Pultruded fibrous composite strip with width and thickness tapered ends for wind turbine spar caps

Abstract

A pultruded fibrous composite strip for wind turbine spar caps, a spar cap having such a strip, and a wind turbine blade having such spar cap. The strip has longitudinally extending unidirectional fibers and an elongate body having first and second edge regions separated in the longitudinal direction of the strip by an intermediate region. The intermediate region has first and second mutually opposed longitudinally extending and parallelly disposed planar surfaces. The strip's thickness is measurable perpendicular to the planar surfaces and the width is measurable parallel to the planar surfaces and perpendicular to the longitudinal direction of the strip. In the strip, the first and/or the second edge regions, starting from the intermediate region and extending longitudinally, simultaneously tapers along the width and the thickness of the strip.

Claims

1. A pultruded fibrous composite strip for a spar cap of a wind turbine rotor blade, the strip comprising: unidirectional fibers extending along a longitudinal direction of the strip, a first edge region and a second edge region separated in the longitudinal direction of the strip by an intermediate region, wherein the intermediate region is defined by first and second mutually opposed longitudinally extending and parallelly disposed planar surfaces, wherein a thickness of the strip is determinable perpendicular to the first and second planar surfaces and a width of the strip is determinable parallel to the first and second planar surfaces and perpendicular to the longitudinal direction of the strip, wherein: at least one of the first edge region and the second edge region simultaneously tapers along the width and the thickness of the strip, starting from the intermediate region and extending longitudinally away from the intermediate region, wherein the at least one of the first edge region and the second edge region that simultaneously tapers along the width and the thickness of the strip comprises first and second planar right-angled polygonal faces disposed perpendicularly to the first and second planar surfaces and that taper in thickness starting from the intermediate region and extending longitudinally away from the intermediate region, and wherein the taper in thickness of the first planar right-angled polygonal face is a ratio between 1:100 and 1:50 and the taper in thickness of the second planar right-angled polygonal face is a ratio between 1:100 and 1:20, wherein the taper of the first planar right-angled polygonal face is more gradual than the taper of the second planar right-angled polygonal face.

2. The pultruded fibrous composite strip according to claim 1, wherein each of the first and the second planar right-angled polygonal faces is a quadrilateral.

3. The pultruded fibrous composite strip according to claim 1, wherein the at least one of the first edge region and the second edge region that simultaneously tapers along the width and the thickness of the strip comprises a planar bottom right trapezoid surface, and wherein an angle between two edges of the planar bottom right trapezoid surface is equal to 45 degrees or less.

4. The pultruded fibrous composite strip according to claim 1, wherein the at least one of the first edge region and the second edge region that simultaneously tapers along the width and the thickness of the strip comprises a planar upper surface.

5. The pultruded fibrous composite strip according to claim 1, wherein the unidirectional fibers are carbon fibers.

6. The pultruded fibrous composite strip according to claim 1, wherein the first and second planar right-angled polygonal faces are non-parallel to each other.

7. A spar cap for a wind turbine rotor blade, wherein the spar cap comprises at least one pultruded fibrous composite strip, wherein the at least one pultruded fibrous composite strip includes: unidirectional fibers extending along a longitudinal direction of the strip, and a first edge region and a second edge region separated in the longitudinal direction of the strip by an intermediate region, wherein the intermediate region is defined by first and second mutually opposed longitudinally extending and parallelly disposed planar surfaces, wherein a thickness of the strip is determinable perpendicular to the first and second planar surfaces and a width of the strip is determinable parallel to the first and second planar surfaces and perpendicular to the longitudinal direction of the strip, wherein at least one of the first edge region and the second edge region includes a tapering geometry that simultaneously tapers along the width and the thickness of the strip, starting from the intermediate region and extending longitudinally away from the intermediate region, wherein the at least one of the first edge region and the second edge region that simultaneously tapers along the width and the thickness of the strip comprises first and second planar right-angled polygonal faces disposed perpendicularly to the first and second planar surfaces and that taper in thickness starting from the intermediate region and extending longitudinally away from the intermediate region, and wherein the taper in thickness of the first planar right-angled polygonal face is a ratio between 1:100 and 1:50 and the taper in thickness of the second planar right-angled polygonal face is a ratio between 1:100 and 1:20, wherein the taper of the first planar right-angled polygonal face is more gradual than the taper of the second planar right-angled polygonal face.

