Method of manufacturing modular wind turbine rotor blade

Abstract

A method of manufacturing a wind turbine rotor blade (1), the wind turbine rotor blade (1) comprising two or more rotor blade segments (11, 12). The invention relates to a method for manufacturing a rotor blade (1), comprising the steps of: providing a mould (3, 30S, 30P) for the entire rotor blade (1), said mould comprising a lower shell (30S) and an upper shell (30P); forming a lower ply (2S) in the lower shell (30S), the lower ply (2S) comprising a connector (15) for adjacent rotor blade segments (11, 12) and a spar cap (13C) on either side of the connector (15); placing a mandrel (31) over the lower layup (2S), the mandrel (31) extending across a connector (15) of the lower layup (2S); forming a corresponding upper ply (2P) over said mandrel (31), said upper ply (2P) comprising a connector (15) for adjacent rotor blade segments (11, 12) and a spar cap (13C) on either side of said connector (15); and placing the upper case (30P) onto the upper layup (2P). The application further describes a wind turbine rotor blade (1) manufactured using said method.

Description

Background Art

[0001] The power output capacity of wind turbines has increased significantly, which has been made possible by developments in the design such as tall towers and long rotor blades. For example, a large horizontal axis wind turbine may have rotor blades with a length of 100 meters or more. However, the length of such rotor blades may cause difficulties if the rotor blades must be transported by rail or road, or if port facilities are insufficient. Therefore, to avoid transportation problems, the rotor blades can be manufactured in segments that can be transported without difficulty. Such wind turbine rotor blades may be referred to as "modular" or "segmented" rotor blades.

[0002] There are many ways to manufacture wind turbine rotor blades. Typically, composite material layups such as glass fiber mats, sheets and rovings are laid up in a mold that is shaped to form the desired aerodynamic profile of the part to be molded. The mold is closed and resin is poured into the composite material. After curing, the part is removed from the mold and the surface is post-processed.

[0003] An important structural component of a wind turbine rotor blade is the spar or "beam", which typically comprises a web at right angles to the chord plane and spar caps at the two ends of the web. The spar caps are embedded in the composite material of the rotor blade body, i.e. one spar cap is included in the layup on the suction side and the other spar cap is included in the layup on the pressure side. Typically, for any given airfoil shape, the design goal is to maximize the distance between the pressure-side and suction-side spar caps, i.e. to maximize the height of the web taking into account Steiner's theorem, which describes a quadratic dependence between the load-bearing capacity of a beam and its beam height. This goal is achieved by arranging the web along the maximum lateral extent of the airfoil and arranging the spar caps directly in the airfoil body.

[0004] In one rotor blade manufacturing technique, a first mold is used to form only the pressure side of the rotor blade, and a separate second mold is used to form only the suction side. After removing the cured parts from the two separate molds, the "shells" of the rotor blade are glued along their trailing and leading edges to complete the rotor blade. This two-mold technique is called the "butterfly mold" technique.

[0005] To manufacture modular rotor blades, butterfly mold technology can be used to form each segment separately, which requires a total of four molds for two-section rotor blades. Complementary connector parts must be embedded in the layup so that the rotor blade segments may be connected later. To this end, the connector parts are embedded in each pressure side mold and in each suction side mold. For the structural stability of the assembled rotor blade, each connector part is thicker than the spar cap and is implemented as a physical extension or continuation of the spar cap, so that the spar cap of one rotor blade segment is structurally connected to the continuation spar cap in the adjacent rotor blade segment (the web also extends across the connection between the rotor blade segments). To obtain a smooth outer surface of the rotor blade, the connector part is shaped so that the "extra thickness" protrudes into the interior of the rotor blade. However, in this method of construction of modular rotor blades, the connector thickness protruding inward reduces the web height in the area of ​​the connector. Since the load-bearing capacity of the airfoil is mainly determined by the height of its beam (as described above), the reduced web height reduces the ability of the rotor blade to withstand the static load of the flap, thereby causing fatigue damage and reduced rotor blade life.

