GB2486047A

GB2486047A - Turbine blade attachment and alignment system with multiple friction plates

Info

Publication number: GB2486047A
Application number: GB1118095.7A
Authority: GB
Inventors: Angus Fleming; Matthew Dawson; Jon Hossell
Original assignee: Aviation Enterprises Ltd
Current assignee: Aviation Enterprises Ltd
Priority date: 2011-10-20
Filing date: 2011-10-20
Publication date: 2012-06-06
Anticipated expiration: 2031-10-20
Also published as: GB2486047B; GB201118095D0

Abstract

A system for attaching a rotor blade, e.g. a marine turbine blade to a turbine shaft, comprises a hub with a blade engagement portion 108 extending from the hub for engagement with a root portion 102 of a rotor blade. The engagement portion 108 has an alignment aperture (114, figure 3) and an alignment device 120 received within the alignment aperture. The alignment device 120 comprises a housing 130 and a liner 132 within the housing 130 defining an alignment space 141 between the housing 130 and the liner 132. Each of the housing 130 and the liner 132 comprise a plurality of friction plates 142 extending partially across the alignment space 141 to overlap and interleave with each other. This allows the liner to be moved radially with respect to the housing for assembly, but firmly fixed by clamping when the though bolt 160 is tightened.

Description

ATTACHMENT SYSTEM

The present invention relates to an attachment system suitable for attaching a rotor blade to a turbine shaft.

Background

There is increasing interest in the use of underwater power generating equipment that makes use of the energy of water flows, such as tidal flows. Such equipment is secured to the bed of a body of water, such as a sea, estuary or river, and makes use of a rotary generator to generate electricity. The generator is driven by a number of rotor blades placed in the water flow. An example of such a tidal power generating installation is illustrated in Figure 1 of the accompanying drawings.

In the example shown in Figure 1, the installation I is located on a bed 2 of a body of water 3. A generating unit 4 is mounted on an underwater support structure 5 which is fixed to the bed 2. The generating unit 4 includes a rotary generator and associated equipment for generating electricity. The generator is driven by a rotor 6 carried on an input shaft of the generator. The rotor 6 has a plurality of rotor blades 14.

Figure 2 of the accompanying drawings illustrates a cross sectional view of a rotor blade 14 which comprises a root 16 by which the rotor blade is attached to the rotor of the generator.

The blade is attached to the rotor using a root fitting 17. A spar 20 extends from the root 16 to a tip 18 of the blade. The blade has a leading edge 22 and a trailing edge 24, and the shape of the blade is defined by a skin 29. The skin 29 is generally of a composite fibre/resin material, and is moulded to the desired blade shape.

Very high loads are generated in under water turbines, particularly at the root fitting of the rotor blades and at the attachment site between the root fitting and the hub of the rotor to which the root fitting is attached. In order to carry these large loads, the root fitting is typically a large component, and is secured to the hub of the rotor using multiple pinned shear joints. Such joints transmit heavy loads in shear through the attachment site and into the turbine. Owing to the very high loads experienced in the shear joints, even very small manufacturing tolerances between the components can result in increased fatigue and failure risk. However, the cost of reducing manufacturing tolerances in such large and heavy components7 together with the difficulties inherent in working under water, mean that in practice, manufacturing tolerances remain in these joints, reducing their longevity.

It is therefore desirable to provide an attachment system that overcomes the disadvantages of known attachment systems for root fittings.

Summary of invention

According to the present invention, there is provided an attachment system for attaching a rotor blade to a turbine shaft, the system comprising: a hub adapted for engagement with the shaft; a blade engagement portion extending from the hub and adapted for engagement with a root portion of a rotor blade, the engagement portion having an alignment aperture extending therethrough, and; an alignment device received within the alignment aperture; wherein the alignment device comprises a housing and a liner received within the housing to define an alignment space between the housing and the liner, each of the housing and the liner comprising a plurality of friction plates extending partially across the alignment space to overlap and interleave with the opposing plurality of friction plates, the liner further comprising an opening extending therethrough.

