Hydrogen transmission pipeline leakage concentration and position combined monitoring system based on grating array

Abstract

The invention provides a hydrogen transmission pipeline leakage concentration and position combined monitoring system based on a grating array, and relates to the technical field of fiber grating sensing, the hydrogen transmission pipeline leakage concentration and position combined monitoring system comprises a signal modulation module, a signal return module, an interference beam splitting module and a data acquisition module, the signal modulation module comprises a narrow linewidth laser light source and a tunable laser light source; the signal return module comprises a co-cable hydrogen temperature and vibration simultaneous measurement unit, and broadband grating reflected light in the co-cable hydrogen temperature and vibration simultaneous measurement unit is coupled to the interference beam splitting module; the co-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 on the outer sides of the first fiber core and the second fiber core to wrap 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 axis of the double-core optical fiber. The second fiber core is arranged on one side close to the coating layer. According to the invention, the accuracy of measuring the hydrogen leakage position and concentration is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber grating sensing, and in particular to a combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array. Background Art

[0002] With the global energy transition and growing environmental awareness, hydrogen, as a clean and efficient energy carrier, is enjoying a broadening application prospect. Hydrogen not only demonstrates enormous potential in fuel cell vehicles and household combined heat and power systems, but also plays a vital role in numerous fields, including industrial production, healthcare, and food processing. However, the flammable and explosive nature of hydrogen necessitates precise monitoring of its concentration to ensure its safe use.

[0003] Chinese patent publication number CN108717042B discloses a fully polarization-maintaining, reflective hydrogen concentration detection device. The device comprises a light source, a fiber polarization beam splitter, a hydrogen sensor head, a spectrum analyzer, and a signal processing unit. The hydrogen sensor head is comprised of a polarization-maintaining photonic crystal fiber (PCF) with palladium coating on its sides and one end connected to a thin, coreless fiber coated with a reflective coating, forming a reflective PCF hydrogen sensor head. The polarization-maintaining pigtail of the light source is fused with the incident polarization-maintaining pigtail of the polarization beam splitter at 0 degrees to form a polarization-maintaining fiber optical path. The polarization-maintaining pigtail output from the polarization beam splitter is fused with 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 optical spectrum analyzer through the polarization beam splitter and the polarization-maintaining pigtail, and is processed and output by the signal processing unit. However, the above scheme only measures the hydrogen concentration at a specific location through a single hydrogen sensor, and cannot provide comprehensive information about the area around the leak source, which may lead to an underestimation of the scope and severity of the leak. Therefore, it is very necessary to provide a combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array to improve the accuracy of measuring hydrogen leak location and concentration. Summary of the Invention

[0004] In light of this, the present invention proposes a combined grating array-based monitoring system for hydrogen pipeline leak concentration and location. By integrating a single-cable hydrogen temperature and vibration measurement unit, this system enables simultaneous monitoring of hydrogen concentration and vibration, simultaneously acquiring wavelength drift and vibration information. Combined with acousto-optic modulation and electro-optic modulation techniques, this system improves signal quality and helps enhance the accuracy of hydrogen leak location and concentration measurements.

[0005] The present invention provides a combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array, comprising a signal modulation module, a signal return module, an interference beam splitting module and a data acquisition module, wherein: The signal modulation module is connected to the signal return module, and the signal modulation module includes a narrow linewidth laser light source and a tunable laser light source. The signal modulation module is used to perform acousto-optic modulation and electro-optic modulation on the continuous light emitted by the narrow linewidth laser light source and the tunable laser light source, respectively, and then couple the resultant light to the signal return module; The signal return module is connected to the interference beam splitting module and the data acquisition module respectively, and the signal return module includes a same-cable hydrogen temperature vibration measurement unit. The signal return module is used to measure the wavelength drift according to the narrowband grating reflected light in the same-cable hydrogen temperature vibration measurement unit, and the broadband grating reflected light in the same-cable hydrogen temperature vibration measurement unit is coupled to the interference beam splitting module; The co-cable hydrogen temperature vibration co-measurement unit includes a dual-core optical fiber, which includes 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 cover the first fiber core and the second fiber core. A coating layer is provided on the surface of the dual-core optical fiber. The first fiber core is arranged on the axis of the dual-core optical fiber, and the second fiber core is arranged on a side close to the coating layer. The interference beam splitting module is connected to the data acquisition module, and is used to interfere with the reflected light of the broadband grating and transmit the obtained interference signal to the data acquisition module for storage.

