Method for joining at least two sections of wind turbine blade using air heater arrangement

Abstract

A method for joining at least two sections (11, 12) of a wind turbine blade (1) comprises gathering together two hollow sections of the wind turbine blade and joining them at a joining region (2) using a curable resin, and providing an air heater device (3), the method comprises placing a first blade section (11) and a second blade section (12) at the joining area (2) and supplying a flow of heated air into the internal hollow space of the first blade section (11) and the second blade section (12) at the joining area (2), and / or placing an external heater (6, Fig. 11) on the external surface of the first blade section (11) and the second blade section (12) at the joining area (2), where the external heater (6) comprises a plurality of individually controlled heating zones (62-69). This allows controlling the temperature, and thereby controlling the curing of the resin, including deep within the blade (1).

Description

Technical Field

[0001] The invention relates to a method for joining at least two sections of a wind turbine blade, the use of an air heater device in a method for joining at least two sections of a wind turbine blade and an external heater for use in a method for joining at least two sections of a wind turbine blade. Background Art

[0002] Wind turbine blades, especially those for offshore use, have been increasing in size as technology develops. In terms of main dimensions, current blades can reach a root diameter of approximately 5 m, a blade length of more than 100 m, and a typical chord length of up to 7 m.

[0003] Because of the truly enormous size of the blades, the production of wind turbine blades often involves the pre-manufacturing of blade sections that are joined together in a subsequent production step. These blades are often referred to as "split blades". A wind turbine blade manufactured according to this method may be split longitudinally and / or angularly so that the finished blade comprises at least two blade sections.

[0004] WO 2020 / 244902 A1 discloses a method for manufacturing a wind turbine blade from at least two longitudinally split blade sections. In order to connect the two blade sections, a joining adapter comprising a fiber stack is arranged between the joining interfaces on both sides within the two blade sections so that it at least partially overlaps both the first blade section and the second blade section. In the region of their joining interface, the blade sections taper on the inside, wherein the joining adapter tapers correspondingly on the outside to match the tapered joining interface on the inside of the blade sections. In a subsequent step, the joining area is tightly sealed using vacuum bags on both the outside and inside of the blade, and the joining area is evacuated. Subsequently, a curable resin is injected into the evacuated joining area. The curable resin penetrates into the fiber structure of the fiber stack of the joining adapter and penetrates into the adjacent fibers at the joining interface of the two blade sections. The curable resin is then cured under an exothermic reaction.

[0005] WO 2021 / 073842 A1 discloses another method for assembling blade parts of a wind turbine blade, wherein the method comprises customizing and / or custom selecting a suitable joining adapter based on the individual geometries of a joining interface of a first blade section and a second blade section.

[0006] Another method for manufacturing a wind turbine blade from at least two angled and / or longitudinally split blade sections is disclosed in EP 3 907 062 A1.

[0007] Curing of the curable resin is a key step in all of the above methods, however this step has not been fully addressed in detail so far and presents potential for improvement.

[0008] The curable resin used in the above method usually consists of an epoxy resin and a hardener, which are mixed when injected into the evacuated joint area. Curing basically occurs in three stages: liquid, gel and solid. In the liquid stage, the hardener and epoxy resin are mixed, during which the epoxy resin-hardener mixture is in the so-called "curing time" because it still remains liquid and can be processed. In the gel stage, the epoxy resin-hardener mixture enters the initial curing stage and begins to gel. In the solid stage, the epoxy resin-hardener mixture has cured to a solid state, that is, the epoxy resin has achieved most of its final mechanical properties.

[0009] Epoxy resins cure in an exothermic reaction during which the molecules in the epoxy-hardener mixture react and generate heat. The amount of heat generated by the exothermic reaction depends on the thickness of the epoxy layer, with thicker layers generating more heat.

[0010] Generally speaking, higher temperatures will accelerate the curing of epoxy resins.

[0011] In practice, at least three factors contribute to the rapid curing reaction of epoxy resins: the ambient temperature, the temperature of the surface to which the epoxy resin is applied, and the heat generated by the epoxy resin as it cures.

[0012] In the manufacture of wind turbine blades, the components of the blade sections adjacent to the joint area act as a thermal mass that "removes" heat from the joint area by conduction. Therefore, it is currently not possible to ensure that the optimum curing temperature is throughout the entire joint area.

[0013] In addition, the thickness of the fiber layup in the joining area is not constant, but varies in both the longitudinal and angular directions of the blade. While in areas with relatively thick fiber layups, a large amount of epoxy resin is provided, which generates a relatively large amount of heat, in areas with relatively thin fiber layups, only a small amount of epoxy resin is provided, so that the heat generated in these areas is significantly smaller. This may further be detrimental to the uniform curing of the epoxy resin in the entire joining area, wherein especially low epoxy resin amount areas may suffer from incomplete curing. For longitudinally split blades, typical areas with relatively thick fiber layups may be located in particular in the spar cap / beam area, while relatively thin fiber layups may be located at the longitudinal end sections of the joining area close to the corresponding inner / outer blade sections.

[0014] Therefore, additional heat is often supplied to the joining area. This is currently done by placing industrial heating blankets onto the outer surface of the joining area after the curable resin has been injected. However, this only partially avoids the above-mentioned disadvantages, because hot matter on the inside of the blade section, such as spar caps / beams, joint mandrels and other components "deep" in the structure of the blade section, such as inner / outer shells and / or core material, cannot be heated to the desired temperature level. In addition, this does try to solve the different thicknesses of the fiber layups in the joining area, so that overheating of relatively high epoxy resin amount areas and underheating of relatively low epoxy resin amount areas may occur. Summary of the invention

[0015] It is therefore an object of the present invention to provide a method for joining at least two sections of a wind turbine blade, characterized by an improved curing of a curable resin used for joining the blade sections.

[0016] An additional object of the present invention is to provide for the use of an air heater device in a method for joining at least two sections of a wind turbine blade.

[0017] Yet another object of the present invention is to provide an external heater for use in a method for joining at least two sections of a wind turbine blade.

[0018] Hence, a method for joining at least two sections of a wind turbine blade is provided.

