Device and method for testing inherent frequency of paddle

Abstract

The invention discloses a device and method for testing the inherent frequency of a blade, and relates to the technical field of rotating blade testing, the blade is installed on a propeller hub, and the device comprises an adapter shaft, the propeller hub is fixedly installed at the front end of the adapter shaft; a driving shaft of the rotation driving mechanism is in transmission connection with the adapter shaft so as to drive and control the adapter shaft to rotate; the monitoring assembly comprises a strain gauge, a wireless strain tester, a wireless data collector and an upper computer; the strain gauges are fixed on the paddles; the wireless strain tester is fixed on the adapter shaft; the strain gauge is electrically connected with the wireless strain tester; the wireless strain tester is in wireless communication connection with the wireless data collector, and the wireless data collector is in communication connection with the upper computer. According to the invention, a dynamic vibration test can be carried out in a blade rotating state to obtain inherent frequency data.

Description

Technical Field

[0001] The present invention relates to the technical field of rotary blade testing, and particularly to an inherent frequency testing device and method for a blade. Background Art

[0002] For a rotary blade, such as the blade of a high-speed helicopter, its inherent frequency is a very important property, which directly affects the vibration quality, fatigue life and structural safety of the product. At present, the testing method for the inherent frequency of a static blade has been quite mature, but the static blade testing cannot effectively and truly reflect the working conditions of the rotary blade; at present, the relevant research on the testing method for the inherent frequency of a blade in the rotating state is still very scarce. The testing method for the inherent frequency of a blade in the rotating state mainly needs to consider the following three aspects of factors:

[0003] First, the excitation mode of the rotary blade. The commonly used excitation methods in the vibration testing of rotary blades include: high-pressure air gun excitation, high-pressure water gun excitation, high-speed ice projectile excitation, piezoelectric patch excitation, etc. Among them, the first three excitation methods have large excitation forces, but have high requirements for the test environment; the piezoelectric patch excitation method is safe and reliable, but the excitation force is small and cannot meet the test requirements. The factors causing blade vibration can be roughly divided into mechanical excitation and aerodynamic excitation. Mechanical excitation usually causes vibration of the disk first, and is transmitted to the root of the rotor blade through the connection between the blade and the disk, thus causing the entire blade to vibrate; aerodynamic excitation causes blade vibration through the periodic pressure change of the airflow acting on the blade surface. When the propeller rotates at high speed, it will cause unstable aerodynamic loads and result in vibration; the vibration of the blade under the action of aerodynamic excitation belongs to fluid-induced vibration. Different rotational speeds result in different aerodynamic excitations. Therefore, the unsteady characteristic is an inherent property of the rotary blade and the essential reason for fluid-induced blade vibration.

[0004] Second, the selection of vibration sensors. For the testing of the inherent frequency of a rotary blade, piezoelectric acceleration sensors and strain gauges can be selected as vibration sensors. The piezoelectric acceleration sensor has high sensitivity, but has a certain mass. When pasted on the blade, the rotational inertia needs to be considered during high-speed rotation to avoid falling off; while the strain gauge is relatively thin and light in mass, and is not easy to fall off during blade rotation.

[0005] Third, the signal transmission method for data acquisition in the rotating state. The commonly used methods are conductive slip rings and wireless signal transmission. The conductive slip ring needs to match the size of the rotating shaft. If the vibration signal is not very large, it is not easy to ensure the signal transmission stability and accuracy; the wireless signal transmission method adds a wireless transmitting and receiving module to the vibration sensor to achieve wireless signal transmission, and the signal transmission stability is good. However, whether it is the conductive slip ring or the wireless signal transmission method, they both need to be set on the rotating shaft, which will inevitably interfere with the rotation of the rotating shaft to a certain extent and affect its motion stability.

