A bionic liquid circulation device for suppressing wind turbine blade flutter and its establishment method

Abstract

The present invention provides a bionic liquid circulation device for suppressing the flutter of a wind turbine blade and a method for establishing the device, and belongs to the technical field of renewable energy. The bionic liquid circulation device for suppressing the flutter of a wind turbine blade comprises a skin, a main beam, a web and a bionic pipe network flutter suppression system, and the bionic pipe network flutter suppression system comprises a bionic pipe network and a testing device, wherein the bionic pipe network is arranged with a bionic liquid circulation device, and the blade is divided into a suction surface and a pressure surface from a mid-arc line; the blade is divided into spanwise and chordwise regions, and the spanwise region is divided into five parts: a blade root, a blade rear section, a blade middle, a blade front section, and a blade tip; the chordwise region is divided into three parts: a leading edge, a middle part of an airfoil, and a trailing edge, wherein the leading edge corresponds to a blade root region, the middle part of an airfoil corresponds to a blade rear section region, and the trailing edge corresponds to a blade middle, a blade front section, and a blade tip region; the present invention designs a bionic liquid circulation device by using a Voronoi diagram, and changes the blade natural frequency by dynamically adjusting the mass distribution of the blade, thereby suppressing the flutter of the blade under complex working conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable energy, and in particular, relates to a bionic liquid circulation device for suppressing flutter of wind turbine blades and a method for establishing the device. Background Art

[0002] As a clean and renewable form of energy, wind power generation has been widely used and developed around the world in recent years. As the core component of the wind power generation system, the design quality of wind turbine blades directly determines the efficiency of wind energy capture, power generation stability and the economic benefits of the entire system. The blades capture wind energy and convert it into mechanical power to drive the generator to generate electricity. However, with the development of wind power generation technology and the promotion of market demand, wind turbine blades are moving towards large-scale, lightweight and high-efficiency, which undoubtedly puts higher requirements on the design and manufacture of blades. Wind turbine blades are usually made of composite materials (such as glass fiber, carbon fiber, etc.), with high specific strength and specific stiffness, and can withstand complex aerodynamic loads. The basic structure of the blade includes the blade root, the blade body (including the leading edge, the middle part of the airfoil, and the trailing edge) and the blade tip. The blade body part is designed into a specific airfoil along the span direction (the length direction of the blade) to optimize the flow of airflow on the blade surface and maximize the conversion into lift. A main beam is usually provided in the middle of the airfoil to strengthen the structural stiffness of the blade, while the leading edge and the trailing edge are responsible for guiding and separating the airflow. The blade root is connected to the wind turbine hub and is responsible for transmitting torque; the blade tip is the farthest end of the blade, is most affected by wind force, and is more sensitive to flutter.

[0003] Although modern wind turbine blades have made significant progress in design, there are still some challenges and drawbacks, which are mainly reflected in the following aspects: The flutter problem is prominent: As the size of the blade increases, its natural frequency decreases, and it is easier to enter the resonance zone caused by wind speed fluctuations, resulting in flutter. Flutter will not only greatly reduce the efficiency of wind energy conversion, but also cause fatigue damage to the blades. In severe cases, it may even cause blade breakage, threatening the safe operation of the wind power generation system. Uneven mass distribution causes vibration amplification: Traditional blade structures often have problems with uneven mass distribution. Especially in large-scale blades, local mass deviations may lead to imbalances in vibration modes, aggravate the vibration response of blades under complex wind field conditions, and increase the risk of flutter. Limitations of passive vibration reduction methods: Existing blade vibration reduction technologies, such as adding dampers, using special materials or structural designs, can suppress vibration to a certain extent, but they often lack dynamic adaptability and cannot cope with actual working conditions with rapidly changing wind speeds and wind directions. In addition, weight gain or complex structures may offset some of the wind energy benefits. Increased difficulty in operation and maintenance: The cost of repairing and replacing large blades is high, especially in remote or offshore wind farms, which places higher demands on the long-term reliability and adaptive vibration control capabilities of the blades. The existing blade structure is difficult to achieve efficient active vibration reduction and self-regulation, which increases the burden of operation and maintenance. Summary of the invention

[0004] In view of this, the present invention provides a bionic liquid circulation device for suppressing wind turbine blade flutter and a method for establishing the device. By imitating the blood circulation mechanism in the wings of a bionic dragonfly and using the Voronoi diagram, a bionic liquid circulation device is designed inside the blade to solve the blade flutter under complex working conditions.

[0005] The present invention is achieved in that:

[0006] A first aspect of the present invention provides a bionic liquid circulation device for flutter suppression of a wind turbine blade, wherein the blade comprises a skin, a main beam, and a web, wherein the blade further comprises a bionic pipe network flutter suppression system, wherein the bionic pipe network flutter suppression system comprises a bionic pipe network and a test device, wherein a bionic liquid circulation device is arranged inside the bionic pipe network, wherein the blade is divided into a suction surface and a pressure surface from a mid-arc line, wherein the suction surface is located on the windward surface of the blade for generating lift, and the pressure surface is located on the leeward surface of the blade;

[0007] The blade is divided into spanwise and chordwise regions. The blade is divided into five parts in the spanwise direction: blade root, blade rear section, blade middle, blade front section, and blade tip; the blade is divided into three parts in the chordwise direction: leading edge, airfoil middle, and trailing edge, wherein the leading edge corresponds to the blade root region, the airfoil middle corresponds to the blade rear section region, and the trailing edge corresponds to the blade middle, the blade front section, and the blade tip region;

[0008] Among them, the bionic pipe network is embedded in the inside of the blade and is constructed by analyzing the influence of mass distribution in different areas on vibration characteristics. The testing device is specifically provided with a force sensor at the blade root, and the force sensor is used to monitor the vibration of the blade by the reaction force of the blade root.

