Acetylene gas detection method, system, device and medium based on laser multiplexing

Abstract

The present application belongs to the technical field of gas detection, and discloses an acetylene gas detection method, system, device and medium based on laser multiplexing, to solve the problems of low detection precision and poor real-time performance in the prior art. The method comprises: emitting two laser beams with different wavelengths; controlling the two laser beams to be emitted alternately in time sequence and transmitted through the same optical path; generating periodic pressure fluctuations through gas molecule absorption of laser energy to generate an acoustic signal; detecting the intensity and phase of the acoustic signal; converting the acoustic signal into an electric signal and performing low-noise amplification and band-pass filtering processing; performing second harmonic demodulation on the signal with improved signal-to-noise ratio to obtain the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the detection laser beam respectively; using differential absorption algorithm analysis to separate the absorption contribution of acetylene gas and water vapor to the absorption signal; and calculating the acetylene concentration according to the separated acetylene net absorption signal by applying Beer-Lambert law.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas detection, and particularly relates to an acetylene gas detection method, system, device and medium based on laser multiplexing. BACKGROUND

[0002] Acetylene (C2H2) is a key characteristic gas generated when high-temperature overheating or discharge faults occur inside a transformer. During the operation of a transformer, the insulating oil will decompose and dissolve multiple gases, and the generation and concentration change of acetylene are sensitive indicators for diagnosing internal serious faults (such as arc discharge) of the transformer. Therefore, accurately and quickly detecting the dissolved acetylene gas in the transformer oil is of great significance for evaluating the health status of the transformer, achieving early warning of faults, and ensuring the safe and stable operation of the power system.

[0003] At present, dissolved gas analysis (DGA) in transformer oil mainly relies on gas chromatography (GC). Although this method can detect more components, it has inherent disadvantages such as long sampling period, complex analysis process, high equipment purchase and maintenance cost, etc., making it difficult to realize online real-time monitoring of fault gases. In recent years, tunable diode laser absorption spectroscopy (TDLAS) has been introduced into the field of dissolved gas detection due to its high sensitivity, fast response, and the ability to realize in-situ measurement, providing a new technical path for real-time diagnosis of transformer faults.

[0004] However, when applying TDLAS technology to the actual detection of acetylene gas in transformer oil, a significant technical challenge is faced. Transformer oil usually contains a certain amount of moisture, and the absorption spectrum of water vapor in the near-infrared band overlaps with the characteristic absorption lines of acetylene. Existing TDLAS detection schemes mostly focus on the analysis of single gas components and often use single-wavelength lasers for measurement. This method cannot effectively distinguish between acetylene absorption signals and water vapor absorption signals, resulting in serious interference with the measurement results in a high-humidity environment, and significantly reducing the detection accuracy and reliability.

[0005] In summary, the existing technology has obvious limitations in the detection of acetylene gas in transformer oil, and it is difficult to meet the detection requirements of high precision and real-time. SUMMARY

[0006] Based on the above-mentioned shortcomings and deficiencies in the prior art, one of the purposes of the present application is to at least solve one or more of the above-mentioned problems in the prior art, or in other words, one of the purposes of the present application is to provide an acetylene gas detection method, system, device and medium based on laser multiplexing to meet one or more of the aforementioned needs, so as to realize high-precision detection of acetylene gas and effectively weaken the interference of water vapor.

[0007] In order to achieve the above-mentioned purposes of the application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a laser multiplexing-based acetylene gas detection method, comprising the steps of: S1, emitting two laser beams with different wavelengths, one of which is an excitation laser beam corresponding to the characteristic absorption line of acetylene, and the other is a probe laser beam; S2, controlling the excitation laser beam and the probe laser beam to be emitted alternately in time sequence and transmitted through the same optical path to irradiate the measured gas sample in the photoacoustic cell; S3, generating a periodic pressure fluctuation by absorbing laser energy through gas molecules in the measured gas sample, thereby generating an acoustic signal; S4, detecting the intensity and phase of the acoustic signal; S5, converting the acoustic signal into an electrical signal, and sequentially performing low-noise amplification and band-pass filtering on the electrical signal to obtain a signal with improved signal-to-noise ratio; S6, using a lock-in amplifier to perform second harmonic demodulation on the signal with improved signal-to-noise ratio to obtain the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the probe laser beam, respectively; S7, based on the amplitude and phase information of the acoustic signal obtained by the second harmonic demodulation, using a differential absorption algorithm for analysis to separate the absorption contribution of acetylene gas and water vapor to the absorption signal; S8, according to the separated acetylene net absorption signal, applying Beer-Lambert law to calculate the acetylene concentration in the measured gas sample.

[0009] As a preferred scheme, the two laser beams with different wavelengths emitted in step S1 are specifically: the wavelength of the excitation laser beam is tuned to the range [1532.82 nm, 1532.84 nm] by a tunable diode laser; the wavelength of the probe laser beam is tuned to the range [1387 nm, 1389 nm] by the tunable diode laser.

