BACKGROUND 1. Field
Example embodiments relate to a structure having a web comprised of angled members. A non-limiting example of a structure using the web comprised of angled members is a wind turbine blade.
2. Description of the Related Art
FIGS. 1A and 1B illustrate a perspective view and a cross-section view of a conventional I beam 10 as is well known in the art. FIGS. 2A and 2B illustrate a modification of the conventional I beam 10. In the first embodiment, the I beam 10 includes a web 12 connecting a first flange 14 to a second flange 16. Similarly, the modified I beam 20 includes a web 22 also connecting a first flange 24 to a second flange 26. As is obvious in the drawings, the first and second flanges 24 and 26 of the modified I beam 20 are curved members whereas the first and second flanges 14 and 16 of the conventional I beam 10 are flat members. In either case, however, the webs 12 and 22 of the I beams 10 and 20 are rectangular shaped members. Such beams have found use in various structures such as buildings and machines.
FIG. 3 illustrates a cross-section of a conventional wind turbine blade 50. As shown in FIG. 3, the conventional wind turbine blade 50 includes a shell 70 which encloses a spar member 60. The spar member 60, like the conventional I-beam 10 and the modified I-beam 20, includes a shear web 62 and two flanges 64 and 66 (referred to as spar caps) arranged at ends of the shear web 62. The spar member 60 generally runs along a length of the wind turbine blade 50 and acts as a primary load bearing member. In use, the wind turbine blade 50 is subject to various loads such as shear, bending, and torsion loads and the spar member 60 must be designed to withstand each of these loads. As is well known in the art, because the spar 60 may be subject to relatively high shear loads, the web 62 is susceptible to buckling. Buckling of the web 62, however, may be prevented by increasing a thickness of the web 62 or by adding various reinforcing structures to the web 62. However, each approach adds weight to a wind turbine blade which is undesirable.
SUMMARY Example embodiments relate to a structure having a web comprised of angled members. A non-limiting example of a structure using the web comprised of angled members is a wind turbine blade.
Example embodiments disclose a structure that may include a first flange, a second flange, and a web connecting the first flange to the second flange. In example embodiments, the web may include at least one end with at least two angled members attaching to one of the first flange and the second flange and another end connecting to the other of the first flange and the second flange. Disclosed also is a wind turbine blade that includes the structure.
BRIEF DESCRIPTION OF THE DRAWINGS Example embodiments are described in detail below with reference to the attached drawing figures, wherein:
FIGS. 1A and 1B are views of a conventional I-beam;
FIGS. 2A and 2B are views of a modified I-beam;
FIG. 3 is a cross-section view of a conventional wind turbine blade;
FIGS. 4A and 4B are views of a structure in accordance with example embodiments;
FIGS. 5A and 5B are views of a structure in accordance with example embodiments;
FIGS. 6A-6C are views of a structure in accordance with example embodiments;
FIGS. 7A-7D are cross section views of structures in accordance with example embodiments
FIG. 8 is a cross-section view of a wind turbine blade in accordance with example embodiments;
FIG. 9 is a cross-section view of a conventional wind turbine blade showing a shear flow pattern;
FIG. 10 is a cross-section view of a wind turbine blade in accordance with example embodiments showing a shear flow pattern;
FIGS. 11A-11C are cross section views of wind turbine blades in accordance with example embodiments; and
FIGS. 12A-12C are section views of conventional wind turbine blades.
DETAILED DESCRIPTION Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are not intended to limit the invention since the invention may be embodied in different forms. Rather, example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the sizes of components may be exaggerated for clarity.
In this application, when an element is referred to as being “on,” “attached to,” “connected to,” or “coupled to” another element, the element may be directly on, directly attached to, directly connected to, or directly coupled to the other element or may be on, attached to, connected to, or coupled to any intervening elements that may be present. However, when an element is referred to as being “directly on,” “directly attached to,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements present. In this application, the term “and/or” includes any and all combinations of one or more of the associated listed items.
In this application, the terms first, second, etc. are used to describe various elements and components. However, these terms are only used to distinguish one element and/or component from another element and/or component. Thus, a first element or component, as discussed below, could be termed a second element or component.
In this application, terms, such as “beneath,” “below,” “lower,” “above,” “upper,” are used to spatially describe one element or feature's relationship to another element or feature as illustrated in the figures. However, in this application, it is understood that the spatially relative terms are intended to encompass different orientations of the structure. For example, if the structure in the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements or features. Thus, the term “below” is meant to encompass both an orientation of above and below. The structure may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
Example embodiments are illustrated by way of ideal schematic views. However, example embodiments are not intended to be limited by the ideal schematic views since example embodiments may be modified in accordance with manufacturing technologies and/or tolerances.
