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Research Papers

Structural Analysis of a Small H-Darrieus Wind Turbine Using Beam Models: Development and Assessment

[+] Author and Article Information
Alessandro Bianchini

Department of Industrial Engineering,
University of Florence,
Via di Santa Marta 3,
Firenze 50139, Italy
e-mail: bianchini@vega.de.unifi.it

Francesco Cangioli

GE Oil & Gas,
Via Felice Matteucci 10,
Firenze 50127, Italy
e-mail: francesco.cangioli@ge.com

Susanna Papini

Department of Industrial Engineering,
University of Florence,
Via di Santa Marta 3,
Firenze 50139, Italy
e-mail: susanna.papini@unifi.it

Andrea Rindi

Department of Industrial Engineering,
University of Florence,
Via di Santa Marta 3,
Firenze 50139, Italy
e-mail: andrea.rindi@unifi.it

Ennio Antonio Carnevale

Department of Industrial Engineering,
University of Florence,
Via di Santa Marta 3,
Firenze 50139, Italy
e-mail: ennio.carnevale@unifi.it

Lorenzo Ferrari

CNR-ICCOM,
National Research Council of Italy,
Via Madonna del Piano 10,
Sesto Fiorentino 50019, Italy
e-mail: lorenzo.ferrari@iccom.cnr.it

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 26, 2014; final manuscript received July 11, 2014; published online September 4, 2014. Editor: Ronald Bunker.

J. Turbomach 137(1), 011003 (Sep 04, 2014) (11 pages) Paper No: TURBO-14-1088; doi: 10.1115/1.4028212 History: Received June 26, 2014; Revised July 11, 2014

In the present wind energy research, Darrieus-type vertical axis wind turbines (VAWTs) are increasingly appreciated, especially in small installations. In particular, H-shaped turbines can provide attractive spaces for novel design solutions, aimed at reducing the visual impact of the rotors and then at improving their degree of integration with several installation contexts (e.g., a built environment); moreover, novel small rotors are thought to be able in the near future to make large use also of new and cheaper materials (e.g., plastic or light alloys) which could notably reduce the final cost of the produced energy. As a consequence, the structural analysis of the rotors becomes more and more important: a continuous check between the design solutions needed to maximize the aerodynamic performance of the blades and the structural constraints must be provided. In addition, the requirements of international standards for certification encourage the development of proper numerical tools, possibly with low computational costs for the manufacturers. In this study, the structural analysis of a novel three-helix-bladed Darrieus turbine is presented; the turbine is a real industrial machine almost entirely produced with plastic with a new complex aesthetic design. In detail, a structural modeling based on beam elements has been developed and assessed in comparison to more complex models, as it was thought to provide a notable reduction of the computational cost of the simulations with an acceptable decrease of the accuracy. Moreover, the 1D structural model was exploited to verify the capabilities of a novel software, able to verify the dynamic response of the wind turbine in real functioning, i.e., with mechanical loads and interactions with the wind flow. Benefits and drawbacks of the proposed modeling approach are finally discussed by analyzing both the calculation time and the accuracy of the simulations.

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References

Figures

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Fig. 1

CAD geometry (left) and experimental model (right) of the WT1KW used in the present study (courtesy of Pramac Spa)

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Fig. 2

Detailed view of a blade's structure with stiffening ribs

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Fig. 4

Whole turbine's model with beam elements

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Fig. 5

Calculated displacements with centrifugal force only: BEAM model (left) versus SHELL model (right)

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Fig. 6

Calculated stresses with centrifugal force only: BEAM model (left) versus SHELL model (right)

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Fig. 7

Calculated stresses with centrifugal force and unbalancing force on the tower: BEAM model (left) versus SHELL model (right)

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Fig. 8

First vibration mode: BEAM model (left) versus SHELL model (right)

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Fig. 9

Second vibration mode: BEAM model (left) versus SHELL model (right)

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Fig. 10

Comparison between numerical estimations and experimental data in the wind tunnel: dimensionless power curves of the WT1KW model

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Fig. 11

Aerodynamic force per unit length calculated with the VARDAR code at15 m/s

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Fig. 12

Dimensionless displacements (left) and stresses (MPa) (right) of the turbine under wind loads only

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Fig. 13

Turbine's model with concentrated masses at each blade section

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Fig. 14

Campbell's diagram: mechanical loads only

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Fig. 15

Campbell's diagram: mechanical and aerodynamic loads

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Fig. 16

Analyzed ramp for the turbine's revolution speed

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Fig. 17

Structural response of the rotor to a revolution speed variation: displacement of a blade's node

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Fig. 18

Analyzed ramp for the wind speed

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Fig. 19

Structural response of the rotor to a wind speed variation: displacement of a blade's node

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Fig. 20

Analyzed turbulent wind trend

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Fig. 21

Structural response of the rotor to a turbulent wind according to IEC 61400-2: displacement of the middle-blade node

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Fig. 22

Structural response of the rotor to a constant wind: displacement of the middle-blade node

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