A WIND TURBINE BLADE

Abstract

The present disclosure provides a blade for a wind turbine, where the blade extends in a lengthwise direction between a root end and a tip end of the blade. The blade comprises a leeward shell portion and a windward shell portion, each of the shell portions defining respective inner and outer surfaces extending in a chordwise direction between a leading edge of the blade and a trailing edge of the blade. The blade further comprises a first windward reinforcement structure, a first leeward reinforcement structure, a second windward reinforcement structure, and a second leeward reinforcement structure, the reinforcement structures being arranged internally within the blade and extending in the lengthwise direction of the blade. The second windward and second leeward reinforcement structures are arranged closer to the trailing edge than the first windward reinforcement structure and the first leeward reinforcement structure, respectively, and the second windward reinforcement structure is longer than the second leeward reinforcement structure in the lengthwise direction.

Claims

1. A blade for a wind turbine (7), the blade extending in a lengthwise direction between a root end (10) and a tip end (12) of the blade, the blade comprising: a leeward shell portion (14) and a windward shell portion (15), each of the shell portions defining respective inner (14a, 15a) and outer surfaces (14b, 15b) extending in a chordwise direction between a leading edge (17) of the blade and a trailing edge (18) of the blade, wherein the blade extends in a thickness direction between the leeward shell portion and the windward shell portion; a main reinforcement structure (21, 22) internally within the blade, the main reinforcement structure comprising a first windward reinforcement structure (21) engaging the windward shell portion (15) and extending in the lengthwise direction of the blade and a first leeward reinforcement structure (22) engaging the leeward shell portion (14) and extending in the lengthwise direction of the blade; a rear reinforcement structure (26, 27) internally within the blade, the rear reinforcement structure comprising a second windward reinforcement structure (26) engaging the windward shell portion (15) and extending in the lengthwise direction of the blade and a second leeward reinforcement structure (27) engaging the leeward shell portion (14) and extending in the lengthwise direction of the blade, wherein the rear reinforcement structure (26, 27) is arranged closer to the trailing edge (18) than the main reinforcement structure (21, 22); and wherein the second windward reinforcement structure (26) is longer than the second leeward reinforcement structure (27) in the lengthwise direction.

2. A blade according to claim 1, wherein a length of the second leeward reinforcement structure (27) is in the range of 80-95% of a length of the second windward reinforcement structure (26).

3. A blade according to claim 1, wherein the second windward reinforcement structure (26) and the second leeward reinforcement structure (27) are formed by a plurality of layers.

4. A blade according to claim 1, wherein the second windward and the second leeward reinforcement structures (26, 27) are formed by layers of pultruded elements.

5. A blade according to claim 1, wherein the respective thicknesses of the second leeward reinforcement structure (27) and the second windward reinforcement structure (26) decrease towards the tip end (12) in the lengthwise direction in a first section of the blade.

6. A blade according to claim 5, wherein the decrease of the thickness of the second windward reinforcement structure (26) is staggered with respect to the decrease of the thickness of the second leeward reinforcement structure (27) at least at one position within the first section.

7. A blade according to claim 1, further comprising an additional leeward reinforcement structure (30) arranged in continuation of the second leeward reinforcement structure (27) in the lengthwise direction, the additional leeward reinforcement structure being arranged closer to the tip end (12) than the second leeward reinforcement structure, and the additional leeward reinforcement structure being formed of a different material to the second leeward reinforcement structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Embodiments of the disclosure will now be further described with reference to the drawings, in which:

[0058] FIG. 1 illustrates the main structural components of a wind turbine;

[0059] FIGS. 2A and 2B illustrate two different cross-sections through an embodiment of a wind turbine blade; and

[0060] FIG. 3 illustrates a windward shell portion with first and second windward reinforcement structures and a leeward shell portion with first and second leeward reinforcement structures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0061] It should be understood that the detailed description and specific examples, while indicating embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.

[0062] FIG. 1 illustrates a typical wind turbine 1 comprising a tower 2, a nacelle 3 mounted at top of the tower 2 and a rotor 4 operatively coupled to a generator 5 within the nacelle 3. The wind turbine 1 converts kinetic energy of the wind into electrical energy. In addition to the generator 5, the nacelle 3 houses the various components required to convert the wind energy into electrical energy and also the various components required to operate and optimize the performance of the wind turbine 1. The tower 2 supports the load presented by the nacelle 3, the rotor 4, and other wind turbine components within the nacelle 3.

[0063] The rotor 4 includes a central hub 6 and three elongated blades 7 extending radially outward from the central hub 6. In operation, the blades 7 are configured to interact with the passing air flow to produce lift that causes the central hub 6 to rotate about its longitudinal axis. Wind speed in excess of a minimum level will activate the rotor 4 and allow it to rotate within a plane substantially perpendicular to the direction of the wind. The rotation is converted to electric power by the generator 5 and is usually supplied to the utility grid.