8. The spar cap according to claim 7, wherein the at least one pultruded fibrous strip of the spar cap comprises at least two pultruded fibrous composite strips, and wherein the at least two pultruded fibrous composite strips have respective tapering geometries that are different.

9. A wind turbine rotor blade comprising at least one spar cap, wherein each spar cap comprises at least one pultruded fibrous composite strip, wherein the at least one pultruded fibrous composite strip includes: unidirectional fibers extending along a longitudinal direction of the strip, and a first edge region and a second edge region separated in the longitudinal direction of the strip by an intermediate region, wherein the intermediate region is defined by first and second mutually opposed longitudinally extending and parallelly disposed planar surfaces, wherein a thickness of the strip is determinable perpendicular to the first and second planar surfaces and a width of the strip is determinable parallel to the first and second planar surfaces and perpendicular to the longitudinal direction of the strip, wherein at least one of the first edge region and the second edge region simultaneously tapers along the width and the thickness of the strip, starting from the intermediate region and extending longitudinally away from the intermediate region, and wherein the at least one of the first edge region and the second edge region that simultaneously tapers along the width and the thickness of the strip comprises first and second planar right-angled polygonal faces disposed perpendicularly to the first and second planar surfaces and that taper in thickness starting from the intermediate region and extending longitudinally away from the intermediate region, and wherein the taper in thickness of the first planar right-angled polygonal face is a ratio between 1:100 and 1:50 and the taper in thickness of the second planar right-angled polygonal face is a ratio between 1:100 and 1:20, wherein the taper of the first planar right-angled polygonal face is more gradual than the taper of the second planar right-angled polygonal face; wherein the at least one spar cap is arranged such that the respective first and second edge regions are separated along a spanwise direction of the blade.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

(2) FIG. 1 schematically depicts a wind turbine having a wind turbine rotor blade in which a spar cap having a pultruded fibrous composite strip of the present technique may be incorporated;

(3) FIG. 2 schematically depicts the wind turbine rotor blade in which a spar cap having a pultruded fibrous composite strip of the present technique may be incorporated;

(4) FIG. 3 schematically shows an orientation of the spar cap having the strip of the present technique with respect to an airfoil of the blade of FIG. 2;

(5) FIG. 4 represents a prior art depicting a conventionally known strip without tapering on top of a similar strip and their orientation with respect to the blade of the wind turbine;

(6) FIG. 5 represents a prior art depicting a conventionally known tapered strip arranged on top of one of the strips of FIG. 4 and their orientation with respect to the blade of the wind turbine;

(7) FIG. 6 schematically depicts location of tapered ends in the pultruded fibrous composite strip of the present technique arranged on top of a conventional strip and the orientation of the tapered ends with respect to the blade of the wind turbine;

(8) FIG. 7 schematically depicts a tapered end in an exemplary embodiment of the pultruded fibrous composite strip of FIG. 6 according to aspects of the present technique;

(9) FIG. 8 schematically depicts the strip of FIG. 7 arranged on top of a conventional strip;

(10) FIG. 9 schematically depicts another exemplary embodiment of the pultruded fibrous composite strip of the present technique; and

(11) FIG. 10 schematically depicts yet another exemplary embodiment of the pultruded fibrous composite strip of the present technique.

DETAILED DESCRIPTION

(12) Hereinafter, above-mentioned and other features of the present technique are described in detail. Various embodiments are described with reference to the figures, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be noted that the illustrated embodiments are intended to explain, and not to limit embodiments of the invention. It may be evident that such embodiments may be practiced without these specific details.

(13) It may be noted that in the present disclosure, the terms “first”, “second”, “third” etc. are used herein only to facilitate discussion and carry no particular temporal or chronological significance unless otherwise indicated.

