Underground pipe gallery leakage gas identification system based on infrared spectroscopic analysis

Abstract

The invention relates to the technical field of gas detection, and discloses an underground pipe gallery leakage gas identification system based on infrared spectroscopic analysis, comprising an acoustic sensor unit passively monitoring a pipe gallery acoustic signal and generating a wake-up instruction and azimuth information, the infrared spectrum analysis module emits infrared beams with specific wavelength combination to a pre-estimated leakage sector according to the azimuth information and receives a returned light signal to generate spectral data; and the control processing unit analyzes the spectral data and judges and confirms a leakage event in cooperation with the azimuth information. According to the method, energy efficiency mode innovation from continuous scanning to event driving is realized through a cooperative mechanism of acoustic triggering and infrared directional detection, and the accuracy and response speed of trace leakage identification in a complex environment are remarkably improved by combining a differential spectrum technology and spatial coding logic verification.

Description

Technical Field

[0001] The present invention relates to a leakage gas identification system for an underground utility tunnel based on infrared spectroscopy analysis, and belongs to the technical field of intelligent monitoring of gas leakage in underground utility tunnels. Background Art

[0002] In the field of gas detection technology, the gas leakage monitoring of underground utility tunnels mainly adopts technical solutions based on infrared spectroscopy analysis. The current mainstream systems achieve gas identification by actively emitting infrared light beams and detecting characteristic absorption, which can meet the basic monitoring requirements in a conventional environment. However, when such solutions are applied to the actual utility tunnel environment, their technical limitations gradually emerge:

[0003] 1. The contradiction between energy efficiency and coverage: In order to achieve comprehensive monitoring, existing systems usually adopt high-density deployment or mechanical scanning mechanisms, resulting in a significant increase in equipment complexity and energy consumption. This continuous active detection mode is difficult to achieve cost-effective long-term operation in long-distance utility tunnels. 2. The balance between environmental interference and identification accuracy: There are temperature and humidity gradient changes, dust interference, and coexistence of multi-component background gases inside the utility tunnel. These factors will significantly affect the infrared spectral characteristics. Although the identification effect can be partially improved through algorithm compensation, the computational complexity increases and new misjudgment risks may be introduced. 3. The limitation of early leakage response ability: Existing technologies mainly rely on the concentration accumulation after gas diffusion for detection, and there is an inherent delay in the response to initial trace leakage, making it difficult to give early warnings in a timely manner. The industry has made various attempts to solve these problems, including optimizing sensor sensitivity, improving algorithm models, etc. Although these improvements have enhanced individual performance indicators to a certain extent, they have not fundamentally solved the internal contradiction among system energy efficiency, environmental adaptability, and response timeliness. Especially when facing the accurate identification requirements of early trace leakage in the complex environment of utility tunnels, the existing technical system still has obvious deficiencies.

[0004] Therefore, how to construct a gas leakage identification system for utility tunnels that can take into account low-power operation, strong anti-interference ability, and fast response characteristics has become the technical problem to be solved by the present invention. Summary of the Invention

[0005] The present invention provides a leakage gas identification system for an underground utility tunnel based on infrared spectroscopy analysis, and its main purpose is to solve the technical contradiction problem that the existing infrared gas monitoring system is difficult to take into account low-power operation, strong anti-interference ability, and fast response characteristics in the complex environment of utility tunnels.

[0006] To achieve the above object, a leakage gas identification system for an underground utility tunnel based on infrared spectroscopy analysis provided by the present invention includes: a) At least one acoustic sensor unit, configured to passively monitor acoustic signals in the pipe gallery, and generate a wake-up instruction and azimuth information indicating the preliminary azimuth of the sound source when detecting a signal that conforms to the preset acoustic characteristics of gas leakage; b) An infrared spectroscopy analysis module, communicatively connected to the acoustic sensor unit, the infrared spectroscopy analysis module includes: i. A tunable infrared light source, responsive to the wake-up instruction, and according to the azimuth information, emits a sequence of infrared detection light beams containing at least two different wavelengths towards the estimated leakage sector, and the at least two different wavelengths respectively correspond to the characteristic absorption peaks of at least two key target gases; ii. An infrared detector, configured to receive the infrared light returned from the estimated leakage sector, and generate target area spectral data containing the intensities of infrared light of at least two different wavelengths; c) A control and processing unit, connected to the acoustic sensor unit and the infrared spectroscopy analysis module, configured to: i. Based on the azimuth information, control the emission direction of the tunable infrared light source and / or the wavelength combination included in the sequence of infrared detection light beams; ii. Receive and process the target area spectral data, and identify the infrared absorption characteristics of potential leakage gases by analyzing the attenuation degrees of the intensities of infrared light of at least two different wavelengths; iii. When identifying the infrared absorption characteristics of at least one potential leakage gas that meet the preset absorption intensity threshold, and the type of the potential leakage gas matches the preset pipeline type in the estimated leakage sector indicated by the azimuth information, confirm the leakage event and output an alarm signal.

[0007] In a preferred embodiment, the acoustic sensor unit includes an acoustic anisotropic microstructure sensor array, and the control and processing unit is further configured to calculate the two-dimensional coordinate information or three-dimensional coordinate information of the sound source based on the time delay or intensity difference between the acoustic signals received by different sensors in the array, so as to optimize the azimuth information and determine the estimated leakage sector.

