|M.Sc Student||Ben Harav Amos|
|Subject||Optimization of a Pulsed-Plasma Controlled Vertical Axis|
|Department||Department of Mechanical Engineering||Supervisor||PROF. David Greenblatt|
|Full Thesis text|
Vertical axis wind turbines (VAWTs) offer several advantages over horizontal axis machines (HAWTs) including insensitivity to wind direction, simple blade design and reduced structural problems (HAWT experience flapping and lead-lag effects) as a result of the proximity of the generator to the ground. However, a drawback of VAWTs is the dynamic stall their blades experience as they are pitched beyond their static stall angle. As a result, the VAWT blades experience a dramatic loss in lift and thus a reduction in turbine efficiency. Furthermore unsteady loads are imposed on the generator.
To control dynamic stall, a novel feed-forward control mechanism was designed and integrated with pulsed dielectric barrier discharge plasma actuators on a high solidity, double-bladed NACA0015, H-Rotor vertical axis wind turbine. The optimum angles of plasma actuation initiation and termination were determined parametrically on the upstream half of the turbine azimuth in a low speed blow-down wind tunnel at typical wind speeds found in nature (5m/s and 7m/s). Three different actuator setups were tested on the turbine. A model for the transient response of turbine under the influence of plasma actuation was developed and compared with experimental results. Finally, particle image velocimetry (PIV) data was taken for open-loop and baseline VAWT operation in order to further characterize and understand the effects of plasma actuation on dynamic stall effects.
A major accomplishment of this work was a net turbine power increase of more than 10%. This was achieved by systematically reducing plasma pulsation duty cycles as well as the optimum plasma initiation and termination angles. Nevertheless PIV measurements of the flow field showed that actuation was not fully successful in controlling the dynamic stall vortex. This indicates even greater potential for improvement with more powerful actuation.