CN114687922A

CN114687922A - Blade design method, blade, and blade manufacturing method

Info

Publication number: CN114687922A
Application number: CN202011558523.XA
Authority: CN
Inventors: 袁渊; 唐浩; 刘信韬
Original assignee: Jiangsu Goldwind Science and Technology Co Ltd
Current assignee: Jiangsu Goldwind Science and Technology Co Ltd
Priority date: 2020-12-25
Filing date: 2020-12-25
Publication date: 2022-07-01
Anticipated expiration: 2040-12-25
Also published as: CN114687922B

Abstract

The present disclosure provides a design method of a blade, and a manufacturing method of a blade, the design method including: calculating aeroelastic damping of the blade relative to wind speed based on the initial design structure of the blade; when the minimum value of the aeroelastic damping is less than or equal to the threshold value, performing at least one of the following three operations: increasing the torsional stiffness of the initially designed structure, increasing the flap stiffness of the initially designed structure, and reducing the shimmy stiffness of the initially designed structure. According to the design method of the blade, the stability problem of the blade can be prevented.

Description

Blade design method, blade, and blade manufacturing method

Technical Field

The present disclosure relates to the field of wind power generation technologies, and more particularly, to a method for designing a blade, and a method for manufacturing a blade.

Background

A wind generating set is a device for converting wind energy into electric energy. In order to pursue reduction of electricity consumption cost, the power of the wind generating set is larger and larger, and the blades of the wind generating set are longer and longer.

As the blade is designed to be longer and longer, particularly for the offshore blade, the aeroelastic damping of the blade is low, abnormal vibration is easy to occur in the operation process of the blade, the vibration can obviously improve the load of the blade, and the service life of the blade is greatly reduced.

The problem of low aeroelastic damping is mainly solved at present through the following three ways: pneumatic accessories (such as spoilers (T-spollers) and w-shaped strips (ZZ-tape) are added to improve the pneumatic resistance; adding a damper inside the blade; by means of a control, for example, the nominal rotational speed is changed.

However, there are drawbacks to all three of the above approaches. It is also unclear whether the addition of aerodynamic appendages will affect the aerodynamic performance of the blade as a whole, and whether these appendages effectively address the vibration problem. For the addition of a blade damper, the damper will lead to a blade weight gain, an increase in fatigue loads and no positive effect on the blade structure itself. For changing the rated rotational speed, increasing the rated rotational speed increases the fatigue load, while decreasing the rated rotational speed increases the risk of blade stall.

Disclosure of Invention

The purpose of the present disclosure is to provide a blade design method, a blade, and a blade manufacturing method that can prevent the blade from having stability problems.

According to an aspect of the present disclosure, there is provided a design method of a blade, the design method including: calculating the aeroelastic damping of the blade relative to the wind speed based on the initial design structure of the blade; when the minimum value of the aeroelastic damping is less than or equal to the threshold value, performing at least one of the following three operations: increasing the torsional stiffness of the initially designed structure, increasing the flap stiffness of the initially designed structure, and reducing the shimmy stiffness of the initially designed structure.

Optionally, the threshold is-0.01.

Optionally, the increase of the torsional stiffness is 5% -20% of the torsional stiffness of the initial design structure, the increase of the flap stiffness is 5% -20% of the flap stiffness of the initial design structure, and the decrease of the shimmy stiffness is 5% -20% of the shimmy stiffness of the initial design structure.

Optionally, the torsional stiffness of the initial design structure is increased by at least one of: using a high-modulus biaxial cloth as a material for at least one layer of an inner skin and/or an outer skin of the blade; the number of layers of each of the inner and outer skin of the blade is increased by 1-3 layers in at least a part of the length of the blade in the range of 30-70% from the root of the blade.

Alternatively, a high modulus biaxial cloth is used as the material of the innermost layer of the inner skin and the material of the outermost layer of the outer skin of the blade.

Optionally, the flap stiffness of the initial design structure is increased by: the chordwise cross-sectional areas of the girders in the upper shell and the girders in the lower shell are increased by 10-20% in at least a part of the range of 30-70% of the length of the blade from the root of the blade.

Optionally, a first main beam lay-up is formed on the main beam of each of the upper and lower housings, the thickness of the first main beam lay-up being 10% -20% of the thickness of the main beam.

Alternatively, second main beam laying layers are formed on the upper surface and the lower surface of each of the main beams in the thickness direction of the upper shell and the lower shell, respectively, and third main beam laying layers are formed at both ends of each of the second main beam laying layers in the width direction.

Optionally, the shimmy stiffness of the initial design structure is reduced by at least one of: reducing 5% -20% of the layup of the leading edge spar and/or the trailing edge spar over at least a portion of the length of the blade in the range of 30% -70%; increasing the staggered layer width of the layers of the leading edge auxiliary beam and/or the trailing edge auxiliary beam by 5mm-10mm in at least one part of the range of 30% -70% of the length of the blade from the blade root of the blade; moving the trailing edge secondary beam 50mm-200mm towards the leading edge direction and/or moving the leading edge secondary beam 20mm-100mm towards the trailing edge direction in at least a part of the range of 30% -70% of the length of the blade from the root of the blade.

According to another aspect of the present disclosure, there is provided a blade comprising an upper shell including an outer skin and an inner skin, and a lower shell including an outer skin and an inner skin, the number of layers of each of the outer skin and the inner skin of the upper shell, the outer skin and the inner skin of the lower shell being 5-6 layers in at least a part of the length of the blade ranging from 30-70% from the blade root of the blade.

Optionally, a high modulus biaxial cloth is used as the material of at least one layer of the outer skin and/or the inner skin of the upper shell, the outer skin and/or the inner skin of the lower shell.

Optionally, each of the upper shell and the lower shell further includes a main beam, second main beam laying layers are respectively formed on an upper surface and a lower surface of the main beam in the thickness direction, third main beam laying layers are formed at both ends of each second main beam laying layer in the width direction, and the third main beam laying layers protrude toward the leading edge or the trailing edge of the blade with respect to the main beam.

Optionally, each of the upper and lower shells comprises a leading edge secondary beam and a trailing edge secondary beam, the split-ply width of the plies of the leading edge secondary beam and/or the trailing edge secondary beam being 15mm-20mm in at least a part of the range of 30% -70% of the length of the blade from the blade root.

Optionally, a filler material is provided between the leading edge and the leading edge secondary spar and/or between the trailing edge and the trailing edge secondary spar from the root of the blade in at least a part of the range of 30-70% of the length of the blade.

According to yet another aspect of the present disclosure, there is provided a manufacturing method of a blade, the manufacturing method including: manufacturing an upper shell, wherein the upper shell comprises an outer skin and an inner skin; manufacturing a lower shell, wherein the lower shell comprises an outer skin and an inner skin; and bonding the upper shell and the lower shell together, wherein the number of layers of each of the outer skin and the inner skin of the upper shell, the outer skin and the inner skin of the lower shell is 5-6 layers in at least a part of the length of the blade ranging from 30-70% from the blade root of the blade.

Optionally, a high-modulus biaxial cloth is used as the material of at least one layer of the outer skin and/or the inner skin of the upper shell, the outer skin and/or the inner skin of the lower shell.

Optionally, each of the upper and lower shells comprises a leading edge secondary beam and a trailing edge secondary beam, the staggered ply width of the plies of the leading edge secondary beam and/or the trailing edge secondary beam being 15mm-20mm in at least a part of the range of 30% -70% of the length of the blade from the blade root of the blade.

Optionally, a filler material is provided between the leading edge and the leading edge secondary beam and/or between the trailing edge and the trailing edge secondary beam in at least a part of the range of 30% -70% of the length of the blade from the blade root.

According to the design method of the blade, by calculating the aeroelastic damping of the initial design structure, when the minimum value of the aeroelastic damping is smaller than the threshold value, at least one of increasing the torsional rigidity of the initial design structure, increasing the flapping rigidity of the initial design structure and reducing the shimmy rigidity of the initial design structure can be executed, so that the stability problem of the blade can be avoided.

According to the design method of the blade disclosed by the invention, the material of the layers of the outer skin and/or the inner skin can be changed into the high-modulus biaxial cloth in at least one part of the length range of 30-70% of the blade, and/or 1-3 layers of the outer skin and/or the inner skin are added, so that the weight increase of the blade can be controlled as much as possible while the torsional rigidity of the whole blade is greatly improved.

According to the design method of the blade disclosed by the invention, the chordwise cross-sectional area of the main beam can be increased by 10-20% in at least one part of the range of 30-70% of the length of the blade, so that the flapping rigidity of the blade can be increased, and the weight increase of the blade can be controlled as much as possible. In addition, the flapping rigidity of the blade is improved, and meanwhile, the clearance problem can be solved.

According to the design method of the blade, in at least one part of the range of 30% -70% of the length of the blade, the layering of the trailing edge auxiliary beam is reduced by 10% -20%, the staggered layer width of the trailing edge auxiliary beam is increased, and/or the trailing edge auxiliary beam is moved towards the leading edge direction, so that the strength of the blade is ensured while the shimmy rigidity of the blade is reduced.

According to the manufacturing method of the blade, the aeroelastic damping of the blade can be improved, and the stability problem of the blade in the operation process can be prevented.

According to the blade disclosed by the invention, abnormal vibration in the operation process can be reduced or avoided, and the blade has better stability and longer service life.

Drawings

The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of a chordwise cross-section of an initial design configuration of a blade;

FIG. 2 is a graph showing the relative loading of the blade as a function of wind speed and torsional stiffness of the blade;

FIG. 3 is a graph showing aeroelastic damping of a blade as a function of wind speed and torsional stiffness of the blade;

FIG. 4 is a graph showing the relative loading of the blades as a function of wind speed and blade flap stiffness;

FIG. 5 is a graph showing aeroelastic damping of a blade as a function of wind speed and blade flap stiffness;

FIG. 6 is a graph showing the relative loading of the blades as a function of wind speed and blade lag stiffness;

FIG. 7 is a graph showing aeroelastic damping of a blade as a function of wind speed and blade lag stiffness;

FIG. 8 is a schematic view of a high modulus biaxial cloth;

FIG. 9 is a chordwise cross-sectional view of the main beam according to the initial design configuration;

FIG. 10 is a chordwise cross-sectional view of a main beam according to a first embodiment of the disclosure;

FIG. 11 is a chordwise cross-sectional view of a main beam according to a second embodiment of the disclosure;

FIG. 12A is a chordwise cross-sectional view of a trailing edge sub-beam according to an initial design configuration;

FIG. 12B is a chordwise cross-sectional view of the trailing edge secondary beam according to the first embodiment of the disclosure;

FIG. 12C is a chordwise cross-sectional view of a trailing edge sub-beam according to a second embodiment of the disclosure;

fig. 12D is a chordwise cross-sectional view of a trailing edge auxiliary beam according to a third embodiment of the present disclosure.

In the drawings: 10 is the blade, 11 is the upper shell, 12 is the lower shell, 111 and 121 are the outer skins, 112 and 122 are the inner skins, 113 and 123 are the core layers, 114 and 124 are the spar, 115 and 125 are the trailing edge spars, 13 is the web, 1141 is the first spar ply, 1142 is the second spar ply, 1143 is the third spar ply, 1151, 1152 and 1153 are the newly formed trailing edge spars, and 1153F is the filler material.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described as follows with reference to the accompanying drawings.

This disclosure may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

FIG. 1 is a schematic view of a chordwise cross-section of an initial design configuration of a blade. As shown in FIG. 1, the blade 10 may include an upper shell 11, a lower shell 12, and a web 13 supported between the upper and

lower shells

11, 12. In manufacturing the blade 10, the upper shell 11 and the lower shell 12 may be separately manufactured using methods known in the art (e.g., lay-up and vacuum infusion of resin), and then the upper shell 11 and the lower shell 12 may be bonded together. A web 13 may be provided between the upper case 11 and the lower case 12 to support the upper case 11 and the lower case 12 before the upper case 11 and the lower case 12 are bonded.

Specifically, the upper shell 11 forms a suction surface (i.e., an SS surface) of the blade. The upper shell 11 may include an outer skin 111, an inner skin 112, a core layer 113, a spar 114, and a trailing edge spar 115. The core layer 113 and the girders 114 are sandwiched between the outer skin 111 and the inner skin 112, and the core layer 113 is divided into two parts in the chord direction by the girders 114. The main beam 114 and the trailing edge secondary beam 115 may both be prefabricated components. The trailing edge secondary beam 115 is disposed near the trailing edge of the blade 10.

In addition, the lower shell 12 forms the pressure surface (i.e., the PS surface) of the blade. The lower shell 12 may include an outer skin 121, an inner skin 122, a core layer 123, a spar 124, and a trailing edge spar 125. The core layer 123 and the girders 124 are sandwiched between the outer skin 121 and the inner skin 122, and the core layer 123 is divided into two parts in the chord direction by the girders 124. Likewise, the main beam 124 and the trailing edge secondary beam 125 may each be a preform. The trailing edge auxiliary beam 125 is disposed near the trailing edge of the blade 10, and is disposed at a position corresponding to the trailing edge auxiliary beam 115 of the upper shell 11.

Further, although not shown, each of the upper shell 11 and the lower shell 12 may include a leading edge sub-beam disposed near the leading edge, and the leading edge sub-beam may also be a preform, similar to the trailing edge sub-beam.

As mentioned earlier, due to the longer and longer blade designs, especially for offshore blades, the aeroelastic damping is low and abnormal vibrations are likely to occur during operation of the blade. At present, the problem of low aeroelastic damping is solved mainly by three modes of increasing pneumatic accessories, increasing dampers inside blades and changing rated rotating speed. However, the above three methods have major disadvantages.

When the blade is subjected to the instability analysis, the inventor of the present disclosure finds that when the minimum value of the aeroelastic damping of the blade is smaller than a threshold value after parameter analysis is performed on a large number of unstable blades, the blade will vibrate abnormally, the load of the blade changes violently, and the stability of the blade will be problematic. In addition, after parameter analysis is carried out on a large number of unstable blades, the inventor also finds that the relative load of the blades and the aeroelastic damping of the blades are related to the torsional rigidity of the blades, the flapping rigidity of the blades and the shimmy rigidity of the blades. Therefore, the present invention proposes that, when designing a new blade, the structure of the destabilized blade may be used as a reference basis for the design, for example, the destabilized blade is used as an initial design structure of the new blade, and corresponding design parameters are adjusted on the basis of the initial design structure.

Fig. 2 to 7 are graphs showing the relative load and aeroelastic damping of a blade according to the variation of wind speed and the variation of torsional stiffness of the blade, the variation of flap stiffness of the blade or the variation of lag stiffness of the blade. In fig. 2 to 7, the analysis software BLADED can be used to calculate the relative load values and the aeroelastic damping according to the variation of the torsional stiffness, flap stiffness and lag stiffness at different wind speeds. However, the present disclosure is not so limited and other analysis software in the field of wind turbine generators may be utilized to perform the above calculations. The baseline in fig. 2, 4 and 6 refers to the relative load values calculated based on the initial design structure of the blade. The larger the relative load value, the larger the actual load of the blade. In the baseline case, the blade load changes significantly over the wind speed range corresponding to 7-15m/s, indicating a stability problem with the blade.

The baseline in fig. 3, 5 and 7 refers to the aeroelastic damping obtained based on the initial design structure calculation of the blade. When the aeroelastic damping is negative, there may be a vibration risk. In the baseline case, negative aeroelastic damping occurs in the blade, and the minimum value of aeroelastic damping is-0.01. Corresponding to the relative load values in the case of the baseline, the load changes significantly at the wind speed section corresponding to 7-15m/s of the blade, leading to stability problems for the blade. That is, when the minimum value of aeroelastic damping is-0.01, the blade may experience stability problems.

In the following, the relation between the relative loads of the blades and the aeroelastic damping of the blades and the torsional stiffness of the blades is investigated with reference to fig. 2 and 3. In fig. 2, the lines corresponding to 10% and 20% refer to relative load values obtained after increasing the torsional rigidity by 10% and 20%, respectively, with respect to the baseline. The lines corresponding to-10% and-20% refer to the relative load values obtained after a 10% and 20% reduction in torsional stiffness, respectively, relative to the baseline.

As shown in fig. 2, the 10% and 20% reduction of the torsional stiffness makes the load change of the blade more severe, and the relative load is also greatly increased, which is quite disadvantageous to the safety and service life of the blade. However, increasing the torsional stiffness by 10% and 20% can reduce the relative loading of the blade very significantly and smooth the load variations. Also, the more the torsional stiffness is increased, the less the relative load of the blade is, and the more smooth the load variation is.

FIG. 3 is a graph showing aeroelastic damping of a blade as a function of wind speed and torsional stiffness of the blade. In fig. 3, the line corresponding to 10% refers to the aeroelastic damping obtained after increasing the torsional rigidity by 10% with respect to the base line. The line corresponding to-10% refers to the aeroelastic damping obtained after a 10% reduction in torsional stiffness relative to the baseline.

Referring to fig. 3, when the torsional stiffness is increased by 10%, the aeroelastic damping of the blade in the section where negative aeroelastic damping wind speed occurs is improved, i.e. the minimum value of aeroelastic damping is increased. Furthermore, although the aeroelastic damping of the blade is slightly reduced when the torsional stiffness is increased by 10% in the high wind speed section, the slight reduction of the aeroelastic damping of the high wind speed section does not affect the stability of the blade because the aeroelastic damping of the blade is still very high. Thus, corresponding to the relative load value in the case of the torsional rigidity increased by 10% in fig. 2, the relative load of the blade can be reduced very significantly, and the load variation tends to be smooth.

With continued reference to FIG. 3, with a 10% reduction in torsional stiffness, the negative aeroelastic damping of the blade is more severe, i.e., the minimum value of aeroelastic damping is reduced. This also results in a severe lifting of the relative loads in fig. 2 in the wind speed section corresponding to 7-15m/s, resulting in stability problems for the blade.

Although the aeroelastic damping in the case of increasing the torsional rigidity by 20% and decreasing the torsional rigidity by 20% are not shown in fig. 3, it can be known from the change of the relative load value in the case of increasing the torsional rigidity by 20% and decreasing the torsional rigidity by 20% in fig. 2 that increasing the torsional rigidity by 20% will further increase the aeroelastic damping of the blade in the wind speed section where the negative aeroelastic damping occurs, which helps to improve the stability of the blade, and decreasing the torsional rigidity by 20% will further decrease the negative aeroelastic damping of the blade, which leads to the stability problem of the blade.

That is, as can be seen from fig. 2 and 3, when the minimum value of the aeroelastic damping is-0.01 or less, the stability of the blade will be problematic, and the aeroelastic damping of the blade can be increased by increasing the torsional rigidity of the blade, so that the relative load value of the blade and the change amplitude of the relative load value are reduced, and the stability of the blade is improved.

In the following, the relation between the relative loads of the blades and the aeroelastic damping of the blades and the flap stiffness of the blades is investigated with reference to fig. 4 and 5.

FIG. 4 is a graph showing the relative loading of the blades as a function of wind speed and blade flap stiffness. In fig. 4, the lines corresponding to 10% and 20% refer to relative load values obtained after increasing flap stiffness by 10% and 20%, respectively, with respect to the baseline. The lines corresponding to-10% and-20% refer to the relative load values obtained after a 10% and 20% reduction in flap stiffness, respectively, relative to baseline.

As shown in FIG. 4, the 10% and 20% reduction in flap stiffness results in more severe blade load variations and also in a large increase in relative loads, which is quite detrimental to blade safety and life. However, increasing flap stiffness by 10% and 20% can very significantly reduce the relative loading of the blade and smooth the load variations. Also, the more the flap stiffness is increased, the smaller the relative load of the blade is, and the smoother the load variation is.

FIG. 5 is a graph showing the aeroelastic damping of a blade as a function of wind speed and blade flap stiffness. In fig. 5, the line corresponding to 10% refers to the aeroelastic damping obtained after increasing the flap stiffness by 10% from the baseline. The line corresponding to-10% refers to the aeroelastic damping obtained after a 10% reduction in flap stiffness relative to the baseline.

Referring to fig. 5, when the flap stiffness is increased by 10%, the aeroelastic damping of the blade in the section where negative aeroelastic damping occurs is improved, i.e., the minimum value of aeroelastic damping is increased. Furthermore, although the blade aeroelastic damping is slightly reduced in the high wind speed section when the flap stiffness is increased by 10%, the blade aeroelastic damping is still very high, so the slight reduction of the blade aeroelastic damping in the high wind speed section does not affect the stability of the blade. Thus, the relative load of the blade can be reduced very significantly and the load variation can be smoothed out corresponding to the relative load value in the case of the flap stiffness increased by 10% in fig. 4.

With continued reference to FIG. 5, with a 10% reduction in flap stiffness, the negative aeroelastic damping of the blade is more severe, i.e., the minimum value of aeroelastic damping is reduced. This also results in a severe lifting of the relative loads in fig. 4 in the wind speed section corresponding to 7-15m/s, resulting in stability problems for the blade.

Although the aeroelastic damping in the case of increasing the flap stiffness by 20% and decreasing the flap stiffness by 20% is not shown in fig. 5, it can be known from the change of the relative load value in the case of increasing the flap stiffness by 20% and decreasing the flap stiffness by 20% in fig. 4 that increasing the flap stiffness by 20% will further increase the aeroelastic damping of the blade in the wind speed section where negative aeroelastic damping occurs, which helps to improve the stability of the blade, and decreasing the flap stiffness by 20% will further decrease the negative aeroelastic damping of the blade, which leads to the stability problem of the blade.

That is, as can be seen from fig. 4 and 5, when the minimum value of the aeroelastic damping is-0.01 or less, the stability of the blade will be problematic, and the aeroelastic damping of the blade can be increased by increasing the flapping stiffness of the blade, so as to reduce the relative load value of the blade and the variation amplitude of the relative load value, and thus, the stability of the blade can be improved.

Hereinafter, the relationship between the relative load of the blade and the aeroelastic damping of the blade and the shimmy stiffness of the blade is studied with reference to fig. 6 and 7.

FIG. 6 is a graph showing the variation of the relative loading of the blade as a function of wind speed and the variation of the blade shimmy stiffness. In fig. 6, the lines corresponding to 10% and 20% refer to the relative load values obtained after increasing the shimmy stiffness by 10% and 20%, respectively, with respect to the baseline. The lines corresponding to-10% and-20% refer to the relative load values obtained after a 10% and 20% reduction in flap stiffness, respectively, relative to the baseline.

As shown in fig. 6, increasing the shimmy stiffness by 10% and 20% makes the load change of the blade more severe, and the relative load also increases greatly, which is quite detrimental to the safety and service life of the blade. However, reducing the shimmy stiffness by 10% and 20% can reduce the relative load of the blade very significantly and smooth the load variation. Further, the more the shimmy stiffness is reduced, the smaller the relative load of the blade is, and the smoother the load variation is.

FIG. 7 is a graph showing aeroelastic damping of a blade as a function of wind speed and blade lag stiffness. In fig. 7, the line corresponding to 10% refers to the aeroelastic damping obtained after 10% increase in the shimmy stiffness with respect to the baseline. The line corresponding to-10% refers to the aeroelastic damping obtained after a 10% reduction in shimmy stiffness relative to the baseline.

Referring to fig. 7, when the lag stiffness is reduced by 10%, the aeroelastic damping of the blade in the section where negative aeroelastic damping wind speed occurs is increased, i.e., the minimum value of aeroelastic damping is increased. Furthermore, although the aeroelastic damping of the blade is slightly reduced when the shimmy stiffness is reduced by 10% in the high wind speed section, the slight reduction of the aeroelastic damping of the high wind speed section does not affect the stability of the blade because the aeroelastic damping of the blade is still very high. Thus, corresponding to the relative load value in the case of the shimmy stiffness reduced by 10% in fig. 6, the relative load of the blade can be reduced very significantly, and the load variation tends to be smooth.

With continued reference to FIG. 7, with a 10% increase in lag stiffness, the negative aeroelastic damping of the blade is more severe, i.e., the minimum value of aeroelastic damping is reduced. This also results in a severe lifting of the relative loads in fig. 6 in the wind speed section corresponding to 7-15m/s, resulting in stability problems for the blade.

Although the aeroelastic damping in the case of increasing the 20% of the shimmy stiffness and decreasing the 20% of the shimmy stiffness is not shown in fig. 7, according to the change of the relative load value in the case of increasing the 20% of the shimmy stiffness and decreasing the 20% of the shimmy stiffness in fig. 6, decreasing the 20% of the shimmy stiffness will further increase the aeroelastic damping of the blade in the wind speed section where the negative aeroelastic damping occurs, which is helpful for improving the stability of the blade, and increasing the 20% of the shimmy stiffness will further decrease the negative aeroelastic damping of the blade, so that the stability problem of the blade occurs.

That is, as can be seen from fig. 6 and 7, when the minimum value of the aeroelastic damping is-0.01 or less, the stability of the blade will be problematic, and the aeroelastic damping of the blade can be increased by reducing the shimmy stiffness of the blade, so that the relative load value of the blade and the change amplitude of the relative load value are reduced, and the stability of the blade is improved. That is, the roll stiffness affects the relative loading and aeroelastic damping of the blade in opposition to the torsional and flap stiffness affects the relative loading and aeroelastic damping of the blade.

From the effects of blade torsional stiffness, blade flap stiffness and blade lag stiffness on the relative loading and aeroelastic damping of the blade described above with reference to fig. 2 to 7, stability problems will arise for the blade if the aeroelastic damping of the blade with respect to the wind speed is less than or equal to a threshold value based on the initial design structure calculation of the blade. In this case, at least one of increasing torsional stiffness of the blade, increasing flapwise stiffness of the blade, and decreasing edgewise stiffness of the blade may be performed.

Accordingly, the present disclosure may provide a method of designing a blade: calculating aeroelastic damping of the blade relative to wind speed based on the initial design structure of the blade; when the minimum value of the aeroelastic damping is less than or equal to the threshold value, performing at least one of the following three operations: increasing the torsional stiffness of the initially designed structure, increasing the flap stiffness of the initially designed structure, and reducing the shimmy stiffness of the initially designed structure.

According to an embodiment of the present disclosure, the aeroelastic damping of the blades with respect to the wind speed may be calculated by the analysis software BLADED, however, the present disclosure is not limited thereto.

According to an embodiment of the present disclosure, the threshold may be determined to be-0.01 based on the baseline minimum aeroelastic damping in fig. 3, 5, and 7. However, no disclosure is limited thereto. Those skilled in the art, having the benefit of the inventive concepts of the present application, may determine the threshold value based on the particular operating requirements of the wind turbine generator set. For example, if the operational requirements for the wind turbine generator set are relatively high, the threshold may be greater than-0.01. Conversely, if the operational requirements on the wind turbine generator set are relaxed, the threshold may be less than-0.01. In addition, it can be clear that the higher the aeroelastic damping, the lower the probability of the blade having stability problems, and when the aeroelastic damping is positive, the risk of blade instability can be basically eliminated.

According to the embodiments of the present disclosure, based on the research of the inventors, when the minimum value of the aeroelastic damping is less than or equal to the threshold value, it is indicated that the blade has a stability problem, and thus the structure of the blade needs to be adjusted. In addition, based on the above research results of the inventors, in order to improve the aeroelastic damping of the blade, the structure of the blade may be adjusted by at least one of increasing the torsional rigidity of the blade, increasing the flapwise rigidity of the blade, and reducing the edgewise rigidity of the blade. For example, if the minimum value of aeroelastic damping of an already produced blade is less than or equal to the threshold value, the structure of an as yet unproductive blade of the same structure may be adjusted according to the ideas provided by the present disclosure, thereby avoiding blade stability problems for later produced blades. On the other hand, for a blade that has not been produced or is being designed, if the minimum value of the aeroelastic damping of the blade is smaller than or equal to the threshold value through calculation, the structure of the blade that has not been produced or the design parameters of the blade can be adjusted according to the idea provided by the present disclosure, so as to avoid producing the blade with stability problem.