[0006] Furthermore, providing a butterfly mould (i.e. a pressure side mould and a suction side mould) for each rotor blade segment is expensive, since all parts must be carefully formed to ensure the continuation of the aerodynamic profile at the connections between the segments. Therefore, each shell may be moulded in a single piece from root to tip, with complementary connector parts embedded in the layup at positions corresponding to the future connection interfaces. After curing and demoulding the shells, the edges of the shells are glued along their trailing and leading edges, and then the "complete" rotor blade is sawn or cut at the connection interfaces to separate the segmented shells. The rotor blade segments may then be assembled at the wind turbine assembly site.

[0007] In another rotor blade manufacturing technology, a single mold or "integrated mold" is used to produce the complete rotor blade. The mold includes a lower mold half ("lower shell") and an upper mold half ("upper shell"), which are shaped to form the suction side and pressure side of the rotor blade. The entire layup is completed in the lower mold, whereby a mandrel that is appropriately shaped is arranged on the lower layup to carry the weight of the upper layup. The mandrel is a supporting tool with a conical shape similar to the conical shape of the inside of the rotor blade, which supports the weight of the upper layup. The mold is closed by placing the upper shell on top of the completed layup. After curing the complete rotor blade and demoulding the complete rotor blade, the mandrel is pulled out in the direction of the root end. This integrated mold technology is particularly suitable for shaping long rotor blades with complex shapes, such as "pre-bent" rotor blades, in which the outer end is shaped to bend towards the wind during low wind conditions. The pre-bent rotor blade shape effectively prevents the tip from colliding with the tower during high wind conditions.

[0008] However, the known one-piece mould technology cannot be used to manufacture long modular rotor blades. This is because the mandrel cannot be deployed. As mentioned above, after the curing and demoulding phases are completed, the mandrel must be removed from the inside of the rotor blade, which means that there must be no inwardly protruding elements inside the rotor blade, which would otherwise hinder the removal of the mandrel. However, the connector parts of the prior art modular rotor blades protrude significantly into the interior of the rotor blade and would hinder the removal of the mandrel. Summary of the invention

[0009] It is therefore an object of the present invention to overcome the problems associated with the manufacture of modular rotor blades.

[0010] This object is achieved by the claimed method of manufacturing a modular wind turbine rotor blade and by the claimed wind turbine rotor blade.

[0011] In the context of the present invention, a modular wind turbine rotor blade is understood to include two or more rotor blade segments. In the case of two segments, the segments may have substantially the same length, i.e. the connection interface is located at mid-span, at a position of about 50% of the rotor blade length. Likewise, segments may be located more inboard (e.g. at 20%-40% of the rotor blade length) and / or more outboard (e.g. at 70%-90% of the rotor blade length).

[0012] According to the present invention, a method for manufacturing such a modular rotor blade comprises the following steps: providing a mold for the entire rotor blade, the mold comprising a lower shell and an upper shell; forming a lower layup in the lower shell, the lower layup comprising two or more segmented layup portions and connectors between adjacent segmented layup portions; placing a mandrel onto the lower layup, the mandrel extending across the connectors between adjacent segmented layup portions; and completing the layup procedure by forming a corresponding upper layup on the mandrel and placing the upper shell onto the upper layup to close the mold.

[0013] A "mould for a complete rotor blade" is understood to be a mould extending from a substantially circular root end to an outermost tip end. The mould comprises a lower half or shell (e.g. for the suction side) and an upper half or shell (e.g. for the pressure side), and each shell has a flange around its periphery to facilitate connection with the other shell when the mould is closed and sealed in preparation for a subsequent resin infusion step. The method of the invention allows the use of a mandrel to support the weight of the upper layup.

[0014] An advantage of the method of the present invention is that the preferred "closed mold" technique may be applied to form segments of a modular rotor blade using a mold constructed for casting a non-modular rotor blade. This avoids the huge cost of having to manufacture molds for separate segments. Existing molds for a particular rotor blade specification may be used to cast a modular rotor blade having the same specification.

