Wind turbine aerodynamic load assessment method

Abstract

The present invention relates to the technical field of wind power engineering, and discloses a method for evaluating aerodynamic loads of a wind turbine, comprising the following steps: obtaining key blade elements of a wind turbine, performing two-dimensional fluid-solid coupling simulation on the key blade elements, obtaining the aerodynamic load values ​​of the key blade elements in the two-dimensional fluid-solid coupling simulation results, and calculating the aerodynamic loads of all blade elements according to the aerodynamic load values ​​of the key blade elements. By obtaining the key blade elements of a wind turbine, the present invention can reduce the waste of computing resources in non-critical areas, improve computing efficiency, and facilitate the realization of practical engineering requirements for rapid iteration. At the same time, it better reflects the dynamic changes of wind speed in different parts of the blades and considers the nonlinear aerodynamic effects caused by wind speed changes, thereby improving the accuracy of dynamic response analysis of aerodynamic loads and the accuracy of prediction of large deformations and complex aerodynamic phenomena.

Description

Technical Field

[0001] The invention relates to the technical field of wind power generation engineering, and in particular to a method for evaluating aerodynamic loads of a wind turbine. Background Art

[0002] Offshore wind power generation has become an important development direction for renewable energy. It can generate electricity from wind energy in deepwater areas (usually areas with a water depth of more than 60 meters). Compared with fixed-base wind turbines, floating wind turbines have a wider range of applications, especially in areas with rich wind resources in deepwater areas. From the perspective of power generation and cost, floating wind turbines are usually large wind turbines of 5MW to 20MW, which means that the wind turbines have longer blades and higher blade tip speeds. The loads caused by the aerodynamic characteristics of the blades, unit vibrations, and platform movements are of great research significance.

[0003] At present, the calculation methods of wind turbine aerodynamic loads are mainly based on the quasi-steady blade momentum theoretical model, the generalized dynamic wake model and the computational fluid dynamics method. The computational fluid dynamics method can perform a fully coupled simulation calculation of the wind turbine and its flow field by setting an appropriate grid size and turbulence model, obtain the entire flow field information, and then perform more accurate vibration and load calculations on the wind turbine, which is more in line with the complex multi-field coupling characteristics of floating wind turbines and can more accurately calculate the aerodynamic loads of floating wind turbines. However, the computational fluid dynamics method has a large number of grids, a large amount of calculations, and low calculation efficiency, which makes it difficult to meet the actual engineering needs of rapid iteration. Summary of the invention

[0004] In view of this, the present invention provides a method for evaluating aerodynamic loads of fans to solve the problem that computational fluid dynamics methods in the prior art for evaluating aerodynamic loads of fans have a large number of grids, a large amount of calculation, and low calculation efficiency, and are difficult to meet the actual engineering needs of rapid iteration.

[0005] The present invention provides a method for evaluating aerodynamic load of a fan, comprising the following steps:

[0006] Obtain key blade elements of the fan;

[0007] Conduct 2D fluid-structure interaction simulation on key blade elements;

[0008] Obtain the aerodynamic load values ​​of key blade elements in the two-dimensional fluid-structure interaction simulation results;

[0009] The aerodynamic loads of all blade elements are calculated based on the aerodynamic load values ​​of the key blade elements.

[0010] Beneficial effects: By obtaining the key blade elements of the wind turbine, the present invention can reduce the waste of computing resources in non-critical areas, improve computing efficiency, and facilitate the realization of rapid iteration of engineering practical needs. At the same time, it better reflects the dynamic changes of wind speed in different parts of the blade and considers the nonlinear aerodynamic effects caused by wind speed changes, thereby improving the accuracy of dynamic response analysis of aerodynamic loads and the accuracy of prediction of large deformation and complex aerodynamic phenomena.

