WO2023175170A1

WO2023175170A1 - In-line one-way vartm valve and infusion method

Info

Publication number: WO2023175170A1
Application number: PCT/EP2023/056945
Authority: WO
Inventors: Lars Nielsen
Original assignee: Lm Wind Power A/S
Priority date: 2022-03-18
Filing date: 2023-03-17
Publication date: 2023-09-21

Abstract

The current disclosure is a distribution layer for vacuum assisted resin transfer molding of a wind turbine blade and/or a wind turbine blade part, a vacuum assisted resin transfer molding assembly comprising the distribution layer and a method for manufacturing a wind turbine blade and/or wind turbine blade parts using the vacuum assisted resin transfer molding assembly. The distribution layer comprises one or more inlets for receiving resin, one or more runners connected to the one or more inlets. The distribution layer further comprises one or more valves located within a runner, restricting flow in one direction.

Description

IN-LINE ONE-WAY VARTM VALVE AND INFUSION METHOD

TECHNICAL FIELD

The present disclosure relates to a vacuum assisted resin transfer molding process for the manufacturing of a wind turbine blade.

BACKGROUND

Wind energy is categorized as a clean energy form and the demand for wind energy has resulted in the manufacture of larger and larger wind turbine blades. With the increase in blade length the demands on the purity and uniformity of the constitutes of the blade have accordingly increased.

Wind turbine blades can be manufactured by a variety of different methods. A common method for the manufacture of wind turbine blades is by the use of vacuum assisted resin transfer molding, wherein a blade is manufactured by using a vacuum to facilitate resin flow in a laminate contained within a mold covered by a vacuum bag. The mold curves follow the contour of the desired shapes of the blade. Particularly when manufacturing blades with pre-bends the mold may be curved along the length of the mold. A distribution layer is normally laid on top of the laminate to distribute the resin throughout the fiber layup. The distribution layer consists of a number of runners which when placed on the laminate conforms to and are placed at different heights on the mold. Normally the lowest located runner is then used to distribute the resin throughout the mold, followed by the next lowest runner and so on in a sequential manner. The blade is thereafter allowed to cure and form the final shape of the blade.

However, current methods for distributing the resin comprise some disadvantages and challenges, in particular when manufacturing large and/or more complex shaped wind turbine blades.

SUMMARY

The inventors of the current invention have found that the resin in the vacuum assisted resin transfer molding process collects at locations where the height gradient of the surface of laminate is large. The resin may therefore flow backwards using the path of least resistance which may be an empty or partly empty runner of the distribution layer, e.g., causing a backfilling process. This creates uneven filling, which may lead to regions of the blade containing dry glass, which may reduce the strength of the blade.

If the distribution layer comprises at least two runners which are filled sequentially, such that one runner is empty during part of the resin filling process, backflow may occur in the empty runner. Thus, the above-described objects are intended to obtain in a first aspect a distribution layer for vacuum assisted resin transfer molding, such as for vacuum assisted resin transfer molding of a wind turbine blade and/or a wind turbine blade part, the distribution layer comprising: an inlet for receiving resin, a first runner and a second runner connected to the inlet and extending away from the inlet, the first and second runners defining a flow direction of the resin, the first and second runner being adapted to distribute the resin throughout a mold for the vacuum assisted resin transfer molding, one or more valves located within the second runner, restricting flow opposite to the flow direction. In other words, the one or more valves restrict flow to one flow direction within the runner.

By distribution layer is preferably meant the layer that distributes resin throughout the laminate, which may also be known as net-kits. Thus, the distribution layer may be a net configured to distribute resin throughout a laminate. The first and second runners do not extend beyond the distribution layer.

By having one or more valves that restrict return in a second runner, an even filling of the laminate with resin is achieved. This reduces the forming of dry glass in the laminate and overall gives an improved and strengthened curing of the laminate and the resulting wind turbine blade.

Main components of a wind turbine blade may include shell members, spar caps and shear webs. The distribution layer of the present disclosure may be used for vacuum assisted resin transfer molding of various parts of a wind turbine blade, such as shell members, spar caps and/or shear webs. The shell members, usually two shell members, are normally made separate from each other, while the spar caps may be made during manufacture of each of the shell members or they may be made offline and arranged in the shell members afterwards. In some embodiments, the vacuum assisted resin transfer molding as referred to herein is a vacuum assisted resin transfer molding of a one or more wind turbine blade parts, such as one or more wind turbine blade shell members or one or more spar caps or one or more shear webs. However, the distribution layer of the present disclosure may be used for vacuum assisted resin transfer molding of any wind turbine blade part.

In some embodiments, the inlet and the first and second runners may be placed to ensure a uniform distribution of resin during the resin transfer molding.

In some embodiments, the one or more valves may restrict flow opposite the flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%.

The valve may not need to completely restrict the return flow through one of the runners but may only need to sufficiently restrict it, such that the main filling of the laminate is achieved by the runners in an even manner and allows resin to flow freely in the flow direction. In some embodiments and for some blade designs it may be that the one or more valves only partially restrict return flow, such as below 50 % of the flow or it may be higher. The valve therefore effectively sectionizes the runners. In some embodiments, the second runner may therefore comprise two or more valves to effectively sectionizes the runners. In some embodiments, the first runner may comprise no valves since it will be the first runner to be filled and no risk of back-filling is present.

In some embodiments, each of the first and the second runner may have an omega-shaped cross section with an opening extending along the length of the respective first and second runner. The resin will in such embodiments flow through the opening of the runner and into the laminate.

In some embodiments, the one or more valves are self-regulating in response to the reversal of the flow. In some embodiments, the one or more valves may be self-regulating. In some embodiments the one or more valves may have one or more, e.g. two pivot pins, and one or more flaps, such as two flaps, respectively connected to the pivot pins. The one or more flaps may create a barrier when the resin flows against the flow direction. In some embodiments, the one or more valves may comprise a flap rotating about a pivot point.

In some embodiments, the first and second runner and the one or more valves are circular in cross-section with a diameter between 20-30 cm. In some embodiments, the valve is housed in a housing that extends 50 mm, such as 30 mm. The valve may therefore be slotted within the runners and held in place by the housing contacting the runner.

Having self-regulating valves allows for the passive use of the current invention, wherein the valves can be placed in the runners and the flow of the resin can be controlled without the need of interaction or instruction from the user.

In some embodiments, the one or more valves are periodically placed along the second runner, such as every 5 meters, such as every 10 meters, such as every 2.5 meter.

In some embodiments, the one or more valves are placed within a longitudinal section of the distribution layer, where the height difference between the lowest point and the highest point of the longitudinal section of the distribution layer when placed on a mold exceeds 250 mm. The longitudinal section may be around 5 meters long or 7 meter long. The valves are generally placed where the resin collects during the filling and curing process, such that backfilling in a runner is eliminated or reduced.

In some embodiments, the location of the one or more valves within the longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on a mold for vacuum assisted resin transfer molding of a wind turbine blade and/or a wind turbine blade part. In some embodiments, the one or more valves are able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction.

