A blade structure and design method

Abstract

An embodiment of the present invention discloses a blade structure and a design method for passive load reduction, including: a blade body including a housing; the housing includes a strengthening region and a torsional weak region, and a first main beam and a web are provided on the inner wall of the strengthening region; the first main beam and the web are used to strengthen the stiffness of the strengthening region; the torsional stiffness of the torsional weak region is less than that of the strengthening region. For the blade structure provided by the present invention, a torsional weak region is provided on the blade body, and by reducing the torsional stiffness of the torsional weak region, the bending-torsion coupling effect is improved. Compared with the aeroelastic tailoring method, it gets rid of the constraint of the blade chord length and has a larger adjustment space; compared with the swept-back load reduction method, since the torsional stiffness of the torsional weak region is reduced, the increase in the load of the blade pitch motor caused by the increase in the torsional load is avoided, and by reducing the torsional stiffness, the bending-torsion coupling effect is more effectively improved, realizing passive load reduction and improving the stability after reducing the blade load.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and more specifically, to a blade structure and a design method. Background Art

[0002] With the development of large-scale wind turbines, the blades of wind power generation are getting longer and longer. In order to reduce the blade load, different load reduction methods have been proposed, which are mainly divided into active load reduction and passive load reduction. Active load reduction uses control systems and actuators to reduce blade loads. Its load reduction effect is better, but the need to add active actuators will increase equipment costs and make maintenance more difficult. Passive load reduction uses the bending-torsion coupling effect of the blade itself to reduce the blade load. Specifically, passive load reduction is achieved by designing the blade shape and ply structure to improve the bending-torsion coupling effect and reduce the blade load. This method does not require additional costs, is simple to maintain, and is easier to promote and apply.

[0003] In the prior art, passive load reduction methods generally include swept load reduction and aeroelastic trimming. The aeroelastic trimming method increases the bending-torsion coupling effect of the blade by adjusting the angle of the blade ply. Limited by the constraint of the blade chord length, the adjustable space is very limited, and the load reduction effect is poor. The swept load reduction method increases the bending-torsion coupling effect of the blade by changing the geometric shape of the blade. This method increases the torsional load of the blade, which in turn causes the aeroelastic stability of the blade to deteriorate, making it more prone to safety issues such as blade cracking. At the same time, due to the increase in torsional load, the load of the blade pitch motor increases, which in turn increases the cost of the blade pitch motor.

[0004] Therefore, how to improve the stability after reducing the blade load has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a blade structure to improve the stability after reducing the blade load;

[0006] Another object of the present invention is to provide a method for designing a blade structure.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A blade structure for passive load reduction, comprising:

[0009] The blade body comprises a shell; the shell comprises a reinforced area and a torsionally weak area, and a first main beam and a web are arranged on the inner wall of the reinforced area; the first main beam and the web are used to strengthen the rigidity of the reinforced area; the torsional rigidity of the torsionally weak area is less than the torsional rigidity of the reinforced area.

[0010] Optionally, in the above blade structure, a second main beam is provided on the inner wall of the torsional weak area, and the second main beam is used to improve the bending stiffness of the torsional weak area.

[0011] Optionally, in the above blade structure, a leading-edge strengthening layer and a trailing-edge strengthening layer are provided in the strengthening area, and the leading-edge strengthening layer and the trailing-edge strengthening layer in the strengthening area are used to improve the bearing capacity of the strengthening area; a leading-edge strengthening layer and a trailing-edge strengthening layer are provided in the torsional weak area, and the leading-edge strengthening layer and the trailing-edge strengthening layer in the torsional weak area are used to improve the bearing capacity of the torsional weak area.

[0012] Optionally, in the above blade structure, the spanwise range of the torsional weak area is 0.5 m to 1.0 m.

[0013] Optionally, in the above blade structure, the distance between the torsional weak area and the tip of the blade body is d, and 5 m ≤ d ≤ 10 m.