[0008] In a preferred embodiment, the infrared spectroscopy analysis module is further configured to, at the same time as or after the tunable infrared light source emits a sequence of infrared detection light beams towards the estimated leakage sector, instruct it to emit the same sequence of infrared detection light beams towards at least one background reference area confirmed by the acoustic sensor unit and currently without leakage acoustic signals, so as to obtain background spectral data; and the control and processing unit is further configured to calculate the intensity difference between the target area spectral data and the background spectral data at the corresponding wavelengths, obtain a differential spectrum, and identify the infrared absorption characteristics based on the differential spectrum.

[0009] In a preferred embodiment, a passive directional reflection structure or a passive directional scattering structure is provided in the area of the inner wall of the pipe gallery corresponding to the estimated leakage sector. The reflection structure or the scattering structure includes a material having a high reflectivity or a high scattering rate for at least two different wavelengths of infrared light, and is used to enhance the intensity of the infrared light signal returned to the infrared detector through the estimated leakage sector.

[0010] In a preferred embodiment, the control processing unit is further configured to access a database storing pipe gallery geographic information system data. The database includes pipeline type information of different areas in the pipe gallery. The control processing unit determines the pipe gallery area where the potential leakage source is located based on the azimuth information, retrieves the pipeline types included in this area from the database, and performs a logical match between the identified potential leakage gas types and the retrieved pipeline types. Only when the matching result is consistent is the leakage event confirmed.

[0011] In a preferred embodiment, the control processing unit calculates the absorbance at the characteristic absorption wavelength of a specific target gas in the differential spectrum where is the light intensity of the background spectrum at wavelength is the light intensity of the target area spectrum at wavelength When the absorbance is greater than a preset leakage determination threshold, a preliminary determination is made that there is a leakage of the target gas.

[0012] In a preferred embodiment, the tunable infrared light source includes a quantum cascade laser array. Each laser in the array emits infrared light at the characteristic absorption wavelength of a specific target gas. The control processing unit selectively activates at least one laser in the array according to the azimuth information.

[0013] In a preferred embodiment, the tunable infrared light source includes a broadband infrared light source and a MEMS Fabry - Perot interferometer. The control processing unit generates a sequence of infrared detection beams including at least two different wavelengths by controlling the transmission wavelength of the interferometer.

[0014] In a preferred embodiment, the preset gas leakage acoustic characteristics include ultrasonic signals in a specific frequency range or acoustic emission signals having a specific time - domain envelope. The acoustic sensor unit includes a piezoelectric ceramic sensor or a MEMS microphone array, and is configured with an acoustic filter for filtering out environmental noise.

[0015] In a preferred embodiment, the control processing unit is further configured to generate alarm information including the leakage gas type and the estimated leakage location after confirming the leakage event, and send the alarm information to the remote monitoring platform.

[0016] ​​​​Compared with the problems of the background art, the beneficial effects of the present invention are as follows: 1. Aiming at the energy efficiency bottleneck caused by continuous scanning in the long-distance monitoring scenario of underground pipe galleries, the system realizes the innovation of the energy efficiency mode from active search to event-driven through the collaborative mechanism of acoustic triggering and infrared directional detection. After the acoustic sensor array captures the transient acoustic characteristics in the initial stage of leakage in the passive listening state, it accurately locks the target sector and wakes up the infrared module for directional scanning. This physical-level triggering mechanism effectively avoids the energy waste in the invalid area of the traditional scheme. The wavelength combination of the tunable light source dynamically matches the absorption peak of the estimated leakage gas, and combined with the secondary focusing of the beam path by the passive reflection structure on the inner wall of the pipe gallery, a characteristic absorption signal can be generated by the trace leakage gas within a limited optical path, fundamentally constructing a technical path for highly sensitive detection under low power consumption conditions.

[0017] 2. Under the superimposed challenges of complex environmental interference and trace absorption of target gases, the system significantly improves the specificity of feature recognition through the double guarantee of differential spectroscopy technology and spatial coding logic verification. When the directional infrared beam detects a suspicious absorption peak in the acoustic positioning area, the synchronous acquisition of the spectral data in the background reference area can effectively strip the baseline drift caused by environmental humidity fluctuations and pipe wall aging. The control unit spatially correlates the attenuation characteristics extracted from the differential spectrum with the sound source azimuth information, and then combines the logical matching of the pipeline medium attributes in the GIS database to form a cross-verification mechanism of multi-dimensional criteria. This composite discrimination mode based on physical propagation characteristics and system topology constraints solves the industry problem that traditional single-spectrum analysis is vulnerable to cross-sensitivity interference.

[0018] 3. Facing the coupling problem of trace gas diffusion and spatial positioning in the initial stage of leakage events, a collaborative positioning system of acoustic anisotropy perception and infrared beam spatial modulation is constructed. The micro-structure sensor array obtains the vector azimuth of the leakage source through the time-delay analysis of the acoustic wave propagation path, and guides the tunable light source to emit a wavelength-coded detection sequence to the target sector. This beam spatial modulation technology driven by acoustic events makes the infrared spectrum acquisition process naturally carry the spatial attribute information of the leakage source. Combined with the constraint characteristics of the pipe gallery structure on the beam propagation path, the synchronous and accurate analysis of gas component identification and leakage source positioning is realized, breaking through the response delay bottleneck caused by the separation of chemical detection and physical positioning in the traditional scheme.

