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Research Papers

The Effect of Turning Vanes on Pressure Loss and Heat Transfer of a Ribbed Rectangular Two-Pass Internal Cooling Channel

[+] Author and Article Information
Marco Schüler

Institut für Thermodynamik der Luft- und Raumfahrt (ITLR), Universität Stuttgart, Pfaffenwaldring 31, Stuttgart D-70569, Germanymarco.schueler@itlr.uni-stuttgart.de

Frank Zehnder, Bernhard Weigand, Jens von Wolfersdorf

Institut für Thermodynamik der Luft- und Raumfahrt (ITLR), Universität Stuttgart, Pfaffenwaldring 31, Stuttgart D-70569, Germany

Sven Olaf Neumann

Institut für Thermodynamik der Luft- und Raumfahrt (ITLR), Universität Stuttgart, Pfaffenwaldring 31, Stuttgart D-70569, Germanyitlr@itlr.uni-stuttgart.de

J. Turbomach 133(2), 021017 (Oct 25, 2010) (10 pages) doi:10.1115/1.4000550 History: Received July 13, 2009; Revised August 03, 2009; Published October 25, 2010; Online October 25, 2010

Gas turbine blades are usually cooled by using ribbed serpentine internal cooling passages, which are fed by extracted compressor air. The individual straight ducts are connected by sharp 180 deg bends. The integration of turning vanes in the bend region lets one expect a significant reduction in pressure loss while keeping the heat transfer levels high. Therefore, the objective of the present study was to investigate the influence of different turning vane configurations on pressure loss and local heat transfer distribution. The investigations were conducted in a rectangular two-pass channel connected by a 180 deg sharp turn with a channel height-to-width ratio of H/W=2. The channel was equipped with 45 deg skewed ribs in a parallel arrangement with e/dh=0.1 and P/e=10. The tip-to-web distance was kept constant at Wel/W=1. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Furthermore static pressure measurements were conducted in order to determine the influence of turning vane configurations on pressure loss. Additionally, the configurations were investigated numerically by solving the Reynolds-averaged Navier–Stokes equations using the finite-volume solver FLUENT . The numerical grids were generated by the hybrid grid generator CENTAUR . Three different turbulence models were considered: the realizable k-ε model with two-layer wall treatment, the k-ω-SST model, and the v2-f turbulence model. The results showed a significant influence of the turning vane configuration on pressure loss and heat transfer in the bend region and the outlet pass. While using an appropriate turning vane configuration, pressure loss was reduced by about 25%, keeping the heat transfer at nearly the same level in the bend region. An inappropriate configuration led to an increase in pressure loss while the heat transfer was reduced in the bend region and outlet pass.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the test rig arrangement

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Figure 2

Schematic of the measurement section

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Figure 3

Geometry of the investigated numerical model

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Figure 4

Grid topology of the investigated domain

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Figure 5

Pressure distribution on the centerline of the bottom wall for the baseline configuration at Re=100,000

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Figure 6

Distribution of the local, normalized Nusselt numbers of the baseline configuration at Re=100,000 from the experimental data

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Figure 7

Heat transfer distribution of the baseline configuration in the computations using the realizable k-ε model at Re=100,000

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Figure 8

Comparison of the experimental and numerical data for the area-averaged Nusselt number of the baseline configuration: (a) top wall, and (b) leading and trailing edges and tip wall

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Figure 9

Normalized pressure distribution in the experiments with different turning vane configurations

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Figure 10

Distribution of the local normalized Nusselt numbers of the investigated turning vane configurations: (a) inner turning vane, (b) outer turning vane, and (c) both turning vanes

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Figure 11

Segmental area-averaged Nusselt number ratio for the investigated turning vane configurations: (a) top wall and (b) leading and trailing edge, and tip wall

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Figure 12

Main flow field in the symmetry plane of the simulations using the realizable k-ε model for (a) baseline configuration, (b) inner turning vane, (c) outer turning vane, and (d) both turning vanes

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Figure 13

(a) The normalized pressure loss of the bend region and the area-averaged Nusselt number ratio for (b) the bend region, (c) the outlet pass rib segment numbers 7–9, and (d) for rib segment numbers 10–12 for both experiments and computations

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