Civil turboshaft engine accessory environment vibration test method

Abstract

The invention discloses a civil turboshaft engine accessory environment vibration test method comprising the following steps: S1, carrying out an engine whole machine maximum imbalance test, and compiling an accessory environment test vibration spectrum according to vibration data in three different directions obtained by three vibration sensors during the test; s2, accessory finite element calculation analysis is carried out, accessory connection rigidity is corrected through an accessory knock frequency test and then substituted, so that the calculated resonance frequency is consistent with the knock frequency resonance frequency, and then accessory vibration safety is preliminarily judged through a finite element vibration response calculation analysis result; s3, carrying out an initial accessory environment vibration test in three vibration directions, and correcting the rigidity design of the switching section according to the maximum unbalance test data; and S4, after rigidity correction of the accessory and the switching section is completed, a final accessory environment vibration test is carried out. According to the method, the vibration environment of the engine in all directions is comprehensively considered, a certain margin is considered, the accessory environment test spectrum is accurately defined, and technical support is provided for engine vibration airworthiness conformity.

Description

Technical Field

[0001] This application relates to the technical field of turboshaft engines, and particularly to a method for environmental vibration testing of accessories of a civil turboshaft engine. Background Art

[0002] According to the requirements of the airworthiness clause CCAR.63, the design and construction of each type of engine must enable the engine to operate properly throughout its declared flight envelope and the entire operating range of speed and power or thrust, and should not cause excessive stress on any engine component due to vibration, nor should it transmit excessive vibration forces to the aircraft structure.

[0003] Engine accessories belong to the external components of the engine. According to the specific requirements of the Airworthiness Authority Advisory Circular AC33.63, "Vibration tests can be carried out on the engine, or on a vibration table in the laboratory, or both methods can be used. To determine whether to conduct a full-engine test or a laboratory test, or both, at least the vibration environment of the external components should be clear, and whether the laboratory test equipment is suitable for that component and can accurately reflect its vibration environment should be considered." For engine accessories, generally, the accessory environmental test is carried out on a vibration table in the laboratory to demonstrate vibration compliance. The determination of the vibration spectrum is the key technology. An overly small vibration spectrum cannot cover the usage requirements of the engine vibration environment, while an overly large vibration spectrum is likely to cause excessive vibration stress on the accessory and lead to damage, resulting in the inability to pass the test.

[0004] The existing method mainly compiles the accessory vibration spectrum based on Chapter 8 "Vibration Tests" of "RTCA / DO-160G Environmental Conditions and Test Procedures for Airborne Equipment". According to the compilation method of "Vibration Tests", following the vibration test procedure for airborne equipment on a helicopter, a test frequency and magnitude of sine superposition random are adopted, and the specified sine frequency is .

[0005] The existing technology has the following technical problems: 1) The sine test magnitudes in each direction are fixed, such as 20g for all, without considering the actual vibration level of the engine. The assessment is too severe, resulting in many accessory assessment tests failing to pass.

[0006] 2) The existing technology only requires according to "RTCA / DO-160G Environmental Conditions and Test Procedures for Airborne Equipment" that "the installation of the equipment under test should make the input vibration motion parallel to one of the three main orthogonal axes of the equipment", without considering the installation direction of the equipment under test on the engine.

[0007] 3) The design confirmation of the adapter section has not been carried out, affecting the correctness of the test. Summary of the Invention

[0008] In view of the above technical problems, the present application provides a method for environmental vibration testing of accessories of a civil turboshaft engine.

[0009] The present application is implemented through the following solutions: A method for environmental vibration testing of accessories of a civil turboshaft engine, including the steps of: S1. Analyze the maximum unbalance of the engine and conduct the maximum unbalance test of the whole engine. During the test, install three vibration sensors for detecting vibrations in the X, Y, and Z directions respectively near the accessories, and compile the vibration spectrum for the accessory environmental test according to the vibration data in three different directions obtained by the three vibration sensors. Among them, when compiling the vibration spectrum for the accessory environmental test, design a single-segment vibration spectrum for the amplitude of the excitation R4 of the power turbine according to a single vibration value, and conduct a segmented vibration spectrum design for the amplitude of the excitation R5 of the gas generator according to different vibration values after segmentation; S2. Conduct finite element calculation and analysis of the accessories. Modify the connection stiffness of the accessories through the accessory frequency knocking test and then substitute it to make the calculated resonance frequency consistent with the frequency knocking resonance frequency, and the error meets the engineering design requirements. Then, preliminarily judge the vibration safety of the accessories through the finite element vibration response calculation and analysis results; S3. Design the adapter section and conduct the initial accessory environmental vibration test in three vibration directions. Among them, the three vibration directions during the accessory environmental vibration test are the same as the vibration directions during the maximum unbalance test of the whole engine, and modify the stiffness design of the adapter section according to the maximum unbalance test data; S4. After completing the stiffness correction of the accessories and the adapter section, conduct the final accessory environmental vibration test.

