Wind turbine blade, method of manufacturing wind turbine blade, and use of fabric in composite structure of wind turbine blade

Abstract

A turbine blade and a method of manufacturing the wind turbine, wherein the wind turbine blade comprises a composite structure and a surrounding layer. The composite structure comprises a stack of pultruded elements where an infusion-promoting layer is arranged between adjacent pairs of pultruded elements (18). The infusion-promoting layers have a higher permeability than the surrounding layer so that the resin flows at a higher speed within the stacked structure than in the surrounding layer.

Claims

1. A wind turbine blade for a wind turbine, comprising: at least one composite structure having a length, a width and a thickness, the at least one composite structure comprising a plurality of pultruded elements arranged in at least one stacked structure, wherein at least one infusion-promoting layer is arranged between at least two adjacent pultruded elements within the at least one stacked structure, the at least one infusion-promoting layer has a first permeability parameter, K.sub.1, in a width direction and further has a permeability parameter, K.sub.2, in a length direction, wherein K.sub.2 is less than K.sub.1, at least one surrounding layer arranged relative to the at least one composite structure, the at least one surrounding layer has a second permeability parameter, K.sub.1a in the width direction, K.sub.1 is greater than K.sub.1a, and wherein a first infusion speed, V.sub.1, of a resin through the at least one infusion-promoting layer is greater than a second infusion speed, V.sub.1a, of the resin through the at least one surrounding layer.

2. The wind turbine blade according to claim 1, wherein the at least one infusion-promoting layer is a fabric with unidirectional fibres.

3. The wind turbine blade according to claim 2, wherein the fibres are orientated between 85-95 degrees relative to the length direction.

4. The wind turbine blade according to claim 2, wherein the fabric comprises untwisted yarns.

5. The wind turbine blade according to claim 1, wherein the at least one infusion-promoting layer has an areal weight of 50-300 gram per square meter.

6. The wind turbine blade according to claim 1, wherein the at least one infusion-promoting layer further has a third permeability parameter, K.sub.3, in a thickness direction, wherein K.sub.1 is greater than K.sub.3.

7. The wind turbine blade according to claim 1, wherein a local width of the at least one infusion-promoting layer corresponds to a local width of the at least one stacked structure or one pultruded element.

8. The wind turbine blade according to claim 1, wherein the at least one surrounding layer forms part of the composite structure or an aerodynamic shell of the wind turbine blade.

9. The wind turbine blade according to claim 1, wherein the composite structure forms a spar cap of the wind turbine blade.

10. A method of manufacturing a wind turbine blade, comprising: providing a plurality of pultruded elements, further providing at least one surrounding layer, wherein the at least one surrounding layer has a second permeability parameter, K.sub.1a, in a width direction, arranging the plurality of pultruded elements in at least one stacked structure, wherein at least the infusion-promoting layer is arranged between adjacent pultruded elements within the at least one stacked structure, the at least one infusion-promoting layer has a first permeability parameter, K.sub.1, in the width direction and further has a permeability parameter, K.sub.2, in a length direction, wherein K.sub.2 is less than K.sub.1, introducing resin into the at least one stacked structure and the at least one surrounding layer using an infusion process, and curing the at least one stacked structure with resin to form a composite structure, the composite structure having a length, a width and a thickness, wherein K.sub.1 is greater than K.sub.1a, so that the resin flows through the at least one infusion-promoting layer at a first infusion speed, V.sub.1, and further through the at least one surrounding layer at a second infusion speed, V.sub.1a, wherein V.sub.1 is greater than V.sub.1a.

11. The method according to claim 10, wherein the resin is introduced in a chordwise direction.

12. The method according to claim 10, wherein the plurality of pultruded elements and infusion-promoting layers are laid up in a blade mould or in a separate mould, and cured when placed the blade mould or separate mould.

