Blade root bolt pre-tightening method

Abstract

The present disclosure provides a method for pre-tightening blade root bolts, which are exposed through openings of a hub web to be fastened, in a state where blades of a wind power generator are hoisted to be fixed to a hub. The method for pre-tightening the blade root bolts includes pre-tightening the blade root bolts exposed through the openings of the hub web with a predetermined torque when the blades are hoisted to an installation position, calculating a pitch angle limit of the blades based on a load calculation model of the hub and the blades and the predetermined torque of the blade root bolts, removing a blade hoist, performing pitch of the blades at a pitch angle not exceeding the pitch angle limit, and pre-tightening the blade root bolts exposed through the openings of the hub web with the predetermined torque after the pitch. The method for pre-tightening the blade root bolts according to an embodiment of the present disclosure can ensure safety during hoisting of the blades.

Description

Technical Field

[0001] This disclosure relates to the field of wind power generation, and more specifically, to a method for pre-tightening root bolts of wind turbine blades. Background Technology

[0002] Wind turbine blade installation methods can be divided into three-blade installation and single-blade installation. Three-blade installation has strict requirements on wind conditions and can only be carried out when the wind speed is low, resulting in a short window for offshore turbine installation. Single-blade installation can be carried out when the wind speed is relatively high, thereby extending the installation window.

[0003] However, during single-blade hoisting, if only a portion of the bolts are pre-tightened, slippage and bolt yielding may occur during pitch control under blade gravity and wind load. Therefore, hoisting safety needs to be carefully assessed. Summary of the Invention

[0004] The present invention provides a simplified overview of the selected concepts, which are further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to help define the scope of the claimed subject matter.

[0005] This disclosure provides a method for pre-tightening blade root bolts. Wind turbine blades are fixed to a hub in a hoisted state using blade root bolts, which are exposed through an opening in the hub web for tightening. The method for pre-tightening the blade root bolts includes: when the blade is hoisted to the installation position, pre-tightening the blade root bolts exposed through the opening in the hub web with a predetermined torque; calculating a pitch angle limit for the blade based on a load calculation model of the hub and blade and the predetermined torque of the blade root bolts; removing the blade hoisting tool; performing pitch control on the blade at a pitch angle not exceeding the pitch angle limit; and after pitch control, pre-tightening the blade root bolts exposed through the opening in the hub web with the predetermined torque. The blade root bolt pre-tightening method according to embodiments of this disclosure ensures safety during blade hoisting.

[0006] The calculation of blade pitch angle limits based on the load calculation model of hub and blade and the preload torque of blade root bolts includes: based on the load calculation model of hub and blade, the load in the blade coordinate system that rotates with the blade is transformed to the fixed hub coordinate system to calculate the blade pitch angle limits.

[0007] Transforming the load in the blade coordinate system, which rotates with the blade, to the fixed hub coordinate system includes: transforming the bending moment load Mx in the blade coordinate system... p and My p and force load Fx p and Fy pBending moment load Mx converted to hub coordinate system b and My b and force load Fx b and Fy b satisfy:

[0008] Mx b =Mx p cosθ0+My p sinθ0;y b =My p cosθ0-Mx p sinθ0;Fx b =Fx p cosθ0+Fy p sinθ0;y b =Fy p cosθ0-Fx p sinθ0, where θ0 is the pitch angle of the propeller in the initial state of hoisting.

[0009] Transforming the load in the blade coordinate system, which rotates with the blade, to the fixed hub coordinate system includes: when the initial angle of the blade pitch angle θ0 in the initial state of hoisting is 0, transforming the bending moment load Mx in the blade coordinate system... p and My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b and My b and force load Fx b and Fy b Satisfy Mx b =Mx p ;y b =My p And Fx b =Fx p ;y b =Fy p When the initial pitch angle θ0 of the blade is 90° during the initial hoisting process, the bending moment load Mx in the blade coordinate system will be... p and My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b and My b and force load Fx b and Fy b Satisfy Mx b =My p ;y b =-Mx p ;x b =Fyp ;y b =-Fx p When the initial angle of the blade pitch angle θ0 during the initial hoisting state is -90°, the bending moment load Mx in the blade coordinate system will be... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b Satisfy Mx b =-My p ;y b =Mx p ;x b =-Fy p ;y b =Fx p .

