A wind turbine modeling and aerodynamic characteristic calculation method based on laser radar scanning

Abstract

The application discloses a wind turbine modeling aerodynamic characteristic calculation method based on laser radar scanning, belonging to the technical field of wind power generation simulation. The wind turbine blade surface is three-dimensionally scanned; the coordinates of the blade are acquired; the blade is processed in sections, and a plurality of cross sections are cut out; the chord length and torsion angle are calculated through the extracted cross section data; the extracted cross section coordinates are normalized, and the airfoil is rotated to the horizontal direction according to the torsion angle; the obtained normalized scattered points are compared with the scattered point coordinates of the existing airfoils in the database, the airfoil type is determined, if the scattered points exist, the aerodynamic data is directly extracted, if the scattered points do not exist, the aerodynamic data of the airfoil is calculated through CFD, and the new airfoil data is returned to the database; the whole machine is modeled, the aerodynamic performance is calculated, and the axial and tangential induction factors at each blade element are obtained. The application is reliable, and effectively solves the problem of data loss existing in part of the blade.

Description

Technical Field

[0001] This invention relates to the field of wind power generation simulation technology, and in particular to a method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning. Background Technology

[0002] In recent years, with the rapid development of the domestic wind power market and the accelerated pace of wind turbine upgrades, blades, a crucial component of wind turbines, have become increasingly difficult to access due to their age. Manufacturers are often unreachable or unable to provide detailed data for some blades. This situation makes it difficult for owners and third-party design firms to obtain effective design parameters, complicating subsequent work. However, with the development of 3D scanning technology (including laser scanning and structured light scanning), the real world can be digitized, providing information for analysis, collaboration, and optimal decision-making to improve and ensure the overall quality of projects and products. 3D scanning, with its high precision, efficiency, and real-time capabilities, is being widely applied in various fields of industrial design and inspection. Therefore, combining the technological advantages of 3D scanning with its application in industrial design and inspection not only significantly improves production efficiency but also reduces production costs and shortens the design cycle. To enable UAV scanning or ground-based laser scanner scanning of wind turbine blades in the field, a method for calculating the aerodynamic characteristics of wind turbines based on lidar scanning is needed. Summary of the Invention

[0003] The purpose of this invention is to propose a method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning, comprising the following steps:

[0004] Step 1: Perform a 3D scan of the wind turbine blade surface using a drone or a ground-based laser scanner;

[0005] Step 2: Read the 3D airfoil coordinate file using a program to obtain the x, y, and z coordinates of the blade;

[0006] Step 3: Segment the blades and cut out multiple cross sections;

[0007] Step 4: Calculate the chord length and twist angle using the extracted cross-sectional data;

[0008] Step 5: Normalize the extracted cross-sectional coordinates and rotate the airfoil to the horizontal direction according to its twist angle;

[0009] Step 6: Compare the obtained normalized scatter points with the scatter point coordinates of existing airfoils in the database to determine the airfoil type. If the scatter points exist, extract their aerodynamic data directly. If they do not exist, calculate the aerodynamic data of this airfoil using CFD and return the new airfoil data to the database.

[0010] Step 7: Based on the blade element momentum theory model and the free vortex wake model, the unit is modeled as a whole, its aerodynamic performance is calculated, the axial induction factor and tangential induction factor at each blade element are obtained, and the power and torque of the wind turbine are further calculated.

[0011] The formula for calculating the chord length in step 4 is as follows:

[0012]

[0013] Where x_max and y_max are the x and y coordinates of the farthest point on the wingspan, respectively, and x_root and y_root are the x and y coordinates of the wing root point, respectively.

[0014] The formula for calculating the torsion angle in step 4 is as follows:

[0015] twist = arctan(k) * 180 / pi

[0016] k=(y_max-y_root) / (x_max-x_root)

[0017] Where x_max and y_max are the x and y coordinates of the farthest point on the wingspan, respectively, and x_root and y_root are the x and y coordinates of the wing root point, respectively.

[0018] The rotation formula for rotating the airfoil to the horizontal direction according to its torsion angle in step 5 is:

[0019] x1=cos(angle)*x-sin(angle)*y

[0020] y1=cos(angle)*y+sin(angle)*x

[0021] In the formula, x1 and y1 represent the coordinates after rotation, angle represents the twist angle, and x and y represent the coordinates before rotation.