[0011] In an optional implementation, the step of obtaining the key blade element of the fan includes:

[0012] Obtain the main motion modes of blades and towers;

[0013] Analyze the expression of the mass matrix, stiffness matrix and load matrix of the fan in generalized coordinates and the variation law of the vibration response of the fan under different wind conditions and different operating states;

[0014] Further determine the calculation method of radial distribution of key blade elements;

[0015] Identify the key blade elements of the wind turbine based on the relative wind speed gradient between the blade element and the incoming wind.

[0016] Beneficial effects: The present invention utilizes relative wind speed gradient to identify key blade elements, which can more accurately capture the aerodynamic load distribution of each part of the blade, especially the wind speed changes at different radii of the blade, and reduce the waste of computing resources in non-critical areas.

[0017] In an optional embodiment, the main motion modes of the blades and the tower include:

[0018] Blade bending freedom, blade twisting freedom, and fore-aft and lateral bending freedom of the tower.

[0019] Beneficial effects: The present invention obtains the blade bending freedom of the wind turbine to describe the bending of the blade relative to the hub in a direction parallel to the wind; obtains the blade torsion freedom to describe the torsion of the blade relative to the hub in a direction perpendicular to the wind; obtains the fore-and-aft and lateral bending freedom of the tower to describe the fore-and-aft and lateral deformation of the tower under the action of wind force and inertia force.

[0020] In an optional embodiment, the step of identifying the key blade element of the wind turbine according to the relative wind speed gradient between the blade element and the incoming wind includes:

[0021] Using the relative changes in local wind speed and surrounding blade element wind speeds, the relative wind speed gradient is calculated and areas of significant wind speed variation are identified.

[0022] Beneficial effect: In the present invention, since the mass matrix and stiffness matrix of the fan blades will not change under generalized coordinates, only the load matrix of the blades will change with the change of the load evaluation method. At the same time, the aerodynamic load of the blades is affected by the relative wind speed between the blade element and the incoming wind. By calculating the relative wind speed gradient and identifying the areas with significant wind speed changes to extract the key blade elements of the fan blades, the accuracy of the simplified evaluation method of the blade aerodynamic load can be ensured.

[0023] In an optional implementation, the step of obtaining the aerodynamic load value of the key blade element in the two-dimensional fluid-structure coupling simulation result includes:

[0024] Obtain key blade elements and build a two-dimensional fluid-solid coupling simulation model;

[0025] The aerodynamic loads of key blade elements are evaluated through fluid-structure interaction simulation results.

[0026] Beneficial effects: The present invention places the key blade elements in a two-dimensional sub-domain for detailed simulation, which can more accurately capture the aerodynamic load distribution and flow field characteristics of these areas. Concentrating computing resources in the key blade element area can more accurately reflect the aerodynamic and structural responses of the area. At the same time, the fluid-solid coupling simulation can better consider the nonlinear deformation effect of the blade under wind load and improve the prediction accuracy of the aerodynamic load.

[0027] In an optional implementation, the steps of obtaining key blade elements and building a two-dimensional fluid-solid coupling simulation model include:

[0028] According to the geometric shape of the fan blades, a two-dimensional fluid-solid coupling simulation model is established;

[0029] Perform preliminary meshing of the fluid domain in the simulation model;

[0030] Obtain the initial fluid flow conditions and initial changes of the blades;

[0031] Perform fluid-structure interaction iteration;

[0032] The grid density and distribution are dynamically adjusted according to the local characteristics of the flow field.

[0033] Beneficial effect: The present invention adopts adaptive grid division, which can dynamically adjust the grid density according to the flow field characteristics, encrypt the grid in the area where fine calculation is required, and coarsen the grid in other areas, thereby improving the calculation efficiency.

[0034] In an optional embodiment, the step of evaluating the aerodynamic load of a key blade element by using the fluid-structure coupling simulation calculation results includes:

[0035] Conduct two-dimensional sub-domain fluid-solid coupling analysis on key blade elements to obtain more accurate aerodynamic load assessment results for key blade elements;

[0036] The aerodynamic loads of key blade elements are calculated synchronously using the quasi-constant blade element momentum theory and compared with the results of two-dimensional fluid-structure coupling analysis to obtain the aerodynamic load correction factors of key blade elements.

