A WIND TURBINE BLADE WITH A FAIRING

Abstract

A prefabricated fairing for a wind turbine blade comprising fairing lips and exterior and interior fairing surfaces, wherein the fairing has a first fairing state in which the fairing is adapted to be mounted to a blade body of the wind turbine blade and a second fairing state in which the fairing is adapted to be fixed to the blade body, the fairing lips being compressed towards each other in the second fairing state relative to the first fairing state, wherein the fairing is brought from the first fairing state to the second fairing state upon application of a compression force onto the exterior fairing surface at fairing lips, wherein a difference between a first fairing lip distance in the first fairing state and a second fairing lip distance in the second fairing state is equal to or greater than 5 mm.

Claims

1. A method of assembling a wind turbine blade (10) extending along a longitudinal axis (L) from a root (16) to a tip (14), the wind turbine blade (10) comprising a root region (30) and an airfoil region (34) with the tip (14), the wind turbine blade (10) comprising a chord line extending between a leading edge (18) and a trailing edge (20), the wind turbine blade (10) comprising an aerodynamic exterior blade surface (22) including a pressure side and a suction side, the method comprising the steps of: providing a prefabricated structural blade body (40) comprising: a first exterior body surface (41) defining part of the pressure side, a second exterior body surface (44) defining part of the suction side, a first attachment surface (42) located adjacent to the first exterior body surface (41), and a second attachment surface (45) located adjacent to the second exterior body surface (44); separately providing a prefabricated fairing (50) extending along the longitudinal axis (L), the fairing (50) extends along a fairing profile (51) terminating at a first fairing lip (52) of the fairing (50) and at a second fairing lip (53) of the fairing (50), the fairing (50) comprising: an exterior fairing surface (54) positioned exteriorly relative to the fairing profile (51), an interior fairing surface (55) positioned interiorly relative to the fairing profile (51), and one or more fibre-reinforced layers (56) extending from the first fairing lip (52) to the second fairing lip (53) and along the longitudinal axis (L), wherein the fairing (50) has a first fairing state (501) and a second fairing state (502), wherein the fairing lips (52, 53) are forced toward each other in the second fairing state (502) relative to the first fairing state (501); while the fairing (50) is in the first fairing state (501), arranging the fairing (50) so that the interior fairing surface (55) faces the attachment surfaces of the blade body (40) and gaps are present respectively between the first attachment surface (42) of the blade body (40) and the first fairing lip (52) of the fairing (50) and between the second attachment surface (45) of the blade body (40) and the second fairing lip (53) of the fairing (50); applying a compression force (FC) onto the fairing lips (52, 53), e.g. onto the exterior fairing surface (54) at the fairing lips (52, 53), to deform the one or more fibre-reinforced layers (56) of the fairing (50) from the first fairing state (501) to the second fairing state (502) so that the first fairing lip (52) and the first attachment surface (42) are brought into contact with a first adhesive (43) and so that the second fairing lip (53) and the second attachment surface (45) are brought into contact with a second adhesive (46); and while maintaining the compression force (FC), curing the first and second adhesives (43, 46) to fix the fairing (50) in its second fairing state (502) to the blade body (40) so that the exterior fairing surface (54) defines a part of the exterior blade surface (22) arranged flush with the first exterior body surface (41) and the second exterior body surface (44) and so that the exterior fairing surface (54) defines either the leading edge (18) of the wind turbine blade (10) or the trailing edge (20) of the wind turbine blade (10).

2. A method according to claim 1, wherein the fairing (50) further has a relaxed fairing state (500) in which the fairing (50) is relaxed and wherein the fairing lips (52, 53) are expanded away from each other in the first and second fairing states (501, 502) relative to the relaxed fairing state (500).

3. A method according to claim 1, further comprising the steps of: providing a jig (60) extending along the longitudinal axis (L) and along a jig profile (61) terminating at a first jig lip (62) of the jig (60) and at a second jig lip (63) of the jig (60) and corresponding in shape to the fairing profile (51), the jig (60) further comprising an interior jig surface (65) positioned interiorly relative to the jig profile (61) and matching the exterior fairing surface (54) of the fairing (50), wherein the jig (60) has a first jig state (601) and a second jig state (602), wherein the jig profile (61) in the first jig state (601) matches the fairing profile (51) in the first fairing state (501) and the jig profile (61) in the second jig state (602) matches the fairing profile (51) in the second fairing state (502).

4. A method according to claim 3, wherein the method comprises performing, prior to the step of arranging the fairing (50), the sub-steps of: applying an expansion force (FE) on the jig lips (62, 63) to expand jig lips (62, 63) of the jig (60); positioning the fairing (50), preferably being in the relaxed fairing state (500), in the jig (60) so that the exterior fairing surface (54) contacts the interior jig surface (65); and releasing the expansion force (FE) until the jig (60) and the fairing (50) are deformed to the first jig state (601) and the first fairing state (501), respectively; wherein the compression force (FC) is applied onto the exterior fairing surface (54) at the fairing lips (52, 53) so that the jig (60) and the fairing (50) are deformed to the second jig state (602) and the second fairing state (502), respectively.

