Dynamic reconfiguration and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device and method

Abstract

The application discloses a dynamic reconfiguration and mixed light path self-calibration photoacoustic spectrum gas detection device and method. The device comprises at least two laser sources, a reconfigurable photoacoustic cell, a light path switching unit, an acoustic sensor and a controller. The controller can select the working mode according to the detection result: in the first mode, the movement of the baffle in the photoacoustic cell is controlled to separate the cell body into multiple independent chambers, and a linear multi-optical-path light path is formed in each chamber to realize rapid parallel detection of multiple gases; in the second mode, when a specific gas concentration anomaly is detected, the baffle is controlled to retract and merge the chambers, and the spiral light path is switched to for high-precision detection of the gas. The application dynamically switches between rapid detection and high-precision detection, and uses the high-precision detection result to perform online self-calibration on the rapid detection result, thereby solving the problem that the prior art cannot balance detection efficiency and precision, and ensuring the accuracy and reliability of detection data throughout the life cycle.

Description

Technical Field

[0001] This application relates to the field of gas detection, specifically to a dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device and method. Background Technology

[0002] Analyzing dissolved gases in the insulating oil of power transformers is a crucial preventative maintenance method for determining the presence of latent faults within the transformer and ensuring the safe and stable operation of the power grid. With the development of the power industry, the demand for gas detection technology is increasing. Accurate and efficient detection of gas composition and concentration is essential for the safety of the power system. Advances in gas detection technology can help identify potential problems inside transformers in a timely manner, preventing faults and thus ensuring the stable operation of the power grid and reducing economic losses caused by power outages and other faults. At the same time, advanced gas detection technology also helps improve the efficiency and quality of power equipment maintenance and reduce maintenance costs.

[0003] Currently, mainstream detection technologies include gas chromatography and traditional photoacoustic spectroscopy. Gas chromatography is a commonly used gas analysis method that determines the concentration of different components in a gas by separating and detecting them. Traditional photoacoustic spectroscopy inverts the concentration by detecting the acoustic signal generated after a gas absorbs modulated light; its core principle lies in the selective absorption characteristics of different gas molecules to different wavelengths of light. To improve the sensitivity of traditional photoacoustic spectroscopy, existing technologies have proposed several improvements, such as using multi-path reflection cells (e.g., Herriott cells) to extend the linear optical path, or using special beams such as spiral beams to increase the interaction path.

[0004] However, existing technologies have many shortcomings. While gas chromatography offers high precision, it suffers from problems such as bulky equipment, long detection cycles, and inability to meet real-time online monitoring requirements. Traditional photoacoustic spectroscopy often uses linear beams, resulting in short optical paths within a limited photoacoustic cell, leading to insufficient detection capabilities for low-concentration gases. Moreover, existing improvements operate in a static, fixed-function mode, making it difficult to balance detection efficiency and accuracy. Furthermore, all detection systems face long-term measurement drift issues caused by environmental temperature and humidity changes, optical component contamination, and electronic device aging, lacking an effective, built-in online self-calibration mechanism to ensure data accuracy throughout their entire lifecycle. Summary of the Invention

[0005] To address the technical problems in the prior art, this application provides a dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device and method.

[0006] This application provides a dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device and method, which adopts the following technical solution:

[0007] A dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device and method, comprising:

[0008] At least two laser sources, each of which emits a wavelength that matches the characteristic absorption spectrum of a different target gas;

[0009] A reconfigurable photoacoustic cell includes a cell body, two fixed mirrors arranged opposite each other, at least one partition and at least one drive assembly. Each partition has movable mirrors on both sides, and the drive assembly is connected to the partition.

[0010] At least two optical path switching units are optically connected to the corresponding laser source and the corresponding reconfigurable photoacoustic cell;

[0011] At least two acoustic sensors are used to convert photoacoustic signals into electrical signals;

[0012] The controller is configured to: select a first detection mode or a second detection mode based on the detection results of the acoustic sensors; in the first detection mode, control the drive assembly to position at least one of the partitions in a separating position to divide the pool into several independent chambers, each of which corresponds to one of the acoustic sensors; and control the optical path switching unit to introduce probe light from the corresponding laser source into each of the independent chambers to form a linear multi-path optical path therein by a pair of opposing reflective mirrors, wherein the reflective mirrors are selected from the fixed reflector and the movable reflector; in the second detection mode, control the drive assembly to position at least one of the partitions in a merging position to merge the independent chambers into a complete chamber; and control the optical path switching unit to form a spiral optical path in the complete chamber using two fixed reflectors as boundaries.

