A fast test identification method for blade detuning frequency of an integral blisk structure

Abstract

The present invention discloses a method for rapid test identification of blade detuning frequencies in an integral blade disk structure. The method involves attaching identical detuning masses to the same positions of all non-test blades, other than the currently tested blade, to significantly reduce the vibration coupling effect between the blade and its adjacent blades. Furthermore, through a dual-blade detuning vibration test, the vibration of a single blade is isolated from the integral blade disk, and the impact of the residual inter-blade vibration coupling effect of the integral blade disk on the vibration frequency test results of the "independent" blades is evaluated to obtain a fully decoupled blade vibration frequency. Furthermore, a differentiated distribution of all blade vibration frequencies is obtained, enabling rapid test identification of blade detuning. This method boasts high test efficiency, strong operability, and high accuracy in identifying blade detuning frequencies, making it suitable for widespread application in engineering practice.

Description

Technical Field

[0001] The invention relates to a method for quickly testing and identifying the detuning frequency of blades in an integral blade disk structure of an axial-flow compressor of an aero-engine, and belongs to the technical field of aerospace. Background Art

[0002] The integrated blisk eliminates the tenon joints and locking mechanisms found in traditional split-blade designs. It is a core technology for the lightweight and integrated design of advanced aeroengine axial compressor / fan components. In an ideal blisk structure, each blade possesses identical geometric and physical properties, resulting in a tuned blisk. However, factors such as manufacturing variations and operational wear in the physical structure of a blisk inevitably lead to minor variations in the geometric and physical properties of individual blades, known as random blade detuning, which is reflected in their vibration frequencies. Random blade detuning has a significant impact on the dynamic characteristics of the blisk. Firstly, random blade detuning disrupts the cyclic symmetry of the ideal blisk structure, causing vibration energy to no longer be evenly distributed across all blades. Instead, it may be concentrated in a few blades, resulting in modal localization and an "amplitude amplification effect." Coupled with its lower structural damping, an integrated blisk typically exhibits higher vibration levels and a higher risk of high-cycle fatigue failure than a split-blade design under the same conditions.

[0003] In engineering practice, engineers often employ specialized vibration testing and identification methods to determine the random detuning distribution of blades within the physical structure of a non-detachable blisk. This process is known as blade detuning identification. Traditional blade detuning identification methods are generally based on a reduced-order dynamic model of the detuned blisk. They take modal test data of the physical blisk structure (including the entire disk's modal frequencies and mode shapes) as input and, through mathematical inverse derivation, obtain the differentiated distribution of "independent" blade frequencies or blade model elastic modulus parameters. Traditional blade detuning identification methods based on blisk modal testing fall into the category of inverse vibration problems. In practical applications, blade detuning identification results are easily affected by errors in the input full-disk modal shape data. Furthermore, obtaining high-quality full-disk modal test data is a significant investment of experimental time and specialized testing skills to ensure the validity of the blade detuning identification results. However, blisks inherently have a densely distributed modal distribution. Furthermore, the heavy modal separation caused by blade detuning further exacerbates this phenomenon. This makes it difficult for standard single-input modal testing to effectively excite all modal vibrations of a detuned blisk. Furthermore, identifying the modal parameters of a detuned blisk is technically challenging. In summary, traditional blade detuning identification based on blisk modal testing and reduced-order dynamic models is inherently difficult and challenging.

[0004] In summary, blisk vibration is highly sensitive to random blade mismatch. Achieving more efficient and reliable identification of random blade mismatch, and thus accurately predicting dangerous blade vibrations in the blisk's physical structure, has long been a challenge in blisk structural dynamics and high-cycle fatigue design. Summary of the Invention

[0005] To solve the problem of random detuning of blades in an axial compressor bladed disk structure, the present invention provides a rapid test and identification method for blade detuning frequency based on a double-blade deharmonic vibration test. The specific steps are as follows:

[0006] Step 1: Obtain the modal vibration shape and modal kinetic energy distribution of the blade finite element model of the integral blade disk under the fixed boundary condition;

[0007] Step 2: Select the detuning mass and attach it to the same position of all non-test blades except the blade j to be tested, thus completing the detuning mass layout.