[0006] Therefore, considering the above factors, how to provide a natural frequency test device and test method for a blade, which can perform dynamic vibration tests under the rotating state of the blade to obtain natural frequency data, and can provide data support for the study of the unsteady characteristics of the aerodynamic parameters of the rotating blade and the blade structure design and product development, is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention proposes a natural frequency test device and test method for a blade, aiming to solve the technical problems of how to perform natural frequency tests under the rotating state of the blade and provide data support for the study of the unsteady characteristics of the aerodynamic parameters of the rotating blade and the blade structure design and product development.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] On the one hand, the present invention provides a natural frequency test device for a blade, the blade is installed on a hub, and includes:

[0010] A transfer shaft, the hub is fixedly installed at the front end of the transfer shaft;

[0011] A rotary drive mechanism, the drive shaft of the rotary drive mechanism is in transmission connection with the transfer shaft to drive and control the rotation of the transfer shaft;

[0012] A monitoring component, the monitoring component includes a strain gauge, a wireless strain tester, a wireless data collector and a host computer; the strain gauge is fixed on the blade; the wireless strain tester is fixed on the transfer shaft; the strain gauge is electrically connected to the wireless strain tester; the wireless strain tester is wirelessly communicatively connected to the wireless data collector, and the wireless data collector is communicatively connected to the host computer.

[0013] It can be seen from the above technical solutions that, compared with the prior art, a natural frequency test device for a blade disclosed by the present invention can perform natural frequency tests by using the excitation (self-excited vibration) generated by the rotation of the blade itself; since the structure of the blade itself will change under the influence of air flow under the rotating condition, that is to say, the difference between the test of the rotating blade and the test of the static blade is that the rotating blade does not have a single natural frequency, and the unsteady characteristic of the rotating blade is its inherent attribute, and the measurement of the vibration mode of the blade under the rotating state can more effectively reflect the true aerodynamic characteristics of the blade. The test device of the present invention can collect the vibration data of the blade by setting different rotational speed values for multiple measurements to study the change of the natural frequency of the blade at different rotational speeds, and can provide data support for the study of the unsteady characteristics of the aerodynamic parameters of the rotating blade and the blade structure design and product development.

[0014] As a further improvement of the above technical solution, a groove is formed in the circumferential wall of the adapter shaft, the wireless strain tester is embedded in the groove, and a fixing ring is sleeved on the adapter shaft corresponding to the groove to limit and constrain the wireless strain tester in the groove.

[0015] The wireless strain tester is embedded in the groove, which can improve the rotational stability of the adapter shaft and the entire rotating system; the fixing ring limits and constrains the wireless strain tester in the groove to prevent the wireless strain tester from shifting or disengaging during high-speed rotation.

[0016] As a further improvement of the above technical solution, there are two or more blades, and the two or more blades are evenly distributed along the circumferential direction of the hub;

[0017] There are multiple strain gauges, and at least one of the blades is provided with a plurality of the strain gauges arranged at intervals along its length direction; the strain gauges are all fixedly attached to the outer wall surface of the blade; the strain gauges are electrically connected to the wireless strain tester through wires, and the wires are fixedly attached to the outer wall surfaces of the corresponding blade, hub and adapter shaft.

[0018] The even distribution of two or more blades along the circumferential direction of the hub realizes the rotational balance of the rotating blades themselves, so as to reduce the interference of centrifugal vibration; arranging a plurality of strain gauges at intervals along the length direction of the blade can collect vibration data at different distances from the rotation center of the blade, providing data support for the study of the mechanical properties of the overall structure of the blade, and more reliable blade natural frequency data can be obtained by taking the average value of the data collected by a plurality of strain gauges distributed at different positions on the blade.

[0019] As a further improvement of the above technical solution, the strain gauge is pasted on the outer wall surface of the blade through an adhesive layer 1, and the surface of the strain gauge away from the blade is covered with an adhesive layer 2; the wire is adhesively bonded to the outer wall surfaces of the blade, hub and adapter shaft through a colloid.

[0020] The adhesive layer 1 tightly adheres the blade to the blade surface; the adhesive layer 2 can play a role in protecting and strengthening the strain gauge, preventing the strain gauge from being torn by the airflow under the high-speed rotation of the blade, thereby reducing the measurement error.

[0021] As a further improvement of the above technical solution, a base is further included, the rotary drive mechanism is installed on the base, and the drive shaft of the rotary drive mechanism is detachably connected to the rear end of the adapter shaft.

[0022] The base provides a stable installation foundation for the rotary drive mechanism to balance the reaction force of the airflow on the rotary drive mechanism under the high-speed rotation of the blade.

[0023] On the other hand, the present invention provides a method for testing the natural frequency of a blade, including the device for testing the natural frequency of the blade, and the testing steps are as follows:

[0024] S1: Install the testing device, install the blade to be tested on the hub, and fixedly install the hub at the front end of the transfer shaft;

[0025] S2: Fix strain gauges on the outer wall of the blade, electrically connect the strain gauges to the wireless strain tester through wires; communicatively connect the wireless data collector to the upper computer;

[0026] S3: Start the test, drive the transfer shaft to rotate through the rotation drive mechanism, and then drive the hub and the blade to rotate; when the blade rotates, it is excited by the airflow and causes vibration. The strain gauges transmit the collected signals to the wireless strain tester, the wireless strain tester wirelessly transmits the signals to the wireless data collector, and the wireless data collector transmits the data signals to the upper computer;

[0027] S4: The upper computer uses dynamic signal test and analysis software to analyze and process the data to obtain the natural frequency.

[0028] As a further improvement of the above technical solution, after the testing device is installed, before starting the test, first perform a dynamic balance test and correction on the testing device to reduce the influence of the eccentric vibration of the testing device on the test results.

[0029] As a further improvement of the above technical solution, the specific method for fixing the strain gauges on the outer wall of the blade is: evenly arrange a plurality of strain gauges from the tip to the root of the blade, apply glue to the side of the strain gauge close to the blade to paste the strain gauge on the blade surface, and apply glue to the side of the strain gauge away from the blade and the periphery of the strain gauge to seal the strain gauge on the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0031] Figure 1 Schematic structural diagram of a device for testing the natural frequency of a blade according to the present invention;

[0032] Figure 2 The present invention Figure 1 Enlarged schematic diagram of the structure at A in;

[0033] Figure 3 Schematic diagram of the state where the rotation drive mechanism of a device for testing the natural frequency of a blade according to the present invention is installed on the base;

[0034] Figure 4 Test results of the natural frequency of the blade of a natural frequency testing device for a blade of the present invention at different rotational speeds;

[0035] In the figure: 1. Blade; 2. Adapter shaft; 21. Groove; 22. Fixed ring; 3. Monitoring component; 31. Strain gauge; 32. Wireless strain tester; 4. Rotary drive mechanism; 5. Adhesive layer 1; 6. Adhesive layer 2; 7. Base; 8. Hub. Detailed implementation manners

[0036] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0038] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0039] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed" and other terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] The present invention selects to utilize the excitation generated by the rotation of the blade itself (self-excited vibration) for natural frequency testing. The necessary condition for self-excited vibration is that the structure is not subjected to external excitation, that is to say, the system does not intake energy, but a vibration form excited by the system itself, which is called self-excited vibration, abbreviated as self-vibration. The difference between it and forced vibration is the different excitation bodies of vibration. Forced vibration is an external excitation, while self-excited vibration comes from the vibration body itself. This vibration form for the blade is the vibration caused by the air flow under the condition of the rotation of the blade structure itself. When the blade undergoes this form of vibration, it will continuously absorb energy from the air flow to provide energy for the structure to continue vibrating. Considering comprehensively, the present invention directly adopts the self-excited vibration method to realize blade excitation.

[0041] Regarding the selection of the vibration sensor, considering that the working performance of the piezoelectric acceleration sensor cannot be stable under the high-speed inertial centrifugal state, a strain gauge that is relatively thin and can be pasted on the blade surface is selected. Finally, on the basis of considering the adhesion firmness and the dynamic balance problem of the rotating blade, the strain gauge is selected as the vibration sensor.

[0042] For the transmission method of the rotating state signal, a wireless signal transmission method is selected to realize wireless transmission of the signal, which has good stability and will not interfere with the rotation of the blade to be tested.

[0043] As Figures 1 to 3 shown, this embodiment provides a device for testing the natural frequency of a blade, including: a rotating blade assembly 1, a transfer shaft 2, a rotation driving mechanism 4, and a monitoring assembly 3. The rotating blade assembly 1 includes a hub 8 and blades 1 mounted on the hub 8; the hub 8 is detachably connected to the front end of the transfer shaft 2;

[0044] The driving shaft of the rotation driving mechanism 4 is in transmission connection with the transfer shaft 2 to drive and control the rotation of the transfer shaft 2;

[0045] The monitoring assembly 3 includes a strain gauge 31, a wireless strain tester 32, a wireless data collector, and a host computer; the strain gauge 31 is fixed on the blade 1; the wireless strain tester 32 is fixed on the transfer shaft 2; the strain gauge 31 is electrically connected to the wireless strain tester 32; the wireless strain tester 32 is in wireless communication connection with the wireless data collector, and the wireless data collector is in communication connection with the host computer.