[0015] A further advantage of the method of the invention is that the height of the web is kept at an advantageously maximum possible across the connection between the rotor blade segments. Thus, the assembled rotor blade features an advantageously high load bearing capacity, although the rotor blade comprises two physically separate parts.

[0016] According to the invention, a wind turbine rotor blade is manufactured using the method described above. After demoulding and removal of the mandrel, the rotor blade segments are separated by cutting between the complementary connector parts. The rotor blade segments may then be transported to an assembly site without difficulty and the rotor blade reassembled by connecting the segments.

[0017] The modular rotor blade of the present invention is characterized by having an internal cavity located at the junction of the rotor blade segments, the internal cavity being free of inwardly protruding connector portions that would hinder the removal of the mandrel. The inner surface of the outboard spar cap and the inner surface of the connector at both the pressure side and the suction side are located in a common plane, which allows the removal of the mandrel: during the manufacture of the modular rotor blade using an integrated mold, the substantially smooth inner surface facilitates the placement of the mandrel across the connection interface; after demoulding the cured rotor blade, the substantially smooth inner surface facilitates the direct removal of the mandrel.

[0018] As a result of the manufacturing method of the invention, the rotor blade has very advantageous structural properties in terms of the connection between the segments. This is because the body of the connector does not protrude into the interior of the rotor blade compared to the segmented rotor blades of the prior art. In the rotor blade of the invention, by arranging the connector so that it does not protrude into the interior, the maximum possible distance between the pressure side and suction side spar caps can be maintained across the joint between the segments.

[0019] Furthermore, the modular rotor blade of the present invention is characterized by the absence of any adhesive joints along the trailing and leading edges (ie between the pressure and suction sides) since the entire rotor blade is formed as a single piece in an integral mold and subsequently separated into segments after demoulding.

[0020] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as revealed in the following description. Features of different claim categories may be combined as appropriate to give further embodiments not described herein.

[0021] In the following, without limiting the invention in any way, it may be assumed that the integrated mould is shaped to form a long wind turbine rotor blade having a root to tip length of 100 meters or more. The mould may be shaped to form a pre-bent rotor blade, i.e. a rotor blade which is bent in the windward direction in its unloaded state.

[0022] When referring to rotor blade segments, the expressions “segment” and “module” are used interchangeably in the following.

[0023] The connection between the rotor blade segments is formed by a pair of complementary connector end parts at the suction side (one in the inner segment and one in the outer segment) and a pair of complementary connector end parts at the pressure side (one in the inner segment and one in the outer segment). The elements of the connector can be made of any suitable material, such as carbon fiber reinforced polymer (CFRP). However, in a particularly preferred embodiment of the invention, the connector is mainly made of fiber reinforced plastic (FRP) or "fiberglass", which is strong and economical.

[0024] In order to join two rotor blade segments, fasteners may be inserted through holes or inserts in the connector end pieces. The inserts preferably extend in the span direction. In an exemplary embodiment, the fasteners for joining segments of long rotor blades may have a diameter of about 15mm to 50mm and a length of about 10cm to 50cm. A suitable number of fasteners (e.g., 5-20, depending on various factors such as connector width, airfoil thickness, expected loads, etc.) may be used to join the connector end pieces at the suction side, and a similar number of fasteners may be used to join the connector end pieces at the pressure side. Hereinafter, the "end piece" of the connector should be understood as the part that receives the fasteners. In an exemplary connection, the fasteners for each side of the rotor blade may protrude on each side of a firm fastener block that is shaped to fit between the complementary end pieces of the connector. In other words, one fastener block is arranged between the end pieces of the suction side connector, and one fastener block is arranged between the end pieces of the pressure side connector. Of course, any suitable type of fastener may be deployed to form a connection between rotor blade segments.

[0025] For this type of connection, each end piece has multiple inserts to receive relatively large fasteners. This "missing material" must be compensated by increasing the thickness of the end piece, thereby introducing a height difference between the spar cap and the connector. When the spar cap and the connector are made of different materials, such as fiberglass (connector) and CFRP (spar cap), the height difference is even greater. In the modular rotor blade of the present invention, the thickness of the end piece exceeds the thickness of the spar cap by at least 130%.

