Patent ID: 12221951

DETAILED DESCRIPTION

FIG.1shows a principal sketch of a wind turbine1comprising a tower2, a nacelle3mounted on top of the tower2and a rotor4comprising three wind turbine blades5attached to a hub6, which is operatively coupled to a generator arranged in the nacelle3, which generator is driven by the rotational energy of the rotor4for producing electric power as commonly known.

Embodiments of the invention relate to the setup of the wind turbine blades5.

FIG.2shows a principle drawing of a turbine blade5of a first embodiment with a root7for attaching the blade5to the hub and with a tip8at the other blade end. It furthermore comprises a leading edge9and a trailing edge10.

FIG.3shows a principle drawing of a turbine blade5of a second embodiment with a root7for attaching the blade5to the hub and with a tip8at the other blade end. It furthermore comprises a leading edge9and a trailing edge10.

The blade5comprises, seeFIG.4, a hollow blade body11, which is made of an upper half shell12and a lower half shell13, which are fixed to each other with an adhesive14and which encase a hollow space15. In this space15a first web16and a second web17are arranged. The first web16is arranged at a position where the upper half12and the lower half13almost have the greatest distance respectively the blade has nearly its maximum profile thickness. AsFIG.2shows, the web16extends almost over the whole length of the blade5starting adjacent to the root7and ending adjacent to the tip8.

The second web17is arranged closer to the trailing edge10. It may be arranged in different way. AsFIG.2shows the second web17may, just like the first web16, extend almost over the whole length of the blade5starting adjacent to the root7and ending adjacent to the tip8. Both webs may extend parallel, but this is not compulsory. AsFIG.3shows, it is also possible that the web17extends only over a part of the blade length close to the trailing edge10.

Both first and second webs16,17are used for supporting the blade shells12,13and for taking and distributing the respective loads resting on the blade and resulting from aerodynamic reasons due to the rotation of the rotor4and mechanical reasons due to the weight of the blade5itself.

While in the following in reference toFIGS.5and6the setup of the first web16is described in detail, it is to be noted that the same description is valid also for the setup of the second web17.

The first web16comprises a web body18which, see for exampleFIG.5showing the enlarged section V ofFIG.4, comprises a core19, for example made of balsa wood, a stable foam or a composite material etc. showing the needed mechanical properties for stiffening the whole web16. The core19is encased in one or more glass fiber layers20which are resin infused, i.e., embedded in a cured resin21.

The web16further comprises two flanges22which are an integral part of the web16and which are integrally attached to the ends of the web body18.FIG.5shows only one flange, the setup of the other flange is the same. Each flange22also comprises an integrated reinforcement structure23comprising a stack24made of several pultrusion strips25comprising carbon fibers embedded in a resin. AlthoughFIG.5shows only three strips25, only two or more than three strips may be provided. Between each pair of adjacent strips25one or more layers26of biaxial glass fiber fabric, which are infused with resin for fixing the strips25, 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 strips25and the fiber layers26is completely embedded in the overall resin21embedding all components of the web16. Thus, the reinforcement structure23, i.e., the carbon pultrusion strips25with the interleaved fiber layers26is an integral part of the web16, which can therefore be produced as a single complete piece external to the respective half shell12,13itself and can be attached to them when the blade5is finally finished.

Due to the separate manufacturing of both webs16,17, which, as mentioned, are identical in their setup, the half shells12,13are also manufactured separately in their respective moulds. As the reinforcement structures23are an integral parts of the respective webs16,17respectively build the respective flanges of each web16,17, no specific reinforcement structures need to be integrated into the respective half shell12,13. It is therefore possible, seeFIGS.5and6, to have a specific design in the areas of the shells12,13, to which the webs16,17are attached by their respective flanges22.

FIG.5shows a first embodiment of such a shell design, while inFIG.5only the design of the respective attachment area for the flange22of the web16of the shell12is shown, but the same description is also valid for the design of the respective attachment zone for the flange22of the web17as well as for the attachment zones of the shell13.

Each shell12,13comprises an outer layer27comprising one or more glass fiber layers28, and an inner layer29also comprising one or more glass fiber layers30. Between the outer and the inner layers28,29respective core elements31are sandwiched. These core elements31may be made of balsa wood, high density foam or any other especially light weight stiffening material.

AsFIG.5clearly shows, in the attachment area, where the web flange is attached, the inner layer29is guided closer to the outer layer27respectively, seeFIG.5, in direct contact, as shown by the respective glass fiber layers28,30. Therefore the shell area is very thin. As shown, it is possible to arrange additional stiffening means32, here in form of additional glass fiber layers33in this area, either adjacent to the glass fiber layer(s)30of the inner layer29, or sandwiched between the glass fiber layers28and30. While inFIG.5only one glass fiber layer28,30and33is shown, it is possible that more of each of these layers may be provided.

In an embodiment, several glass fiber layers33are 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.

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

For attaching the respective flange22of each web16,17to the half shell12,13, an adhesive34is used, by which the flange22is firmly attached to the respective shell12,13.

For manufacturing the inventive blade5, as already mentioned, both the webs16,17and the shells12,13are manufactured separately in respective moulds. The respective components of the webs16,17and the shells12,13are 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 resin21, while the shell components are embedded in the resin35.

Thereafter both half shells12,13are arranged above each other, with the webs16,17being arranged between them and fixed to the respective shells12,13by the adhesive34. Also, the adhesive14is provided, so that the whole blade5is firmly fixed.

FIG.6shows another embodiment of a blade design in the attachment region for the respective web flange22. Again, the inner layer(s)29respectively their glass fiber layers30are guided to the outer shell surface closer to the outer layer27respectively the outer glass fiber layer(s)30, but not in direct contact. As shown, at least one core element36is sandwiched or interpost between the outer and the inner layer27,29respectively the outer and inner glass fiber layers28,30. This core element36may also be made of a lightweight stiffening material, which is adapted to act as a stiffening means32, like balsa wood, high density foam or the like.

Even if such a core element31is integrated, again the overall thickness of the shell12,13in this attachment area is clearly smaller than the thickness of the shell12,13in the adjacent parts, in which the core elements31are sandwiched. Therefore, it is possible, as shown inFIGS.5and6, to integrate the respective flanges22of the web16and the flanges of the web17into respective recesses provided in the surface of the inner layer29of the respective shell12,13by the adhesive34. This allows to sink the respective flange22into the inner layer29or 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 structure23and the shell12,13. As no adhesive joint between the respective reinforcement structure23, i.e., their respective spar cap comprising the stack24of the pultrusion carbon strips25, and the web body18is given, the robustness of the blade design can be increased.

Another advantage is that the joint itself, realised by the adhesive34, can be repaired, if need be, as it is possible to drill into this joint area from the outside of the blade5, as only glass fiber layers in a matrix resin35, may be also a core element36, are arranged in this area, which can easily be drilled.

Another advantage resulting from the separate manufacturing of the H-shaped webs16,17is 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.

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.

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.

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.