The system may further comprise a shear element which may be closely received within the opening of the liner and which may comprise a securing opening extending therethrough for receiving a securing element.

The shear element may for example comprise a shear pin, which may be suitable for receiving a securing element in the form of a bolt.

According to one embodiment, the housing and liner may be substantially cylindrical, and may thus define an annular alignment space between them.

The friction plates extending partially across the alignment space may thus comprise annular friction plates, and may for example take the form of washers attached to a respective one of the housing or liner.

According to another embodiment, at a region of the alignment space where the opposing pluralities of friction plates overlap, the alignment space may be completely occupied by the friction plates.

The housing may comprise an inwardly extending annular clamping shoulder on which an end of the liner may be engaged and which may define a limit of the alignment space.

The alignment device may further comprise a damping head operaWe to damp the interleaved pluralities of friction plates against the clamping shoulder of the housing.

The housing may further comprise an outwardly extending fixation shoulder at an opposite end of the housing to the clamping shoulder.

s The housing may be slidably received within the alignment opening of the blade engagement portion, and the alignment device may further comprise at least one fixation element which may be operable to fix the position of the housing within the alignment opening.

The fixation element may pass through an opening on the fixation shoulder to engage the blade engagement portion substantially adjacent the alignment opening.

The blade engagement portion may comprise a pair of side wall members which extend from the hub, and which may be substantially parallel to one another.

Each side wall member may include a corresponding alignment aperture and associated alignment device. Each side wall member may include a plurality of such apertures and associated alignment devices.

According to another aspect of the present invention, there is provided a rotor blade system comprising: a hub adapted for engagement with a shaft; a blade engagement portion extending from the hub and adapted for engagement with a root portion of a rotor blade, the engagement portion having an alignment aperture extending therethrough; an alignment device received within the alignment aperture; wherein the alignment device comprises a housing and a liner received within the housing to define an alignment space between the housing and the liner, each of the housing and the liner comprising a plurality of friction plates extending partially across the alignment space to overlap and interleave with the opposing plurality of friction plates, the liner further comprising an opening extending therethrough; a rotor blade having a root portion received within the blade engagement portion, the root portion having at least one aperture therein for receiving a securing element therethrough; and a securing element that extends through the alignment device and root portion of the rotor blade, and is adapted to secure the rotor blade to the blade engagement portion.

The system may further comprise a shear element which may be closely received within the opening of the liner and which may comprise a securing opening extending therethrough, with the securing element extending through the securing opening.

The root portion of the rotor Wade may further comprise at feast one support tube extending through the root portion and bounding the at east one aperture, the support tube may be arranged to receive the securing element.

The support tube may also receive the shear element.

S The blade engagement portion may comprise a pair of side wall members which extend from the hub and which may be substantially parallel to one another. The securing component may extend through both side wall members.

Each side wall member may include a corresponding alignment aperture and associated alignment device.

Each side wall member may include a plurality of such apertures and associated alignment devices.

According to embodiments of the invention, the rotor blade may be a water current turbine blade, or may be a wind turbine blade.

According to another aspect of the present invention, there is provided an apparatus for forming a shear joint between first and second components, the apparatus comprising an alignment device operable to be received within an opening in the first component; and a shear element, operable to extend through the alignment device and engage the second component, wherein the alignment device comprises a housing and a liner received within the housing to define an alignment space between the housing and the liner, each of the housing and the liner comprising a plurality of friction plates extending partially across the alignment space to overlap and interleave with the opposing plurality of friction plates, the liner further comprising an opening extending therethrough which closely receives the shear element.

The housing and liner may be substantially cylindrical, and may thus define an annular alignment space between them.

At a region of the alignment space where the opposing pluralities of friction plates overlap, the alignment space may be completSy occupied by the friction plates.

S The alignment device may further comprise a clamping head operable to clamp the interleaved plura'ities of friction plates against the clamping shoulder of the housing.