[0026] The spar caps of the modular rotor blade of the present invention may be made of any suitable material, such as fiberglass. However, in a particularly preferred embodiment of the present invention, the spar caps of the modular rotor blade are made using a carbon fiber reinforced material, such as a carbon fiber reinforced polymer (CFRP), which allows for an advantageously thin spar cap construction with the desired structural properties. Of course, any suitable combination of materials may be used in the construction of the spar caps.

[0027] Since the CFRP spar caps may be significantly thinner and narrower than the fiberglass connector end pieces, the connector preferably includes a suitably shaped transition section extending between the spar caps and the end pieces. For example, in the case of a two-piece rotor blade having a length of 100 meters or more and a joint located in the middle of the rotor blade, the spar caps may have a height of about 50 mm and a width of about 400 mm in the vicinity of the joint. The end pieces at the joint may require a thickness of about 90 mm to meet structural strength requirements, and a width of about 900 mm to accommodate the required number of fasteners. The connector may include a section that gradually transitions between the spar caps and the end pieces (e.g., spanning a length of several meters). The transition section may be formed as a scarf joint that engages with the spar caps.

[0028] The step of forming the layup includes arranging layers of composite parts in a predetermined order and embedding the spar caps into the composite layup. The lower layup is formed in the lower shell and the upper layup is formed on a mandrel. The mandrel has essentially the shape of the internal cavity of the rotor blade and fills the cavity to facilitate the formation of the upper layup. As the width and height of the rotor blade taper gradually in the tip direction, the mandrel also has a gradually tapering shape between the essentially circular root end and the flatter airfoil region. It may not be necessary to support the upper layup over the entire length of the mold, for example the last 5% of the length of the outboard end of the rotor blade may incorporate structural elements such as ribs. Therefore, a mandrel may be required over 95% of the length of the rotor blade.

[0029] As indicated above, the purpose of the spar caps is to anchor the structurally associated web (or "shear web") in the internal cavity of the rotor blade in the spanwise direction. For a rotor blade having a length of about 100 meters and a root diameter of about 6 meters, the web may have a diameter of nearly 6 meters at its inboard end and taper to a flat "airfoil" shape at its outboard end. In the inventive method, the web is attached to a first spar cap (located in the lower layup) before the mandrel is placed in the lower shell. A second spar cap may then be mounted to the upper edge of the web and embedded in the upper layup.

[0030] To account for the presence of the shear web during the layup procedure, the mandrel comprises: a first mandrel portion shaped for placement along the leading edge side of the shear web; and a second mandrel portion shaped for placement along the trailing edge side of the shear web. Each mandrel portion may be a single-piece portion extending "root to tip", for example having a semi-circular shape at the root end, tapering to a flatter outboard end, and having a straight vertical surface to abut the shear web.

[0031] Along the entire length of the mandrel, the inner surface of the layup must be free of any protrusions, i.e., the inner surface of the layup must be advanced in a smooth manner. To this end, during the lower layup procedure, the inwardly facing surfaces of the spar caps are arranged to lie in the same plane as the inwardly facing surfaces of the lower layup connectors. Similarly, when forming the upper layup, the inwardly facing surfaces of the spar caps are arranged to lie in the same plane as the inwardly facing surfaces of the upper layup connectors.

[0032] However, as mentioned above, the thickness of the end piece may significantly exceed the thickness of the spar cap, for example about 1.5 times the thickness of the spar cap. This means that the "extra height" of the connector is arranged towards the outside of the rotor blade. As a result, the thickness factor of the airfoil (ratio of airfoil thickness to chord length) increases towards the connection between adjacent segments.

[0033] The invention is based on the recognition that any effect of increased external thickness at the joint between the rotor blade segments is outweighed by the benefit of maximizing the distance between the pressure side spar cap and the suction side spar cap, i.e. maximizing the height of the beam across the connection interface. By avoiding or minimizing a reduction in the height of the beam, the ability of the airfoil to withstand static flap loads can be maintained according to Steiner's theorem. Thanks to the advantageous beam height across the connection interface, the ability of the rotor blade to withstand static flap loads is not impaired by the connection interface, making it possible to avoid fatigue damage.

