Continuous shell model for wind turbine tower aeroelastic response simulation and method of manufacturing the same

Abstract

This application discloses a continuous shell model for simulating the aeroelastic response of wind turbine towers and its manufacturing method. The model is cylindrical or conical in shape and employs an integrally formed hollow continuous shell structure to ensure surface continuity and dimensional accuracy. It also exhibits continuously varying mechanical properties along the height direction to simulate the stiffness and mass distribution characteristics of a real wind turbine tower. This model's continuous structure and high dimensional accuracy allow for a reasonable match between overall stiffness and elastic deformation capacity, significantly improving the model's response stability and data reliability in wind tunnel testing.

Description

Technical Field

[0001] This invention belongs to the field of wind energy engineering and experimental aerodynamics, and specifically relates to a continuous shell model for simulating the aeroelastic response of wind turbine towers and its manufacturing method. Background Technology

[0002] Wind power generation technology is developing rapidly worldwide. As the supporting structure of wind turbines, the tower directly bears the aerodynamic loads and environmental disturbances transmitted from the wind turbine. With the development of large wind turbine units, the tower is becoming more and more flexible, and its aeroelastic response characteristics under wind loads are becoming increasingly significant.

[0003] Most existing wind tunnel tests of wind turbine towers use rigid scaled-down models, which have the main advantages of being simple to manufacture and low in cost. However, these models ignore the deformation response of the structure under wind loads and cannot simulate the elastic deformation, vibration characteristics and coupling mechanism between the tower and aerodynamic loads. Therefore, they cannot truly reflect the structural response of flexible towers under conditions such as gusts and vortex-induced vibrations, and are difficult to use for the assessment of key issues such as aeroelastic stability and resonance risk.

[0004] Currently, a few wind turbine tower wind tunnel tests also use flexible models, but the following problems still exist: 1) Segmented assembly of flexible models, resulting in structural discontinuity: Existing flexible models attempt to introduce variable stiffness components to achieve limited deformation response. They adopt a segmented assembly structure, which is composed of multiple rigid or semi-flexible segments connected by connectors. This method destroys the structural continuity, which not only causes abrupt changes in stiffness and distortion of dynamic response at the connection points, but also easily leads to local stress concentration at the connection points, affecting the accuracy and reproducibility of experimental data.

[0005] 2) Insufficient manufacturing precision makes it difficult to uniformly control stiffness and deformation capacity: Flexible tower models involve the precise control of various geometric and physical factors such as wall thickness, material elastic modulus, and gradual shape changes. However, existing methods have large process errors during manufacturing, which often lead to inconsistent stiffness distribution and deviation of model response from the real structure, seriously affecting the representativeness and practicality of aeroelastic response simulation.

[0006] 3) Poor repeatability of response measurement and experiment: Due to the inconsistency of structural design and the non-uniformity of material properties, the flexible model has poor repeatability in actual wind tunnel tests. For high-frequency coupling phenomena such as gust response and vortex-induced vibration in complex wind fields, the existing model is difficult to capture the real response mode, thus restricting the credibility and promotion value of experimental data. Summary of the Invention

[0007] The purpose of this application is to provide a continuous shell model for simulating the aeroelastic response of wind turbine towers, and a method for manufacturing the above model. The model has a continuous structure and high dimensional accuracy, which allows for a reasonable match between overall stiffness and elastic deformation capacity, significantly improving the response stability and data reliability of the model in wind tunnel tests.

[0008] The technical solution adopted in this application is: A continuous shell model for simulating the aeroelastic response of wind turbine towers is provided. The model is cylindrical or conical in shape and adopts an integrally formed hollow continuous shell structure to ensure the continuity of the model surface and dimensional accuracy. It also has mechanical properties that change continuously along the height direction to simulate the stiffness and mass distribution characteristics of a real tower.

[0009] Preferably, the mechanical properties that vary continuously along the height direction are achieved by at least one of the following methods: a) Use a low-density flexible material with internal friction characteristics to make the elastic modulus or density of the model material change continuously from bottom to top; b) Employ a functional gradient structure, where the wall thickness of the model changes continuously from bottom to top; c) An internal reinforcement structure is adopted, that is, biomimetic spiral ribs or mesh-like reinforcing ribs are set on the inner wall of the shell. The geometric parameters of the biomimetic spiral ribs or mesh-like reinforcing ribs vary along the height direction, thereby simulating the flexibility difference at different heights.