[0019] The method comprises the following steps:

[0020] a) providing a first blade segment and a second blade segment, each of which comprises an interior hollow space;

[0021] b) arranging the first blade section and the second blade section such that they abut each other in a joining region;

[0022] c) sealing the joint area against adjacent areas of the first blade section and the second blade section to create a sealed joint area;

[0023] d) evacuating the sealed joint area;

[0024] e) injecting a curable resin into the sealed joint area;

[0025] f) curing the curable resin by performing at least one heating step comprising applying heat to at least the joining area, wherein the heating step comprises:

[0026] ff) providing an air heater device and supplying a heated air flow into the inner hollow space of at least the first blade section and / or the second blade section in the joining region with the air heater device; and / or

[0027] fff) placing an external heater on the outer surface of the first blade segment and / or the second blade segment in the joining area, wherein the external heater comprises a plurality of heating zones, wherein the heating powers in the heating zones are individually controlled.

[0028] Directional references such as "longitudinal" and "radial" herein refer to the shape of the wind turbine blade.

[0029] The curable resin may include an epoxy resin and a hardener that are mixed prior to injection into the sealed joint area.

[0030] Heating the inner hollow space of at least the first blade section and / or the second blade section in the joining region by means of an air heater device has the advantage that the hot mass inside the blade section, in particular the shear web, the spar cap / beam and / or the joint mandrel within the blade section in the joining region, can be adjusted to a temperature level which is conducive to the curing of the curable resin. Thus, conduction temperature losses can be minimized. This results in an overall improvement in the curing of the curable resin, so that a blade joint with higher quality and better mechanical properties is achieved.

[0031] The application of an external heater with multiple (at least two or more) individually (i.e., independently) controlled heating zones has the advantage that the local heating power can be adjusted to the local structure of the bonding area. For example, a lower heating power can be applied in a high epoxy resin amount area, and a higher heating power can be applied in a low epoxy resin amount area. This helps to compensate for the different levels of heat generated by the curing reaction of the curable resin. As a result, the complete curing of the curable resin can be ensured for the low epoxy resin amount area, while overheating can be avoided for the high epoxy resin amount area. In short, the entire bonding area can be temperature controlled in the best possible way, which helps the curing of the curable resin in the best possible way.

[0032] In an embodiment, step ff) can be performed as follows: the inner hollow space is heated to a temperature level of 90° C. (+ / - 5° C.) at least in the joining region by means of an air heater device and this temperature level is maintained for a predetermined time interval. The predetermined time interval can in particular be between 10 h and 20 h, in particular between 14 h and 18 h.

[0033] The step of heating the inner hollow space can in particular be performed with a ramp-up of a maximum of 0.5° C. per minute, so that starting from an ambient temperature of 20° C., the heating step in the embodiment takes about 140 minutes.

[0034] According to one embodiment, the first blade segment and the second blade segment may comprise at least one internal partition wall, in particular a shear web, which in particular extends in the longitudinal direction. The at least one internal partition wall may define at least two internal chambers in the internal hollow space of the first blade segment and the second blade segment. In step ff), at least two separate heated air flows may be supplied to the at least two internal chambers.

[0035] The two internal chambers may be specific chambers associated with the leading edge and the trailing edge of the blade section.The two separate heated air flows may in particular comprise different characteristics, for example be provided with different temperature levels.

[0036] According to another embodiment, the method may comprise step a2) of providing a joining adapter comprising a first matching zone corresponding to an interface of the first blade section and the joining area and a second matching zone corresponding to an interface of the second blade section and the joining area.

[0037] Additionally, the method may comprise a step b1) of placing the joint adapter in the joint area between the interface of the first blade section and the second blade section.

[0038] In particular, step a2) may be performed during or after step a) and before step b), and step b1) may be performed before step b).

[0039] The joining adapter may in particular be placed within the first blade segment and the second blade segment in the joining area. The joining adapter may comprise a tapered outer surface in its first and second matching zones, the tapered outer surface corresponding to the inner tapered surface of the first blade segment and the second blade segment at their joining interface. The joining adapter in particular comprises a fiber stack comprising glass, carbon and / or aramid fiber mats. At least at its free edge, the fiber mat of the joining adapter may be non-impregnated so that an optimal joining with the corresponding joining interface of the first blade segment and the second blade segment can be achieved.

[0040] In yet another embodiment, the method may include a step f1) of providing at least two sealing plugs and positioning the at least two sealing plugs inside the first blade segment and the second blade segment at positions adjacent to the joining area so that a fluid-enclosed internal heating chamber is formed around the joining area. In particular, step f1) is performed before step f).

[0041] By using the sealing plug, a space affected by the heated air flow supplied by the air heater device can be defined.The sealing plug can be arranged so that the internal heating chamber comprises a junction area and a specific border area of ​​the first blade section and / or the second blade section adjacent to the junction area.

[0042] The sealing plug can be made of polymer foam and / or (balsa) wood, for example. Generally speaking, thermally insulating materials are advantageous for the sealing plug, since heat losses can thereby be minimized. The sealing against the inner wall of the respective blade section can in particular be accomplished by means of an inflatable seal arranged on the outer surface of the sealing plug facing the inner wall.

[0043] Generally speaking, the use of a sealing plug has the advantage that the spatial extension of the internal heating chamber can be limited to the joining area, optionally including a border area of ​​the first blade section and / or the second blade section adjacent to the joining area.

[0044] According to another embodiment, the air heater device may comprise at least one central unit, which comprises at least one heat source and at least one flow generating device. The central unit may comprise at least one heating outlet, which is fluidically connected to the joining area via at least one air duct. In particular, the central unit may be arranged outside the first blade segment and / or the second blade segment, in particular at a root segment of the first blade segment and / or the second blade segment.

[0045] The heat source of the air heater device may be electrically driven or alternatively driven by other primary energy sources such as gaseous or liquid fuels, for example operated by gas or oil.The flow generating device may be adapted to draw air from the environment and process it through the heat source and further to the heating outlet.

[0046] As an alternative to arranging the central unit outside the first blade segment and / or the second blade segment, the central unit may be arranged inside the first blade segment or the second blade segment. In particular, the central unit may be arranged inside the inner blade segment. Since typical blades provide a diameter of several meters at least close to the root, there is sufficient installation space available for placing the central unit inside. This has the advantage that the required length of the air duct is minimized and valuable surface area in the production facility is saved.

