Serrated trailing edge device for a wind turbine blade

Abstract

Serrated Trailing Edge Device A wind turbine blade assembly comprises a wind turbine blade (10) and a serrated device (20) attached at the trailing edge (14) of the blade. The serrated device has a two-part construction and comprises a first panel (24) having a mounting portion (28) and a slitted portion (30) comprising a plurality of first teeth (32) defined between the slits (34); and a second panel (26) having a mounting portion (44) and a slitted portion (46) comprising a plurality of second teeth (48) defined between the slits (34). The mounting portion of the first panel is attached to one of the pressure side (16) or the suction side (18) of the wind turbine blade in the region of the trailing edge. The mounting portion of the second panel is attached to the other of the pressure side or the suction side of the wind turbine blade in the region of the trailing edge. The slitted portion of the first panel is connected to the slitted portion of the second panel such that the slits of the first panel are aligned with the slits of the second panel and the first teeth are aligned with the second teeth. Each second tooth of the second panel is connected to a respective first tooth of the first panel to form a respective serration (22) of the serrated device.

Description

[0001] Serrated Trailing Edge Device for a Wind Turbine Blade

[0002] Technical field

[0003] The present invention relates generally to wind turbine blades, and more specifically to a serrated device for mounting to the trailing edge of a wind turbine blade.

[0004] Background

[0005] It is known to attach aerodynamic devices to the outer surface of wind turbine blades to improve the performance of the blades and / or to reduce noise emissions. For example, serrated panels may be fitted to the trailing edge of a blade to reduce noise emissions. Such devices may be installed on a blade in a factory when the blade is first produced. Alternatively, the devices may be retrofitted to existing wind turbine blades, which can be challenging. It is therefore desirable to develop reliable and straightforward installation procedures for fitting these devices.

[0006] An example of a serrated device is described in the applicant’s previous application W02017088880A1. This device comprises a plurality of serrations that extend from a baseplate. The baseplate is attached to the pressure surface of the blade at the trailing edge of the blade such that the serrations extend in a chordwise direction from the trailing edge of the blade. The baseplate is attached to the pressure surface of the blade using double-sided adhesive tape.

[0007] As wind turbine blades are becoming larger, serrated devices must also be scaled up in size to fit larger blades. However, the use of longer or more substantial serrations increases the stresses on the parts in use. Significant stresses are concentrated in the region between the serrations and the baseplate. One option when designing larger serrated devices is to make the baseplate larger and more substantial to support the larger serrations and to ensure the device remains securely attached to the blade.

[0008] However, simply increasing the dimensions of existing devices presents problems. For example, a thicker baseplate is aerodynamically unfavourable and may become a source of noise. The pressure surface of wind turbine blades is also often highly curved near the trailing edge. A thicker baseplate may not be sufficiently flexible to adapt to this curvature. Against this background it is an object of the present invention to provide an improved serrated trailing edge device, which is particularly suitable for mounting to larger blades and that avoids some of the problems discussed above.

[0009] Summary of the invention

[0010] According to the present invention there is provided a wind turbine blade assembly comprising: a wind turbine blade extending longitudinally in a spanwise direction and extending transversely in a chordwise direction between a leading edge and a trailing edge, the wind turbine blade having a pressure side and a suction side, a serrated device attached at the trailing edge of the blade, the serrated device having a plurality of serrations extending beyond the trailing edge of the blade in a generally chordwise direction, the serrated device having a two-part construction and comprising: a first panel having a mounting portion and a slitted portion comprising a plurality of first teeth defined between the slits; and a second panel having a mounting portion and a slitted portion comprising a plurality of second teeth defined between the slits; wherein the mounting portion of the first panel is attached to one of the pressure side or the suction side of the wind turbine blade in the region of the trailing edge; and the mounting portion of the second panel is attached to the other of the pressure side or the suction side of the wind turbine blade in the region of the trailing edge; the slitted portion of the first panel is connected to the slitted portion of the second panel such that the slits of the first panel are aligned with the slits of the second panel and the first teeth are aligned with the second teeth; and wherein each second tooth of the second panel is connected to a respective first tooth of the first panel to form a respective serration of the serrated device.

