Wind turbine tower bolt loosening quantification method based on visual detection

Abstract

The present application relates to the field of wind power generation technology, provide based on visual detection's wind turbine tower drum bolt loosening quantity identification method, the present application detects the actual maximum displacement variable of tower drum top along the cabin body direction when the fan runs, the actual maximum displacement variable of the flange plane along the cabin body direction where the bolt to be identified is located and the distance from the center of the bolt to the center of the flange plane where the bolt to be identified is located, calculates the maximum total external load suffered by the tower drum bolt, thereby identifying the loosening condition of the tower drum bolt, providing a new way to prevent the damage of the fan caused by the loosening of the tower drum bolt, thereby prolonging the operating life of the fan tower drum, improving the maintenance efficiency, reducing the maintenance cost, improving the safety and stability of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation, in particular to a method for quantitatively identifying loosening of bolts of a tower drum of a wind turbine generator system based on visual detection. BACKGROUND

[0002] The tower drum of a wind turbine generator is a key supporting structure of the wind turbine, and plays an important role in supporting the impeller, the nacelle and transmitting loads. The tower drum of the whole machine is composed of multiple steel structure tower drums spliced together, and the joints are connected by flanges and bolts, and the bottom is fixed to the foundation by flanges and bolts. Due to the strong wind, vibration, alternating loads (such as starting and stopping, variable pitch, yawing) and the like during the operation of the wind turbine generator, the bolts are subjected to shear force, tensile force and torque fluctuation for a long time, which causes the failure of the anti-loosening device (such as fatigue of the spring washer and wear of the thread), and even causes the tower to collapse in severe cases. Therefore, it is necessary to study a method for identifying the loosening of the bolts of the tower drum of the wind turbine generator.

[0003] At present, most of the methods for identifying the loosening of the bolts of the tower drum of the wind turbine are to install various sensors to obtain the loosening of the bolts during the operation of the wind turbine. For example, Chinese patent CN 222046007U discloses a monitoring device for the bolts of the tower drum of a wind turbine generator, which can monitor the nuts by using a positioning rod and a pressure sensor. When the nuts are loosened, the positioning rod is driven to press the pressure sensor, and the pressure sensor converts the received pressure into an electrical signal and feeds back to the maintenance terminal of the worker. This method requires installing sensors and positioning rods on each nut to identify, and the device is relatively complex. Therefore, it is necessary for a person skilled in the art to design a method for quantitatively identifying the loosening of the bolts of the tower drum without installing sensors. SUMMARY

[0004] The present application aims at the deficiencies of the prior art, and provides a method for quantitatively identifying the loosening of the bolts of the tower drum of a wind turbine generator based on visual detection. The actual maximum displacement deformation of the top of the tower drum along the nacelle direction during the operation of the wind turbine, the actual maximum displacement deformation of the flange plane along the nacelle direction where the bolts of the tower drum to be identified are located, and the distance from the center of the bolts to the center of the flange plane where the bolts are located are detected by a high-speed camera, and the maximum total external load on the bolts of the tower drum is calculated, so as to identify the loosening of the bolts of the tower drum, improve the maintenance efficiency, and reduce the maintenance cost and downtime.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] The present application provides a method for quantitatively identifying the loosening of the bolts of the tower drum of a wind turbine generator based on visual detection, which comprises:

[0007] (1) Real-time shooting of the fan tower drum in operation is carried out through a high-speed camera, real-time images are saved and transmitted to an image processing module to pre-process the images, based on position information in the processed images, actual maximum displacement deformation variables of the tower drum top along the cabin body direction are calculated , actual maximum displacement deformation variables of the flange plane where the required identified tower drum bolt is located along the cabin body direction , and distances from the center of the required identified tower drum bolt to the center of the flange plane where the bolt is located ; ;

[0008] (2) Maximum external axial load borne by the required identified tower drum bolt is calculated ;

[0009] (3) Maximum total load borne by the required identified tower drum bolt is calculated ;

[0010] (4) Whether is less than or equal to is determined, if yes, it is identified that the tower drum bolt of the flange plane has not loosened; if no, it is identified that the tower drum bolt of the flange plane has loosened.

