A WIND TURBINE ROTOR BLADE WITH A LEADING EDGE MEMBER

Abstract

A wind turbine rotor blade (10) is provided with a lightning protection device (84) and a leading edge member (70), the leading edge member (70) comprising an erosion shield (78, 80), deicing means, and an electrically conductive outer surface (80) which is operatively connected to the lightning protection device (84). The invention also relates to the use of the leading edge member (70) for providing leading edge erosion protection, ice mitigation and lightning protection of a wind turbine rotor blade.

Claims

1. A wind turbine rotor blade (10) having a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root, wherein the rotor blade comprises a lightning protection device (84) and a leading edge member (70), the leading edge member (70) comprising an erosion shield (78, 80), deicing means (118), and an electrically conductive outer surface (80) which is operatively connected to the lightning protection device (84).

2. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) comprises one or more metal film layers, which at least partly form the electrically conductive surface of the leading edge member (70).

3. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) is manufactured during a shell moulding operation of the wind turbine blade, wherein the shell moulding operation comprises co-infusing a fibre material forming at least part of the shell of the rotor blade and one or more layers forming the leading edge member.

4. A wind turbine rotor blade according to claim 1, wherein the leading edge member is embedded in the blade.

5. A wind turbine blade according to claim 1, wherein the deicing means comprises a resistive heating element comprising a metal film layer, a metallic alloy, a ceramic material, and/or a ceramic metal.

6. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) comprises a polymer material and/or a ceramic material.

7. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) comprises a first region (78) extending in a spanwise direction and a second region (80) adjacent to the first region and extending in a spanwise direction, wherein the second region (80) is closer to the blade tip than the first region (78), wherein the boundary (79) between the first and second region extends in a substantially chordwise direction, and wherein the first region is composed of a different material than the second region.

8. A wind turbine rotor blade according to claim 7, wherein the leading edge member (70) further comprises a third region (82) extending in a spanwise direction adjacent to the first region (78), wherein the boundary (81) between the first and the third region extends in a substantially spanwise direction, wherein the third region is closer to the trailing edge than the first region.

9. A wind turbine rotor blade according to claim 1, wherein the chordwise width (W1, W2) of the leading edge member (70) decreases stepwise towards the tip (14) of the blade.

10. A wind turbine rotor blade according to claim 1, wherein the deicing means, such as an electrical heating element, and the lightning protection device are operably connected to a joint control unit.

11. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) comprises a film layer comprising a metal material and a polymer layer, the film layer being bonded on top of the polymer layer, wherein the film layer forms part of the outer surface of the leading edge member (70).

12. A wind turbine rotor blade according to claim 11, wherein the polymer layer is a rubber layer.

13. A wind turbine rotor blade according to claim 1, wherein the leading edge member (70) is mounted to the rotor blade by a snap-fit or by a clip-on interlocking connection.

14. A method of manufacturing at least a segment of a wind turbine rotor blade according to claim 1, the method comprising providing a mould having a moulding surface configured for forming at least part of the outer surface of the shell of the rotor blade or of the rotor blade segment, and for forming the outer surface of the leading edge member, laying a metal film layer onto the moulding surface, optionally followed by one or more additional layers for forming the leading edge member, laying a fibre material on the metal film layer and the optional additional layers for forming the shell of the rotor blade or of the rotor blade segment, and co-infusing the fibre material, the metal film layer and the optional additional layers with a resin.

15. Use of a leading edge member (70) as defined in claim 1 for providing leading edge erosion protection, ice mitigation and lightning protection of a wind turbine rotor blade.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0053] The invention is explained in detail below with reference to embodiments shown in the drawings, in which corresponding components are identified by the same reference numerals, wherein

[0054] FIG. 1 shows a wind turbine,

[0055] FIG. 2 shows a schematic view of a wind turbine blade,

[0056] FIG. 3 shows a schematic view of an airfoil profile through section I-I of FIG. 4,

[0057] FIG. 4 shows a schematic view of the wind turbine blade, seen from above and from the side,

[0058] FIG. 5a is a partial perspective view of a wind turbine blade with a leading edge member according to one embodiment of the present invention,

[0059] FIG. 5b is a schematic cross sectional view taken along the line I-I in FIG. 5a,

[0060] FIG. 6 is a schematic top view and simplified circuit diagram of two blade halves according to one of embodiment of the present invention,

[0061] FIG. 7 is a schematic perspective view of a wind turbine blade according to one embodiment of the present invention, and

[0062] FIG. 8 illustrates a moulding system for manufacturing at least part of wind turbine blade of the present invention.

DETAILED DESCRIPTION

[0063] FIG. 1 illustrates a conventional modern upwind wind turbine according to the so-called “Danish concept” with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.

[0064] FIG. 2 shows a schematic view of an exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.