[0010] As a preferred scheme, the emission in time sequence in step S2 is specifically: the switching of the two laser beams is controlled by an electro-optic modulator according to a preset time sequence signal; the total modulation period is set as T, the working period of the excitation laser beam is set as 0 to T / 2, the working period of the probe laser beam is set as T / 2 to T, and the switching frequency range is [5 HZ, 35 HZ].

[0011] As a preferred scheme, the intensity of the acoustic signal in step S3 is proportional to the laser power and the gas absorption coefficient, and satisfies the following relationship: , wherein, represents the intensity of the acoustic signal, represents the gas absorption coefficient, represents the laser beam power, represents the photoacoustic cell constant.

[0012] As a preferred scheme, the electric signal is sequentially subjected to low noise amplification and band pass filtering in step S5, specifically: the acoustic sensor converts the sound wave signal into an initial electric signal with a frequency matching the laser beam modulation; the low noise amplifier amplifies the initial electric signal; the band pass filter filters the amplified electric signal with the laser beam modulation frequency as the center frequency point to filter out the environmental noise.

[0013] As a preferred scheme, the differential absorption algorithm analysis in step S6 is specifically: normalizing the sound wave signal amplitude obtained by the second harmonic demodulation to correct the laser power fluctuation; calculating the differential signal of the normalized excitation laser beam signal and the detection laser beam signal; based on the standard absorption spectrum of acetylene and water vapor provided by the HITRAN database, fitting the differential signal by the least square method to decompose the absorption contribution of acetylene and water vapor.

[0014] In a second aspect, the present application provides an acetylene gas detection system based on laser multiplexing, which is used to realize the acetylene gas detection method as described in the first aspect, and includes: a laser generation and modulation module, which is used to emit two laser beams with different wavelengths, one of which is an excitation laser beam corresponding to the acetylene characteristic absorption line, and the other of which is a detection laser beam located in a weak water vapor absorption band; an optical path transmission module, which is used to make the excitation laser beam and the detection laser beam emit alternately in time sequence and transmit through the same optical path to irradiate the measured gas sample in an optoacoustic cell; an optoacoustic detection module, which includes the optoacoustic cell and an acoustic sensor, the optoacoustic cell is used to contain the measured gas sample, and a periodic pressure fluctuation is generated by the gas molecules in the measured gas sample absorbing laser energy, thereby generating a sound wave signal; the acoustic sensor is used to detect the intensity and phase of the sound wave signal; a signal processing module, which is used to convert the sound wave signal into an electric signal, and sequentially perform low noise amplification and band pass filtering on the electric signal to obtain a signal with improved signal-to-noise ratio, and is also used to use a lock-in amplifier to perform second harmonic demodulation on the signal with improved signal-to-noise ratio to obtain the sound wave signal amplitude and phase information corresponding to the excitation laser beam and the detection laser beam, respectively; a data processing module, which is used to analyze based on the sound wave signal amplitude and phase information obtained by the second harmonic demodulation by using a differential absorption algorithm to separate the absorption contribution of acetylene gas and water vapor to the absorption signal, and calculate the acetylene concentration in the measured gas sample according to the separated acetylene net absorption signal by applying Beer-Lambert law.

[0015] As a preferred scheme, the laser generation and modulation module includes a tunable diode laser and an electro-optical modulator; the optoacoustic cell in the optoacoustic detection module is a resonant cavity structure and is connected with a temperature controller and a pressure controller; the signal processing module includes a low noise amplifier, a band pass filter and a lock-in amplifier;

[0016] The data processing module is connected to a HITRAN database.

[0017] In a third aspect, the application provides an electronic device, the computer device comprising a memory, a processor and a computer program, the computer program being executed by the processor to implement the acetylene gas detection method according to the first aspect.

[0018] In a fourth aspect, the application provides a computer readable storage medium, the computer readable storage medium storing a computer program, the computer program being executed by a processor to implement the acetylene gas detection method according to the first aspect.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] 1. The application adopts dual-wavelength laser and time division multiplexing technology, and combines differential absorption algorithm. This combination of technologies effectively reduces the interference of water vapor on acetylene gas detection, greatly improves the detection accuracy, and also enhances the reliability of the system.

[0021] 2. The application simplifies the system design architecture, reduces hardware cost investment, realizes double optimization of economic benefit and technical performance, and provides efficient and practical technical support for early diagnosis of transformer faults.

[0022] 3. The application successfully solves two major problems faced by existing TDLAS technology in detecting dissolved gases in transformer oil: one is that analysis is mainly focused on single gas components, and the other is that single-wavelength laser is difficult to effectively deal with multi-component interference and humidity influence, filling the technical gap in this field.

[0023] Further or more detailed beneficial effects will be described in the specific embodiments in conjunction with specific examples. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 is a flowchart of the acetylene gas detection method according to the first embodiment of the application.

[0026] Figure 2 is a structural schematic diagram of the acetylene gas detection system according to the second embodiment of the application.

[0027] Figure 3is a structural diagram of the electronic device according to Embodiment Three of the present application.

