A method and system for evaluating the damping effect of an aircraft APU vibration isolation device

Abstract

The application belongs to the field of aviation technology, and is a kind of evaluation method and system for the damping effect of an aircraft APU vibration isolation device. A ground test bench with relatively large rigidity is selected, the APU body is horizontally arranged at the middle part of the ground test bench, and three groups of vibration isolation devices are arranged at different positions of the APU body. Two groups of data acquisition devices are arranged corresponding to each vibration isolation device. Then, secondary ground driving is carried out through the vibration isolation devices and rigid dummy parts respectively, and elastic acceleration measurement results and rigid acceleration measurement results are obtained respectively. The damping effect of each pull rod mounting support is calculated through root mean square. The vibration isolation device and the mounting pull rod are regarded as an integral elastic unit, and the effective damping effect can be obtained by measuring the vibration acceleration on the test bench with large rigidity. The evaluation result caused by the foundation rigidity is effectively avoided, and the root mean square of the acceleration power spectrum density representing the vibration energy is introduced, so that the damping effect can be effectively evaluated.

Description

Technical Field

[0001] This application belongs to the field of aerospace technology, and specifically relates to a method and system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device. Background Technology

[0002] The aircraft APU (Auxiliary Power Unit) is an auxiliary power unit for aircraft. During installation design, vibration isolation devices must be considered to reduce the transmission of APU vibration to the aircraft, while also providing a favorable installation environment to prevent excessive vibration during APU operation. For system design, the primary concern is achieving vibration isolation...

[0003] To what extent has the vibration magnitude of the APU been attenuated or controlled? In system vibration isolation design, the optimization of structural parameters generally revolves around vibration isolation efficiency; therefore, determining the method for evaluating vibration reduction effectiveness is crucial.

[0004] Currently, commonly used vibration isolation performance evaluation indicators both domestically and internationally include force transmissibility, insertion loss, level difference, and power flow. Force transmissibility is generally used as the theoretical basis for predicting vibration isolation performance; however, for actual performance measurement, since force transmissibility is difficult to measure, insertion loss or level difference is usually used to evaluate the system's vibration isolation effect. With the level difference method, under certain conditions of the vibration isolation device, changes in the impedance characteristics of the installation foundation will greatly affect the level difference, making it difficult to accurately evaluate the vibration isolation effect. The power flow method is convenient for measuring the transmitted power spectral density through the vibration isolation device; it is an absolute quantity and does not reflect the vibration isolation effect itself. Power flow transmissibility can be used to evaluate the vibration isolation effect. For APU vibration isolation systems, which are multi-excitation source, multi-support system, the power flow transmissibility becomes more complex. The commonly used insertion loss method compares displacement, velocity, and acceleration, requiring high foundation rigidity to replace transmissibility and effectively demonstrate vibration isolation. Considering that the APU is installed with 7 tie rods and vibration isolation devices, the foundation rigidity of the APU's 7 mounting tie rods combined with the ground driving test bench is not high, so the conclusions drawn from previous tests were exaggerated. Summary of the Invention

[0005] The purpose of this 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 mitigate at least one of the problems in the prior art.

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

[0007] A ground test rig with sufficient stiffness is selected, and the APU body, aircraft APU vibration isolation device, mounting rods, and data acquisition device are assembled. The APU body is horizontally positioned in the middle of the ground test rig. There are three sets of vibration isolation devices, each located at a different position on the APU body. The aircraft APU vibration isolation device on the left side is connected to the ground test rig by three mounting rods, while the aircraft APU vibration isolation devices on the right side and tail are each connected to the ground test rig by two mounting rods. The data acquisition device includes a three-dimensional acceleration vibration sensor and a rod mounting bracket.

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

[0009] The vibration isolation device was replaced with a rigid dummy, and the ground driving was performed a second time to measure the installation acceleration parameters, and the rigid acceleration measurement results were obtained.

[0010] By comparing and analyzing the results of elastic acceleration measurement and rigid acceleration measurement, the acceleration power spectral density is obtained. The root mean square values ​​of elastic and rigid acceleration 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 bracket, a mounting tie rod, and a triaxial acceleration sensor. The tie rod mounting bracket is located on the side wall of the ground test platform, and the mounting tie rod is hinged between the tie rod mounting bracket and the ground test platform. The triaxial acceleration sensor is located on the tie rod mounting bracket.

[0012] Preferably, one set of the vibration isolation device is located at the top of one end of the APU body, and the other two sets are symmetrically located on both sides of the other end of the APU body.

[0013] Preferably, the root mean square of the elastic acceleration measurement result is defined as a1, and the root mean square of 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 5-2000Hz.

