EXPERIMENTAL INVESTIGATION OF A DOUBLE-STAGE SHROUDED HORIZONTAL AXIS WIND TURBINE

An experimental study is presented in this paper to check the ability of using a new power system, which utilizes the destroyed energy that is caused by the lens of a shrouded wind turbine. Instead of destroying the outer wind energy surrounding the wind turbine shroud by means of the lens, the lens will be replaced by a ring cascade that gives the duty of the lens in creating a low energy region behind the shroud to permit the flow with low energy to pass to the surrounding and in the same time can give excess power from the surrounding wind. A ring cascade working as second-stage wind turbine will be placed in the same location of the lens with its main dimensions. Experimental measurements are performed on three cases, namely a constant chord non twisted three blades wind turbine of 0.94 m outer diameter without shroud (bar wind turbine), shrouded wind turbine with lens, and shrouded wind turbine with second stage (ring cascade). The experimental results demonstrated that, the maximum power coefficient for the wind turbine in case of using a second stage is 0.4 compared to 0.34 for a flanged diffuser wind turbine. Furthermore, relatively uniform and wider operation range is obtained for different tip speed ratios.