[0046] An inherent frequency testing device for a blade provided in this embodiment can perform inherent frequency testing by using the excitation (self-excited vibration) generated by the rotation of the blade itself; since the structure of the blade itself will change under the influence of air flow during rotation, that is to say, the difference between testing a rotating blade and a static blade is that a rotating blade does not have a single inherent frequency, and the unsteady characteristics of a rotating blade are its inherent properties, and measuring the vibration mode of the blade in the rotating state can more effectively reflect the true aerodynamic characteristics of the blade. The testing device of the present invention can collect blade vibration data through multiple measurements by setting different rotational speed values to study the change of the inherent frequency of the blade at different rotational speeds, and can provide data support for the research on the unsteady characteristics of the aerodynamic parameters of the rotating blade and the structural design and product development of the blade.

[0047] In some embodiments, a groove 21 is formed in the peripheral wall of the adapter shaft 2, and the wireless strain tester 32 is embedded and fixed in the groove 21 with screws. A fixing ring 22 is sleeved on the adapter shaft 2 corresponding to the groove 21 to further limit and constrain the wireless strain tester 32 in the groove 21.

[0048] Specifically, a battery for powering the wireless strain tester 32 is also placed in the groove 21; the battery is fixed to the inner wall of the groove 21 with screws; the fixing ring 22 can be selected as a clamp.

[0049] The wireless strain tester 32 being embedded in the groove 21 can improve the rotational stability of the adapter shaft 2 and the entire rotating system; the fixing ring 22 limits and constrains the wireless strain tester 32 in the groove 21 to prevent the wireless strain tester 32 from shifting or coming out during high-speed rotation.

[0050] In some embodiments, there are two or more blades 1, and the two or more blades 1 are evenly distributed circumferentially along the hub 8; there are multiple strain gauges 31, and at least one blade 1 is provided with multiple strain gauges 31 arranged at intervals along its length direction; the strain gauges 31 are all fixedly attached to the outer wall surface of the blade 1; the strain gauges 31 are electrically connected to the wireless strain tester 32 through wires, and the wires are fixedly attached to the outer wall surfaces of the corresponding blade 1, hub 8, and adapter shaft 2.

[0051] The even distribution of two or more blades 1 along the circumference of the hub 8 realizes the rotational balance of the rotating blade itself to reduce the interference of centrifugal vibration; arranging multiple strain gauges 31 at intervals along the length direction of the blade 1 can collect vibration data at different distances from the rotation center of the blade 1, providing data support for the research on the mechanical properties of the overall structure of the blade, and more reliable blade inherent frequency data can be obtained by taking the average of the data collected by multiple strain gauges 31 distributed at different positions on the blade.

[0052] In some embodiments, the strain gauge 31 is adhered to the outer wall surface of the blade 1 through the first adhesive layer 5, and the surface of the strain gauge 31 away from the blade 1 is covered with the second adhesive layer 6; the wire is arranged closely along the outer wall surfaces of the blade 1, the hub 8 and the adapter shaft 2 and is fixedly bonded through a colloid.

[0053] Specifically, the first adhesive layer 5 can be selected from double-sided tape or AB glue; the second adhesive layer 6 is selected as AB glue, and the AB glue covering the outside of the strain gauge 31 can be cured to form a protective shell layer.

[0054] The first adhesive layer 5 tightly adheres the blade 1 to the surface of the blade 1; the second adhesive layer 6 can play a role in protecting and strengthening the strain gauge 31, preventing the strain gauge 31 from being torn or shredded by the airflow under the high-speed rotation of the blade, thereby reducing the measurement error.

[0055] The pasting of the strain gauge and the layout of the wires for transmitting signals have an important impact on the aerodynamic load of the blade, and the firmness of its fixation has a great impact on the experimental safety. In addition, in order to ensure the safety of the test under the high-speed rotation state, static tests and dynamic balance tests should be carried out on the blades and related equipment used in the test before the test.

[0056] In some embodiments, it further includes a base 7, the rotary drive mechanism 4 is installed on the base 7, and the drive shaft of the rotary drive mechanism 4 is detachably connected to the rear end of the adapter shaft 2; the adapter shaft 2 is arranged horizontally.

