Patent Description:
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, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles and 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.

The construction of a modern rotor blade generally includes skin or shell components, spar caps, and one or more shear webs extending between opposing spar caps. The skin, typically manufactured from layers of fiber composite and a lightweight core material, forms the exterior aerodynamic airfoil shape of the rotor blade. Further, the spar caps provide increased rotor blade strength by integrating one or more structural elements running along the length of the rotor blade on both interior sides of the rotor blade. The shear web(s) includes structural beam-like components running essentially perpendicular between the top and bottom spar caps and extend across the interior portion of the rotor blade between the outer skins. The spar caps have typically been constructed from glass fiber reinforced composites, though some larger blades may include spar caps constructed from carbon fiber reinforced composites.

The size, shape, and weight of rotor blades are factors that contribute to energy efficiencies of wind turbines. An increase in rotor blade size increases the energy production of a wind turbine, while a decrease in weight also furthers the efficiency of a wind turbine. Furthermore, as the size of wind turbines increases, particularly the size of the rotor blades, so do the respective costs of manufacturing, transporting, and assembly of the wind turbines. The economic benefits of increased wind turbine sizes must be weighed against these factors.

One known strategy for reducing the costs of pre-forming, transporting, and erecting wind turbines having rotor blades of increasing sizes is to manufacture the rotor blades in blade segments. The blade segments may be assembled to form the rotor blade after, for example, the individual blade segments are transported to an erection location. For example, some rotor blades include either bonded or bolted joints. One such bolted joint includes a chord-wise extending pin securing a male shear web member or spar member within a female shear web member so as to join adjacent blade segments.

However, certain issues are associated with the chord-wise extending pin. For example, the edge loading of the joint without pin contact is indeterminate. Further, it is challenging to provide a suitable joint within the limited space of the airfoil. In addition, the connections between blade segments are difficult to complete in the field. Moreover, fitting structural materials into the airfoil shape to support the loads but also being able to assemble the joint can be problematic. Still further issues include with segmented rotor blades includes maximizing the structural efficiency of the joint structure and while also maintaining the joint mass as low as possible.

Thus, there is a need for a joint assembly for a segmented rotor blade that addresses the aforementioned issues. Accordingly, the present disclosure is directed to a joint assembly for wind turbine rotor blades having a locally increased height of the male shear web member at the location of the chord-wise extending pin.

<CIT> discloses a sectional blade for a wind turbine. The blade comprises at least a first blade portion and a second blade portion extending in opposite directions from a joint. The first blade portion and the second blade portion are structurally connected by at least one spar bridge extending into both blade portions to facilitate joining of said blade portions. <CIT> discloses a rotor blade of a wind turbine with a first rotor blade segment and a second rotor blade segment is provided. The rotor blade has a hollow space surrounded by a shell. The first rotor blade segment is connected with the second rotor blade segment by a bolt connection. The bolt connection has a first connection of the first rotor blade segment, a second connection of the second rotor blade segment, and a bolt establishing a bolted joint between the first connection and the second connection. At least the bolt is situated in the hollow space of the rotor blade. Furthermore, a method of connecting a first rotor blade segment of a rotor blade of a wind turbine and a second rotor blade segment of the rotor blade is provided. <CIT> discloses a modular rotor blade for a power generating turbine allows simple replacement of individual rotor blade sections in case of damage to or malfunction of a section. The modular rotor blade includes at least two rotor blade sections, wherein each rotor blade section includes at least one connecting part having at least one conical opening. The connecting parts of adjacent rotor blade sections rest against each other such that the conical openings of the connecting parts are aligned with each other and form a continuous conical connecting opening. Receiving elements for receiving tensioning elements are arranged at the smaller diameter end of the conical connecting opening. A conical bolt corresponding to the continuous conical connecting opening is arranged therein, and at least one tensioning element passes through the conical bolt and tensions the conical bolt against the receiving element.