[0006] On the basis of the above technical solution, preferably, the signal modulation module further includes a waveform generator, an electro-optical modulator, an acousto-optic modulator, a first erbium-doped fiber amplifier and a second erbium-doped fiber amplifier, the electro-optical modulator is respectively connected to the tunable laser light source, the waveform generator and the first erbium-doped fiber amplifier, the acousto-optic modulator is respectively connected to the narrow-linewidth laser light source and the second erbium-doped fiber amplifier, and the first erbium-doped fiber amplifier and the second erbium-doped fiber amplifier are both connected to the signal feedback module.

[0007] On the basis of the above technical solution, preferably, the signal return module also 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 respectively connected to the first erbium-doped fiber amplifier and the second erbium-doped fiber amplifier, 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 co-cable hydrogen temperature vibration co-measurement unit, the dense wavelength division multiplexer is respectively connected to the third end of the circulator, the third erbium-doped fiber amplifier and the first photodetector, the first photodetector is connected to the data acquisition module, and the third erbium-doped fiber amplifier is connected to the interference beam splitting module.

[0008] More preferably, the interference beam splitting module includes a second coupler, a first Faraday mirror, a delay optical fiber and a second Faraday mirror, and the second coupler is respectively connected to the data acquisition module, the first Faraday mirror, the delay optical fiber and the second Faraday mirror.

[0009] Further 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 respectively, the third photodetector is connected to the second coupler and the host computer respectively, the fourth photodetector is connected to the second coupler and the host computer respectively, and the phase difference of the interference signals received by the second photodetector, the third photodetector and the fourth photodetector is 120 degrees.

[0010] More preferably, the first fiber core includes a plurality of equidistantly arranged vibration signal gratings, the second fiber core includes a plurality of equidistantly arranged hydrogen temperature detection units, the hydrogen temperature detection units include a first grating group and a second grating group arranged at intervals, the first grating group and the second grating group both include temperature measurement FBG gratings and hydrogen measurement FBG gratings, 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 the 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.

[0011] More preferably, the dual-core optical fiber is wound on the hydrogen transmission pipeline, and the ratio between the length of the vibration signal grating and the length of the coating layer is 0% to 100%.

[0012] 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.

[0013] More preferably, the central wavelength range of the fiber Bragg grating is 1530 nm to 1625 nm, the central wavelengths of the narrow-linewidth laser light source (12) and the tunable laser light source (11) are both 1550.1 nm, and the optical powers of the narrow-linewidth laser light source (12) and the tunable laser light source (11) are both 14.6 Mw.

[0014] More preferably, the first coupler is a 1×2 coupler, and the second coupler is a 3×3 coupler.

[0015] The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and location provided by the present invention has the following advantages over the prior art: (1) The simultaneous monitoring of hydrogen concentration and vibration is achieved through the same-cable hydrogen, temperature and vibration measurement unit, which can simultaneously obtain hydrogen concentration, temperature and vibration information, significantly improving the comprehensiveness of the combined monitoring system. The integration of hydrogen, temperature and vibration detection in the same system not only reduces the complexity of the combined monitoring system, but also reduces the equipment deployment cost, improves the overall monitoring efficiency, and helps to improve the accuracy of measuring hydrogen leakage location and concentration. The dual-core optical fiber design effectively avoids interference between the two signals, ensures the independence of vibration signals and hydrogen temperature signals, helps to improve the accuracy of measuring hydrogen leakage location and concentration, and supports continuous data acquisition and storage. At the same time, the combined monitoring system detects small environmental changes through vibration sensing, and realizes early leakage detection in combination with hydrogen concentration monitoring, effectively improving the early warning capability of the combined monitoring system.

