Method and system for evaluating vibration reduction effect of aircraft APU vibration isolation device

Abstract

The invention belongs to the technical field of aviation, and relates to a method and system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, a ground test bench with high rigidity is selected, an APU body is horizontally arranged in the middle of the ground test bench, and three groups of vibration isolation devices are arranged at different positions of the APU body respectively; each vibration isolation device is correspondingly provided with two groups of data acquisition devices; and then secondary ground driving is carried out through the vibration isolation device and the rigid false part, an elastic acceleration measurement result and a rigid acceleration measurement result are obtained, and the vibration isolation effect of each pull rod mounting support is calculated through root mean square. The vibration isolation device and the mounting pull rod are taken as an integral elastic unit, and an effective vibration isolation effect can be obtained by measuring the vibration acceleration on the large-rigidity test bed; the situation that the evaluation result is not real due to the foundation rigidity is effectively avoided, meanwhile, the root-mean-square of the acceleration power spectral density representing the vibration energy is introduced, and the vibration isolation effect can be effectively evaluated.

Description

Technical Field

[0001] The present application belongs to the field of aviation technology, and in particular, relates to a method and system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device. Background Art

[0002] Aircraft APU is an auxiliary power unit. When designing the installation, it is necessary to consider installing a vibration isolation device to reduce the transmission of APU vibration to the aircraft, and at the same time provide a favorable installation environment so that the APU does not exceed the vibration standard when working. For system design, the most important thing is to use vibration isolation.

[0003] To what extent is the vibration level of the APU attenuated or controlled? When designing the system vibration isolation, the optimization design of the system's structural parameters is generally carried out around the vibration isolation efficiency. Therefore, the determination of the vibration reduction effect evaluation method is very critical.

[0004] At present, the commonly used vibration isolation effect evaluation indicators at home and abroad include force transfer rate, insertion loss, vibration level drop, power flow, etc. Generally, the force transfer rate is used as the theoretical prediction basis for the vibration isolation effect; however, for the determination of the actual effect, since the force transfer rate is not easy to measure, insertion loss or vibration level drop is usually used to evaluate the vibration isolation effect of the system. Under certain conditions of the vibration isolation device, the change of the impedance characteristics of the installation foundation will have a great impact on the vibration level drop, making it difficult to accurately evaluate the vibration isolation effect. The power flow method is convenient for testing the power spectrum density transmitted through the vibration isolation device. It is an absolute quantity and does not reflect the vibration isolation effect itself. The power flow transfer rate can be used to evaluate the vibration isolation effect. For the APU vibration isolation system, it is a multi-excitation source and multi-support system, and the power flow transfer rate tends to be complicated. The commonly used insertion loss method compares displacement, velocity and acceleration, and requires a large foundation rigidity to replace the transmission rate and effectively demonstrate the vibration isolation effect. Considering that the APU is installed with 7 tie rods and the vibration isolation device, the foundation stiffness of the combination of the 7 mounting tie rods of the APU and the ground start-up test bench is not large, so the conclusions drawn from the previous test have been exaggerated. Summary of the invention

[0005] The purpose of the present application is to provide a method and system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, so as to solve or alleviate at least one problem in the background technology.

[0006] The technical solution of the present application is: a method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, comprising:

[0007] A ground test bench with a certain stiffness is selected, and an APU body, an aircraft APU vibration isolation device, a mounting tie rod and a data acquisition device are assembled; the APU body is horizontally arranged in the middle of the ground test bench, and there are three sets of vibration isolation devices, which are respectively arranged at different positions of the APU body; the aircraft APU vibration isolation device on the left is connected to the ground test bench through three mounting tie rods, and the aircraft APU vibration isolation devices on the right and tail are both connected to the ground test bench through two mounting tie rods, and the data acquisition device includes a three-axis acceleration vibration sensor and a tie rod mounting support;

[0008] After determining the vibration corresponding test data range and the test sampling rate of vibration parameters for the ground test run, a ground run is carried out, and the APU body generates random vibrations. The vibration amount is attenuated by the elastic unit composed of the vibration isolation device and the mounting rod, and then transmitted to the ground test run bench. The acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement results;

[0009] Replace the vibration isolation device with a rigid dummy, perform ground driving a second time and measure the installation acceleration parameters to obtain the rigid acceleration measurement results;

[0010] The elastic acceleration measurement results and the rigid acceleration measurement results are compared and analyzed to obtain the acceleration power spectrum density. The root mean square values ​​of elasticity and rigidity are calculated respectively to determine the vibration isolation effect R of each tie rod mounting support.