[0009] The technical effects of a bionic liquid circulation device for suppressing the flutter of wind turbine blades provided by the present invention are as follows: the present invention designs a bionic liquid circulation device inside the blade by biomimetic blood circulation in the wings of a dragonfly using a Voronoi diagram, adjusts the mass distribution of the blade through dynamic liquid circulation, and then changes the natural frequency of the blade to deviate from the flutter frequency, thereby achieving the suppression of the flutter of wind turbine blades under complex working conditions.

[0010] Through the dual division of spanwise and chordwise, the blade structure is divided into multiple sub-areas with specific functions and characteristics, such as blade root, blade tip, leading edge, etc. This method helps to accurately identify the mechanical properties, aerodynamic performance and potential failure points of various parts of the blade, facilitates targeted structural optimization, vibration control, maintenance decisions, etc., and improves the overall efficiency, reliability and economy of the wind power generation system.

[0011] On the basis of the above technical solution, the bionic liquid circulation device for wind turbine blade flutter suppression of the present invention can also be improved as follows:

[0012] Wherein, the middle part of the airfoil is located where the main beam is located.

[0013] Furthermore, the area division is performed from the blade root to the blade tip.

[0014] A second aspect of the present invention provides a method for establishing a bionic liquid circulation device for suppressing wind turbine blade flutter, wherein the bionic liquid circulation device for suppressing wind turbine blade flutter mentioned above is included, and the establishment method comprises the following steps:

[0015] S10, obtaining the design factors of the blade and establishing a blade model;

[0016] S20, performing prestressed harmonic response analysis on the blade at different wind speeds, calculating the displacement ratio at the first and second order natural frequencies, and constructing a vibration reduction rate calculation function according to the displacement ratio;

[0017] S30, performing an orthogonal test and a range analysis on the blade according to the influencing factors and taking the constructed vibration reduction rate as an evaluation index;

[0018] S40, fitting the vibration reduction rate in the blade span direction and the blade chord direction using a quadratic function, constructing the bionic pipe network and the bionic liquid circulation device, and setting the position of the liquid storage cavity;

[0019] S50, performing harmonic response analysis on the bionic pipe network of the liquid storage cavity and other parts of the bionic liquid circulation device to obtain the flutter suppression effect of the bionic liquid circulation device. Based on the above technical solution, the method for establishing a bionic liquid circulation device for suppressing flutter of wind turbine blades of the present invention can also be improved as follows:

[0020] Furthermore, the design factors include wind speed, blade span direction, blade chord direction, medium density, suction surface, and pressure surface.

[0021] The design factors include five factors: wind speed (10 levels), blade span direction (5 levels), blade chord direction (3 levels), medium density (3 levels), and suction and pressure surface (2 levels).

[0022] Furthermore, the step S20 specifically includes:

[0023] Use vibration analysis tools to perform harmonic response analysis on the blade model in a prestressed state;

[0024] Input different wind speeds as excitations, calculate the dynamic response of the blade under different wind speeds, and output a blade tip displacement amplitude-frequency diagram;

[0025] Extracting the tip displacement peak values ​​corresponding to the first-order and second-order natural frequencies of the blade from the tip displacement amplitude-frequency diagram;

[0026] The displacement ratio at the first and second order natural frequencies is calculated, and the vibration reduction rate calculation function is constructed based on the displacement ratio.

[0027] Harmonic response analysis is used to determine the steady-state response of a linear structure when it is subjected to a load that changes sinusoidally (or harmonically) over time. During the analysis, only the steady-state forced vibration of the structure is calculated, and the transient vibration at the beginning of the excitation is not considered. The purpose of harmonic response analysis is to calculate the response value (usually displacement) of the structure at several frequencies versus frequency, so that designers can predict the continuous dynamic characteristics of the structure and verify whether the design can overcome the harmful effects caused by resonance, fatigue and other forced vibrations.

[0028] Use finite element analysis software or other suitable vibration analysis tools to perform harmonic response analysis on the blade model in the prestressed state. Input different wind speeds as excitation, calculate the dynamic response of the blade under the corresponding wind speed, especially the change of the displacement of the blade tip with frequency, and output the amplitude-frequency diagram of the blade tip displacement.

[0029] Furthermore, the step S30 specifically includes:

[0030] Obtain influencing factors: including wind speed, medium density, and regional division, generate a mixed level orthogonal table based on the influencing factors, and set up an orthogonal experiment;

[0031] Selecting a medium density, wherein the medium density is specifically the density of a liquid medium used for vibration reduction inside the blade, wherein the liquid medium is specifically a fluid material, and the fluid material includes water, oil, and emulsion;

[0032] According to the conditions of each set of orthogonal experiments, a prestressed modal analysis is performed to calculate the natural frequency and tip displacement of the blade after filling liquid media with different densities in different blade span and blade chord regions;

[0033] Calculate the corresponding vibration reduction rate according to the vibration reduction rate calculation function and the displacement ratio at the first and second order natural frequencies obtained by simulation;

[0034] For each of the influencing factors, calculate the range between different levels, that is, the maximum value of the difference between the average vibration reduction rate of all test results at the same level and the total average vibration reduction rate of all test results, and obtain the range analysis result;

[0035] According to the range analysis result, each of the influencing factors is ranked according to its importance in affecting the vibration reduction rate, and the factor with the most significant vibration reduction effect on the blade is identified.