[0034] Furthermore, by avoiding inwardly protruding elements at the connector interface, the segmented rotor blade may be manufactured using an integral mould as described above.

[0035] The molding techniques described above can be implemented in an integrated mold that is shaped to receive an outwardly protruding connection interface area. For example, the lower shell and the upper shell can be formed to have appropriately shaped grooves. However, in a particularly preferred embodiment of the present invention, an existing available integrated mold is modified for the production of segmented rotor blades. For example, before starting the lower layup, a height adapter or "dummy" is arranged in the lower shell on either side of the connection between the segments. The dummy may have a wedge shape that tapers gradually on all sides, wherein the dummy has a maximum height at the transition from the spar cap to the scarfing. In this way, there is no need to construct a mold that is shaped to receive the connector portion that protrudes outwardly, which would result in considerable expense.

[0036] After the layup is completed, the mold is closed by connecting the upper shell to the lower shell. In a subsequent step, vacuum-assisted resin infusion is performed to thoroughly infuse the composite layup with resin. The resin-infused layup is allowed to cure, after which the mold is opened and the cured rotor blade is demoulded. Subsequently, the mandrel is pulled out of the root end of the cured modular rotor blade. The rotor blade segments are then separated by cutting or sawing at the connections between the segments. After completion of various post-processing steps (grinding, polishing, application of protective coatings, attachment of aerodynamic attachments, etc.), the rotor blade segments can be transferred to a storage area or transported to an assembly site.

[0037] Likewise, butterfly molding techniques may also benefit from the method of forming the connection interface between segments of the present invention. In the butterfly molding technique, the lower shell and the upper shell are manufactured separately. In this case, each shell mold may also be shaped to receive a connection interface area protruding outwardly. Alternatively, as described above, by arranging filler blocks at appropriate locations in the shell mold (on either side of the predetermined connection between the segments), existing available shell molds may be modified for the production of segmented rotor blades. Likewise, using filler blocks to modify existing shell molds may be preferred because this avoids the cost of manufacturing dedicated shell molds. After completing the layup in the shell mold, vacuum assisted resin infusion is performed and the cured shell is demoulded. The shell is glued along its outer edges to form a complete rotor blade, and the segments are subsequently separated by cutting or sawing at the connection between the segments. The rotor blade thus manufactured benefits from the advantageously maximized distance between the pressure side and suction side spar caps, i.e., the height of the web in the "butterfly-molded" modular rotor blade does not need to be sacrificed across the connection interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It should be understood, however, that the drawings are designed only for purposes of illustration and not as a definition of the limits of the present invention.

[0039] Figure 1 is a schematic diagram of a connector for a segmented wind turbine rotor blade;

[0040] Figure 2-5 Various ways of arranging the connectors during the manufacturing method of the present invention are presented;

[0041] Figure 6 shows the stages in the manufacturing method of the present invention;

[0042] Figure 7 A side view showing an embodiment of a rotor blade of the present invention;

[0043] Figure 8 and Fig. 9 Explain the manufacturing method of the prior art.

[0044] In the drawings, like numbers refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0045] Figure 1 is a schematic plan view of a connector 15 for a segmented wind turbine rotor blade. The rotor blade will have one connector at the pressure side and another (substantially identical) connector at the suction side.

[0046] The figure shows an inner spar cap 13C and an outer spar cap 13C. The inner and outer spar caps end at a distance from the connection between the rotor blade segments. 11-12 At the wind turbine, two complementary end pieces 151 face each other (a gap is shown here for illustration, but a gap need not exist). Each of the end pieces 151 has a number of inserts 152 or bolt bushings to receive fasteners (e.g., threaded studs) when the segments have been assembled for assembly at the wind turbine. The inserts 152 are sealed in preparation for the resin infusion step.

[0047] In this exemplary embodiment, the end piece 151 of the connector 15 transitions into a tapered portion 153 which in turn transitions into a scarf portion 155 which engages the spar cap 13C.

