An airfoil variable stiffness non-linear energy sink for mooring vibration reduction of floating offshore wind turbines

Abstract

An airfoil variable stiffness non-linear energy sink for mooring vibration reduction of a floating offshore wind turbine belongs to the field of mooring of floating offshore wind turbines. The non-linear material plate is bolted to the mooring line through a fastener; the non-linear material plate consists of two parts, a damping plate and a connecting rod, wherein the damping plate contains a plurality of particles inside, and a plurality of bolt holes are provided in the connecting rod part; one end of the fastener is bolted to the mooring line, and the other end is bolted to the non-linear material plate; it is in a relatively static state in the initial state; when the mooring line vibrates, the vibration of the mooring line is transmitted to the non-linear material plate through the fastener, causing the vibration of the non-linear material plate, converting the vibration energy of the mooring line into the vibration energy of the non-linear material plate, then causing the vibration of the particles in the non-linear material plate, and converting the vibration energy of the non-linear material plate into the kinetic energy of a plurality of particles, or a plurality of particles convert their own kinetic energy into internal energy through collisions, thereby reducing the vibration of the mooring line.

Description

Technical Field

[0001] The present invention belongs to the field of mooring systems for floating offshore wind turbines. Background Art

[0002] The mooring system of a floating offshore wind turbine plays a role in fixing the floating foundation. Therefore, the safety and stability of the mooring system are crucial for the safety of the entire floating offshore wind turbine structure. Since the floating offshore wind turbine is in a harsh working environment and is often affected by wind, waves, and earthquakes, this can cause the vibration of the mooring system. In particular, seismic loads will directly act on the anchoring foundation. Compared with wind loads and wave loads, seismic actions will cause greater vibrations in the mooring system. Therefore, earthquakes are more dangerous to the mooring system of floating offshore wind turbines, and excessive vibrations of the mooring system lead to risks such as mooring fracture, fatigue failure, and anchoring foundation failure, and will transmit the vibrations to the upper wind turbine structure, all of which are very dangerous to the entire floating offshore wind turbine structure. Currently, the relevant research on the vibration control of floating offshore wind turbines mainly focuses on the vibration control of the wind turbine structure or the floating foundation. For the vibration control of the mooring system, there is less research in this area. Therefore, how to effectively control the vibration of the mooring system has become a hot issue in the field of vibration control of floating offshore wind turbines.

[0003] Vibration control means include active control, semi-active control, and passive control. Both active control and semi-active control require external energy to exert their vibration control effects. However, for the mooring system in seawater, it is very difficult to safely and stably transfer energy to the active control or semi-active control device. Therefore, for the vibration reduction of the mooring system of floating offshore wind turbines, passive control means have the advantages of easy installation and no need for external energy. For the existing vibration control means, they are mainly passive tuning types, and traditional tuning dampers have disadvantages such as large mass and long stroke, which will increase the mass of the entire structure and are disadvantageous to the vibration control of the structure in some cases. In addition, traditional tuning dampers can only control a single mode, and the mooring system often produces very complex dynamic responses under complex dynamic loads. Therefore, for the mooring system of floating offshore wind turbines, it is very necessary to develop lightweight and efficient multi-modal vibration control means.

[0004] Although there are corresponding studies on the vibration control of floating offshore wind turbine structures, however, there are still multiple problems that have not been solved, including but not limited to:

[0005] (1) There is still a lack of vibration control devices for mooring systems: In the field of vibration control of floating offshore wind turbines, the application of vibration damping devices mainly focuses on the upper wind turbine structure and the lower floating platform part, ensuring the safety of the entire floating offshore wind turbine structure by reducing the vibration of the upper wind turbine structure and the floating foundation. However, for floating offshore wind turbines in deep sea areas, earthquakes directly act on the anchoring foundation, thus affecting the mooring system. Therefore, the impact of earthquakes on the mooring system is greater than that on the upper wind turbine structure and the lower floating platform.

