Vortex vibration principle-based blade fatigue test device and method

Abstract

The invention relates to the technical field of fatigue testing, and discloses a blade fatigue testing device and method based on a vortex-induced vibration principle, the blade fatigue testing device based on the vortex-induced vibration principle comprises a test bench foundation and at least one excitation unit, the test bench foundation is suitable for fixing a blade root of a tested blade; the excitation unit comprises a blade cover body and a pneumatic loading module, the blade cover body is of an annular structure fixedly arranged on the periphery of a test blade in a sleeving mode, the pneumatic loading module is arranged below the blade cover body, and the pneumatic loading module comprises a frame and at least one air blowing piece installed on the frame; wherein the air blowing piece is configured to blow air to the blade cover body, and turbulent flow is formed at the blade cover body. Non-contact excitation is achieved through aerodynamic coupling, the additional mass influence caused by mechanical connection is avoided, and full-size fatigue verification of the blade is completed under the condition that the natural vibration characteristic is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue testing, and in particular to a blade fatigue testing system and method based on the vortex vibration principle. Background Art

[0002] Blade fatigue testing simulates the alternating stresses experienced by blades during long-term operation through cyclic loading. Under the action of the resonant excitation system, the blades need to complete millions of flapping and oscillating motions to verify their structural reliability. Fatigue testing usually lasts for several months or even a year.

[0003] The fatigue test content of the blade mainly includes three aspects: flapping fatigue test, swing fatigue test and torsional fatigue test. The flapping fatigue test is to make the blade complete millions of reciprocating deformation movements in the up and down (pressure side-suction side) bending direction), and the swing fatigue test is to make the blade complete millions of reciprocating deformation movements in the front and back (leading edge-trailing edge) bending direction. The torsional fatigue test is not required to be implemented in the current standards, and there are few related testing equipment and supporting methods in the industry. The fatigue testing device of the blade can be divided into two types according to the working principle: forced displacement type (forcing the displacement of the blade through a mechanical structure) and resonance excitation type. The core idea of ​​the resonance excitation type is to apply a force to the blade with a frequency close to its natural frequency to stimulate the resonance of the blade. Compared with the forced displacement type, the resonance fatigue test has low energy consumption and a short test cycle, which is more in line with the testing needs of large blades.

[0004] The excitation devices of existing resonant excitation fatigue testing equipment are relatively heavy, and because the exciter is usually fixed by bolts or clamps, the installation point will be subject to additional local loads, which may lead to local stress concentration, further increasing the risk of structural failure. In addition, when the amplitude is large, the blade section near the exciter location may be subjected to greater shear force and bending moment, leading to increased local fatigue. At the same time, because the exciter itself is a high-mass component (especially the rotating mass type), its centrifugal force may affect the amplitude distribution of the entire blade. Summary of the Invention

[0005] In view of this, the present invention provides a blade fatigue testing device and method based on the vortex vibration principle to solve the above-mentioned problems existing in the existing resonance excitation fatigue testing equipment.

[0006] In a first aspect, the present invention provides a blade fatigue testing device based on the vortex vibration principle, comprising:

[0007] Test bench foundation, suitable for fixing the root of the test blade;

[0008] At least one excitation unit, the excitation unit including a blade cover and a pneumatic loading module, the blade cover is an annular structure fixedly mounted on the outer periphery of the test blade, the pneumatic loading module is arranged below the blade cover, and the pneumatic loading module includes a frame and at least one blowing member mounted on the frame;

[0009] Wherein, the blowing member is configured to blow air toward the blade cover and form a turbulent flow at the blade cover.

[0010] When the blade fatigue test device based on the vortex vibration principle is working, the air blowing member in the aerodynamic loading module generates a directional airflow through rotation to act on the surface of the blade cover, forming a vortex structure that periodically and alternately sheds behind the blade cover. The alternating pressure field generated by the vortex shedding process is transmitted to the surface of the wrapped test blade through the blade cover, forming an aerodynamic pulsation distributed along the span of the blade. By adjusting the speed of the air blowing member to control the outlet wind speed, the vortex shedding frequency is matched with the natural frequency of the test blade in a specific direction (flapping or swinging), thereby exciting the blade to enter a vortex-induced resonance state. The test blade generates millions of reciprocating bending deformations during the continuous resonance process, and its blade root is kept in a fixed constraint state by the test bench foundation, forming an alternating stress distribution equivalent to the actual working condition. This working mode realizes non-contact excitation through aerodynamic coupling, avoids the influence of additional mass brought by mechanical connection, and enables the blade to complete full-scale fatigue verification while maintaining its inherent vibration characteristics.