[0010] The calculation of blade pitch angle limits based on the load calculation model of hub and blade and the preload torque of blade root bolts also includes: calculating blade pitch angle limits based on load and bolt slip boundary values ​​in hub coordinate system.

[0011] The slip boundary value for pre-tightened bolts is no greater than half the difference between the bolt hole diameter and the minimum bolt diameter.

[0012] The slip boundary value for untightened bolts is no greater than half the difference between the bolt hole diameter and the bolt major diameter.

[0013] The slip value between the opposing surfaces of the blade flange and the hub flange is compared with the displacement vector of each bolt hole to obtain the pitch angle limit.

[0014] The pre-tightening method further includes: performing a cyclic calculation for each bolt hole, matching the state value of whether the bolt is pre-tightened and recording the average displacement of each grid node of the two flanges at the bolt hole in the parallel plane, calculating the maximum slip at the bolt hole based on the vector difference of the average displacement of the two flanges; and performing slip evaluation based on the slip boundary values ​​of the pre-tightened bolts and the non-pre-tightened bolts respectively.

[0015] The pre-tightening method for the blade root bolts further includes: performing multiple pitch changes on the blade at a pitch angle not exceeding the pitch angle limit, until all blade root bolts are pre-tightened with a predetermined torque, wherein the pitch angle limit of the blade calculated based on the load calculation model of the hub and the blade and the pre-tightening torque of the blade root bolts is larger in each pitch change operation than the previous one.

[0016] The pre-tightening method for the blade root bolts further includes: after all the blade root bolts have been pre-tightened with a predetermined torque, tightening all the blade root bolts with a standard torque.

[0017] This disclosure provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the pre-tightening method for the leaf root bolt as described above.

[0018] This disclosure provides a computer device, the computer device comprising: a processor; and a memory storing a computer program, wherein when the computer program is executed by the processor, the pre-tightening method for the leaf root bolt as described above is implemented.

[0019] Other features and aspects will be readily understood from the following detailed description and accompanying drawings. Attached Figure Description

[0020] Figure 1a It is a single-leaf hoisting method with the left front being hoisted;

[0021] Figure 1b This is a schematic diagram of the right rear hoisting method of single-leaf hoisting;

[0022] Figure 2 This is a flowchart of the pre-tightening method for the blade root bolts according to an embodiment;

[0023] Figure 3 This is a schematic diagram of load transformation under the initial installation and hoisting condition where the pitch angle is 0°;

[0024] Figure 4 This is a schematic diagram of load transformation under the condition of a pitch angle of 90° in the initial state of initial installation and hoisting;

[0025] Figure 5 This is a schematic diagram of load transformation under the initial installation and hoisting condition with a pitch angle of -90°;

[0026] Figure 6 This is a schematic diagram of load transformation under the initial installation and hoisting condition with a pitch angle of θ0;

[0027] Figure 7 This is a schematic diagram showing the change in load on a pre-tightened bolt;

[0028] Figure 8 This is a schematic diagram showing the change in load on an untightened bolt;

[0029] Figure 9 This is a schematic diagram of displacement values ​​in two parallel planes;

[0030] Figure 10 This is a schematic diagram of pitch operation according to an embodiment of the present disclosure.

[0031] Throughout the accompanying drawings and detailed embodiments, the same reference numerals may indicate the same or similar elements. The drawings may not be drawn to scale, and for clarity, illustration, and convenience, the relative sizes, scales, and depictions of the elements in the drawings may be exaggerated. Detailed Implementation

[0032] The following detailed embodiments are provided to help the reader gain a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, after understanding the disclosure of this application, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will be readily understood. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein; rather, changes that will be readily understood after understanding the disclosure of this application are possible, except for operations that must occur in a specific order. Furthermore, for the purpose of improving clarity and conciseness, descriptions of known features may be omitted after understanding the disclosure of this application. Note that the omission of features and their descriptions is not intended to acknowledge that they are common knowledge.

