Protective cover system

Abstract

Provided is a protective cover system including a first protective cover and a second protective cover, both include a polymer and being pre-formed into a curved shape so as to accommodate at least a part of a wind turbine blade to be protected, each of the first and second protective covers has a tip end and a root end, wherein the first protective cover includes a first overlap portion at the root end, and the second protective cover includes a second overlap portion at the tip end, wherein the shape of the first overlap portion is substantially complementary to the shape of the second overlap portion such that when overlapping the first and second overlap portions, the resulting cross section of the overlapped overlap portions substantially corresponds to the cross sections of the first or second protective covers outside the overlap portions.

Claims

1. A protective cover system for protecting a leading edge of a wind turbine rotor blade from erosion, the system comprising: a first protective cover and a second protective cover, both comprising a polymer and being pre-formed into a curved shape so as to accommodate at least a part of the wind turbine rotor blade to be protected, wherein each of the first protective cover and the second protective cover has a tip end and a root end; wherein the first protective cover comprises a first overlap portion at the root end, and the second protective cover comprises a second overlap portion at the tip end; wherein a shape of the first overlap portion is substantially complementary to a shape of the second overlap portion such that when overlapping the first overlap portion and the second overlap portion, a resulting cross section of the overlapped overlap portions substantially corresponds to cross sections of at least one of the first protective cover and the second protective cover outside the overlap portions; wherein one of the first protective cover and the second protective cover comprises a protruding element in the respective first overlap portion or the second overlap portion and the other one of the first protective cover and the second protective cover comprises a recess in the other respective first overlap portion or the second overlap portion, the recess configured to accommodate the protruding element for guiding the first protective cover and the second protective cover when being mounted to the wind turbine rotor blade; wherein the recess is a through hole extending through the first overlap portion or the second overlap portion, and the protruding element is shaped to be insertable within the through hole.

2. The protective cover system according to claim 1, wherein at least one of the protective covers comprise an elastomer comprising polyurethane or polyethylene.

3. The protective cover system according to claim 1, wherein a length of at least one of the first and second protective cover amounts to 2000 mm at maximum.

4. A wind turbine blade comprising the protective cover system according to claim 1, wherein the protective cover system is connected to the wind turbine blade along a leading edge of the blade.

5. A method for mounting the protective cover system according to claim 1 to a leading edge of a wind turbine blade, the method comprising: providing a wind turbine blade, the protective cover system according to claim 1, and an adhesive; applying the adhesive on the wind turbine blade and/or on an inner surface of the first and the second protective covers; placing the first and the second protective covers onto the wind turbine blade, wherein the first and the second overlap portions of the protective covers are arranged such that the first and the second overlap portions overlap; applying further adhesive between the first and the second overlap portions; and allowing the adhesive to connect the first and the second protective covers to the wind turbine blade.

6. The protective cover system according to claim 1 further comprising a first set of protective covers, each of the protective covers of the first set of protective covers correspond to a true copy of said first protective cover, a second set of protective covers, each of the protective covers of the second set of protective covers corresponds to a true copy of said second protective cover, a protective tip cover, and a protective root cover.

7. The protective cover system according to claim 6, wherein the protective tip cover has a swept end to cover and fit the blade tip.

8. The protective cover system according to claim 6, wherein the protective root cover features a smooth transition towards the leading edge on the root side.

9. The protective cover system according to claim 1, wherein a leading edge radius of the first protective cover is different from a leading edge radius of the second protective cover.

Description

BRIEF DESCRIPTION

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

(2) FIG. 1 shows a wind turbine;

(3) FIG. 2 shows a plan view of a wind turbine blade;

(4) FIG. 3 shows the profile of a wind turbine blade together with the protective cover system according to embodiments of the invention;

(5) FIG. 4 shows a cross-sectional view of a protective cover according to embodiments of the invention;

(6) FIG. 5 shows decline transitions at different positions of the leading edge according to embodiments of the invention;

(7) FIG. 6 shows a detailed view of a transition according to embodiments of the invention;

(8) FIG. 7 shows overlap portions of a protective cover according to embodiments of the invention;

