Hydrogen pipeline leak concentration and location combined monitoring system based on grating array

Abstract

The application provides a grating array-based hydrogen pipeline leakage concentration and position combined monitoring system and relates to the technical field of fiber grating sensing, which comprises a signal modulation module, a signal return module, an interference beam splitting module and a data acquisition module, wherein the signal modulation module comprises a narrow linewidth laser light source and a tunable laser light source; the signal return module comprises a same-cable hydrogen temperature and vibration simultaneous measurement unit, broadband grating reflected light in the same-cable hydrogen temperature and vibration simultaneous measurement unit is coupled to the interference beam splitting module; the same-cable hydrogen temperature and vibration simultaneous measurement unit comprises a double-core optical fiber, the double-core optical fiber comprises an optical medium layer, a first fiber core and a second fiber core, the optical medium layer is arranged outside the first fiber core and the second fiber core to coat the first fiber core and the second fiber core, a coating layer is arranged on the surface of the double-core optical fiber, the first fiber core is arranged on the axis of the double-core optical fiber, and the second fiber core is arranged on the side close to the coating layer. The application is helpful to improve the measurement accuracy of hydrogen leakage position and concentration.

Description

Technical Field

[0001] This invention relates to the field of fiber optic grating sensing technology, and in particular to a combined monitoring system for leakage concentration and location of hydrogen pipelines based on grating arrays. Background Technology

[0002] With the transformation of the global energy structure and the increasing awareness of environmental protection, hydrogen, as a clean and efficient energy carrier, has increasingly broad application prospects. Hydrogen not only shows great potential in fuel cell vehicles and residential combined heat and power systems, but also plays an important role in many fields such as industrial production, medical care, and food processing. However, the flammable and explosive properties of hydrogen require precise monitoring of its concentration to ensure safe use.

[0003] Chinese Patent CN108717042B discloses a polarization-maintaining reflective hydrogen concentration detection device. The device includes a light source, an optical fiber polarization beam splitter, a hydrogen sensor head, a spectrometer, and a signal processing unit. The main body of the hydrogen sensor head is a section of polarization-maintaining photonic crystal fiber, with a palladium film coated on its sides and one end connected to a thin, coreless optical fiber coated with a reflective film, forming a reflective photonic crystal fiber hydrogen sensor head. The polarization-maintaining fiber of the light source is fused to the polarization-maintaining fiber of the incident polarization-maintaining fiber at 0 degrees to form a polarization-maintaining fiber optical path. The polarization-maintaining fiber output from the polarization-maintaining fiber is fused to the polarization-maintaining photonic crystal fiber of the hydrogen sensor head at an angle θ. The signal light reflected from the end face of the polarization-maintaining photonic crystal fiber reaches the spectrometer through the polarization-maintaining fiber and the polarization-maintaining fiber, and the signal processing unit processes and outputs the results. However, the above scheme only measures the hydrogen concentration at a specific location using a single hydrogen sensor, which cannot provide comprehensive information about the area around the leak source, and may lead to an underestimation of the leak range and severity. Therefore, it is necessary to provide a combined monitoring system for hydrogen pipeline leak concentration and location based on a grating array to improve the accuracy of measuring the location and concentration of hydrogen leaks. Summary of the Invention

[0004] In view of this, the present invention proposes a combined monitoring system for hydrogen pipeline leakage concentration and location based on a grating array. By using a co-cable hydrogen temperature and vibration measurement unit, synchronous monitoring of hydrogen concentration and vibration is achieved, enabling simultaneous acquisition of wavelength drift and vibration information. Combined with acousto-optic modulation and electro-optic modulation techniques, signal quality is improved, which helps to enhance the accuracy of measuring hydrogen leakage location and concentration.

[0005] This invention provides a combined monitoring system for the concentration and location of leaks in hydrogen pipelines based on a grating array, comprising a signal modulation module, a signal feedback module, an interferometric beam splitting module, and a data acquisition module, wherein...

[0006] The signal modulation module is connected to the signal feedback module. The signal modulation module includes a narrow linewidth laser source and a tunable laser source. The signal modulation module is used to couple the continuous light emitted by the narrow linewidth laser source and the tunable laser source to the signal feedback module after performing acousto-optic modulation and electro-optic modulation, respectively.

[0007] The signal return module is connected to the interference beam splitter and the data acquisition module respectively. The signal return module includes a co-cable hydrogen temperature vibration and measurement unit. The signal return module is used to measure the wavelength drift based on the narrowband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit. The broadband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit is coupled to the interference beam splitter.