[0033] Wind turbine blade installation methods can be divided into three-blade installation and single-blade installation. Three-blade installation involves assembling the three blades, pitch bearing, hub, and other rotor system components on the ground. After all work, including component assembly and pre-tightening of blade root bolts, the entire rotor system is then lifted into place. Single-blade installation involves first lifting and installing the turbine head assembly, such as the hub, and then sequentially lifting and connecting the individual blades to the flanges.

[0034] Figure 1a It is a single-leaf hoisting method with the left front being lifted. Figure 1b This is a schematic diagram of the right rear hoisting method of single-leaf hoisting.

[0035] Reference Figure 1a and Figure 1b Currently, single-blade lifting can be carried out in either the left front lifting method (the lifting device for lifting the blade is located on the left front side of the wind turbine) or the right rear lifting method (the lifting device for lifting the blade is located on the right rear side of the wind turbine) depending on the type of lifting vessel and its lifting capacity.

[0036] After the blade is hoisted to the predetermined position at the top of the tower and connected to the hub, the blade root bolts are pre-tightened one by one. Due to the obstruction of the hub web, only the opening portion of the web can be used for bolt pre-tightening. Specifically, single-blade hoisting can be performed as follows: when the lifting device hoists the blade to the predetermined position, the bolts that can be pre-tightened are pre-tightened to a predetermined torque (e.g., 50% of the standard torque). Then, after removing the lifting device, the pitch is adjusted. After the pitch is adjusted, the bolts that are re-exposed in the web opening are pre-tightened to the same torque. The above pitch adjustment operation is repeated until all bolts are pre-tightened. Finally, all bolts are tightened to the standard torque to complete the hoisting of a single blade. The unit impeller is rotated, and the hoisting of the remaining blades is repeated in the same way.

[0037] However, during single-blade hoisting, when only some bolts are pre-tightened, slippage or even bolt yielding may occur during pitch control under blade gravity and wind load. Therefore, hoisting safety needs to be carefully assessed. Current calculation methods require that after the initial angle load calculation is completed, the blade root bolts in the load calculation model need to be rotated to a new position corresponding to the pitch control angle, and the load recalculated. During this process, the position of the pre-tightened bolts in the load calculation model needs to be adjusted according to the pitch angle; that is, for each pitch angle, the position of the pre-tightened bolts in the load calculation model needs to be adjusted before applying the load at that pitch angle. Especially when using finite element analysis, frequent and extensive model reconstruction and mesh re-division are required for component models and corresponding loads at multiple pitch angles, leading to a significant increase in workload and a significant decrease in computational efficiency.

[0038] Figure 2 This is a flowchart of the pre-tightening method for the leaf root bolts according to an embodiment.

[0039] Reference Figure 2 According to the blade root bolt pre-tightening method of the embodiments of this disclosure, the blade of a wind turbine is fixed to the hub by blade root bolts in a hoisted state, and the blade root bolts are exposed through an opening in the hub web for tightening. The blade root bolt pre-tightening method includes: in step 201, when the blade is hoisted to the installation position, the blade root bolts exposed through the opening in the hub web are pre-tightened with a predetermined torque; in step 202, a pitch angle limit for the blade is calculated based on a load calculation model of the hub and the blade and the predetermined torque of the blade root bolts; in step 203, the blade hoisting device is removed, the blade is pitched at a pitch angle not exceeding the pitch angle limit, and after the pitch is adjusted, the blade root bolts exposed through the opening in the hub web are pre-tightened with a predetermined torque.

[0040] The pre-tightening method for blade root bolts according to embodiments of this disclosure can ensure safety during blade hoisting.

[0041] Figure 3This is a schematic diagram of load conversion when the initial installation pitch angle is 0°. Figure 4 This is a schematic diagram of load conversion under the initial installation pitch angle of 90°. Figure 5 This is a schematic diagram of load conversion under the initial installation pitch angle of -90°.

