Turbine blade and method of fabricating the same

A turbine blade includes at least two blade segments. Each blade segment includes first and second shells joined together, a base region, at least one joint region including a mating face. Each of the first and second shells includes an outer skin, a base spar cap attached to an inner surface of the outer skin in the base region, a joint spar cap attached to the inner surface of the outer skin in the joint region and adjacent to at least a portion of the base spar cap. The joint spar cap includes holes in the mating face of the joint region. The turbine blade further includes fasteners within the holes for securing the at least two blade segments together.

BACKGROUND

The invention relates generally to turbine blades, and, more particularly, to multiple-piece turbine blades and methods of fabricating the turbine blades.

Turbine blades such as those used for wind turbines usually have large sizes. Shipment of a large blade from where it was made to where it will be assembled is inconvenient and costly.

There is a need in the art to ship the turbine blades in segments and then join the segments together at a remote assembly location. However, conventional methods for addressing this need often result in undesirable levels of complexity and expense. Accordingly, an improved joint system and a corresponding method are needed to address one or more of the foregoing issues.

BRIEF DESCRIPTION

In accordance with an embodiment disclosed herein, a turbine blade is provided. The turbine blade includes at least two blade segments. Each blade segment includes first and second shells joined together, a base region, at least one joint region including a mating face. Each of the first and second shells includes an outer skin, a base spar cap attached to an inner surface of the outer skin in the base region, a joint spar cap attached to the inner surface of the outer skin in the joint region and adjacent to at least a portion of the base spar cap. The joint spar cap includes holes in the mating face of the joint region. The turbine blade further includes fasteners within the holes for securing the at least two blade segments together.

In accordance with another embodiment disclosed herein, a blade segment is provided. The blade segment includes first and second shells joined together, a base region, and at least one joint region including a mating face. Each of the first and second shells further includes an outer skin, a base spar cap attached to an inner surface of the outer skin in the base region, and a joint spar cap attached to the inner surface of the outer skin in the joint region and respectively adjacent to at least a portion of a corresponding base spar cap. The joint spar cap includes holes in the mating face of the joint region for insertion of fasteners.

In accordance with still another embodiment disclosed herein, a method of fabricating a blade segment is provided. The method includes providing first and second outer skins of the first and second shells; providing joint spar caps respectively on inner surfaces of the first and second outer skins in joint regions of the first and second outer skins; positioning base spar caps respectively on each inner surface of the first and second outer skins in base regions of the first and second outer skins and adjacent to the joint spar caps; positioning at least one shear web between the pair of base spar caps and between the pair of joint spar caps; attaching the first and second shells; and providing holes in the joint spar caps in mating faces of the joint regions for insertion of fasteners.

DETAILED DESCRIPTION

As discussed in detail below, embodiments of the present invention include turbine blades and methods for fabricating turbine blades. As used herein, the term “turbine blades” refers to blades used in various applications such as, but not limited to, wind turbines and aircraft systems.

As used herein, singular forms such as “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. For example, although a two-segment blade is shown in the drawings for purposes of illustration, more segments may be included if desired.

FIGS. 1-7show embodiments of the invention used in a wind turbine system10. Referring toFIG. 1, wind turbine system10includes a rotor14and several blades12. Each blade12includes at least first and second blade segments16and18. As used herein after, the term “outboard” means farther from rotor14, and “inboard” means closer to rotor14. Thus, in the exemplary embodiment, first blade segment16is an inboard blade segment, and second blade segment18is an outboard blade segment. The blades12are mounted atop a tower20.

FIG. 2is an exemplary perspective view of inboard blade segment16, which includes a base region22, a joint region24, a pressure side shell23, and a suction side shell21. Each shell includes an outer skin26,27, a core36,37, an inner skin44,45, and spar caps which are shown in more detail below with respect toFIG. 4. Joint region24includes a mating face28for engaging with outboard blade segment18. Joint region24is formed in a shape of an airfoil section and has a leading edge30and a training edge32. In certain embodiments, outer skin26and27is made from glass reinforced composites such as, for example biaxial glass, uniaxial glass, or triaxial glass, or any combination of thereof. In certain embodiments, cores36and37comprise wood, for example, balsa, or foam, or a combination of both. In certain embodiments, inner skin44,45is formed from glass reinforced composites such as, for example, biaxial glass layers.

In one embodiment, joint region24has a stepped inner surface, and includes joint spar caps34which have larger thicknesses than cores36and37. In one example, joint spar cap34of joint region24comprises triaxial glass layers.

One or more longitudinal crossbeams38, also referred to as shear webs, are disposed within joint region24and between upper and lower joint spar caps34. Shear web38is adapted to withstand aerodynamic shear loading on blade12. In certain embodiments, shear web38is made from foam strengthened with biaxial glass.

A plurality of longitudinal holes40extend into mating face28in the longitudinal direction. In the exemplary embodiment, holes40in joint spar caps34have a larger diameter than holes40in cores36and37. Joint region24may additionally define a plurality of access slots42along an outer and/or inner periphery thereof. Each access slot42extends at least partially through joint region24and communicates with a corresponding hole40. In the exemplary embodiment, two rows of access slots42are respectively defined in upper and lower joint spar caps34, and the two rows of access slots42are staggered in the longitudinal direction.

