Pipe flow-induced and sound-induced vibration detection and acoustic mode analysis experimental device and method

Abstract

The application discloses a pipeline flow-induced and sound-induced vibration detection and sound mode analysis experimental device, which comprises a main pipeline, wherein one end of the main pipeline is connected with an air source, the other end of the main pipeline is connected with a first silencer, the other end of the first silencer is connected with a replaceable experimental pipeline, and the other end of the replaceable experimental pipeline is connected with a second silencer; the main pipeline and the replaceable experimental pipeline are on the same straight line; a flow regulating part is arranged at a position close to the air source of the main pipeline; a mode analysis part and a pressure detection part are sequentially arranged along the air flow direction at a position close to the second silencer of the replaceable experimental pipeline; and the experimental device further comprises an experimental data acquisition part which is connected with the flow regulating part, the pressure detection part and the mode analysis part respectively. The application further discloses a pipeline flow-induced and sound-induced vibration detection and sound mode analysis method. The pipeline vibration test result obtained by the experimental device has high precision and high reliability, and meanwhile, the test part is convenient to disassemble and replace.

Description

Technical Field

[0001] This invention belongs to the field of pipeline flow-induced and acoustic vibration experimental technology, specifically involving experimental apparatus for pipeline flow-induced and acoustic vibration detection and acoustic modal analysis, and also involving methods for pipeline flow-induced and acoustic vibration detection and acoustic modal analysis. Background Technology

[0002] Valves and orifice plates are widely used in process piping systems in the petroleum, chemical, and energy industries, as well as in air distribution systems in aircraft, automobiles, and buildings to control flow rates. The disturbance of fluids caused by valves and orifice plates can lead to localized backflow and vortices, causing localized pressure pulsations within the pipe and generating significant noise. This can result in pipeline vibration, and in severe cases, structural cracking and fluid leakage. To fundamentally prevent pipeline damage, it is necessary to test pipeline vibration to facilitate appropriate adjustments during the design phase. Current pipeline vibration testing methods mainly rely on theoretical analysis and numerical simulation. However, many conditions are simplified in theoretical analysis and numerical simulation, resulting in results with low accuracy and reliability. Therefore, theoretical analysis and numerical simulation have significant limitations. Summary of the Invention

[0003] The purpose of this invention is to provide an experimental device for detecting and analyzing the flow-induced and acoustic vibrations of pipelines. The pipeline vibration test results obtained by this experimental device are highly accurate and reliable, and the test parts are easy to disassemble and replace.

[0004] The technical solution adopted in this invention is an experimental device for detecting and analyzing flow-induced and acoustic vibrations in pipelines, characterized in that it includes a main pipeline, one end of which is connected to an air source, and the other end of which is connected to a first silencer. The other end of the first silencer is connected to a replaceable experimental pipeline, and the other end of the replaceable experimental pipeline is connected to a second silencer. The main pipeline and the replaceable experimental pipeline are on the same straight line. A flow regulation section is provided on the main pipeline near the air source. A modal analysis section and a pressure detection section are sequentially arranged along the airflow direction on the replaceable experimental pipeline near the second silencer. The device also includes an experimental data acquisition section, which is connected to the flow regulation section, the pressure detection section, and the modal analysis section respectively.

[0005] The invention is further characterized by:

[0006] A flexible pipe is installed between the main pipeline and the gas source.

[0007] The flow regulation section includes a regulating ball valve and a gas mass flow meter arranged sequentially along the airflow direction on the main pipeline. The regulating ball valve and the gas mass flow meter are respectively connected to the experimental data acquisition section.

[0008] The pressure detection section includes a pressure gauge and a vibration acceleration sensor, which are sequentially installed along the airflow direction on the replaceable experimental pipeline. The pressure gauge and the vibration acceleration sensor are respectively connected to the experimental data acquisition section.

[0009] The modal analysis section includes several microphone arrays and a signal amplifier. Each microphone array includes several microphones, which are arranged at equal angles along the circumference of the replaceable experimental tubing. The signal amplifier is connected to the microphones and to the experimental data acquisition section.

[0010] The air source was a centrifugal fan; the experimental data acquisition was done by a computer.

[0011] Another technical solution adopted in this invention is a method for detecting and analyzing the flow-induced and acoustic vibrations of a pipeline, using an experimental apparatus for detecting and analyzing the flow-induced and acoustic vibrations of a pipeline, including a method for detecting the flow-induced and acoustic vibrations of a pipeline and a method for analyzing the acoustic modes.

