Blade forming method and blade

Abstract

The invention discloses a blade forming method and a blade, and the method comprises the following steps: carrying out vacuum filling in a forming mold to respectively obtain two filled half shells; the forming mold is pre-cured and heated until the exothermic peak temperature of the poured half shell is higher than the glass-transition temperature, and a pre-cured half shell is obtained; the pre-cured half shells and the web are bonded through bonding glue, heating is conducted at the bonding curing temperature lower than the exothermic peak temperature, the bonding glue is cured, and two to-be-assembled half shells are obtained; the two to-be-assembled half shells are subjected to mold closing and bonding, and a mold closing mold and a mold closing blade are obtained; and post-curing heating is conducted on the mold closing mold at the post-curing temperature lower than the bonding curing temperature, so that the mold closing blade reaches the preset temperature, and a formed blade is obtained. According to the blade forming method, repeated expansion and shrinkage of resin can be avoided, the intense degree of release of internal stress of the resin is reduced, crazing is reduced, and the blade quality is improved.

Description

Technical Field

[0001] The present application belongs to the field of wind power technology, and in particular relates to a blade forming method and a blade. Background Art

[0002] Wind turbine blades are the foundation and core components of wind power generation systems. Their good design, reliable quality and superior performance are the decisive factors to ensure the stable operation of wind power generation systems.

[0003] As blades become larger, the diameter of the blade root and the thickness of the fiber cloth in the blade structure have increased significantly, which has led to the problem of silver streaks on super-large blades. The existence of silver streaks affects the quality of wind turbine blades, and has become a problem that technicians in this field need to solve urgently. Summary of the invention

[0004] The embodiments of the present application provide a blade forming method and a blade, which can reduce the generation of silver streaks during the blade curing process and improve the quality of the blade.

[0005] In a first aspect, an embodiment of the present application provides a blade forming method, which includes: performing vacuum infusion in a forming mold to obtain two infused rear half shells, respectively, the two infused rear half shells including a windward shell and a leeward shell; pre-curing and heating the forming mold until the exothermic peak temperature of the infused rear half shells is higher than the glass transition temperature to obtain a pre-cured half shell; bonding the pre-cured half shell and the web with adhesive, and heating at a bonding curing temperature lower than the exothermic peak temperature to cure the adhesive to obtain two half shells to be assembled; closing and bonding the two half shells to be assembled to obtain a closing mold and a closing mold blade; post-curing and heating the closing mold at a post-curing temperature lower than the adhesive curing temperature to allow the closing mold blade to reach a predetermined temperature to obtain a molded blade.

[0006] In some embodiments, the molding mold is pre-cured and heated until the exothermic peak temperature of the half shell after infusion is higher than the glass transition temperature to obtain a pre-cured half shell, including: dividing the molding mold into a blade root curing area and a remaining curing area; heating the blade root curing area at a first pre-curing temperature, and heating the remaining curing area at a second pre-curing temperature, wherein the first pre-curing temperature is increased in a gradient from below the second pre-curing temperature to above the second pre-curing temperature.

[0007] In some embodiments, the forming mold is divided into a blade root solidification area and a remaining solidification area, including: dividing the infusion rear half shell into a blade root reinforcement area and a remaining area along the length direction, deriving the blade root solidification area based on the blade root reinforcement area, and deriving the remaining solidification area based on the remaining area.

[0008] In some embodiments, the blade root strengthening region starts from the free end of the blade root of the latter half of the infusion shell and is the region from 0 m to 15 m of the latter half of the infusion shell.

[0009] In some embodiments, the forming mold is pre-cured and heated to a temperature at which the exothermic peak temperature of the latter half of the infusion shell is higher than the glass transition temperature to obtain a pre-cured half shell, including: heating the forming mold to a pre-curing temperature lower than the exothermic peak temperature for a predetermined time, stopping heating and naturally cooling to room temperature.

[0010] In some embodiments, the exothermic peak temperature is the temperature peak of the blade root strengthening region during pre-curing, the difference between the exothermic peak temperature and the glass transition temperature is 5°C to 15°C, the exothermic peak temperature is 90°C to 100°C; the glass transition temperature is greater than the pre-curing temperature.

[0011] In some embodiments, the blade root curing region is heated at a first pre-curing temperature, and at the same time the remaining curing region is heated at a second pre-curing temperature. The first pre-curing temperature is gradient heated from a temperature lower than the second pre-curing temperature to a temperature higher than the second pre-curing temperature, including: heating the blade root pre-curing region in three temperature steps with gradually increasing temperatures, heating the blade root curing region at the first temperature step for a first duration, heating the blade root curing region at the second temperature step for a second duration, heating the blade root curing region at the third temperature step for a third duration; wherein, the second temperature step is equal to the second pre-curing temperature, and the sum of the first duration, the second duration, and the third duration is equal to the heating duration of the remaining curing region.

[0012] In some embodiments, the first duration is greater than the second duration, the second duration is less than the third duration, and the difference between the second temperature step and the first temperature step is greater than the difference between the third temperature step and the second temperature step.

[0013] In some embodiments, the first temperature step is 50°C, the first duration is 3 hours, the second temperature step is 65°C, the second duration is 1 hour, the third temperature step is 75°C, and the third duration is 3 hours.

[0014] In some embodiments, the pre-cured half shell and the web are bonded with an adhesive, and heated at an adhesive curing temperature lower than the exothermic peak temperature to cure the adhesive to obtain two half shells to be assembled, including: heating the forming mold at the adhesive curing temperature, keeping the temperature of the pre-cured half shell lower than the glass transition temperature, and stopping heating after the adhesive reaches a predetermined hardness.