[0037] Focusing on the key blade element, the aerodynamic load correction factor of each blade element within the full length of the blade is continuously solved, and the aerodynamic load calculated by the quasi-steady blade element momentum theory is corrected using the correction factor.

[0038] In an optional implementation, the method for evaluating aerodynamic loads of a fan further includes:

[0039] The calculation results are corrected using the two-dimensional fluid-structure coupling simulation results of the key blade elements.

[0040] Beneficial effects: The present invention utilizes the two-dimensional fluid-solid coupling simulation results of key blade elements to correct the calculation results, which can effectively reduce the dispersion error in the numerical calculation and improve the accurate simulation of the aerodynamic load distribution.

[0041] In an optional implementation, the step of correcting the calculation result using the two-dimensional fluid-solid coupling simulation result of the key blade element includes:

[0042] Design a finite interval second-order nonlinear dispersion correction model;

[0043] The model is used to continuously solve the aerodynamic load correction factor of each blade element within the entire length of the blade;

[0044] The aerodynamic loads calculated by quasi-constant blade element momentum theory are corrected using correction factors.

[0045] Beneficial effects: The present invention introduces a second-order nonlinear correction term through the design model, which can more accurately capture the high-order nonlinear effects of blades under complex aerodynamic loads. It is more suitable for processing large deformation, nonlinear material properties and complex fluid dynamics phenomena.

[0046] In an optional embodiment, the key blade elements are distributed along the radial direction of the blade.

[0047] Beneficial effects: The present invention distributes the key blade elements along the radial direction of the blade so that the analysis method can be regarded as a 2.5-dimensional fluid-solid coupling analysis of the blade, thereby simplifying the evaluation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1A wind turbine dynamic response analysis model diagram under generalized coordinates in a wind turbine aerodynamic load assessment method according to an embodiment of the present invention;

[0050] Figure 2 A schematic diagram of the distribution of key blade elements that affect the vibration response of a large fan in a method for evaluating aerodynamic loads of a fan according to an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of radial identification of key blade elements in a method for evaluating aerodynamic loads of a fan according to an embodiment of the present invention;

[0052] Figure 4 A flow chart of a large-scale wind turbine dynamic response analysis in a method for evaluating aerodynamic loads of a wind turbine according to an embodiment of the present invention;

[0053] Figure 5 A two-dimensional fluid-solid coupling simulation analysis diagram of a key blade element in a method for evaluating aerodynamic loads of a fan according to an embodiment of the present invention;

[0054] Figure 6 This is a diagram of a key blade element load correction and a finite interval second-order nonlinear dispersion correction model in a method for evaluating aerodynamic loads of a fan according to an embodiment of the present invention.

[0055] Description of reference numerals:

[0056] 1. Key blade elements; 2. Finite interval second-order nonlinear dispersion correction; 3. Correction results; 4. Quasi-steady results. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0058] In the related technology, for floating wind turbines, most of the existing studies adopt the quasi-steady blade element momentum theory, which assumes that the wake and induced velocity field change rapidly with the change of the load on the blades, and does not consider the impact of dynamic inflow and dynamic stall effects on aerodynamic loads. However, the actual floating wind turbine operates in an extremely unstable environment, and the pitch motion under the combined action of wind and wave loads is significant, which leads to obvious dynamic stall of the blades. The existing dynamic stall model is generally a semi-empirical theoretical formula, which has not yet been applied to the calculation of aerodynamic loads of floating wind turbines. In addition to the obvious pitch motion, the complex six-degree-of-freedom coupled motion of the floating wind turbine will also change the interaction between the wind wheel and the flow field, affecting its aerodynamic characteristics. Therefore, the quasi-steady blade element momentum theory has a large error and is difficult to meet the engineering accuracy requirements.

