

(a) Jet mass velocity (Gj) distribution and (b) crossflow (Gcf) development, for various channel geometries and flow conditions. X/D = 5.

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Fig. 6

Crossflow effect on the local heat transfer coefficients for small channel areas. ReD = 19,200.

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Fig. 7

Local heat transfer coefficient distributions for all channel interior surfaces. ReD = 19,200.

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Fig. 8

Spanwise-averaged NuD distributions for all channel interior surfaces. ReD = 19,200, X/D = Y/D = 5, Z/D = 2, and Δy∕D = 0.

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Fig. 9

Local area averaged heat transfer rate. X/D = 5, Δy∕D = 0, and ReD = 19,200.

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Fig. 10

Target plate and sidewalls area averaged NuD for various channel configurations over the complete range of ReD

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Fig. 11

Local area averaged heat transfer rate. X/D = Y/D = 5, ReD = 19,200.

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Fig. 12

Comparison with Florschuetz's [25] correlation over the full range of flow conditions. X/D = Y/D = 5, Δy∕D = 0.

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Fig. 13

Schematic representation of the correlation flow domain

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Fig. 14

Model prediction capabilities for the target plate of the channel

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