Performance Improvement of a Darrieus Tidal Turbine with Active Variable Pitch

Pierre-Luc Delafin (1) , François Deniset (2) , Jacques-André Astolfi (2) , Frédéric Hauville (2)

1 LEGI - Laboratoire des Écoulements Géophysiques et Industriels [Grenoble]
2 IRENAV - Institut de Recherche de l'Ecole Navale

Vertical axis turbines, also called Darrieus turbines, present interesting characteristics for offshore wind and tidal applications but suffer from vibrations and a lower efficiency than the more conventional horizontal axis turbines. The use of variable pitch, in order to control the angle of attack of the blades continuously during their rotation, is considered in this study to overcome these problems. 2D blade-resolved unsteady Reynolds-Averaged Navier–Stokes (RANS) simulations are employed to evaluate the performance improvement that pitching blades can bring to the optimal performance of a three-straight-blade vertical axis tidal turbine. Three pitching laws are defined and tested. They aim to reduce the angle of attack of the blades in the upstream half of the turbine. No pitching motion is used in the downstream half. The streamwise velocity, monitored at the center of the turbine, together with the measurement of the blades’ angle of attack help show the effectiveness of the proposed pitching laws. The decrease in the angle of attack in the upstream half of a revolution leads to a significant increase in the power coefficient (+40%) and to a better balance of the torque generated in the upstream and downstream halves. Both torque and thrust ripples are therefore significantly reduced.

Mots clés: marine renewable energy; Vertical Axis Tidal Turbine (VATT)

Mots clés: Variable pitch; CFD

Domaines: Génie mécanique [physics.class-ph]

Pierre-Luc Delafin, François Deniset, Jacques-André Astolfi, Frédéric Hauville. Performance Improvement of a Darrieus Tidal Turbine with Active Variable Pitch. Energies, 2021, 14 (3), pp.667. ⟨10.3390/en14030667⟩. ⟨hal-03132161⟩