(9) FIG. 7a shows an end of the protective cover according to embodiments of the invention;

(10) FIG. 8 shows a height of a shell according to embodiments of the invention;

(11) FIG. 9 shows a protective cover system according to embodiments of the invention;

(12) FIG. 10 shows bondline features of the protective cover according to embodiments of the invention;

(13) FIG. 11 shows a tailored tip of the protective cover according to embodiments of the invention;

(14) FIG. 12 shows an alternative tip of the protective cover according to embodiments of the invention;

(15) FIG. 13 shows an embodiment of the protective cover according to embodiments of the invention;

(16) FIG. 14 shows an embodiment of the protective cover according to embodiments of the invention;

(17) FIG. 15 shows a root shell according to embodiments of the invention;

(18) FIG. 16 show a pressure side and a suction side according to embodiments of the invention;

(19) FIG. 17 shows a tip shell according to embodiments of the invention;

(20) FIG. 18 shows an inner shell according to embodiments of the invention;

(21) FIG. 19 shows a pressure side and a suction side according to embodiments of the invention;

(22) FIG. 20 shows an outer shell according to embodiments of the invention;

(23) FIG. 21 shows a pressure side and a suction side according to embodiments of the invention;

(24) FIG. 22 shows a rotor blade according to embodiments of the invention; and

(25) FIG. 23 shows how flexible the protective covers may be.

DETAILED DESCRIPTION

(26) A “wind turbine rotor blade” may also be referred to as “wind turbine blade”. A “protective cover” for protecting a leading edge of a wind turbine blade from erosion may also be referred to as “shell” or “shield”.

(27) The “protective cover” according to embodiments of the present invention is preformed. The protective cover is brought into a curved shape before being mounted. It may be machined. It is pre-casted. The term “preformed” may also be referred to as pre-shaped. According to embodiments of the present invention, the “protective cover” is pre-shaped into a curved shape so as to accommodate at least a part of a wind turbine blade (55). The “curved shape” may also be described as a channel-like shape or as a substantially parabolic channel.

(28) It is known in the art to cast a male part on the blade by use of a male mold. The resulting bond may be of superior quality. In contrast to this concept, a female mound may be used in addition to the male mold to pre-cast the first and second protective covers (1, 2) instead of casting over the blade (55) with one or more protective covers (1, 2).

(29) Covers of an Elastomeric Polyurethane are preferred. This may be a rubbery, elastic and flexible material to allow the protective shell to be easily form-fitted to a wind turbine blade surface and to provide it with sufficient elasticity so as to dampen the impact of erosive influences.

(30) The protective cover may be flexible. In other words, it may have some flexibility. That means the protective cover may be flexible in such a way that it is less flexible than a tape but more flexible than a stiff component. The advantage of a preformed but flexible protective cover is on the one hand a curved shape which facilitates handling of the cover and provides for a good fit to a curved surface, and on the other hand the fact that the protective cover may easily adapt to a range of differently curved surfaces, e.g. at different locations along a leading edge of a wind turbine blade. In other words, a preformed and flexible protective cover, e.g. made of a Polyurethane based Elastomer, may adapt to different curved surfaces having a range of different bending rates (angle) in a predetermined range of bending rates.

(31) To keep the protective covers 1,2 on the blade 55 even after being struck by a relatively large foreign object, such as a bird or an ice fragment, without a protective cover 1,2 peeling off, the protective cover system 10 is bonded to the blade 55, e.g. by means of a heat-activatable adhesive. In so doing, the adhesive may be heated, e.g. by a heating blanket or a vacuum heating blanket.

(32) FIG. 1 shows a typical wind turbine (51) comprising a tower (52), a nacelle (53), a generator (56), and blades (55). The blades (55) are attached to a hub (54). They capture the energy of the wind, spinning a generator (56) in the nacelle (53). The tower (52) comprises the electrical conduits, supports the nacelle (53), and provides access to the nacelle (53) for maintenance.

(33) FIG. 2 shows a plan view of a wind turbine rotor blade (55) comprising a tip (57) and a root (58), a leading edge (59) and a trailing edge (60). The rotor blade (55) further comprises a shoulder (61) near the blade root (58) and an airfoil portion (62).

