An acetylene fiber photoacoustic detection system based on π-shaped cantilever beam and its application

Abstract

The invention discloses an acetylene optical fiber photoacoustic detection system based on a π-shaped cantilever beam and an application thereof, and relates to the technical field of acetylene gas detection in transformer oil. The detection system comprises a photoacoustic cell; a π-shaped cantilever beam arranged in the photoacoustic cell, with one end of the π-shaped cantilever beam fixed and the other end combined with a single-mode optical fiber to form an F-P cavity; a semiconductor laser for irradiating the gas to be detected entering the photoacoustic cell; an SLED detection light source tube, which is a broadband light source, for coupling the emitted broadband light into the F-P cavity through a single-mode optical fiber and an optical fiber circulator to generate an interference spectrum; a spectrometer for collecting the interference spectrum; a data collection and control circuit module for transmitting the interference spectrum data collected by the spectrometer to a data analysis and computer module; and the data analysis and computer module for analyzing the change in the length of the F-P cavity and obtaining the acetylene concentration after calibration. The π-shaped cantilever beam of the invention exhibits extremely high sensitivity when detecting trace acetylene gas.

Description

Technical Field

[0001] The present invention relates to the technical field of acetylene gas detection in transformer oil, and in particular to an acetylene optical fiber photoacoustic detection system based on a π-shaped cantilever beam and applications thereof. Background Art

[0002] Transformer fault monitoring technology is a key area of ​​the power industry. It aims to monitor the transformer's operating status in real time, promptly detecting and diagnosing potential faults to ensure stable power system operation and equipment safety. As one of the foundational industries of the national economy, the power industry places extremely high demands on the reliability and safety of power equipment. Therefore, transformer fault monitoring technology has significant application value and development prospects.

[0003] This technology is primarily used in the power system sector, including monitoring and diagnosis of power transformers and distribution transformers. Transformers, as crucial components of power systems, perform the crucial task of converting and transmitting electrical energy. Failures can lead to power outages, losses, and safety incidents, making timely and accurate monitoring crucial.

[0004] At present, acetylene is produced when the following phenomena occur inside the transformer: arc discharge (such as winding short circuit, insulation breakdown, etc.), high temperature (over 3000℃) will cause the oil and solid insulation material to crack; local overheating (temperature over 800℃); poor contact of tap changer, loose winding, multiple grounding of core, etc., may cause local discharge or overheating; improper treatment of transformer oil (such as oil filter failure causing excessive oil temperature), external arc spread, etc.

[0005] Therefore, acetylene is the main gas diagnosed when a transformer fails. In the existing technology, rectangular cantilever beams are usually made of metal materials such as stainless steel for fiber optic photoacoustic gas detection. The Young's modulus of the metal cantilever beam is large, resulting in low sensitivity, which is difficult to meet the needs of trace gas detection. At the same time, the sensitivity of the rectangular cantilever beam is also relatively low, which limits the accuracy of gas detection. In terms of acetylene detection technology, although certain progress has been made, some defects and challenges still exist. The accuracy and sensitivity of traditional detection methods are limited, and they are easily affected by electromagnetic interference and cannot meet the needs of high-precision monitoring. Summary of the Invention

[0006] The present invention provides an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam and its application, which can solve the following problems existing in the prior art:

[0007] 1) In the existing technology, cantilever beams made of metal materials are used for optical fiber photoacoustic gas detection. The Young's modulus of cantilever beams made of metal materials is large, resulting in low sensitivity and difficulty in meeting the requirements of trace gas detection.

[0008] 2) The sensitivity of the rectangular cantilever beam in the existing technology is relatively low, which limits the accuracy of gas detection;

[0009] 3) The accuracy and sensitivity of detection methods in existing technologies are limited, and they are easily affected by external interference and cannot meet the needs of high-precision monitoring.

[0010] An acetylene optical fiber photoacoustic detection system based on a π-shaped cantilever beam, comprising:

[0011] The photoacoustic cell is provided with an air inlet and an air outlet for the inlet and outlet of the gas to be measured;

[0012] A π-shaped cantilever beam is placed in the photoacoustic cell, one end of which is fixed and the other end is combined with a single-mode optical fiber to form an FP cavity;

[0013] A semiconductor laser is used to irradiate the gas to be measured entering the photoacoustic cell;

[0014] The SLED detection light source tube is a broadband light source, which is used to couple the emitted broadband light into the FP cavity through a single-mode optical fiber and a fiber circulator to generate an interference spectrum.

[0015] A spectrometer for collecting interference spectra;

[0016] The data acquisition and control circuit module is used to transmit the interference spectrum data collected by the spectrometer to the data analysis and computer module;

[0017] The data analysis and computer module is used to analyze the change in the length of the FP cavity and obtain the acetylene concentration after calibration.

[0018] Preferably, the π-shaped cantilever beam is a π-shaped composite material cantilever beam, and the π-shaped composite material cantilever beam is made of carbon fiber and epoxy resin composite material;

[0019] The volume fraction of the carbon fiber is 60%-70%, and the volume fraction of the epoxy resin is 30%-40%.

[0020] Preferably, the preparation method of the π-shaped composite cantilever beam is as follows:

[0021] Carbon fiber and epoxy resin are selected as raw materials, with the volume fraction of carbon fiber controlled at 60%-70% and the volume fraction of epoxy resin controlled at 30%-40%;

[0022] Mix the carbon fiber and epoxy resin raw materials evenly;

[0023] Using the compression molding process, the evenly mixed carbon fiber and epoxy resin are cured and formed under preset temperature and pressure in the mold.

[0024] Preferably, the beam length L1 of the π-shaped composite cantilever beam is 1 mm, the beam width W1 is 0.5 mm, the π-shaped head width W2 is 1.5 mm, the length L2 is 4 mm, and the thickness t is 0.2 mm.