[0016] (2) By integrating the monitoring functions of vibration, hydrogen concentration, and temperature into the same optical fiber, multi-parameter collaborative monitoring is achieved, which can fully reflect the operating status of the environment or equipment. The vibration signal grating and hydrogen temperature detection unit are arranged at equal intervals at 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, which is suitable for monitoring long-distance hydrogen pipelines. This alternating distribution design can further improve the positioning accuracy of the leak location through the 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 versatility. 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0018] Figure 1 A schematic diagram of the process of the combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array provided by the present invention; Figure 2 A schematic diagram of the structure of a dual-core optical fiber provided by the present invention;

[0019] Figure 3 This is a schematic diagram of the layout of the same-cable hydrogen temperature vibration measurement unit provided by the present invention.

[0020] Explanation of reference numerals: 1. signal modulation module; 11. tunable laser light source; 12. narrow linewidth laser light 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 return module; 21. first coupler; 22. circulator; 23. dense wavelength division multiplexer; 24. third erbium-doped fiber amplifier; 25. same-cable hydrogen temperature-vibration co-measurement unit; 251. optical medium layer; 252 , 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 splitting 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 DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0022] The present invention discloses a combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array, referring to Figure 1 The above system includes a signal modulation module 1, a signal return 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 return 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 perform acousto-optic modulation and electro-optic modulation on the continuous light emitted by the narrow-linewidth laser light source 12 and the tunable laser light source 11, respectively, and then couple them to the signal return module 2.

[0023] In this embodiment, the signal modulation module 1 also includes a waveform generator 13, an electro-optical modulator 14, an acousto-optic modulator 15, a first erbium-doped fiber amplifier 16, and a second erbium-doped fiber amplifier 17. The electro-optical modulator 14 is connected to the tunable laser light 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 light 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.

[0024] The central wavelengths of the narrow-linewidth laser light source 12 and the tunable laser light source 11 are both 1550.1 nm, and the optical powers of the narrow-linewidth laser light source 12 and the tunable laser light source 11 are both 14.6 Mw.

[0025] Furthermore, the signal modulation module 1 generates optical signals with different characteristics through the coordinated operation of the tunable laser light source 11 and the narrow-linewidth laser light source 12. The combined use of the 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 light source 11 to provide precise waveform control, while the acousto-optic modulator 15 modulates the narrow-linewidth laser light source 12 to achieve efficient optical signal pulse modulation. Together 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-optically modulated and acousto-optically modulated signals, respectively, ensuring that the signals have sufficient intensity for subsequent processing, effectively improving the system's signal-to-noise ratio and detection sensitivity. The connections between the various components have been optimized to reduce signal loss, achieve efficient signal transmission and processing, and improve the stability and reliability of the overall system.

[0026] The signal return module 2 is connected to the interference beam splitting module 3 and the data acquisition module 4 respectively. The signal return module 2 includes a same-cable hydrogen temperature vibration measurement unit 25. The signal return module 2 is used to measure the wavelength drift based on the narrowband grating reflected light in the same-cable hydrogen temperature vibration measurement unit 25. The broadband grating reflected light in the same-cable hydrogen temperature vibration measurement unit 25 is coupled to the interference beam splitting module 3.

[0027] In this embodiment, the signal return module 2 also 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 respectively connected to the first erbium-doped fiber amplifier 16 and the second erbium-doped fiber amplifier 17, 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 co-cable hydrogen temperature vibration co-measurement unit 25, the dense wavelength division multiplexer 23 is respectively connected to the third end of the circulator 22, the third erbium-doped fiber amplifier 24 and the first photodetector 26, the first photodetector 26 is connected to the data acquisition module 4, and the third erbium-doped fiber amplifier 24 is connected to the interference beam splitting module 3.