[0028] Figure 4 is a result schematic diagram of the verification experiment according to Embodiment Five of the present application.

[0029] Reference Signs:

[0030] 1, laser driver; 2, laser; 3, modulation signal generator; 4, electro-optical modulator; 5, beam combiner; 6, optical collimator; 7, optical fiber; 8, photoacoustic cell; 9, temperature controller; 10, pressure controller; 11, high-sensitivity acoustic sensor; 12, low-noise amplifier; 13, band-pass filter; 14, lock-in amplifier; 15, signal generator; 16, data acquisition card; 17, data processor; 18, controller;

[0031] 300, electronic device; 301, processor; 302, communication bus; 303, user interface; 304, network interface; 305, memory. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0033] In the following description, a plurality of embodiments of the present application are provided, and different embodiments can be replaced or combined, so that the present application can be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B and C, and another embodiment includes features B and D, the present application should also be considered to include embodiments including one or more of all other possible combinations of A, B, C and D, even if the embodiment is not explicitly described in the following content.

[0034] The following description provides examples, and does not limit the scope, applicability or examples set forth in the claims. Changes can be made to the functions and arrangements of described elements without departing from the scope of the present content. Various processes or components can be appropriately omitted, replaced or added in various examples. For example, the described methods can be performed in different orders from the described order, and various steps can be added, omitted or combined. In addition, features described with respect to some examples can be combined into other examples.

[0035] In order to better understand the embodiments of the present application, before the specific embodiments of the present application are explained in detail, the application scenarios thereof are described.

[0036] The acetylene gas detection method described in the embodiments of the present specification is applied to transformer operation monitoring, chemical production safety control, gas pipeline leakage detection and the like. In these scenarios, the application of the acetylene gas detection method aims to accurately and efficiently detect the concentration of acetylene gas, timely discover potential safety hazards, avoid serious accidents such as explosions and fires caused by acetylene gas leakage or accumulation, and ensure the safe and stable operation of the production process and the safety of personnel and property.

[0037] The following is a brief explanation of laser multiplexing, acetylene gas, excitation laser beam, probe laser beam, second harmonic demodulation, and Beer-Lambert law involved in the embodiments of the present specification:

[0038] Laser multiplexing: In the present application, laser multiplexing refers to using dual-wavelength laser technology to make the excitation laser beam corresponding to the acetylene characteristic absorption line and the probe laser beam used for auxiliary detection alternately exit according to a specific time sequence and be transmitted through the same optical path to irradiate the measured gas sample. This technology makes full use of laser resources, realizes effective use of different functional lasers in the same detection system, and improves the efficiency and accuracy of detection.

[0039] Acetylene gas: Acetylene is a colorless and flammable gas with the chemical formula C2H2. It has a wide range of applications in industrial production, such as being used as a fuel gas for welding and cutting. However, acetylene gas has certain risks, and when its concentration in the air reaches a certain range, it may explode when exposed to a fire or high temperature. Therefore, accurately detecting the concentration of acetylene gas is crucial for ensuring production safety.

[0040] Excitation laser beam refers to a laser beam with a wavelength that matches the acetylene characteristic absorption line. When this laser beam irradiates a sample containing acetylene gas, acetylene molecules absorb the energy of the laser and transition from the ground state to the excited state. This process provides the basis for subsequent detection of the presence and concentration of acetylene gas and is one of the key links in the entire detection method.

[0041] The probe laser beam is another laser beam with a different wavelength from the excitation laser beam. It plays an auxiliary role in the detection process and is alternately emitted with the excitation laser beam. By comparing the sound wave signals and other information generated by the gas sample under the action of the probe laser beam and the excitation laser beam, the absorption of acetylene gas to the laser can be more accurately analyzed, other interference factors can be excluded, and the detection accuracy can be improved.

[0042] The second harmonic demodulation is a signal processing technique. In the acetylene gas detection method of the present application, the electrical signal after amplification and filtering processing contains rich information, but also has noise and other interference. By the second harmonic demodulation of the signal through the phase-locked amplifier, the specific frequency component related to the acetylene gas absorption, i.e. the second harmonic signal, can be extracted from the complex signal. In this way, the amplitude and phase information of the acoustic wave signal can be more accurately obtained, providing reliable data for subsequent analysis of the acetylene gas concentration.

[0043] The Beer-Lambert law is an important law in the field of optics and spectral analysis. It describes the relationship between the absorption of light by a substance and the concentration of the substance, the optical path length, and the absorption coefficient. In the acetylene gas detection method of the present application, according to the separated acetylene net absorption signal, the Beer-Lambert law can be applied to calculate the acetylene concentration in the measured gas sample. Specifically, by measuring the intensity change of the light before and after passing through the gas sample, combined with the known absorption coefficient and optical path length, the concentration value of the acetylene gas can be accurately obtained.