FIG. 3is a cross-sectional view of base region22of inboard blade segment16along line3-3ofFIG. 2. Base region22includes longitudinal bending load bearing structures or base spar caps46between inboard outer skin26,27and inner skin44,45. In one embodiment, base spar caps46are formed from continuous fiber reinforced composites such as carbon composites. In certain other embodiments, the base spar caps46may be formed of glass or carbon. One or more shear webs48,38to be used for withstanding aerodynamic shear loading on the wind turbine blade12are disposed within the airfoil section between the base spar caps46. In one embodiment, shear webs48and38of base region22and joint region24are separately made and joined with each other to extend along a full length of the inboard blade segment16. In an alternative embodiment, shear webs48and38are portions of one integral shear web.

FIG. 4is an illustrative cross-sectional view of one embodiment of inboard blade segment16along line4-4ofFIG. 2. In this embodiment, base spar caps46of base region22and upper and lower joint spar caps34of joint region24respectively have a first and a second tapered edge33and35engaging with each other. With this embodiment, a load on base spar caps46can be transferred to the joint spar caps34of the joint region24. First and second tapered edges33and35inFIG. 4are very exaggerated for purposes of illustration and are not drawn to scale.

With continued reference toFIG. 4, an exemplary process of fabricating a pressure side shell23of inboard blade segment16includes providing an outer skin26for example, laying up a plurality of biaxial glass layers.

A joint spar cap34is provided on an inner surface of outer skin26in joint region of pressure side shell23. In one embodiment, joint spar cap34is formed by thickening outer skin26at joint region24with triaxial glass layers. In one embodiment, the triaxial glass layers are designed to have different length and width, so when they are laid up, a second tapered edge35is formed. In another embodiment, the outer shell is molded, and joint spar cap34is integrally molded together with the outer shell.

Base spar cap46is positioned on the inner surface of outer skin26in base region22of pressure side shell23adjacent to joint spar cap34. As discussed above, in one embodiment, base spar cap46has a first tapered edge33to engage with second tapered edge35of joint spar cap34. In one embodiment, the first and second tapered edges33and35are cured together after base spar cap46is properly positioned. A core36(FIGS. 2 and 3), comprising a material such as wood or foam, is laid on non-spar cap areas of outer skin26.

In certain embodiments, the process of producing pressure side shell23of inboard blade segment16further includes laying an inner skin44. For example, a joint of the first and second tapered edges33and35may be covered by inner skin44. In certain embodiments, inner skin44includes biaxial glass layers.

Shear web48(FIG. 3) is positioned on inner skin44and adhered thereto. A suction side shell21of the inboard blade segment16is produced with one fabricating example being similar to the process of pressure side shell23described above. The suction side and pressure side shells21,23are attached to each other in any structurally appropriate matter with one example being by adhesive.

In one embodiment, holes40and access slots42are machined in joint region24after suction side and pressure side shells26,27are assembled together. In another embodiment, machining of holes40and access slots42can be performed immediately after joint spar cap34is produced. In still another embodiment, machining holes40and access slots42can be performed after the inner skin44,45is laid on.

FIG. 5illustrates a perspective view of outboard blade segment18which may be fabricated in a similar process as inboard blade segment16described above and may have a similar structure as that of inboard blade segment16. Outboard blade segment18has a mating face50adapted for engaging with inboard blade segment16. A plurality of longitudinal holes52extend from mating face50into outboard blade segment18, in the longitudinal direction. Holes52are respectively in alignment with holes40of inboard blade segment16when assembling the inboard and outboard blade segments16and8together. Outboard blade segment18defines a plurality of access slots54along a periphery direction, and each access slot54communicates with a corresponding hole52. Inboard and outboard blade segments16and18can be manufactured in the same or different factories.

After shipment, inboard and outboard blade segments16and18may be secured together as shown inFIG. 6. In one embodiment, the securing is accomplished with a T-bolt connection. In a more specific embodiment, a plurality of T-bolts56(shown inFIG. 5) may be pre-attached to one of the inboard and outboard blade segments16and18. For example, T-bolts56may be pre-assembled to outboard blade segment18as shown inFIG. 5.

Referring toFIGS. 6 and 7, each T-bolt56includes a longitudinal stud58with opposite thread ends60and62(inboard and outboard thread ends) for engaging with barrel nuts64and66. In the exemplary embodiment, outboard thread end60of each T-bolt56is secured in outboard blade segment18by a corresponding barrel nut66before being shipped, and, after shipping, inboard thread end62of each T-bolt56is extended into a corresponding access slot42of inboard blade segment16through a corresponding inboard longitudinal hole40. In certain embodiments, barrel nuts66are glued to outboard blade segment18through adhesive. In a non-limiting example, the adhesive includes epoxy, an infusion resin, or combinations thereof.

It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. The various features described, as well as other known equivalents for each feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure.