CN103321853A - Method for restraining wind turbine blade adopting compound damping structure from vibrating - Google Patents

Abstract

The invention is specifically a method for suppressing flutter of wind turbine blades using a composite damping structure, which solves the problem that large flexible blades are prone to flutter and lack effective prevention and control methods. The vibration suppression method of wind turbine blades using a composite damping structure is specifically to set a co-cured constrained damping layer on the surface of the blade, and set a free damping layer on the outer surface of the main beam; the free damping layer is composed of a single layer of damping material, and the damping viscoelastic material or Damping alloy or damping composite material; the co-cured constrained damping layer is co-cured and formed by the interstitial arrangement of the composite material layer and the damping material layer. Use damping viscoelastic material. Compared with the prior art, the present invention has universal applicability, effective tremor suppression, economy and designability.

Description

Wind Turbine Blade Vibration Control Method Using Composite Damping Structure

technical field

The invention relates to the technical field of wind power generation, in particular to a vibration suppression method for wind turbine blades using a composite damping structure. the

Background technique

As environmental issues are getting more and more attention, clean energy has gradually become the mainstream of world energy development. As a renewable clean energy, wind energy has developed rapidly in recent years, and MW-level wind turbines have become the mainstream models of wind turbines. In order to meet the high power output requirements of wind turbines, wind turbine blades are becoming larger and thinner (for example, the length of a single blade produced by a foreign company has reached 55 meters). Large slender blades flutter under complex loads of aerodynamic force, elastic force and inertial force, and the main flutter forms are edgwise vibration and flapwise vibration. The fluttering of the blades not only reduces the power output of the wind rotor, but more importantly, the alternating stress of the fluttering of the blades will cause fatigue cracks or even breakage of the blades; in addition, the fluttering blades interact with the air to generate aerodynamic noise, causing noise pollution to the environment, It affects the lives of residents near the wind farm and the normal activities of other animals. the

For blade noise, the existing solutions mainly include:

The patent (CN 101619705 B) discloses a horizontal axis wind turbine blade with a bionic blade top boss, which can improve the flow loss at the tip of the blade, thereby reducing the noise of the wind turbine blade and the blade tip vortex. The purpose of reducing the noise of the entire wind wheel is achieved.

The patent (CN 102003333 A) discloses a wind turbine blade with noise reduction function. The contour lines of the tip part, transition part and trailing edge part of the blade are wavy and provided with sawtooth segments. the

The patent (CN 102562436 A) discloses a noise reducer for wind turbine rotor blades, which contains bristles, hair groups and porous layers. The noise reducer can have a good noise reduction effect on the blades under the condition of wind flow in different directions. the

Patent (EP 0652367) discloses a wind turbine blade with different toothed trailing edges; patent (EP 1314885) discloses a wind turbine blade with toothed panels; patent (EP 1338793) discloses a wind turbine blade with variable A wind turbine blade with a toothed trailing edge. the

The above solutions all change the shape of the blade tip, and improve the shape of the airflow of the blade tip with different tooth profiles, so as to achieve the purpose of noise reduction. However, the tooth-shaped blade tip in the above scheme is difficult to process, which changes the aerodynamic shape of the original airfoil, and its overall aerodynamic capability needs to be verified. the

For blade flutter, existing solutions mainly include:

The patent (CN 102322391A) discloses a protection method for predicting and analyzing the vibration of wind turbine blades. According to the calculation, the dangerous moment of the blades is predicted, and the dangerous blades are stopped in advance to achieve the protection of the blades. This method can effectively protect the blade, but it does not improve the ability of the blade itself to suppress vibration and improve the stability of the blade.

