WO2010084320A2

WO2010084320A2 - Composite blade

Info

Publication number: WO2010084320A2
Application number: PCT/GB2010/000097
Authority: WO
Inventors: Andrew Cox
Original assignee: Aquamarine Power Limited
Priority date: 2009-01-21
Filing date: 2010-01-21
Publication date: 2010-07-29
Also published as: GB201000955D0; GB2467226A; GB0900945D0; WO2010084320A3

Abstract

A composite blade structure (10) for a rotodynamic assembly (4) comprises a composite blade portion (24) and an integrally formed composite flange portion (20) configured to permit the blade structure (10) to be secured to a rotor (12). In one disclosed arrangement the composite blade structure (10) is utilised on a tidal turbine assembly (2).

Description

COMPOSITE BLADE

FIELD OF THE INVENTION

The present invention relates to a composite blade, a method of manufacture of a composite blade and a rotodynamic assembly comprising such a blade. The composite blade is particularly suitable for, though is not exclusively limited to, use in turbines such as tidal turbines.

BACKGROUND OF THE INVENTION

Composite blades are known for use in wind turbines. Such blades generally have an aerodynamic control surface and are attached to a rotor at one end. Conventionally, each blade has an end face that faces the rotor and metal inserts are bonded into the end face. Each insert typically has an internal thread formed therein thus permitting attachment of the blade to the rotor via fasteners which extend from the rotor into threaded engagement with the metal inserts.

Such a blade attachment arrangement can withstand maximum shear forces and maximum bending moments which may be determined, at least in part, by the strength of the bonding between the metal inserts and the composite blade.

In addition, the strength of the bonding between the metal inserts and the composite blade may be degraded by the ingress of moisture or other fluids over time thereby reducing the lifetime of, or increasing the frequency of maintenance work required for, a wind turbine using such a blade attachment arrangement. Furthermore, such problems may be exacerbated when such a blade attachment arrangement is immersed in a liquid such as water, for example, when such a blade attachment arrangement is used in a stream of water such as a tidal stream or the like.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a composite blade structure for a rotodynamic assembly, the blade structure comprising a composite blade portion and an integrally formed composite flange portion configured to permit the blade structure to be secured to a rotor.

The blade structure may be formed, at least partially, of a composite material having fibres that extend from the flange portion at least partially along a length of the blade portion. At least some of the fibres may comprise a first portion that extends in a plane of the flange portion and a second portion that extends at least partially along the length of the blade portion. At least some of the fibres may comprise a third portion intermediate the first and second portions. The third portion may be curved. The third portion of at least some of the fibres may be curved through an angle substantially equal to 90°.

The blade structure may extend along a blade axis. The blade axis may, for example, be substantially perpendicular to the flange portion.

The composite blade structure may comprise a composite neck portion intermediate the flange and blade portions wherein the flange portion, the neck portion and the blade portion are integrally formed.

The blade structure may be formed of a composite material having fibres at least some of which extend from the flange portion at least partially along the neck portion. The blade structure may be formed of a composite material having fibres at least some of which extend from the neck portion at least partially along the blade portion. The fibres may comprise glass fibres, carbon fibres or metal fibres or the like. Additionally or alternatively, the composite material may comprise other structural elements such as particulates, nanotubes or the like.

The flange portion may comprise an inner face that is adapted to engage a rotor. The inner face may extend in a plane which is parallel to a rotational axis of the rotor. Alternatively or additionally, the inner face may extend in a plane which is obliquely aligned relative to a rotor axis. The flange may comprise an outer face opposite the inner face.

The blade structure may have an integrally formed engagement feature that is adapted to co-operate with a corresponding engagement feature of a rotor in order to locate the blade structure with respect to the rotor prior to the blade structure being secured to the rotor.

The blade structure may comprise at least one of an integrally formed projecting portion or an aperture or a recess or the like. The blade structure may, for example, comprise a projecting portion that is adapted to co-operate with a corresponding aperture or a recess or the like formed in the rotor. The projecting portion may extend away from the inner face of the flange portion in a direction away from the blade portion. Additionally or alternatively the blade structure may comprise an aperture or a recess or the like that is adapted to co-operate with a corresponding projecting portion of the rotor.