5. A method according to claim 3, wherein the jig (60) has a relaxed jig state (600) and wherein the jig lips (62, 63) are expanded in the first jig state (601) and second jig state (602) relative to the relaxed jig state (600), wherein the step of applying the compression force (FC) is at least partly, preferably entirely, achieved by a spring back force of the jig (60) upon releasing the expansion force (FE) on the jig lips (62, 63).

6. A method according to claim 1, further comprising a step of: providing one or more clamping tool sets (80), wherein each clamping tool set (80) comprises: a first clamping tool (81) having a first clamping head (82) and being secured to the blade body (40) adjacent to one of the attachment surfaces (42, 45), and preferably a second clamping tool (81) having a second clamping head (82) and being secured to the blade body (40) adjacent to the other one of the attachment surfaces (42, 45), wherein the step of applying the compression force (FC) is at least partly, preferably entirely, achieved by actuating the clamping tools (81) of each clamping tool set (80) to urge the clamping heads (82) to apply the compression force (FC) onto the fairing (50) via the exterior jig surface (64).

7. A method according to claim 1, wherein the compression force is at least partly applied by inflating one or more bladders (68, 69).

8. A method according to claim 1, further comprising a step of: providing one or more alignment tool sets (90), wherein each alignment tool sets (90) comprises: a first tool pair including a first jig tool part (91) secured to one of the fairing lips (52, 53) or jig lips (62, 63), and a first blade tool part (93) secured to the blade body (40) or the fixture lip adjacent to the corresponding attachment surface; and preferably a second tool pair including a second jig tool part (91) secured to the other fairing lip or jig lip, and a second blade tool part (93) secured to the blade body (40) or other fixture lip adjacent to the corresponding other attachment surface, respectively; wherein one of the tool parts (91, 93) of each tool pair comprises a pin (92) and the other one of the tool parts (91, 93) of each tool pair comprises a guide (94), the guide (94) being configured for retaining the respective pin (92) while allowing the pin (92) to move along a predefined guide course (95) from a pin entry position (95E) to a pin terminal position (95T), wherein the step of arranging the fairing (50) comprises inserting each pin (92) in the respective guide (94) to the pin entry position (95E) to bring the fairing (50) to the first fairing state (501), each pin (92) being retained in the respective guide, and wherein the step of applying the compression force (FC) causes each pin (92) to move from the pin entry position (95E) to the pin terminal position (95T) of the respective guide.

9. A method according to claim 8, wherein the guide (94) of each tool pair comprises a sloping section (95S) between a pin entry position (95E) and the first pin position (95A), wherein the step of inserting each pin (92) in the respective guide (94) comprises sliding each pin (92) along the sloping section (95S) of the respective guide (94) from the pin entry position (95E) to the first pin position (95A) to gradually increase the expansion force (FE) on the jig lips (62, 63).

10. A method according to claim 8, further comprising a step of: providing a fixture (70) comprising a fixture profile (71) terminating at a first fixture lip (72) of the fixture (70) and at a second fixture lip (73) of the fixture (70); and securing the fixture (70) on the exterior blade surface (22) of the blade body (40) so that the first fixture lip (72) and the second fixture lip (73) are positioned adjacent to the first attachment surface (42) and the second attachment surface (45), respectively; wherein the blade tool parts (93) of the one or more alignment tool sets (90) are fixed to the fixture (70) thereby securing the blade tool parts (93) to the blade body (40), and/or wherein the first clamping tool (81) and/or the second clamping tool (81) is/are fixed to the fixture (70) thereby securing the clamping tool(s) (81) to the blade body (40).

11. A prefabricated fairing (50) for being attached to a structural blade body (40) to form a wind turbine blade (10), the wind turbine blade (10) extending along a longitudinal axis (L) from a root (16) to a tip (14), the wind turbine blade (10) comprising a root region (30) and an airfoil region (34) with the tip (14), the wind turbine blade (10) comprising a chord line extending between a leading edge (18) and a trailing edge (20) thereof, the wind turbine blade (10) comprising an aerodynamic exterior blade surface (22) including a pressure side and a suction side, the fairing (50) extending along the longitudinal axis (L) and along a fairing profile (51) terminating at a first fairing lip (52) of the fairing (50) and at a second fairing lip (53) of the fairing (50), the fairing (50) comprising: an exterior fairing surface (54) positioned exteriorly relative to the fairing profile (51); an interior fairing surface (55) positioned interiorly relative to the fairing profile (51); and one or more fibre-reinforced layers (56) extending from the first fairing lip (52) to the second fairing lip (53) and along the longitudinal axis (L); wherein the fairing (50) has a first fairing state (501) in which the fairing (50) is adapted to be mounted to a blade body (40) prior to being fixed and has a second fairing state (502) in which the fairing (50) is adapted to be fixed to the blade body (40), the fairing lips (52, 53) of the fairing (50) being compressed towards each other in the second fairing state (502) relative to the first fairing state (501), wherein the one or more fibre-reinforced layers (56) of the fairing (50) are configured for being deformed so that, upon application of a compression force (FC) onto the exterior fairing surface (54) at fairing lips (52, 53), the fairing (50) is brought from the first fairing state (501) to the second fairing state (502), wherein a difference between a first fairing lip distance (D1) and a second fairing lip distance (D2) is equal to or greater than 5 mm, 10 mm, 15 mm, 20 mm, or preferably 25 mm, the first fairing lip distance (D1) corresponding to a distance between the fairing lips (52, 53) when the fairing (50) is in the first fairing state (501) and the second fairing lip distance (D2) corresponding to a distance between the fairing lips (52, 53) when the fairing (50) is in the second fairing state (502), the first fairing lip distance (D1) being greater than the second fairing lip distance (D2).