[0011] In an optional embodiment, the blade cover is a cylindrical structure.

[0012] When the blade fatigue test device based on the vortex vibration principle is working, the air blowing member in the aerodynamic loading module generates a directional airflow through rotation to act on the surface of the blade cover, forming a vortex structure that periodically and alternately sheds behind the blade cover. The alternating pressure field generated by the vortex shedding process is transmitted to the surface of the wrapped test blade through the blade cover, forming an aerodynamic pulsation distributed along the span of the blade. By adjusting the speed of the air blowing member to control the outlet wind speed, the vortex shedding frequency is matched with the natural frequency of the test blade in a specific direction (flapping or swinging), thereby exciting the blade to enter a vortex-induced resonance state. The test blade generates millions of reciprocating bending deformations during the continuous resonance process, and its blade root is kept in a fixed constraint state by the test bench foundation, forming an alternating stress distribution equivalent to the actual working condition. This working mode realizes non-contact excitation through aerodynamic coupling, avoids the influence of additional mass brought by mechanical connection, and enables the blade to complete full-scale fatigue verification while maintaining its inherent vibration characteristics.

[0013] In an optional embodiment, the blade cover is made of a lightweight foam material or a hollow composite material shell.

[0014] The blade cover is made of a lightweight foam material or a hollow composite material shell. The low density of the lightweight foam material significantly reduces the weight of the cover itself, avoiding changes in the inherent vibration characteristics of the test blade due to the added mass. The hollow composite shell is lightweight through the internal cavity design, while using the rigidity of the outer composite material to maintain the geometric shape of the cover, prevent structural deformation caused by airflow scouring, and ensure the precise control of the vortex generation position and shedding frequency. Both materials optimize the mass distribution and structural stiffness of the cover to efficiently transfer the aerodynamic load to the test blade surface. Under the premise of avoiding local stress concentration, a resonant response matching the blade's inherent mode is excited through aerodynamic coupling, thereby simulating the fatigue damage effect of alternating stress on the blade in a real wind field environment.

[0015] In an optional embodiment, a plurality of supporting legs are provided at the bottom of the frame, and the supporting legs are telescopically adjustable structures.

[0016] In an optional embodiment, there are multiple blowing members, and several of the blowing members are arranged in an array on the frame.

[0017] In an optional embodiment, the blowing member is an axial flow fan or a centrifugal fan.

[0018] In an optional embodiment, the wind speed V output by the blowing member is obtained by the following formula:

[0019]

[0020] Where S t is the Strouhal number, which is between 0.15 and 0.25. D is the diameter of the corresponding blade cover. f is the natural frequency of the blade, and its specific value is determined according to the direction of the fatigue test.

[0021] By adjusting the speed of the blower so that the output wind speed V satisfies the formula, the frequency of periodic vortex shedding behind the blade cover is precisely matched to the natural frequency of the test blade in the flapping or swinging direction, forming a locking effect of vortex-induced resonance. The physical meaning of D is the characteristic scale of the blade cover (such as the diameter of a cylinder). Its size parameters and the blade modal vibration shape together determine the spanwise distribution law of the vortex energy input; the value of f is directly related to the first-order bending natural frequency of the blade in the flapping or swinging direction. By matching the target frequency, the aerodynamic excitation force and the blade elastic restoring force are synchronized in frequency and phase, thereby stimulating a continuous and stable resonant response. This formula achieves precise control of the non-contact excitation frequency through the dynamic coupling of aerodynamic parameters and structural parameters, allowing the test blade to complete a million-order alternating stress loading process equivalent to the actual wind load without the interference of additional mass.

[0022] In an optional embodiment, there are multiple excitation units, and several of the excitation units are arranged at intervals along the extension direction of the test blade, and the blade covers of adjacent excitation units have different characteristic diameters, and the characteristic diameters are proportional to the cross-sectional dimensions of the corresponding positions of the test blade.