[0011] The application provides a visual detection-based loosening quantification identification method for a wind turbine generator tower drum bolt, and the calculation process of the maximum external axial load borne by the required identified tower drum bolt in step (2) is as follows:

[0012] Supposing that the height of the fan cabin body from the ground is , the height of the flange plane where the required identified tower drum bolt is located from the ground is , the sum of the gravity of the fan blade and the hub is , the gravity of the cabin is , the gravity of the tower drum top to the flange plane where the required identified tower drum bolt is located is , the horizontal distance from the hub to the tower drum center is , and the horizontal distance from the cabin center point to the tower drum center is .

[0013] The total overturning bending moment borne by the bolt is:

[0014] .

[0015] Wherein, is the wind wheel axial horizontal thrust, , is a thrust coefficient, the size of is different under different operating states, is air density,​ is the wind speed at the hub, is the swept area, , is the blade radius, is the moment of the wind pressure load on the tower experienced by the tower bolts at the flange plane center of the required identification .

[0016] Further, the calculation process is as follows:

[0017] ,

[0018] is the equivalent concentrated force of the wind pressure load, ,

[0019] is the action point of the equivalent concentrated force (also the centroid of the distributed load), .

[0020] where is the load intensity of the wind pressure load.

[0021] Since the wind turbine tower is usually a slender cylindrical structure (the height is much greater than the diameter), the wind pressure load acts on the outer surface of the tower. For a certain cross section perpendicular to the axis of the tower (height direction), the wind pressure can be approximately uniformly distributed (i.e., the circumferential pressure at the same height is equal), and the tower is an axisymmetric structure. When the wind direction is perpendicular to the axis of the tower, the circumferential (circumferential) wind pressure can be approximately symmetrically canceled out, and only the distribution along the height direction needs to be considered. Therefore, the three-dimensional curved surface load can be simplified to a linear problem along the height direction (one-dimensional). Therefore .

[0022] where is the wind pressure at the tower height , , is the wind resistance coefficient of the tower (dimensionless, related to Reynolds number, surface roughness), is the wind speed at the tower height , , is the wind speed at the reference height , is the wind shear exponent, is the diameter at the tower height , , is the diameter of the tower bottom ( ), is the diameter of the tower top ( ).

[0023] Therefore ;

[0024] So ;

[0025] Let ;

[0026] Therefore .

[0027] Finally .

[0028] Therefore the maximum external axial load received by the tower bolt to be identified ;

[0029] Wherein is the total number of bolts in the flange plane where the tower bolt to be identified is located, is the maximum distance.

[0030] The application provides a wind turbine tower bolt loosening quantification identification method based on visual detection, wherein the maximum total load received by the tower bolt to be identified in step (3) .

[0031] Wherein is the pre-tightening force of the bolt, is the load distribution coefficient, which is related to the size of the bolt and the flange.

[0032] The application provides a wind turbine blade unbalanced load quantification identification method based on power time domain waveform, wherein the is the yield load of the bolt, .

[0033] Wherein is the yield strength of the bolt, is the effective cross-sectional area of the bolt, for standard thread, , is the pitch diameter of the thread, is the number of teeth per millimeter (or calculated by the pitch , ).