The engagement feature may facilitate the transfer of forces between the blade structure and the rotor. The engagement feature may, for example, facilitate the transfer of shear or bending forces between the blade structure and rotor.

The blade structure or the rotor may comprise a seal which serves to prevent the penetration of a fluid such as water along an interface between the blade structure and the rotor. Thus, the seal may act to prevent the passage of fluid from an environment surrounding the blade structure and the rotor to an internal cavity formed between the blade structure and the rotor. The seal may be configured to be mounted in a groove defined in one or both of the blade structure and rotor. For example, the groove may be formed in a surface of an engagement feature of the blade structure that is adapted to co-operate with a corresponding engagement feature of the rotor. Alternatively, the groove may be formed in a surface of an engagement feature of the rotor that is adapted to cooperate with a corresponding engagement feature of the blade structure.

The flange portion may be adapted to be secured to a rotor by means of a fastening arrangement. The fastening arrangement may comprise at least one or any combination of, for example, of a stud, a nut, a bolt, a threaded connection, a clamp assembly, a lock assembly, a clip assembly or the like.

The flange portion may comprise a flange through-hole. The flange portion may comprise a plurality of flange through-holes. The flange through-holes may be circumferentially arranged around a blade axis. The flange through-holes may have a uniform angular distribution around the blade axis. The flange through-hole may, for example, be adapted to accommodate a corresponding stud, pin, bolt or protrusion or the like for attachment of the flange portion to a rotor.

The flange through-hole may have a wear-resistant internal surface to protect the or each flange through-hole from mechanical damage when the blade is installed or removed thus serving to prevent mechanical failure of the blade when in use.

The flange through-hole may comprise an insert. The insert may at least partially line an inner surface of the flange through-hole. The insert may comprise a wear-resistant tube. The wear-resistant tube may be secured to a surface of the flange through-hole. The wear-resistant tube may, for example, be in threaded engagement with, interference fitted, bonded or the like into the flange through-hole. The wear-resistant tube may be formed from any wear-resistant material. The wear- resistant tube may, for example, be formed of a metallic material such as stainless steel, brass or the like. The wear-resistant tube may alternatively, or additionally, be formed of a non-metallic material such as nylon, PTFE or the like. The flange through-hole may be adapted to receive a fastener therein to permit the flange to be secured to a rotor. The flange portion may have a thickness between the inner and outer faces thereof such that a fastener may extend from the rotor through the flange through-hole so as to secure the flange portion to the rotor. Examples of such a fastener include a stud and nut arrangement or a bolt or the like.

The fastener may, for example, comprise a stud. The stud may be in threaded engagement at a first end with a corresponding internally threaded hole formed in the rotor. Alternatively, a first end of the stud may extend through a through-hole formed in a rotor wall and a nut may be in threaded engagement with the first end of the stud on a side of the rotor wall opposite the flange portion of the blade structure. The stud may extend through a through-hole of the flange portion and have a second end opposite the first end which second end protrudes beyond an outer face of the flange portion wherein a nut is in threaded engagement with the second end of the stud. The nut or nuts may be tensioned so as to secure the flange portion to the rotor.

The fastener arrangement may comprise a clamping arrangement. An outer face of the flange portion may, for example, be adapted to co-operate with a clamp. The clamp may be adapted to engage the outer face of the flange portion and compress the flange portion such that an inner face of the flange portion engages the rotor. The clamp may, for example, be adapted to compress the flange portion by means of at least one fastener that extends from the rotor, through the flange portion and the clamp. Examples of such fasteners include a stud and nut arrangement or a bolt or the like.

The clamp may comprise a unitary clamp. The clamp may comprise a clamping ring. The clamp may comprise at least first and second clamping parts. Providing component parts of the clamp may have the advantage that the individual clamping parts may be fitted around the blade so as to engage the outer face of the flange portion without having to pass the individual clamping parts over the blade portion of the blade structure. The clamp may be formed from a non-composite material such as steel or the like. Alternatively, the clamp may be formed from a composite material.

