Active Enhancement of Wind Turbine Blades Performance

The feasibility of using synthetic jet actuators to enhance the performance of wind turbine blades was explored in wind tunnel experiments. Using this technique, the global flow field over the blade was altered such that flow separation was mitigated. This, in turn, resulted in a significant decrease in the vibration of the blade. Global flow measurements were conducted, where the moments and forces on the blade were measured using a six component wall-mounted load cell. The effect of the actuation was also examined on the surface static pressure at two spanwise locations; near the blade’s root and near the tip. In addition, Particle Image Velocimetry (PIV) technique was used to quantify the flow field over the blade. Using synthetic jets, the flow over the blade was either fully or partially reattached, depending on the angle of attack and the Reynolds number. Furthermore, the changes induced on the moments and forces, as well as on the blades vibrations were found to be proportionally controlled by either changing the momentum coefficient, the number of synthetic jets used, or by the driving waveform. Finally, a proof-of-concept closed-loop control system was developed to test the ability of using synthetic jet actuators to restore and maintain flow attachment and reduce the vibrations in the blade during dynamic pitch. The synthetic jets were switched on when the root strain vibration spectrum exceeds a predetermined threshold at a given frequency. While the control system implementation used is simplistic, it demonstrated the ability of synthetic jet actuators to reduce blade’s vibrations (by restoring and maintaining attached flow) during the dynamic motion, analogous to the wind gusts seen in wind turbine operation.

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