[0023] By adjusting the speed of the blower so that the output wind speed V satisfies the formula, the frequency of periodic vortex shedding behind the blade cover is precisely matched to the natural frequency of the test blade in the flapping or swinging direction, forming a locking effect of vortex-induced resonance. The physical meaning of D is the characteristic scale of the blade cover (such as the diameter of a cylinder). Its size parameters and the blade modal vibration shape together determine the spanwise distribution law of the vortex energy input; the value of f is directly related to the first-order bending natural frequency of the blade in the flapping or swinging direction. By matching the target frequency, the aerodynamic excitation force and the blade elastic restoring force are synchronized in frequency and phase, thereby stimulating a continuous and stable resonant response. This formula achieves precise control of the non-contact excitation frequency through the dynamic coupling of aerodynamic parameters and structural parameters, allowing the test blade to complete a million-order alternating stress loading process equivalent to the actual wind load without the interference of additional mass.

[0024] In a second aspect, the present invention further provides a blade fatigue testing method, which uses the blade fatigue testing device based on the vortex vibration principle described above, and includes the following steps:

[0025] Fix the test blade to the test bench foundation through the positioning flange;

[0026] The excitation units are arranged at preset intervals along the length direction of the blade;

[0027] The aerodynamic loading module generates a multi-band exciting airflow, and the blade cover guides the airflow to form a vortex vibration effect.

[0028] Specifically, the blade fatigue test method fixes the test blade to the test bench foundation through a positioning flange, realizes a fully constrained connection of the blade root end face through high-strength bolts, maintains the fixed boundary conditions of the blade root section during the test, and simulates the root stress state of the blade in the actual unit; the excitation units are arranged at a preset spacing along the length direction of the blade, and the spacing value is dynamically adjusted according to the vibration mode node distribution of the blade flapping and swing modes. A dense arrangement strategy is adopted in the area with the maximum amplitude (such as the middle of the blade), and the spacing is appropriately increased near the vibration mode node (such as the blade root or blade tip) to ensure the efficient transmission of vortex-induced resonance energy in the blade span direction; a multi-band excitation airflow is generated by the aerodynamic loading module, and based on the Strouhal number formula (V=f·D / S t) The output wind speed of the blowing element in each excitation unit is independently adjusted, so that the vortex shedding frequency generated by the blade cover at different positions is locked to the first-order or high-order natural frequency of the flapping and swinging directions of the test blade, and at the same time, the wide-band vortex-induced force coupling loading is achieved through the gradient change of the characteristic diameter between adjacent excitation units. During the test, the blade cover guides the airflow to form a periodic vortex street with time and space correlation behind it. The alternating pressure is transmitted to the blade surface through aerodynamic coupling, which stimulates a large-amplitude resonance response that matches the target mode. The blade undergoes millions of reciprocating bending deformations under continuous vortex-induced vibration. The distribution state of the shear stress between the internal fiber layers and the alternating stress of the main beam web is monitored in real time by strain gauges. Finally, the full-scale fatigue life verification equivalent to the actual wind field turbulence spectrum is completed without the interference of additional mass.

[0029] In an optional embodiment, the step of arranging the excitation units at preset intervals along the length direction of the blade includes:

[0030] The extension and contraction amount of the support legs is adjusted so that the blade cover of each excitation unit forms a preset interval with the test blade, and the blowing angle can be adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 Schematic diagram of the structure of a blade fatigue testing device based on the vortex vibration principle according to an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of the structure of a pneumatic loading module in a blade fatigue testing device based on the vortex vibration principle according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of a vibration excitation unit in a blade fatigue testing device based on the vortex vibration principle according to an embodiment of the present invention.

[0035] Description of reference numerals:

[0036] 1. Test bench foundation; 2. Test blade; 3. Blade cover; 4. Pneumatic loading module; 5. Frame; 6. Blower; 7. Support leg; 8. Positioning flange. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0038] Blade fatigue testing simulates the alternating stresses experienced by blades during long-term operation through cyclic loading. Under the action of the resonant excitation system, the blades need to complete millions of flapping and oscillating motions to verify their structural reliability. Fatigue testing usually lasts for several months or even a year.

