WO2025027009A1

WO2025027009A1 - Method for molding a wind turbine blade using preforms

Info

Publication number: WO2025027009A1
Application number: PCT/EP2024/071523
Authority: WO
Inventors: Henrik BARSLEV; Bosky PATEL; Gerrit Jan De Jong; Hao Li; Oscar LOPEZ PEREZ
Original assignee: LM Wind Power AS; LM Wind Power Spain SL; Ge Renewable Management; LM Wind Power Blades France SAS; LM Wind Power R&D Holland BV
Current assignee: LM Wind Power AS; LM Wind Power Spain SL; Ge Renewable Management; LM Wind Power Blades France SAS; LM Wind Power R&D Holland BV
Priority date: 2023-08-03
Filing date: 2024-07-30
Publication date: 2025-02-06
Anticipated expiration: 2026-02-03

Abstract

The present invention relates to a method and mold assembly for manufacturing a wind turbine blade part (52, 54). A plurality of preforms (98a-c) comprising a fiber material and a binding agent is arranged in a blade mold (96), followed by resin infusion and curing or hardening the resin in order to form the blade part. Arranging the plurality of preforms (98a-c) in the blade mold cavity (97) comprises placing a first preform (98a) into the blade mold cavity (97), preferably from the root end (65) of the blade mold (96), such that the first preform (98a) extends along the longitudinal direction of the blade mold (96), and such that the first preform (98a) is arranged at the longitudinal central axis (69) of the mold cavity (97). Subsequently, a second preform (98b) is placed into the blade mold cavity (97) from the first lateral edge (67) of the blade mold (96) such that the second preform (98b) slides within the mold cavity (97) until the second preform (98b) abuts the first preform (98a) along a first longitudinally extending interface (70). A third preform (98c) is placed into the blade mold cavity (97) from the second lateral edge (68) of the blade mold (96) such that the third preform (98c) slides within the mold cavity (97) until the third preform (98c) abuts the first preform (98a) along a second longitudinally extending interface (71).

Description

Title

Method for molding a wind turbine blade using preforms

Field of the invention

The present invention relates to a method of manufacturing a wind turbine blade part, such as a shell half of a wind turbined blade, and to a blade mold assembly for carrying out a method according to the present invention.

Background of the invention

Climate change has created an urgent need for sustainable energy, raising the interest in wind power as an emissions-free source of energy. In 2022, wind electricity generation reached more than 2100 TWh on the global scale. Wind turbines typically comprise a tower, generator, gearbox, nacelle, and one or more rotor blades, which capture kinetic energy of wind using known airfoil principles. With increasing energy demand, modern wind turbines can have power ratings of above 10 MW and may have rotor blades that exceed 100 meters in length.

Wind turbine rotor blades are typically made from a fiber- re info reed polymer material, comprising a pressure side shell half and a suction side shell half, also called blade halves. The cross-sectional profile of a typical blade includes an airfoil for creating an air flow leading to a pressure difference between both sides. The resulting lift force generates torque for producing electricity.

The shell halves of rotor blades are often manufactured using blade molds. First, a blade gel coat or primer is applied to the mold. Subsequently, fiber reinforcement and/or fabrics are placed into the mold followed by resin infusion. A vacuum is typically used to draw resin material, such as epoxy, polyester and/or vinyl ester, into the mold. Alternatively, prepreg technology can be used in which a fiber or fabric pre-impregnated with resin forms a homogenous material which can be introduced into the mold. Several other molding techniques are known for manufacturing wind turbine blades, including compression molding and resin transfer molding. The shell halves are assembled by being glued or bolted together substantially along a chord plane of the blade. In blade manufacturing processes, the use of preforms has become increasingly important. A preform is a shaped arrangement of fibers, such as multiple layers thereof, which has been bound and/or consolidated for later use as part of the fiber lay-up in the blade mold. The rationale for using preforms for blade manufacturing is to reduce cycle time in the blade mold. In addition, using preforms may reduce the number of required repairs due to the pre-consolidated structure of the preforms. As blade lengths increase, using preforms for blade lay-up adds efficiency and precision.

Typically, multiple preforms will be used in manufacturing a wind turbine blade. This usually requires a large space for manufacturing and transferring the preforms to the blade mold. A shell half of a modern wind turbine blade may comprise different preforms of 20 or more slightly different geometries, which provides certain challenges in particular with regard to transferring the different preforms from their respective preform molds to the blade mold, and with respect to arrangement of multiple preforms in the blade mold. Known solutions include the use of a plurality of different transfer jigs in combination with lifting devices such as cranes. However, this may be a tedious and costly process, in particular as manual labor is typically still required for the correct preform placement in the blade mold.

However, the layup process of the preforms in the blade mold can be complicated and ergonomically challenging, in particular for large blades for which multiple preforms are required. In particular at the root end of a blade mold the layup process and the correct positioning of the preforms can be difficult, also due to the steep geometry of the molding cavity at the root end.

It is therefore a first object of the present invention to provide a simple, ergonomically beneficial and cost-efficient way of using preforms for manufacturing wind turbine blade parts such as shell halves.

It is a further object of the present invention to provide flexible and efficient tools for such manufacturing methods.

It is another object of the present invention to provide an improved method of manufacturing a wind turbine blade using multiple preforms. It is another object of the present invention to provide a simplified mold assembly for forming wind turbine parts from preforms. of the invention

The present invention addresses one or more of the above-discussed objects by providing a method of manufacturing a wind turbine blade part, the method comprising the steps of providing a plurality of preforms, preferably including a first, second and third preform, each preform comprising a fiber material and a binding agent, arranging the plurality of preforms in a blade mold comprising a blade mold cavity, a root end, a tip end, and opposing first and second lateral edges extending along a longitudinal direction of the blade mold between the root end and the tip end, infusing resin to the blade mold cavity, and curing and/or hardening the resin in order to form the blade part, wherein arranging the plurality of preforms in the blade mold cavity comprises placing the first preform into the blade mold cavity, preferably from the root end of the blade mold, such that the first preform extends along the longitudinal direction of the blade mold, and such that the first preform is arranged at a longitudinal central axis of the mold cavity, placing the second preform into the blade mold cavity, preferably from the first lateral edge of the blade mold, such that the second preform slides within the mold cavity until the second preform abuts the first preform along a first longitudinally extending interface between the first and second preforms, and preferably placing the third preform into the blade mold cavity, preferably from the second lateral edge of the blade mold, such that the third preform slides within the mold cavity until the third preform abuts the first preform along a second longitudinally extending interface between the first and third preforms.