[0011] The mounting portion of the first panel and the mounting portion of the second panel together effectively define two halves of a baseplate. The trailing edge of the blade is advantageously sandwiched between the baseplate halves. The two mounting portions together define a slot in which the trailing edge of the blade is received. The slot preferably has a substantially V-shaped profile in transverse cross section.

[0012] The serrated device is advantageously arranged to reduce noise and / or improve the performance of the blade. The two-part design of the device presents numerous benefits over prior art devices that are attached to only one side of the blade. In particular, attaching the device to both sides of the blade provides a more robust connection between the device and the blade. This also allows the overall dimensions of the device to be increased beyond those possible with prior art designs whilst still providing a robust connection to the blade. As stresses are distributed over both sides of the blade, high stress concentrations are avoided. The device may therefore accommodate relatively large serrations and is particularly suitable for large blades and / or for fitting to inboard locations where the blade chord is large and hence large serrations are required.

[0013] The robust connection achieved by connecting the device to both sides of the blade also enables the mounting portions to be made relatively thin. For example, the mounting portions may be made thinner than the single baseplates of existing serrated devices designed to attach to only one side of the blade. The mounting portions may therefore be advantageously flexible and able to curve to conform to the curvature of the blade surface. The device is therefore particularly suitable for attaching to heavily curved surfaces, such as may be found at the pressure side of some blades near the trailing edge.

[0014] The thin mounting portions also minimise the size of any step between the mounting portion and the blade surface and therefore minimise any adverse impacts of the device in relation to noise emission or blade performance.

[0015] The serrations could equally be called teeth. However, the term serration is used herein to avoid confusion with the teeth of the panels.

[0016] The second tooth of the second panel is connected to the respective first tooth of the first panel such that they are stacked together in a thickness direction, the thickness direction being perpendicular to both the spanwise direction and the chordwise direction.

[0017] The second tooth of the second panel is connected to the respective first tooth of the first panel such that the first tooth forms at least part of a pressure surface or a suction surface of the respective serration and the second tooth forms at least part of the other of the pressure surface or the suction surface of the respective serration.

[0018] Preferably, the pressure surface of the respective serration is a flush surface and / or the suction surface of the respective serration is a flush surface.

[0019] The panels are preferably made from plastic, and most preferably made from thermoplastic, which is advantageously recyclable. Each panel is preferably a moulded part, for example formed by injection moulding or a 3D printed part. Preferably the first and second panels are each plastic moulded or 3D printed parts.

[0020] The mounting region of the first and / or second panel is preferably flexible such that it can curve to conform to a curvature of the pressure side or suction side in the region of the trailing edge.

[0021] The mounting portions of the first and second panel are preferably bonded to the blade. Preferably the mounting portions are bonded to the blade by double-sided adhesive tape. The slitted portion of the first panel is preferably bonded to the slitted portion of the second panel, preferably by double-sided adhesive tape. The double-sided adhesive tape preferably comprises a pressure sensitive adhesive. The tape may be pre-applied to one or both of the panels before the parts are installed on the blade. A paste adhesive or liquid resin may be used in addition to or instead of double-sided tape. However, double-sided tape is convenient and easy to use, particularly when retrofitting the device to an existing wind turbine blade in the field.

[0022] The first teeth are preferably longer than the second teeth. The first teeth are longer than the second teeth in a generally chordwise direction. The first teeth may therefore extend further from the trailing edge than the second teeth. The first teeth preferably extend beyond the second teeth. Tips of the second teeth preferably terminate before tips of the first teeth. The tips of the first teeth preferably define tips of the serrations.

[0023] In one embodiment, the second teeth have a length of approximately 25% of the length of the first teeth. In another embodiment the second teeth have a length of approximately 66% of the length of the first teeth. However, the second teeth may have any suitable length in other embodiments. Preferably the second teeth have a length between 10%- 90% of the length of the first teeth.

[0024] The slitted portion of the first panel may further comprise a plurality of second teeth defined between the slits and the slitted portion of the second panel may further comprise a plurality of first teeth defined between the slits. Each second tooth of the first panel is preferably connected to a respective first tooth of the second panel to form a respective serration of the serrated device. The first teeth are arranged alternately with the second teeth along both the first and second panels. The first teeth of the first panel may be longer than the second teeth of the second panel and the first teeth of the first panel may be longer than the second teeth of the first panel and the first teeth of the second panel may be longer than the second teeth of the second panel. The first teeth of the first panel may be substantially the same length as the first teeth of the second panel. The second teeth of the first panel may be substantially the same length as the second teeth of the second panel.