[0047] In an embodiment, the flow generating device may be adapted to generate a flow between 3000 m 3 / h and 15.000m 3 / h, especially between 5.000m 3 / h and 12.000m 3 The air flow rate is between / h.

[0048] In an embodiment, the heat source may be adapted to provide a heating power between 50 kW and 400 kW, in particular between 100 kW and 300 kW.

[0049] Additionally or alternatively, the air heater device may be adapted to generate a temperature level between 70°C and 130°C, in particular between 75°C and 120°C at the heating outlet, in particular at the flow rates defined above.

[0050] In an embodiment, the at least one air duct may be provided with a diameter between 200 mm and 600 mm, in particular between 300 mm and 500 mm. The air duct may in particular be provided as a flexible duct and / or an air hose. The air duct may in particular be thermally insulated to minimize heat losses.

[0051] According to another embodiment, the method may include step ff1), which recirculates the air flow from the internal hollow space of the first blade segment and / or the second blade segment in the joining area as a recirculation air flow back to the air heater device, reheats the recirculation air flow, and re-supplies it to the internal hollow space of the first blade segment and / or the second blade segment in the joining area as a reheated air flow.

[0052] In particular, the central unit of the air heater device may comprise a recirculation inlet which is fluidly connected to the inner hollow space of the joining area and is adapted to receive the recirculation air flow.

[0053] In particular, step ff1) may be performed continuously during step ff).

[0054] In an embodiment, the central unit of the air heater device may be equipped with at least one temperature probe, which may be arranged at the at least one heating outlet. The temperature probe may in particular be connected to a control device of the central unit to control the heating power of the at least one heat source so that the temperature of the hot air flow provided through the heating outlet is maintained within a desired temperature range of preferably 90° C. (+ / - 5° C.). Alternatively or additionally, the temperature probe may be arranged at the recirculation inlet.

[0055] According to another embodiment, the heated air flow supplied by the air heater device in step ff) at least partially comprises a heated ambient air flow. In particular, the heated air flow supplied by the air heater device in step ff) additionally comprises a reheated air flow, wherein, in particular, the ratio between the heated ambient air flow and the reheated air flow is adjustable.

[0056] Using at least part of the reheated recirculated air to produce the heated air flow has significant energy advantages, as the amount of primary energy required to power the at least one heat source of the air heater device can be minimised.

[0057] According to another embodiment, the air heater device may comprise at least one recirculation valve adapted to adjust, in particular continuously adjust, the ratio between the heated ambient air flow and the reheated air flow. The method may then comprise the additional step of controlling the ratio between the heated ambient air flow and the reheated air flow using the recirculation valve.

[0058] In an embodiment, the recirculation valve may be manually operated or coupled to an actuator, in particular an electromechanical actuator. The electromechanical actuator may in particular be functionally coupled to a control device of a central unit of the air heater device to control the recirculation ratio based on a predetermined setpoint.

[0059] According to another embodiment, the method may include a step g), which performs a cooling cycle after the curable resin is cured to a desired level, wherein performing the cooling cycle comprises: supplying an unheated air flow into the internal hollow space of the first blade section and / or the second blade section in the joining area using the air heater device, wherein the unheated air flow is in particular an air flow drawn directly from the environment.

[0060] The unheated air flow can be provided at ambient temperature, i.e. at surrounding temperature, or alternatively, additionally cooled by a cooling device incorporated in the air heater device. The technical benefit of performing this cooling step is that the joining blades reach the surrounding temperature more quickly, so that waiting times are reduced, and the joining blades are ready for further processing earlier, so that the overall cycle time of the joining process is reduced.

[0061] During this cooling cycle, the external heater can be completely switched off.

[0062] According to another embodiment, the first blade segment and the second blade segment may be longitudinally split segments, wherein the first blade segment is an inner blade segment and the second blade segment is an outer blade segment, wherein, in particular, in step f1), the inner sealing plug is placed in an area of ​​the inner blade segment adjacent to the joining area on the longitudinal inner side, and the outer sealing plug is placed in an area of ​​the outer blade segment adjacent to the joining area on the longitudinal outer side.

[0063] In yet another embodiment, the outer sealing plug and / or the inner sealing plug may comprise two separate sub-sealing plugs, which are matched to the inner cross-section of the inner chamber of the blade segment defined by the inner partition wall. Additionally or alternatively, the inner sealing plug may be arranged as an integral inner sealing plug in the region of the root section close to the inner blade segment.

[0064] In an embodiment, the separate volumes of the "plugs" in the two separate chambers may be approximately 130-180 m for the trailing edge chamber. 3, and for the leading edge chamber it can be about 70-110m 3 Based on the relatively large volume of air within the chamber, and taking into account the thermal mass adjacent the chamber, the primary heating power required of the air heater device is well understood.

[0065] According to another embodiment, the method may include a step b2), which places at least one joint spindle inside the first blade section and the second blade section at least in the joining area, wherein the joint spindle includes at least one hole providing a flow opening for the heated air flow, wherein, in particular, the joint spindle includes at least one additional hole providing a flow opening for the recirculating air flow.

[0066] In an embodiment, the joint mandrel may be retracted / raised before the heating step is performed. This has the advantage that an air gap may be created between the outer surface of the joint mandrel and the inner surface of the blade segment. This allows for better heat transfer from the heated air flow to both the joining area and the shell / core structure of the blade segment to be joined.

[0067] In another embodiment, in step f), in particular in steps ff) and fff), the heating step comprises heating a boundary region of the first blade segment and / or the second blade segment directly adjoining the joining region.

[0068] By not strictly limiting the effect of the heating step to the joining region, the thermal mass of the first blade segment and / or the second blade segment adjacent to the joining region can be beneficially moderated, so that conductive heat losses driven by the temperature difference between the joining region and the adjacent boundary region of the first blade segment and / or the second blade segment can be minimized. This further facilitates the curing of the curable resin and in particular ensures complete and rapid curing in low epoxy resin amount regions.

[0069] According to a further embodiment, the external heater may comprise at least one contact heater.Alternatively or additionally, the individually controllable or controlled heating zones may be distributed around the joining area in the circumferential direction and / or in the longitudinal direction.