[0048] The connector parts 151 , 153, 155 may be made entirely of fiberglass, as this material can withstand the stresses at the joints when the assembled rotor blade is in operation. The spar caps 13C may comprise CFRP elements, as they have low weight and high strength.

[0049] Figure 2-5 Various ways of arranging the connectors 15 during the manufacturing method of the invention are presented. Each figure shows a pair of connectors 15 in cross section, one on each side of the finished layup, corresponding to their position in the assembled rotor blade. In the figures, the dashed line indicates the final outer surface 100 of the rotor blade 1 after casting, and the outer surface 800 of a conventional rotor blade cast in the same mold. The figures indicate the difference ΔH between the height H15 of the end piece 151 and the height H13C of the corresponding spar cap 13C.

[0050] exist Figure 2, all the "extra material" is positioned towards the outside of the rotor blade, i.e., the connector portion is "turned over". Thus, the inwardly facing surface 130 of the pressure side spar cap 13C and the inwardly facing surface 150 of the pressure side connector 15 both lie in a common plane 13P. Similarly, the inwardly facing surface 130 of the suction side spar cap 13C and the inwardly facing surface 150 of the suction side connector 15 both lie in a common plane 13S.

[0051] Figure 3 Shows how this can be achieved Figure 2 The figure shows a lower shell 30S containing a lower layer 2S, a mandrel 31, and an upper shell 30P located above an upper layer 2P. The lower shell 30S is initially connected by a predetermined connection X between the segments. 11-12 The upper layer 2P is completed and the upper layer 2P is formed at the connection part X. 11-12 On either side of the pressure side connector 15 and the pressure side spar cap 13C, appropriately shaped filler blocks are placed to compensate for the height difference between the pressure side connector 15 and the pressure side spar cap 13C. The upper shell 30P is then placed on the upper layup 2P.

[0052] Figure 4 An alternative embodiment is shown in which only the outer connector 15 (located at the connection portion X) 11-12 The right-hand side of the connector is "turned over" or turned outward. The inner connector part (located at the connection part X 11-12 The left hand side of the mandrel 31 is arranged in a conventional manner, wherein the increased thickness protrudes into the interior. This embodiment also allows the mandrel 31 to cross the connection X 11-12 is placed and facilitates the removal of the mandrel 31 from the cured rotor blade. Here too, it is possible to 11-12 The right-hand side of the housing is provided with a suitably shaped filler block. This embodiment is based on the recognition that it is sufficient for the outer segment to be formed without an inwardly protruding connector portion, since this configuration facilitates the removal of the mandrel.

[0053] In each of the above embodiments, the insert 152 of the inboard end piece 151 is aligned with the insert 152 of the outboard end piece 151 , and fasteners such as threaded studs may later be inserted to extend between the complementary end pieces 151 during reassembly of the modular rotor blade.

[0054] Figure 5 A similar embodiment is shown in which the outer connector portion is "flipped" or turned outward. Figure 4 In a similar configuration, the inner connector portion is arranged in a conventional manner, with the extra thickness being located on the inside. However, in this embodiment, the outer connector portion is placed Figure 4In the embodiment, the inserts of the outboard end piece 151 are spaced further apart in order to increase the distance between the pressure side spar cap 13C and the suction side spar cap 13C. Therefore, the inserts of the outboard end piece 151 are offset from the inserts of the inboard end piece 151. The segments 11, 12 may later be joined by suitable fastener blocks 16 having fasteners 160 arranged offset as indicated herein. This configuration is based on the recognition that the increased web height in the outboard region may result in a significant improvement in the structural characteristics of the assembled rotor blade. This embodiment also allows the mandrel 31 to span the connection X 11-12 is placed and facilitates the removal of the mandrel 31 from the cured rotor blade. Here too, a suitably shaped filler block may be deployed at the connection portion X 11-12 on the right hand side.

[0055] Figure 6 The various stages of the manufacturing method of the invention are shown. Each method stage is explained by a simplified view on the circular root end of a rotor blade being moulded.

