Pipeline leakage monitoring instrument based on optical fiber interference and monitoring method thereof

Abstract

The invention discloses a pipeline leakage monitor based on optical fiber interference and a monitoring method thereof, and belongs to the technical field of pipe network leakage monitoring. According to the invention, through the cooperation of the differential deformation of the outer cylinder and the inner cylinder and the air cavity, the two paths of sensing optical fibers are driven to generate reverse and equal-length length strain, and the improvement of the sensitivity of pipeline micro leakage sound pressure signal-optical phase signal conversion and the suppression of environmental common-mode noise are realized; a sound pressure signal generated in the leakage process of a pipeline is converted into phase change of light through a balanced optical fiber interferometer, a leakage signal is demodulated through a phase detection technology, and high-precision pickup of the tiny leakage sound pressure signal of the pipeline is achieved; the sound velocity is calibrated in real time through the temperature sensor and the sound velocity compensation module, and microsecond-level wireless signal time service is combined, so that the technical effects of large positioning error and difficulty in multi-device synchronous sampling caused by temperature drift of the sound velocity along with a transmission medium are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline leakage monitoring, in particular to a pipeline leakage monitor based on fiber optic interference and its monitoring method. Background Art

[0002] At present, the technical means for pipeline leakage detection based on sound pressure signal pickup mainly include picking up the sound pressure signal generated during the pipeline leakage process through a piezoelectric hydrophone, and using distributed or quasi-distributed fiber optic sensing technology for monitoring. The former has insufficient sensitivity and cannot be used for monitoring tiny leakage signals; the latter requires the sensor and transmission optical cable to be laid along the pipeline in advance, increasing the difficulty and detection cost of pipeline leakage monitoring means; there is also a pipeline leakage monitoring technology based on fiber optic hydrophone sensing technology, but most of them require connecting the hydrophone to the demodulation host through an optical cable, or laying multiple fiber optic hydrophones along the pipeline through an optical cable connection, which has a large amount of construction work, is difficult to implement on old water supply pipe networks, and has a high cost. Summary of the Invention

[0003] In view of the above problems, a pipeline leakage monitor based on fiber optic interference and its monitoring method are provided. The present invention synergistically drives two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder and the inner cylinder and the air cavity, realizes the improvement of the conversion sensitivity of the pipeline micro-leakage sound pressure signal - optical phase signal and the suppression of environmental common-mode noise; converts the sound pressure signal generated during the leakage process of the pipeline into a phase change of light through a balanced fiber optic interferometer, and demodulates the leakage signal through phase detection technology to realize the high-precision pickup of the pipeline micro-leakage sound pressure signal.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows.

[0005] A pipeline leakage monitor based on fiber optic interference includes a sound pressure sensitive unit, a balanced interferometer for converting the sound pressure signal generated by pipeline leakage into an optical phase signal, a laser, a photodetector for converting the optical phase signal into an electrical signal, and a main control demodulation module; the sound pressure sensitive unit includes an inner cylinder and an outer cylinder coaxially sleeved, and a sealed air cavity is formed between the two; the balanced interferometer includes a first sensing optical fiber and a second sensing optical fiber that are respectively helically wound on the surfaces of the outer cylinder and the inner cylinder with prestress and have equal lengths, a coupler, and a Faraday rotator mirror; the sound pressure sensitive unit synergistically drives the two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder and the inner cylinder and the air cavity, realizing the improvement of the conversion sensitivity of the pipeline micro-leakage sound pressure signal - optical phase signal and the suppression of environmental common-mode noise.

[0006] Preferably, the sound pressure sensitive unit further includes a PEEK housing, and the outer wall of the PEEK housing is in direct contact with the transmission medium in the pipeline for receiving and transmitting the leakage sound pressure signal.

[0007] An impedance matching medium for enhancing the sound pressure transmission efficiency is filled between the outer cylinder and the PEEK housing.

[0008] Preferably, the impedance matching medium adopts an acoustic impedance matching medium or an acoustic couplant that is consistent with the material of the PEEK housing; the impedance matching medium is made of a composite material of polyetheretherketone, polyurethane, and silicon carbide.

[0009] Preferably, the monitor further includes a battery; a light source driving module for providing a low-noise power supply and temperature control; an antenna module for data communication and obtaining time synchronization signals, and a mounting base.