The present invention provides an improved wind turbine rotor blade design that addresses the considerations discussed above. Additional aspects and advantages of the invention may 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 one aspect, the present disclosure is directed to a segmented rotor blade for a wind turbine. The rotor blade includes a first rotor blade segment having a female structural member with first bore holes on opposing sides thereof that are aligned in a chord-wise direction. The rotor blade also includes a second rotor blade segment having a male structural member extending therefrom and through the female structural member such that the first and second rotor blade segments are aligned and connected. Further, the male structural member includes second bore holes on opposing sides thereof that are aligned with the first bore holes. The rotor blade also includes at least one chord-wise extending pin extending through the first and second bore holes so as to join the first and second rotor blade segments together. In addition, the male structural member has a height that increases from a blade root of the rotor blade towards the at least one chord-wise extending pin.

In one embodiment, the height increases to a maximum height at the at least one chord-wise extending pin. In another embodiment, the rotor blade includes at least one gap defined between an outer side surface of the male structural member and an inner side surface of the female structural member. In such embodiments, the maximum height of the male structural member closes the gap at the chord-wise extending pin. In certain embodiments, the height of the male structural member decreases from the maximum height towards a blade tip of the rotor blade.

In further embodiments, the rotor blade further includes at least one span-wise extending pin extending through either or both of the male and female structural members so as to secure the plurality of rotor blade segments to a root ring of the rotor blade.

In additional embodiments, the male structural member contacts the female structural member only at the at least one span-wise extending pin and the at least one chord-wise extending pin. In several embodiments, the rotor blade may further include at least one bushing for receiving each of the at least one span-wise extending pin and the at least one chord-wise extending pin.

In another aspect, the present disclosure is directed to a joint assembly for joining a plurality of rotor blade segments of a rotor blade of a wind turbine. The joint assembly includes a female structural member secured within a first rotor blade segment. The female structural member includes first bore holes on opposing sides thereof that are aligned in a chord-wise direction. Further, the joint assembly includes a male structural member extending longitudinally from an end face of a second rotor blade segment. As such, the male structural member is received within the female structural member of the first rotor blade segment such that the first and second rotor blade segments are aligned and connected. The male structural member includes second bore holes on opposing sides thereof. Further, the second bore holes are aligned with the first bore holes. Moreover, the joint assembly includes at least one chord-wise extending pin extending through the first and second bore holes so as to join the first and second rotor blade segments. In addition, the male structural member has a height that increases from a blade root of the rotor blade towards the at least one chord-wise extending pin. It should be understood that the joint assembly may further include any of the additional features and/or embodiments described herein.

In yet another aspect, the present disclosure is directed to a method for joining a plurality of rotor blade segments of a rotor blade. The method includes providing a first rotor blade segment having a female structural member secured therein. The method also includes providing a second rotor blade segment having a male structural member extending therefrom. Further, the male structural member has a height that increases from a blade root of the rotor blade towards an intermediate location. As such, the method includes inserting the male structural member into the female structural member so as to align first bore holes on opposing sides of the female structural member with second bore holes on opposing sides of the male structural member. Moreover, the method includes inserting at least one chord-wise extending pin through the aligned first and second bore holes so as to join the first and second rotor blade segments at a joint.

In one embodiment, the method also includes aligning the intermediate location of the male structural member with the joint. For example, in one embodiment, the intermediate location corresponds to maximum height of the male structural member. It should be understood that the method may further include any of the additional steps, features and/or embodiments described herein.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the embodiments of the invention and, together with the description, serve to explain the principles 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 of the appended claims.

Referring now to the drawings, <FIG> illustrates a perspective view of one embodiment of a wind turbine <NUM>. As shown, the wind turbine <NUM> generally includes a tower <NUM>, a nacelle <NUM> mounted on the tower <NUM>, and a rotor <NUM> coupled to the nacelle <NUM>. The rotor <NUM> includes a rotatable hub <NUM> and at least one rotor blade <NUM> coupled to and extending outwardly from the hub <NUM>. For example, in the illustrated embodiment, the rotor <NUM> includes three rotor blades <NUM>. However, in an alternative embodiment, the rotor <NUM> may include more or less than three rotor blades <NUM>. Each rotor blade <NUM> may be spaced about the hub <NUM> to facilitate rotating the rotor <NUM> to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub <NUM> may be rotatably coupled to an electric generator (not shown) positioned within the nacelle <NUM> to permit electrical energy to be produced.

