GB2494389A

GB2494389A - Rotor blade

Info

Publication number: GB2494389A
Application number: GB1115055.4A
Authority: GB
Inventors: Angus Fleming; Matthew Dawson
Original assignee: Aviation Enterprises Ltd
Current assignee: Aviation Enterprises Ltd
Priority date: 2011-09-01
Filing date: 2011-09-01
Publication date: 2013-03-13
Anticipated expiration: 2031-09-01
Also published as: GB2494389B; GB201115055D0

Abstract

A rotor blade 102, especially for a wind or water current turbine, has a skin 104 which defines an outer shape, having a root portion 106, a tip portion 108 and leading and trailing surfaces 116, 118 extending between the root and tip. The skin defines an inner void 120 in which is located a support structure 122 in the form of a plurality of support webs 126 spanning between the leading and trailing surfaces and extending substantially longitudinally from the root to the tip. Preferably the support webs are beams with leading and trailing surface flanges, such as I or C section beams. At the root of the blade there may be a pair of apertures extending through the leading and trailing surfaces for a securing component. A support tube for receiving the securing component may span the thickness between the apertures and may pass through an enlargement in a support web.

Description

ROTOR BLADE

The present invention relates to a rotor blade and in particular to a rotor blade for use in underwater tidal power generation installations.

Background to the Invention

There is increasing interest in the use of underwater power generating equipment that makes use of the energy of 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 instaflation I is located on a bed 2 of a body of water 3. A generating unit 4 is mounted on an underwater support structure S 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 iflustrates 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 forms leading and trailing surfaces of the blade, each of which surfaces extends from the leading edge 22 to the trailing edge 24 and from the root 16 to the tip 18. The skin 29 is generally of a composite fibre/resin material, and is moulded to the desired blade shape. The skin is supported by the spar which provides the blade 14 with additional strength.

One technique that can be used to generate more electricity from a given flow is to use larger diameter rotor blades. However, large rotor blades can be restrictively heavy if constructed using traditional techniques. It has therefore been proposed that hollow composite blades be used, in which a shaping skeleton is covered by a thin skin to provide the required blade shape. However, it has been discovered that the significant pressure

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differences experienced by the underwater rotor blade leads to significant flexing of the blade skin, and hence to significant problems with failure due to fatigue of the blade material.

Various solutions have been attempted to this problem, such as flooding the blade with water to even hydrostatic pressure. However, these solutions are not completely effective and also have associated disadvantages. There remains, therefore, a need for an improved rotor blade that addresses the disadvantages of the prior art.

Summary of Invention

According to the present invention, there is provided a rotor blade for a turbine, the blade comprising: a skin which defines an outer shape of the blade having a root portion, a tip portion, and leading and trailing surfaces extending between the root and tip portions, the skin defining an inner void of the blade; and a support structure occupying the inner void of the blade, the support structure comprising a plurality of support webs, each web spanning a thickness between the leading and trailing surfaces of the blade and extending substantially longitudinally from the root portion to the tip portion.

In one example, each support web may be a component part of a beam, each beam having a leading surface flange and a trailing surface flange such that the support web extends between the leading and trailing surface flanges.

At least one of the plurality of beams forming the support structure may comprise an I section beam.

The plurality of beams may be bounded at its edges by longitudinally extending C section beams. Such C section beams may be oriented such that the leading and trailing surface flanges extend away from the support web towards a central region of the blade.

According to another example, the plurality of beams may be connected along adjacent flange portions to form an integral support component.

In another example, adjacent flanges of at least some of the plurality of beams may be separated by a spacing.

The rotor blade may further comprise at least one support cap incorporated within the skin of the blade and extending substantially over one of the leading and/or trailing surfaces.

The rotor blade may comprise two support caps incorporated within the skin of the blade; which may comprise a leading surface support cap extending substantially over the leading surface and a trailing surface support cap extending substantially over the trailing surface.

The root portion of the blade may comprise at least one pair of aligned apertures extending through the leading and trailing surfaces of the root portion for receiving a securing component.

The root portion may further comprise at least one support tube spanning the thickness between the aligned apertures for receiving a securing element.

The at least one support tube may be aligned with a support web of the support structure, and the support web may comprise a hollow enlargement which may be operable to receive the support tube such that the support tube extends through the support web between the leading and trailing surfaces.

The rotor blade may be a water current turbine blade or may be a wind turbine blade.