The housing may be operable to be slidably received within the opening of the first component, and the alignment device may further comprise at least one fixation element which may be operable to fix the position of the housing within the opening.

The fixation element may pass through an opening on the fixation shou'der to engage the first component substantially adjacent the opening.

Brief Description of Drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which:-Figure 1 illustrates an underwater tidal power generation installation; Figure 2 is a cross sectional view of a rotor blade for use in the installation of Figure 1; Figure 3 is a partial cross section view through a rotor blade and socket illustrating a rotor blade system and attachment system according to the present invention; Figure 4 is a partial expanded view of the attachment system shown in Figure 3; Figure 5 is a detailed view of the highlighted part of Figure 4; and Figure 6 is a representation illustrating a functionality of the invention.

Detailed Description of Embodiments

An embodiment of the invention wifl now be described with reference to a tidal turbine blade, but it will be appreciated that the invention may be embodied in a range of other applications.

s Figure 3 is a part sectional view through a rotor blade system, and attachment system, according to the present invention. The illustrated rotor blade comprises a root portion, shown in sectional view at 102. The root portion 102 of the rotor blade is received within a blade engagement portion 104 of a hub (not shown) of a turbine. The blade engagement portion 104 comprises a socket 106 formed from first and second side walls 108, 110 that define a void, within which the root portion 102 is received. The root portion 102 comprises a plurality of securing apertures 112, each of which extends through the root portion and communicates at either end with corresponding upper and lower alignment apertures 114, extending through the first and second side walls 108, 110 of the socket 106. A support tube 116 extends through each securing aperture 112 in the root portion, bounding the aperture 112 and providing additional strength and rigidity to the aperture 112.

With particular reference to the circled region of Figure 3, each cooperating assembly of support tube 116 and securing aperture 112, upper alignment aperture 114 and lower alignment aperture 115 comprises an attachment site. A plurality of such attachment sites are provided across the root portion. In the following disclosure, a single attachment site and associated components will be described, but it will be appreciated that each one of the plurality of attachment sites may conform to the following description.

Referring to the highlighted attachment site, an upper alignment device 120 is received within the upper alignment aperture 114, and a lower alignment device 122 is received within the ower alignment aperture 115. Each alignment device 120, 122, described in further detail below, comprises a central opening 124, through which is received a shear element 126 and a securing element 128. The shear element 126 and securing element 128 extend through the upper alignment device 120, through the securing aperture 112 in the root portion, bounded by the support tube 1167 and through the lower alignment device 122.

Referring now to Figures 4 and 5, the upper alignment device 120 will be described in detail.

It will be appreciated that the lower alignment device 122 comprises corresponding features.

With reference to Figures 4 and 5, the alignment device 120 comprises a housing 130 and a liner 132. The housing 130 comprises a substantially cylindrical main body 134, having an inwardly extending annular clamping shoulder 136 at a lower edge of the body 134, and an outwardly extending annular fixation shoulder 138 at an upper edge of the body 134. The liner 132 comprises a substantially cylindrical main body 140 and is received in a substantially concentric manner within the housing 130, defining an annular alignment space 141 between the two cylindrical main bodies, 134, 140. An annular edge of the liner 132 is received and engages on an upper surface of the annular clamping shoulder 136 of the housing 130. An inner diameter of the liner 132 is slightly smaller than an inner diameter of the annular clamping shoulder 136, the difference d between the two diameters being seen most clearly in Figure 5. With particular reference to Figure 5, each of the housing 130 and liner 132 comprises a plurality of friction plates 142, the friction plates 142 extending partially across the annular alignment space 141. As illustrated, the friction plates 142 are of annular form and may for example comprise metal washers attached either to the outer cylindrical surface of the liner 132 or the inner cylindrical surface of the housing 130 as appropriate. As illustrated in Figure 5, the two opposing pluralities of friction plates 142 do not extend the full depth of the annular alignment space 141, but do extend sufficiently to overlap one another, so as to define an overlap region 144. The opposing pluralities of friction plates 142 are interleaved, such that a friction plate attached to the liner 132 is bounded on upper and lower sides by friction plates attached to the housing 130, and vice versa.