[0059] Combine the following Figures 1 to 6 , describing an embodiment of the present invention.

[0060] According to an embodiment of the present invention, a method for evaluating aerodynamic loads of a wind turbine is provided, comprising the following steps:

[0061] Get the key blade element 1 of the fan;

[0062] Perform two-dimensional fluid-structure coupling simulation on key blade element 1;

[0063] Obtain the aerodynamic load value of the key blade element 1 in the two-dimensional fluid-structure interaction simulation results;

[0064] The aerodynamic loads of all blade elements are calculated based on the aerodynamic load value of key blade element 1.

[0065] Specifically, the wind turbine in this embodiment is a floating wind turbine, which is floated in the sea.

[0066] In this embodiment, the blades of the fan impeller are divided into blade units with infinitely thin thickness along the radial direction, called "blade elements". When air flows through the blade elements, the pressure difference on the surface of the blade elements forms a momentum change of the air flow in and out of the blade elements, thereby driving the impeller to rotate and do work.

[0067] In this embodiment, when evaluating the aerodynamic load of the fan, the key blade element 1 is first identified, and a two-dimensional fluid-solid coupling simulation is performed on the key blade element 1. The aerodynamic load value of the key blade element 1 is extracted from the two-dimensional fluid-solid coupling simulation results, and then the aerodynamic loads of all blade elements are calculated using the Bayesian expectation maximization method, namely the BEM (Bayesian Expectation Maximization) algorithm. The two-dimensional fluid-solid coupling simulation results of the key blade element 1 are used to correct the BEM algorithm calculation results, and finally an efficient evaluation of the aerodynamic load of the fan considering the fluid-solid coupling effect is achieved.

[0068] By obtaining the key blade element 1 of the wind turbine, the present invention can reduce the waste of computing resources in non-critical areas, improve computing efficiency, and facilitate the realization of rapid iteration of engineering practical needs. At the same time, it better reflects the dynamic changes of wind speed in different parts of the blade and considers the nonlinear aerodynamic effects caused by wind speed changes, thereby improving the accuracy of dynamic response analysis of aerodynamic loads and the accuracy of prediction of large deformations and complex aerodynamic phenomena.

[0069] In one embodiment, the step of obtaining the key blade element 1 of the fan includes:

[0070] Obtain the main motion modes of blades and towers;

[0071] Analyze the expression of the mass matrix, stiffness matrix and load matrix of the fan in generalized coordinates and the variation law of the vibration response of the fan under different wind conditions and different operating states;

[0072] Further determine the calculation method of radial distribution of key blade element 1;

[0073] The key blade element 1 of the wind turbine is identified according to the relative wind speed gradient between the blade element and the incoming wind.

[0074] Specifically, in this embodiment, by analyzing the expression of the mass matrix, stiffness matrix and load matrix of the eight-degree-of-freedom fan in generalized coordinates and the vibration response change law of the large fan under different wind conditions and different operating states, the calculation method of the radial distribution of the key blade element 1 is further determined. The mass matrix M(t) of the eight-degree-of-freedom fan in generalized coordinates is a symmetric and positive definite matrix, which mainly consists of two parts, namely:

[0075] M(t)=M1(t)+M2 (1)

[0076] Where M1(t) is provided by the blades and is a time-varying symmetric matrix that is related to time, while M2 is provided by the nacelle and tower.

[0077] The stiffness matrix K also consists of two parts, namely:

[0078]

[0079] In the formula, K l Provided by the blade, K g Provided by the tower.