[0006] (2) Traditional vibration damping devices are relatively heavy: Traditional passive tuned dampers need to have a large mass to exert vibration control effects. However, for mooring systems with relatively low stiffness, a large mass is actually not conducive to the vibration control of the mooring system. Moreover, the mooring system is relatively long, and it is impossible to install dampers with a large mass.

[0007] (3) Traditional vibration damping devices have a large additional mass: Traditional tuned mass dampers are installed on the mooring line, and the additional mass will bring significant permanent loads to the mooring system, increasing the burden on the mooring.

[0008] (4) The control effect of traditional tuned vibration damping devices is limited: The mooring system is affected by energy transmitted by earthquakes, waves, ocean currents, and the upper structure, and will have relatively complex dynamic responses. However, traditional tuned dampers can only control a single mode. For the complex working conditions in the environment of floating offshore wind turbines, passive tuned dampers cannot fully exert their vibration control capabilities.

[0009] In summary, there are many deficiencies in the existing technologies, and a more innovative and effective vibration control method is needed to solve the vibration problems of the mooring system and improve durability and structural stability. Summary of the Invention

[0010] The innovative points of the present invention are as follows:

[0011] (1) Applicability to mooring systems: Installing multiple dampers on the mooring line can greatly reduce the vibration of the mooring system caused by earthquakes, ocean currents, waves, and the vibration of the upper structure, thus ensuring the safety of the mooring system.

[0012] (2) Lightweight design: By utilizing the additional mass generated by the movement of the damper in water, the mass of the damper itself can be greatly reduced, thereby reducing the impact of the mass of the damper itself on the mooring system and the entire floating offshore wind turbine structure.

[0013] (3) Adjustable stiffness: By changing the length of the damper to change the stiffness of the damper, it can adapt to the stiffness requirements of different structures for the damper.

[0014] (4) Energy consumption and efficiency improvement: The present invention can not only consume energy through the movement of the damper itself. The damper contains multiple particles inside, and the movement and collision of the particles further enhance the energy consumption ability.

[0015] (5) Multi-modal vibration control: The non-linear energy sink introduces non-linear stiffness, which can ensure that the non-linear energy sink resonates with the mooring in a relatively wide frequency band.

[0016] Through these improvement points, the airfoil non-linear energy sink not only solves many limitations of the traditional tuned mass damper, but also provides a more innovative, stable and economical solution for the vibration control of the mooring system.

[0017] The present invention is an airfoil non-linear energy sink for the vibration control of a floating offshore wind turbine mooring system. The main components include a non-linear material plate, fasteners, particles, and bolts.

[0018] 1. An airfoil variable stiffness non-linear energy sink for the vibration reduction of a floating offshore wind turbine mooring, characterized in that:

[0019] The non-linear material plate is bolt-connected to the mooring line through fasteners; the non-linear material plate consists of two parts, a damping plate and a connecting rod. The damping plate contains multiple particles inside, and multiple bolt holes are opened in the connecting rod part; one end of the fastener is bolt-connected to the mooring line, and the other end is bolt-connected to the non-linear material plate;

[0020] In the initial state, the non-linear material plate, the particles and the mooring line are in a relatively static state; when the mooring line vibrates, the vibration of the mooring line will be transmitted to the non-linear material plate through the fastener, causing the vibration of the non-linear material plate, converting the vibration energy of the mooring line into the vibration energy of the non-linear material plate, and then causing the vibration of the particles in the non-linear material plate, and converting the vibration energy of the non-linear material plate into the kinetic energy of multiple particles, or multiple particles convert their own kinetic energy into internal energy through collision, thereby reducing the vibration of the mooring line;

[0021] Through the above process, the vibration energy of the mooring line is transmitted to the non-linear material plate, and part of the energy is transmitted to the particles in the non-linear material plate, and then the energy is dissipated through collision or by using the damping of water. And the vibration direction of the non-linear material plate is opposite to the vibration direction of the mooring line, achieving the effect of tuned vibration reduction. The vibration direction of the particles is opposite to that of the non-linear material plate, which also plays a role in tuned vibration reduction.