[0013] In some embodiments, a plurality of incident transparent windows are formed on the outer wall of the pool body, each corresponding to one of the independent chambers;

[0014] The optical path switching unit includes an optical fiber switch, a first optical fiber, a second optical fiber, a first collimator, a second collimator, and a spiral phase plate. The input end of the optical fiber switch is connected to the output end of the laser source. The two output ends of the optical fiber switch are respectively connected to one end of the first optical fiber and one end of the second optical fiber. The other end of the first optical fiber is connected to the input end of the first collimator. The output end of the first collimator is positioned relative to the corresponding incident transparent window and is used to introduce the probe light into the corresponding independent cavity, so that the linear multi-path optical path is formed therein by a pair of opposing reflective mirrors. The other end of the second optical fiber is connected to the input end of the second collimator. The output end of the second collimator is positioned relative to the corresponding incident transparent window and is used to introduce the probe light into the complete cavity, using the two fixed reflective mirrors as boundaries to form the spiral optical path.

[0015] In some embodiments, the sidewall of the pool body is provided with a plurality of receiving slots for accommodating the partitions. When the partitions are in the combined position, the partitions are accommodated in the receiving slots.

[0016] In some embodiments, a rotating shaft is fixed to one end of the partition, and the rotating shaft is rotatably disposed within the receiving groove;

[0017] The drive assembly includes a drive motor, a drive sprocket, a driven sprocket, and a chain. The drive sprocket is fixed to the output end of the drive motor, the driven sprocket is fixed to the shaft, and the chain is closed, with its two ends respectively sleeved on the drive sprocket and the driven sprocket.

[0018] In some embodiments, the pool body has a plurality of air inlets that are connected to each of the independent chambers in a one-to-one manner and a plurality of air outlets that are connected to each of the independent chambers in a one-to-one manner.

[0019] In some embodiments, the dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device further includes an inlet / outlet mechanism, which includes an inlet manifold and an outlet manifold. The inlet manifold is used to introduce the gas to be measured, and the inlet manifold is connected to each of the inlets. The outlet manifold is used to discharge the gas to be measured, and the outlet manifold is connected to each of the outlets.

[0020] In some embodiments, the pool body is further provided with a plurality of transparent exit windows corresponding to each of the individual chambers.

[0021] This application also discloses a dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection method, applicable to the aforementioned dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device, and includes the following steps:

[0022] a) Operation in the first detection mode: controlling the at least one partition to be in the separation position, dividing the pool into several independent chambers; introducing probe light from the corresponding laser source into each of the independent chambers to form a linear multi-optical-path optical path therein; using the acoustic sensor to detect the photoacoustic signal and calculating the first concentration value R of several of the target gases;

[0023] b) Determine whether any of the first concentration values ​​R or its rate of change meets the preset triggering condition, and determine the target gas that triggers the triggering condition;

[0024] c) If the triggering condition is met, the system automatically switches to the second detection mode: controls each of the partitions to move to the merged position, so that each of the independent chambers merges into a complete chamber; and introduces a beam of probe light whose wavelength matches the characteristic absorption spectrum of the target gas corresponding to the triggering condition into the chamber, forming a spiral optical path in the complete chamber, detecting the photoacoustic signal through each of the acoustic sensors, and calculating the second concentration value P of the target gas that meets the triggering condition.

[0025] d) Perform online self-calibration: Calculate and update a dynamic calibration coefficient K based on the second concentration value P and the corresponding first concentration value R, and correct the concentration values ​​subsequently obtained in the first detection mode.

[0026] In some embodiments, the linear multipath optical path in each of the independent chambers is a Heriot-Limiter cell structure composed of two opposing mirrors.

[0027] In some embodiments, the dynamic calibration coefficient K in step d) is calculated using the formula K=P / R.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] 1. By dynamically changing the reconfigurable photoacoustic cell and flexibly switching the optical path, different detection modes can be selected. In the first detection mode, multiple gases can be detected rapidly simultaneously, improving detection efficiency; in the second detection mode, a single suspected gas can be detected with high precision. Simultaneously, the high-precision detection results are used to calibrate the rapid detection results, eliminating drift caused by long-term system operation, ensuring data accuracy and reliability, and solving the problems of difficulty in balancing detection efficiency and accuracy, as well as the lack of an online self-calibration mechanism in existing technologies.