[0012] The methods for detecting flow-induced and acoustic-induced vibrations in pipelines specifically include the following steps:

[0013] Step 1: Select two microphone groups along the airflow direction, and the microphones at corresponding positions in the two microphone groups form a microphone pair;

[0014] Step 2: Start the gas source to fill the main pipeline with airflow, and at the same time start the flow regulation section to regulate the airflow.

[0015] Step 3: Measure the fluid excitation signal and acoustic excitation signal using different microphone spacings, and use cross-spectral density to characterize the flow-induced and acoustic pressure;

[0016] The mean cross-spectral density of the signals obtained from several microphone pairs is calculated using the following formula:

[0017]

[0018] In the formula, X(ω) and Y(ω) are the frequency domain signals obtained by Fourier transform of the time-domain pressure pulsation signals collected by microphones at two measurement points (i.e., two corresponding positions), X*(ω) is the conjugate complex number of X(ω), and N represents the number of sampling points; f s The sampling frequency is represented by Hz; ω = 2πf is the angular frequency, in rad / s, where f represents the frequency, in Hz.

[0019] Step 4: The vibration acceleration sensor collects vibration signals from the pipe surface;

[0020] The acoustic modal analysis method specifically includes the following steps:

[0021] Step 1: Place the component under test in the experimental apparatus for detecting and analyzing flow-induced and acoustic vibrations in a pipeline;

[0022] Step 2: With no flow in the pipe, first set up loudspeakers at several microphone measuring points upstream of the device under test, turn on the loudspeaker at any one microphone and collect the sound pressure signals from the other microphones; then repeat the operation downstream of the device under test to obtain the incident sound wave modal pressure amplitude matrix a upstream and downstream of the device under test. in (ω) and the amplitude matrix of the reflected acoustic wave modal pressure a out (ω), calculate the scattering matrix S(ω) between the incident sound wave and the reflected sound wave;

[0023] Step 3: Turn off the signal amplifier, start the centrifugal fan and adjust the flow regulation section to a suitable opening. Select a cross-section at the upstream and downstream of the replaceable experimental pipeline to form a cross-section pair. Measure the cross-spectral density of the two cross-section pairs at different locations. Sound reflections are generated at both ends of the pipeline flow-induced and acoustic-induced vibration detection and acoustic modal analysis experimental device. Calculate the terminal matrix R and the acoustic modal pressure amplitude matrix a generated by the element itself under no-reflection conditions. s (ω);

[0024] Step 4: Analyze and calculate the acoustic modes using the 2N port method.

[0025] Another feature of the present invention is that:

[0026] In the acoustic modal analysis method, step 2 involves setting up loudspeakers at several microphone measurement points upstream of the component under test. The loudspeaker at any one microphone is turned on, and the sound pressure signals from the other microphones are collected. The pressure signals from the multiple microphones at the measurement points are represented as follows:

[0027]

[0028] In the formula, s l Let z represent the l-th microphone group, z represent the axial coordinate, and e represent the electrical signal from the signal amplifier. It is the transfer function between the l-th microphone and the electrical signal;

[0029] This operation is then repeated downstream of the device under test to obtain the amplitude matrix a of the incident acoustic wave modal pressure upstream and downstream of the device under test. in (ω) and the amplitude matrix of the reflected acoustic wave modal pressure a out (ω), at this time there is no sound source inside the tube, and the scattering matrix S(ω) between the incident sound wave and the reflected sound wave is:

[0030] s(ω)=a out (ω)[a in (ω)] -1

[0031] In the formula, [] -1 This represents the pseudo-inverse matrix.

[0032] In the acoustic modal analysis method, step 3, the terminal matrix R is:

[0033] R = a in (ω)[a out (ω)] -1

[0034] The amplitude matrix of the acoustic wave modal pressure generated by the component itself under non-reflection conditions, a s (ω) is:

[0035] a s (ω)=[I 2N -S(ω)R]a out (ω)

[0036] In the formula, I 2N It is an identity matrix with dimension 2N.