The subject matter of example embodiments, as disclosed herein, is described with specificity to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different features or combinations of features similar to the ones described in this document, in conjunction with other technologies. Generally, example embodiments relate to a structure having a web comprised of angled members. A non-limiting example of a structure using the web comprised of angled members is a wind turbine blade.
FIGS. 4A and 4B represent a perspective view and a cross section view of a structure 100 in accordance with example embodiments. Like a conventional I beam, the structure 100 may include a first flange 110 and a second flange 120. However, unlike the conventional I beam, which uses a rectangular shaped web to connect a first flange to a second flange, the structure 100 includes a web having members angled with respect to the first and second flanges 110 and 120. In this particular nonlimiting example, the angled members form an X-shaped web 130 connecting the first flange 110 to the second flange 120. In example embodiments, the first and second flanges 110 and 120 may be substantially plate shaped members. For example, each of the first and second flanges 110 and 120 may resemble rectangular plates having substantially the same dimensions.
FIGS. 5A and 5B represent a perspective view and a cross section view of a structure 200 in accordance with example embodiments. Like a conventional I beam, the structure 200 may include a first flange 210 and a second flange 220. However, unlike the conventional I beam which uses a rectangular shaped web to connect a first flange to a second flange, the structure 200 includes angled members to connect the first flange 210 to the second flange 220. In this particular nonlimiting example, the angled members form an X-shaped web 230 connecting the first flange 210 to the second flange 220. In example embodiments, the first and second flanges 210 and 220 may be substantially plate shaped members. However, unlike the flat plate shaped flanges 110 and 120 of structure 100, the first and second flanges 210 and 220 may resemble curved plates or shells.
In example embodiments, the structures 100 and 200 are illustrated as structures have substantially constant cross sections. However, this aspect of example embodiments is not intended to limit the invention. For example, FIG. 6A illustrates another example of a structure 300 in accordance with example embodiments. In example embodiments, the cross-section of the structure 300 changes along a length L of the structure 300. As in the previous examples, the structure 300 includes a substantially X-shaped web 330 that connects a first flange 310 to a second flange 320. FIG. 6B is a section view of the structure 300 taken near a first end 6B of the structure 300 and FIG. 6C is a view of the structure 300 taken near a second end 6C of the structure 300. As shown in FIGS. 6B and 6C the dimensions of the flanges 310 and 320 as well as the dimensions and configuration of the web 330 of the structure 300 may change along a length of the beam.
It is understood that the structures 100, 200, and 300 are exemplary structures only and are not intended to limit example embodiments. For example, in structures 100 and 200 the flanges are illustrated as being substantially identical to each other. For example, in structure 100 the first flange 110 and the second flange 120 are both substantially rectangular plate shaped members having substantially the same dimensions. Similarly, in structure 200, the first flange 210 and the second flange 220 are both substantially curved plate shaped members having substantially the same dimensions. However, example embodiments also include structures having an X-web wherein the structure has a first flange of a first shape, for example, a flat rectangular plate such as flange 110, and a second flange of a second shape, for example, a curved plate such as flange 220. Furthermore, the sizes of the flanges may be different. For example, example embodiments also include structures having an X-web and a first and second flange wherein the first and second flanges have different thicknesses, widths, and/or shapes.
In example embodiments, each of the components of the structures 100, 200, and 300 may be made from an isotropic material, for example, metal; or an orthotropic or anisotropic material, such as a laminated composite material, or a combination thereof. For example, each of the webs and flanges may be made from laminated composite materials wherein a core member, such as balsa, is sandwiched between glass layers.