(14) FIG. 1 shows an exemplary embodiment of a wind turbine 100 of the present technique. The wind turbine 100 includes a tower 120, which is mounted on a fundament (not shown). A nacelle 122 is mounted on top of the tower 120 and rotatable with regard to the tower 120 by means of a yaw angle adjustment mechanism 121 such as yaw bearings and yaw motors. The yaw angle adjustment mechanism 121 functions to rotate the nacelle 122 around a vertical axis (not shown) referred to as a yaw axis, which is aligned with the longitudinal extension of the tower 120. The yaw angle adjustment mechanism 121 rotates the nacelle 122 during operation of the wind turbine 100 to ensure that the nacelle 122 is appropriately aligned with the current wind direction to which the wind turbine 100 is subjected.

(15) The wind turbine 100 further includes a rotor 110 having at least a rotor blade 10, and generally three rotor blades 10, although in the perspective view of FIG. 1 only two rotor blades 10 are visible. One of the rotor blades 10 is schematically depicted in FIG. 2. The rotor 110 is rotatable around a rotational axis 110a. The rotor blades 10, hereinafter also referred to as the blades 10 or as the blade 10 when referring to one of the blades 10, are generally mounted at a driving collar 112, also referred to as a hub 112. The hub 112 is mounted rotatable with regard to the nacelle 122 by means of a main bearing (not shown). The hub 112 is rotatable about the rotational axis 110a. Each of the blades 10 extends radially with respect to the rotational axis 110a and has an airfoil section 20.

(16) In between the hub 112 and each of the rotor blades 10, is provided a blade adjustment mechanism 116 to adjust the blade pitch angle of the blade 10 by rotating the respective blade 10 about a longitudinal axis (not shown) of the blade 10. The longitudinal axis of each of the blade 10 is aligned substantially parallel with the longitudinal extension of the respective blade 10. The blade adjustment mechanism 116 functions to adjust blade pitch angles of the respective blade 10.

(17) The wind turbine 100 includes a main shaft 125 that rotatably couples the rotor 110, particularly the hub 112, to a generator 128 housed within the nacelle 122. The hub 112 is connected to a rotor of the generator 128. In an exemplary embodiment (not shown) of the wind turbine 100, the hub 112 is connected directly to the rotor of the generator 128, thus the wind turbine 100 is referred to as a gearless, direct drive wind turbine 100. As an alternative, as shown in the exemplary embodiment of FIG. 1, the wind turbine 100 includes a gear box 124 provided within the nacelle 122 and the main shaft 125 connects the hub 112 to the generator 128 via the gear box 124, thereby the wind turbine 100 is referred to as a geared wind turbine 100. Furthermore, a brake 126 is provided to stop the operation of the wind turbine 100 or to reduce the rotational speed of the rotor 110 for instance in case of a very strong wind and/or in case of an emergency.

(18) The wind turbine 100 further includes a control system 150 for operating the wind turbine 100 at desired operational parameters. The wind turbine 100 may further include different sensors for example a rotational speed sensor 143, a power sensor 144, angle sensors 142, etc. that provide inputs to the control mechanism 150 or other components of the wind turbine 100 to optimize operation of the wind turbine 100.

(19) Furthermore, as shown in FIG. 2, the rotor blade 10 includes a root section 11 having a root 11a and an airfoil section 20. Generally, the rotor blade 10 includes a transition section 90 in between the root section and the airfoil section 20. The airfoil section 20, hereinafter also referred to as the airfoil 20, includes a tip section 12 having a tip 12a. The root 11a and the tip 12a are separated by a span 16, of the rotor blade 10, which follows the shape of the rotor blade 10. A direction along or parallel to the span 16 is referred to as span-wise direction 16d. The tip section 12, including the tip 12a therein, extends from the tip 121 towards the root 11a up to a span-wise position of approx. 33.3% (percent), i.e. one third of the total length of the blade 10, as measured from the tip 12a. The tip 12a extends within the tip section 12 towards the root 11a up to a spanwise position of approx. one meter. The rotor blade 10 includes a leading-edge section 14 having a leading edge 14a, and a trailing edge section 13 having a trailing edge 13a. The trailing edge section 13 surrounds the trailing edge 13a. Similarly, the leading-edge section 14 surrounds the leading edge 14a. A protective shell (not shown in FIG. 2) may be mounted on the blade 10, especially around the leading edge 14a.