[0034] The beneficial effects of the present application are: the present application calculates the maximum total external load borne by the tower bolt by detecting the actual maximum displacement deformation variable of the tower top along the cabin direction, the actual maximum displacement deformation variable of the flange plane where the tower bolt to be identified along the cabin direction and the distance from the center of the tower bolt to be identified to the center of the flange plane where the bolt is located, thereby identifying the loosening of the tower bolt, providing a new way to prevent damage to the wind turbine due to loosening of the tower bolt, thereby prolonging the operating life of the wind turbine tower, improving maintenance efficiency, reducing maintenance cost, improving the safety and stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a flowchart of the method of the present application;

[0036] Figure 2 is a structure diagram of the visual detection system in the present application;

[0037] Figure 3 is a force diagram of the external load of the wind turbine in the present application. DETAILED DESCRIPTION

[0038] The specific embodiments of the present application are described in detail below with reference to the accompanying drawings, it should be pointed out that the embodiments are only specific elaboration of the application, should not be regarded as limitation of the application, the purpose of the embodiments is to enable those skilled in the art to better understand and reproduce the technical solutions of the present application, the protection scope of the present application should still be limited by the scope defined in the claims.

[0039] As shown in Figure 1 , the present application provides a wind turbine tower bolt loosening quantitative identification method based on visual detection, the method comprises the following steps:

[0040] S1, based on the visual detection system, the real-time image is saved and transmitted to the image processing module by the high-speed camera, the image processing module carries out pretreatment such as noise reduction filtering to the real-time image, the image is high-definition, based on the position information in the processed image, the actual maximum displacement deformation variable of the tower top along the cabin direction , the actual maximum displacement deformation variable of the flange plane where the tower bolt to be identified along the cabin direction and the distance from the center of the tower bolt to be identified to the center of the flange plane where the bolt is located ; the structure diagram of the visual detection system is shown in . Figure 2

[0041] S2, calculate the maximum external axial load borne by the tower bolt to be identified ; ​

[0042] As shown in Figure 3 , a plane rectangular coordinate system is established, assuming that the height of the fan cabin from the ground is , the height of the flange plane where the tower bolt to be identified is located from the ground is , the sum of the gravity of the fan blade and the hub is , the gravity of the cabin is , the gravity of the tower top to the flange plane where the tower bolt to be identified is located is , the horizontal distance from the hub to the tower center is , and the horizontal distance from the cabin center point to the tower center is .

[0043] The total overturning bending moment on the bolt is:

[0044] .

[0045] where, is the horizontal thrust of the wind wheel axis, , is the thrust coefficient, which is different in different operating states, , is the air density, is the wind speed at the hub, is the swept wind area, , is the blade radius, is the moment of the wind pressure load on the tower on the center of the flange plane where the tower bolt to be identified is located .

[0046] Further, the calculation process is as follows:

[0047] ,

[0048] is the equivalent concentrated force of the wind pressure load, ,

[0049] is the action point of the equivalent concentrated force (also the centroid of the distributed load), .

[0050] where is the load intensity of the wind pressure load.

[0051] Since the wind turbine tower is usually a slender cylindrical structure (height much greater than diameter), the wind pressure acts on the outer surface of the tower, for a certain cross section perpendicular to the axis of the tower (height direction), the wind pressure can be approximately uniformly distributed (i.e. the circumferential pressure at the same height is equal), and the tower is an axisymmetric structure, when the wind direction is perpendicular to the axis of the tower, the circumferential (circumferential direction) wind pressure can be approximately symmetrical to offset, only need to consider the distribution along the height direction. Therefore, the three-dimensional curved surface load can be simplified to a linear problem along the height direction (one-dimensional). So .

[0052] where is the wind pressure at the height of the tower, , , is the wind resistance coefficient of the tower (dimensionless, related to Reynolds number, surface roughness), is the wind speed at the height of the tower, , is the wind speed at the reference height, is the wind shear exponent, is the diameter at the height of the tower, , is the diameter at the bottom of the tower , , is the diameter at the top of the tower . Therefore ;

[0053] So ;

[0054] Let ;

[0055] Therefore ;

[0056] ;

[0057] Finally .

[0058] Therefore the maximum external axial load required to identify the tower bolt ;

[0059] where is the total number of bolts in the flange plane where the tower bolt to be identified is located, is the maximum distance.

