A fan blade torsional fatigue test device and test method thereof

Abstract

The present invention discloses a wind turbine blade torsional fatigue test device and a test method thereof, comprising a driving device, a lever arm frame, a blade section fixture and a limit support device; the driving device is mounted on a foundation through a ball joint bearing, and its driving rod is connected to the lever arm frame above it through a ball joint bearing; the blade section fixture is sleeved on the blade, and the blade section fixture is connected to the lever arm frame; the limit support device is supported below the blade section fixture, one end of the limit support device is connected to the blade section fixture through a ball joint bearing, and the other end is supported on the foundation through a ball joint bearing. The wind turbine blade torsional fatigue test device and the test method thereof of the present invention fill the gap in blade torsional fatigue testing in existing fatigue tests, and by applying torsional fatigue loads to the blades, the blade life can be more accurately evaluated, which is of great significance to the structural design of blades of large wind turbines and the reduction of economic losses caused by blade fatigue failure.

Description

Technical Field

[0001] The invention relates to the technical field of wind turbine blade fatigue testing, and in particular to a wind turbine blade torsional fatigue testing device and a testing method thereof. Background Art

[0002] Among the various components of a wind turbine, the wind turbine blade is an important component that converts wind energy into mechanical energy. It is one of the core components of a wind turbine. Its structure, strength and stability play an important role in the reliability of the unit. In the design of wind turbine blades, it is generally required that onshore wind turbine blades can meet a service life of 20 years, and offshore wind turbine blades require a service life of 25 years. The operating characteristics of wind turbines under unsteady loads make wind turbine blades prone to fatigue damage, which seriously affects the reliability and service life of the safe operation of wind turbines. Due to the complexity of the material, structure, process and working environment of wind turbine blades, the fatigue performance of the blades is usually tested by fatigue testing of full-size wind turbine blades to confirm the reliability of the design.

[0003] In the prior art, the bending movement of the blade along the thickness direction of the airfoil section is generally called flapping motion, while the bending movement along the chord length direction is called swing motion. The specific method of the existing dynamic fatigue test of blades is to fix the root of the blade on the test bench, and then install an excitation device on the specified cross section to make the blade perform a certain number of cyclic reciprocating motions of a certain amplitude in the flapping and swinging directions, so that the corresponding cross section can achieve the purpose of fatigue damage, thereby verifying the ability of the blade to withstand fatigue loads in the flapping and swinging directions. With the increase in the installed capacity of a single wind turbine, the length of the blades continues to grow, and the blades become softer and longer. As the blades become longer and softer, the impact of torsional fatigue loads on the blades will become greater and greater, and it becomes increasingly necessary to verify the safety of the blades under torsional fatigue loads. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a wind turbine blade torsional fatigue test device and a test method thereof, which fills the gap in blade torsional fatigue testing in existing fatigue tests. By applying a torsional fatigue load to the blade through the torsional fatigue test device, the torsional stiffness change of the blade under the torsional fatigue load and the influence of the shear stress on the cross section under the torsional load on fatigue damage are verified, and the blade life can be evaluated more accurately, which is of great significance to the structural design of blades of large wind turbines and the reduction of economic losses caused by blade fatigue failure.

[0005] To achieve the above-mentioned purpose, the technical solution provided by the present invention is: a wind turbine blade torsional fatigue test device, comprising a driving device, a lever arm frame, a blade section fixture and a limit support device; the driving device is installed on the foundation through a ball joint bearing, and its driving rod is connected to the lever arm frame above it through a ball joint bearing, and a torsional torque is generated by the up and down movement of the driving rod acting on the lever arm frame; the blade section fixture is sleeved on the blade, and its inner side surface wraps the airfoil section on the blade to be loaded with a torsional load, and the blade section fixture is connected to the lever arm frame; the limit support device is supported below the blade section fixture, one end of the limit support device is connected to the blade section fixture through a ball joint bearing, and the other end is supported on the foundation through a ball joint bearing, and in the initial equilibrium state, the axis of the limit support device coincides with the torsional center of the blade section to be loaded with a torsional load, and the blade section fixture rotates around the support point connected to the limit support device under the action of the torsional torque.

[0006] Furthermore, a first force sensor and a displacement sensor are respectively installed on the driving rod, wherein the first force sensor is used to measure the driving force of the driving rod, and the displacement sensor is used to measure the displacement change at the loading position.

[0007] Furthermore, the driving device is a hydraulic cylinder or an electric cylinder.