[0057] Specifically, a shaft hole adapted to the drive shaft of the rotary drive mechanism 4 is opened on the rear end surface of the adapter shaft 2, and the drive shaft of the rotary drive mechanism 4 is inserted into the shaft hole and fixedly connected by bolts.

[0058] The base 7 provides a stable installation foundation for the rotary drive mechanism 4 to balance the reaction thrust of the airflow on the rotary drive mechanism 4 under the high-speed rotation of the blade; the drive shaft of the rotary drive mechanism 4 is detachably connected to the rear end of the adapter shaft 2, which is convenient for replacing different specifications of the adapter shaft 2 or replacing and repairing the adapter shaft 2.

[0059] Specifically, the rotary drive mechanism 4 can be selected from a motor or an engine.

[0060] On the other hand, the present invention provides a method for testing the natural frequency of a blade, including the above-mentioned device for testing the natural frequency of a blade, and the testing steps are as follows:

[0061] S1: Install the test device, install the blade to be tested on the hub, and fixedly install the hub at the front end of the adapter shaft;

[0062] S2: Fix a strain gauge on the outer wall of the blade, electrically connect the strain gauge to a wireless strain tester through a wire; communicatively connect the wireless data collector to the upper computer;

[0063] S3: Start the test. Drive the adapter shaft to rotate through the rotation drive mechanism, thereby driving the hub and the blades to rotate. When the blades rotate, they are excited by the air flow and vibrate. The strain gauges transmit the collected signals to the wireless strain tester, the wireless strain tester wirelessly transmits the signals to the wireless data collector, and the wireless data collector transmits the data signals to the host computer.

[0064] S4: The host computer uses dynamic signal test and analysis software to analyze and process the data to obtain the natural frequency.

[0065] In some embodiments, after the test device is installed, before starting the test, the test device is first subjected to dynamic balance test and correction to reduce the influence of the eccentric vibration of the test device on the test results.

[0066] Specifically, a plurality of threaded holes are evenly formed in the circumferential direction on the outer peripheral wall of the adapter shaft 2 near one side of the hub 8. Adapted adjustment bolts are threadedly connected in the threaded holes. The function of the adjustment bolts is to adjust and reduce the running eccentricity of the test device, so as to reduce the influence of the device eccentric vibration on the test. During the dynamic balance test and correction process, rotate the test device and observe the eccentric vibration condition of the adapter shaft 2. The mass distribution condition of the test device relative to the rotation center line of the adapter shaft 2 can be adjusted by adjusting the depth of the adjustment bolts screwed into the threaded holes, so as to correct the dynamic balance of the test device and reduce the rotation eccentric vibration amplitude of the adapter shaft 2 to meet the test requirements.

[0067] In some embodiments, the specific method for fixing the strain gauges on the outer wall of the blade is as follows: A plurality of strain gauges are evenly arranged from the tip to the root of the blade. Glue is coated on the side of the strain gauge close to the blade to paste the strain gauge on the blade surface, and glue is coated on the side of the strain gauge away from the blade and the periphery of the strain gauge to seal the strain gauge on the blade. Specifically, the strain signals of the blade collected by the strain gauges are transmitted to the wireless strain tester through wires, and the test signals are transmitted through the built-in wireless transmission module and the wireless router. On the host computer, that is, the PC side, the test data is collected, displayed and analyzed through the dynamic signal analysis software, and the test results are finally output through time-frequency conversion - spectrum analysis.

[0068] In some embodiments, the natural frequency test device of the rotating blade is arranged in a wind tunnel. The wind tunnel provides a constant-speed air flow, and the air flow direction of the wind tunnel is conveyed along the rotation axis direction of the rotating blade to test the natural frequency of the rotating blade under the impact of the air flow.

[0069] Specifically, the wireless strain tester, the wireless data collector and the host computer of the present invention are all selected from existing products.

[0070] Such as Figure 4As shown, the present invention tested the natural frequency test results of the blade to be measured at rotational speeds from 200 rpm to 2000 rpm, with the external wind speed being zero. Seven strain gauges were evenly distributed on the blade, and the selected strain gauge model was BF350-2HA. The test results show that as the rotational speed increases, the natural frequency of the blade shows an increasing trend; and the average natural frequency at different rotational speeds was given. Since the test method adopted by the present invention is closer to the actual working conditions of the propeller blades of an aircraft or other equipment, therefore, the natural frequency data obtained by the present invention through dynamic vibration testing under the rotating state of the blade is more reliable than the static blade test data, can more comprehensively reflect the aerodynamic characteristics of the blade, and the credibility of the test results is also higher.