[0010] Further, the X direction is consistent with the engine axis direction, and the Y direction is orthogonal to the X direction and the Z direction.

[0011] Further, in step S1, when designing a single-segment vibration spectrum for the amplitude of the excitation R4 of the power turbine according to a single vibration value, conduct single-segment vibration spectrum design respectively according to the vibration data in three different directions obtained by the three vibration sensors, and the selected single-segment vibration spectrum amplitude meets the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1.

[0012] Further, in step S1, when conducting a segmented vibration spectrum design for the amplitude of the excitation R5 of the gas generator according to different vibration values after segmentation, it specifically includes the steps of: Analyze the vibration response of the accessories at different frequencies, and determine in advance the maximum vibration excitation that the accessories can withstand at different frequencies through tests; Segment the amplitude of the excitation R5 of the gas generator according to the maximum vibration excitation that the attachment can withstand at different frequencies, and then design the segmented vibration spectrum according to different vibration magnitudes. Among them, the amplitude of each segmented vibration spectrum satisfies the following condition: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1.

[0013] Furthermore, when segmenting the amplitude of the excitation R5 of the gas generator and designing the segmented vibration spectrum according to different vibration magnitudes, only design the segmented vibration spectrum based on the vibration data obtained by the X-direction vibration sensor. Among them, the amplitude of each segmented vibration spectrum satisfies the following condition: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1; For the vibration data obtained by the Y-direction vibration sensor and the vibration data obtained by the Z-direction vibration sensor, respectively design a single-segment vibration spectrum for the amplitude of the excitation R5 of the power turbine according to a single vibration magnitude. The selected single-segment vibration spectrum amplitude satisfies the following condition: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1.

[0014] Furthermore, in step S2, initially judge the vibration safety of the attachment through the finite element vibration response calculation and analysis results, which specifically includes the steps: Establish a finite element model of the attachment, input the vibration spectrum as the excitation condition, and calculate the vibration response of the attachment under random excitation; In the calculated vibration response, take the vibration response stress value at a 3σ confidence level, and find the maximum vibration response stress in the entire attachment; When the maximum vibration response stress at a 3σ confidence level × 1.2 < the allowable stress value of the material, it is judged that the attachment structure design is safe. Otherwise, it is judged that the attachment structure design is unsafe and the attachment structure design needs to be modified.

[0015] Furthermore, establish a finite element model of the attachment through the commercial software ansys.

[0016] Furthermore, in step S3, when correcting the stiffness design of the adapter section according to the maximum unbalance test data, when the error between all the resonance frequencies within the operating speed range in the initial attachment environmental vibration test in each direction of the component and the resonance frequencies in the engine's maximum unbalance test is less than or equal to 5%, the stiffness design of the adapter section is completed.

[0017] Furthermore, all the resonance frequencies specifically refer to the ones with the largest amplitude within the operating speed range in the initial attachment environmental vibration test in each direction of the component, and there are no more than four resonance frequencies.

[0018] Furthermore, step S4 specifically includes the steps: Based on the modified adapter section and the accessory, connect the accessory to the shaker through the adapter section. The excitation direction of the shaker is the same as that during the maximum unbalance test of the entire engine, and conduct the final accessory environmental vibration test according to the specified test procedures.

[0019] Compared with the prior art, the present application has the following beneficial effects: 1) The present application uses the test value of the maximum unbalance test (with a certain margin considered) as the vibration value of R4 and R5, which is more in line with the actual situation.

[0020] 2) The present application requires the engine placement direction to be the test direction, which is more representative. Only in this way can the test values of component tests correspond to those of the entire engine test (maximum unbalance test).

[0021] 3) The present application requires the adapter section design confirmation work to be carried out before the accessory environmental test, so as to more accurately simulate the installation environment of the accessory.