Description

DESCRIPTION OF THE DRAWING

(1) The invention is described by example only and with reference to the drawings, wherein:

(2) FIG. 1 shows an exemplary embodiment of a wind turbine,

(3) FIG. 2 shows a first embodiment of the wind turbine blade,

(4) FIG. 3 shows a second embodiment of the wind turbine blade,

(5) FIG. 4 shows a first embodiment of the composite structure,

(6) FIG. 5 shows a second embodiment of the composite structure,

(7) FIG. 6 shows the composite structure and aerodynamic shell during resin infusion,

(8) FIG. 7 shows the first embodiment of the composite structure,

(9) FIG. 8 shows a second embodiment of the composite structure,

(10) FIG. 9 shows a third embodiment of the composite structure,

(11) FIG. 10 shows a fourth embodiment of the composite structure,

(12) FIGS. 11a-e show the resin flow through the composite structure during the infusion process, and

(13) FIG. 12 shows a test setup for determining the permeability parameters of the infusion-promoting layer.

(14) In the following text, the figures will be described one by one, and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

DETAILED DESCRIPTION OF THE INVENTION

(15) FIG. 1 shows a wind turbine 1 comprising a wind turbine tower 2 and a nacelle 3 arranged on top of the wind turbine tower 2 using a yaw mechanism 4. The yaw mechanism 4 is configured to yaw the nacelle 3 into a yaw angle. A rotor comprising at least two wind turbine blades 5 mounted to a rotor hub 6 via a pitch mechanism 7. The pitch mechanism 7 is configured to pitch the wind turbine blades 5 into a pitch angle. The rotor hub 6 is rotatably connected to a generator arranged in the wind turbine 1 via a rotor shaft.

(16) Each wind turbine blade 5 comprises a tip end 8 and a blade root 9, wherein the wind turbine blade 5 has an aerodynamic profile defining a leading edge 10 and a trailing edge 11.

(17) FIG. 2 shows a first embodiment of the wind turbine blade 5 where the wind turbine blade 5 is shaped as a full-span blade. The wind turbine blade 5 comprises a spar cap 12 extending from a local first end towards the root end 9 to a local second end towards the tip end 8.

(18) FIG. 3 shows a second embodiment of the wind turbine blade 5 where the wind turbine blade 5 is shaped as a modular blade. The wind turbine blade 5 comprises an inner blade section extending from a first end, e.g. the blade root 9, to a second end 13 and further from a leading edge 10′ to a trailing edge 11′. The wind turbine blade 5 further comprises an outer blade section extending from a first end 14 to a second end, e.g. the tip end 8 and further from a leading edge 10′ to a trailing edge 11′.

(19) Similarly, the spar cap 12′ is split into an inner part arranged in the inner blade section and an outer part arranged in the outer blade section. The two blade sections, incl. the spar cap 12′ parts, are joined at the interface defined by the first and second ends 13, 14.

(20) The wind turbine blade 5 may also be shaped as a partial-pitch blade where the pitch mechanism 7 is arranged at the second end 13. In this configuration, the pitch mechanism 7 is configured to pitch the outer blade section relative to the inner blade section.

(21) FIG. 4 shows a first embodiment of the spar cap 12, 12′ formed by a composite structure 15. Here, the composite structure 15 is manufactured in a separate mould (not shown) and then positioned in a recess 16 in an aerodynamic shell 17 of the wind turbine blade 5. The composite structure 15 is subsequently bonded to the aerodynamic shell 17 using an adhesive or resin infusion.

(22) Here, the composite structure 15 and aerodynamic shell 17 are illustrated as having no curvature in the width direction. However, the composite structure 15 and aerodynamic shell 17 may both be curved in the width direction.

(23) FIG. 5 shows a second embodiment of the composite structure 15′ which is manufactured directly in the recess 16 of the aerodynamic shell 17. Here, a stacked structure is laid up in the recess 16, and then infused with resin. The stacked structure with resin is then set to cure to bond the composite structure 15′ to the aerodynamic shell 17.

(24) A structural component in the form of a shear web 18 is subsequently arranged on the spar cap 12, e.g. the composite structure 15′.