[0010] Preferably, the model is formed using fused deposition modeling additive manufacturing process, employing dual-nozzle or multi-material printing equipment. During the printing process, printing materials with different elastic moduli are continuously switched or mixed to achieve a functional gradient material distribution along the height direction of the model. After printing, support removal, post-processing, and heat setting processes are performed to improve strength and smoothness.

[0011] Preferably, the model is formed using a precision casting process employing the disappearing wax pattern method or the disappearing resin pattern method: first, a disappearing wax pattern or resin mold with the same shape as the tower model is made using stereolithography or selective laser sintering technology; then, refractory slurry is coated on the surface of the disappearing mold and sand is sprinkled to form a ceramic shell; then, heating is used to melt and flow out the internal wax pattern or resin mold to obtain a ceramic cavity shell; finally, liquid polymer material is poured into the ceramic shell, and after solidification, the shell is removed to obtain a continuous shell model.

[0012] Preferably, when pouring liquid polymer material into the ceramic shell, the poured liquid polymer material is a two-component or multi-component material. The mixing ratio of each component is continuously changed during the pouring process by controlling the dynamic mixing pouring system, thereby realizing the functional gradient material distribution of the model along the height direction.

[0013] Preferably, the main material of the model is polypropylene, thermoplastic polyurethane, or copolyester elastomer.

[0014] Preferably, the mass scaling ratio of the model is... ,in This is the ratio of model quality to prototype quality. This is the ratio of the model material density to the prototype material density. The model's geometric scaling ratio; the model's damping ratio is the same as or similar to the prototype's damping ratio, achieved through the model material's internal friction characteristics or by adding a damping layer.

[0015] Preferably, the model is equipped with a variety of measurement mechanisms for observing the local and overall aeroelastic response of the model in wind tunnel tests: the model surface is covered with feature recognition patterns, and the visual recognition system can construct the three-dimensional displacement field of the model by recognizing the feature recognition patterns; the model surface is covered with laser displacement gauge reflective targets, which, together with the laser displacement gauges, can provide feedback on the point displacement at the location; the model surface is covered with micro strain gauges or fiber optic grating sensors, which can provide feedback on the force and deformation at the location.

[0016] A method for manufacturing the above-mentioned model includes the following steps: S1) A scaled-down tower model is constructed using 3D modeling software, and finite element analysis is used to perform structural static and modal analysis on the model to analyze the stress and deformation distribution of the structure under wind load and optimize its stiffness distribution. S2) A continuous shell model with continuously varying mechanical properties along the height direction is manufactured using an integrated molding process; S3) Arrange the measuring mechanism on the model.

[0017] Preferably, in step S1), the three-dimensional modeling of the scaled-down tower model includes biomimetic spiral ribs or mesh-like reinforcing ribs on the inner wall, and in step S2), the integrated molding process can completely reproduce the biomimetic spiral ribs or mesh-like reinforcing ribs.

[0018] The beneficial effects of this application are: The model features a continuous structure with an integrated continuous shell design, avoiding abrupt stiffness changes and local stress concentrations caused by segmented splicing. This results in a more realistic dynamic response and improved simulation accuracy of the structural response, along with high dimensional accuracy. The model exhibits continuously varying mechanical properties along the height direction, allowing for a reasonable match between overall stiffness and elastic deformation capacity. This realistically reflects the coupled vibration behavior of the flexible tower under aerodynamic loads and more accurately simulates the nonlinear aeroelastic behavior of a real tower. Therefore, this model significantly improves the response stability and data reliability in wind tunnel tests, providing reliable experimental data for evaluating the aeroelastic response of wind turbine towers under different wind conditions and promoting in-depth research on the aerodynamic characteristics of flexible structures. Attached Figure Description

[0019] Figure 1 This is a comparison diagram of the first-order vibration mode of the model obtained in Embodiment 2 of the present invention and the first-order vibration mode of the finite element model.

[0020] Figure 2 This is a comparison diagram of the second-order vibration mode of the model obtained in Embodiment 2 of the present invention and the second-order vibration mode of the finite element model.

[0021] Figure 3 This is the power spectral density diagram of the model obtained in Embodiment 2 of the present invention.

