Method and system for manufacturing a shear web for a wind turbine

Abstract

The present invention relates to a method and to a mould system (70) for manufacturing a shear web for a wind turbine blade as well as to a backing plate (66) for such method and mould system. The method involves arranging one or more fibre layers on top of a web mould part (61), arranging backing plates (66) at each end to create a mould cavity between the first and second backing plate (66, 68) and the web mould part (61). Each backing plate (66, 68) comprises an inner moulding surface (80), outer surfaces (98, 100) and a channel (82) or groove (83) extending between at least one of the outer surfaces (98, 100) and the inner moulding surface (80). Resin is supplied to the mould cavity via each channel or groove of the first and second backing plate (66, 68), and subsequently the resin is cured or hardened to form the shear web.

Claims

1. A method of manufacturing a shear web (50) for a wind turbine blade, the shear web having a web body and a first web foot flange at a first end of the web body and a second web foot flange at a second end of the web body, wherein the method comprises the steps of: a) providing an elongated lower web mould part (61) having a moulding surface with a central portion (71), which is substantially flat, a first downwardly extending moulding surface portion (72) at a first end of the lower web mould part (61), and a second downwardly extending moulding surface portion (73) at a second end of the lower web mould part (61); b) arranging one or more fibre layers (62, 64) on top of the elongated lower web mould part (61) and at least partly covering the first downwardly extending moulding surface portion (72), the central portion (71), and the second downwardly extending moulding surface portion (73); c) arranging a first backing plate (66) opposite to the first downwardly extending moulding surface portion (72) and arranging a second backing plate (68) opposite to the second downwardly extending moulding surface portion (73) to create a mould cavity between the first and second backing plates (66, 68) and the lower web mould part (61), wherein each of the first and second backing plates comprises an inner moulding surface (80), one or more outer surfaces (98, 100), and a groove (83) extending between at least one of the outer surfaces (98, 100) and the inner moulding surface (80) of the respective one of the first and second backing plates, wherein the one or more outer surfaces of each of the first and second backing plates comprise opposing first and second lateral surfaces, and wherein the groove (83) of each of the first and second backing plates extends through the inner moulding surface (80) between the opposing first and second lateral surfaces of the corresponding one of the first and second backing plates, the groove (83) extending from the first lateral surface to the second lateral surface; d) supplying resin to the mould cavity via the respective groove (83) of the first and second backing plates (66, 68); and e) curing or hardening the resin in order to form the shear web.

2. The method according to claim 1, wherein the lower web mould part (61) comprises magnetic material, and wherein the first and/or second backing plate (66, 68) further comprises a recess (90) in its outer surface and wherein one or more magnets (88) are arranged in the recess (90) for retaining the backing plate against the lower web mould part (61) during moulding.

3. The method according to claim 2, wherein the recess (90) of the backing plate is located in an opposing back surface (96) that is substantially parallel to the inner moulding surface of the backing plate.

4. The method according to claim 1, wherein the shear web is I-shaped.

5. The method according to claim 1, wherein the first downwardly extending moulding surface portion (72) and/or the second downwardly extending moulding surface portion (73) comprises a ledge (84) which forms part of the moulding surface of the lower web mould part (61).

6. The method according to claim 1, wherein the first and the second downwardly extending moulding surface portion (73) of the lower web mould part (61) are diverging from the central portion (71) along at least a part of the elongated lower web mould part (61).

7. The method according to claim 1, wherein step b) further comprises arranging a core material (63) on top of the one or more fibre layers in the central part of the lower web mould part (61), optionally followed by arranging one or more fibre layers on top of the core material (63).

8. The method according to claim 1, wherein step c) further comprises retaining one or more of the fibre layers against the inner moulding surface (80) of the first and/or the second backing plate (66, 68).

9. The method according to claim 1, wherein step b) further comprises arranging an upper web mould part on top of the fibre layers, the upper web mould part having a moulding surface with a central portion (91), which is substantially flat, a first upwardly extending moulding surface portion at a first end of the upper web mould part, and a second upwardly extending moulding surface portion at a second end of the upper web mould part, and wherein step b) optionally comprises wrapping ends of the second fibre layers against the first and the second upwardly extending moulding surface of the upper web mould part.

10. The method according to claim 9, wherein the first and the second upwardly extending moulding surface portion of the upper web mould part are converging from the central portion (91) along at least a part of the elongated upper web mould part.