In some embodiments, the one or more valves may be active valves, which may comprise an actuator that is adapted to change the valve from the open state to the restricted state and from the restricted state to the open, the actuator may be connected to a controller, the controller may be adapted to control the actuator.

In a second aspect a vacuum assisted resin transfer molding assembly for the manufacturing of a wind turbine blade and/or a wind turbine blade part is provided, the vacuum assisted resin transfer molding assembly comprising: a wind turbine blade mold or a wind turbine blade part mold having a mold surface for receiving a laminate, the distribution layer according to the first aspect to be placed over the laminate such that the laminate is between the mold surface and the distribution layer, a vacuum bag to be placed over the distribution layer, such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, and an outlet connectable to a vacuum pump for creating a vacuum between the mold surface and the vacuum bag.

In some embodiments, the mold is configured to be arranged on a horizontal surface, and the mold has a varying mold surface height along a longitudinal direction and/or a transversal direction (e.g. a chord wise direction) of the mold with respect to the horizontal surface.

In some embodiments, the mold surface has a height difference between the lowest point and the highest point in the longitudinal direction and wherein the height difference between the lowest point and the highest point in the longitudinal direction of the mold exceeds 250 mm.

In some embodiments, the location of the one or more valves within the longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on the mold for vacuum assisted resin transfer of the wind turbine blade and/or the wind turbine blade part.

In some embodiments, the first runner of the distribution layer when placed on the mold is lowest located and the second runner is located at a higher level than the first runner.

In some embodiments, the one or more runners extend along the extension of the mold, such as at least along 90 %, or 80 %, or 70%, of the extension of the mold.

In a third aspect, a method for manufacturing a wind turbine blade and/or a wind turbine blade part is provided. The method comprises: providing the vacuum assisted resin transfer molding assembly according to the second aspect, laying up one or more laminates on the mold surface of the mold, laying the distribution layer over the one or more laminates such that the one or more laminates are arranged between the mold surface and the distribution layer, connecting the inlet of the distribution layer to a resin reservoir, laying the vacuum bag over the distribution layer such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, connecting the outlet to a vacuum pump, creating a vacuum using the vacuum pump to draw resin into the distribution layer, curing the resin.

In some embodiments, the step of drawing resin into the distribution layer may further comprise sequentially filling the laminate with resin by first distributing resin using the first runner followed by distributing resin using the second runner.

In a fourth aspect, the present disclosure relates to a distribution layer for vacuum assisted resin transfer molding of a wind turbine blade part in a mold placed on a horizontal surface, wherein the mold has a varying mold surface height along a longitudinal direction of the mold with respect to the horizontal surface, the distribution layer comprising:

- a number of runners, including a first runner, extending in a longitudinal direction and being adapted to distribute resin throughout the mold,

- a plurality of inlets, including a first inlet and a second inlet, for receiving resin and being connected to one or more of the number of runners, wherein the first inlet and the second inlet are connected to the first runner,

- one or more valves, including a first valve, located within the number of runners, wherein the first valve is located in the first runner between the first and second inlet and configured to restrict flow within the first runner to one flow direction between the first inlet and the second inlet.

The resin inlets are preferably located at the runner such that when the runner is placed in the mold, the resin inlets are arranged at different elevations of the mold along the longitudinal direction, such that the laminate can be sequentially filled by resin from the lower to the higher located parts of the runner in the longitudinal direction. This is particularly advantageous when the resin has to travel up a height gradient. In this way, the resin does not have to travel as far and accumulation of resin at the lowest height compared to the horizontal surface may be avoided.

Each of the first and second inlets may comprise an entry-valve or other means for connecting the runner to the resin reservoir for allowing resin to flow through a specific inlet in a specific filling schedule. Thus, in cases where the lower parts of the mold have been sufficiently filled with resin, the resin inlet located in this part of the mold can be blocked such that resin only flows in through inlets at higher located parts of the runner, where the mold have not yet been sufficiently filled. This is advantageous, since it helps to prevent overfilling of the lower located parts of the mold.

However, if resin is only added to the runner at a higher position, it may also travel down the height gradient risking accumulation of resin in some areas of the mold. Particularly, if a runner is empty or partly empty, the resin may flow backwards using the path of least resistance which may be the runner e.g., causing a backfilling process. This creates uneven filling, which may lead to regions of the molded part containing dry fiber and/or regions of excessive amount of resin, which may reduce the strength of the molded part.

The present disclosure solves this problem by having one or more valves located within a runner, such as the first runner, adapted to restrict flow to one flow direction. Particularly, the one or more valves may be arranged between two adjacent resin inlets configured to be arranged at different elevations along the longitudinal direction of the mold and restrict flow from the highest located inlet to the lowest located inlet.

In some embodiments, the wind turbine blade part is a wind turbine blade shell member or a spar cap or a shear web.

In some embodiments, the mold surface has a convex shape along part of the longitudinal direction of the mold. In some embodiments, the mold surface has a concave shape along part of the longitudinal direction of the mold.

In some embodiments, the distribution layer is configured to be arranged in the mold such that the first runner extends along the longitudinal direction of the mold.

In some embodiments, the distribution layer is configured to be arranged in the mold such that the first inlet is arranged lower than the second inlet with respect to the horizontal surface or such that the first inlet is arranged higher than the second inlet with respect to the horizontal surface, when the distribution layer is placed in the mold for vacuum assisted resin transfer molding of the wind turbine blade part.

In some embodiments, the first runner is arranged along a longitudinal section of the distribution layer, where the height difference between the lowest point and the highest point in the longitudinal section of the distribution layer, when placed on a mold for vacuum assisted resin transfer molding of a wind turbine blade part, exceeds 250 mm. In some embodiments, the resin flow and pressure through each of the number of inlets can be individually controlled for each of the number of inlets.

It is advantageous to have several separately controlled resin inlets arranged at different heights compared to the horizontal surface, since it allows resin filling in different areas of the mold to be better controlled. Particularly when the resin has to travel up a height gradient, it is advantageous to have one inlet arranged at the lowest height compared to the horizontal surface, and one or more inlets arranged higher compared to the horizontal surface. In this way, the resin does not have to travel as far against the height gradient and accumulation of resin at the lowest height compared to the horizontal surface may be avoided or at least reduced.

In some embodiments, the distribution layer comprises at least three inlets, including the first inlet, the second inlet and a third inlet. In some embodiments, the second inlet is arranged between the first and third inlet. In some embodiments, the first and third inlet are configured to be arranged lower than the second inlet with respect to the horizontal surface. In some embodiments, the first and third inlet are configured to be arranged higher than the second inlet with respect to the horizontal surface.

In some embodiments, the one or more valves are configured to restrict resin flow to one flow direction between two inlets, such as two adjacent inlets, of the number of inlets.

In some embodiments, the first runner comprises at least two valves, e.g. including the first valve and a second valve. In some embodiments, the first valve is configured to restrict resin flow in a first flow direction, and the second valve is configured to restrict resin flow in a second flow direction. In some embodiments, the first flow direction is the same as the second flow direction. In some embodiments, the first flow direction is opposite the second flow direction.

In some embodiments, the first valve is arranged between the first inlet and the second inlet and the second valve is arranged between the second inlet and the third inlet.

In some embodiments, the first valve restricts flow to a first flow direction within the first runner between the first and second inlet and wherein the second valve restricts flow to a second flow direction within the first runner between the second and third inlet, wherein the first flow direction is opposite the second flow direction within the first runner. In some embodiments, the first valve restricts flow from the first inlet to the second inlet and the second valve restricts flow from the third inlet to the second inlet. In some embodiments, the first valve restricts flow from the second inlet to the first inlet and the second valve restricts flow from the second inlet to the third inlet. In some embodiments, the one or more valves are configured to restrict resin flow to one flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%.

In some embodiments, the one or more valves are self-regulating comprising two pivot pins and two flaps respectively connected to the pivot pins, the flaps creating a barrier when the resin flows against the flow direction. In some embodiments, the one or more valves may comprise a flap rotating around a pivot point.

In some embodiments, the one or more valves are able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction.

In some embodiments, the one or more valves are self-regulating in response to the reversal of the flow.

In some embodiments, the one or more valves comprises an actuator that is adapted to change the valve from the open state to the restricted state and from the restricted state to the open state, the actuator is connected to a controller, the controller being adapted to control the actuator.

In some embodiments, each of the number of runners has an omega-shaped cross section with an opening extending along the length of the respective number of runners.

In some embodiments, the distribution layer comprises at least two runners, including the first runner and a second runner. The number of runners generally depends on the size of the molded part. For the manufacture of a shell member, several runners would normally be used due to the size of the laminate. However, for other wind turbine blade parts, such as a spar cap made offline i.e., separate from the blade shell, a single runner may be sufficient. Thus, the distribution layer may comprise one or several runners, wherein one or more runners are connected to at least two resin inlets.

In some embodiments, the second runner is connected to a plurality of inlets for receiving resin and wherein the second runner comprises one or more valves configured to restrict resin flow to one flow direction between two inlets.

In some embodiments, the first inlet, the second inlet and the first runner, and optionally the second runner, are placed to ensure a uniform distribution of resin during the resin transfer molding. In some embodiments, the distribution layer is a net configured to distribute resin throughout a laminate.

In some embodiments, the first and/or second runner does not extend beyond the distribution layer.

In a fifth aspect, the present disclosure relates to a vacuum assisted resin transfer molding assembly for the manufacturing of a wind turbine blade part, the vacuum assisted resin transfer molding assembly comprising:

- a wind turbine blade part mold configured to be arranged on a horizontal surface and having a mold surface for receiving a laminate,

- a distribution layer according to the third aspect of the disclosure to be placed over the laminate such that the laminate is arranged between the mold surface and the distribution layer (50),

- a vacuum bag (60) to be placed over the distribution layer (50) such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, and

- an outlet (54) connectable to a vacuum pump (62) for creating a vacuum between the mold surface and the vacuum bag (60).

In some embodiments, the mold is configured to be arranged on a horizontal surface, and the mold have a varying mold surface height along a longitudinal direction and/or a transversal direction (e.g. a chord wise direction) of the mold with respect to the horizontal surface.

In some embodiments, the location of the one or more valves within a longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on the mold for vacuum assisted resin transfer of the wind turbine blade and/or wind turbine blade part.

In a sixth aspect, the present disclosure relates to a method for manufacturing a wind turbine blade part, the method comprising:

- providing the vacuum assisted resin transfer molding assembly according to the fifth aspect of the disclosure, - laying up one or more laminates on the mold surface of the mold,

- laying the distribution layer over the one or more laminates such that the one or more laminates are arranged between the mold surface and the distribution layer,

- connecting the inlet of the distribution layer to a resin reservoir,

- laying the vacuum bag over the distribution layer such that the distribution layer and the laminate are enclosed by the mold surface and the vacuum bag,

- connecting the outlet to a vacuum pump,

- creating a vacuum using the vacuum pump to draw resin into the distribution layer,

- curing the resin.

In some embodiments, when the mold surface comprises a convex shape in the longitudinal direction, the step of drawing resin into the distribution layer comprises,

- sequentially filling the laminate with resin by first distributing resin using the first and/or third inlet followed by distributing resin using the second inlet.

In some embodiments, when the mold surface comprises a concave shape in the longitudinal direction, the step of drawing resin into the distribution layer comprises,

- sequentially filling the laminate with resin by first distributing resin using the second inlet followed by distributing resin using the first and/or third inlet.

A person skilled in the art will appreciate that any one or more of the above aspects of this disclosure and embodiments thereof may be combined with any one or more of the other aspects of this disclosure and embodiments thereof.

Furthermore, a person skilled in the art will appreciate that terms such as "first", "second" and "third" are not to be construed as limiting but is simply meant to differentiate between several elements of the same type. For example, the term "first runner" and "second runner" as used in the first aspect of the disclosure may be different from the "first runner" and "second runner" in the fourth aspect of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present disclosure and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Fig. 1 is a schematic perspective view of a wind turbine, Fig. 2 is a schematic perspective view of a wind turbine blade for a wind turbine as shown in Fig. 1,

Fig. 3 is a schematic illustration of a vacuum assisted resin transfer molding set-up,

Fig. 4 is a schematic illustration of an embodiment of the distribution layer,

Fig. 5 is a schematic illustration of the problems of a distribution layer,

Fig. 6 is a schematic illustration of resin filling using the distribution layer,

Figs. 7 A), B), and C) are schematic illustrations of a self-regulating valve that restricts return flow,

Figs. 8 A) and B) are schematic illustrations of an aspect where the distribution layer comprises one runner and two resin inlets.

DETAILED DESCRIPTION

In the following figure description, the same reference numbers refer to the same elements and may thus not be described in relation to all figures. The figures show one way of implementing the system and is not to be construed as being limiting to other possible embodiments falling with the scope of the attached claim set.

Fig. 1 illustrates a conventional modern upwind wind turbine 2 according to the so-called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft which may include a tilt angle of a few degrees. 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 exemplary wind turbine blade 10. The wind turbine blade 10 has the shape of a conventional wind turbine blade with a root end 17 and a tip end 15 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 8, 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 region 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

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.

In order to manufacture the wind turbine blade vacuum assisted resin transfer molding assembly and method is utilized. As shown in fig. 3, a transfer molding vacuum assisted resin transfer molding assembly comprises a wind turbine blade mold 44 having a mold surface for receiving a laminate 48 or fiber layup, a distribution layer 50 placed over the laminate in such a way that the laminate is between the mold surface and the distribution layer 50, a vacuum bag 60 placed over the distribution layer 50. The vacuum bag being placed in such a manner that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag. The vacuum bag 60 further comprises an outlet 54 connectable to a vacuum pump 62 for creating a vacuum between the mold surface and the vacuum bag 60.