[0070] In an embodiment, the contact heater may be configured as a heating blanket or a heating pad. Additionally or alternatively, the external heater may include an electric heater, in particular a resistance heater and / or a PTC heater. The resistance heater may be particularly configured as a graphite-based heater. The contact heater implemented as a heating blanket or a heating pad may be particularly configured as a silicone rubber heating pad. Alternatively, the external heater may include a heat exchanger, through which a heated heat transfer medium (e.g. water) flows.

[0071] For example, the external heater comprises at least 6, in particular at least 8, individually controllable heating zones.

[0072] In an embodiment, the external heater comprises individually controllable heating zones arranged at the following locations of the split blade:

[0073] - an upper section of the inner blade section adjacent to the joining area;

[0074] - a lower section of the inner blade section adjacent to the joining area;

[0075] - an upper section of the outer blade section adjacent to the joining area;

[0076] - a lower section of the outer blade section adjacent to the joining area;

[0077] - an upper section of the joining area;

[0078] - A lower section of the joining area.

[0079] In addition, a separate gap heating zone may be provided in the gap between the above-mentioned heating zones, in particular between the upper / lower section and the inner / outer blade section in the joint region.

[0080] Typical heating powers in the above mentioned heating zones can be as follows:

[0081] - Upper section of the inner blade section adjacent to the junction area: 10.000 W - 15.000 W;

[0082] - the lower section of the inner blade section adjacent to the junction area: 10.000 W - 15.000 W;

[0083] - Upper section of the outer blade section adjacent to the joining area: 10.000 W - 15.000 W;

[0084] - the lower section of the outer blade section adjacent to the junction area: 10.000 W - 15.000 W;

[0085] - Upper section of the junction area: 8.000 W–12.000 W;

[0086] - Lower section of the junction area: 8.000 W–12.000 W;

[0087] - Gap heating zones between the above mentioned heating zones: 1.500W – 3.000W.

[0088] In an embodiment, the heating power per unit area in the heating zone may range from 400 W / m 2 Up to 750W / m 2 .

[0089] In an embodiment, one or more of the above-mentioned heating zones can be subdivided into sub-heating zones in a circumferentially and / or longitudinally distributed manner, wherein the heating powers in these sub-heating zones can also be controlled individually.

[0090] The external heater may comprise a central unit which provides an individually controlled heating power output for each heating zone. In addition, the external heater may comprise at least one temperature probe per heating zone, which is arranged in the respective heating zone. In an embodiment, each heating zone may be provided with more than one temperature probe, for example 5 or 6 temperature probes. This has the particular advantage that redundancy may be provided and an average temperature value per heating zone may be calculated, so that local temperature deviations may be compensated. The temperature probe may in particular be provided as a PT-100 resistance thermometer, a thermocouple or any other temperature probe deemed suitable by the skilled person.

[0091] Furthermore, the central unit may be equipped with a control device, which is functionally coupled to the temperature probe, to control the temperature in the heating zone by adapting the heating power based on a predetermined temperature setpoint. The setpoint may in particular be in the range of 20° C.-120° C. The control device may in particular be adapted to provide a heating cycle with a predetermined ramp-up (° C. / time unit) to the temperature setpoint.

[0092] The method according to the invention may be implemented at least in part in hardware and / or software. If the method is implemented in hardware, it may be implemented as a device, such as a computer or a processor or a part of a system, such as a computer system. If the method is implemented in software, it may be implemented as a computer program product, a function, a routine, a program code or an executable object.

[0093] According to another aspect of the invention, the use of an air heater device in a method according to the invention for joining at least two sections of a wind turbine blade is proposed.

[0094] According to a further aspect of the invention, an external heater for use in a method according to the invention for joining at least two sections of a wind turbine blade is proposed. The external heater comprises a plurality of heating zones, wherein the heating powers in the heating zones are individually controllable.

[0095] Embodiments and features described with reference to the method of the invention apply mutatis mutandis to the apparatus of the invention and vice versa.

[0096] Other possible implementations or alternatives of the present invention also encompass combinations of features not explicitly mentioned herein that are described above or below with respect to the embodiments. A person skilled in the art may also add individual or isolated aspects and features to the most basic form of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Other embodiments, features and advantages of the present invention will become apparent from the following description and the dependent claims in conjunction with the accompanying drawings, in which:

[0098] Figure 1-Figure 9 Flowcharts showing different embodiments of the method according to the present invention;

[0099] Fig. 9 shows a schematic cross-sectional view of a split blade with an air heater device used in the method according to the invention;

[0100] Fig.10 shows another schematic cross-sectional view of a split blade with an air heater device used in the method according to the invention;

[0101] Fig.11 An isometric view of a split blade having an external heater according to the present invention is shown;

[0102] Fig.12 An external heater according to the invention is shown in detail.

[0103] Figure 13-Figure 18 Various contact heaters are shown according to the external heater of the present invention.

[0104] In the drawings, like reference numbers indicate identical or functionally equivalent elements unless otherwise indicated.

[0105] exist Figure 1-8 The reference numerals mentioned in the description of the method steps shown in Figure 9-18 At least one of the . DETAILED DESCRIPTION

[0106] Figure 1 A flow chart showing a first embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0107] The method comprises the following steps:

[0108] a) providing a first blade section 11 and a second blade section 12, each of which comprises an inner hollow space;

[0109] b) arranging the first blade section 11 and the second blade section 12 such that they abut one another in the joining region 2;

[0110] c) sealing the joint area 2 against adjacent areas 21 , 22 of the first blade segment 11 and the second blade segment 12 to produce a sealed joint area 2;

[0111] d) evacuating the sealed joint area 2;

[0112] e) injecting a curable resin into the sealed joint area 2;

[0113] f) curing the curable resin by performing at least one heating step comprising applying heat to at least the joining area 2, wherein the heating step comprises:

[0114] ff) An air heater device 3 is provided and a heated air flow is supplied with the air heater device 3 into the inner hollow space of the first blade segment 11 and / or the second blade segment 12 at least in the joining region 2 .

[0115] Figure 2 A flow chart of a second embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0116] In which, instead of step ff), step fff) is performed, which places an external heater 6 on the outer surface of the first blade segment 11 and / or the second blade segment 12 at least in the joining area 2, wherein the external heater 6 includes a plurality of heating zones 62-69, wherein the heating power in the heating zones 62-69 is individually controlled.

