Flap control for wind turbine blades

Abstract

A wind turbine blade has one or more trailing edge flaps. An actuator mechanism for the flaps comprises a shaft extending along the blade length driven by a motor arrangement toward the blade root. The flap is connected to the shaft through a linkage so that rotation of the shaft pivots the flap about a hinge line. The linkage may be non-rigid and coupled to the shaft through a roller, or rigid and coupled to the shaft through a crank arm mounted on the shaft. An offset actuation mechanism is provided for imparting movement to the linkage in addition to movement due to rotation of the shaft.

1 . A wind turbine blade comprising at least one control flap on an edge of the blade, and an actuation mechanism for controlling movement of the flap, the actuation mechanism comprising an actuator shaft extending along at least a portion of the length of the blade, an actuator coupled to the shaft to rotate the shaft, the actuator being arranged towards the root end of the blade, a linkage coupled between the flap and the actuator shaft, whereby rotary movement of the shaft moves the flap, and an offset actuation mechanism for imparting movement to the linkage in addition to movement due to rotation of the shaft. 
     
     
         2 . The wind turbine blade according to  claim 1 , wherein the linkage comprises a rigid rod coupled at one end thereof to a first end of an L-shaped crank mounted for rotation about the shaft, the L-shaped crank being coupled to a crank arm mounted on the shaft for rotation therewith through an offset actuator, whereby actuation of the offset actuator moves the L-shaped crank with respect to the shaft to provide an offset movement to the flap. 
     
     
         3 . The wind turbine blade according to  claim 2 , wherein the offset actuator is a piezo-electric stack and excitation of the piezo-electric stack moves the L-shaped crank with respect to the shaft to provide an offset movement to the shaft. 
     
     
         4 . The wind turbine blade according to  claim 1 , wherein the linkage comprises a control wire coupled to the shaft through a roller, and the offset movement mechanism comprises a motor and gear mechanism for rotating the roller with respect to the shaft. 
     
     
         5 . The wind turbine blade according to  claim 1 , wherein the flap is pivotable about a hinge line and wherein rotary movement of the shaft causes the linkage to pivot the flap about the hinge line. 
     
     
         6 . The wind turbine blade according to  claim 2 , wherein the rigid rod is attached to the rotatable shaft through a crank arm mounted on the shaft for rotation therewith. 
     
     
         7 . The wind turbine blade according to  claim 4 , wherein the control wire is coupled to the actuator shaft through a roller fixed to the shaft for rotation therewith. 
     
     
         8 . The wind turbine blade according to  claim 1  wherein the linkage comprises a first linkage and a second linkage and the flap is pivotable about a mid-point, wherein the first linkage is attached to the flap at a point above the midpoint and the second linkage is attached to the flap at a point below the midpoint, and wherein the first and second linkages are coupled to the shaft through a double arm crank fixed to the shaft for rotation therewith. 
     
     
         9 . The wind turbine blade according to  claim 1  comprising a spring arranged between the flap and the blade, the spring biasing the flap towards an extended position. 
     
     
         10 . The wind turbine blade according to  claim 1 , comprising a plurality of control flaps, each control flap being movable by rotation of the shaft through a respective linkage. 
     
     
         11 . The wind turbine blade according to  claim 1 , wherein the actuator shaft extends substantially along a structural member of the blade. 
     
     
         12 . wind turbine blade according to  claim 1 , wherein the actuation mechanism and the flap are formed as a unit detachable from the blade. 
     
     
         13 . A wind turbine having a rotor comprising a plurality of rotor blades, each rotor blade comprising at least one control flap on an edge of the blade, and an actuation mechanism for controlling movement of the flap, the actuation mechanism comprising an actuator shaft extending along at least a portion of the length of the blade, an actuator coupled to the shaft to rotate the shaft, the actuator being arranged towards the root end of the blade, a linkage coupled between the flap and the actuator shaft, whereby rotary movement of the shaft moves the flap, and an offset actuation mechanism for imparting movement to the linkage in addition to movement due to rotation of the shaft.