(34) FIG. 3 shows the profile of a wind turbine rotor blade 55 including a leading edge 59, a trailing edge 60 as well as the suction and the pressure sides 65, 64 between the leading and the trailing edges 59, 60. The profile shown in FIG. 3 further comprises a protective cover system according to embodiments of the present invention which is positioned along the leading edge 59 of the rotor blade 55.

(35) FIG. 4 shows the protective cover system 10 for protecting a leading edge 59 of a wind turbine blade 55 from erosion comprises a first protective cover and a second protective cove. The first and the second protective covers 1, 2 comprise a polymer material. The covers 1, 2 are pre-formed into a curved shape so as to accommodate at least a part of a wind turbine blade 55, especially along the leading edge 59 of the blade 55.

(36) FIG. 5 shows that each of the first and second protective covers 1, 2 has a tip end 3 and a root end 4. The first protective cover 1 comprises a first overlap portion 4a at the root end 4 and the second protective cover 2 comprises a second overlap portion 3a at the tip end 3a, as shown in FIG. 7. The shape of the first overlap portion 4a at the root end 4 of the first protective cover 1 is substantially complementary to the shape of the second overlap portion 3a at the tip end 3 of the second protective cover 2 such that when overlapping these first and second overlap portions 4a, 3a, the resulting cross section of the overlapped overlap portions 4a, 3a substantially correspond to the cross sections of at least one of the first and second protective covers outside the overlap portions.

(37) The wind turbine blade comprises a protective cover system according to embodiments of the invention, wherein the protective cover system is connected to the wind turbine blade along a leading edge of this blade. The method for mounting a protective system to a leading edge 59 of a wind turbine rotor blade 55 from erosion, the method comprises the steps of: Providing a wind turbine blade, a first and a second protective cover according to embodiments of the invention, and an adhesive; Applying the adhesive on the wind turbine blade and/or on an inner surface of the first and second protective cover; Placing the first protective cover onto the wind turbine blade; Placing the second protective cover onto the wind turbine blade, wherein the step of placing the second protective cover onto the wind turbine blade involves arranging the first and second overlap portions such that these first and second overlap portions overlap; Optionally, applying further adhesive between the first overlap portion and the second overlap portion; and Allowing the adhesive to firmly connect the first and second protective cover to the wind turbine blade.

(38) The embodiments are directed towards having a plastic shell 1, 2 that is bonded to the outer surface of the blade 55, more specific of the leading edge 59. The shell 1, 2 is referred herein to as protective cover. It may have a width W of +/−100 mm with respect to the leading edge 59 of the wind turbine blade 55, see FIG. 3.

(39) The shell may be made of a polymer comprising polyurethane and a further component. The shell is a curved protective plate in the shape of a parabolic channel. It is designed to be mounted lengthwise along the leading edge of a wind turbine blade. The shell is moulded in a moulding process. The shell is pre-moulded but still pliable enough to provide a tight fit to the turbine blade.

(40) The shell system comprises a first shell and a second shell. Each shell has two short edges, herein also referred to as tip end and root end 3, 4 and two long edges, herein also referred to as outer edges. The long edges are longer than the short edges. The first short edge 4 is located at one end of the parabolic channel, and the second short edge is located at the opposite end of the parabolic channel. The two long edges 9 are perpendicular to the two short edges.

(41) The shell has a centerline C running lengthwise along the substantially parabolic channel in parallel to the long edges 9. The thickness Tn of the shell is greatest along the centerline C and gradually diminishes toward the two long edges 9. The thickness Tn may be 3 mm at the centerline C, see FIG. 4.

(42) Overlap section: A shell system comprises at least two of above-mentioned shells 1, 2 touching one another at their short edges 3, 4. The shells may be connected to each other or interconnected by various means, e.g. by edge chamfer and protrusion 6, see FIG. 7. The protrusion 6 can be a guiding nipple.

(43) The overlap portions 3a, 4a may have a length Lo of 30 mm in longitudinal direction of the protective cover 1, 2. The protrusion 6 may have a diameter Dp of 2 mm and the recess 7 may also have diameter Dr of 2 mm. The length Lp of the protrusion may be 3 mm, see FIG. 7.