[0008] Step 3: Carry out the first blade deharmonic vibration test for the blade j to be tested, and obtain the first deharmonic vibration test frequency response function of a single measuring point of the blade j to be tested;

[0009] Step 4: For the first deharmonic vibration test frequency response function obtained in step 3, extract the first isolated peak frequency and record it as ;

[0010] Step 5: Based on the detuning mass layout scheme of step 2, an additional set of detuning masses identical to the detuning masses selected in step 2 is added at the same positions of all non-test blades except the blade j to be tested;

[0011] Step 6: Perform a second deharmonic vibration test on the blade j to be tested, and obtain a second deharmonic vibration test frequency response function of the same measuring point of the blade j to be tested;

[0012] Step 7: For the second deharmonic vibration test frequency response function obtained in step 6, extract the second isolated peak frequency and record it as ;

[0013] Step 8: Compare the first isolated peak frequency extracted in step 4 and step 7 and the second isolated peak frequency ,like and If the difference between the two values ​​is less than the set threshold, it is considered that the blade j to be tested has reached the ideal vibration decoupling state in the two blade deharmonic vibration tests, and the second isolated peak frequency is regarded as the detuning frequency of the blade j to be tested; otherwise, return to step 2 and re-do the detuning mass layout until the blade to be tested reaches the ideal vibration decoupling state in the two blade deharmonic vibration tests;

[0014] Step 9, for all leaves ( ) Repeat steps 2 to 8 to obtain the detuning frequency of each blade and complete the rapid test identification of the detuning frequency of the blades of the entire blade disk structure, where N is the total number of blades.

[0015] The present invention also provides a device for rapid testing and identifying the detuning frequency of blades in an integral blade disk structure, comprising a soft pad and an integral blade disk structure placed horizontally thereon, a tuning mass arranged at the same position of all non-test blades except the blade to be tested, a force hammer, a non-contact Doppler laser vibrometer, and a data acquisition system;

[0016] A hammer is used to apply excitation to the blade to be tested at a set position, and a non-contact Doppler laser vibrometer is used to pick up vibration at the tip of the blade to be tested;

[0017] Based on the above method, the data acquisition system obtains two blade detuning vibration test results of all blades, completing the rapid experimental identification of the blade detuning frequency of the entire blade disk structure.

[0018] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0019] 1. This paper proposes a rapid test-based identification method for detuned frequencies of blisks based on blade deharmonic vibration testing. This method can directly and rapidly measure the nearly "independent" vibration frequencies of each blade and obtain the distribution of random detuned frequencies at low test costs and time. Compared to traditional blade detuning identification methods based on blisks modal testing and reduced-order dynamic models, this method offers the advantages of high test efficiency, strong operability, and simplified data post-processing, making it more suitable for practical engineering applications.

[0020] 2. The dual-blade deharmonic vibration test method proposed in this invention experimentally evaluates the impact of the residual inter-blade vibration coupling effect of the integral blade disk on the "independent" blade vibration frequency test results. On the one hand, it provides a simple and efficient technical approach for evaluating the effectiveness of blade deharmonic vibration testing (i.e., the degree of "single" blade vibration decoupling); on the other hand, it can also improve the accuracy of the blade random detuned frequency identification results. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1Schematic diagram of the rapid test and identification device for blade detuning frequency of an integral blisk structure.

[0022] Figure 2 This is the frequency response function of the conventional vibration test of blade No. 1 when the integral blade disk has no additional detuning mass.

[0023] Figure 3 This is a comparison chart of the frequency response functions of the deharmonic vibration test of blade No. 1 in the first blade deharmonic vibration test of the integral blade disk.

[0024] Figure 4 Schematic diagram of the second blade deharmonic vibration test of the integral blisk.

[0025] Figure 5 This is a comparison chart of the frequency response functions of the deharmonic vibration test of blade No. 1 in the second blade deharmonic vibration test of the integral blade disk. DETAILED DESCRIPTION

[0026] Below Figure 1 Taking the axial flow compressor integral blade disk structure in the embodiment as an example, the blade deharmonic vibration test device and the blade detuning frequency rapid test identification method involved in the present invention are described.

[0027] like Figure 1 The device for rapid testing and identification of blade detuning frequencies of an integral blade disk structure is shown, wherein the integral blade disk structure is placed horizontally on a soft cushion, and detuning masses are provided at the same positions of all non-test blades except the blade currently under test. A force hammer is used to apply excitation to the blade currently under test at a set position, while a non-contact Doppler laser vibrometer is used to pick up vibrations at the tip of the blade currently under test. Based on the excitation signal applied by the force hammer and the velocity response signal obtained by the non-contact Doppler laser vibrometer, the data acquisition system obtains the detuning vibration test frequency response function of two blade detuning vibration tests of the blade currently under test, thereby completing the rapid test identification of the blade detuning frequencies of the integral blade disk structure. It should be noted that the method for rapid testing and identification of blade detuning frequencies proposed in the present invention is also applicable to integral blade disk structures in an installed state.