[0022] The formulas for calculating the axial induction factor and the tangential induction factor in step 7 are as follows:

[0023]

[0024]

[0025] In the formula, B is the number of blades of the wind turbine, C is the airfoil chord length, r is the radius at the airfoil section, and C t The tangential force coefficient at the leaf element section, C n The normal force coefficient at the leaf element section, where a is the axial induction factor and b is the tangential induction factor.

[0026] The formulas for calculating the power and torque of the wind turbine in step 7 are as follows:

[0027]

[0028] M=∫dM=4πV1ρΩ(1-a)br 3 dr

[0029] In the formula, ρ is the air density, V1 is the airflow velocity in front of the wind turbine, R is the wind turbine radius, r is the radius at the airfoil section, a is the axial induction factor, b is the tangential induction factor, and Ω is the rotational angular velocity of the wind turbine.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention uses the established leaf element momentum theory (BEM) model and free vortex wake (FVW) model for calculation, and the results are reliable, effectively solving the problem of missing data for some blades. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for calculating the aerodynamic characteristics of a wind turbine model based on lidar scanning, according to the present invention.

[0033] Figure 2 A cross-sectional view of the NREL5MW blade;

[0034] Figure 3 A normalized and rotated cross-sectional view of the NREL5MW blade;

[0035] Figure 4 A comparison chart of the power curves of the model established for this invention and the NREL5MW standard model is shown. Detailed Implementation

[0036] This invention proposes a method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning. The invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1 This is a flowchart of a method for calculating the aerodynamic characteristics of a wind turbine model based on lidar scanning, according to the present invention; the specific implementation is as follows:

[0038] The first step is to perform a three-dimensional scan of the wind turbine blade surface using a drone or a ground-based laser scanner, and then use advanced sensor technology to achieve high-precision measurement.

[0039] The second step is to read the point cloud coordinate file through the program to obtain the x, y, and z coordinates of the blade. The direction of the spanwise coordinate axis of the blade can be determined by drawing. The length of the unknown blade can be obtained by reading the maximum and minimum positions of the spanwise coordinate axis using the existing three-dimensional coordinate points.

[0040] The third step involves segmenting the blade, cutting it along its length in 5% increments, and aligning the coordinates of the cut points with the axial coordinates of the densest data points in the spanwise direction. The density of the data points can be customized by modifying the `num` value in the program, allowing for filtering. Based on this, multiple cross-sections are cut. Taking the NREL5MW blade as an example, the cut cross-sections are as follows: Figure 2 As shown.

[0041] The fourth step involves obtaining the chord length and twist angle data from the extracted cross-sectional data. By determining the trailing edge point, the point farthest from the trailing edge is defined as the leading edge point, and its chord length and angle are calculated. The chord length can be obtained through:

[0042]

[0043] The distance between the leading edge and trailing edge is obtained, where x_max and y_max are the x and y coordinates of the farthest point on the wingspan, respectively, and x_root and y_root are the x and y coordinates of the wing root point, respectively. Then, the slope of the line connecting the farthest point on the wingspan and the wing root is calculated:

[0044] k=(y_max-y_root) / (x_max-x_root)

[0045] Finally, calculate the torsion angle:

[0046] twist = arctan(k) * 180 / pi

[0047] The fifth step is to normalize the extracted cross-sectional coordinates and rotate the airfoil to the horizontal direction according to its torsion angle. The rotation formula is:

[0048] x1=cos(angle)*x-sin(angle)*y

[0049] y1=cos(angle)*y+sin(angle)*x

[0050] In the formula, x1 and y1 represent the coordinates after rotation, angle represents the twist angle, x and y represent the coordinates before rotation, the position of the airfoil before rotation is represented by "+", and the position of the airfoil after rotation is represented by "|". The rotation result is shown in the figure below. Figure 3 As shown.

[0051] The sixth step is to compare the obtained normalized scatter points with the scatter point coordinates of existing airfoils in the database to determine the airfoil type. If it exists, its aerodynamic data is extracted directly. If it does not exist, the aerodynamic data of this airfoil is calculated by CFD and the new airfoil data is returned to the database.