[0015] In some embodiments, the bonding and curing temperature is 85 °C, and the predetermined hardness is 50 HD Shore hardness.

[0016] In some embodiments, the two to-be-assembled half-shells are clamped and bonded to obtain a clamped mold and a clamped blade, including: cooling to room temperature, applying glue to the to-be-assembled half-shell bonded with the web and the to-be-assembled half-shell not bonded with the web, bonding the two to-be-assembled half-shells at the joint, and clamping the forming mold.

[0017] In some embodiments, the clamped mold is post-cured and heated at a post-curing temperature lower than the bonding and curing temperature, so that the clamped blade reaches a predetermined temperature to obtain a formed blade, including: heating the clamped mold, heating to the post-curing temperature at a predetermined temperature rise and maintaining it, stopping heating after heating to the clamped blade reaches the predetermined temperature, and naturally cooling to room temperature.

[0018] In some embodiments, the post-curing temperature is 80 °C, the predetermined temperature is 70 °C, and the predetermined temperature rise is 0.5 °C / min to 1 °C / min.

[0019] In a second aspect, an embodiment of the present application further provides a blade manufactured by using the above blade forming method.

[0020] Analysis shows that compared with the prior art, the advantages and beneficial effects of the present application are as follows: The embodiment of the present application provides a blade forming method. In this blade forming method, the exothermic peak temperature during pre-curing is higher than the glass transition temperature, the bonding and curing temperature during web bonding is lower than the exothermic peak temperature, and the post-curing temperature during post-curing is lower than the bonding and curing temperature. During pre-curing, web bonding, and post-curing, the temperature of the resin decreases in sequence, and the amplitude of thermal expansion and contraction of the resin decreases in sequence, which can avoid repeated expansion and contraction of the resin, strengthen the connection between the resin and the laying material, and reduce crazing. Moreover, during the web bonding stage and the post-curing stage, the actual heating temperature of the pre-cured half-shell and the clamped blade is lower than the glass transition temperature, which can reduce the severity of the release of internal stress in the resin. Compared with the blade forming method of the prior art (heating up in sequence during the pre-curing stage, web bonding stage, and post-curing stage), it can reduce the generation of crazing and improve the quality of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0022] Figure 1Schematic flow diagram of the blade forming method according to some embodiments of the present application; Figure 2 Schematic pre-curing process diagram of the blade forming method according to some embodiments of the present application; Figure 3 Schematic diagram of vacuum infusion in the blade forming method according to some embodiments of the present application; Figure 4 Schematic diagram of web bonding in the blade forming method according to some embodiments of the present application; Figure 5 Schematic diagram of post-curing in the blade forming method according to some embodiments of the present application; Figure 6 Schematic structural diagram of the closed-mold blade according to some embodiments of the present application.

[0023] In the accompanying drawings: 1 - forming mold; 2 - windward shell; 3 - leeward shell; 4 - half shell to be assembled; 5 - web; 6 - closed-mold blade; 7 - closed-mold die. Detailed implementation manners

[0024] The features and exemplary embodiments of various aspects of the present application will be described in detail below. To make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0025] It should be noted that in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, elements defined by the statement "comprising..." do not exclude the presence of additional identical elements in the process, method, article or device comprising the said elements.

[0026] Wind turbine blades are the foundation and core components of wind power generation systems. Their good design, reliable quality and superior performance are the decisive factors to ensure the stable operation of wind power generation systems. With the development of large-scale blades, the blade root diameter and the thickness of the fiber cloth in the blade structure have increased significantly, which has led to the silver streak problem of super-large blades (blade length not less than 95 meters).

[0027] Silver streaks refer to tiny and dense cracks that appear on the surface or inside glassy polymers or some semi-crystalline polymers and epoxy resins due to stress or environmental factors. The cross section of the crack can cause total reflection of light, resulting in a silver flash, hence the name silver streaks.

[0028] In the production process of wind turbine blades, after vacuum infusion, the resin (such as epoxy resin) infiltrates the reinforcement layer (such as fiber cloth), and after the resin is cured, it combines with the reinforcement layer, and stress exists on the bonding surface. During the repeated heating process of wind turbine blade molding, the molecular chain segments of the resin slip under the action of stress to form micro-cavities, and are oriented along the stress direction, thereby forming cracks with a silvery white luster. The presence of silver streaks affects the quality of wind turbine blades, and thus becomes a problem that technicians in this field need to solve urgently.

[0029] To improve the silver streak defect, the relevant technology uses infusion curing to eliminate the silver streak, that is, by adjusting the infusion sequence and timing of different areas of the blade, the time difference in the completion of the infusion of each part is shortened. Its main drawback is that due to the complexity of the blade design structure, it is difficult to achieve synchronous infusion by adjusting the infusion sequence and timing, which is prone to serious blade quality problems.

[0030] In view of this, the present application provides a blade forming method and a blade, which can reduce the generation of silver streaks during the blade curing process and improve the quality of the blade.

[0031] Please refer to Figures 1 to 6 ,in, Figure 1 A schematic diagram of a blade forming method according to some embodiments of the present application; Figure 2 A schematic diagram of the pre-curing process of the blade forming method according to some embodiments of the present application; Figure 3 A schematic diagram of vacuum infusion in a blade forming method according to some embodiments of the present application; Figure 4 A schematic diagram of web bonding in a blade forming method according to some embodiments of the present application; Figure 5 A schematic diagram of post-curing in a blade forming method according to some embodiments of the present application; Figure 6 This is a schematic diagram of the structure of the mold clamping blades of some embodiments of the present application.