[0014] A design method for a blade structure. For the design method of the blade structure as described above, it includes the steps:

[0015] Initial blade design, designing the initial blade that meets the standard requirements;

[0016] Setting the torsional weak area, setting the torsional weak area on the shell of the initial blade;

[0017] Load extraction, extracting the load of the torsional weak area;

[0018] Setting initial parameters, giving the initial elastic torsional angle, and the initial parameters of the second main beam, the leading-edge strengthening layer and the trailing-edge strengthening layer in the weak area;

[0019] Calculating the torsional stiffness, calculating the torsional stiffness of the torsional weak area according to the load of the torsional weak area and the initial elastic torsional angle;

[0020] Determining the ply parameters, obtaining the ply parameters of the shell of the torsional weak area by using a torsional stiffness calculation program;

[0021] Adjusting the bending stiffness, adjusting the bending stiffness of the torsional weak area so that the bending stiffness of the torsional weak area is the same as that of the initial blade;

[0022] Strength checking, calculating the ply strength of the torsional weak area according to the load of the torsional weak area and checking the ply strength;

[0023] Determine the target ply, where the ply strength meets the requirements, and output the ply of the torsional weak area as the target ply.

[0024] Optionally, in the above-mentioned blade structure design method, the following steps are further included:

[0025] Load check: Recalculate the blade load and check the elastic torsional angle according to the target ply of the determined torsional weak area to ensure the load reduction effect and safety.

[0026] Optionally, in the above-mentioned blade structure design method, in the step of adjusting the bending stiffness, by adjusting the second main girder, the leading edge reinforcement layer of the weak area, and the trailing edge reinforcement layer of the weak area, the bending stiffness of the torsional weak area is made the same as the bending stiffness of the initial blade.

[0027] Optionally, in the above-mentioned blade structure design method, by reducing the laying layers and width of the leading edge reinforcement layer of the weak area, the torsional stiffness of the torsional weak area is reduced; and / or,

[0028] By reducing the laying layers and width of the trailing edge reinforcement layer of the weak area, the torsional stiffness of the torsional weak area is reduced.

[0029] Optionally, in the above-mentioned blade structure design method, the value range of the initial elastic torsional angle is 1° to 5°.

[0030] Optionally, in the above-mentioned blade structure design method, the loads of the torsional weak area include torsional load and bending load; the torsional load is used to calculate the torsional stiffness or elastic torsional angle; the bending load is used to calculate the ply strength of the shell of the torsional weak area, the leading edge reinforcement layer of the weak area, the trailing edge reinforcement layer of the weak area, and the second main girder.

[0031] The blade structure provided by the present invention, by setting a strengthening area and a torsional weak area on the shell of the blade body, and arranging a first main girder and a web on the inner wall of the strengthening area to enhance the stiffness of the strengthening area, and the torsional stiffness of the torsional weak area is less than the torsional stiffness of the strengthening area, so that the torsional deformation of the torsional weak area increases, thereby improving the bending-torsion coupling effect and realizing passive load reduction.

[0032] Compared with the passive load reduction method in the prior art, the blade structure provided by the present invention sets a torsional weak area on the blade body. By reducing the torsional stiffness of the torsional weak area and increasing the torsional deformation, the bending-torsion coupling effect is improved. Compared with the aeroelastic tailoring method, it gets rid of the constraint of the blade chord length and has a larger adjustment space. Compared with the swept-back load reduction method, since the torsional stiffness of the torsional weak area is reduced, the increase in the torsional load resulting in an increase in the load of the blade pitch motor is avoided, and the cost of the blade pitch motor is reduced to a certain extent. Moreover, by reducing the torsional stiffness of the torsional weak area, the bending-torsion coupling effect is more effectively improved, realizing passive load reduction and improving the stability after reducing the blade load. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0034] Figure 1 The lamination design process of the torsional weak area provided by the embodiment of the present invention Figure 1 ;

[0035] Figure 2 The lamination design process of the torsional weak area provided by the embodiment of the present invention Figure 2 ;

[0036] Figure 3 The lamination design process of the torsional weak area provided by the embodiment of the present invention Figure 3 ;

[0037] Figure 4 The schematic diagram of the blade structure provided by the embodiment of the present invention;

[0038] Figure 5 The schematic diagram of the internal structure of the blade structure provided by the embodiment of the present invention;

[0039] Figure 6 The schematic diagram of the torsional weak area of the blade structure provided by the embodiment of the present invention;

[0040] Figure 7 is Figure 6 the sectional view taken along line A-A in

[0041] Among them, 100 is the housing, 101 is the blade root, 102 is the blade tip, 103 is the leading edge, 1031 is the strengthening layer of the leading edge in the strengthening area, 104 is the trailing edge, 1041 is the strengthening layer of the trailing edge in the strengthening area, 105 is the first main beam, 106 is the web, 107 is the torsion-weak area, 1071 is the second main beam, 1072 is the strengthening layer of the leading edge in the weak area, 1073 is the strengthening layer of the trailing edge in the weak area, and 108 is the strengthening area. Detailed implementation mode

[0042] The core of the present invention lies in providing a blade structure to improve the stability after reducing the blade load;

[0043] Another core of the present invention lies in providing a design method for the blade structure.