FIGS. 7A-7D illustrate various non-limiting examples of structures in accordance with example embodiments. In FIG. 7A, for example, the structure 400 is comprised of a first flange 410, a second flange 420, and an X-web 430 connecting the first flange 410 to the second flange 420. In example embodiments the X-web 430 is comprised of a first V-shaped member 440 and a second V-shaped member 450 connected together by an adhesive 460. As shown in FIG. 7A, the first V-shaped member 440 may be comprised of a first core 442 sandwiched between a first layer 444 and a second layer 446. Similarly, the second V-shaped member 450 may be comprised of a second core 452 sandwiched between a third layer 454 and a fourth layer 456. In example embodiments, either of the cores 442 and 452 may be made from materials such as end grain balsa, cork, styrene acrylonitrile (SAN) foam, polyvinyl chloride (PVC) foam, polyethylene terephthalate (PET) foam, and/or a combination thereof. The first, second, third, and fourth layers 444, 446, 454, and 456 may be made from materials such as plastic reinforced by glass, carbon, high-modulus aromatic polyamide (i.e. aramid), basalt, and/or a combination thereof. These materials are provided as nonlimiting examples and should not be construed as a limitation on the invention. In example embodiments, the first and second flanges 410 and 420 may likewise be made from a laminated composite material. In this particular nonlimiting example embodiment, the first V-shaped member 440 and the second V-shaped member 450 may be manufactured separately and then joined together by the adhesive 460.
FIG. 7B illustrates another example of a structure 500 in accordance with example embodiments. As shown in FIG. 7B, the structure 500 may be comprised of a first flange 510, a second flange 520, and an X-web 530 connecting the first flange 510 to the second flange 520. In example embodiments the X-web 530 may be comprised of a X-shaped core 540. As shown in FIG. 7B, surfaces of the X-shaped core 540 may be covered by a layer or layers of materials. For example, the X-shaped core 540 may be covered by a first layer 541, a second layer 542, a third layer 543, and a fourth layer 544. In example embodiments, the core 540 may be made from materials such as end grain balsa, cork, styrene acrylonitrile (SAN) foam, polyvinyl chloride (PVC) foam, polyethylene terephthalate (PET) foam, and/or a combination thereof. The first, second, third, and fourth layers 541, 542, 543, and 544 may be made from materials such as plastic reinforced by glass, carbon, high-modulus aromatic polyamide (i.e. aramid), basalt, and/or a combination thereof. In example embodiments, the first and second flanges 510 and 520 may likewise be made from a laminated composite material. These materials are provided as nonlimiting examples and should not be construed as a limitation on the invention.
FIG. 7C illustrates another example of a structure 600 in accordance with example embodiments. As shown in FIG. 7C, the structure 600 may be comprised of a first flange 610, a second flange 620, and an X-web 630 connecting the first flange 610 to the second flange 620. In example embodiments the X-web 630 may be comprised of a first rectangular shaped core 640 to which a second rectangular shaped core 660 and a third rectangular shaped core 670 are attached. In example embodiments, the first, second, and third rectangular shaped cores 640, 660, and 670 may be attached to one another, for example, by an adhesive or another fastening means, and then covered by first layer 671, a second layer 672, a third layer 673, and a fourth layer 674. In example embodiments, the first, second, and third cores 640, 660, and 670 may be made from materials such as end grain balsa, cork, styrene acrylonitrile (SAN) foam, polyvinyl chloride (PVC) foam, polyethylene terephthalate (PET) foam, and/or a combination thereof. The first, second, third, and fourth layers 671, 672, 673, and 674 may be may be made from materials such as plastic reinforced by glass, carbon, high-modulus aromatic polyamide (i.e. aramid), basalt, and/or a combination thereof. In example embodiments, the first and second flanges 610 and 620 may likewise be made from a laminated composite material. These materials are provided as nonlimiting examples and should not be construed as a limitation on the invention.
FIG. 7D illustrates another example of a structure 700 in accordance with example embodiments. As shown in FIG. 7D, the structure 700 may be comprised of a first flange 710, a second flange 720, and an X-web 730 connecting the first flange 710 to the second flange 720. In example embodiments the X-web 730 may be comprised of a first V-shaped core 740 and a second V-shaped core 750 connected together by an adhesive 760. In example embodiments, the structure 700 may further include a first layer 751, a second layer 752, a third layer 753, and a fourth layer 754 covering the V-shaped cores 740 and 750 as well as the adhesive 760. In example embodiments, the first and second V-shaped cores 740 and 750 may be made from materials such as end grain balsa, cork, styrene acrylonitrile (SAN) foam, polyvinyl chloride (PVC) foam, polyethylene terephthalate (PET) foam, and/or a combination thereof. The first, second, third, and fourth layers 751, 752, 753, and 754 may be made from materials such as plastic reinforced by glass, carbon, high-modulus aromatic polyamide (i.e. aramid), basalt, and/or a combination thereof. In example embodiments, the first and second flanges 710 and 720 may likewise be made from a laminated composite material. In this particular nonlimiting example embodiment, the first core 740 and the second core 750 may be manufactured separately and then joined together by the adhesive 460. These materials are provided as nonlimiting examples and should not be construed as a limitation on the invention.
