Development of a shrouded wind turbine with a flanged diffuser

We have developed a wind turbine system that consists of a diffuser shroud with a broad-ring flange at the exit periphery and a wind turbine inside it. The flanged-diffuser shroud plays a role of a device for collecting and accelerating the approaching wind. Emphasis is placed on positioning the flange at the exit of a diffuser shroud. Namely, the flange generates a low-pressure region in the exit neighborhood of the diffuser by vortex formation and draws more mass flow to the wind turbine inside the diffuser shroud. To obtain a higher power output of the shrouded wind turbine, we have examined the optimal form of the flanged diffuser, such as the diffuser open angle, flange height, hub ratio, centerbody length, inlet shroud shape and so on. As a result, a shrouded wind turbine equipped with a flanged diffuser has been developed, and demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 4–5 compared to a standard (bare) wind turbine. In a field experiment using a prototype wind turbine with a flanged diffuser shroud, the output performance was as expected and equalled that of the wind tunnel experiment.