[0030] 2. By switching between different detection modes, a rapid detection is first performed. When an anomaly is detected, a high-precision detection supported by physical principles is conducted. The high-precision detection results are then used to calibrate the rapid detection results, achieving a balance between detection efficiency and accuracy. Simultaneously, the online self-calibration mechanism eliminates drift caused by long-term system operation, ensuring data accuracy and reliability, and resolving problems existing in current technologies. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of a dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device provided in one embodiment of this application;

[0032] Figure 2 yes Figure 1 The enlarged schematic diagram at point A shows the detailed structure of the driving component;

[0033] Figure 3 yes Figure 1 Schematic diagram of the optical path switching unit;

[0034] Figure 4 yes Figure 1 The diagram shows the structure of the device in the second detection mode.

[0035] Figure 5 This is a schematic diagram of the optical path in the first detection mode of Embodiment 3, showing the situation where multiple independent chambers are detected simultaneously;

[0036] Figure 6 This is a schematic diagram of the optical path in the second detection mode of Example 3, showing the scenario where multiple independent chambers are combined for detection;

[0037] Explanation of reference numerals in the attached drawings: 1. Laser source; 2. Reconfigurable photoacoustic cell; 21. Cell body; 211. Entrance transparent window; 212. Receiving groove; 213. Air inlet; 214. Air outlet; 215. Exit transparent window; 22. Fixed reflector; 23. Partition plate; 231. Movable reflector; 24. Drive assembly; 241. Drive motor; 242. Driving sprocket; 243. Driven sprocket; 244. Chain; 25. Air inlet / outlet mechanism; 251. Main air inlet pipe; 252. Main air outlet pipe; 3. Optical path switching unit; 31. Fiber optic switch; 32. First fiber optic cable; 33. Second fiber optic cable; 34. First collimator; 35. Second collimator; 36. Spiral phase plate; 37. Fiber optic coupler; 4. Acoustic sensor. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of the present invention, but are not limited thereto. Other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are also within the protection scope of the present invention.

[0039] This application mainly adopts dynamic reconstruction of the photoacoustic cell and switching of the optical path for gas detection and calibration, which achieves the effect of balancing detection efficiency and accuracy and online self-calibration. The following is a further detailed description of this application.

[0040] Example 1

[0041] Please refer to Figures 1-4 The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device provided in this application includes at least two laser sources 1, a reconfigurable photoacoustic cell 2, at least two optical path switching units 3, at least two acoustic sensors 4, and a controller. The laser source 1 is used to emit light that matches the characteristic absorption spectrum of the target gas. The reconfigurable photoacoustic cell 2 can change the chamber shape in different modes. The optical path switching unit 3 can introduce the light from the laser source 1 into the corresponding chamber to form different optical paths. The acoustic sensor 4 converts the photoacoustic signal into an electrical signal. The controller controls the working mode of the device according to the detection result of the acoustic sensor 4. It achieves the effect of intelligently adapting to different detection needs, balancing efficiency and accuracy, and having online self-calibration capability. This is because the dynamic change of the reconfigurable photoacoustic cell 2 and the flexible switching of the optical path can select the appropriate detection method according to different situations, and at the same time use high-precision detection results to calibrate the rapid detection results.

[0042] For details, please refer to Figures 1-4 Laser source 1 can be a semiconductor laser, a solid-state laser, or similar device. Semiconductor lasers offer advantages such as small size, high efficiency, and long lifespan; solid-state lasers feature high output power and good beam quality. The emission wavelength of each laser source 1 is matched to the characteristic absorption spectrum of a different target gas. For example, for acetylene gas, a laser source 1 with an emission wavelength corresponding to the acetylene characteristic absorption spectrum can be selected; for methane gas, a corresponding laser source 1 can be selected. This ensures high selectivity for different target gases and avoids cross-interference between different gases.