(20) At each span-wise position perpendicular to the span 16, a chord line 17 that connects the leading edge 14a and the trailing edge 13a can be defined. A direction along or parallel to the chord line 17 is referred to as chord-wise direction 17d. FIG. 2 depicts two such chord lines 17 at two different span-wise positions. Furthermore, a direction mutually perpendicular to the span-wise direction 16d and to the chord-wise direction 17d is referred to as a flap-wise direction 9d. The rotor blade 10 has a shoulder 18 that is a section of the rotor blade 10 where the chord line 17 has maximum chord length, i.e. in example of FIG. 2 at the chord line 17 that is depicted towards the root 11a.

(21) As shown in FIG. 3 in combination with FIG. 2, in the wind turbine 100, the blade 10 includes a blade shell 22. The blade 10 of the wind turbine 100 may have a ‘butterfly blade’ construction (not shown) having leeward and windward shells that are separately manufactured and then joined together to form the blade 10, or may have the well-known ‘integral blade’ construction of Siemens as shown in FIG. 3, where unlike butterfly blade construction the leeward and windward shells are not separately manufactured. In the integral blade construction, the entire shell is manufactured in one-part as an integral shell and thus does not have a separately manufactured leeward and windward side. The blade 10 includes a plurality of spar caps 30, although FIG. 3 only shows a pair of spar caps 30, namely 30a and 30b, there may be more spar cap pairs. The spar caps 30a, 30b of the pair are separated and supported by a web 34 forming an ‘I’-beam. One spar cap 30 for example the spar cap 30a is integrated in the shell 22 at one side for example the suction side 26 whereas the other spar cap 30 for example the spar cap 30b is integrated in the shell 22 at the other side for example the pressure side 24, as shown in FIG. 3.

(22) Hereinafter FIGS. 6 and 7, in combination with FIG. 3, have been used to explain the orientation of the spar cap 30, and orientation and configuration of the constituents of the spar cap 30, i.e. the pultruded fibrous composite strip 1 of the present technique. The pultruded fibrous composite strip 1, hereinafter referred to as the strip 1, has a longitudinal axis 9, as shown in FIGS. 6 and 7. The strip 1 extends along the longitudinal axis 9, in other words the strip 1 has an elongate structure. The strip 1 has unidirectional fibers 99, for example carbon fibers, extending along the longitudinal axis 9, i.e. in longitudinal direction, of the strip 1. The strip 1 has a first edge region 40 and a second edge region 60 i.e. the two ends of the elongate strip 1 as shown in FIG. 6 which depicts the positions of the edge regions 40, 60 with respect to each other. It may be noted that the strip 1 generally extends through a considerable distance of the total span of the blade 10, and the depiction of FIG. 6 showing apparently the strip 1 extending only in part of the blade 10 is schematic and simplified for the purpose of simplicity and for ease of understanding. It may also be noted that FIG. 7, and later FIGS. 8 to 10, depict only one of the edge regions 40, 60, and have been used to explain the depicted first edge region 40, however the same features may be applied to the second edge region 60, when both the edge regions 40, 60 of the strip 1 are tapered in accordance with aspects of the present technique.

