Patent Application
20110286853
This application claims priority of European Patent Office application No. 10163580.3 EP filed May 21, 2010, which is incorporated by reference herein in its entirety.
The invention relates to a blade of a wind turbine
Modern blades of a wind turbine are manufactured typically by help of the so called “Vacuum Assisted Resin Transfer Moulding, VARTM” process.
For this process a number of layers, which contain fibers, mats, balsa-wood, prefabricated components, balloons filled with any kind of shaping material, . . . , etc. is put onto a so called “lower mould” to build up the three-dimensional shape of the blade. The lower mould is used to support the “sandwich structure” of the blade.
The lower mould is connected with an “upper mould” to form a closed mould structure. The moulds enclose or better encapsulate the blade structure.
During the VARTM-process a technical vacuum is applied to the closed mould structure, thus air is evacuated out from this structure while resin is infused into the structure accordingly.
The resin is allowed to cure out and the blade can be removed from the dismounted moulds.
The VARTM-process allows the production of very strong blades and of very strong composites and components.
The composites and components may be designed and constructed to be located inside a blade later, while the blade is manufactured in a subsequent VARTM-process.
The products, which are manufactured by help of the VARTM-process, even show a reduced weight due to the balsa-wood and due to balloons used. The balloons stay inside the product while it is manufactured, but will be removed later, thus a kind of an air-filled cavity remains inside the product.
The most part of the product, especially of the manufactured blade, is built up reinforcing materials, especially by glass-fibers, carbon fibers, woven mats, etc.
Within this VARTM-process a problem arises. The closed mould system may contain deep and concave-shaped cross-sections and areas, which are needed to build up the specific and needed shape of the product.
For example the trailing edge and/or the leading edge belong to those sections.
Fiber mats, which are used to build up the shape of the section, may not be aligned close and firm to an intended surface of the blade. The intended surface is determined by the curvature of the inner surface of the later closed mould system.
During the build-up process of the blade the fiber mats might follow a curvature which is different to the intended one. For example the fiber mats may tend to a shape like catenaries (hanging chain) in certain circumstances.
This effect results in a number of voids, which are located between the inner surface of the closed mould system and the fiber mats. Due to the VARTM process the voids will be filled with resin.
In this case the weight of the blade is increased due to the weight of the resin, while the structure of the blade might be weakened by the resin, as the resin shows no inner support structure (fibers) at theses locations. Cracks may be the result on the blade surface.
The wind turbine blade is exposed to fatigue load, thus the leading edge and the trailing edge of the blade may show fatigue-cracks in the blade surface.
Cracks need to be repaired by hand. This work is time consuming and expensive.
It is therefore the aim of the invention, to provide an improved wind turbine blade to overcome the problems mentioned above.
This aim is reached by the features of the claims.
Preferred embodiments of the invention are object of the dependent claims.
According to the invention the blade of a wind turbine contains different layers, which are used to build up the three-dimensional shape of the blade. Resin is applied to connect the layers while the blade is manufactured. A reinforcement structure is arranged close to the surface of the blade and at a resin-rich-section of the blade, where a certain amount of resin is gathered during the manufacture of the blade.
According to the invention the reinforcement structure is a shaped and preferably open laminate, which is arranged at sections of the blade, where a big amount of resin will usually arise, for example during an applied VARTM process.
These sections contain sharp corners of the blade for example, like the trailing edge or like the leading-edge of the blade.
Due to the invention the production of the blade is cheaper, as the number of cracks are minimized or even avoided due to the reinforcement structure. Thus the repair-work is reduced or even avoided.
Due to the invention the weight of the blade is reduced as the number of resin-filled-voids is even reduced.
Due to the invention the blade structure, especially the leading and the trailing edge, is stronger. Resin-rich areas are supported by the reinforcement structure, which is an integrated part of the blade.
The invention is shown in more detail by help of figures now.
The figures show preferred embodiments and do not limit the scope of the invention.
A lower mould LM is used within a VARTM-process to support the blade BL of a wind turbine.
The structure of the blade BL is built up by fibers, mats, balsa-wood, prefabricated components, balloons filled with any kind of shaping material, . . . , etc. (not shown here in detail) as described above. Thus these elements form different layers of the wind turbine blade.
Thus the lower mould LM is used to support this “sandwich structure” of the blade BL.
An upper mould UM is connected with the lower mould LM and is also used to build up the closed-mould-structure as described above.
The cross sectional view shows the trailing edge TE of the blade BL.
Due to the inner surface IS of the closed-mould-structure and due to the specific shape of the trailing edge TE a resin rich area RRA will be created.
If no further steps are taken the VARTM-process would lead to cracks, as described above and will lead to voids. The voids might be located between the inner surface IS of the closed mould structure and the surface of the blade BL (or better and the fiber-mat-surface of the blade BL) along the trailing edge TE.
To overcome these problems a shaped laminate structure SLS is used as reinforcement structure. It is located along the trailing edge TE and within the resin rich area RRA.
Preferably the shaped laminate structure SLS is shaped like a rail, showing an angle in its cross section.
The angle is chosen in a way that the shaped laminate structure SLS, used as reinforcement structure, is attached in a form-fit-manner to the layers of the blade.
The angle might be a right angle with 90°, for example.
Preferably the shaped laminate structure SLS is made as an open structure, like a grid. This allows that resin penetrates the laminate structure SLS during the VARTM process.
When the VARTM process is applied and when the blade BL is finished the shaped laminate structure SLS is an integrated part of the blade BL.
As the resin gets inside the shaped laminate structure SLS it is used as a reinforcement-structure inside the blade BL.
Preferably the shaped laminate structure SLS is made as pre-casted open structure. The pre-casted structure is integrated and fixed by the resin within the blade BL.
The arrangement invented minimizes the need for post-repairs. Additionally the manual work during the lay-up process of the blade elements (fiber, mats, wood, etc.) is easier than before as the “hanging chain” effect as described above is reduced.
Thus an easier and simplified lay-up of the fiber material at sharp corners of the blade is allowed. It is even possible to implement and to achieve more difficult curvatures for the shape of the blade.
Preferably the shaped laminate structure SLS is arranged close to the surface of the blade BL.
The shaped laminate structure SLS is used as an edge-protection, especially for the trailing edge and/or for the leading edge or other relevant sections of the blade BL.
| Number | Date | Country | Kind |
|---|---|---|---|
| EP10163580 | May 2010 | EP | regional |