[0022] 4) The segmented design of the accessory environmental vibration spectrum in the present application is more in line with the actual situation, facilitating the accurate grasp of the excitation magnitude of the engine on the accessory.

[0023] 5) The present application comprehensively considers the vibration environments in all directions of the engine, with a certain margin considered, and precisely defines the accessory environmental test spectrum, providing technical support for the engine vibration airworthiness compliance.

[0024] In addition to the purposes, features, and advantages described above, the present application has other purposes, features, and advantages. The following will further elaborate on the present application with reference to the drawings. Brief Description of the Drawings

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application: Figure 1 It is a schematic flow diagram of the method for the accessory environmental vibration test of a civil turboshaft engine in a preferred embodiment of the present application; Figure 2 It is a schematic diagram of the engine installation direction in the present application; Figure 3 It is a schematic diagram of the accessory vibration R4 test spectrum and the measured vibration test amplitude (X direction); Figure 4 It is a schematic diagram of the accessory vibration R5 test spectrum and the measured vibration test amplitude (X direction); Figure 5 It is a schematic diagram of the installation position of the accessory on the engine; Figure 6 It is a schematic diagram of the installation position of the accessory on the shaker.

[0026] In the figure: 1. Main installation section; 2. Aeroengine; 3. Engine axis; 4. Auxiliary installation section; 5. Accessories; 6. Adapter section; 7. Shaker table. Specific implementation manners

[0027] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. However, the present application can be implemented in many different ways defined and covered by the following.

[0028] As Figure 1 shown, a preferred embodiment of the present application provides a method for environmental vibration test of civil turboprop engine accessories, including the steps of: S1. Analyze the maximum unbalance of the engine and conduct the maximum unbalance test of the whole engine. During the test, install three vibration sensors for detecting vibrations in the X, Y, and Z directions respectively near the accessories, and compile the vibration spectrum for the accessory environmental test according to the vibration data in three different directions obtained by the three vibration sensors. Among them, when compiling the vibration spectrum for the accessory environmental test, design a single-segment vibration spectrum for the amplitude of the excitation R4 of the power turbine according to a single vibration value, and design a segmented vibration spectrum for the amplitude of the excitation R5 of the gas generator in segments according to different vibration values; S2. Conduct finite element calculation and analysis of the accessories. Modify the connection stiffness of the accessories through the accessory frequency knocking test and then substitute it to make the calculated resonance frequency consistent with the frequency knocking resonance frequency, and the error meets the engineering design requirements. Then, preliminarily judge the vibration safety of the accessories through the finite element vibration response calculation and analysis results; S3. Design the adapter section and conduct the initial accessory environmental vibration test in three vibration directions. Among them, the three vibration directions during the accessory environmental vibration test are the same as those during the maximum unbalance test of the whole engine, and modify the stiffness design of the adapter section according to the maximum unbalance test data; S4. After completing the stiffness modification of the accessories and the adapter section, conduct the final accessory environmental vibration test.

[0029] Compared with the prior art, the present embodiment has the following beneficial effects: 1) In this embodiment, the test values of the maximum unbalance test of the whole engine (with a certain margin considered) are used as the vibration values of R4 and R5, which is more in line with the actual situation.

[0030] 2) This embodiment requires that the test direction be the placement direction of the engine, which is more representative. The test values of the component test can correspond to the test values of the whole engine test (maximum unbalance test).

[0031] 3) This embodiment requires that the design confirmation work of the adapter section be carried out before the accessory environmental test, so that the installation environment of the accessories can be simulated more accurately.

[0032] 4) The segmented design of the accessory environmental vibration spectrum of this application is more in line with the actual situation, facilitating the accurate grasp of the excitation magnitude of the engine on the accessories.

[0033] 5) This embodiment comprehensively considers the vibration environment in all directions of the engine and takes into account a certain margin, precisely defining the accessory environmental test spectrum, providing technical support for the airworthiness compliance of engine vibration.

[0034] Specifically, the X direction is consistent with the direction of the engine axis 3, and the Y direction is orthogonal to the X and Z directions. Analyze the maximum unbalance of the aeroengine 2 and conduct the maximum unbalance test of the whole machine. The aeroengine 2 is installed on the test bench through the main mounting bracket 1 and the auxiliary mounting bracket 4. Three vibration sensors in different directions are installed near the accessory 5 to obtain vibration data in three different directions. The three vibration sensors must be axial and radial (for example: horizontal, vertical), defined as the X direction, Y direction, and Z direction, and the Y direction is the horizontal direction, orthogonal to the X and Z directions. As Figure 2 shown. Then, use the vibration data obtained by the three vibration sensors in the X, Y, and Z directions to compile the accessory environmental test vibration spectrum.