[0008] The co-cable hydrogen temperature vibration and measurement unit includes a dual-core optical fiber, which includes an optical dielectric layer, a first core, and a second core. The optical dielectric layer is disposed outside the first core and the second core to cover the first core and the second core. A coating layer is disposed on the surface of the dual-core optical fiber. The first core is disposed on the axis of the dual-core optical fiber, and the second core is disposed on the side close to the coating layer.

[0009] The interference beam splitter is connected to the data acquisition module. The interference beam splitter is used to interfere the reflected light from the broadband grating and transmit the resulting interference signal to the data acquisition module for storage.

[0010] Based on the above technical solutions, preferably, the signal modulation module further includes a waveform generator, an electro-optic modulator, an acousto-optic modulator, a first erbium-doped fiber amplifier, and a second erbium-doped fiber amplifier. The electro-optic modulator is connected to the tunable laser source, the waveform generator, and the first erbium-doped fiber amplifier, respectively. The acousto-optic modulator is connected to the narrow-linewidth laser source and the second erbium-doped fiber amplifier, respectively. Both the first erbium-doped fiber amplifier and the second erbium-doped fiber amplifier are connected to the signal feedback module.

[0011] Based on the above technical solutions, preferably, the signal feedback module further includes a first coupler, a circulator, a dense wavelength division multiplexer, a third erbium-doped fiber amplifier, and a first photodetector. One end of the first coupler is connected to the first erbium-doped fiber amplifier and the second erbium-doped fiber amplifier, respectively. The other end of the first coupler is connected to the first end of the circulator. The second end of the circulator is connected to the same-cable hydrogen temperature vibration and measurement unit. The dense wavelength division multiplexer is connected to the third end of the circulator, the third erbium-doped fiber amplifier, and the first photodetector, respectively. The first photodetector is connected to the data acquisition module. The third erbium-doped fiber amplifier is connected to the interference beam splitter module.

[0012] More preferably, the interference beam splitting module includes a second coupler, a first Faraday mirror, a time-delay fiber, and a second Faraday mirror, wherein the second coupler is connected to the data acquisition module, the first Faraday mirror, the time-delay fiber, and the second Faraday mirror, respectively.

[0013] More preferably, the data acquisition module includes a second photodetector, a third photodetector, a fourth photodetector, and a host computer. The second photodetector is connected to the second coupler and the host computer, the third photodetector is connected to the second coupler and the host computer, and the fourth photodetector is connected to the second coupler and the host computer. The phase difference of the interference signals received by the second photodetector, the third photodetector, and the fourth photodetector is 120 degrees.

[0014] More preferably, the first fiber core includes a plurality of vibration signal gratings arranged at equal intervals, and the second fiber core includes a plurality of hydrogen temperature detection units arranged at equal intervals. The hydrogen temperature detection unit includes a first grating group and a second grating group arranged at intervals. Both the first grating group and the second grating group include a temperature-measuring FBG grating and a hydrogen-measuring FBG grating. The distance between any two adjacent hydrogen temperature detection units is a first preset distance, the distance between any two adjacent vibration signal gratings is a first preset distance, and the horizontal distance between any vibration signal grating and an adjacent hydrogen temperature detection unit is half of the first preset distance.

[0015] More preferably, the dual-core optical fiber is wound around the hydrogen pipeline, and the ratio between the length of the vibration signal grating and the length of the coating layer is 0% to 100%.

[0016] More preferably, the hydrogen-sensitive material coated on the hydrogen-sensitive material coating layer is any one of WO3, Pt / WO3, Pd / WO3, MoO3, Pt / Mo3, and Pd / MoO3.

[0017] More preferably, the center wavelength range of the fiber Bragg grating is 1530nm~1625nm, the center wavelength of the narrow linewidth laser source (12) and the tunable laser source (11) is 1550.1nm, and the optical power of the narrow linewidth laser source (12) and the tunable laser source (11) is 14.6Mw.

[0018] More preferably, the first coupler is a 1×2 coupler and the second coupler is a 3×3 coupler.