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

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

[0018] The APU assembly module uses a ground test bench with sufficient stiffness to assemble the APU body, aircraft APU vibration isolation device, mounting rods, and data acquisition device. The APU body is horizontally positioned in the middle of the ground test bench. There are three sets of vibration isolation devices, each located at a different position on the APU body. The aircraft APU vibration isolation device on the left side is connected to the ground test bench via mounting rods, while the aircraft APU vibration isolation devices on the right side and tail are also connected to the ground test bench via mounting rods. The data acquisition device includes a three-dimensional acceleration vibration sensor and a rod mounting bracket.

[0019] After determining the vibration response test data range and vibration parameter test sampling rate for the ground test, the sampling module performs a ground test. The APU body generates random vibration, which is attenuated by the elastic unit composed of vibration isolation device and mounting tie 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] The acceleration measurement module replaces the vibration isolation device with a rigid dummy, performs a second ground-based driving test, and measures 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 spectral density, calculates the root mean square values ​​of elastic and rigid acceleration respectively, and determines the vibration of each tie rod mounting support.

[0022] Preferably, the data acquisition device specifically includes a tie rod mounting bracket and a triaxial acceleration sensor. The tie rod mounting bracket is located on the side wall of the ground test bench; the triaxial acceleration sensor is located on the tie rod mounting bracket.

[0023] Preferably, one set of the vibration isolation device is located at the top of one end of the APU body, and the other two sets are symmetrically located on both sides of the other end of the APU body.

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

[0025] Let the root mean square (RMS) of the elastic acceleration measurement result be , and the RMS of the rigid acceleration measurement result be , then the vibration isolation effect R is:

[0026]

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

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

[0029] This application discloses a method and system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device. A ground test bench with high stiffness is selected, with the APU body horizontally positioned in the center of the bench. Three sets of vibration isolation devices are installed at different locations on the APU body. Each isolation device is equipped with two sets of data acquisition devices. Secondary ground testing is then conducted using both the isolation devices and rigid dummy components to obtain elastic acceleration and rigid acceleration measurements. The vibration isolation effect of each tie rod mounting support is calculated using the root mean square (RMS) method. By treating the isolation device and mounting tie rod as a single elastic unit, and measuring the vibration acceleration on the high-stiffness test bench, an effective vibration isolation effect can be obtained. This effectively avoids inaccurate evaluation results caused by foundation stiffness. Furthermore, the introduction of the RMS method for the acceleration power spectral density, representing vibration energy, allows for effective evaluation of the vibration isolation effect. Attached Figure Description

[0030] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this 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 in this application.

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

[0034] Figure 4 The acceleration power spectrum in the Y direction under the condition of installing vibration isolation device in this application;

[0035] Figure 5 The Z-direction acceleration power spectrum under the condition of installing vibration isolation device in this application;

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

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

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

[0039] Figure 9 This is a comparison diagram 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. Mounting tie rod; 5. Three-dimensional acceleration sensor; 6. Tie rod mounting bracket. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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, it includes the following steps:

[0043] Step S100: Select a high-rigidity ground test bench 1, and assemble the APU body (2), aircraft APU vibration isolation device 3, mounting rods 4, and data acquisition device; the APU body 2 is horizontally positioned in the middle of the ground test bench 1, and there are three sets of vibration isolation devices 3, which are respectively located 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 by 3 mounting rods 4, and the aircraft APU vibration isolation devices 3 on the right side and tail are connected to the ground test bench 1 by 2 mounting rods 4. The data acquisition device includes a triaxial acceleration vibration sensor 5 and a rod mounting bracket 6.

[0044] The data acquisition devices are connected to the ground test bench 1. Each vibration isolation device 3 corresponds to two sets of data acquisition devices. Specifically, each data acquisition device includes a tie rod mounting bracket 6 and a triaxial acceleration sensor 5. The tie rod mounting bracket 6 is located on the side wall of the ground test bench 1, and the triaxial acceleration sensor 5 is mounted on the tie rod mounting bracket 6 for collecting acceleration parameters. That is, there are a total of seven sets of data acquisition devices and seven tie rod mounting brackets 6, namely the left center bracket, left front bracket, left rear bracket, right front bracket, right rear bracket, rear left bracket, and rear right bracket.

[0045] In step S200, after determining the vibration response test data range and vibration parameter test sampling rate for the ground test, a ground test is performed. The APU body 2 generates random vibration. The vibration is attenuated by the elastic unit composed of the vibration isolation device 3 and the mounting tie rod 4, and then transmitted to the ground test stand 1. The acceleration parameters are measured by the triaxial acceleration sensor 5 to obtain the elastic acceleration measurement result.