[0010] Preferably, a threaded interface is provided at the lower end of the mounting base, which is adapted to the fire hydrant hose interface or the exhaust valve.

[0011] Preferably, the main control demodulation module further includes a temperature sensor for real-time monitoring of the temperature of the transmission medium in the pipeline and a sound velocity compensation module.

[0012] Preferably, the main control demodulation module converts the electrical signal into corresponding characteristic data through a wavelet threshold denoising algorithm and an eigenvalue extraction algorithm, and uploads it to the cloud platform through the antenna module.

[0013] A pipeline leakage monitoring method based on fiber optic interference includes synchronously sampling the pipeline leakage acoustic wave signal through the wireless signal timing of the monitors arranged at intervals along the pipeline; receiving the data synchronously collected by each monitor through the cloud platform and executing a generalized cross-correlation algorithm to calculate the time difference between the pipeline leakage acoustic wave reaching the monitors on both sides L , and calculating the leakage point position according to the pipeline leakage point positioning formula.

[0014] Preferably, the pipeline leakage point positioning formula is as follows: L Where L 1. v 2 are the distances from the leakage point to the monitors on both sides; L is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration through the temperature compensation module, is the distance between the monitors on both sides of the pipeline leakage point.

[0015] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects.

[0016] (1)The present invention synergistically drives two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder and the inner cylinder and the air cavity, so as to improve the conversion sensitivity of the pipeline micro-leakage sound pressure signal to the optical phase signal and suppress the environmental common-mode noise; the sound pressure signal generated during the leakage process of the pipeline is converted into a phase change of light through a balanced fiber interferometer, and the leakage signal is demodulated through a phase detection technology to achieve high-precision pickup of the pipeline micro-leakage sound pressure signal. Compared with the technical means based on piezoelectric ceramics, the sensitivity is higher. When monitoring pipeline leakage, fewer monitors can be arranged on the pipeline of the same length to form a monitoring network, or smaller leakage signals can be monitored at the same laying distance interval.

[0017] (2)The present invention realizes synchronous sampling of the pipeline leakage sound pressure signal by each monitor through wireless signal timing, and the timing accuracy can reach the microsecond level. The combined leakage monitors can perform time synchronization in signal sampling, so as to achieve precise positioning of the leakage point; in addition, the present invention uses a narrow-linewidth semiconductor laser (linewidth <500 kHz) with a TO package as the sensing light source, and can realize high-precision detection of the sound pressure signal. Compared with other solutions, it has the advantages of smaller volume and lower cost.

[0018] (3)The present invention synergistically drives two equal-length sensing optical fibers to generate reverse strains through the double-cylinder differential structure and the closed air cavity, solves the technical problems of low sensitivity and poor anti-interference of the traditional single-cylinder structure, improves the conversion sensitivity of the pipeline micro-leakage sound pressure signal to the optical phase signal and suppresses the environmental common-mode noise, the strain gain coefficient ≥ 2, and the common-mode noise suppression > 15 dB; an acoustic impedance matching layer is filled between the outer cylinder and the PEEK shell, combined with a narrow-linewidth laser, solves the technical problems of low acoustic wave transmission efficiency and large phase noise of the light source, and realizes high-sensitivity transmission of the sound pressure signal and low-phase noise output of the light source.

[0019] (4)The present invention calibrates the sound speed in real time through an integrated temperature sensor, combined with microsecond-level wireless signal timing, solves the technical effects of large positioning errors caused by the temperature drift of the sound speed with the transmission medium and difficult synchronous sampling of multiple devices, and the positioning accuracy < 0.5 m; the electrical signal is converted into corresponding characteristic data through a wavelet threshold denoising algorithm and an eigenvalue extraction algorithm, and high-precision monitoring of micro pipeline leakage is realized through the generalized cross-correlation algorithm and the pipeline leak point positioning algorithm of the cloud platform, solving the technical problems that the micro-leakage characteristics are submerged by background noise, the cloud platform processes a large amount of data, and the delay is high.