As seen in fig. 3, the distribution layer 50 comprises a first runner 56 and a second runner 72, that runs along the length of the mold, as seen in fig. 4. In fig. 4 multiple runners are shown. The first and second runner are preferably located at different elevations of the mold, such that the laminate can be sequentially filled by resin from the lowest to the highest located runner. As seen in fig. 3 in an embodiment the first runner is the lowest located runner. Each of the first and second runner may comprise an entry-valve at the inlet 52 or other means for connecting the runners to the resin reservoir 46 for allowing resin to flow through a specific runner in a specific filling schedule. In another embodiment a single inlet may be interchangeable between the runners or multiple inlets connected to the resin reservoir. Therefore, different means can be used to sequentially fill the mold.

As shown in fig. 5 a distribution layer may have the disadvantage that during the filling process accumulation of resin occurs in the laminate. In fig. 5 the arrows represent the flow of resin. This resin will flow through the path of least resistance which, when filling with the first runner, may be the second runner, which due to the sequential filling schedule is empty. This is further seen by the arrows in fig. 5 which represent the flow of the resin. This creates an uneven and/or uncontrolled filling of the laminate and may create patches of dry glass in the laminate, which can compromise the integrity of the blade.

The current disclosure therefore provides for a distribution layer that creates a more even filling of the laminate. As seen in fig. 4 the current disclosure provides for a distribution layer 50 and vacuum assisted resin transfer molding assembly 42, wherein the distribution layer includes a first runner 56 and a second runner 58, and one or more valves located within the second runner, e.g. placed inline in the second runner. Accordingly, the one or more valves are placed within the runner. The valves are adapted to restrict return flow, with the flow 68 being from the inlet to the end of the runners, as seen in the fig. 4. The one or more valves provides a restrictive force to the resin trying to back-fill through the second runner and will accordingly modify the path of least resistance and allow the laminate to be filled more evenly and with increased control, as seen in fig. 6. As seen in fig. 6 by having valves 58 that restrict return flow, a more even and controlled filling process is achieved, since the runners are sectionalized.

As seen in fig. 6 each runner may in some embodiments comprise more than one valve and the general placement of the valve may be provided to ensure that the resin does not flow back through a higher placed runner when a lower placed runner is filling the laminate with resin. The first runner, which, in the illustrated examples, is the lowest located runner, will in some embodiments not contain a valve, since it will be the first runner distributing resin, thereby always filled, and the path of least restriction will typically not be backfilling through the lowest runner, since it will in most circumstances contain resin throughout. However, it may be advantageous in some embodiments for the first runner to include a valve.

The one or more valves may ensure that the path of least resistance for the resin is not through a different or a higher placed runner. The one or more valves are adapted to in some embodiments restrict flow opposite the flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%. However, other percentages may be envisioned. The one or more valves creates a barrier for the return flow and thereby ensures that return flow is eliminated or at least reduced in non-distributing runners. The effect of the one or more valves can be seen in fig. 6, where it is shown that a more even and controlled filling of the laminate is achieved compared to a situation without the valves as seen in fig. 5.

In some embodiments, the first and second runner and the one or more valves are circular in crosssection with a diameter between 20-30 cm. In some embodiments, the one or more valves may not cover the entire cross-section of the runner, as seen in fig. 7 A), where the valve only partially covers the cross-sectional area of the runner. The runners have in some embodiments an omega-shaped cross-section 70 as shown in fig. 7 A) comprising a continuous or partially continuous opening 72 for distributing the resin throughout the mold. The resin is therefore drawn out by the created vacuum in the runners and is distributed by the open channel throughout the laminate.

As seen in fig. 4, the inlets 52 and runners 56 are placed to ensure a uniform distribution of resin during the resin transfer molding. For the wind turbine blade shown in fig. 4 five runners are illustrated in order to ensure a uniform distribution. Further, as seen in fig. 4 the second runner may in some embodiments comprise two or more valves. The number of valves is generally chosen and located such that the filling of the laminate is uniform. As seen in fig. 4 one of the runners, e.g., a third runner, contains three valves. In some embodiments, the one or more valves are periodically placed along the second runner, such as every 5 meters. In some embodiments only certain sections of the runner contain valves, for example the section with the greatest height difference. In one embodiment, the one or more valves comprises a primary valve and a secondary valve, wherein the primary valve and the secondary valve are located in the second runner with a distance between the primary valve and the secondary valve is 3 meters, or 5 meters.

In some embodiments, the placement of the one or more valves in the runner is based on the height gradient of the distribution layer when the distribution layer is placed on the mold. Since the valves are designed to stop the return flow in the filling process, it is a particular problem in areas where the heigh gradient is large, due to the mold being curved. Therefore, the one or more valves are placed within a longitudinal section of the distribution layer, when the height difference between the lowest point and the highest point of the longitudinal section of the distribution layer when placed on the mold of the vacuum assisted resin transfer molding assembly exceeds 250 mm. In other embodiments the height difference may be 2500 mm. The valves can in some embodiments be placed periodically within the longitudinal section. The length of the longitudinal sections depends on the blade length, but may in some embodiments be between 5 meters and 10 meters.

In one embodiment, the valves are mechanically self-regulating, as seen in fig. 7. As seen in fig. 7 A), the valve comprises two pivot pins 64 and two flaps 66 respectively connected to the pivot pins 64, the flaps creating a barrier when the resin flows against the flow direction. Shown in fig. 7 B) is the open configuration of the flaps, where the arrow represents the flow. As seen, when the flow is in the flow direction, the flaps are open and allow resin to flow in the runner. In fig. 7 c) when the flow is opposite to the flow direction, the flaps are closed restricting return flow. As seen in fig. 7 the flaps are closed or opened by the reversal of the flow, thereby allowing for a self-regulating valve. Other types of self-regulating valves can be used or active valves facilitating manual opening and/or closing may be used. In some embodiments, the valves may be of a butterfly type valve. In some embodiments, the valve may comprise a flap rotating around a pivot point. The one or more valves may be able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction. An actuator or other opening and/or closing means may be connected to the valve for actively changing the state of the valve from the closed to the opened state and vice versa. The actuator may be controllable by a controller. In some embodiments, the state of the valve may be controlled by the use of magnet, wherein the closing and opening mechanism of the valve is controllable by the use of magnet. A user or operator of the process could therefore use a magnet on the exterior of the vacuum pump to change the state of the valve from the open state to the close state or vice versa.

In some embodiments the second runner may contain one or more sensors, which is adapted to sense when resin is backfilling through the second runner. The sensor may be in communication with the controller and the controller may, based on the sensed signal, open or close the valve using the actuator.