[0036] Furthermore, the step S40 specifically includes:

[0037] Obtain vibration reduction rate data of each area in the blade span direction and the blade chord direction in the orthogonal test results, and divide the vibration reduction rate data into two groups, one group includes the vibration reduction rate corresponding to the blade span direction area, that is, span direction data, and the other group includes the vibration reduction rate corresponding to the blade chord direction area, that is, chord direction data;

[0038] Selecting quadratic function models for the spanwise data and the chordwise data respectively, and using MATLAB functions to perform quadratic fitting on the spanwise data and the chordwise data respectively, to obtain fitting curves and chordwise ratios;

[0039] Mapping the calculated blade spanwise and chordwise node coordinates into the blade region, taking the leading edge and trailing edge contours of the blade as boundaries, and dividing the blade according to the calculated chordwise ratio;

[0040] Using the Voronoi diagram algorithm, the nodes are mapped onto the partition curve to generate Voronoi diagram nodes, and the nodes are connected into a closed loop through flexible pipes to form a bionic pipe network;

[0041] The center coordinates of the nodes are read in the CAD software and then input into the MATLAB software for processing;

[0042] Generate corresponding grids according to the chord lengths and offsets at different positions of the blade: that is, generate a hexagonal grid at the blade root, generate a grid close to a quadrilateral in the blade, and generate a conical grid at the blade tip;

[0043] A liquid storage cavity is arranged in the area with the highest vibration reduction rate, and the area with the highest vibration reduction rate is specifically the blade tip and the middle part of the airfoil.

[0044] The beneficial effect of adopting the above-mentioned improvement scheme is that the vibration reduction rate data of the spanwise and chordwise positions are fitted by quadratic functions to form continuous vibration reduction rate curves. These curves intuitively show the vibration reduction demand intensity of each part of the blade, provide precise guidance for the design of the distribution, capacity and control strategy of the vibration reduction device, and help to maximize the vibration reduction effect.

[0045] The Voronoi diagram generation technology is used to determine the node distribution of the device in the span and chord directions of the blade according to the vibration reduction rate curve. This method imitates the efficient vibration reduction mechanism in nature, designs the layout of the liquid circulation device that matches the blade vibration reduction requirements, improves the vibration reduction effect, and reduces the vibration loss of the wind power generation system.

[0046] Furthermore, the step S50 specifically includes:

[0047] Acquire the position of the liquid storage cavity and the bionic pipe network of other parts of the bionic liquid circulation device;

[0048] Conduct experiments under set wind speed conditions;

[0049] The harmonic response analysis of the bionic pipe network, the liquid storage cavity, the bionic blade with the bionic pipe network and the liquid storage cavity and the original blade was carried out respectively to obtain the response variation with frequency.

[0050] At the first-order natural frequency of the original blade, the bionic pipe network liquid circulation is carried out;

[0051] The results verified that the anti-tremor effect of the bionic tube network plus the liquid storage cavity is better than that of the single bionic tube network or the liquid storage cavity.

[0052] The beneficial effects of adopting the above-mentioned improvement scheme are: optimizing vibration reduction through the bionic liquid circulation device inside the blade, improving the stability and efficiency of the overall operation of the system. This system design takes into account both wind energy capture and equipment protection, which helps to reduce operation and maintenance costs and improve the economy and environmental friendliness of wind power generation.

[0053] Furthermore, the ratio of the blade span length to the blade chord length is 4.2:1, the grid includes a blade span grid and a blade chord length grid, and the ratio of the blade span grid to the blade chord length grid is 3.3:1.

[0054] The ratio of the number of nodes in the span direction and the chord direction of the blade is based on the dragonfly wing. The ratio of the maximum span-to-chord length of the dragonfly wing is 4.2:1, and the ratio of the span-to-chord grid is about 3.3:1.

[0055] Compared with the prior art, the beneficial effects of the bionic liquid circulation device for wind turbine blade flutter suppression and the method for establishing the device provided by the present invention are: by arranging the bionic pipe network inside the blade, the blood circulation in the wings of a dragonfly is simulated to achieve a method for flutter suppression. The core principle of this method is to dynamically adjust the mass distribution of the blade so that the natural frequency of the blade deviates from the flutter frequency, thereby effectively suppressing the occurrence of flutter. The present invention uses the Voronoi diagram to construct a bionic flutter suppression pipe network system inside the wind turbine blade across scales;

[0056] In this system, through the careful design and arrangement of the pipe network structure, a liquid flow path similar to biological blood circulation can be formed inside the blade. This bionic design can not only effectively increase the uniformity of the mass distribution of the blade, but also introduce a dynamic adjustment mechanism so that the blade can work more stably under the action of wind. At the same time, through the hydraulic control system, liquid circulation in the bionic pipe network in different areas of the blade can be realized, which can realize dynamic intelligent regulation of the flutter suppression effect and improve the adaptability and stability of the system.

[0057] Compared with the traditional anti-flutter structure, this anti-flutter system based on bionic pipe network has many advantages. First, it does not require major changes to the existing blade structure. It only needs to introduce the bionic pipe network anti-flutter system inside, which will not have a significant impact on the aerodynamic performance of the blade. Secondly, because the bionic pipe network system has high flexibility and intelligence, it can better adapt to various complex wind conditions and improve the reliability and efficiency of the entire wind turbine system.

[0058] Therefore, the wind turbine blade design concept based on the bionic pipe network flutter suppression system has broad application prospects and development space. Through continuous optimization and improvement, it is believed that this innovative design concept will bring more technological breakthroughs and development opportunities to the field of wind power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0060] Figure 1 A flow chart of a method for establishing a bionic liquid circulation device for suppressing wind turbine blade flutter;

[0061] Figure 2 This is a schematic diagram of the spanwise division of blade regions of the present invention;

[0062] Figure 3 It is a fitting curve diagram of the vibration reduction rate of the blade in the span direction and the chord direction of the present invention;

[0063] Figure 4 A diagram showing the construction process of the bionic liquid circulation device in a blade of the present invention;

[0064] Figure 5 This is a harmonic response analysis diagram of the blade bionic pipe network of the present invention;

[0065] Figure 6 It is a schematic diagram of the division of the chord-wise area of ​​the blade of the present invention;

[0066] Figure 7 It is a schematic diagram of the blade profile division of the present invention;

[0067] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0068] 11. Suction surface; 111. Blade root; 112. Blade rear section; 113. Blade middle; 114. Blade front section; 115. Blade tip; 12. Pressure surface; 121. Leading edge; 122. Middle part of airfoil; 123. Trailing edge. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0070] Embodiment 1:

[0071] like Figure 1 As shown, the present invention provides a first embodiment of a bionic liquid circulation device for flutter suppression of wind turbine blades and a method for establishing the same. In this embodiment, the blade includes a skin, a main beam, a web, and a bionic pipe network flutter suppression system. The bionic pipe network flutter suppression system includes a bionic pipe network and a test device. A bionic liquid circulation device is arranged inside the bionic pipe network. The blade is divided into a suction surface 11 and a pressure surface 12 from the mid-arc. The suction surface 11 is located on the windward side of the blade for generating lift, and the pressure surface 12 is located on the leeward side of the blade.