[0037] In the acoustic modal analysis method, step 4,

[0038] The component under test is placed in an experimental setup for detecting and analyzing flow-induced and acoustic vibrations in a pipeline. The pressure field in the pipeline satisfies the Helmholtz equation, which is given at point s1 = (s1, z1):

[0039]

[0040] In the formula, the center of the main pipeline air inlet section is taken as the origin of the coordinate system, s1 represents the circumferential and radial positions of the measuring point, and z1 represents the axial distance between the microphone and the main pipeline air inlet; p ac For sound pressure, Ψ pq To normalize the pipeline modes, The amplitude of the downstream propagation mode. The amplitude of the upstream propagation mode, where i is the imaginary unit. ω is the angular frequency; The axial wave number is expressed as:

[0041]

[0042] In the formula, M is the Mach number, k ⊥ It is the circumferential wave number; k = ω / c is the wave number, and c = 340 m / s is the speed of sound;

[0043] The 2N-port method is used for acoustic modal analysis and calculation. The formula for the 2N-port method is as follows:

[0044] a out (ω)=S(ω)a in (ω)+a s (ω)

[0045] In the formula, a in(ω), a out (ω) represents the modal pressure amplitude matrix of the incident and reflected sound waves upstream and downstream of the element under test, respectively. and Let a be a vector consisting of acoustic modal coefficients. s (ω) is the amplitude matrix of the acoustic wave modal pressure generated by the element itself under non-reflection conditions, S(ω)∈c [2N×2N] Let I be the scattering matrix between the incident and reflected sound waves, and let I and II represent the upstream and downstream sides of the 2N port.

[0046] Calculate the cross-spectral density G s , is represented as:

[0047] G s =E[a s (ω)(a s (ω)) c ]

[0048] In the formula, E[] represents the expectation, and c represents the conjugate transpose of the matrix.

[0049] The beneficial effects of this invention are:

[0050] 1. The experimental apparatus for detecting and analyzing flow-induced and acoustic vibrations in pipelines according to this invention can simulate flow-induced and acoustic vibrations under different working conditions and perform modal analysis. It has high experimental reliability and accuracy and can provide theoretical support for pipeline design. This invention's apparatus can detect pipeline vibrations while simultaneously analyzing the acoustic modes within the pipe.

[0051] 2. The experimental device for detecting and analyzing flow-induced and acoustic vibrations in pipelines according to the present invention has a detachable and replaceable test section. It can replace the test section according to different test requirements, simulate different working conditions, and can also be replaced in time when the experimental equipment suffers fatigue failure. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the experimental device for detecting and analyzing the flow-induced and acoustic vibrations of pipelines according to the present invention.

[0053] Figure 2 This is a schematic diagram of the microphone array structure in the modal analysis section of this invention.

[0054] In the diagram, 1-1, main pipeline; 1-2, replaceable experimental pipeline; 2, gas source; 3, flow regulation section; 3-1, regulating ball valve; 3-2, gas mass flow meter; 4-1, first silencer; 4-2, second silencer; 5, pressure detection section; 5-1, pressure gauge; 5-2, vibration acceleration sensor; 6, modal analysis section; 6-1, microphone; 7, experimental data acquisition section. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0056] Experimental apparatus for detecting and analyzing flow-induced and acoustic-induced vibrations in pipelines, such as... Figure 1 As shown, it includes a main pipeline 1-1, one end of which is connected to a gas source 2, which is a centrifuge that provides test gas to the main pipeline 1-1. The gas source 2 and the main pipeline 1-1 are connected by a flexible tube, which is used to isolate the vibration of the gas source 2 and the main pipeline 1-1.

[0057] One end of the main pipeline 1-1 is connected to a first silencer 4-1, and the other end of the first silencer 4-1 is connected to a replaceable experimental pipeline 1-2, which is used to simulate the flow-induced and acoustic vibrations of different pipeline components. The other end of the replaceable experimental pipeline 1-2 is connected to a second silencer 4-2; the main pipeline 1-1 and the replaceable experimental pipeline 1-2 are on the same straight line. A flow regulating section 3 is installed near the air source 2 on the main pipeline 1-1, which is used to regulate the average flow rate within the pipeline. The first silencer 4-1 is used to reduce the noise generated by the air source 2 and the flow regulating section 3; air is discharged into the atmosphere through the second silencer 4-2, which is used to reduce the noise returning from the exhaust port to the pipeline and reduce the noise discharged into the atmosphere.

[0058] The flow regulation section 3 includes a regulating ball valve 3-1 and a gas mass flow meter 3-2, which are sequentially arranged on the main pipeline 1-1 along the airflow direction.

[0059] The replaceable experimental pipeline 1-2 is equipped with a modal analysis section 6 and a pressure detection section 5, which are arranged sequentially along the airflow direction near the second silencer 4-2. The pressure detection section 5 is used to detect the air pressure flowing through the replaceable experimental pipeline; the modal analysis section 6 is used to analyze the acoustic modes of the pipeline.

