Design method of circumferential Lamb wave-like sensor array for detecting gas content of pipeline

Abstract

The invention discloses a circumferential Lamb wave sensor array design method for detecting the gas content of a pipeline, and the method comprises the steps: determining the arrangement mode of a circumferential Lamb wave sensor array according to an application scene; establishing a sensor unit model, and determining an incident angle of a sensor transmitting signal; sensitivity testing is carried out on various geometrical parameters of the sensor unit, and geometrical parameters which have great influence on various response characteristics are found out; simulating different conditions of the obtained geometric parameters with relatively large influence on each response characteristic, designing and manufacturing a single sensor unit to obtain proper sensor unit parameters, and completing the design of the sensor unit; and carrying out a vibration test on the designed sensor unit, and if the performance of the sensor unit meets the design requirement, completing the design of the circumferential Lamb wave-like sensor array. The method is simple and practical, and the circumferential Lamb wave sensor array designed by the method can effectively excite the circumferential Lamb waves.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor arrays, and in particular to a design method for a circumferential Lamb wave-like sensor array. Background Art

[0002] Gas content is a crucial flow parameter in two-phase flow. It is not only a key variable for analyzing the mechanism of the production process, but also an important indicator for monitoring the stability of the production control system. It also plays an important role in accurately evaluating the production volume of products such as oil and natural gas. At present, the use of ultrasonic detection technology to measure the gas content in pipelines has become one of the main research directions at home and abroad. The advantage of ultrasonic detection technology is that it has a high resolution in the pipeline space. Through the penetration method, detailed information on the liquid level in the pipeline can be obtained, and then the gas content in the pipeline can be inferred.

[0003] However, ultrasonic detection technology also faces some challenges in practical applications. First, ultrasonic waves will experience a large attenuation during the propagation process in the liquid, which limits its detection distance and accuracy. Second, ultrasonic detection can only obtain information changes on the ultrasonic propagation path, and it is difficult to capture information between radial interfaces of the pipeline profile. Especially when facing fluids with complex boundary conditions, traditional ultrasonic detection methods are insufficient in the accuracy of detecting gas content.

[0004] When Lamb-like waves propagate in the pipeline, they can cover the entire pipeline section, and then carry the information between the solid / liquid, solid / gas, and gas / liquid interfaces in the circumferential direction of the entire pipeline section. The gas content information between the wall / liquid, wall / gas, and gas / liquid interfaces of the actual horizontal gas-liquid two-phase flow pipeline section is usually more complicated. At the same time, when the circumferential Lamb-like waves are used to propagate along the pipeline section, due to the different acoustic properties of the pipeline material and the transmission medium in the pipeline, the propagation characteristics of the Lamb-like waves on the pipeline section will change accordingly, which is usually reflected in the changes in the signal characteristics of the Lamb-like waves (such as amplitude, phase, mode, etc.). However, the method of using circumferential Lamb-like waves to detect gas content still faces a problem in application, that is, most of the existing sensors are axially excited rather than circumferentially excited, and cannot fully cover the changes in the distribution of each phase of the pipeline multiphase flow. The detection sensitivity and accuracy of the gas content in the pipeline are limited. Therefore, it is necessary to explore the design method of the sensor array for circumferentially excited Lamb-like waves. Summary of the invention

[0005] In order to solve the technical problem of lack of excitation for sensor arrays propagating circumferentially along the pipeline when detecting the gas content of the pipeline, the present invention proposes a method for designing a circumferential Lamb wave sensor array for detecting the gas content of the pipeline. The sensor array designed by the present invention can excite circumferential guided waves.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A method for designing a circumferential Lamb wave sensor array for pipeline gas content detection, comprising the following steps:

[0008] S1. Determine the arrangement of the circumferential Lamb wave sensor array according to the application scenario;

[0009] S2. Establish a sensor unit model and determine the incident angle of the sensor emission signal;

[0010] S3, perform sensitivity tests on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on each response characteristic;

[0011] S4, simulating different situations of the geometric parameters that have a greater impact on each response characteristic found in step S3 and designing and manufacturing a single sensor unit to obtain appropriate sensor unit parameters and complete the design of the sensor unit;

[0012] S5. Perform a vibration test on the designed sensor unit. If the performance of the sensor unit meets the design requirements, the design of the circumferential Lamb wave sensor array is completed. Otherwise, return to step S4.