[0072] The blade is divided into spanwise and chordwise regions. The blade is divided into five parts in the spanwise direction: blade root 111, blade rear section 112, blade middle 113, blade front section 114, and blade tip 115; the blade is divided into three parts in the chordwise direction: leading edge 121, airfoil middle section 122, and trailing edge 123. The leading edge 121 corresponds to the blade root 111 region, the airfoil middle section 122 corresponds to the blade rear section 112 region, and the trailing edge 123 corresponds to the blade middle 113, blade front section 114, and blade tip 115 regions.

[0073] Among them, the bionic pipe network is embedded in the inside of the blade and is constructed by analyzing the influence of mass distribution in different areas on vibration characteristics. The test device is specifically provided with a force sensor at the blade root 111, and the force sensor is used to monitor the vibration of the blade by the reaction force of the blade root 111.

[0074] When the force sensor detects a sudden increase in amplitude, it controls the circulation of the liquid in the bionic liquid circulation device. Based on the principle of minimizing the increase in blade mass, the mass distribution on the blade is changed, and the natural frequency is adjusted to deviate from the current flutter frequency, thereby achieving blade flutter suppression.

[0075] Refer to the design data of NREL 15MW original blades to clarify basic information such as blade geometry and shape.

[0076] The blade is divided into five parts along its span direction: blade root, blade rear section, blade middle, blade front section, and blade tip, ensuring that the boundaries of each part are compatible with the aerodynamic characteristics and structural features of the blade.

[0077] The airfoil is divided into three parts along the chord direction of the blade: the leading edge, the middle part of the airfoil (where the main beam is located), and the trailing edge, ensuring that the boundaries of each part are consistent with the airfoil contour.

[0078] The blade is divided into the suction side and the pressure side by the mid-arc line, so as to facilitate the subsequent independent aerodynamic analysis, structural design or vibration reduction treatment of the two side surfaces.

[0079] Among them, in the above technical solution, the middle part 122 of the airfoil is located at the position of the main beam.

[0080] Furthermore, in the above technical solution, the area division is performed from the blade root 111 to the blade tip 115 .

[0081] A bionic liquid circulation device for suppressing wind turbine blade flutter, the establishment method of which comprises the following steps:

[0082] S10, obtaining the design factors of the blade and establishing a blade model;

[0083] S20, performing prestressed harmonic response analysis on the blade at different wind speeds, calculating the displacement ratio at the first and second order natural frequencies, and constructing a vibration reduction rate calculation function according to the displacement ratio;

[0084] S30, performing an orthogonal test and a range analysis on the blade according to the influencing factors and taking the constructed vibration reduction rate as an evaluation index;

[0085] S40, fitting the vibration reduction rate in the blade span direction and the blade chord direction using a quadratic function, constructing the bionic pipe network and the bionic liquid circulation device, and setting the position of the liquid storage cavity;

[0086] S50, performing harmonic response analysis on the position of the liquid storage cavity and the bionic pipe network of other parts of the bionic liquid circulation device to obtain the damping effect of the bionic liquid circulation device.

[0087] Furthermore, in the above technical solution, the design factors include wind speed, blade span direction, blade chord direction, medium density, suction surface, and pressure surface.

[0088] Furthermore, in the above technical solution, step S20 specifically includes:

[0089] Use vibration analysis tools to perform harmonic response analysis on the blade model in a prestressed state;

[0090] Input different wind speeds as excitation, calculate the dynamic response of the blade under different wind speeds, and output the amplitude-frequency diagram of blade tip displacement;

[0091] From the tip displacement amplitude-frequency diagram, extract the tip displacement peak values ​​corresponding to the first-order and second-order natural frequencies of the blade;

[0092] The displacement ratio at the first and second order natural frequencies is calculated, and the vibration reduction rate calculation function is constructed based on the displacement ratio.

[0093] Harmonic response analysis under wind speed prestressing was introduced. By obtaining the blade tip displacement amplitude-frequency diagram and calculating the blade tip displacement ratio, a key proportional factor was provided for the subsequent vibration reduction rate calculation. This method helps to quantitatively evaluate the flutter sensitivity of blades under different wind speed conditions, guide the optimal configuration of vibration reduction measures, effectively reduce the risk of blade flutter, and extend its service life.

[0094] The blade model of the divided area is simulated or tested under different wind speed prestress.

[0095] Perform harmonic response analysis, generate blade tip displacement amplitude-frequency diagram, and record blade tip displacement data under different wind speeds.

[0096] The tip displacement ratio at the first and second order natural frequencies is calculated as the basis for the subsequent blade vibration reduction rate calculation.

[0097] Furthermore, in the above technical solution, step S30 specifically includes:

[0098] Obtain influencing factors: including wind speed, medium density, and regional division, generate a mixed level orthogonal table based on the influencing factors, and set up an orthogonal experiment;

[0099] Selecting a medium density, the medium density specifically refers to the density of a liquid medium used for vibration reduction inside the blade, the liquid medium specifically refers to a fluid material, and the fluid material includes water, oil, and emulsion;

[0100] According to the conditions of each set of orthogonal experiments, prestressed modal analysis is carried out to calculate the natural frequency and tip displacement of the blade after filling the liquid medium with different densities in different blade span and blade chord regions;

[0101] According to the vibration reduction rate calculation function and the displacement ratio at the first and second order natural frequencies obtained by simulation, the corresponding vibration reduction rate is calculated;

[0102] For each influencing factor, calculate its range between different levels, that is, the maximum value of the difference between the average vibration reduction rate of all test results at the same level and the total average vibration reduction rate of all test results, and obtain the range analysis result;

[0103] According to the results of the range analysis, each of the influencing factors is ranked according to its importance in affecting the vibration reduction rate, and the factor with the most significant vibration reduction effect on the blade is identified.