[0008] Furthermore, the limit support device includes a limit support rod and a second force sensor, the two ends of the limit support rod are respectively connected to the foundation and the blade section clamp through ball joint bearings, and the second force sensor is installed on the limit support rod to measure the supporting force transmitted to the blade by the limit support rod.

[0009] Furthermore, the lever arm frame is processed with a plurality of connection holes along its length direction, and different connection holes are selected to connect with the blade section fixture to change the length of the lever arm, thereby adjusting the magnitude of the torsional moment.

[0010] Furthermore, an oblique support for transferring load is provided between the blade section fixture and the force arm support.

[0011] Furthermore, the blade section fixture includes an iron frame and a wooden core built into the iron frame. The wooden core is made according to the shape of the airfoil section of the blade to be loaded with a torsional load, and a rubber pad is provided between the wooden core and the blade.

[0012] Furthermore, the blade can be equipped with a torsion angle meter at a suitable position as required, so as to observe the change of torsion angle of different sections of the blade under the action of torsional load.

[0013] Furthermore, the blade can be attached with strain gauges at appropriate positions as required, so as to observe the strain distribution at specific positions of the blade under the action of torsional load.

[0014] A testing method for a fan blade torsional fatigue testing device comprises the following steps:

[0015] 1) According to the requirements of the blade torsional fatigue load, select the section that needs to be verified for torsional fatigue, design and determine the loading position of the blade to be tested, determine the target torque at the loading position, and determine the torsional deformation and loading load at the loading position;

[0016] 2) Fix the root of the blade on the test bench through the flange, and make the 0° chord direction of the blade horizontal. Put the blade section fixture on the blade so that the blade section fixture covers the section that needs to be verified for torsional fatigue;

[0017] 3) Select the target section to be tested between the blade root and the position where the blade section fixture is installed to install the torsion meter and the strain gauge;

[0018] 4) Determine the torsion center of the section of the blade in the blade section fixture where torsional fatigue verification is required, and then determine the connection position of the limit support device and the blade section fixture to ensure that the axis of the limit support device coincides with the torsion center of the blade loading section in the initial equilibrium state;

[0019] 5) Clear all sensors in the initial equilibrium state;

[0020] 6) Debug the torsional fatigue test device, gradually increase the driving load, so that the torsional moment and the deformation of the blade torsional can reach the target value of the test, and complete the debugging to meet the design requirements. The calculation formula of the torsional moment M is as follows:

[0021] M=(F 驱动 -F 支撑 ) / 2×L

[0022] In the formula, F 驱动 is the loading force on the driving rod, F 支撑 is the supporting force of the limit support rod of the limit support device, and L is the horizontal distance from the driving rod to the limit support rod;

[0023] 7) Blade torsion fatigue test: the driving rod of the driving device moves up and down to drive the force arm to drive the blade to be tested to rotate around the limit support rod at a set angle, so that the blade is cyclically twisted a set number of times, and the load change is obtained in real time through the force sensor, and the torsion angle change and strain change are obtained in real time through the torsion meter and strain gauge;

[0024] 8) Evaluate torsional fatigue test damage and complete torsional fatigue testing of blades.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] The wind turbine blade torsional fatigue test device and the test method thereof of the present invention broaden the existing fatigue test scope and fill the gap in blade torsional fatigue testing in existing fatigue tests. By applying torsional fatigue loads to blades through the torsional fatigue test device, the torsional stiffness changes of the blades under torsional fatigue loads and the influence of shear stress on the cross section under torsional loads on fatigue damage are verified, and the blade life can be evaluated more accurately, which is of great significance to the structural design of blades of large wind turbines and the reduction of economic losses caused by blade fatigue failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the torsional fatigue testing device of the present invention.

[0028] Figure 2 The figure is a schematic diagram of the movement of the torsional fatigue testing device of the present invention when performing a blade torsional fatigue test.

[0029] Figure 3 The figure is a schematic diagram of the installation of the torsional fatigue test device, the blade and the test bench of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments.