[0019] 4. To address the false alarm risk caused by the coexistence of multiple types of pipelines in the underground utility tunnel, the system constructs a leakage verification system with environmental self-consistency through the logical coupling mechanism of gas absorption characteristics and pipeline spatial attributes. When the infrared spectrum identifies the absorption characteristics of a specific gas, the control unit indexes the pipeline distribution data in the geographical database based on the acoustic positioning information, verifies the matching degree between the detected gas type and the physical and chemical properties of the preset pipeline medium in the target area, and realizes the verification logic of physically coupling the chemical fingerprint characteristics with the system topology information, effectively suppressing the false alarm phenomenon caused by environmental cross-contamination or misjudgment of pipeline media, and achieving an essential safety improvement in the discrimination of leakage events under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. is the working timing diagram of the underground utility tunnel leakage gas identification system based on infrared spectrum analysis of the present invention; Figure 2 FIG. is the infrared optical path schematic diagram of the underground utility tunnel leakage gas identification system based on infrared spectrum analysis of the present invention; Figure 3 FIG. is the gas leakage judgment flow chart of the underground utility tunnel leakage gas identification system based on infrared spectrum analysis of the present invention.

[0021] The implementation, functional features, and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The embodiment of the present application provides an underground utility tunnel leakage gas identification system based on infrared spectrum analysis, including: a) At least one acoustic sensor unit configured to passively monitor the acoustic signals in the utility tunnel and generate a wake-up instruction and azimuth information indicating the preliminary azimuth of the sound source when detecting a signal that conforms to the preset acoustic characteristics of gas leakage; b) An infrared spectrum analysis module communicatively connected to the acoustic sensor unit, and the infrared spectrum analysis module includes: i. A tunable infrared light source that responds to the wake-up instruction and emits a sequence of infrared detection light beams containing at least two different wavelengths towards the estimated leakage sector according to the azimuth information, and the at least two different wavelengths respectively correspond to the characteristic absorption peaks of at least two key target gases; ii. An infrared detector for receiving the infrared light returned from the estimated leakage sector and generating target area spectral data containing the intensities of infrared light of at least two different wavelengths; c) A control processing unit connected to the acoustic sensor unit and the infrared spectrum analysis module, configured to: i. Based on the azimuth information, control the emission direction of the tunable infrared light source and / or the wavelength combination included in the infrared detection beam sequence; ii. Receive and process the spectral data of the target area, and identify the infrared absorption characteristics of potential leakage gases by analyzing the attenuation degrees of at least two different wavelength infrared light intensities; iii. When identifying the infrared absorption characteristics of at least one potential leakage gas that meets the preset absorption intensity threshold, and the type of the potential leakage gas matches the preset pipeline type in the estimated leakage sector indicated by the azimuth information, confirm the leakage event and output an alarm signal.

[0024] In a preferred embodiment, the acoustic sensor unit includes an acoustic anisotropic microstructure sensor array, and the control and processing unit is further configured to calculate the two-dimensional coordinate information or three-dimensional coordinate information of the sound source based on the time delay or intensity difference between the acoustic signals received by different sensors in the array, so as to optimize the azimuth information and determine the estimated leakage sector; in actual deployment and operation, the system takes the sound source azimuth as a reference, dynamically locks the target area through an acoustic trigger mechanism, and guides the infrared spectroscopy detection module to perform directional sampling. This estimated area can also be regarded as the detection area or the leakage sector, and its expression can be flexibly switched according to the different focuses of the module responsibilities. In the information processing process, the microstructure array acoustic unit exerts its anisotropic response characteristics, realizes the high-precision analysis of the sound source position, and effectively ensures the accuracy of the detection direction selection. Combining with the differential contrast analysis mechanism of the background reference area makes the absorption peaks of trace gases more distinguishable under a complex interference background, which all belong to the extended embodiments known to those of ordinary skill in the art.

[0025] In a preferred embodiment, the infrared spectroscopy analysis module is further configured to, when the tunable infrared light source emits an infrared detection beam sequence towards the estimated leakage sector, or after that, instruct it to emit the same infrared detection beam sequence towards at least one background reference area confirmed by the acoustic sensor unit and having no leakage acoustic signal at present, so as to obtain background spectral data; and the control and processing unit is further configured to calculate the intensity difference between the target area spectral data and the background spectral data at the corresponding wavelength to obtain a differential spectrum, and identify the infrared absorption characteristics based on the differential spectrum.

[0026] In a preferred embodiment, a passive directional reflection structure or a passive directional scattering structure is provided in the area of the inner wall of the pipe gallery corresponding to the estimated leakage sector, and the reflection structure or the scattering structure includes materials with high reflectivity or high scattering rate for at least two different wavelengths of infrared light, which is used to enhance the intensity of the infrared light signal returned to the infrared detector through the estimated leakage sector.

[0027] In a preferred embodiment, the control processing unit is further configured to access a database storing the data of the utility tunnel geographic information system, where the database contains the pipeline type information of different areas in the utility tunnel; the control processing unit determines the utility tunnel area where the potential leakage source is located based on the orientation information, retrieves the pipeline types included in this area from the database, and performs a logical match between the identified potential leakage gas types and the retrieved pipeline types. Only when the matching result is consistent is the leakage event confirmed.

[0028] In a preferred embodiment, the control processing unit calculates the absorbance at the characteristic absorption wavelength of a specific target gas in the differential spectrum where , where , is the light intensity of the background spectrum at the wavelength , is the light intensity of the target area spectrum at the wavelength ; when the absorbance is greater than the preset leakage determination threshold, it is preliminarily determined that there is a leakage of this target gas.