11. The method according claim 1, wherein the mould cavity is further sealed by at least one vacuum bag.

12. The method according to claim 1, wherein at least a first insert is arranged at the first end of the lower web mould part, wherein said first insert is adapted to provide a gradual transition from the web body to the first web foot flange and/or a second insert is arranged at the first end of the lower web part, wherein said first insert is adapted to provide a gradual transition from the web body to another part of the first web foot flange.

13. A mould system (70) for manufacturing a shear web for a wind turbine blade, the shear web having a web body and a first web foot flange at a first end of the web body and a second web foot flange at a second end of the web body, wherein the system comprises: an elongated lower web mould part (61) having a moulding surface with a central portion (71), which is substantially flat, a first downwardly extending moulding surface portion (72) at a first end of the lower web mould part (61), and a second downwardly extending moulding surface portion (73) at a second end of the lower web mould part (61), and first and second backing plates (66, 68), wherein each of the first and second backing plates comprises an inner moulding surface (80), one or more outer surfaces (98, 100), and a groove (83) extending between at least one of the outer surfaces (98, 100) and the inner moulding surface (80) of the respective one of the first and second backing plates, wherein the one or more outer surfaces of each of the first and second backing plates comprise opposing first and second lateral surfaces, and wherein the groove (83) of each of the first and second backing plates extends through the inner moulding surface (80) between the opposing first and second lateral surfaces of the corresponding one of the first and second backing plates, the groove (83) extending from the first lateral surface to the second lateral surface.

14. The mould system according to claim 13, wherein the lower web mould part (61) comprises magnetic material, and wherein the first and/or second backing plate (66, 68) further comprises a recess (90) in its outer surface and wherein one or more magnets are arranged in the recess (90) for retaining the backing plate against the lower web mould part (61) during moulding.

15. The mould system according to claim 14, wherein the recess (90) of the backing plate is located in an opposing back surface (96) that is substantially parallel to the inner moulding surface of the backing plate.

16. The mould system according to claim 13, wherein the outer surfaces of each backing plate comprise two opposing lateral surfaces (98, 100), and wherein the groove (83) is extending throughout the inner moulding surface (80) between the two opposing lateral surfaces (98, 100) of the backing plate.

17. The mould system according to claim 13, wherein the first downwardly extending moulding surface portion (72) and/or the second downwardly extending moulding surface portion (73) comprises a ledge (84) which forms part of the moulding surface of the lower web mould part (61).

18. The method according to claim 7, wherein the core material (63) comprises balsawood or a foamed polymer.

19. The method according to claim 12, wherein at least one of the first insert and the second insert is substantially wedge shaped.

Description

DESCRIPTION OF THE INVENTION

(1) The invention is explained in detail below with reference to an embodiment shown in the drawings, in which

(2) FIG. 1 shows a wind turbine,

(3) FIG. 2 shows a schematic view of a wind turbine blade,

(4) FIG. 3 shows a schematic view of a cross-section of a wind turbine blade,

(5) FIG. 4 shows a schematic view of a cross-section of a shear web mould system according to the present invention,

(6) FIG. 5 shows a schematic view of a cross-section of another embodiment of a shear web mould system according to the present invention,

(7) FIG. 6 shows a schematic view of a cross-section of another embodiment of a shear web mould system according to the present invention,

(8) FIG. 7 shows a perspective view of a backing plate according to the present invention,

(9) FIG. 8 shows a partially cut-away perspective view of a backing plate according to the present invention,

(10) FIG. 9 shows a perspective view of a backing plate according to another embodiment of the present invention, and

(11) FIG. 10 shows a perspective view of a backing plate according to yet another embodiment of the present invention.

DETAILED DESCRIPTION

(12) FIG. 1 illustrates a conventional modern upwind wind turbine 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 farthest from the hub 8. The rotor has a radius denoted R.

(13) FIG. 2 shows a schematic view of a wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 farthest 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.

(14) 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.

(15) 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.

(16) 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.

(17) The blade is typically made from a pressure side shell part 36 and a suction side shell part 38 that are glued to each other along bond lines at the leading edge 18 and the trailing edge of the blade 20.