[0031] like Figure 1 , Figure 2As shown, the wind turbine blade torsional fatigue test device described in this embodiment includes a driving device 1, a force arm frame 2, a blade section fixture 3 and a limit support device 4; the driving device 1 is a hydraulic cylinder or an electric cylinder, the bottom of which is installed on the foundation through a ball joint bearing 5, and its driving rod 101 is connected to the force arm frame 2 above it through the ball joint bearing 5. The driving rod 101 is respectively installed with a first force sensor 102 and a displacement sensor (not shown in the figure), the first force sensor 102 is used to measure the driving force of the driving rod 101, and the displacement sensor is used to measure the load The displacement change at the position is applied to the lever frame 2 through the up and down movement of the driving rod 101 to generate a torsional moment; the blade section fixture 3 includes an iron frame 301 and a wood core 302 built into the iron frame 301, the wood core 302 is made according to the shape of the airfoil section of the blade to be loaded with a torsional load, and a rubber pad (not shown in the figure) is provided between the wood core 302 and the blade 7, the blade section fixture 3 is put on the blade 7, the wood core 302 wraps the airfoil section of the blade 7 to be loaded with a torsional load, and the rubber pad is used to protect the blade 7 to prevent surface damage , the outer iron frame 301 is connected to the arm frame 2, and an inclined support 6 for transmitting the load is also provided between the iron frame 301 and the arm frame 2, and the loading torque is applied to the blade 7 through the arm frame 2, the inclined support 6 and the blade section fixture 3; the limit support device 4 includes a limit support rod 401 and a second force sensor 402, and the two ends of the limit support rod 401 are respectively connected to the foundation and the upper iron frame 301 through a ball joint bearing 5, and the second force sensor 402 is installed on the limit support rod 401, and is used to measure the limit support rod 401 The transmission torque is applied to the blade 7. The supporting force is given to the blade 7, and the axis of the limit support rod 401 in the initial equilibrium state coincides with the torsion center of the section of the blade 7 to be loaded with the torsion load, so that the vertical displacement of the blade 7 can be limited to the maximum extent, so as to get rid of the influence of the vertical load and deformation on the torsion fatigue test in the torsion fatigue test; the entire blade section fixture 3 and the blade 7 mounted thereon rotate around the supporting point at the top of the limit support rod 401 under the action of the torsional moment, and the displacement of the drive rod 101 and the limit support rod 401 in the horizontal direction and along the span direction of the blade 7 is not limited by the ball joint bearing 5.

[0032] In addition, by processing multiple connecting holes along the length direction of the force arm frame 2, different connecting holes are selected to connect with the blade section fixture 3 to change the length of the force arm, thereby adjusting the size of the torsional moment; the blade 7 can be installed with a torsion angle meter (not shown in the figure) at a suitable position as needed to observe the torsion angle changes of different sections of the blade under the action of torsional load; the blade 7 can be pasted with a strain gauge (not shown in the figure) at a suitable position as needed to observe the strain distribution of a specific position of the blade under the action of torsional load.

[0033] The testing method of the fan blade torsional fatigue testing device described in this embodiment includes the following steps:

[0034] 1) According to the torsional fatigue load requirements of the blade 7, select the section that needs to be verified for torsional fatigue, design and determine the loading position of the blade 7 to be tested, determine the target torque at the loading position, and determine the torsional deformation and loading load at the loading position;

[0035] 2) If Figure 3 As shown, the root of the blade 7 is fixed on the test bench 8 through a flange, and the 0° chord direction of the blade 7 is horizontal, and the blade section fixture 3 is put on the blade 7 so that the blade section fixture 3 wraps the section that needs to be verified for torsional fatigue;

[0036] 3) Select a target section for testing between the blade root and the position where the blade section fixture 3 is installed on the blade 7 to install a torsion meter and a strain gauge;

[0037] 4) Determine the torsion center of the section of the blade 7 in the blade section fixture 3 that needs to be verified for torsion fatigue, and then determine the connection position of the limit support device 4 and the blade section fixture 3 to ensure that the axis of the limit support rod 401 coincides with the torsion center of the blade loading section in the initial equilibrium state;

[0038] 5) Clear all sensors in the initial equilibrium state;

[0039] 6) Debug the torsional fatigue test device, gradually increase the driving load, so that the torsional moment and the torsional deformation of the blade 7 can reach the target value of the test, and the debugging is completed after the design requirements are met. The calculation formula of the torsional moment M is as follows:

[0040] M=(F 驱动 -F 支撑 ) / 2×L

[0041] In the formula, F 驱动 is the loading force at the driving rod 101, F 支撑 is the supporting force of the limiting support rod 401 of the limiting support device 4, and L is the horizontal distance from the driving rod 101 to the limiting support rod 401;

[0042] 7) Perform torsional fatigue test on blade 7, drive arm 2 to drive blade 7 to be tested to rotate around limit support rod 401 by up and down movement of driving rod 101 of driving device 1, so that blade 7 is cyclically twisted for a set number of times, load change is obtained in real time through two force sensors, and torsion angle change and strain change are obtained in real time through torsion meter and strain gauge;

[0043] 8) Evaluate the torsional fatigue test damage and complete the torsional fatigue test of blade 7.