It is found that this method is significantly more efficient, leading to a reduction of cycle time for the blade molding process by up to 50%. Also, the method of the present invention is found to be ergonomically beneficial as compared to known layup methods for manufacturing wind turbine blades. By arranging the first preform at the longitudinal central axis of the mold cavity, and by subsequently sliding additional preforms within the mold cavity until they abut the first preform the layup process is simplified in that the first preform can be used as anchoring element for subsequent preforms. Thus, gravity can be efficiently used to apply three-dimensional glass fiber preforms into the blade mold. Furthermore, the method of the present invention is found to enable a faster layup process by eliminating wrinkle defects in the resulting shell laminate. Also, known fiber layup methods for blade manufacturing often require the glass layer to extend over the edge of the blade mold, as critical areas of the layup are not preferred to be stitched or treated with adhesives. This leads to the formation of residues at the edges of the molded shell half, which has to be removed after demolding, for example by cutting or grinding, which leads to unnecessary waste and/or laminate cracks. By placing the preforms according to the method of the present invention, the formation of such residues can be avoided, thus reducing the amount of waste and potential blade defects.

It is thus preferred that the step of arranging the plurality of preforms in the blade mold cavity comprises placing a first preform into the blade mold cavity such that the first preform extends along the longitudinal direction of the blade mold, and such that the first preform is arranged at the longitudinal central axis of the mold cavity, placing a second preform into the blade mold cavity from the first lateral edge of the blade mold, such that the second preform slides within the mold cavity until the second preform abuts the first preform along a first longitudinally extending interface, and placing a third preform into the blade mold cavity from the second lateral edge of the blade mold such that the third preform slides within the mold cavity until the third preform abuts the first preform along a second longitudinally extending interface.

In some embodiments, the wind turbine blade part is a root laminate, a main laminate or a part thereof. In another embodiment, the blade part is a blade half or shell half, such as a pressure side shell half or a suction side shell half. In another embodiment, the wind turbine blade part is a bulkhead. In another embodiment, the wind turbine blade part is a shear web. In a preferred embodiment, the wind turbine blade part is a shell half, such as a pressure side shell half or a suction side shell half.

The blade mold cavity preferably conforms to a shape of at least a portion of a wind turbine blade. In some embodiment, the blade mold is a mold for a half shell of a wind turbined blade, preferably extending over the whole length of the blade.

The plurality of preforms for manufacturing the wind turbine blade part may include at least 10 preforms, preferably at least 20 preforms, such as at least 30 preforms. Preferably, the preforms used in the method of the present invention are a consolidated arrangement of material comprising fibers, such as glass fibers, and a binding agent. The material comprising fibers may be a fabric. The preform will typically be used for manufacturing a blade half of a wind turbine blade. The preforms can be placed within the root region of a blade mold, thus constituting part of the root laminate of the blade. The root region may correspond to a region of the blade having a substantially circular or elliptical cross-section. However, the preforms could also be used for other parts and regions of a wind turbine blade, such as trailing edge or leading edge reinforcements or adhesive flanges. Alternatively, the preforms could be used for a full blade layup, or the central load carrying laminates as the main laminate.

In a preferred embodiment, each of the preforms used in the method of the present invention is configured to form a blade section starting from the root end of the wind turbine blade. Thus, preferably each of the preforms is configured to be arranged at the root end of the blade mold. Most preferably, the preform is configured to form a subsection of the root section extending from the root end of the blade together with other subsections of the root section equally extending from the root end of the blade.

Preferably, the preforms are elongate preforms. Each preform typically has a thickness, a width and a length. In some embodiments, each preform has a length-width ratio of at least 5:1. In other embodiments, each preform has a length-width ratio of at least 5:1 , such as at least 10:1. In a preferred embodiment, each preform has a length-width ratio of at least 15:1. In some embodiments, each preform has a length-width ratio of up to 100:1. It is preferred that the preforms are substantially plate-shaped, preferably as a rectangular plate. Typically, each preform will be shaped like cuboid or rectangular prism.

In other embodiments, the preform may comprise on or more trapezoid shaped surfaces, such as opposing trapezoid shaped surfaces. Thus, in a preferred embodiment, one or more of the preforms have the shape of a trapezoidal prism. Such preform shape is found to be particularly useful when forming, for example, a trailing edge, a flatback section or a shear web of a wind turbine blade. For example, the first preform can be shaped like a rectangular prism and the second and third preforms can each be shaped like a trapezoidal prism.

Preferably, each preform has a length of at least 5 meters, preferably at least 10 meters. In a preferred embodiment, each preform has a width of 1-5 meters, preferably 1-3 meters. The thickness of each preform is typically between 1 and 20 mm, preferably between 1 and 10 mm. Each preform comprises a fiber material and a binding agent. The fiber material may comprise glass fibers, carbon fibers or a combination thereof. In another embodiment, the fiber material may include fiber rovings, such as glass fiber rovings. Such binding agent is preferably present in an amount of 0.1-15 wt% relative to the weight of the fiber material. The binding agent may also be present in an amount of 10-20 gram per square meter of glass surface. In other embodiments, the binding agent may be present in an amount of 1-100 gram per square meter of glass surface.

The binding agent may also be present in an amount of 5-40, preferably 10-20, gram per square meter of fiber surface. In preferred embodiments, the binding agent is present in an amount of 0.5-5 wt%, preferably 0.5-2.5 wt%, relative to the weight of the fiber material. Advantageously, the binding agent is a thermoplastic binding agent. The binding agent may comprise a polyester, preferably a bisphenolic polyester.

An example of a suitable binding agent is a polyester marketed under the name NEOXI L 940. Examples include NEOXIL 940 PMX, NEOXIL 940 KS 1 and NEOXIL 940 HF 2B, all manufactured by DSM Composite Resins AG. Another example is a polyester resin marketed under the name C.O.I.M. FILCO® 661 FPG 005, which is a bisphenolic unsaturated polyester resin in powder form. Preferably, the binding agent is a polyester, preferably a bisphenolic polyester. In other embodiments, the binding agent is a hotmelt adhesive or based on a prepreg resin. In some embodiments, the preform comprises an epoxy material.

According to another embodiment, the binding agent is a thermoplastic binding agent. Typically, the fiber material comprises fiber rovings which are at least partially joined together by means of the binding agent by thermal bonding. In some embodiments, the fiber material comprises a fabric. For example, a plurality of fabrics may be joined by the binding agent, e.g., disposed in between layers of fabric. Preferably, the joining of the fiber material, such as a plurality of fabrics, is done without stitching or kitting. In a preferred embodiment, the binding agent is a binding powder, such as a thermoplastic binding powder.

In one embodiment, the preforms of the present invention essentially consist of the fiber material and the binding agent. This means that the preforms contain no more than 10 wt%, preferably not more than 5 wt% or not more than 1 wt%, of material other than fiber material and binding agent relative to the total weight of the preform. According to another embodiment, the preform consists of fiber material and the binding agent.