According to embodiments of the present disclosure, the torsional stiffness of the blade may be increased by 5% -20% of the torsional stiffness of the initial design configuration. When the increase of the torsional rigidity of the blade is less than 5% of the torsional rigidity of the initial design structure, the increase range of aeroelastic damping of the blade is small, and the effect is not obvious. In addition, when the torsional rigidity of the blade is increased by more than 20% of that of the original design structure, the cost and weight are excessively increased. In addition, according to the embodiments of the present disclosure, when the torsional rigidity of the blade is increased, the strength of the blade is also improved.

According to embodiments of the present disclosure, the increase in flap stiffness of the blade may be 5% -20% of the flap stiffness of the original design structure. When the increase of the flapping rigidity of the blade is less than 5% of the flapping rigidity of the initial design structure, the increase range of aeroelastic damping of the blade is small, and the effect is not obvious. In addition, when the flap stiffness of the blade is increased more than 20% of the flap stiffness of the original design structure, the cost and weight are increased too much. In addition, according to the embodiments of the present disclosure, when the flapping stiffness of the blade is increased, the clearance and the strength of the blade can be improved at the same time.

According to embodiments of the present disclosure, the droop in the drag stiffness of the blade may be 5-20% of the drag stiffness of the initial design structure. When the amplitude of the blade shimmy stiffness is less than 5% of the shimmy stiffness of the initial design structure, the aeroelastic damping of the blade is increased to a smaller extent, and the effect is not obvious. In addition, when the roll stiffness of the blade is reduced by more than 20% of the flap stiffness of the original design structure, the strength of the blade may be adversely affected.

Hereinafter, a method of increasing torsional rigidity of the blade, increasing flapwise rigidity of the blade, and reducing edgewise rigidity of the blade will be described with reference to fig. 8 to 12.

Method for increasing torsional stiffness of blade

Hereinafter, two structural adjustment methods of increasing the torsional rigidity of the blade will be described. It is to be understood that either of the two structure adjustment methods may be performed only, or both of the structure adjustment methods may be performed simultaneously.

As a first structural adjustment method, at least one layer of the

outer skins

111 and 121 and/or the

inner skins

112 and 122 in fig. 1 may be formed using a high modulus biaxial cloth according to an embodiment of the present disclosure.

Fig. 8 is a schematic view of a high modulus biaxial cloth. As shown in fig. 8, the high modulus biaxial cloth may be woven from high modulus unidirectional fiberglass (e.g., H-glass or S-glass) at an angle (e.g., ± 45 °). The outer skin and the inner skin of the existing blade are woven by using common biaxial cloth (woven by using common glass fiber (E-glass)). The shear modulus of the high-modulus biaxial cloth woven by the high-modulus unidirectional glass fiber (H-glass) is 12-18% of that of the common biaxial cloth woven by the common glass fiber (E-glass). The shear modulus of the high modulus biaxial cloth is higher when the high modulus biaxial cloth is woven with unidirectional glass fibers (S-glass) having a higher modulus.

In addition, under the same layering area, the torsional rigidity provided by the high-modulus biaxial cloth is more than 7% higher than that provided by the common biaxial cloth. And the resin content of the high-modulus biaxial cloth is lower, and the high-modulus biaxial cloth with the same layering area is lighter than the common biaxial cloth after being poured. The high modulus biaxial cloth is therefore advantageous in that it can provide better performance at a lighter weight.

According to the embodiment of the disclosure, the shear strength of the outer skin and/or the inner skin can be improved by changing the material of the layer of the outer skin and/or the inner skin into the high-modulus biaxial cloth, so that the torsional rigidity of the blade is improved.

According to an embodiment of the present disclosure, replacing at least one layer of the

outer skins

111 and 121 and/or the

inner skins

112 and 122 with a high modulus biaxial cloth may serve to increase the torsional stiffness of the blade. Preferably, only the material of the outermost layer (i.e., the layer closest to the outside) of the

outer skins

111 and 121 may be replaced with the high modulus biaxial cloth and the material of the innermost layer (i.e., the layer closest to the inside) of the

inner skins

112 and 122 may be replaced with the high modulus biaxial cloth. More preferably, all the layers of the

outer skins

111 and 121 and the

inner skins

112 and 122 may be replaced with high modulus biaxial cloth.

According to the embodiment of the disclosure, the torsional rigidity of the blade can be improved, the mass and mass moment of the blade can be reduced, and the limit and fatigue load of the blade can be reduced by replacing the material of the skin and only increasing a small amount of cost.

As a second structural adjustment method, according to an embodiment of the present disclosure, the blade torsional rigidity may also be increased by increasing the number of layers of the

outer skins

111 and 121 and the

inner skins

112 and 122. According to embodiments of the present disclosure, in order to try to control the weight increase of the blade while increasing the torsional stiffness of the blade, the number of layers of the

outer skins

111 and 121 and the

inner skins

112 and 122 may be increased only in a certain region of the length of the blade 10.

According to an embodiment of the present disclosure, the number of layers of each of the

inner skins

112 and 122 and the

outer skins

111 and 121 of the blade 10 may be increased by 1-3 layers, forming 5-6 layers (more than the number of layers of the

inner skins

112 and 122 and the

outer skins

111 and 121 of the corresponding region of the blade in the related art), only in at least a portion of the length of the blade 10 (from the blade root of the blade 10). The 30% -70% length of the blade 10 (hereinafter referred to as from the root of the blade 10) has the most significant effect on the torsional stiffness of the blade, and therefore the lay-up of the skin may be increased only in at least a portion of this area, with the lay-up remaining unchanged in other areas of the blade, thereby increasing the torsional stiffness of the blade while minimizing the increase in weight of the blade.

According to embodiments of the present disclosure, the number of layers of the skin may be increased for the entire 30% -70% section of the length of the blade 10. According to embodiments of the present disclosure, it may also be selected to add skin plies over a section of 30% -50% of the length of the blade 10, for example, the number of plies of skin may be increased over the entire section of 30% -50% of the length of the blade 10.

According to the embodiment of the present disclosure, in a specific example of structural adjustment of the blade, for a certain offshore large blade having a length of 80m or more, the biaxial cloth of the outer skin and the inner skin in the initial design structure of the blade is entirely replaced with high modulus biaxial cloth (woven with high modulus unidirectional glass fiber (H-glass)), and the plies of the outer skin and the inner skin in the upper shell and the lower shell are increased to 5-6 layers in an area of 30% -70% of the blade. Through structural adjustment, the overall torsional rigidity of the blade is improved by about 10%, and the maximum local torsional rigidity is increased by 20%. In addition, the weight of the blade is increased less, and is within the required range. Therefore, the blade torsional rigidity can be increased with little cost and weight increase, so that the blade aeroelastic damping is increased, and the vibration risk of the blade is reduced.