[0071] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0072] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention. Therefore, the improvements and modifications made by those skilled in the art to the present invention based on the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. An inherent frequency testing device for a blade, wherein the blade (1) is installed on a hub (9). Characterized in that: Comprising: A transfer shaft (2), and the hub (9) is fixedly installed at the front end of the transfer shaft (2); A rotary drive mechanism (4), and a drive shaft of the rotary drive mechanism (4) is in transmission connection with the transfer shaft (2) to drive and control the rotation of the transfer shaft (2); A monitoring assembly (3), the monitoring assembly (3) includes a strain gauge (31), a wireless strain tester (32), a wireless data collector and a host computer; the strain gauge (31) is fixed on the blade (1); the wireless strain tester (32) is fixed on the transfer shaft (2); the strain gauge (31) is electrically connected to the wireless strain tester (32); the wireless strain tester (32) is in wireless communication connection with the wireless data collector, and the wireless data collector is in communication connection with the host computer.

2. The inherent frequency testing device for a blade according to claim 1, Characterized in that: A groove (21) is formed in the peripheral wall of the transfer shaft (2), the wireless strain tester (32) is embedded in the groove (21), and a fixing ring (22) is sleeved on the transfer shaft (2) corresponding to the groove (21) to limit and constrain the wireless strain tester (32) in the groove (21).

3. The inherent frequency testing device for a blade according to claim 1, Characterized in that: There are two or more blades (1), and two or more blades (1) are evenly distributed along the circumferential direction of the hub (9); There are multiple strain gauges (31), and at least one of the blades (1) is provided with multiple strain gauges (31) arranged at intervals along its length direction; the strain gauges (31) are all fixedly attached to the outer wall surface of the blade (1); the strain gauges (31) are electrically connected to the wireless strain tester (32) through wires, and the wires are fixedly attached to the outer wall surfaces of the corresponding blade (1), hub (9) and transfer shaft (2).

4. The inherent frequency testing device for a blade according to claim 3, Characterized in that: The strain gauge (31) is pasted on the outer wall surface of the blade (1) through an adhesive layer 1 (5), and the surface of the strain gauge (31) away from the blade (1) is covered with an adhesive layer 2 (6); the wire is adhesively bonded to the outer wall surfaces of the blade (1), hub (9) and transfer shaft (2) through a colloid.

5. The inherent frequency testing device for a blade according to claim 1, Characterized in that: It further includes a base (7), the rotary drive mechanism (4) is installed on the base (7), and the drive shaft of the rotary drive mechanism (4) is detachably connected to the rear end of the transfer shaft (2).

6. An inherent frequency testing method for a blade, Characterized in that: It includes the inherent frequency testing device for a blade according to any one of claims 1-5, and the testing steps are: S1: Install the testing device, install the blade to be tested on the hub, and fixedly install the hub at the front end of the transfer shaft; S2: Fix strain gauges on the outer wall of the blade, and electrically connect the strain gauges to a wireless strain tester through wires; communicatively connect the wireless data collector to the host computer; S3: Start the test. Drive the adapter shaft to rotate through the rotary drive mechanism, thereby driving the hub and the blade to rotate; when the blade rotates, it is excited by the airflow to cause vibration. The strain gauge transmits the collected signal to the wireless strain tester, the wireless strain tester wirelessly transmits the signal to the wireless data collector, and the wireless data collector transmits the data signal to the host computer; S4: The host computer uses dynamic signal test and analysis software to analyze and process the data to obtain the natural frequency.

7. The method for testing the natural frequency of a blade according to claim 6, wherein, after the test device is installed, before starting the test, the test device is first subjected to dynamic balance test and calibration.

8. The method for testing the natural frequency of a blade according to claim 6, wherein, the specific method for fixing the strain gauge on the outer wall of the blade is as follows: a plurality of strain gauges are uniformly arranged from the tip to the root of the blade, glue is coated on the side of the strain gauge close to the blade to paste the strain gauge on the blade surface, and glue is coated on the side of the strain gauge away from the blade and the periphery of the strain gauge to seal the strain gauge on the blade.

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