[0029] In a preferred embodiment, the tunable infrared light source includes a quantum cascade laser array, and each laser in the array emits infrared light at the characteristic absorption wavelength of a specific target gas. The control processing unit selectively activates at least one laser in the array according to the orientation information.

[0030] In a preferred embodiment, the tunable infrared light source includes a broadband infrared light source and a MEMS Fabry - Perot interferometer. The control processing unit generates a sequence of infrared detection beams containing at least two different wavelengths by controlling the transmission wavelength of the interferometer.

[0031] In a preferred embodiment, the preset gas leakage acoustic characteristics include ultrasonic signals in a specific frequency range or acoustic emission signals with a specific time - domain envelope. The acoustic sensor unit includes a piezoelectric ceramic sensor or a MEMS microphone array and is configured with an acoustic filter for filtering out environmental noise.

[0032] In a preferred embodiment, the control processing unit is further configured to generate alarm information containing the leakage gas type and the estimated leakage location after confirming the leakage event, and send the alarm information to the remote monitoring platform.

[0033] Embodiment 1: In this embodiment, a typical underground utility tunnel is selected as the test environment. This tunnel contains various types of pipelines such as gas pipelines, communication optical cables, and sewage drainage pipes, and has typical structural features such as dual channels, long distances, and multiple branches. The purpose is to verify the effectiveness of the leakage identification system based on the collaborative mechanism of infrared spectroscopy analysis and acoustic positioning described in the present invention under complex working conditions and its engineering feasibility. The overall system follows the integrated deployment principle of node self-sustainment, no mechanical scanning, and module collaboration. The control and processing unit realizes function integration through an embedded edge intelligent platform, and the overall power consumption of the system is controlled within 20 watts, which is significantly lower than that of traditional infrared spectroscopy full-coverage scanning systems.

[0034] In the standby state of the system, the microstructural acoustic sensor array deployed at the intersection node of the main ventilation channel on the top of the tunnel is in a low-power passive listening mode. Based on the principle of anisotropic response of sound wave propagation, this sensor array has the ability to capture instantaneous abnormal pulse waveforms in the frequency band of 30 kHz to 80 kHz. Four groups of evenly distributed MEMS acoustic sensing elements are integrated inside the sensor array, and each group of units is arranged at a 45-degree angle. The two-dimensional azimuth information of the sound source is calculated in the control and processing unit through the time difference of arrival positioning algorithm, and the positioning error is controlled within ±0.5 meters. The system's setting of the leakage acoustic characteristics includes high-amplitude short-time pulse waveforms and time-domain envelopes with characteristic peaks having a width of approximately 0.3 milliseconds. When the acoustic sensor array detects an abnormal signal that meets the above characteristics, the system immediately wakes up the infrared spectroscopy analysis module. The tunable infrared light source integrated in this module is a quantum cascade laser array, and each laser in the array corresponds to the characteristic absorption wavelength of a target gas (such as methane, hydrogen sulfide, or ammonia), such as 3.31 microns, 4.05 microns, and 4.25 microns, etc. The infrared pulses emitted by the lasers are set with a pulse width of 100 nanoseconds and a repetition frequency of 1 kHz. The emission direction of the infrared beam is precisely regulated by the control circuit according to the sound source azimuth information, and its emission angle is limited within a fan-shaped area of ±10 degrees to achieve directional irradiation of the estimated leakage area and avoid false interference caused by redundant detection.

[0035] The infrared beam is reflected by the high-reflectivity coating material arranged on the inner wall of the pipe gallery to the target area, which is used to enhance the interaction path length between the beam and the leaked gas, thereby improving the detection sensitivity. The reflective material used is an aluminum fluoride composite material with a reflectivity greater than 92% in the wavelength band of 3 to 5 microns, which has good environmental stability and infrared optical properties. The infrared detector is installed on the opposite wall of the pipe gallery. Its response time is less than 10 nanoseconds, and it has a signal-to-noise ratio of more than 60 dB. It can receive the retroreflected signal in real time and upload the infrared spectral data containing multiple target wavelength information to the control and processing unit. To improve the reliability of the determination result, after the system completes the data acquisition of the target area, the laser is directed to an area where no abnormal sound signal is confirmed by the acoustic sensor, and the infrared beam of the same wavelength combination is also emitted and the return signal is collected to obtain the background spectral data. The control and processing unit calculates the differential spectrum based on the light intensity data of the target area and the reference area at the same wavelength to exclude environmental noise and background gas interference.

[0036] For example, in the identification of methane, if the light intensity at the wavelength of 3.31 microns in the target area is 0.53 (normalized value) and the corresponding light intensity in the background area is 0.89, then its absorbance is calculated to be approximately 0.23 according to A = log10(Ibackground / Itarget). The leakage determination threshold set by the system is 0.15. If the measured value is higher than this threshold and the leakage azimuth information matches the area where the natural gas pipeline is recorded in the GIS database, the system will confirm the leakage event and generate an alarm message containing the gas type, leakage azimuth coordinates (such as x = 32.7 m, y = 8.4 m), and judgment confidence level (such as 97.2%), and send it to the remote monitoring platform; to further reduce the false alarm rate, the control and processing unit constructs a joint determination model, comprehensively considering acoustic characteristic parameters (such as spectral center frequency, energy distribution), infrared spectral morphological characteristics (such as absorption peak morphology, amplitude index), and the pipeline attribute matching degree in the GIS database. If the above comprehensive score is lower than 80%, the event will be marked as "requiring manual review" and the automatic alarm will be suspended to avoid misjudgment.