[0013] Preferably, the circumferential Lamb wave sensor array is arranged in a circular annular array;

[0014] The circumferential Lamb wave sensor array includes four sensor units, two sensor units are used for transmitting signals, and two sensor units are used for receiving signals.

[0015] Preferably, the sensor unit includes a probe, a wedge-shaped base is arranged on the lower side of the probe, the probe includes a shell, a PZT element is arranged in the shell, one side of the PZT element is connected to the wedge-shaped base, and the other side of the PZT element is connected to the coaxial cable, and the lower half of the space in the shell is filled with a mixture of epoxy resin and tungsten powder, and the filling interface extends from the bottom to the middle of the shell, completely covering the connection between the PZT element and the coaxial cable.

[0016] Preferably, a notch is provided at the bottom of the wedge-shaped base, and a groove surface of the notch is an arc-shaped groove surface. The top of the wedge-shaped base has an inclined surface, and the shell is arranged on the inclined surface.

[0017] Preferably, the method for determining the incident angle of the sensor emission signal is: ① obtaining the pipeline material, the type of gas in the pipeline, the type of liquid in the pipeline and the speed of sound in the gas, and calculating the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface based on Snell's theorem; ② selecting the larger value of the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface; ③ the incident angle of the sensor emission signal is greater than the larger value selected in step ②.

[0018] Preferably, the geometric parameters of the sensor unit include a wedge-shaped base length, a wedge-shaped base width, a wedge-shaped base height and a wedge-shaped base notch depth;

[0019] The step of performing sensitivity testing on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on various response characteristics includes:

[0020] Standardizing the geometric parameters of the sensor unit, and using the standardized geometric parameters of the sensor unit as input variables;

[0021] Assign a mutually prime integer as the basic frequency to each geometric parameter in the input variable, then generate a periodic search curve, map the multidimensional parameter space to the one-dimensional curve parameter, and for each geometric parameter, evenly select N points along the one-dimensional curve parameter to generate N sample points, obtain a standardized value sequence for each geometric parameter, and combine them into a multidimensional sample matrix; obtain the output response of each sample point through finite element simulation, perform discrete Fourier transform on the output response, calculate the spectrum amplitude, and then ignore the DC component to obtain the total energy;

[0022] The main effect sensitivity index is used to represent the contribution of the geometric parameters to the output variance, and the total effect sensitivity index is used to represent the total contribution of the geometric parameters and their interactions. The importance of the geometric parameters of the sensor unit is evaluated based on the main effect sensitivity index and the total effect sensitivity index, and the geometric parameters that have a greater impact on each response characteristic are obtained.

[0023] Preferably, the expression of the geometric parameter is:

[0024]

[0025] in, is the random phase offset, ω i is the basic frequency, s∈[0,1] is the one-dimensional curve parameter; for each geometric parameter X i , uniformly select N points along the one-dimensional curve parameter to generate N sample points X i (s k ),in, k=1,2,…,N.

[0026] Preferably, the sample point X i (s k )’s output response Y(s k ) = {Z, M, ξ}, where Z is the amplitude ratio, M is the sensor unit mass, and ξ is the characteristic frequency;

[0027] The output response Y(s k )The expression for discrete Fourier transform is:

[0028]

[0029] Spectrum Amplitude A p =|Y p |, Y p The output response Y(s k ), is the frequency in the discrete Fourier transform; the total energy is: Where p is the frequency component number.

[0030] Preferably, the calculation formula of the main effect sensitivity index is:

[0031]

[0032] In the formula, S i is the main effect sensitivity index, P i Represents the fundamental frequency ω i associated frequency bands;

[0033] The calculation formula of the total effect sensitivity index is:

[0034]

[0035] In the formula, is the total effect sensitivity index;

[0036] If S i >0.1 or Then the geometric parameter X i is the key parameter; if Indicates the geometric parameters X i The output is significantly affected by the interaction, and the geometric parameters that have the greatest influence on each response characteristic are the wedge base width and the wedge base notch depth.