[0060] The pressure detection section 5 includes a pressure gauge 5-1 and a vibration acceleration sensor 5-2, which are sequentially arranged along the airflow direction on the replaceable experimental pipeline 1-2. The pressure detection section 5 is used to detect the air pressure flowing through the replaceable experimental pipeline 1-2.

[0061] Modal analysis section 6 includes several microphone arrays and a signal amplifier. Each microphone array includes several microphones 6-1, which are arranged at equal angles around the circumference of the replaceable experimental tubing 1-2. Figure 2 As shown; the signal amplifier is connected to several microphones 6-1. The modal analysis section 6 can distinguish between acoustic pressure and flow pressure, and measures the cross-spectral density at different distances using two sets of microphone arrays located upstream and downstream with different spacing.

[0062] It also includes an experimental data acquisition section 7, which is a computer. The experimental data acquisition section 7 is connected to the flow regulation section 3, the pressure detection section 5, and the modal analysis section 6, respectively, and is used to acquire data generated by the pressure detection section and the modal analysis section. Specifically, the regulating ball valve 3-1, the gas mass flow meter 3-2, the pressure gauge 5-1, the vibration acceleration sensor 5-2, and the signal amplifier are all connected to the experimental data acquisition section 7.

[0063] Methods for detecting and analyzing flow-induced and acoustic vibrations in pipelines, using experimental apparatus for detecting and analyzing flow-induced and acoustic vibrations in pipelines, including methods for detecting flow-induced and acoustic vibrations and methods for analyzing acoustic modes.

[0064] The methods for detecting flow-induced and acoustic-induced vibrations in pipelines specifically include the following steps:

[0065] Step 1: Select two microphone groups along the airflow direction. The microphones 6-1 at corresponding positions in the two microphone groups form a microphone pair.

[0066] Step 2: Start the air source 2 to fill the main pipeline with airflow, and at the same time start the flow regulation section 3 to regulate the airflow.

[0067] Step 3: Measure the fluid excitation signal and acoustic excitation signal using different microphone spacings, and use cross-spectral density to characterize the flow-induced and acoustic pressure;

[0068] The mean cross-spectral density of the signals obtained from several microphone pairs is calculated using the following formula:

[0069]

[0070] In the formula, X(ω) and Y(ω) are the frequency domain signals obtained by Fourier transform of the time-domain pressure pulsation signals collected by microphones at two measurement points (i.e., two corresponding positions), X*(ω) is the conjugate complex number of X(ω), and N represents the number of sampling points; f s The sampling frequency is represented by Hz; ω = 2πf is the angular frequency, in rad / s, where f represents the frequency, in Hz.

[0071] Generally, the microphone spacing for measuring flow-induced pressure signals is smaller than that for measuring acoustic pressure signals.

[0072] Step 4: The vibration acceleration sensor collects the vibration signal on the surface of the pipe.

[0073] The acoustic modal analysis method specifically includes the following steps:

[0074] Step 1: Place the component under test in the experimental apparatus for detecting and analyzing flow-induced and acoustic vibrations in a pipeline;

[0075] Step 2: With no flow in the pipe, first set up speakers at several microphone measuring points upstream of the component under test, turn on the speaker at any one microphone and collect the sound pressure signals from the other microphones;

[0076] The pressure signals from multiple microphones at the measurement point are represented as follows:

[0077]

[0078] In the formula, s l Let z represent the l-th microphone group, z represent the axial coordinate, and e represent the electrical signal from the signal amplifier. It is the transfer function between the l-th microphone and the electrical signal;

[0079] This operation is then repeated downstream of the device under test to obtain the amplitude matrix a of the incident acoustic wave modal pressure upstream and downstream of the device under test. in (ω) and the amplitude matrix of the reflected acoustic wave modal pressure a out (ω), at which point there is no sound source inside the tube, calculate the scattering matrix S(ω) between the incident sound wave and the reflected sound wave:

[0080] S(ω)=a out (ω)[a in (ω)] -1

[0081] In the formula, [] -1 This represents the pseudo-inverse matrix.

