A FLEXIBLE PREFORM MOULD FOR MANUFACTURING A PREFORM FOR A WIND TURBINE BLADE

Abstract

A preform mould (90) is provided for manufacturing a preform for a wind turbine blade. The preform mould (90) comprises one or more support elements (70) and a plurality of strip members (88) comprising a top surface, a groove (64), a tongue (66), and preferably a sealing member arranged in the groove (64). The strip members (88) are arranged in juxtaposition such that the tongue (66) of a strip member (88) is releasably fixed within the groove (64) of an adjacent strip member (88).

Claims

1. A preform mould (90) for manufacturing a preform for a wind turbine blade, the preform mould (90) comprising one or more support elements (70) and a plurality of strip members (88) arranged on the one or more support elements (70), wherein at least one of the strip members (88) comprises: a top surface extending between a first lateral edge (91) and an opposing second lateral edge (92), a groove (64) extending along the first lateral edge (91), and a tongue (66) extending along the second lateral edge (92), wherein the strip members (88) are arranged in juxtaposition, and wherein the tongue (66) of a strip member (88) is releasably fixed within the groove (64) of an adjacent strip member (88), the respective top surfaces (89) of the strip members (88) forming a moulding surface (87) for moulding the preform.

2. A preform mould (90) according to claim 1, wherein the strip member further comprises a sealing member (68) arranged in the groove (64).

3. A preform mould (90) according to claim 2, wherein the tongue (66) of a strip member (88) is releasably fixed within the groove (64) of an adjacent strip member (88) such that the tongue (66) abuts the sealing member.

4. A preform mould (90) according to claim 1, wherein the tongue (66) has an at least partially circular cross section.

5. A preform mould (90) according to claim 1, wherein the groove (64) is upwardly open and the tongue (66) is projecting downwardly.

6. A preform mould (90) according to claim 1, wherein the groove (64) comprises opposing inner side walls, wherein a recess (67) is provided in each of the opposing inner side walls for receiving the tongue (66) in a locking arrangement.

7. A preform mould (90) according to claim 2, wherein the groove (64) comprises opposing shoulders for retaining the sealing member.

8. A preform mould (90) according to claim 2, wherein the sealing member is a gasket, preferably comprising a silicone material.

9. A preform mould (90) according to claim 1, wherein the moulding surface (87) is substantially gas-tight.

10. A preform mould (90) according to claim 1, wherein the strip member (88) comprises a first downward projecting leg near the first lateral edge (91) and a second downward projecting leg near the second lateral edge (92).

11. A preform mould (90) according to claim 1, wherein the groove (64) is formed between a downward projecting first leg and an upward projecting arm of the strip member (88).

12. A preform mould (90) according to claim 11, wherein the upward projecting arm is elastically displaceable to receive the tongue (66) of an adjacent strip member (88) in the groove (64) in a locking arrangement.

13. A preform mould (90) according to claim 1, wherein the strip members (88) comprise glass fibres.

14. A preform mould (90) according to claim 1, wherein a cavity between the lateral edges of adjacent strip members (88) is filled with a filler, such as a silicone filler, at least along part of the respective lateral edges.

15. A method of manufacturing a preform for a wind turbine blade using the preform mould (90) of claim 1, the method comprising the steps of laying a fibre material, and optionally a binding agent, on at least part of the moulding surface (87), and applying negative pressure to the fibre material and optionally binding agent for consolidating the preform.

16. A method of manufacturing a preform for a wind turbine blade according to claim 15, wherein the method further comprises the step of heating the fibre material and the binding agent to a temperature of between 40 and 200° C., such as 100-130° C., to form the preform.

17. A method of manufacturing a wind turbine blade part, the method comprising: manufacturing one or more preforms according to the method of claim 15, arranging the preforms in a blade mould cavity, optionally together with additional material, infusing resin to the blade mould cavity, curing or hardening the resin in order to form the blade part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0086] The invention is explained in detail below with reference to embodiments shown in the drawings, in which

[0087] FIG. 1 shows a wind turbine,

[0088] FIG. 2 shows a schematic view of a wind turbine blade,

[0089] FIG. 3 shows a schematic view of an airfoil profile through section I-I of FIG. 4,

[0090] FIG. 4 shows a schematic view of the wind turbine blade, seen from above and from the side,

[0091] FIG. 5 is a perspective drawing of a preform mould according to the present invention,

[0092] FIG. 6 is a side view of a strip member according to the present invention,

[0093] FIG. 7 is a side view of plurality of strip members in a first arrangement,