(23) As shown in FIG. 7 in combination with FIG. 6, the strip 1 has an intermediate region 50 that separates, along the longitudinal direction i.e. along the longitudinal axis 9 of the strip 1, the first and the second edge regions 40, 60. The intermediate region 50 has a first planar surface 52 and a second planar surface 54. The planar surfaces 52, 54 are mutually opposed longitudinally extending and parallelly disposed with respect to each other. In the strip 1, a thickness of the strip 1 is determinable or measurable perpendicular to the first and the second planar surfaces 52, 54 i.e. along the axis 9t of FIG. 7, whereas a width of the strip 1 is determinable or measurable parallel to the first and the second planar surfaces 52, 54 and perpendicular to the longitudinal direction of the strip 1, i.e. along an axis 9w which is mutually perpendicular to the longitudinal axis 9 of the strip 1 and the axis 9t of the strip 1. In the strip 1, at least one of the first and the second edge regions 40, 60, in example of FIG. 7 the first edge region 40, starting from the intermediate region 50 and extending longitudinally, i.e. along the longitudinal axis 9, simultaneously tapers along the width and the thickness of the strip 1.

(24) As shown in FIG. 7, the tapered edge region i.e. the first edge region 40 in case of example of

(25) FIG. 7 has a first planar right-angled polygonal face 41 represented by line segments marked a-d-d1-a and a second planar right-angled polygonal face 42 represented by line segments marked b-c-c1-b. It may be noted that albeit the example of FIG. 7 shows polygonal faces 41, 42 to be triangular faces, in another embodiment of the present technique the polygonal faces may be quadrilateral for example as shown in FIG. 10. As shown in FIGS. 7 and 10 the polygonal faces 41, 42 are disposed perpendicularly to the planar surfaces 52, 54. Thus, the tapered edge region i.e. the first end region 40 in FIG. 7 is a wedge shaped volume as represented by shape defined by side c-c1-d1-d-c, the polygonal faces 41, 42, a planar bottom right trapezoid surface a-b-c-d-a, and a planar upper surface a-b-c1-d1-a. A side 41a, represented by edge d1-a, of the first polygonal face 41 starting from the intermediate region 50 tapers in thickness at a rate between 1:100 and 1:50 whereas a side 42a, represented by edge c1-b, of the second polygonal face 42 starting from the intermediate region 50 tapers in thickness at a rate between 1:100 and 1:20. The taper of the side 41a of the polygonal face 41 is different from the taper of the side 42a of the polygonal face 42. The phrase ‘taper’ and its quantitative measure as used herein are also generally referred to as grade, slope, incline, gradient, mainfall, pitch or rise. As shown in FIG. 7, the taper of the side 41a of the first polygonal face 41 is less than the taper of the side 42a of the second polygonal face 42.

(26) Furthermore, as shown in FIGS. 7 and 10, the polygonal faces 41, 42 are parallel to each other in one embodiment of the strip 1, whereas non-parallel to each other in another embodiment of the strip 1 as shown in FIG. 9.

(27) As shown in FIG. 7, in an exemplary embodiment of the strip 1, an angle A of the right trapezoid surface a-b-c-d-a is equal to 45 degree or less.

(28) FIG. 8 depicts the strip 1 positioned on top of a conventional strip 201 to form a stack of strips for the spar cap 30. However, in another embodiment (not shown), the strip 1 may be positioned on top of a conventional tapered strip 201a of FIG. 5 and in yet another embodiment (not shown), the strip 1 may be positioned on top of a similar strip 1 having same or different tapering geometries. The strip 1 of the present technique, and as depicted schematically in examples of FIGS. 6 to 10, is incorporated in one or more of the spar caps 30 of FIG. 3 which in turn is incorporated in the wind turbine rotor blade 10 of FIG. 2.

(29) Although in the present technique, particularly in FIG. 8, the stack is shown to comprise only one tapered strip 1, in other embodiment of the present technique, the stack may include two or more such tapered strips 1. Furthermore, when having two or more tapered strips the taperings of the strip 1 i.e. the tapering along the width and thickness of one of the strips 1 may differ from the tapering along the width and thickness of one of other strips 1. It may be noted that although in the present disclosure, particularly in FIG. 6, only one stack of strip 1 has been depicted to form the spar cap 30, the spar cap 30 may comprise two or more parallelly disposed stacks of the strips 1 placed adjacent to each other and each extending longitudinally.

(30) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(31) For the sake of clarity, it is to be understood that the use of ‘a’ or ‘an’ throughout this application does not exclude a plurality, and ‘comprising’ does not exclude other steps or elements.