[0037] In this embodiment, the setting of each core parameter is based on engineering verification tests. For example, the adjustable laser emission angle of ±10 degrees is the result of achieving the optimal balance between the target recognition accuracy and the system response time; the absorbance determination threshold of 0.15 is the optimal threshold determined through large-sample statistical analysis under the condition of coexistence of multiple interfering gases, enabling the system to operate under the conditions that the false alarm rate is controlled below 5% and the missed alarm rate is controlled within 2%. The matching design of the response time of the infrared detector and the laser pulse width ensures high time resolution and effectively suppresses signal overlap caused by multiple reflections, thereby achieving the real-time response ability at the millisecond level, which all belong to the extended implementation methods known to those of ordinary skill in the art.

[0038] Example 2: This example combinesFigures 1 to 3 , an implementation description of an underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis is provided. As Figure 1 shown, the entire process starts with the acoustic sensor unit monitoring the acoustic signal. When the acoustic sensor unit monitors the acoustic signal and detects that it conforms to the leakage acoustic characteristics, the system executes a conditional branch (represented by an alt box), generates a wake-up instruction and orientation information, and sends the wake-up instruction and orientation information to the infrared spectroscopy analysis module; the infrared spectroscopy analysis module responds to the wake-up instruction, then controls the tunable infrared light source to emit a sequence of beams (estimated sector), then receives the returned optical signal, and sends the spectral data to the control processing unit. After receiving the sent spectral data, the control processing unit starts to receive and analyze the spectral data (cooperating with the orientation information), then performs differential spectral calculation, and queries the corresponding pipeline type data to obtain information from the utility tunnel geographic information system. The utility tunnel geographic information system returns the pipeline type data to the control processing unit. The control processing unit performs logical coupling (acoustic positioning, infrared characteristics, GIS), then conducts a final leakage verification determination, and issues a determination result (leakage / non-leakage). The process ends at the control processing unit and the utility tunnel geographic information system. As Figure 2 shown, the entire process starts with a quantum cascade laser. The tuning range of this laser is 3 to 5 micrometers, and it emits a pulsed coded beam with a pulse width of 100 nanoseconds. This beam irradiates the target gas area, and the absorption rate of this area is 30%. After the beam is absorbed, an attenuation signal is formed, and finally this attenuation signal reaches the reflection structure. As Figure 3 shown, the process starts with receiving the acoustic signal, and then makes a judgment: whether it conforms to the leakage characteristics. If the judgment result is no, the process loops back to receiving the acoustic signal for continuous monitoring; if the judgment result is yes, the sound source orientation is calculated, then the corresponding wavelength combination is activated, then a directional infrared beam is emitted, then the spectral data of the target area is collected, then the data of the background reference area is obtained, then the differential spectrum is calculated, and then the absorbance threshold judgment is made; if the result of the absorbance threshold judgment is greater than the threshold, the pipeline type is retrieved, and then it is judged whether the gas matches the pipeline. If the matching result is yes, the leakage event is confirmed. If the matching result is no, continuous monitoring is entered; if the result of the absorbance threshold judgment is less than the threshold, continuous monitoring is directly entered. Finally, the process ends at continuous monitoring.

[0039] Example 3: Performance verification test of trace methane leakage identification system based on acoustic-optical synergistic mechanism under multi-source interference background, the test background and purpose, in the typical urban underground integrated pipe gallery environment, due to the high degree of space closure, complex gas composition, frequent interference factors, the existing infrared spectrum detection system generally has problems such as response lag, frequent false alarms and high power consumption in the identification of trace methane leakage. In order to verify the effectiveness and feasibility of the directional infrared spectrum recognition mechanism with acoustic triggering as the core of the present invention under complex environmental conditions, this systematic test is designed. The test objectives include: verifying the trigger sensitivity of the acoustic sensor array to typical leakage acoustic signals and its spatial positioning accuracy; evaluating the ability of the differential spectrum mechanism to extract the characteristic absorption peak of the target gas in a complex interference background; quantitatively analyzing the minimum detectable concentration (Minimum Detectable Level, MDL) of the system for trace methane leakage; confirming through data analysis whether the closed-loop judgment path of the triple mechanism of sound source orientation determination, infrared feature recognition and GIS logic coupling described in the technical solution has engineering feasibility.

[0040] In the experiment, the test section was about 96 meters long and was divided into four functional sections from A to D. Each section simulated typical pipeline environments such as gas, water supply, electricity and communications. Section B was equipped with a gas simulation pipeline made of PE composite materials. The interior was filled with a methane and air mixture with a volume fraction of 0.8% to 1.5%. A controllable release device was used to simulate instantaneous rupture leakage scenarios. In order to reproduce complex interference conditions, a high-humidity steam source, a temperature disturbance generator and a diesel engine exhaust simulator were introduced into the non-leakage area D to simulate common interference sources such as water vapor, temperature rise and volatile organic compounds (VOCs). During the test, the ambient humidity was maintained at 75% to 88%, the background temperature fluctuated between 22°C and 34°C, and the background VOCs concentration was controlled between 50 and 120 ppm.

