Wind turbine blade

Abstract

Provided is a turbine blade, with a first and a second elongated web connected to an upper and a lower half shell, with each web including an upper and a lower flange connecting the respective web to the respective half shell, and with the first and second webs being supported by respective first and second reinforcement structures, which reinforcement structures extend in the lengthwise direction of the blade, wherein each first and second reinforcement structure supporting the first and second web includes at least one stack composed of several pultruded composite strips including carbon fibers with the strips being fixed in a resin matrix, wherein each at least one stack composed of the pultruded composite strips is an integral part of the respective first and second web and builds the respective flange, which is attached to the inner layer of the respective upper and lower shell.

Claims

1. A wind turbine blade, with a generally hollow blade body comprising: an upper half shell and a lower half shell, and a first elongated web and a second elongated web each extending in a lengthwise direction of the wind turbine blade and being disposed between and connected to the upper half shell and the lower half shell, the first elongated web and the second elongated web each comprising: a web body and an upper flange including a first reinforcement structure and a lower flange including a second reinforcement structure integrally attached to ends of the web body, the upper flange and the lower flange connecting the respective elongated web to the respective half shell, and with the first elongated web and the second elongated web being supported by the first reinforcement structure and the second reinforcement structure, respectively, relative to the respective half shell, the first reinforcement structure and the second reinforcement structure extending in the lengthwise direction of the wind turbine blade, wherein each of the first reinforcement structure and the second reinforcement structure supporting the first elongated web and the elongated second web comprises at least one stack composed of several pultruded composite strips comprising carbon fibers with the several pultruded composite strips being fixed in a resin matrix, each at least one stack of the respective reinforcement structures comprises biaxial glass and/or carbon fiber layers between adjacent strips within the at least one stack which layers are infused with resin, further wherein the resin matrix of each at least one stack composed of the several pultruded composite strips is integral with a resin matrix of the web body of the elongated webs so that the at least one stack is an integral part of the respective first elongated web and the second elongated web and builds the respective flange, which is attached to an inner layer of the respective upper or lower half shell; wherein the inner layer is arranged closer to an outer layer in an area where the respective flange of the respective web is attached to the inner layer, and a stiffening means entirely disposed in the area and between the outer layer and the inner layer.

2. The wind turbine blade according to claim 1, wherein both webs extend over a same length of the wind turbine blade, or the second web is arranged closer to a trailing edge of the wind turbine blade and extends only along a part of the trailing edge.

3. The wind turbine blade according to claim 1, wherein each reinforcement structure comprises more than one stack arranged in parallel.

4. The wind turbine blade according to claim 1, wherein the stiffening means comprises several glass fiber layers or a core element embedded in resin.

5. The wind turbine blade according to claim 4, wherein several further core elements are provided between the outer layer and the inner layer of the respective upper half shell and lower half shell.

6. The wind turbine blade according to claim 5, wherein the core element or the several further core elements are made of foam, wood, polymer or a composite material.

7. A wind turbine comprising several wind turbine blades according to claim 1.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

(2) FIG. 1 shows a principal sketch of a wind turbine;

(3) FIG. 2 shows a view of an inventive wind turbine blade of a first embodiment comprising a first web and a second web;

(4) FIG. 3 shows a view of an inventive wind turbine blade of a second embodiment comprising a first web and a second web;

(5) FIG. 4 shows a cross section through the blade of FIG. 2 along the line IV-IV;

(6) FIG. 5 shows an enlarged view of the section V of FIG. 3 of a first embodiment; and

(7) FIG. 6 shows an enlarged view of the section V of FIG. 3 of a second embodiment.

DETAILED DESCRIPTION

(8) FIG. 1 shows a principal sketch of a wind turbine 1 comprising a tower 2, a nacelle 3 mounted on top of the tower 2 and a rotor 4 comprising three wind turbine blades 5 attached to a hub 6, which is operatively coupled to a generator arranged in the nacelle 3, which generator is driven by the rotational energy of the rotor 4 for producing electric power as commonly known.

(9) Embodiments of the invention relate to the setup of the wind turbine blades 5.

(10) FIG. 2 shows a principle drawing of a turbine blade 5 of a first embodiment with a root 7 for attaching the blade 5 to the hub and with a tip 8 at the other blade end. It furthermore comprises a leading edge 9 and a trailing edge 10.

(11) FIG. 3 shows a principle drawing of a turbine blade 5 of a second embodiment with a root 7 for attaching the blade 5 to the hub and with a tip 8 at the other blade end. It furthermore comprises a leading edge 9 and a trailing edge 10.