12. A fairing (50) according to claim 11, wherein the fairing (50) further has a relaxed fairing state (500) in which the fairing profile (51) assumes an unloaded shape, and wherein the fairing lips (52, 53) are compressed towards each other in the first fairing state (501) relative to the relaxed fairing state (500).

13. A fairing (50) according to claim 11, wherein the one or more fibre-reinforced layers (56) forms part of a plurality of layers further including an exterior erosion-resistant elastomer layer (57) forming at least a portion of the exterior fairing surface (54) and being configured for defining the leading edge (18) of the wind turbine blade (10), wherein the exterior erosion-resistant elastomer layer (57) is preferably made of polyurethane.

14. A fairing (50) according to claim 13, further comprising a cured first resin (58) binding the erosion-resistant elastomer layer and the one or more fibre-reinforced layers (56) together.

15. A kit of parts for assembly into a wind turbine blade (10) extending along a longitudinal axis (L) from a root (16) to a tip (14), the wind turbine blade (10) comprising a root region (30) and an airfoil region (34) with the tip (14), the wind turbine blade (10) comprising a chord line extending between a leading edge (18) and a trailing edge (20), the wind turbine blade (10) comprising an aerodynamic exterior blade surface (22) including a pressure side and a suction side, the kit of parts comprising: a prefabricated structural blade body (40) comprising: a first exterior body surface (41) defining part of the pressure side, a second exterior body surface (44) defining part of the suction side, a first attachment surface (42) located adjacent to the first exterior body surface (41), and a second attachment surface (45) located adjacent to the second exterior body surface (44); a prefabricated fairing (50) according to any one of claims 11-14 configured for being fixed to the blade body (40) so that the exterior fairing surface (54) defines a part of the exterior blade surface (22) connecting the first exterior body surface (41) and the second exterior body surface (44), and so that the exterior fairing surface (54) defines either the leading edge (18) of the wind turbine blade (10) or the trailing edge (20) of the wind turbine blade (10); and a jig (60) extending along the longitudinal axis (L) and along a jig profile (61) terminating at a first jig lip (62) of the jig (60) and at a second jig lip (63) of the jig (60), the jig (60) comprising: an interior jig surface (65) positioned interiorly relative to the jig profile (61) and configured to match and receive the exterior fairing surface (54) of the fairing (50), wherein the jig (60) has a first jig state (601) and a second jig state (602), wherein the jig profile (61) in the first jig state (601) matches the fairing profile (51) in the first fairing state (501) and the jig profile (61) in the second jig state (602) matches the fairing profile (51) in the second fairing state (502);

16. A kit of parts according to claim 15, further comprising one or more clamping tool sets (80) each including: a first clamping tool (81) having a first clamping head (82) and configured for being secured to the blade body (40) adjacent to one of the attachment surfaces (42, 45); and preferably a second clamping tool (81) having a second clamping head (82) and being secured to the blade body (40) adjacent to the other one of the attachment surfaces (42, 45); wherein each clamping tool set (80) is configured for actuating the clamping tools (81) of each clamping tool set (80) to urge the clamping heads (82) to apply a compression force (FC) onto the exterior fairing surface (54).

17. A kit of parts according to claim 15, wherein the jig comprises one or more bladders (68, 69) configured for, when being inflated, forcing the jig lips (62, 63) towards each other to bring the jig (60) to the second jig state.

18. A kit of parts according to claim 15 further comprising one or more alignment tool sets (90) each including: a first tool pair including a first jig tool part (91) and a first blade tool part (93) secured to one of the fairing lips (52, 53) and to the blade body (40) adjacent to the corresponding attachment surface (42, 45), respectively; and preferably a second tool pair including a second jig tool part (91) and a second blade tool part (93) secured to the other fairing lip and to the blade body (40) adjacent to the corresponding other attachment surface (42, 45), respectively; wherein one of the tool parts of each tool pair comprises a pin (92) and the other one of the tool parts of each tool pair comprises a guide (94) configured for retaining the respective pin (92) while allowing the pin (92) to move along a predefined guide course (95) from a pin entry position (95E) to a pin terminal position (95T); wherein each tool pair is configured so that, when the pin (92) is positioned in the pin entry position (95E) in the respective guide, the fairing (50) is in the first fairing state (501), and so that, when the pin (92) has been moved from the pin entry position (95E) to the pin terminal position (95T) along the predefined guide course (95), the fairing (50) is in the second fairing state (502).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0178] Embodiments of this 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.

[0179] FIG. 1 is a schematic perspective view of a wind turbine.

[0180] FIG. 2 is a schematic perspective view of a wind turbine blade with a fairing for the wind turbine as shown in FIG. 1.