[0028] Further, if Figure 2 and Figure 3As shown, the same-cable hydrogen temperature vibration measurement unit 25 includes a dual-core optical fiber, which includes an optical medium layer 251, a first fiber core 252 and a second fiber core 253. The optical medium layer 251 is arranged on the outside of 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 provided on the surface of the dual-core optical fiber. The first fiber core 252 is arranged on the axis of the dual-core optical fiber, and the second fiber core 253 is arranged on the side close to the coating layer. The first fiber core 252 includes a plurality of equidistantly arranged vibration signal gratings 254, and the second fiber core 253 includes a plurality of equidistantly arranged hydrogen temperature detection units 255. The hydrogen temperature detection units 255 include a first grating group 2551 and a second grating group 2552 that are spaced apart. The first grating group 2551 and the second grating group 2552 both include temperature measurement FBG gratings and hydrogen measurement FBG gratings. The distance between any two adjacent hydrogen temperature detection units 255 is a first preset distance, and the distance between any two adjacent vibration signal gratings 254 is the first preset distance. The horizontal distance between any vibration signal grating 254 and an adjacent hydrogen temperature detection unit 255 is half of the first preset distance.

[0029] In this embodiment, by distributing a first core and a second core within a dual-core optical fiber, with a vibration signal grating 254 positioned on the first core and a hydrogen temperature detection unit 255 positioned on the second core, simultaneous multi-parameter detection of vibration signals, temperature, and hydrogen concentration is achieved. The vibration signal grating 254 and the hydrogen temperature detection unit 255 are spaced equidistantly (a first preset distance), with the horizontal distance between them being half the first preset distance. This evenly spaced design ensures high spatial resolution of the detection signals, facilitating precise localization of changes in vibration, temperature, and hydrogen concentration. The first grating group 2551 and the second grating group 2552 within the hydrogen temperature detection unit 255, comprising temperature-measuring FBG gratings and hydrogen-measuring FBG gratings, respectively, simultaneously detect 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. Furthermore, 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.

[0030] A dual-core optical fiber is wound around the hydrogen transmission 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 coating layer is coated with 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 central wavelength of the fiber Bragg grating is in the range of 1530nm to 1625nm. The monitoring device, consisting of a hydrogen sensor and a vibration sensing unit, is spirally wound around the surface of the hydrogen transmission pipeline.

[0031] The hydrogen sensor used in the above description is a fiber Bragg Grating (FBG) hydrogen sensor. This sensor combines hydrogen-sensitive materials with a fiber Bragg Grating (FBG) to detect hydrogen concentration by exploiting the exothermic effect of hydrogen absorption. Changes in the ambient hydrogen concentration cause changes in the FBG temperature, which in turn alters the FBG period. The hydrogen concentration is then determined by measuring the central wavelength of the reflected light. The hydrogen-sensitive materials described above include, but are not limited to, metal oxides that absorb hydrogen and release heat, such as Pt / WO3 and Pt / MoO3. Vibration sensing units (vibration monitoring devices) include all fiber optic sensing systems that utilize the demodulated vibration effect, including OFDR based on Rayleigh scattering, OFDR based on ultra-weak fiber grating arrays (UWFBGs), and distributed fiber acoustic wave sensors (DAS) based on UWFBGs.

[0032] The same-cable hydrogen, temperature, and vibration measurement unit 25 also collects signals from distributed optical fiber hydrogen sensors and vibration sensors and performs adjustment analysis, the steps of which include: Check whether 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 collected signal, including removing trend items, signal noise reduction, and zero-meaning.