[0060] S3, calculate the maximum total load required to identify the tower bolt ;

[0061] ;​

[0062] wherein is the pre-tightening force designed for the bolt, is the load distribution coefficient, which is related to the size of the bolt and the flange.

[0063] S4, judging whether is less than or equal to if yes, it is identified that the tower bolt on the flange plane has not been loosened; if no, it is identified that the tower bolt on the flange plane has been loosened.

[0064] .

[0065] wherein is the yield strength of the bolt, is the effective cross-sectional area of the bolt, for standard thread, , is the pitch diameter of the thread, is the number of teeth per millimeter (or the pitch of the thread is calculated, .

[0066] While the preferred embodiments of the application have been described, additional alternatives, modifications, and variations can become apparent to those skilled in the art once given the benefit of the foregoing description. Accordingly, it is intended that the appended claims shall embrace all alternatives and modifications as fall within the true spirit and scope of the application.

Claims

1. A method for quantitatively identifying loose bolts in wind turbine towers based on visual inspection, characterized in that: The method comprises: (1) The wind turbine tower is photographed in real time by a camera, and the real-time image is saved and transmitted to the image processing module; the image is pre-processed by the image processing module, and the actual maximum displacement deformation of the tower top along the cabin direction is calculated based on the position information in the processed image. , the actual maximum displacement deformation of the flange plane where the tower bolts to be identified are located along the cabin direction From the center of the tower bolt to the center of the flange plane where the bolt is located distance , , The total number of bolts on the flange plane where the tower bolts to be identified are located; (2) Calculate the maximum external axial load on the tower bolts to be identified ; (3) Calculate the maximum total load on the tower bolts to be identified ; (4) Judgment Is it less than or equal to If yes, it is determined that the tower bolts on the flange plane are not loose; if no, it is determined that the tower bolts on the flange plane are loose. is the yield load of the bolt.

2. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 1, characterized in that: The maximum external axial load on the tower bolts to be identified in (2) The calculation formula is: ； in, is the total overturning bending moment on the bolt, is the total number of bolts on the flange plane where the tower bolts to be identified are located. is the maximum distance, is the sum of the weights of the fan blades and hub, is the gravity of the cabin, It is the gravity from the top of the tower to the flange plane where the tower bolts to be identified are located.

3. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 2, characterized in that: described The calculation formula is as follows: ； in, is the horizontal thrust of the wind wheel, is the horizontal distance from the hub to the center of the tower, is the horizontal distance from the center of the nacelle to the center of the tower, is the height of the wind turbine cabin from the ground, The height from the ground to the flange plane where the tower bolts to be identified are located. , is the thrust coefficient, under different operating conditions, The sizes are different, is the air density, is the wind speed at the hub, is the swept area, , is the blade radius, The wind pressure load on the tower is the center of the flange plane where the tower bolts to be identified are located. torque.

4. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 3 is characterized in that: described The calculation formula is as follows: , is the equivalent concentrated force of wind pressure load, , is the point of action of the equivalent concentrated force, , in is the load concentration of wind pressure load, and z is the coordinate in the height direction.

5. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 4 is characterized in that: described The calculation process is as follows: Simplify the three-dimensional surface load into a linear problem along the height direction, then , in is the tower height The wind pressure at , is the wind resistance coefficient of the tower, is the tower height The wind speed at , is the reference altitude The wind speed at is the wind shear index, is the tower height The diameter at , is the diameter of the tower base, is the diameter of the tower top; but .

6. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 4, characterized in that: described The final simplified result is: ； make ; therefore , final .

7. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 1, characterized in that: In (3), the maximum total load on the tower bolts to be identified is , in The preload designed for the bolt, is the load distribution factor, which is related to the size of the bolts and flanges.

8. The method for quantitatively identifying loose tower bolts of a wind turbine generator set based on visual inspection according to claim 1, characterized in that: In (4), , in is the yield strength of the bolt, is the effective cross-sectional area of ​​the bolt. For standard threads, , is the thread pitch diameter, The number of teeth per millimeter.

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