[0011] Preferably, the data acquisition device specifically includes a tie rod mounting support, an installation tie rod and a three-axis acceleration sensor. The tie rod mounting support is arranged on the side wall of the ground test bench, and the installation tie rod is hinged between the tie rod mounting support and the ground test bench; the three-axis acceleration sensor is arranged on the tie rod mounting support.

[0012] Preferably, one group of the vibration isolation devices is arranged at the top of one end of the APU body, and the other two groups are symmetrically arranged on both sides of the other end of the APU body.

[0013] Preferably, the root mean square corresponding to the elastic acceleration measurement result is defined as a1, and the root mean square corresponding to the rigid acceleration measurement result is defined as a 1R , then the vibration isolation effect R is:

[0014]

[0015] Preferably, the vibration response test data range is 5-2000 Hz.

[0016] Preferably, the test sampling rate of the vibration parameters is not less than 2000 times / s; each ground start-up test is conducted at least twice.

[0017] As a specific implementation, a system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device includes:

[0018] The APU assembly module selects a ground test bench with a certain stiffness, and assembles the APU body, the aircraft APU vibration isolation device, the installation rod and the data acquisition device; the APU body is horizontally arranged in the middle of the ground test bench, and there are three groups of vibration isolation devices, which are respectively arranged at different positions of the APU body; the aircraft APU vibration isolation device on the left is connected to the ground test bench through a mounting rod, and the aircraft APU vibration isolation devices on the right and tail are both connected to the ground test bench through a mounting rod, and the data acquisition device includes a three-axis acceleration vibration sensor and a rod mounting support;

[0019] The sampling module determines the vibration corresponding test data range and the test sampling rate of the vibration parameters of the ground test, and then conducts a ground test. The APU body generates random vibrations, and the vibration amount is attenuated by the elastic unit composed of the vibration isolation device and the installation rod, and then transmitted to the ground test bench. The acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement results;

[0020] Acceleration measurement module: replace the vibration isolation device with a rigid dummy, conduct a second ground drive and measure the installation acceleration parameters to obtain the rigid acceleration measurement results;

[0021] The comparative analysis module compares and analyzes the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectrum density, calculates the root mean square value of elasticity and rigidity respectively, and determines the vibration amount of each tie rod mounting support.

[0022] Preferably, the data acquisition device specifically includes a tie rod mounting support and a three-axis acceleration sensor. The tie rod mounting support is arranged on the side wall of the ground test bench; the three-axis acceleration sensor is arranged on the tie rod mounting support.

[0023] Preferably, one group of the vibration isolation devices is arranged at the top of one end of the APU body, and the other two groups are symmetrically arranged on both sides of the other end of the APU body.

[0024] Preferably, the vibration isolation effect R is specifically determined by:

[0025] Define the root mean square of the elastic acceleration measurement result as , and the root mean square of the rigid acceleration measurement result as , then the vibration isolation effect R is:

[0026]

[0027] Preferably, the vibration response test data range is 5-2000 Hz.

[0028] Preferably, the test sampling rate of the vibration parameters is not less than 2000 times / s; each ground start-up test is conducted at least twice.

[0029] The present application discloses an evaluation method and system for the vibration reduction effect of an aircraft APU vibration isolation device. A ground test bench with relatively large rigidity is selected. The APU body is horizontally arranged in the middle of the ground test bench. There are three groups of vibration isolation devices, which are arranged at different positions of the APU body. Two groups of data acquisition devices are arranged corresponding to each vibration isolation device. Then, a secondary ground test is performed using the vibration isolation device and a rigid dummy to obtain elastic acceleration measurement results and rigid acceleration measurement results, respectively. The vibration isolation effect of each tie rod mounting support is calculated by the root mean square. The vibration isolation device and the mounting tie rod are regarded as an integral elastic unit. By measuring the vibration acceleration on a large rigidity test bench, an effective vibration isolation effect can be obtained. The unrealistic evaluation result caused by the foundation stiffness is effectively avoided. At the same time, the root mean square of the acceleration power spectrum density representing the vibration energy is introduced to effectively evaluate the vibration isolation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0031] Figure 1 This is a schematic diagram of the overall process of this application;

[0032] Figure 2 This is a schematic diagram of the connection structure between the ground test bench and the aircraft APU vibration isolation device of this application;

[0033] Figure 3 The acceleration power spectrum in the X direction under the condition of installing the vibration isolation device for this application;

[0034] Figure 4 This is the acceleration power spectrum in the Y direction when the vibration isolation device is installed for this application;

[0035] Figure 5 The power spectrum of acceleration in the Z direction when the vibration isolation device is installed for this application;

[0036] Figure 6 The acceleration power spectrum in the X direction under the condition of installing rigid dummy for this application;

[0037] Figure 7 The acceleration power spectrum in the Y direction under the condition of installing rigid dummy for this application;

[0038] Figure 8 The acceleration power spectrum in the X direction under the condition of installing rigid dummy for this application;

[0039] Fig. 9 This is a comparison chart of the vibration attenuation effects of the vibration isolation device and the rigid dummy in this application.