The flange portion may be pre-stressed. For example, the flange portion may be compressed prior to use of the blade. For example, compressive forces may be applied to the inner and outer faces of the flange portion. Such forces may be applied either prior to attachment of the blade to a rotor or during attachment of the blade to the rotor.

The or each fastener extending from the rotor through the flange portion and the clamp may be tensioned so as to compress the flange portion by a predetermined amount. This may result in the transmission of shear forces via friction between the outer face of the flange portion and the clamp and between the inner face of the flange portion and the rotor. This blade attachment arrangement results in the transfer of minimal shear forces between the blade structure and the rotor through any integrally formed engagement feature of the blade structure that engages a corresponding engagement feature of the rotor. This also results in any bending moments that act on the blade structure during use being resisted by forces in the fasteners and the blade structure.

Such a blade attachment arrangement may therefore avoid shear loading between the composite blade structure and any metallic components and results in direct bearing loads between the composite blade structure and the clamp and between the composite blade structure and the rotor. In particular, such a blade attachment arrangement does not incorporate metal inserts bonded into the composite blade structure and consequently provides a stronger more reliable attachment arrangement. Such an attachment arrangement may be less prone to mechanical failure due to moisture or liquid ingress than other attachment arrangements known in the art and may, therefore, have a greater lifetime or require less maintenance work. The blade flange portion may be adapted to be secured to a portion of the rotor that is configured or functions to rotate the blade structure about a blade axis along which the blade portion extends. For example, the flange portion may be adapted to be secured to a pitching arrangement. In one exemplary use, the flange portion may be adapted to be secured to part of a pitch ring. The part of the pitch ring to which the flange portion is secured may, for example, rotate with respect to the rotor.

The blade structure may comprise a control surface such as a fluid control surface for use in a fluid stream such as a liquid or gaseous stream. The control surface may, for example, be configured for use in a tidal, current, wind or air stream or the like.

The blade structure may be used in a turbine apparatus. For example, the blade structure may be used in a turbine apparatus such as that disclosed in published international patent application WO2005/103484.

The blade structure may be at least partially hollow. The blade structure may, for example, contain a cavity. The cavity may extend through the flange portion. Additionally or alternatively, the cavity may extend through any integrally formed engagement feature of the blade that is adapted to co-operate with a corresponding engagement feature of the rotor.

The flange portion may be circularly symmetric. The flange portion may, for example, be tubular. The engagement feature may also be circularly symmetric. The engagement feature may, for example, be tubular. The engagement feature may, for example, be an integrally formed tubular projecting portion extending from the flange portion in a direction away from the blade portion. The flange portion and the engagement feature may be concentric.

According to a second aspect of the present invention there is provided a rotodynamic assembly comprising a rotor and at least one blade structure according to the first aspect of the present invention, wherein the blade structure is secured to the rotor via the integrally formed flange.

The rotodynamic assembly may comprise a plurality of blade structures wherein each blade structure is provided in accordance with the first aspect of the present invention.

The blade structure or the rotor may comprise a seal which serves to prevent the penetration of a fluid such as water along an interface between the blade structure and the rotor. Thus, the seal may act to prevent the passage of fluid from an environment surrounding the blade structure and the rotor to an internal cavity formed between the blade structure and the rotor.

The blade structure or the rotor may comprise a groove formed in a surface thereof to accommodate the seal. For example, the groove may be formed in a surface of an engagement feature of the blade structure that is adapted to co-operate with a corresponding engagement feature of the rotor. Alternatively, the groove may be formed in a surface of an engagement feature of the rotor that is adapted to cooperate with a corresponding engagement feature of the blade structure.

The rotodynamic assembly may further comprise a fastener arrangement. The fastener arrangement may comprise a clamping arrangement. An outer face of the flange portion of the blade structure may, for example, be adapted to co-operate with a clamp. The clamp may be adapted to engage the outer face of the flange portion and compress the flange portion such that an inner face of the flange portion engages the rotor. The rotodynamic assembly may further comprise at least one fastener that may extend from the rotor, through a flange through-hole and through a clamp through-hole. Examples of such fasteners include a stud and nut arrangement or a bolt or the like.