[0044] Embodiment one:

[0045] As shown in Figure 1 , the present embodiment provides an acetylene gas detection method based on laser multiplexing, the specific steps are as follows:

[0046] Step S1: emitting two laser beams with different wavelengths, one of which is an excitation laser beam, and the other is a detection laser beam, laying the foundation for subsequent differential analysis. The excitation laser beam selects a wavelength corresponding to the characteristic absorption line of acetylene, which is used to detect acetylene gas. The detection laser beam selects a wavelength in the region where water vapor absorption is weak, which is used to assist in separating water vapor interference.

[0047] Specifically, the present embodiment realizes the generation and modulation of laser beams through a tunable diode laser, tunes the wavelength to the range [1532.82nm, 1532.84nm] to obtain the excitation laser beam, and the present embodiment is preferably 1532.83nm; tunes the wavelength to the range [1387nm, 1389nm] to obtain the detection laser beam, and the present embodiment is preferably 1388nm.

[0048] Step S2: control the excitation laser beam and the detection laser beam to be emitted alternately in time sequence, and transmitted through the same optical path to irradiate the measured gas sample in the photoacoustic cell.

[0049] Specifically, the embodiment controls the switching of the two laser beams according to a preset timing signal through an electro-optical modulator, sets a total modulation period as T, sets a working period of the excitation laser beam as 0 to T / 2, sets a working period of the probe laser beam as T / 2 to T, and sets a switching frequency range as [5 HZ, 35 HZ]. It should be noted that the switching frequency range depends on the response time of the system and the detection requirement.

[0050] Step S3: Periodic pressure fluctuation is generated by gas molecules in the measured gas sample absorbing laser energy, so as to generate an acoustic signal. Specifically, acetylene molecules absorb laser energy and are excited to a high-energy state, and then energy is converted into heat through a non-radiation relaxation process, so as to cause local temperature rise. The change of the temperature causes gas expansion or contraction, so as to generate an acoustic wave matching the modulation frequency.

[0051] Specifically, the intensity of the acoustic signal is proportional to the laser power and the gas absorption coefficient, and satisfies the following relationship: , wherein, represents the intensity of the acoustic signal, represents the gas absorption coefficient, represents the laser beam power, represents a photoacoustic cell constant.

[0052] Step S4: The intensity and phase of the acoustic signal are detected.

[0053] In the specific operation, the photoacoustic cell used in the embodiment is a resonant cavity structure. After the acoustic signal is amplified by the resonant cavity of the photoacoustic cell, the high-sensitivity acoustic sensor completes the detection of the intensity and phase of the acoustic signal.

[0054] Step S5: The acoustic signal is converted into an electric signal, and the electric signal is sequentially subjected to low-noise amplification and band-pass filtering, so as to obtain a signal with improved signal-to-noise ratio.

[0055] Specifically, the embodiment first converts the acoustic signal into an initial electric signal with a frequency matching the modulation of the laser beam by using the acoustic sensor; then, the initial electric signal is amplified by using a low-noise amplifier; finally, the amplified electric signal is filtered by using a band-pass filter with the modulation frequency of the laser beam as a center frequency point, so as to filter out environmental noise.

[0056] Step S6: The signal with the improved signal-to-noise ratio is subjected to second-harmonic demodulation by using a lock-in amplifier, so as to obtain the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the probe laser beam, respectively.

[0057] In the specific operation, the embodiment first normalizes the amplitude of the sound wave signal obtained by the second harmonic demodulation to correct the laser power fluctuation; then calculates the difference signal of the normalized excitation laser beam signal and the probe laser beam signal; finally, based on the standard absorption spectrum of acetylene and water vapor provided by the HITRAN database, the least square method is used to fit the difference signal to decompose the absorption contribution of acetylene and water vapor respectively.

[0058] More specifically, the normalization processing is represented by the following formula:

[0059] ,

[0060] ,

[0061] In the formula, represents the normalized acetylene photoacoustic signal, represents the photoacoustic signal of acetylene absorption laser, represents the photoacoustic signal of acetylene absorption laser, represents the normalized background photoacoustic signal, represents the photoacoustic signal of background laser, represents the power of acetylene background laser.

[0062] More specifically, the expression of the difference signal is:

[0063] ,

[0064] In the formula, represents the difference signal.

[0065] More specifically, the least square fitting of the difference signal is represented by the following formula:

[0066] ,

[0067] ,

[0068] In the formula, represents the absorption coefficient of acetylene, represents the absorption coefficient of water, represents the concentration of acetylene, represents the concentration of water, represents noise.

[0069] Step S7: Based on the amplitude and phase information of the sound wave signal obtained by the second harmonic demodulation, a difference absorption algorithm is used for analysis to separate the absorption contribution of acetylene gas and water vapor to the absorption signal;

[0070] Step S8: According to the separated acetylene net absorption signal, the acetylene concentration in the measured gas sample is calculated by applying Beer-Lambert law.