[0181] FIG. 3 is a schematic side view of the fairing being attached to a blade body to form the wind turbine blade of FIG. 2.

[0182] FIG. 4a is a schematic side view of a step of arranging a fairing lip of the fairing in a first fairing state adjacent to an attachment surface of the blade body. An outline of the relaxed fairing state and second fairing state are shown with dashed lines.

[0183] FIG. 4b is a schematic side view of a step subsequent of FIG. 4a of bringing the fairing lip in contact with an adhesive to attach the fairing lip to the attachment surface in order to bring the fairing to its second fairing state. An outline of the relaxed fairing state and first fairing state are shown with dashed lines.

[0184] FIG. 5 is a schematic perspective view of a slice of the tip region of the wind turbine blade of FIG. 2 illustrating the fairing attached to the blade body.

[0185] FIG. 6 is a schematic cross-sectional view of a jig and fairing arrangement for attaching the fairing to the blade body in their respective second jig state and second fairing state. An outline of the first jig and fairing state and the relaxed jig and fairing state are also shown with dashed lines.

[0186] FIG. 7 is a schematic cross-sectional view of a clamping tool set for applying a compression force to bring a fairing lip of the fairing and an attachment surface of the blade body in contact with an adhesive.

[0187] FIG. 8 is a schematic cross-sectional view of a first embodiment of an alignment tool set for attaching the fairing to the blade body.

[0188] FIG. 9a is a schematic cross-sectional view of a second embodiment of an alignment tool for attaching the fairing to the blade body.

[0189] FIGS. 9b-9d are schematic side views of steps of attaching the fairing to the blade body using the alignment tool set of FIG. 9a.

[0190] FIGS. 10a-c are schematic cross-sectional views of steps of arranging a fairing on a blade body via a jig comprising bladders. The reference numerals have intentionally not been repeated on all of FIGS. 10a-c to avoid cluttering the figures, but the reader will appreciate that a reference numeral shown in one figure applies to the corresponding element of the other figures.

[0191] FIG. 11a is a schematic cross-sectional view of the wind turbine blade having a first embodiment of a fairing with an erosion-resistant elastomer layer.

[0192] FIG. 11b is a schematic cross-sectional view of the wind turbine blade having a second embodiment of a fairing with an erosion-resistant elastomer layer.

[0193] FIG. 12 is a schematic cross-sectional view of a mould set up for manufacturing a fairing.

DETAILED DESCRIPTION OF THE INVENTION

[0194] 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 which may include a tilt angle of a few degrees. 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.

[0195] 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 10 extending along a longitudinal axis L between a root end 17 and a tip end 15 and comprises an aerodynamic exterior blade surface 22 including 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 airfoil region 34 includes a tip region 36 with the tip end 15. 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 8, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0196] 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 region 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 radial distance 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 radial distance from the hub.

[0197] A shoulder 38 of the blade 10 is defined as the position where the blade 10 has its largest chord length. The shoulder 38 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0198] 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.

[0199] The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. 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 26 are fastened together with adhesive, such as glue, along bond lines or glue joints extending along the trailing edge 20 and the leading edge 18 of the blade 10 to form a blade body 40. Typically, the root end of the blade shell parts 24, 26 have a semi-circular or semi-oval outer cross-sectional shape. The blade shell parts 24, 26 define the aerodynamic shape of the wind turbine blade and comprise a plurality of spar components (not shown) extending along the longitudinal axis L. The spar components provide the main bending stiffness of the blade 10. The blade body 40 comprises a section located in the tip region 36 to which a fairing 50 is attached.

[0200] The fairing 50 defines a part of the leading edge 18 and has been separately manufactured from the blade body 40 and subsequently attached to the blade body 40 so as to form the wind turbine blade 10. The fairing 50 is an external structure added to a structural blade body of the wind turbine blade 10 exposed to the air stream during operation of the wind turbine blade 10. The fairing 50 has the purpose of altering the air stream around the blade body 40 relative to the blade body 40 without the fairing 50 to more closely approximate an ideal airfoil profile. The blade body 40 and the fairing 50 define the wind turbine blade 10. The fairing 50 will typically extend to the tip end 15 of the wind turbine blade since the highest speeds occur at the tip end 15 and typically not in the root region 30 as the rotor speed there is relatively low. In the shown embodiment, the fairing 50 is located in the tip region 36 of the wind turbine blade 10 and extends from about two thirds of the blade length from the blade root 17 to the tip end 15 of the wind turbine blade 10. In other embodiments, the fairing 50 may be arranged differently, e.g. be located in the airfoil region 34 and/or not extend to the tip end 15.

[0201] The fairing 50 may be attached to the blade body by the method described in connection with FIGS. 3-9. The fairing may be of the types described in connection with FIGS. 11a-11b. The fairing may be manufactured by the method described in connection with FIG. 12.