[0033] After signal preprocessing is completed, feature extraction is performed on the signal, including extracting key features from the signals collected by vibration and hydrogen sensors, such as peak value, frequency, duration, energy time domain features (such as peak value, mean value, variance, etc.) and frequency domain features (such as power spectrum analysis). The constructed feature vector F Can be composed of multiple features, such as peak f peak ,frequency f freq and energy EEtc., then the eigenvector F It can be expressed as F =[ f peak , f freq , E ,...]. Combine the extracted features into a feature vector F Then, this feature vector F This is used to match against templates in the database. The database contains a series of predefined abnormal event templates, each representing a specific abnormality type, such as a hydrogen leak or equipment failure. Templates can be created and updated using historical data, expert knowledge, or simulation experiments.

[0034] The extracted feature vector F Match the abnormal signal features stored in the database, and the matching algorithm can choose Euclidean distance. Assume that the feature vector F is the feature vector extracted from the sensor, T i The first i The feature vector of the template.

[0035] Euclidean distance D i It can be expressed as:

[0036] in, n represents the number of features, j Indicates the j Features.

[0037] The matching algorithm uses cosine similarity, cosine similarity θ i Used to measure the angle between two vectors. The calculation formula can be expressed as:

[0038] where · represents the dot product of vectors, || F || represents the feature vector F The model of || T i || means the first i The modulus of the feature vector of the template.

[0039] Select an appropriate matching algorithm, such as Euclidean distance, cosine similarity, or dynamic time warping (DTW), to assess the similarity between the feature vector and the templates in the database. 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, the match is considered successful.

[0040] If a match is successful, the combined monitoring system identifies the type of abnormal event and takes further action. If a match fails, the system may need to collect more data or update the database template. If a match is successful, the abnormal situation is confirmed; if a match fails, the process ends.

[0041] Once a hydrogen leak is confirmed, the combined monitoring system will use the vibration signal characteristics to locate the leak and determine which two adjacent hydrogen sensors the leak occurred between. Leak location (based on signal propagation time difference): If the distance between the two sensors is d , the propagation speed of the signal in the medium is v , the propagation time difference Δ from the leak point to the two sensors t It can be expressed as Δ t = d / v , the leak location can be determined by measuring the time difference.

[0042] Based on the matching results and leak location, the system automatically initiates emergency measures, such as activating ventilation systems, to mitigate potential safety risks. Matching results and emergency response details are recorded in the system for subsequent analysis and system optimization. The combined monitoring system continuously updates its database templates based on new data and events to improve matching accuracy and system responsiveness.

[0043] The time-frequency diagram of the hydrogen sensor adjacent to the leak location is derived and multiple verifications are performed to confirm the stability and accuracy of the leak signal. The implementation of Fourier transform is optimized to improve the efficiency and accuracy of spectrum analysis. Advanced spectrum estimation techniques such as maximum entropy method or wavelet transform are introduced to extract more detailed spectrum features. Spectral analysis of vibration signals: for vibration signal s(t), its spectrum S ( f ) can be obtained by Fourier transform:

[0044] The final confirmed leak location and related data will be recorded in the system for subsequent analysis and maintenance.

[0045] In this embodiment, the same-cable hydrogen, temperature and 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. A fiber Bragg grating coated with hydrogen-sensitive material is used 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.

[0046] Hydrogen sensors can detect small hydrogen leaks, while vibration sensors can detect subtle environmental changes caused by leaks. Combining these two approaches can identify potential leaks earlier. Vibration sensors provide clues to the leak's location, while hydrogen sensors confirm its presence. By analyzing changes in vibration patterns and hydrogen concentrations, the leak source can be more precisely located. Hydrogen sensors alone can generate false alarms due to environmental fluctuations (such as temperature and humidity). Vibration sensors provide additional data, helping the system distinguish between real leaks and environmental disturbances. By monitoring vibration and hydrogen levels, the system can predict equipment wear and potential failures, optimizing maintenance schedules and reducing unplanned downtime. Reducing false alarms and optimizing maintenance schedules can reduce costs and labor associated with leaks and equipment failures. Common electronic sensors must withstand high-temperature and high-pressure environments and are relatively expensive, costing between 300,000 and 400,000 yuan each. The number of sensors used is affected by cost and environmental factors, and the acquisition length is also limited. This system utilizes a high-capacity weak grating array and low-cost hydrogen sensors, significantly reducing the cost of industrial applications. Combined with intelligent data analysis, it can identify potential patterns and trends to support decision-making.