It is understood that the structures 400, 500, 600, and 700 are for purposes of illustration only and are not intended to limit the invention. For example, although each of the structures 400, 500, 600, and 700 are illustrated as having flanges with a rectangular cross-section having substantially the same dimensions, the flanges may assume another configuration such as, but not limited to, a curved flange or an irregular shaped flange. Furthermore, the pairs of flanges provided in each of the structures 400, 500, 600, and 700 are not required to have the same configuration or dimension. For example, the first flange 410 may have a rectangular cross-section as shown in FIG. 7A and the second flange 420 may have a curved cross-section, for example, as shown in FIG. 5A. In addition, the X-webs 430, 530, 630, and 730 are for purposes of illustration only since the X-webs are not required to be comprised of a core sandwiched between layers. For example, the X-webs 430, 530, 630, and 730 may alternatively be made from a metal, for example, aluminum. Furthermore, the dimensions illustrated in the figures are for purposes of illustration and are not intended to limit example embodiments. For example, the X-web 530 of structure 500 appears to be a substantially symmetric structure, however, none of the X-webs are required to have the degree of symmetry provided in the figures.
In example embodiments, the aforementioned structures are well suited for use in various structures. For example, FIG. 8 illustrates a cross section of a wind turbine blade 1000 which includes angled members in accordance with example embodiments. In this particular nonlimiting example embodiment, the angled members form an X-web. As shown in FIG. 8, the example wind turbine blade 1000 includes a shell 1170 which encloses a spar member 1160. The spar member 1160, includes an X-web 1162 (an example of the angled members) and two flanges 1164 and 1166 (sometimes referred to as spar caps) arranged at ends of the X-web 1162. In example embodiments, the spar member 1160 may have a cross-section that is substantially similar to the previously described structure 200. As in the conventional art, the spar member 1160 generally runs along a length of the wind turbine blade 1000 and acts as the primary load bearing structure.
FIGS. 9 and 10 illustrate shear flow through the conventional wind turbine blade 50 and the wind turbine blade 1000 in accordance with example embodiments. As shown in FIG. 10, the shear flow through the web of the conventional wind turbine blade 50 may be relatively high. Accordingly, a width or thickness of the web of the conventional wind turbine blade 50 may be relatively large to accommodate the relatively significant shear stress. The straight web, as illustrated in FIG. 9, is essentially an unsupported column which, when subject to this shear stress, could have the tendency to buckle. This requires additional width or thickness of core material in order to stabilize the column. In the wind turbine blade 1000 according to example embodiments, the X-web members may be designed with a reduced thickness in the core and/or face sheet(s) (compared to the conventional art) due to the redirection of the shear flow path. Furthermore, the angled members of the X-web tend to stabilize the web against buckling. Thus, a thickness of the components associated with the X-web may be substantially thinner than a thickness of the components of the web of the conventional turbine blade. As such, a reduction in the material required for the web may lead to reduced material costs leading to significant cost savings for the blade.
Example embodiments are directed to a structure which uses angled members (for example, an X-web) as a method of transferring shear from two spar flanges. When incorporated in a wind turbine blade, the angled members transfer shear between the flanges on each side of the spar (pressure and suction) of the wind turbine blade. In example embodiments, the angled members may be constructed from one member or several members.
In example embodiments, the angled members have been illustrated as an X-web that may be attached to two flanges. However, the inventive concepts are not limited thereto. For example, FIG. 11A illustrates another example of a structure 4000 (for example, a wind turbine blade) in accordance with example embodiments. In this latter example, the angled members form a Y-shape rather than an X-shape. FIG. 12B illustrates another example of a structure 5000 (for example, a wind turbine blade) in accordance with example embodiments. In this latter example, the main support member is configured to provide four points of contact and resembles a Ψ. FIG. 12C illustrates another example of a wind turbine blade 6000 in accordance with example embodiments. In this latter example, the main support member is configured to provide four points of contact and resembles two Y's connected end to end. In example embodiments, the Y-shaped web, the Ψ-shape web, and the double Y shaped webs provide multiple points of contact while providing support against buckling.
Example embodiments have particular advantages over the prior art. For example, when employed in a wind turbine blade, the angled members reduce the requirements for core on the flanges, reduce the propensity for buckling of the webs by providing a more favorable closed-section shear flow path in bending, and eliminate some of the traditional straight vertical components of shear webs in order to form a more favorable closed-section shear flow path in torsion, that is, a more torsionally stiff blade.