[0041] The system installation plan includes: the acoustic sensor array: installed at the central axis of the ceiling of the pipe gallery in Section B, 2.2 meters above the ground, consisting of four groups of MEMS acoustic arrays, with an array spacing of 0.5 meters and units arranged in a cross-symmetric manner; the infrared transmitting module: set on the wall on one side of Section B, with a built-in quantum cascade laser array, covering the 3.2 micron to 4.4 micron band, and the main emission wavelength is set to the characteristic absorption peak of methane at 3.31 microns; the infrared receiving module: set on the opposite wall, with an optical path length of about 8.7 meters, and the wall is coated with high reflectivity materials to enhance the optical signal; the control processing unit: integrated in the mobile test platform, with differential spectral analysis and GIS database linkage identification functions. The pulse width of the infrared laser is set to 100 nanoseconds and the emission frequency is 1 kHz; the absorbance threshold is preset to 0.15, and the lower limit of the comprehensive confidence required for the final leakage event judgment is set to 80%.

[0042] Before the formal test, the system completed three rounds of preliminary debugging tests to optimize the infrared laser emission angle (finally set to ±10°) and the sound source time delay judgment threshold (set to 0.12 milliseconds); in the formal test, each set of tests was implemented according to the complete process of "acoustic pre-triggering-infrared directional detection-background contrast difference". The following is the fourth set of typical data records (the initial leakage concentration is 1.1%, and the discharge aperture is 1.5 mm):

[0043] The above data were tested three times after each set of sampling, and the absorbance deviation was less than 0.02, indicating that the system showed good stability. After receiving the positioning data, the control processing unit matched the pipe segment with the GIS database, confirmed that Section B was the gas pipeline area, and then generated an alarm message and uploaded it to the remote platform through the LTE module. The overall response delay of the system was controlled within 1.2 seconds.

[0044] The test results show that when the leakage volume fraction is 1.1%, the system can stably extract the characteristic absorption peak of methane at a wavelength of 3.31 microns through the differential spectroscopy mechanism, and the measured absorbance average is 0.24, which is higher than the preset judgment threshold; after sound source positioning, infrared identification and GIS attribute matching, the average confidence of the leakage event generated by the system reaches 96.4%, the false alarm rate is controlled within 2%, and the missed alarm rate is about 1.5%; under the simulated interference environment, the system can achieve reliable identification of methane leaks with a minimum volume fraction of 0.6%, and the response time does not exceed 1.5 seconds, showing a higher response speed and adaptability than the traditional continuous scanning infrared system; at the same time, it was observed that when the discharge aperture is less than 0.7 mm, the main frequency of the acoustic signal shifts to below 40 kHz, resulting in the failure of triggering of some test groups. It is recommended to expand the frequency response range of the acoustic array in the subsequent optimization design to further improve the system's coverage of weak leaks.

[0045] Example 4: In a typical urban integrated pipeline operation and maintenance scenario, in order to achieve rapid response and precise positioning of trace gas leakage incidents, the leaking gas identification system based on infrared spectroscopy analysis described in the present invention is deployed. The system mainly serves a dual-channel multi-type pipeline area that passes through residential areas and municipal hubs. The gas pipelines in the area are staggered with communications, electricity, and water supply and drainage systems. The environment is complex and changeable. Once a leakage incident occurs, it is very likely to cause major safety hazards. Therefore, this embodiment is centered around the background of "automatic identification of micro-gas leakage incidents in the case of weak guards during the early morning hours" to specifically demonstrate the actual operation process and key technical details of the system of the present invention.

[0046] The system enters low-power monitoring mode during the weak nighttime watch period, and four groups of acoustic sensor arrays distributed at the intersection of the top of the main ventilation pipe continuously sample background acoustic data. The frequency range of the array is set to 28,000 Hz to 75,000 Hz, and the sampling rate is 350,000 Hz. It is mainly used to capture non-continuous pulse wave signals generated by the instantaneous escape of high-pressure gas penetrating microcracks. Each array consists of four micro-electromechanical acoustic elements, evenly distributed at a 45-degree angle to achieve spatial vector positioning. The output signal is fed into the local edge processor through a parallel analog-to-digital conversion module and enters the preset abnormal waveform matching model for real-time judgment.

[0047] At about 3:21 a.m., the second zone group of the sensor array triggered abnormal acoustic events that met the set trigger conditions three times in a row. The signal characteristics were narrow-band transient signals with an amplitude jump greater than five times the standard noise within 0.32 milliseconds and a center frequency between 37,000 Hz and 43,000 Hz. According to the difference in sound wave propagation time between array groups, the local control processing unit located the azimuth of the leak sound source to be 12 degrees east of north, and the spatial error was controlled within 0.4 meters. The system immediately used the azimuth information as a parameter to start the infrared spectrum analysis module, and drove the preset methane characteristic absorption wavelength laser in the quantum cascade laser array through a synchronous clock pulse.

