System and method for manufacturing a reinforced wind turbine blade

Abstract

The present invention relates to a method and system for manufacturing a wind turbine blade. The method comprising the steps of forming a cured blade element (102) of a first blade shell, forming a cured blade element (102) of a second blade shell, transferring the cured blade element (102) of the first blade shell to a first cradle (92), and transferring the cured blade element (102) of the second blade shell to a second cradle (94). Each cradle comprises a mould body (96, 98) having a moulding surface for abutting against a surface of the cured blade element to advantageously form a seal therebetween.

Claims

1. A method of manufacturing a wind turbine blade, the method comprising the steps of: forming a cured blade element (102) of a first blade shell; forming a cured blade element (102) of a second blade shell; transferring the cured blade element (102) of the first blade shell to a first cradle (92); transferring the cured blade element of the second blade shell to a second cradle (94), wherein each cradle comprises a mould body (96, 98) having a moulding surface (97), and wherein each cured blade element is arranged in its respective cradle such that the moulding surface (97), or a part thereof, abuts against a surface of the cured blade element (102); forming a reinforced section (104) on the cured blade element of the first blade shell in the first cradle; forming a reinforced section (104) on the cured blade element of the second blade shell in the second cradle; closing said first and second blade shells (100) to form a closed wind turbine blade shell; and bonding said first and second blade shells in said closed wind turbine blade shell to form a wind turbine blade.

2. The method according to claim 1, wherein each cured blade element (102) is arranged in its respective cradle such that a section of the moulding surface is placed underneath a part of the cured blade element (102), said part comprising a recess for receiving the reinforced section.

3. The method according to claim 1, wherein each cured blade element is arranged in its respective cradle such that the moulding surface (97), or a part thereof, abuts against a surface of the cured blade element (102) to form a seal therebetween.

4. The method according to claim 1, wherein the mould body (96) comprises a plurality of movable suction cups (100) embedded in the moulding surface (97) for engaging a surface of the cured blade element.

5. The method according to claim 4, wherein the suction cups (100) are movable between an advanced position for engaging a surface of the cured blade element (102) and a retracted position for forcing a surface of the cured blade element (102) against the moulding surface of the mould body (96).

6. The method according to claim 1, wherein the moulding surface of the mould body (96) comprises one or more sealing elements (110).

7. The method according to claim 6, wherein the sealing element (110) is a sealing strip enclosing a section (112) of the moulding surface.

8. The method according to claim 6, wherein each cured blade element (102) is arranged in its respective cradle such that a section of the moulding surface enclosed by the sealing element is placed underneath a part of the cured blade element (102), said part comprising a recess for receiving the reinforced section.

9. The method according to claim 1, wherein the mould body (96, 98) is elastically deformable.

10. The method according to claim 1, wherein the first cradle (92) is hingedly coupled to the second cradle (94).

11. The method according to claim 1, wherein the reinforced section is a main laminate, a spar cap or a spar beam.

12. The method according to claim 1, wherein the method comprises the step of turning said first blade shell relative to said second blade shell to form a closed blade shell, and wherein the bonding step is performed on the closed blade shell to form a wind turbine blade.

13. The method according to claim 1, wherein the method further comprises the step of aligning the first blade shell with the second blade shell such that a leading edge and a trailing edge of the first blade shell are in register with a respective leading edge and a respective trailing edge of the second blade shell during said bonding step.

14. A manufacturing system for the manufacture of a wind turbine blade formed from a pair of cured blade shells bonded together, the system comprising: a first blade mould (72) for forming a cured blade element (102) of a first blade shell; a second blade mould (74) for forming a cured blade element (102) of a second blade shell; a reinforcing station (90) comprising a first cradle (92) for receiving the cured blade element of the first blade shell and for forming a reinforced section (104) on the cured blade element of the first blade shell, and a second cradle (94) for receiving the cured blade element of the second blade shell and for forming a reinforced section (104) on the cured blade element of the second blade shell; and a closing mechanism operable to close said first and second blade shells to form a wind turbine blade, wherein each cradle (92, 94) comprises a mould body (96, 98) having a moulding surface, and wherein each cured blade element (102) is arrangeable in its respective cradle such that the moulding surface, or a part thereof, abuts against a surface of the cured blade element.

15. The manufacturing system according to claim 14, wherein each cured blade element (102) is arrangeable in its respective cradle such that a section of the moulding surface is placed underneath a part of the cured blade element (102), said part comprising a recess for receiving the reinforced section.