Patent (CN 2737980Y) and patent (CN 102348892A) respectively disclose a structural damper for wind turbine blades. The damper is attached to the inner wall of the blade by bonding or other means, and can effectively control the vibration of the blade within a wide operating frequency. However, there are defects such as the detachment of the damper, the increase of the quality of the blade, and the complicated structure. the

In summary, the current research on large blade vibration suppression mainly focuses on the aerodynamic method and the additional damper method. The aerodynamic method is mainly to change the aerodynamic shape of the blade to make it have good stall performance, so as to achieve the purpose of suppressing vibration in the high wind speed area, but this method will reduce the dynamic capacity of the blade, thereby reducing the output power of the wind rotor. And the flutter suppression effect is poor in low and medium wind speed areas; the additional damper method is to use additional dampers on the blades to suppress the flutter of the blades, but it only works in a certain frequency range or in a certain flutter direction , and will add extra mass to the blade, and the damper is easy to fall off, causing a safety hazard. the

Contents of the invention

In order to solve the problem that large flexible blades of wind turbines are prone to flutter and lack effective prevention and control methods, the invention provides a method for suppressing flutter of wind turbine blades using a composite damping structure. the

The present invention is realized by adopting the following technical scheme: a method for suppressing vibration of wind turbine blades using a composite damping structure, specifically setting a co-solidified constrained damping layer on the surface of the blades, and setting a free damping layer on the outer surface of the main beam; the free damping layer consists of a single layer Damping viscoelastic materials or single-layer damping alloys or single-layer damping composite materials are specifically bonded to the outer surface of the main beam, and the thickness of the free damping layer can be calculated by the following formula:

为主梁结构损耗因子，

为主梁厚度，

为阻尼层厚度，

为主梁杨氏模量，

为阻尼材料杨氏模量,

为阻尼材料损耗因子； in

Loss factor of the main beam structure,

is the main beam thickness,

is the damping layer thickness,

Young's modulus of the main beam,

is the Young's modulus of the damping material,

is the loss factor of the damping material;

The co-cured constrained damping layer is co-cured and formed by the composite material layer and the damping material layer interlaced (specifically, one layer of composite material layer and one layer of damping material layer are stacked alternately), and the uppermost and lowermost layers are composite material layers, and the damping material layer At least one layer is provided, the composite material layer is made of glass fiber composite material or carbon fiber composite material or glass and carbon fiber mixed composite material, and the damping material layer is made of damping viscoelastic material; Calculated:

为蒙皮共固化约束阻尼层结构损耗因子，l为复合材料层的厚度，L为共固化约束阻尼层的总厚度，N为阻尼材料层层数，H _v 为阻尼材料层厚度；β为阻尼材料层损耗因子；G为阻尼材料的剪切模量；f为叶片所受流体载荷（风载）的激振频率；W为共固化约束阻尼层单位长度的质量；g为重力加速度；A _i 为第i层复合材料层的面积；E _i 为第i层复合材料层的弹性模量；d _i 为第一层复合材料层至第i层复合材料层的距离；I _i 为第i层复合材料层对于其中性面的惯性矩，中性面指结构发生弯曲振动时既没有拉力也没有压力的面（中性面指结构发生弯曲振动时既没有拉力也没有压力的面）；K _i 为第i层的复合材料层的拉伸刚度，(EI) _∞ 为共固化约束阻尼层中性面的弯曲刚度；(EI) ₀ 为各复合材料层以自身中性面计算弯曲刚度的总和；(EI) _r 为共固化约束阻尼层的弯曲刚度实部。Re为取实部，Im为取虚部，

为过渡量，i、j、e为计数变量，R为计算算法的中间量。 in

is the structural loss factor of the skin co-cured constrained damping layer, l is the thickness of the composite material layer, L is the total thickness of the co-cured constrained damping layer, N is the number of damping material layers, H _v is the thickness of the damping material layer; β is the damping Material layer loss factor; G is the shear modulus of the damping material; f is the excitation frequency of the fluid load (wind load) on the blade; W is the mass per unit length of the co-cured constrained damping layer; g is the acceleration of gravity; A _i is the area of the i -th composite material layer; E _i is the elastic modulus of the i-th composite material layer; d _i is the distance from the first composite material layer to the i-th composite material layer; I _i is the i-th composite material layer The moment of inertia of the material layer with respect to its neutral plane, the neutral plane refers to the surface that has neither tension nor pressure when the structure undergoes bending vibration (the neutral plane refers to the surface that has neither tension nor pressure when the structure undergoes bending vibration); K _i is The tensile stiffness of the composite material layer of the i-th layer, (EI) _∞ is the bending stiffness of the neutral plane of the co-cured constrained damping layer; (EI) ₀ is the sum of the bending stiffness calculated by each composite material layer with its own neutral plane; ( EI) _r is the real part of the bending stiffness of the co-cured constrained damping layer. Re is to take the real part, Im is to take the imaginary part,

is the transition quantity, i, j, e are the counting variables, and R is the intermediate quantity of the calculation algorithm.