[0022] Adjust the connection of the bolts at different positions of the fastener and the connecting rod of the non-linear material plate according to the natural vibration frequency of the engineering structure to adjust the length of the connecting rod of the non-linear material plate, thereby changing the stiffness of the airfoil non-linear energy sink, so as to achieve the optimal frequency; and perform vibration control in multiple directions through multi-directional arrangement according to the direction of the applied load.

[0023] The installation space of this energy well is located on the mooring line underwater, and the material used is a material with a non-linear constitutive relationship, or non-linear stiffness is generated through geometric optimization.

[0024] The technical principle is as follows:

[0025] In Figures 1 to 8 The airfoil non-linear energy well for mooring vibration reduction of floating offshore wind turbines shown consists of a non-linear material plate, fasteners, particles, and bolts. Multiple of the present invention are evenly installed on the mooring line at equal intervals as required. The mooring is connected to the damper through fasteners and tightened with bolts. The non-linear material plate consists of a damping plate and a connecting rod. The damping plate is used to increase the added mass generated by movement in water, and the connecting rod has multiple bolt holes for connection with the fasteners. The non-linear material plate selects appropriate bolt holes according to the required stiffness to adjust the upper length and is connected to the fasteners through bolts. Multiple particles are placed inside the damping plate of the non-linear material plate.

[0026] When the mooring system vibrates due to energy such as earthquakes, waves, or energy transmitted from the upper structure, the airfoil non-linear energy well will generate "reverse resonance", transfer the vibration energy of the mooring system to the airfoil non-linear energy well, and dissipate the energy through the water body. In addition, multiple particles in the airfoil non-linear energy well will also move inside the non-linear energy well, transfer part of the energy of the airfoil non-linear energy well to the internal particles, and dissipate energy through collisions, further enhancing the energy dissipation ability.

[0027] The airfoil non-linear energy well generates non-linear stiffness by using non-linear materials or through geometric optimization, and adjusts the stiffness by adjusting the length of the connecting rod of the non-linear material plate to achieve the optimal frequency, so as to maximize the vibration control effect of the airfoil non-linear energy well. In addition, the airfoil non-linear energy well can transfer the mechanical energy of vibration to multiple internal particles, and the internal particles convert the mechanical energy of the airfoil non-linear energy well into the mechanical energy or internal energy of the particles through their own movement or collisions.

[0028] Due to the inconsistent directions of external loads, or sometimes there is vibration in more than one direction, multiple airfoil non-linear energy wells are placed on the mooring line as required and in different orientations to control vibrations in multiple directions. When arranging on the mooring line, the mass distribution should be uniform to improve the stability of the mooring line. Description of the Drawings

[0029] Figure 1 Stereogram of the airfoil non-linear energy well

[0030] Figure 2 Top view of the airfoil non-linear energy well

[0031] Figure 3 Front view of the airfoil non-linear energy well

[0032] Figure 4 Rear view of airfoil non - linear energy sink

[0033] Figure 5 Left view of airfoil non - linear energy sink

[0034] Figure 6 Right view of airfoil non - linear energy sink

[0035] Figure 7 Arrangement diagram of airfoil non - linear energy sink in mooring line

[0036] Figure 8 Sectional view of non - linear material plate Specific implementation manner

[0037] The in - tube - type tuned mass damper of the present invention mainly consists of the following components: mooring line 1, non - linear material plate 2 (the non - linear material plate is divided into two parts, the part with a larger cross - section is the damping plate 2a, and the part with a smaller cross - section is the connecting rod 2b), fastener 3, and particles 4.

[0038] The airfoil non - linear energy sink for mooring vibration reduction of floating offshore wind turbines of the present invention is mainly formed by bolting the non - linear material plate 2 to the mooring line 1 through the fastener 3. In the figure, the non - linear material plate 2 consists of two parts, the damping plate 2a and the connecting rod 2b. The damping plate 2a contains multiple particles 4 inside, and the connecting rod 2b is provided with multiple bolt holes. One end of the fastener 3 is bolted to the mooring line 1, and the other end is bolted to the non - linear material plate 2.