(12) The blade 5 comprises, see FIG. 4, a hollow blade body 11, which is made of an upper half shell 12 and a lower half shell 13, which are fixed to each other with an adhesive 14 and which encase a hollow space 15. In this space 15 a first web 16 and a second web 17 are arranged. The first web 16 is arranged at a position where the upper half 12 and the lower half 13 almost have the greatest distance respectively the blade has nearly its maximum profile thickness. As FIG. 2 shows, the web 16 extends almost over the whole length of the blade 5 starting adjacent to the root 7 and ending adjacent to the tip 8.

(13) The second web 17 is arranged closer to the trailing edge 10. It may be arranged in different way. As FIG. 2 shows the second web 17 may, just like the first web 16, extend almost over the whole length of the blade 5 starting adjacent to the root 7 and ending adjacent to the tip 8. Both webs may extend parallel, but this is not compulsory. As FIG. 3 shows, it is also possible that the web 17 extends only over a part of the blade length close to the trailing edge 10.

(14) Both first and second webs 16, 17 are used for supporting the blade shells 12, 13 and for taking and distributing the respective loads resting on the blade and resulting from aerodynamic reasons due to the rotation of the rotor 4 and mechanical reasons due to the weight of the blade 5 itself.

(15) While in the following in reference to FIGS. 5 and 6 the setup of the first web 16 is described in detail, it is to be noted that the same description is valid also for the setup of the second web 17.

(16) The first web 16 comprises a web body 18 which, see for example FIG. 5 showing the enlarged section V of FIG. 4, comprises a core 19, for example made of balsa wood, a stable foam or a composite material etc. showing the needed mechanical properties for stiffening the whole web 16. The core 19 is encased in one or more glass fiber layers 20 which are resin infused, i.e., embedded in a cured resin 21.

(17) The web 16 further comprises two flanges 22 which are an integral part of the web 16 and which are integrally attached to the ends of the web body 18. FIG. 5 shows only one flange, the setup of the other flange is the same. Each flange 22 also comprises an integrated reinforcement structure 23 comprising a stack 24 made of several pultrusion strips 25 comprising carbon fibers embedded in a resin. Although FIG. 5 shows only three strips 25, only two or more than three strips may be provided. Between each pair of adjacent strips 25 one or more layers 26 of biaxial glass fiber fabric, which are infused with resin for fixing the strips 25, are interposed. A biaxial fiber layer or fabric comprises fibers being arranged in an angle of 0 with other fibers being arranged at an angle of e.g., 45. The whole arrangement of the strips 25 and the fiber layers 26 is completely embedded in the overall resin 21 embedding all components of the web 16. Thus, the reinforcement structure 23, i.e., the carbon pultrusion strips 25 with the interleaved fiber layers 26 is an integral part of the web 16, which can therefore be produced as a single complete piece external to the respective half shell 12, 13 itself and can be attached to them when the blade 5 is finally finished.

(18) Due to the separate manufacturing of both webs 16, 17, which, as mentioned, are identical in their setup, the half shells 12, 13 are also manufactured separately in their respective moulds. As the reinforcement structures 23 are an integral parts of the respective webs 16, 17 respectively build the respective flanges of each web 16, 17, no specific reinforcement structures need to be integrated into the respective half shell 12, 13. It is therefore possible, see FIGS. 5 and 6, to have a specific design in the areas of the shells 12, 13, to which the webs 16, 17 are attached by their respective flanges 22.

(19) FIG. 5 shows a first embodiment of such a shell design, while in FIG. 5 only the design of the respective attachment area for the flange 22 of the web 16 of the shell 12 is shown, but the same description is also valid for the design of the respective attachment zone for the flange 22 of the web 17 as well as for the attachment zones of the shell 13.

(20) Each shell 12, 13 comprises an outer layer 27 comprising one or more glass fiber layers 28, and an inner layer 29 also comprising one or more glass fiber layers 30. Between the outer and the inner layers 28, 29 respective core elements 31 are sandwiched. These core elements 31 may be made of balsa wood, high density foam or any other especially light weight stiffening material.

(21) As FIG. 5 clearly shows, in the attachment area, where the web flange is attached, the inner layer 29 is guided closer to the outer layer 27 respectively, see FIG. 5, in direct contact, as shown by the respective glass fiber layers 28, 30. Therefore the shell area is very thin. As shown, it is possible to arrange additional stiffening means 32, here in form of additional glass fiber layers 33 in this area, either adjacent to the glass fiber layer(s) 30 of the inner layer 29, or sandwiched between the glass fiber layers 28 and 30. While in FIG. 5 only one glass fiber layer 28, 30 and 33 is shown, it is possible that more of each of these layers may be provided.

