Research Papers: Gas Turbines: Turbomachinery

Aerodynamic Design of S-Shaped Diffusers Using Ball–Spine Inverse Design Method

[+] Author and Article Information
A. Madadi

Department of Mechanical Engineering,
Amirkabir University of Technology
(Tehran Polytechnic),
Tehran 15875-4413, Iran
e-mail: Ali.madadi@gmail.com

M. J. Kermani

Department of Mechanical Engineering,
Amirkabir University of Technology
(Tehran Polytechnic),
Tehran 15875-4413, Iran
e-mail: mkermani@aut.ac.ir

M. Nili-Ahmadabadi

Department of Mechanical Engineering,
Isfahan University of Technology,
Isfahan 84156-83111, Iran
e-mail: m.nili@cc.iut.ac.ir

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 5, 2014; final manuscript received June 7, 2014; published online July 15, 2014. Assoc. Editor: Joseph Zelina.

J. Eng. Gas Turbines Power 136(12), 122606 (Jul 15, 2014) (8 pages) Paper No: GTP-14-1141; doi: 10.1115/1.4027905 History: Received March 05, 2014; Revised June 07, 2014

Recently, an inverse design algorithm called ball–spine algorithm (BSA) was introduced for the design of 2D ducts. In this approach, the walls are considered as a set of virtual balls that can move freely along the straight directions called spines. In the present work, the method is developed for quasi-three-dimensional (quasi-3D) design of S-shaped ducts with a predefined width. To do so, the upper and lower lines of the S-duct symmetric section are modified under the BSA and then, the 3D S-duct geometry is obtained based on elliptic cross-sectional profiles. The target pressure distributions (TPDs) along the upper and lower lines are prescribed so that separation does not occur. Finally, the flow through the designed S-duct is numerically analyzed using a viscous flow solver with the SST turbulence model to validate the designed S-duct performance. The performance of the designed S-duct is compared to original and optimized versions of a benchmark S-duct diffuser. Results show that the present S-duct has a better performance.

Copyright © 2014 by ASME
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Fig. 1

Simulation of a 2D duct with balls and spines

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Fig. 2

Applying the target and computed pressures on a sample ball

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Fig. 3

Free-body diagram of a sample ball on the duct wall

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Fig. 4

Wall boundary before and after filtration

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Fig. 6

Evolution of geometries and their corresponding pressure distributions from the initial guess (generation 0) to the target geometry

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Fig. 9

The design flowchart

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Fig. 10

Comparison between wall shear for three grid sizes

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Fig. 11

The benchmark S-duct diffuser

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Fig. 12

Computational domain for validation test case

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Fig. 13

Comparison between test data and computation results for benchmark S-duct

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Fig. 14

A sample of results with flow separation (corresponds to station “A” in Fig. 9)

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Fig. 15

Correction of TPD to omit the flow separation

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Fig. 16

Initial and designed geometries

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Fig. 17

Streamlines in symmetric plane correspond to station “B” in Fig. 9

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Fig. 18

Mach number contours at the duct outlet

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Fig. 19

Contours of stagnation pressure in various axial positions

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Fig. 20

Performance of present and benchmark S-duct on the Sovran and Klomp map




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