[0065] The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0066] A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

[0067] It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

[0068] The wind turbine blade 10 comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part 24 and a second blade shell part 26, typically made of fibre-reinforced polymer. The wind turbine blade 10 may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part 24 is typically a pressure side or upwind blade shell part. The second blade shell part 26 is typically a suction side or downwind blade shell part. The first blade shell part 24 and the second blade shell part 26 are fastened together with adhesive, such as glue, along bond lines or glue joints 28 extending along the trailing edge 20 and the leading edge 18 of the blade 10. Typically, the root ends of the blade shell parts 24, 26 has a semi-circular or semi-oval outer cross-sectional shape.

[0069] The wind turbine blade 10 comprises a leading edge member 70 on the leading edge 18 of the wind turbine blade 10. The leading edge member 70 extends in a spanwise direction between a first lateral edge 75 and a second lateral edge 76. The leading edge member 70 also has a first longitudinally extending edge 73 and a second longitudinally extending edge 74. The longitudinal direction of the leading edge member 70 may be parallel to the longitudinal direction of the wind turbine blade 10. The length L1 of the leading edge member, e.g. the distance between the first lateral edge 75 and the second lateral edge 76, may be the same as the length of the leading edge 18 of the wind turbine blade 10. The length L1 may be smaller than the length of the leading edge 18 of the wind turbine blade 10, as illustrated. The leading edge member 70 has an outer surface 71 and an inner surface 72. The inner surface 72 of the leading edge member faces the leading edge 18 of the wind turbine blade.

[0070] FIGS. 3 and 4 depict parameters which are used to explain the geometry of the wind turbine blade. FIG. 3 shows a schematic view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use—i.e. during rotation of the rotor—normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber (or suction side camber) and lower camber (or pressure side camber), which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

[0071] Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position d.sub.f of the maximum camber f, the maximum airfoil thickness t, which is the largest diameter of the inscribed circles along the median camber line 62, the position d.sub.t of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c. Thus, a local relative blade thickness t/c is given as the ratio between the local maximum thickness t and the local chord length c. Further, the position d.sub.p of the maximum pressure side camber may be used as a design parameter, and of course also the position of the maximum suction side camber.

[0072] FIG. 4 shows other geometric parameters of the blade. The blade has a total blade length L. As shown in FIG. 3, the root end is located at position r=0, and the tip end located at r=L. The shoulder 40 of the blade is located at a position r=L.sub.w, and has a shoulder width W, which equals the chord length at the shoulder 40. The diameter of the root is defined as D. The curvature of the trailing edge of the blade in the transition region may be defined by two parameters, viz. a minimum outer curvature radius r.sub.o and a minimum inner curvature radius r.sub.i, which are defined as the minimum curvature radius of the trailing edge, seen from the outside (or behind the trailing edge), and the minimum curvature radius, seen from the inside (or in front of the trailing edge), respectively. Further, the blade is provided with a prebend, which is defined as Δy, which corresponds to the out of plane deflection from a pitch axis 22 of the blade.

[0073] FIG. 5a is a partial perspective view of a wind turbine blade 10 with a leading edge member 70 according to one embodiment of the present invention, whereas FIG. 5b is a schematic cross sectional view taken along the line I-I in FIG. 5a. In the illustrated embodiment, the leading edge member 70 comprises a first region 78 extending in a spanwise direction and a second region 80 adjacent to the first region and extending in a spanwise direction. The second region 80 is closer to the blade tip 14 than the first region 78. The boundary 79 between the first and second region extends in a substantially chordwise direction. The first region 78 is preferably composed of a different material than the second region 80. The edge erosion shield of the leading edge member 70 is formed by the first and second regions 78, 80.

[0074] In addition, the leading edge member 70 of FIG. 5 comprises a third region 82 extending in a spanwise direction adjacent to the first region 78. The boundary 81 between the first and the third region extends in a substantially spanwise direction, wherein the third region 82 is closer to the trailing edge 20 than the first region 78. The first, second and third regions 78, 80, 82 may form an electrical heating element as further illustrated below. Also, at least the second region 80 may form the electrically conductive outer surface 80 which is operatively connected to the lightning protection device. Each of the first, second and third regions 78, 80, 82 may comprise one or more metal film layers at their outer surface, which at least partly form the electrically conductive surface of the leading edge member.

[0075] Thus, as seen in FIG. 5, the chordwise width W1 of the leading edge member 70 decreases towards the tip end 14 in a discrete step, i.e. to chordwise width W2.