为主梁结构损耗因子、

为蒙皮共固化约束阻尼层结构损耗因子，这是设计要求所决定的；上述设计过程中其余各参数为风力机叶片设计过程中的已知参数，如主梁厚度、主梁杨氏模量、阻尼材料杨氏模量、阻尼材料损耗因子等，是本领域技术人员在不同的设计过程中容易得到的。  The co-cured constrained damping layer on the surface of the blade and the free damping layer on the outer surface of the main girder in the present invention specifically adopt the co-curing forming process, which is well known to those skilled in the field of material forming. The above method of determining the thickness of the co-cured constrained damping layer and the free damping layer is based on a large number of experiments to establish a mathematical model, using a reasonable calculation process and using appropriate numerical simulations. This method can describe co-curing more accurately Relationship between the thickness of constrained and free damping layers and other parameters in the wind turbine blade design process.

Loss factor of the main beam structure,

is the structural loss factor of the skin co-cured constrained damping layer, which is determined by the design requirements; the other parameters in the above design process are known parameters in the design process of the wind turbine blade, such as the thickness of the main girder, the Young's modulus of the main girder , Young's modulus of damping material, loss factor of damping material, etc., are easily obtained by those skilled in the art in different design processes.

The beneficial effects of the invention are as follows: the co-cured constrained damping layer and the free damping layer are added to the blades of the wind turbine through detailed design and calculation, and the vibration suppression of the wind turbine is realized. Compared with the prior art, the present invention has:

1) Universal Applicability. Because the present invention mainly performs relevant damping treatment on the internal structure of the blade, the aerodynamic shape of the blade is not modified, and the link between the blade root and the hub of the wind wheel adopts a traditional method. Therefore the present invention can be applicable to the lower wind turbine wind wheel of most situations.

2) Effective anti-fibrillation properties. In the present invention, the co-cured constrained damping layer structure of composite material + damping material + composite material is adopted for the blade skin, and the main beam adopts a free damping layer structure, so the composite damping structure blade has a higher structural loss factor and can be used in a wider frequency range. The flutter of the blades can be effectively suppressed in the field, and the aerodynamic stability of the wind turbine rotor can be improved. the

3) Economical. Co-solidification damping and free damping treatment will not significantly increase the production cost of the blade, so the present invention has certain economic efficiency while obtaining better vibration suppression performance. the

4) Designability. The damping parameters can be designed and optimized according to the actual needs to obtain the required loss factor of the blade structure and meet the design needs. the

the

Description of drawings

Fig. 1 is the schematic diagram of blade section structure;

Fig. 2 is a schematic diagram of the structure of the co-cured constrained damping layer.

In the figure: 1-blade, 2-free damping layer, 3-co-cured constrained damping layer, 4 main beam, 5-composite material layer, 6-damping material layer. the

Detailed ways

The vibration suppression method of wind turbine blades using a composite damping structure is specifically to set a co-cured constrained damping layer 3 on the surface of the blade 1, and set a free damping layer 2 on the outer surface of the main beam 4; the free damping layer 2 is made of a single-layer damping viscoelastic material or Single-layer damping alloy or single-layer damping composite material is specifically bonded to the outer surface of the main beam, and the thickness of the free damping layer can be calculated by the following formula: 

为主梁结构构损耗因子，

为主梁厚度，

为阻尼层厚度，

为主梁杨氏模量，为阻尼材料杨氏模量,

为阻尼材料损耗因子； in

Structural loss factor of the main beam structure,

is the main beam thickness,

is the damping layer thickness,

Young's modulus of the main beam, is the Young's modulus of the damping material,

is the loss factor of the damping material;

The co-cured constrained damping layer 3 is co-cured and formed by the interstitial arrangement of the composite material layer and the damping material layer, and the uppermost layer and the lowermost layer are composite material layers, and at least one damping material layer is provided, and the composite material layer is made of glass fiber composite material or carbon fiber Composite materials or glass and carbon fiber mixed and matched composite materials, the damping material layer is made of damping viscoelastic material; the thickness of the co-cured constrained damping layer 3 can be calculated by the following formulas simultaneously and iteratively:

为蒙皮共固化约束阻尼层结构损耗因子，l为复合材料层厚度，L为共固化结构总厚度，N为阻尼材料层层数，H _v 为阻尼材料层厚度；β为阻尼材料层损耗因子；G为阻尼材料的剪切模量； _f 为叶片所受流体载荷（风载）的激振频率；W为共固化约束阻尼层单位长度的质量；g为重力加速度；A _i 为第i层复合材料层的面积；E _i 为第i层复合材料层的弹性模量；d _i 为第一层复合材料层至第i层复合材料层的距离；I _i 为第i层复合材料层对于其中性面的惯性矩，中性面指结构发生弯曲振动时既没有拉力也没有压力的面；K _i 为第i层的复合材料层的拉伸刚度，(EI) _∞ 为共固化约束阻尼层中性面的弯曲刚度；(EI) ₀ 为各复合材料层以自身中性面计算弯曲刚度的总和；(EI) _r 为共固化约束阻尼层的弯曲刚度实部。 in

is the loss factor of the skin co-cured constrained damping layer structure, l is the thickness of the composite material layer, L is the total thickness of the co-cured _structure , N is the number of damping material layers, Hv is the thickness of the damping material layer; β is the loss factor of the damping material layer ; G is the shear modulus of the damping material; _f is the excitation frequency of the fluid load (wind load) on the blade; W is the mass per unit length of the co-cured constrained damping layer; g is the acceleration of gravity; A _i is the i-th layer The area of the composite material layer; E _i is the modulus of elasticity of the i-th composite material layer; d _i is the distance from the first composite material layer to the i-th composite material layer; I _i is the i-th composite material layer for which The moment of inertia of the neutral plane, the neutral plane refers to the surface where there is neither tension nor pressure when the structure undergoes bending vibration; K _i is the tensile stiffness of the i-th composite material layer, (EI) _∞ is the The bending stiffness of the neutral plane; (EI) ₀ is the sum of the bending stiffness of each composite material layer based on its own neutral plane; (EI) _r is the real part of the bending stiffness of the co-cured constrained damping layer.

In the specific implementation process, an expansion layer is set between the outer surface of the main beam 4 and the free damping layer 2, and the expansion layer is made of hard foam plastic with a spherical cavity structure inside, or an inner layer made of metal or polymer material. Honeycomb structure material. the

Example 1

Take a certain 2 500 kW wind turbine as an example. The wind turbine is mainly used in offshore wind farms. Its design power is 2.5 MW. It adopts three-blade form. The material of the leaf skin is GRP. The main design parameters are shown in Table 1.

Table 1 Main Design Parameters serial number Design volume design value 1 Number of wind rotor blades 3 2 Speed/rpm 10.5～19.0 3 Rotor diameter/m 80 4 Windward area/m ² 5 026 5 Power adjustment method variable pitch 6 Start wind speed/m/s 4 7 Rated power wind speed/m/s 15 8 Shutdown wind speed/m/s 25 9 Safe wind speed/m/s 65 10 pitch adjustment single drive 11 Total weight of wind wheel/kg 50 000 12 Blade length/m 38.8 13 Blade weight/kg 8 700 14 blade material GRP

(1) airfoil selection

According to the design requirements, the NACA 6413 airfoil is selected for all blades, which has a large lift-to-drag ratio and good stall performance.

(2) Damping structure

Composite materials, damping materials, and co-cured constrained damping layer structure of composite materials are used; I-beam steel beams are used for the main beam, and the free damping layer is treated, that is, the damping material is pasted on the web of the main beam with epoxy resin. The damping material is epoxy viscoelastic material (SMRD 100 F50), its loss factor β = 0.89, and can withstand the temperature of 120°C for a long time, which meets the working condition requirements of large wind turbine blades.