[0104] Furthermore, in the above technical solution, step S40 specifically includes:

[0105] Obtain vibration reduction rate data of each area in the blade span direction and the blade chord direction in the orthogonal test results, and divide the vibration reduction rate data into two groups, one group includes the vibration reduction rate corresponding to the blade span direction area, that is, span direction data, and the other group includes the vibration reduction rate corresponding to the blade chord direction area, that is, chord direction data;

[0106] Selecting quadratic function models for the spanwise data and the chordwise data respectively, and using MATLAB functions to perform quadratic fitting on the spanwise data and the chordwise data respectively, to obtain fitting curves and chordwise ratios;

[0107] The calculated blade spanwise and chordwise node coordinates are mapped into the blade region, and the blade leading edge and trailing edge contours are used as boundaries to divide the blade according to the calculated chordwise ratio;

[0108] Using the Voronoi diagram algorithm, the nodes are mapped onto the partition curve to generate the Voronoi diagram nodes. The nodes are connected into a closed loop through flexible pipes to form a bionic pipe network.

[0109] Read the center coordinates of the nodes in the CAD software and then input them into the MATLAB software for processing;

[0110] According to the chord length and offset of different positions of the blade, corresponding grids are generated: that is, a hexagonal grid is generated at the blade root 111, a grid close to a quadrilateral is generated at the blade middle 113, and a conical grid is generated at the blade tip 115;

[0111] The liquid storage cavity is arranged in the area with the highest vibration reduction rate, and the area with the highest vibration reduction rate is specifically the blade tip 115 and the middle part 122 of the airfoil.

[0112] The design and establishment steps of the bionic pipe network are as follows:

[0113] First, a detailed analysis of the influence of mass distribution on vibration characteristics of different areas of the blade is carried out. This includes but is not limited to:

[0114] Theoretical modeling and simulation: Establish a blade model, consider factors such as the blade's structural characteristics, material properties, aerodynamic loads, and simulate the impact of mass distribution in different regions on vibration parameters such as the blade's natural frequency, vibration mode, and damping characteristics.

[0115] Experimental verification: In a laboratory environment, vibration tests are performed using scaled models or full-size blades. By changing the local mass loading, the effects of different mass distributions on the vibration characteristics of the blades are measured to verify the theoretical analysis results.

[0116] The analysis results clearly point out that mass adjustment in specific areas can effectively change the vibration characteristics of the blade. In particular, by appropriately increasing or reducing the mass in certain key areas, the natural frequency of the blade can be significantly changed, moving it away from the excitation frequency corresponding to the specific wind speed that is prone to cause flutter, thereby achieving effective flutter suppression.

[0117] Bionics and network topology: Inspired by the blood circulation in dragonfly wings, the topological structure of the bionic pipe network is constructed. Specifically include:

[0118] Voronoi diagram optimization: Using the Voronoi diagram algorithm, the optimal layout of the liquid chamber nodes in the span and chord directions of the blade is determined based on the blade's geometric shape, mechanical properties, and vibration characteristics analysis results. This layout ensures that the liquid chamber nodes are evenly or unevenly distributed in space, and can flexibly adapt to the needs of mass adjustment in different areas of the blade.

[0119] Pipeline network connection mode: The liquid chamber nodes are connected into a closed circulation loop through flexible pipes. The pipeline path design imitates the bifurcation, convergence and ring structure of the blood circulation in the wings of a dragonfly, ensuring the smooth flow of liquid in the pipeline network. At the same time, it is conducive to dispersing stress and enhancing the robustness of the overall structure.

[0120] Liquid chamber node design:

[0121] Liquid chamber structure: The liquid chamber node is designed as a closed cavity that can accommodate low-viscosity, high specific heat capacity liquids (such as silicone oil). Its shape and volume are customized according to the vibration characteristics requirements and space limitations of the location, ensuring that the internal liquid amount can be quickly adjusted in response to instructions from the central controller to achieve precise increase or decrease in mass.

[0122] Liquid management interface: Each liquid chamber node is equipped with necessary liquid delivery interfaces (such as pipe joints, valves) to seamlessly connect with the pipelines and control elements (such as liquid pumps, flow controllers) of the liquid delivery system to achieve liquid injection, discharge and transfer between nodes.

[0123] Pipeline network integration and packaging:

[0124] Embedded installation: The bionic tube network is designed to be completely embedded in the blade without changing the outer contour and aerodynamic shape of the blade, ensuring that its impact on the aerodynamic performance of the blade is minimized.

[0125] Protection and sealing: The pipe network and liquid chamber nodes are made of weather-resistant materials to ensure long-term stable operation in harsh wind power generation environments (such as high and low temperatures, humidity, salt spray, etc.). All joints and interfaces use reliable sealing technology to prevent liquid leakage and ensure the safety and reliability of the system.

[0126] Furthermore, in the above technical solution, step S50 specifically includes:

[0127] Obtaining the location of the liquid storage cavity and the bionic pipe network of other parts of the bionic liquid circulation device;

[0128] Conduct experiments under set wind speed conditions;

[0129] The harmonic response analysis of the bionic pipe network, the liquid storage cavity, the bionic blade with the bionic pipe network and the liquid storage cavity and the original blade was carried out respectively to obtain the response variation with frequency.

[0130] At the first-order natural frequency of the original blade, the bionic pipe network liquid circulation is carried out;

[0131] The results verified that the anti-tremor effect of the bionic tube network plus the liquid storage cavity is better than that of the single bionic tube network or the liquid storage cavity.