Accordingly manufacturing the wind turbine blade by using the distribution layer and vacuum assisted resin transfer molding assembly of the current disclosure may comprise: laying up one or more laminates on the surface of the mold, laying the distribution layer over the one or more laminates such that the one or more laminates are arranged between the mold surface and the distribution layer, connecting the inlet of the distribution layer to a resin reservoir, laying the vacuum bag over the distribution layer such that the distribution layer and the laminate are enclosed by the mold surface and the vacuum bag, connecting the outlet to a vacuum pump, creating a vacuum using the vacuum pump to draw resin into the distribution layer, and curing the resin.

In some embodiments, the method may further comprise sequentially filling the laminate with resin by first distributing resin using the first runner followed by distributing resin using the second runner. Fig. 8 A) and B) show schematic illustrations of another aspect of the disclosure, namely one where the distribution layer in its simplest form comprises only one runner and two resin inlets connected to that runner instead of comprising two runners and one resin inlet as is the case in the simplest embodiment of another aspect of the disclosure.

The number of runners generally depends on the size of the molded element. For the manufacture of a shell member, several runners would normally be used due to the size of the laminate.

However, for other wind turbine blade parts, such as a spar cap made offline i.e., separate from the blade shell, a single runner may be sufficient. Thus, the distribution layer in accordance with the present aspect may comprise one or several runners, wherein one or more runners are connected to at least two resin inlets. The distribution layer 50 in accordance with fig. 8 is configured for vacuum assisted resin transfer molding of a spar cap mold 44. Fig. 8A illustrates one mold for a spar cap, e.g. an upwind spar cap. Fig. 8A illustrates another mold for a spar cap, e.g. a downwind spar cap. Each of Figs. 8A and 8B illustrates a side view (upper part of the figure) showing the varying height of the respective mold

44 along the longitudinal direction and a top view of the distribution layer 50 (lower part of the figure) to be arranged over the mold 44. The two spar cap mold surfaces 45 illustrated in figs. 8A and 8B both have a varying mold surface height 76 along a longitudinal direction 74 of the mold with respect to a horizontal surface. This is because the spar cap mold 44 follows the contour of the desired shape of the wind turbine blade in which the spar cap is to be arranged. Thus, when manufacturing spar caps for wind turbine blades with pre-bend, the spar cap mold 44 also need to be curved along part of the longitudinal direction 74 of the mold. In Fig 8A, the mold surface 45 has a convex shape along part of a longitudinal direction 74 of the mold and in Fig. 8B, the mold surface

45 has a concave shape along part of a longitudinal direction 74 of the mold.

The distribution layer 50 as illustrated in Fig. 8A, and 8B, comprises one runner referred to as a first runner 56 with reference to fig. 8. The first runner 56 extends in a longitudinal direction 74 and is adapted to distribute resin throughout the spar cap mold 44.

As illustrated, the distribution layer 50 is configured to be arranged in the spar cap mold 44 such that the first runner 56 extends along the longitudinal direction 74 of the spar cap mold 44. Thus, the first runner 56 in the distribution layer 50 will follow the shape of the mold surface 45 when arranged in the mold on top of the laminate.

Furthermore, the distribution layer 50 of fig. 8 comprises three inlets, including a first inlet 52a, a second inlet 52b and a third inlet 52c, connected to the first runner 56 and being configured for receiving resin.

The individually controlled resin inlets 52 are preferably located at the runner 56 such that when the distribution layer 50 is placed in the mold 44, the resin inlets are arranged at different elevations of the mold along the longitudinal direction of the mold 74, such that the laminate can be sequentially filled by resin from the lower to the higher located parts of the first runner 56 along the longitudinal direction 74. This is particularly advantageous when the resin has to travel up a height gradient, as seen in the illustrated example. In this way, the resin does not have to travel as far and accumulation of resin at the lowest height compared to the horizontal surface may be avoided.

Each of the inlets 52a, 52b, 52c may comprise an entry-valve or other means for connecting the runner to the resin reservoir 46 for allowing resin to flow through a specific inlet 52a, 52b, 52c in a specific filling schedule. Thus, in cases where the lower parts of the mold 44 have been sufficiently filled with resin, the resin inlet (e.g. 52a or 52c in fig. 8A, and 52b in Fig. 8B) located in this part of the mold can be blocked, such that resin is only added at higher located parts of the first runner 56, where the mold 44 have not yet been sufficiently filled. This is advantageous, since it helps to prevent overfilling of the lower located parts of the mold 44.

However, if resin is only added to the first runner 56 at a high position, it may also travel downwards risking accumulation of resin in some areas of the mold 44. Particularly, if a runner is empty or partly empty, the resin may flow backwards using the path of least resistance which may be the runner e.g., causing a backfilling process. This may cause uneven filling, which may lead to regions of the blade containing dry glass and/or regions comprising excessive amount of resin, which may reduce the strength of the blade.

The present disclosure solves this problem by having valves 58a, 58b located within the first runner 56, adapted to restrict flow to one flow direction. The valves 58a, 58b are arranged between two adjacent resin inlets 52a, 52b, 52c arranged at different elevations along the longitudinal direction of the mold.

As seen in fig. 8, two valves are arranged within the first runner, including a first valve 58a and a second valve 58b. The first valve 58a is arranged between the first and second inlet 52a, 52b and the second valve 58b is arranged between the second and third inlet 52b, 52c. In both embodiments, the first valve 58a restricts flow to a first flow direction within the first runner 56 between the first and second inlet 52a, 52b, whereas the second valve 58b restricts flow to a second flow direction within the first runner 56 between the second and third inlet 52b, 52c. The first flow direction is opposite the second flow direction within the first runner 56.

In Fig. 8A, the first valve 58a restricts flow from the second inlet 52b to the first inlet 52a, whereas the second valve 58b restricts flow from the second inlet 52b to the third inlet 52c. In Fig. 8B, the first valve 58a restricts flow from the first inlet 52a to the second inlet 52b and the second valve 58b restricts flow from the third inlet 52c to the second inlet 52b.

Thus, the valves 58a, 58b located within the first runner 56 provides a restrictive force to the resin trying to back-fill through the runner 56 from the highest located resin inlet towards the lowest located resin inlet. This allows resin filling in different areas of the mold to be better controlled. By having valves 58a, 58b that restrict return flow, a more even and controlled filling process may be achieved. Itemized list of embodiments of the disclosure:

1. A distribution layer for vacuum assisted resin transfer molding of a wind turbine blade part in a mold placed on a horizontal surface, wherein the mold has a varying mold surface height along a longitudinal direction of the mold with respect to the horizontal surface, the distribution layer comprising:

2. A distribution layer according to item 1, wherein the wind turbine blade part is a wind turbine blade shell member or a spar cap or a shear web.

3. A distribution layer according to any of the preceding items, wherein the mold surface has a convex shape along part of a longitudinal direction of the mold.

4. A distribution layer according to any of the preceding items, wherein the mold surface has a concave shape along part of a longitudinal direction of the mold.

5. A distribution layer according to any of the preceding items, wherein the distribution layer is configured to be arranged in the mold such that the first runner extend along the longitudinal direction of the mold.