[0039] In the initial state, the non - linear material plate 2, particles 4 and mooring line 1 are in a relatively stationary state. When the mooring line 1 vibrates due to reasons such as earthquakes, waves, and vibration of the upper structure, the vibration of the mooring line 1 is transmitted to the non - linear material plate 2 through the fastener 3, causing the non - linear material plate 2 to vibrate. The vibration energy of the mooring line 1 is converted into the vibration energy of the non - linear material plate 2, and then the vibration of the non - linear material plate 2 causes the vibration of the particles 4 in the non - linear material plate 2, and the vibration energy of the non - linear material plate 2 is converted into the kinetic energy of multiple particles 4, or multiple particles 4 convert their own kinetic energy into internal energy through collisions, thereby reducing the vibration of the mooring line 1. Through the above process, the vibration energy of the mooring line 1 is transmitted to the non - linear material plate 2, and part of the energy is transmitted to the particles 4 in the non - linear material plate 2, and then the energy is dissipated through collisions or by using the damping of water, etc. Moreover, the vibration direction of the non - linear material plate 2 is opposite to the vibration direction of the mooring line 1, achieving the effect of tuned vibration reduction. The vibration direction of the particles 4 is opposite to that of the non - linear material plate 2, also playing a role in tuned vibration reduction. The above measures effectively protect the structural safety of the mooring line 1.

[0040] In the present invention, the connection of bolts at different positions of the connecting rod 2b between the fastener 3 and the non-linear material plate can be adjusted according to the natural vibration frequency of the engineering structure to adjust the length of the connecting rod of the non-linear material plate 2, so as to change the stiffness of the airfoil non-linear energy sink, thereby achieving the optimal frequency. And according to the direction of the applied load, multi-directional arrangement is carried out to control vibrations in multiple directions.

[0041] The installation space of the device is located on the mooring line 1 underwater. Such an installation method can utilize the added mass generated by the movement of the airfoil non-linear energy sink in water to reduce the mass of the damper itself, thereby achieving a light weight effect. Moreover, the cross-section of the damping plate in the non-linear material plate 2 is relatively large, which can increase the added mass generated during movement. The material used is a material with a non-linear constitutive relationship or geometric optimization is used to generate non-linear stiffness, reducing the stroke of the damper itself and the length of the fastener 3, so as to reduce its own mass and increase the structural stability of the damper itself.

[0042] It should be noted that in the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "under" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0043] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0044] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0045] In the present invention, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation", etc. shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] The technical solution of the present invention brings a number of remarkable technical advantages and provides an innovative solution for the vibration control of the floating offshore wind turbine mooring system:

[0047] (1) Efficient vibration control: The stiffness provided by the damper is non-linear, which improves the vibration control efficiency. When the damper moves in water, it can utilize the damping generated by water to dissipate part of the energy. Moreover, there are multiple particles inside the damper to further tune and reduce vibration and dissipate energy through collisions.

[0048] (2) Light weight, reducing the impact on the main structure: The cross-section of the damper plate is relatively large, which will increase the added mass generated during movement in water, thus greatly reducing the mass of the damper itself.

[0049] (3) Multi-directional and multi-modal vibration control: Since the mooring of the floating offshore wind turbine is relatively long and the damper itself occupies little space, it can be distributed on the mooring line. In this way, good vibration control effects can be achieved when the mooring bears external dynamic loads in different directions. And the non-linear energy sink itself has the ability of multi-modal vibration control, so that the mooring system still has good vibration control effects under the action of complex loads.

[0050] (4) Flexible adjustment of vibration reduction ability: By changing the length of the connecting rod of the non-linear material plate, the stiffness of the airfoil non-linear energy sink is controlled, so that the damper reaches the optimal frequency.