[0071] Embodiment two:

[0072] The embodiment provides an acetylene gas detection system based on laser multiplexing, which is used for realizing the acetylene gas detection method as described in embodiment one, and comprises a laser generation and modulation module, which is used for emitting two laser beams with different wavelengths, one of which is an excitation laser beam corresponding to an acetylene characteristic absorption line, and the other is a detection laser beam located in a weak water vapor absorption band; an optical path transmission module, which is used for alternately emitting the excitation laser beam and the detection laser beam in time sequence and transmitting them through the same optical path to irradiate a measured gas sample in an optoacoustic cell; an optoacoustic detection module, which comprises the optoacoustic cell and an acoustic sensor, the optoacoustic cell is used for containing the measured gas sample, and a periodic pressure fluctuation is generated by absorbing laser energy through gas molecules in the measured gas sample, so that an acoustic signal is generated; the acoustic sensor is used for detecting the intensity and phase of the acoustic signal; a signal processing module, which is used for converting the acoustic signal into an electric signal, and sequentially performing low-noise amplification and band-pass filtering on the electric signal to obtain a signal with improved signal-to-noise ratio, and is also used for using a lock-in amplifier to perform second harmonic demodulation on the signal with improved signal-to-noise ratio, and acquiring the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the detection laser beam respectively; and a data processing module, which is used for analyzing the amplitude and phase information of the acoustic signal obtained through the second harmonic demodulation by using a differential absorption algorithm, separating the absorption contribution of acetylene gas and water vapor to the absorption signal, and calculating the acetylene concentration in the measured gas sample according to the separated acetylene net absorption signal by applying Beer-Lambert law.

[0073] Specifically, the laser generation and modulation module comprises a tunable diode laser and an electro-optical modulator.

[0074] The optoacoustic cell in the optoacoustic detection module is a resonant cavity structure, and is connected with a temperature controller and a pressure controller; the signal processing module comprises a low-noise amplifier, a band-pass filter and a lock-in amplifier; and the data processing module is connected with a HITRAN database.

[0075] Referring to Figure 2 , the embodiment provides a preferred embodiment of an acetylene gas detection system, which comprises a laser driver 1, a laser 2, a modulation signal generator 3, an electro-optical modulator 4, a beam combiner 5, an optical collimator 6, an optical fiber 7, an optoacoustic cell 8, a temperature controller 9, a pressure controller 10, a high-sensitivity acoustic sensor 11, a low-noise amplifier 12, a band-pass filter 13, a lock-in amplifier 14, a signal generator 15, a data acquisition card 16, a data processor 17 and a controller 18.

[0076] More specifically, Figure 2 The functions of the components in the system are as follows:

[0077] The laser driver 1 is responsible for ensuring that the laser 2 can accurately generate two laser beams of different wavelengths, namely the excitation laser beam and the probe laser beam. It cooperates with the modulation signal generator 3 to provide a modulation signal to the laser 2, so that the modulation frequency of the laser beam matches the resonance frequency of the photoacoustic cell, thereby enhancing the generation and detection of the photoacoustic signal. At the same time, the laser driver 1 works with the controller 18 to ensure that the two laser beams are alternately emitted in time sequence, realizing time division multiplexing, ensuring that they share the same optical path and have consistent measurement conditions, providing key support for the stable operation of the system and high-precision acetylene detection.

[0078] The laser 2 is used to generate the excitation laser beam and the probe laser beam. The excitation laser beam excites acetylene molecules to absorb laser energy, generating a photoacoustic signal to realize the detection of acetylene gas; the probe laser beam is used to detect the background signal, assisting in the separation of water vapor interference, and providing a reference for the subsequent differential absorption algorithm. The two laser beams are alternately emitted through time division multiplexing technology, sharing the same optical path, ensuring consistent measurement conditions, and laying the foundation for high-precision, low-humidity-sensitive acetylene concentration detection.

[0079] The modulation signal generator 3 cooperates with the controller 18 and the electro-optical modulator 4 to generate time sequence signals, control the alternate emission of the two laser beams, and ensure the implementation of time division multiplexing technology.

[0080] The electro-optical modulator 4 realizes time division multiplexing by rapidly switching the excitation laser beam and the probe laser beam, so that the two laser beams share the same optical path, avoid optical path deviation, and ensure consistent measurement conditions.

[0081] The beam combiner 5 cooperates with the electro-optical modulator 4 to ensure that the two laser beams still propagate along the same optical path when they are alternately transmitted, reducing the interference of environmental factors on the signal.

[0082] The optical collimator 6 collimates the two laser beams to ensure that they are transmitted along the same optical path during time division multiplexing, acting on the same target area within the photoacoustic cell 8, improving the consistency of measurement conditions and detection accuracy. The optical fiber 7 uses its single-mode or multi-mode transmission characteristics to ensure that the two laser beams propagate along the same optical path during time division multiplexing, avoiding optical path deviation and maintaining the consistency of measurement conditions.

