Wind turbine blade with angled girders

Abstract

The present invention relates to a reinforced blade for a wind turbine, particularly to a blade having a new arrangement of two or more girders in the blade, wherein each of the girders is connected to the upper part and the lower part of the shell and forms an angle with another girder thereby strengthening the shell against transverse shear distortion.

1 . A wind turbine blade, comprising:
 a shell having a section with an aerodynamic profile; and   two girders for increasing the strength of the blade and extending in a longitudinal direction of the blade, and wherein each of the two girders is connected to the upper part and the lower part of the shell and forms an angle with the other girder of the two girders thereby strengthening the shell against transverse shear distortion.   
     
     
         2 . A wind turbine blade according to  claim 1 , wherein
 the two girders form part of a U-profile having a bottom part that extends between the two girders and the shell has a first shell part and a second shell part, and wherein   the wind turbine blade further comprises a box cap part for closing the open end of the U-profile, the girder and the box cap part constituting, when assembled, a load carrying box profile of the blade, and wherein   the bottom part of the U-profile and the box cap part conform to the outer surface of the blade, and wherein   the box cap part, the first shell part and the second shell part are connected to the U-profile.   
     
     
         3 . A wind turbine blade according to  claim 2 , wherein the first shell part constitutes a leading edge section of the blade, and the second shell part constitutes a trailing edge section of the blade, and wherein the bottom part of the U-profile constitutes a part of the outer surface of the blade substantially opposite the box cap part. 
     
     
         4 . A wind turbine blade according to  claim 2 , wherein the first shell part constitutes an upper shell part of the blade, and the second shell part constitutes a lower part of the blade. 
     
     
         5 . A wind turbine blade according to  claim 1 , further comprising a reinforcing floor connected inside the shell for increasing the strength of the blade and having a cross section transversely to the longitudinal extension of the blade that extends substantially in a direction from the trailing edge to the leading edge of the blade. 
     
     
         6 . A wind turbine blade according to  claim 1 , wherein the angle ranges from 5°-125°, such as from 10°-110°, such as from 20°-100°, such as from 30° to 90°. 
     
     
         7 . A wind turbine blade according to  claim 1 , wherein the angle ranges from 10°-90°, such as from 20° to 90°, such as from 30° to 90°. 
     
     
         8 . A wind turbine blade according to  claim 1 , further comprising more than two girders. 
     
     
         9 . A wind turbine blade according to  claim 1 , wherein the two girders comprise at least one element selected from the group consisting of a rod, a plate, and a tube. 
     
     
         10 . A wind turbine blade according to  claim 1 , wherein at least one of the girders comprises cut-outs. 
     
     
         11 . A wind turbine blade according to  claim 1 , wherein at least one of the at least two girders comprise a plate of a sandwich construction. 
     
     
         12 . A wind turbine blade according to  claim 1 , wherein two girders of the at least two girders form part of a spar that is manufactured in one piece with an upper cap and a lower cap interconnecting respective adjacent longitudinal edges of the two girders. 
     
     
         13 . A wind turbine blade according to  claim 1 , wherein the two girders include a plurality of girders positioned in spaced relationship along the longitudinal extension of the blade with a mutual distance that is less than 2×D, wherein D is the distance between opposing connections of one of the plurality of straight girders to the upper part and lower part of the shell, respectively. 
     
     
         14 . A wind turbine blade according to  claim 1 , wherein at least one of the two girders is made of fiber reinforced plastics, such as glass fiber reinforced plastics, carbon fiber reinforced plastics, or plastics reinforced with aramid fibers. 
     
     
         15 . A wind turbine blade according to  claim 1 , wherein at least one of the girders is made of wood, such as bamboo, birch or plywood. 
     
     
         16 . A wind turbine blade according to  claim 1 , wherein at least one of the girders is made of a material based on plant fibers with high cellulose content, such as bast fibers, such as flax, jute, etc. 
     
     
         17 . A method of producing a wind turbine blade with increased strength against transverse shear distortion and having a shell with a section having an aerodynamic profile, the method comprising:
 positioning and connecting two girders inside the shell for extension in a longitudinal direction of the blade; and   connecting each of the girders to the upper part and the lower part of the shell in such a way that one of the girders forms an angle with the other girder.   
     
     
         18 . A method of producing a wind turbine blade according to  claim 17 , comprising:
 producing a U-profile with the two girders and a bottom conforming to a predetermined aerodynamic profile;   producing a first shell part having the shape of a part of the predetermined aerodynamic profile;   producing a second shell part having the shape of a part of the predetermined aerodynamic profile;   producing a box cap part having the shape of a part of the predetermined aerodynamic profile;   connecting the box cap part to the U-profile at the open end of the U-profile thereby forming a load carrying box profile of the blade; and   connecting the first shell part and the second shell part to the U-profile.   
     
     
         19 . A method according to  claim 18 , wherein the first shell part constitutes a leading edge section of the blade and the second shell part constitutes a trailing edge section of the blade and wherein the bottom part of the U-profile constitutes a part of the outer surface of the blade substantially opposite the box cap part. 
     
     
         20 . A method according to  claim 18 , the first shell part constitutes an upper shell part of the blade and the second shell part constitutes a lower part of the blade. 
     
     
         21 . A method according to  claim 17 , further comprising positioning and connecting a reinforcing floor inside the shell for extension substantially in a direction from the trailing edge to the leading edge of the blade. 
     
     
         22 . A method according to  claim 17 , wherein the individual components are manufactured separately. 
     
     
         23 . A method according to  claim 17 , wherein one or more of the individual components are at least partly made of fiber reinforced plastics, such as glass fiber reinforced plastics, carbon fiber reinforced plastics or plastics reinforced with aramid fibers; or of wood, such as bamboo, birch or plywood; or of a material based on plant fibers with high cellulose content, such as bast fibers, such as flax, jute, etc.