The clamp may comprise a unitary clamp. The clamp may comprise a c\amping ring. The clamp may comprise at least first and second clamping parts. Providing component parts of the clamp may have the advantage that the individual clamping parts may be fitted around the blade so as to engage the outer face of the flange portion without having to pass the individual clamping parts over the blade portion of the blade structure. The clamp may be formed from a non-composite material such as steel or the like. Alternatively, the clamp may be formed from a composite material.

Such a blade attachment arrangement may therefore avoid shear loading between the composite blade structure and any metallic components and results in direct bearing loads between the composite blade structure and the clamp and between the composite blade structure and the rotor. In particular, such a blade attachment arrangement does not incorporate metal inserts bonded into the composite blade structure and consequently provides a stronger more reliable attachment arrangement. Such an attachment arrangement may be less prone to mechanical failure due to moisture or liquid ingress than other attachment arrangements known in the art and may, therefore, have a greater lifetime or require less maintenance work.

The blade flange portion may be adapted to be secured to a portion of the rotor that is adapted to rotate the blade about a blade axis along which the blade extends. The rotodynamic assembly may, for example, comprise a pitching arrangement. The pitching arrangement may comprise a pitch ring having a part to which the blade flange portion is secured. The part of the pitch ring to which the blade flange portion is secured may, for example, rotate with respect to the rotor.

The rotodynamic assembly may be used in a turbine apparatus. For example, the rotodynamic assembly may be used in a turbine apparatus such as that disclosed in published international patent application WO2005/103484.

According to a third aspect of the present invention there is provided a turbine apparatus comprising a support structure, a rotodynamic assembly according to the second aspect of the present invention and a generator wherein the support structure supports the rotodynamic assembly and the rotodynamic assembly drives the generator.

According to a fourth aspect of the present invention there is provided a method of manufacturing a composite blade structure for use in a rotodynamic assembly, said method comprising integrally forming a flange portion that is configured to permit the blade structure to be secured to a rotor.

According to a fifth aspect of the present invention there is provided a method of connecting a composite blade structure to a rotor comprising: providing a composite blade structure according to the first aspect of the present invention; engaging a first surface of the flange portion of the blade structure with a surface of the rotor; engaging a second surface of the flange portion with a clamp; and applying a clamping force to the clamp so as to hold the flange portion against the rotor.

The clamping force applied to the flange portion may be pre-determined so as to achieve a pre-determined compression of the flange portion.

This approach may serve to prevent a reduction in thickness of the flange portion on connection to the rotor. This may also serve to eliminate creep in the flange portion after connection to the rotor. In addition, this may prevent any reduction in the clamping force provided, for example, by an attachment arrangement during use.

According to a sixth aspect of the present invention there is provided a composite blade for a rotodynamic assembly, the blade comprising an integrally formed composite flange portion configured to permit the blade to be secured to a rotor.

BRIEF PESCRtPTION OF THE DRAWINGS

The present invention will be further described by way of non-limiting example only with reference to the following figures of which:

Figure 1 shows a tidal turbine comprising six composite blades each composite blade structure constituting an embodiment of the present invention; Figure 2 shows a blade structure constituting an embodiment of the present invention and clamping plates in (a) front elevation and (b) plan view; Figure 3 shows a cross-section of the blade structure and the clamping plates of Figure 2 taken on XX; Figure 4 shows a detailed view of a portion of the cross-section of Figure 3; and Figure 5 is a perspective view of an attachment arrangement between a blade structure constituting an embodiment of the present invention and a rotor. DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a tidal turbine generally designated 2 of a type described in WO2005/103484. The tidal turbine 2 comprises two rotodynamic assemblies 4 and 6 supported by a support structure 8. Each rotodynamic assembly 4,6 comprises three composite blade structures 10 and a corresponding rotor 12,14 respectively. Each of the composite blade structures 10 is attached at one end to a corresponding rotor 12,14.