[0042] Calculating the blade pitch angle limit based on the hub-and-blade load calculation model and the preload torque of the blade root bolts can include: transforming the load in the blade coordinate system (which rotates with the blade) to a fixed hub coordinate system to calculate the blade pitch angle limit. Here, it is assumed that the stiffness near the blade root bolts is approximately uniform along the circumference. Based on this assumption, the load is orthogonally decomposed, and load transformation is performed according to the initial installation pitch angle corresponding to different hoisting methods.

[0043] Reference Figure 3 , Figure 3 Figure (a) shows the initial hoisting state, with an initial pitch angle of 0°. The concentric inner ring in the figure represents the inner bearing ring and is fixedly connected to the blade (blade root), rotating with pitch control. The outer ring represents the outer bearing ring and is fixedly connected to the hub. Opening 3 in the hub web is the area where bolts 1 and 2 can be pre-tightened. (Coordinate axis x) p and y p The coordinate system in question is the blade coordinate system (or a user-defined coordinate system) that rotates with the blade, with the x-axis... b and y b The coordinate system in question is a fixed hub coordinate system (or a fixed blade root coordinate system). M represents the applied bending moment load.

[0044] When the inner pitch circle adjusts to a pitch angle of θ, the force situation is as follows: Figure 3 As shown in (b), the direction of the resultant bending moment is towards the x-axis of the hub coordinate system. b The magnitude is M. At this point, the resultant bending moment causes both bolts 1 and 2 to be under tension, and the angle between the direction of the resultant bending moment and bolt 2 is θ. According to the leaf root bolt preload method of the embodiments of this disclosure, a load calculation model is proposed without adjustment, that is, the bolt position in the load calculation model is as follows... Figure 3 As shown in (c), the positions of bolt 1 and bolt 2 are... Figure 3 The initial position is the same as in (a). Transforming the equivalent load from the blade coordinate system (rotating with the blade) to the hub coordinate system, this load, with an initial pitch angle of 0°, can be the same angle θ as in the hub coordinate system. That is, we can obtain... Figure 3 In (b), in x p and y p In the blade coordinate system, the resultant bending moment is related to x p The included angle is θ; for example Figure 3 As shown in (c) in xb and y b In the hub coordinate system, we apply the load from the blade coordinate system to the hub coordinate system, and the resultant bending moment is related to x. b The angle between the two bolts is also θ. This bending moment causes bolts 1 and 2 to be under tension, and the direction of the bending moment makes an angle θ with bolt 2. Ignoring the non-uniformity of circumferential stiffness, this equivalent load is... Figure 3 (a) in the text is consistent.

[0045] When the initial angle of the blade pitch angle θ0 is 0, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b Satisfy Mx b =Mx p ;y b =My p And Fx b =Fx p ;y b =Fy p .

[0046] Reference Figure 4 , Figure 4 Figure (a) shows the initial state during hoisting, with an initial pitch angle of 90°. At this time, bolt 1 is located at x in the blade coordinate system. p On the shaft, bolt 2 is located at y in the blade coordinate system. p On the axis.

[0047] When the inner pitch circle adjusts to a pitch angle of θ, the force situation is as follows: Figure 4 As shown in (b), the direction of the resultant bending moment is towards the x-axis of the hub coordinate system. b The magnitude is M. The resultant bending moment at this time causes bolt 1 to be under tension and bolt 2 to be under compression, and the angle between the direction of the resultant bending moment and bolt 1 is θ. According to the leaf root bolt preload method of the embodiments of this disclosure, a load calculation model without adjustment is proposed, that is, the bolt position in the load calculation model is as follows... Figure 4 As shown in (c), the positions of bolt 1 and bolt 2 are... Figure 4 The initial positions are the same as in (a). The equivalent load is transformed from the load in the blade coordinate system (which rotates with the blade) to the load in the hub coordinate system. Figure 4 (c) The transformed load M' is applied to the hub coordinate system, with a resultant bending moment M' causing bolt 1 to be under tension and bolt 2 to be under compression. The direction of the resultant bending moment makes an angle θ with bolt 1. Neglecting the non-uniformity of circumferential stiffness, this equivalent load is... Figure 4 (a) in the text is consistent.