[0080] For fluid-structure coupling simulation and quasi-steady method, the mass matrix and stiffness matrix of the blades of the eight-degree-of-freedom wind turbine will not change in generalized coordinates. Only the load matrix of the blades will change with the change of the load evaluation method. At the same time, the aerodynamic load of the blades is affected by the relative wind speed between the blade element and the incoming wind. Therefore, a key blade element 1 identification method based on relative wind speed gradient is established:

[0081]

[0082] In the formula, Ω represents the impeller speed; r is the blade length; β represents the impeller azimuth; and Respectively represent the vibration speed of the blade in the plane and out of the plane; V x 、V y and V z are the wind speeds in the x, y and z directions respectively, where the positive direction of the x-axis is along the wind direction of the wind, the positive direction of the z-axis is vertically upward, and the positive direction of the y-axis can be determined by the right-hand rule; i and x j are the distances from two adjacent leaf elements to the leaf root; k b is the constant term coefficient. Through a large number of numerical simulation studies, the full fluid-solid coupling simulation and the quasi-constant constant blade element quantitative theoretical calculation results are systematically compared. In order to ensure the criticality of the identified blade element and thus ensure the accuracy of the simplified evaluation method for blade aerodynamic loads, in this embodiment, k b The value is 1.79.

[0083] In this embodiment, formula (3) is used to identify the key leaf element 1.

[0084] The present invention utilizes the relative wind speed gradient to identify the key blade element 1, and can more accurately capture the aerodynamic load distribution of each part of the blade, especially the wind speed variation at different radii of the blade, thereby reducing the waste of computing resources in non-key areas.

[0085] In one embodiment, the main motion modes of the blades and tower include:

[0086] Blade bending freedom, blade twisting freedom, and fore-aft and lateral bending freedom of the tower.

[0087] Specifically, in this embodiment, in a generalized coordinate system, the eight degrees of freedom of the wind turbine describe the movement and deformation of the wind turbine and its foundation system. These degrees of freedom include the main motion modes of the blades and towers. Specifically, it is divided into the blade bending degree of freedom {q1(t), q2(t), q3(t)}, which represents the bending movement of the blade in the windward direction, which is usually the main deformation caused by wind force, and is used to describe the bending of the blade relative to the hub in the direction parallel to the wind; the blade torsion degree of freedom {q4(t), q5(t), q6(t)}, the bending movement of the blade in the tangential direction (perpendicular to the windward direction), which is mainly caused by centrifugal force and aerodynamic torque, and is used to describe the torsion of the blade relative to the hub in the direction perpendicular to the wind; and the front-to-back and lateral bending degrees of freedom of the tower {q7(t), q8(t)}, which are used to describe the deformation of the tower in the front-to-back direction and lateral direction under the action of wind force and inertial force.

[0088] The present invention obtains the blade bending freedom of the wind turbine to describe the bending of the blade relative to the hub in a direction parallel to the wind; obtains the blade torsion freedom to describe the torsion of the blade relative to the hub in a direction perpendicular to the wind; and obtains the fore-and-aft and lateral bending freedom of the tower to describe the fore-and-aft and lateral deformation of the tower under the action of wind force and inertia force.

[0089] In one embodiment, the step of identifying the key blade element 1 of the wind turbine according to the relative wind speed gradient between the blade element and the incoming wind includes:

[0090] Using the relative changes in local wind speed and surrounding blade element wind speeds, the relative wind speed gradient is calculated and areas of significant wind speed variation are identified.

[0091] In the present invention, since the mass matrix and stiffness matrix of the fan blades will not change under generalized coordinates, only the load matrix of the blades will change with the change of the load evaluation method. At the same time, the aerodynamic load of the blades is affected by the relative wind speed between the blade element and the incoming wind. By calculating the relative wind speed gradient and identifying the area with significant wind speed changes to extract the key blade element 1 of the fan blade, the accuracy of the simplified evaluation method of the blade aerodynamic load can be guaranteed.

[0092] In one embodiment, the step of obtaining the aerodynamic load value of the key blade element 1 in the two-dimensional fluid-structure coupling simulation results includes:

[0093] Obtain key blade element 1 and build a two-dimensional fluid-solid coupling simulation model;

[0094] The aerodynamic load of the key blade element 1 is evaluated through fluid-structure interaction simulation results.