16. The manufacturing system according to claim 14, wherein each cured blade element (102) is arrangeable in its respective cradle such that the moulding surface, or a part thereof, abuts against a surface of the cured blade element to form a seal therebetween.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying 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 an airfoil profile of the blade of FIG. 2;

(5) FIG. 4 is a perspective view of a blade shell manufactured using the method of the present invention comprising a cured blade element and a reinforced section;

(6) FIG. 5 is a perspective view of a manufacturing system according to the present invention,

(7) FIG. 6 is a perspective view of a mould body according to the present invention,

(8) FIG. 7 is a partial, enlarged view of a mould body according to the present invention,

(9) FIG. 8 is a partial, sectional view of a mould body according to the present invention,

(10) FIG. 9 is a perspective view of another embodiment of a mould body according to the present invention,

(11) FIG. 10 is a perspective view of another embodiment of a mould body according to the present invention,

(12) FIG. 11 shows different sectional views of a mould body according to the present invention, and

(13) FIG. 12 is a sectional view of another embodiment of a mould body according to the present invention.

(14) 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 furthest from the hub 8. The rotor has a radius denoted R. While a three-bladed upwind wind turbine design is presented here, it will be understood that the invention may equally apply to blades of other wind turbine designs, e.g. two-bladed, downwind, etc.

(15) FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to the invention. 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 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

(16) 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.

(17) 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.

(18) 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.

(19) FIG. 3 shows a schematic view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use—i.e. during rotation of the rotor—normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber and lower camber, which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

(20) Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position df of the maximum camber f, the maximum airfoil thickness t, which is the largest diameter of the inscribed circles along the median camber line 62, the position dt of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c.

(21) The wind turbine blades may further comprise pre-bent blades, wherein the body of the blade is designed having a bend or curve, preferably in the direction of the pressure side of the blade. Pre-bent blades are designed to flex during operation of the wind turbine, such that the blades straighten under the effect of optimum wind speed at the wind turbine. Such a pre-bent blade will provide improved performance during wind turbine operation, resulting in numerous advantages, e.g. tower clearance, swept area, blade weight, etc.

(22) One way of constructing a wind turbine blade 10 comprises forming the blade 10 as two separate shell pieces—a first piece which substantially forms the pressure or upwind side 52 of the blade 10, and a second piece which substantially forms the suction or downwind side 54 of the blade 10. Such shell pieces are normally formed in separate open blade moulds conforming to the aerodynamic shapes of the respective sides, and are subsequently joined together by closing the blade moulds to form a wind turbine blade 10.

(23) FIG. 4 shows a perspective view of a blade shell 100 which can be manufactured using the method and system of the present invention, which is made up of a cured blade element 102, which comprises an aerodynamic shell part and a root laminate, and an integrated reinforced section 104, which forms a spar cap or main laminate of the blade shell. The cured blade element 102 may also comprise a number of sandwich core material arranged on lateral sides of the reinforced section 104 (not shown). It will be understood that the invention may apply for the manufacture of straight blades or of pre-bent blades. FIG. 4 generally shows the top surface of the blade shell or cured blade element according to the present invention, while its bottom surface is facing downward in the view of FIG. 4.

(24) An embodiment of a manufacturing system for the manufacture of a wind turbine blade according to the invention is illustrated in FIG. 5. The manufacturing system comprises a blade moulding station 70 and a reinforcing station 90. The blade moulding station 70 comprises a set of first and second blade shell moulds 72, 74. The blade moulds 72, 74 comprise respective first and second internal surfaces 76, 78 which are arranged to produce first and second shaped blade shells having an aerodynamic profile substantially corresponding to respective upwind (or pressure side) and downwind (or suction side) halves of a wind turbine blade.

(25) During manufacture of a wind turbine blade, a lay-up operation is performed at the blade moulding station 70, wherein a plurality of layers of a preferably fibre-based composite material are applied to the internal surfaces 76, 78 of the blade moulds 72, 74. The fibre layers are applied to conform to the mould shape, and may be arranged at various thicknesses or densities dependent on the structural requirements of the wind turbine blade to be manufactured.

(26) In the embodiment shown in FIG. 5, the blade moulding station 70 is provided with an automatic fibre lay-up apparatus 80, which allows for machine-controlled lay-up of the layers of fibre-based material in the blade moulds 72, 74. The automatic fibre lay-up apparatus comprises at least one fibre applicator device suspended on a moveable gantry provided above the blade moulds 72, 74, the at least one fibre applicator device operable to move along the length of the blade moulds 72, 74 to apply fibre layers, e.g. fibre tape, to the internal surfaces 76, 78 of the blade moulds 72, 74.