[0047] The signal return module 2 effectively combines two optical signals through a first coupler 21, ensures directional signal transmission with the aid of a circulator 22, and precisely separates signals of different wavelengths using a dense wavelength division multiplexer 23. Three erbium-doped fiber amplifiers amplify the signal 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 converts the optical signal into electrical and optical signals. This, in conjunction with the data acquisition module 4 and the interferometric beam splitting module 3, ensures that the combined monitoring system can accurately collect and process monitoring data in real time.

[0048] The interference beam splitting module 3 is connected to the data acquisition module 4. The interference beam splitting module 3 is used to interfere with the reflected light of the broadband grating and transmit the obtained interference signal to the data acquisition module 4 for storage.

[0049] 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 respectively connected to the data acquisition module 4, the first Faraday mirror 32, the delay fiber 33, and the second Faraday mirror 34. The first coupler 21 is a 1×2 coupler, and the second coupler 31 is a 3×3 coupler.

[0050] 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, respectively, the third photodetector 42 is connected to the second coupler 31 and the host computer 44, respectively, and 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.

[0051] Implementation principle: The continuous light emitted by the tunable laser light source 11 is modulated into the first pulse light by the electro-optic modulator 14, and the continuous light emitted by the narrow linewidth laser light source 12 is modulated into the second pulse light by the acousto-optic modulator 15. The first pulse light 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 merged into a pulse light at the first coupler 21, and injected into the same cable hydrogen temperature vibration and measurement unit 25 through the circulator 22. The same cable hydrogen temperature vibration and measurement unit 25 includes a hybrid fiber grating array composed of multiple gratings. Each grating in the hybrid fiber grating array will reflect back a pulse light at different times. The returned pulse light uses a dense wavelength division multiplexer 23 to divide the two reflected lights of different wavelengths into The two paths are uploaded to the host computer 44 respectively through the photoelectric detector. The reflected light of the narrowband grating is used to measure the wavelength drift. The optical power is detected by the first photodetector 26. The reflected light of the broadband grating enters the interference beam splitting module 3 through the third erbium-doped fiber amplifier 24. The return light of the first Faraday mirror 32 and the second Faraday mirror 34 will interfere in the second coupler 31. The interference signal is divided into three signals with a phase difference of 120° through the second coupler 31. They are converted into electrical signals by the second photodetector 41, the third photodetector 42 and the fourth photodetector 43 and uploaded to the data acquisition card. Then, the high-speed acquisition card collects the data and demodulates it using the 3×3 algorithm. The demodulation result is uploaded to the host computer 44 for storage.

[0052] The simultaneous monitoring of hydrogen concentration and vibration is achieved through the same-cable hydrogen, temperature, and vibration measurement unit 25. This allows for simultaneous acquisition of hydrogen concentration, temperature, and vibration information, significantly improving the 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, improves overall monitoring efficiency, and helps improve the accuracy of measuring hydrogen leak locations and concentrations. The dual-core fiber design effectively avoids interference between the two signals, ensuring the independence of vibration and hydrogen temperature signals, helping to improve the accuracy of measuring hydrogen leak locations and concentrations, and supporting continuous data acquisition and storage. At the same time, the combined monitoring system detects minor environmental changes through vibration sensing, and combines this with hydrogen concentration monitoring to achieve early leak detection, effectively improving the early warning capabilities of the combined monitoring system.

[0053] 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 in the scope of protection of the present invention.