[0019] The hydrogen pipeline leakage concentration and location combined monitoring system based on grating array provided by this invention has the following advantages over existing technologies:

[0020] (1) The simultaneous monitoring of hydrogen concentration and vibration was achieved through the co-cable hydrogen temperature and vibration measurement unit, which can simultaneously acquire hydrogen concentration, temperature and vibration information, significantly improving the monitoring comprehensiveness of the combined monitoring system. The integration of hydrogen, temperature and vibration detection into the same system not only reduces the complexity of the combined monitoring system, but also reduces equipment deployment costs and improves the overall monitoring efficiency. It helps to improve the accuracy of measuring the location and concentration of hydrogen leaks. In addition, the dual-core fiber design effectively avoids interference between the two signals, ensuring the independence of vibration signal and hydrogen temperature signal, which helps to improve the accuracy of measuring the location and concentration of hydrogen leaks, and supports continuous data acquisition and storage. At the same time, the combined monitoring system detects minor environmental changes through vibration sensing and achieves early leak detection by combining hydrogen concentration monitoring, which effectively improves the early warning capability of the combined monitoring system.

[0021] (2) By integrating vibration, hydrogen concentration, and temperature monitoring functions into the same optical fiber, multi-parameter collaborative monitoring is achieved, which can comprehensively reflect the operating status of the environment or equipment. The vibration signal grating and hydrogen temperature detection unit are arranged at equal intervals with a first preset distance, ensuring the uniform distribution of monitoring points and improving the spatial resolution of the system. It can accurately locate the location of vibration anomalies or hydrogen leaks, and is suitable for monitoring long-distance hydrogen pipelines. This alternating distribution design can further improve the location accuracy of leaks through comprehensive analysis of vibration signals and hydrogen temperature signals. The first grating group and the second grating group both include temperature measurement FBG gratings and hydrogen measurement FBG gratings, which can simultaneously detect changes in temperature and hydrogen concentration. Through the collaborative work of multiple grating groups, the combined monitoring system can quickly respond to changes in environmental parameters and has high sensitivity and multifunctionality. The vibration signal grating and hydrogen temperature detection unit are integrated into the same dual-core optical fiber, which is compact and easy to deploy, and is suitable for use in complex environments such as long-distance hydrogen pipelines. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array provided by the present invention.

[0024] Figure 2This is a schematic diagram of the structure of the dual-core optical fiber provided by the present invention;

[0025] Figure 3 This is a schematic diagram of the layout of the co-cable hydrogen temperature vibration and measurement unit provided by the present invention.

[0026] Figure reference numerals: 1. Signal modulation module; 11. Tunable laser source; 12. Narrow linewidth laser source; 13. Waveform generator; 14. Electro-optic modulator; 15. Acousto-optic modulator; 16. First erbium-doped fiber amplifier; 17. Second erbium-doped fiber amplifier; 2. Signal feedback module; 21. First coupler; 22. Circulator; 23. Dense wavelength division multiplexer; 24. Third erbium-doped fiber amplifier; 25. Co-cable hydrogen temperature vibration and measurement unit; 251. Optical dielectric layer; 252. 1. First fiber core; 253. Second fiber core; 254. Vibration signal grating; 255. Hydrogen temperature detection unit; 2551. First grating group; 2552. Second grating group; 26. First photodetector; 3. Interference beam splitter module; 31. Second coupler; 32. First Faraday mirror; 33. Delay fiber; 34. Second Faraday mirror; 4. Data acquisition module; 41. Second photodetector; 42. Third photodetector; 43. Fourth photodetector; 44. Host computer. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] This invention discloses a combined monitoring system for leakage concentration and location in hydrogen pipelines based on a grating array, with reference to... Figure 1 The aforementioned system includes a signal modulation module 1, a signal feedback module 2, an interference beam splitting module 3, and a data acquisition module 4, wherein...

[0029] The signal modulation module 1 is connected to the signal feedback module 2. The signal modulation module 1 includes a narrow linewidth laser source 12 and a tunable laser source 11. The signal modulation module 1 is used to couple the continuous light emitted by the narrow linewidth laser source 12 and the tunable laser source 11 to the signal feedback module 2 after performing acousto-optic modulation and electro-optic modulation respectively.

[0030] In this embodiment, the signal modulation module 1 further includes a waveform generator 13, an electro-optic modulator 14, an acousto-optic modulator 15, a first erbium-doped fiber amplifier 16, and a second erbium-doped fiber amplifier 17. The electro-optic modulator 14 is connected to the tunable laser source 11, the waveform generator 13, and the first erbium-doped fiber amplifier 16, respectively. The acousto-optic modulator 15 is connected to the narrow linewidth laser source 12 and the second erbium-doped fiber amplifier 17, respectively. The first erbium-doped fiber amplifier 16 and the second erbium-doped fiber amplifier 17 are both connected to the signal feedback module 2.