[0202] As seen in FIGS. 3 and 5, the blade body 40 is a prefabricated structural blade body manufactured in a conventional way. The blade body 40 comprises a first exterior body surface 41 defining part of the pressure side of the wind turbine blade 10, a second exterior body surface 44 defining part of the suction side of the wind turbine blade 10, a first attachment surface 42 located adjacent to the first exterior body surface 41, a second attachment surface 45 located adjacent to the second exterior body surface, and a third exterior body surface 47 extending between the attachment surfaces 42, 45 opposite of the first and second exterior body surfaces 41, 44. The blade body 40 is composed of the pressure side shell part 24 and the suction side shell part 26 joined at a joint located at the midpoint of the third exterior body surface 47. A first uncured adhesive 43 is arranged on the first attachment surface 42, and a second uncured adhesive 46 is arranged on the second attachment surface 45 (alternatively, the adhesives 43, 46 may be arranged on the interior fairing surface 55 at the corresponding fairing lip 52, 53).

[0203] As seen in FIGS. 3 and 5, the fairing 50 is a double-curved (best seen in FIG. 5), plate-shaped prefabricated part fabricated separately from the blade body 40. The fairing 50 extends along the longitudinal axis L of the wind turbine blade 10 (the longitudinal axis L is perpendicular to the plane of FIG. 3) and along a U-shaped fairing profile 51 terminating at a first fairing lip 52 of the fairing 50 and at a second fairing lip 53 of the fairing 50. The fairing profile 51 defines the centre line of each cross-section of the fairing 50 along the longitudinal axis L, and the exterior fairing surface 54 and the interior fairing surface are arranged equidistant from the fairing profile 51. The fairing 50 further comprises an exterior fairing surface 54 positioned exteriorly relative to the fairing profile 51, an interior fairing surface 55 positioned interiorly relative to the fairing profile 51, and one or more fibre-reinforced layers (in the present embodiment, 5-6 glass fibre layers or carbon fibre layers are found advantageous) extending along the fairing profile 51 from the first fairing lip 52 to the second fairing lip 53 and along the longitudinal axis L.

[0204] When the fairing profile (and subsequently the jig profile and fixture profile) are referred to but not shown in the associated figures, the profile is found as the centre line between the associated exterior and interior surfaces of the associated element, e.g. the fairing, jig, or fixture.

[0205] In this disclosure, the reference numeral subscripts .sub.0, 1, and .sub.2, denote the associated quantity or element when in its respective relaxed, first, and second state. For example in FIG. 3, the fairing 50.sub.2 is shown in its second fairing state. In this second fairing state, the fairing lips 52, 53 are distanced from each other by a fairing lip distance D.sub.2. This fairing lip distance D.sub.2 is the distance between the fairing lips 52, 53 when the fairing 50 is attached to the blade body 40. FIG. 4a show the fairing in a first fairing state 50.sub.1 in which the fairing lips 52, 53 are distanced from each other by a fairing lip distance D.sub.1.

[0206] Prior to attaching the fairing 50 to the blade body 40, an expansion force F.sub.E is applied to the fairing lips 52, 53 urging them away from each other and increasing the fairing lip distance D until the fairing 50 is brought to its first fairing state 50.sub.1 with the fairing lip distance D.sub.1 (which is best seen in FIG. 4a). The expansion force F.sub.E may for example be applied by pulling the fairing lips 52, 53 apart or may be applied by the fairing itself, e.g. if the fairing is relaxed in the second fairing state, then the fairing will attempt to revert to this second fairing state once stress is relieved. The fairing lips 52, 53 of the fairing 50.sub.1 are then moved (upwards on FIG. 3 along the arrow between the fairing 50 and the blade body 40) so that the blade body 40 is arranged between the fairing lips 52, 53 and the interior fairing surface 55 faces the attachment surfaces 42, 45 of the blade body 40. In this position, gaps are present respectively between the first attachment surface 42 of the blade body 40 and the first fairing lip 52 of the fairing 50.sub.2 (not shown but corresponds to the mirror image of FIG. 4a) and between the second attachment surface 45 of the blade body 40 and the second fairing lip 53 of the fairing 502 to arrive at the arrangement shown in FIG. 4a. Furthermore, the fairing 50 is arranged with a spacing between the interior fairing surface 55 and the entire third exterior body surface 47 of the blade body 40 as best seen on FIGS. 5, 11a-11b, and 9a. During the movement of the fairing lips 52, 53 towards this position, it is advantageous to avoid scraping the first adhesive 45 off the first attachment surface 42 and avoid scraping the second adhesive 46 off the second attachment surface 45. This can be achieved by providing the fairing in this way with a second fairing state in which the fairing lip distance D.sub.2 is sufficiently larger than the distance between the attachment surfaces 42, 45.

[0207] Once the fairing is moved in the position shown in FIG. 4a, a compression force F.sub.c is applied onto the exterior fairing surface 54 at the fairing lips 52, 53 to deform the fibre-reinforced layers of the fairing 50 from the first fairing state 50.sub.1 to the second fairing state 502 so that the first fairing lip 52 and the first attachment surface 42 are brought into contact with the first adhesive 43 (not shown but corresponds to a mirroring of FIG. 4b) and so that the second fairing lip 53 and the second attachment surface 45 are brought into contact with the second adhesive 46 as shown in FIG. 4b. In the present embodiment, the compression force F.sub.c is applied by the fairing itself since the relaxed fairing state has a smaller fairing lip distance than in the second fairing state, this is illustrated in FIGS. 4a-4b outlining the fairing in the relaxed fairing state 50.sub.0 overlapping the blade body 40. Thus, the fairing will attempt to revert to this relaxed shape applying the compression force F.sub.c. In other embodiments, the second fairing state 50.sub.2 is equal to the relaxed fairing state 50.sub.0, and thus the compression force F.sub.c is applied through other means, for example by pushing the fairing lips 52, 53 towards each other.