[0028] The blade deharmonic vibration test requires the addition of the same detuning mass at the same position on all non-test blades other than the currently tested blade to completely destroy the cyclic symmetry of the overall blade disk structure, thereby weakening the inter-blade vibration coupling effect of the overall blade disk. The size, size and position of the detuning mass on the blade determine the success of the blade deharmonic vibration test. The selection and arrangement criteria for the detuning mass are: the size of the detuning mass should cover the area with the maximum kinetic energy density in the target order modal vibration of the blade, so that the modal vibration frequency of the "single" blade after the detuning mass is added can reach the maximum possible variation range. The weight of the detuning mass (g) This is not a strict requirement and can be reasonably adjusted based on the results of subsequent blade deharmonic vibration tests.

[0029] In order to illustrate the necessity of blade detuning vibration testing, the conventional vibration test frequency response function of the blade is first obtained using the above-mentioned test device and hammer method for the integral blade without any detuning mass. Figure 2 The measured frequency response function of blade number 1 within the frequency range of the first bending mode family of the blisk is shown. This figure shows that vibration coupling between adjacent blades in the blisk results in a densely distributed modal pattern. This, combined with the heavy mode separation effect caused by blade detuning, results in multiple peaks in the frequency response function of the blade's conventional vibration test. Clearly, the frequency response function of a conventional hammer vibration test cannot identify the vibration frequencies of "independent" blades.

[0030] To further illustrate the technical solution of the present invention, the following takes a detuning mass composed of two identical disc-shaped magnets as an example. Figure 1 As shown in the figure, two identical disc-shaped magnets are attached to a fixed position on the blade by mutual attraction. The essence of the blade detuning vibration test is to use the hammer method to obtain the test frequency response function of a single measuring point on the blade to be tested without additional detuning mass, so as to quickly measure the vibration frequency of an approximately "independent" blade. Figure 1 As shown, a small hammer can be used to excite the blade at the appropriate location, while a non-contact Doppler laser vibrometer is used to pick up vibrations at the blade tip. The hammer excitation signal and the laser vibrometer velocity response signal are input into the data acquisition system. After signal processing, the deharmonic vibration test frequency response function corresponding to the blade is obtained.

[0031] Since the detuning mass can be weakened, but the inter-blade vibration coupling effect of the integral blade disk cannot be completely eliminated. For this reason, the present invention proposes to carry out a second blade detuning vibration test to evaluate the impact of the residual inter-blade vibration coupling effect and improve the accuracy of the blade detuning frequency identification results. The present invention "isolates" the vibration of a "single" blade from the integral blade disk through a double blade detuning vibration test, thereby obtaining a completely decoupled blade vibration frequency, and further obtains a differentiated distribution of all blade vibration frequencies, thereby realizing rapid experimental identification of blade detuning. The implementation process is described in detail below.

[0032] 1. First blade deharmonic vibration test:

[0033] (1) The finite element model of the blade is obtained from the integral blade disk design model. Displacement constraints are imposed on its root. Simulation calculations are performed in the finite element software to obtain the modal vibration shape and modal kinetic energy distribution of the target order of the clamped blade.

[0034] (2) Adoption Figure 1 The disc-shaped magnet shown serves as a detuning mass and is attached to the same location on all non-test blades except the blade currently under test.

[0035] (3) Carry out the first blade deharmonic vibration test for the blade No. 1 to be tested, that is, use the hammer method to obtain the deharmonic vibration test frequency response function of a single measuring point of the blade. Note that for different target modal orders of the blade, it is usually necessary to change its hammer excitation position until a smooth test frequency response function with significant vibration decoupling is generated, such as Figure 3 In addition, when the integral blade disk does not have any detuning mass attached, the frequency response function of the conventional hammer vibration test of blade 1 is also Figure 3 Make a comparative display.

[0036] (4) Observation Figure 3 , additional detuning mass of the non-test blade of the integral blisk After that, the deharmonic vibration test frequency response function of blade 1 shows a significant isolated peak in the frequency range of the first bending mode family of the integral blade. The peak frequency is extracted and recorded as , where the superscript “ ” indicates the first detuned vibration test, with the subscript “1” corresponding to blade number 1. This demonstrates that the presence of the detuned mass significantly weakens the vibration coupling between blade number 1 and its adjacent blades. When blade number 1 is subjected to hammer excitation, the vast majority of the vibration energy of the entire blisk is concentrated on that blade, causing it to exhibit vibration characteristics similar to those of an “independent” blade, a phenomenon known as vibration decoupling.