(18) FIG. 3 shows a schematic view of a cross section of the blade along the line I-I shown in FIG. 2. As previously mentioned, the blade 10 comprises a pressure side shell part 36 and a suction side shell part 38. The pressure side shell part 36 comprises a spar cap 41, also called a main laminate, which constitutes a load bearing part of the pressure side shell part 36. The spar cap 41 comprises a plurality of fibre layers 42 mainly comprising unidirectional fibres aligned along the longitudinal direction of the blade in order to provide stiffness to the blade. The suction side shell part 38 also comprises a spar cap 45 comprising a plurality of fibre layers 46. The pressure side shell part 38 may also comprise a sandwich core material 43 typically made of balsawood or foamed polymer and sandwiched between a number of fibre-reinforced skin layers. The sandwich core material 43 is used to provide stiffness to the shell in order to ensure that the shell substantially maintains its aerodynamic profile during rotation of the blade. Similarly, the suction side shell part 38 may also comprise a sandwich core material 47.

(19) The spar cap 41 of the pressure side shell part 36 and the spar cap 45 of the suction side shell part 38 are connected via a first shear web 50 and a second shear web 55. The shear webs 50, 55 are in the shown embodiment shaped as substantially I-shaped webs. The first shear web 50 comprises a shear web body and two web foot flanges. The shear web body comprises a sandwich core material 51, such as balsawood or foamed polymer, covered by a number of skin layers 52 made of a number of fibre layers. The second shear web 55 has a similar design with a shear web body and two web foot flanges, the shear web body comprising a sandwich core material 56 covered by a number of skin layers 57 made of a number of fibre layers. The sandwich core material 51, 56 of the two shear webs 50, 55 may be chamfered near the flanges in order to transfer loads from the webs 50, 55 to the main laminates 41, 45 without the risk of failure and fractures in the joints between the shear web body and web foot flange. However, such a design will normally lead to resin rich areas in the joint areas between the legs and the flanges. Further, such resin rich area may comprise burned resin due to high exothermic peeks during the curing process of the resin, which in turn may lead to mechanical weak points.

(20) In order to compensate for this, a number of filler ropes 60 comprising glass fibres are normally arranged at these joint areas. Further, such ropes 60 will also facilitate transferring loads from the skin layers of the shear web body to the flanges. However, according to the invention, alternative constructional designs are possible.

(21) The blade shells 36, 38 may comprise further fibre-reinforcement at the leading edge and the trailing edge. Typically, the shell parts 36, 38 are bonded to each other via glue flanges in which additional filler ropes may be used (not shown). Additionally, very long blades may comprise sectional parts with additional spar caps, which are connected via one or more additional shear webs.

(22) FIG. 4 illustrates a method of manufacturing a shear web for a wind turbine blade according to the present invention. The shear web mould system 70 of FIG. 4 comprises a lower mould part 61 and a first backing plate 66 for forming an outer surface of a first web foot flange of the shear web, and a second backing plate 68 for forming an outer surface of a second web foot flange of the shear web. The lower web mould part 61 has a moulding surface, which defines an outer part of a shear web manufactured via the shear web moulding system. The moulding surface comprises a central portion 71, which is substantially flat, and which is utilised to form a web body of the shear web. Further, the lower web mould part 61 comprises a first side part at a first side end of the lower web mould part 61, the first side part having a first downwardly extending moulding surface portion 72. Similarly, the lower web mould part 61 comprises a second side part at a second side end, the second side part having a second downwardly extending moulding surface portion 73. The first and the second moulding surface portions 72, 73 are diverging from the central portion 71 along at least a part of the elongated lower web mould part 61.

(23) The process according to the present invention may involve arranging a number of first fibre layers 62 on top of the lower web mould part 61 and covering the downwardly extending moulding surface portions 72, 73 of the lower web mould part 61. The first fibre layers 62 form part of an outer skin of the finished shear web. A core material 63, such as balsawood or foamed polymer, is arranged on top of the first fibre layers 62 in the central portion 71 of the lower web mould part 61. Thus, the web body of the shear web may be formed as a sandwich construction having the first fibre layers 62 as a first skin and second fibre layers 64 as a second skin. Further, a first insert 74 may be arranged at the first side end of the lower web mould part 61 and at a first side of the core material 63. The first insert 74 may have a shape so as to provide a gradual transition from the web body to a first web foot flange. Similarly, a second insert 75 may be arranged at the second side end of the lower web mould part 61 and at the first side of the core material 63. The second insert 75 may have a shape so as to provide a gradual transition from the web body to a second web foot flange.