(27) However, it will be understood that the manufacturing system of the invention may be implemented using any suitable lay-up mechanism, e.g. hand lay-up. Furthermore, the layup operation may comprise the use of pultruded elements or pre-pregs of composite material within the blade moulds, either as an alternative to or in addition to the layers of fibre-based material.

(28) Once sufficient layers of the fibre-based material have been applied to the surfaces of the moulds 72, 74, a curing operation is then performed to cure the fibre layers to a relatively hardened state. In one embodiment, this may comprise applying a cover or vacuum bag over the fibre layers to form a container, and subsequently applying a vacuum pressure to the interior of the container defined by the vacuum bag and the surface of the blade mould 72, 74.

(29) A curing resin is then infused or injected into the interior of the container, the resin spreading throughout the fibre layers by the action of the vacuum pressure. The resin is then allowed to cure and accordingly harden and join the layers of fibre-based material into a cured blade element, preferably comprising a cavity for later integration of a reinforced section (not shown); the cured blade element having a structural profile corresponding to the shape of the surface of the blade moulds 72, 74.

(30) The term “cured blade element” is used herein to refer to blade elements which have been substantially cured by the curing operation, preferably to a level where the blade elements can be handled without undergoing significant deformation of the shell structure. The duration of the curing operation performed will depend on the type of curing resin used in the manufacture of the blade shells, but may be of the order of 2-3 hours using standard resins. However, it will be understood that the blade elements themselves may continue to undergo a curing process within the body of the blade elements for several hours after the denoted curing operation.

(31) Accordingly, once the blade elements have substantially cured, the associated cover or vacuum bag may be removed, and the cured blade elements can be demoulded from the blade moulds 72, 74. To demould the blade elements, any manufacturing equipment which may be provided above the blade moulds 72, 74, e.g. automatic fibre applicator device 80, may be removed, and a lifting apparatus (not shown) may be positioned above the blade elements contained in the blade moulds 72, 74. The lifting apparatus is operable to lift the cured blade elements out of the blade moulds 72, 74, and to transfer the cured blade elements to the reinforcing station 90, where reinforcing and optionally post-moulding operations may be performed.

(32) It will be understood that the transferring operation may be performed using any suitable lifting apparatus for the transferral of a wind turbine blade elements, e.g. a vacuum lifting device, a crane, a manual lifting operation, etc.

(33) The reinforcing station 90 comprises a first cradle 92 and a second cradle 94 each comprising a mould body 96, 98 supported by respective support frames. Each cured blade element can be arranged in its respective cradle for forming a reinforced section on the cured blade element of each blade shell. Forming of the reinforced section will typically include the lay-up of additional fibre material on the cured blade element, preferably in cavity prepared therein, followed by vacuum-assisted resin infusion and curing.

(34) The first and second cradles 92, 94 are arranged in a parallel longitudinal relationship, the first cradle 92 being coupled to the second cradle 94 via a plurality of hinging mechanisms 95. The first cradle 92 is arranged to be hinged relative to the second cradle 94, such that the first cradle 92 is positioned above the second cradle 94 to form a closed arrangement. The first cradle 92 may also be translationally movable relative to the second cradle 94 when in the closed position, in order to correct the alignment between the first and second cradles 92, 94. The first cradle 92 may be moveable along the horizontal and/or vertical axis with respect to the second cradle 94.

(35) Examples of post-moulding operations which can be performed at the reinforcing station 90 on the blade shells can include, but are not limited to: a blade shell repair operation, involving a repair of any minor defects in a cured blade shell; a blade shell cutting or grinding operation, wherein a portion of a surface of the cured blade shell can be cut away or ground to present a relatively smooth profile; a blade root flange coupling operation, wherein a pair of blade root flanges which are provided on first and second blade shells are coupled together to form a single integral blade root flange; a gluing operation, wherein an adhesive is applied to a surface of a blade shell to bond components or blade shells together; a coating operation, wherein an external surface of a blade shell is coated with a coating layer, e.g. a gel coat or suitable erosion resistant material; a laminate installation operation, wherein a main laminate or other element of the interior of a wind turbine blade may be fixed to an internal surface of one of the blade shells for positioning in the interior of a wind turbine blade; an overlamination operation; installation of internal blade components, e.g. load or deflection monitoring sensors, lightning protection systems, etc.; a survey of blade shell geometry; a secondary curing operation in, for example, an oven; or any other suitable manufacturing or assembly operations.