[0117] Figure 3 A flow chart showing a third embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0118] Therein, both steps ff) and fff) mentioned above may be performed, wherein the execution may be performed simultaneously or continuously.

[0119] Figure 4 A flow chart showing a fourth embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0120] Before step f), step f1) is additionally performed, which provides at least two sealing plugs 51, 52 and positions the at least two sealing plugs inside the first blade segment 11 and the second blade segment 12 at positions adjacent to the joining area 2, so that a fluid-enclosed internal heating chamber 53 is formed around the joining area 2.

[0121] Figure 5 A flow chart showing a fifth embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0122] Wherein, during the execution of step ff) and / or step fff), step ff1) is continuously executed, which recirculates the air flow as a recirculating air flow from the internal hollow space of the first blade segment 11 and / or the second blade segment 12 in the joining area 2 back to the air heater device 3, reheats the recirculating air flow, and re-supplies it as a reheated air flow to the internal hollow space of the first blade segment 11 and / or the second blade segment 12 in the joining area 2, wherein, in particular, the central unit 31 of the air heater device 3 includes a recirculation inlet 392, which is fluidly connected to the internal hollow space of the joining area 2 and is suitable for receiving the recirculating air flow.

[0123] Figure 6 A flow chart showing a sixth embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0124] Wherein, after step ff) and / or step fff), step g) is performed, in which a cooling cycle is performed after the curable resin has been cured to a desired level, wherein performing the cooling cycle includes: using an air heater device 3 to supply an unheated air flow to the internal hollow space of the first blade segment 11 and / or the second blade segment 12 in the joining area 2, wherein the unheated air flow is particularly an air flow directly drawn from the environment.

[0125] Figure 7 A flow chart showing a seventh embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0126] wherein step b2) is performed after step b). Step b2) comprises placing at least one joint spindle 4 inside the first blade section 11 and the second blade section 12 at least in the joining region 2, wherein the joint spindle 4 comprises at least one hole 41 providing a flow-throughlet for the heated air flow, wherein, in particular, the joint spindle 4 comprises at least one further hole providing a flow-throughlet for the recirculation air flow.

[0127] Figure 8 A flow chart showing an eighth embodiment of a method according to the invention for joining at least two sections of a wind turbine blade is shown.

[0128] After step a), at least step a2) is performed. Step a2) includes providing a joint adapter including a first matching region corresponding to the interface between the first blade segment 11 and the joint area 2 and a second matching region corresponding to the interface between the second blade segment 12 and the joint area 2 .

[0129] Furthermore, the method may comprise a step b1) of placing a joint adapter in the joint area 2 between the interface of the first blade section 11 and the second blade section 12 .

[0130] Alternatively, step a2) may be performed during step a) but before step b).Step b1) may be performed before step b).

[0131] Fig. 9 and Fig.10 A cross section of a split wind turbine blade 1 is shown, comprising an inner blade section 11 and an outer blade section 12 joined together in a joining region 2. Furthermore, an air heater device 3 for performing method step ff) of the method according to the invention is shown.

[0132] Both the air heater device 3 and the execution details of step ff) are described below.

[0133] The air heater device 3 comprises a central unit 31 having a heat source 33 and a flow generating device 32. The central unit 31 is arranged outside the inner blade section 11 and the outer blade section 12 at the root portion 16 of the split blade 1. The central unit comprises a heating outlet 391 which feeds a heated air flow (white arrows) into air ducts 35, 36 for the heated air flow. The heated air flow may at least partially consist of heated ambient air drawn from the environment by the air heater device 3.

[0134] The joining area 2 is sealed by two sealing plugs 51, 52, which are positioned inside the first blade segment 11 and the second blade segment 12 at a position adjacent to the joining area 2, so that a fluid-enclosed internal heating chamber 53 is formed around the joining area 2. Specifically, the inner sealing plug 51 is placed in an area of ​​the inner blade segment 11 adjacent to the joining area 2 on the inner side of the longitudinal direction L (close to the root segment 16), and the outer sealing plug 52 is placed in an area of ​​the outer blade segment 12 adjacent to the joining area 2 at the outer side of the longitudinal direction. The sealing plugs 51, 52 seal the joining area 2 by suitable seals, which are arranged on the outer surface of the respective sealing plugs 51, 52 abutting against the inner surface of the inner blade segment 11 and / or the outer blade segment 12. The spatial extension of the internal heating chamber 53 in the longitudinal direction L includes the joining area 2, but extends further into the respective inner and outer boundary areas 21, 22 of the blade segments 11, 12; for example, the longitudinal extension of the internal heating chamber 53 may be about 10m.

[0135] The blade sections 11, 12 comprise a shear web 15 extending in the longitudinal direction L, wherein the shear web 15 defines at least two inner chambers 131, 141 in the inner hollow space of the first blade section 11 and the second blade section 12. There are two separate air ducts 35, 36 for the heating air flow, one connected to the inner chamber 131 and the other connected to the inner chamber 141. The inner chamber 131 is the leading edge 13 chamber, while the inner chamber 141 is the trailing edge 14 chamber.

[0136] Since the blade segments 11, 12 are “divided” internally by the shear web 15 in the longitudinal direction L, the inner / outer sealing plugs 51, 52 comprise two separate sub-sealing plugs 511, 512, 521, 522, which match the inner cross-section of the inner chamber 131, 141 of the blade segments 11, 12 defined by the shear web 15. Therefore, each of these sub-sealing plugs seals the joint area 2 by a suitable seal provided on the outer surface of the respective sub-sealing plug 511, 512, 521, 522, which seals with some sections thereof against the inner surface of the inner blade segment 11 and / or the outer blade segment 12 and with other sections thereof against the shear web 15.

[0137] The inner sealing plug 51 , more specifically the inner sub-sealing plugs 511 , 512 , each include an opening that allows a heated air flow to pass through the corresponding sub-sealing plug 511 , 512 into the inner chamber 131 , 141 .