[0048] After this trigger, the system completes the infrared beam direction adjustment within 0.5 seconds. According to the aforementioned azimuth setting, the emission angle of the laser is adjusted to 12 degrees east of north in the horizontal plane and 15 degrees in the vertical plane. The emission pulse waveform is set to a width of 100 nanoseconds and a repetition frequency of 1 kHz. The incident beam is reflected by the highly reflective aluminum fluoride material set on the inner wall of the pipe gallery and focused on the estimated leakage sector. The infrared detector is deployed on the opposite pipe wall and is encapsulated with a dust-proof filter membrane and temperature stabilization to enhance environmental adaptability. To form a comparable differential spectrum, after the system completes sampling of the target sector, it immediately points the laser to the background reference area where the acoustic array is not triggered and collects the reflected infrared signals under the same wavelength combination. The control processing unit calculates the absorbance peaks based on the light intensity ratio of the same wavelength points in the two regions within the current frame through the absorbance function, and obtains a differential value of 0.24 at the characteristic absorption wavelength of 3.31 microns. The absorbance judgment threshold built into the system is 0.15. According to the distribution fitting of 120 groups of experimental data in the early stage, this value is the optimal judgment critical point to ensure that the false alarm rate is less than 3% and the missed alarm rate is less than 1%. At the same time, the system queries the local pipe gallery geographic information database and confirms that the current spatial coordinates correspond to the main gas pipe, and the material of this pipe section is high-pressure polyethylene composite pipe, which has typical methane leakage risks. Since all three of the infrared absorption characteristics, acoustic positioning results, and GIS pipe section attributes meet the leakage conditions, the system confirms that this event is a real leakage and generates a complete alarm data packet containing the type of leaked gas, estimated coordinates (such as 35.4 meters east longitude, 6.8 meters north latitude), absorbance value, and judgment confidence (96.38%).

[0049] To further reduce the misjudgment risk of the system and enhance the pertinence of subsequent response strategies, the control processing unit calculates the combined judgment score for this event. The judgment score includes three sub-items: First, the acoustic signal similarity score is 88 points (out of 100); second, the infrared spectrum matching score is 93 points, calculated based on spectral symmetry, peak shift rate, and spectral amplitude; third, the GIS pipeline attribute matching score is 95 points, weighted and combined based on the leakage area type, physical properties of the contained gas, and past maintenance records. The weights of the three items are set to 3:4:3 respectively, and the weighted average score is 91.6 points, far higher than the system alarm lower limit of 80.0.

[0050] Subsequent tracking data of this operation indicate that the gas maintenance personnel in this area arrived at the scene at 4:10 am, confirmed that the leakage source was a micro-crack on the pipe wall, the leaked gas was methane, the concentration was in line with the estimated value before the system alarm, and the error between the actual leakage location and the system positioning result was less than 0.6 meters. This result fully verifies that the system of the present invention has extremely high response sensitivity and spatial recognition accuracy for trace gas leakage events in a low-interference scenario at night, and also further shows that the multi-modal fusion judgment system constructed based on the triple verification mechanism of acoustic wake-up, infrared differential absorption, and GIS can effectively reduce the risks of false alarms and missed alarms, and achieve an intelligent gas leakage monitoring solution for utility tunnels with high engineering practicability.

[0051] Embodiment 5: In this embodiment, the acoustic sensor array continuously monitors the background acoustic environment. When a characteristic pulse waveform is detected, the system constructs a two-dimensional positioning model based on the time delay of the received signals between the sensors, obtains the spatial coordinates (x, y) of the leakage sound source, and transmits this coordinate information to the control and processing unit. In order to clarify the physical relationship between the sound source positioning and the infrared spectral response, a spatial domain constraint condition is introduced in the control logic in this embodiment, that is, the infrared detection module is only activated when the sound source positioning result satisfies a coordinate error less than 0.6 meters and the center frequency of the signal waveform is within a preset recognition window (for example, 35 kHz to 45 kHz).

[0052] After the infrared detection module is activated, the tunable quantum cascade laser array selects the emission direction according to the acoustic positioning result to construct a light beam sector. The returned infrared signals are collected in the target area, and the reference signals are collected synchronously in the background reference area. Subsequently, the control and processing unit calculates the differential absorbance according to the following formula:

[0053] , where, represents the infrared light intensity returned from the background reference area at wavelength , represents the infrared light intensity returned from the target area at the same wavelength . This calculation process is automatically completed by the internal module of the control and processing unit, and the calculation result is used to determine whether there is characteristic absorption attenuation. Specifically: the variables and They are all the sampling averages of the infrared detector with an integration time of 1 millisecond, in the unit of normalized light intensity ratio (a floating-point number between 0 and 1), and are automatically normalized by the digital signal processing module. To exclude systematic errors caused by environmental temperature fluctuations, short-term light source drift, etc., the system automatically performs baseline calibration before each measurement, and checks the state stability of the laser with a wavelength deviation less than ±0.02 μm as the standard to ensure that the calculation logic of absorbance strictly corresponds to the actual gas absorption behavior. In addition, in this embodiment, the control processing unit also constructs an absorbance threshold decision logic. Set the warning threshold to be 0.15, which is obtained from the analysis of the distribution of a large number of offline background samples and can effectively distinguish gas leakage from normal fluctuations under a certain confidence level. If , it is considered that a characteristic absorption peak is detected; otherwise, this wavelength band is judged as non-leakage.