One of the composite blade structures 10 is shown in more detail in Figure 2 and comprises an integrally formed composite flange portion 20. The flange portion 20 is circularly symmetric about a blade axis 21 along which the blade structure 10 extends. The composite blade structure further comprises a neck portion 22 and a blade portion 24 wherein the flange portion 20, the neck portion 22 and the blade portion 24 are integrally formed. The composite material from which the blade structure 10 is formed comprises glass fibres. At least some of the glass fibres have a first portion that extends in a plane of the flange portion 20, a second portion that extends at least partially along the neck portion 22 towards or into the blade portion 24 and a third portion intermediate the first and second portions.

As shown more clearly in Figures 3 to 5, the blade structure 10 further comprises an integrally formed composite projecting portion 26 that projects away from a flange inner face 28 of the flange portion 20. The projecting portion 26 is circularly symmetric and is adapted to be received within a corresponding cylindrical recess 30 in a corresponding steel pitch ring 32. More specifically, the projecting portion 26 has an external cylindrical surface 34 which is adapted to engage a corresponding internal cylindrical surface 36 of the cylindrical recess 30 in the pitch ring 32 as shown in Figure 5. The flange inner face 28 is adapted to engage a planar surface 38 of the pitch ring 32. The flange portion 20 further comprises a flange outer face 40 opposite the flange inner face 28. As shown most clearly in Figure 4 a groove 44 is formed in the cylindrical surface 34 of the projecting portion 26. In use, the groove 44 accommodates an O- ring seal 46 that forms a seal against the internal cylindrical surface 36 of the pitch ring 32, as shown in Figure 5. The seal 46 serves to prevent the penetration of fluid along an interface formed between the blade surface 34 and the pitch ring surface 36. The seal 46 serves to prevent the penetration of fluid from an external environment into a blade cavity 48 or the cylindrical recess 30 of the pitch ring 32. In particular, when the rotodynamic assembly 4,6 to which the blade structure 10 is attached is immersed in water, the seal 46 serves to prevent the penetration of water into the blade cavity 48 or the cylindrical recess 30 of the pitch ring 32.

A plurality of circumferentially arranged axially-extending flange through-holes 50 are formed through the flange portion 20 of the blade structure 10 between the inner and outer surfaces 28,40 of the flange portion 20. Each flange through-hole 50 extends in a direction of the blade axis 21. As shown most clearly in Figure 5, the flange through-holes 50 are circumferentially distributed with a uniform angular pitch around the blade axis 21. As shown most clearly in Figure 4, each flange through- hole 50 is provided with a stainless steel tube 54 which is bonded in place to provide a wear-resistant lining for the flange through-hole 52.

A blade attachment arrangement for securing the blade structure 10 to the pitch ring 32 is shown in Figure 5. The pitch ring 32 comprises a plurality of circumferentially arranged internally threaded holes 56. The threaded holes 56 are circumferentially distributed with a uniform angular pitch that corresponds to the angular pitch of the flange through-holes 50. A stud 58 is in threaded engagement with each threaded hole 56. Each stud 58 extends in a direction away from the planar surface 38 of the pitch ring 32. Each flange through-hole 50 is sized so as to accommodate a corresponding stud 58 so that the blade structure 10 is fitted to the pitch ring 32 by engaging each of the flange through-holes 50 with a corresponding stud 58, and by engaging the projecting portion 26 with the corresponding pitch ring recess 30.

The attachment arrangement further comprises a clamping ring which in the embodiment shown is diametrically split into two halves 60,62. The clamping ring 60,62 is formed of steel. The clamping ring 60,62 comprises a plurality of circumferentially arranged through-holes 64. The through-holes 64 are circumferentially distributed with a uniform angular pitch that corresponds to the angular pitch of the flange through-holes 50. Each through-hole 64 is sized so as to accommodate a corresponding stud 58. The clamping ring 60,62 is fitted to the blade structure 10 by engaging each of the through-holes 64 with a corresponding stud 58. The clamping ring 60,62 engages the outer surface 40 of the flange portion 20 of the blade 10 as shown in Figure 3 to 5. Each stud 58 has a corresponding nut (not shown) that is fitted onto the stud 58 and tensioned so as to hold the flange portion 20 of the blade structure 10 between the clamping ring 60,62 and the planar surface 38 of the pitch ring 32.