[0031] The center wavelengths of both the narrow-linewidth laser source 12 and the tunable laser source 11 are 1550.1 nm, and the optical power of both is 14.6 Mw.

[0032] Furthermore, the signal modulation module 1, through the coordinated operation of the tunable laser source 11 and the narrow-linewidth laser source 12, generates optical signals with different characteristics. The combined use of these two light sources significantly improves the measurement accuracy and flexibility of the combined monitoring system. In terms of signal modulation, the electro-optic modulator 14 modulates the tunable laser source 11, providing precise waveform control, while the acousto-optic modulator 15 modulates the narrow-linewidth laser source 12, achieving efficient optical signal pulse modulation. Combined with the precise modulation control signal provided by the waveform generator 13, a complete signal modulation system is formed. Two erbium-doped fiber amplifiers amplify the electro-optic and acousto-optic modulated signals respectively, ensuring sufficient signal strength for subsequent processing and effectively improving the system's signal-to-noise ratio and detection sensitivity. The connections between the various components are optimized to reduce signal loss, achieving efficient signal transmission and processing, and improving the overall system's stability and reliability.

[0033] The signal feedback module 2 is connected to the interference beam splitter module 3 and the data acquisition module 4 respectively. The signal feedback module 2 includes a co-cable hydrogen temperature vibration and measurement unit 25. The signal feedback module 2 is used to measure the wavelength drift based on the narrowband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit 25. The broadband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit 25 is coupled to the interference beam splitter module 3.

[0034] In this embodiment, the signal feedback module 2 further includes a first coupler 21, a circulator 22, a dense wavelength division multiplexer 23, a third erbium-doped fiber amplifier 24, and a first photodetector 26. One end of the first coupler 21 is connected to the first erbium-doped fiber amplifier 16 and the second erbium-doped fiber amplifier 17, respectively. The other end of the first coupler 21 is connected to the first end of the circulator 22. The second end of the circulator 22 is connected to the same cable hydrogen temperature vibration and measurement unit 25. The dense wavelength division multiplexer 23 is connected to the third end of the circulator 22, the third erbium-doped fiber amplifier 24, and the first photodetector 26, respectively. The first photodetector 26 is connected to the data acquisition module 4. The third erbium-doped fiber amplifier 24 is connected to the interference beam splitter module 3.

[0035] Furthermore, such as Figure 2 and Figure 3 As shown, the co-cable hydrogen temperature vibration and measurement unit 25 includes a dual-core optical fiber. The dual-core optical fiber includes an optical dielectric layer 251, a first fiber core 252, and a second fiber core 253. The optical dielectric layer 251 is disposed outside the first fiber core 252 and the second fiber core 253 to cover the first fiber core 252 and the second fiber core 253. A coating layer is disposed on the surface of the dual-core optical fiber. The first fiber core 252 is disposed on the axis of the dual-core optical fiber, and the second fiber core 253 is disposed on the side close to the coating layer. The first fiber core 252 includes a plurality of vibration signal gratings 254 arranged at equal intervals, and the second fiber core 253 includes a plurality of hydrogen temperature detection units 255 arranged at equal intervals. The hydrogen temperature detection unit 255 includes a first grating group 2551 and a second grating group 2552 arranged at intervals. Both the first grating group 2551 and the second grating group 2552 include a temperature measuring FBG grating and a hydrogen measuring FBG grating. The distance between any two adjacent hydrogen temperature detection units 255 is a first preset distance, the distance between any two adjacent vibration signal gratings 254 is a first preset distance, and the horizontal distance between any vibration signal grating 254 and an adjacent hydrogen temperature detection unit 255 is half of the first preset distance.

[0036] In this embodiment, by setting a first fiber core and a second fiber core in a dual-core optical fiber, and arranging a vibration signal grating 254 on the first fiber core and a hydrogen temperature detection unit 255 on the second fiber core, multi-parameter synchronous detection of vibration signal, temperature, and hydrogen concentration is achieved. The vibration signal grating 254 and the hydrogen temperature detection unit 255 are arranged at equal distances (a first preset distance), with the horizontal distance between them being half of the first preset distance. This uniform distribution design ensures high spatial resolution of the detected signal, facilitating precise location of changes in vibration, temperature, and hydrogen concentration. The first grating group 2551 and the second grating group 2552 in the hydrogen temperature detection unit 255 respectively include a temperature-measuring FBG grating and a hydrogen-measuring FBG grating, enabling simultaneous detection of changes in temperature and hydrogen concentration. By collaboratively analyzing these parameters, a more comprehensive assessment of environmental conditions or equipment operating status can be achieved. The dual-core optical fiber design makes the entire sensing unit compact, facilitating deployment in confined spaces. Simultaneously, the protective coating enhances the mechanical strength and environmental adaptability of the optical fiber, making it suitable for use in complex or harsh environments. The rational distribution design of the vibration signal grating 254 and the hydrogen temperature detection unit 255, combined with the fast response characteristics of the fiber Bragg grating (FBG), enables the system to monitor changes in vibration, temperature and hydrogen concentration in real time, meeting the monitoring needs in highly dynamic environments.