[0094] FIG. 8 is a side view of plurality of strip members in a second arrangement,

[0095] FIG. 9 is a side view of plurality of strip members in a third arrangement,

[0096] FIG. 10 is an enlarged side view of part of the strip member of FIG. 6,

[0097] FIG. 11 is a perspective drawing of an arrangement of support elements for a preform mould according to the present invention,

[0098] FIG. 12 is a perspective drawing of a blade mould for lay up of preforms according to the present invention,

[0099] FIG. 13 is a perspective drawing of another embodiment of a preform mould according to the present invention, illustrated without the strip members, and

[0100] FIG. 14 is a perspective drawing of the preform mould of FIG. 13 illustrated with the strip members.

DETAILED DESCRIPTION

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] FIGS. 3 and 4 depict parameters which are used to explain the geometry of the wind turbine blade according to the invention. 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.

[0107] 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 (or suction side camber) and lower camber (or pressure side camber), which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

[0108] Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position d.sub.f 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 d.sub.t of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c. Thus, a local relative blade thickness t/c is given as the ratio between the local maximum thickness t and the local chord length c. Further, the position d.sub.p of the maximum pressure side camber may be used as a design parameter, and of course also the position of the maximum suction side camber.

[0109] FIG. 4 shows other geometric parameters of the blade. The blade has a total blade length L. As shown in FIG. 3, the root end is located at position r=0, and the tip end located at r=L. The shoulder 40 of the blade is located at a position r=L.sub.w, and has a shoulder width W, which equals the chord length at the shoulder 40. The diameter of the root is defined as D. The curvature of the trailing edge of the blade in the transition region may be defined by two parameters, viz. a minimum outer curvature radius r.sub.o and a minimum inner curvature radius r.sub.i, which are defined as the minimum curvature radius of the trailing edge, seen from the outside (or behind the trailing edge), and the minimum curvature radius, seen from the inside (or in front of the trailing edge), respectively. Further, the blade is provided with a prebend, which is defined as Δy, which corresponds to the out of plane deflection from a pitch axis 22 of the blade.

[0110] FIG. 5 is a schematic perspective drawing of a preform mould 90 according to the present invention. The preform mould 90 comprises a support element 70 and nine strip members 88a-i arranged on the support element 70. Each of the strip members 88a-i has a top surface 89 extending between a first lateral edge 91 and an opposing second lateral edge 92. Together, the top surfaces of the respective strip members form a moulding surface 87 for moulding a preform for a rotor blade moulding process. The moulding surface 87 extends between a left edge 102, a right edge 104, a rear edge 106 and a front edge 108. FIG. 5 also illustrates the length L and width W of the top surface 89 of the strip member 88a.

[0111] As best seen in FIG. 6, a groove 64 extends along the first lateral edge 91 substantially parallel to the same. The groove 64 is provided for receiving a tongue 66 of an adjacent strip member 88. The tongue 66 extends along the second lateral edge 92, substantially parallel to the same. In the embodiment shown in FIG. 6, the tongue 66 has an at least partially circular cross section. As seen in FIG. 6b, a sealing member 68 such as a silicone gasket may be arranged in the groove 64. The groove 64 is open towards the top of the strip member 88 and the tongue 66 is projecting downwards.

[0112] The strip member of FIG. 6 also comprises a first downward projecting leg 93 near the first lateral edge 91 and a second downward projecting leg 95 near the second lateral edge 92. The groove 64 is preferably formed between the downward projecting first leg 93 and an upward projecting arm 99 of the strip member 88, as best seen in FIG. 10. The upward projecting arm 99 may be elastically displaceable to receive the tongue 66 of an adjacent strip member 88 in the groove 64 in a locking arrangement.

[0113] FIG. 7 illustrates strip members 88a-c arranged in juxtaposition, wherein the tongue 66b of a strip member 88b is releasably fixed within the groove of an adjacent strip member 88c such that the tongue 66b abuts the sealing member 68c. Thus, the respective top surfaces 89a-c of the strip members 88a-c form a moulding surface 87 for moulding the preform.

[0114] While the moulding surface 87 illustrates in FIG. 7 is substantially flat, the strip members of the present invention also enable other configurations. As shown in FIGS. 8 and 9, the moulding surface 87 may be arranged to form a substantially concave surface or a substantially convex surface, respectively. FIG. 9 also illustrates a cavity 100 that is formed between the lateral edges of adjacent strip members 88a-c. In some embodiments, this cavity 100 can be filled with a filler, such as a silicone filler, at least along part of the respective lateral edges (not shown). This may be useful if the mould is covered with a vacuum bag in order to consolidate the preform. In such cases a sealant tape or tacky tape may be used. Advantageously, such tape is in contact with the sealing member 68 for rendering the arrangement vacuum tight. The silicone or epoxy filler may be useful in the area in which the tape is added.