[0037] Preferably, the method for simulating different situations of the geometric parameters having a greater impact on each response characteristic found in step S3 and designing and manufacturing a single sensor unit is as follows: taking the maximum displacement response of the contact surface between the sensor unit and the pipeline as the design goal, taking the sensor unit satisfying the set operating frequency and having the lowest impedance as the constraint conditions, obtaining the most suitable set of geometric parameters and designing and manufacturing the sensor unit.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention provides an innovative method for designing a circumferential Lamb wave sensor array for pipeline gas content detection. The present invention is simpler than the existing design method, and the angle of transmitting ultrasonic signals can be adjusted as needed. The circumferential Lamb wave sensor array designed by the present invention can effectively excite circumferential Lamb waves, and the transmission and reception of signals are respectively realized by using different sensor unit signals, so that the signal transmission is more efficient. The sensor unit designed by the present invention can achieve the maximum displacement response at the designed working frequency, thereby significantly measuring the accuracy and sensitivity of the pipeline gas content. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 It is a flow chart of the present invention.

[0042] Figure 2 Schematic diagram of a circumferential Lamb wave sensor array in one embodiment of the present invention.

[0043] Figure 3 The figure is a schematic diagram of sending and receiving signals of a circumferential Lamb wave sensor array in one embodiment of the present invention.

[0044] Figure 4 FIG. 4 is an overall structural diagram of a sensor unit in an embodiment of the present invention.

[0045] Figure 5 FIG. 1 is a schematic diagram of the probe structure of a sensor unit in one embodiment of the present invention.

[0046] Figure 6 1 is a three-view diagram of a wedge-shaped base of a sensor unit in one embodiment of the present invention.

[0047] Figure 7 FIG. 4 is a frequency-displacement response diagram in one embodiment of the present invention.

[0048] Figure 8 This is a schematic diagram of the vibration test principle of the present invention.

[0049] In the figure, 1-probe, 2-wedge base, 3-housing, 4-PZT element, 5-coaxial cable, 6-epoxy resin and tungsten powder mixture. DETAILED DESCRIPTION

[0050] 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.

[0051] like Figure 1 As shown, a method for designing a circumferential Lamb wave sensor array for pipeline gas content detection comprises the following steps:

[0052] S1. Determine the arrangement of the circumferential Lamb wave sensor array according to the application scenario.

[0053] Since the circumferential Lamb wave sensor array is used for pipeline gas content detection, the circumferential Lamb wave sensor array is arranged in a circular ring array.

[0054] The circumferential Lamb wave sensor array includes four sensor units and sensor unit fasteners, such as Figure 2 As shown, two sensor units are used for transmitting signals, and two sensor units are used for receiving signals. When in use, the sensor units are fixed on the pipeline by fasteners.

[0055] like Figure 3 As shown, in some feasible implementations, the sensor units for transmitting signals are respectively arranged above and below the pipeline, and the sensor units for receiving signals are respectively arranged on the left and right sides of the pipeline; taking the sensor unit arranged on the right side of the pipeline for receiving signals as an example, when the Lamb-like wave is emitted clockwise, the sensor unit arranged on the right side of the pipeline for receiving signals will first receive the signal emitted by the sensor unit arranged above the pipeline for transmitting signals, and then receive the signal emitted by the sensor unit arranged below the pipeline for transmitting signals.

[0056] In order to allow the Lamb-like wave emitted by the sensor unit for transmitting signals to be transmitted along the circumference of the pipeline and the sensor unit for receiving signals to receive signals emitted by two sensor units for transmitting signals, it is necessary to determine the incident angle of the sensor transmitting signal.

[0057] S2. Establish a sensor unit model and determine the incident angle of the sensor's transmitted signal.