[0020] (5) By means of the balanced fiber optic interferometer in combination with the symmetric fiber winding design of the inner and outer cylinders of the sound pressure sensitive unit and the air cavity structure, the present invention solves the problems of insufficient sensitivity and complex construction in the existing piezoelectric hydrophones and distributed fiber optic sensing technologies, achieving the effect of highly sensitive pickup of tiny leakage sound pressure signals; by filling the acoustic impedance matching medium between the outer cylinder and the PEEK housing, the problem of low acoustic wave transmission efficiency is solved, achieving the effect of enhancing the acoustic pressure signal coupling efficiency and the sensor sensitivity; by using TO package narrow linewidth semiconductor lasers (linewidth < 500 kHz) and wireless signal time synchronization, the problems of large volume, high cost and insufficient positioning accuracy in the existing systems are solved, achieving the effects of miniaturization, low cost and precise positioning; by installing the base thread interface and the main control demodulation module, the problem of cable laying by excavation required for the renovation of old pipe networks is solved, achieving the effects of construction-free deployment and real-time intelligent monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The fabrication and application of the preferred embodiments of the present invention are discussed in detail below. It should be understood, however, that the present invention provides many applicable inventive concepts that can be embodied in various specific environments. The specific embodiments discussed are merely illustrative of the specific ways of making and using the present invention and do not limit the scope of the present invention. Those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0022] Figure 1 It is a schematic structural diagram of the present invention.

[0023] Wherein, 1 - acoustic impedance matching medium; 2 - PEEK housing; 3 - first sensing optical fiber; 4 - second sensing optical fiber; 5 - outer cylinder; 6 - inner cylinder; 7 - mounting base; 8 - photodetector; 9 - laser; 10 - light source driving module; 11 - temperature sensor; 12 - sound velocity compensation module; 13 - battery; 14 - main control demodulation module; 15 - antenna module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The fabrication and application of the preferred embodiments of the present invention are discussed in detail below. It should be understood, however, that the present invention provides many applicable inventive concepts that can be embodied in various specific environments. The specific embodiments discussed are merely illustrative of the specific ways of making and using the present invention and do not limit the scope of the present invention.

[0025] A pipeline leakage monitoring instrument based on fiber optic interference includes a sound pressure sensitive unit, a balanced interferometer for converting the sound pressure signal generated by pipeline leakage into an optical phase signal, a laser 9, a photodetector 8 for converting the optical phase signal into an electrical signal, and a main control demodulation module 14; the main control demodulation module further includes a temperature sensor 11 for real-time monitoring of the temperature of the transmission medium in the pipeline and a sound speed compensation module 12. The main control demodulation module 14 converts the electrical signal into corresponding characteristic data through a wavelet threshold denoising algorithm and an eigenvalue extraction algorithm, and uploads it to the cloud platform through an antenna module 15.

[0026] The sound pressure sensitive unit includes an inner cylinder 6 and an outer cylinder 5 coaxially sleeved, and a sealed air cavity is formed between the two; the sound pressure sensitive unit further includes a PEEK housing 2, and the outer wall of the PEEK housing 2 is in direct contact with the transmission medium in the pipeline for receiving and transmitting the leakage sound pressure signal. An impedance matching medium 1 for enhancing the sound pressure transmission efficiency is filled between the outer cylinder 5 and the PEEK housing 2. The impedance matching medium 1 adopts a sound impedance matching medium or an acoustic couplant with the same material as the PEEK housing 2; the impedance matching medium 1 is made of a composite material of polyether ether ketone, polyurethane and silicon carbide.

[0027] The balanced interferometer includes a first sensing optical fiber 3 and a second sensing optical fiber 4 that are respectively helically wound on the surfaces of the outer cylinder 5 and the inner cylinder 6 with prestress and have equal lengths, a coupler and a Faraday rotator mirror; the sound pressure sensitive unit drives the two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder 5 and the inner cylinder 6 and the air cavity in cooperation, so as to improve the conversion sensitivity of the pipeline micro-leakage sound pressure signal - optical phase signal and suppress the environmental common-mode noise. The monitoring instrument further includes a battery 13; a light source driving module 10 for providing a low-noise power supply and temperature control; an antenna module 15 for data communication and obtaining time synchronization signals, and a mounting base 7. The lower end of the mounting base 7 is provided with a threaded interface, which is adapted to a fire hydrant hose interface or an exhaust valve.

