WIND TURBINE BLADE AND METHOD FOR PRODUCING A WIND TURBINE BLADE

Abstract

Disclosed is a wind turbine blade and a method for its manufacture. The wind turbine blade comprises an upwind side shell part, a downwind side shell part, a leading edge and a trailing edge. A flatback web is arranged at the trailing edge, which couples the upwind side shell part with the downwind side shell part, wherein the flatback web comprises at least one U-shaped end section with a recess, into which the upwind side shell part and/or the downwind side shell part is inserted and bonded to the U-shaped end section by an adhesive.

Claims

1. A wind turbine blade, comprising: an upwind side shell part, a downwind side shell part, a leading edge and a trailing edge, a flatback web being arranged at the trailing edge, which couples the upwind side shell part with the downwind side shell part, wherein the flatback web comprises at least one U-shaped end section with a recess, into which at least part of the upwind side shell part and/or at least part of the downwind side shell part is inserted and bonded to the U-shaped end section.

2. The wind turbine blade according to claim 1, wherein the flatback web comprises a first U-shaped end section at a first end, and a second U-shaped end section at a second end.

3. The wind turbine blade according to claim 1, wherein a thickness of the upwind side shell part and/or a thickness of the downwind side shell part tapers towards the trailing edge of the respective shell part.

4. The wind turbine blade according to claim 1, wherein a surface of the upwind side shell part and/or a surface of the downwind side shell part is aligned with an adjacent surface of the U-shaped end section of the flatback web.

5. The wind turbine blade according to claim 1, wherein the flatback web has a varying geometry over its length.

6. The wind turbine blade according to claim 1, wherein an angle between the U-shaped end section of the flatback web and a middle section of the flatback web varies over the length of the flatback web, in particular wherein the wind turbine blade has a section with a positive flatback angle and a section with a negative flatback angle.

7. The wind turbine blade according to claim 1, wherein the U-shaped end section comprises a first arm and a second arm, wherein at least one of the arms of the U-shaped end section is connected to the upwind or downwind side shell part by a form locked connection, in particular by a tongue and groove connection.

8. The wind turbine blade according to claim 1, wherein the flatback web comprises a fibre reinforced laminate.

9. A wind turbine, comprising a wind turbine blade according to claim 1.

10. A method for manufacturing a wind turbine blade, the method comprising the steps of: providing an upwind side shell part and a downwind side shell part, each shell part having a leading edge end and a trailing edge end, providing a flatback web with one or more U-shaped end sections, each end section comprising a recess, applying adhesive into the recesses of the respective U-shaped end sections of the flatback web and/or onto the respective trailing edge ends of the upwind side shell part and the downwind side shell part, pushing the flatback web onto the upwind side shell part and the downwind side shell part such that at least part of the upwind side shell part and the downwind side shell part is inserted into the recesses of the respective U-shaped end sections of the flatback web, to form at least part of a trailing edge of the wind turbine blade.

11. The method according to claim 10, wherein the flatback web is pushed onto the shell parts in a mould which is closed for connecting the shell parts.

12. The method according to claim 10, wherein the flatback web is pushed onto the shell after the upwind side shell part and the downwind side shell part have been connected and removed from a mould.

13. The method according to claim 1, wherein the flatback web is pushed onto the shell parts by using a flatback web jig, which comprises a wall with a bearing surface for the flatback web and which is pushed onto the flatback web, in particular by using clamps.

14. The method according to claim 1, wherein the flatback web is produced comprising a step of forming a fibre reinforced laminate in a mould.

15. The method according to claim 14, wherein the recess of the U-shaped end section of the flatback web is produced by placing an insert in or on the fibre reinforced laminate, wherein the insert is removed after curing.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0061] Embodiments of the disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0062] FIG. 1 is a schematic diagram illustrating an exemplary wind turbine,

[0063] FIG. 2 is a schematic diagram illustrating an exemplary wind turbine blade,

[0064] FIG. 3 shows a wind turbine blade with a flatback profile at the trailing edge in more detail,

[0065] FIG. 4 is a cross sectional view of the trailing edge region of a wind turbine blade,

[0066] FIG. 5 is a cross sectional view of the trailing edge region of a wind turbine blade of an embodiment with a tongue and groove connection between flatback web and shells,

[0067] FIG. 6 is a cross sectional view of an entire wind turbine blade,

[0068] FIG. 7 is a schematic illustration of the use of a flatback web jig,

[0069] FIG. 8 is a cross sectional view of the trailing edge region of a wind turbine blade according to an embodiment of the invention, wherein the edge of the shell comprises a flattened section in the region of the joint,

[0070] FIG. 9 in an illustration how the flatback angle varies over the length of the blade,

[0071] FIG. 10 is a cross sectional view of mould for manufacturing a flatback web,

[0072] FIG. 11 shows the flatback web after removing from the mould,

[0073] FIG. 12 is a flowchart showing the steps of producing a wind turbine blade according to an embodiment of the invention.

