Patent Description:
As will be appreciated, during operation of a wind turbine, the wind turbine blades tend to deflect towards the tower. This may in turn lead to damage to the wind turbine blade and the tower. In order to avoid collision of the wind turbine blade to the tower, it is desirable to have acceptable tower clearance. The term 'tower clearance,' as used herein, refers to a clearance provided for the wind turbine blades to rotate without striking the tower. More specifically, the term 'tower clearance' refers to a distance maintained between the tower and the rotating wind turbine blades to prevent the rotating wind turbine blades from striking the tower.

In recent times, the length of wind turbine blades has increased considerably and this increase in length of wind turbine blades contribute to increased scenarios of wind turbine blade to tower collision.

Different sensing and control techniques for managing the tower clearance have been proposed. These techniques utilize sensors disposed on the tower and/or blades to determine a distance between the rotating blades and the tower. Based on the determined distance, control strategies are used to improve the tower clearance. However, these strategies provide the clearance information only when the blades are in front of the tower, and thus may be less likely to be effective.

In addition, different design modifications to the wind turbine blade to provide better tower clearance have been proposed. This would aid having built in features in the wind turbine blade while manufacturing the wind turbine blade. In one example, the wind turbine blade is manufactured with a pre-bend to have a better tower clearance. In other example, described in <CIT>, a wind turbine blade is divided into two separate parts , where the coning angle of an outer blade part can be varied relative to an inner blade part. This design is not feasible in practice, in particular for very long blades. However, manufacturing and transport of the wind turbine blade with a pre-bend is challenging. Also, for a jointed blade with pre-bend there is a huge stress specifically at chord-wise joint. Hence, there lies a need to have tower clearance by using simpler techniques to create pre-bend in jointed wind turbine blades.

In accordance with aspects of the present specification, a wind turbine blade is disclosed. The wind turbine blade includes a tip blade segment and a root blade segment extending in opposite directions from a chord-wise joint, where each of the tip blade segment and the root blade segment includes a pressure side shell member and a suction side shell member. Further, wind turbine blade includes a beam structure. The beam structure includes a first section, where the first section is received at a receiving section of the root blade segment and a second section disposed in the tip blade segment and extending at an angle with respect to the first section, such that at least a portion of the tip blade segment is disposed outwardly with respect to a blade axis.

In accordance with another aspect of the present specification, a method of manufacturing a wind turbine blade. The method includes arranging a tip blade segment and a root blade segment in opposite directions from a chord-wise joint, where each of the tip blade segment and the root blade segment comprises a pressure side shell member and a suction side shell member. Further, the method includes inserting a first section of a beam structure into a receiving section of the root blade segment, where a second section of a beam structure is disposed inside the tip blade segment and extending at an angle with respect to the first section, such that at least a portion of the tip blade segment is disposed outwardly with respect to a blade axis.

It is understood that the beam is utilised to connect the tip blade segment and the root blade segment such that the assembled blade comprises said two blade segments and the beam.

In a preferred embodiment, the wind turbine blade comprises a continuous shell structure, such that the wind turbine blade appears with a single continous aerodynamic profile. The shell structure comprises the pressure side shell member and the suction side shell member of the tip blade segment as well as the pressure side shell member and the suction side shell member of the root blade segment. The shell members of the tip blade segment may be directly connected to the corresponding shell members of the root blade segment, either directly or via one or more connecting shell members. Accordingly, the various shell members may abut each other at a common interface. The common interface may extend substantially in a chordwise direction of the blade. The members may also be connected via e.g. an overlamination. In general, the continuous shell structure is smooth such that the blade appears as a single assembled wind turbine blade.

According to the invention, the beam structure connects the tip blade segment and the root blade segment, such that the two parts are disposed in a fixed relative angle to each other (disregarding the deflection of the blade during operation).

In a preferred embodiment, the wind turbine blade includes one or more first joint pins located at a first end of the first section for operatively coupling with the receiving section of the root blade segment.

In yet another preferred embodiment, wind turbine blade includes one or more pin joint slots located proximate to the chord-wise joint and oriented in chord-wise direction.

In yet another preferred embodiment, the one or more pin joint slots are configured to receive corresponding second joint pins.

In yet another preferred embodiment, the first and second joint pins include a bolt, a pin, a bush, or combinations thereof.

It is clear that the one or more first and second pin joints are internal joints.

In yet another preferred embodiment, the at least a portion of the tip blade segment is disposed outwardly in a curved manner with respect to a blade axis.

In yet another preferred embodiment, the wind turbine blade is coupled to a hub, extending outwards from the hub and then extending outwardly with respect to the blade axis in a curved manner.

In yet another preferred embodiment, the beam structure is made of composite material.