(44) The shells may be interconnected by means of connecting elements 5, 20, 21 that serve for a guiding/connecting of the two shells 1, 2. Mechanical interlocking between the shells 1, 2 is achieved by having connecting elements 5, 20, 21 that have a nipple shape. This shape reduces stress concentration for the connecting element 5, 20, 21.

(45) Transition consideration: an internal chamfer results in no exposure for the blade. A stepwise decline transition provides thickness and strength which prolong the lifetime of the cover system.

(46) Different decline transitions at different positions of the leading edge are possible, e.g. step-like connecting elements 5 at the leading edge (that means at the Centerline C) of the shell 1, 2), step-like connecting elements 20 having rounded edges onto a width of the shell of +/−50 mm from the Leading edge (Centerline C) and tapered connecting elements 21 from +/−50 mm on to a width of +/−100 m (that means until the outer edges 9, 9a, 9b), see FIG. 5 and FIG. 6.

(47) The blade chord length is decisive of the aero dynamic property—therefore it needs to be as thin as possible. The thickness Tne at an end 4 of the shell may be around 0.05 mm. Corner rounding of corner 8 with a radius R5 help avoiding peeling off of the shell, see FIG. 7a.

(48) At an end 3, 4 in lengthwise direction of the shell, the overlap area 3a, 4a may have a length of 20-40 mm, such as 30 mm, in one embodiment. The thickness of the shell may diminish in the overlap area to a very small thickness in the range of 0.03 mm to 0.07 mm, to about 0.05 mm.

(49) The shell may have a peel height Hp, referred to in Danish language as Peelhejde (in English language Sagitta height). That means the shell 1, 2 may be curved with a radius R2, that means the centerline C is curved. see FIG. 8.

(50) It is known to extrude plastic elements. The embodiments are directed towards overcoming the disadvantage of having extruded element.

(51) Having a sagitta height Hp enables the shells to be drapable. The height difference between an outer end of the shell and a position at the centerline in the middle of the shell may be 3 to 7 mm, about 5 mm.

(52) The sagitta height Hp is achieved during the manufacturing of the shell. Each of the shells will be moulded as one piece. Another advantage of casting the shells is that each shell can be tailored.

(53) The protective cover system 10 comprising a first and a second protective cover 1, 2 (first and second shell) may have an open angle at the Overlap OV. That means the angle between centerline C and root or tip end 3, 4 is smaller than 90 degrees and the angle between outer edge 9 and root or tip end 3, 4 is greater than 90 degrees. At the outer edge 9 the distance Dd may be 3 mm, see FIG. 9.

(54) Each overlap influences the aerodynamic performance of the blade. It is important to avoid excess overlap and thereby material. Therefore, the overlap is less than 30 mm.

(55) Bondline Features: Indentation, e.g. with 20 mm spacing in between the indentations, on the inner surface ensure a better bonding due to the fact that the indentation entrap glue, see FIG. 10.

(56) A tailored tip as shown in FIG. 11 may have a length Lt in the range of around 530 mm to 630 mm, a width Wt1 of around 50 mm at the tip end 3 of the shell 1 and a width Wt1 of around 100 mm at the root end 4 of the shell 1. In addition, at the tip end 3 of the shell 1 Wt1 may be slightly greater such that a Radius R30 is generated at the outer edge of the shell. So, the tip of the blade is very well enclosed and thus protected from erosion, see FIG. 11 showing a tip shell (soft tip shell).

(57) Enclosing the tip of the blade is an option, as also shown in FIG. 12. Better transition of the tip. One unique shell could be used for the tip end.

(58) As an alternative, the tip shell 1, may be designed to leave the tip of the blade 30 blank, that means not covered, see FIG. 12.

(59) Advantages Compared to coating and tape solutions embodiments of this invention offers a method that can be done in one working step Having a peel height enables the shells to be drapable. The peel height is achieved during the manufacturing of the shell. Each shell will be moulded as one piece. Another advantage of casting the shells is that each shell can be tailored Cost and repair reduced.

