Passive control of dynamic stall in a H-Darrieus Vertical Axis Wind Turbine using blade leading-edge protuberances

Dynamic stall flow conditions affect the performance of most Vertical Axis Wind Turbine (VAWT) designs; however, the associated losses are especially relevant in smaller turbines, such as those typically used in urban environment applications. The work described in this paper experimentally evaluated the effectiveness of leading-edge protuberances in controlling the aforementioned stall behavior. A numerical study was first performed to define the leading-edge geometry to be subsequently tested in the wind tunnel. A custom experimental setup was also developed for this purpose. The wind tunnel measurements of the modified turbine showed significant performance gains over the baseline and a considerably improved self-starting behavior. The power coefficient increase was between 46% and 20% for wind velocities ranging from 5.5 m/s to 9 m/s, respectively. Nevertheless, the tip-speed ratio characteristics of the studied turbine were not meaningfully affected by the use of leading-edge protuberances.