In yet another preferred embodiment, the beam structure is manufactured using additive manufacturing technique.

In yet another preferred embodiment, the composite material comprises at least one of carbon fibre, aramid fibre, and fibreglass.

In yet another preferred embodiment, the wind turbine blade includes an internal support structure, wherein the beam structure forms a portion of the internal support structure.

In a preferred embodiment, the wind turbine includes a hub and at least one wind turbine blade, where the at least one wind turbine blade is coupled to a hub, extending outwards from the hub and then extending outwardly with respect to the blade axis in a curved manner.

In yet another preferred embodiment, the method includes operatively coupling first end of the first section with the receiving section of the root blade segment using one or more first joint pins.

In a preferred embodiment, the angle between the first section and the second section is <NUM>-<NUM> degrees, more preferably <NUM>-<NUM> degrees, and even more preferably <NUM>-<NUM> degrees.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this specification belongs. The terms "first", "second", and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The use of "including," "comprising" or "having" and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. Furthermore, terms "circuit" and "circuitry" and "controlling unit" may include either a single component or a plurality of components, which are active and/or passive and are connected or otherwise coupled together to provide the described function. In addition, the term operatively coupled as used herein includes wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software-based communication, or combinations thereof.

As will be described in detail hereinafter, various embodiments of a wind turbine blade and a method of manufacturing a wind turbine blade are disclosed. Specifically, a jointed wind turbine blade with a pre-bend is disclosed. More specifically, a jointed wind turbine blade with a pre-bend formed by having a section of a beam structure of the jointed wind turbine blade at an angle with respect to other section of the beam structure of the jointed wind turbine blade is presented. As will be appreciated, typically the pre-bend in the wind turbine blade is created by manufacturing the wind turbine blade shell with an inbuilt pre-bend. In order to manufacture the wind turbine blade shell with a pre-bend, the mould employed needs to have the desired pre-bend. The process of resin infusion is challenging when a mould having a pre-bend is employed. As will be appreciated, this shape of the mould contributes to hydrostatic pressure, which in turn is detrimental to the resin infusion process and laminate control.

In order to avoid issues with respect to the pre-bend, the present specification discloses use of an angled beam structure to create a pre-bend, without employing a wind turbine blade shell having a pre-bend. In other words, the use of angled beam structure aids in avoiding creation of pre-bend in the wind turbine blade shells. Accordingly, the angled beam structure may aid in creating a pre-bend for the wind turbine blade. Specifically, the angled beam structure aids in moving the wind turbine blade outwardly and away from the wind turbine tower. Accordingly, the tower clearance of a desired value is maintained thereby avoiding collision of the wind turbine blade with the wind turbine tower. Although the present specification describes one embodiment of pre-bending the wind turbine blade, other embodiments of pre-bending the wind turbine blade by using different geometries of the beam structure is also anticipated.

<FIG> illustrates a diagrammatical representation of a wind turbine. The wind turbine as represented in <FIG> includes a wind turbine tower <NUM>, a nacelle <NUM> and a main shaft <NUM> with a hub <NUM> for wind turbine blades <NUM>. As will be appreciated, when subjected to wind pressure the wind turbine blades <NUM> bend backwards and herewith inwards towards the tower <NUM>.

In accordance with aspects of the present specification, the wind turbine blade <NUM> is designed in such a manner that the wind turbine blade is bent away from the tower <NUM>. Specifically, the wind turbine blades <NUM> coupled to the hub <NUM>, have an outwardly directed curvature towards an outward direction <NUM>. More specifically, tip blade segment <NUM> of the wind turbine blades <NUM> have an outwardly directed curvature towards a direction <NUM>. More specifically, the wind turbine blades <NUM> extend outwards, in a direction <NUM>, from the hub <NUM> and then extend outwardly, in the direction <NUM>, with respect to a blade axis <NUM> in a curved manner, as represented by reference numeral <NUM>. It may be noted that when the blades <NUM> are at rest, the blades <NUM> may stand at a distance <NUM> from the blade axis <NUM>. The blade axis <NUM> is an axis drawn along the length of the wind turbine blade <NUM> from root end <NUM> of the blade to tip end <NUM> of the blade and perpendicular to root plane <NUM>. In one example, the blade axis <NUM> passes through a centre point on the root plane <NUM>. According to aspects of the present specification, during strong winds, the wind turbine blades <NUM> may bend towards the tower <NUM>, however, the wind turbine blades <NUM> may still be at a safe distance from the tower <NUM>. While the blades <NUM> are depicted as extending substantially radially from the hub <NUM>, it is understood that the rotor often is slightly coned, such that the blades <NUM> are angled slightly forward from the hub. Further, it is appreciated that the rotor may also be slightly tilted, such that the blades <NUM>, when facing downwards are further angled away from the tower <NUM>.