[0046] In step S300, the vibration isolation device 3 is replaced with a rigid dummy, and the ground driving is performed a second time to measure the installation acceleration parameters and obtain the rigid acceleration measurement results.

[0047] Step S400: Compare and analyze the elastic acceleration measurement results and rigid acceleration measurement results to obtain the acceleration power spectral density, calculate the root mean square values ​​of elastic and rigid acceleration respectively, and determine the vibration amount of each tie rod mounting support 6.

[0048] Compared to traditional methods that measure the acceleration at both ends of the vibration isolation device 3, this application treats the vibration isolation device 3 and the mounting rod 4 as a single elastic unit. By measuring the vibration acceleration on a high-stiffness test bench, an effective vibration isolation effect can be obtained. Furthermore, since traditional testing methods measure acceleration values, and APU vibration is random, the acceleration values ​​generated during APU operation change over time, resulting in a massive amount of data for comparison. Moreover, not every acceleration measurement reflects the characteristic that the vibration isolation device 3 is smaller than the rigid dummy component, ultimately leading to the inability to guide the determination of the vibration isolation device 3's design specifications using acceleration comparison. In contrast, this application, after obtaining the acceleration parameters corresponding to rigidity and elasticity, effectively avoids inaccurate evaluation results caused by foundation stiffness by comparing the root mean square of the two acceleration power spectral densities. Simultaneously, by introducing the root mean square of the acceleration power spectral density, representing vibration energy, the vibration isolation effect can be effectively evaluated.

[0049] Define the root mean square (RMS) of the elastic acceleration measurement result as a1, and the RMS of the rigid acceleration measurement result as a. 1R The vibration isolation effect R is defined as:

[0050]

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

[0052] The following is an example to illustrate this:

[0053] Taking the vibration reduction effect evaluation of an APU vibration isolation device for a certain type of aircraft as an example, the feasibility of the above evaluation method is illustrated. The test requirements are: a vibration parameter sampling rate of no less than 2000 times / s; no fewer than two ground start-up tests per test; and vibration response test data range of 5-2000Hz. Based on the typical operating conditions of the APU, from start-up to shutdown (12 stages), the acceleration power spectral density of each stage is calculated, and the average value of the 12 stages is taken. A total of two start-up tests are conducted. 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 its rated speed, without bleed air and without power extraction. The acceleration power spectra in the X, Y, and Z directions are as follows: Figures 3-5 As shown.

[0054] Under the condition of installing a rigid dummy vibration isolation device, the acceleration power spectrum in the X, Y, and Z directions. Figures 6-8 As shown.

[0055] As illustrated above, the acceleration power spectral density map on the mounting bracket can be measured during the second APU startup. A single APU startup yields the acceleration power spectral density for 12 operating stages of the APU. The root mean square value of the corresponding acceleration power spectral density can be calculated, and its average value can be obtained. Then, by averaging the data from the second startup, the following can be obtained:

[0056]

[0057] The above values ​​represent the vibration isolation effect at the right front support, with a 46.2% reduction in vibration energy. Using the same method, the acceleration at the other six tie rod supports can be measured simultaneously. By calculating the root mean square value of the acceleration power spectral density, the vibration attenuation at each tie rod support can be obtained. The vibration attenuation effect at each measuring point is shown below. Figure 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 significantly better than that of the rigid dummy, which is in line with the test expectations.

[0058] As one specific implementation, it also includes an evaluation system for the vibration reduction effect of an aircraft APU vibration isolation device, comprising:

[0059] The APU assembly module uses a ground test bench 1 with a certain stiffness to assemble the APU body (2), aircraft APU vibration isolation device 3, mounting rods 4, and data acquisition device. The APU body 2 is horizontally positioned in the middle of the ground test bench 1. There are three sets of vibration isolation devices 3, which are respectively located at different positions on the APU body 2. The aircraft APU vibration isolation device 3 on the left side is connected to the ground test bench 1 by three mounting rods 4. The aircraft APU vibration isolation devices 3 on the right side and the tail are connected to the ground test bench 1 by two mounting rods 4. The data acquisition device includes a triaxial acceleration vibration sensor 5 and a rod mounting bracket 6.

[0060] After determining the vibration response test data range and vibration parameter test sampling rate for the ground test, the sampling module performs a ground test. The APU body 2 generates random vibration. The vibration is attenuated by the elastic unit composed of the vibration isolation device 3 and the mounting tie 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 results.

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

[0062] The comparative analysis module compares and analyzes the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectral density. It then calculates the root mean square values ​​for both elastic and rigid acceleration to determine the vibration amount of each tie rod mounting support 6.