[0043] Please refer to Figures 1-4The reconfigurable photoacoustic cell 2 includes a cell body 21, two fixed reflectors 22 arranged opposite each other, at least one partition 23, and at least one drive assembly 24. The cell body 21 is typically made of materials such as metal or glass, providing good sealing and stability. The fixed reflectors 22 can be concave reflectors, which can better focus light and extend the optical path. Each partition 23 has movable reflectors 231 on both sides, which can also be concave reflectors. The partitions 23 can be made of lightweight metal or plastic to facilitate movement control by the drive assembly 24. The drive assembly 24 controls the movement of the corresponding partitions 23 between separated and merged positions. Several incident transparent windows 211, corresponding to each independent chamber, are formed on the outer wall of the cell body 21. These incident transparent windows 211 can be made of transparent materials such as optical glass to ensure that the laser can smoothly enter the chamber. The side wall of the pool body 21 has several receiving slots 212 for accommodating the partitions 23. When the partitions 23 are in the closed position, they are housed within the receiving slots 212. One end of each partition 23 is fixed to a rotating shaft, which is rotatably positioned within the receiving slots 212. The drive assembly 24 includes a drive motor 241, a drive sprocket 242, a driven sprocket 243, and a chain 244. The drive sprocket 242 is fixed to the output end of the drive motor 241, the driven sprocket 243 is fixed to the rotating shaft, and the chain 244 is closed, with its two ends respectively fitted onto the drive sprocket 242 and the driven sprocket 243. When the drive motor 241 rotates, it drives the driven sprocket 243 to rotate via the drive sprocket 242 and the chain 244, thereby causing the partitions 23 to rotate around the rotating shaft, realizing the movement of the partitions 23 between the separated and closed positions. Alternatively, the drive assembly 24 can also use a device such as an electric push rod to directly drive the partitions 23 in linear motion. The pool body 21 has several air inlets 213 corresponding to and communicating with each independent chamber, and several air outlets 214 corresponding to and communicating with each independent chamber. It also includes an air intake / exhaust mechanism 25, which includes an air intake manifold 251 and an air outlet manifold 252. The air intake manifold 251 is used to introduce the gas to be tested and is connected to each air inlet 213. The air outlet manifold 252 is used to discharge the gas to be tested and is connected to each air outlet 214. The pool body 21 also has several transparent exit windows 215 corresponding to each independent chamber. These transparent exit windows 215 are made of transparent materials such as optical glass and are used for light emission.

[0044] In this embodiment, please refer to Figures 1-4 The partition 23 is one in number, which can divide the space into two independent chambers, allowing for the simultaneous detection of two target gas components and their contents. In other embodiments, the number of partitions 23 may also be different.

[0045] Please refer to Figures 1-4The optical path switching unit 3 is optically connected to the corresponding laser source 1 and the corresponding reconfigurable photoacoustic cell 2. The optical path switching unit 3 includes an optical fiber switch 31, a first optical fiber 32, a second optical fiber 33, a first collimator 34, a second collimator 35, a spiral phase plate 36, and an optical fiber coupler 37. The optical fiber switch 31 can be a mechanical optical fiber switch 31 or a thermo-optical optical fiber switch 31, etc. Mechanical optical fiber switches 31 have advantages such as fast switching speed and low insertion loss; thermo-optical optical fiber switches 31 have advantages such as small size and easy integration. The input end of the optical fiber switch 31 is connected to the output end of the laser source 1, and the two output ends of the optical fiber switch 31 are connected to one end of the first optical fiber 32 and one end of the second optical fiber 33, respectively. The first optical fiber 32 and the second optical fiber 33 are used to transmit the laser. They can be single-mode or multi-mode fibers. Single-mode fibers ensure high-quality laser transmission, while multi-mode fibers are suitable for transmitting lasers with higher power. The other end of the first optical fiber 32 is connected to the input end of the first collimator 34. The output end of the first collimator 34 is positioned relative to the corresponding incident transparent window 211 to introduce the probe light into the corresponding independent chamber, where a linear multi-path optical path is formed by a pair of opposing reflective mirrors, wherein the reflective mirrors are selected from the fixed reflector 22 and the movable reflector. The other end of the second optical fiber 33 is connected to the input end of the optical fiber coupler 37. The output end of the optical fiber coupler 37 is connected to the input end of the second collimator 35. The output end of the second collimator 35 is positioned relative to the corresponding incident transparent window 211 to introduce the probe light into the complete chamber. In the second detection mode, the probe light emitted from the second collimator 35 passes through the spiral phase plate 36 before entering the complete chamber to form a spiral optical path, using the two fixed reflectors 22 as boundaries to form the spiral optical path. The spiral phase plate 36 can be a liquid crystal spiral phase plate 36 or an optical crystal spiral phase plate 36, etc. It can convert ordinary laser light into spiral light. At the same time, the light from all the second optical fibers 33 from different optical path switching units 3 will be converged by the fiber coupler 37 and then emitted from the single second collimator 35. With this design, in the second detection mode, no matter which target gas laser source is switched to, its beam will eventually be introduced into the complete cavity through the same second collimator 35. Therefore, only one second collimator 35 is needed, which greatly simplifies the system structure and facilitates precise control of the incident angle.