<FIG> is a diagrammatical representation of a wind turbine blade for use in <FIG>. The wind turbine blade <NUM> includes a root blade segment <NUM> and a tip blade segment <NUM>. The root blade segment <NUM> is nearer to the root end of the wind turbine blade <NUM> and includes the root end of the wind turbine blade <NUM>. Further, the tip blade segment <NUM> is nearer to the tip end of the wind turbine blade <NUM> and includes the tip end of the wind turbine blade <NUM>. The root blade segment <NUM> and the tip blade segment <NUM> extend in opposite directions from a chord-wise joint <NUM>. Each of the tip blade segment <NUM> and the root blade segment <NUM> includes pressure side shell member <NUM>, a suction side shell member <NUM> and an internal support structure <NUM>. Furthermore, the wind turbine blade <NUM> includes a beam structure <NUM>. The beam structure <NUM> may form a portion of the internal support structure <NUM>.

The beam structure <NUM> is an angled structure. The beam structure <NUM> includes a first section <NUM> and a second section <NUM>. The first section <NUM> is received at a receiving section of the root blade segment <NUM>. The second section <NUM> is disposed inside the tip blade segment <NUM>. The second section <NUM> extends at an angle with respect to the first section <NUM>. In one example, the second section <NUM> is at an angle with respect to the blade axis <NUM>. As a result, the tip blade segment <NUM> is disposed outwardly with respect to the blade axis <NUM>. Accordingly, the tip blade segment <NUM> of the wind turbine blade <NUM> may be disposed outwardly, away from the tower <NUM>. Specifically, the tip blade segment <NUM> of the wind turbine blade <NUM> may extend outwardly with respect to the blade axis <NUM> in a curved manner.

Additionally, the beam structure <NUM> is made of composite material. The composite material may include at least one of carbon fibre, aramid fibre, and fibreglass. In one embodiment, the beam structure <NUM> may be formed using additive manufacturing technique/Three-Dimensional (3D) printing technique. As will be appreciated, 3D printing technique builds a three-dimensional object from a computer-aided design (CAD) model, usually by successively adding material layer by layer. The 3D printing technique may also be alternatively referred to as additive manufacturing technique. The beam structure <NUM> may form a part of the internal support structure <NUM> for the wind turbine blade <NUM>. In one embodiment, the internal support structure <NUM> may also include a shear web (not shown in <FIG>) connected with a suction side spar cap (not shown in <FIG>) and a pressure side spar cap (not shown in <FIG>). The term 'internal support structure' as used herein refers to a structure disposed internal to the wind blade which provides support to the wind blade to effectively withstand loads/stress/strain/torsion.

In accordance with aspects of the present specification, the location where the tip blade segment <NUM> joins the root blade segment <NUM> is referred to as a chord-wise joint <NUM>. In one embodiment, the root blade segment <NUM> to tip blade segment <NUM> ratio may be about <NUM>-<NUM>% of total length of the wind turbine blade <NUM>. In another embodiment, the root blade segment <NUM> to tip blade segment <NUM> ratio may be about <NUM>-<NUM>% of total length of the wind turbine blade <NUM>.

In the example of <FIG>, the wind turbine blade <NUM> is a jointed wind turbine blade, where the root blade segment <NUM> and the tip blade segment <NUM> are separate sections. Once the first section <NUM> is received at the receiving section of the root blade segment <NUM>, the tip blade segment <NUM> and the root blade segment <NUM> are coupled to one another. In addition, glue or laminate may be employed to securely couple the root blade segment <NUM> to the tip blade segment <NUM>. Accordingly, an entirely assembled wind turbine blade <NUM> is achieved. Once the tip blade segment <NUM> and the root blade segment <NUM> are assembled to form the wind turbine blade <NUM>, this wind turbine blade <NUM> may be installed on the tower <NUM>. In one embodiment, if there is a damage in the tip blade segment <NUM>, the tip blade segment <NUM> may be replaced.

During transportation, in one example, the root blade segment <NUM> and the tip blade segment <NUM> may be transported separately. Accordingly, transport of the wind turbine blade <NUM> may be relatively easier. It may be noted that in one example, while transporting the tip blade segment <NUM>, the first section <NUM> of the beam structure <NUM> extends from the tip blade segment <NUM>.