(22) In an embodiment, several glass fiber layers 33 are provided. They may be uniaxial layers or biaxial layers, while also both types may be integrated in a random order, e.g., a uniaxial layer is followed by a biaxial layer which is followed by a uniaxial layer etc, or any other order. A biaxial fiber layer or fabric comprises fibers being arranged in an angle of 0 with other fibers being arranged at an angle of e.g., 45. Such a biaxial layer is advantageous, as it allows to take loads of different directions respectively of different types, e.g., loads from a flapwise or an edgewise bending of the blade. A uniaxial layer is adapted to stiffen against a flapwise bending.

(23) The respective attachment area is a way thinner than the blade sections adjacent to the attachment section.

(24) For attaching the respective flange 22 of each web 16, 17 to the half shell 12, 13, an adhesive 34 is used, by which the flange 22 is firmly attached to the respective shell 12, 13.

(25) For manufacturing the inventive blade 5, as already mentioned, both the webs 16, 17 and the shells 12, 13 are manufactured separately in respective moulds. The respective components of the webs 16, 17 and the shells 12, 13 are arranged in the specific mould, whereupon the mould respectively the component setup is infused with resin for firmly embedding all components. The web components are embedded in the resin 21, while the shell components are embedded in the resin 35.

(26) Thereafter both half shells 12, 13 are arranged above each other, with the webs 16, 17 being arranged between them and fixed to the respective shells 12, 13 by the adhesive 34. Also, the adhesive 14 is provided, so that the whole blade 5 is firmly fixed.

(27) FIG. 6 shows another embodiment of a blade design in the attachment region for the respective web flange 22. Again, the inner layer(s) 29 respectively their glass fiber layers 30 are guided to the outer shell surface closer to the outer layer 27 respectively the outer glass fiber layer(s) 30, but not in direct contact. As shown, at least one core element 36 is sandwiched or interpost between the outer and the inner layer 27, 29 respectively the outer and inner glass fiber layers 28, 30. This core element 36 may also be made of a lightweight stiffening material, which is adapted to act as a stiffening means 32, like balsa wood, high density foam or the like.

(28) Even if such a core element 31 is integrated, again the overall thickness of the shell 12, 13 in this attachment area is clearly smaller than the thickness of the shell 12, 13 in the adjacent parts, in which the core elements 31 are sandwiched. Therefore, it is possible, as shown in FIGS. 5 and 6, to integrate the respective flanges 22 of the web 16 and the flanges of the web 17 into respective recesses provided in the surface of the inner layer 29 of the respective shell 12, 13 by the adhesive 34. This allows to sink the respective flange 22 into the inner layer 29 or surface, it may be almost flush with the surface. A very compact design and setup can be realised, which reduces the overall mass of the blade and with advantage provides only one adhesive joint between the web integral reinforcement structure 23 and the shell 12, 13. As no adhesive joint between the respective reinforcement structure 23, i.e., their respective spar cap comprising the stack 24 of the pultrusion carbon strips 25, and the web body 18 is given, the robustness of the blade design can be increased.

(29) Another advantage is that the joint itself, realised by the adhesive 34, can be repaired, if need be, as it is possible to drill into this joint area from the outside of the blade 5, as only glass fiber layers in a matrix resin 35, may be also a core element 36, are arranged in this area, which can easily be drilled.

(30) Another advantage resulting from the separate manufacturing of the H-shaped webs 16, 17 is that the web quality can be inspected thoroughly, so that a perfect web quality can be secured and, in case of need, any repair may be done directly at the web manufacturing side without affecting the shell mould lead time.

(31) Again, the basic setup of all webs arranged in the blade is the same. Each web comprises a respective web body with a core and resin in view outer glass fiber layer, and an integrated flange comprising an integrated reinforcement structure composed of at least one stack of pultruded strips comprising carbon fibers, no matter if the respective web extends almost over the whole blade length or only over a part of it. Each of these web flange integrated reinforcement structure may also comprise two or more parallel carbon pultrusion stacks allowing to shape the geometry of the respective flange according to the geometry of the attachment area, if necessary. Independent of the final web setup, they all have in common that the respective reinforcement structure respectively the spar cap is completely integrated into the web.

(32) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(33) For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.