In use, each nut is tensioned so as to provide a pre-determined compression of the flange portion 20. When in use, this results in the transmission of shear forces via friction between the outer face 40 of the flange portion 20 and the clamping ring 60,62 and between the inner face 28 of the flange portion 20 and the planar surface 38 of the pitch ring 32. Such a blade attachment arrangement results in the transfer of minimal shear forces between the external cylindrical surface 34 of the projection portion 26 of the blade structure 10 and the internal cylindrical surface 36 of the pitch ring 32. This also results in any bending moments that act on the blade structure 10 during use being resisted by forces in the studs 58, forces in the nuts and forces in the blade structure 10.

It should be understood that the flange portion 20 of each blade structure 10 may, additionally or alternatively, be pre-stressed or compressed prior to assembly. This approach may serve to prevent a reduction in thickness of the flange portion 20 on attachment to a corresponding rotor. This may also serve to eliminate creep in the flange portion 20 after attachment. In addition, this may prevent any reduction in the fastening forces provided by the attachment arrangement during use.

The pitch ring 32 forms part of a pitch ring bearing that is adapted to rotate the blade structure 10 around the blade axis 21 so as to control a pitch of the blade portion 24 in response to different fluid flow conditions. Accordingly, the pitch ring 32 comprises gear teeth 66 configured to be driven to rotate the blade structure 10. In one embodiment, the rotor 12,14 comprises a gear wheel (not shown) that engages the gear teeth 66. The rotor gear wheel is rotatable so as to rotate the pitch ring 32 relative to the rotor 12,14 and thereby control the pitch of the blade portion 24. Furthermore, the flange 20 and/or the pitch ring 32 may have a mark or a feature formed on an outer surface thereof to ensure that the blade structure 10 is fitted with the correct orientation about the blade axis 21 with respect to the pitch ring 32.

The clamping ring 60,62 may additionally be bonded to the flange outer face 40. Such bonding of the clamping ring 60,62 may be advantageous in ensuring an even distribution of load between the clamping ring 60,62 and the blade structure 10, thus avoiding any localised stress points on the flange outer face 40 of the flange portion 20.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made without departing from the scope of the present invention.

The turbine 2 may, for example, not be a tidal turbine but be driven by flowing water in a river estuary, a river or a pipe. The rotodynamic assembly 4,6 may form part of a rotating machine other than a turbine. For example, the rotodynamic assembly may be part of a propeller assembly. The propeller assembly may be used to pump a fluid. The propeller assembly may be used to propel a craft such as an aircraft, a ship, boat, hovercraft or the like.

Claims

CLAIMS:

1. A composite blade structure for a rotodynamic assembly, the blade structure comprising a composite blade portion and an integrally formed composite flange portion configured to permit the blade structure to be secured to a rotor.

2. The blade structure according to claim 1 , wherein the blade structure is formed, at least partially, of a composite material having fibres that extend from the flange portion at least partially along a length of the blade portion.

3. The blade structure according to claim 2, wherein at least some of the fibres comprise a first portion that extends in a plane of the flange portion and a second portion that extends at least partially along the length of the blade portion.

4. The blade structure according to claim 3, wherein at least some of the fibres comprise a curved third portion intermediate the first and second portions.

5. The blade structure according to any preceding claim, wherein the blade structure extends along a blade axis, wherein the blade axis is substantially perpendicular to the flange portion.

6. The blade structure according to any preceding claim, comprising a composite neck portion intermediate the flange and blade portions wherein the flange portion, the neck portion and the blade portion are integrally formed.

7. The blade structure according to claim 6, wherein the blade structure is formed of a composite material having fibres at least some of which extend from the flange portion at least partially along the neck portion.

8. The blade structure according to claim 6 or 7, wherein the blade structure is formed of a composite material having fibres at least some of which extend from the neck portion at least partially along the blade portion.

9. The blade structure according to any preceding claim, wherein the flange portion comprises an inner face that is adapted to engage a rotor.

10. The blade structure according to claim 9, wherein the inner face extends in a plane which is parallel to a rotational axis of the rotor.