[0035] The existing technology only requires according to "RTCA / DO-160G Environmental Conditions and Test Procedures for Airborne Equipment" that "the installation of the equipment under test should make the input vibration motion parallel to one of the three main orthogonal axes of the equipment". The installation direction of the equipment under test on the engine is not considered. This embodiment requires taking the placement direction of the aeroengine as the test direction, which is more representative. Only in this way can the test values of the component test correspond to the test values of the whole machine test (maximum unbalance test).

[0036] The existing method mainly compiles the accessory vibration spectrum based on Chapter 8 "Vibration Test" of "RTCA / DO-160G Environmental Conditions and Test Methods for Airborne Equipment". According to the compilation method of "Vibration Test", following the vibration test procedure of airborne equipment on helicopters, using the test frequency and magnitude of sine superposition random, the method for determining the vibration test spectrum frequency is shown in Table 1, and the method for determining the vibration test magnitude is shown in Table 2. The specified sine frequency is in the range of fn 0.90 to fn 1.10.

[0037] Table 1 Helicopter Random and Sine Vibration Test Frequencies

[0038] Table 2 Helicopter Random and Sine Vibration Test Magnitudes

[0039] Referring to the vibration test requirements of "RTCA / DO-160G Environmental Conditions and Test Procedures for Aircraft Equipment" in the prior art and combining with the maximum unbalance test of the entire engine, an engine accessory vibration test spectrum (see Table 3) is compiled. The vibration test spectrum is applicable to accessories installed on the engine body and subjected to environmental tests according to RTCA / DO-160G.

[0040] Table 3 Frequencies and Test Magnitudes of the Sine Spectrum Part of the Durability Vibration Test of a Certain Engine (Existing Scheme)

[0041] During the test, according to the vibration test procedure of the aircraft equipment on the helicopter, the test frequencies and magnitudes of sine superposed random are adopted, and the specified sine frequencies are in the range.

[0042] R1 represents the excitation of 1 times the main rotor, R2 represents the excitation of 2 times the main rotor, R3 represents the excitation of the main reduction gear, R4 represents the excitation of the power turbine, and R5 represents the excitation of the gas generator.

[0043] It can be seen that the sine test magnitudes in all directions in the prior art are fixed, such as all being 20g. The actual vibration level of the engine is not considered, and the assessment is too severe, resulting in many accessory assessment tests failing to pass. It may also be that the assessment is too lenient, affecting the safety of the engine.

[0044] Therefore, in the preferred embodiment of the present application, in step S1, when designing a single-segment vibration spectrum for the amplitude of the excitation R4 of the power turbine according to a single vibration magnitude, single-segment vibration spectra are designed respectively according to the vibration data in three different directions obtained by three vibration sensors, and the selected single-segment vibration spectrum amplitude satisfies the following condition: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1.

[0045] In this embodiment, the vibration spectra of the excitation R1 of 1 times the main rotor, the excitation R2 of 2 times the main rotor, and the excitation R3 of the main reduction gear are similar to those in the prior art, and the details are shown in Table 4.

[0046] Table 4 Frequencies and Test Magnitudes of the Sine Spectrum Part of the Durability Vibration Test of a Certain Engine (R1-R3) (This Application)

[0047] Such as Figure 3As shown in Table 5, when the amplitude of the excitation R4 of the power turbine is designed with a single-segment vibration spectrum according to a single vibration quantity value, the single-segment vibration spectrum design is carried out separately based on the vibration data in three different directions obtained by three vibration sensors. The amplitude of the selected single-segment vibration spectrum satisfies the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1, which is no longer fixed at 20g but is 5g, taking into account the vibration level of the actual engine and avoiding the problem that many accessory assessment tests cannot pass due to overly severe assessment.