[0028] A pipeline leakage monitoring method based on fiber optic interference includes synchronous sampling of the pipeline leakage acoustic wave signal through the wireless signal timing of the monitoring instruments arranged along the pipeline at intervals L ; receiving the data synchronously collected by each monitoring instrument through the cloud platform and executing the generalized cross-correlation algorithm to calculate the time difference between the arrival of the pipeline leakage acoustic wave at the two-side monitoring instruments , and calculating the leakage point position according to the pipeline leakage point positioning formula. The pipeline leakage point positioning formula is as follows: Among them, L 1, L 2 are the distances from the leakage point to the two-side monitoring instruments; vis the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration by the temperature compensation module. L is the distance between the monitors on both sides of the pipeline leak point.

[0029] The present invention synergistically drives two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder 5 and the inner cylinder 6 and the air cavity, so as to improve the conversion sensitivity of the pipeline micro-leakage sound pressure signal - optical phase signal and suppress the environmental common-mode noise; the sound pressure signal generated during the leakage process of the pipeline is converted into a phase change of light through a balanced fiber interferometer, and the leakage signal is demodulated through phase detection technology to achieve high-precision pickup of the pipeline micro-leakage sound pressure signal. The sound velocity is calibrated in real time through the temperature sensor 11 and the sound velocity compensation module 12, and combined with microsecond-level wireless signal timing, the technical effects of large positioning errors caused by the temperature drift of the sound velocity with the transmission medium and difficult synchronous sampling of multiple devices are solved.

[0030] The following is further elaborated in conjunction with the attached Figure 1 For further elaboration. As shown in the attached Figure 1 Schematic diagram of the structure of the pipeline leakage monitor. A pipeline leakage monitor based on fiber optic interference includes a sound pressure sensitive unit, a balanced interferometer for converting the sound pressure signal generated by pipeline leakage into an optical phase signal, a laser 9, a photodetector 8 for converting the optical phase signal into an electrical signal, and a main control demodulation module 14; the main control demodulation module further includes a temperature sensor 11 for real-time monitoring of the temperature of the transmission medium in the pipeline and a sound velocity compensation module 12. The sound velocity compensation module 12 calculates the sound velocity according to v =1402 + 4.91×T - 0.047×T 2 + 3.3×10 -4 ×T 3 where T is the temperature of the transmission medium in the pipeline, v is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration by the temperature compensation module.

[0031] The main control demodulation module 14 converts the electrical signal into corresponding characteristic data through a wavelet threshold denoising algorithm and an eigenvalue extraction algorithm, and uploads it to the cloud platform through the antenna module 15. Among them, the wavelet threshold denoising algorithm is mainly used to denoise and enhance the original sound pressure signal of pipeline leakage. The steps are as follows: the original sound pressure signal containing noise collected on the pipeline is decomposed into multi-scale coefficients through wavelet transform, and then according to the distribution difference between the signal and the noise in the wavelet domain, the coefficient amplitude of the signal is large and concentrated, while the coefficient amplitude of the opposite noise is small and dispersed. In this way, the noise can be removed through threshold processing, and then the denoised signal is reconstructed.

[0032] The specific steps of the wavelet threshold denoising algorithm are as follows: S1: Use wavelet packet decomposition to denoise the original sound pressure signal, and the threshold function is: wherein, is the standard deviation of the wavelet coefficients of the j layer, N j is the number of coefficients.

[0033] S2: Then, the coefficients with values less than are set to zero, and the remaining coefficients remain unchanged. The processed coefficients are subjected to inverse wavelet transform to finally recover the denoised sound pressure signal x ( i ).

[0034] The specific steps of the eigenvalue extraction algorithm are as follows: Step 1: Calculate the x ( i ) value of the sound pressure signal: level wherein, N represents the total number of sampling points, i i represents the i th sampling point.

[0035] Step 2: Perform Fourier transform on the sound pressure signal x ( i ) to obtain the sound pressure frequency domain signal X ( f i ): wherein, f i represents the i th discrete frequency point, N represents the total number of sampling points, j represents the imaginary unit.

[0036] Step 3: Calculate the center frequency X ( f i ) of the sound pressure frequency domain signal f c : wherein, f i represents the i th discrete frequency point, i represents the i th sampling point, N represents the total number of sampling points.