[0058] like Figure 4As shown, the sensor unit includes a probe 1, a wedge-shaped base 2 is arranged at the lower side of the probe 1, the probe 1 includes a shell 3, a PZT (Lead Zirconate Titanate, lead zirconate titanate piezoelectric ceramic) element 4 is arranged in the shell 3, one side of the PZT element 4 is connected to the wedge-shaped base 2, and the other side of the PZT element 4 is connected to the coaxial cable 5, the coaxial cable 5 is led out from the top of the probe 1, and the lower half of the space in the shell 3 is filled with a mixture of epoxy resin and tungsten powder 6, and the filling interface extends from the bottom to the middle of the shell, completely covering the connection between the PZT element 4 and the coaxial cable 5.

[0059] Further, the probe 1 is used to generate circumferential Lamb-like waves, and the wedge-shaped base 2 is used to fix the probe 1 on the pipeline, and to make the circumferential Lamb-like waves generated by the probe 1 be applied to the pipeline at a specific incident angle;

[0060] Specifically, the PZT element 4 is used as a sensor; the epoxy resin and tungsten powder mixture 6 has an acoustic impedance similar to that of PZT, and the epoxy resin and tungsten powder mixture 6 is used to reduce the reverse emission of the circumferential Lamb-like wave during the transmission process.

[0061] PZT is a ceramic commonly used in piezoelectric materials. It has excellent piezoelectric properties and is widely used in sensors, actuators, ultrasonic equipment, etc. The piezoelectric effect of PZT enables it to convert mechanical stress into electrical signals, or convert electrical signals into mechanical motion.

[0062] Specifically, the PZT element 4 and the coaxial cable 5 are connected by welding.

[0063] Furthermore, when selecting the model of the PZT element 4, the PZT element 4 in the sensor unit for transmitting the signal preferably has a high-voltage electric strain constant (piezoelectric strain constant is 500-800 pC / N) and a low dielectric loss model (dielectric loss tangent value ≤ 0.005), such as PZT-5H or PZT-8; the PZT element 4 in the sensor unit for receiving the signal preferably has a high-voltage electric voltage constant (piezoelectric voltage constant is 20-30×10 -3 V·m / N) and high mechanical quality factor (mechanical quality factor is 500-2000), such as PZT-4.

[0064] In some feasible implementations, the PZT element 4 in the sensor unit for receiving signals may be replaced by other flexible composite material elements, such as rubber.

[0065] In the present embodiment, a wraparound PZT element is used, the model of the PZT element 4 in the sensor unit for transmitting signals is PZT-5H, and the model of the PZT element 4 in the sensor unit for receiving signals is PZT-4.

[0066] like Figure 5 As shown, the wraparound PZT element can integrate two electrodes on one surface, so that the wiring is completed on one surface and the other surface is used as the area for transmitting and receiving signals. The mini coaxial cable is soldered to the two electrodes of the PZT and then converted to a larger coaxial cable for output through the SMB plug.

[0067] like Figure 6 As shown, a notch is provided at the bottom of the wedge-shaped base 2, and the groove surface of the notch is an arc-shaped groove surface, and the curvature of the groove surface is the same as the curvature of the pipe. The top of the wedge-shaped base 2 has an inclined surface, and the shell 3 is arranged on the inclined surface.

[0068] Furthermore, the method for determining the incident angle of the sensor emission signal is:

[0069] ① Obtain the pipeline material, the type of gas in the pipeline, the type of liquid in the pipeline and the speed of sound in the gas, and calculate the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface based on Snell's theorem; ② Select the larger value of the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface; ③ The incident angle of the sensor transmitting the signal is greater than the larger value selected in step ②, so that the circumferential Lamb-like wave can achieve total reflection at the interface between the pipeline and the liquid and the gas.