[0082] Step 3: Turn off the signal amplifier, start the centrifugal fan and adjust the flow regulation section 3 to a suitable opening. Select a cross section upstream and downstream of the replaceable experimental pipeline 1-2 to form a cross section pair. Take two cross section pairs at different locations and measure their cross-spectral density. Sound reflections are generated at both ends of the pipeline flow-induced and acoustic vibration detection and acoustic modal analysis experimental device. Calculate the terminal matrix R and the acoustic modal pressure amplitude matrix a generated by the element itself under no-reflection conditions. s (ω);

[0083] The terminal matrix R is:

[0084] R = a in (ω)[a out (ω)] -1

[0085] The amplitude matrix of the acoustic wave modal pressure generated by the component itself under non-reflection conditions, a s (ω) is:

[0086] a s (ω)=[I 2N -S(ω)R]a out (ω)

[0087] In the formula, I2N It is an identity matrix with dimension 2N.

[0088] Step 4: Analyze and calculate the acoustic modes using the 2N port method.

[0089] The component under test is placed in an experimental setup for detecting and analyzing flow-induced and acoustic vibrations in a pipeline. The pressure field in the pipeline satisfies the Helmholtz equation, which is given at point s1 = (s1, z1):

[0090]

[0091] In the formula, the center of the main pipeline air inlet section is taken as the origin of the coordinate system, s1 represents the circumferential and radial positions of the measuring point, and z1 represents the axial distance between the microphone and the main pipeline air inlet; p ac For sound pressure, ψ pq To normalize the pipeline modes, The amplitude of the downstream propagation mode. The amplitude of the upstream propagation mode, where i is the imaginary unit. ω is the angular frequency; The axial wave number is expressed as:

[0092]

[0093] In the formula, M is the Mach number, k ⊥ ω is the circumferential wavenumber; k = ω / c is the wavenumber, and c = 340 m / s is the speed of sound. The purpose of in-tube acoustic modal measurement is to obtain the amplitude of each higher-order acoustic mode.

[0094] The 2N-port method is used for acoustic modal analysis and calculation. The formula for the 2N-port method is as follows:

[0095] a out (ω)=S(ω)a in (ω)+a s (ω)

[0096] In the formula, a in (ω), a out (ω) represents the modal pressure amplitude matrix of the incident and reflected sound waves upstream and downstream of the element under test, respectively. and Let a be a vector consisting of acoustic modal coefficients. s (ω) is the amplitude matrix of the acoustic wave modal pressure generated by the element itself under non-reflection conditions, S(ω)∈c [2N×2N] Let I be the scattering matrix between the incident and reflected sound waves, and let I and II represent the upstream and downstream sides of the 2N port.

[0097] Calculate the cross-spectral density G s , is represented as:

[0098] G s =E[a s (ω)(a s (ω)) c ]

[0099] In the formula, E[] represents the expectation, and c represents the conjugate transpose of the matrix.

[0100] Example 1

[0101] This embodiment provides an experimental apparatus for detecting and analyzing the flow-induced and acoustic-induced vibrations of pipelines, such as... Figure 1 As shown, it includes a main pipeline 1-1, one end of which is connected to an air source 2, and the other end of which is connected to a first silencer 4-1. The other end of the first silencer 4-1 is connected to a replaceable experimental pipeline 1-2, and the other end of the replaceable experimental pipeline 1-2 is connected to a second silencer 4-2. The main pipeline 1-1 and the replaceable experimental pipeline 1-2 are on the same straight line. A flow regulation section 3 is provided on the main pipeline 1-1 near the air source 2. A modal analysis section 6 and a pressure detection section 5 are arranged sequentially along the airflow direction on the replaceable experimental pipeline 1-2 near the second silencer 4-2. It also includes an experimental data acquisition section 7, which is connected to the flow regulation section 3, the pressure detection section 5, and the modal analysis section 6, respectively.

[0102] Example 2

[0103] Based on Example 1, the air source 2 is a centrifugal fan; a flexible pipe is installed between the main pipeline 1-1 and the centrifugal fan. The experimental data acquisition section 7 is a computer.

[0104] Example 3

[0105] Based on Example 2, the flow regulation section 3 includes a regulating ball valve 3-1 and a gas mass flow meter 3-2 arranged sequentially along the airflow direction on the main pipeline 1-1. The regulating ball valve 3-1 and the gas mass flow meter 3-2 are respectively connected to the experimental data acquisition section 7.

[0106] The pressure detection section 5 includes a pressure gauge 5-1 and a vibration acceleration sensor 5-2, which are sequentially installed on the replaceable experimental pipeline 1-2 along the airflow direction. The pressure gauge 5-1 and the vibration acceleration sensor 5-2 are respectively connected to the experimental data acquisition section 7.