Example embodiments have additional advantages over the prior art. For example, FIG. 12A illustrates another example of a cross-section of a conventional wind turbine blade 7000. In FIG. 12A, the wind turbine blade 7000 includes a pair of webs 7100 and 7200 (also known as spars) which act to transfer shear from a suction side of the of the wind turbine blade 7000 to a pressure side of the wind turbine blade 7000. This type of configuration forms what is called a “box” profile. Symbol C in FIG. 12A illustrates transverse shear forces that are induced by various loadings on the blade 7000 due to various types of loadings (for example, wind loads WF in a flapwise direction of the blade, wind loads WE along an edgewise direction of the blade, and torsional loads WT exerted on the blade). As shown in FIG. 12B, the transverse shear forces C cause the section of the blade to distort which has an adverse effect on the blade's ultimate strength. Furthermore, if the transverse shear distortion exceeds a certain limit (which depends on the geometry of the blade and material of the blade), the blade's resistance to a crushing pressure is reduced and a sudden collapse of the blade can occur. As is well known in the art, the crushing pressure is caused by the flapwise loads and occurs in a box due to its longitudinal curvature. This effect is also referred to as the Brazier effect.
Some artisans have sought to reduce the shear distortions in conventional wind turbine blades by using various stiffeners and/or reinforcing members. For example, as shown in FIG. 12C, some artisans have sought to reduce shear distortions by introducing X-shaped reinforcing members 7300 to reinforce the flanges of the box beam. However, while the reinforcing members 7300 do reduce torsional distortion of the blade 7000, they do very little to prevent flange buckling of the blade 7000.
Unlike the prior art, the X-web according to example embodiments alleviates many of the aforementioned problems. For example, in the embodiment of FIG. 10, a transverse distortion of the wind turbine load due to transverse shear forces results in loads which are substantially along a length of the legs of the X-web. Thus, while the axial loads of the legs may increase, the bending loads of the legs of the X-web are lower than the bending loads seen in the webs of the conventional art. Furthermore, and as alluded to earlier, because the legs of the X-web are joined together, each leg reinforces the other against buckling. This allows for a thinner web design compared to the conventional art and thus allows for a wind turbine blade with less core material. In addition, the X-web also reinforces the flanges by spreading shear forces along a chordwise direction of the wind turbine blade (for example, compared to an I-beam configuration as in FIG. 3). Furthermore, because a section of a wind turbine blade using the X-web according to example embodiments is inherently stiffer than either a conventional box-type configuration or a I-type configuration, distortion of the flange is reduced further reinforcing the shell of the wind turbine blade and reducing its tendency to buckle under transverse loading.
When implemented in a wind turbine blade, the angled members may be placed in various locations. For example, the angled members may be placed on a wind turbine's main flanges (as shown in at least FIG. 8), across a dual flange configuration with flanges positioned with nonzero chordwise separation, between dual flanges positioned with nonzero chordwise separation, fore of a main flange (i.e. towards a leading edge of wind turbine blade), or aft the main flange (i.e. towards a trailing edge of the wind turbine blade).
In example embodiments, the material from which the angled members may be made are not limited to sandwich composite materials and may include, but are not limited to, metals, unreinforced plastics, and composite plastic without sandwich core reinforced with fibers that might include, but are not limited to, glass, carbon, boron, or an aramid.
It is understood that fabrication processes can include, but are not limited to, 1, 2, 3, and 4 or more individual pieces, which are then bonded, welded, etc. (based on the material) together to form the desired shape. It is also noted that the final component does not necessarily have to be bonded into the shell as one piece. For example, the bonding surfaces may be laminated between the inner and outer skins of the shell prior to the bonding application of the angled structures.
In example embodiments, the example structures include a first flange, a second flange and a web connecting the first flange to the second flange. In example embodiments, the web may have at least one end with at least two angled members. For example, in the event the web is X-shaped, each end of the web is includes two angled members, in the event the web is Y-shaped, only one end of the web includes two angled members, in the event the web is Ψ-shaped, only one end of the web includes angled members, in the event the web is double Y-shaped, both ends of the web include angled members. The angled members allow for forces to be spread across a larger area thereby reducing shear at the points of contact.
Example embodiments of the invention have been described in an illustrative manner. It is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of example embodiments are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.