[0070] Take the water-air gas-liquid two-phase flow in a carbon steel pipeline as an example:

[0071] Phase velocity of circumferential Lamb-like waves in carbon steel pipes: V 1 =3200m / s; Speed ​​of sound in water: V 2 =1500m / s; speed of sound in air: V 3 =343m / s;

[0072] Therefore, the critical angle of the circumferential Lamb-like wave to the water interface is: The critical angle of circumferential Lamb-like wave to air interface:

[0073] Substituting into numerical calculation, we can get the critical angle θ of the circumferential Lamb-like wave to the water interface: 1 =27.96°, the critical angle θ of the circumferential Lamb-like wave to the air interface 2 =6.15°, the incident angle θ of the sensor emission signal is greater than 27.96°. The incident angle can be adjusted by adjusting the angle of the inclined surface of the wedge-shaped base.

[0074] S3. Perform sensitivity tests on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on each response characteristic.

[0075] Furthermore, the EFAST (Extended Fourier Amplitude Sensitivity Test) method is used to perform sensitivity tests on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on each response characteristic.

[0076] The specific steps are as follows:

[0077] Firstly, the geometric parameters of the sensor unit are standardized, and the actual value range of each geometric parameter is standardized to the interval [0, 1], so that each geometric parameter varies within the same interval, which is convenient for comparing the sensitivity of each geometric parameter to the system output and quickly identifying the key design variables.

[0078] The geometric parameters of the sensor unit include the length of the wedge-shaped base 2 , the width of the wedge-shaped base 2 , the height of the wedge-shaped base 2 and the depth of the notch of the wedge-shaped base 2 .

[0079] The standardized geometric parameters of the sensor unit are used as input variables X={L, W, H, dh}, where L is the length of the wedge base 2, W is the width of the wedge base, H is the height of the wedge base, and dh is the depth of the wedge base notch.

[0080] Assign a coprime integer to each geometric parameter in the input variable as the fundamental frequency ω i (e.g. ω = [11, 13, 17, 19]) to ensure that there is no harmonic interference between frequencies. Then, a periodic search curve is generated to map the multidimensional parameter space to a one-dimensional curve parameter s∈[0, 1]. Then the geometric parameter X i for:

[0081]

[0082] in, is a random phase offset used to avoid duplication of sampling points.

[0083] For each geometric parameter X i , uniformly select N points along the one-dimensional curve parameter s to generate N sampling points X i (s k ), obtain the standardized value sequence of each geometric parameter, and combine them into a multidimensional sample matrix X = {X 1 (s k ), X 2 (s k ), X 3 (s k ), X 4 (s k )…X N (s k )};

[0084]

[0085] For each sample point X i (s k ), and obtain the output response Y(s) through finite element simulation k )={Z,M,ξ}, Z is the amplitude ratio, M is the sensor unit mass, and ξ is the characteristic frequency.

[0086] The output response Y(s k ) to perform discrete Fourier transform (DFT) and calculate the spectrum amplitude A p and

[0087]

[0088] Y p Y(s k ), A p is the spectrum amplitude, is the frequency in the discrete Fourier transform.

[0089] Ignoring the DC component, the total energy is:

[0090]

[0091] Where p is the frequency component number.

[0092] The main effect sensitivity index S i Represents the geometric parameter X i The contribution of a single molecule to the output variance is calculated as:

[0093]

[0094] Among them, P i Represents the fundamental frequency ω i The associated frequency band.

[0095] Total Effect Sensitivity Index Characterization of geometric parameters X i and geometric parameters X i The total contribution of the interaction is calculated as:

[0096]

[0097] Finally, according to the main effect sensitivity index S i and total effect sensitivity index Evaluate the importance of geometric parameters of sensor units: If S i >0.1 or Then the geometric parameter X i is the key parameter; if Indicates the geometric parameters X i The output is significantly affected by the interaction. The geometric parameters with the greatest influence on each response characteristic are the wedge base width and the wedge base notch depth.

[0098] S4. Simulate different situations of the geometric parameters that have a greater impact on each response characteristic found in step S3 and design and manufacture a single sensor unit to obtain appropriate sensor unit parameters and complete the design of the sensor unit.

[0099] Taking the maximum displacement response of the contact surface between the sensor unit and the pipeline as the design goal and the sensor unit meeting the set operating frequency and minimum impedance as the constraints, the most suitable set of geometric parameters is obtained and the sensor unit is designed and manufactured.