[0037] A dual-core optical fiber is wound around the hydrogen pipeline, and the ratio between the length of the vibration signal grating 254 and the length of the coating layer is 0% to 100%. The hydrogen-sensitive material coated on the layer is any one of WO3, Pt / WO3, Pd / WO3, MoO3, Pt / Mo3, and Pd / MoO3. The hydrogen-sensitive material can be various alloys of WO3, such as Pt / Co WO3, Pd / PtWO3, and Pt / Co WO3. The hydrogen-sensitive material can also be various alloys of MoO3, such as Pt / Co MoO3, Pd / Pt MoO3, and Pt / Co MoO3. The center wavelength range of the fiber Bragg grating is 1530nm to 1625nm, and the monitoring device, consisting of a hydrogen sensor and a vibration sensing unit, is wound around the surface of the hydrogen pipeline in a spiral structure.

[0038] The hydrogen sensor used above is a fiber Bragg grating (FBG) type hydrogen sensor. This sensor combines a hydrogen-sensitive material with a fiber grating and utilizes the hydrogen absorption and exothermic effect to detect hydrogen concentration. When the hydrogen concentration in the environment changes, it causes a change in the temperature of the FBG, thereby altering the FBG period. The hydrogen concentration is then obtained by measuring the center wavelength of the reflected light. The hydrogen-sensitive materials described above include, but are not limited to, metal oxide materials that can absorb hydrogen and release heat, such as Pt / WO3 and Pt / MoO3. Vibration sensing units (vibration monitoring devices) include all fiber optic sensing systems with demodulated vibration effects, such as OFDR based on Rayleigh scattering, OFDR based on a weak grating array (UWFBG), and distributed fiber acoustic wave sensor (DAS) based on a weak grating array (UWFBG).

[0039] The co-cable hydrogen temperature and vibration measurement unit 25 also collects and analyzes signals by acquiring distributed fiber optic hydrogen sensors and vibration sensors. The steps include:

[0040] Check if the vibration sensor signal amplitude is greater than the preset minimum amplitude threshold. If the signal amplitude is less than the minimum amplitude threshold, it is considered normal, and the process ends. Perform necessary preprocessing on the acquired signal, including trend removal, signal noise reduction, and zero-mean normalization.

[0041] After signal preprocessing, feature extraction is performed, including extracting key features from signals collected by vibration and hydrogen sensors, such as peak value, frequency, duration, energy time-domain features (e.g., peak value, mean, variance), and frequency-domain features (e.g., power spectrum analysis). The constructed feature vector... F It can be composed of multiple features, such as peak values. f peak ,frequency f freq and energy E If so, then the eigenvectors F It can be represented as F =[ f peak , f freq , E The extracted features are combined into a feature vector. F Then, this feature vector F This will be used to match against templates in the database. The database stores a series of predefined exception event templates, each representing a specific exception type, such as hydrogen leaks or equipment malfunctions. Templates can be created and updated using historical data, expert knowledge, or simulations.

[0042] Extracted feature vectorsF The feature vector is matched against abnormal signal features stored in the database, and the matching algorithm can be Euclidean distance. F It is a feature vector extracted from the sensor. T i It is the first in the database i The feature vectors of the template.

[0043] Euclidean distance D i It can be represented as:

[0044]

[0045] in, n Indicates the number of features, j Indicates the first j One characteristic.

[0046] The matching algorithm uses cosine similarity. θ i The formula for measuring the angle between two vectors can be expressed as:

[0047]

[0048] Where · represents the dot product of vectors, || F || represents the eigenvector F The model, || T i || indicates the first in the database i The modulus of the feature vector of a template.

[0049] Choose an appropriate matching algorithm, such as Euclidean distance, cosine similarity, or dynamic time warping (DTW), to evaluate the similarity between the feature vector and the database templates. Use the matching algorithm to compare the feature vector with each template in the database and calculate a similarity score. Set a threshold; when the similarity score exceeds this threshold, a match is considered successful.