[0046] Please refer to Figures 1-4 The acoustic sensor 4 corresponds to each independent chamber and is used to convert photoacoustic signals into electrical signals. The acoustic sensor 4 can be a piezoelectric acoustic sensor 4 or a capacitive acoustic sensor 4, etc. The piezoelectric acoustic sensor 4 has the advantages of high sensitivity and fast response speed; the capacitive acoustic sensor 4 has the characteristics of good stability and strong anti-interference ability.

[0047] The controller is configured to select either a first detection mode or a second detection mode based on the detection result of the acoustic sensor 4. In the first detection mode, the control drive assembly 24 positions at least one partition 23 in a separating position to divide the pool body 21 into several independent chambers, and controls the optical path switching unit 3 to introduce probe light from the corresponding laser source 1 into each independent chamber, where a linear multi-path optical path is formed by a pair of opposing reflective mirrors, wherein the reflective mirrors are selected from fixed reflectors 22 and movable reflectors. For example, when the partition 23 is in the separating position, mirror groups M1 and M2 constitute one chamber, and mirror groups M3 and M4 constitute another chamber. The optical path switching unit 3 introduces the laser beam into these two chambers respectively, forming a Heriotett pool optical path within them. In the second detection mode, the control drive assembly 24 positions at least one partition 23 in a merging position to merge the independent chambers into a complete chamber, and controls the optical path switching unit 3 to form a spiral optical path within the complete chamber, using two fixed reflectors 22 as boundaries. When the partition 23 is completely retracted into the groove on one side of the pool wall by the drive assembly 24, a longer large cavity is formed by the mirror group M1 and the mirror group M4. The optical path switching unit 3 routes the beam of the target laser to a special optical path through the spiral phase plate 36, generates a spiral beam, and then guides it into the large cavity.

[0048] The physical principle behind this application's use of a spiral optical path for high-precision detection is as follows:

[0049] 1. Enhanced light-matter interaction: The spiral beam possesses a unique spiral phase wavefront and a ring-shaped intensity distribution. Compared to traditional linear beams, this structure results in a longer and more complex interaction path between photons and gas molecules per unit volume, thereby significantly improving the absorption efficiency of light energy and generating a stronger photoacoustic signal, especially sensitive to low-concentration gases.

[0050] 2. Unique orbital angular momentum (OAM) effect: When the orbital angular momentum carried by the helical beam interacts with gas molecules, it may excite new transition channels that cannot be excited by conventional beams, or change the selection rules of existing absorption lines, thereby further enhancing the absorption cross-section of specific spectral lines and improving the selectivity and signal-to-noise ratio of detection.

[0051] 3. More optimized light field distribution: The "dark core" characteristic of the spiral light center with zero light intensity can effectively reduce the background noise signal caused by the scattered light from the pool wall or the surface of the optical element, making the signal-to-noise ratio of the detection result naturally better than that of a linear beam filling the entire chamber.

[0052] In summary, the spiral optical path does not simply increase the optical path length, but rather enhances the signal strength and suppresses noise at the physical level by changing the interaction mode between light and gas molecules. Therefore, it can achieve higher precision measurements and serve as a reliable benchmark for calibrating rapid detection results.

[0053] It should be noted that this application employs a linear multi-path optical path in the first detection mode and a spiral optical path in the second detection mode. This is based on a comprehensive trade-off between the overall system performance, complexity, cost, and the requirements of different application scenarios. In the first mode, to achieve parallel detection of multiple gases, the pool 21 is divided into several physically isolated independent chambers by the partition 23. Linear multi-path optical paths (such as the Heriot-Limited Pool structure) are mature and simple in structure, making them very suitable for deployment in these relatively small independent chambers. They can achieve a sufficiently long effective optical path with a compact structure, fully meeting the sensitivity requirements of rapid screening. In the second mode, the spiral beam has unique physical properties (such as orbital angular momentum), which can enhance the interaction with gas molecules and suppress background noise, thereby achieving a higher signal-to-noise ratio and detection accuracy. However, this special beam usually requires more propagation space to maintain its beam shape. Therefore, this design chooses to use the spiral optical path only after the partition 23 is retracted and the chambers are merged to form a "complete chamber," ensuring that its high-precision performance is fully utilized. To generate and maintain a high-quality spiral beam in each independent chamber of the first mode would require an independent optical vortex generator and a matching precision calibration system for each beam path. This would significantly increase the overall complexity, size, failure rate, and manufacturing cost of the system, contradicting the reliability and cost-effectiveness requirements of online monitoring equipment. However, employing mature linear multipath technology can achieve efficient parallel monitoring at a lower cost and with higher reliability.