[0048] When the initial angle of the blade pitch angle θ0 is 90°, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b Satisfy Mx b =My p ;y b =-Mx p ;x b =Fy p ;y b =-Fx p .

[0049] Reference Figure 5 , Figure 5 Image (a) shows the initial state during hoisting, with an initial pitch angle of -90°. At this point, bolt 1 is located at x in the blade coordinate system. p On the shaft, bolt 2 is located at y in the blade coordinate system. p On the axis.

[0050] When the inner pitch circle adjusts to a pitch angle of θ, the force situation is as follows: Figure 5 As shown in (b), the direction of the resultant bending moment is towards the x-axis of the hub coordinate system. b The magnitude is M. At this point, the resultant bending moment causes both bolt 1 and bolt 2 to be under tension, and the angle between the direction of the resultant bending moment and bolt 1 is θ. According to the leaf root bolt preload method of the embodiments of this disclosure, a load calculation model is proposed without adjustment, that is, the bolt position in the load calculation model is as follows... Figure 5 As shown in (c), the positions of bolt 1 and bolt 2 are... Figure 5 The initial positions are the same as in (a). The equivalent load is transformed from the load in the blade coordinate system (which rotates with the blade) to the load in the hub coordinate system. Figure 5 In (c), the transformed load M' is applied to the hub coordinate system, with a resultant bending moment of M'. Both bolts 1 and 2 are under tension, and the direction of the resultant bending moment makes an angle θ with bolt 1. Neglecting the non-uniformity of circumferential stiffness, this equivalent load is... Figure 4 (a) in the text is consistent.

[0051] When the initial angle of the blade pitch angle θ0 is -90°, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy pBending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b Satisfy Mx b =-My p ;y b =Mx p ;x b =-Fy p ;y b =Fx p .

[0052] Figure 6 This is a schematic diagram of load conversion when the initial installation pitch angle is θ0.

[0053] Considering the initial pitch angles described above, the loads in the blade coordinate system are projected onto the blade coordinate system, which coincides with the hub coordinate system at the initial pitch angle of 0°. In other words, the loads in the blade coordinate system, which rotates with the blade, are converted into loads in the hub coordinate system at the initial pitch angle of 0°. Furthermore, a coordinate transformation is performed on the loads to obtain the bending moment load Mx in the blade coordinate system. p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b Satisfy Mx b =Mx p cosθ0+My p sinθ0;y b =My p cosθ0-Mx p sinθ0, Fx b =Fx p cosθ0+Fy p sinθ0;y b =Fy p cosθ0-Fx p sinθ0, the transformed load is applied to the load calculation model in the hub coordinate system.

[0054] The pre-tightening method for the leaf root bolts according to the embodiment can reduce the workload of modeling without changing the load calculation model. In particular, in the calculation process using finite element analysis, the load calculation model is realized as a three-dimensional finite element model, which can significantly reduce the time spent on mesh re-division, thereby greatly improving the calculation efficiency.

[0055] The calculation of blade pitch angle limits based on the hub and blade calculation model and the preload torque of the blade root bolts can also include calculating the blade pitch angle limits based on the load and bolt slip boundary values ​​in the hub coordinate system. In current blade root bolt preload methods, the slip determination condition is to apply the ultimate load at each pitch angle under minimum preload and then observe the contact slip value between the bearing and the blade root. This method is relatively accurate when the flange is not open, but the slip value determination becomes inaccurate after the flange is open, and this method does not consider bearing necking or the difference between preloaded and unpreloaded bolts. The blade root bolt preload method according to the embodiment proposes to calculate preloaded and unpreloaded bolts separately.

[0056] Figure 7 This is a schematic diagram showing the changes in load on a pre-tightened bolt.