[0083] The photoacoustic cell 8, in conjunction with the temperature controller 9 and the pressure controller 10, maintains the temperature and pressure of the gas sample in the cell stable, ensuring consistent measurement conditions and reducing environmental factors' interference with the photoacoustic signal. When the laser beam transmitted by the optical fiber 7 irradiates the gas sample in the photoacoustic cell 8, the acetylene molecules absorb the laser energy, convert it into heat through non-radiative relaxation, causing local pressure changes, and generating acoustic signals matching the laser modulation frequency. The high-sensitivity acoustic sensor 11 accurately captures the acoustic signals generated in the photoacoustic cell 8 due to the absorption of laser energy by acetylene molecules, including the intensity and phase of the acoustic waves, whose frequency matches the laser modulation frequency. It detects the acoustic signals generated by the excitation laser beam (acetylene absorption) and the probe laser beam (background signal) respectively, providing data for the differential absorption algorithm.

[0084] The low-noise amplifier 12 amplifies the weak electrical signals converted by the high-sensitivity acoustic sensor 11, improving signal strength and providing high-quality input for subsequent signal processing.

[0085] The band-pass filter 13 performs frequency-selective filtering on the electrical signals output by the low-noise amplifier 12, removing environmental noise and improving the signal-to-noise ratio, providing purer signals for subsequent signal processing.

[0086] The lock-in amplifier 14 performs second harmonic (2f) demodulation on the electrical signals output by the band-pass filter 13, extracting amplitude and phase information related to acetylene absorption and background signals, further improving the signal-to-noise ratio of the signals, and providing high-quality data for subsequent differential analysis.

[0087] The signal generator 15 generates a reference signal corresponding to the laser modulation frequency (especially the second harmonic 2f frequency) for the lock-in amplifier 14 to perform 2f demodulation, extracting the amplitude and phase of the acoustic signals of the acetylene absorption laser (excitation laser beam) and the background laser (probe laser beam).

[0088] The data acquisition card 16 receives the 2f signals output by the lock-in amplifier 14 (including the amplitude and phase information of the acetylene absorption laser and the background laser), converting them from analog signals to high-precision digital signals.

[0089] The data processor 17 provides high-precision, low-interference concentration detection results for the low-humidity-sensitive acetylene gas detection system based on laser multiplexing through efficient signal processing and algorithm analysis.

[0090] The controller 18 coordinates and controls the operation of each component in the system, ensuring the synchronization and stability of the overall system.

[0091] More specifically, Figure 2The connections of the components in the system shown are as follows: laser driver 1 is connected to laser 2; laser 2 is connected to modulation signal generator 3; modulation signal generator 3 is connected to electro-optic modulator 4; electro-optic modulator 4 is connected to beam combiner 5; beam combiner 5 is connected to optical collimator 6; optical collimator 6 is connected to photoacoustic cell 8 via optical fiber 7. Photoacoustic cell 8 is connected to high-sensitivity acoustic sensor 11; high-sensitivity acoustic sensor 11 is connected to low-noise amplifier 12; low-noise amplifier 12 is connected to bandpass filter 13; bandpass filter 13 is connected to lock-in amplifier 14; lock-in amplifier 14 is connected to signal generator 15; signal generator 15 is connected to data acquisition card 16; data acquisition card 16 is connected to data processor 17. Controller 18 coordinates components such as electro-optic modulator 4, temperature controller 9, pressure controller 10, and signal generator 15 to ensure timing synchronization and system stability.

[0092] Example 3:

[0093] like Figure 3 As shown, this embodiment provides an electronic device, which may include: at least one processor, at least one network interface, a user interface, a memory, and at least one communication bus.

[0094] The communication bus can be used to enable communication between the various components mentioned above.

[0095] The user interface may include buttons, and optional user interfaces may also include standard wired interfaces and wireless interfaces.

[0096] The network interface may include, but is not limited to, Bluetooth modules, NFC modules, Wi-Fi modules, etc.

[0097] The processor may include one or more processing cores. It connects various parts of the electronic device via various interfaces and lines, executing instructions, programs, code sets, or instruction sets stored in memory, and accessing data stored in memory to perform various functions and process data. Optionally, the processor can be implemented using at least one hardware form of DSP, FPGA, or PLA. The processor may integrate one or more of the following: CPU, GPU, and modem. The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content required for display; and the modem handles wireless communication. It is understood that the modem may also be implemented as a separate chip without being integrated into the processor.

[0098] The memory can include a RAM and can also include a ROM. Optionally, the memory includes a non-transitory computer-readable medium. The memory can be used to store instructions, programs, codes, code sets, or instruction sets. The memory can include a program storage area and a data storage area, wherein the program storage area can store the instructions for implementing the operating system, the instructions for at least one function (such as a touch function, a sound playing function, an image playing function, etc.), the instructions for implementing the various method embodiments described above, etc.; and the data storage area can store the data involved in the various method embodiments described above, etc. The memory can also optionally be at least one storage device located away from the aforementioned processor. The memory, as a kind of computer storage medium, can include an operating system, a network communication module, a user interface module, and a detection application program. The processor can be used to invoke the detection application program stored in the memory and execute the steps of the acetylene gas detection method mentioned in the foregoing embodiments.