[0039] The fatigue test content of the blade mainly includes three aspects: flapping fatigue test, swing fatigue test and torsional fatigue test. The flapping fatigue test is to make the blade complete millions of reciprocating deformation movements in the up and down (pressure side-suction side) bending direction), and the swing fatigue test is to make the blade complete millions of reciprocating deformation movements in the front and back (leading edge-trailing edge) bending direction. The torsional fatigue test is not required to be implemented in the current standards, and there are few related testing equipment and supporting methods in the industry. The fatigue testing device of the blade can be divided into two types according to the working principle: forced displacement type (forcing the displacement of the blade through a mechanical structure) and resonance excitation type. The core idea of ​​the resonance excitation type is to apply a force to the blade with a frequency close to its natural frequency to stimulate the resonance of the blade. Compared with the forced displacement type, the resonance fatigue test has low energy consumption and a short test cycle, which is more in line with the testing needs of large blades.

[0040] The excitation devices of existing resonant excitation fatigue testing equipment are relatively heavy, and because the exciter is usually fixed by bolts or clamps, the installation point will be subject to additional local loads, which may lead to local stress concentration, further increasing the risk of structural failure. In addition, when the amplitude is large, the blade section near the exciter location may be subjected to greater shear force and bending moment, leading to increased local fatigue. At the same time, because the exciter itself is a high-mass component (especially the rotating mass type), its centrifugal force may affect the amplitude distribution of the entire blade.

[0041] The following combination Figures 1 to 3 , describing embodiments of the present invention.

[0042] According to an embodiment of the present invention, on the one hand, a blade fatigue testing device based on the vortex vibration principle is provided, including a test bench base 1 and at least one excitation unit, the test bench base 1 is suitable for fixing the root of the test blade 2; the excitation unit includes a blade cover 3 and a pneumatic loading module 4, the blade cover 3 is an annular structure fixed on the outer periphery of the test blade 2, the pneumatic loading module 4 is arranged below the blade cover 3, the pneumatic loading module 4 includes a frame 5 and at least one blowing member 6 installed on the frame 5; wherein the blowing member 6 is configured to blow air toward the blade cover 3 and form a turbulent flow at the blade cover 3.

[0043] When the blade fatigue test device based on the vortex vibration principle is working, the blower 6 in the pneumatic loading module 4 generates a directional airflow through rotation to act on the surface of the blade cover 3, forming a vortex structure that periodically and alternately sheds behind the blade cover 3. The alternating pressure field generated by the vortex shedding process is transmitted to the surface of the wrapped test blade 2 through the blade cover 3, forming an aerodynamic pulsation distributed along the span of the blade. By adjusting the rotation speed of the blower 6 to control the outlet wind speed, the vortex shedding frequency is matched with the natural frequency of the test blade 2 in a specific direction (flapping or swinging), thereby stimulating the blade to enter a vortex-induced resonance state. The test blade 2 produces millions of reciprocating bending deformations during the continuous resonance process, and its blade root is kept in a fixed constraint state by the test bench foundation 1, forming an alternating stress distribution equivalent to the actual working condition. This working mode realizes non-contact excitation through aerodynamic coupling, avoids the additional mass influence brought by mechanical connection, and enables the blade to complete full-scale fatigue verification while maintaining its inherent vibration characteristics.

[0044] In one embodiment, the blade cover 3 is a cylindrical structure or a regular body of other shapes.

[0045] In the above embodiment, the blade cover 3 is a cylindrical structure. Its axially symmetrical geometric features allow the airflow generated by the blower 6 to flow evenly along the outer wall of the cover, forming symmetrically distributed periodic vortex shedding on the leeward side of the cylinder. The smooth curvature of the cylindrical cover surface reduces the randomness of the airflow separation point, ensuring that the vortex generation position and shedding timing remain highly consistent in the circumferential direction, thereby forming a stable alternating pressure distribution around the blade cover 3. When the airflow velocity is adjusted to a specific threshold by the blower 6, the vortex shedding frequency behind the cylinder forms a locked relationship with the natural frequency of the flapping or swinging direction of the test blade 2. At this time, the periodic lift of the vortex and the elastic restoring force of the blade are coupled to each other, stimulating a continuous large-amplitude resonant response. The structural rigidity of the cylindrical cover can suppress asymmetric deformation and ensure uniform transmission of excitation energy along the blade span. At the same time, its closed ring design avoids lateral leakage of airflow, improves the energy utilization rate of vortex-induced vibration, and enables the test blade 2 to achieve a fatigue damage accumulation process consistent with the actual wind field environment under fixed constraints.

[0046] In one embodiment, the blade cover 3 is made of a lightweight foam material or a hollow composite material shell.