[0040] 1. Ground test bench; 2. APU body; 3. Vibration isolation device; 4. Installation rod; 5. Three-axis acceleration sensor; 6. Rod installation support. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] A method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, such as Figure 1 As shown, the following steps are included:

[0043] Step S100, select a ground test bench 1 with high rigidity, assemble an APU body (2), an aircraft APU vibration isolation device 3, a mounting tie rod 4 and a data acquisition device; the APU body 2 is horizontally arranged in the middle of the ground test bench 1, and there are three groups of vibration isolation devices 3, which are respectively arranged at different positions of the APU body 2; the aircraft APU vibration isolation device 3 on the left side is connected to the ground test bench 1 through three mounting tie rods 4, and the aircraft APU vibration isolation devices 3 on the right side and the rear are both connected to the ground test bench 1 through two mounting tie rods 4, and the data acquisition device includes a three-axis acceleration vibration sensor 5 and a tie rod mounting support 6.

[0044] The data acquisition device is connected to the ground test bench 1. Two sets of data acquisition devices are correspondingly arranged for each vibration isolation device 3. The data acquisition device specifically includes a tie rod mounting support 6 and a three-dimensional acceleration sensor 5. The tie rod mounting support 6 is arranged on the side wall of the ground test bench 1. The three-dimensional acceleration sensor 5 is arranged on the tie rod mounting support 6 for collecting acceleration parameters. That is, there are seven sets of data acquisition devices and seven tie rod mounting supports 6, which are the left middle support, the left front support, the left rear support, the right front support, the right rear support, the tail left support and the tail right support.

[0045] Step S200, after determining the vibration corresponding test data range and the test sampling rate of the vibration parameters of the ground test run, a ground start-up is performed, and the APU body 2 generates random vibration. The vibration amount is attenuated by the elastic unit composed of the vibration isolation device 3 and the installation rod 4, and then transmitted to the ground test run bench 1. The acceleration parameters are measured by the three-axis acceleration sensor 5 to obtain the elastic acceleration measurement result.

[0046] Step S300, replace the vibration isolation device 3 with a rigid dummy, perform ground driving for a second time and measure the installation acceleration parameters to obtain the rigid acceleration measurement results.

[0047] Step S400 , compare and analyze the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectrum density, calculate the root mean square value of the elasticity and the rigidity respectively, and determine the vibration amount of each tie rod mounting support 6 .

[0048] Compared with the traditional measurement of the acceleration at both ends of the vibration isolation device 3, the present application regards the vibration isolation device 3 and the installation rod 4 as an integral elastic unit, and can obtain an effective vibration isolation effect by measuring the vibration acceleration on the large stiffness test bench; and because the traditional test method tests the acceleration value, the APU vibration is a random vibration, and the vibration acceleration value generated when the APU is working changes with time. The amount of data to be compared is very large, and not every acceleration value reflects the characteristic that the installation of the vibration isolation device 3 is smaller than that of the rigid dummy, which ultimately leads to the use of acceleration comparison cannot guide the determination of the design indicators of the vibration isolation device 3. After obtaining the acceleration parameters corresponding to the rigidity and elasticity, the present application effectively avoids the unrealistic evaluation results caused by the foundation stiffness by comparing the root mean square of the two acceleration power spectrum densities, and at the same time introduces the root mean square of the acceleration power spectrum density representing the vibration energy, which can effectively evaluate the effect of vibration isolation.

[0049] Define the root mean square of the elastic acceleration measurement result as a1, and the root mean square of the rigid acceleration measurement result as a 1R , and define the vibration isolation effect R as:

[0050]

[0051] The vibration isolation capability of the current vibration isolation device can be effectively evaluated by the specific value of the vibration isolation effect R.