Referring now to <FIG>, a perspective view of one of the rotor blades <NUM> of the wind turbine <NUM> of <FIG> is illustrated. As shown, the rotor blade <NUM> includes a blade root <NUM> which is used to mount the rotor blade <NUM> to the hub <NUM> and a blade tip <NUM> opposite the blade root <NUM>. Further, as shown, the body section of the rotor blade <NUM> includes a plurality of individual blade segments <NUM>, <NUM> aligned in an end-to-end order from the blade root <NUM> to the blade tip <NUM>. More specifically, as shown, the rotor blade <NUM> includes, at least, a first rotor blade segment <NUM> and a second rotor blade segment <NUM>. As such, each of the individual blade segments <NUM>, <NUM> may be uniquely configured so that the plurality of segments <NUM>, <NUM> define the complete rotor blade <NUM> having the designed blade profile, length, and other desired characteristics. Thus, the rotor blade <NUM> may have a swept shape giving it a curved contour running from the blade root <NUM> to the blade tip <NUM>. Alternatively, the segmented rotor blade <NUM> may have a non-swept shape. Further, the longitudinal end faces of the individual blade segments <NUM>, <NUM> may have a profile so as to align with the end face of an adjacent blade segment.

In addition, as shown in <FIG>, each of the individual blade segments <NUM>, <NUM> may be formed from a first shell component <NUM> and a second shell component <NUM>. Such shell components <NUM>, <NUM> may be individually formed and joined together at the leading and trailing edges of the rotor blade <NUM>. The individual shell components <NUM>, <NUM> may each include an inner and outer skin, and may be constructed, for example, from a dry fibrous material. In addition, each of the shell components <NUM>, <NUM> may include a core material sandwiched between the inner and outer skins. This core material may be, for example, a lightweight material, such as balsa wood, extruded polystyrene foam, or the like, as is known in the art.

In further embodiments, the rotor blade <NUM> may also include any manner of internal structural components or other support webs between the upper and lower shell components <NUM>, <NUM> of the blade segments <NUM>, <NUM>. For example, as shown in <FIG>, <FIG>, and <FIG>, the rotor blade <NUM> may include spar caps <NUM>, <NUM> extending along substantially the full longitudinal length of the rotor blade <NUM> and are bonded to an inner skin or surface of the rotor blade <NUM>. Further, as shown, the spar caps <NUM>, <NUM> may have a shape and curvature that essentially matches the shape and curvature of the internal skins of the respective shell components <NUM>, <NUM> or any additional internal web adhered to the inner skin surfaces.

Referring particularly to <FIG>, <FIG>, and <FIG>, the rotor blade <NUM> may also include a joint assembly <NUM> formed by a longitudinally extending (e.g. span-wise) rigid male structural member <NUM> that extends through a female structural member <NUM>. For example, in one embodiment, the male structural member <NUM> may form part of a shear web of the rotor blade <NUM> as well as part of the spar caps thereof <NUM>, <NUM>. Further, as shown, the female structural member <NUM> may form part of the shear web as well. Thus, as shown, the joint assembly <NUM> provides structural integrity to the rotor blade <NUM> (i.e. by acting as the shear web between opposing spar caps <NUM>, <NUM>) and joins adjacent rotor blade segments <NUM> together as described herein.