[0107] Modal analysis section 6 includes several microphone arrays and a signal amplifier. Each microphone array includes several microphones 6-1, which are arranged at equal angles around the replaceable experimental tubing 1-2. The signal amplifier is connected to the microphones 6-1 and the experimental data acquisition section 7.

[0108] Example 4

[0109] This embodiment provides a method for detecting flow-induced and acoustic-induced vibrations in pipelines, using the experimental apparatus for detecting and analyzing flow-induced and acoustic-induced vibrations in pipelines and acoustic modal analysis provided in Embodiment 3. The method specifically includes the following steps:

[0110] Step 1: Select two microphone groups along the airflow direction. The microphones 6-1 at corresponding positions in the two microphone groups form a microphone pair.

[0111] Step 2: Start the air source 2 to fill the main pipeline 1-1 with airflow, and at the same time start the flow regulation section 3 to regulate the airflow.

[0112] Step 3: Measure the fluid excitation signal and acoustic excitation signal using different microphone spacings, and use cross-spectral density to characterize the flow-induced and acoustic pressure;

[0113] The mean cross-spectral density of the signals obtained from several microphone pairs is calculated using the following formula:

[0114]

[0115] In the formula, X(ω) and Y(ω) are the frequency domain signals obtained by Fourier transform of the time-domain pressure pulsation signals collected by microphones at two measurement points (i.e., two corresponding positions), X*(ω) is the conjugate complex number of X(ω), and N represents the number of sampling points; f s The sampling frequency is represented by Hz; ω = 2πf is the angular frequency, in rad / s, where f represents the frequency, in Hz.

[0116] Step 4: The vibration acceleration sensor collects the vibration signal on the surface of the pipe.

[0117] Example 5

[0118] This embodiment provides an acoustic modal analysis method, using the pipeline flow-induced and acoustic-induced vibration detection and acoustic modal analysis experimental apparatus provided in Embodiment 3, specifically including the following steps:

[0119] Step 1: Place the component under test in the experimental apparatus for detecting and analyzing flow-induced and acoustic vibrations in a pipeline;

[0120] Step 2: In the absence of flow in the pipe, first set up loudspeakers at several microphone measuring points upstream of the component under test, turn on the loudspeaker at any microphone and collect the sound pressure signals from the other microphones; then repeat the operation downstream of the component under test to obtain the modal pressure amplitude matrix of the incident sound wave and the reflected sound wave upstream and downstream of the component under test, and calculate the scattering matrix S(ω) between the incident sound wave and the reflected sound wave.

[0121] Step 3: Turn off the signal amplifier, start the centrifugal fan and adjust the flow regulation section 3 to a suitable opening. Select a cross section upstream and downstream of the replaceable experimental pipeline 1-2 to form a cross section pair. Take two cross section pairs at different locations and measure their cross-spectral density. Sound reflections are generated at both ends of the pipeline flow-induced and acoustic vibration detection and acoustic modal analysis experimental device. Calculate the terminal matrix R and the acoustic modal pressure amplitude matrix a generated by the element itself under no-reflection conditions. s (ω);

[0122] Step 4: Analyze and calculate the acoustic modes using the 2N port method.

[0123] Example 6

[0124] Based on Example 5, in step 2, speakers are first set up at several microphone measurement points upstream of the component under test. The speaker at any one microphone is turned on, and the sound pressure signals from the other microphones are collected. The multiple microphone pressure signals at the measurement points are represented as follows:

[0125]

[0126] In the formula, s l Let z represent the l-th microphone group, z represent the axial coordinate, and e represent the electrical signal from the signal amplifier. It is the transfer function between the l-th microphone and the electrical signal;

[0127] This operation is then repeated downstream of the device under test to obtain the amplitude matrix a of the incident acoustic wave modal pressure upstream and downstream of the device under test. in (ω) and the amplitude matrix of the reflected acoustic wave modal pressure a out (ω), at this time there is no sound source inside the tube, and the scattering matrix S(ω) between the incident sound wave and the reflected sound wave is:

[0128] S(ω)=a out (ω)[a in (ω)] -1

[0129] In the formula, [] -1 This represents the pseudo-inverse matrix.

[0130] In step 3, the terminal matrix R is:

[0131] R = a in (ω)[a out (ω)] -1

[0132] The amplitude matrix of the acoustic wave modal pressure generated by the component itself under non-reflection conditions, a s (ω) is:

[0133] a s (ω)=[I 2N-S(ω)R]a out (ω)

[0134] In the formula, I 2N It is an identity matrix with dimension 2N.