[0138] Inside the first blade section 11 and the second blade section 12, the joint mandrel 4 is arranged in the joint area 2. The joint mandrel 4 has a hole 41 that provides a flow opening for the heated air flow. The air ducts 35, 36 for the heated air flow are connected to the hole 41 of the joint mandrel 4, so that the heated air flow passes through the joint mandrel 4 in the longitudinal direction and leaves the joint mandrel 4 at the longitudinal opposite ends. From there, the heated air flow is distributed in the corresponding internal chambers 131, 141 at the leading edge 13 and the trailing edge 14 and heats the joint area 2 from the inside. In particular, the heated air flow heats the shear web 15, the spar cap / beam, the joint mandrel 4 itself and other components of the blade structure, such as the shell and the core. The joint mandrel 4 extends in the longitudinal direction L in the joint area 2 and further extends into the corresponding inner and outer side boundary areas 21, 22 of the blade sections 11, 12.

[0139] In addition, the airflow from the internal chambers 131, 141 is recirculated back to the air heater device 3 as a recirculation airflow. The recirculation airflow is depicted with a black arrow. In order to allow this, the inner sealing plug 51, more specifically the inner sub-sealing plugs 511, 512, each include an opening, which allows the recirculation airflow to pass through the corresponding sub-sealing plugs 511, 512 back to the air heater device 3. The corresponding openings of the sub-sealing plugs 511, 512 are connected to the air ducts 37, 38 for the recirculation airflow, which are fluidly connected to the recirculation inlet 392 of the air heater device 3 that receives the recirculation airflow. In the air heater device 3, the recirculation airflow is reheated and then resupplied back to the internal chambers 131, 141 as a reheated airflow. That is, the heated airflow supplied by the air heater device 3 includes the reheated airflow and a portion of the heated ambient air. The air heater device can provide a device for adjusting the ratio between the heated ambient airflow and the reheated airflow.

[0140] The air heater device 3 comprises a temperature probe 34 arranged at least at the heating outlet 391. In addition, the air heater device 3 may comprise a further temperature probe 34 at the recirculation inlet 392.

[0141] Fig.10 The cross section of the split wind turbine blade 1 shown in FIG. Fig. 9 Very similar. However, the difference is that the inboard sealing plug 51 is arranged at the root section 16 of the blade 1, respectively at the root section 16 of the inboard blade section 11. Since there is no shear web 15 in the root section 16, this has the advantage that the inboard sealing plug 51 can be arranged as an integral part that seals against the inner wall of the inboard blade section 11. However, since other parts of the inboard blade section 11 located further away from the actual joint area 2 are heated, a slightly higher energy consumption must be accepted.

[0142] A joining adapter for joining the inner blade segment 11 and the outer blade segment 12 is not specifically shown in the figures but may be arranged in the joining region, in particular on the inner side thereof, when carrying out the method according to the invention.

[0143] Fig.11 An external heater 6 used in the method according to the invention is shown. The split blade 1 is received in a lower mold 81 which holds the inner blade segment 11 and the outer blade segment 12 adjacent to each other in the joining area 2 so that the blade segments 11, 12 are correctly positioned for the joining process. On the upper side, the joining area 2 is spanned by an upper rod 82 which provides further support for the joining area 2.

[0144] The external heater 6 comprises at least six heating zones 62-67, which are arranged as follows:

[0145] - an upper section (64) of the inner blade section adjacent to the joining area;

[0146] - a lower section (65) of the inner blade section adjacent to the joining area;

[0147] - an upper section (66) of the outer blade section adjacent to the joining area;

[0148] - a lower section (67) of the outer blade section adjacent to the joining area;

[0149] - an upper section (62) of the joining area;

[0150] - A lower section (63) of the joining area.

[0151] The heating zones 64 , 65 , 66 , 67 in the sections of the inner / outer blade sections 11 , 12 adjacent to the joining region 2 may cover a length of at least 2 m, in particular at least 5 m, from the joining region 2 .

[0152] Additional heating zones are arranged between the above mentioned heating zones, ie at the gaps between the joining region and the upper / lower sections of the inner / outer blade sections 11, 12. These gap heating zones are not shown in this figure.

[0153] The heating power in the heating zones 62-67 is controlled individually. For this purpose, the external heater 6 comprises a central unit 61 which provides an individually controlled heating power output for each heating zone 62-67. The external heater 6 also comprises at least one temperature probe in each heating zone 62-67 which allows the central unit 61 to control the heating power in the heating zones 62-67 to reach a predetermined temperature level.

[0154] Heating zone:

[0155] - a lower section (65) of the inner blade section adjacent to the joining area; and / or

[0156] - a lower section (67) of the outer blade section adjacent to the joining area; and / or

[0157] - an upper section (62) of the joining area; and / or

[0158] - a lower section (63) of the joining area,

[0159] Each comprises a contact heater implemented as a silicone rubber heating pad. The contact heaters of the above-mentioned heating zones are in particular arranged, preferably fixedly attached, to the lower mold 81 and / or the upper rod 82 respectively.

[0160] Heating zone:

[0161] - an upper section (64) of the inner blade section adjacent to the joining area; and / or

[0162] - The upper sections (66) of the outer blade sections adjacent to the joining area each comprise a contact heater embodied as a heating blanket with reinforcing straps and rings, which allow the heating blanket to be pulled onto the blade sections 11, 12. The contact heaters of the aforementioned heating zones are in particular loosely arranged on the upper side of the blade sections 11, 12 and temporarily fixed by means of the straps and rings. Alternatively, the contact heaters of the aforementioned heating zones can be fixed to the upper side of the blade sections 11, 12 with adhesive tape.

[0163] Fig.12 A schematic diagram of an external heater 6 according to the invention is shown. In this embodiment, the central unit 61 has three main heating power outputs.

[0164] The first heating power output is connected to the heating zone 65 of the lower section of the inner blade section adjacent to the joint area. From this heating zone, the heating power is further distributed to the heating zone 64 of the upper section of the inner blade section adjacent to the joint area, wherein the heating zone 64 is divided into three separate sub-heating zones. Further, the heating power is distributed to the heating zone 68 of the gap heater, which covers the gap between the joint area heater and the inner heater.

[0165] The second heating power output is connected to the heating zone 63 of the lower section of the joining area. From this heating zone, the heating power is further distributed to the heating zone 62 of the upper section of the joining area.