[0025] An inboard portion of each serration may be formed by a second tooth in combination with a first tooth. An outboard portion of each serration may be formed entirely by a first tooth. More specifically, an inboard portion of each serration may be formed on one side (e.g. a suction side or a pressure side) by a second tooth and on the other side by an inboard portion of a first tooth. An outboard portion of each serration may be formed entirely by an outboard portion of a first tooth. Tips of the serrations are preferably formed entirely by tips of the first teeth.

[0026] The inboard portion of the serration preferably comprises a root end of the serration. The outboard portion of the serration preferably comprises a tip end of the serration. The inboard portion of the serration is closer to the trailing edge than the outboard portion in a generally chordwise direction.

[0027] The shape and dimensions of the teeth and serrations may be defined in terms of a length, width and thickness. The length of a tooth or serration is its dimension generally in the chordwise direction. The term ‘generally’ is used because the teeth may be inclined somewhat relative to the local chord of the blade where the device is attached. The width of a tooth or serration is its dimension generally in the spanwise direction. The thickness of a tooth or serration is its dimension perpendicular to both its length and width.

[0028] Each tooth extends lengthwise from a fixed root end to a tip end. The root ends of the teeth may be contiguous with a mounting portion of the respective panel. Alternatively the root ends of the teeth may be spaced from the mounting portion. Expressed another way, the slitted region of a panel may be contiguous with the mounting portion or it may be spaced from the mounting portion. For example, the first and / or second panel may include a spacer region between the mounting portion and the slitted region. The serrations preferably taper in thickness towards their tips. As the tips of the serrations are preferably formed entirely by the first teeth, the first teeth preferably taper in thickness towards their tips. Alternatively or additionally, the second teeth may taper in thickness towards their tips.

[0029] The serrations may be relatively thin at their tips. For example the tips of the serrations may have a thickness of just a few millimetres or less. Such low thicknesses can be realised by forming the outboard portion of each serration entirely by the first panel or entirely by the second panel, e.g. entirely by a first tooth of a panel. If the tips of the serrations were formed in two parts like the inboard ends of the serrations, then each part may be too thin to produce and fit together reliably. Therefore, the two-part construction of the serrations preferably does not extend all the way to the tips of the serrations.

[0030] The serrations preferably taper in width towards their tips. Accordingly, the first and / or second teeth may taper in width towards their teeth. The serrations may be generally triangular in planform.

[0031] The serrations preferably have a sharp or pointed tip end. This is advantageous for reducing noise and improving the performance of the blade. The tip end of a serration may comprise a single point, or multiple points, for example a double point. As the tip ends of the serrations are preferably formed entirely by the first teeth, it follows that the first teeth also preferably have a sharp or pointed tip end, for example comprising a single point or multiple points.

[0032] The tip ends of the second teeth are preferably blunt. As the second teeth preferably terminate before the tips of the serrations they may not be required to form a sharp point, and therefore can be formed with a blunt edge, which provides manufacturing advantages. The tip ends of the second teeth may have a straight edge extending in the width direction of the teeth, i.e. generally in the spanwise direction.

[0033] Preferably, each second tooth of one panel is nested within a respective first tooth of the other panel. For example, each second tooth of one panel may be received within a recess in a respective first tooth of the other panel. Preferably the recess is defined in an inboard portion of a first tooth. For example, inboard portions of the first teeth may have a reduced thickness in comparison to the thickness of an outboard portion of the first teeth immediately adjacent the inboard portion. The depth of the recess preferably corresponds to the thickness of the second teeth. The recesses enable the outer surface of a second tooth to sit flush with the outer surface of the first tooth on the same side of the device (e.g. the pressure side or suction side) when the teeth are connected together. The serrations may therefore advantageously have smooth and continuous outer surfaces.