[0051] (5) Low control cost and wide application range: The selection range of materials for the underwater airfoil non-linear energy sink is wide, such as materials with non-linear constitutive relations like polyethylene. The mooring and fasteners are fastened by bolts, and the construction cost is low. It is applicable to moorings of various diameters and can select appropriate stiffness according to the characteristics of different structures, so it is applicable to the mooring systems of different types of floating offshore wind turbines.

[0052] (6) Applicable to the mooring system: The present invention is specifically used for the vibration control of the underwater mooring system of floating offshore wind turbines and can provide lightweight and efficient vibration control for the mooring system.

[0053] The flexibility and adaptability of this solution are reflected in the alternative choices for key components, providing users with more options in terms of personalization and cost-effectiveness:

[0054] (1) Alternative for the non-linear material plate: In this solution, the non-linear material plate provides non-linear stiffness by using a material with a non-linear constitutive relationship. However, the geometric cross-section can be optimized through calculation so that this solution can provide non-linear stiffness during vibration. In this way, a suitable cross-section or non-linear material can be selected according to the natural vibration frequency of the fan.

[0055] (2) Alternative for adjusting the length: In this solution, the length of the non-linear material plate is changed by changing the positions of different connecting bolts, thereby changing the stiffness of the damper. Engineers can choose a snap-on slide rail to control the length according to their own stiffness adjustment requirements, so that the length of the non-linear material plate can be controlled more precisely.

[0056] (3) Alternative for fasteners: In this solution, the fasteners are fastened to the mooring by bolts, which can be changed to direct bolt connection or welding between the fasteners and the mooring.

[0057] (4) Anti-corrosion measures: Each component can resist seawater corrosion by applying an anti-corrosion coating (such as an aluminum coating) on the surface.

Claims

1. An airfoil variable stiffness non - linear energy sink for mooring vibration reduction of floating offshore wind turbines, characterized in that: It is bolt - connected to the mooring line by a fastener with a non - linear material plate. The non - linear material plate consists of two parts, a damping plate and a connecting rod. The damping plate contains multiple particles inside, and the connecting rod part has multiple bolt holes. One end of the fastener is bolt - connected to the mooring line, and the other end is bolt - connected to the non - linear material plate. In the initial state, the non - linear material plate, the particles and the mooring line are in a relatively static state. When the mooring line vibrates, the vibration of the mooring line is transmitted to the non - linear material plate through the fastener, causing the vibration of the non - linear material plate, converting the vibration energy of the mooring line into the vibration energy of the non - linear material plate, then causing the vibration of the particles in the non - linear material plate, and converting the vibration energy of the non - linear material plate into the kinetic energy of multiple particles, or multiple particles convert their own kinetic energy into internal energy through collisions, thus reducing the vibration of the mooring line. Through the above process, the vibration energy of the mooring line is transmitted to the non - linear material plate, and part of the energy is transmitted to the particles in the non - linear material plate, and then the energy is dissipated through collisions or by using the damping of water. And the vibration direction of the non - linear material plate is opposite to the vibration direction of the mooring line, achieving the effect of tuned vibration reduction. The vibration direction of the particles is opposite to that of the non - linear material plate, which also plays a role in tuned vibration reduction.

2. The airfoil variable stiffness non - linear energy sink for mooring vibration reduction of floating offshore wind turbines according to claim 1, characterized in that: According to the natural vibration frequency of the engineering structure, the connection of bolts at different positions between the fastener and the connecting rod of the non - linear material plate is adjusted to adjust the length of the connecting rod of the non - linear material plate, so as to change the stiffness of the airfoil non - linear energy sink, and thus achieve the optimal frequency. And according to the direction of the applied load, multi - directional arrangement is used to control the vibration in multiple directions.

3. The airfoil variable stiffness non - linear energy sink for mooring vibration reduction of floating offshore wind turbines according to claim 1, characterized in that: The installation space of this energy sink is on the mooring line underwater, and the materials used are materials with non - linear constitutive relations, or non - linear stiffness is generated through geometric optimization.

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