Claims

1. A combined monitoring system for hydrogen pipeline leakage concentration and location based on a grating array, characterized in that: It comprises a signal modulation module (1), a signal return 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 return module (2), the signal modulation module (1) comprises a narrow linewidth laser light source (12) and a tunable laser light source (11), and the signal modulation module (1) is used to perform acousto-optic modulation and electro-optic modulation on the continuous light emitted by the narrow linewidth laser light source (12) and the tunable laser light source (11), respectively, and then couple the resultant light to the signal return module (2); The signal return module (2) is connected to the interference beam splitting module (3) and the data acquisition module (4) respectively. The signal return module (2) includes a co-cable hydrogen temperature vibration co-measurement unit (25). The signal return module (2) is used to measure the wavelength drift amount based on the narrowband grating reflected light in the co-cable hydrogen temperature vibration co-measurement unit (25). The broadband grating reflected light in the co-cable hydrogen temperature vibration co-measurement unit (25) is coupled to the interference beam splitting module (3). The co-cable hydrogen temperature vibration co-measurement unit (25) comprises a dual-core optical fiber, the dual-core optical fiber comprising an optical medium layer (251), a first fiber core (252) and a second fiber core (253), the optical medium layer (251) being arranged 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 being arranged on the surface of the dual-core optical fiber, the first fiber core (252) being arranged on the axis of the dual-core optical fiber, and the second fiber core (253) being arranged on a side close to the coating layer; The interference beam splitting module (3) is connected to the data acquisition module (4), and the interference beam splitting module (3) is used to interfere with the broadband grating reflected light and transmit the obtained interference signal to the data acquisition module (4) for storage.

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

3. The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to claim 2, characterized in that: The signal return module (2) further comprises 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 respectively connected to the first erbium-doped fiber amplifier (16) and the second erbium-doped fiber amplifier (17); 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 co-cable hydrogen temperature vibration co-measurement unit (25); the dense wavelength division multiplexer (23) is respectively connected to the third end of the circulator (22), the third erbium-doped fiber amplifier (24) and the first photodetector (26); the first photodetector (26) is connected to the data acquisition module (4); and the third erbium-doped fiber amplifier (24) is connected to the interference beam splitting module (3).

4. The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to claim 3, characterized in that: The interference beam splitting module (3) comprises a second coupler (31), a first Faraday mirror (32), a time-delay optical fiber (33) and a second Faraday mirror (34); the second coupler (31) is respectively connected to the data acquisition module (4), the first Faraday mirror (32), the time-delay optical fiber (33) and the second Faraday mirror (34).

5. The combined monitoring system for hydrogen pipeline leakage concentration and position based on grating array according to claim 4, characterized in that: The data acquisition module (4) comprises 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; and 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 grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to claim 2, characterized in that: The first fiber core (252) includes a plurality of equidistantly arranged vibration signal gratings (254), the second fiber core (253) includes a plurality of equidistantly arranged hydrogen temperature detection units (255), the hydrogen temperature detection units (255) include a first grating group (2551) and a second grating group (2552) arranged at intervals, the first grating group (2551) and the second grating group (2552) both include temperature measurement FBG gratings and hydrogen measurement FBG gratings, 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 the 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.

7. The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to claim 6, characterized in that: The dual-core optical fiber is wound on the hydrogen transmission pipeline, and the ratio between the length of the vibration signal grating (254) and the length of the coating layer is 0% to 100%.

8. The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to claim 7, characterized in that: 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.

9. The combined monitoring system for hydrogen pipeline leakage concentration and position based on a grating array according to claim 7, characterized in that: The central wavelength range of the fiber Bragg grating is 1530 nm to 1625 nm, the central wavelengths of the narrow-linewidth laser light source (12) and the tunable laser light source (11) are both 1550.1 nm, and the optical powers of the narrow-linewidth laser light source (12) and the tunable laser light source (11) are both 14.6 Mw.

10. The grating array-based combined monitoring system for hydrogen pipeline leakage concentration and position according to 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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