[0054] To enhance the physical interpretability of the system's spectral response, the first derivative change trend of the absorbance curve shape is introduced as an auxiliary judgment basis in this embodiment. If both the absorption amplitude jump and spectral line symmetry are satisfied in the vicinity of the target wavelength (±0.05 μm interval), it is further confirmed that this characteristic has the characteristics of gas absorption behavior. This judgment is realized through the curve fitting algorithm embedded in the software module, without adding additional sensors. Combining the aforementioned acoustic positioning results and absorbance judgment results, the system enters the logical coupling judgment stage. The control processing unit calls the local database to retrieve the pipeline type in the coordinate area where the sound source is located. If the gas type corresponding to the identified absorption peak wavelength logically matches the pipeline medium in this area, the leakage event is finally confirmed; if not, this event is marked as a suspicious signal and enters the manual review mechanism. And in this embodiment, to avoid the system from being mis-triggered in a strong interference environment, the selection mechanism of the background reference area is further clarified. The background area needs to meet the condition that no high-energy acoustic emission event has been confirmed by the acoustic array in the past 5 seconds and the distance from the target area does not exceed 8 meters to ensure the environmental background consistency. This constraint ensures that the reference signal truly reflects the current environmental baseline state and avoids misjudgment caused by background fluctuations.

[0055] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An underground pipe gallery leakage gas identification system based on infrared spectroscopy analysis, characterized in that Comprising: a) At least one acoustic sensor unit configured to passively monitor acoustic signals in the pipe gallery and generate a wake-up instruction and azimuth information indicating the preliminary azimuth of the sound source when a signal conforming to the preset acoustic characteristics of gas leakage is detected; b) An infrared spectroscopy analysis module communicatively connected to the acoustic sensor unit, the infrared spectroscopy analysis module comprising: i. A tunable infrared light source that responds to the wake-up instruction and, based on the azimuth information, emits a sequence of infrared detection light beams containing at least two different wavelengths towards the estimated leakage sector, the at least two different wavelengths corresponding to the characteristic absorption peaks of at least two key target gases; ii. An infrared detector for receiving the infrared light returned from the estimated leakage sector and generating target area spectral data containing the intensities of infrared light of at least two different wavelengths; c) A control processing unit connected to the acoustic sensor unit and the infrared spectroscopy analysis module, configured to: i. Based on the azimuth information, control the emission direction of the tunable infrared light source and / or the wavelength combination included in the infrared detection light beam sequence; ii. Receive and process the target area spectral data, and identify the infrared absorption characteristics of potential leakage gases by analyzing the attenuation degrees of the intensities of infrared light of at least two different wavelengths; iii. When the infrared absorption characteristics of at least one potential leakage gas that meet the preset absorption intensity threshold are identified and the type of the potential leakage gas matches the preset pipeline type in the estimated leakage sector indicated by the azimuth information, confirm the leakage event and output an alarm signal.

2. The underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis according to claim 1, characterized in that The acoustic sensor unit includes an acoustic anisotropic microstructure sensor array, and the control processing unit is further configured to calculate the two-dimensional coordinate information or three-dimensional coordinate information of the sound source based on the time delay or intensity difference between the acoustic signals received by different sensors in the array to optimize the azimuth information and determine the estimated leakage sector.

3. The underground utility tunnel leakage gas identification system based on infrared spectrum analysis according to claim 2, characterized in that, The infrared spectroscopy analysis module is further configured to, simultaneously or after the tunable infrared light source emits a sequence of infrared detection light beams towards the estimated leakage sector, instruct it to emit the same sequence of infrared detection light beams towards at least one background reference area confirmed by the acoustic sensor unit and currently without leakage acoustic signals to obtain background spectral data; and the control processing unit is further configured to calculate the intensity difference between the target area spectral data and the background spectral data at the corresponding wavelengths to obtain a differential spectrum and identify the infrared absorption characteristics based on the differential spectrum.

4. The underground utility tunnel leakage gas identification system based on infrared spectrum analysis according to claim 1, characterized in that, The control processing unit is further configured to access a database storing pipe gallery geographic information system data, the database containing pipeline type information of different areas in the pipe gallery; the control processing unit determines the pipe gallery area where the potential leakage source is located based on the azimuth information, retrieves the pipeline type included in this area from the database, and performs a logical match between the identified type of potential leakage gas and the retrieved pipeline type, and only when the match result is consistent, confirm the leakage event.

5. The underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis according to claim 3, characterized in that The control processing unit calculates the absorbance at the characteristic absorption wavelength of a specific target gas in the differential spectrum where the absorbance is , where , is the light intensity of the background spectrum at the wavelength , and is the light intensity of the target area spectrum at the wavelength . When the absorbance is greater than the preset leakage determination threshold, it is preliminarily determined that there is a leakage of the target gas 6. The underground pipe gallery leakage gas identification system based on infrared spectrum analysis according to claim 1, characterized in that, The tunable infrared light source includes a quantum cascade laser array, each laser in the array emits infrared light at the characteristic absorption wavelength of the target gas, and the control processing unit selectively activates at least one laser in the array according to the azimuth information.

7. The underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis according to claim 1, characterized in that The tunable infrared light source includes a broadband infrared light source and a MEMS Fabry-Perot interferometer. The control and processing unit generates an infrared detection beam sequence containing at least two different wavelengths by controlling the transmission wavelength of the interferometer.

8. The underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis according to claim 1, characterized in that The preset acoustic characteristics of gas leakage include ultrasonic signals in a specific frequency range or acoustic emission signals with a specific time-domain envelope. The acoustic sensor unit includes a piezoelectric ceramic sensor or a MEMS microphone array and is configured with an acoustic filter for filtering out ambient noise.

9. The underground utility tunnel leakage gas identification system based on infrared spectroscopy analysis according to claim 1, characterized in that The control and processing unit is also configured to generate alarm information including the type of leaked gas and the estimated leakage location after confirming a leakage event, and send the alarm information to the remote monitoring platform.

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