According to the embodiment of the disclosure, by increasing each of the outer skin and the inner skin to 5-6 layers, the torsional rigidity of the whole blade can be greatly improved, and the blade vibration risk is greatly reduced.

Method for increasing flapping rigidity of blade

The flapping stiffness of the blade can be increased by adjusting the structure of the blade as follows.

According to embodiments of the present disclosure, the flapping stiffness of the blade may be increased by increasing the chordwise cross-sectional area of the spar. According to embodiments of the present disclosure, to maximize the weight gain of the blade while increasing the blade flapping stiffness, the chordwise cross-sectional area of the spar may be increased in a region of the length of the blade 10.

According to embodiments of the present disclosure, the chordwise cross-sectional area of the

spar

114, 124 may be increased by 10% -20% over at least a portion of the length of the blade 10 in the range of 30% -70%. The blade 10 length of 30-70% has the most significant effect on blade flap stiffness, so that the chordwise cross-sectional area of the

spars

114 and 124 in at least part of this region can be increased only, while the chordwise cross-sectional area of the spars in other regions of the blade remains unchanged, thereby maximizing the weight gain of the blade while increasing the blade flap stiffness. According to embodiments of the present disclosure, the chordwise cross-sectional area of the spar may be increased for the entire 30% -70% of the length of the blade 10. According to embodiments of the present disclosure, the chordwise cross-sectional area of the spar may also be increased for a section of 30-50% of the length of the blade 10, for example, the chordwise cross-sectional area of the spar may be increased for a section of the blade 10 that is entirely 30-50% of the length.

According to the embodiment of the present disclosure, when the chordwise sectional area of the spar is increased by less than 10% with respect to the initial design structure of the blade 10, the flapping stiffness improving effect of the blade is insufficient. When the chordwise cross-sectional area of the spar increases by more than 20% relative to the initial design configuration of the blade 10, cost and weight are increased too much.

Fig. 9 is a chordwise cross-sectional view of a main beam according to the prior art, fig. 10 is a chordwise cross-sectional view of a main beam according to a first embodiment of the present disclosure, and fig. 11 is a chordwise cross-sectional view of a main beam according to a second embodiment of the present disclosure. In fig. 9 to 11, only the main beams 114 in the upper case 11 are described as an example, but the same description is applicable to the main beams 124 in the lower case 12.

The initial height (height measured in the height direction of the blade) and the initial width (width measured in the chord direction of the blade) of the spar 114 are shown in FIG. 9.

Fig. 10 illustrates a main beam adjustment method according to a first embodiment of the present disclosure. As shown in fig. 10, the main beam 114 may be thickened only (thickened in the thickness direction of the blade). In this case, in order to increase the chordwise cross-sectional area of the spar 114 by 10-20% relative to the original design configuration of the blade 10, the spar 114 may be thickened by 10-20%. Specifically, a first main beam layer 1141 may be newly added to the original main beam 114, and the thickness of the newly added first main beam layer 1141 is 10% to 20% of the thickness of the main beam 114.

According to embodiments of the present disclosure, the main beams 114 may be prefabricated and a first main beam layup 1141 may be added while prefabricating the main beams 114. However, the present disclosure is not so limited and the first girder lay 1141 may also be added when installing the girder 114. In addition, the main beams 114 are not necessarily prefabricated members, and in this case, the first main beam layer 1141 may be formed together when the main beams 114 are layered. The present disclosure is not limited to a particular manner of forming the first main beam lay 1141. Additionally, it should be understood that the line of demarcation is drawn between the original main beam 114 and the first main beam layup 1141 in FIG. 10 only for the purpose of distinguishing between them, and that the actual structurally adjusted main beam does not exist.

According to the embodiment of the present disclosure, when the thickness of the main beam 114 is thicker, the main beam may be adjusted by using the main beam adjusting manner of the first embodiment.

Fig. 11 illustrates a main beam adjustment method according to a second embodiment of the present disclosure. As shown in fig. 11, the main beam 114 may be thickened (thickened in the thickness direction of the blade) and widened (widened in the chord direction of the blade). In this case, the magnitude of thickening and widening of the spar 114 is not particularly limited, as long as it is ensured that the area of the spar 114 in a chordwise cross-section is increased by 10-20% relative to the original design configuration of the blade 10.

According to an embodiment of the present disclosure, the girder may be thickened by newly adding the second girder plies 1142 to the upper and lower surfaces in the thickness direction of the girder 114, respectively, and the girder 114 may be widened by newly adding the third girder plies 1143 to both ends in the width direction (chord direction of the blade) of each second girder ply 1142. The third spar ply 1143 protrudes relative to the spar 114 towards the leading or trailing edge of the blade.

According to embodiments of the present disclosure, the main beam 114 may be a preform, and a second main beam lay-up 1142 may be added when prefabricating the main beam 114, and a third main beam lay-up 1143 may be added in the housing when installing the main beam 114. However, the present disclosure is not so limited and both the second and third girder plies 1142, 1143 may be added at the same time as the girder 114 is installed. In addition, the main beam 114 is not necessarily a preform, and in this case, the second main beam layer 1142 and the third main beam layer 1143 may be formed together when the main beam 114 is layered. The specific manner in which the second and third main beam plies 1142, 1143 are formed is not a limitation of the present disclosure. Additionally, it should be understood that the line of demarcation is drawn in FIG. 10 only to distinguish the original main beam 114 from the second and third main beam plies 1142, 1143, and is not present in the actual structurally adjusted main beam.

According to the embodiment of the present disclosure, when the thickness of the main beam 114 is relatively thin, the main beam can be adjusted by the main beam adjusting method of the second embodiment.

Further, although not shown, the chordwise cross-sectional area of the main beams 114 may also be increased by making the main beams 114 wider (wider in the chordwise direction) only without thickening.

According to the embodiment of the disclosure, the blade flapping rigidity is improved, and the clearance problem can be solved at the same time, so that the clearance condition can be improved while the blade vibration risk is reduced for the blade with insufficient clearance or insufficient girder safety margin although the blade quality and the cost are slightly increased.

The inventor discovers that the original blade has the problem of insufficient clearance when the structure of the offshore blade with stability problem is adjusted, and needs to adopt a laser radar to monitor the clearance condition.

Method for reducing the drag stiffness of a blade

In the following, three embodiments for reducing the shimmy stiffness of the blade will be described. It is to be understood that any one of the three embodiments may be used alone, or the three embodiments may be used simultaneously.

Fig. 12A is a chordwise sectional view of a trailing edge secondary beam according to the related art, fig. 12B is a chordwise sectional view of a trailing edge secondary beam according to a first embodiment of the present disclosure, fig. 12C is a chordwise sectional view of a trailing edge secondary beam according to a second embodiment of the present disclosure, and fig. 12D is a chordwise sectional view of a trailing edge secondary beam according to a third embodiment of the present disclosure. Fig. 12A to 12D show only the trailing edge auxiliary beam 115 in the upper shell 11, however, it should be understood that the description of the trailing edge auxiliary beam 115 is also applicable to the trailing edge auxiliary beam 125 in the lower shell 12.

