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Research Papers: Alternative Energy Sources

An Experimental Study of the Aerodynamics and Performance of a Vertical Axis Wind Turbine in a Confined and Unconfined Environment

[+] Author and Article Information
Vincenzo Dossena

Dipartimento di Energia,
Laboratorio di Fluidodinamica delle Macchine,
Politecnico di Milano,
Via Lambruschini 4,
Milano I-20156, Italy
e-mail: vincenzo.dossena@polimi.it

Giacomo Persico

Dipartimento di Energia,
Laboratorio di Fluidodinamica delle Macchine,
Politecnico di Milano,
Via Lambruschini 4,
Milano I-20156, Italy

Berardo Paradiso

Dipartimento di Energia,
Laboratorio di Fluidodinamica delle Macchine,
Politecnico di Milano, Via Lambruschini 4,
Milano I-20156, Italy

Lorenzo Battisti

Department of Civil, Environmental
and Mechanical Engineering,
Università degli Studi di Trento,
Interdisciplinary Laboratory
of Energetic Technologies,
Via Mesiano 77,
Trento I-38123, Italy
e-mail: lorenzo.battisti@unitn.it

Sergio Dell'Anna, Alessandra Brighenti, Enrico Benini

Department of Civil, Environmental
and Mechanical Engineering,
Università degli Studi di Trento,
Interdisciplinary Laboratory
of Energetic Technologies,
Via Mesiano 77,
Trento I-38123, Italy

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 16, 2015; final manuscript received April 21, 2015; published online May 14, 2015. Assoc. Editor: Ryo Amano.

J. Energy Resour. Technol 137(5), 051207 (Sep 01, 2015) (12 pages) Paper No: JERT-15-1067; doi: 10.1115/1.4030448 History: Received February 16, 2015; Revised April 21, 2015; Online May 14, 2015

This paper presents the results of a wide experimental study on an H-type vertical axis wind turbine (VAWT) carried out at the Politecnico di Milano. The experiments were carried out in a large-scale wind tunnel, where wind turbines for microgeneration can be tested in real-scale conditions. Integral torque and thrust measurements were performed, as well as detailed aerodynamic measurements to characterize the flow field generated by the turbine downstream of the rotor. The machine was tested in both a confined (closed chamber) and unconfined (open chamber) environment, to highlight the effect of wind tunnel blockage on the aerodynamics and performance of the VAWT under investigation. The experimental results, compared with the blockage correlations presently available, suggest that specific correction models should be developed for VAWTs. The experimental thrust and power curves of the turbine, derived from integral measurements, exhibit the expected trends with a peak power coefficient of about 0.28 at tip-speed ratio equal to 2.5. Flow measurements, performed in three conditions for tip speed ratio equal to 1.5, 2.5, and 3.5, show the fully three-dimensional character of the wake, especially in the tip region where a nonsymmetrical wake and tip vortex are found. The unsteady evolution of the velocity and turbulence fields further highlights the effect of aerodynamic loading on the wake unsteadiness, showing the time-dependent nature of the tip vortex and the onset of dynamic stall for tip speed ratio lower than 2.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

(a) Sketch of measurement section and (b) picture of the VAWT and the traversing system in CC configuration

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Fig. 2

(a) H-shaped Darrieus rotor tested in wind tunnel and (b) sketch of the power train

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Fig. 3

Streamwise thrust curve coefficient in OC

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Fig. 4

Power coefficient curve in OC

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Fig. 10

Schematic of VAWT operation

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Fig. 11

Turbine wake for different loading conditions in OC configuration: (a) high loading case: λ = 3.5, (b) midloading case: λ = 2.5, and (c) low loading case: λ = 1.5

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Fig. 7

Experimental thrusts measured in open and closed chamber with their interpolating curves

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Fig. 6

Power coefficient measured in CC

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Fig. 5

Streamwise thrust coefficient measured in CC

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Fig. 12

Flow angle distribution at low loading conditions (λ = 1.5, V0 = 14.2 m/s) in OC configuration

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Fig. 13

Turbine wake for low loading (λ = 1.5, V0 = 13.7 m/s) in CC configuration (near traverse only)

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Fig. 14

Turbine wake for different loading conditions in CC configuration (far traverse only): (a) high loading case: λ = 3.5 (V0 = 5.9 m/s) and (b) low loading case: λ = 1.5 (V0 = 13.7 m/s)

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Fig. 15

Space–time wake representation at midspan for different operating conditions in OC configuration: (a) high loading case: λ = 3.5 (V0 = 6.5 m/s) and (b) low loading case: λ = 1.5 (V0 = 14.2 m/s)

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Fig. 9

Blockage correction coefficient V0'/V0 versus CC thrust coefficient CTX

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Fig. 16

Space–time wake representation at the turbine tip section for λ = 1.5 in OC configuration

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Fig. 17

Space–time wake representation at midspan for λ = 3.5 (top) and λ = 1.5 (bottom) in CC configuration

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