More specifically, as shown in <FIG>, the first rotor blade segment <NUM> includes the female structural member <NUM> therein. Further, as shown in <FIG> and <FIG>, the female structural member <NUM> defines an internal passageway <NUM>. Moreover, as shown, the female structural member <NUM> has a certain keyed profile that corresponds or matches the cross-sectional profile of the male structural member <NUM>. In addition, the female structural member <NUM> may be adhered to the inner skins of the shell components <NUM>, <NUM> and spar caps <NUM>, <NUM> using any suitable adhesive material or bonding method. For example, the female structural member <NUM> may be attached directly to the inner skin surfaces of the shell components <NUM>, <NUM> or may be attached to a separate web that is adhered to the inner skin surfaces for added support and rigidity. In addition, as shown particularly in <FIG>, the male structural member <NUM> extends from an end face <NUM> the second blade segment <NUM> and has a particular cross-sectional profile that generally corresponds to the cross-sectional shape of the internal passageway <NUM> of the female structural member <NUM>.

It should be understood that the male and female structural members <NUM>, <NUM> may take on various shapes and configurations. For example, as shown generally in <FIG> and <FIG>, the male structural member <NUM> corresponds to a beam-like structure and a hollow box beam structure, respectively. Similarly, as shown in <FIG>, <FIG>, and <FIG>, the internal passageway <NUM> of the female structural member <NUM> have a generally box-like cross-sectional profile that corresponds to the profile of the male structural member <NUM>. More specifically, as shown, the male structural member <NUM> may have a hollow square or rectangular configuration, with the spar caps <NUM>, <NUM> defined by opposite sides of the box beam structure. In alternate embodiments, as shown in <FIG>, the male structural member <NUM> may have a hollow beam structure with concave or convex walls extending between the spar caps <NUM>, <NUM>.

The male and female structural members <NUM>, <NUM> may be formed of any suitable material conventionally used as internal shear webs for wind turbine blades. For example, the male and/or female structural members <NUM>, <NUM> may be formed of a carbon fiber reinforced matrix or a glass fiber reinforced polymer, or other strong, light-weight material.

Referring now to <FIG> and <FIG>, the female structural member <NUM> may also include first bore holes <NUM> on opposing sides thereof. More specifically, as shown, the first bore holes <NUM> may be aligned in a chord-wise direction. Similarly, as shown in <FIG>, <FIG> and <FIG>, the male structural member <NUM> includes second bore holes <NUM> on opposing sides thereof that are aligned with the first bore holes <NUM>.

Further, as shown in <FIG>, at least one gap <NUM> is defined between an outer side surface <NUM> of the male structural member <NUM> and an inner side surface <NUM> of the female structural member <NUM>. Moreover, as shown, the joint assembly <NUM> includes at least chord-wise extending pin <NUM> extending through the first and second bore holes <NUM>, <NUM> so as to join the first and second rotor blade segments <NUM>, <NUM> together at a joint <NUM>.

Referring particularly to <FIG>, the rotor blade <NUM> may also include at least one span-wise extending pin <NUM> extending through either or both of the male and female structural members <NUM>, <NUM> so as to secure the plurality of rotor blade segments <NUM> to the root ring <NUM> of the rotor blade <NUM>. More specifically, as shown, each joint <NUM> may further include at least one bushing <NUM> for receiving the span-wise extending pin(s) <NUM> and the chord-wise extending pin(s) <NUM>.

Referring now to <FIG> and <FIG>, cross-sectional views of a segmented rotor blade according to conventional construction and according to the present disclosure are illustrated, respectively. As shown in <FIG>, the male structural member <NUM> has a constant height from the blade root <NUM> to the chord-wise extending pin <NUM>. Thus, for conventional joint assemblies, the deflected shape of the male structural member <NUM> contacts the female structural member <NUM> between the pins <NUM>, <NUM>, which decrease the clearance at the edges of the bushings <NUM> for the pins <NUM>, <NUM>.

