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Research Papers: Flows in Complex Systems

Design Optimization of a Vaneless “Fish-Friendly” Swirl Injector for Small Water Turbines

[+] Author and Article Information
Ajith Airody

Mechanical and Mechatronics Engineering,
University of Waterloo,
200 University Avenue West,
Waterloo, ON N2L 3G1, Canada
e-mail: aairody@uwaterloo.ca

David De Montmorency

AlfaStar Hydro,
Kitchener, ON N2R 1J4, Canada
e-mail: dave@alfastarhydro.com

Sean D. Peterson

Mechanical and Mechatronics Engineering,
University of Waterloo,
200 University Avenue West,
Waterloo, ON N2L 3G1, Canada
e-mail: peterson@mme.uwaterloo.ca

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 3, 2016; final manuscript received April 6, 2017; published online June 28, 2017. Assoc. Editor: Elias Balaras.

J. Fluids Eng 139(9), 091105 (Jun 28, 2017) (6 pages) Paper No: FE-16-1076; doi: 10.1115/1.4036667 History: Received February 03, 2016; Revised April 06, 2017

Large-scale power generation and delivery to remote locales is often prohibitively expensive, due in part to the excessive costs of delivering the materials required to build the necessary infrastructure. In addition, these facilities can have deleterious effects on the local ecosystem. With their reduced physical and environmental footprints, small-scale run-of-river hydroelectric facilities capable of generating power from the modest head provided by streams and rivers are attractive alternatives. Concern remains, however, for the health and safety of the local fish population in these waterways. In order to further reduce the impact of small-scale axial turbine-based hydroelectric facilities on the local fauna, AlfaStar Hydro has proposed a vaneless swirl injector to replace traditional inlet guide vanes (IGVs), as well as a “fish-friendly” rotor designed to rotate relatively slowly and with wide passages between the blades to enable the safe egress of fish drawn into the turbine. Herein, we perform a numerical study of the flow development in the vaneless swirl injector as a function of the number of revolutions and the pitch angle of the rifling in the absence of a rotor toward maximizing turbine efficiency. Swirl intensity, pressure loss in the injector, and axial and circumferential velocity distributions are incorporated as performance metrics into an objective function to optimize the casing design. Results indicate that the number of revolutions of the injector has considerably less influence on overall injector performance than does pitch angle. The casing with the best predicted performance consists of four revolutions at a pitch angle of 25 deg.

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Figures

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Fig. 1

(a) Image of the vaneless casing and runner assembly developed by AlfaStar Hydro and (b) schematic of the casing with analysis variable definitions

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Fig. 2

Isometric view of the full computational domain

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Fig. 3

Streamlines for the N2P25 case. The streamlines are colored by the local normalized velocity magnitude.

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Fig. 4

Contours showing the development of the (a) axial, (b) circumferential velocity components, and (c) pressure for the N2P25 care. Velocity contours are normalized by the bulk velocity, while the pressure is normalized by the dynamic pressure. The pressure is scaled by a factor of 1.5 for clarity.

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Fig. 5

Deviation of the axial (solid lines) and circumferential (dashed lines) velocities at z/D = 0.5 from the average velocity profiles, computed from Eq. (5), versus n for the various pitch angles.

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Fig. 6

Pressure loss (solid lines) and swirl number (dashed lines) as functions of n for various values of Ψ

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Fig. 7

Contour plot of the objective function used for optimizing the vaneless swirl injector geometry

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