[0054] The implementation principle of this embodiment is as follows: the device achieves the selection of different detection modes through the dynamic changes of the reconfigurable photoacoustic cell 2 and the flexible switching of the optical path. In the first detection mode, multiple gases can be detected rapidly at the same time, improving detection efficiency; in the second detection mode, a single suspicious gas can be detected with high precision. At the same time, the rapid detection results are calibrated using the high-precision detection results, eliminating the drift caused by long-term system operation, ensuring the accuracy and reliability of the data, and solving the problems of difficulty in balancing detection efficiency and accuracy and the lack of online self-calibration mechanism in the prior art.

[0055] Example 2

[0056] The difference between this embodiment and the previous embodiment is that the drive assembly 24 uses an electric push rod to control the movement of the partition 23. The electric push rod has advantages such as simple structure, easy installation, and large thrust. One end of the electric push rod is fixed to the pool body 21, and the other end is connected to the partition 23. When the electric push rod extends or retracts, it directly pushes the partition 23 to move linearly between the separated position and the merged position.

[0057] The implementation principle of this embodiment is as follows: an electric push rod is used as the driving component 24, which simplifies the driving structure, reduces the cost, and can also reliably realize the motion control of the partition 23, ensuring the normal operation of the reconfigurable photoacoustic cell 2 in different modes. It can also achieve the effect of balancing detection efficiency and accuracy and having online self-calibration capability.

[0058] Example 3

[0059] Please refer to Figure 5 and Figure 6 The difference between this embodiment and the above embodiment is that there are multiple partitions 23, which can divide more independent chambers and allow for the simultaneous detection of more target gas components and contents.

[0060] Example 4

[0061] The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection method provided in this application includes the following steps:

[0062] S1, operating in the first detection mode: At least one partition 23 is controlled to be in a separating position, dividing the pool body 21 into several independent chambers. A command can be sent from the controller to the drive assembly 24, which controls the partition 23 to move to the separating position, dividing the pool body 21 into multiple independent chambers. Probe light from the corresponding laser source 1 is introduced into each independent chamber to form a linear multi-path optical path. The fiber optic switch 31 of the optical path switching unit 3, according to the controller's command, introduces the light from the corresponding laser source 1 into the independent chamber through the first fiber optic cable 32 and the first collimator 34, forming a linear multi-path optical path of the Heriot-Lewis cell structure between the reflecting surfaces composed of the fixed reflector 22 and the movable reflector 231. The photoacoustic signal is detected using the acoustic sensor 4, and the first concentration value R of several target gases is calculated. The acoustic sensor 4 converts the photoacoustic signal into an electrical signal and transmits it to the controller, which calculates the first concentration value of the target gas according to a preset algorithm.

[0063] S2 determines whether any first concentration value R or its rate of change meets the preset trigger conditions and identifies the target gas for triggering the conditions. Trigger conditions can be preset in the controller; for example, when the first concentration value of a target gas exceeds a certain threshold, or its rate of change exceeds a certain range, the trigger condition is deemed met. The controller monitors and compares the first concentration values ​​and their rates of change of each target gas in real time to determine the target gas for triggering the conditions.

[0064] The preset triggering conditions can be set in multiple dimensions and levels based on the hazard of the gas to be tested, relevant industry safety regulations (e.g., warning values ​​for dissolved gas content in transformer oil in the power industry), and equipment operating status. As a non-limiting example, the triggering conditions may include at least one of the following:

[0065] a) Absolute Concentration Threshold: The first concentration value R of any target gas exceeds a preset first-level or second-level alarm threshold. This threshold is usually related to the gas's safety limit or fault indication characteristic concentration. For example, in transformer oil and gas monitoring applications, the attention value for acetylene (e.g., several ppm) can be set as the first-level threshold, and the excess value (e.g., tens of ppm) can be set as the second-level threshold. When the detected value R exceeds the first-level threshold, the second mode can be triggered for high-precision verification.