[0048] Table 5 Frequency and test quantity value (R4) of the test sine spectral line part of the durability vibration test spectrum of a certain engine (this application)

[0049] Specifically, in step S1, when the amplitude of the excitation R5 of the gas generator is segmented and the segmented vibration spectrum is designed according to different vibration quantity values, it specifically includes the following steps: S11. Analyze the vibration response of the accessory at different frequencies, and determine in advance the maximum vibration excitation that the accessory can withstand at different frequencies through tests; S12. Segment the amplitude of the excitation R5 of the gas generator according to the maximum vibration excitation that the accessory can withstand at different frequencies, and then design the segmented vibration spectrum according to different vibration quantity values. Among them, the amplitude of each segment of the vibration spectrum after segmentation satisfies the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency > 1.1.

[0050] Table 6 Frequency and test quantity value (R5) of the test sine spectral line part of the durability vibration test spectrum of a certain engine (this invention)

[0051] Tables 4 - 6 are the environmental vibration test spectra of the accessories of a certain engine compiled according to the method of the present invention. Compared with the existing scheme, the present invention uses the vibration data of the maximum unbalance test to carry out a refined design of the vibration quantity values of R4 and R5. The maximum unbalance test considers the most severe vibration state that the engine may withstand. Only by using the vibration data of the maximum unbalance test can the vibration safety be fully considered. Considering the actual situation of the accessory test, a single-segment vibration spectrum design is carried out for the amplitude of R4, and a segmented vibration spectrum design is carried out for the amplitude of R5, as Figure 3 、 Figure 4 shown.

[0052] See Figure 4 、Table 6. The logic of the segmented vibration spectrum design for the amplitude of R5 in this application is as follows: The natural frequency of a certain accessory is 480 Hz. During the environmental vibration test, the vibration response at 480 Hz is very large, resulting in the accessory failing to pass the environmental test. The preliminary investigation test found that the accessory can only withstand a vibration excitation of 7 - 8 g at 480 Hz. Exceeding 8 g will cause vibration damage to the accessory and lead to the failure of the test. If a single-segment spectrum of 8 g is used, it cannot meet the condition of "vibration spectrum amplitude at each frequency / test amplitude at each frequency > 1.1". If a single-segment vibration spectrum of 10 g is used, the test cannot pass, and additional modification of the accessory structure is required, resulting in delays in the schedule and unnecessary structural improvements. Therefore, in this embodiment, the above problems can be solved through the segmented design of the vibration spectrum. Each segment is designed according to the vibration excitation that can be withstood, instead of a one-size-fits-all approach, thereby reducing the vibration excitation at 480 Hz, meeting the condition of "vibration spectrum amplitude at each frequency / test amplitude at each frequency > 1.1", avoiding unnecessary structural improvement designs, improving design efficiency, and reducing design costs.

[0053] Specifically, when the amplitude of the excitation R5 of the gas generator is segmented and the segmented vibration spectrum is designed according to different vibration magnitudes, the segmented vibration spectrum is designed only based on the vibration data obtained by the X-direction vibration sensor. Among them, the amplitude of each segment of the vibration spectrum after segmentation satisfies the following condition: vibration spectrum amplitude at each frequency / test amplitude at each frequency > 1.1; For the vibration data obtained by the Y-direction vibration sensor and the vibration data obtained by the Z-direction vibration sensor, the amplitude of the excitation R5 of the power turbine is designed with a single-segment vibration spectrum according to a single vibration magnitude, and the selected single-segment vibration spectrum amplitude satisfies the following condition: vibration spectrum amplitude at each frequency / test amplitude at each frequency > 1.1.

[0054] Compared with the previous embodiment, when the amplitude of the excitation R5 of the gas generator is segmented and the segmented vibration spectrum is designed according to different vibration magnitudes in this embodiment, the segmented vibration spectrum is designed only based on the vibration data obtained by the X-direction vibration sensor, and the single-segment vibration spectrum design is still used for the Y-direction and Z-direction. This is because: according to the results of the preliminary investigation test, the vibration tolerance of the X-direction is lower, and the vibration tolerances of the Y-direction and Z-direction are higher. This can simplify the vibration spectrum design process, improve design efficiency, and reduce design costs.

[0055] Specifically, in step S2, the vibration safety of the accessory is preliminarily judged through the finite element vibration response calculation and analysis results, which specifically includes the steps: S21. Establish a finite element model of the accessory through the commercial software ansys, input the vibration spectrum as the excitation condition, and calculate the vibration response of the accessory under random excitation; S22. Take the vibration response stress value at a 3σ confidence level in the calculated vibration response, and find the maximum vibration response stress in the entire accessory; S23. When the maximum vibration response stress value under 3σ confidence level × 1.2 < the allowable stress value of the material, it is determined that the accessory structure design is safe; otherwise, it is determined that the accessory structure design is unsafe and the accessory structure design needs to be modified.

