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Research Papers

Drag and Lift Characteristics of a Novel Elliptical-Bladed Savonius Rotor With Vent Augmenters

[+] Author and Article Information
Nur Alom

Department of Mechanical Engineering,
National Institute of Technology Meghalaya,
Shillong 793003, India
e-mail: nur.alam@nitm.ac.in

Ujjwal K. Saha

Professor
Department of Mechanical Engineering,
Indian Institute of Technology Guwahati,
Guwahati 781039, India
e-mail: saha@iitg.ac.in

Contributed by the Solar Energy Division of ASME for publication in the Journal of Solar Energy Engineering: Including Wind Energy and Building Energy Conservation. Manuscript received July 13, 2018; final manuscript received March 23, 2019; published online May 2, 2019. Assoc. Editor: Douglas Cairns.

J. Sol. Energy Eng 141(5), 051007 (May 02, 2019) (12 pages) Paper No: SOL-18-1319; doi: 10.1115/1.4043516 History: Received July 13, 2018; Accepted April 10, 2019

Savonius rotor, a class of drag-driven vertical axis wind turbine, has been extensively investigated mainly to calculate the torque and power coefficients (CT and CP) by various investigators. Hitherto, studies related to lift and drag characteristics are very few and have mainly been restricted to a semicircular-bladed rotor. A deeper investigation into the drag and lift coefficients (CD and CL) can result in the better design of rotor blades leading to an increment in CT and CP. In view of this, in the present investigation, CD and CL of an elliptical-bladed rotor with vent augmenters have been studied numerically. Initially, two-dimensional (2D) unsteady simulations using an ansys fluent solver is carried out to estimate the instantaneous CD and CL. The shear stress transport (SST) k–ω turbulence model is selected to solve the Reynolds averaged Navier Stokes (RANS) equations. Finally, three-dimensional (3D) unsteady simulations are carried out for the vented elliptical-bladed rotor. The unsteady simulations are performed for the nonvented elliptical- and semicircular-bladed rotors at the identical condition in order to have a direct comparison. From the unsteady simulations, the average CD for the vented elliptical profile is found to be 1.45; whereas, the average CD for the nonvented elliptical and semicircular profiles is found to be 1.43 and 1.35, respectively.

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Figures

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Fig. 1

Geometric details of a typical Savonius rotor

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Fig. 2

Illustration of (a) lift and drag forces, (b) relative wind speed, and (c) differential drag

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Fig. 3

Sectional cut angle of the ellipse

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Fig. 4

Mesh generation around the rotor: (a) 2D and (b) 3D mesh

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Fig. 5

Grid independence test: (a) 2D and (b) 3D grids

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Fig. 6

Time independence test

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Fig. 7

Computational domain and boundary conditions

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Fig. 8

Validation of present 2D drag coefficient (CD) with the available data

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Fig. 9

Validation of present 2D lift coefficient (CL) with the available data

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Fig. 10

Validation of present 3D results with the available data

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Fig. 11

Comparison of CT for the tested nonvented profiles at TSR = 0.6

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Fig. 12

Variation of CD for the tested profiles at TSR = 0.6

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Fig. 13

Variation of CL for the tested profiles at TSR = 0.6

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Fig. 14

Velocity magnitude (m/s) contours of elliptical and semicircular profiles at TSR = 0.6

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Fig. 15

Total pressure (N/m2) contours of elliptical and semicircular profiles at TSR = 0.6

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Fig. 16

Turbulence intensity (%) contours of vented and nonvented elliptical profiles (α = 90 deg, TSR = 0.6)

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Fig. 17

Variation of CD for the elliptical- and semicircular-bladed rotors at TSR = 0.6

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Fig. 18

Variation of CL for the elliptical- and semicircular-bladed rotors at TSR = 0.6

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Fig. 19

Comparison of CD and CL of the vented elliptical profile/blade at TSR = 0.6

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Fig. 20

Comparison of CD and CL of the vented semicircular profile/blade at TSR = 0.6

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Fig. 21

Velocity magnitude (m/s) contours of elliptical- and semicircular-bladed rotors at TSR = 0.6

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Fig. 22

Total pressure (N/m2) contours of vented and nonvented elliptical rotors (α = 90 deg, TSR = 0.6)

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Fig. 23

Turbulence intensity (%) contours of vented and nonvented elliptical rotors (α = 90 deg, TSR = 0.6).

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