[0032] The blade forming method provided in the embodiment of the present application is introduced below.

[0033] like Figure 1 ,Figures 3 to 5 As shown in the figure, an embodiment of the present application provides a blade forming method, which may include the following steps: S110-S150.

[0034] S110. Perform vacuum infusion in the forming mold 1 to obtain two infusion rear half shells respectively. The two infusion rear half shells include the windward side shell 2 and the leeward side shell 3.

[0035] In a wind power blade, the skin is located on the outer layer of the blade, covering the entire surface. In order to enhance the buckling characteristics of the skin, the skin adopts a sandwich structure design. The function of the skin is to capture wind energy and resist blade torsion and shell buckling. During the forming process of the wind power blade, the skin is formed in two parts separately. The part where the windward side is located and the part where the leeward side is located are formed separately and then assembled into the wind power blade.

[0036] When a blade (wind power blade) is subjected to vacuum infusion, it includes mold preparation, material laying, and infusion molding. Among them, mold preparation includes cleaning the mold, coating a release agent on the mold surface, and, depending on process requirements, heating the mold or not heating the mold. Material laying includes laying of reinforcing materials (such as fiberglass cloth, carbon fiber cloth, etc.), laying of core materials (such as balsa wood, PVC foam, etc.), and laying of auxiliary materials (such as release cloth, flow guiding net, vacuum bag film, etc.). Infusion molding includes vacuum system construction and resin infusion; when constructing the vacuum system, a sealed vacuum system is constructed using a vacuum bag and sealant to ensure no air leakage; when infusing the resin, air is pumped out by a vacuum pump to form a negative pressure in the mold, and the resin is sucked into the mold under the action of atmospheric pressure, permeating the filling materials in the mold and filling the mold cavity.

[0037] When the wind power blade is subjected to vacuum infusion, the windward side shell 2 and the leeward side shell 3 are separately subjected to vacuum infusion, each being infused on the forming mold 1. After infusion, two infusion rear half shells are obtained. One of the two infusion rear half shells is the windward side shell 2, and the other is the leeward side shell 3.

[0038] S120. Pre-cure the forming mold 1 by heating it to a temperature where the exothermic peak temperature of the infusion rear half shell is higher than the glass transition temperature to obtain a pre-cured half shell.

[0039] The resin releases significant heat during curing, and the principle of heat release during curing is heat release from chemical reactions. The resin undergoes a polycondensation reaction with a curing agent (such as amines, acid anhydrides, etc.) to form a three-dimensional network structure. During this process, the formation of chemical bonds releases stored chemical energy, mainly manifested in the form of heat. The heat release of the resin is related to temperature. At low temperatures (such as at room temperature), the curing reaction is slow and the heat release is small. At high temperatures (such as in a heated state), the curing reaction is fast and the heat release increases significantly. The heat release of the resin is also related to the amount of resin. Less resin results in less heat release, and more resin results in more heat release. During the curing process of the resin, heat is released and the temperature rises. When it reaches the peak, it is the heat release peak. During pre-curing by heating, the heat release peak temperature is higher than the heating temperature of pre-curing.

[0040] The glass transition temperature (Tg) is the adjacent temperature at which an amorphous polymer (such as the resin in the embodiments of the present application) transitions from a glassy state (hard and brittle) to a highly elastic state (soft and tough). When the temperature is below the glass transition temperature, the movement of molecular segments is frozen and the material is a rigid solid (glassy state); when the temperature is above the glass transition temperature, the molecular segments begin to move and the material exhibits high elasticity and flexibility (highly elastic state).

[0041] After the vacuum infusion of the rear half shell is completed during the infusion, the molding die 1 is pre-cured. During pre-curing, heating the molding die 1 can improve the curing speed. When heated to a temperature where the heat release peak temperature of the rear half shell during infusion is higher than the glass transition temperature, the curing reaction accelerates, the activity of molecular segments increases, the reaction rate between the curing agent and the resin increases, and the curing time can be shortened; the properties of the cured product are improved, the cross-linking density of the resin molecules increases, and the hardness, heat resistance, and mechanical strength of the cured product are all improved.

[0042] When heated to a temperature where the heat release peak temperature of the rear half shell during infusion is higher than the glass transition temperature, stop the pre-curing heating to obtain pre-cured half shells. There are two pre-cured half shells, one is the windward pre-cured shell and the other is the leeward pre-cured shell.

[0043] S130. Bond the pre-cured half shells and the web 5 with an adhesive and heat at an adhesive curing temperature lower than the heat release peak temperature to cure the adhesive and obtain two half shells 4 to be assembled.

[0044] In a wind turbine blade, the web 5 is located between two skins. The web 5 is part of the beam system and connects the beams on the upper and lower skins. The web 5 is composed of a sandwich structure, with the core material being foam and double-axis glass layers on both sides of the foam. The function of the web 5 is to provide support for the beam, improve the beam's anti-instability ability, and bear the shear force formed by the deformation of the two skins of the blade.

[0045] After pre-curing is completed to obtain a pre-cured semi-shell, a web 5 is bonded to the pre-cured semi-shell. When bonding the web 5, an adhesive is used to bond the web 5 to a pre-cured semi-shell (the windward pre-cured shell), and the pre-cured semi-shell is heated, so that the adhesive cures, realizing the bonded connection between the windward pre-cured shell and the web 5.