[0037] Step 4: Calculate the characteristic data P :

[0038] Upload the calculated characteristic data P to the cloud platform through the antenna module 15. The cloud platform receives the data synchronously collected by each monitor and executes the generalized cross-correlation algorithm to calculate the time difference of the arrival of the pipeline leakage sound wave at the two-side monitors. The calculation formula of the generalized cross-correlation algorithm is as follows: = where argmax is the index for taking the peak value; f is the frequency of the leakage sound pressure signal; is the weighting function for phase weighting of the cross-power spectrum; v is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration through the temperature compensation module; G AB ( f )is the cross-power spectral density function. And G AB ( f )=1 / .

[0039] Then calculate the leakage point position according to the pipeline leakage point positioning formula. The pipeline leakage point positioning formula is as follows: where, L 1. L 2 are the distances from the leakage point to the two-side monitors; v is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration through the temperature compensation module; L is the distance between the monitors on both sides of the pipeline leakage point.

[0040] The sound pressure sensitive unit includes an inner cylinder 6 and an outer cylinder 5 which are coaxially sleeved, and a sealed air cavity is formed between the two.

[0041] The sound pressure sensitive unit further includes a PEEK housing 2. The outer wall of the PEEK housing 2 is in direct contact with the transmission medium in the pipeline and is used to receive and transmit the leakage sound pressure signal. An impedance matching medium 1 for enhancing the sound pressure transmission efficiency is filled between the outer cylinder 5 and the PEEK housing 2. The impedance matching medium 1 adopts an acoustic impedance matching medium or an acoustic couplant having the same material as the PEEK housing 2; in this embodiment, the impedance matching medium 1 is made of a composite material of polyether ether ketone, polyurethane and silicon carbide.

[0042] The balanced interferometer includes a first sensing optical fiber 3 and a second sensing optical fiber 4 of equal length, which are respectively spirally wound on the surface of the outer cylinder 5 and the inner cylinder 6 with prestress, a coupler and a Faraday rotating mirror; the sound pressure sensitive unit drives the two sensing optical fibers to produce opposite and equal length strains through the differential deformation of the outer cylinder 5 and the inner cylinder 6 and the coordination of the air cavity, so as to improve the sensitivity of the conversion of the sound pressure signal of the pipeline micro leakage-optical phase signal and suppress the common mode noise of the environment. The monitor also includes a battery 13; a light source driving module 10 for providing low-noise power supply and temperature control; an antenna module 15 and a mounting base 7 for data communication and time synchronization signal acquisition. The lower end of the mounting base 7 is provided with a threaded interface, which is adapted to the fire hydrant hose interface or exhaust valve.

[0043] The principle of the monitor picking up the tiny sound pressure signal of pipeline leakage is as follows: when the main control demodulation module 14 receives the working instruction through the antenna or reaches the preset working time, the main control demodulation module 14 controls the battery 13 to power the light source driving module 10, and the light source driving module 10 provides low-noise power supply and temperature control processing to the laser 9 to ensure that the laser 9 continuously provides a narrow line width light source at the optimum temperature. The laser 9 adopts a TO packaged narrow line width semiconductor laser 9, and the line width of its output light source is less than 500kHz. The monitor is directly fixedly connected to the fire hydrant hose interface or exhaust valve of the pipeline through the threaded interface at the lower end of the mounting base 7. At this time, the PEEK shell 2 is in full contact with the transmission medium in the pipeline. According to different monitoring requirements, the pipeline leakage monitor is installed at intervals of 50 to 1000 meters to form a regional monitoring network, and regional intelligent monitoring can be achieved through the monitoring platform.

[0044] When the sound pressure signal generated by the pipeline leakage is transmitted to the impedance matching medium 1 through the PEEK shell 2 and reaches the outer cylinder 5, the outer cylinder 5 and the inner cylinder 6 produce deformations of equal magnitude and opposite direction, so that the lengths of the first sensing optical fiber 3 and the second sensing optical fiber 4 spirally wound on the surface thereof expand radially and become longer, and contract radially and become shorter at the same time, thereby causing the two sensing optical fibers to produce opposite and equal length strains, thereby improving the sensitivity of the conversion of the pipeline micro-leakage sound pressure signal to the optical phase signal. When the monitor is working, it may be disturbed by the ambient temperature, vibration, etc. These environmental common-mode noises will cause the outer cylinder 5 and the inner cylinder 6 to produce the same direction deformation, thereby weakening and offsetting the opposite and equal length strains caused by the sound pressure signal generated by the pipeline leakage, and finally resulting in the offset of the phase change output by the balanced interferometer. The closed air cavity formed between the outer cylinder 5 and the inner cylinder 6 has a low elastic modulus (close to 0). The air cavity blocks the environmental common mode noise from being transmitted to the inner cylinder 6 through mechanical decoupling, and ensures that the outer cylinder 5 and the inner cylinder 6 produce the same direction of strain under the ambient temperature / vibration interference. After differential interference, the common mode noise signal self-cancels, and the interference suppression of the environmental common mode noise of >15 dB can be achieved.