DETAILED DESCRIPTION

[0074] FIG. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called “Danish concept” with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8, and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.

[0075] FIG. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0076] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0077] A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0078] It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0079] The wind turbine blade 10 comprises a blade shell may comprise two blade shell parts, a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part are typically glued together along bond lines or glue joints 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 have a semi-circular or semi-oval outer cross-sectional shape.

[0080] The trailing edge 20 may be embodied as a flatback trailing edge, wherein the edge is flattened in order to achieve better aerodynamic properties. This construction increases the efficiency of the wind turbine blade in comparison with a sharp edge design.

[0081] FIG. 3 shows a wind turbine blade 10 with a flatback profile at the trailing edge in more detail. The trailing edge 20 has a flattened profile. The flattened profile increases the aerodynamic efficiency and also helps to reduce the chord width.

[0082] The flatback profile is provided by a flatback web 50 which connects the upwind side shell part 24 with the downwind side shell part 26. Details of this flatback web will be explained in more detail with respect to following drawings.

[0083] FIG. 4 is a cross sectional view of the trailing edge region of a wind turbine blade. The upwind side shell part 24 is connected with the downwind side shell part 26 at the trailing edge by a flatback web 50.

[0084] The flatback web 50 comprises a middle section 56 which forms the geometry of the trailing edge. In order to bond the flatback web 50 to the shell parts 24, 26, the flatback web 50 comprises U-shaped end sections 51, which are angled with respect to the middle section 56, such that the ends of the shell parts 24, 26 can be inserted into the recesses 54 between the inner arm 52 and the outer arm 53 of the U-shaped end sections 51.

[0085] The U-shaped end sections 51 are bonded with an adhesive to the shell parts 24, 26. Accordingly, the shell parts 24, 26 are bonded to the flatback web at its inner and also at its outer surface. This type of joint results in a connection which sustains high forces and sheer loads.

[0086] Therefore, the flatback web 50 can be embodied as an integral component of the load bearing structure of the blade.

[0087] In this embodiment, there is placed a web 60 between the shell parts 24, 26, being arranged adjacent to the flatback web.

[0088] FIG. 5 is a cross sectional views of the trailing according to another embodiment of the invention, wherein the flatback web 50 is also connected to the shell parts 14, 16 by a tongue and groove connection.

[0089] The shell parts 24, 26 comprise grooves 11 being arranged on both sides of the shell. Corresponding tongues 55 at the arms 52, 53 of the U-shaped end sections 51 engage the grooves 11, thereby forming a form locked connection between the flatback web 50 and the shell parts, 24, 26.

[0090] According to this embodiment, the flatback web 50 can be snapped onto the blade. The form locked connection holds the flatback web 50 in position until the adhesive is cured.

[0091] However, according to this embodiment of the invention, it is necessary to provide a shell part 24, 26 with a groove 11.

[0092] FIG. 6 is a cross sectional view of an entire wind turbine blade 10. According to this embodiment of the invention, the shell parts 24, 26 are connected in the region of the trailing edge by the flatback web 50 only. Further webs 61, 62, which couple the shell parts 24, 26, are spaced apart from the trailing edge.

[0093] This is possible, since the flatback web 50 is an integral part of the load bearing structure of the wind turbine blade 10.

[0094] As the geometry transitions towards the tip, the internal flanges 61, 62 may taper away and the flatback web 50 flange may taper out.

[0095] FIG. 7 is a schematic illustration of the use of a flatback web jig 70. The flatback web jig comprises a wall 71, which serves as a bearing surface for the flatback web 50.

[0096] The wall 71 can be divided into segments. The wall 71, respectively each wall section, is pivotable so that the wall can be easily tilted to the flatback web 50.

[0097] After tilting the wall 71, clamps 72 may be tightened in order to achieve the desired chord pressure to squeeze out the glue and to achieve the desired glue distribution.

[0098] FIG. 8 is a cross sectional views of the trailing edge region of a wind turbine blade according to an embodiment of the invention, wherein the edge of the shell comprises a flattened section in the region of the joint.