[0037] However, it must be emphasized that the isolated peak frequencies in the frequency response function of the blade deharmonic vibration test are not strictly speaking the modal vibration frequencies of the "independent" blade. During deharmonic vibration testing, the residual inter-blade vibration coupling effects within the integral blade disk structure depend not only on the adequacy of the detuned mass vibration decoupling effect but also on the strength of the inter-blade vibration coupling effects within the different modal families of the integral blade disk itself. This can still have a significant impact on the measured isolated peak frequencies.

[0038] To this end, the present invention proposes to carry out a second blade detuning vibration test to evaluate the influence of the residual inter-blade vibration coupling effect and improve the accuracy of the blade detuning frequency identification results.

[0039] 2. Second blade deharmonic vibration test:

[0040] (1) Based on the detuning mass layout scheme in the first blade detuning vibration test, an additional set of identical disc-shaped magnets is added at the same position of all non-test blades except the blade to be tested, so that the detuning mass is (g), such as Figure 4 shown.

[0041] (2) Carry out the second blade deharmonic vibration test on blade No. 1, that is, use the hammer method to obtain the deharmonic vibration test frequency response function of a single measuring point on the blade.

[0042] (3) Compare the deharmonic vibration test frequency response functions of the two deharmonic vibration tests of blade No. 1, as shown in Figure 2. Figure 5 shown. Figure 5 The additional detuned mass of the non-test blades of the blisk is shown in After that, the deharmonic vibration test frequency response function of blade 1 also shows a significant isolated peak in the frequency range of the first bending mode family of the integral blade. The peak frequency obtained in the first detuning vibration test is There are only slight differences, which are far smaller than the set threshold and can be ignored.

[0043] The above test results show that in the first blade detuning vibration test, the residual inter-blade vibration coupling effect of the entire blade disk is already at an extremely low level, and the No. 1 test blade has achieved a relatively sufficient vibration decoupling effect. After that, the peak frequencies obtained from the two deharmonic vibration tests for the same test blade are basically the same. At this point, it can be considered that in the second blade deharmonic vibration test, the bending mode vibration of the "single" blade has been completely "isolated" from the entire blade disk, and its isolated peak frequency is This can be considered the fully decoupled vibration frequency of blade 1, i.e., the detuned frequency. Therefore, the dual-blade detuned vibration test proposed in this invention rapidly evaluates the impact of residual inter-blade vibration coupling through experiments, providing a simple and efficient technical approach for measuring the vibration frequencies of nearly completely "independent" blades.

[0044] 3. Refer to the second blade deharmonic vibration test and test all The blade repeats the blade deharmonic vibration test to obtain the corresponding blade deharmonic vibration test isolated peak frequency , and the differentiated distribution of blade detuning frequency can be further calculated: ,in Represents the average of all isolated peak frequencies of blade deharmonic vibration tests.

[0045] The present invention proposes a rapid test identification method for the detuned frequency of blades in an integral blade disk structure to obtain the vibration frequency distribution of each "independent" blade in an integral blade disk structure of an axial flow compressor with non-detachable blades. The core of the blade detuned vibration test is to attach the same detuned mass to the same position of all non-test blades other than the current blade to be tested to significantly weaken the vibration coupling effect between the blade and its adjacent blades. In this way, the vibration of a single blade can be isolated from the integral blade disk structure, and the nearly completely "independent" vibration frequency of each blade can be directly and quickly measured at a low test economy and time cost. The dual-blade detuned vibration test aims to evaluate the impact of the residual inter-blade vibration coupling effect of the integral blade disk on the vibration frequency test results of the "independent" blades through experiments, further improving the accuracy of the blade random detuned frequency identification results. This method has the advantages of high test efficiency, strong operability and high accuracy of blade detuned frequency identification, and is suitable for promotion and application in engineering practice.

[0046] Based on the same technical solution, the present invention also provides an electronic device, comprising:

[0047] Memory for storing computer programs;

[0048] The processor is configured to implement the steps of the above-mentioned method for rapid test identification of detuned frequency of blades in an integral blade disk structure when executing the computer program.