[0066] b) Concentration change rate threshold: The short-term change rate (e.g., hourly change rate) or long-term trend (e.g., daily / weekly change rate) of any target gas concentration exceeds a preset value. For example, even if the absolute value of the gas concentration is not high, if its growth rate exceeds 50% within 24 hours, it may indicate that a latent fault is developing rapidly, and the second mode should be triggered immediately for accurate diagnosis.

[0067] c) Combined conditions: The concentrations of two or more related gases are abnormal simultaneously, or their concentration ratio deviates from the normal range. For example, in fault diagnosis, the concentration ratio of acetylene and ethylene is an important basis for determining the fault type. When this ratio deviates from the range under normal operating conditions, even if the concentration of a single gas is not exceeded, a second mode should be triggered to perform high-precision measurements of these two key gases to obtain more reliable diagnostic information.

[0068] The controller monitors and compares the first concentration value and its rate of change of each target gas in real time. Based on the above multi-dimensional preset conditions, it intelligently determines whether to start the high-precision detection mode and identifies the target gases that need to be focused on.

[0069] S3, if the trigger condition is met, the system automatically switches to the second detection mode: controlling each partition 23 to move to the merging position, so that each independent chamber merges into a complete chamber. The controller sends a command to the drive component 24, which controls the partition 23 to move to the merging position, so that each independent chamber merges into a complete chamber. A beam of probe light whose wavelength matches the characteristic absorption spectrum of the target gas corresponding to the trigger condition is introduced into the chamber, forming a spiral optical path in the complete chamber. The fiber optic switch 31 of the optical path switching unit 3 introduces the light corresponding to the laser source 1 into the complete chamber through the second fiber 33, the fiber optic coupler 37, and the second collimator 35. After passing through the spiral phase plate 36, the light forms a spiral beam and propagates in the complete chamber bounded by two fixed reflectors 22. The photoacoustic signal is detected by each acoustic sensor 4, and the second concentration value P of the target gas that meets the trigger condition is calculated. The acoustic sensor 4 converts the detected photoacoustic signal into an electrical signal, and the controller calculates the second concentration value of the target gas according to a preset algorithm.

[0070] S4, Perform online self-calibration: Based on the second concentration value P and the corresponding first concentration value R, calculate and update a dynamic calibration coefficient K, and correct subsequent concentration values ​​obtained in the first detection mode. The dynamic calibration coefficient K is calculated using the formula K=P / R. The controller stores the calculated dynamic calibration coefficient K, and when a new concentration value is obtained in a subsequent first detection mode, it multiplies it by the updated K value for correction.

[0071] The implementation principle of this embodiment is as follows: This method switches between different detection modes, first performing rapid detection. When an anomaly is detected (based on specific and multi-dimensional conditional judgments), high-precision detection supported by physical principles is performed. Then, the high-precision detection results are used to calibrate the rapid detection results, achieving a balance between detection efficiency and accuracy. Simultaneously, the online self-calibration mechanism eliminates drift caused by long-term system operation, ensuring data accuracy and reliability, and solving problems existing in the prior art.

[0072] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of this application.

Claims

1. A dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device, characterized in that, include: At least two laser sources (1), each of which emits a wavelength that matches the characteristic absorption spectrum of a different target gas; A reconfigurable photoacoustic cell (2) includes a cell body (21), two fixed mirrors (22) arranged opposite each other, at least one partition (23) and at least one drive assembly (24). Each partition (23) has movable mirrors (231) on both sides, and the drive assembly (24) is connected to the partition (23). At least two optical path switching units (3) are optically connected to the corresponding laser source (1) and the corresponding reconfigurable photoacoustic cell (2); At least two acoustic sensors (4) are used to convert photoacoustic signals into electrical signals; The controller is configured to: select a first detection mode or a second detection mode based on the detection result of the acoustic sensor (4); in the first detection mode, control the drive assembly (24) to place at least one of the partitions (23) in a separated position to divide the pool body (21) into several independent chambers, each of the independent chambers corresponding to one of the acoustic sensors (4); and control the optical path switching unit (3) to introduce probe light from the corresponding laser source (1) into each of the independent chambers to form a linear multi-path optical path therein by a pair of opposing reflective mirrors, wherein the reflective mirrors are selected from the fixed reflector (22). In the first detection mode, the drive assembly (24) is controlled to make at least one of the partitions (23) merged into a single chamber, and the optical path switching unit is controlled to introduce the probe light into the single chamber. The probe light passes through the spiral phase plate (36) before entering the single chamber and forms a spiral optical path using two fixed mirrors (22) as boundaries. In the second detection mode, multiple gases are detected simultaneously. In the third detection mode, a single gas is detected. The detection results in the second detection mode are used to calibrate the detection results in the first detection mode.

2. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 1, characterized in that, The outer wall of the pool body (21) is formed with a plurality of incident transparent windows (211) corresponding to each of the independent chambers; The optical path switching unit (3) includes an optical fiber switch (31), a first optical fiber (32), a second optical fiber (33), a first collimator (34), a second collimator (35), and an optical fiber coupler (37). The input end of the optical fiber switch (31) is connected to the output end of the laser source (1). The two output ends of the optical fiber switch (31) are respectively connected to one end of the first optical fiber (32) and one end of the second optical fiber (33). The other end of the first optical fiber (32) is connected to the input end of a first collimator (34). The output end of the first collimator (34) is relative to the corresponding incident transparent window (2). 11) The optical path is set to introduce the probe light into the corresponding independent chamber, in which the linear multi-path optical path is formed by a pair of opposing reflective mirrors. The other end of the second optical fiber (33) in all optical path switching units (3) is connected to the input end of the same optical fiber coupler (37). The output end of the optical fiber coupler (37) is connected to the input end of the second collimator (35). The output end of the second collimator (35) is set relative to the corresponding incident transparent window (211). The probe light is emitted from the second collimator (35) and passes through the spiral phase plate (36) into the complete chamber.

3. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 1, characterized in that, The side wall of the pool body (21) is provided with a plurality of receiving slots (212) for accommodating the partition (23). When the partition (23) is in the combined position, the partition (23) is accommodated in the receiving slots (212).

4. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 3, characterized in that, One end of the partition (23) is fixed with a rotating shaft, which is rotatably disposed within the receiving groove (212); The drive assembly (24) includes a drive motor (241), a drive sprocket (242), a driven sprocket (243), and a chain (244). The drive sprocket (242) is fixed to the output end of the drive motor (241), the driven sprocket (243) is fixed to the shaft, and the chain (244) is closed, with its two ends respectively sleeved on the drive sprocket (242) and the driven sprocket (243).

5. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 1, characterized in that, The pool body (21) has several air inlets (213) that are connected to each of the independent chambers and several air outlets (214) that are connected to each of the independent chambers.

6. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 5, characterized in that, It also includes an inlet / outlet mechanism (25), which includes an inlet manifold (251) and an outlet manifold (252). The inlet manifold (251) is used to introduce the gas to be tested, and the inlet manifold (251) is connected to each of the inlets (213). The outlet manifold (252) is used to discharge the gas to be tested, and the outlet manifold (252) is connected to each of the outlets (214).

7. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection device according to claim 1, characterized in that, The pool body (21) also has a number of transparent windows (215) that correspond to each of the independent chambers.

8. A dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection method, characterized in that, The photoacoustic spectroscopy gas detection device with dynamic reconstruction and hybrid optical path self-calibration as described in any one of claims 1-7 includes the following steps: a) Operation in the first detection mode: control the at least one partition (23) to be in the separation position, dividing the pool body (21) into several independent chambers; introduce the probe light from the corresponding laser source (1) into each of the independent chambers to form a linear multi-path optical path therein; use the acoustic sensor (4) to detect the photoacoustic signal and calculate the first concentration value R of several of the target gases; b) Determine whether any of the first concentration values ​​R or its rate of change meets the preset triggering condition, and determine the target gas that triggers the triggering condition; c) If the triggering condition is met, the system automatically switches to the second detection mode: each of the partitions (23) is controlled to move to the merged position, so that each of the independent chambers is merged into a complete chamber; and a beam of probe light whose wavelength matches the characteristic absorption spectrum line corresponding to the triggering condition is introduced into it, forming a spiral optical path in the complete chamber, and the photoacoustic signal is detected by each of the acoustic sensors (4), and the second concentration value P of the target gas that meets the triggering condition is calculated. d) Perform online self-calibration: Calculate and update a dynamic calibration coefficient K based on the second concentration value P and the corresponding first concentration value R, and correct the concentration values ​​subsequently obtained in the first detection mode.

9. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection method according to claim 8, characterized in that, The linear multi-path optical path in each of the independent chambers is a Heriot-Limiter cell structure composed of two opposing reflective mirrors.

10. The dynamic reconstruction and hybrid optical path self-calibration photoacoustic spectroscopy gas detection method according to claim 8, characterized in that, The dynamic calibration coefficient K in step d) is calculated using the formula K=P / R.

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