The alignment device 120 further comprises an annular clamping head 146, which is arranged above the overlapping pluralities of friction plates, so as to clamp the friction plates against each other and the annular clamping shoulder 136 of the housing 130. The housing is slidably received within the alignment aperture 114. The height of the cylindrical body 134 of the housing is greater than the depth of the side wall 108 of the socket 106 within which it is received, such that the housing may protrude slightly from the lower surface 109 of the side wall 108 if desired. The depth to which the housing is inserted within the alignment aperture 114 is fixed by a plurality of fixation elements, in the form of bolts 150.

The bolts 150 extend through fixation openings 148 formed in the fixation shoulder 138 of the housing. After passing through the fixation openings 148 in the housing, the bolts extend into and engage corresponding fixation openings 152 formed in the upper surface 111 of the side wall 108. The depth to which the bolts are inserted into the fixation holes 152 formed in the side wall 108 determines the depth to which the housing 130, and hence alignment device 120, are inserted into the alignment aperture 114. The fixation bolts 150 thus determine the position of the alignment device 120 along the axis of the alignment aperture 114.

A main clamping head 154 is received within the upper region of the housing 130 and engages on the annular clamping head 146. A seal, for example in the form of an 0 ring 158, may be provided to seal the connection between the main clamping head 154 and the housing 130. At the lower end of the housing, a lower surface of the annular clamping S shoulder 136 engages on an upper annular surface of the support tube 116 of the root portion 102. A seal, for example in the form of an 0 ring 156 may be provided to seal the connection between the lower surface of the clamping shoulder 136 and the upper surface of the support tube 116.

The shear element 126, which may be in the form of a hollow cylindrical shear pin, is closely received within the liner 132, and within the support tube 116. If the components have been manufactured to exact manufacturing tolerances, the alignment aperture 114 and securing aperture 112 will be perfectly aligned. However, should the two apertures not be perfectly aligned, the liner 132 may adjust its position within the housing 130, shifting until the central axis of the liner 132 is perfectly aligned with the central axis of the support tube 116. This process of alignment is described in further detail below.

The securing element 128, which may be in the form of a bolt, is received within the shear element 126. A bolt head 160 is engaged on an upper end of the bolt, a lower surface of the bolt head engaging upon, and clamping the main clamping head 154. It will be appreciated that with a similar bolt head engaging upon a main clamping head and lower alignment device at the other end of the securing element 128, the root portion of the blade will be securely clamped between the two side walls 108, 110 of the socket 106. A waterproof cap 162 extends over the bolt head, protecting the bolt head and main clamping head. The waterproof cap may be sealed with an 0 ring 164.