(36) FIG. 6 illustrates one embodiment of a cradle 92 according to the present invention. The cradle 92 comprises a mould body 96 having a moulding surface 97. The mould body 96 is supported by a support frame 99. The mould body 96 also comprises a plurality of movable suction cups 100 embedded in the moulding surface for engaging a surface of the cured blade element. This is best seen in the partial sectional view of FIG. 8 taken along the hatched line in FIG. 6.

(37) By contrast to FIG. 6, FIG. 8 shows the mould body in a situation where the cured blade element 102 has already been received therein. The suction cup 100 is movable, e.g. by a linearly displaceable rod 105, between an advanced position for engaging a bottom surface of the cured blade element 102 (see FIG. 8a) and a retracted position for forcing a bottom surface of the cured blade element 102 against the moulding surface of the mould body 96 (see FIG. 8b). In the embodiment illustrated, the suction cup 100 is movable via an airtight sheath 103 provided within the mould body, allowing linear movement of the rod 105 to which the suction cup 100 is fixed. This arrangement allows for improved resin infusion during the formation of the reinforced section since the tightness of the arrangement no longer depends on the tightness of the cured blade element. The moulding surface abutting against a surface of the cured blade element 102 to form a seal therebetween provides the require tightness independent of the thickness or material of the cured blade element. FIG. 8b also illustrates a vacuum bag 120 held in place by adhesive tape 122, which is applied on an edge of the mould body prior to vacuum-assisted resin infusion. During the vacuum-assisted resin infusion, the shell part will be pressed towards the mould surface to keep the aerodynamic shape of the profile. In this embodiment, it is advantageous that the sheaths of the suction cups are airtight.

(38) The partial enlarged view of FIG. 7 illustrates another embodiment of the present invention. Here, the support frame 99 comprises a stationary support member 99a and a movable support member 99b hinged to the stationary support member 99a via a hinge 108. In particular in combination with a deformable mould body 96, this mechanism may be used to adjust the leading and trailing edges of the blade shells prior to closing and bonding.

(39) FIG. 9 illustrates another embodiment of a cradle 92 according to the present invention. Again, the cradle 92 comprises a mould body 96 having a moulding surface 97. The mould body 96 is supported by a support frame 99. The moulding surface 97 of the mould body 96 comprises a sealing element 110 in the form of a sealing strip enclosing a section 112 of the moulding surface. Thus, the cured blade element can be arranged in the cradle 92 such that the section 112 of the moulding surface enclosed by the sealing element 110 is placed underneath a part of the cured blade element, said part comprising a recess for receiving the reinforced section. This is best seen in the sectional views of FIG. 11, which is taken along the hatched line in FIG. 9. The embodiment shown in FIG. 10 additionally comprises a plurality of movable suction cups 100 embedded in the moulding surface for engaging a surface of the cured blade element.

(40) FIG. 11 shows different sectional views of one embodiment of a mould body 96 according to the present invention, taken along the hatched line in FIG. 9, but shown without the support frame. As seen in FIG. 11a, the mould body 96 comprises a groove 116 enclosing a section 112 of the moulding surface. A sealing strip 110 is arranged in the groove 116, see FIG. 11b. As seen in FIG. 11c, a cured blade element 102 is placed into the mould body 96, the cured blade element 102 comprising a recess 114 for later forming of an integrated reinforced section therein. The section 112 of the moulding surface enclosed by the sealing element 110 is located underneath the part of the cured blade element 102 which comprises the recess 114 for receiving the reinforced section 104 (see FIG. 11d). Thus, an efficient vacuum-assisted resin transfer is enabled by the seal provided underneath the relevant part of the cured blade element 102.

(41) FIG. 12 shows a sectional view of another embodiment of a mould body for a cradle according to the present invention. Here, the mould body 116 is provided such that it contacts only part of the lower surface of a cured blade element 102. Again, a sealing strip 110 is provided to enclose part of the moulding surface which is provided for forming a reinforced section 104 on the cured blade element 102. In this embodiment, the cradle may comprise a plurality of movable suction cups 100 placed outside of the enclosed sealed section 104 for engaging a surface of the cured blade element 102 and to secure the cross section geometry. In this embodiment, the suction cups 100 may be arranged outside of the mould body 116. A local vacuum bag may be fastened using an adhesive tape on the cured blade element 102 around the reinforced section (not shown). In this case the suction cups and their respective linearly displaceable rods 105 could be provided even without airtight sheaths.

(42) The invention is not limited to the embodiment described herein, and may be modified or adapted without departing from the scope of the present invention.