11. The blade structure according to claim 9 or 10, wherein the inner face extends in a plane which is obliquely aligned relative to a rotor axis.

12. The blade structure according to any preceding claim, comprising an integrally formed engagement feature that is adapted to co-operate with a corresponding engagement feature of a rotor in order to locate the blade structure with respect to the rotor prior to the blade structure being secured to the rotor.

13. The blade structure according to claim 12, comprising at least one of an integrally formed projecting portion, an aperture and a recess.

14. The blade structure according to any preceding claim, comprising a seal which serves to prevent the penetration of a fluid along an interface between the blade structure and the rotor.

15. The blade structure according to claim 14, wherein the seal acts to prevent the passage of fluid from an environment surrounding the blade structure and the rotor to an internal cavity formed between the blade structure and the rotor.

16. The blade structure according to any preceding claim, wherein the flange portion is adapted to be secured to a rotor by means of a fastening arrangement.

17. The blade structure according to claim 16, wherein the fastening arrangement comprises at least one or any combination of a stud, a nut, a bolt, a threaded connection, a clamp assembly, a lock assembly and a clip assembly.

18. The blade structure according to any preceding claim, wherein the flange portion comprises a plurality of flange through-holes, wherein each flange through- hole is adapted to accommodate a corresponding stud for attachment of the flange portion to a rotor.

19. The blade structure according to claim 18, wherein at least one flange through-hole has a wear-resistant internal surface to protect the flange through-hole.

20. The blade structure according to claim 18 or 19, wherein the flange through- hole comprises an insert.

21. The blade structure according to claim 20, wherein the insert at least partially lines an inner surface of the flange through-hole.

22. The blade structure according to claim 20 or 21 , wherein the insert is secured to a surface of the flange through-hole.

23. The blade structure according to claim 22, wherein the insert is secured to a surface of the flange through-hole by at least one of threaded engagement, interference fitting and bonding.

24. The blade structure according to any one of claims 16 to 23, wherein the fastener arrangement comprises a clamping arrangement.

25. The blade structure according to claim 24, wherein an outer face of the flange portion is adapted to co-operate with a clamp, wherein the clamp is adapted to engage the outer face of the flange portion and compress the flange portion such that an inner face of the flange portion engages the rotor.

26. The blade structure according to claim 25, wherein the clamp comprises a clamping ring.

27. The blade structure according to any preceding claim, wherein the flange portion is pre-stressed.

28. The blade structure according to any one of claims 25 to 27, wherein at least one fastener extending from the rotor through the flange portion and the clamp may be tensioned so as to compress the flange portion by a pre-determined amount.

29. The blade structure according to any preceding claim, wherein flange portion is adapted to be secured to a portion of a rotor that is configured to rotate the blade structure about a blade axis along which the blade portion extends.

30. The blade structure according to any preceding claim, wherein the flange portion is adapted to be secured to a pitching arrangement.

31. The blade structure according to any preceding claim, wherein the flange portion is adapted to be secured to part of a pitch ring.

32. The blade structure according to any preceding claim, configured for use in at least one of a tidal, current, wind and air stream.

33. The blade structure according to any preceding claim, comprising an internal cavity.

34. A rotodynamic assembly comprising a rotor and at least one blade structure according to any preceding claim, wherein the blade structure is secured to the rotor via the integrally formed flange.

35. A turbine apparatus comprising a support structure, a rotodynamic assembly according to claim 34, and a generator, wherein the support structure supports the rotodynamic assembly and the rotodynamic assembly drives the generator.

36. A method of manufacturing a composite blade structure for use in a rotodynamic assembly, said method comprising integrally forming a flange portion that is configured to permit the blade structure to be secured to a rotor.

37. A method of connecting a composite blade structure to a rotor comprising: providing a composite blade structure according to any one of claims 1 to 33; engaging a first surface of the flange portion of the blade structure with a surface of the rotor; engaging a second surface of the flange portion with a clamp; and applying a clamping force to the clamp so as to hold the flange portion against the rotor.

38. A composite blade for a rotodynamic assembly, the blade comprising an integrally formed composite flange portion configured to permit the blade to be secured to a rotor.