In another embodiment, the fiber material used for the preforms of the present invention essentially consists of glass fibers. This means that the fiber material contains not more than 10 wt%, preferably not more than 5 wt% or not more than 1 wt%, of material other than glass fibers relative to the total weight of the fiber material. According to another embodiment, the fiber material consists of glass fibers.

In one embodiment, the binding agent is present in an amount of 1-6 wt% relative to the weight of the fiber material in the preform. According to another embodiment, the melting point of the binding agent is between 40° and 220 °C, preferably between 40 and 160 °C. According to another embodiment, the binding agent comprises a polyester, preferably a bisphenolic polyester.

In one embodiment of the present invention, each preform essentially consists of the fiber material and the binding agent. According to another embodiment, the fiber material comprises fiber rovings, preferably glass fiber rovings. In other embodiments, the fiber material may comprise carbon fibers or a hybrid material. According to another embodiment, the fiber material comprises a fiber fabric, such as a fiber mat. In another embodiment, a preform may further comprise at least one fiber fabric such as a fiber mat. Fiber rovings may be arranged on top and/or below such fabric. Each preform may contain a plurality of fiber layers which are bound together by the binding agent, e.g., by heating a stack of the plurality of fiber layers and interposed binding agent to form the preform.

According to another embodiment, the preform has an elastic modulus (Young's modulus) of between 0.01 and 250 GPa, preferably 0.01-100 GPa, such as between 0.01-45 GPa or between 0.01-10 GPa. It is most preferred that the preform has an elastic modulus (Young's modulus) of between 0.01 and 10 GPa, preferably between 0.01 and 5 GPa, such as between 0.01 and 4 GPa, between 0.01 and 3 GPa, between 0.01 and 2 GPa, between 0.01 and 1 GPa, or between 0.01 and 0.5 GPa. Preforms with such elasticity and comparatively low stiffness were found to be particularly well suited for a blade manufacturing process according to the present invention. The skilled reader will understand that the elastic modulus, also known as Young's modulus, defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material. Thus, the elastic modulus is a measure of the stiffness of a material. The elastic modulus can be determined by the cantilever beam test, as is well known in the art.

In a preferred embodiment, the preforms are used as part of the root region of a wind turbine blade, such as the root laminate. The root region may extend up to 40 meters, such as up to 25 meters, from the root end of the blade, as seen in its longitudinal direction. In other embodiments, the root region may extend to the shoulder of the blade +/- 5 meters. However, the preforms could also be used for other parts and regions of a wind turbine blade. In other embodiments, the preforms manufactured according to the afore-mentioned method are used over a length of 10-35% of the total blade length. In another embodiment, the preforms are used in a region of the blade extending between its root end and a shoulder of the blade.

The plurality of preforms can be successively arranged in the blade mold, wherein the blade mold comprises a blade mold cavity, a root end, a tip end, and opposing first and second lateral edges extending along a longitudinal direction of the blade mold between the root end and the tip end. Typically, the first and second lateral edges will be linearly extending edges, usually a left edge and a right edge of the blade mold, as seen in the longitudinal direction. The blade mold cavity advantageously corresponds substantially to the outer aerodynamic surface of a shell half of the blade. The root end and the tip end will usually correspond to the root end and the tip end of the later wind turbine blade. The blade mold cavity will typically have a substantially U-shaped or semi-circular transverse cross section at the root end of the blade mold. The blade mold preferably has a length of at least 30 meters, such as at least 50 meters. In a preferred embodiment, the blade mold has a length of at least 90 meters, such as at least 100 meters.

The mold cavity has a longitudinal central axis, which usually extends in the longitudinal direction of the mold through the midpoint of a transverse cross section at any given location along the length of the mold cavity. For example, if the mold cavity has a U- shaped cross section or a semi-circular cross section at the root end of the mold, the longitudinal central axis will be located at the center or at the lowest point of the U-shape or of the semi-circle.

Once the preforms have been arranged in the blade mold cavity, optionally together with additional material such as core material, reinforcing sections such as spar caps, or other blade components, resin is infused to the blade mold cavity, and the resin is subsequently cured and/or hardened in order to form the blade part. Typically, the resin infusion step comprises vacuum assisted resin transfer molding. In a preferred embodiment, the resin dissolves the binding agent of the preform.

The resin for infusing the blade mold cavity may be an epoxy, a polyester, a vinyl ester or a suitable thermoplastic or duroplastic material. In other embodiments, the resin may be a thermosetting resin, such as epoxy, vinyl ester or polyester, or a thermoplastic resin, such as nylon, PVC, ABS, polypropylene or polyethylene.

The step of arranging the plurality of preforms in the blade mold cavity comprises placing a first preform into the blade mold cavity, preferably from the root end of the blade mold, such that the first preform extends along the longitudinal direction of the blade mold, and such that the first preform is arranged at the longitudinal central axis of the mold cavity. It is particularly preferred that the first preform acts as an anchoring element for the subsequently placed second and third preforms. In a preferred embodiment, the first preform is fixed to the mold cavity, for example by using one or more fasteners or an adhesive, to form an anchoring element for placement of the second and third preforms. In other embodiments, the first preform acts as anchoring element by way of its own weight keeping the first preform in place.

It is preferred that the first preform is placed into the blade mold cavity from the root end of the blade mold, as this offers a particularly easy and effective placement method. However, in other embodiments, the first preform can be placed into the blade mold cavity from lateral edges or from above, for example by using a crane or a scaffold.

According to a preferred embodiment, the mold cavity has a substantially U-shaped or semi-circular transverse cross section at the root end of the blade mold, wherein the first preform is arranged at the center of, or in other words at the lowest point of, said substantially U-shaped or semi-circular transverse cross section. Thus, the first preform is preferably placed at a location where it is no longer prone to gravitational movement. This results in a stable configuration which helps using the first preform as anchoring element for accurately placing subsequent preforms. The mold cavity may comprise respective predetermined placement regions of each preform arranged in the mold, such as a first placement region for the first preform, a second placement region for the second preform, and a third placement region for the third preform. Preferably after arranging the first preform in the mold cavity, the second preform is placed into the blade mold cavity, preferably from the first lateral edge of the blade mold, such that the second preform slides within the mold cavity until the second preform abuts the first preform along a first longitudinally extending interface. Typically, this will involve lifting the second preform above the first lateral edge of the blade mold and aligning its longitudinal direction with the longitudinal direction of the blade mold. Then the second preform can be lowered to the mold cavity where it slides within the mold cavity until the second preform abuts the first preform along the first longitudinally extending interface. The sliding motion can take place directly on the surface of the mold or on a gelcoat or other coating material which has been applied to the mold surface. For a second layer of preforms arranged on a first layer of preforms, the sliding motion can take place on the top surfaces of the preforms of the first layer. The sliding motion is typically a transverse sliding, i.e., substantially in a direction perpendicular to the longitudinal direction of the blade mold. Thus, it is preferred that the first preform acts as an anchoring element or as a stop to prevent further sliding motion when the second/third perform has reached its intended placement region.