[0052] The following is a specific example:

[0053] The evaluation of the vibration reduction effect of the APU vibration isolation device of a certain type of aircraft is taken as an example to illustrate the feasibility of the above evaluation method. The test requires that the test sampling rate of vibration parameters should not be less than 2000 times / s; each ground start-up test should be conducted at least twice; the vibration response test data range is 5-2000Hz. According to the typical working state of the APU, there are 12 stages from starting to stopping. The acceleration power spectrum density of each stage is calculated, and the average value of the 12 stages is taken, with a total of two starts. Taking the rod mounting bracket 6 marked in the drawing as an example, under the condition of installing the vibration isolation device, the second stage of APU operation is when the APU is operating at rated speed, without bleed air and power extraction. The acceleration power spectra in the X, Y and Z directions are as follows Figure 3-Figure 5 shown.

[0054] Acceleration power spectrum in the X, Y and Z directions when the rigid dummy of the vibration isolation device is installed Figure 6-Figure 8 shown.

[0055] As mentioned above, the acceleration power spectrum density diagram on the mounting bracket can be measured by the APU second start-up. The acceleration power spectrum density of the APU in 12 working stages can be obtained by starting the APU once. The corresponding RMS value of the acceleration power spectrum density can be calculated and its average value can be obtained. When the data of the second start-up are counted, the average value of the two start-up data can be obtained:

[0056]

[0057] The above value is the vibration isolation effect at the right front support, and the vibration energy value is reduced by 46.2%. According to the above method, the acceleration at the other 6 mounting rod supports can be measured at the same time. The root mean square value of the acceleration power spectrum density can be calculated to obtain the vibration attenuation at each mounting rod support. The vibration attenuation effect at each measuring point is as follows: Fig. 9 As shown, ① is a rigid dummy and ② is a vibration isolation device. It can be seen that the vibration isolation performance of the vibration isolation device on each support is much better than that of the rigid dummy, which is in line with the test expectations.

[0058] As a specific implementation, a system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device is also included, including:

[0059] An APU assembly module is provided, wherein a ground test bench 1 having a certain stiffness is selected, and an APU body (2), an aircraft APU vibration isolation device 3, a mounting tie rod 4 and a data acquisition device are assembled; the APU body 2 is horizontally arranged in the middle of the ground test bench 1, and there are three groups of vibration isolation devices 3, which are respectively arranged at different positions of the APU body 2; the aircraft APU vibration isolation device 3 on the left side is connected to the ground test bench 1 through three mounting tie rods 4, and the aircraft APU vibration isolation devices 3 on the right side and the tail are both connected to the ground test bench 1 through two mounting tie rods 4, and the data acquisition device includes a three-dimensional acceleration vibration sensor 5 and a tie rod mounting support 6;

[0060] The sampling module determines the vibration corresponding test data range and the test sampling rate of the vibration parameters of the ground test, and then conducts a ground start-up. The APU body 2 generates random vibration, and the vibration amount is attenuated by the elastic unit composed of the vibration isolation device 3 and the installation rod 4, and then transmitted to the ground test bench 1. The acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement result;

[0061] The acceleration measurement module replaces the vibration isolation device 3 with a rigid dummy, performs ground driving for the second time and measures the installation acceleration parameters to obtain the rigid acceleration measurement results;

[0062] The comparison and analysis module compares and analyzes the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectrum density, calculates the root mean square value of elasticity and rigidity respectively, and determines the vibration amount of each tie rod mounting support 6.

[0063] Preferably, the data acquisition device specifically includes a tie rod mounting support 6 and a three-axis acceleration sensor 5 . The tie rod mounting support 6 is arranged on the side wall of the ground test bench 1 ; the three-axis acceleration sensor 5 is arranged on the tie rod mounting support 6 .

[0064] Preferably, one group of the vibration isolation devices 3 is arranged at the top of one end of the APU body 2 , and the other two groups are symmetrically arranged on both sides of the other end of the APU body 2 .

[0065] Preferably, the vibration isolation effect R is specifically determined by:

[0066] Define the root mean square of the elastic acceleration measurement result as , and the root mean square of the rigid acceleration measurement result as , then the vibration isolation effect R is:

[0067]

[0068] Preferably, the vibration response test data range is 5-2000 Hz.

[0069] Preferably, the test sampling rate of the vibration parameters is not less than 2000 times / s; each ground start-up test is conducted at least twice.