(24) A number of second fibre layers 64 are arranged on top of the core material 63. Further, a third insert 76 may be arranged at the first side end of the lower web mould part 61 and at a second side of the core material 63. The third insert 76 may have a shape so as to provide a gradual transition from the web body to a first web foot flange. Similarly, a fourth insert 77 may be arranged at the second side end of the lower web part 61 and at the second side of the core material 63. The fourth insert 77 may have a shape so as to provide a gradual transition from the web body to a second web foot flange. Additionally, a number of third fibre layers 78 may be provided for the first web foot flange, and a number of fourth fibre layers 79 may be provided for the second web foot flange. The additional fibre layers 78, 79 may form the bonding surfaces of the web foot flanges. An infusion mesh and/or peel ply may be applied on top of the third and/or fourth fibre layers prior to arranging the backing plates in their positions, or they may replace the third and/or fourth fibre layers.

(25) Once the first fibre reinforcement layers 62 making up the first skin of the shear web body and the first sides of the web foot flanges, and optionally the core material and/or any inserts, are arranged on top of the lower web mould part 61, the first backing plate 66 is clamped against the first fibre layers 62 and the first downwardly extending moulding surface portion 72 of the lower web mould part 61 by use of a first clamp 67. Similarly, the second backing plate 68 is clamped against the first fibre layers 64 and the second downwardly extending moulding surface portion of the lower web mould part 61 by use of a second clamp 69. Each backing plate 66, 68 comprises a respective inner moulding surface 80a, 80b and a groove 83a, 83b extending throughout the moulding surface between two opposing lateral surfaces (best seen in FIG. 9).

(26) The second fibre layers 64 making up the second skin of the shear web body and the second sides of the web foot flanges may be wrapped around a top part of the backing plates 66, 68, or they may be retained against the moulding surfaces of the two backing plates by retaining means, such as a tackifier, a clamp, or magnets.

(27) Once the fibre material 62, 64, 78, 79, core material 63, and possible inserts 74, 75, 76, 77 have been arranged, a vacuum foil (not shown) is arranged on top of the material and the shear web mould system 70, and in a next step, not shown, a vacuum source is connected to the mould cavity, and the mould cavity is evacuated by use of the vacuum source. The mould cavity is further connected to a resin source, and liquid resin is injected into the mould cavity so as to wet the fibre material and the core material. The resin is supplied to the mould cavity between the backing plates 66, 68 and the lower mould part 61 via each of the grooves 83a, 83b of the first and second backing plates 66, 68. Subsequently, the resin is cured or hardened to form the shear web.

(28) FIG. 5 illustrates another embodiment of a mould system of the present invention (only one end shown in cross sectional view). Here, the lower mould part 61 comprises a ledge 84 within the downwardly extending moulding surface portion 72. The ledge 84 may define an end section of the side of the web foot flange and/or may be used for carrying the external web foot flange. In such a setup, it might not be necessary to use clamps. The backing plate 66 further comprises a recess 90 wherein a magnet 88 is arranged in the recess for retaining the backing plate 66 in its position during moulding. In such embodiments it is preferred that the lower mould part 61 comprises steel or substantially consists of steel. A vacuum bag 86 is placed on top of the array of fibre layers and core material on the lower web mould part and over the back surface 96 of the backing plate 66.

(29) An alternative embodiment of a mould system of the present invention is illustrated in FIG. 6 (only one end shown in cross sectional view). The web mould system of FIG. 6 comprises both a lower web mould part 61 and an upper web mould part 65. The web mould parts may for instance comprise a core part made of a foamed polymer, which is covered by a hard surface coating, e.g. a polyurea material. The upper web mould part 65 comprises a moulding surface with a central portion 91, which is substantially flat, a first upwardly extending moulding surface portion 93 at a first end of the upper web mould part 65, and a second upwardly extending moulding surface portion at a second end of the upper web mould part (not shown).

(30) The fibre material 62, 64 and core material 63 forming part of the finished shear web is arranged between the lower web mould part 61 and the upper web mould part 65. The lower web mould part 61 is provided with a ledge 84, for defining an end section of the first side of the web foot flange and/or may be used for carrying the external web foot flange. As in the previously described embodiment, the backing plate 66 contains a groove 83 extending between opposing outer lateral surfaces. A vacuum bag 86 is arranged on top of the two web mould parts 61, 65 and the backing plate 66. Resin is then injected through the groove 83 and finally hardened or cured in order to form the final shear web.

(31) The reinforcement fibre material described for the various embodiments is preferably glass fibres. However, it could also be other suitable fibre reinforcement material, such as carbon fibres. While the various embodiments have been shown for shear webs having a rounded transition from the web body to the web foot flange, it is also recognized that an angled configuration between the two parts may be utilised instead.