6. A distribution layer according to any of the preceding items, wherein the distribution layer is configured to be arranged in the mold such that the first inlet is arranged lower than the second inlet with respect to the horizontal surface or such that the first inlet is arranged higher than the second inlet with respect to the horizontal surface, when the distribution layer is placed in the mold for vacuum assisted resin transfer molding of the wind turbine blade part.

7. The distribution layer according to any of the preceding items, wherein the first runner is arranged along a longitudinal section of the distribution layer, where the height difference between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on a mold for vacuum assisted resin transfer molding of a wind turbine blade part exceeds 250 mm.

8. The distribution layer according to any of the preceding items, wherein resin flow and pressure through each of the number of inlets can be individually controlled for each of the number of inlets.

9. The distribution layer according to any of the preceding items, wherein the distribution layer comprises at least three inlets, including the first inlet, the second inlet and a third inlet.

10. The distribution layer according to item 9, wherein the second inlet is arranged between the first and third inlet.

11. The distribution layer according to any of items 9-10, wherein the first and third inlet are configured to be arranged lower than the second inlet with respect to the horizontal surface.

12. The distribution layer according to any of items 9-11, wherein the first and third inlet are configured to be arranged higher than the second inlet with respect to the horizontal surface.

13. The distribution layer according to any of the preceding items, wherein the one or more valves are configured to restrict resin flow to one flow direction between two inlets.

14. The distribution layer according to any of the preceding items, wherein the one or more valves are configured to restrict resin flow to one flow direction between two adjacent inlets of the number of inlets.

15. The distribution layer according to any of the preceding items, wherein the first runner comprises at least two valves including the first valve and a second valve,

16. The distribution layer according to item 15, wherein the first valve is configured to restrict resin flow in a first flow direction, and the second valve is configured to restrict resin flow in a second flow direction,

17. The distribution layer according to item 16, wherein the first flow direction is the same as the second flow direction

18. The distribution layer according to item 16, wherein the first flow direction is opposite the second flow direction. 19. The distribution layer according to any of items 15-18, as dependent on any of items 9-12, wherein the first valve is arranged between the first inlet and the second inlet and the second valve is arranged between the second inlet and the third.

20. The distribution layer according to item 19, wherein the first valve restricts flow from the first inlet to the second inlet and wherein the second valve restricts flow from the third inlet to the second inlet.

21. The distribution layer according to item 19, wherein the first valve restricts flow from the second inlet to the first inlet and wherein the second valve restricts flow from the second inlet to the third inlet.

22. The distribution layer according to any of the preceding items, wherein the one or more valves are configured to restrict resin flow to one flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%.

23. The distribution layer according to any of the preceding items, wherein the one or more valves are self-regulating comprising two pivot pins and two flaps respectively connected to the pivot pins, the flaps creating a barrier when the resin flows against the flow direction or wherein the one or more valves comprises a flap rotating around a pivot point.

24. The distribution layer according to any of the preceding items, wherein the one or more valves are able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction.

25. The distribution layer according to any of the preceding items, wherein the one or more valves are self-regulating in response to the reversal of the flow.

26. The distribution layer according to item 24, wherein the one or more valves comprises an actuator that is adapted to change the valve from the open state to the restricted state and from the restricted state to the open, the actuator is connected to a controller, the controller being adapted to control the actuator.

27. The distribution layer according to any of the preceding items, wherein each of the number of runners has an omega-shaped cross section with an opening extending along the length of the respective number of runners. 28. The distribution layer according to any of the preceding items, wherein the distribution layer comprises at least two runners, including the first runner and a second runner.

29. The distribution layer according to any of the preceding items, wherein the second runner is connected to a plurality of inlets for receiving resin and wherein the second runner comprises one or more valves configured to restrict resin flow to one flow direction between two inlets.

30. The distribution layer according to any of the preceding items wherein the first inlet, the second inlet and the first runner are placed to ensure a uniform distribution of resin during the resin transfer molding.

31. The distribution layer according to any of the preceding items wherein the distribution layer is a net configured to distribute resin throughout a laminate.

32. The distribution layer according to any of the preceding items wherein the first and second runner does not extend beyond the distribution layer.

33. A vacuum assisted resin transfer molding assembly for the manufacturing of a wind turbine blade part, the vacuum assisted resin transfer molding assembly comprising:

- a wind turbine blade part mold configured to be arranged on a horizontal surface and having a mold surface for receiving a laminate (48),

- a distribution layer according to any of items 1-32 to be placed over the laminate such that the laminate is arranged between the mold surface and the distribution layer,

- a vacuum bag to be placed over the distribution layer such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, and

- an outlet connectable to a vacuum pump for creating a vacuum between the mold surface and the vacuum bag.

34. The vacuum assisted resin transfer molding assembly according to item 33, wherein the mold is configured to be arranged on a horizontal surface, and the mold have a varying mold surface height along a longitudinal direction and/or a transversal direction (e.g. a chord wise direction) of the mold with respect to the horizontal surface. 35. The vacuum assisted resin transfer molding assembly according to any of items 33 or 34, wherein the mold surface has a height difference between the lowest point and the highest point in the longitudinal direction and wherein the height difference between the lowest point and the highest point in the longitudinal direction of the mold exceeds 250 mm.

36. The vacuum assisted resin transfer molding assembly according to any of items 33-35, wherein the location of the one or more valves within a longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on the mold for vacuum assisted resin transfer of the wind turbine blade and/or the wind turbine blade part.

37. A method for manufacturing a wind turbine blade part, the method comprising:

- providing the vacuum assisted resin transfer molding assembly according to any of items 33-36,

- laying up one or more laminates on the mold surface of the mold,

- connecting the inlet of the distribution layer to a resin reservoir,

- laying the vacuum bag over the distribution layer such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag,

- connecting the outlet to a vacuum pump,

- curing the resin.

38. A method according to item 37, wherein when the mold surface comprises a convex shape in the longitudinal direction, the step of drawing resin into the distribution layer comprises

39. A method according to item 37, wherein when the mold surface comprises a concave shape in the longitudinal direction, the step of drawing resin into the distribution layer comprises

40. A distribution layer for vacuum assisted resin transfer molding such as for vacuum assisted resin transfer molding of a wind turbine blade and/or a wind turbine blade part, the distribution layer comprising: - an inlet for receiving resin,

- a first runner and a second runner connected to the inlet and extending away from the inlet, the first and second runners defining a flow direction of the resin, the first and second runner being adapted to distribute the resin throughout a mold for the vacuum assisted resin transfer molding,

- one or more valves (58) located within the second runner, restricting flow opposite to the flow direction.

41. The distribution layer according to item 40, wherein the inlet and the first and second runners are placed to ensure a uniform distribution of resin during the resin transfer molding.

42. The distribution layer according to any of items 40 or 41, wherein the one or more valves restrict flow opposite the flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%.