[0166] The third heating power output is connected to the heating zone 67 of the lower section of the outer blade section adjacent to the joint area. From this heating zone, the heating power is further distributed to the heating zone 66 of the upper section of the outer blade section adjacent to the joint area, wherein the heating zone 66 is divided into three separate sub-heating zones. Further, the heating power is distributed to the heating zone 69 of the gap heater, which covers the gap between the joint area heater and the outer heater.

[0167] The heating powers in the heating zones 62 - 69 and the corresponding sub-heating zones can be controlled individually by the central unit 61 .

[0168] In order to allow effective temperature control and monitoring of the heating step, the external heater 6 comprises at least one temperature probe in each heating zone 62-69. The central unit 61 also comprises a controller, which is coupled to the temperature probes, to control the temperature in the heating zones 62-69 by adapting the heating power based on a predetermined temperature setting value. The temperature setting value may be in the range of 20°C-120°C.

[0169] Fig.13 A contact heater 71 of the heating zone 62 is shown at the upper section of the joining area 2. The contact heater 71 comprises sub-heating zones 711, 712, 713 of heater types A, D and E arranged adjacent to each other in the circumferential direction C of the blade.

[0170] The specifications in the example of the present invention may be specifically as follows:

[0171] Heater Type A:

[0172] Silicone heater with adhesive on top

[0173] 1000mm x 2000mm

[0174] 1200W / 230V

[0175] Heater Type D:

[0176] Silicone heater with adhesive on top

[0177] 800 / 780mm x 2000mm

[0178] 1050W / 230V

[0179] Heater Type E (flipped version of D):

[0180] Silicone heater with adhesive on top

[0181] 800 / 780mm x 2000mm

[0182] 1050W / 230V

[0183] Overall dimensions:

[0184] Length 1: 2x800+7x1000=8600mm

[0185] Length 2: 2x780+7x1000=8560mm

[0186] Width: 2000mm

[0187] Total power: 10.500W / 652W / m 2

[0188] Fig.14 The contact heater 72 of the heating zone 63 is shown at the lower section of the joining area 2. The contact heater 71 comprises sub-heating zones 721, 722, 723 of heater types A, B and C arranged adjacent to each other in the circumferential direction C of the blade.

[0189] The specifications can be as follows:

[0190] Heater Type A:

[0191] Silicone heater with adhesive on top

[0192] 900mm x 2000mm

[0193] 1200W / 230V

[0194] Heater Type B:

[0195] Silicone heater with adhesive on top

[0196] 900 / 800mm x 2000mm

[0197] 1110W / 230V

[0198] Heater Type C (flipped version of B):

[0199] Silicone heater with adhesive on top

[0200] 900 / 800mm x 2000mm

[0201] 1110W / 230V

[0202] Overall dimensions:

[0203] Length 1: 9x900=8100mm

[0204] Length 2: 2x800+7x900=7900mm

[0205] Width: 2000mm

[0206] Total power: 10.620W / 652W / m 2

[0207] Fig.15 A contact heater 73 of the heating zone 67 at the lower section of the outboard blade section 12 adjacent to the joint area 2 is shown. The contact heater 73 comprises sub-heating zones 731, 732, 733 of heater types I, J and K arranged adjacent to each other in the circumferential direction C of the blade.

[0208] The specifications can be as follows:

[0209] Heater Type I:

[0210] Silicone heater with foam and adhesive on foam

[0211] 700mm x 2800mm

[0212] 1120W / 230V

[0213] Heater Type J:

[0214] Silicone heater with foam and adhesive on foam

[0215] 500 / 690mm x 2800mm

[0216] 1025W / 230V

[0217] Heater Type K (flipped version of J):

[0218] Silicone heater with foam and adhesive on foam

[0219] 500 / 690mm x 2800mm

[0220] 1025W / 230V

[0221] Overall dimensions:

[0222] Length 1: 2x690+10x700=8380mm

[0223] Length 2: 2x500+10x700=8000mm

[0224] Width: 2800mm

[0225] Total power: 13.250W / 600W / m 2

[0226] Fig.16 A contact heater 74 of the heating zone 65 is shown at the lower section of the inner blade section 11 adjacent to the joining area 2. The contact heater 74 comprises sub-heating zones 741, 742, 743 of heater types F, G and H arranged adjacent to each other in the circumferential direction C of the blade.

[0227] The specifications can be as follows:

[0228] Heater Type F:

[0229] Silicone heater with foam and adhesive on foam

[0230] 690mm x 2800mm

[0231] 1160W / 230V

[0232] Heater Type G:

[0233] Silicone heater with foam and adhesive on foam

[0234] 650 / 700mm x 2800mm

[0235] 1125W / 230V

[0236] Heater Type H (flip version of G):

[0237] Silicone heater with foam and adhesive on foam

[0238] 650 / 700mm x 2760mm

[0239] 1125W / 230V

[0240] Overall dimensions:

[0241] Length 1: 2x700+10x690=8300mm

[0242] Length 2: 2x650+10x690=8200mm

[0243] Width: 2800mm

[0244] Total power: 13.850W / 604W / m 2

[0245] Fig.17 A contact heater 75 of the heating zones 64, 66 at the upper sections of both the inner and outer blade sections 11, 12 adjacent to the joining area 2 is shown. The contact heater 75 comprises sub-heating zones 751 of heater type L arranged adjacent to each other in the longitudinal direction, which is a direction perpendicular to the circumferential direction C of the blade.

[0246] The specifications can be as follows:

[0247] Heater L:

[0248] Heating blanket with reinforcing straps and loops for pulling over the blades

[0249] Size: 8000x900mm

[0250] Power: 4600W / 3X 400V

[0251] Total power: 13.800W

[0252] Fig.18A contact heater 76 is shown joining the heating zones 69, 69 at the gap between the zone heater and the inboard / outboard heaters. The contact heater 76 comprises a sub-heating zone 761 of heater type N and comprises a strap 763 for pulling the heater onto the blade and a buckle 762 for closing it around the perimeter of the blade.

[0253] The specifications can be as follows:

[0254] Heater N:

[0255] Heating blanket with strap and buckle

[0256] Dimensions: 250x16.000mm

[0257] Power: 2300W / 230V

[0258] Although the invention has been described in terms of preferred embodiments, it will be apparent to those skilled in the art that modifications are possible in all embodiments.