[0034] A tip of each second tooth may interlock with a retaining portion of a respective first tooth at an end of the recess. For example, a retaining portion of the first tooth may overhang the recess slightly at the end of the recess and define a slot. The tip of the second tooth may be received in the slot. When assembling the first and second panels together, the tips of the second fingers may be inserted into the slots and the overhanging portion of the first tooth retains the tip ends of the second teeth in position. The slot could have a curved profile. Similarly the tip ends of the second teeth may be correspondingly curved. This advantageously allows the tips of the second teeth to pivot within the slots when the two parts are fitted together. The retaining portions may advantageously hook over the tip ends of the second teeth

[0035] The slitted portion of the first panel may be connected to the slitted portion of the second panel by means of snap fit features. The slitted portion of the first panel may be provided with snap fit features that engage with corresponding snap fit features of the second panel. One or more snap fit features may be provided on each tooth. The snap fit features provide a convenient means of connecting the two panels together and ensuring the correct positioning of the two panels.

[0036] The snap fit features may be used instead of bonding but are preferably used in addition to bonding. The snap fit helps to compress or otherwise exert pressure on the adhesive (e.g. adhesive tape) between the two panels and prevents the two parts from coming apart.

[0037] The panels may be connected by other means instead of, or in addition to, snap fit connections or bonding. For example, plastic welding may be used or the parts may be clipped together, or otherwise fastened together, e.g. using plastic rivets.

[0038] According to the invention there is also provided a serrated device for attaching to a trailing edge of a wind turbine blade, the serrated device having a plurality of serrations and a two- part construction, wherein the serrated device comprises: a first panel having a mounting portion configured to attach to a first side of a wind turbine blade in the region of a trailing edge, and a slitted portion comprising a plurality of first teeth defined between the slits; and a second panel having a mounting portion configured to attach to a second side of a wind turbine blade in the region of the trailing edge, and a slitted portion comprising a plurality of second teeth defined between the slits; wherein the slitted portion of the first panel is configured to connect to the slitted portion of the second panel such that the slits of the first panel align with the slits of the second panel and the first teeth align with the second teeth; and wherein each second tooth of the second panel is configured to connect to a respective first tooth of the first panel to form a respective serration of the serrated device.

[0039] Optional and / or advantageous features discussed above, and / or recited in the dependent claims, in relation to the invention when expressed in terms of a wind turbine blade assembly apply equally to the invention when expressed in terms of a device for attachment to a wind turbine blade. Repetition of these features is avoided for reasons of conciseness.

[0040] Brief description of the drawings

[0041] Embodiments of the invention will now be described, by way of non-limiting example, with reference to the following figures, in which:

[0042] Figure 1 is a schematic plan view of a wind turbine blade comprising a plurality of serrated devices attached to a trailing edge of the blade;

[0043] Figure 2 is a perspective view of a serrated device;

[0044] Figure 3 is a perspective view of a first panel of the serrated device;

[0045] Figures 4 and 5 are perspective views of a second panel of the serrated device;

[0046] Figure 6 is a chordwise cross-sectional view of a serrated device attached to the trailing edge of a blade;

[0047] Figure 7 is an exploded view of the serrated device;

[0048] Figure 8 shows an interlocking region between the first and second panels; Figure 9 shows a variant of the serrated device;

[0049] Figures 10 and 11 show a further variant of the serrated device; and

[0050] Figure 12 shows an alternative tip shape of a serration.

[0051] Detailed

[0052] Figure 1 shows a wind turbine blade assembly according to an example of the present invention. The wind turbine blade assembly comprises a wind turbine blade 10 extending longitudinally in a spanwise direction S and extending transversely in a chordwise direction C between a leading edge 12 and a trailing edge 14. The wind turbine blade 10 has a pressure side 16 and a suction side 18 (visible in Figure 6).

[0053] The wind turbine blade assembly further comprises a plurality of serrated devices 20 attached at the trailing edge 14 of the blade 10. Each serrated device 20 has a plurality of serrations 22 extending beyond the trailing edge 14 of the blade 10 in a generally chordwise direction.

[0054] The dimensions of the serrated devices 20 are scaled approximately in proportion to the local chord of the blade 10 at the position of the device 20. As the blade chord generally decreases towards the tip of the blade 10, the serrated devices 20 located near the tip have smaller dimensions than the devices 20 located at more inboard locations. The most inboard serrated devices 20 have relatively large dimensions. The pressure side 16 of the blade 10 may also have a high degree of curvature near the trailing edge 14, in particular in more inboard positions.

[0055] Figure 2 shows a serrated device 20 according to an example of the present invention. A suction side of the device 20 is shown in Figure 2. The serrated device 20 has a two-part construction comprising a first panel 24 and a second panel 26. Each panel 24, 26 may be made from plastic, preferably a thermoplastic, and may be formed by injection moulding.