[0135] In step 4,

[0136] The component under test is placed in an experimental setup for detecting and analyzing flow-induced and acoustic vibrations in a pipeline. The pressure field in the pipeline satisfies the Helmholtz equation, which is given at point s1 = (s1, z1):

[0137]

[0138] In the formula, the center of the main pipeline air inlet section is taken as the origin of the coordinate system, s1 represents the circumferential and radial positions of the measuring point, and z1 represents the axial distance between the microphone and the main pipeline air inlet; p ac For sound pressure, ψ pq To normalize the pipeline modes, The amplitude of the downstream propagation mode. The amplitude of the upstream propagation mode, where i is the imaginary unit. ω is the angular frequency; The axial wave number is expressed as:

[0139]

[0140] In the formula, M is the Mach number, k ⊥ It is the circumferential wave number; k = ω / c is the wave number, and c = 340 m / s is the speed of sound;

[0141] The 2N-port method is used for acoustic modal analysis and calculation. The formula for the 2N-port method is as follows:

[0142] a out (ω)=S(ω)a in (ω)+a s (ω)

[0143] In the formula, a in (ω), a out (ω) represents the modal pressure amplitude matrix of the incident and reflected sound waves upstream and downstream of the element under test, respectively. and Let a be a vector consisting of acoustic modal coefficients. s (ω) is the amplitude matrix of the acoustic wave modal pressure generated by the element itself under non-reflection conditions, S(ω)∈c [2N×2N] Let I be the scattering matrix between the incident and reflected sound waves, and let I and II represent the upstream and downstream sides of the 2N port.

[0144] Calculate the cross-spectral density G s , is represented as:

[0145] G s =E[a s (ω)(a s (ω)) c ]

[0146] In the formula, E[] represents the expectation, and c represents the conjugate transpose of the matrix.

Claims

1. A method for detection of flow-induced and acoustic-induced vibrations and acoustic mode analysis of a pipe, characterized in that, The application relates to a pipeline flow-induced and sound-induced vibration detection and sound modal analysis experimental device, which comprises a main pipeline (1-1), one end of the main pipeline (1-1) is connected with an air source (2), the other end of the main pipeline (1-1) is connected with a first silencer (4-1), the other end of the first silencer (4-1) is connected with a replaceable experimental pipeline (1-2), and the other end of the replaceable experimental pipeline (1-2) is connected with a second silencer (4-2); the main pipeline (1-1) and the replaceable experimental pipeline (1-2) are on the same straight line; a flow adjusting part (3) is arranged at a position close to the air source (2) of the main pipeline (1-1); a modal analysis part (6) and a pressure detection part (5) are sequentially arranged at a position close to the second silencer (4-2) of the replaceable experimental pipeline (1-2) along the air flow direction; and an experimental data acquisition part (7) is further arranged and connected with the flow adjusting part (3), the pressure detection part (5) and the modal analysis part (6). The application further discloses a pipeline flow-induced and sound-induced vibration detection method and a sound modal analysis method. The pipeline flow-induced and sound-induced vibration detection method comprises the following steps: Step 1: selecting two microphone groups along the air flow direction, and arranging the microphones (6-1) at the corresponding positions of the two microphone groups to form a microphone pair; Step 2: starting the air source (2) to fill the air flow into the main pipeline (1-1), and starting the flow adjusting part (3) to adjust the air flow; Step 3: measuring the fluid excitation signal and the sound excitation signal by adopting different microphone spacings, and adopting the cross-spectral density to represent the flow-induced and sound-induced pressure; calculating the mean value of the cross-spectral density of the signals obtained by the microphone pairs, and the formula is as follows: In the formula, , is the frequency domain signal obtained by Fourier transform of the time domain pressure fluctuation signal collected by the two microphones at two measuring points, i.e., two corresponding positions, is the conjugate complex of , N represents the number of sampling points; represents the sampling frequency, in Hz; is the angular frequency, in rad / s , represents the frequency, in Hz ; Step 4: collecting the pipeline surface vibration signal by adopting the vibration acceleration sensor; The sound modal analysis method comprises the following steps: Step 1: placing the element to be detected in the pipeline flow-induced and sound-induced vibration detection and sound modal analysis experimental device; Step 2: Set up loudspeakers at several microphone measuring points upstream of the element to be measured in the absence of flow in the pipeline, open the loudspeaker at any one microphone and collect the sound pressure signals of other microphones; repeat the operation downstream of the element to be measured to obtain the incident sound wave modal pressure amplitude matrix upstream and downstream of the element to be measured and the reflected sound wave modal pressure amplitude matrix , calculate the scattering matrix between the incident sound wave and the reflected sound wave ; Step 3: Close the signal amplifier, start the centrifugal fan and adjust the flow regulating part (3) to the appropriate opening, select one cross section on the upstream and downstream of the replaceable experimental pipeline (1-2) to form a cross section pair, measure the cross spectrum density of two different cross section pairs, the sound reflection is generated on both sides of the terminal of the pipeline flow-induced, sound-induced vibration detection and sound mode analysis experimental device, calculate the terminal matrix R and the sound wave mode pressure amplitude matrix generated by the element itself under the condition of no reflection ; Step 4: analyzing and calculating the sound modal by adopting the 2N port method, and the specific method is as follows: The element to be tested is placed in the pipeline flow-induced and acoustic vibration detection and acoustic modal analysis experimental device, the pressure field in the pipeline satisfies the Helmholtz equation, at point : where the center of the cross section of the inlet of the main pipe is taken as the coordinate origin, is the circumferential and radial position of the measuring point, is the axial distance of the microphone from the inlet of the main pipe; is the sound pressure, is the normalized pipe mode, is the amplitude of the downstream propagating mode, is the amplitude of the upstream propagating mode, i is the imaginary unit, and ω is the angular frequency; is the axial wave number, expressed as: wherein is the Mach number, is the circumferential wave number; is the wave number, is the sound speed; The 2N port method formula for analyzing and calculating the sound modal is as follows: wherein, , , , , are the incident and reflected acoustic mode pressure amplitude matrices of the upstream and downstream sides of the element under test, respectively, and are the vectors of acoustic mode coefficients, is the acoustic mode pressure amplitude matrix of the element itself without reflections, is the scattering matrix between the incident and reflected acoustic waves, and I and II indicate the upstream and downstream sides of the 2N-port. Computing the cross-spectral density is expressed as: wherein denotes the expectation, denotes the conjugate transpose of a matrix.