[0099] The shell parts 24, 26 each comprise a thinned end section 25, 27, wherein the outer surface of the shell is thinned.

[0100] The U-shaped end sections 51 of the flatback web 50 are bonded by an adhesive 80 to the thinned end sections 25, 27 of the shell. Due to the thinned surface, a step on the outer surface between the outer arm 53 of the flatback web 50 and the adjacent shell can be avoided. The outer arm 53 is rather aligned with the adjacent surface of the shell.

[0101] FIG. 9 in an illustration how the flatback angle may vary over the length of the blade. Since the flatback web 50 can be provided with any desired geometry, a flatback trailing edge with a positive flatback angle in one section and a negative flatback angle in another section can be easily provided.

[0102] Also the width of the flatback web 50 may vary over its length. In particular, the flatback web 50 may also run out to the tip and/or to the root end of the blade.

[0103] FIG. 10 is a cross sectional view of mould 81 for manufacturing a flatback web 50. The mould 50 can be provided with a three-dimensional shape which is a negative of the shape of the flatback web 50.

[0104] Fibre (e.g. glass or carbon fibres) layers are inserted into the mould 81. Then a resin is injected and cured to form a laminate.

[0105] In order to provide a flatback web 50 with U-shaped end sections 51, an insert 82 is placed between the fibre layers.

[0106] According to this embodiment of the invention, the insert 82 is covered by at least one laminate layer 57. This procedure facilitates the application of the fibre layers, since the fibre layers can be drawn to the edge of the mould 81.

[0107] After curing of the resin, the at least one laminate layer 57, covering the insert 82, is cut off and the insert 82 is removed.

[0108] As shown in FIG. 11, a flatback web 50 comprising angled U-shaped end sections 51 each comprising a recess 54 for bonding to the shell parts is produced.

[0109] According to a preferred embodiment of the invention, the recess has a width w between 10 mm and 30 mm, preferably between 18 mm and 20 mm. The recess may have a depth d between 50 mm and 300 mm, preferably between 150 mm and 200 mm.

[0110] FIG. 12 is a flowchart showing the steps of producing a wind turbine blade according to an embodiment of the invention.

[0111] First, an upwind side shell part and a downwind side shell part are manufactured in a mould 100.

[0112] A flatback web with U-shaped end sections comprising a recess is manufactured offline as a separate component 101.

[0113] The shell parts are placed in a mould upon each other 102.

[0114] In order to bond the flatback web to the shell parts, adhesive is applied into the recesses of the end sections of the flatback web and/or onto the end sections of the shell parts 103.

[0115] Then, the flatback web is pushed onto the shell parts 104. For this step, a flatback web jig might be used as described before.

[0116] After curing the adhesive, a wind turbine blade with a flatback profile is produced, wherein the flatback web is an integral part of the load bearing structure.

[0117] The invention has been described with reference to preferred embodiments. However, the scope of the invention is not limited to the illustrated embodiments, and alterations and modifications can be carried out without deviating from the scope of the invention.

List of References

[0118] 2 wind turbine [0119] 4 tower [0120] 6 nacelle [0121] 8 hub [0122] 10 blade [0123] 11 groove [0124] 14 blade tip [0125] 15 tip end [0126] 16 blade root [0127] 17 root end [0128] 18 leading edge [0129] 20 trailing edge [0130] 24 first blade shell part (upwind/pressure side shell part) [0131] 25 thinned end section of the blade [0132] 26 second blade shell part (downwind/suction side part) [0133] 27 thinned end section of the blade [0134] 28 bond lines/glue joints [0135] 30 root region [0136] 32 transition region [0137] 34 airfoil region [0138] 40 shoulder [0139] 50 flatback web [0140] 51 U-shaped end section [0141] 52 inner arm [0142] 53 outer arm [0143] 54 recess [0144] 55 tongue [0145] 56 middle section [0146] 57 laminate layer [0147] 60 web [0148] 61 web [0149] 62 web [0150] 70 flatback web jig [0151] 71 wall [0152] 72 clamp [0153] 80 adhesive [0154] 81 mould for producing flatback web [0155] 82 insert [0156] 100 Manufacturing an upwind side shell part and a downwind side shell part [0157] 101 Manufacturing a flatback web with U-shaped end sections comprising a recess [0158] 102 Placing the shell parts upon each other [0159] 103 Applying adhesive into the recesses of the end sections of the flatback web and/or onto the shell parts [0160] 104 Pushing the flatback web onto the shell parts