The terms “second preform" and "third preform”, as used herein, are intended to imply a location of these preforms relative to the first preform, after having been arranged in the mold, i.e., the second preform abuts the first preform along a first longitudinally extending interface, and the third preform abuts the first preform along a second longitudinally extending interface. Thus, the terms “second preform" and "third preform”, as used herein, do not imply a specific order or sequence of layup of the second or third preform, nor do they include the layup of additional preforms before or after placing the second preform or the third preform in the mold cavity. For example, after placing the second preform in the mold cavity, and prior to placing the third preform in the mold cavity, one or more additional preforms may be placed in the mold cavity, preferably from the first lateral edge of the blade mold, preferably such that the one or more additional preforms slide within the mold cavity until the additional preform abuts the second preform, or another additional preform, along an additional longitudinally extending interface.

Preferably after the second preform is arranged in the mold cavity, the third preform is placed into the blade mold cavity, preferably from the second lateral edge of the blade mold, such that the third preform slides within the mold cavity until the third preform abuts the first preform along a second longitudinally extending interface. The first longitudinally extending interface will typically be closer to the first lateral edge of the blade mold than the second longitudinally extending interface. Likewise, the second longitudinally extending interface will typically be closer to the second lateral edge of the blade mold than the first longitudinally extending interface. The placement of the third preform will usually involve lifting the third preform above the second lateral edge of the blade mold and aligning its longitudinal direction with the longitudinal direction of the blade mold. Then the third preform can be lowered to the mold cavity where it slides within the mold cavity until the third preform abuts the first preform along the second longitudinally extending interface. The sliding motion can take place directly on the surface of the mold or on a gelcoat or other coating material which has been applied to the mold surface. The sliding motion is typically a transverse sliding, i.e., substantially in a direction perpendicular to the longitudinal direction of the blade mold. Thus, it is preferred that the first preform acts as an anchoring element or as a stop to prevent further sliding motion when the third perform has reached its intended placement region. It is preferred that the first preform is enclosed from both sides, i.e., by the second and the third preform. In a preferred embodiment, the first, second and third preforms have substantially the same length. The first, second and third preforms can also have substantially the same thickness, and optionally substantially the same width.

In some embodiments, one or more additional preforms are placed in the mold cavity, preferably from the first lateral edge of the blade mold, such that the one or more additional preforms extend along the longitudinal direction of the blade mold, prior to placing the third preform into the blade mold cavity, preferably such that the one or more additional preforms slide within the mold cavity until the additional preform abuts the second preform along a longitudinally extending interface opposing the first longitudinally extending interface. Thus, in some embodiments the left side of the mold cavity, as seen in the transverse cross section, can be filled with preforms, prior to placing the third preform in the mold cavity on the right side of the mold cavity, as seen in the transverse cross section, or vice versa. In some embodiments, placing the second preform into the blade mold cavity is done simultaneously with placing the third preform into the blade mold cavity, optionally simultaneously with placing additional preforms into the blade mold cavity.

In a preferred embodiment, the second preform is joined to the first preform along said first longitudinally extending interface. Preferably, this is done prior to placing the third preform into the blade mold cavity. Likewise, the third preform can be joined to the first preform along said second longitudinally extending interface. Preferably, this is done prior to placing additional preforms into the blade mold cavity. Advantageously, this can be done by applying heat to said first/second longitudinally extending interface. In other embodiments, the joining can be achieved by using an adhesive or mechanical fasteners.

In a preferred embodiment, said joining is carried out by passing a heated ironing device along at least part of the top surfaces of the first and second preforms over the first longitudinally extending interface, and along at least part of the top surfaces of the first and third preforms over the second longitudinally extending interface. Thus, the heated ironing device is preferably passed over an area of the top surface in the longitudinal direction of the blade mold, said area comprising the first or second longitudinally extending interface. In a preferred embodiment, the joining operation makes use of a binding agent or an adhesive, which upon heating, joins the preforms along said interface. In some embodiments, a heating blanket or another heating means can be used to join the preforms along the longitudinally extending interface.

In a preferred embodiment, the step of placing the first preform into the blade mold cavity is carried out using a drawer assembly comprising a support body and at least one drawer slidably supported on the support body, wherein the first preform is transferred from the drawer to the blade mold cavity. In a preferred embodiment, the drawer assembly comprises two or more drawers each slidably supported on the support body, preferably at different vertical levels, e.g., a first drawer at a top level of the drawer assembly and a second drawer at a lower level of the drawer assembly. Each drawer preferably has a rectangular cuboid shape and a top surface for receiving a preform, such as the first preform. It is particularly preferred that each drawer forms a tray for receiving a preform.

Each drawer is preferably slidably mounted on the support body, for example by corresponding rails that are disposed between the drawer and the support body, or by a sliding track assembly. The two rails can be slidably fitted with each other so that the drawer can be pushed and pulled relative to the support body. In some embodiments, the support body is mounted on wheels for facilitating transfer and correct positioning of the drawer assembly and the blade mold.

In a preferred embodiment, said transfer of the first preform comprises extending the drawer relative to the support body such that the drawer is located above the blade mold cavity and gradually lowering or dropping the first preform from the drawer into the blade mold cavity. Preferably, the drawer is retracted while gradually lowering or dropping the first preform from the drawer into the blade mold cavity. In some embodiments the drawer comprises a ramp or slope at its distal edge to facilitate the lowering or dropping of the preform over the distal edge of the drawer. In some embodiments, the drawer assembly can have height adjustment means to align one or more drawers to the height of the mold or to the placement location.

In some embodiments, one or more of the preforms can be manufactured on a drawer of the drawer assembly. Thus, a top surface of the drawer can act as a preform molding surface, wherein a fiber material and a binding agent are laid on the top surface of the drawer. The fiber material and the binding agent can be covered with a vacuum bag, and negative pressure can be applied to the fiber material and binding agent on the drawer. Heat can be applied to the fiber material and binding agent, for example by using a heating blanket, to form the preform. This can also apply when using one or more fabrics as fiber material.