2. The method of claim 1, wherein, A flexible pipe is arranged between the main pipeline (1-1) and the air source (2).

3. The method of claim 1, wherein the method further comprises: The flow adjusting part (3) comprises a regulating ball valve (3-1) and a gas mass flow meter (3-2) which are sequentially arranged on the main pipeline (1-1) along the air flow direction, and the regulating ball valve (3-1) and the gas mass flow meter (3-2) are connected with the experimental data acquisition part (7).

4. The method of claim 1, wherein the method further comprises: The pressure detection part (5) comprises a pressure gauge (5-1) and a vibration acceleration sensor (5-2) which are sequentially arranged on the replaceable experimental pipeline (1-2) along the air flow direction, and the pressure gauge (5-1) and the vibration acceleration sensor (5-2) are connected with the experimental data acquisition part (7).

5. The method of claim 1, wherein the method further comprises: The modal analysis part (6) comprises a plurality of groups of microphone arrays and a signal amplifier, each group of the microphone arrays comprises a plurality of microphones (6-1), the plurality of microphones (6-1) are arranged at equal angles along the replaceable experimental pipeline (1-2) in a circumferential direction, the signal amplifier is connected with the plurality of microphones (6-1), and the signal amplifier is connected with the experimental data acquisition part (7).

6. The method of claim 1, wherein, The air source (2) is a centrifugal fan, and the experimental data acquisition part (7) is a computer.

7. The method of claim 1, wherein the method further comprises: In the sound modal analysis method, in step 2, a loudspeaker is arranged at each microphone measuring point upstream of the element to be measured, the loudspeaker at any microphone is turned on, and sound pressure signals of other microphones are collected, and the pressure signals of the plurality of microphones at the measuring point are represented as: wherein represents the first group of microphones, z represents the axial coordinate, e is an electrical signal of the signal amplifier, is the first transfer function between the first microphone and the electrical signal; The operation is repeated downstream of the element under test to obtain the matrix of incident and reflected acoustic wave modal pressure amplitudes upstream and downstream of the element under test and reflected acoustic wave modal pressure amplitudes The scattering matrix between the incident and reflected acoustic waves when there is no sound source in the tube is then : In the formula, denotes the pseudo-inverse matrix.

8. The method of claim 7, wherein the method further comprises: In the sound modal analysis method, in step 3, the terminal matrix R is: Amplitude matrix of acoustic modes generated by an element itself without reflection conditions is: In the formula, is a unit matrix of dimension is a unit matrix of dimension

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