[0063] Preferably, the data acquisition device specifically includes a tie rod mounting bracket 6 and a triaxial acceleration sensor 5. The tie rod mounting bracket 6 is disposed on the side wall of the ground test platform 1; the triaxial acceleration sensor 5 is disposed on the tie rod mounting bracket 6.

[0064] Preferably, one set of the vibration isolation device 3 is located at the top of one end of the APU body 2, and the other two sets are symmetrically located on both sides of the other end of the APU body 2.

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

[0066] Let the root mean square (RMS) of the elastic acceleration measurement result be , and the RMS of the rigid acceleration measurement result be , then the vibration isolation effect R is:

[0067]

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

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

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

[0071] In conclusion, 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 within 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), mounting rods (4) and a data acquisition device are assembled. The APU body (2) is horizontally located in the middle of the ground test bench (1). There are three sets of vibration isolation devices (3) and they are located at different positions on the APU body (2). The aircraft APU vibration isolation device (3) on the left side is connected to the ground test bench (1) by three mounting rods (4). The aircraft APU vibration isolation devices (3) on the right side and the tail are connected to the ground test bench (1) by two mounting rods (4). The data acquisition device includes a three-dimensional acceleration sensor (5) and a rod mounting bracket (6). After determining the vibration response test data range and vibration parameter test sampling rate for the ground test, a ground test is conducted. The APU body (2) generates random vibration. The vibration is attenuated by the elastic unit composed of the vibration isolation device (3) and the mounting tie 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 results. Replace the vibration isolation device (3) with a rigid dummy, perform ground driving a second time and measure the installation acceleration parameters to obtain the rigid acceleration measurement results; Comparative analysis of the elastic acceleration measurement results and the rigid acceleration measurement results was conducted to obtain the acceleration power spectral density. The root mean square values ​​of elastic and rigid acceleration were calculated respectively to determine the vibration of each tie rod mounting support (6). The specific method for determining the vibration reduction effect R is as follows: Define the root mean square of the elastic acceleration measurement result as: The root mean square corresponding to the rigid acceleration measurement result is Then the vibration reduction effect R is: 。 2. The method for evaluating the vibration reduction effect of the aircraft APU vibration isolation device as described in claim 1, characterized in that: The data acquisition device specifically includes a tie rod mounting bracket (6) and a triaxial acceleration sensor (5). The tie rod mounting bracket (6) is located on the side wall of the ground test bench (1); the triaxial acceleration sensor (5) is located on the tie rod mounting bracket (6).

3. The method for evaluating the vibration reduction effect of the aircraft APU vibration isolation device as described in claim 1, characterized in that: One set of the vibration isolation device (3) is located at the top of one end of the APU body (2), and the other two sets are symmetrically located 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 as described in claim 1, characterized in that: The vibration response test data range is 5-2000Hz.

5. The method for evaluating the vibration reduction effect of the aircraft APU vibration isolation device as described in claim 1, characterized in that: The sampling rate for the vibration parameters shall be no less than 2000 times / s; each ground-based start-up test shall be conducted no less than twice.

6. A system for evaluating the vibration reduction effect of an aircraft APU vibration isolation device, employing the method described in any one of claims 1-5, characterized in that, include: The APU assembly module uses a ground test bench (1) with a certain stiffness to assemble the APU body (2), aircraft APU vibration isolation device (3), mounting rods (4) and data acquisition device. The APU body (2) is horizontally positioned in the middle of the ground test bench (1). There are three sets of vibration isolation devices (3) located at different positions on the APU body (2). The aircraft APU vibration isolation device (3) on the left side is connected to the ground test bench (1) by three mounting rods (4). The aircraft APU vibration isolation devices (3) on the right side and tail are connected to the ground test bench (1) by two mounting rods (4). The data acquisition device includes a three-dimensional acceleration sensor (5) and a rod mounting bracket (6). After determining the vibration response test data range and vibration parameter test sampling rate of the ground test vehicle test, the sampling module performs a ground test vehicle test. The APU body (2) generates random vibration. The vibration is attenuated by the elastic unit composed of the vibration isolation device (3) and the mounting tie rod (4), and then transmitted to the ground test vehicle test bench (1). The acceleration parameters are measured by the data acquisition device to obtain the elastic acceleration measurement results. 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; The comparative analysis module compares and analyzes the elastic acceleration measurement results and the rigid acceleration measurement results to obtain the acceleration power spectral density, calculates the root mean square values ​​of elastic and rigid acceleration respectively, and determines the vibration of each tie rod mounting support (6).

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