[0208] The first and second adhesives 43, 46 are then cured, while the compression force F.sub.c is maintained, to fix the fairing 50 in its second fairing state 50.sub.2 to the blade body 40. Accordingly, the exterior fairing surface 54 defines a part of the exterior blade surface 22 of the wind turbine blade 10 and are arranged flush with the first exterior body surface 41 and the second exterior body surface 44 (as shown in FIGS. 4b, 5, and 11a-11b). Further, the exterior fairing surface 54 defines the leading edge 18 of the wind turbine blade 10. Thus, the fairing 50 is preferably a leading-edge protection fairing. In an alternative embodiment, a corresponding method could be applied to attach a trailing edge fairing to a blade body thereby defining the trailing edge of the wind turbine blade 10.

[0209] After the first and second adhesives 43, 46 are cured, the compression force F.sub.c is relieved. Any excess adhesive extending beyond the exterior blade surface 22 is removed and gaps G in the exterior blade surface 22 between the fairing lips 52, 53 and the blade body 40 as shown in FIGS. 4b and 5 are filled with fillers 48, 49, as best seen in FIGS. 11a-11b, which may be polished afterwards to ensure a smooth exterior blade surface 22.

[0210] In another embodiment, a jig 60 as shown in FIGS. 6 and 9a is provided. The jig 60 extends along the longitudinal axis L (out of the plane of FIG. 6) and along a jig profile 61 terminating at a first jig lip 62 of the jig 60 (as best seen in FIG. 8) and at a second jig lip 63 of the jig. The jig is made of a resilient material, preferably a fibre-reinforced composite. The jig is preferably less stiff than the blade body 40. The jig profile 61 corresponds in shape essentially to the fairing profile 51 albeit being slightly larger so as to be configured for being arranged exteriorly of the fairing. The jig 60 further comprises an interior jig surface 65 positioned interiorly relative to the jig profile 61 and matching in shape the exterior fairing surface 54 of the fairing 50, and an exterior jig surface 64 positioned exteriorly relative to the jig profile 61. The jig 60 has a relaxed jig state 60.sub.0, a first jig state 60.sub.1 and a second jig state 602. The jig profile 61 in the first jig state 60.sub.1 matches the fairing profile 51 in the first fairing state 50.sub.1. The jig profile 61 in the second jig state 60.sub.2 matches the fairing profile 51 in the second fairing state 502 as best seen in FIG. 6. As seen in FIG. 6, the jig profile 61 in the second jig state 60.sub.2 is expanded relative to the jig profile 61 in the relaxed jig state 60.sub.0. Furthermore, as can also be seen in FIG. 6, the fairing profile 51 in the first fairing state 50.sub.1 is compressed relative to relaxed fairing state 50.sub.0.

[0211] The jig 60 of this embodiment is used by performing the following sub-steps prior to the step of arranging the fairing as was shown in FIG. 4a. Firstly, an expansion force is applied on the jig lips 62, 63 to expand jig lips of the jig so that the jig profile 61 matches the fairing profile 51 in the relaxed fairing state 50.sub.0. Secondly, the fairing 50 is positioned in the jig 60 so that the exterior fairing surface 54 abuts or contacts the interior jig surface 65 as shown in FIGS. 6 and 9a. Thirdly, the expansion force is then released so that the jig 60 and the fairing 50 are deformed to the first jig state 50.sub.1 and the first fairing state 60.sub.1, respectively. Advantageously, by arranging the relaxed jig state 50.sub.0 in this way, good contact between the interior jig surface 65 and the exterior fairing surface 54 is achieved in both the first states 50.sub.1, 60.sub.1 and second states 502, 60.sub.2 as the fairing 50 will attempt to revert to its relaxed fairing state 50.sub.0 while the jig 60 will attempt to revert in the opposite direction to its relaxed jig state 60.sub.0.

[0212] Then the step of arranging the fairing as described in connection with FIG. 4a can be advantageously performed by handling the jig instead of the fairing reducing risk of damage to the fairing 50 and ensuring that the fairing 50, which may be a relatively dimensionally unstable part before being attached to the blade body, is kept in a stable state. Furthermore, the compression force F.sub.c can then be applied onto the exterior fairing surface 64 at the fairing lips 62, 63 so that the jig 60 and the fairing 50 are deformed to the second jig state 60.sub.2 and the second fairing state 502, respectively. Advantageously, when the jig profile 61 in the relaxed jig state 60.sub.0 is arranged in this way, the compression force F.sub.c may be partly or entirely achieved by the spring back force of the jig 60 attempting to revert to its relaxed jig state 60.sub.0. However, if a simpler construction is desired (not shown), this can be achieved by arranging the relaxed jig state 60.sub.0 equal to the first jig state 60.sub.1 and/or the relaxed fairing state 50.sub.0 equal to the second fairing state 50.sub.2.