[0115] FIG. 10 is an enlarged side view of the part of a strip member encircled in Fig. The groove 64 comprises opposing inner side walls 65a,b, wherein a recess 67 is provided in each of the opposing inner side walls for receiving the tongue in a locking arrangement. In the embodiment shown in FIG. 10 the groove 64 also comprises opposing shoulders 69 for retaining the sealing member.

[0116] FIG. 11 is a perspective drawing of an arrangement of support elements which may be used for a preform mould according to the present invention. The arrangement of FIG. 11 comprises four support elements 70a-d, each support element comprising a planar member 72 having a front surface 74 and an opposing back surface 76, a curved top surface 78 and an opposing bottom surface 80, and two opposing lateral surfaces 82, 84 (shown for support element 70a). The top surface 78 of each support element is curved, corresponding to a cross sectional profile of a wind turbine blade half or a part thereof. In the embodiment shown in FIG. 11, the support elements 70a-d are arranged substantially parallel to each other and are interconnected by two lateral rails 86a, 86b.

[0117] As illustrated in FIG. 12, the manufactured preforms 98a, 98b, 98c can be laid up in a blade mould 96 to form part of a wind turbine blade, such as the root laminate. It is particularly preferred that the preforms manufactured according to the present invention are used for a blade section starting from the root end of the blade, such as the root region. The preforms 98a, 98b, 98c are arranged in the blade mould cavity 97, usually together with additional fibre material 94. Then, resin is infused to the blade mould cavity 97, which is subsequently cured or hardened in order to form the blade part, such as a blade half.

[0118] FIGS. 13 and 14 illustrate another embodiment of the preform mould of the present invention, wherein FIG. 13 shows the preform mould without the strip members. The preform mould 90 comprises a support element with a plurality of planar members 72 and a plurality of strip members 88 arranged on the support element to form a moulding surface 87 for moulding a preform for a rotor blade moulding process.

[0119] The invention is not limited to the embodiments described herein, and may be modified or adapted without departing from the scope of the present invention.

LIST OF REFERENCE NUMERALS

[0120] 2 wind turbine

[0121] 4 tower

[0122] 6 nacelle

[0123] 8 hub

[0124] 10 blade

[0125] 14 blade tip

[0126] 16 blade root

[0127] 18 leading edge

[0128] 20 trailing edge

[0129] 22 pitch axis

[0130] 30 root region

[0131] 32 transition region

[0132] 34 airfoil region

[0133] 40 shoulder/position of maximum chord

[0134] 50 airfoil profile

[0135] 52 pressure side

[0136] 54 suction side

[0137] 56 leading edge

[0138] 58 trailing edge

[0139] 60 chord

[0140] 62 camber line/median line

[0141] 64 groove

[0142] 65 inner sidewalls of groove

[0143] 66 tongue

[0144] 67 recess

[0145] 68 sealing member

[0146] 69 shoulder

[0147] 70 support element

[0148] 72 planar member

[0149] 74 front surface

[0150] 76 back surface

[0151] 78 top surface of support element

[0152] 80 bottom surface

[0153] 82 lateral surface

[0154] 84 lateral surface

[0155] 86 rail

[0156] 87 moulding surface of preform mould

[0157] 88 strip member

[0158] 89 top surface of strip member

[0159] 90 preform mould

[0160] 91 first lateral edge of top surface

[0161] 92 second lateral edge of top surface

[0162] 93 first leg

[0163] 94 fibre material

[0164] 95 second leg

[0165] 96 blade mould

[0166] 97 blade mould cavity

[0167] 98 preform

[0168] 99 arm

[0169] 100 cavity

[0170] 102 left edge of preform moulding surface

[0171] 104 right edge of preform moulding surface

[0172] 106 rear edge of preform moulding surface

[0173] 108 front edge of preform moulding surface

[0174] c chord length

[0175] d.sub.t position of maximum thickness

[0176] d.sub.f position of maximum camber

[0177] d.sub.p position of maximum pressure side camber

[0178] f camber

[0179] L blade length

[0180] r local radius, radial distance from blade root

[0181] t thickness

[0182] Δy prebend