[0050] If a match is successful, the integrated monitoring system will identify the type of abnormal event and take further action. If a match fails, the system may need to collect more data or update the database template. A successful match confirms an abnormal situation; a failed match terminates the process.

[0051] Once a hydrogen leak is confirmed, the combined monitoring system will use vibration signal characteristics to pinpoint the leak location, determining which two adjacent hydrogen sensors are leaking. Leak location (based on signal propagation time difference): If the distance between the two sensors is... d The speed of signal propagation in the medium is vThe propagation time difference Δ from the leak point to the two sensors t It can be represented as Δ t = d / v The location of the leak can be determined by measuring the time difference.

[0052] Based on the matching results and leak location, the system automatically initiates emergency measures, such as activating the ventilation system, to reduce potential safety risks. Detailed information on the matching results and emergency response is recorded in the system for subsequent analysis and system optimization. The integrated monitoring system continuously updates its database templates based on new data and events to improve matching accuracy and system responsiveness.

[0053] The time-frequency plots of hydrogen sensors adjacent to the leak location were exported and verified multiple times to confirm the stability and accuracy of the leak signal. The implementation of the Fourier transform was optimized to improve the efficiency and accuracy of the spectral analysis. Advanced spectral estimation techniques, such as the maximum entropy method or wavelet transform, were introduced to extract more refined spectral features. Spectral analysis of the vibration signal was performed; for the vibration signal s(t), its spectrum... S ( f It can be obtained through Fourier transform:

[0054]

[0055] The final confirmed leak location and related data will be recorded in the system for subsequent analysis and maintenance.

[0056] In this embodiment, the co-cable hydrogen temperature vibration measurement unit 25 achieves comprehensive coverage of the monitoring area through the alternating arrangement of hydrogen sensors and vibration sensing units and optical fiber connection. It uses a fiber Bragg grating coated with hydrogen-sensitive material as the core sensing element, and with an adjustable coating ratio, it provides flexible detection capabilities. At the same time, the ambient temperature compensation grating connected in series at the tail effectively eliminates the influence of ambient temperature, significantly improving the measurement accuracy. It not only realizes the integration of hydrogen detection and vibration monitoring, but also reduces the complexity of the combined monitoring system and improves the overall monitoring efficiency.

[0057] Hydrogen sensors can detect minute hydrogen leaks, while vibration sensors can detect subtle environmental changes caused by leaks. Combining the two allows for earlier detection of potential leaks. Vibration sensors provide clues to the location of leaks, while hydrogen sensors confirm their presence. By analyzing vibration patterns and changes in hydrogen concentration, the leak source can be located more precisely. A standalone hydrogen sensor may produce false alarms due to environmental changes (such as temperature and humidity variations). Vibration sensors provide additional data, helping the system distinguish between genuine leaks and environmental disturbances. By monitoring vibration and hydrogen levels, the system can predict equipment wear and potential failures, thereby optimizing maintenance plans and reducing unexpected downtime. Reducing false alarms and optimizing maintenance plans lowers costs associated with leaks and equipment failures, as well as labor costs for maintenance. Commonly used electronic sensors require high-temperature and high-pressure environments and are expensive, with individual prices ranging from 300,000 to 400,000 RMB. The number of sensors used is limited by cost and environmental factors, and the acquisition length is also limited. This system uses a high-capacity, low-voltage grating array and a low-cost hydrogen sensor, significantly reducing the cost of industrial applications. Combined with intelligent data analysis, potential patterns and trends can be identified, providing support for decision-making.

[0058] The signal feedback module 2 effectively combines two optical signals through the first coupler 21 and ensures directional signal transmission with the help of the circulator 22. Simultaneously, it utilizes a dense wavelength division multiplexer 23 to achieve precise separation of signals of different wavelengths. Three erbium-doped fiber amplifiers amplify the signals at different locations, effectively ensuring signal strength during transmission and significantly improving the signal-to-noise ratio of the combined monitoring system. Furthermore, the first photodetector 26 performs photoelectric signal conversion, and in conjunction with the data acquisition module 4 and the interference beam splitter 3, ensures that the combined monitoring system can acquire and process monitoring data in real time and accurately.

[0059] The interference beam splitter module 3 is connected to the data acquisition module 4. The interference beam splitter module 3 is used to interfere the reflected light from the broadband grating and transmit the resulting interference signal to the data acquisition module 4 for storage.