[0046] When heating the windward pre-cured shell, the entire windward pre-cured shell is heated instead of only heating the area where the adhesive is located. This is not only convenient for heating but also can optimize the internal stress of the entire windward pre-cured shell.

[0047] After the windward pre-cured shell is heated at the bonding and curing temperature, the adhesive cures to obtain an assembled semi-shell 4; the leeward pre-cured shell is not heated and serves as the other assembled semi-shell 4.

[0048] When heating the molding die 1 at the bonding and curing temperature, due to the self-cooling of the molding die 1 and other losses during heat transfer, the actual heating temperature of the windward pre-cured shell is lower than the bonding and curing temperature. Moreover, when the bonding and curing temperature is lower than the exothermic peak temperature, the actual heating temperature of the windward pre-cured shell is lower than the glass transition temperature, which can prevent the cured windward pre-cured shell from becoming highly elastic, thereby reducing or even avoiding the generation of silver streaks.

[0049] S140. The two assembled semi-shells 4 are clamped and bonded to obtain a clamped die 7 and a clamped blade 6.

[0050] After obtaining the two assembled semi-shells 4, an adhesive is applied to the bonding area on the two assembled semi-shells 4, and then the two assembled semi-shells 4 are assembled. The two assembled semi-shells 4 are assembled into a clamped blade 6, and the corresponding molding dies 1 of the two assembled semi-shells 4 become a clamped die 7 after clamping.

[0051] S150. The clamped die 7 is post-cured and heated at a post-curing temperature lower than the bonding and curing temperature, so that the clamped blade 6 reaches a predetermined temperature to obtain a formed blade.

[0052] After obtaining the clamped blade 6 and the clamped die 7, post-curing heating is carried out, and the clamped blade 6 is heated by heating the clamped die 7. When heating the clamped die 7, the clamped die 7 gradually heats up, and the clamped blade 6 heats up with the clamped die 7. There is heat dissipation and other heat losses in the clamped die 7, so that the actual heating temperature of the clamped blade 6 is lower than the post-curing temperature of heating the clamped die 7.

[0053] During heating, the actual temperature of the mold - closing blade 6 is used as a reference for post - curing. When the actual temperature of the mold - closing blade 6 reaches the predetermined temperature, heating is stopped, and the post - curing heating is completed. After cooling, the mold is opened to take out the mold - closing blade 6, and the formed blade is obtained.

[0054] For measuring the temperature of the mold - closing blade 6, the temperature detection can be achieved by using thermocouple temperature - measuring technology; or a wireless sensor network can be used, and wireless temperature sensor nodes are arranged on the surface or inside of the mold - closing blade 6, and the temperature data is transmitted to the central processing unit through wireless communication. When measuring the temperature, other temperature - measuring means can also be used as long as the temperature detection of the mold - closing blade 6 can be achieved.

[0055] In the embodiment of the present application, when pre - curing and heating the forming mold 1, heating to a temperature higher than the glass transition temperature at the exothermic peak temperature of the post - perfusion half - shell can accelerate the curing reaction, shorten the curing time, and improve the hardness, heat resistance and mechanical strength of the pre - cured half - shell. When the pre - cured half - shell is bonded and cured with the web 5, heating the entire pre - cured half - shell can optimize the internal stress of the pre - cured half - shell; the bonding and curing temperature is lower than the exothermic peak temperature, which can control the actual heating temperature of the pre - cured shell on the windward side to be lower than the glass transition temperature and reduce the generation of crazes. When performing post - curing heating, taking the actual temperature of the mold - closing blade 6 as a reference index for post - curing can more accurately control the quality of post - curing. In the blade forming method of this embodiment, the exothermic peak temperature during pre - curing is higher than the glass transition temperature, the bonding and curing temperature during the bonding of the web 5 is lower than the exothermic peak temperature, and the post - curing temperature during post - curing is lower than the bonding and curing temperature. The three temperatures decrease in turn, which can avoid the resin from expanding and contracting repeatedly, strengthen the connection between the resin and the laying material, and reduce crazes. Moreover, during the bonding stage of the web 5 and the post - curing stage, the actual heating temperatures of the pre - cured half - shell and the mold - closing blade 6 are both lower than the glass transition temperature, which can reduce the severity of the release of resin internal stress and reduce the generation of crazes, thereby improving the blade quality.

[0056] As Figure 2 shown, in some embodiments, S120 (pre - curing and heating the forming mold 1 to a temperature higher than the glass transition temperature at the exothermic peak temperature of the post - perfusion half - shell to obtain a pre - cured half - shell) includes: S121 - S122.

[0057] S121. Divide the forming mold 1 into a root - curing area and a remaining - curing area.

[0058] Along the length direction, the wind turbine blade can be divided into three parts, namely the root section, the middle section and the tip section. The root section is the part where the wind turbine blade is connected to the hub, the middle section is the part between the root section and the tip section, and the tip section is the outermost end of the blade.

[0059] In a wind turbine blade, the wall thickness of the root section is large, the resin consumption is high, and silver streak defects are likely to occur. In this application, the wind turbine blade and the intermediate product during its molding process are divided into two parts along the length direction, one part corresponding to the root section and the other part being the remaining section; similarly, corresponding to the molding die 1, the area for assisting the molding of the root section is the root curing area, and the area for assisting the molding of the remaining section is the remaining curing area.