In a preferred embodiment, the step of placing the second preform and/or the third preform into the blade mold cavity is carried out by using a ramp arranged on the first lateral edge and/or the second lateral edge of the blade mold. In some embodiments, one or more of the drawers from the drawer assembly can be used on the ramps for holding and carrying the preforms that are to be slid from the lateral edges of the mold. The heights of the drawers can be adjusted to the height of the edge. Multiple drawer assemblies may be used from the root end and either lateral edges simultaneously to save time. In some embodiments, the drawer assembly comprises widthwise slidable drawers with respect to the support body.

In a preferred embodiment, the step of arranging the plurality of said preforms in the blade mold cavity further comprises placing one or more additional preforms into the blade mold cavity from the first lateral edge and/or from the second lateral edge of the blade mold, such that the one or more additional preforms slide within the mold cavity until the additional preform abuts a previously placed preform along a further longitudinally extending interface. For example, a fourth preform can be placed into the blade mold cavity, preferably from the first lateral edge of the blade mold, such that the fourth preform slides within the mold cavity until the fourth preform abuts the second preform along a third longitudinally extending interface. Similarly, a fifth preform can be placed into the blade mold cavity, preferably from the second lateral edge of the blade mold, such that the fifth preform slides within the mold cavity until the fifth preform abuts the third preform along a fourth longitudinally extending interface.

In a preferred embodiment, a first layer of preforms is formed by said steps of placing the first, second and third preforms, and optionally additional preforms, and wherein the steps of placing the first, second and third preforms, and optionally additional preforms, are repeated once or more times to form one or more additional layers of preforms on top of the first layer of preforms. In this way, a stack of preforms can be formed, for example comprising two or more layers, such as five or more layers of preforms.

In a preferred embodiment, each of the preforms has a length-width ratio of at least 5:1 , preferably at least 10:1. Typically, each preform has two opposing lateral edges extending along the longitudinal direction of the preform, and two opposing transverse edges extending substantially perpendicularly to the longitudinal direction of the preform. Usually, the above-discussed longitudinally extending interfaces between the preforms in the mold cavity will be formed by abutting longitudinal edges of the preforms. It is preferred that the longitudinally extending interfaces between adjacent preforms in the mold cavity have a length of at least 5 meters, preferably at least 10 meters.

In a preferred embodiment, each preform is manufactured in a process comprising the steps of providing a preform mold comprising a mold surface, laying a fiber material and a binding agent on the mold surface, covering the fiber material and the binding agent with a vacuum bag, and applying negative pressure to the fiber material and binding agent via the one or more channel members for consolidating the preform, and applying heat to the fiber material and binding agent to form the preform. In some embodiments, the mold surface of the preform mold has a length of between 15 and 30 meters. In other embodiments, the mold surface of the preform mold has a width of 2-5 meters. In some embodiments, the preform mold has a height of between 0.5 and 2 meters. The mold surface of the preform mold may have a molding surface area of between 10 and 100 square meters, such as between 30 and 80 square meters, preferably between 50 and 70 square meters. In a preferred embodiment, the mold surface is substantially gas tight. In some embodiments, the preform mold has a concave, or inwardly curved, mold surface. The fiber laying step in the manufacturing of the preforms will typically comprise the use of one or more fiber lay-up devices. Vacuum or negative pressure is then typically applied to the fiber material and binding agent via one or more channel members for consolidating the preform. In a preferred embodiment, the preform manufacturing method further comprises a step of heating the fiber material and the binding agent to form a preform. Preferably, the fiber material and the binding agent are heated, preferably during or following the consolidation step, using one or more heating devices, such as an oven. Preferably, a binding agent is added to the fibers prior to the heating step. The binding agent can be applied to the fiber material during layup on the preform mold. In other embodiments, the binding agent is applied to the fiber material prior to the layup of the fiber material. Typically, the fiber material is placed successively onto the preform molding surface together with the binding agent. According to a preferred embodiment of the preform manufacturing method, a glass fiber material is placed onto the strip members, such as multiple layers of glass fiber material. The fiber material may advantageously be brought into contact with a binding agent before or during the fiber lay-up. In another embodiment, the fiber material may include fiber rovings, such as glass fiber rovings. The lay-up process on the preform mold may include placing multiple single roving bundles into the mold, the roving bundles being preferably aligned unidirectionally. In a preferred embodiment, multiple layers of fiber rovings or roving bundles are successively placed onto each preform mold.

In a preferred embodiment of manufacturing the preforms, a heating step is carried out during or after applying negative pressure to the fiber material, such as one or more fabrics, and binding agent, wherein heating of the fiber material, such as one or more fabrics, and the binding agent takes place at a temperature of between 40 and 200 °C, preferably between 70 and 160 °C, most preferably between 70 and 80 °C.

The method of manufacturing a wind turbine blade part of the present invention may further comprise using a computing unit to assist in the determination and monitoring of the correct layup sequence and layup locations of the preforms in the blade mold. Said computing unit may comprise a hardware computing unit or a cloud-based computing unit. Furthermore, at least one algorithm may be used by the computing unit to determine and/or monitor the layup sequence and the correct layup locations of the preforms in the blade mold. In another aspect, the present invention relates to a blade mold assembly for carrying out a method according to the present invention, the mold assembly comprising a blade mold comprising a blade mold cavity, a root end, a tip end, and opposing first and second lateral edges extending along a longitudinal direction of the blade mold between the root end and the tip end, and a drawer assembly, preferably installed at the root end of the blade mold, the drawer assembly comprising a support body and at least one drawer slidably supported on the support body. The drawer assembly can be releasably fixed to the blade mold. In a preferred embodiment, the drawer assembly comprises two or more drawers each slidably supported on the support body, preferably at different vertical levels, e.g., a first drawer at a top level of the drawer assembly and a second drawer at a lower level of the drawer assembly. Each drawer preferably has a rectangular cuboid shape and a top surface for receiving a preform, such as the first preform. It is particularly preferred that each drawer forms a tray for receiving a preform. Each drawer is preferably slidably mounted on the support body, for example by corresponding rails that are disposed between the drawer and the support body, or by a sliding track assembly. The two rails can be slidably fitted with each other so that the drawer can be pushed and pulled relative to the support body. In some embodiments, the support body is mounted on wheels for facilitating transfer and correct positioning of the drawer assembly and the blade mold. The drawer assembly may also comprise height adjustment means to align one or more drawers to the height of the mold or to the placement location, wherein said height adjustment means include height-adjustable rails or sliding track assemblies.

In a preferred embodiment, the blade mold assembly further comprises a heated ironing device which is movable along the blade mold cavity. In another preferred embodiment, the blade mold assembly comprises a first ramp arranged on the first lateral edge and/or a second ramp arranged on the second lateral edge of the blade mold. The ramp may extend over at least 30%, such as at least 50%, of the length of the respective lateral edge of the blade mold. The ramp may have a slope which is substantially the same or smaller than the slope of the molding cavity adjacent to the respective lateral edge of the blade mold.