[0095] Specifically, in this embodiment, in order to obtain the aerodynamic load value of the key blade element 1 in the two-dimensional fluid-solid coupling simulation results, the steps of extracting the key blade element 1 and building a two-dimensional fluid-solid coupling simulation model are adopted, and the aerodynamic load of the key blade element 1 is evaluated through the fluid-solid coupling simulation calculation results.

[0096] The present invention places the key blade element 1 in a two-dimensional sub-domain for detailed simulation, which can more accurately capture the aerodynamic load distribution and flow field characteristics of these areas. Concentrating computing resources in the key blade element 1 area can more accurately reflect the aerodynamic and structural responses of the area. At the same time, the fluid-solid coupling simulation can better consider the nonlinear deformation effect of the blade under wind load and improve the prediction accuracy of the aerodynamic load.

[0097] In one embodiment, the steps of obtaining the key blade element 1 and building a two-dimensional fluid-solid coupling simulation model include:

[0098] According to the geometric shape of the fan blades, a two-dimensional fluid-solid coupling simulation model is established;

[0099] Perform preliminary meshing of the fluid domain in the simulation model;

[0100] Obtain the initial fluid flow conditions and initial changes of the blades;

[0101] Perform fluid-structure interaction iteration;

[0102] The grid density and distribution are dynamically adjusted according to the local characteristics of the flow field.

[0103] Specifically, in this embodiment, according to the geometric shape of the wind turbine blades, a two-dimensional fluid-solid coupling simulation model is established, including the blades and the surrounding fluid domain, and the fluid domain is preliminarily meshed to obtain the initial fluid flow conditions and the preliminary changes of the blades, and fluid-solid coupling iterations are performed. Then, the adaptive meshing technology is used to dynamically adjust the mesh density and distribution according to the local characteristics of the flow field.

[0104] The present invention adopts adaptive grid division, and can dynamically adjust the grid density according to the flow field characteristics, encrypt the grid in the area where fine calculation is required, and coarsen the grid in other areas, thereby improving the calculation efficiency.

[0105] In one embodiment, the step of evaluating the aerodynamic load of the key blade element 1 by using the fluid-structure coupling simulation calculation results includes:

[0106] Conduct a two-dimensional sub-domain fluid-solid coupling analysis on the key blade element 1 to obtain a more accurate aerodynamic load assessment result for the key blade element 1;

[0107] The aerodynamic load of key blade element 1 is calculated synchronously using the quasi-constant blade element momentum theory, and compared with the results of two-dimensional fluid-structure coupling analysis to obtain the aerodynamic load correction factor of key blade element 1.

[0108] Focusing on the key blade element 1, the aerodynamic load correction factor of each blade element within the full length of the blade is continuously solved, and the aerodynamic load calculated by the quasi-steady blade element momentum theory is corrected using the correction factor.

[0109] In one embodiment, the wind turbine aerodynamic load assessment method further includes:

[0110] The calculation results are corrected using the two-dimensional fluid-structure coupling simulation results of the key blade element 1.

[0111] The present invention utilizes the two-dimensional fluid-solid coupling simulation result of the key blade element 1 to correct the calculation result, which can effectively reduce the dispersion error in the numerical calculation and improve the accurate simulation of the aerodynamic load distribution.

[0112] In one embodiment, the step of correcting the calculation result using the two-dimensional fluid-structure coupling simulation result of the key blade element 1 includes:

[0113] Design a finite interval second-order nonlinear dispersion correction model;

[0114] The model is used to continuously solve the aerodynamic load correction factor of each blade element within the entire length of the blade;

[0115] The aerodynamic loads calculated by quasi-constant blade element momentum theory are corrected using correction factors.