[0060] S122. Heat the root curing area at a first pre-curing temperature, and at the same time heat the remaining curing area at a second pre-curing temperature. Among them, the first pre-curing temperature rises in a gradient manner, rising from a temperature lower than the second pre-curing temperature to a temperature higher than the second pre-curing temperature.

[0061] Arrange a set of heating systems in the root curing area for heating the root curing area of the molding die 1; arrange another set of heating systems in the remaining curing area for heating the remaining curing area of the molding die 1. The two sets of heating systems are independently set and do not interfere with each other during operation. The first set of heating systems can heat the root curing area at the first pre-curing temperature, and the second set of heating systems can heat the remaining curing area at the second curing temperature. Among them, the value of the second curing temperature is constant, and the first curing temperature rises in a gradient manner, and the heating temperature gradually increases with the curing time. At the beginning of pre-curing, the first pre-curing temperature is lower than the second pre-curing temperature, and in the later stage of pre-curing, the first pre-curing temperature is higher than the second pre-curing temperature.

[0062] When the first pre-curing temperature rises in a gradient manner, there can be multiple heating temperature values. For example, the first pre-curing temperature can have multiple temperature values, and each temperature value is heated for a period of time. When rising between adjacent temperature values, the temperature rise is carried out slowly, and the temperature rise amplitude can be less than or equal to 1°C per minute.

[0063] In the embodiment of this application, dividing the molding die 1 into areas and heating them independently can optimize the internal stress distribution of the pre-cured half shell. And the first pre-curing temperature rises in a gradient manner, rising from a temperature lower than the second pre-curing temperature to a temperature higher than the second pre-curing temperature. In the area of the root section with more resin, the starting heating temperature is lower, which can reduce the problem of local stress concentration. In the later stage, the heating temperature is higher, which can shorten the curing time, so that the root section and the remaining section of the pre-cured half shell can complete pre-curing at the same time. In addition, the first pre-curing temperature is from low to high during the pre-curing process. Even if there is local stress concentration in the root section in the early stage of pre-curing, the internal stress can be released when the temperature is high (higher than the glass transition temperature) in the later stage, thereby reducing silver streaks.

[0064] In some embodiments, S121 (dividing the molding die 1 into a root curing area and a remaining curing area) includes: dividing the post-infusion rear half shell along the length direction into a root strengthening area and a remaining area, obtaining the root curing area based on the root strengthening area, and obtaining the remaining curing area based on the remaining area.

[0065] The root strengthening area corresponds to the root section of the post-infusion rear half shell, and the remaining area corresponds to the remaining sections (the middle section and the tip section) of the post-infusion rear half shell.

[0066] The root curing area is used for curing the root strengthening area, and the remaining curing area is used for curing the remaining area. Preferably, the root strengthening area is the area from the free end of the root of the post-infusion rear half shell to 15 m of the post-infusion rear half shell.

[0067] In the embodiments of the present application, curing the root strengthening area and the remaining area separately facilitates controlling the pre-curing process of the root strengthening area. In particular, dividing the 0 m to 15 m in the length direction of the post-infusion rear half shell into the root strengthening area is helpful for realizing the standardization of the curing process for large wind turbine blades (with a length of not less than 95 meters and a similar root section length).

[0068] In some embodiments, S120 (pre-curing and heating the molding die 1 until the exothermic peak temperature of the post-infusion rear half shell is higher than the glass transition temperature to obtain a pre-cured half shell) includes: heating the molding die 1 to a pre-curing temperature lower than the exothermic peak temperature for a predetermined duration, stopping heating, and naturally cooling to room temperature.

[0069] When heating the molding die 1 at the pre-curing temperature, the post-infusion rear half shell is heated, the curing reaction intensifies, and the resin exotherm makes the actual temperature of the post-infusion rear half shell higher than the pre-curing temperature and higher than the glass transition temperature. By continuously heating the molding die 1 at the pre-curing temperature, the curing reaction can be efficiently carried out during the pre-curing heating for the predetermined duration.

[0070] In the embodiments of the present application, considering the resin curing exotherm, the pre-curing temperature is lower than the exothermic peak temperature: firstly, it can reduce the exothermic rate of the resin and lower the internal stress; secondly, it can improve the molding quality, contribute to the uniform infiltration of the resin and the laying material, improve the cross-section bonding force of the composite material, and thus improve the overall performance of the pre-cured half shell; thirdly, it can make the heating of the molding die 1 more gentle, thereby reducing the thermal stress of the molding die 1 and extending its service life.

[0071] In some embodiments, the exothermic peak temperature is the temperature peak of the root strengthening area during pre-curing, the difference between the exothermic peak temperature and the glass transition temperature is 5°C to 15°C, the exothermic peak temperature is 90°C to 100°C; the glass transition temperature is greater than the pre-curing temperature.

[0072] The exothermic peak temperature is greater than the glass transition temperature, and the glass transition temperature is greater than the pre-curing temperature. The exothermic peak temperature is controlled between 90°C and 100°C. Exemplarily, depending on the resin and curing agent, the exothermic peak temperature can be any value among 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, or any intermediate value between any two adjacent of the above values.

[0073] The difference between the exothermic peak temperature and the glass transition temperature can be any value among 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, or any intermediate value between any two adjacent of the above values. Preferably, the glass transition temperature (the temperature peak during pre-curing in the blade root strengthening region) is 85°C.

[0074] In the embodiments of the present application, the pre-curing temperature is less than the glass transition temperature, and the glass transition temperature is less than the exothermic peak temperature, which can improve the curing performance and reduce the generation of silver streaks.