[0100] Specifically, the excitation frequency is determined through the finite element analysis method to achieve the design goal of the sensor unit. The excitation frequency is to select the frequency of the Lamb-like wave signal to be excited. Lamb-like waves of different frequencies cause different displacement responses on the pipeline. Modeling and simulation are performed using COMSOL software: After the sensor unit used to transmit the signal is installed on the pipeline, the displacement response of the sensor unit and the contact surface of the pipeline is obtained using different excitation frequencies; the corresponding frequency-displacement response diagram is obtained, and the frequency with the largest displacement response is selected as the excitation frequency. A large displacement response means that at this frequency, the vibration amplitude of the Lamb-like wave is large and easier to detect. Because in actual detection, the signal may be affected by attenuation and noise. If the displacement response is large and the signal strength is high, the signal-to-noise ratio will be better and the detection result will be more reliable.

[0101] Taking a carbon steel pipeline with an inner diameter of 36 mm and an outer diameter of 32 mm as an example, a frequency sweep simulation is performed in the range of 20 kHz to 30 kHz. According to the corresponding frequency-displacement response diagram, the frequency with the largest displacement response is selected as the frequency of the circumferential Lamb-like wave to be excited, such as Figure 7 As shown, the displacement response is maximum when the excitation frequency is 22900 Hz, so the excitation frequency is determined to be 22900 Hz.

[0102] In this embodiment, based on the sensitivity analysis results, the optimal sensor unit performance is obtained by adjusting the wedge base width and the wedge base notch depth.

[0103] S5. Perform a vibration test on the designed sensor unit. If the performance of the sensor unit meets the design requirements, the design of the circumferential Lamb wave sensor array is completed. Otherwise, return to step S4.

[0104] In this embodiment, a vibration test is performed on the designed sensor unit by using a laser vibrometer, and the method is as follows:

[0105] like Figure 8As shown, the signal generator generates an excitation signal and transmits it to the power amplifier. The power amplifier performs power amplification processing on the input excitation signal. The power-amplified signal is transmitted to the sensor unit. The sensor unit emits a Lamb-like wave based on the received signal. At the same time, the laser vibrometer emits a laser signal to the carbon steel pipeline. When the carbon steel pipeline vibrates under the excitation of the Lamb-like wave, it will reflect the laser signal. The reflected laser signal is received by the laser vibrometer. By analyzing and processing the reflected laser signal, information such as the vibration characteristics of the carbon steel pipeline can be obtained, thereby realizing the performance evaluation of the sensor unit. Since the sensor unit emits a Lamb-like wave to make the pipeline vibrate, the performance of the sensor unit can be evaluated based on information such as the vibration characteristics of the carbon steel pipeline.

[0106] 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for designing a circumferential Lamb wave sensor array for pipeline gas content detection, characterized in that the steps include: S1. Determine the arrangement of the circumferential Lamb wave sensor array according to the application scenario; S2. Establish a sensor unit model and determine the incident angle of the sensor emission signal; S3, perform sensitivity tests on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on each response characteristic; S4, simulating different situations of the geometric parameters that have a greater impact on each response characteristic found in step S3 and designing and manufacturing a single sensor unit to obtain appropriate sensor unit parameters and complete the design of the sensor unit; S5. Perform a vibration test on the designed sensor unit. If the performance of the sensor unit meets the design requirements, the design of the circumferential Lamb wave sensor array is completed. Otherwise, return to step S4.

2. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 1, characterized in that: The circumferential Lamb wave sensor array is arranged in a circular annular array; The circumferential Lamb wave sensor array includes four sensor units, two sensor units are used for transmitting signals, and two sensor units are used for receiving signals.

3. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 2, characterized in that: The sensor unit comprises a probe (1), a wedge-shaped base (2) is arranged at the lower side of the probe (1), the probe (1) comprises a shell (3), a PZT element (4) is arranged in the shell (3), one side of the PZT element (4) is connected to the wedge-shaped base (2), and the other side of the PZT element (4) is connected to the coaxial cable (5), and the lower half space in the shell (3) is filled with a mixture of epoxy resin and tungsten powder (6), and the filling interface extends upward from the bottom to the middle of the shell, completely covering the connection between the PZT element (4) and the coaxial cable (5).

4. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 3, characterized in that: The bottom of the wedge-shaped base (2) is provided with a notch, the groove surface of the notch is an arc-shaped groove surface, the top of the wedge-shaped base (2) is provided with an inclined surface, and the outer shell (3) is arranged on the inclined surface.

5. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 4, characterized in that: The method for determining the incident angle of the sensor emission signal is as follows: ① obtaining the pipeline material, the type of gas in the pipeline, the type of liquid in the pipeline and the speed of sound in the gas, and calculating the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface based on Snell's theorem; ② selecting the larger value of the critical angle of the circumferential Lamb-like wave for the liquid interface and the critical angle of the circumferential Lamb-like wave for the gas interface; ③ the incident angle of the sensor emission signal is greater than the larger value selected in step ②.

6. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 5, characterized in that: The geometric parameters of the sensor unit include a wedge-shaped base length, a wedge-shaped base width, a wedge-shaped base height, and a wedge-shaped base notch depth; The step of performing sensitivity testing on various geometric parameters of the sensor unit to find out the geometric parameters that have a greater impact on various response characteristics includes: Standardizing the geometric parameters of the sensor unit, and using the standardized geometric parameters of the sensor unit as input variables; Assign a mutually prime integer as the basic frequency to each geometric parameter in the input variable, then generate a periodic search curve, map the multidimensional parameter space to the one-dimensional curve parameter, and for each geometric parameter, evenly select N points along the one-dimensional curve parameter to generate N sample points, obtain a standardized value sequence for each geometric parameter, and combine them into a multidimensional sample matrix; obtain the output response of each sample point through finite element simulation, perform discrete Fourier transform on the output response, calculate the spectrum amplitude, and then ignore the DC component to obtain the total energy; The main effect sensitivity index is used to represent the contribution of the geometric parameters to the output variance, and the total effect sensitivity index is used to represent the total contribution of the geometric parameters and their interactions. The importance of the geometric parameters of the sensor unit is evaluated based on the main effect sensitivity index and the total effect sensitivity index, and the geometric parameters that have a greater impact on each response characteristic are obtained.

7. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 6, characterized in that: The expression of the geometric parameters is: in, is the random phase offset, ω i is the basic frequency, s∈[0,1] is the one-dimensional curve parameter; for each geometric parameter X i , uniformly select N points along the one-dimensional curve parameter to generate N sample points X i (s k ),in, k=1,2,…,N.

8. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 7, characterized in that: Sample point X i (s k )’s output response Y(s k ) = {Z, M, ξ}, where Z is the amplitude ratio, M is the sensor unit mass, and ξ is the characteristic frequency; The output response Y(s k )The expression for discrete Fourier transform is: Spectrum Amplitude A p =|Y p |, Y p The output response Y(s k ), is the frequency in the discrete Fourier transform; the total energy is: Where p is the frequency component number.

9. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 8, characterized in that: The calculation formula of the main effect sensitivity index is: In the formula, S i is the main effect sensitivity index, P i Represents the fundamental frequency ω i associated frequency bands; The calculation formula of the total effect sensitivity index is: In the formula, is the total effect sensitivity index; If S i >0.1 or Then the geometric parameter X i is the key parameter; if Indicates the geometric parameters X i The output is significantly affected by the interaction, and the geometric parameters that have the greatest influence on each response characteristic are the wedge base width and the wedge base notch depth.

10. The method for designing a circumferential Lamb wave sensor array for pipeline gas content detection according to claim 1 or 9, characterized in that: The method for simulating different situations of the geometric parameters that have a greater impact on each response characteristic found in step S3 and designing and manufacturing a single sensor unit is as follows: taking the maximum displacement response of the contact surface between the sensor unit and the pipeline as the design goal, and taking the sensor unit meeting the set operating frequency and the lowest impedance as the constraint conditions, obtaining the most suitable set of geometric parameters and designing and manufacturing the sensor unit.

Images