(60) The length of at least one of the first and second protective cover (1, 2) may amount to about 2000 mm at maximum, to about 1000 mm.

(61) Advantage: good length blade, in view of operational window (1.7 m). w/o repositioning worker himself.

(62) Method for mounting a protective cover system (10) to a leading edge (59) of a wind turbine blade (55),

(63) the method comprises the steps of:

(64) Providing a wind turbine blade (55), the protective cover system (10) and an adhesive; Applying the adhesive on the wind turbine blade (55) and/or on an inner surface (12) of the first and the second protective covers (1, 2); Placing the first and the second protective covers (1, 2) onto the wind turbine blade (55), wherein the first and the second overlap portions (4a, 3a) of the protective covers (1, 2) are arranged such that the first and the second overlap portions (3a, 4a) overlap; Optionally, applying further adhesive between the first and the second overlap portions (4a, 3a); and Allowing the adhesive to firmly connect the first and the second protective covers (1, 2) to the wind turbine blade (55).

(65) The protective cover system (10) further comprising a first set of protective covers, each of the protective covers of the first set of protective covers corresponds to a true copy of said first protective cover (1), a second set of protective covers, each of the protective covers of the second set of protective covers corresponds to a true copy of said second protective cover (2), a protective tip cover, and a protective root cover.

(66) It is possible for some blades that first set is a true copy of second set, depending on a shape and/or shorter length, and depending on repair length.

(67) The protective cover system, wherein the LE radius of the first protective cover (1) is different from the LE radius of the second protective cover (2).

(68) bending rate.fwdarw.LE radius

(69) more open curvature vs., more closed curvature

(70) only 4 diff cover types.fwdarw..

(71) The protective cover system, wherein the first protective cover 1 has a chord length corresponding to a chord length of the blade between 0.5 (2 m from tip/1 m-3 m) and 1.3 (12 m from tip/pref. 9-24 m/more pref. 10-14 m) meters and the second protective cover 2 has a chord length corresponding to the chord length of the blade of about 1.3 meters or more. Outer ⅓ (−½ to) of the length of LE—50%/50% for diff. sets of shells.

(72) The protective cover system, wherein the first protective cover (1) has a chord length between 0.5 and 1.3 meters and the second protective cover (2) has a chord length of about 1.3 meters or more.

(73) The protective cover system, wherein the protective tip cover has a swept end to cover and fit the blade tip.

(74) Pre-bend—more curved than other shells

(75) not exact copy of blade tip but more curved—so it is stretched when mounted to the blade

(76) Valid for all shells, but more exaggerated for tip shell

(77) Tip covered or not covered/

(78) open tip—easier fit to all variations of blade tips, but less erosion protection performance than closed one

(79) close tip—better protection, but requires little variance in blade tips therefore more shell variants are needed.

(80) The protective cover system, wherein the protective root cover features a smooth transition towards the leading edge on the root side. root end w/o overlap portion, w/o pin hole
smooth transition towards the leading edge on the root side.
Option: No root shell

(81) Advantages:

(82) Compared to a rigid protection shell that can be only mounted on a predefined part of the leading-edge surface, the material of which the protective covers according to embodiments of the present invention are built has a certain flexibility which allows their mounting along a much greater surface area along the leading-edge. As a result, the total number of individually designed protective covers can be reduced to a strict minimum. The resulting economic advantages with respect to production costs and logistic are quite obvious and important. Since in many cases, the surface shape along the leading-edge of a wind turbine blade changes only smoothly, it's even possible to use just two different sets of protective covers, plus a protective tip cover and a protective root cover. It is even possible to do with just two one set of protective covers, plus a protective tip cover.

(83) As stated before, the surface shape, and more precisely the leading-edge radius, along the leading-edge of a wind turbine blade changes only smoothly. Therefore, the same manufacturing process can be used to build the protective covers of the different sets. Same 3D-mould may be used for multiple blades types. This is be advantageously used to reduce furthermore the associated production costs.

(84) Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiment, the invention is not limited to the examples disclosed, and further variations can be inferred by a person skilled in the art, without departing from the scope of protection of the invention.

(85) 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.