[0075] In some embodiments, S122 (heating the blade root curing region at a first pre-curing temperature while heating the remaining curing region at a second pre-curing temperature, with the first pre-curing temperature increasing in a gradient manner from below the second pre-curing temperature to above the second pre-curing temperature) includes: heating the blade root pre-curing region in three temperature steps that gradually increase, heating the blade root curing region at the first temperature step for a first duration, heating the blade root curing region at the second temperature step for a second duration, and heating the blade root curing region at the third temperature step for a third duration. Among them, the second temperature step is equal to the second pre-curing temperature, and the sum of the first duration, the second duration, and the third duration is equal to the heating duration of the remaining curing region.

[0076] The first temperature step is lower than the second pre-curing temperature, and the third temperature step is higher than the second pre-curing temperature. The blade root strengthening region is divided into three time periods during pre-curing, the first time period is the first duration, the second time period is the second duration, and the third time period is the third duration. The sum of the first duration, the second duration, and the third duration is equal to the heating duration of the remaining region, so that the blade root strengthening region and the remaining region complete pre-curing simultaneously.

[0077] In the embodiments of the present application, dividing the first pre-curing temperature into three temperature steps facilitates the control of the pre-curing process of the blade root strengthening region and enables the blade root strengthening region and the remaining region to complete pre-curing simultaneously, reducing the time difference between their pre-curing processes, thereby improving the pre-curing quality.

[0078] In some embodiments, the first duration is greater than the second duration, the second duration is less than the third duration, and the difference between the second temperature step and the first temperature step is greater than the difference between the third temperature step and the second temperature step.

[0079] The first duration is greater than the second duration, the third duration is greater than the second duration, and the third duration may or may not be equal to the first duration.

[0080] In the embodiments of the present application, the first gear temperature is low and the heating time is long, which can enable the resin to be steadily cured and gradually crosslinked, having a stable adaptation process. The third gear temperature is high and the heating time is long, which can enable the resin to be quickly cured, accelerate the curing rate, and improve the curing strength. The second gear temperature is between the first gear temperature, and the heating duration is less than the first duration and the second duration, which can provide a transition between the first gear temperature and the third gear temperature. The difference between the second gear temperature and the first gear temperature is greater than the difference between the third gear temperature and the second gear temperature, which can further improve the stability during the transition.

[0081] In some embodiments, the first gear temperature is 50 °C, the first duration is 3 hours, the second gear temperature is 65 °C, the second duration is 1 hour, the third gear temperature is 75 °C, and the third duration is 3 hours.

[0082] The heating duration of the blade root curing area is 7 hours, and the heating duration of the remaining curing area is 7 hours. The heating durations of the two during pre-curing are equal. The second pre-curing temperature is 65 °C.

[0083] In the embodiments of the present application, the first gear temperature is 50 °C and it is heated for 3 hours, which can improve the fluidity of the resin and provide a stable curing environment. The second gear temperature is 65 °C and it is heated for 1 hour, which can transition the heating temperature to the third gear temperature; the third gear temperature is 75 °C and it is heated for 3 hours, which can improve the curing efficiency and curing quality. In addition, through the above temperature values and heating durations, the highest temperature in the blade root strengthening area can reach about 95 °C (for example, 95 ± 5 °C), and the glass transition temperature in the area prone to crazing can reach about 85 °C (for example, 85 ± 5 °C).

[0084] In some embodiments, S130 (adhesively bonding the pre-cured half shell and the web 5 and heating at an adhesive curing temperature lower than the exothermic peak temperature to cure the adhesive to obtain two half shells 4 to be assembled) includes: heating the forming die 1 at the adhesive curing temperature, keeping the temperature of the pre-cured half shell lower than the glass transition temperature, and stopping heating after the adhesive reaches a predetermined hardness.

[0085] When heating the forming die 1, the entire forming die 1 where the pre-cured half shell to be bonded is located is heated. During heating, the hardness of the adhesive is used as the control basis, and heating is completed when the adhesive reaches a predetermined hardness.

[0086] Preferably, the adhesive curing temperature is 85 °C and the predetermined hardness is 50 HD of Shore hardness.

[0087] In an embodiment of the present application, heating is performed at a bonding and curing temperature lower than the exothermic peak temperature. On the premise of considering the heat loss of the forming mold 1, the temperature of the pre-cured half shell is lower than the glass transition temperature, which can reduce the severity of stress release in the pre-cured half shell during heating; using the hardness of the bonding adhesive as the control basis can ensure the curing quality of the bonding adhesive.

[0088] As Figure 5 and Figure 6 shown, in some embodiments, S140 (performing mold closing and bonding on two half shells 4 to be assembled to obtain a mold closing mold 7 and a mold closing blade 6) includes: cooling to room temperature, applying glue to the half shell 4 to be assembled bonded with the web 5 and the half shell 4 to be assembled not bonded with the web 5, bonding the two half shells 4 to be assembled at the joint, and closing the forming mold 1.

[0089] After completing S130, the forming mold 1 where the windward pre-cured shell is located is naturally cooled to room temperature and the mold is opened. Glue is applied to the bonding area on the two half shells 4 to be assembled. After the glue application is completed, one of the forming molds 1 where the half shell 4 to be assembled is located is flipped so that the two half shells 4 to be assembled are assembled into a mold closing blade 6. The two forming molds 1 are assembled into a mold closing mold 7, and the mold closing blade 6 is restricted in the cavity.