[0132] Furthermore, in the above technical solution, the ratio of the span-wise length to the chord-wise length of the blade is 4.2:1, the grid includes a span-wise grid and a chord-wise grid, and the ratio of the span-wise grid to the chord-wise grid is 3.3:1.

[0133] Embodiment 2:

[0134] The present invention provides a second embodiment of a bionic liquid circulation device for suppressing wind turbine blade flutter. In this embodiment, regions are divided based on the original NREL 15MW blade. An orthogonal test is performed to obtain the mass distribution region with the greatest impact on blade flutter. Based on the orthogonal test results, the vibration reduction rate curves in the span direction and the chord direction are fitted to construct a node distribution of a bionic liquid circulation device generated by a Voronoi diagram.

[0135] (1) Analyze the harmonic response of prestressed blades at different wind speeds and obtain the amplitude-frequency diagram of blade tip displacement. Calculate the tip displacement ratio rd at the first and second order natural frequencies. This parameter will be used as a proportional factor for blade vibration reduction rate calculation.

[0136] (2) Orthogonal test. Different locations of the blade structure are divided into regions, such as Figure 2 , Figure 6 , Figure 7 As shown. The blade is divided into five parts in span direction: blade root, blade rear section, blade middle, blade front section, and blade tip. The airfoil is divided into three parts in chord direction: leading edge, airfoil middle, and trailing edge. The middle of the airfoil is where the main beam is located. In addition, the blade is divided into suction side and pressure side from the mid-arc line.

[0137] Define the dimensionless quantity damping rate:

[0138]

[0139] Where f1 and f2 are the two-order natural frequencies of the original blade, 0.555 Hz and 0.642 Hz, respectively, m is the original blade mass, 65392 kg, and the corresponding f1′, f2′, and m′ are the first two-order natural frequencies and mass of the blade after the regional mass distribution is changed. d is the tip displacement ratio at the first and second order natural frequencies.

[0140] The orthogonal experimental design factor level table is shown in Table 1, which includes five factors: wind speed (10 levels), span direction (5 levels), chord direction (3 levels), medium density (3 levels), and suction pressure surface (2 levels).

[0141] Table 1 Blade area division table

[0142]

[0143]

[0144] A mixed horizontal orthogonal table was designed for the test, and a total of 50 sets of numerical simulation tests were designed to conduct prestressed modal analysis on wind turbine blades with different density liquid media at different wind speeds and in different regions. The vibration reduction rates at different chord and span directions were obtained.

[0145] (3) Construction method of bionic liquid circulation device. Use quadratic function to fit the vibration reduction rate of blade span and chord position, such as Figure 3 The ratio of the number of nodes in the span direction and the chord direction of the blade is based on the dragonfly wing. The ratio of the maximum span-to-chord length of the dragonfly wing is 4.2:1, and the ratio of the span-to-chord mesh is about 3.3:1. The number of chord-to-gravity meshes in the blade is set to 5 to reflect the Figure 3 The quadratic function variation trend of the damping rate at the chord position is shown in the fitting. According to the ratio of the maximum span-to-chord length of the blade of 16.7:1, and considering the smaller chord length at the tip of the blade, the number of span-wise grids of the blade is set to 45. The 45×5 node matrix is ​​arranged in Figure 4 (a) is the red area. Fit the damping rate at the spanwise position of Figure (3) and the intercept constant of the quadratic function in (b) to zero, so that the function passes through the origin. Figure 4 (a) The spanwise and chordwise lengths of the blade in the red area are equally divided according to the number of nodes, and the spanwise and chordwise positions are substituted as independent variables into Figure 3 , calculate the dependent variable value. Taking the dependent variable value near the tip and leading edge (the trailing edge is set to 0) as the benchmark, after normalization, the blade span and chord length are proportionally enlarged to obtain Figure 4 (a) The red area is shown.

[0146] Map the nodes to the effective area of ​​the blade. Use the leading and trailing edge contours of the blade as the boundary and divide the blade according to the chord-wise ratio calculated by the fitting formula, such as Figure 4 (b) is shown as the red curve. Then, the nodes are mapped to the curves respectively, and the Voronoi diagram nodes required for constructing the blade bionic liquid circulation device can be obtained. The center point coordinates are read in CAD, input into MATLAB software, and the built-in voronoi function is called to automatically generate the required Voronoi diagram, as shown in Figure 4(c) As shown. The chord length at the blade root is relatively large, and there is a certain offset between the nodes, mainly generating a hexagonal grid. The chord length in the middle of the blade decreases, the relative offset of the nodes at the trailing edge decreases, and the generated grid is close to a quadrilateral. At the leading edge of the blade tip, the distance between the nodes in the chord direction is much smaller than that in the span direction, and the grid gradually narrows near the blade root, forming a conical grid. In order to improve the flutter suppression efficiency, a liquid storage cavity is set in the area with the highest damping rate δ (blade tip, middle part of the airfoil).

[0147] (4) Verification of the flutter suppression effect of the bionic liquid circulation device. The device is divided into two parts: the liquid storage chamber and the pipe network of other circulation parts. Under a wind speed of 12m / s, the harmonic response analysis of the pipe network, liquid storage chamber, pipe network + bionic blade of liquid storage chamber and original blade is carried out, and the amplitude-frequency response is obtained as follows Figure 5 As shown, at the first-order natural frequency of the original blade, the attenuation effect of the bionic pipe network liquid circulation on the blade tip displacement is: pipe network + liquid storage cavity > pipe network > liquid storage cavity. This result verifies the effectiveness of the present invention.