[0116] Specifically, in this embodiment, a finite interval second-order nonlinear diffusion correction model is designed around the flexible blade of the key blade element 1. The Gaussian function is a very effective low-pass filter in both the spatial domain and the frequency domain, and has been effectively used by engineers in actual data processing. The expression of the Gaussian function is as follows:

[0117]

[0118] In the formula, c controls the position of the Gaussian function; σ controls the slope of the curve or the influence range of the neuron, and the smaller σ is, the steeper the curve is and the smaller the influence range of the Gaussian function is. j is between 0 and 1. When the distance from x to the center of Gaussian is 0, G j is equal to 1. As the distance from x to the center of the Gaussian increases, G j Furthermore, this embodiment proposes a finite interval second-order nonlinear dispersion correction model as shown below:

[0119]

[0120] Finally, focusing on the key blade element 1, this model is used to continuously solve the aerodynamic load correction factor of each blade element within the full length of the blade, and the correction factor is used to correct the aerodynamic load calculated by the quasi-steady blade element momentum theory.

[0121] The present invention introduces a second-order nonlinear correction term by designing a model, which can more accurately capture the high-order nonlinear effects of blades under complex aerodynamic loads and is more suitable for processing large deformations, nonlinear material properties and complex fluid dynamics phenomena.

[0122] In one embodiment, the key blade elements 1 are distributed along the radial direction of the blade.

[0123] Specifically, in this embodiment, since each key blade element 1 uses a two-dimensional sub-domain fluid-solid coupling analysis to evaluate its aerodynamic load, and the number of key blade elements 1 is limited, the computational efficiency of the simplified analysis method in this embodiment is much higher than that of the full fluid-solid coupling analysis. At the same time, since the key blade elements 1 are distributed along the radial direction of the blade, the simplified analysis method can be regarded as a 2.5-dimensional fluid-solid coupling analysis of the blade.

[0124] The present invention distributes the key blade element 1 along the radial direction of the blade so that the analysis method can be regarded as a 2.5-dimensional fluid-solid coupling analysis of the blade, thereby simplifying the evaluation method.

[0125] In summary, the wind turbine aerodynamic load evaluation method provided by the present invention is as follows:

[0126] Establish a wind turbine dynamic response analysis model under generalized coordinates, such as Figure 1 The eight degrees of freedom of the wind turbine dynamic response analysis in a generalized coordinate system are shown, which is used to describe the motion and deformation of the wind turbine and its foundation system. The relative wind speed gradient is calculated using the relative change of the local wind speed and the surrounding blade wind speed to identify areas with significant wind speed changes.

[0127] like Figure 2 and Figure 3 As shown, based on the relative wind speed gradient, formula (3) is used to extract the key blade element 1 of the wind turbine blade.

[0128] like Figure 4 The figure shows the algorithm flow of the two-dimensional sub-domain adaptive flow field simulation for the fluid-solid coupling analysis of the key blade element 1. The area where the key blade element 1 is located is divided into two-dimensional sub-domains for detailed simulation to improve the local calculation accuracy. Adaptive grid technology is used in the two-dimensional sub-domain to dynamically adjust the grid density according to the flow field characteristics.

[0129] like Figure 5 As shown, a fluid-structure coupling analysis is then performed in the two-dimensional sub-domain, taking into account the mutual influence of wind speed and structural deformation. The coupling equations of fluid and structure are solved by an iterative method to ensure the accuracy and stability of the results.

[0130] like Figure 6 As shown, the second-order nonlinear dispersion correction model (Formula 5) is then introduced to perform second-order nonlinear dispersion correction on the flexible blade finite interval of the key blade element 1, and the aerodynamic load calculated by the quasi-steady blade element momentum theory is corrected using the correction factor. The dispersion correction model is used to reduce the error in the numerical calculation and improve the accuracy of the simulation results. Figure 6 In the coordinates, the middle shaded area is the finite interval second-order nonlinear dispersion correction area 2, the dotted line above the area is the correction result 3, and the dotted line below the area is the quasi-steady result 4.