[0044] Next, the technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0045] As Figure 1 shown, the embodiment of the present invention discloses a blade structure, including a blade body. It should be noted that for the blade structure disclosed in the embodiment of the present invention, the torsional stiffness in a partial area range on the blade body is mainly reduced, so that the torsional deformation in this area increases. Those skilled in the art can understand that under the condition of a certain bending deformation, the larger the torsional deformation, the greater the bending-torsion coupling effect. By increasing the bending-torsion coupling effect, the passive load reduction of the blade is realized. Of course, the blade load reduction method and the blade structure disclosed in the embodiment of the present invention can be applied not only to the initial blade (the blade meeting the standard requirements), but also to the blade that realizes passive load reduction by changing the blade geometric shape, so as to further realize the blade load reduction. As long as the blade structure, the design method of the blade structure, and the load reduction method disclosed in the embodiment of the present invention are adopted, they are all within the protection scope of the present application.

[0046] Specifically, as Figures 3 to 5As shown, the blade body includes a housing 100. Among them, the housing 100 includes a strengthening region 108 and a torsional weak region 107. On the inner wall of the strengthening region 108, a first main beam 105 and a web 106 are provided, and the first main beam 105 and the web 106 are arranged inside the housing 100. The first main beam 105 plays a role in supporting the entire blade structure, and the first main beam 105 and the web 106 work together to enhance the torsional stiffness and bending stiffness of the strengthening region 108. In order to improve the bending-torsion coupling effect of the blade structure and achieve blade load reduction, in the blade structure disclosed in the embodiments of the present invention, by reducing the torsional stiffness of the torsional weak region 107, the torsional stiffness of the torsional weak region 107 is made smaller than the torsional stiffness of the strengthening region 108, thereby increasing the torsional deformation of the torsional weak region 107, improving the bending-torsion coupling effect of the blade structure, achieving passive blade load reduction, and by reducing the torsional stiffness of the torsional weak region 107, more effectively improving the bending-torsion coupling effect, achieving passive load reduction, and improving the stability after reducing the blade load. It should be noted that the strengthening region 108 is the region of the housing 100 of the blade body other than the torsional weak region 107.

[0047] The blade structure provided by the present invention, by providing a strengthening region 108 and a torsional weak region 107 on the housing 100 of the blade body, and arranging a first main beam 105 and a web 106 on the inner wall of the strengthening region 108 to enhance the stiffness of the strengthening region 108, and the torsional stiffness of the torsional weak region 107 is smaller than the torsional stiffness of the strengthening region 108, so that the torsional deformation of the torsional weak region 107 is increased, thereby improving the bending-torsion coupling effect and achieving passive load reduction.

[0048] Compared with the passive load reduction methods in the prior art, the blade structure provided by the present invention sets a torsional weak region 107 on the blade body. By reducing the torsional stiffness of the torsional weak region 107 and increasing the torsional deformation, the bending-torsion coupling effect is improved. Compared with the aeroelastic tailoring method, it gets rid of the constraint of the blade chord length and has a larger adjustment space; compared with the swept-back load reduction method, due to reducing the torsional stiffness of the torsional weak region 107, it avoids the increase in the load of the blade pitch motor caused by the increase in the torsional load, reduces the cost of the blade pitch motor to a certain extent, and by reducing the torsional stiffness of the torsional weak region 107, more effectively improves the bending-torsion coupling effect, achieves passive load reduction, and improves the stability after reducing the blade load.

[0049] Furthermore, as Figure 6As shown, a second main beam 1071 is provided on the inner wall of the weak torsion area 107, and the second main beam 1071 is arranged inside the housing 100. The second main beam 1071 is used to improve the bending stiffness and strength of the weak torsion area 107. It should be noted that no web 106 is provided on the inner wall of the weak torsion area 107, so that the torsional stiffness of the weak torsion area 107 is less than that of the strengthening area 108, thereby reducing the torsional stiffness of the weak torsion area 107, increasing the torsional deformation within the weak torsion area 107, and enhancing the bending-torsion coupling effect.