Assembly of the attachment system of the present invention will now be described, with reference to Figures 3 to 6. Initially, the root portion 102 of the blade is inserted into the socket 106 defined by the two side walls 108, 110, until the securing apertures 112 in the root portion 102 are aligned with the appropriate pairs of alignment apertures 114, 115 in the side walls 108, 110. The upper and lower alignment devices 120, 122 may then be inserted into the alignment apertures 114, 115. Only insertion of the upper alignment device 120 will be described, but it will be understood that a corresponding procedure is followed for the lower alignment device 122. The alignment device 120 is inserted into the alignment aperture 114, with the housing 130 being closely received in the aperture 114. Despite efforts to manufacture the components to very close tolerances, a is almost inevitable that there will be a small gap 166 between the upper surface of the root portion 102 and the lower surface of the side wall 108. The aUgnment device 120 is thus inserted until the lower surface of the annular clamping shoulder 136 on the housing 130 engages on the support tube 116 of the root portion 102, bridging the gap 166. With the alignment device 120 inserted to the correct distance, the housing 130 is secured to the side wall 108 via the fixation bolts 150 which engage the annular fixation shoulder 138 and fixation openings 152 in the side wall 108. The shear element 126 is then inserted through the lining 132 and support tube 116, and is closely received within both these components. As noted above, owing to the impracticality of achieving extremely fine manufacturing tolerances, it is almost impossible to ensure perfect alignment between the axes of the alignment aperture 114 and the securing aperture 112. The alignment device functions to allow for such misalignment by allowing adjustment of the position of the liner 132 within the housing 130 of the alignment device. The liner 132 is held in axial position with respect to the housing by the interleaved friction plates. However, the radial position of the liner 132 may be adjusted, such that the liner is no longer perfectly concentrically received within the housing. The fact that the friction plates to not extend all the way across the alignment space, together with the difference d between the inner diameters of the liner 132 and clamping shoulder 136, allows for some play in the position of the liner within the housing, and this play can be exploited to allow for minor misalignment between the alignment aperture 114 in the side wall and the securing aperture 112 in the root portion of the rotor blade. In this manner, the shear element 126 is closely held along its entire length, regardless of any minor misalignment between the alignment and securing apertures. By closely receiving the shear element along its entire length, the risk of fatigue damage and failure of the shear element 126 is greatly reduced. In addition, the ability to compensate for manufacturing tolerances ensures that larger tolerances can be accepted in the components, reducing cost of manufacture and increasing ease of assembly of the components.

With the shear element 126 inserted fully into the liner 132 and support tube 116, and the liner 132 hence in its correct position with respect to the housing 130, the securing element 128 is passed through the shear element 126. The annular clamping head 146 and main clamping head 154 are placed in position and the bolt head 160 is engaged and tightened to clamp the friction plates together and clamp the root portion between the side walls of the socket 106. The majority of the shear forces experienced in the assembled joint are transmitted via the shear element 126, which is capable to transmitting large shear loads. At the region of the alignment device, shear is also transmitted via the interleaved friction plates 142. These friction plates transmit the shear forces in a highly efficient manner, owing to the plurality of overlapping friction surfaces. The principle employed by the multiple friction plates 142 is illustrated in Figure 6. On the left of Figure 6, a single friction interface between two friction plates is illustrated. With this arrangement, the maximum applied load that can be carried by the joint, P2, is given by the equation: app = R 1czarnp Where p is the interface coefficient of friction, and Pcamp is the clamping force damping the two plates together. On the right side of Figure 6, a plurality of friction plates are clamped S together by the same force camp' resulting in multiple friction interfaces between the elements. With this arrangement, the maximum applied load that can be carried by the joint, is given by the equation: app = N R clamp Thus for the same damping force, the applied load that can be carried by the joint is increased by a factor of N, where N is the number of friction interfaces. By employing overlapping pluralities of friction plates, the alignment device of the present invention is thus capable of transmitting large loads in shear, while still allowing for misalignment between the alignment aperture 114 in the side wall 108 and the securing aperture 112 in the root portion 102.

The present invention thus combines advantages of two major manners by which shear Is force may be carried. The shear element 126 of the invention is ideal for the transmission of the heavy shear loads experienced in under water turbines. However, in order to reduce the risk of failure, a shear element of this type must be received with very close tolerances between the two components. Such tolerances are extremely difficult to achieve in the large and heavy components of an underwater turbine. The present invention thus also employs multiple friction plates, the multiple plates also being capable of transmitting high shear loads and most advantageously allowing for a certain tolerance in the alignment between components.

