Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations
With the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuse...
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| Format: | Article |
| Language: | English |
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MDPI AG
2019-01-01
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| Series: | Energies |
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| Online Access: | http://www.mdpi.com/1996-1073/12/2/272 |
| _version_ | 1798005266999934976 |
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| author | Stefania Zanforlin Fulvio Buzzi Marika Francesconi |
| author_facet | Stefania Zanforlin Fulvio Buzzi Marika Francesconi |
| author_sort | Stefania Zanforlin |
| collection | DOAJ |
| description | With the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuser, equipped with a pair of counter-rotating turbines, and a bi-directional symmetrical diffuser were compared in terms of coefficient of power (CP), torque ripple, overall thrust on diffuser and wake characteristics. Slightly better CP were predicted for the symmetrical diffuser, due to the convergent walls that address the flow towards the blade with a greater attack angle during early and late upwind and to the viscous interactions between the turbine wakes and strong vortices shed by the diffuser. A CP’s extraordinary improving resulted when yaw increased up to 22.5° for the hydrofoil shaped and up to 30° for the symmetrical diffuser. Similar behaviour in yawed flows also occurred in case of a ducted single rotor, demonstrating that it is a characteristic of CFTs. The insertion of a straight throat in the diffuser design proved to be an effective way to mitigate torque ripple, but a CP loss is expected. |
| first_indexed | 2024-04-11T12:36:41Z |
| format | Article |
| id | doaj.art-683809ccfdc249c69a601e01bbefee5a |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-04-11T12:36:41Z |
| publishDate | 2019-01-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-683809ccfdc249c69a601e01bbefee5a2022-12-22T04:23:36ZengMDPI AGEnergies1996-10732019-01-0112227210.3390/en12020272en12020272Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor ConfigurationsStefania Zanforlin0Fulvio Buzzi1Marika Francesconi2Department of Energy, Systems, Territory and Constructions Engineering, University of Pisa, l.go Lucio Lazzarino, 56122 Pisa, ItalyDepartment of Energy, Systems, Territory and Constructions Engineering, University of Pisa, l.go Lucio Lazzarino, 56122 Pisa, ItalyDepartment of Energy, Systems, Territory and Constructions Engineering, University of Pisa, l.go Lucio Lazzarino, 56122 Pisa, ItalyWith the aim of finding efficient solutions for cross flow turbine (CFT) bi-directional diffusers able to harvest non perfectly rectilinear tidal currents, a 2D CFD analysis of ducted CFTs was carried out with focus on the effects of diffuser shape and yaw angle. The HARVEST hydrofoil shaped diffuser, equipped with a pair of counter-rotating turbines, and a bi-directional symmetrical diffuser were compared in terms of coefficient of power (CP), torque ripple, overall thrust on diffuser and wake characteristics. Slightly better CP were predicted for the symmetrical diffuser, due to the convergent walls that address the flow towards the blade with a greater attack angle during early and late upwind and to the viscous interactions between the turbine wakes and strong vortices shed by the diffuser. A CP’s extraordinary improving resulted when yaw increased up to 22.5° for the hydrofoil shaped and up to 30° for the symmetrical diffuser. Similar behaviour in yawed flows also occurred in case of a ducted single rotor, demonstrating that it is a characteristic of CFTs. The insertion of a straight throat in the diffuser design proved to be an effective way to mitigate torque ripple, but a CP loss is expected.http://www.mdpi.com/1996-1073/12/2/272tidal currentscross flow turbinediffuservortex sheddingyawed flows |
| spellingShingle | Stefania Zanforlin Fulvio Buzzi Marika Francesconi Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations Energies tidal currents cross flow turbine diffuser vortex shedding yawed flows |
| title | Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations |
| title_full | Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations |
| title_fullStr | Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations |
| title_full_unstemmed | Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations |
| title_short | Performance Analysis of Hydrofoil Shaped and Bi-Directional Diffusers for Cross Flow Tidal Turbines in Single and Double-Rotor Configurations |
| title_sort | performance analysis of hydrofoil shaped and bi directional diffusers for cross flow tidal turbines in single and double rotor configurations |
| topic | tidal currents cross flow turbine diffuser vortex shedding yawed flows |
| url | http://www.mdpi.com/1996-1073/12/2/272 |
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