[0057] Reference Figure 7 For pre-tightened bolts, such as Figure 7 The distribution of pre-tightened bolts 71 and untightened bolts 72 shown in (a) indicates that only the bolts 71 at the hub web opening 3 can be pre-tightened; the bolts 72 in other locations inside the blade root are not pre-tightened. Figure 7 For the pre-tightened bolt 72, in (b) and (c), since the slippage between the gasket and the flange is very small, the bolt moves with the gasket. Considering that the distance [δ]2 between the bolt necking position and the flange can be greater than the distance [δ]1 between the bolt major diameter and the hole wall, [δ]1 can be 1.5mm. At the same time, the slippage δ1 between the upper gasket and the flange interface is generally much smaller than [δ]1. Therefore, the actual clearance of the bolt should be considered to limit the maximum slippage distance. The slippage δ2 between the flange interfaces is not greater than half of the difference between the bolt hole diameter and the minimum bolt diameter [δ]2. In addition, the slippage δ1 between the gasket and the flange interface is not greater than half of the difference between the bolt hole diameter and the bolt major diameter.

[0058] Figure 8 This is a schematic diagram showing the changes in load on an untightened bolt.

[0059] Reference Figure 8 For untightened bolts, such as Figure 8 The distribution of pre-tightened bolts 81 and untightened bolts 82 shown in (a) indicates that only the bolts 81 at the hub web opening 3 can be pre-tightened; the bolts 82 in other locations inside the blade root are not pre-tightened. Figure 8 In (b) and (c), for bolt 82 that is not pre-tightened, the bolt does not deform before and after loading. When the interface slip δ2 between the flanges exceeds half of the difference between the bolt hole diameter and the bolt major diameter, the upper end of the bolt will contact the bearing hole wall. Therefore, the interface slip δ2 between the flanges is not greater than half of the difference between the bolt hole diameter and the bolt major diameter [δ]1.

[0060] The pre-tightening method for leaf root bolts according to embodiments of the present disclosure improves the effectiveness of slip boundary values ​​by calculating pre-tightened bolts and non-pre-tightened bolts separately.

[0061] Traditional methods for determining slippage involve calculating the ultimate load at various angles under minimum preload conditions, then reviewing the software's results file to examine the contact slippage between the bearing and the flange cross-section at the blade root. This method is relatively accurate when the flange is not open, but the accuracy of the slippage value decreases once the flange is open. Therefore, embodiments of this disclosure propose calculating the slippage distance by the difference in displacement values ​​between two parallel planes.

[0062] Figure 9 This is a schematic diagram of displacement values ​​in two parallel planes.

[0063] Historical results from multiple units show that the deformation differences between various grid nodes within a single bolt hole are relatively small. (Refer to...) Figure 9 Since the diameter of the bolt hole differs little from the pitch circle diameter, the average displacement of each grid node in the parallel plane can be used as the displacement value of the hole to assess the slippage between the two mating surfaces at the bolt hole. Alternatively, the maximum or minimum displacement of each grid node can be used instead of the average value. The slippage value between the opposing surfaces of the blade flange and the hub flange is compared with the displacement vector of each bolt hole to obtain the pitch angle limit.

[0064] According to the pre-tightening method for the leaf root bolts in the embodiments of this disclosure, the average displacement values ​​ux1,uy1 and ux2,uy2 corresponding to the bolt holes on the two flange faces can be calculated respectively. The maximum slip at the bolt hole is obtained by the vector difference of the average displacement values ​​between the two corresponding holes. That is, the embodiments of this disclosure only consider the displacement of each grid node of the bolt hole in the parallel plane, and remove the influence of the displacement in the normal direction of the flange on the slip value.

[0065] For each bolt hole, perform a loop calculation, match the state value of whether the bolt is preloaded and record the average displacement of each grid node of the two flanges at the bolt hole in the parallel plane. Calculate the maximum slip at the bolt hole based on the vector difference of the average displacement of the two flanges. Perform slip evaluation according to the slip boundary values ​​of preloaded and unpreloaded bolts respectively.