[0099] Embodiment Four

[0100] The embodiment provides a computer readable storage medium, which stores instructions, and when the instructions run on a computer or a processor, the computer or the processor executes the steps of one or more of the embodiments shown above. When each component module of the above electronic device is implemented in the form of a software function unit and sold or used as an independent product, it can be stored in the computer readable storage medium. Figure 1

[0101] ​In the above embodiments, all or part of the methods can be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the methods can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present specification are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in or transmitted by a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through a wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) manner. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server, data center, etc. that includes one or more available media sets. The available media can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a digital versatile disc (DVD)), or a semiconductor medium (for example, a solid state disk (SSD)), etc.

[0102] A person of ordinary skill in the art can understand that all or part of the processes in the method of the above embodiments can be completed by instructing related hardware through a computer program, which can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above embodiments of each method. The aforementioned storage medium includes ROM, RAM, magnetic or optical disks, and various program code storage media. In the case of no conflict, the technical features in the embodiments and the implementation solutions can be combined arbitrarily.

[0103] Embodiment Five

[0104] In order to verify the effectiveness of the laser multiplexing-based acetylene gas detection method described in the present specification, the present embodiment relies on the actual application scene, and uses the acetylene gas detection system as shown in Figure 2 The specific operation steps are as follows:

[0105] First, the laser driver 1 drives the laser 2 to generate two laser beams: one is an excitation laser beam with a wavelength of about 1532.83 nm, targeting the acetylene absorption line; the other is a probe laser beam with a wavelength of about 1388 nm, with weak water vapor absorption. The modulation signal generator 3 works with the controller 18 to control the two laser beams to be alternately emitted in time sequence through the electro-optical modulator 4, that is, the excitation laser is emitted from 0 to T / 2 period, and the probe laser is emitted from T / 2 to T period, and the switching frequency ranges between several hertz to several tens of hertz. Subsequently, the beam combiner 5, the optical collimator 6 and the optical fiber 7 together ensure that the two laser beams are transmitted along the same optical path and act on the same gas region in the photoacoustic cell 8.

[0106] When the laser beam irradiates the transformer oil gas sample in the photoacoustic cell 8, the acetylene molecules absorb the energy of the excitation laser and are excited to a high-energy state, and then converted into heat through a non-radiative relaxation process, resulting in local temperature rise and pressure change, and further generating an acoustic wave matching the modulation frequency. The photoacoustic cell 8 amplifies the acoustic wave signal by utilizing its resonant cavity characteristics, while the temperature controller 9 and the pressure controller 10 maintain the stability of the environment in the cell.

[0107] Then, the high-sensitivity acoustic sensor 11 detects the intensity and phase of the acoustic wave and converts it into an electrical signal, the frequency of which matches the laser modulation frequency. The low-noise amplifier 12 amplifies the weak electrical signal, and the band-pass filter 13 filters out environmental noise centered on the modulation frequency, thereby improving the signal-to-noise ratio. The lock-in amplifier 14 uses the 2f reference signal provided by the signal generator 15 to perform second harmonic (2f) demodulation, extracting the amplitude and phase information of the acetylene and background signals. The data acquisition card 16 converts the demodulated 2f signal into a digital signal and sends it to the data processor 17. The data processor 17 first corrects the laser power fluctuation and calculates the normalized signal; then calculates the differential signal using the differential absorption algorithm; finally, fits the absorption spectra of acetylene and water vapor using the H IT RAN database, decomposes the absorption contribution, extracts the net absorption signal of acetylene, and calculates the acetylene concentration by applying the Beer-Lambert law.

[0108] Throughout the process, the controller 18 is responsible for coordinating the work of each component to ensure that the laser beams are alternately emitted, the signals are synchronized, and the environment is stable, thereby achieving high-precision, low-humidity-sensitive acetylene concentration detection. Through time division multiplexing technology and differential absorption algorithm, the system can effectively separate water vapor interference, accurately measure the acetylene gas concentration in the transformer oil, and provide high signal-to-noise ratio and stable detection results. The results obtained in the experiment are shown in Figure 4 .

[0109] Based on the above, the present embodiment verifies the effectiveness of the acetylene gas detection method based on laser multiplexing according to the present specification.

[0110] It should be noted that, for the aforementioned method embodiments, the sequences of the described actions are not the only ones that can be used to implement the present application, and certain steps can be performed in other sequences or even at the same time. Additionally, it should be noted that the embodiments described in the specification are preferred embodiments only and do not limit the scope of the present application.

[0111] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0112] The above description is merely illustrative of the present application, and cannot limit the scope of the present application. Any equivalent changes and modifications made in accordance with the teachings of the present application are still within the scope of the present application. Those skilled in the art will readily conceive of other implementations of the present application upon considering the specification and practicing the disclosure herein. The present application is intended to cover any variations, uses, or adaptive changes of the present application that follow the general principles of the present application and include common knowledge or conventional techniques in the art that are not described in the present application. The specification and examples are merely illustrative, and the scope and spirit of the present application are defined by the claims.