[0131] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for evaluating aerodynamic load of a fan, characterized in that: The following steps are involved: Obtain key blade elements of the fan (1); Perform two-dimensional fluid-structure interaction simulation on the key blade element (1); Obtain the aerodynamic load value of the key blade element (1) in the two-dimensional fluid-structure interaction simulation results; The aerodynamic loads of all blade elements are calculated based on the aerodynamic load value of the key blade element (1).

2. The method for evaluating aerodynamic load of a fan according to claim 1, characterized in that: The step of obtaining the key blade element of the fan (1) comprises: Obtain the main motion modes of blades and towers; Analyze the expression of the mass matrix, stiffness matrix and load matrix of the fan in generalized coordinates and the variation law of the vibration response of the fan under different wind conditions and different operating states; Further determine the calculation method of radial distribution of key blade elements (1); The key blade elements of the wind turbine are identified based on the relative wind speed gradient between the blade elements and the incoming wind (1).

3. The method for evaluating aerodynamic load of a fan according to claim 2, characterized in that: The main motion modes of the blades and tower include: Blade bending freedom, blade twisting freedom, and fore-aft and lateral bending freedom of the tower.

4. The method for evaluating aerodynamic load of a fan according to claim 2, characterized in that: The step of identifying the key blade element of the wind turbine according to the relative wind speed gradient between the blade element and the incoming wind (1) comprises: Using the relative changes in local wind speed and surrounding blade element wind speeds, the relative wind speed gradient is calculated and areas of significant wind speed variation are identified.

5. The method for evaluating aerodynamic load of a fan according to claim 1, characterized in that: The step of obtaining the aerodynamic load value of the key blade element (1) in the two-dimensional fluid-solid coupling simulation result comprises: Obtain key blade elements (1) and build a two-dimensional fluid-solid coupling simulation model; The aerodynamic loads of the key blade element (1) are evaluated through fluid-structure interaction simulation calculation results.

6. The method for evaluating aerodynamic load of a fan according to claim 5, characterized in that: The steps of obtaining the key blade element (1) and building a two-dimensional fluid-solid coupling simulation model include: According to the geometric shape of the fan blades, a two-dimensional fluid-solid coupling simulation model is established; Perform preliminary meshing of the fluid domain in the simulation model; Obtain the initial fluid flow conditions and initial changes of the blades; Perform fluid-structure interaction iteration; The grid density and distribution are dynamically adjusted according to the local characteristics of the flow field.

7. The method for evaluating aerodynamic load of a fan according to claim 5, characterized in that: The step of evaluating the aerodynamic load of the key blade element (1) by using the fluid-solid coupling simulation calculation results comprises: Conduct a two-dimensional sub-domain fluid-solid coupling analysis on the key blade element (1) to obtain a more accurate aerodynamic load evaluation result of the key blade element (1); The aerodynamic load of the key blade element (1) is calculated synchronously using the quasi-constant blade element momentum theory, and compared with the two-dimensional fluid-structure coupling analysis results to obtain the aerodynamic load correction factor of the key blade element (1); Focusing on the key blade element (1), the correction factor of the aerodynamic load of each blade element within the full length of the blade is continuously solved, and the correction factor is used to correct the aerodynamic load calculated by the quasi-steady blade element momentum theory.

8. The method for evaluating aerodynamic load of a fan according to claim 1, characterized in that: Also includes: The calculation results are corrected using the two-dimensional fluid-structure interaction simulation results of the key blade element (1).

9. The method for evaluating aerodynamic load of a fan according to claim 8, characterized in that: The step of correcting the calculation result using the two-dimensional fluid-solid coupling simulation result of the key blade element (1) comprises: Design a finite interval second-order nonlinear dispersion correction model; The model is used to continuously solve the aerodynamic load correction factor of each blade element within the entire length of the blade; The aerodynamic loads calculated by quasi-constant blade element momentum theory are corrected using correction factors.

10. The method for evaluating aerodynamic load of a fan according to claim 1, characterized in that: The key blade elements (1) are distributed along the radial direction of the blade.

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