Brief Description of the 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 illustrates a first cross sectional view of a rotor blade for use in the installation of Figure 1; Figure 3 illustrates a partial cross sectional view of a rotor blade according to the invention; Figure 4 illustrates a partial cross sectional view of a root portion of a rotor blade according to the invention; Figure 5 illustrates a sectional view along the line V-V in Figure 4; and Figure 6 illustrates a sectional view along the line Vl-VI in Figure 4.

Detailed Description of Embodiments

An embodiment of the invention will now be described with reference to a tidal turbine blade, but it will be appreciated that the support structure embodying the present invention can be applied to a range of other rotor blades.

With reference to Figure 3, a rotor blade 102 according to the present invention comprises an outer skin 104 which may be formed from a composite material having glass fibres incorporated in an epoxy resin matrix. Other suitable composite materials may also be considered for the skin, such materials being known in the field of turbine blades. The skin 104 defines the outer shape of the blade 102 which extends from a root portion 106, towards the right of Figure 3 and illustrated in Figure 4, to a tip portion 108, towards the left of Figure 3. The rotor blade 102 is of an aerofoil shape having two principal longitudinal edges, a leading edge 110 and a trailing edge 112. The leading edge 110 is reinforced with a leading edge moulding 114 which is also formed from a composite material of glass fibres embedded in an epoxy resin matrix. Extending between the root 106 and tip 108 portions of the blade 102, and between the leading 110 and trailing 112 edges of the blade are the two principal surfaces of the blade, a leading surface 116 and a trailing surface 118 (obscured in Figure 3). In use, the leading surface 116 faces into the water current of the body of water in which the rotor blade is installed, with the opposed trailing surface 118 facing away from the current.

The rotor blade 102 is hollow; the skin 104 of the blade 102 defining an inner void 120 of the blade. The inner void 120 is occupied by a support structure 122 which comprises a plurality of beams 124 extending longitudinally through the void 120 from the root portion 106 to the tip portion 108 of the blade 102. The beams 124 that form the support structure 120 are each comprised of a central supporting web 126 that spans a thickness between leading and trailing surface flanges 128, 130. The leading and trailing surface flanges 128, 130 are in contact with and provide support to the inner extent of the leading and trailing surfaces 116, 118 of the blade. The beams 124 are comprised of two different beam structures. A plurality of I section beams occupy the central region of the void 120, with these I section beams bounded at the leading and trailing edges of the void 120 by two C section beams.

Each C section beam is oriented to present the C opening towards a central region of the void 120, as illustrated in Figure 3. Also as illustrated in Figure 3, the beams 124 are of varying heights, formed to correspond to the thickness of the void 120 which varies across both the length and the width of the blade 102.

The plurality of beams 124 that form the support structure 122 may each be separated by a small spacing 132 between adjacent flanges, as illustrated in Figure 3. In this manner, the support structure 122 is formed from a plurality of cooperating, yet independent beam structures 124, allowing a certain degree of flexion and twisting motion in the blade 102. In an alternative embodiment, not shown, the plurality of beams 124 may be connected along adjacent flanges, so as to form a single integrally formed support structure 122. Such a structure provides increased rigidity to the blade 102 which may be desirable under certain operating conditions.

The rotor blade 102 further comprises leading and trailing surface support caps 134, 136, each of which is incorporated into the skin 104 of the blade in the region of the leading and trailing surfaces 116, 118 respectively. Each support cap 134, 136 extends over a significant area of the respective blade surface and provides additional rigidity to the skin 104, absorbing and reacting the supporting forces provided by the support structure 122 during use. The support caps 134, 136 are formed from a composite material of carbon fibres embedded in an epoxy resin matrix.

Referring now to Figures 4 to 6, the particular features of the root portion 106 of the blade 102 will be described. The root portion 106 comprises a root fitting 133 that is designed to interact with a cooperating fitting 139 on a turbine hub. The root fitting 138 includes a plurality of pairs of attachment apertures 140 extending through the leading and trailing surfaces 116, 118 ot the blade 102, and adapted to receive a securing element 144 there through. The apertures 140 extend through the support caps 134, 136 incorporated into the skin 104 of the blade 102 on the leading and trailing surfaces 116, 118. Extending between each pair of aligned attachment apertures 140 is a support tube 142 which is preferably formed from steel or another appropriate metal, and is designed to closely receive a securing element 144. The support tubes 142 provide additional support and rigidity to the root fitting 138 when a securing element 144 is engaged to connect the root fitting 138 to the cooperating hub fitting. Each pair of aligned apertures 140 and associated support tube 142 is aligned with the support web 126 of a respective beam 124 of the support structure 122.