[0022] Figure 4 This is the normalized power spectral density diagram of the model obtained in Embodiment 2 of the present invention. Detailed Implementation

[0023] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0024] Example 1 This embodiment discloses a continuous shell model for simulating the aeroelastic response of wind turbine towers. The model is cylindrical or conical in shape and employs an integrated, hollow, continuous shell structure to ensure surface continuity and dimensional accuracy. It also exhibits continuously varying mechanical properties along the height direction to simulate the stiffness and mass distribution characteristics of a real wind turbine tower. The continuous structure and integrated continuous shell design avoid abrupt stiffness changes and local stress concentrations caused by segmented splicing, resulting in a more realistic dynamic response and improved simulation accuracy. Furthermore, the model boasts high dimensional accuracy. Its continuously varying mechanical properties along the height direction allow for a reasonable match between overall stiffness and elastic deformation capacity, thus realistically reflecting the coupled vibration behavior of flexible wind turbine towers under aerodynamic loads and more accurately simulating the nonlinear aeroelastic behavior of real wind turbine towers. Therefore, this model significantly improves the response stability and data reliability in wind tunnel tests, providing reliable experimental data for evaluating the aeroelastic response of wind turbine towers under different wind conditions and promoting in-depth research on the aerodynamic characteristics of flexible structures.

[0025] Preferably, the mechanical properties that vary continuously along the height direction are achieved by at least one of the following methods: a) Use a low-density flexible material with internal friction characteristics to make the elastic modulus or density of the model material change continuously from bottom to top; b) Employ a functional gradient structure, where the wall thickness of the model changes continuously from bottom to top; c) An internal reinforcement structure is adopted, that is, biomimetic spiral ribs or mesh-like reinforcing ribs are set on the inner wall of the shell. The geometric parameters of the biomimetic spiral ribs or mesh-like reinforcing ribs vary along the height direction, thereby simulating the flexibility difference at different heights.

[0026] Preferably, the mass scaling ratio of the model is... ,in This is the ratio of model quality to prototype quality. This is the ratio of the model material density to the prototype material density. The geometric scaling ratio of the model (typically 1:50 to 1:100) is used. The damping ratio of the model is the same as or similar to that of the prototype, achieved through the internal friction characteristics of the model material or by adding a damping layer. In wind tunnel testing, to meet the similarity requirements of the aeroelastic response of the wind turbine tower, the model needs to consider the matching relationship of the mass scaling ratio. The model is designed based on the geometric scaling ratio, and the mass distribution is controlled by selecting low-density flexible materials. According to similarity theory, the ratio of the model mass to the prototype mass should meet the following requirements. This ensures the similarity between the structural modal response and mass inertia characteristics. Since the influence of the structural thickness on the aeroelastic response is negligible, the thickness scaling only needs to meet the mass scaling ratio. Furthermore, to ensure that the wind turbine tower model has dynamic similarity to the prototype structure in terms of aeroelastic response, the damping ratio between the model and the prototype needs to be reasonably controlled. According to similarity theory, the damping ratio is a dimensionless quantity. The model should maintain the same or similar damping ratio as the prototype as possible to accurately reflect the vibration attenuation characteristics of the structure under wind load excitation. This application selects a flexible material with certain internal friction characteristics to meet the equivalent damping of the model.

[0027] Preferably, the model is equipped with various measurement mechanisms for observing the local and overall aeroelastic response of the model in wind tunnel tests: the model surface is covered with feature recognition patterns (e.g., checkerboard, speckle pattern, geometrically coded dot matrix), and the visual recognition system can construct a three-dimensional displacement field of the model by recognizing these feature recognition patterns; the model surface is covered with laser displacement gauge reflective targets (e.g., highly reflective film, microstructure reflective patch), which, in conjunction with the laser displacement gauge, can provide feedback on the point displacement at its location; the model surface is covered with micro strain gauges or fiber optic grating sensors, which can provide feedback on the force and deformation at its location. The three-dimensional displacement field constructed by the visual recognition system can reflect the overall shape and deformation of the model, the laser displacement gauge can improve the accuracy of local displacement recognition, and the micro strain gauges or fiber optic grating sensors can collect deformation and force data at key locations.

[0028] Example 2 This embodiment discloses a method for manufacturing the model in Embodiment 1 above, including the following steps: S1) A scaled-down tower model is constructed using 3D modeling software, and finite element analysis is used to perform structural statics and modal analysis on the model to analyze the stress and deformation distribution of the structure under wind load and optimize its stiffness distribution.