[0056] The first panel 24, shown in isolation in Figure 3, comprises a mounting portion 28 and a slitted portion 30. The slitted portion 30 may be contiguous with the mounting portion 28. The slitted portion 30 comprises a plurality of first teeth 32 defined between the slits 34. The first teeth 32 are generally triangular in planform and have pointed tip ends 36. A recess 38 may be defined in an inboard portion 40 of each first tooth 32. Female snap fit features in the form of holes 42 may be provided in the recesses 38.

[0057] Referring now to Figure 4, which shows a suction side of the second panel 26. The second panel 26 also has a mounting portion 44 and a slitted portion 46. The slitted portion 46 may be contiguous with the mounting portion 44. The slitted portion 46 of the second panel 26 comprises a plurality of second teeth 48 defined between the slits 34. The second teeth 48 may have blunt tip ends 50. Figure 5 shows a reverse side of the second panel 26. Male snap fit features 52 in the form of protrusions may be provided on the reverse side of the each second tooth 48.

[0058] As shown in Figure 2, the slitted portion 30 of the first panel 24 is connected to the slitted portion 46 of the second panel 26 such that the slits 34 of the first panel 24 are aligned with the slits 34 of the second panel 26 and the first teeth 32 are aligned with the second teeth 48. Each second tooth 48 is connected to a respective first tooth 32 to form a respective serration 22 of the serrated device 20. The serrations 22 in this example are generally triangular in plan view.

[0059] An inboard portion 54 of each serration 22 is formed by a second tooth 48 in combination with a first tooth 32, and an outboard portion 56 of each serration 22 is formed entirely by a first tooth 32. The tips 36 of the first teeth 32 form the tips of the serrations 22. The serrations 22 taper in thickness towards their tips 36. As the tips 36 of the serrations 22 are made entirely from the first teeth 32, this allows the serrations 22 to taper to a lower thickness than would be possible if the serrations 22 were made in two halves at their tips 36.

[0060] Each serration 22 of the device 20 is therefore formed in part by a tooth 32 of the first panel 24, and in part by a tooth 48 of the second panel 26. The serrations 22 are themselves teeth, and each serration 22 may alternatively be referred to as a tooth. However, to avoid confusion, the term ‘serration’ is used herein to refer to the structure formed when a first tooth 32 of one panel 24, 26 is joined with a second tooth 48 of the other panel 24, 26.

[0061] Figure 6 is a cross-sectional view of the device 20 attached to the trailing edge 14 of the wind turbine blade 10. The mounting portion 28 of the first panel 24 is attached to a pressure side 16 of the blade 10 in the region of the trailing edge 14. The mounting portion 44 of the second panel 26 is attached to the suction side 18 of the blade 10 in the region of the trailing edge 14. Each mounting portion 28, 44 effectively defines one half of a baseplate. The trailing edge 14 is sandwiched between the baseplate halves 28, 44. The two mounting portions 28, 44 together define a V-shaped slot in which the trailing edge 14 of the blade 10 is received.

[0062] As the serrated device 20 is attached to both the suction side 18 and the pressure side 16 of the blade 10, a robust connection is made to the blade 10. This allows the mounting portions 28, 44 to be made relatively thin and flexible so that they may adapt to the curvature of the blade 10 near the trailing edge 14.

[0063] As shown in Figure 6, the second tooth 48 of the second panel 26 is connected to the respective first tooth 32 of the first panel 24 such that they are stacked together in a thickness direction. The thickness direction is perpendicular to both the spanwise direction and the chordwise direction.

[0064] The first tooth 32 of the first panel 24 forms a pressure surface 58 of the respective serration 22 and an outboard part of a suction surface 60 of the respective serration 22. The second tooth 48 of the second panel 26 forms an inboard part of the suction surface 60 of the respective serration 22.

[0065] Both the pressure and suction surfaces 58, 60 of the serrations 22 may be flush surfaces, i.e. smooth surfaces without discontinuities or steps. This is achieved on the suction side 18 because the second teeth 48 may be received in the recesses 38 defined in the first teeth 32. The depth of the recesses 38 corresponds to the thickness of the second teeth 48. Accordingly, each second tooth 48 may be nested within a respective first tooth 32.