[0050] Furthermore, as Figures 3 to 6 shown, in a specific embodiment, the blade body includes a leading edge 103 and a trailing edge 104. Among them, a leading-edge strengthening layer 1031 of the strengthening area is provided at the leading edge 103 of the strengthening area 108, and a trailing-edge strengthening layer 1041 of the strengthening area is provided at the trailing edge 104 of the strengthening area 108. The leading-edge strengthening layer 1031 of the strengthening area and the trailing-edge strengthening layer 1041 of the strengthening area are used to improve the bearing capacity of the strengthening area 108. A leading-edge strengthening layer 1072 of the weak area is provided at the leading edge 103 of the weak torsion area 107, and a trailing-edge strengthening layer 1073 of the weak area is provided at the trailing edge 104 of the weak torsion area 107. The leading-edge strengthening layer 1072 of the weak area and the trailing-edge strengthening layer 1073 of the weak area are used to improve the bearing capacity of the weak torsion area 107. By adjusting the laying layers, width, and laying position of the leading-edge strengthening layer 1072 of the weak area, and / or the laying layers, width, and laying position of the trailing-edge strengthening layer 1073 of the weak area, the torsional stiffness of the weak torsion area 107 is further reduced, the torsional deformation of the weak torsion area 107 is increased, and the bending-torsion coupling effect is enhanced. It should be noted that the torsional stiffness of the weak torsion area 107 can be reduced by reducing the laying layers and width of the leading-edge strengthening layer 1072 of the weak area, and / or the laying layers and width of the trailing-edge strengthening layer 1073 of the weak area. At the same time, in order to ensure that the bending stiffness of the weak torsion area 107 is the same as that of the initial blade, the laying position of the leading-edge strengthening layer 1072 of the weak area, and / or the laying position of the trailing-edge strengthening layer 1073 of the weak area can be changed so that the bending stiffness of the weak torsion area 107 is the same as that of the initial blade. Of course, the torsional stiffness of the weak torsion area 107 can also be reduced by reducing the laying layers of the leading-edge strengthening layer 1072 of the weak area, and / or the laying layers of the trailing-edge strengthening layer 1073 of the weak area. At the same time, in order to ensure that the bending stiffness of the weak torsion area 107 is the same as that of the initial blade, the bending stiffness of the weak torsion area 107 can be increased by increasing the width of the leading-edge strengthening layer 1072 of the weak area, and / or the width of the trailing-edge strengthening layer 1073 of the weak area, so that the bending stiffness of the weak torsion area 107 is the same as that of the initial blade.

[0051] Furthermore, asFigure 5 As shown, in a specific embodiment, the blade body further includes a blade root 101 and a blade tip 102. Among them, the distance between the torsional weak area 107 and the blade tip 102 of the blade body is d, and 5m ≤ d ≤ 10m. The spanwise range of the torsional weak area 107 is 0.5m to 1.0m. It should be noted that the spanwise range refers to the range of the torsional weak area 107 in the direction from the blade root 101 to the blade tip 102 of the blade body. In order to minimize the influence of the setting of the torsional weak area 107 on the strength and operation of the entire blade structure, in this embodiment, the distance between the torsional weak area 107 and the blade tip 102 of the blade body is in the range of 5m ≤ d ≤ 10m to reduce the influence of the torsional weak area 107 on the blade root 101 of the blade body. At the same time, the spanwise range of the torsional weak area 107 is taken as 0.5m to 1.0m, so that the influence of the torsional weak area 107 on the entire blade structure is within a controllable range.

[0052] The embodiment of the present invention also discloses a design method for a blade structure. This design method is for the blade structure disclosed in the above embodiment. This blade structure has all the technical effects of the above blade structure and will not be elaborated here. Among them, the design method of the blade structure is as Figure 1 shown, and includes the following steps:

[0053] S100, Initial blade design, design an initial blade that meets the standard requirements. It should be noted that the initial blade is a blade without a torsional weak area 107 and meets the design standard indicators such as strength and stiffness.

[0054] S101, Setting of the torsional weak area 107, set the torsional weak area 107 on the shell of the initial blade. The torsional weak area 107 is formed on the shell 100 of the blade body by not setting the web 106 and adjusting the number of plies, width, and ply position of the leading-edge reinforcement layer 1072 and / or the trailing-edge reinforcement layer 1073 of the weak area to reduce the torsional stiffness, thereby forming the torsional weak area 107.

[0055] S102, Load extraction, perform load calculation on the entire blade structure to obtain the loads of each area of the entire blade structure, and extract the load of the torsional weak area 107 from them.

[0056] S103, Initial parameter setting, set the initial elastic torsional angle, initial parameters of the second main beam 1071, the leading-edge reinforcement layer 1072 of the weak area, and the trailing-edge reinforcement layer 1073 of the weak area. It should be noted that the initial elastic torsional angle is generally taken as 1° to 5°.

