Experimental characterization of a variable-pitch Wells turbine

Wells turbines coupled with systems based on the oscillating water column (OWC) principle represent a convenient solution for sea-wave energy conversion. The possibility to operate under the bi-directional airflow that is established within OWC systems is obtained with a symmetrical blade profile staggered at 90 degrees with respect to the turbine’s axis of rotation, resulting in a highly reliable machine. On the other hand, the limited operating range represents a relevant drawback which can be overcome introducing a variable-pitch control of the rotating blades. This control solution has been only marginally investigated with experiments, due to the complexity of devising a mechanism capable to change the stagger angle of the rotating blades. In this work, a Wells turbine prototype with variable-pitch blades has been built and preliminary investigations are presented, with the aim of characterizing its aerodynamic behavior for different blade stagger angles. The performance of the turbine have been evaluated under regular-wave conditions, for different blade-pitch angles, in order to obtain the information required to define the pitch laws for the maximization of rotor performance.