[0148] Embodiment three:

[0149] The present invention provides a third embodiment of a bionic liquid circulation device for suppressing wind turbine blade flutter. In this embodiment, the device comprises the following components:

[0150] Bionic liquid circulation device: This device is embedded inside the wind turbine blade and consists of multiple flexible pipes and several liquid chamber nodes distributed between them. The liquid chamber nodes are arranged according to the positions generated by the Voronoi diagram optimization algorithm, and are evenly or unevenly distributed along the span direction (length direction) and chord direction (width direction) of the blade. Each liquid chamber node is filled with a low-viscosity, high-specific heat capacity liquid (such as silicone oil), and is connected to other nodes through pipes to form a closed circulation loop;

[0151] Liquid delivery system: including components such as liquid pumps, flow controllers, pressure sensors and valves. Liquid pumps are used to drive the liquid to flow in the circulation device, flow controllers accurately control the distribution ratio of liquid between nodes, and pressure sensors monitor pressure changes in the pipeline to ensure safe and stable operation of the system. Valves are used to isolate or connect specific nodes to achieve rapid deployment of liquid in different areas;

[0152] Wind speed and direction monitoring system: including anemometers, wind vanes and other sensors installed on wind turbine towers or blades, used to collect wind speed and direction data in real time and transmit these data to the central controller;

[0153] Central controller: Receives data from the wind speed and direction monitoring system, and calculates the optimal blade mass distribution mode required under the current working conditions based on the preset flutter suppression strategy and algorithm. The central controller then issues instructions to the liquid delivery system to adjust the amount of liquid in each liquid chamber node to achieve dynamic optimization of blade mass distribution;

[0154] Communication and feedback module: realizes data exchange and command transmission between the central controller and the wind speed and direction monitoring system and liquid delivery system. At the same time, the vibration sensor integrated inside the blade monitors the vibration status of the blade in real time and provides feedback information to the central controller to further optimize the vibration reduction strategy;

[0155] Implementation steps and effect description:

[0156] System initialization: Before the wind turbine is started, the central controller sets the initial liquid distribution ratio of each liquid chamber node according to the initial design parameters of the blades and the preset vibration reduction strategy to ensure that the blades have a reasonable natural frequency under basic wind conditions and avoid flutter during the startup phase.

[0157] Real-time monitoring and analysis: The wind speed and direction monitoring system continuously collects on-site wind data. The central controller calculates the new optimal mass distribution mode based on the received data and the current vibration state of the blade. For example, when the wind speed suddenly increases or the wind direction changes dramatically, the blade may approach the critical state of flutter. At this time, the central controller needs to quickly adjust the liquid distribution and improve the quality of the relevant area to raise the blade's natural frequency and keep it away from the flutter frequency.

[0158] Dynamically adjust the blade mass distribution: The central controller sends instructions to the liquid delivery system to change the amount of liquid in each liquid chamber node by controlling the speed of the liquid pump, adjusting the valve opening, and setting the flow controller parameters. For example, if it is predicted that the wind direction will turn from the front to the side wind, which may induce strong vibration in a certain area of ​​the blade, the central controller can deliver more liquid to the liquid chamber node in this area in advance to increase the local mass, thereby changing the vibration characteristics of the blade and avoiding flutter.

[0159] Verification of vibration suppression effect: The vibration of the blades is continuously monitored by vibration sensors, and the central controller evaluates the effectiveness of the vibration reduction strategy based on the feedback information. If the actual vibration level is still higher than the expected threshold, the central controller will further optimize the liquid distribution plan until the blade vibration is effectively controlled. Conversely, if the wind conditions return to normal, the central controller will gradually restore the initial or standard mass distribution of the blades to ensure efficient energy conversion under normal wind conditions.

[0160] Specifically, the principle of the present invention is:

[0161] Design of Bionic Liquid Circulation Device:

[0162] The present invention is inspired by the efficient vibration suppression mechanism of dragonfly wings in nature. Dragonfly wings contain a complex network of blood vessels, which can dynamically adjust the mass and stiffness of the wings by changing the blood distribution, thereby effectively suppressing vibrations during flight. Drawing on this principle, the present invention designs a bionic liquid circulation device built into the blade. The device consists of a series of nodes, which are connected by pipes to form a liquid flow network similar to blood circulation;

[0163] Voronoi diagram application and mass distribution adjustment:

[0164] By using the Voronoi diagram generation technology, the present invention determines the node distribution of the bionic liquid circulation device in the span direction (length direction) and chord direction (width direction) of the blade according to the vibration reduction requirements of various parts of the blade. The Voronoi diagram can automatically generate the optimal node layout according to the preset vibration reduction rate curve to ensure that the liquid circulation device has sufficient coverage density in the key vibration reduction area. When the wind speed or wind direction changes, by adjusting the distribution of the liquid in the device, that is, changing the mass distribution of each area of ​​the blade, the natural frequency of the blade can be dynamically adjusted to keep it away from the critical value that may cause flutter;

[0165] Vibration reduction effect and chatter suppression:

[0166] By real-time regulation of the blade mass distribution by the bionic liquid circulation device, the present invention realizes the dynamic optimization of the blade natural frequency, effectively avoids the flutter frequency under various wind speed conditions, and significantly reduces the probability of blade flutter. This active vibration reduction method can not only adapt to the complex and changeable wind field environment, but also avoids the extra weight or structural complexity that may be brought by traditional passive vibration reduction measures, which is conducive to maintaining the lightweight design of the blade and improving the efficiency of wind energy capture.