43. The distribution layer according to any of the preceding items 40-42, wherein the one or more valves (58) restrict flow to one flow direction within the runner.

44. The distribution layer according to any of the preceding items 40-43, wherein each of the first and the second runner has an omega-shaped cross section with an opening extending along the length of the respective first and second runner.

45. The distribution layer according to any of the preceding items 40-44, wherein the second runner comprises two or more valves and/or the first runner comprises no valves.

46. The distribution layer according to any of the preceding items 40-45, wherein the one or more valves are self-regulating comprising two pivot pins and two flaps respectively connected to the pivot pins, the flaps creating a barrier when the resin flows against the flow direction or wherein the one or more valves comprise a flap rotating around a pivot point.

47. The distribution layer according to any of the preceding items 40-46, wherein the one or more valves are placed within a longitudinal section of the distribution layer, where the height difference between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on a mold of a vacuum assisted resin transfer molding assembly exceeds 250 mm.

48. The distribution layer according to any of the preceding items 40-47, wherein the location of the one or more valves within the longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on a mold for vacuum assisted resin transfer of a wind turbine blade and/or wind turbine blade part.

49. The distribution layer according to any of the preceding items 40-48, wherein the one or more valves is able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction.

50. The distribution layer according to any of the preceding items 40-49, wherein the one or more valves are self-regulating in response to the reversal of the flow.

51. The distribution layer according to any of the preceding items 40-50, wherein the one or more valves comprises an actuator that is adapted to change the valve from the open state to the restricted state and from the restricted state to the open, the actuator is connected to a controller, the controller being adapted to control the actuator.

52. The distribution layer according to any of the preceding items 40-51, wherein the distribution layer is a net configured to distribute resin throughout a laminate.

53. The distribution layer according to any of the preceding items 40-52, wherein the first and second runner do not extend beyond the distribution layer.

54. A vacuum assisted resin transfer molding assembly for the manufacturing of a wind turbine blade and/or a wind turbine blade part, the vacuum assisted resin transfer molding assembly comprising:

- a wind turbine blade mold or a wind turbine blade part mold having a mold surface for receiving a laminate,

- a distribution layer according to any of items 40-53 to be placed over the laminate such that the laminate is between the mold surface and the distribution layer,

- a vacuum bag to be placed over the distribution layer and such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, and

55. The vacuum assisted resin transfer molding assembly according to item 54, wherein the mold is configured to be arranged on a horizontal surface, and the mold have a varying mold surface height along a chord-wise and a longitudinal direction of the mold with respect to the horizontal surface. 56. The vacuum assisted resin transfer molding assembly according to any of items 54-55, wherein the mold surface has a height difference between the lowest point and the highest point in the longitudinal direction and wherein the height difference between the lowest point and the highest point in the longitudinal direction of the mold exceeds 250 mm.

57. The vacuum assisted resin transfer molding assembly according to any of items 54-56, wherein the location of the one or more valves within the longitudinal section of the distribution layer is determined such that the one or more valves are placed between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on the mold for vacuum assisted resin transfer of the wind turbine blade and/or the wind turbine blade part.

58. The vacuum assisted resin transfer molding assembly according to any of items 54-57, wherein the first runner of the distribution layer when placed on the mold is lowest located and the second runner is higher located than the first runner.

59. The vacuum assisted resin transfer molding assembly according to any of items 54-58, wherein the one or more runners extend along the extension of the mold, such as at least along 90% of the extension of the mold.

60. A method for manufacturing a wind turbine blade and/or a wind turbine blade part, the method comprising:

- providing the vacuum assisted resin transfer molding assembly according to any of items 54-59,

- laying up one or more laminates on the mold surface of the mold,

- connecting the inlet of the distribution layer to a resin reservoir,

- connecting the outlet to a vacuum pump,

- curing the resin.

61. A method according to item 60, wherein the step of drawing resin into the distribution layer further comprises

- sequentially filling the laminate with resin by first distributing resin using the first runner followed by distributing resin using the second runner. LIST OF REFERENCES

2 wind turbine 64 pivot pin

4 tower 66 flap

6 nacelle 68 flow direction

8 hub 70 opening 10 blade 40 72 second runner

13 shell 74 longitudinal direction of mold

14 blade tip 76 height of mold

15 tip end

16 blade root 17 root end

18 leading edge

20 trailing edge

30 root region

32 transition region

34 airfoil region

36 tip region

40 shoulder

42 vacuum assisted resin transfer molding assembly

44 wind turbine blade part mold

45 mold surface

46 resin reservoir

48 laminate

50 distribution layer

52 inlet

52a first inlet

52b second inlet

52c third inlet

54 outlet

56 first runner

58 valves

58a first valve

58b second valve

60 vacuum bag

62 vacuum pump

Claims

1. A distribution layer (50) for vacuum assisted resin transfer molding of a wind turbine blade part in a mold (44) placed on a horizontal surface, wherein the mold has a varying mold surface height (76) along a longitudinal direction (74) of the mold (44) with respect to the horizontal surface, the distribution layer (50) comprising:

- a number of runners, including a first runner (56), extending in a longitudinal direction and being adapted to distribute resin throughout the mold (44),

- a plurality of inlets (52), including a first inlet (52a) and a second inlet (52b), for receiving resin and being connected to one or more of the number of runners, wherein the first inlet (52a) and the second inlet (52b) are connected to the first runner (56),

- one or more valves, including a first valve (58a), located within the number of runners, wherein the first valve (58a) is located in the first runner (56) between the first and second inlet (52a, 52b) and configured to restrict flow within the first runner (56) to one flow direction between the first inlet (52a) and the second inlet (52b).

2. A distribution layer (50) according to claim 1, wherein the wind turbine blade part is a wind turbine blade shell member or a spar cap or a shear web.

3. A distribution layer (50) according to any of the preceding claims, wherein the distribution layer (50) is configured to be arranged in the mold (44) such that the first runner (56) extend along the longitudinal direction of the mold (74) and wherein the distribution layer (50) is configured to be arranged in the mold (44) such that the first inlet (52a) is arranged lower than the second inlet (52b) with respect to the horizontal surface or such that the first inlet (52a) is arranged higher than the second inlet (52b) with respect to the horizontal surface, when the distribution layer is placed in a mold (44) for vacuum assisted resin transfer molding of a wind turbine blade part.

4. The distribution layer (50) according to any of the preceding claims, wherein resin flow and pressure through each of the number of inlets (52) can be individually controlled for each of the number of inlets (52).

5. The distribution layer (50) according to any of the preceding claims, wherein the distribution layer comprises at least three inlets (52), including the first inlet (52a), the second inlet (52b) and a third inlet (52c).

6. The distribution layer (50) according to claim 5, wherein the second inlet (52b) is arranged between the first inlet (52a) and the third inlet (52c).