Claims

1. A laser multiplexing-based acetylene gas detection method, characterized by, The method comprises the steps of: S1, emitting two laser beams with different wavelengths, one of which is an excitation laser beam corresponding to the characteristic absorption line of acetylene, and the other is a probe laser beam; In step S1, the two laser beams with different wavelengths are emitted as follows: The wavelength of the excitation laser beam is tuned to the range [1532.82 nm, 1532.84 nm] by a tunable diode laser; The wavelength of the probe laser beam is tuned to the range [1387 nm, 1389 nm] by the tunable diode laser; S2, controlling the excitation laser beam and the probe laser beam to be emitted alternately in time sequence and transmitted through the same optical path to irradiate the measured gas sample in the photoacoustic cell; In step S2, the two laser beams are emitted alternately in time sequence as follows: The switching of the two laser beams is controlled by an electro-optical modulator according to a preset time sequence signal; The total modulation period is set as T, the working period of the excitation laser beam is set as 0 to T / 2, the working period of the probe laser beam is set as T / 2 to T, and the switching frequency range is [5 HZ, 35 HZ]; S3, generating an acoustic signal by the gas molecules in the measured gas sample absorbing laser energy to generate periodic pressure fluctuations; S4, detecting the intensity and phase of the acoustic signal; S5, converting the acoustic signal into an electric signal, and sequentially performing low-noise amplification and band-pass filtering on the electric signal to obtain a signal with improved signal-to-noise ratio; S6, using a lock-in amplifier to perform second harmonic demodulation on the signal with improved signal-to-noise ratio to obtain the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the probe laser beam, respectively; S7, performing normalization processing on the amplitude of the acoustic signal obtained by the second harmonic demodulation to correct the laser power fluctuation, calculating the differential signal of the normalized excitation laser beam signal and probe laser beam signal, and fitting the differential signal by the least square method based on the standard absorption spectrum of acetylene and water vapor provided by the HITRAN database to separate the absorption contributions of acetylene and water vapor; S8, calculating the acetylene concentration in the measured gas sample according to the separated acetylene net absorption signal by applying the Beer-Lambert law. 2.The laser multiplexing based acetylene gas detection method of claim 1, wherein, In step S3, the intensity of the acoustic signal is proportional to the laser power and the gas absorption coefficient, and satisfies the following relationship: ， wherein represents the intensity of the acoustic wave signal, represents the gas absorption coefficient, represents the laser beam power, represents the photoacoustic cell constant. 3.The laser multiplexing based acetylene gas detection method of claim 2, wherein, In step S5, the low-noise amplification and band-pass filtering of the electric signal are performed as follows: The acoustic signal is converted into an initial electric signal with a frequency matching the modulation of the laser beam by an acoustic sensor; The initial electric signal is amplified by a low-noise amplifier; The amplified electric signal is filtered by a band-pass filter with the laser beam modulation frequency as the center frequency to filter out environmental noise.

4. A laser multiplexing based acetylene gas detection system characterized by, The method for detecting acetylene gas according to any one of claims 1 to 3 comprises: A laser generation and modulation module for emitting two laser beams with different wavelengths, one of which is an excitation laser beam corresponding to the characteristic absorption line of acetylene, and the other is a probe laser beam located in a weak water vapor absorption band; The optical path transmission module controls the excitation laser beam and the probe laser beam to be emitted alternately in time sequence and transmitted through the same optical path to irradiate the measured gas sample in the photoacoustic cell. The photoacoustic detection module includes a photoacoustic cell and an acoustic sensor, the photoacoustic cell is used to accommodate the measured gas sample, and a periodic pressure fluctuation is generated by absorbing laser energy by gas molecules in the measured gas sample, thereby generating an acoustic signal; the acoustic sensor is used to detect the intensity and phase of the acoustic signal; The signal processing module is used to convert the acoustic signal into an electrical signal, and sequentially perform low-noise amplification and band-pass filtering on the electrical signal to obtain a signal with improved signal-to-noise ratio, and is also used to use a lock-in amplifier to perform second harmonic demodulation on the signal with improved signal-to-noise ratio, and respectively obtain the amplitude and phase information of the acoustic signal corresponding to the excitation laser beam and the probe laser beam. The data processing module is used to analyze the amplitude and phase information of the acoustic signal obtained by the second harmonic demodulation based on the differential absorption algorithm to separate the absorption contribution of acetylene gas and water vapor to the absorption signal, and calculate the acetylene concentration in the measured gas sample according to the separated acetylene net absorption signal by applying Beer-Lambert law.

5. The acetylene gas detection system based on laser multiplexing according to claim 4, characterized in that: The laser generation and modulation module includes a tunable diode laser and an electro-optical modulator; The photoacoustic cell in the photoacoustic detection module is a resonant cavity structure and is connected with a temperature controller and a pressure controller; The signal processing module includes a low-noise amplifier, a band-pass filter and a lock-in amplifier; The data processing module is connected with a HITRAN database.

6. A computer device comprising a memory, a processor and a computer program, characterized in that The computer program is executed by the processor to realize the acetylene gas detection method according to any one of claims 1 to 3.

7. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the acetylene gas detection method according to any one of claims 1 to 3.

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