It will be understood that any of the embodiments and features described above in relation to the method of manufacturing a wind turbine blade part likewise apply to the blade mold assembly, and vice versa. In another aspect, the present invention relates to a method of manufacturing a wind turbine blade part, the method comprising the steps of providing a plurality of preforms, preferably including a first, second and third preform, each preform comprising a fiber material and a binding agent, arranging the plurality of preforms in a mold comprising a mold cavity and opposing first and second lateral edges extending along a longitudinal direction of the mold, infusing resin to the mold cavity, and curing and/or hardening the resin in order to form the blade part, wherein arranging the plurality of preforms in the mold cavity comprises placing the first preform into the mold cavity such that the first preform extends along the longitudinal direction of the mold, and such that the first preform is arranged at a longitudinal central axis of the mold cavity, placing the second preform into the mold cavity, preferably from the first lateral edge of the mold, such that the second preform slides within the mold cavity until the second preform abuts the first preform along a first longitudinally extending interface between the first and second preforms, and preferably placing the third preform into the mold cavity, preferably from the second lateral edge of the mold, such that the third preform slides within the mold cavity until the third preform abuts the first preform along a second longitudinally extending interface between the first and third preforms.

In another aspect, the present invention relates to a drawer assembly for placing a preform into a mold cavity in a method according to the present invention, the drawer assembly comprising a support body and at least one drawer slidably supported on the support body.

In a preferred embodiment, the drawer assembly comprises two or more drawers, such as three or more drawers, each slidably supported on the support body at different vertical levels, including a first drawer at a top level of the drawer assembly and a second drawer at a lower level of the drawer assembly.

In another preferred embodiment, each drawer has a rectangular cuboid shape and a top surface for receiving a preform, thus forming a tray for receiving a preform. Preferably, each drawer is slidably mounted on the support body by corresponding rails that are disposed between the drawer and the support body or by a sliding track assembly. According to a preferred embodiment, the support body is mounted on wheels. In another preferred embodiment, the drawer assembly further comprises height adjustment means including height-adjustable rails or height-adjustable sliding track assemblies.

As used herein, the term “wt%” means weight percent. The term “relative to the weight of the fiber material” means a percentage that is calculated by dividing the weight of an agent, such as a binding agent, by the weight of the fiber material. As an example, a value of 1 wt% relative to the weight of the fiber material corresponds to 10 g of binding agent per kilogram of fiber material.

As used herein, the term “longitudinal” means an axis or direction running substantially parallel to the maximum linear dimension of the element in question, for example a blade mold.

Detailed description of the invention

The invention is explained in detail below with reference to embodiments shown in the drawings, in which

Fig. 1 shows a wind turbine,

Fig. 2 shows a schematic view of a wind turbine blade,

Fig. 3 shows a schematic view of an airfoil profile through section l-l of Fig. 4,

Fig. 4 shows a schematic view of the wind turbine blade, seen from above and from the side,

Fig. 5a) and 5b) show a perspective drawing of a preform mold,

Figs. 6-10 are schematic drawings of a blade mold, illustrating various stages of the method of the present invention,

Figs. 11-13 are schematic drawings of a mold assembly according to the present invention, Figs. 14-17 are perspective drawings illustrating various steps of a method according to the present invention,

Figs. 18 and 19 are perspective drawings illustrating various steps of a method according to another embodiment of the present invention,

Fig. 20 is a perspective schematic drawing illustrating the layup of multiple preforms according to the present invention,

Fig. 21 is a schematic representation of a blade mold assembly according to the present invention, and

Fig. 22 is a schematic representation of a drawer assembly according to the present invention.

Detailed

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.

Fig. 2 shows a schematic view of an embodiment of a wind turbine blade 10 according to the invention. 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.

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 rfrom 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 rfrom the hub.

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.

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.

Figs. 3 and 4 depict parameters which are used to explain the geometry of the wind turbine blade according to the invention. 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 centers 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. Airfoil profiles are often characterized by the following parameters: the chord length c, the maximum camber f, the position df 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 dt 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_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.

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_w, and has a shoulder width l/l/, 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 r₀ and a minimum inner curvature radius n, 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 Ay, which corresponds to the out of plane deflection from a pitch axis 22 of the blade.

Fig. 5 illustrates a method of manufacturing a preform for a wind turbine blade using a preform mold 90 comprising a mold surface 87. As shown in Fig. 5a), vacuum channels 72 can be fastened to the mold surface 87. Then, a fiber material 85, such as one or more fabrics, and a binding agent is laid on the mold surface 87. Subsequently, the fiber material 85, the binding agent and the vacuum channels 72 are covered with a vacuum bag 91 ; see Fig. 5b). Negative pressure can then be applied to the fiber material and binding agent via the channel members 72, using a vacuum source 92 and connected tubes 93. Thereby, the fiber layup is consolidated. Advantageously, heat is applied during or after this step to further join the fibers using the binding agent, to form the preform. In the illustrated embodiment, the preform mold is substantially flat, however, other shapes can be used. It is preferred that each of the preforms has a length-width ratio of at least 5:1 , preferably at least 10:1. Figs. 6-10 are schematic drawings of a blade mold, illustrating various stages of the method of manufacturing a wind turbine blade part, such as a pressure side shell half or a suction side shell half, of the present invention. Fig. 6 is a schematic illustration of a blade mold 96 for forming a shell half of a wind turbine blade. The blade mold 96 comprises a blade mold cavity 97 which corresponds substantially to the outer aerodynamic surface of the shell half. In the illustrated embodiment, the mold cavity 97 has a substantially U-shaped or semi-circular transverse cross section at the root end 65 of the blade mold 96. The blade mold 96 also comprises a root end 65, a tip end 66, and opposing first and second lateral edges 67, 68 extending along a longitudinal direction Lm of the blade mold 96 between the root end 65 and the tip end 66. Fig. 6 also illustrates a first, second and third placement regions 81 , 82, 83, see hatched lines. A first preform 98a is to be placed in the first placement region 81 , as illustrated in Figs. 7 and 8. The preform 98a comprises a fiber material and a binding agent.

Arranging the plurality of preforms 98a-c in the blade mold cavity 97 comprises placing the first preform 98a into the blade mold cavity 97, preferably from the root end 65 of the blade mold 96, such that the first preform 98a extends along the longitudinal direction Lm of the blade mold 96, see Figs. 6-8. The first preform 98a is arranged at the longitudinal central axis 69 of the mold cavity 97, for example such that a center line of the preform is aligned with the central axis 69 of the mold cavity, see Fig. 8. Thus, the first preform 98a is arranged at the lowest point of said substantially U-shaped or semicircular transverse cross section of the mold cavity 97.