(25) FIG. 6 shows the composite structure 15 and aerodynamic shell 17 during the resin infusion. Here, a stack of six pultruded elements 19 is shown.

(26) A number of fibre layers forms an inner skin 20 of the wind turbine blade 5. Further, a number of fibre layers forms an outer skin 21 of the wind turbine blade 5. A plurality of core elements 22 is arranged between the inner and outer skins 20, 21 to a sandwich structure.

(27) The stack is arranged between the core elements 22, as illustrated in FIG. 6, to form an integrated composite structure. A plurality of infusion-promoting layers 23, 24 is arranged between adjacent pultruded elements 19. Here, some of the infusion-promoting layers 23 extend in the width direction 26 and have a local width that corresponds to the width of a pultruded element 19. Other infusion-promoting layers 24 extend in the thickness direction 28 and have a local width corresponding to the thickness of the stack.

(28) The composite structure 15, e.g. the pultruded elements 19 and the infusion-promoting layers, further extends in the length direction 27, as illustrated in FIG. 6.

(29) The infusion-promoting layers 23, 24 have a permeability parameter, K.sub.1, in the width direction, a permeability parameter, K.sub.2, in the length direction, and a permeability parameter, K.sub.3, in the thickness direction.

(30) Resin is fed into a series of inlet channels 25 arranged on the aerodynamic shell 17 and, optionally, on the composite structure 15. The resin is fed into the inlet channels 25 at a feeding speed, V.sub.0. The resin is then introduced into the aerodynamic shell 17 and further into the composite structure 15 in the width direction.

(31) The resin flows through the infusion-promoting layers 23, and thus the stacked structure, at an infusion speed, V.sub.1. The resin further flows through the surrounding layers, e.g. the inner skin 20, at an infusion speed, V.sub.1a. In this configuration, the infusion speed V.sub.1 is greater than the infusion speed V.sub.1a which ensures that the stacked structure is infused properly.

(32) FIG. 7 shows the first embodiment of the composite structure 15 where the pultruded elements 19 are arranged in a rows and columns. An infusion-promoting layer 23 is arranged between adjacent pultruded elements 19 in each column. Further, an infusion-promoting layer 24 is arranged between adjacent columns of pultruded elements 19.

(33) FIG. 8 shows a second embodiment of the composite structure 15″ where an inner skin 29 is arranged on a first side of the stack of pultruded elements 19. Further, an outer skin 30 is arranged on a second side of the stack of pultruded elements 19. The inner and outer skins 29, 30 each comprise a number of fibre layers extending in the width direction and further in the length direction.

(34) A further infusion-promoting layer 23 is arranged between the inner skin 29 and the stack. Similarly, a further infusion-promoting layer 23 may be arranged between the outer skin 30 and the stack. Here, an infusion-promoting layer 23 is arranged between one column of the stack and the outer skin 30 while another infusion-promoting layer 23′ is arranged between the other column of the stack and the outer skin 30. This infusion-promoting layer 23′ further extends in the thickness direction between the two columns of pultruded elements 19.

(35) FIG. 9 shows a third embodiment of the composite structure 15′″ where the pultruded elements 19 are arranged in a zig-zag pattern. A second row of pultruded elements 19 is offset relative to a first and a third row of pultruded elements, as illustrated in FIG. 9. The infusion-promoting layers 23″ extend along the entire width of a row of pultruded elements 19 to ensure a proper resin infusion of the composite structure.

(36) FIG. 10 shows a third embodiment of the composite structure 15″″ where the pultruded elements 19 are arranged in an offset pattern. A second row of pultruded elements 19 is offset relative to a first row of pultruded elements. A third row of pultruded elements 19 is further offset relative to the second row of pultruded elements, and so forth, as illustrated in FIG. 9. The infusion-promoting layers 23′″ extends along the entire width of a row of pultruded elements 19 to ensure a proper resin infusion of the composite structure.

(37) FIGS. 11a-e show the resin flow through the composite structure 15 and the aerodynamic shell 17 during the infusion process. FIG. 11a shows a cross-section of the composite structure 15 arranged between upper fibre layers and lower fibre layers of the wind turbine blade 5 after completion of the lay-up process.