[0064] FIGS. 2A and 2B illustrate two different cross-sections through an embodiment of a wind turbine blade 7, section A-A and section B-B (see FIG. 3).

[0065] The blade 7 extends in a lengthwise direction L (see FIG. 3) between a root end 10 and a tip end 12 of the blade, where the root end 10 (see FIG. 3) is configured for attachment to the hub.

[0066] The blade 7 comprises a leeward shell portion 14 and a windward shell portion 15, where each of the shell portions 14, 15 defines respective inner 14a, 15a and outer surfaces 14b, 15b extending in a chordwise direction C between a leading edge 17 of the blade and a trailing edge 18 of the blade. The inner surface 14a of the leeward shell portion 14 faces the inner surface 15a of the windward shell portion 15, whereby a hollow blade is defined by the two shell portions 14, 15.

[0067] The blade 7 extends in a thickness direction T between the leeward shell portion 14 and the windward shell portion 15.

[0068] The blade 7 comprises a main reinforcement structure 21, 22 comprising a first windward reinforcement structure 21 internally within the blade 7, where the first windward reinforcement structure 21 engages the windward shell portion 15. Additionally, the main reinforcement structure 21, 22 comprises a first leeward reinforcement structure internally 22 within the blade 7, where the first leeward reinforcement structure 22 engages the leeward shell portion 14.

[0069] The main reinforcement structure 21, 22 comprising first windward and first leeward reinforcement structures 21, 22 extend in the lengthwise direction L of the blade 7 (see FIG. 3) and have a thickness in the thickness direction T of the blade. The first windward and the first leeward reinforcement structures 21, 22 form a pair and are arranged so that they face each other when the shell portions 14, 15 are assembled to form the complete blade 7.

[0070] A first shear web 23 extends in the lengthwise direction L of the blade 7 and bridges the first windward and the first leeward reinforcement structures 21, 22. As illustrated, the first shear web 23 in combination with the first windward and the first leeward reinforcement structures 21, 22 form an I-beam structure/a spar structure which may transfer loads effectively from the rotating blade 7 to the hub 6 (see FIG. 1) of the wind turbine.

[0071] The blade 7 further comprises rear reinforcement structure 26, 27 comprising a second windward reinforcement structure 26 and a second leeward reinforcement structure 27 internally within the blade, where the second windward reinforcement structure 26 engages the windward shell portion 15 and the second leeward reinforcement structure 27 engages the leeward shell portion 14. The rear reinforcement structure 26, 27 comprising second windward and second leeward reinforcement structures 26, 27 extend in the lengthwise direction L and are arranged closer to the trailing edge 18 than the main reinforcement structure 21, 22 (see FIG. 3).

[0072] The second windward reinforcement structure 26 is longer than the second leeward reinforcement structure 27 in the lengthwise direction, which is illustrated in FIG. 3. It is additionally illustrated by the difference between FIG. 2A and FIG. 2B, where the cross-section A-A illustrated in FIG. 2A is closer to the root end 10 than the cross-section B-B illustrated in FIG. 2B. The longer second windward reinforcement structure 26 is illustrated in both FIG. 2A and FIG. 2B, whereas the shorter second leeward reinforcement structure 27 is only illustrated in FIG. 2A.

[0073] A second shear web 28 may extend in the lengthwise direction L of the blade 7 and bridges the second windward and the second leeward reinforcement structures 26, 27.

[0074] As illustrated in FIG. 2B, the blade 7 may comprise an additional leeward reinforcement structure 30 which is arranged in continuation of the second leeward reinforcement structure 27 in the lengthwise direction L. The second leeward reinforcement structure may transition into the additional leeward reinforcement structure so that there is not an abrupt change in stiffness in the blade structure.

[0075] Each of the first and second leeward and first and second windward reinforcement structures 22, 27, 21, 26 may be formed as a layered structure of a plurality of elements, such as a plurality of pultruded strips of carbon-fibre reinforced plastic. The additional leeward reinforcement structure 30 may be of a different material which preferably has a lower stiffness modulus in comparison to the material of the first and second leeward and first and second windward reinforcement structures 22, 27, 21, 26. The additional leeward reinforcement structure 30 may be formed from glass-fibre reinforced plastic. The glass-fibre material may preferably be provided in the form of dry mats.

[0076] FIG. 3 illustrates a windward shell portion 15 with the first and second windward reinforcement structures 21, 26 and a leeward shell portion 14 with first and second leeward reinforcement structures 22, 27. The first and second windward reinforcement structures 21, 26 may be arranged substantially in parallel. Likewise, the first and second leeward reinforcement structures 22, 27 may be arranged substantially in parallel.

[0077] The first windward and first leeward reinforcement structures 21, 22 may be of substantially the same length, whereas the second windward reinforcement structure 26 is longer than the second leeward reinforcement structure 27.