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Research Papers

Studies on Unsteady Flow Characteristics in a High Pressure Turbine Cascade Based on a High-Order Large Eddy Simulation Turbulence Model

[+] Author and Article Information
Tomohiko Jimbo

Debasish Biswas

 Corporate Research and Development Center,  Toshiba Corporation, 1 Komukai-toshiba-cho, Saiwai-ku, Kawasaki, 212-8582, Japandebasish.biswas@toshiba.co.jp

Yoshiki Niizeki

 Power and Industrial System Research and Development Center,  Toshiba Corporation, 2-4 Suehiro-cho, Tsurumi-ku, Yokohama, 230-0045, Japanyoshiki.niizeki@toshiba.co.jp

J. Turbomach 134(5), 051018 (May 11, 2012) (9 pages) doi:10.1115/1.4003974 History: Received February 22, 2011; Revised March 08, 2011; Published May 11, 2012; Online May 11, 2012

In the present paper, unsteady viscous flow analysis around turbine blade cascade using a high-order LES turbulence model is carried out to investigate the basic physical process involved in the pressure loss mechanism. This numerical analysis is assessed to the wind tunnel cascade test. Basically, all the physical phenomena occurring in nature are the effect of some cause, and the effect can somehow be measured. However, to understand the cause, detail information regarding the visualization of the phenomena, which are difficult to measure, are necessary. Therefore, in the present paper, firstly the computed results are compared with the measured data, which are the final outcome of the cause (of the phenomena under investigation), to verify whether our physics-based model could qualitatively predict the measured facts or not. It was found that the present model could well predict measured data. Therefore, the rest of the computed information, which were difficult to measure, were used to visualize the overall flow behavior for acquiring some knowledge of the physical process associated with the pressure loss mechanism. The present study led to an understanding that the interaction of the vortex generated on the suction and pressure surface of the blade and the secondary vortex generated on the end wall, downstream of the trailing edge, resulted in the formation of a large vortex structure in this region. This unsteady three-dimensional flow characteristic is expected to play an important role in the pressure loss mechanism.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Computational grid (around blade, 2D computation)

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Figure 2

Computational grid (around blade, 3D computation)

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Figure 3

Boundary conditions

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Figure 4

Definition of inlet angle

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Figure 5

Pressure loss coefficient

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Figure 6

Wall pressure distribution on the turbine blade

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Figure 7

Time varying inlet pressure and velocity fluctuation (20 deg)

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Figure 8

Fluctuating pressure distribution for a complete cycle of oscillation (20 deg)

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Figure 9

Fluctuating velocity distribution for a complete cycle of oscillation (20 deg)

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Figure 10

Time averaged static pressure, velocity, and vorticity (20 deg)

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Figure 11

Instantaneous vorticity, relative turbulent intensity, and rms pressure (20 deg)

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Figure 12

Instantaneous vorticity, relative turbulent intensity, and rms pressure (31.3 deg)

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Figure 13

Instantaneous vorticity, relative turbulent intensity, and rms pressure (55 deg)

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Figure 14

Instantaneous vorticity isosurface (20 deg)

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Figure 15

Instantaneous vorticity isosurface (70 deg)

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Figure 16

Instantaneous near-wall horse-shoe vortex structure

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Figure 17

Pressure loss coefficient distribution at 32 mm downstream of blade trailing edge (upper: computed results, lower: experimental results)

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Figure 18

Vorticity, axial velocity, and span-wise velocity at 32 mm downstream of blade trailing edge (20 deg)

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Figure 19

Vorticity, axial velocity and span-wise velocity at 32 mm downstream of blade trailing edge (31.3 deg)

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Figure 20

Vorticity, axial velocity, and span-wise velocity at 32 mm downstream of blade trailing edge (55 deg)

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