[0047] In the above embodiment, the blade cover 3 is made of a lightweight foam material or a hollow composite material shell. The low density of the lightweight foam material significantly reduces the weight of the cover itself, avoiding changes in the inherent vibration characteristics of the test blade 2 due to the added mass. The hollow composite material shell is lightweight through the internal cavity design, while the rigidity of the outer composite material is used to maintain the geometric shape of the cover, prevent structural deformation caused by airflow scouring, and ensure the precise control of the vortex generation position and shedding frequency. Both materials optimize the mass distribution and structural stiffness of the cover so that the aerodynamic load is efficiently transferred to the surface of the test blade 2. Under the premise of avoiding local stress concentration, a resonant response matching the blade's inherent mode is excited through aerodynamic coupling, thereby simulating the fatigue damage effect of alternating stress on the blade in a real wind field environment.

[0048] In one embodiment, a plurality of support legs 7 are provided at the bottom of the frame 5 , and the support legs 7 are telescopically adjustable structures.

[0049] like Figure 2 As shown, the frame 5 is provided with four support legs 7 at the bottom. The support legs 7 are retractable and adjustable structures, such as electric telescopic rods or screws. By adjusting the extension length of the support legs 7, the overall height of the frame 5 above the ground can be changed. This allows for adjustment of the frame 5's height above the ground and the blowing angle, thereby optimizing the contact area between the airflow and the hood surface and the flow direction.

[0050] In some other embodiments, the number of supporting legs 7 may also be set to three.

[0051] In one embodiment, there are multiple air blowing members 6 , and the air blowing members 6 are arranged on the frame 5 in an array.

[0052] In the above embodiment, there are multiple blower members 6, and several blower members 6 are arranged in an array on the frame 5. By optimizing the spacing between adjacent blower members 6, the airflow generated by each blower member 6 in the array forms a continuous and uniformly covered flow field on the surface of the blade cover 3, eliminating the problem of vortex shedding phase misalignment caused by local flow velocity differences. The rotation speed of each blower member 6 in the array can be adjusted independently. Through the gradient distribution strategy of high rotation speed in the central area and low rotation speed in the edge area, the vortex shedding intensity at different positions of the blade cover 3 is matched with the modal vibration amplitude distribution of the test blade 2, thereby optimizing the resonance energy input efficiency. The redundant design of the array arrangement allows compensation to be achieved by speeding up the adjacent units when a single blower member 6 fails, ensuring the continuity of vortex-induced vibration excitation during the test process. At the same time, through the coordinated start-stop control of multiple blowers 6, the turbulent spectrum characteristics of the wind field can be simulated, forming a random-periodic composite load spectrum on the blade surface that is closer to the actual working conditions.

[0053] Specifically, such as Figure 2 In the structure shown, the number of the blowing members 6 is six.

[0054] In one embodiment, the blowing member 6 is an axial flow fan or a centrifugal fan.

[0055] In one embodiment, the air blowing member 6 is an axial flow fan or a centrifugal fan. Axial flow fans generate high-flow, low-pressure directional flow through high-speed airflow parallel to the axis. Their linear flow field characteristics cause span-wise uniform periodic vortex shedding behind the blade cover 3, making them suitable for low-frequency, high-amplitude flapping fatigue testing. Centrifugal fans generate high-pressure, low-flow concentrated jets through centrifugal force-driven radial airflow. Localized high-pressure disturbances enhance the spatiotemporal coherence of vortex shedding, making them suitable for high-frequency, low-amplitude shimmy fatigue testing.

[0056] In one embodiment, the wind speed V output by the blowing member 6 is obtained by the following formula:

[0057]

[0058] Where S t is the Strouhal number, which is between 0.15 and 0.25. D is the diameter of the corresponding blade cover 3. f is the natural frequency of the blade, and its specific value is determined according to the direction of the fatigue test.