[0056] In this embodiment, the vibration safety of the accessory is preliminarily judged through S21 - S23, and its benefits include: predicting the vibration tolerance of the accessory and ensuring the success rate of the environmental test.

[0057] Specifically, in step S3, when modifying the stiffness design of the transition section according to the maximum unbalance test data, when the error between all the resonance frequencies within the operating speed range in the initial accessory environmental vibration test in all directions of the component and the resonance frequencies in the engine's maximum unbalance test is less than or equal to 5%, the stiffness design of the transition section is completed.

[0058] In this embodiment, the initial accessory environmental vibration test is carried out in three vibration directions. Among them, the three vibration directions during the accessory environmental vibration test are the same as those during the engine's maximum unbalance test. When modifying the stiffness design of the transition section according to the maximum unbalance test data, it is judged whether the stiffness design of the transition section meets the requirements based on whether the error between all the resonance frequencies within the operating speed range in the initial accessory environmental vibration test in all directions of the component and the resonance frequencies in the engine's maximum unbalance test is less than or equal to 5%. Its purposes and benefits include: more accurately simulating the actual installation environment of the engine.

[0059] Specifically, all the resonance frequencies are specifically the ones with the largest amplitude within the operating speed range in the initial accessory environmental vibration test in all directions of the component, and there are no more than four resonance frequencies. The purposes and benefits of such a selection include: being more in line with the requirements of the environmental test (the environmental test requires staying at no more than four resonance frequencies).

[0060] Specifically, step S4 specifically includes the steps: Based on the modified transition section and accessory, as Figure 5 、 Figure 6 shown, connect the accessory to the vibration table through the transition section. The excitation direction of the vibration table is the same as that during the engine's maximum unbalance test, and carry out the final accessory environmental vibration test according to the specified test procedure.

[0061] In this embodiment, when carrying out the final accessory environmental vibration test according to the specified test procedure, connect the accessory to the vibration table through the transition section, and the excitation direction of the vibration table is the same as that during the engine's maximum unbalance test. Its purposes and benefits are: ensuring that the vibration excitation direction of the accessory is the same as the actual vibration excitation direction of the engine.

[0062] In summary, compared with the prior art, the civil turboshaft engine accessory environmental vibration test method provided by the above embodiments has the following advantages: 1) In this application, the maximum unbalance test value (with a certain margin considered) is used as the vibration value of R4 and R5 in Table 1, which is more in line with the actual situation. The fixed value of 20g in the prior art may be too strict in assessment, affecting the pass rate of accessory tests; or it may be too lenient in assessment, affecting the safety of the engine.

[0063] 2) According to the "RTCA / DO-160G Environmental Conditions and Test Procedures for Airborne Equipment" in the prior art, it only requires that "the installation of the equipment under test should make the input vibration motion parallel to one of the three main orthogonal axes of the equipment". The installation direction of the equipment under test on the engine is not considered. This application requires that the placement direction of the engine be used as the test direction, which is more representative. Only in this way can the test values of component tests correspond to those of the whole machine test (maximum unbalance test).

[0064] 3) This invention requires that the design confirmation work of the adapter section needs to be carried out before the accessory environmental test. There is no such requirement in the prior art. The benefits of carrying out the design confirmation work of the adapter section are as follows: it can more accurately simulate the installation environment of the accessory. The inconsistency of the installation environment may lead to different vibration responses of the "accessory - adapter section system" and the "accessory - engine mounting flange system" under the excitation of the same accessory spectrum, thus affecting the effectiveness of the test. The design requirements of the adapter section are that the natural frequency error between the "accessory - adapter section system" and the "accessory - engine mounting flange system" does not exceed 5%. Only when the natural frequencies are the same can the consistency of the installation environment be ensured.

[0065] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0066] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these changes and modifications.