[0056] The lower shell 30S is prepared in stage 60, which may be assumed hereinafter to be shaping the suction side of the rotor blade. The rotor blade will consist of two segments but will be molded in a single piece, the cured rotor blade will be at the connection X between the segments. 11-12 Place was cut.

[0057] In stage 61, by connecting the 11-12 After preparing the mold by placing filler blocks 32 on either side of the lower shell 30S, the lower layup 2S for the two sections is arranged in the lower shell 30S, the lower layup including the suction side spar cap 13C and the suction side connector 15, the suction side connector may be as shown above. Figures 2 to 5 In any of the above described ways, the connection portion X 11-12 The inwardly facing surfaces 130, 150 at the connection point lie in a common plane 13P. 11-12 The surrounding area is shown in cross section on the left.

[0058] In stage 62 , the web 13W is connected to the suction side spar cap 13C and in stage 63 , the two parts 31LE, 31TE of the mandrel 31 are placed on either side of the web 13W.

[0059] In stage 64, the upper layup 2P for both segments is arranged over the mandrels 31LE, 31TE, said upper layup including the pressure side spar cap 13C and the pressure side connector 15. Here again, at the connection X 11-12 The inwardly facing surfaces 130, 150 lie in a common plane 13S, as shown on the left.

[0060] In stage 65, the mold is closed by placing the upper shell 30P over the upper layup 2P. Casting and curing steps are carried out in stage 66, and the cured rotor blade 1 is demoulded in stage 67. The mandrels 31LE, 31TE are removed in stage 68. On the left, a partial cross-section of the cured rotor blade 1 shows the shear web 13W in the outer segment 12. In a final stage 69, the rotor blade 1 is 11-12 12 is cut to separate the segments 11, 12. As shown on the left, the "extra material" required in the connector 15 is located towards the outside of the rotor blade. This has the beneficial effect that the height of the web 13W is maintained at an advantageous maximum height across the connection between the segments 11, 12, so that the assembled rotor blade 1 is characterized by an advantageously high load bearing capacity, even if the rotor blade is assembled from two physically separate parts. The partial cross-section shows a shear web 13W in the inner segment 12 and a shear web 13W in the outer segment 12. When the rotor blade 1 is assembled, the shear web segments may be connected.

[0061] Figure 7 An exemplary embodiment of a rotor blade 1 of the invention is shown, indicating a connection X between an inner segment 11 and an outer segment 12. 11-12 , and a slight "bulge" in said area caused by the placement of connector 15.

[0062] Figure 8 and Fig. 9 Problems associated with prior art manufacturing methods are explained. Figure 8 8 shows a connection between two rotor blade segments 81 , 82 , wherein the dashed lines indicate the connector 15 and the spar cap 13C. Fig. 9The connectors 15 and the spar caps 13C are shown in cross section. For the structural stability of the assembled rotor blade, each connector is thicker than the spar cap and is implemented as a physical extension of the spar cap so that the spar cap of one rotor blade segment is structurally connected to its continued spar cap in the adjacent rotor blade segment. In order to obtain a smooth outer surface of a conventional rotor blade 8, the connectors 15 are placed so that the "extra thickness" protrudes into the interior of the rotor blade. The internal cavity of the inner segment 81 narrows in the direction of the joint and widens again in the internal cavity of the outer segment 82. Therefore, it is not possible to use a "closed mold" or an integrated molding method mold to manufacture the rotor blade 8. This is because the mandrel shaped to support the upper layup of the inner segment 81 and the outer segment 82 will necessarily have an "undercut" and it will be impossible to pull such a mandrel out of the cured rotor blade 8. Therefore, at least the outboard segment 82 of such a rotor blade 8 must be manufactured using a "butterfly" molding method with separate molds for the suction side and the pressure side, which significantly increases the overall manufacturing costs. A further disadvantage of conventional modular rotor blades 8 is the reduction in the height of the web extending across the connection between the segments 81, 82. In the connector area, the web height is significantly less than the web height at the outboard end of the inboard segment 82, as shown in the figure. The total reduction of 2·ΔH in the web height (i.e. beam height) at the connection interface means that the load carrying capacity of the rotor blade 8 is significantly reduced.