Fig. 12A shows a schematic view of the ply state of the original trailing edge secondary beam 115. The trailing edge secondary beam 115 is formed by laying a plurality of plies in layers in a direction from the trailing edge toward the leading edge in the thickness direction of the blade. Specifically, a first layer of the trailing edge secondary beam 115 is spaced a predetermined distance from the trailing edge, and then other plies are sequentially laid toward the leading edge at a certain staggered width. Wherein, the distance between the adjacent layers in the chord direction is the staggered width.

As a first embodiment of the present disclosure, as shown in fig. 12B, the lag stiffness of the blade may be reduced by reducing the ply of the trailing edge secondary beam 115 by 10% -20% in at least a portion in the range of 30% -70% of the length of the blade 10 to form a new trailing edge secondary beam 1151.

Since the blade strength is reduced when the blade shimmy stiffness is reduced, considering the blade shimmy stiffness and the blade strength together, the layer of the trailing edge auxiliary beam 115 may be reduced only in at least a part of the section of 30% -70% of the length of the blade (the influence on the blade shimmy stiffness is most significant), and the layer of the trailing edge auxiliary beam 115 in other areas of the blade may be kept unchanged.

According to embodiments of the present disclosure, the layup of the trailing edge secondary spar 115 may be reduced throughout the 30% -70% of the length of the blade 10. According to embodiments of the present disclosure, the layering of the trailing edge spar 115 may also be selected to be reduced over a section of 30% -50% of the length of the blade 10, for example, the layering of the trailing edge spar 115 may be reduced over the entire section of 30% -50% of the length of the blade 10.

When the reduction of the ply of the trailing edge secondary beam 115 is less than 10%, the effect on the shimmy stiffness of the blade is insufficient. When the reduction of the ply of the trailing edge secondary beam 115 is more than 20%, the strength of the blade is adversely affected.

According to the embodiment of the disclosure, by reducing the layering of the auxiliary trailing edge beam, the problem of blade vibration can be solved while the weight and the cost of the blade are reduced.

As a second embodiment of the present disclosure, as shown in fig. 12C, the shimmy stiffness of the blade can be reduced by increasing the stagger width of the trailing edge secondary beam. Considering the blade lag stiffness and strength together, the split width of the plies of the trailing edge spar 115 may be increased by 5mm to 10mm to form a new trailing edge spar 1152 for only at least a portion of the range of 30% to 70% of the length of the blade 10. According to embodiments of the present disclosure, the staggered ply width of the ply of the adjusted trailing edge secondary beam 1152 is 15mm to 20 mm. According to embodiments of the present disclosure, the ply width of the trailing edge secondary spar 115 may also be increased by between 5mm and 10mm at a section that is between 30% and 50% of the length of the blade 10.

As a third embodiment of the present disclosure, as shown in fig. 12D, the shimmy stiffness of the blade can be reduced by moving the trailing edge secondary beam toward the leading edge. Considering the blade lag stiffness and strength together, the trailing edge secondary beam 115 may be moved toward the leading edge by a distance d of 50mm to 200mm to form a new trailing edge secondary beam 1153 only in at least a portion of the range of 30% to 70% of the length of the blade 10. According to an embodiment of the present disclosure, the trailing edge secondary beam 115 may also be selectively moved 50mm to 200mm in the direction of the leading edge at a section of 30% to 50% of the length of the blade 10. In addition, according to the embodiment of the present disclosure, a filler material 1153F (e.g., a mold clamping core material or a cloth liner) is provided in the moving region of the trailing edge sub-beam 115 (i.e., between the new trailing edge sub-beam 1153 and the trailing edge) to ensure that the trailing edge bonding gap is appropriate.

According to the embodiment of the disclosure, similar to the embodiment of reducing the laying of the trailing edge auxiliary beam and increasing the staggered width of the trailing edge auxiliary beam, the laying of the leading edge auxiliary beam can be reduced and the staggered width of the leading edge auxiliary beam can be increased, so that the shimmy stiffness of the blade can be reduced. For example, the layup of the leading edge spar may be reduced by 10% -20% over at least a portion of the length of the blade 10 in the range of 30% -70% to form a new leading edge spar. The staggered ply width of the plies of the leading edge secondary may be increased by 5mm-10mm, up to 15mm-20mm, over at least a portion of the length of the blade 10 in the range 30% -70% to form a new leading edge secondary. In addition, similarly to the embodiment in which the trailing edge sub-beams are moved in the direction of the leading edge, the leading edge sub-beams may be moved in the direction of the trailing edge to reduce the shimmy stiffness of the blade. For example, the leading edge secondary beam may be moved 20mm to 100mm in the trailing edge direction for at least a portion in the range of 30% -70% of the length of the blade 10 to form a new leading edge secondary beam. In addition, a filler material may also be disposed between the leading edge and the newly formed leading edge secondary beam.

In the above, specific methods of increasing torsional stiffness of the blade, increasing flapwise stiffness of the blade, and reducing edgewise stiffness of the blade have been described in detail, however, it should be understood that other methods of structural adjustment of the blade within the inventive concepts of the present disclosure are also within the scope of the present disclosure.

As described above, according to the embodiments of the present disclosure, by calculating the aeroelastic damping of the initially designed structure of the blade, when the minimum value of the aeroelastic damping is less than or equal to the threshold value, at least one of increasing the torsional rigidity of the initially designed structure, increasing the flapwise rigidity of the initially designed structure, and reducing the shimmy rigidity of the initially designed structure may be performed, thereby improving the aeroelastic damping of the blade and preventing the blade from having a stability problem.

In addition, the disclosure also provides a manufacturing method of the blade, and by the manufacturing method, the aeroelastic damping of the blade can be improved, and the stability problem of the blade in the operation process can be prevented.

The manufacturing method comprises the following steps: manufacturing an upper shell, wherein the upper shell comprises an outer skin and an inner skin; manufacturing a lower shell, wherein the lower shell comprises an outer skin and an inner skin; and bonding the upper shell and the lower shell together, wherein the number of layers of each of the outer skin and the inner skin of the upper shell, the outer skin and the inner skin of the lower shell is 5-6 layers in at least a part of the length of the blade ranging from 30-70% from the blade root of the blade.

According to an embodiment of the present disclosure, a high modulus biaxial cloth is used as a material of at least one layer of the outer skin and/or the inner skin of the upper case, the outer skin and/or the inner skin of the lower case.

According to an embodiment of the present disclosure, each of the upper and lower cases further includes a girder, second girder laid layers are respectively formed on upper and lower surfaces of the girder in a thickness direction, third girder laid layers are formed at both ends of each second girder laid layer in a width direction, and the third girder laid layers protrude toward a leading edge or a trailing edge of the blade with respect to the girder.

According to an embodiment of the present disclosure, each of the upper shell and the lower shell includes a leading edge secondary beam and a trailing edge secondary beam, and a staggered layer width of a ply of the leading edge secondary beam and/or the trailing edge secondary beam is 15mm to 20mm in at least a part in a range of 30% to 70% of a length of the blade from a blade root of the blade.