[0029] S2) A continuous shell model with continuously varying mechanical properties along the height direction is manufactured using an integrated molding process; The model is formed in one piece using fused deposition modeling additive manufacturing process. It uses dual-nozzle or multi-material printing equipment and continuously switches or mixes printing materials with different elastic moduli during the printing process to achieve functional gradient material distribution along the height direction of the model. After printing, the model undergoes support removal, post-processing, and heat setting processes to improve strength and surface finish.

[0030] S3) Arrange the measuring mechanism on the model.

[0031] The main material of the model can be polypropylene, thermoplastic polyurethane, copolyester elastomer, etc., with polypropylene being preferred. Polypropylene (PP) material has excellent flexibility, toughness and a certain elastic modulus, adjustable tensile strength and sufficient deformation recovery ability, which can meet the repeatability response caused by aerodynamic loads.

[0032] In step S1), the 3D modeling of the scaled-down tower model includes biomimetic spiral ribs or mesh-like reinforcing ribs on the inner wall. In step S2), the integrated forming process can completely reproduce the biomimetic spiral ribs or mesh-like reinforcing ribs.

[0033] After manufacturing, the model and its matching base are assembled and fixed in the wind tunnel testing area. A laser level and universal joint are used to level the model, and freedom constraint boundaries are set (fixed bottom, free top). Then, the model is connected to the measurement system and airflow simulation system, ready for wind tunnel testing. Finally, the accuracy of the model's parameters is verified by comparing finite element simulation with experimental modal testing, ensuring that it can truly reflect the coupled response behavior of the prototype structure under aerodynamic loads in wind tunnel testing. Figures 1 to 4 As shown, the experimental results indicate that the natural frequency, mode shape, and damping ratio of the model are in high agreement with the finite element simulation results, and can accurately simulate the aeroelastic response of the tower under vortex-induced vibration.

[0034] Example 3 This embodiment discloses another method for manufacturing the model in Embodiment 1 above, including the following steps: S1) A scaled-down tower model is constructed using 3D modeling software, and finite element analysis is used to perform structural statics and modal analysis on the model to analyze the stress and deformation distribution of the structure under wind load and optimize its stiffness distribution.

[0035] S2) A continuous shell model with continuously varying mechanical properties along the height direction is manufactured using an integrated molding process; The model is formed using a precision casting process employing either the disappearing wax model method or the disappearing resin model method: First, stereolithography or selective laser sintering technology is used to create a disappearing wax model or resin model that matches the shape of the tower model; then, refractory slurry is coated on the surface of the disappearing mold and sand is sprinkled to form a ceramic shell; then, heating is used to melt and flow out the internal wax model or resin model to obtain a ceramic cavity shell; finally, liquid polymer material is poured into the ceramic shell, and after solidification, the shell is removed to obtain a continuous shell model.

[0036] When pouring liquid polymer material into the ceramic shell, the liquid polymer material is a two-component or multi-component material. The mixing ratio of each component is continuously changed during the pouring process by controlling the dynamic mixing pouring system, thereby realizing the functional gradient material distribution of the model along the height direction.

[0037] The model is formed in one piece using fused deposition modeling additive manufacturing process. It uses dual-nozzle or multi-material printing equipment and continuously switches or mixes printing materials with different elastic moduli during the printing process to achieve functional gradient material distribution along the height direction of the model. After printing, the model undergoes support removal, post-processing, and heat setting processes to improve strength and surface finish.

[0038] S3) Arrange the measuring mechanism on the model.

[0039] The main material of the model can be polypropylene, thermoplastic polyurethane, copolyester elastomer, etc., with polypropylene being preferred. Polypropylene (PP) material has excellent flexibility, toughness and a certain elastic modulus, adjustable tensile strength and sufficient deformation recovery ability, which can meet the repeatability response caused by aerodynamic loads.

[0040] In step S1), the 3D modeling of the scaled-down tower model includes biomimetic spiral ribs or mesh-like reinforcing ribs on the inner wall. In step S2), the integrated forming process can completely reproduce the biomimetic spiral ribs or mesh-like reinforcing ribs.

[0041] After manufacturing, the model and its matching base are assembled and fixed in the wind tunnel test area. The model is leveled using a laser level and a universal bracket. Freedom constraint boundaries are set (fixed bottom, free top). Then, the model is connected to the measurement system and the airflow simulation system, and is ready for wind tunnel testing. Finally, the accuracy of various parameters of the model is verified by comparing finite element simulation and experimental modal testing, ensuring that it can truly reflect the coupled response behavior of the prototype structure under aerodynamic loads in the wind tunnel test.