[0057] S104, Torsional stiffness calculation. The torsional stiffness of the torsional weak area 107 is calculated based on the load and the initial elastic torsional angle of the torsional weak area 107.

[0058] S105, Ply parameter determination. The ply parameters of the shell 100 in the torsional weak area 107 are obtained by using the torsional stiffness calculation program and method.

[0059] S106, Bending stiffness adjustment. By adjusting the second main beam 1071, the leading edge reinforcement layer 1072 of the weak area, and the trailing edge reinforcement layer 1073 of the weak area, the bending stiffness of the torsional weak area 107 is made the same as that of the initial blade.

[0060] S107, Strength check. The ply strength of the torsional weak area 107 is calculated by using finite element analysis software according to the load of the torsional weak area 107, and the ply strength is checked. If the ply strength meets the design requirements, proceed to the next step. If the ply strength does not meet the design requirements, return to S106 until the ply strength meets the design requirements.

[0061] S108, Target ply determination. When the ply strength meets the requirements, the ply of the torsional weak area 107 is obtained as the target ply.

[0062] Further, after the step S108 is completed, as Figure 2 shown, the design method of the blade structure further includes the step:

[0063] S109, Load check. According to the target ply of the determined torsional weak area 107, the blade load is recalculated. Based on whether the elastic torsional angle of the blade structure after loading is within the preset value range, it is judged whether the magnitude of the load meets the requirements. If the elastic torsional angle after loading exceeds 5°, the blade reduces the load too much, resulting in poor aeroelastic stability of the blade, and the aeroelastic stability of the blade exceeds the controllable range, then it is necessary to return to S103 and repeat S104 - S109. If the elastic torsional angle after loading is less than 1°, the blade reduces the load too little and fails to achieve the purpose of reducing the blade load. Therefore, it is necessary to return to S103 and repeat S104 - S109 until the elastic torsional angle after loading is within the range of 1° - 5°.

[0064] As Figure 3 shown, in a specific embodiment, the design method of the blade structure includes the following specific steps:

[0065] S100, Initial blade design. Design an initial blade that meets the standard requirements. It should be noted that the initial blade is a blade without a torsional weak area 107 and meets the design standard indicators such as strength and stiffness.

[0066] S101, Setting the torsional weak area 107. Set the torsional weak area 107 on the housing of the initial blade. The torsional weak area 107 is formed on the housing 100 of the blade body by not setting the web 106 and adjusting the number of plies, width, and ply position of the leading-edge reinforcement layer 1072 and / or trailing-edge reinforcement layer 1073 of the weak area to reduce the torsional stiffness.

[0067] S206, Load calculation. By calculating the loads of the entire blade structure, obtain the loads of the entire blade structure, and perform S209 to extract the loads of the torsional weak area 107, specifically including S210, extraction of torsional loads, and S211, extraction of bending loads. This step can refer to S102 in the above embodiment.

[0068] S200, Provide the initial parameters of the second main beam and the front and rear reinforcement layers of the weak area, and simultaneously perform S208 to provide the initial elastic torsional angle. This step can refer to S103 in the above embodiment. It should be noted that the front and rear reinforcement layers of the weak area refer to the leading-edge reinforcement layer 1072 and trailing-edge reinforcement layer 1073 of the weak area.

[0069] S201, Determine the torsional stiffness of the torsional weak area 107 according to the initial elastic torsional angle provided in step S208 and the torsional loads extracted in step S210. This step can refer to S104 in the above embodiment.

[0070] S202, According to the torsional stiffness of the torsional weak area 107 determined in step S201, use the torsional stiffness calculation program and method to obtain the ply parameters of the housing 100 of the torsional weak area 107. This step can refer to S105 in the above embodiment.

[0071] S203, According to the bending loads extracted in step S211, by adjusting the second main beam 1071 and the front and rear edge reinforcement layers of the weak area, make the bending stiffness of the torsional weak area 107 the same as that of the initial blade. This step can refer to S106 in the above embodiment.

[0072] S204, Check whether the strength meets the design requirements. Based on the bending loads extracted in step S211, use finite element analysis software to calculate the ply strength of the torsional weak area 107 and check the ply strength. If the ply strength meets the design requirements, enter S205. If the ply strength does not meet the design requirements, return to S203 until the ply strength meets the design requirements. This step can refer to S107 in the above embodiment.