[0213] One way of applying the compression force F.sub.c is by using one or more clamping tool sets. Such a clamping tool set 80 is shown in FIG. 7 and comprises a clamping tool 81 having a clamping head 82. The clamping tool 81 is secured to the blade body 40 adjacent to one of the attachment surfaces 42, 45. The clamping tool 81 is advantageously secured by a fixture 70. Such a fixture 70 is described after the clamping tool set 80.

[0214] Each clamping tool set 80 is capable of applying the compression force F.sub.c by actuating the clamping tool 81 and thereby urging the clamping head 82 towards the exterior fairing surface 54 to apply the compression force F.sub.c preferably via the exterior jig surface 64. In this embodiment, the clamping tool set is lever-actuated by operating a lever arm 84 of the clamping tool set 80. In other embodiments the clamping tool set 80 may be pneumatically, hydraulically, spring or electrically actuated. In order to efficiently distribute the force applied by the clamping head, a load distribution element 83, here a bar extending along the longitudinal axis L, can advantageously be positioned between the clamping head and the exterior jig surface 64. Advantageously, a plurality of clamping tool sets is distributed about 2 metres apart along the longitudinal axis L both along the first attachment surface 42 and the second attachment surface 45. This ensures that sufficient compression force F.sub.c can be applied.

[0215] As best seen in FIG. 9a, the fixture 70 extends along the longitudinal axis L and along a fixture profile 71 terminating at a first fixture lip 72 of the fixture 70 and at a second fixture lip 73 of the fixture 70. The fixture 70 is secured on the exterior blade surface 22 of the blade body 40 so that the first fixture lip 72 and the second fixture lip 73 are positioned adjacent to the first attachment surface 42 and the second attachment surface 45, respectively. Advantageously, the clamping tool 81 of each clamping tool set 80 can then be fixed to the fixture 70 thereby securing the clamping tools 81 to the blade body 40.

[0216] In order to aid with aligning the fairing 50 relative to the blade body 40, one or more alignment tool sets 90 can be provided as shown in FIGS. 8 and 9a-9d. A first embodiment of such an alignment tool 90 is shown in FIG. 8. The alignment tool set 90 comprises a first tool pair and a second tool pair. The first tool pair includes a first jig tool part 91 secured to one of the jig lips 62, 63 and a blade tool part 93 secured to the corresponding fixture lip 72, 73 adjacent to the corresponding attachment surface 42, 45. The second tool pair is identical to the first tool pair but arranged on the opposite side of the blade body, i.e. to the other jig lip and the other fixture lip. Each jig tool part 91 comprises a pin 92, and the blade tool part 93 comprises a guide 94 configured for retaining the pin 92 while allowing the pin 92 to move along a predefined guide course 95 from a pin entry position 95E to a pin terminal position 95T via a second pin position 95B. When initiating the step of arranging the fairing 50 adjacent to the blade body 40, each pin 92 is brought to the pin entry position 95E. Upon moving each pin 92 to the second pin position 95B, the spring back force of the jig 60 snaps each pin 92 to the pin terminal position 95T thus arriving at the arrangement shown in FIG. 8. Accordingly, the fairing 50 is advantageously aligned relative to the blade body 40.

[0217] Turning to FIGS. 9a-9d, a second embodiment of the alignment tool set 90 is shown. In this embodiment, the guide course 95 comprises a first pin position 95A and a sloping section 95s extending between the pin entry position 95E and the first pin position 95A and gradually increasing the fairing lip distance. Thus, when each pin 92 is located in the pin entry position 95E, the fairing 50 and jig 60 are in their second state, and upon moving each pin 92 to the first pin position 95A, the fairing 50 and jig 60 are brought to their first state, thereby eliminating this risk of scraping the first and second adhesive 43, 46 off the attachment surfaces 42, 45 of the blade body 40. Further, the jig tool parts 91 are attached to the exterior jig surface 64 via jig attachment plates 97, and the blade tool parts 93 are attached to the fixture lips 72, 73 via a fixture attachment plate 98. This allows further adjustability of the alignment tool set 90. Sealers 66 are arranged between the interior jig surface 65 and the exterior fairing surface 54 to increase the retention of the fairing 50 by the jig 60. A retention latch (not shown) may be provided on each blade tool parts 93 to ensure that each pin 92 does not leave the pin terminal position 95T.

[0218] Turning to FIGS. 10a-c, a sequence of steps of fitting the fairing 50 to the blade body 40 is shown. In this embodiment, the jig 60 comprises a base part 67, a first bladder 68, and a second bladder 69. The jig lips 62, 63 are attached to the base part 67 via a bolt at the midpoint of the jig profile 61. In the present embodiment, the first and second adhesive 43, 46 are arranged on the fairing lips 52, 53 but may alternatively be arranged on the attachment surfaces 42, 45. The first bladder 68 is arranged between the base part 67 and the first jig lip 62 and the second bladder is arranged between the base part 67 and the second jig lip 63. When the first fairing lip 52 and the first attachment surface 42 as well as the second fairing lip 53 and the second attachment surface 45 are arranged adjacent, respectively (as shown in FIG. 10a), the first and second bladder 68, 69 are inflated to apply the compression force to urge the jig lips 62, 63 and thus the fairing lips 52, 53 towards the attachment surfaces 42, 45 (as shown in FIG. 10b). The base part 67 is rigid compared to the jig lips 62, 63 so that when the bladders 68, 69 are inflated, the base part 67 substantially retains its original geometry while the jig lips 62, 63 are forced towards each other. When the first and second adhesive 43, 46 are cured, the first and second bladders 68, 69 are deflated and the jig 60 is removed to leave the fairing 50 attached to the blade body 40 as shown in FIG. 10c.

