Abstract
Although a Darrieus-type wind turbine has a high efficiency, its starting torque is small, which means that either a high wind speed or a specialized mechanism is required to make it begin rotating. This paper presents a new starting method based on an opening-and-closing aileron attached to the main blade of a Darrieus-type straight-bladed vertical axis wind turbine. To investigate the effect of the aileron, we conducted wind tunnel experiments to determine the starting torque and wind speed to initiate rotation. The ailerons tested were a fixed-angle aileron and two types of opening-and-closing ailerons. The H-type aileron comprised an aluminum plate with a spring-loaded hinge and aluminum angle adjuster. The R-type aileron comprised a plastic resin sheet and an aluminum angle adjuster. The turbines with the H- or R-type ailerons were designed to be normally open, but the aileron closes when wind flows against the head of the main blade.
Compared to the case of using no aileron, the starting torque for the turbine with the fixed-angle aileron is sometimes higher and sometimes lower, depending on the position angle. On average, there is no net increase in starting torque by the use of a fixed-angle aileron. In contrast, the starting torque for the 2-, 3- or 4-blade turbine with opening-and-closing ailerons is positive for all position angles and increases more than that without an aileron. The average starting torque for the turbine with H- and R-type ailerons is larger than that for the turbine without ailerons. In addition, the wind speed to initiate rotation for the turbines with H- and R-type ailerons is less than that for no aileron.