[0060] In this embodiment, the interference beam splitting module 3 includes a second coupler 31, a first Faraday mirror 32, a delay fiber 33, and a second Faraday mirror 34. The second coupler 31 is connected to the data acquisition module 4, the first Faraday mirror 32, the delay fiber 33, and the second Faraday mirror 34, respectively. The first coupler 21 is a 1×2 coupler, and the second coupler 31 is a 3×3 coupler.

[0061] In this embodiment, the data acquisition module 4 includes a second photodetector 41, a third photodetector 42, a fourth photodetector 43, and a host computer 44. The second photodetector 41 is connected to the second coupler 31 and the host computer 44, the third photodetector 42 is connected to the second coupler 31 and the host computer 44, and the fourth photodetector 43 is connected to the second coupler 31 and the host computer 44. The phase difference of the interference signals received by the second photodetector 41, the third photodetector 42, and the fourth photodetector 43 is 120 degrees.

[0062] Implementation principle: Continuous light emitted from the tunable laser source 11 is modulated into a first pulse by the electro-optic modulator 14. Continuous light emitted from the narrow-linewidth laser source 12 is modulated into a second pulse by the acousto-optic modulator 15. The first pulse and the first coupler 21 are amplified by the first erbium-doped fiber amplifier 16 and the second erbium-doped fiber amplifier 17, respectively, and then converged into a single pulse at the first coupler 21. This pulse is then injected into the co-cable hydrogen temperature resonator unit 25 via the circulator 22. The co-cable hydrogen temperature resonator unit 25 includes a hybrid fiber grating array composed of multiple gratings. Each grating in the hybrid fiber grating array reflects a pulse at different times. The returned pulse is then split into two different wavelengths by a dense wavelength division multiplexer 23. The two signals are transmitted to the host computer 44 via photodetectors. The reflected light from the narrowband grating is used to measure the wavelength shift, and the optical power is detected by the first photodetector 26. The reflected light from the broadband grating enters the interference beam splitting module 3 through the third erbium-doped fiber amplifier 24. The returned light from the first Faraday mirror 32 and the second Faraday mirror 34 will interfere in the second coupler 31. The interference signal is split into three signals with a phase difference of 120° by the second coupler 31. These signals are converted into electrical signals by the second photodetector 41, the third photodetector 42, and the fourth photodetector 43, respectively, and transmitted to the data acquisition card. The high-speed acquisition card then acquires the data and demodulates it using a 3×3 algorithm. The demodulation result is then transmitted to the host computer 44 for storage.

[0063] The simultaneous monitoring of hydrogen concentration and vibration is achieved through the co-cable hydrogen temperature and vibration measurement unit 25, enabling the simultaneous acquisition of hydrogen concentration, temperature, and vibration information, significantly improving the comprehensiveness of the combined monitoring system. Integrating hydrogen, temperature, and vibration detection into the same system not only reduces the complexity of the combined monitoring system but also lowers equipment deployment costs and improves overall monitoring efficiency. This contributes to improving the accuracy of measuring hydrogen leak location and concentration. Furthermore, the dual-core fiber optic design effectively avoids interference between the two signals, ensuring the independence of vibration and hydrogen temperature signals, further enhancing the accuracy of measuring hydrogen leak location and concentration, and supporting continuous data acquisition and storage. Simultaneously, the combined monitoring system detects minute environmental changes through vibration sensing, combined with hydrogen concentration monitoring, to achieve early leak detection, effectively improving the early warning capability of the combined monitoring system.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined monitoring system for leakage concentration and location in hydrogen pipelines based on a grating array, characterized in that, It includes a signal modulation module (1), a signal feedback module (2), an interference beam splitting module (3), and a data acquisition module (4), wherein, The signal modulation module (1) is connected to the signal feedback module (2). The signal modulation module (1) includes a narrow linewidth laser light source (12) and a tunable laser light source (11). The signal modulation module (1) is used to couple the continuous light emitted by the narrow linewidth laser light source (12) and the tunable laser light source (11) to the signal feedback module (2) after performing acousto-optic modulation and electro-optic modulation respectively. The signal feedback module (2) is connected to the interference beam splitter module (3) and the data acquisition module (4) respectively. The signal feedback module (2) includes a co-cable hydrogen temperature vibration and measurement unit (25). The signal feedback module (2) is used to measure the wavelength drift based on the narrowband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit (25). The broadband grating reflected light in the co-cable hydrogen temperature vibration and measurement unit (25) is coupled to the interference beam splitter module (3). The co-cable hydrogen temperature vibration and measurement unit (25) includes a dual-core optical fiber, which includes an optical dielectric layer (251), a first core (252) and a second core (253). The optical dielectric layer (251) is disposed outside the first core (252) and the second core (253) to cover the first core (252) and the second core (253). A coating layer is disposed on the surface of the dual-core optical fiber. The first core (252) is disposed on the axis of the dual-core optical fiber, and the second core (253) is disposed on the side close to the coating layer. The first fiber core (252) includes a plurality of vibration signal gratings (254) arranged at equal intervals, and the second fiber core (253) includes a plurality of hydrogen temperature detection units (255) arranged at equal intervals. The hydrogen temperature detection unit (255) includes a first grating group (2551) and a second grating group (2552) arranged at intervals. Both the first grating group (2551) and the second grating group (2552) include a temperature measuring FBG grating and a hydrogen measuring FBG grating. The distance between any two adjacent hydrogen temperature detection units (255) is a first preset distance, the distance between any two adjacent vibration signal gratings (254) is a first preset distance, and the horizontal distance between any vibration signal grating (254) and an adjacent hydrogen temperature detection unit (255) is half of the first preset distance. The dual-core optical fiber is wound around the hydrogen pipeline, and the ratio between the length of the vibration signal grating (254) and the length of the coating layer is 0%~100%. The hydrogen-sensitive material coated on the surface of the dual-core optical fiber is any one of WO3, Pt / WO3, Pd / WO3, MoO3, Pt / Mo3 and Pd / MoO3. The interference beam splitting module (3) is connected to the data acquisition module (4). The interference beam splitting module (3) is used to interfere the reflected light of the broadband grating and transmit the obtained interference signal to the data acquisition module (4) for storage.

2. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 1, characterized in that, The signal modulation module (1) further includes a waveform generator (13), an electro-optic modulator (14), an acousto-optic modulator (15), a first erbium-doped fiber amplifier (16), and a second erbium-doped fiber amplifier (17). The electro-optic modulator (14) is connected to the tunable laser source (11), the waveform generator (13), and the first erbium-doped fiber amplifier (16), respectively. The acousto-optic modulator (15) is connected to the narrow linewidth laser source (12) and the second erbium-doped fiber amplifier (17), respectively. The first erbium-doped fiber amplifier (16) and the second erbium-doped fiber amplifier (17) are both connected to the signal feedback module (2).

3. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 2, characterized in that, The signal feedback module (2) further includes a first coupler (21), a circulator (22), a dense wavelength division multiplexer (23), a third erbium-doped fiber amplifier (24), and a first photodetector (26). One end of the first coupler (21) is connected to the first erbium-doped fiber amplifier (16) and the second erbium-doped fiber amplifier (17), respectively. The other end of the first coupler (21) is connected to the first end of the circulator (22). The second end of the circulator (22) is connected to the same cable hydrogen temperature vibration and measurement unit (25). The dense wavelength division multiplexer (23) is connected to the third end of the circulator (22), the third erbium-doped fiber amplifier (24), and the first photodetector (26), respectively. The first photodetector (26) is connected to the data acquisition module (4). The third erbium-doped fiber amplifier (24) is connected to the interference beam splitter module (3).

4. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 3, characterized in that, The interference beam splitting module (3) includes a second coupler (31), a first Faraday mirror (32), a time delay fiber (33), and a second Faraday mirror (34). The second coupler (31) is connected to the data acquisition module (4), the first Faraday mirror (32), the time delay fiber (33), and the second Faraday mirror (34), respectively.

5. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 4, characterized in that, The data acquisition module (4) includes a second photodetector (41), a third photodetector (42), a fourth photodetector (43), and a host computer (44). The second photodetector (41) is connected to the second coupler (31) and the host computer (44) respectively. The third photodetector (42) is connected to the second coupler (31) and the host computer (44) respectively. The fourth photodetector (43) is connected to the second coupler (31) and the host computer (44) respectively. The phase difference of the interference signals received by the second photodetector (41), the third photodetector (42), and the fourth photodetector (43) is 120 degrees.

6. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 1, characterized in that, The center wavelength range of the fiber Bragg grating is 1530nm~1625nm, the center wavelength of the narrow linewidth laser source (12) and the tunable laser source (11) is 1550.1nm, and the optical power of the narrow linewidth laser source (12) and the tunable laser source (11) is 14.6Mw.

7. The combined monitoring system for hydrogen pipeline leakage concentration and location based on grating array as described in claim 5, characterized in that, The first coupler (21) is a 1×2 coupler, and the second coupler (31) is a 3×3 coupler.

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