[0073] S205, When the ply strength of the torsional weak area 107 meets the design requirements, determine the ply of the torsional weak area 107 as the target ply. This step can refer to S108 in the above embodiment.

[0074] S206, Load calculation. After the target ply of the torsional weak area 107 is determined, recalculate the blade load and obtain the elastic torsional angle after loading. This step can refer to S109 in the above embodiment.

[0075] S207, Determine whether the load meets the requirements according to whether the elastic torsional angle after loading obtained in step S206 is within the preset value range. When the elastic torsional angle after loading exceeds 5°, the blade reduces the load too much, resulting in poor aeroelastic stability of the blade, and the aeroelastic stability of the blade exceeds the controllable range. Then, it is necessary to return to S208 to adjust the initial elastic torsional angle, and repeat S209-S211 and S201-S207. If the elastic torsional angle after loading is less than 1°, the blade reduces the load too little, and the purpose of blade load reduction is not achieved. Therefore, it is still necessary to return to S208 to adjust the initial elastic torsional angle, and repeat S209-S211 and S201-S207 until the elastic torsional angle after loading is within the range of 1° to 5°. This step can refer to S109 in the above embodiment.

[0076] The terms "first" and "second" etc. in the specification, claims and above drawings of the present invention are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may include steps or units not listed.

[0077] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A design method for a blade structure, characterized in that, Including the steps: Initial blade design, designing an initial blade that meets the standard requirements; Setting of the torsional weak area (107), setting a torsional weak area (107) on the shell of the initial blade; Load extraction, extracting the load of the torsional weak area (107), the torsional weak area (107) is provided with a leading-edge reinforcement layer (1072) of the weak area and a trailing-edge reinforcement layer (1073) of the weak area, and a second main beam (1071) is arranged on the inner wall of the torsional weak area (107); Initial parameter setting, giving the initial elastic torsional angle, and the initial parameters of the second main beam (1071), the leading-edge reinforcement layer (1072) of the weak area and the trailing-edge reinforcement layer (1073) of the weak area; Torsional stiffness calculation, calculating the torsional stiffness of the torsional weak area (107) according to the load of the torsional weak area (107) and the initial elastic torsional angle; Determination of the ply parameters, obtaining the ply parameters of the shell (100) of the torsional weak area (107) by using a torsional stiffness calculation program; Bending stiffness adjustment, by adjusting the bending stiffness of the torsional weak area (107), making the bending stiffness of the torsional weak area (107) the same as the bending stiffness of the initial blade; Strength check, calculating the ply strength of the torsional weak area (107) according to the load of the torsional weak area (107) and checking the ply strength; Determination of the target ply, the ply strength meets the requirements, and taking the ply of the torsional weak area (107) as the target ply for output.

2. The design method of the blade structure according to claim 1, characterized in that, It further includes the steps: Load check, re-calculating the blade load and checking the elastic torsional angle according to the determined target ply of the torsional weak area (107) to ensure the load reduction effect and safety.

3. The design method of the blade structure according to claim 1, characterized in that In the step of the bending stiffness adjustment, by adjusting the second main beam (1071), the leading-edge reinforcement layer (1072) of the weak area and the trailing-edge reinforcement layer (1073) of the weak area, making the bending stiffness of the torsional weak area (107) the same as the bending stiffness of the initial blade.

4. The design method of the blade structure according to claim 1, characterized in that, By reducing the laying layers and width of the leading-edge reinforcement layer (1072) of the weak area to reduce the torsional stiffness of the torsional weak area (107); and / or, By reducing the laying layers and width of the trailing-edge reinforcement layer (1073) of the weak area to reduce the torsional stiffness of the torsional weak area (107).

5. The design method of the blade structure according to claim 1, characterized in that The value range of the initial elastic torsional angle is 1° to 5°.

6. The design method of the blade structure according to claim 1, characterized in that, The load of the torsional weak area (107) includes torsional load and bending load; the torsional load is used to calculate the torsional stiffness or the elastic torsional angle; the bending load is used to calculate the ply strength of the shell (100) of the torsional weak area (107), the leading-edge reinforcement layer (1072) of the weak area, the trailing-edge reinforcement layer (1073) of the weak area and the second main beam (1071).

7. The blade structure according to claim 1, characterized in that, The spanwise range of the torsional weak area (107) is 0.5 m to 1.0 m.

8. The blade structure according to claim 1, characterized in that, The distance between the torsional weak area (107) and the tip (102) of the initial blade is d, and 5m ≤ d ≤ 10m.

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