Next, a second preform 98b is placed into the blade mold cavity 97 from the first lateral edge 67 of the blade mold 96 such that the second preform 98b slides within the mold cavity 97 until the second preform 98b abuts the first preform 98a along a first longitudinally extending interface 70, see Figs. 9 and 10. Thus, the first preform 98a advantageously acts as an anchoring element for placement of the second and subsequent preforms. In some embodiment, the first preform fixed to the mold cavity 97 to form an anchoring element for placement of the second and third preforms 98b, 98c. In a preferred embodiment, the second preform 98b is joined to the first preform 98a along said first longitudinally extending interface 70 prior to placing the third preform 98c into the blade mold cavity 97.

Also, a third preform 98c is placed into the blade mold cavity 97 from the second lateral edge 68 of the blade mold 96 such that the third preform 98c slides within the mold cavity 97 until the third preform 98c abuts the first preform 98a along a second longitudinally extending interface 71. Again, preferably, the third preform 98c is joined to the first preform 98a along said second longitudinally extending interface 71 prior to placing additional preforms into the blade mold cavity 97.

These steps are preferably repeated, and/or additional material such as reinforcing sections and core material is also placed into the mold along with the preforms. Once all material is laid into the mold resin can be infused to the blade mold cavity 97, e.g., in a VARTM process. Subsequently, the resin is cured and/or hardened the resin in order to form the blade part, such as the shell half.

Figs. 11-13 are schematic drawings of a mold assembly 100 according to the present invention, illustrating another embodiment of a method of manufacturing a wind turbine blade part according to the present invention. The blade mold assembly 100 comprises the blade mold 96 with the blade mold cavity 97, and a drawer assembly 77, preferably installed at the root end of the blade mold 96. The drawer assembly 77 comprises a support body 78 and at least one drawer 79 slidably supported on the support body 78. The step of placing the first preform 98a into the blade mold cavity 97 is carried out using a drawer assembly 77 comprising a support body 78 and at least one drawer 79 slidably supported on the support body 78. The first preform 98a can be transferred from the drawer 79 to the blade mold 96 cavity by extending the drawer 79 relative to the support body 78 such that the drawer is located above the blade mold cavity 97. Then, the preform 98a can be gradually dropped or lowered from the drawer 79 into the blade mold cavity 97, see Fig. 13. The drawer assembly 77 may also comprise height adjustment means to align one or more drawers 79 to the height of the mold or to the placement location.

Figs. 14-17 are perspective drawings illustrating an example of a method of joining preforms along their longitudinally extending interface. In Fig. 14, a first preform 98a is placed centrally into the blade mold cavity 97, followed by placement of a second preform 98b, see Fig. 15. The joining process is carried out by passing a heated ironing device 75 along at least part of the top surfaces 99a, 99b of the first and second preforms 98a, 98b over the first longitudinally extending interface 70, as illustrated in Fig. 16. Also, an additional preform 98d is placed in the mold cavity, and again the heated ironing device is passed along at least part of the top surfaces 99a, 99d of the second preform 98b and the additional preform 98d over the longitudinally extending interface between said preforms. The same process can be carried out at the opposing side 68 of the blade mold, which is not illustrated here for the sake of simplicity.

Figs. 18 and 19 illustrate another embodiment of a method according to the present invention. Here, the step of placing the second preform 98b and/or the third preform 98c into the blade mold cavity 97 is carried out by using a ramp 80 arranged on the first lateral edge 67 and/or the second lateral edge 68 of the blade mold 96. The preform 98b can be slid over the ramp to facilitate a smooth lowering and ergonomically beneficial placement method.

Fig. 20 is a perspective schematic drawing illustrating the layup of multiple preforms according to the present invention. In this embodiment, several additional preforms 98d- j have been placed into the blade mold cavity 97 from the first lateral edge 67 and/or from the second lateral edge 68 of the blade mold 96, such that the one or more additional preforms slide within the mold cavity 97 until the additional preform abuts a previously placed preform along a further longitudinally extending interface 72, 73. Thus, a first layer of preforms 98a-e is formed by said steps, followed by a second layer of preforms 98f-j , placed by repeating the above-discussed steps. Also, a third and a fourth layer of preforms are illustrated in Fig. 20.

Fig. 21 is a schematic representation of a blade mold assembly according to another embodiment of the present invention. Here, the step of placing the preforms into the blade mold cavity 97 is carried out by using a first drawer assembly 77a at the root end of the blade mold 96, and a second drawer assembly 77b at a lateral edge 68 of the blade mold 96. Each of the two drawer assemblies 77a, 77b comprises a support body 78 and three drawers 79, each slidably supported on the support body 78. The three drawers 79 are arranged at different vertical levels, i.e. , a first drawer at a top level of the drawer assembly 77, a second drawer at a middle level of the drawer assembly 77, and a third drawer at a bottom level of the drawer assembly 77. Thus, each preform 98 can be transferred from its drawer to the blade mold cavity.

Fig. 22 is a schematic representation of a drawer assembly according to another embodiment. The drawer assembly 77 comprises a support body 78 and three drawers 79, each slidably supported on the support body 78. The three drawers 79 are arranged at different vertical levels, i.e., a first drawer at a top level of the drawer assembly 77, a second drawer at a middle level of the drawer assembly 77, and a third drawer at a bottom level of the drawer assembly 77. Also, in the illustrated embodiment, the preforms 98 are manufactured on the respective drawers 79 of the drawer assembly 77, as illustrated in the middle and bottom level of the drawer assembly of Fig. 22. A top surface 76 of the drawer 79 is used as a preform molding surface, wherein a fiber material and a binding agent are laid on the top surface of the drawer, which is then covered with a vacuum bag and a heating blanket 94 to form the preform by applying negative pressure and by heating the fiber material and binding agent.