[0066] Table 1 below shows examples of the calculation and slip assessment results, where the wind speed condition is 18 m / s, the initial pitch angle is 90°, and the pitch operation angle limits are 0°, 10°, 20°, 30°, and 40°. In Table 1, Mx, My, and Mz represent the bending moment loads in the x, y, and z directions, respectively, and the combined bending moment load of Mx and My is Mxy. In Table 1, Fx, Fy, and Fz represent the force loads in the x, y, and z directions, respectively, and the combined force load of Fx and Fy is Fxy.

[0067] Table 1

[0068] Angle Limit Mx My Mz Fx Fy Fz 0° -22 116 -3 4 1 0 10° 5 155 3 5 0 0 20° 38 205 2 5 -1 0 30° 64 92 1 5 -2 0 40° 86 82 1 5 -3 0

[0069] The load is transformed based on the initial pitch angle during hoisting. Then, the transformed load is applied in the load calculation model using the hub coordinate system as the reference coordinate system. Slip is evaluated based on the minimum deviation of the preload of the predetermined torque, and the bolt ultimate load is evaluated based on the maximum deviation of the preload of the predetermined torque. The slip boundary values ​​are used to determine whether the corresponding pitch angle limit is safe. For example, in Table 1, the slip evaluation result shows that a 10° pitch angle limit is safe.

[0070] The pre-tightening method for blade root bolts also includes performing multiple pitch adjustments on the blade at pitch angles not exceeding the pitch angle limit until all blade root bolts are pre-tightened to a predetermined torque. The pitch angle limit for the blade, calculated based on the hub-and-blade model and the pre-tightening torque of the blade root bolts, is larger in each pitch adjustment operation than the previous one. The pre-tightening method further includes: after all blade root bolts have been pre-tightened to the predetermined torque, tightening all blade root bolts to a standard torque.

[0071] Figure 10 This is a schematic diagram of pitch operation according to an embodiment of the present disclosure.

[0072] Reference Figure 10 Based on the above calculation results, the maximum pitch angle limit for a single operation is 10°. Therefore, the blade is pitched according to the pitch angle limit of no more than 10°, and after the pitch is adjusted, the blade root bolts exposed through the opening in the hub web are pre-tightened with a predetermined torque until all bolts are pre-tightened.

[0073] However, this disclosure is not limited to a pitch angle limit of 10°, and pitch angle limits of 20° or greater can also be obtained by calculation depending on the different aircraft type and operating conditions.

[0074] An exemplary embodiment of the present invention also provides a computer-readable storage medium storing a computer program. The computer-readable storage medium stores a computer program that, when executed by a processor, causes the processor to perform a pre-tightening method for the leaf root bolt according to the present invention. The computer-readable recording medium is any data storage device capable of storing data read by a computer system. Examples of computer-readable recording media include: read-only memory, random access memory, read-only optical disc, magnetic tape, floppy disk, optical data storage device, and carrier waves (such as data transmission via the Internet through wired or wireless transmission paths).

[0075] An exemplary embodiment of the present invention also provides a computer device. The computer device includes a processor and a memory. The memory stores a computer program. The computer program is executed by the processor, causing the processor to perform a computer program for pre-tightening a leaf root bolt according to the present invention.

[0076] The embodiments of this disclosure provide a pre-tightening method for blade root bolts, which can adjust the load only without adjusting the load calculation model, and match the initial hoisting pitch angle by establishing the load calculation model only once, which significantly improves calculation efficiency and saves calculation time.

[0077] To address the inaccuracy in slip assessment results due to flange opening, which includes the normal distance, a method is proposed to determine slip by using the average displacement of each grid node in the bolt hole in a parallel plane. Furthermore, pre-tightened bolts and non-pre-tightened bolts are assessed separately, which significantly improves the accuracy of slip judgment.

[0078] Although this disclosure includes specific examples, it will be readily understood by those skilled in the art, upon understanding the disclosure of this application, that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example is to be considered applicable to similar features or aspects in other examples. Suitable results may be obtained if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner, and / or if components in the described system, architecture, apparatus, or circuit are replaced or added by other components or their equivalents. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents shall be construed as included in this disclosure.