[0059] By adjusting the rotation speed of the blower 6, the output wind speed V satisfies the formula relationship. At this time, the periodic vortex shedding frequency behind the blade cover 3 is precisely matched with the natural frequency of the test blade 2 in the flapping or swinging direction, forming a locking effect of vortex-induced resonance. The physical meaning of D is the characteristic scale of the blade cover 3 (such as the diameter of a cylinder). Its size parameters and the blade modal vibration shape jointly determine the spanwise distribution law of the vortex energy input; the value of f is directly related to the first-order bending natural frequency of the blade in the flapping or swinging direction. By matching the target frequency, the aerodynamic excitation force and the blade elastic restoring force are made to be of the same frequency and phase, thereby stimulating a continuous and stable resonant response. This formula realizes the precise control of non-contact excitation frequency through the dynamic coupling of aerodynamic parameters and structural parameters, so that the test blade 2 completes a million-order alternating stress loading process equivalent to the actual wind load without the interference of additional mass.

[0060] In one embodiment, there are multiple excitation units, and several excitation units are arranged at intervals along the extension direction of the test blade 2, and the blade covers 3 of adjacent excitation units have different characteristic diameters, which are proportional to the cross-sectional dimensions of the corresponding positions of the test blade 2.

[0061] like Figure 1In the structure shown, there are four excitation units, which are arranged at intervals along the extension direction of the test blade 2, and the blade covers 3 of adjacent excitation units have different characteristic diameters. The characteristic diameter is proportional to the cross-sectional dimensions of the corresponding position of the test blade 2, that is, the smaller the cross-sectional dimensions of the corresponding position of the test blade 2, the smaller the characteristic diameter of the blade cover 3, so that the characteristic diameter can be wrapped and fixed on the outer peripheral side of the test blade 2. By arranging blade covers 3 of different diameters along the spanwise gradient of the blade, the vortex shedding frequency generated by each excitation unit is matched with the local modal characteristics of the blade at the corresponding position, wherein the large-diameter cover in the root area adapts to the low-frequency characteristics of the low-order mode, and the small-diameter cover in the tip area adapts to the high-frequency characteristics of the high-order mode. Each excitation unit independently controls the output wind speed of the blower 6, so that the vortex energy input intensity at different spanwise positions forms a spatial coupling with the amplitude distribution of the blade bending vibration mode, thereby improving the transmission efficiency of the resonance energy along the spanwise direction of the blade. The ratio design of the characteristic diameter to the blade cross-sectional size ensures that the alternating pressure field generated by vortex shedding fully covers the blade surface, while avoiding the flow separation delay caused by an overly large cover or the vortex coherence attenuation caused by a too small cover.

[0062] According to an embodiment of the present invention, on the other hand, a blade fatigue testing method is provided, which uses the above-mentioned blade fatigue testing device based on the vortex vibration principle, and includes the following steps:

[0063] Fix the test blade 2 on the test bench foundation 1 through the positioning flange 8;

[0064] The excitation units are arranged at preset intervals along the length direction of the blade;

[0065] A multi-band exciting airflow is generated by the aerodynamic loading module 4, and the airflow is guided by the blade cover 3 to form a vortex vibration effect.

[0066] Specifically, the blade fatigue test method fixes the test blade 2 on the test bench foundation 1 through the positioning flange 8, realizes the full constraint connection of the blade root end face through the high-strength bolts, maintains the fixed boundary condition of the blade root section during the test, and simulates the root stress state of the blade in the actual unit; arranges the excitation units at a preset spacing along the length direction of the blade, and the spacing value is dynamically adjusted according to the vibration mode node distribution of the blade flapping and swing modes. A dense arrangement strategy is adopted in the area with the maximum amplitude (such as the middle of the blade), and the spacing is appropriately increased near the vibration mode node (such as the blade root or blade tip) to ensure the efficient transmission of vortex-induced resonance energy in the blade span direction; generates a multi-band excitation airflow through the aerodynamic loading module 4, and based on the Strouhal number formula (V=f·D / S t) The output wind speed of the blowing element 6 in each excitation unit is independently adjusted so that the vortex shedding frequency generated by the blade cover 3 at different positions is locked to the first-order or high-order natural frequency of the test blade 2 in the flapping and swinging directions respectively. At the same time, a wide-band vortex-induced force coupling loading is achieved through the gradient change of the characteristic diameter between adjacent excitation units. During the test, the blade cover 3 guides the airflow to form a periodic vortex street with temporal and spatial correlation behind it. The alternating pressure is transmitted to the blade surface through aerodynamic coupling, which stimulates a large-amplitude resonance response that matches the target mode. The blade undergoes millions of reciprocating bending deformations under continuous vortex-induced vibration. The distribution state of the shear stress between the internal fiber layers and the alternating stress of the main beam web is monitored in real time by strain gauges. Finally, a full-scale fatigue life verification equivalent to the actual wind field turbulence spectrum is completed without the interference of additional mass.