[0045] The narrow-linewidth light source generated by the laser 9 is output to a balanced interferometer. First, it is split into sensing light and reference light after passing through a coupler. The sensing light and the reference light respectively pass through the first sensing optical fiber 3 and the second sensing optical fiber 4, and then pick up the differential deformation between the outer cylinder 5 and the inner cylinder 6 and cooperate with the air cavity, and drive the two sensing optical fibers to generate reverse and equal-length length strains. Then, the sound pressure signal generated by the pipeline leakage is converted into an optical phase signal after passing through the sound pressure sensitive unit and the balanced interferometer, and is reflected by the Faraday rotator mirror and returned along the original path to the coupler. The returned sensing light and reference light interfere in the coupler and output the interfered optical phase signal to the photodetector 8. The photodetector 8 converts the optical phase signal into an electrical signal and outputs it to the main control demodulation module 14. Then, the main control demodulation module 14 converts the electrical signal into corresponding characteristic data through the wavelet threshold denoising algorithm and the eigenvalue extraction algorithm, and uploads it to the cloud platform through the antenna module 15. Finally, the cloud platform calculates the time difference between the arrival of the pipeline leakage sound wave at the two side monitors according to the generalized cross-correlation algorithm. , and finally calculates the leakage point position by combining the pipeline leakage point positioning formula.

[0046] A pipeline leakage monitoring method based on fiber optic interference includes synchronously sampling the pipeline leakage sound wave signal through the wireless signal timing of the monitors arranged at intervals L along the pipeline; the pipeline leakage monitors can be installed at intervals of L =50 - 1000 meters according to different monitoring requirements, and a regional monitoring network can be formed. Through the cloud platform, regional intelligent monitoring can be realized.

[0047] The cloud platform receives the data synchronously collected by each monitor and executes the generalized cross-correlation algorithm to calculate the time difference between the arrival of the pipeline leakage sound wave at the two side monitors . The calculation formula of the generalized cross-correlation algorithm is as follows: = where argmax is the index for taking the peak value; f is the frequency of the leakage sound pressure signal; is the weighting function for phase weighting of the cross-power spectrum; v is the propagation speed of the leakage sound speed in the pipeline medium after real-time calibration through the temperature compensation module; G AB ( f )is the cross-power spectral density function. And G AB ( f )=1 / .

[0048] Calculate the leak point location according to the pipeline leak point location formula. The pipeline leak point location formula is as follows: Wherein, L 1. L 2 is the distance from the leak point to the monitors on both sides; v is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration through the temperature compensation module, L is the distance between the monitors on both sides of the pipeline leak point.

[0049] The present invention solves the problems of insufficient sensitivity and complex construction of the existing piezoelectric hydrophone and distributed optical fiber sensing technology through the balanced fiber optic interferometer combined with the symmetrical fiber winding design and air cavity structure of the inner and outer cylinders 5 of the sound pressure sensitive unit, achieving the effect of highly sensitive pickup of tiny leakage sound pressure signals; by filling the acoustic impedance matching medium 1 between the outer cylinder 5 and the PEEK housing 2, the problem of low acoustic wave transmission efficiency is solved, achieving the effect of enhancing the acoustic pressure signal coupling efficiency and sensor sensitivity; by TO packaging the narrow linewidth semiconductor laser 9 (linewidth < 500 kHz) and wireless signal timing, the problems of large volume, high cost and insufficient positioning accuracy of the existing system are solved, achieving the effects of miniaturization, low cost and precise positioning; by installing the threaded interface of the base 7 and the main control demodulation module 14, the problem of difficult cable laying by excavation in the renovation of old pipe networks is solved, achieving the effects of construction-free deployment and real-time intelligent monitoring.

