Patent Application
20130216388
The present disclosure relates in general to wind turbine blades, and more particularly to an internal shear web configuration for a wind turbine blade.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
As wind turbines increase in size and rotor height, the costs and logistics associated with constructing the turbine blades grow proportionately, and the industry is continuously seeking new constructions that are lighter, stronger, and more economical.
The main function of a shear web in a wind turbine rotor blade is to keep the pressure and suction side shell members from collapsing and for transferring shear stresses from one shell to the other. The thickness of the shear web is limited by the buckling strength of the web and the bond length between the shear web and spar cap required to maintain the shear web in position. Often, shear clips are added to increase this bond length. However, placement of the shear clips is done after closure of the blade shells, which is a difficult and time consuming process, and full-length placement of shear clips depends on accessibility of the shear web/spar cap interface.
A shear web construction would be welcome in the art that is robust, uses less material, and provides a significantly improved bond length between the shear web and spar caps.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In accordance with aspects of the invention, a wind turbine blade includes a pressure side shell member with an internal side spar cap, and a suction side shell member with an internal side spar cap. The pressure and suction side shell members are joined at a leading and trailing edge of the blade. A box-shaped shear web assembly spans between the spar caps and has a generally hollow interior volume. The shear web assembly includes end walls affixed to a respective spar cap by glue or other suitable bonding materials, and spaced-apart side walls extending transversely between the end walls. The end walls and side walls define a continuous box-shaped assembly structurally interposed between the spar caps.
In a particular embodiment, the side walls have a lighter weight material core, which may be any suitable high shear modulus/high strength materials, such as foam, balsa wood, and so forth. For example, the shear web assembly may include at least one inner box member that is circumscribed by and an outer box member, with the material core disposed between sides of the inner and outer box members. The material core may also be disposed between the end sides of the inner and outer box members such that the material core defines a generally continuous ring between the inner and outer box members. In an alternate embodiment, the inner box member may be joined directly to the outer box member at the end sides of the respective box members.
In a further embodiment, the shear web assembly may include two inner box members joined at a central wall extending through the interior volume of the shear web assembly. Alternatively, the inner box member may be formed from separate components that are attached to together, for example separate C-shaped partial box members joined to define a continuous box member.
The inner and outer box members may be separately formed and subsequently joined with the material core placed between the sides of the inner and outer box members. For example, the material core may be injected between the sides of the inner and outer box members. Alternatively, the material core may be separately formed as panels that are placed between the sides of the inner and outer box members.
In still a further embodiment, the material core pieces are placed between the side walls and end walls of the inner and outer box members.
The box members may be variously formed. For example, the end walls and side walls may be defined by an outer box member formed by a continuously wound bi-axial fiber layer. The inner box member may also be formed by a continuously wound bi-axial fiber layer, wherein the material core is placed between the sides of the inner and outer box members. For example, the material cores may be attached to the sides of the inner box member, with the outer box member being wound as a bi-axial fiber layer around the inner box member and attached material cores.
The wind turbine blade may include any number of the separately formed shear web assemblies longitudinally connected together along the length of said blade.
The present invention also encompasses various method embodiments for making the shear web assemblies. A particular method embodiment includes forming an inner box member and forming an outer box member around the inner box member with a space between respective sides of the inner and outer box members. Material core pieces, such as foam pieces, are disposed in the space between the sides of the inner and outer box members.
In a particular method embodiment, the inner box member is formed by winding one or more fiber layers around a mandrel. Foam material core pieces are placed on the mandrel against the wound inner box member and the outer box member is subsequently formed by continuing to wind one or more fiber layers with the mandrel around the inner box member and foam material core pieces. The inner and outer box members may be wound as bi-axial fiber layers.
In forming the shear web assemblies with a mandrel, the method may include collapsing the mandrel to remove the wound shear web assembly from the mandrel. For example, the mandrel may be formed from an inner axial component flanked by outer axial components, whereby the mandrel is collapsed by removing the inner axial component from the mandrel.
In an alternative method embodiment, the inner and outer box members may be separately formed, with the inner box member being subsequently placed within the outer box member. Material core pieces are then disposed between the sides of the inner and outer box members.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
Referring to
It should be appreciated from the general embodiment of
Still referring to
The material core 42 may be incorporated into the side walls 40 by various construction means. For example, referring particularly to the embodiment of
For example, referring to the partial assembly views of
Although not depicted in the figures, it should be readily appreciated that, in an alternate embodiment, the inner box member 44 may be placed within the outer box member 50 with a space between the respective side walls of the boxes 44, 50. In this embodiment, the material core 42 may then be injected into the space between the box members 44, 50, or separately formed material core panels 60 may be fitted into the spaces between the boxes 44, 50.
As can be appreciated from the embodiments depicted in
In an alternate embodiment depicted, for example, in
The inner box member 44 may be variously configured. For example, in the embodiment of
In the embodiment of
Referring to
The present invention also encompasses various method embodiments for forming a box-shaped shear web assembly 34 in accordance with aspects of the invention. For example, as discussed above, the inner 44 and outer 50 box members may be separately formed from any suitable material, with the inner box member 44 being placed within the outer box member 50. The material core 42 may be injected between the sides of the boxes, or separately formed as core panel pieces 60 and placed within the space between the sides of the respective boxes 44, 50.
With the embodiments of
With the shape of the mandrel 66 depicted in
Once the outer box member 50 is wound onto the mandrel 66 (around the foam core panels 60 and end sides 48 of the inner box member 44), the mandrel may be collapsed and removed from the shear web assembly 34. For example, referring to the mandrel 66 depicted in
It should be appreciated that the mandrel winding process described and illustrated herein is just one of a number of suitable methods that may be utilized to form a shear web assembly 34 in accordance with aspects of the invention, and that the invention is not limited to this particular method of construction.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
