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Research Papers

# Heat Transfer in an Oblique Jet Impingement Configuration With Varying Jet Geometries

[+] Author and Article Information
Simon Schueren

Jens von Wolfersdorf

Institute of Aerospace Thermodynamics (ITLR),
University of Stuttgart,
Pfaffenwaldring 31,
D-70569 Stuttgart, Germany

Shailendra Naik

Alstom Power,
Brown Boveri Strasse 7,

On wall D, ‘downstream’ corresponds to falling $sD'$ according to the definition of $s$ (see Fig. 4).

1Address all correspondence to this author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 21, 2011; final manuscript received October 28, 2011; published online November 1, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021010 (Nov 01, 2012) (10 pages) Paper No: TURBO-11-1214; doi: 10.1115/1.4006598 History: Received September 21, 2011; Revised October 28, 2011

## Abstract

The experimental and numerical heat transfer results in a trapezoidal duct with two staggered rows of inclined impingement jets are presented. The influence of changes in the jet bore geometry on the wall heat transfer is examined. The goal of this project is to minimize the thermal load in an internal gas turbine blade channel and to provide sufficient cooling for local hot spots. The dimensionless pitch is varied between $p/djet=3$ − 6. For $p/djet=3$, cylindrical and conically narrowing bores with a cross section reduction of 25% and 50%, respectively, are investigated. The studies are conducted at $10,000≤Re≤75,000$. Experimental results are obtained using a transient thermochromic liquid crystal technique. The numerical simulations are performed solving the RANS equations with FLUENT using the low- $Re$ k- $ω$ -SST turbulence model. The results show that for a greater pitch, the decreasing interaction between the jets leads to diminished local wall heat transfer. The area averaged Nusselt numbers decrease by up to 15% for $p/djet=4.5$, and up to 30% for $p/djet=6$, respectively, if compared to the baseline pitch of $p/djet=3$. The conical bore design accelerates the jets, thus increasing the area-averaged heat transfer for identical mass-flow by up to 15% and 30% for the moderately and strongly narrowing jets, respectively. A dependency of the displacement between the $Nu$ maximum and the geometric stagnation point from the jet shear layer is shown.

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## Figures

Fig. 1

Schematic of an impingement cooled mid-chord passage of a turbine blade

Fig. 2

Schematic of the experimental facility

Fig. 3

Schematic of the test section geometry in its baseline configuration

Fig. 4

Schematic of the test channel

Fig. 5

Sketch of the cylindrical (left) and conical (right) bore configurations; see Table 1 for details

Fig. 6

Computational grid

Fig. 7

Streaklines for p/djet=3, Re=75,000; left: front view; right: back view

Fig. 8

Vorticity magnitude at Re=75,000 in slides through jet axes and between jets; top: p/djet=3; center: p/djet=4.5; bottom: p/djet=6

Fig. 9

Experimental results: local Nusselt number ratios at Re=45,000; top: p/djet=3; bottom: p/djet=4.5

Fig. 10

Numerical results: local Nusselt number ratios at Re=45,000; top: p/djet=3; center: p/djet=4.5; bottom: p/djet=6

Fig. 11

Line-averaged Nusselt numbers on wall C (left) and wall D (right) for different p/djet at various Reynolds numbers; top: Re=10,000; center: Re=45,000; bottom: Re=75,000

Fig. 12

Experimental results: local Nusselt number ratios at Re=45,000; top: cylindrical bores; center: conical bores I; bottom: conical bores II

Fig. 13

Numerical results: local Nusselt number ratios at Re=45,000; top: cylindrical bores; center: conical bores I; bottom: conical bores II

Fig. 14

Line-averaged Nusselt numbers for different bore shapes at Re=45,000; left: wall C; right: wall D

Fig. 15

Correlation between the jet shear layer and the location of maximum Nusselt number; left column: jet A1; right column: jet A2; top: cylindrical bores; center: conical bores I; bottom: conical bores II

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