According to an embodiment of the disclosure, a filler material is provided between the leading edge and the leading edge secondary beam and/or between the trailing edge and the trailing edge secondary beam in at least a part of the length of the blade in the range of 30-70% from the blade root of the blade.

The present disclosure also provides a vane that can reduce or avoid abnormal vibration during operation, with better stability and longer life.

According to an embodiment of the disclosure, the blade comprises an upper shell comprising an outer skin and an inner skin, and a lower shell comprising an outer skin and an inner skin, the number of layers of each of the outer skin and the inner skin of the upper shell, the outer skin and the inner skin of the lower shell being 5-6 layers in at least a part of the length of the blade ranging from 30-70% from the blade root of the blade.

According to an embodiment of the disclosure, a filler material is provided between the leading edge and the leading edge secondary beam and/or between the trailing edge and the trailing edge secondary beam in at least a part of the range of 30-70% of the length of the blade from the blade root of the blade.

Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.

Claims

1. A method of designing a blade, the method comprising:

calculating the aeroelastic damping of the blade (10) with respect to the wind speed based on the initial design structure of the blade;

when the minimum value of the aeroelastic damping is less than or equal to a threshold value, performing at least one of the following three operations: increasing torsional stiffness of the initially designed structure, increasing flap stiffness of the initially designed structure, and reducing lag stiffness of the initially designed structure.

2. The design method of claim 1, wherein the threshold is-0.01.

3. The design method of claim 1, wherein the increase in torsional stiffness is 5% -20% of the torsional stiffness of the initial design structure, the increase in flap stiffness is 5% -20% of the flap stiffness of the initial design structure, and the decrease in lag stiffness is 5% -20% of the lag stiffness of the initial design structure.

4. The design method of claim 1, wherein the torsional stiffness of the initial design structure is increased by at least one of:

using a high modulus biaxial cloth as material for at least one layer of the inner skin (112, 122) and/or the outer skin (111, 121) of the blade (10);

-increasing the number of layers of each of the inner skin (112, 122) and the outer skin (111, 121) of the blade (10) by 1-3 layers in at least a part of the length of the blade (10) in the range of 30-70% from the root of the blade.

5. The design method according to claim 4, characterized in that a high modulus biaxial cloth is used as the material of the innermost layer of the inner skin (112, 122) and the material of the outermost layer of the outer skin (111, 121) of the blade (10).

6. The design method of claim 1 or 4, wherein the flap stiffness of the initial design structure is increased by:

increasing the chordwise cross-sectional area of the spar (114) in the upper shell (11) and the spar (124) in the lower shell (12) by 10-20% over at least a portion of the length of the blade (10) in the range 30-70% from the root of the blade.

7. The design method of claim 6, wherein a first main beam lay-up (1141) is formed on a main beam of each of the upper shell (11) and the lower shell (12), the thickness of the first main beam lay-up (1141) being 10% -20% of the thickness of the main beam.

8. The design method according to claim 6, wherein second main beam plies are formed on upper and lower surfaces in a thickness direction of the main beam of each of the upper case (11) and the lower case (12), respectively, and third main beam plies are formed on both ends in a width direction of each second main beam ply.

9. The design method of claim 1 or 4, wherein the shimmy stiffness of the initial design structure is reduced by at least one of:

reducing 5% -20% of the lay-up of leading and/or trailing edge joists (115, 125) in at least a portion of the length of the blade (10) in the range 30% -70%;

increasing the staggered ply width of the plies of the leading and/or trailing edge secondary spar (115, 125) by 5mm-10mm in at least a part of the length of the blade (10) in the range of 30% -70% from the blade root of the blade;

moving a trailing edge secondary beam (115, 125) by 50mm-200mm in a direction towards a leading edge and/or moving a leading edge secondary beam by 20mm-100mm in a direction towards a trailing edge in at least a part of the range of 30-70% of the length of the blade from the root of the blade.

10. Blade comprising an upper shell (11) and a lower shell (12), the upper shell (11) comprising an outer skin (111) and an inner skin (112), the lower shell (12) comprising an outer skin (121) and an inner skin (122),

characterized in that the number of layers of each of the outer skin (111) and the inner skin (112) of the upper shell (11), the outer skin (121) and the inner skin (122) of the lower shell (12) is 5-6 layers in at least a part of the blade (10) in the range of 30-70% of the length thereof from the blade root.

11. Blade according to claim 10, characterized in that a high modulus biaxial cloth is used as material for at least one layer of the outer skin (111) and/or the inner skin (112) of the upper shell (11), the outer skin (121) and/or the inner skin (122) of the lower shell (12).

12. The blade according to claim 10, wherein each of the upper shell (11) and the lower shell (12) further comprises a girder, wherein second girder plies are formed on upper and lower surfaces of the girder in a thickness direction thereof, respectively, and third girder plies are formed at both ends of each second girder ply in a width direction thereof, the third girder plies protruding toward a leading edge or a trailing edge of the blade with respect to the girder.

13. Blade according to claim 10 or 12, characterized in that each of the upper shell (11) and the lower shell (12) comprises a leading edge secondary beam and a trailing edge secondary beam,

the staggered ply width of the plies of the leading edge and/or trailing edge secondary spar is 15mm-20mm in at least a part of the length of the blade (10) in the range of 30% -70% from the blade root of the blade.

14. The blade according to claim 13, wherein a filler material is provided between the leading edge and the leading edge secondary beam and/or between the trailing edge and the trailing edge secondary beam in at least a part of the range of 30-70% of the length of the blade from the blade root of the blade.

15. A method of manufacturing a blade, the method comprising:

manufacturing an upper shell (11), wherein the upper shell (11) comprises an outer skin (111) and an inner skin (112);

manufacturing a lower shell (12), the lower shell (12) comprising an outer skin (121) and an inner skin (122);

bonding the upper case (11) and the lower case (12) together,

wherein the number of layers of each of the outer skin (111) and the inner skin (112) of the upper shell (11), the outer skin (121) and the inner skin (122) of the lower shell (12) is 5-6 layers in at least a part of the length of the blade (10) in the range of 30-70% from the blade root of the blade.

16. Manufacturing method according to claim 15, characterized in that a high-modulus biaxial cloth is used as material for at least one layer of the outer skin (111) and/or the inner skin (112) of the upper shell (11), the outer skin (121) and/or the inner skin (122) of the lower shell (12).

17. The manufacturing method according to claim 15, wherein each of the upper shell (11) and the lower shell (12) further includes a girder, second girder plies are formed on upper and lower surfaces of the girder in a thickness direction thereof, respectively, and third girder plies are formed at both ends of each second girder ply in a width direction thereof, the third girder plies protruding toward a leading edge or a trailing edge of the blade with respect to the girder.

18. The manufacturing method according to claim 15 or 17, characterized in that each of the upper shell (11) and the lower shell (12) comprises a leading edge secondary beam and a trailing edge secondary beam,

19. A manufacturing method according to claim 18, characterized in that a filler material is provided between the leading edge and the leading edge secondary beam and/or between the trailing edge and the trailing edge secondary beam in at least a part of the range of 30-70% of the length of the blade from the blade root of the blade.