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Research Papers

# The Effect of Side Wall Mass Extraction 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, D-70569 Stuttgart, 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, D-70569 Stuttgart, Germany

Sven Olaf Neumann

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

J. Turbomach 133(2), 021002 (Oct 19, 2010) (11 pages) doi:10.1115/1.4000552 History: Received July 14, 2009; Revised August 03, 2009; Published October 19, 2010; Online October 19, 2010

## Abstract

Gas turbine blades are often cooled by using combined internal and external cooling methods where for internal cooling purposes, usually, serpentine passages are applied. In order to optimize the design of these serpentine passages it is inevitable to know the influence of mass extraction due to film cooling holes, dust holes, or due to side walls for feeding successive cooling channels as for the trailing edge on the internal cooling performance. Therefore, the objective of the present study was to analyze the influence of side wall mass extraction on pressure loss and heat transfer distribution in a two-pass internal cooling channel representing a cooling scheme with flow towards the trailing edge. The investigated rectangular two-pass channel consisted of an inlet and outlet duct with a height-to-width ratio of $H/W=2$ connected by a 180 deg sharp bend. The tip-to-web distance was kept constant at $Wel/W=1$. The mass extraction was realized using several circular holes in the outlet pass side wall. Two geometric configurations were investigated: A configuration with mass extraction solely in the outlet pass and a configuration with mass extraction in the bend region and outlet pass. The extracted mass flow rate was 0%, 10%, and 20% of the inlet channel mass flow. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal technique. Pressure losses were determined in separate experiments by local static pressure measurements. Furthermore, a computational study was performed solving the Reynolds-averaged Navier–Stokes equations using the commercial finite-volume solver FLUENT . The numerical grids were generated using 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 $v2-f$ model. The experimental data of the investigation of side wall ejection showed that the heat transfer in the bend region slightly increased when the ejection were in operation, while the heat transfer in the section of the outlet channel with side wall ejection was nearly not affected. After this section, a decrease in heat transfer was observed, which can be attributed to the decreased mainstream mass flow rate.

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## Figures

Figure 1

Schematic of the test facility

Figure 2

Geometry of the investigated two-pass configuration

Figure 3

Geometry of the investigated numerical model

Figure 4

Grid topology of the investigated domain: The extraction compartment was cut away and the detail is showing the vicinity of a bleed hole

Figure 5

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

Figure 6

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

Figure 7

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 edge and tip wall

Figure 8

Pressure distribution in on the centerline of the bottom wall for all investigated configurations at Re=100,000

Figure 9

Distribution of the local, normalized Nusselt numbers of the bleed configuration S2 (outlet pass) with 20% bleed mass flow from the experiments at Re=100,000

Figure 10

Distribution of the Nusselt number ratio of the bleed configuration S2 (outlet pass) with 20% bleed mass flow at from the computations at Re=100,000

Figure 11

Comparison of the segmental area-averaged Nusselt number ratio for the experiments and simulations of bleed configuration S2: (a) top wall and (b) leading and trailing edge and tip wall

Figure 12

Normalized Nusselt number distribution of the experiments for the bleed configuration S1+S2 (bend region and outlet pass) for a bleed mass flow rate of 20% at Re=100,000

Figure 13

Heat transfer distribution in the simulations of the bleed configuration S1+S2 for a bleed mass flow rate of 20% at Re=100,000

Figure 14

Comparison of the segmental area-averaged Nusselt number ratio for the experiments and simulations of bleed configuration S1+S2: (a) top wall and (b) leading and trailing edge and tip wall

Figure 15

Secondary flow field in the plane at z=0.85dh (cut X-X, see Fig. 1) in bend region of the baseline configuration from the computations using the realizable k-ε model

Figure 16

Main flow field in the symmetry plane of the simulations using the realizable k-ε model for (a) baseline configuration, (b) bleed S1 (20%), and (c) bleed S1+S2 (20%)

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