[0044] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, all changes made according to the shape and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fan blade torsional fatigue test device, characterized in that: It includes a driving device, a lever arm frame, a blade section clamp and a limit support device; the driving device is installed on the foundation through a ball joint bearing, and its driving rod is connected to the lever arm frame above it through a ball joint bearing, and a torsional torque is generated by the up and down movement of the driving rod acting on the lever arm frame; the blade section clamp is sleeved on the blade, and its inner side surface wraps the airfoil section on the blade to be loaded with a torsional load, and the blade section clamp is connected to the lever arm frame; the limit support device is supported below the blade section clamp, one end of the limit support device is connected to the blade section clamp through a ball joint bearing, and the other end is supported on the foundation through a ball joint bearing, and in the initial equilibrium state, the axis of the limit support device coincides with the torsional center of the blade section to be loaded with a torsional load, and under the action of the torsional torque, the blade section clamp rotates around the support point connected to the limit support device.

2. The fan blade torsional fatigue test device according to claim 1, characterized in that: A first force sensor and a displacement sensor are respectively installed on the driving rod. The first force sensor is used to measure the driving force of the driving rod, and the displacement sensor is used to measure the displacement change at the loading position.

3. The fan blade torsional fatigue testing device according to claim 1 is characterized in that: The driving device is a hydraulic cylinder or an electric cylinder.

4. The fan blade torsional fatigue test device according to claim 1, characterized in that: The limit support device includes a limit support rod and a second force sensor. The two ends of the limit support rod are respectively connected to the foundation and the blade section clamp through ball joint bearings. The second force sensor is installed on the limit support rod to measure the supporting force transmitted to the blade by the limit support rod.

5. The fan blade torsional fatigue testing device according to claim 1, characterized in that: The lever arm frame is processed with a plurality of connection holes along its length direction, and different connection holes are selected to connect with the blade section clamp to change the length of the lever arm, thereby adjusting the magnitude of the torsional moment.

6. The fan blade torsional fatigue testing device according to claim 1, characterized in that: An oblique support for transferring load is provided between the blade section fixture and the force arm support.

7. The fan blade torsional fatigue testing device according to claim 1, characterized in that: The blade section fixture comprises an iron frame and a wood core built in the iron frame. The wood core is made according to the shape of the airfoil section of the blade to be loaded with a torsional load, and a rubber pad is provided between the wood core and the blade.

8. The fan blade torsional fatigue testing device according to claim 1, characterized in that: The blade can be equipped with a torsion angle meter at a suitable position as required, so as to observe the torsion angle changes of different sections of the blade under the action of torsional load.

9. The fan blade torsional fatigue testing device according to claim 1, characterized in that: The blade can be attached with strain gauges at appropriate positions as required, so as to observe the strain distribution at specific positions of the blade under the action of torsional load.

10. The testing method of the fan blade torsional fatigue testing device according to any one of claims 1 to 9, characterized in that: The following steps are included: 1) According to the requirements of the blade torsional fatigue load, select the section that needs to be verified for torsional fatigue, design and determine the loading position of the blade to be tested, determine the target torque at the loading position, and determine the torsional deformation and loading load at the loading position; 2) Fix the root of the blade on the test bench through the flange, and make the 0° chord direction of the blade horizontal. Put the blade section fixture on the blade so that the blade section fixture covers the section that needs to be verified for torsional fatigue; 3) Select the target section to be tested between the blade root and the position where the blade section fixture is installed to install the torsion meter and the strain gauge; 4) Determine the torsion center of the section of the blade in the blade section fixture where torsional fatigue verification is required, and then determine the connection position of the limit support device and the blade section fixture to ensure that the axis of the limit support device coincides with the torsion center of the blade loading section in the initial equilibrium state; 5) Clear all sensors in the initial equilibrium state; 6) Debug the torsional fatigue test device, gradually increase the driving load, so that the torsional moment and the deformation of the blade torsional can reach the target value of the test, and complete the debugging to meet the design requirements. The calculation formula of the torsional moment M is as follows: M=(F 驱动 -F 支撑 ) / 2×L In the formula, F 驱动 is the loading force on the driving rod, F 支撑 is the supporting force of the limit support rod of the limit support device, and L is the horizontal distance from the driving rod to the limit support rod; 7) Blade torsion fatigue test: the driving rod of the driving device moves up and down to drive the force arm to drive the blade to be tested to rotate around the limit support rod at a set angle, so that the blade is cyclically twisted a set number of times, and the load change is obtained in real time through the force sensor, and the torsion angle change and strain change are obtained in real time through the torsion meter and strain gauge; 8) Evaluate torsional fatigue test damage and complete torsional fatigue testing of blades.

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