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

2 wind turbine

4 tower

6 nacelle

8 hub

10 blade

14 blade tip

16 blade root

18 leading edge

20 trailing edge

22 pitch axis

30 root region

32 transition region

34 airfoil region

40 shoulder I position of maximum chord

50 airfoil profile

52 pressure side

54 suction side

56 leading edge

58 trailing edge

60 chord

62 camber line / median line 65 root end of mold

66 tip end of mold

67 first lateral edge of blade mold

68 second lateral edge of blade mold

69 longitudinal central axis of mold cavity

70 first longitudinally extending interface

71 second longitudinally extending interface

72 third longitudinally extending interface

73 fourth longitudinally extending interface

75 heated ironing device

76 top surface of drawer

77 drawer assembly

78 support body

79 drawer

80 ramp

81 first placement region

82 second placement region

83 third placement region

85 fiber material

87 molding surface of preform mold

90 preform mold

92 vacuum source

93 tubes

94 heating blanket

96 blade mold

97 blade mold cavity

98 preform

99 top surface of preform

100 blade mold assembly c chord length dt position of maximum thickness df position of maximum camber d_p position of maximum pressure side camber f camber

L blade length r local radius, radial distance from blade root t thickness

Ay prebend

Lm longitudinal direction of blade mold

Claims

1. A method of manufacturing a wind turbine blade part (52, 54), the method comprising the steps of providing a plurality of preforms (98a-c), each preform comprising a fiber material and a binding agent, arranging the plurality of preforms (98a-c) in a blade mold (96) comprising a blade mold cavity (97), a root end (65), a tip end (66), and opposing first and second lateral edges (67, 68) extending along a longitudinal direction (Lm) of the blade mold (96) between the root end (65) and the tip end (66), infusing resin to the blade mold cavity (97), and curing or hardening the resin in order to form the blade part, wherein the step of arranging the plurality of preforms (98a-c) in the blade mold cavity (97) comprises placing a first preform (98a) into the blade mold cavity (97) such that the first preform (98a) extends along the longitudinal direction of the blade mold (96), and such that the first preform (98a) is arranged at the longitudinal central axis (69) of the mold cavity (97), placing a second preform (98b) into the blade mold cavity (97), preferably from the first lateral edge (67) of the blade mold (96), such that the second preform (98b) slides within the mold cavity (97) until the second preform (98b) abuts the first preform (98a) along a first longitudinally extending interface (70), and optionally placing a third preform (98c) into the blade mold cavity (97), preferably from the second lateral edge (68) of the blade mold (96), such that the third preform (98c) slides within the mold cavity (97) until the third preform (98c) abuts the first preform (98a) along a second longitudinally extending interface (71).

2. A method of manufacturing a wind turbine blade part according to claim 1 , wherein the first preform (98a) is fixed to the mold cavity (97) to form an anchoring element for placement of the second and third preforms (98b, 98c).

3. A method of manufacturing a wind turbine blade part according to claims 1 or 2, wherein the mold cavity (97) has a substantially U-shaped or semi-circular transverse cross section at the root end of the blade mold (96), and wherein the first preform (98a) is arranged at the center of, or at the lowest point of, said substantially U-shaped or semicircular transverse cross section.

4. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein the second preform (98b) is joined to the first preform (98a) along said first longitudinally extending interface (70), preferably prior to placing the third preform (98c) into the blade mold cavity (97).

5. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein the third preform (98c) is joined to the first preform (98a) along said second longitudinally extending interface (71), preferably prior to placing additional preforms into the blade mold cavity (97).

6. A method of manufacturing a wind turbine blade part according to claim 5, wherein said joining is carried out by passing a heated ironing device (75) along at least part of the top surfaces (99a, 99b) of the first and second preforms (98a, 98b) over the first longitudinally extending interface (70), and along at least part of the top surfaces (99a, 99c) of the first and third preforms (98a, 98c) over the second longitudinally extending interface (71).

7. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein the step of placing any of the first, second or third preform (98a) into the blade mold cavity (97) is carried out using a drawer assembly (77) comprising a support body (78) and at least one drawer (79) slidably supported on the support body (78), wherein the first, second or third preform (98a) is transferred from the drawer to the blade mold (96) cavity.

8. A method of manufacturing a wind turbine blade part according to claim 7, wherein said transfer of the first preform (98a) comprises extending the drawer relative to the support body such that the drawer is located above the blade mold cavity (97) and gradually dropping the first preform (98a) from the drawer into the blade mold cavity (97).

9. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein the step of placing the second preform (98b) and/or the third preform (98c) into the blade mold cavity (97) is carried out by using a ramp (80) arranged on the first lateral edge (67) and/or the second lateral edge (68) of the blade mold (96).

10. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein the step of arranging the plurality of said preforms in the blade mold (96) cavity further comprises placing one or more additional preforms (98d) into the blade mold cavity (97) from the first lateral edge (67) and/or from the second lateral edge (68) of the blade mold (96), such that the one or more additional preforms (98d) slide within the mold cavity (97) until the additional preform abuts a previously placed preform (98b) along a further longitudinally extending interface (72).

11. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein a first layer of preforms is formed by said steps of placing the first, second and third preforms (98a-c), and optionally additional preforms, and wherein the steps of placing the first, second and third preforms, and optionally additional preforms, are repeated once or more times to form one or more additional layers of preforms on top of the first layer of preforms.

12. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein each of the preforms has a length-width ratio of at least 5:1 , preferably at least 10:1.

13. A method of manufacturing a wind turbine blade part according to any of the preceding claims, wherein each preform is manufactured in a process comprising the steps of providing a preform mold comprising a mold surface, laying a fiber material, such as one or more fabrics, and a binding agent on the mold surface, covering the fiber material and the binding agent with a vacuum bag, and applying negative pressure to the fiber material and binding agent via the one or more channel members for consolidating the preform, and applying heat to the fiber material and binding agent to form the preform.

14. A blade mold assembly (100) for carrying out a method according to any of claims 1-13, the mold assembly comprising a blade mold (96) comprising a blade mold cavity (97), a root end (65), a tip end (66), and opposing first and second lateral edges (67, 68) extending along a longitudinal direction of the blade mold (96) between the root end and the tip end, and a drawer assembly (77), preferably installed at the root end of the blade mold (96), the drawer assembly (77) comprising a support body (78) and at least one drawer (79) slidably supported on the support body (78).

15. A blade mold assembly according to claim 14, further comprising a heated ironing device (75) which is movable along the blade mold cavity (97), a ramp (80) arranged on the first lateral edge (67) and/or a ramp (80) arranged on the second lateral edge (68) of the blade mold.

16. A drawer assembly (77) for placing a preform in a method according to any of claims 1-13, the drawer assembly (77) comprising a support body (78) and at least one drawer (79) slidably supported on the support body (78).

17. A drawer assembly (77) according to claim 16, wherein the drawer assembly comprises two or more drawers each slidably supported on the support body at different vertical levels, including a first drawer at a top level of the drawer assembly and a second drawer at a lower level of the drawer assembly.

18. A drawer assembly (77) according to claims 16 or 17, wherein each drawer has a rectangular cuboid shape and a top surface for receiving a preform, thus forming a tray for receiving a preform.

19. A drawer assembly (77) according to any of claims 16-18, wherein each drawer is slidably mounted on the support body by corresponding rails that are disposed between the drawer and the support body or by a sliding track assembly.

20. A drawer assembly (77) according to any of claims 16-19, wherein the support body is mounted on wheels.

21 . A drawer assembly (77) according to any of claims 16-20, further comprising height adjustment means including height-adjustable rails or height-adjustable sliding track assemblies.