[0090] In an embodiment of the present application, first natural cooling is performed, and then bonding and mold closing are carried out, which not only helps the curing of the bonding adhesive between the web 5 and the half shell 4 to be assembled, improves the bonding strength, but also can reduce the safety risk and prevent high-temperature scalding.

[0091] In some embodiments, S150 (performing post-curing heating on the mold closing mold 7 at a post-curing temperature lower than the bonding and curing temperature so that the mold closing blade 6 reaches a predetermined temperature to obtain a formed blade) includes: heating the mold closing mold 7, raising the temperature to the post-curing temperature at a predetermined temperature rise and maintaining it, stopping heating after heating the mold closing blade 6 to the predetermined temperature, and naturally cooling to room temperature.

[0092] Exemplarily, the post-curing temperature is 80 °C, the predetermined temperature is 70 °C, and the predetermined temperature rise is 0.5 °C / min to 1 °C / min. The predetermined temperature rise can be any value among 0.5 °C / min, 0.6 °C / min, 0.7 °C / min, 0.8 °C / min, 0.9 °C / min, 1 °C / min, or any intermediate value between any two adjacent values above.

[0093] In the embodiments of the present application, using the actual temperature of the mold closing blade 6 as the control basis for post-curing can improve the reliability of post-curing; a predetermined temperature rise not exceeding 1 °C / min can improve the quality of post-curing. Especially when the post-curing temperature is 80 °C, the predetermined temperature of 70 °C can be reached relatively quickly, which can improve the production efficiency of the mold closing blade 6 and make the glass transition temperature of the mold closing blade 6 meet the standard.

[0094] The embodiments of the present application also provide a blade, which is made by using the above-mentioned blade forming method. By controlling the pre-curing temperature, the web 5 bonding temperature, the post-curing temperature, and the temperature in sub-regions during pre-curing during molding, the stress release can be alleviated, thereby reducing silver streaks and improving the blade quality.

[0095] The present application is described below by comparing different blade forming methods:

[0096] Example 1 When pre-curing the molding die by heating to a temperature at which the exothermic peak temperature of the half shell during pouring is higher than the glass transition temperature to obtain a pre-cured half shell, in the root strengthening region (0 m to 15 m), it is heated at 50 °C for 3 hours, 65 °C for 1 hour, and 75 °C for 3 hours in sequence. At the same time, other regions except the root strengthening region are heated at 65 °C for 7 hours. When bonding the pre-cured half shell and the web with an adhesive, it is heated at 85 °C after completion of bonding. When post-curing the mold closing die by heating at a post-curing temperature lower than the bonding curing temperature, it is heated at 80 °C.

[0097] Comparative Example 1 When pre-curing the molding die by heating to obtain a pre-cured half shell, it is heated at 65 °C for 7 hours. When bonding the pre-cured half shell and the web with an adhesive, it is heated at 80 °C after completion of bonding. When post-curing the mold closing die by heating, it is heated at 85 °C.

[0098] Comparative Example 2 When pre-curing the molding die by heating to obtain a pre-cured half shell, in the root strengthening region (0 m to 15 m), it is heated at 45 °C for 3 hours, 65 °C for 1 hour, and 75 °C for 3 hours in sequence. At the same time, other regions except the root strengthening region are heated at 65 °C for 7 hours. When bonding the pre-cured half shell and the web with an adhesive, it is heated at 80 °C after completion of bonding. When post-curing the mold closing die by heating, it is heated at 85 °C.

[0099] In the examples and each comparative example, the heating temperatures at each stage and the relevant parameters of the total silver streak area of the formed blades are shown in Table 1.

[0100] Table 1

[0101] As can be seen from the table, the molded blade of Example 1 has no silver streak defect after demolding, the molded blade of Comparative Example 1 has large-area silver streak defects after demolding, and the molded blade of Comparative Example 2 has small-area silver streak defects after demolding.

[0102] Further analysis shows that the thickness of the blade root region of the molded blade is large, the amount of resin required is large, and it is the region where silver streaks are likely to appear.

[0103] Compared with Example 1, in Comparative Example 1, the blade root strengthening region was not heated in a stepped manner during pre-curing. The resin in the blade root strengthening region faced a relatively high temperature at the beginning of heating. There were differences in the curing times of the resins in different layers. The resin closer to the heat source cured first, resulting in the accumulation of a large amount of internal stress, which was likely to cause silver streaks. Moreover, during post-curing, the heating temperature was increased, further releasing a large amount of internal stress, thus generating large-area silver streaks.

[0104] Compared with Comparative Example 1, in Comparative Example 2, the blade root strengthening region was heated in a stepped manner, with a low initial heating temperature. During the stepped heating process, the difference in the curing times of the resins in each layer was small, and the accumulated internal stress was small, which could effectively reduce the generation of silver streaks.

[0105] Compared with Example 1, in Comparative Example 2, the heating rate during pre-curing was slightly larger, and the heating temperature during post-curing was higher than the heating temperature during web bonding. Increasing the heating temperature during post-curing exacerbated the intensity of the internal stress release in the molded blade, and a small amount of silver streaks were generated in the local area (the area where the internal stress release was concentrated) of the blade.

[0106] By comparing Example 1 with Comparative Example 1 and Comparative Example 2 in the web bonding stage and the post-curing stage, it can be seen that making the heating temperature during post-curing lower than the heating temperature during web bonding helps to inhibit the intensity of internal stress release.