(3) Analysis of anti-fibrillation characteristics

The wind turbine blade is modeled in Matlab/Simulink environment. The performance parameters of the co-cured constrained damping layer are: E ₁₁ = 42.6GPa, E ₁₂ = 16.5 GPa, G ₁₂ = 5.5 GPa, ν ₁₂ = 0.22, ρ = 1 950 kg/m ^-3 . The performance parameters of the damping material are: β = 0.89, G = 3.43×10 ⁶ N/m, E=1.14×10 ⁶ N/m, and the temperature-frequency effect of the damping material is ignored. Based on the ONERA nonlinear aerodynamic model, normal blades and damping blades are tested at starting wind speed V ₁ = 4 m/s, rated wind speed V ₂ = 15 m/s, shutdown wind speed V ₃ = 25 m/s and safe wind speed V ₄ = 45 m /s four kinds of wind speed for numerical simulation comparison. The structural damping of ordinary blades is neglected during the simulation process. Table 2 shows the performance comparison of ordinary blades and damping blades under various working conditions.

Table 2 Comparative data

  

Based on the simulation data and formula (23), the structural loss factors of the damping blades at four wind speeds are calculated as η ₁ = 0.617, η ₂ = 0.579, η ₃ = 0.523 and η ₄ = 0.439. It can be seen from Table 2 that under the four wind speeds, the standard deviation of the shimmy displacement of the damped blade is reduced by 51.1%, 48.1%, 43.6%, and 37.1%, respectively, and the standard deviation of the shimmy velocity is reduced by 51.1%, 47.9% compared with the normal blade. %, 43.7%, 37.1%; the standard deviation of waving displacement decreased by 37.9%, 34.8%, 30.8%, and 25.2%, respectively, and the standard deviation of waving speed decreased by 37.9%, 35.0%, 30.8%, and 25.0%, respectively.

To sum up, the damping blade converts part of the flutter energy into heat energy and dissipates it through the internal friction of the damping material, which can effectively suppress the flapping flutter, spanwise flutter, and torsional flutter of the blade, and significantly improve the blade's own flutter suppression. Ability to give full play to the advantages of flexible blades. the

Claims (2)

1. A wind turbine blade vibration suppression method utilizing a composite damping structure, characterized in that: specifically, a co-cured constrained damping layer (3) is set on the surface of the blade (1), and a free damping layer is set on the outer surface of the main beam (4) (2); The free damping layer (2) is a single-layer damping viscoelastic material or a single-layer damping alloy or a single-layer damping composite material, which is specifically bonded to the outer surface of the main beam (4), wherein the thickness of the free damping layer can be determined from the following The formula calculates:

in

Loss factor of the main beam structure,

is the main beam thickness,

is the damping layer thickness,

Young's modulus of the main beam,

is the Young's modulus of the damping material,

is the loss factor of the damping material; The co-cured constrained damping layer (3) is co-cured and formed by the interstitial arrangement of the composite material layer and the damping material layer, and the uppermost layer and the lowermost layer are composite material layers, and at least one damping material layer is provided, and the composite material layer is made of glass fiber composite material Or carbon fiber composite material or glass and carbon fiber mixed composite material, the damping material layer is made of damping viscoelastic material; the thickness of the composite material layer and damping material layer of the co-cured constrained damping layer (3) can be calculated by the following formulas simultaneously and iteratively out:

in

is the structural loss factor of the co-cured constrained damping layer, l is the thickness of the composite material layer, L is the total thickness of the co-cured constrained damping layer, N is the number of composite material layers, H _v is the thickness of the damping material layer; β is the damping material layer loss factor; G is the shear modulus of the damping material; f is the excitation frequency of the fluid load (wind load) on the blade; W is the mass per unit length of the co-cured constrained damping layer; g is the gravity acceleration; A _i is The area of the i -th composite material layer; E _i is the elastic modulus of the i-th composite material layer; d _i is the distance from the outermost composite material layer to the i-th composite material layer; I _i is the i-th composite material layer The moment of inertia of the layer with respect to its neutral plane, K _i is the tensile stiffness of the i-th composite material layer; (EI) _∞ is the bending stiffness of the neutral plane of the co-cured constrained damping layer; (EI) ₀ is the composite material layer Calculate the sum of the bending stiffness at its own neutral plane; (EI) _r is the real part of the bending stiffness of the co-cured constrained damping layer. 2. The method for suppressing vibration of wind turbine blades using a composite damping structure according to claim 1, characterized in that: an expansion layer is set between the outer surface of the main beam (4) and the free damping layer (2), and the expansion layer The hard foam plastic with spherical cavity structure inside is selected, or the material with internal honeycomb structure made of metal or polymer material is selected for use.

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