Claims

1. A bionic liquid circulation device for flutter suppression of wind turbine blades and a method for establishing the same, wherein the blade comprises a skin, a main beam, and a web, wherein the web is located inside the blade, and the skin is an external covering layer of the blade, wherein: The blade also includes a bionic pipe network anti-flutter system, which includes a bionic pipe network and a testing device, wherein a bionic liquid circulation device is arranged inside the bionic pipe network, and the blade is divided into a suction surface (11) and a pressure surface (12) from the mid-arc line, wherein the suction surface (11) is located on the windward side of the blade and is used to generate lift, and the pressure surface (12) is located on the leeward side of the blade; The blade is divided into regions in the span direction and the chord direction. The blade is divided into five parts in the span direction: a blade root (111), a blade rear section (112), a blade middle (113), a blade front section (114), and a blade tip (115); and the blade is divided into three parts in the chord direction: a leading edge (121), an airfoil middle section (122), and a trailing edge (123), wherein the leading edge (121) corresponds to the blade root (111) region, the airfoil middle section (122) corresponds to the blade rear section (112) region, and the trailing edge (123) corresponds to the blade middle section (113), the blade front section (114), and the blade tip (115) region; The bionic pipe network is embedded in the blade and constructed by analyzing the influence of mass distribution in different regions on vibration characteristics. The testing device is specifically provided with a force sensor at the blade root (111), and the force sensor is used to monitor the vibration of the blade by the reaction force of the blade root (111); The establishment method comprises the following steps: S10, obtaining the design factors of the blade and establishing a blade model; S20, performing prestressed harmonic response analysis on the blade at different wind speeds, calculating the displacement ratio at the first and second order natural frequencies, and constructing a vibration reduction rate calculation function according to the displacement ratio; S30, performing an orthogonal test and a range analysis on the blade according to the influencing factors and taking the constructed vibration reduction rate as an evaluation index; S40, fitting the vibration reduction rate in the blade span direction and the blade chord direction using a quadratic function, constructing the bionic pipe network and the bionic liquid circulation device, and setting the position of the liquid storage cavity; S50, performing harmonic response analysis on the position of the liquid storage cavity and the bionic pipe network of other parts of the bionic liquid circulation device to obtain the damping effect of the bionic liquid circulation device.

2. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 1, characterized in that: The middle part (122) of the airfoil is located at the position of the main beam.

3. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 2, characterized in that: The area division is performed from the blade root (111) to the blade tip (115).

4. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 3, characterized in that: The design factors include wind speed, blade span direction, blade chord direction, medium density, suction surface, and pressure surface.

5. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 4, characterized in that: The step S20 specifically includes: Use vibration analysis tools to perform harmonic response analysis on the blade model in a prestressed state; Input different wind speeds as excitations, calculate the dynamic response of the blade under different wind speeds, and output a blade tip displacement amplitude-frequency diagram; Extracting the tip displacement peak values ​​corresponding to the first-order and second-order natural frequencies of the blade from the tip displacement amplitude-frequency diagram; The displacement ratio at the first and second order natural frequencies is calculated, and the vibration reduction rate calculation function is constructed based on the displacement ratio.

6. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 5, characterized in that: The step S30 specifically includes: Obtain influencing factors: including wind speed, medium density, and regional division, generate a mixed level orthogonal table based on the influencing factors, and set up an orthogonal experiment; Selecting a medium density, wherein the medium density is specifically the density of a liquid medium used for vibration reduction inside the blade, wherein the liquid medium is specifically a fluid material, and the fluid material includes water, oil, and emulsion; According to the conditions of each set of orthogonal experiments, a prestressed modal analysis is performed to calculate the natural frequency and tip displacement of the blade after filling liquid media with different densities in different blade span and blade chord regions; Calculate the corresponding vibration reduction rate according to the vibration reduction rate calculation function and the displacement ratio at the first and second order natural frequencies obtained by simulation; For each of the influencing factors, calculate the range between different levels, that is, the maximum value of the difference between the average vibration reduction rate of all test results at the same level and the total average vibration reduction rate of all test results, and obtain the range analysis result; According to the range analysis result, each of the influencing factors is ranked according to its importance in affecting the vibration reduction rate, and the factor with the most significant vibration reduction effect on the blade is identified.

7. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 6, characterized in that: The step S40 specifically includes: Obtain vibration reduction rate data of each area in the blade span direction and the blade chord direction in the orthogonal test results, and divide the vibration reduction rate data into two groups, one group includes the vibration reduction rate corresponding to the blade span direction area, that is, span direction data, and the other group includes the vibration reduction rate corresponding to the blade chord direction area, that is, chord direction data; Selecting quadratic function models for the spanwise data and the chordwise data respectively, and using MATLAB functions to perform quadratic fitting on the spanwise data and the chordwise data respectively, to obtain fitting curves and chordwise ratios; Mapping the calculated blade spanwise and chordwise node coordinates into the blade region, taking the leading edge and trailing edge contours of the blade as boundaries, and dividing the blade according to the calculated chordwise ratio; Using the Voronoi diagram algorithm, the nodes are mapped onto the partition curve to generate the Voronoi diagram nodes; The center coordinates of the nodes are read in the CAD software and then input into the MATLAB software for processing; Generate corresponding grids according to the chord length and offset conditions at different positions of the blade: that is, generate a hexagonal grid at the blade root (111), generate a grid close to a quadrilateral at the blade center (113), and generate a conical grid at the blade tip (115); A liquid storage cavity is arranged in an area with the highest vibration reduction rate, and the area with the highest vibration reduction rate is specifically the blade tip (115) and the middle part (122) of the airfoil.

8. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 7, characterized in that: The step S50 specifically includes: Acquire the position of the liquid storage cavity and the bionic pipe network of other parts of the bionic liquid circulation device; Conduct experiments under set wind speed conditions; The harmonic response analysis of the bionic pipe network, the liquid storage cavity, the bionic blade with the bionic pipe network and the liquid storage cavity and the original blade was carried out respectively to obtain the response variation with frequency. At the first-order natural frequency of the original blade, the bionic pipe network liquid circulation is carried out; The results verified that the anti-tremor effect of the bionic tube network plus the liquid storage cavity is better than that of the single bionic tube network or the liquid storage cavity.

9. A bionic liquid circulation device for wind turbine blade flutter suppression and a method for establishing the same according to claim 8, characterized in that: The ratio of the blade span length to the blade chord length is 4.2:1, and the grid includes a blade span grid and a blade chord length grid, and the ratio of the blade span grid to the blade chord length grid is 3.3:1.

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