[0042] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A continuous shell model for simulating the aeroelastic response of wind turbine towers, characterized in that: The model is cylindrical or conical in shape and adopts an integrated hollow continuous shell structure to ensure the continuity of the model surface and dimensional accuracy. It also has mechanical properties that change continuously along the height direction to simulate the stiffness and mass distribution characteristics of a real tower.

2. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in claim 1, characterized in that, The mechanical properties that vary continuously along the height direction are achieved through at least one of the following methods: a) Use a low-density flexible material with internal friction characteristics to make the elastic modulus or density of the model material change continuously from bottom to top; b) Employ a functional gradient structure, where the wall thickness of the model changes continuously from bottom to top; c) An internal reinforcement structure is adopted, that is, biomimetic spiral ribs or mesh-like reinforcing ribs are set on the inner wall of the shell. The geometric parameters of the biomimetic spiral ribs or mesh-like reinforcing ribs vary along the height direction, thereby simulating the flexibility difference at different heights.

3. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in claim 2, characterized in that, The model is formed using an additive manufacturing process of fused deposition modeling: a dual-nozzle or multi-material printing device is used, and printing materials with different elastic moduli are continuously switched or mixed during the printing process to achieve a functional gradient material distribution along the height direction of the model. After printing, the model undergoes support removal, post-processing, and heat setting to improve strength and smoothness.

4. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in claim 2, characterized in that, The model is formed using a precision casting process employing either the disappearing wax model method or the disappearing resin model method: First, a disappearing wax model or resin model with the same shape as the tower model is created using stereolithography or selective laser sintering technology; then, refractory slurry is coated on the surface of the disappearing mold and sand is sprinkled to form a ceramic shell; then, heating is used to melt and flow out the internal wax model or resin model to obtain a ceramic cavity shell; finally, liquid polymer material is poured into the ceramic shell, and after solidification, the shell is removed to obtain a continuous shell model.

5. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in claim 4, characterized in that: When pouring liquid polymer material into a ceramic mold shell, the poured liquid polymer material is a two-component or multi-component material. The mixing ratio of each component is continuously changed during the pouring process by controlling the dynamic mixing pouring system, thereby realizing the functional gradient material distribution of the model along the height direction.

6. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in any one of claims 1 to 5, characterized in that: The main material of the model is polypropylene, thermoplastic polyurethane, or copolyester elastomer.

7. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in any one of claims 1 to 5, characterized in that: The mass scale of the model ,in This is the ratio of model quality to prototype quality. This is the ratio of the model material density to the prototype material density. The model's geometric scaling ratio; the model's damping ratio is the same as or similar to the prototype's damping ratio, achieved through the model material's internal friction characteristics or by adding a damping layer.

8. The continuous shell model for simulating the aeroelastic response of wind turbine towers as described in any one of claims 1 to 5, characterized in that: The model is equipped with various measurement mechanisms for observing the local and overall aeroelastic response of the model in wind tunnel tests: the model surface is covered with feature recognition patterns, and the visual recognition system can construct the three-dimensional displacement field of the model by recognizing the feature recognition patterns; the model surface is covered with laser displacement gauge reflective targets, which, together with the laser displacement gauges, can provide feedback on the point displacement at the location; the model surface is covered with micro strain gauges or fiber optic grating sensors, which can provide feedback on the force and deformation at the location.

9. A model manufacturing method as described in any one of claims 1 to 8, characterized in that, Including the following steps: S1) A scaled-down tower model is constructed using 3D modeling software, and finite element analysis is used to perform structural static and modal analysis on the model to analyze the stress and deformation distribution of the structure under wind load and optimize its stiffness distribution. S2) A continuous shell model with continuously varying mechanical properties along the height direction is manufactured using an integrated molding process; S3) Arrange the measuring mechanism on the model.

10. The model manufacturing method as described in claim 9, characterized in that: In step S1), the three-dimensional modeling of the scaled-down tower model includes biomimetic spiral ribs or mesh-like reinforcing ribs on the inner wall. In step S2), the integrated molding process can completely reproduce the biomimetic spiral ribs or mesh-like reinforcing ribs.

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