Claims

CLAIMS1. An attachment system for attaching a rotor blade to a turbine shaft, the system comprising: a hub adapted for engagement with the shaft; a blade engagement portion extending from the hub and adapted for engagement with a root portion of a rotor blade, the engagement portion having an alignment aperture extending therethrough, and; an alignment device received within the alignment aperture; wherein the alignment device comprises a housing and a liner received within the housing to define an alignment space between the housing and the liner, each of the housing and the liner comprising a plurality of friction plates extending partially across the alignment space to overlap and interleave with the opposing plurality of friction plates, the liner further comprising an opening extending therethrough.
2. A system as claimed in claim 1, further comprising a shear element closely received within the opening of the liner and comprising a securing opening extending therethrough for receivng a securing element.
3. A system as claimed in claim I or 2, wherein the housing and liner are substantially cylindrical, defining an annular alignment space therebetween.
4. A system as claimed in any one of claims 1 to 3, wherein at a region of the alignment space where the opposing pluralities of friction plates overlap, the alignment space is completely occupied by the friction plates.
5. A system as claimed in any one of the preceding claims, wherein the housing comprises an inwardly extending annular clamping shoulder on which an end of the liner is engaged and which defines a limit of the alignment space.
6. A system as claimed in claim 5, wherein the alignment device further comprises a clamping head operable to clamp the interleaved pluralities of friction plates against the clamping shoulder of the housing.
7. A system as claimed in any one of the preceding claims, wherein the housing further comprises an outwardly extending fixation shoulder at an opposite end of the housing to the clamping shoulder.
8. A system as claimed in any one of the preceding claims, wherein the housing is slidably received within the alignment opening of the blade engagement portion, and the alignment device further comprises at least one fixation element operable to fix the position of the housing within the alignment opening.
9. A system as claimed in claim 8, when dependent on claim 7, wherein the fixation element passes through an opening on the fixation shoulder to engage the blade engagement portion substantially adjacent the alignment opening.
10. A system as claimed in any one of the preceding claims, wherein the blade engagement portion comprises a pair of side wall members which extend from the hub, and which are substantially parallel to one another.
11. A system as claimed in claim 10, wherein each side wall member includes a corresponding alignment aperture and associated alignment device.
12. A system as claimed in claim 11, wherein each side wall member includes a plurality of such apertures and associated alignment devices.
13. A rotor blade system comprising: a hub adapted for engagement with a shaft; a blade engagement portion extending from the hub and adapted for engagement with a root portion of a rotor blade, the engagement portion having an alignment aperture extending therethrough; an alignment device received within the alignment aperture; wherein the alignment device comprises a housing and a liner received within the housing to define an alignment space between the housing and the liner, each of the housing and the liner comprising a plurality of friction plates extending partially across the alignment space to overlap and interleave with the opposing plurality of friction plates, the liner further comprising an opening extending therethrough; a rotor blade having a root portion received within the blade engagement portion, the root portion having at least one aperture therein for receiving a securing element therethrough, and; a secudng element that extends through the alignment device and root portion of the rotor blade, and is adapted to secure the rotor blade to the blade engagement portion.
14. A system as claimed in claim 13, further comprising a shear element closely received within the opening of the liner and comprising a securing opening extending therethrough, the securing element extending through the securing opening.
15. A system as claimed in claim 13 or 14, wherein the root portion of the rotor blade further comprises at least one support tube extending through the root portion and bounding the at least one aperture, the support tube arranged to receive the securing element.
16. A system as claimed in claim 15, when dependent on claim 14, wherein the support tube also receives the shear element.
17. A system as claimed in any one of claims 13 to 16, wherein the blade engagement portion comprises a pair of side wall members which extend from the hub and which are substantially parallel to one another, and wherein the securing component extends through both side wall members!
18. A system as claimed in claim 17, wherein each side wall member includes a corresponding alignment aperture and associated alignment device.
19. A system as claimed in claim 11, wherein each side wall member includes a plurality of such apertures and associated alignment devices.
20. A system as claimed in any one of the preceding claims, wherein the rotor blade is a water current turbine blade.
21. A system as claimed in any one of claims Ito 19, wherein the rotor blade is a wind turbine blade!
22. An attachment system for attaching a rotor blade to a turbine shaft substantially as described herein with reference to, and as shown in, Figures 3 to 6 of the accompanying drawings.
23. A rotor bfade system substantially as described herein with reference to, and as shown in, Figures 3 to 6 of the accompanying drawings.