[0107] It can be seen that in this application, heating the blade root strengthening region in a stepped manner during pre-curing helps to alleviate the difference in the curing times of the resins in different layers and reduce the accumulation of internal stress. During web bonding and post-curing heating, the temperature is gradually decreased, that is, the highest temperature in the molded blade during repeated heating (pre-curing, web bonding, post-curing) decreases successively, which can alleviate the intensity of internal stress release and avoid the generation of silver streaks.

[0108] The above is only the specific implementation manner of this application. Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems, modules, and units can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A blade forming method, characterized in that: include: Performing vacuum infusion in the forming mold to obtain two infusion rear half shells, respectively, wherein the two infusion rear half shells include a windward shell and a leeward shell; Pre-curing and heating the molding die until the exothermic peak temperature of the half shell after infusion is higher than the glass transition temperature, thereby obtaining a pre-cured half shell; Bonding the pre-cured half shell and the web with adhesive, and heating them at an adhesive curing temperature lower than the exothermic peak temperature so that the adhesive is cured to obtain two half shells to be assembled; Perform mold closing and bonding on the two half shells to be assembled to obtain a mold closing mold and a mold closing blade; The mold clamping die is subjected to post-curing heating at a post-curing temperature lower than the bonding curing temperature, so that the mold clamping blade reaches a predetermined temperature to obtain a molded blade.

2. The blade forming method according to claim 1, characterized in that: The pre-curing and heating of the molding die until the exothermic peak temperature of the half shell after infusion is higher than the glass transition temperature to obtain the pre-cured half shell includes: Dividing the forming mold into a blade root curing area and a remaining curing area; The blade root curing area is heated at a first pre-curing temperature, and the remaining curing area is heated at a second pre-curing temperature. The first pre-curing temperature is increased in a gradient from lower than the second pre-curing temperature to higher than the second pre-curing temperature.

3. The blade forming method according to claim 2, characterized in that: The step of dividing the forming mold into a blade root solidification area and a remaining solidification area comprises: Dividing the infused rear half shell into a blade root reinforcement area and a remaining area along the length direction, deriving the blade root solidification area according to the blade root reinforcement area, and deriving the remaining solidification area according to the remaining area; Preferably, the blade root reinforcement area is an area from 0m to 15m of the infusion rear half shell starting from the blade root free end of the infusion rear half shell.

4. The blade forming method according to claim 3, characterized in that: The pre-curing and heating of the molding die until the exothermic peak temperature of the half shell after infusion is higher than the glass transition temperature to obtain the pre-cured half shell includes: Heating the molding die at a pre-curing temperature lower than the exothermic peak temperature for a predetermined time, stopping the heating and cooling naturally to room temperature; Preferably, the exothermic peak temperature is the peak temperature of the blade root reinforcement area during pre-curing, the difference between the exothermic peak temperature and the glass transition temperature is 5°C to 15°C, the exothermic peak temperature is 90°C to 100°C; the glass transition temperature is greater than the pre-curing temperature.

5. The blade forming method according to claim 2, characterized in that: The step of heating the blade root curing area at a first pre-curing temperature and heating the remaining curing area at a second pre-curing temperature, wherein the first pre-curing temperature is increased in a gradient from lower than the second pre-curing temperature to higher than the second pre-curing temperature, comprises: The blade root pre-curing area is heated in sequence at three gradually increasing temperature levels, the blade root curing area is heated at a first temperature level for a first time, the blade root curing area is heated at a second temperature level for a second time, and the blade root curing area is heated at a third temperature level for a third time; The second temperature is equal to the second pre-curing temperature, and the sum of the first time duration, the second time duration, and the third time duration is equal to the heating time duration of the remaining curing area.

6. The blade forming method according to claim 5, characterized in that: The first duration is greater than the second duration, the second duration is less than the third duration, and the difference between the second temperature range and the first temperature range is greater than the difference between the third temperature range and the second temperature range; Preferably, the first temperature is 50° C., the first duration is 3 hours, the second temperature is 65° C., the second duration is 1 hour, the third temperature is 75° C., and the third duration is 3 hours.

7. The blade forming method according to claim 1, characterized in that: The pre-cured half shell and the web are bonded with adhesive and heated at an adhesive curing temperature lower than the exothermic peak temperature so that the adhesive is cured to obtain two half shells to be assembled, including: The molding die is heated at the bonding curing temperature to keep the temperature of the pre-cured half shell lower than the glass transition temperature, and the heating is stopped after the bonding glue reaches a predetermined hardness; Preferably, the bonding curing temperature is 85° C., and the predetermined hardness is Shore hardness 50 HD.

8. The blade forming method according to claim 1, characterized in that: The method of performing mold closing and bonding on the two half shells to be assembled to obtain a mold closing mold and a mold closing blade comprises: After cooling to room temperature, the half shell to be assembled with the web bonded thereto and the half shell to be assembled without the web bonded thereto are coated with glue, the two half shells to be assembled are bonded at the joint, and the molding mold is closed.

9. The blade forming method according to claim 1, characterized in that: The post-curing heating of the mold clamping die at a post-curing temperature lower than the bonding curing temperature so that the mold clamping blade reaches a predetermined temperature to obtain a molded blade comprises: The mold clamping mold is heated to the post-curing temperature at a predetermined temperature rise and maintained, and the heating is stopped after the mold clamping blade reaches the predetermined temperature, and the mold is naturally cooled to room temperature; Preferably, the post-curing temperature is 80° C., the predetermined temperature is 70° C., and the predetermined temperature rise is 0.5° C. / min to 1° C. / min.

10. A blade, characterized in that: include: The blade is manufactured by the blade forming method according to any one of claims 1 to 9.

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