[0050] Although the specification has been described in detail, it should be understood that various changes, substitutions and alterations can be made without departing from the spirit and scope of the present invention as defined by the appended claims. In addition, the specific embodiments described do not limit the scope of the present invention. Those of ordinary skill in the art can easily understand based on the present invention that currently existing or later to be developed processes, machines, manufactures, compositions of matter, means, methods, or steps can perform functions substantially the same as those of the embodiments of the present invention or obtain results substantially the same as those of the embodiments of the present invention. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods or steps within their scope.

Claims

1. A pipeline leakage monitor based on fiber optic interference, characterized in that: It includes a sound pressure sensitive unit, a balanced interferometer for converting the sound pressure signal generated by pipeline leakage into an optical phase signal, a laser, a photodetector for converting the optical phase signal into an electrical signal, and a main control demodulation module; the sound pressure sensitive unit includes an inner cylinder and an outer cylinder coaxially sleeved, and a sealed air cavity is formed between the two; the balanced interferometer includes a first sensing optical fiber and a second sensing optical fiber, a coupler and a Faraday rotator mirror that are respectively helically wound on the surfaces of the outer cylinder and the inner cylinder with prestress and have equal lengths; the sound pressure sensitive unit drives the two sensing optical fibers to generate reverse and equal-length length strains through the differential deformation of the outer cylinder and the inner cylinder and the air cavity, so as to improve the conversion sensitivity of the pipeline micro-leakage sound pressure signal-optical phase signal and suppress the environmental common-mode noise.

2. The pipeline leakage monitor based on fiber optic interference according to claim 1, wherein: The sound pressure sensitive unit further includes a PEEK housing, and the outer wall of the PEEK housing is in direct contact with the transmission medium in the pipeline for receiving and transmitting the leakage sound pressure signal.

3. The pipeline leakage monitor based on fiber optic interference according to claim 2, characterized in that: An impedance matching medium for enhancing the sound pressure transmission efficiency is filled between the outer cylinder and the PEEK housing.

4. The pipeline leakage monitor based on fiber optic interference according to claim 3, characterized in that: The impedance matching medium adopts an acoustic impedance matching medium or an acoustic couplant with the same material as the PEEK housing; the impedance matching medium is made of a composite material of polyether ether ketone, polyurethane and silicon carbide.

5. The pipeline leakage monitor based on fiber optic interference according to claim 1, wherein: The monitor further includes a battery; a light source driving module for providing a low-noise power supply and temperature control; an antenna module for data communication and obtaining time synchronization signals, and a mounting base.

6. The pipeline leakage monitor based on fiber optic interference according to claim 5, characterized in that: The lower end of the mounting base is provided with a threaded interface, which is adapted to the fire hydrant hose interface or the exhaust valve.

7. The pipeline leakage monitor based on fiber optic interference according to claim 1, characterized in that: The main control demodulation module further includes a temperature sensor for real-time monitoring of the temperature of the transmission medium in the pipeline and a sound speed compensation module.

8. The pipeline leakage monitor based on fiber optic interference according to claim 1, wherein: The main control demodulation module converts the electrical signal into corresponding characteristic data through a wavelet threshold denoising algorithm and an eigenvalue extraction algorithm, and uploads it to the cloud platform through the antenna module.

9. A pipeline leakage monitoring method based on fiber optic interference, characterized in that: including synchronously sampling the pipeline leakage acoustic wave signals by realizing the time synchronization of the wireless signals of the monitors arranged at intervals along the pipeline as described in any one of claims 1-8; receiving the data synchronously collected by each monitor through a cloud platform and performing a generalized cross-correlation algorithm to calculate the time difference of the pipeline leakage acoustic wave reaching the monitors on both sides L and calculating the leakage point position according to the pipeline leakage point positioning formula. ​ 10. A pipeline leakage monitoring method based on fiber optic interference as described in claim 9, characterized in that: The pipeline leak point positioning formula is as follows: Among them, L 1. L 2 is the distance from the leakage point to the monitors on both sides; v is the propagation speed of the leakage sound velocity in the pipeline medium after real-time calibration through the temperature compensation module, L is the distance between the monitors on both sides of the pipeline leakage point.

Images