(38) Here, the lower fibre layers are formed at least the outer skin 21 of the aerodynamic shell 17. The upper fibre layers are formed by the inner skin 20 extending over the composite structure 15. Alternatively, the upper fibre layers may be formed by additional fibre layers extending over the top of the composite structure 15 and further along a portion of the inner skin 20 on both sides of the composite structure 15.

(39) Inlet channels and outlet channels are afterwards positioned on the inner surface and the entire structure is encapsulated in a vacuum bag by sealing off the various edges. A resin infusion system is then coupled to the respective inlets and outlets and air is evacuated from the enclosed space.

(40) For illustrative purposes, only one outlet channel 25a is illustrated in FIGS. 11b-d. Optionally, more than one outlet channel 25a may be positioned above the composite structure as indicated by the dashed lines.

(41) Resin is introduced from the side edge in the chordwise direction, as illustrated in FIG. 11b. During infusion, the front of the resin flow will faster within the composite structure 15 than in the lower and upper fibre layers, as illustrated in FIGS. 11b-d. The permeability parameter, K.sub.1, of the infusion-promoting layers 23 is higher than the permeability parameter, K.sub.1a, of the lower and upper fibre layers, therefore the internal infusion speed, V.sub.1, is greater than the external infusion speed, V.sub.1a, as illustrated in FIG. 11b.

(42) When the resin front reaches the resin-promoting layer 24 between stacks or columns of pultruded elements 19, the resin additionally flows in the thickness direction along the resin-promoting layer 24 while continuing to flow in the chordwise direction. Resin will then enter the lower and upper fibre layers at the interface between the stacks or columns and begin to flow in opposite chordwise directions, as illustrated in FIG. 11d. Excess resin will then enter the outlet channel 25a from opposite sides.

(43) Similarly, when the resin front reaches the opposite side edge of the composite structure 15, the resin will flow in the thickness direction. Resin will then enter the lower and upper fibre layers at the side edge and begin to flow in the opposite chordwise direction towards the outlet channel 25a. The resin may also continue flowing along the inner and outer skins 20, 21 to an outlet channel (not shown) on the aerodynamic shell 17.

(44) This prevents dry spots from forming in the fibre laminate and ensures that the composite structure 15 is correctly infused with resin. FIG. 11e shows the composite structure 15 and the lower and upper fibre layers after infusion. Here, the inlet and outlet channels as well as the vacuum bag are omitted for illustrative purposes. The infused structure is then set to cure.

(45) FIG. 12 shows a test setup for determining the permeability parameters of the infusion-promoting layer 23, 24. Here, the test setup is configured to determine in-plane the first and second permeability parameters, k.sub.1 and k.sub.2, of the infusion-promoting layer 23, 24.

(46) A test sample 23′, 24′ of the infusion-promoting layer 23, 24 is arranged on a substrate 31, e.g. a glass plate or tray. A lid or cover 32 is placed on top of the test sample 23′, 24′ and the spacing between the substrate 31 and the cover 32 is sealed off by means of a seal 33. A vacuum channel 34 is arranged within the enclosed spacing and connected to an outlet 35 for evacuating the enclosed spacing.

(47) Resin is then introduced into the test sample 23′, 24′ via an inlet 36, e.g. at the centre of the test sample 23′, 24′. The permeability of the test sample 23′, 24′ is then measured in-plane using standardised measuring techniques. The first and second permeability parameters, k.sub.1 and k.sub.2, in the respective directions are then determined based on the measurements, as illustrated in FIG. 12.

(48) Test results have surprisingly shown that the present glass fibre fabric with untwisted yarns has an improved resin flow over conventional glass fibre fabrics with twisted yarns. Furthermore, the test results have also surprisingly shown that the present unidirectional fabric has an improved resin flow over conventional biaxial fabrics. The tests have surprisingly shown that the best result is achieved by the combination of a unidirectional glass fibre fabric with untwisted yarns.