[0070] Finally, it should be noted that: the drawings of the embodiments disclosed in the present invention only involve structures related to the embodiments disclosed in the present invention, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other;

[0071] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, characterized in that: include: A ground test bench (1) with a certain stiffness is selected, and an APU body (2), an aircraft APU vibration isolation device (3), a mounting tie rod (4) and a data acquisition device are assembled; the APU body (2) is horizontally arranged in the middle of the ground test bench (1), and there are three groups of vibration isolation devices (3) which are respectively arranged at different positions of the APU body (2); the aircraft APU vibration isolation device (3) on the left side is connected to the ground test bench (1) through three mounting tie rods (4), and the aircraft APU vibration isolation devices (3) on the right side and the tail are both connected to the ground test bench (1) through two mounting tie rods (4), and the data acquisition device includes a three-dimensional acceleration vibration sensor (5) and a tie rod mounting support (6); After determining the vibration corresponding test data range and the test sampling rate of the vibration parameters of the ground test run, a ground start-up is carried out, and the APU body (2) generates random vibration, and the vibration amount is attenuated by the elastic unit composed of the vibration isolation device (3) and the installation rod (4), and then transmitted to the ground test run bench (1), and the acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement result; The vibration isolation device (3) is replaced with a rigid dummy, the ground drive is performed a second time and the installation acceleration parameters are measured to obtain the rigid acceleration measurement results; Comparative analysis is performed on the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectrum density, and the root mean square values ​​of the elasticity and rigidity are calculated respectively to determine the vibration amount of each tie rod mounting support (6).

2. The method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 1, characterized in that: The data acquisition device specifically comprises a tie rod mounting support (6) and a three-dimensional acceleration sensor (5); the tie rod mounting support (6) is arranged on the side wall of a ground test bench (1); and the three-dimensional acceleration sensor (5) is arranged on the tie rod mounting support (6).

3. The method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 1, characterized in that: One group of the vibration isolation devices (3) is arranged at the top of one end of the APU body (2), and the other two groups are symmetrically arranged on both sides of the other end of the APU body (2).

4. The method for evaluating the vibration reduction effect of the aircraft APU vibration isolation device according to claim 1, characterized in that: The specific method for determining the vibration isolation effect R is: Define the root mean square of the elastic acceleration measurement result as , and the root mean square of the rigid acceleration measurement result as , then the vibration isolation effect R is:

5. The method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 1, characterized in that: The vibration response test data range is 5-2000Hz.

6. The method for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 1, characterized in that: The test sampling rate of the vibration parameters shall not be less than 2000 times / s; each ground start-up test shall be conducted at least twice.

7. A system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, using the method according to claims 1 to 6, characterized in that: include: An APU assembly module is provided, wherein a ground test bench (1) having a certain stiffness is selected, and an APU body (2), an aircraft APU vibration isolation device (3), a mounting tie rod (4) and a data acquisition device are assembled; the APU body (2) is horizontally arranged in the middle of the ground test bench (1), and there are three groups of vibration isolation devices (3) which are respectively arranged at different positions of the APU body (2); the aircraft APU vibration isolation device (3) on the left side is connected to the ground test bench (1) through three mounting tie rods (4), and the aircraft APU vibration isolation devices (3) on the right side and the rear are both connected to the ground test bench (1) through two mounting tie rods (4), and the data acquisition device comprises a three-dimensional acceleration vibration sensor (5) and a tie rod mounting support (6); The sampling module determines the vibration corresponding test data range and the test sampling rate of the vibration parameters of the ground test run, and then performs a ground start-up. The APU body (2) generates random vibration, and the vibration amount is attenuated by the elastic unit composed of the vibration isolation device (3) and the installation rod (4), and then transmitted to the ground test run bench (1). The acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement result; The acceleration measurement module replaces the vibration isolation device (3) with a rigid dummy, performs ground driving for a second time and measures the installation acceleration parameters to obtain a rigid acceleration measurement result; The comparison and analysis module compares and analyzes the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectrum density, calculates the root mean square value of the elasticity and the rigidity respectively, and determines the vibration amount of each tie rod mounting support (6).

8. The system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 7, characterized in that: The data acquisition device specifically comprises a tie rod mounting support (6) and a three-dimensional acceleration sensor (5); the tie rod mounting support (6) is arranged on the side wall of a ground test bench (1); and the three-dimensional acceleration sensor (5) is arranged on the tie rod mounting support (6).

9. The system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 7, characterized in that: One group of the vibration isolation devices (3) is arranged at the top of one end of the APU body (2), and the other two groups are symmetrically arranged on both sides of the other end of the APU body (2).

10. The system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 7, characterized in that: The specific method for determining the vibration isolation effect R is: Define the root mean square of the elastic acceleration measurement result as , and the root mean square of the rigid acceleration measurement result as , then the vibration isolation effect R is:

11. The system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 7, characterized in that: The vibration response test data range is 5-2000Hz.

12. The system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device according to claim 7, characterized in that: The test sampling rate of the vibration parameters shall not be less than 2000 times / s; each ground start-up test shall be conducted at least twice.

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