[0219] Two embodiments of the fairing 50 fitted to the blade body 40 are shown in FIGS. 11a and 11b. In both embodiments, the fairing 50 comprises an erosion-resistant elastomer layer 57 of polyurethane forming part of the exterior fairing surface 54 and being configured to be in contact with the external environment of the wind turbine blade 10. The erosion-resistant elastomer layer 57 is preferably formed by an extrusion process. Furthermore, the fairing 50 comprises a number of fibre-reinforced layers 56 including a first fibre-reinforced layer forming part of the interior fairing surface 55 and faces the third blade body surface 47, and a number, e.g. 4-5, of second fibre-reinforced layers arranged between the first fibre-reinforced layer and the erosion-resistant elastomer layer 57. A cured first resin (not visible on the figures) binds the erosion-resistant elastomer layer 57 and the one or more fibre-reinforced layers 56 together. The number of fibre-reinforced layers 56 are preferably biaxial glass fibre sheets. In the second embodiment shown in FIG. 11b, the erosion-resistant elastomer layer 57 comprises a reinforced portion at the leading edge 18 of the wind turbine blade 10, to increase the erosion resistance of the fairing 50.

[0220] The erosion-resistant fairing 50 described above in connection with FIGS. 11a-11b may be manufactured in a mould set up as shown in FIG. 12 and in the following way: [0221] provide an erosion-resistant elastomer layer 57; [0222] provide a fairing mould 100 comprising a moulding surface 101; [0223] arrange the erosion-resistant elastomer layer 57 on and conforming it to the moulding surface 101; [0224] apply a first vacuum 103 at a first interface 105 between a lower surface of the erosion-resistant elastomer layer 57 and the moulding surface; [0225] arrange fibre-reinforced layers 56 on top of the erosion-resistant elastomer layer 57; [0226] arrange a cover 102 on top of the fibre-reinforced layers 56; [0227] apply a second vacuum 104 at the second interface 106 between an upper surface of the fibre-reinforced layers 56 and a lower surface of the cover 102 arranged on top of the fibre-reinforced layers 56 so as to pull the cover 102 towards the fibre-reinforced layers 56; [0228] adjust the temperature of the erosion-resistant elastomer layer 57 to 50? C., and then immediately inject a first resin 58 via a resin inlet 108 in the cover 102 so as to wet out the fibre-reinforced layers 56 and so as to contact the erosion-resistant elastomer layer 57 in the fairing mould 100; and [0229] curing the first resin at a temperature of 80? C. for 8 hours so as to form and bind the erosion-resistant elastomer layer 57 and the fibre-reinforced layers 56 as a unitary fairing 50 via the first resin 58, wherein curing of the first resin preferably forms crosslinks between the first resin 58 and the erosion-resistant elastomer layer 57.

[0230] Once the fairing 50 is cured, the cover layer is removed, and any excess resin may be cleaned off. The fairing can then be removed from the fairing mould 100 and cut to the desired shape along a cut plane 107.

TABLE-US-00001 LIST OF REFERENCES 2 wind turbine 4 tower 6 nacelle 8 hub 10 blade 13 shell 14 blade tip 15 tip end 16 blade root 17 root end 18 leading edge 20 trailing edge 22 exterior blade surface 24 pressure side shell part 26 suction side shell part 30 root region 32 transition region 34 airfoil region 36 tip region 38 shoulder 40 blade body 41 first exterior body surface 42 first attachment surface 43 first adhesive 44 second exterior body surface 45 second attachment surface 46 second adhesive 47 third exterior body surface 48 first filler 49 second filler 50 fairing 51 fairing profile 52 first fairing lip 53 second fairing lip 54 exterior fairing surface 55 interior fairing surface 56 fibre-reinforced layer 57 exterior erosion-resistant elastomer layer 58 first resin 60 jig 61 jig profile 62 first jig lip 63 second jig lip 64 exterior jig surface 65 interior jig surface 66 sealer 67 base part 68 first bladder 69 second bladder 70 fixture 71 fixture profile 72 first fixture lip 73 second fixture lip 80 clamping tool set 81 clamping tool 82 clamping head 83 load distribution element 84 lever arm 90 alignment tool set 91 jig tool part 92 pin 93 blade tool part 94 guide 95 guide course 95.sub.E pin entry position 95.sub.A first pin position 95.sub.B second pin position 95.sub.T pin terminal position 95.sub.S sloping section 97 jig attachment plate 98 fixture attachment plate 100 fairing mould 101 moulding surface 102 cover 103 first vacuum 104 second vacuum 105 first interface 106 second interface 107 cut plane 108 resin inlet L longitudinal axis F.sub.C compression force F.sub.E expansion force D fairing lip distance G gap