[0066] The mounting portion 28 of the first panel 24 may be bonded to the pressure side 16 of the blade 10 using a first layer of double-sided adhesive tape 62. The mounting portion 44 of the second panel 26 may be bonded to the suction side 18 of the blade 10 using a second layer of double-sided adhesive tape 64. The second teeth 48 may also be secured to the first teeth 32 using the second layer of double-sided adhesive tape 64.

[0067] The double-sided tape 62, 64 is shown more clearly in the exploded view of Figure 7. The first layer of double-sided adhesive tape 62 is pre-applied to the mounting portion 28 of the first panel 24. The first layer 62 may be substantially rectangular and similar in shape to the first mounting portion 28. The second layer 64 of double-sided adhesive tape may be pre-applied to the reverse side of the second panel 26. The second layer of tape 64 has a similar planform shape to the second panel 26. The second layer 64 may comprise a rectangular portion that is pre-applied to the mounting portion 44 (shown best in Figure 5) of the second panel 26 and a slitted portion that is pre-applied to the slitted portion 46 of the second panel 26.

[0068] To install the device 20 at the trailing edge 14 of the blade 10, a protective covering layer may be removed from the first layer of tape 62 and the mounting portion 28 of the first panel 24 is pressed against the pressure side 16 of the blade 10 at the trailing edge 14 (see also Figure 6). A protective covering layer may then be removed from the second layer of tape 64 and the mounting portion 44 of the second panel 26 is pressed against the suction side 18 of the blade 10 at the trailing edge 14. The teeth 32, 48 of the first and second panels 24, 26 are pressed together, causing the snap-fit features 42, 52 between the teeth 32, 48 to engage and retain the teeth together. This also helps to compress the adhesive tape 64 between the teeth 32, 48. The device 20 is therefore relatively straightforward to install on a wind turbine blade.

[0069] As shown in Figure 8, the tip ends 50 of the second teeth 48 may interlock with retaining portions of the first teeth 32. In this example, the tip end 50 of a second tooth 48 comprises a tongue 66 that is received within a groove 68 of the first tooth 32 at an end of the recess 38. To connect the second panel 26 and the first panel 24 together, the tongues 66 at the tips 50 of the second teeth 48 are initially inserted into the grooves 68 and then the panels 24, 26 are pressed together to engage the snap fit features 42, 52 (shown in Figures 3 and 5).

[0070] In this example, the first teeth 32 are longer than the second teeth 48. More specifically, in this example the second teeth 48 are approximately 25% of the length of the first teeth 32. In a variant, as shown in Figure 9, the second teeth 48 have a length of approximately 66% of the length of the first teeth 32.

[0071] Figures 10 and 11 show a further variant, in which Figure 10 shows a suction side of the device 20 and Figure 11 shows a pressure side of the device. In this variant, the slitted portion 30 of the first panel 24 comprises a plurality of first teeth 32 and a plurality of second teeth 70 defined between the slits 34. The first teeth 32 are arranged alternately with the second teeth 48 along the length of the first panel 24. Likewise, the slitted portion 46 of the second panel 26 comprises a plurality of first teeth 72 and a plurality of second teeth 48 defined between the slits 34. The first teeth 72 are arranged alternately with the second teeth 48 along the length of the second panel 26.

[0072] In both panels 24, 26, the first teeth 32, 72 are longer than the second teeth 48, 70. The first teeth 32 of the first panel 24 are the same length as the first teeth 72 of the second panel 26. The second teeth 70 of the first panel 24 are the same length as the second teeth 48 of the second panel 26.

[0073] Each first tooth 32 of the first panel 24 is connected to a respective second tooth 48 of the second panel 26 to form a respective serration 22. Likewise, each first tooth 72 of the second panel 26 is connected to a respective second tooth 70 of the first panel 24 to form a respective serration 22.

[0074] As shown in Figure 10, a suction surface 60 of every second serration is formed entirely by the first teeth 72 of the second panel 26, whereas the suction surface 60 of every other serration is formed partly by a second tooth 48 of the second panel and partly by a first tooth 32 of the first panel 24. As shown in Figure 11 , a pressure surface 58 of every second serration is formed entirely by the first teeth 32 of the first panel 24, whereas the pressure surface 58 of every other serration is formed partly by a second tooth 70 of the first panel 24 and partly by a first tooth 72 of the second panel 26.