[0052] Step 7: Establish blade element momentum theory (BEM) and free vortex wake (FVW) models to model the entire wind turbine and calculate its aerodynamic performance. BEM combines momentum theory and blade element theory, allowing calculation of axial and tangential induction factors at each blade element, and further enabling the calculation of the wind turbine's power and thrust. The formula is as follows:

[0053]

[0054]

[0055] From the above two equations, we can derive the formulas for calculating the axial induction factor and the tangential induction factor, namely:

[0056]

[0057] The torque M exerted by the airflow on the entire wind turbine can be expressed as:

[0058] M=∫dM=4πV1ρΩ(1-a)br 3 dr

[0059] The wind turbine absorbs energy from the wind, and the mechanical power it generates is the product of the turbine torque and the rotational angular velocity, which can be expressed as:

[0060]

[0061] In the formula, ρ is the air density (kg / m3), B is the number of blades of the wind turbine, C is the airfoil chord length (m), V0 is the resultant velocity (m / s), V1 is the airflow velocity in front of the wind turbine (m / s), R is the wind turbine radius, r is the radius at the airfoil section (m), and C t The tangential force coefficient at the leaf element section, C n The normal force coefficient at the blade element section, a is the axial induction factor, b is the tangential induction factor, and Ω is the rotational angular velocity of the wind turbine (rad / s).

[0062]

[0063] The results are as follows Figure 4 As shown, the model established by inputting the slice airfoil identification data is compared with the power curve of the NREL5MW standard data, and there is good consistency.

[0064] This invention utilizes 3D scanning equipment to scan wind turbine blades, acquiring their three-dimensional information. Through operations such as slicing, extraction, normalization, and identification, the airfoil type comprising the blade is determined. Then, calculations are performed using an established blade element momentum theory (BEM) model and a free vortex wake (FVW) model. The results are reliable and effectively solve the problem of missing data for some blades. This provides a practical and effective modeling method for third-party design companies and owners.

Claims

1. A method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning, characterized in that, Includes the following steps: Step 1: Perform a 3D scan of the wind turbine blade surface using a drone or a ground-based laser scanner; Step 2: Read the 3D airfoil coordinate file using a program to obtain the x, y, and z coordinates of the blade; Step 3: Segment the blades and cut out multiple cross sections; Step 4: Calculate the chord length and twist angle using the extracted cross-sectional data; Step 5: Normalize the extracted cross-sectional coordinates and rotate the airfoil to the horizontal direction according to its twist angle; Step 6: Compare the obtained normalized scatter points with the scatter point coordinates of existing airfoils in the database to determine the airfoil type. If the scatter points exist, extract their aerodynamic data directly. If they do not exist, calculate the aerodynamic data of this airfoil using CFD and return the new airfoil data to the database. Step 7: Based on the blade element momentum theory model and the free vortex wake model, the unit is modeled as a whole, its aerodynamic performance is calculated, the axial induction factor and tangential induction factor at each blade element are obtained, and the power and torque of the wind turbine are further calculated. The formulas for calculating the axial induction factor and the tangential induction factor in step 7 are as follows: In the formula, B is the number of blades of the wind turbine, C is the airfoil chord length, r is the radius at the airfoil section, and C t The tangential force coefficient at the leaf element section, C n Normal force coefficient at the leaf element section, where a is the axial induction factor and b is the tangential induction factor; The formulas for calculating the power and torque of the wind turbine in step 7 are as follows: M=∫dM=4πV1ρΩ(1-a)br 3 doctor In the formula, P represents the mechanical power generated by the wind turbine, M represents the torque of the entire wind turbine, ρ is the air density, V1 is the airflow velocity in front of the wind turbine, R is the radius of the wind turbine, r is the radius at the airfoil section, a is the axial induction factor, b is the tangential induction factor, and Ω is the rotational angular velocity of the wind turbine.

2. The method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning according to claim 1, characterized in that, The formula for calculating the chord length in step 4 is as follows: Where x_max and y_max are the x and y coordinates of the farthest point on the wingspan, respectively, and x_root and y_root are the x and y coordinates of the wing root point, respectively.

3. The method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning according to claim 1, characterized in that, The formula for calculating the torsion angle in step 4 is as follows: twist = arctan(k) * 180 / pi k=(y_max-y_root) / (x_max-x_root) Where twist represents the twist angle, pi represents the mathematical constant π, k represents the intermediate variable, x_max and y_max are the x and y coordinates of the farthest point on the wingspan, respectively, and x_root and y_root are the x and y coordinates of the wing root point, respectively.

4. The method for calculating the aerodynamic characteristics of wind turbine models based on lidar scanning according to claim 1, characterized in that, The rotation formula for rotating the airfoil to the horizontal direction according to its torsion angle in step 5 is as follows: x1=cos(angle)*x-sin(angle)*y y1=cos(angle)*y+sin(angle)*x In the formula, x1 and y1 represent the coordinates after rotation, angle represents the twist angle, and x and y represent the coordinates before rotation.

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