In contrast, as shown in <FIG>, the male structural member <NUM> has a height <NUM> that increases from the blade root <NUM> of the rotor blade <NUM> towards the chord-wise extending pin <NUM>. More specifically, as shown, the height <NUM> of the male structural member <NUM> increases to a maximum height at the chord-wise extending pin(s) <NUM>. In such embodiments, as shown, the maximum height of the male structural member <NUM> closes the gap <NUM> at the chord-wise extending pin <NUM>. Still referring to <FIG>, the height <NUM> of the male structural member <NUM> of the present disclosure may also decrease from the maximum height at the chord-wise extending pin <NUM> towards the blade tip <NUM> of the rotor blade <NUM>.

Due to the localized increase height of the male structural member <NUM>, the male structural member <NUM> can contact the female structural member <NUM> only at the locations of the pins <NUM>, <NUM>. In other words, the male structural member <NUM> can be sized such that its deflected profile (<FIG>) within the female structural member <NUM> is small enough that the members <NUM>, <NUM> do not make contact outside of the pins constraining the members <NUM>, <NUM> together. Due to the arrangement, however, there is no difference in deflection at the pins <NUM>, <NUM> between the female structural member <NUM> and the male structural member <NUM>. This allows the height <NUM> of the male structural member <NUM> to increase locally at least at the chord-wise extending pin <NUM>, thereby creating more head-room for the pin <NUM> to occupy space.

As such, the present disclosure provides many advantages not present in the prior art. For example, the joint assembly <NUM> of the present disclosure provides increased space for the chord-wise extending pin(s) <NUM>. Further, the male structural member <NUM> is more efficient for the same amount of material. In addition, the joint assembly <NUM> of the present disclosure allows for longer blade tips.

Referring now to <FIG>, a flow diagram of one embodiment of a method <NUM> for joining a plurality of rotor blade segments <NUM> is illustrated. Thus, as shown at <NUM>, the method <NUM> includes providing a first rotor blade segment <NUM> having a female structural member <NUM> secured therein. As shown at <NUM>, the method includes providing a second rotor blade segment <NUM> having a male structural member <NUM> having a height <NUM> that increases from the blade root <NUM> of the rotor blade <NUM> towards an intermediate location <NUM>. As shown at <NUM>, the method <NUM> includes inserting the male structural member <NUM> into the female structural member <NUM> so as to align the first bore holes <NUM> on opposing sides of the female structural member <NUM> with second bore holes <NUM> on opposing sides of the male structural member <NUM>. Thus, as shown at <NUM>, the method <NUM> include inserting at least one chord-wise extending pin <NUM> through the aligned first and second bore holes <NUM>, <NUM> so as to join the first and second rotor blade segments <NUM>, <NUM> at a joint <NUM>.

In one embodiment, the method <NUM> also includes aligning the intermediate location <NUM> of the male structural member <NUM> with the joint <NUM>. For example, as shown in <FIG>, the intermediate location <NUM> corresponds to maximum height of the male structural member <NUM>.

Claim 1:
A segmented rotor blade (<NUM>) for a wind turbine (<NUM>), comprising:
a first rotor blade segment (<NUM>) comprising a female structural member (<NUM>), the female structural member (<NUM>) comprising first bore holes (<NUM>) on opposing sides thereof, the first bore holes (<NUM>) aligned in a chord-wise direction;
a second rotor blade segment (<NUM>) comprising a male structural member (<NUM>) protruding therefrom, the male structural member (<NUM>) comprising a beam-like structure extending longitudinally through the female structural member (<NUM>) such that the first and second rotor blade segments (<NUM>, <NUM>) are aligned and connected, the beam-like structure of the male structural member (<NUM>) comprising second bore holes (<NUM>) on opposing sides thereof, the second bore holes (<NUM>) aligned with the first bore holes (<NUM>); and,
at least one chord-wise extending pin (<NUM>) extending through the first and second bore holes (<NUM>, <NUM>) so as to join the first and second rotor blade segments (<NUM>, <NUM>) together, characterised in that the beam-like structure of the male structural member (<NUM>) comprising a height (<NUM>) that increases from a blade root (<NUM>) of the rotor blade (<NUM>) towards the at least one chord-wise extending pin (<NUM>).