Claims

1. A method for pre-tightening blade root bolts, wherein the blades of a wind turbine are fixed to the hub in a suspended state by blade root bolts, the blade root bolts being exposed and tightened through an opening in the hub web, characterized in that, The pre-tightening method for the blade root bolts includes: When the blade is hoisted to the installation position, the blade root bolts exposed through the opening in the hub web will be pre-tightened to a predetermined torque; The blade pitch angle limit is calculated based on the load calculation model of hub and blade and the predetermined torque of blade root bolt. Remove the blade lifting tool, adjust the blade pitch by an angle not exceeding the stated pitch angle limit, and after pitch adjustment, pre-tighten the blade root bolts exposed through the opening in the hub web with the stated predetermined torque. The calculation of the blade pitch angle limit based on the load calculation model of the hub and blade and the preload torque of the blade root bolts includes: based on the load calculation model of the hub and blade, transforming the load in the blade coordinate system that rotates with the blade to the fixed hub coordinate system to calculate the blade pitch angle limit. Among them, the calculation of the blade pitch angle limit based on the load calculation model of hub and blade and the preload torque of blade root bolt also includes: calculating the blade pitch angle limit based on the load and the slip boundary value of bolt in hub coordinate system.

2. The pre-tightening method for the blade root bolt according to claim 1, wherein, Transforming the load in the blade coordinate system, which rotates with the blade, to the fixed hub coordinate system includes: The bending moment load Mx in the blade coordinate system p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b satisfy: ； ， in, It is the pitch angle at the initial stage of hoisting.

3. The pre-tightening method for the blade root bolt according to claim 1, wherein, Transforming the load in the blade coordinate system, which rotates with the blade, to the fixed hub coordinate system includes: When the pitch angle is at the initial state of hoisting When the initial angle is 0, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b satisfy and ; When the pitch angle is at the initial state of hoisting When the initial angle is 90°, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b satisfy ; When the pitch angle is at the initial state of hoisting When the initial angle is -90°, the bending moment load Mx in the blade coordinate system is... p And My p and force load Fx p and Fy p Bending moment load Mx converted to hub coordinate system b And My b and force load Fx b and Fy b satisfy .

4. The pre-tightening method for the blade root bolt according to claim 1, wherein, The slip boundary value for pre-tightened bolts is no greater than half the difference between the bolt hole diameter and the minimum bolt diameter.

5. The pre-tightening method for the blade root bolt according to claim 1, wherein, The slip boundary value for untightened bolts is no greater than half the difference between the bolt hole diameter and the bolt major diameter.

6. The pre-tightening method for the blade root bolt according to claim 4 or 5, wherein, The slip value between the opposing surfaces of the blade flange and the hub flange is compared with the displacement vector of each bolt hole to obtain the pitch angle limit.

7. The pre-tightening method for the blade root bolt according to claim 1, wherein, The pre-tightening method further includes: performing a cyclic calculation for each bolt hole, matching the state value of whether the bolt is pre-tightened and recording the average displacement of each grid node of the two flanges at the bolt hole in the parallel plane, calculating the maximum slip at the bolt hole based on the vector difference of the average displacement of the two flanges; and performing slip evaluation based on the slip boundary values ​​of the pre-tightened bolts and the non-pre-tightened bolts respectively.

8. The pre-tightening method for the blade root bolt according to claim 1 further includes: The blade is pitched multiple times at pitch angles not exceeding the pitch angle limit until all blade root bolts are pre-tightened with a predetermined torque. The pitch angle limit of the blade, calculated based on the load calculation model of the hub and blade and the pre-tightening torque of the blade root bolts, is larger in each pitch operation than the previous one.

9. The pre-tightening method for the blade root bolt according to claim 8 further includes: After all the blade root bolts have been pre-tightened to the predetermined torque, all the blade root bolts are then tightened to the standard torque.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the pre-tightening method for the leaf root bolt as described in any one of claims 1 to 9.

11. A computer device, characterized in that, The computer device includes: processor; The memory stores a computer program that, when executed by a processor, implements the pre-tightening method for the leaf root bolt as described in any one of claims 1 to 9.

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