Claims

1. A method for testing environmental vibration of accessories of a civil turboshaft engine, characterized in that: Includes steps: S1. Analyze the maximum imbalance of the engine and conduct the maximum imbalance test of the whole engine. During the test, three vibration sensors are installed near the accessories to detect vibration in the X, Y and Z directions respectively. The vibration spectrum of the accessory environment test is compiled based on the vibration data in three different directions obtained by the three vibration sensors. When compiling the vibration spectrum of the accessory environment test, the amplitude of the excitation R4 of the power turbine is designed as a single-segment vibration spectrum according to a single vibration value, and the amplitude of the excitation R5 of the gas generator is segmented and then segmented vibration spectrum is designed according to different vibration values; S2. Carry out finite element calculation and analysis of accessories, correct the accessory connection stiffness through accessory knock frequency test and then substitute it into the accessory, so that the calculated resonance frequency is consistent with the knock frequency resonance frequency, and the error meets the engineering design requirements, and then preliminarily judge the vibration safety of the accessory through the finite element vibration response calculation and analysis results; S3. Design the transition section and carry out the initial accessory environmental vibration test in three vibration directions. The three vibration directions in the accessory environmental vibration test are consistent with the vibration directions in the maximum imbalance test of the whole engine. The stiffness design of the transition section is modified according to the maximum imbalance test data. S4. After completing the stiffness correction of the accessories and transition sections, carry out the final accessory environmental vibration test.

2. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: The X direction is consistent with the engine axis direction, and the Y direction is orthogonal to the X direction and the Z direction.

3. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: In step S1, when the amplitude of the excitation R4 of the power turbine is designed for a single-segment vibration spectrum according to a single vibration value, the single-segment vibration spectrum is designed respectively according to the vibration data in three different directions obtained by three vibration sensors, and the selected single-segment vibration spectrum amplitude meets the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency>1.

1.

4. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: In step S1, after the amplitude of the excitation R5 of the gas generator is segmented and segmented vibration spectrum design is performed according to different vibration magnitudes, the specific steps include: Analyze the vibration response of the accessories at different frequencies, and conduct experiments in advance to determine the maximum vibration excitation that the accessories can withstand at different frequencies; According to the maximum vibration excitation that the accessories can withstand at different frequencies, the amplitude of the excitation R5 of the gas generator is segmented and then the segmented vibration spectrum is designed according to different vibration values. Among them, the amplitude of each vibration spectrum after segmentation meets the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency>1.

1.

5. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: When the amplitude of the excitation R5 of the gas generator is segmented and segmented vibration spectrum design is performed according to different vibration values, the segmented vibration spectrum design is performed only based on the vibration data obtained by the X-axis vibration sensor, wherein the amplitude of each segmented vibration spectrum meets the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency>1.1; For the vibration data obtained by the Y-direction vibration sensor and the vibration data obtained by the Z-direction vibration sensor, a single-segment vibration spectrum design is performed for the amplitude of the excitation R5 of the power turbine according to a single vibration value, and the selected single-segment vibration spectrum amplitude meets the following conditions: the vibration spectrum amplitude at each frequency / the test amplitude at each frequency>1.

1.

6. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: In step S2, the vibration safety of the accessory is preliminarily determined by the finite element vibration response calculation and analysis results, which specifically includes the following steps: Establish a finite element model of the accessory, input the vibration spectrum as the excitation condition, and calculate the vibration response of the accessory under random excitation; Take the vibration response stress value at 3σ confidence level in the calculated vibration response and find the maximum value of the vibration response stress in the entire accessory; When the maximum value of the vibration response stress under the 3σ confidence level × 1.2 < the allowable stress value of the material, the accessory structure design is judged to be safe; otherwise, the accessory structure design is judged to be unsafe and needs to be modified.

7. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 6, characterized in that: The finite element model of the accessories is established using the commercial software ANSYS.

8. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: In step S3, when the transition section stiffness design is corrected according to the maximum imbalance test data, the transition section stiffness design is completed when the error between all resonant frequencies within the working speed range in the initial accessory environmental vibration test in all directions of the component and the resonant frequency in the maximum imbalance test of the entire engine is less than or equal to 5%.

9. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 8, characterized in that: The above-mentioned all resonant frequencies are specifically the ones with the largest amplitude within the working speed range in the initial accessory environmental vibration test of the component in all directions, and shall not exceed four resonant frequencies.

10. The environmental vibration test method for accessories of a civil turboshaft engine according to claim 1, characterized in that: The step S4 specifically comprises the following steps: Based on the revised adapter section and accessories, the accessories are connected to the vibration table through the adapter section. The excitation direction of the vibration table is consistent with the direction during the maximum imbalance test of the engine as a whole. The final accessory environmental vibration test is carried out according to the prescribed test procedures.

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