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As illustrated more dearly in the sectional views of Figures 5 and 6, the beams 124 each comprise a hollow enlargement 146 that forms a tube shaped structure and extends the height of the support web 126, opening through the leading and trailing surface flanges 128, to cooperate with the aligned attachment apertures 140 on the leading and trailing surfaces 116, 118. Received within this hollow enlargement 146 is the support tube 142. An insulating collar 148 may be provided within the skin 104 of each surface 116, 118 to insulate the support caps 134, 136 from the metal support tube 142. In one example of the invention, the hollow enlargement 146 of each beam 124 of the support structure 122 may in fact be moulded around its associated support tube 142 durhg manufacture, thus ensuring a secure engagement between the two components.

An embodiment of the present invention thus provides a rotor blade having an internal support structure that imparts the required rigidity and robustness to the blade without unduly increasing the weight of the blade or adversely affecting the performance of the blade in use. It will be appreciated that an embodiment of the present invention provides a rotor blade having a very slim structure, which allows for very efficient blade performance.

It will be appreciated that the support structure of the present invention may be employed advantageously in any blade structure, for example in rotor blades for wind power generation.

Claims

<claim-text>CLAIMS1 A rotor blade for a turbine, the blade comprising: a skin which defines an outer shape of the blade having a root portion, a tip portion, and leading and trailing surfaces extending between the root and tip portions. the skin defining an inner void of the blade; and a support structure occupying the inner void of the blade, the support structure comprising a plurality of support webs, each web spanning a thickness between the leading and trailing surfaces of the blade and extending substantially longitudiriafly from the root portion to the tip portion.</claim-text> <claim-text>2 A rotor blade as claimed in claim 1, wherein each support web is a component part of a beam, each beam having a leading surface flange and a trailing surface flange with the support web extending between the leading and trailing surface flanges.</claim-text> <claim-text>3 A rotor blade as claimed in claim 2, wherein at least one of the plurality of beams forming the support structure comprises an I beam.</claim-text> <claim-text>4 A rotor blade as claimed in claim 2 or 3. wherein the plurality of beams is bounded at its edges by longitudinally extending C section beams.</claim-text> <claim-text>A rotor blade as claimed in any one of claims 2 to 4, wherein the plurality of beams are connected along adjacent flange portions to form an integral support component.</claim-text> <claim-text>6 A rotor blade as claimed in any one of claims 2 to 5, wherein adjacent flanges of at least some of the plurality of beams are separated by a spacing.</claim-text> <claim-text>7 A rotor blade as claimed in any one of the preceding claims, wherein the blade further comprises at least one support cap incorporated within the skin of the blade and extending substantially over one of the leading and/or trailing surfaces.</claim-text> <claim-text>8 A rotor blade as claimed in any one of the preceding claims, wherein the blade comprises two support caps incorporated within the skin of the blade; a leading surface support cap extending substantially over the leading surface and a trailing surface support cap extending substantially over the trailing surface.</claim-text> <claim-text>9 A rotor blade as claimed in any one of the preceding claims, wherein the root portion of the blade comprises at least one pair of aUgned apertures extending through the leading and trailing surfaces for receiving a securing component.</claim-text> <claim-text>A rotor blade as claimed in claim 9, wherein the root portion further comprises at least one support tube spanning the thickness between the aligned apertures for receiving a securing element.</claim-text> <claim-text>11 A rotor blade as claimed in claim 10, wherein the at least one support tube is aligned with a support web of the support structure, and wherein the support web comprises a hollow enlargement operable to receive the support tube such that the support tube extends through the web between the leading and trailing surfaces.</claim-text> <claim-text>12 A rotor blade as claimed in any one of the preceding claims, wherein the rotor blade is a water current turbine blade.</claim-text> <claim-text>13 A rotor blade as claimed in any one of claims 1 to ii, wherein the rotor blade is a wind turbine blade.</claim-text> <claim-text>14 A rotor blade substantially as described herein, with reference to and as shown in Figures 3 to 6 of the accompanying drawings.B</claim-text>