7. The distribution layer (50) according to any of claims 5-6, wherein the first and third inlet (52a, 52c) are configured to be arranged lower than the second inlet (52b) with respect to the horizontal surface or wherein the first and third inlet (52a, 52c) are configured to be arranged higher than the second inlet (52b) with respect to the horizontal surface.

8. The distribution layer (50) according to any of the preceding items, wherein the first runner (56) comprises at least two valves including the first valve (58a) and a second valve (58b), wherein the first valve (58a) is configured to restrict resin flow in a first flow direction, and the second valve (58b) is configured to restrict resin flow in a second flow direction, and wherein the first flow direction is opposite the second flow direction.

9. The distribution layer (50) according to claim 8, as dependent on any of claims 5-7, wherein the first valve (58a) is arranged between the first inlet (52a) and the second inlet (52b) and the second valve (58b) is arranged between the second inlet (52b) and the third inlet (52c).

10. The distribution layer (50) according to claim 9, wherein the first valve (58a) restricts flow from the first inlet (52a) to the second inlet (52b) and wherein the second valve (58b) restricts flow from the third inlet (52c) to the second inlet (52b) or wherein the first valve (58a) restricts flow from the second inlet (52b) to the first inlet (52a) and wherein the second valve (58b) restricts flow from the second inlet (52b) to the third inlet (52c).

11. The distribution layer (50) according to any of the preceding claims, wherein the one or more valves (58) are self-regulating comprising two pivot pins (64) and two flaps (66) respectively connected to the pivot pins (64), the flaps creating a barrier when the resin flows against the flow direction or wherein the one or more valves comprise a flap rotating around a pivot point.

12. The distribution layer (50) according to any of the preceding claims, wherein the one or more valves (58) are self-regulating in response to the reversal of the flow.

13. The distribution layer (50) according to any of the preceding claims, wherein each of the number of runners has an omega-shaped cross section with an opening extending along the length of the respective number of runners.

14. A vacuum assisted resin transfer molding assembly (42) for the manufacturing of a wind turbine blade part, the vacuum assisted resin transfer molding assembly (42) comprising: - a wind turbine blade part mold (44) configured to be arranged on a horizontal surface and having a mold surface (45) for receiving a laminate (48),

- a distribution layer (50) according to any of claims 1-13 to be placed over the laminate (48) such that the laminate (48) is arranged between the mold surface (45) and the distribution layer (50),

- a vacuum bag (60) to be placed over the distribution layer (50) such that the distribution layer (50) and the laminate (48) is enclosed by the mold surface (45) and the vacuum bag, and

- an outlet (54) connectable to a vacuum pump (62) for creating a vacuum between the mold surface (45) and the vacuum bag (60).

15. A method for manufacturing a wind turbine blade part, the method comprising:

- providing the vacuum assisted resin transfer molding assembly according to claim 14,

- laying up one or more laminates (48) on the mold surface (45) of the mold (44),

- laying the distribution layer (50) over the one or more laminates (48) such that the one or more laminates (48) are arranged between the mold surface (45) and the distribution layer (50),

- connecting the inlets (52a, 52b, 52c) of the distribution layer (50) to a resin reservoir,

- laying the vacuum bag over the distribution layer (50) such that the distribution layer (50) and the laminate (44) are enclosed by the mold surface (45) and the vacuum bag,

- connecting the outlet to a vacuum pump,

- curing the resin.

16. A distribution layer (50) for vacuum assisted resin transfer molding such as for vacuum assisted resin transfer molding of a wind turbine blade (10) and/or a wind turbine blade part, the distribution layer comprising:

- an inlet (52) for receiving resin,

- a first runner (56) and a second runner (72) connected to the inlet and extending away from the inlet, the first and second runners defining a flow direction of the resin, the first and second runner being adapted to distribute the resin throughout a mold for the vacuum assisted resin transfer molding,

17. The distribution layer according to claim 16, wherein the inlet (52) and the first and second runners (56,72) are placed to ensure a uniform distribution of resin during the resin transfer molding.

18. The distribution layer according to any of the preceding claims 16-17, wherein the one or more valves (58) restrict flow opposite the flow direction by at least 70%, more preferably at least 80%, most preferred at least 90%.

19. The distribution layer according to any of the preceding claims 16-18, wherein each of the first and the second runner has an omega-shaped cross section with an opening extending along the length of the respective first and second runner.

20. The distribution layer according to any of the preceding claims 16-19, wherein the second runner comprises two or more valves and/or the first runner comprises no valves.

21. The distribution layer according to any of the preceding claims 16-20, wherein the one or more valves are self-regulating comprising two pivot pins (64) and two flaps (66) respectively connected to the pivot pins (64), the flaps creating a barrier when the resin flows against the flow direction or wherein the one or more valves comprise a flap rotating around a pivot point.

22. The distribution layer according to any of the preceding claims 16-21, wherein the one or more valves are placed within a longitudinal section of the distribution layer, where the height difference between the lowest point and the highest point in the longitudinal section of the distribution layer when placed on a mold of a vacuum assisted resin transfer molding assembly exceeds 250 mm.

23. The distribution layer according to any of the preceding claims 16-22, wherein the one or more valves is able to be in an open state allowing flow of the resin in the flow direction and in a restricted state restricting flow opposite the flow direction.

24. The distribution layer according to any of the preceding claims 16-23, wherein the one or more valves are self-regulating in response to the reversal of the flow.

25. The distribution layer according to claim 23, wherein the one or more valves comprises an actuator that is adapted to change the valve from the open state to the restricted state and from the restricted state to the open, the actuator is connected to a controller, the controller being adapted to control the actuator.

26. A vacuum assisted resin transfer molding assembly (42) for the manufacturing of a wind turbine blade and/or a wind turbine blade part, the vacuum assisted resin transfer molding assembly (42) comprising:

- a wind turbine blade mold (44) or a wind turbine blade part mold having a mold surface for receiving a laminate (48),

- a distribution layer (50) according to any of claims 16-25 to be placed over the laminate such that the laminate is between the mold surface and the distribution layer (50),

- a vacuum bag (60) to be placed over the distribution layer (50) and such that the distribution layer and the laminate is enclosed by the mold surface and the vacuum bag, and

27. The vacuum assisted resin transfer molding assembly according to claim 26, wherein the first runner of the distribution layer when placed on the mold is lowest located and the second runner is higher located than the first runner.

28. The vacuum assisted resin transfer molding assembly according to any of claims 26 or 27, wherein the one or more runners extend along the extension of the mold, such as at least along 90 % of the extension of the mold.

29. A method for manufacturing a wind turbine blade and/or a wind turbine blade part, the method comprising:

- providing the vacuum assisted resin transfer molding assembly according to any of claims 26-28,

- laying up one or more laminates on the mold surface of the mold,

- connecting the inlet of the distribution layer to a resin reservoir,

- connecting the outlet to a vacuum pump,

- curing the resin.

30. A method according to claim 29, wherein the step of drawing resin into the distribution layer further comprises

- sequentially filling the laminate with resin by first distributing resin using the first runner followed by distributing resin using the second runner.