(32) FIGS. 7 and 8 further illustrate some details of a backing plate 66 according to one embodiment of the present invention, wherein FIG. 8 is a cut-away perspective view of the backing plate 66 cut open along the plane A in FIG. 7. The backing plate 66 comprises a moulding surface 80 which faces the mould cavity during moulding of the shear web according to the present invention. It also comprises an opposing outer back surface 96 that is substantially parallel to the inner moulding surface and facing away from the mould cavity during operation. Also, the backing plate comprises a lateral surface 98 containing an opening 92. As can be seen in FIG. 8, the opening 92 is part of an integrated channel 82 leading to an opening 94 in the moulding surface 80 of the backing plate. Thus, during operation, resin flows through the opening 92, through the channel 82, through the opening 94 and finally into the mould cavity to mould the shear web.

(33) FIG. 9 shows a perspective view of a backing plate 66 according to another embodiment of the present invention. The backing plate 66 comprises a moulding surface 80 which faces the mould cavity during moulding of the shear web according to the present invention. It also comprises an opposing back surface 96 that is substantially parallel to the inner moulding surface 80 and facing away from the mould cavity during operation. The backing plate 66 of FIG. 9 comprises a first lateral surface 98 and an opposing second lateral surface 100. It further comprises a third lateral surface 102 and an opposing fourth lateral surface 104. A groove 83 is extending across the moulding surface 80 between the two opposing lateral surfaces 98, 100. In this way, resin can be supplied to the mould cavity via the groove 83 from one or both lateral surfaces of the backing plate. This could be done, for example, by inserting a pipe or hose into the opening in one or both of the lateral surfaces 98, 100.

(34) The invention has been described with reference to advantageous 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, which is defined by the claims.

(35) FIG. 10 shows a side view of a backing plate 66′ according to yet another embodiment of the present invention. The backing plate 66′ comprises a moulding surface 80′ which faces the mould cavity during moulding of the shear web according to the present invention. It also comprises an opposing back surface 96′ that is substantially parallel to the inner moulding surface 80′ and facing away from the mould cavity during operation. A groove 83′ is extending across the moulding surface 80′ between two transverse sides of the backing plate 66′. In this way, resin can be supplied to the mould cavity via the groove 83′ from one or both lateral surfaces of the backing plate in a similar way to that described in relation to FIG. 9. As shown in this embodiment, a recess may be formed in one of the surfaces of the backing plate, e.g. as shown in the back surface 96′. A magnet 88′ may be inserted in the recess, which may be closed or locked in place by use of a closure 89 or lid.

(36) A height h of the groove 83, 83′ may for instance be between 5 mm and 20 mm, e.g. around 12 mm. The width w of the groove 83, 83′ may be between 15 mm and 55 mm, e.g. around 31 mm or 32 mm. The area of the groove may be between 100 mm.sup.2 and 500 mm.sup.2, e.g. around 250 mm.sup.2.

(37) The invention has been described with reference to advantageous 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, which is defined by the claims.

LIST OF REFERENCE NUMERALS

(38) 4 tower 6 nacelle 8 hub 10 blades 14 blade tip 16 blade root 18 leading edge 20 trailing edge 30 root region 32 transition region 34 airfoil region 36 pressure side shell part 38 suction side shell part 40 shoulder 41 spar cap 42 fibre layers 43 sandwich core material 45 spar cap 46 fibre layers 47 sandwich core material 50 first shear web 51 sandwich core material of shear web 52 skin layers 55 second shear web 56 sandwich core material of second shear web 57 skin layers of second shear web 60 filler ropes 61 lower mould part 62 first fibre layers 63 core material 64 second fibre layers 65 upper mould part 66, 66′ first backing plate 67 first clamp 68 second backing plate 69 second clamp 70 web mould system 71 central portion 72 first downwardly extending moulding surface portion 73 second downwardly extending moulding surface portion 74 first insert 75 second insert 76 third insert 77 fourth insert 78 third fibre layers 79 fourth fibre layers 80, 80′ inner moulding surface of backing plate 82 channel 83, 83′ groove 84 ledge 86 vacuum foil 88, 88′ magnet 89 closure 90 recess 91 central portion of moulding surface of upper web mould part 92 opening in side surface 93 upwardly extending moulding surface portion of upper web mould part 94 opening in inner moulding surface 96, 96′ back surface of backing plate 98 first lateral surface of backing plate 100 second lateral surface of backing plate 102 third lateral surface of backing plate 104 fourth lateral surface of backing plate R rotor radius r distance from hub