[0063] Although the present invention has been disclosed in the form of preferred embodiments and variations thereof, it should be understood that many additional modifications and variations may be made thereto without departing from the scope of the present invention. For example, the segmented or modular rotor blades may be shaped for assembly to a three-blade horizontal axis wind turbine, a two-blade horizontal axis wind turbine, a vertical axis wind turbine, etc.

[0064] 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.

Claims

1. A method for manufacturing a wind turbine rotor blade (1), the wind turbine rotor blade (1) comprising two or more rotor blade segments (11, 12), the method comprising the following steps: - providing a mold (3, 30S, 30P) for the entire rotor blade (1), said mold comprising a lower shell (30S) and an upper shell (30P); - forming a lower layup (2S) in the lower shell (30S), the lower layup (2S) comprising connectors (15) for adjacent rotor blade segments (11, 12) and spar caps (13C) on either side of the connectors (15); - placing a mandrel (31) onto the lower layer (2S), the mandrel (31) extending across the connector (15) of the lower layer (2S); - forming a corresponding upper layup (2P) above the mandrel (31), the upper layup (2P) comprising connectors (15) for adjacent rotor blade segments (11, 12) and spar caps (13C) on either side of the connectors (15); and - Placing the upper shell (30P) onto the upper layer (2P).

2. The method according to the preceding claim, wherein: The step of forming a layup (2S, 2P) comprises arranging a layer (20) of composite material and embedding a spar cap (13C) for each rotor blade segment (11, 12) in the layer (20) of composite material.

3. A method according to any one of the preceding claims, wherein: The spar caps (13C) of the layups (2S, 2P) and the inwardly facing surfaces (130, 150) of the connectors (15) are arranged to lie in a common plane (13P).

4. The method according to any one of the preceding claims, comprising the step of connecting a modular shear web (13W) between the spar caps (13C) of the lower laminate (2S) and the spar caps (13C) of the upper laminate (2P), the modular shear web (13W) comprising an inner section and an outer section.

5. A method according to the preceding claim, wherein: The mandrel (31) includes: a first mandrel portion (31LE), which is shaped to be placed on one side of the shear web (13W); and a second mandrel portion (31TE), which is shaped to be placed on the other side of the shear web (13W).

6. Method according to any of the preceding claims, comprising the step of forming a scarf connection (155) between the spar cap (13C) and the connector (15).

7. Method according to any of the preceding claims, comprising the step of arranging a height adapter (32) between the shell (30S, 30P) and the layup (2S, 2P).

8. The method according to any one of the preceding claims, comprising the following subsequent steps: - performing resin infusion to penetrate the plies (2S, 2P), and curing the resin-infused plies (2S, 2P); - opening the mould (3) and removing the cured rotor blade (1); and - Removing the mandrel (31) from the interior of the cured rotor blade (1).

9. Method according to the preceding claim, comprising the step of cutting the solidified rotor blade (1) to separate the rotor blade segments (11, 12).

10. Method according to the preceding claim, comprising the step of connecting the shear web section (13W) of the inner segment (11) to the shear web section (13W) of the outer segment (12).

11. A wind turbine rotor blade (1) manufactured using the method according to any one of claims 1-10.

12. A wind turbine rotor blade according to the preceding claim, wherein the connector (15) between the rotor blade segments (11, 12) comprises: Complementary end pieces (151) at the suction side (1S) and complementary end pieces (151) at the pressure side (1P).

13. A wind turbine rotor blade according to claim 11 or 12, wherein: The thickness (H15) of the connector end member (151) is at least 130% of the thickness (H13C) of the spar cap (13C).

14. A wind turbine rotor blade according to any one of claims 11 to 13, wherein: The complementary end piece (151) of the connector (15) comprises an arrangement of matching span inserts (152) arranged to receive fasteners (160) during assembly of the rotor blade (1).

15. A wind turbine rotor blade according to any one of claims 11 to 14, comprising: A fastener block (16) is arranged between the end pieces (151) of each of the connectors (15).

Images