[0076] FIG. 6 is a schematic top view and simplified circuit diagram of two blade halves according to one embodiment of the present invention, wherein at least part of the surface of the leading edge member forms the deicing means in the form of a resistive heating layer 118 placed at, or just below, the outer surface of the leading edge member 70. To that end, the resistive heating layer 118 of the leading edge member may comprise a metal film layer, a metallic alloy, a ceramic materials, and/or a ceramic metal. The leading edge member 70 extends in a substantially spanwise direction over about 40% of the total blade length in the illustrated embodiment. The resistive heating layer 118, or part thereof may act as a resistive heating element for ice mitigation by connecting a power supply 86 via lines 88, 90 to various contact points 92, 94, 96, 98 on both sides of the resistive heating layer 118.

[0077] FIG. 7 illustrates schematically that an electrically conductive outer surface 71 of the leading edge member 70 is operatively connected to lightning protection device 84 comprising a cable, such as a copper cable. The lightning protection device 84 is disposed at least partially in the interior of the rotor blade. The lightning protection device 84 may be connected to a tip end lightning receptor 97, which in turn is electrically connected to the electrically conductive outer surface 71 of the leading edge member 70. In other embodiments, the electrically conductive outer surface 71 of the leading edge member 70 may be connected directly to eh lightning protection device 84. The electrical heating element and the lightning protection device can be operably connected to a joint control unit.

[0078] FIG. 8 is a schematic diagram illustrating a moulding system 99 with a mould 100 for manufacturing a leading edge member 70 and a shell of a wind turbine blade. The mould 100 comprises a moulding surface 102 configured for forming the outer surface 71 of the leading edge member. The leading edge member 70 is laid up on a first part 104 of the moulding surface 102 of the mould, e.g. by orienting the leading edge member 70 such that the outer surface 71 of the leading edge member faces the moulding surface 82 of the mould. As a first layer forming the leading edge member a film layer 114, for example a metal film layer, may be laid onto the moulding surface 102. As a second layer, a polymer layer 116, for example a rubber layer, may be laid onto the film layer 114. A shell material 112, such as fibre reinforced material, is then laid in the mould 80 covering the inner surface 72 of the leading edge member 70, which is formed by the polymer layer 116 in the illustrated embodiment. The shell material 112 may be a sheet of material, such as glass fibre. The shell material 112 may be laid up such that the shell material 112 covers a second part 106 and/or a third part 108 of the moulding surface 102 of the mould 100. A coating 110 may be applied to the second part 106 of the moulding surface and/or the third part 108 of the moulding surface. The shell material 112 and the leading edge member 70 is then consolidated, e.g. by co-infusing the shell material 112 and the leading edge member 70 with a resin and curing the resin, to form at least part of the wind turbine blade. Vacuum assisted resin transfer moulding (VARTM) may be applied.

[0079] The invention is not limited to the embodiments described herein and may be modified or adapted without departing from the scope of the present invention.

LIST OF REFERENCE NUMERALS

[0080] 2 wind turbine [0081] 4 tower [0082] 6 nacelle [0083] 8 hub [0084] 10 blade [0085] 14 blade tip [0086] 16 blade root [0087] 18 leading edge [0088] 20 trailing edge [0089] 22 pitch axis [0090] 24 first blade shell part (pressure side) [0091] 26 second blade shell part (suction side) [0092] 28 bond lines/glue joints [0093] 30 root region [0094] 32 transition region [0095] 34 airfoil region [0096] 40 shoulder/position of maximum chord [0097] 50 airfoil profile [0098] 52 pressure side [0099] 54 suction side [0100] 56 leading edge [0101] 58 trailing edge [0102] 60 chord [0103] 62 median camber line [0104] 70 leading edge member [0105] 71 outer surface of leading edge member [0106] 72 inner surface of leading edge member [0107] 73 first longitudinally extending edge of leading edge member [0108] 74 second longitudinally extending edge of leading edge member [0109] 75 first lateral edge of leading edge member [0110] 76 second lateral edge of leading edge member [0111] 78 first region of leading edge member [0112] 79 boundary between first and second region [0113] 80 second region of leading edge member [0114] 81 boundary between first and third region [0115] 82 third region of leading edge member [0116] 84 lightning protection device [0117] 86 power source [0118] 88 first line [0119] 90 second line [0120] 92 first contact [0121] 94 second contact [0122] 96 third contact [0123] 97 tip end lightning receptor [0124] 98 fourth contact [0125] 99 moulding system [0126] 100 mould [0127] 102 moulding surface [0128] 104 first part of moulding surface [0129] 106 second part of moulding surface [0130] 108 third part of moulding surface [0131] 110 coating [0132] 112 shell material [0133] 114 film layer [0134] 116 polymer layer [0135] 118 resistive heating layer [0136] c chord length [0137] d.sub.t position of maximum thickness [0138] d.sub.f position of maximum camber [0139] d.sub.p position of maximum pressure side camber [0140] f camber [0141] L blade length [0142] r local radius, radial distance from blade root [0143] t thickness [0144] Δy prebend