Claims

1. A method for joining at least two sections (11, 12) of a wind turbine blade (1), comprising the following steps: a) providing a first blade section (11) and a second blade section (12), each of which comprises an inner hollow space; b) arranging the first blade section (11) and the second blade section (12) such that they abut each other in a joining region (2); c) sealing the joint area (2) against adjacent areas (21, 22) of the first blade section (11) and the second blade section (12) to produce a sealed joint area (2); d) evacuating the sealed joint area (2); e) injecting a curable resin into the sealed joint area (2); f) curing the curable resin by performing at least one heating step, the heating step comprising applying heat to at least the joining area (2), wherein the heating step comprises: ff) providing an air heater device (3) and supplying a heated air flow into the inner hollow space of at least the first blade section (11) and / or the second blade section (12) in the joining area (2) by means of the air heater device (3); and / or fff) placing an external heater (6) on the outer surface of the first blade segment (11) and / or the second blade segment (12) at least in the joining area (2), wherein the external heater (6) includes a plurality of heating zones (62-69), wherein the heating powers in the heating zones (62-69) are individually controlled.

2. The method according to claim 1, wherein: The first blade segment (11) and the second blade segment (12) comprise at least one internal partition wall (15), in particular a shear web (15), extending in particular in the longitudinal direction (L), wherein the at least one internal partition wall (15) defines at least two internal chambers (131, 141) in the internal hollow space of the first blade segment (11) and the second blade segment (12), and wherein, in step ff), at least two separate heated air flows are supplied to the at least two internal chambers (131, 141).

3. The method according to claim 1 or 2, wherein: The method comprises the following steps: f1) providing at least two sealing plugs (51, 52) and positioning the at least two sealing plugs inside the first blade section (11) and the second blade section (12) at positions adjacent to the joining area (2) so that a fluid-enclosed internal heating chamber (53) is formed around the joining area (2), In particular, step f1) is performed before step f).

4. The method according to any one of claims 1 to 3, in, The air heater device (3) comprises at least one central unit (3), the central unit (3) comprising at least one heat source (33) and at least one flow generating device (32), wherein the central unit (31) comprises at least one heating outlet (391), the heating outlet (391) being fluidically connected to the joining area (2) via at least one air duct (35, 36), wherein, in particular, the central unit (31) is arranged outside the first blade segment (11) and / or the second blade segment (12), in particular at the root segment (16) of the first blade segment (11) and / or the second blade segment (12).

5. The method according to any one of claims 1 to 4, wherein: The method comprises a step ff1) of recirculating an airflow from the inner hollow space of the first blade segment (11) and / or the second blade segment (12) in the joining area (2) back to the air heater device (3) as a recirculating airflow, reheating the recirculating airflow and resupplying it as a reheated airflow to the inner hollow space of the first blade segment (11) and / or the second blade segment (12) in the joining area (2), wherein, in particular, the central unit (31) of the air heater device (3) comprises a recirculation inlet (392) which is fluidly connected to the inner hollow space of the joining area (2) and is adapted to receive the recirculation airflow, And wherein, in particular, step ff1) is performed continuously during step ff).

6. The method according to any one of claims 1 to 5, wherein: The heated air flow supplied by said air heater device (3) in step ff) comprises at least partly heating the ambient air flow, and Therein, in particular, the heated air flow supplied by the air heater device (3) in step ff) additionally comprises the reheated air flow, wherein in particular the ratio between the heated ambient air flow and the reheated air flow is adjustable.

7. The method according to claim 6, wherein: The air heater device (3) comprises at least one recirculation valve adapted to adjust, in particular continuously adjust, the ratio between the heated ambient air flow and the reheated air flow.

8. The method according to any one of claims 1 to 7, wherein: The method comprises a step g) of performing a cooling cycle after the curable resin has been cured to a desired level, wherein performing the cooling cycle comprises supplying an unheated air flow into the internal hollow space of the first blade section (11) and / or the second blade section (12) in the joining area (2) using the air heater device (3), wherein the unheated air flow is in particular an air flow drawn directly from the environment.

9. The method according to any one of claims 1 to 8, wherein: The first blade section (11) and the second blade section (12) are longitudinal (L) split sections, wherein the first blade section (11) is an inner blade section (11) and the second blade section (12) is an outer blade section (12), wherein, in particular, in step f1), an inner sealing plug (51) is placed in an area of ​​the inner blade section (11) adjacent to the joining area (2) on the inner side in the longitudinal direction (L), and an outer sealing plug (52) is placed in an area of ​​the outer blade section (12) adjacent to the joining area (2) on the outer side in the longitudinal direction.

10. The method according to claim 9, wherein: The outer sealing plug (52) and / or the inner sealing plug (51) comprises two separate sub-sealing plugs (511, 512, 521, 522), which are matched with the inner cross-section of the inner chamber (131, 141) of the blade section (11, 12) defined by the inner partition wall (15), and / or wherein, The inner sealing plug (51) is arranged as an integral inner sealing plug (51) in a region close to a root section (16) of the inner blade section (11).

11. The method according to any one of claims 1 to 10, wherein: The method comprises a step b2) of placing at least one joint spindle (4) inside the first blade section (11) and the second blade section (12) at least in the joining area (2), wherein the joint spindle (4) comprises at least one hole (41) providing a flow opening for the heated air flow, wherein, in particular, the joint spindle (4) comprises at least one additional hole providing a flow opening for the recirculated air flow.

12. The method according to any one of claims 1 to 11, wherein: In step f), in particular in step ff) and step fff), the heating step comprises heating a boundary region (21, 22) of the first blade section (11) and / or the second blade section (12) directly adjoining the joining region (2).

13. The method according to any one of claims 1 to 12, wherein: The external heater (6) comprises at least one contact heater (71-76), and / or wherein, Individually controllable heating zones (62-69) are distributed around the joining region (2) in a circumferential direction (C) and / or in a longitudinal direction (L).

14. Use of an air heater device (3) in a method for joining at least two sections (11, 12) of a wind turbine blade (1) according to any of the preceding claims.

15. An external heater (6) for use in a method for joining at least two sections (11, 12) of a wind turbine blade (1) according to any of the preceding claims, wherein: The external heater (6) comprises a plurality of heating zones (62-69), wherein the heating powers in the heating zones (62-69) are individually controllable.

Images