[0049] Based on the same technical solution, the present invention also provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the steps of the aforementioned method for rapidly testing and identifying the detuned frequency of blades in an integral blisk structure. The computer-readable storage medium may include any medium capable of storing program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0050] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the above-described method embodiments. Any reference to memory, storage, database, or other media used in the various embodiments provided herein may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct RAMbus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM).

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for rapid test identification of blade detuning frequency of an integral blisk structure, characterized in that: The specific steps are as follows: Step 1: Obtain the modal vibration shape and modal kinetic energy distribution of the blade finite element model of the integral blade disk under the fixed boundary condition; Step 2: Select the detuning mass and attach it to the same position of all non-test blades except the blade to be tested, thus completing the detuning mass layout. Step 3: Carry out the first blade deharmonic vibration test for the current blade to be tested, and obtain the first deharmonic vibration test frequency response function of a single measuring point of the current blade to be tested; Step 4: extracting the first isolated peak frequency from the first deharmonic vibration test frequency response function obtained in step 3; Step 5: Based on the detuning mass layout scheme of step 2, an additional set of detuning masses identical to the detuning masses selected in step 2 is added at the same positions of all non-test blades except the current blade to be tested; Step 6: Conduct a second deharmonic vibration test on the blade to be tested, and obtain a second deharmonic vibration test frequency response function of the same measuring point of the blade to be tested; Step 7: extracting the second isolated peak frequency from the second deharmonic vibration test frequency response function obtained in step 6; Step 8: Compare the first and second isolated peak frequencies extracted in Step 4 and Step 7. If the difference between the first and second isolated peak frequencies is less than the set threshold, it is considered that the current blade to be tested has reached the ideal vibration decoupling state in the two blade deharmonic vibration tests, and the second isolated peak frequency is regarded as the detuned frequency of the current blade to be tested; otherwise, return to Step 2 and re-perform the detuned mass layout until the current blade to be tested reaches the ideal vibration decoupling state in the two blade deharmonic vibration tests; Step 9: Repeat steps 2 to 8 for all blades to obtain the detuning frequency of each blade, and complete the rapid test identification of the detuning frequency of the blades of the entire blade disk structure.

2. The method according to claim 1, characterized in that Step 1 is as follows: The finite element model of the blade is obtained from the integral blade disk design model, displacement constraints are imposed on its root, and simulation calculations are carried out in the finite element software to obtain the modal vibration shape and modal kinetic energy distribution of the target order of the clamped blade.

3. The method according to claim 1, characterized in that The selection and layout criteria for the detuning mass in step 2 are: The size of the detuning mass is such that it covers the region with the maximum kinetic energy density in the target-order modal vibration of the blade.

4. The method according to claim 1, wherein In both steps 3 and 6, the hammering method is used to obtain the first and second deharmonic vibration test frequency response functions of a single measuring point of the blade to be tested: A hammer is used to apply excitation to the blade to be tested at a set position, and a non-contact Doppler laser vibrometer is used to pick up vibration at the tip of the blade to be tested; Based on the excitation signal applied by the hammer and the velocity response signal obtained by the non-contact Doppler laser vibrometer, the deharmonic vibration test frequency response function of the blade to be tested is obtained.

5. The method according to claim 1, wherein The method further includes: Based on the detuning frequency of each blade, the frequency detuning amount of each blade is calculated to obtain the differentiated distribution of the blade detuning frequency.

6. The method according to claim 5, characterized in that The frequency detuning of each blade is: ， Where, is the frequency detuning of blade j, is the detuned frequency of blade j, is the mean of the detuned frequencies of all blades, and N is the total number of blades.

7. A device for rapid testing and identifying the detuning frequency of blades in an integral blade disk structure, characterized in that: It includes a soft pad and an integral blade disk structure placed horizontally thereon, a tuning mass set at the same position of all non-test blades except the blade to be tested, a force hammer, a non-contact Doppler laser vibrometer, and a data acquisition system; A hammer is used to apply excitation to the blade to be tested at a set position, and a non-contact Doppler laser vibrometer is used to pick up vibration at the tip of the blade to be tested; The data acquisition system obtains two blade detuning vibration test results of all blades based on the method according to any one of claims 1 to 6, and completes the rapid test identification of the detuning frequency of the blades of the integral blade disk structure.

8. The device according to claim 7, characterized in that Each tuning mass consists of two identical magnets attached to the blades by mutual attraction.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which implements the steps of the method according to any one of claims 1 to 6 when executed by a processor.

10. An electronic device, characterized in that: include: memory for storing computer programs; A processor, configured to implement the steps of the method according to any one of claims 1 to 6 when executing the computer program.

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