[0067] In one embodiment, the step of arranging the excitation units at a preset interval along the length direction of the blade includes: adjusting the extension amount of the support legs 7 so that the blade cover 3 of each excitation unit forms a preset interval with the test blade 2, and the blowing angle can be adjusted.

[0068] In the above embodiment, the step of arranging the excitation units at a preset spacing along the length of the blade includes: adjusting the extension and contraction of the support legs 7 so that the blade cover 3 of each excitation unit forms a preset spacing with the test blade 2. By synchronously adjusting the extension and contraction of the support legs 7 of each excitation unit, the gap between the blade cover 3 and the surface of the test blade 2 is controlled within the range of 10-50 mm. This gap range ensures that the high-speed airflow output by the blowing member 6 forms a fully developed wall-attached jet on the outer wall of the blade cover 3, while avoiding the problem of airflow boundary layer separation caused by too small a spacing or energy dissipation caused by too large a spacing. At the same time, by adjusting the extension and contraction of the support legs 7, the blowing angle of the pneumatic loading module can be adjusted.

[0069] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A blade fatigue testing device based on the vortex vibration principle, characterized in that: include: A test bench foundation (1) adapted to secure the root of a test blade (2); At least one excitation unit, the excitation unit comprising a blade cover (3) and a pneumatic loading module (4), the blade cover (3) being an annular structure sleeved and fixed on the outer periphery of the test blade (2), the pneumatic loading module (4) being arranged below the blade cover (3), the pneumatic loading module (4) comprising a frame (5) and at least one blowing member (6) mounted on the frame (5); The blowing member (6) is configured to blow air toward the blade cover (3) and form a turbulent flow at the blade cover (3).

2. The blade fatigue testing device based on the vortex vibration principle according to claim 1 is characterized in that: The blade cover (3) is a cylindrical structure.

3. The blade fatigue testing device based on the vortex vibration principle according to claim 1 is characterized in that: The blade cover (3) is made of a lightweight foam material or a hollow composite material shell.

4. The blade fatigue testing device based on the vortex vibration principle according to any one of claims 1 to 3, characterized in that: A plurality of supporting legs (7) are provided at the bottom of the frame (5), and the supporting legs (7) are telescopically adjustable structures.

5. The blade fatigue testing device based on the vortex vibration principle according to claim 4 is characterized in that: There are multiple blowing members (6), and several of the blowing members (6) are arranged on the frame (5) in an array.

6. The blade fatigue testing device based on the vortex vibration principle according to claim 5 is characterized in that: The air blowing member (6) is an axial flow fan or a centrifugal fan.

7. The blade fatigue testing device based on the vortex vibration principle according to any one of claims 1 to 6, characterized in that: The wind speed V output by the blowing member (6) is obtained by the following formula: Where S t is the Strouhal number, which takes a value of 0.15-0.25, D is the diameter of the corresponding blade cover (3), and f is the natural frequency of the test blade, which takes a specific value according to the direction of the fatigue test.

8. The blade fatigue testing device based on the vortex vibration principle according to any one of claims 1 to 7, characterized in that: There are a plurality of excitation units, and several of the excitation units are arranged at intervals along the extension direction of the test blade (2), and the blade covers (3) of adjacent excitation units have different characteristic diameters, and the characteristic diameters are proportional to the cross-sectional dimensions of the corresponding positions of the test blade (2).

9. A blade fatigue testing method, using the blade fatigue testing device based on the vortex vibration principle according to any one of claims 4 to 6, characterized in that: The steps include: Fixing the test blade (2) on the test bench foundation (1) via the positioning flange (8); Arranging the vibration excitation units at preset intervals along the length direction of the test blade (2); A multi-band exciting airflow is generated by the aerodynamic loading module (4), and the airflow is guided by the blade cover (3) to form a vortex vibration effect.

10. The blade fatigue testing method according to claim 9, characterized in that: The step of arranging the excitation units at preset intervals along the length direction of the test blade (2) comprises: The extension and contraction amount of the support legs (7) is adjusted so that the blade cover (3) of each excitation unit and the test blade (2) form a preset interval, and the blowing angle can be adjusted.

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