The pressure side shell members <NUM> and suction side shell members <NUM> of the tip blade segment <NUM> and the root blade segment <NUM> may be directly connected, e.g. via gluing or the like, to each other in order to form a continuous aerodynamic shell structure. Alternatively, they may be connected via one or more intermediate shell members (not shown) to form the continuous aerodynamic shell structure. The various shell members may also be connected to each other via overlaminations. Now referring to <FIG>, a detailed diagrammatical representation of at least a portion of the wind turbine blade of <FIG> is represented. Specifically, <FIG> depicts the beam structure <NUM> of the wind turbine blade of <FIG> and the coupling of the beam structure <NUM>. The beam structure <NUM> includes a first section <NUM> and a second section <NUM>. The first section <NUM> is received in a receiving section <NUM>. The receiving section <NUM> is disposed internally in the root blade segment <NUM>.

Further, the first section <NUM> extends from the second section <NUM>. The second section <NUM> is at an angle with respect to the first section <NUM>. The angle is represented by reference numeral <NUM>. In a preferred embodiment, the angle <NUM> is an acute angle. The angle <NUM> is in such a manner that the second section is away from the tower when the wind blade is installed. The second section <NUM> is disposed internal to the tip blade segment <NUM>. The angle <NUM> may preferably be <NUM>-<NUM> degrees, more preferably <NUM>-<NUM> degrees, and even more preferably <NUM>-<NUM> degrees.

Further, a first joint pin <NUM> is located at a first end <NUM> of the first section <NUM> for operatively coupling with the receiving section <NUM> of the root blade segment <NUM>. The receiving section <NUM> includes an aperture <NUM>. The first joint pin <NUM> is securely received in the aperture <NUM>. This would in turn aid is securely coupling the tip blade segment <NUM> to the root blade segment <NUM>.

Furthermore, a pin joint slot <NUM> is located proximate to the chord-wise joint <NUM> and oriented in chord-wise direction. The pin joint slot <NUM> is configured to receive corresponding second joint pin (not shown in <FIG>). This would aid is further securely coupling the tip blade segment <NUM> to the root blade segment <NUM>.

In some embodiments, the tip blade segment <NUM> is coupled to the root blade segment <NUM> before transportation. In another embodiment, the tip blade segment <NUM> and the root blade segment <NUM> may be transported separately and joined at the site of installation. In such embodiments, the tip blade segment <NUM> and the root blade segment <NUM> may be coupled to one another by inserting the first joint pin <NUM> into the receiving section <NUM> on-site. Subsequently, in some embodiments, the tip blade segment <NUM> is permanently joined to the root blade segment <NUM> at the chord-wise joint <NUM>. Specifically, an adhesive (glue) or lamination may be employed to permanently couple the tip blade segment <NUM> with the root blade segment <NUM>. Accordingly, a jointed wind turbine blade <NUM> with a pre-bend is obtained. The number of pin joint slots and the first and second joint pins may vary in different embodiments.

According to aspects of the present specification, a jointed wind turbine blade with a pre-bend and a method of manufacture of such a jointed wind turbine blade is disclosed. In accordance with aspects of the present specification, the pre-bend in the wind turbine blade is shaped by having an angled beam structure instead of physically shaping a pre-bend in the shells of the wind turbine. Since the wind turbine blade shells are devoid of pre-bends, infusion process in the wind turbine blades would be relatively easier. Also, the number of infusion machines that need to be employed may be reduced per shell.

Furthermore, since the moulds no longer need to have pre-bend to form a pre-bend in the wind turbine blade shell, structure of the mould may be simpler, lighter, and will be relatively cheaper. In one example, the mould may have reduced turning height and hence, the height of the wind blade manufacturing facility may also be lesser. Additionally, since the moulds do not have pre-bend, the infusion across the shell may be uniform thereby contributing to lesser defects and repairs. The proposed system and method may find application in blades of varying length and may be preferred in blades which are substantially longer, such as the <NUM> meter blade.

Claim 1:
A wind turbine blade (<NUM>), comprising:
a tip blade segment (<NUM>) and a root blade segment (<NUM>) extending in opposite directions from a chord-wise joint (<NUM>), wherein each of the tip blade segment (<NUM>) and the root blade segment (<NUM>) comprises a pressure side shell member and a suction side shell member;
a beam structure (<NUM>) comprises:
a first section (<NUM>), wherein the first section (<NUM>) is configured to be received at a receiving section of the root blade segment (<NUM>); and
a second section (<NUM>) disposed in the tip blade segment (<NUM>) and extending at an angle with respect to the first section (<NUM>), such that at least a portion of the tip blade segment (<NUM>) is disposed outwardly with respect to a blade axis, wherein the beam structure connects the tip blade segment (<NUM>) and the root blade segment (<NUM>), such that the tip blade segment (<NUM>) and the root blade segment (<NUM>) are disposed in a fixed relative angle to each other, disregarding the deflection of the blade during operation.