Method of adaptively adjusting lift and drag on an airfoil-shaped sail, sail, and wind turbine

A vertical-axis wind turbine comprising a rotatable annular operating platform and a plurality of airfoil-shaped sails as blades mounted vertical to the platform plane and evenly in an annulus, wherein each airfoil-shaped sail comprises an airfoil-shaped sail body provided with an upper cambered surface and a lower cambered surface;

• one or more unidirectional air jet channels each having a Y-shaped cross section are horizontally arranged inside the airfoil-shaped sail body for improving the dynamic characteristics of the airfoil-shaped sail;
• each Y-shaped air jet channel comprises an air inlet defined at a leading edge of the sail body, and two air outlets defined in the upper cambered surface of the sail body;
• a flow regulating gate responsive to wind direction and speed and capable of automatically opening and closing a cross section of the Y-shaped air jet channel is further arranged in the Y-shaped air jet channel;
• wherein in response to an oncoming flow with a varying direction and speed, the flow regulating gate automatically adjusts an opening extent of the gate and of the cross section, to regulate the airflow within the air jet channel and accordingly change an angle of attack to improve the airfoil-shaped sail's dynamic characteristics, thereby automatically adjusting the lift and drag on the airfoil-shaped sail as the wind speed changes, to obtain a maximum lift-to-drag ratio and an optimal resultant force facilitating airfoil-shaped sail's circular motion, wherein to enable the vertical-axis wind turbine to obtain an optimal resultant force facilitating circular motion of the airfoil-shaped sails, wherein the airfoil-shaped sail blades satisfy the following conditions:
• (1) the number of the airfoil-shaped sail blades arranged on the operating platform is an odd number, avoiding that when the wind turbine faces the wind the airflow blows in from a gap between two adjacent blades and then blows out of an opposite diagonal gap, and that the airflow produces resistance against the circular motion of the wind turbine;
• (2) for considerations of dynamic characteristics and safety factors, a height H of each airfoil-shaped sail blade and a radius R of the operating platform of the vertical-axis wind turbine satisfy the following relation:
• 0.8H≤R≤H (7).