[0075] Whilst the tips of the serrations 22 in the above examples have a single point, in other examples the tips of the serrations 22 may have multiple points, for example a double point is shown schematically in Figure 12.

[0076] Various other modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims

Claims1. A wind turbine blade assembly comprising: a wind turbine blade extending longitudinally in a spanwise direction and extending transversely in a chordwise direction between a leading edge and a trailing edge, the wind turbine blade having a pressure side and a suction side, a serrated device attached at the trailing edge of the blade, the serrated device having a plurality of serrations extending beyond the trailing edge of the blade in a generally chordwise direction, the serrated device having a two-part construction and comprising: a first panel having a mounting portion and a slitted portion comprising a plurality of first teeth defined between the slits; and a second panel having a mounting portion and a slitted portion comprising a plurality of second teeth defined between the slits; wherein the mounting portion of the first panel is attached to one of the pressure side or the suction side of the wind turbine blade in the region of the trailing edge; and the mounting portion of the second panel is attached to the other of the pressure side or the suction side of the wind turbine blade in the region of the trailing edge; the slitted portion of the first panel is connected to the slitted portion of the second panel such that the slits of the first panel are aligned with the slits of the second panel and the first teeth are aligned with the second teeth; and wherein each second tooth of the second panel is connected to a respective first tooth of the first panel to form a respective serration of the serrated device.

2. The wind turbine blade assembly of Claim 1 , wherein the first and second panels are each plastic moulded parts or 3D printed parts.

3. The wind turbine blade assembly of Claim 1 or Claim 2, wherein the mounting region of the first and / or second panel is flexible such that it can curve to conform to a curvature of the pressure side or suction side in the region of the trailing edge.

4. The wind turbine blade assembly of any preceding claim, wherein the mounting portions of the first and second panel are bonded to the blade, preferably by double-sided adhesivetape, and / or the slitted portion of the first panel is bonded to the slitted portion of the second panel, preferably by double-sided adhesive tape.

5. The wind turbine blade assembly of any preceding claim, wherein the slitted portion of the first panel further comprises a plurality of second teeth defined between the slits and the slitted portion of the second panel further comprises a plurality of first teeth defined between the slits, and wherein each second tooth of the first panel is connected to a respective first tooth of the second panel to form a respective serration of the serrated device.

6. The wind turbine blade assembly of Claim 5, wherein the first teeth alternate with the second teeth along both the first and second panels.

7. The wind turbine blade assembly of any preceding claim, wherein the first teeth are longer than the second teeth.

8. The wind turbine blade assembly of any preceding claim, wherein an inboard portion of each serration is formed by a second tooth in combination with a first tooth, and an outboard portion of each serration is formed entirely by a first tooth.

9. The wind turbine blade assembly of any preceding claim, wherein tips of the serrations are formed entirely by tips of the first teeth.

10. The wind turbine blade assembly of any preceding claim, wherein the serrations taper in thickness towards their tips.11 . The wind turbine blade assembly of any preceding claim, wherein tip ends of the first teeth are pointed and tip ends of the second teeth are blunt.

12. The wind turbine blade assembly of any preceding claim, wherein each second tooth of one panel is received within a recess in a respective first tooth of the other panel.

13. The wind turbine blade assembly of Claim 12, wherein a tip of each second tooth interlocks with a retaining portion of a respective first tooth at an end of the recess.

14. The wind turbine blade assembly of any preceding claim, wherein the slitted portion of the first panel is connected to the slitted portion of the second panel by means of snap fit features.

15. A serrated device for attaching to a trailing edge of a wind turbine blade, the serrated device having a plurality of serrations and a two-part construction, wherein the serrated device comprises: a first panel having a mounting portion configured to attach to a first side of a wind turbine blade in the region of a trailing edge, and a slitted portion comprising a plurality of first teeth defined between the slits; and a second panel having a mounting portion configured to attach to a second side of a wind turbine blade in the region of the trailing edge, and a slitted portion comprising a plurality of second teeth defined between the slits; wherein the slitted portion of the first panel is configured to connect to the slitted portion of the second panel such that the slits of the first panel align with the slits of the second panel and the first teeth align with the second teeth; and wherein each second tooth of the second panel is configured to connect to a respective first tooth of the first panel to form a respective serration of the serrated device.

Images