[0025] Preferably, the π-shaped composite material cantilever beam is combined with the single-mode optical fiber via an optical fiber ceramic sleeve to form the FP cavity.

[0026] Preferably, the π-shaped cantilever beam operates in a dynamic mode, and the resonant frequency f of the cantilever beam is:

[0027]

[0028] Where: λ is the wavelength; E is the Young's modulus; t is the cantilever beam thickness; ρ is the density; L is the cantilever beam head length.

[0029] Preferably, the semiconductor laser has a central wavelength of 1532.83 nm and a power of 100 mW;

[0030] Wherein, the output power of the SLED detection light source tube is 10mW.

[0031] Preferably, the optical fiber circulator is used to transmit the broadband light of the superluminescent diode through an FP cavity formed by a single-mode optical fiber and a π-shaped composite cantilever beam, and transmit the interference light output by the FP cavity to a spectrometer.

[0032] Preferably, the data acquisition and control circuit module includes a control circuit, and the data analysis and computer module includes a computer;

[0033] The control circuit module is used to control the working state of the spectrometer and transmit the collected interference spectrum data to the computer; the computer demodulates the cavity length change of the FP cavity in the interference spectrum through a white light interference signal demodulation algorithm.

[0034] Preferably, the data acquisition and control circuit module further includes a microcontroller and a data acquisition chip, and the microcontroller is responsible for controlling the working parameters of the spectrometer;

[0035] The data acquisition chip is used to convert the analog signal output by the spectrometer into a digital signal and transmit the data to the computer through a data transmission interface.

[0036] Preferably, the computer and white light interference signal demodulation algorithm further includes:

[0037] Data analysis software is set up in the computer. The data analysis software integrates a white light interference signal demodulation algorithm to process the collected interference spectrum data and calculate the concentration of acetylene gas. The calculation process is as follows:

[0038] Acetylene gas is excited in the photoacoustic cell by a semiconductor laser. Acetylene absorbs light energy and converts it into heat. By modulating the semiconductor laser to generate periodic light energy, the periodic heat generation generates pressure waves caused by thermal expansion and contraction. The specific formula is as follows:

[0039] Where: P PA is the photoacoustic pressure; is the gas adiabatic index; C is the acetylene gas concentration in the photoacoustic cell; P0 is the incident light power of the semiconductor laser; α is the acetylene gas absorption coefficient; is the optical path length in the photoacoustic cell; v is the volume of the photoacoustic cell; Modulate the angular frequency of the laser; is the gas damping time;

[0040] The photoacoustic pressure drives the cantilever beam to deflect, causing the FP cavity length to change. The specific formula is as follows:

[0041] Where: ΔL is the change in the FP cavity length; A is the cross-sectional area of ​​the cantilever beam; E is the elastic modulus of the cantilever beam material; t is the thickness of the cantilever beam. When the gas concentration in the photoacoustic cell changes, the deformation of the cantilever beam changes, which in turn causes the cavity length to change.

[0042] The change in cavity length causes the phase of the interference spectrum to shift, which can be expressed by the following specific formula:

[0043] Where: is the interference phase change; is the initial phase; n is the refractive index of the medium in the cavity; L0 is the initial cavity length; is the laser center wavelength; is the SLED interference light intensity; is the incident light intensity of SLED; r1, r2 are the reflectivity of the front and rear mirrors of FP cavity;

[0044] After obtaining the spectral signal using a spectrometer, the interference spectrum is Fourier transformed to obtain the frequency characteristic signal;

[0045] By combining the above formulas, the relationship between the phase and the acetylene gas concentration C can be obtained:

[0046] .

[0047] An application of an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam in comprehensive monitoring of transformer body faults includes the following steps:

[0048] A π-shaped composite cantilever beam was prepared, and one end of the cantilever beam was combined with a single-mode optical fiber to form an FP cavity.

[0049] The gas to be measured is introduced into the photoacoustic cell through the gas inlet of the photoacoustic cell, and a semiconductor laser is used as an excitation light source to irradiate the gas to be measured;

[0050] The SLED detection light source tube emits a broad spectrum of light, which enters the FP cavity through a fiber circulator. When acetylene absorbs the specific wavelength of the excitation light source and generates a pressure wave that acts on the cantilever beam, causing the FP cavity length to change, an interference spectrum carrying information about the cavity length change is generated.

[0051] The spectrometer collects interference spectra;

[0052] The data acquisition and control circuit module controls the operation of the spectrometer and transmits the collected data to the data analysis and computer module;

[0053] The data analysis and computer module demodulates the FP cavity length change through the white light interference signal demodulation algorithm, and obtains the acetylene concentration after calibration, thereby realizing comprehensive monitoring of transformer body faults.

[0054] The present invention provides an acetylene optical fiber photoacoustic detection system based on a π-shaped cantilever beam and its application, which has the following beneficial effects:

[0055] 1) The photoacoustic cell of the present invention features innovative designs in its structure and gas guidance method to improve the efficiency and accuracy of acetylene gas detection. The multi-reflection mirror wall design increases the interaction path between gas and light, improving the photoacoustic conversion efficiency. The sealed air inlet and outlet ensure the tightness of the photoacoustic cell, preventing the intrusion of external gas and internal gas leakage, thereby ensuring the stability of the detection environment. The gas pretreatment process effectively removes interfering substances, reduces background noise, and improves the sensitivity and reliability of detection. Through these optimization measures, the photoacoustic cell can provide a more stable and efficient environment for acetylene gas detection, improving the performance of the entire detection system.

[0056] 2) The resonant frequency of the π-shaped cantilever beam of the present invention is related to its elastic modulus and mass. For trace gas detection, a dynamic operating mode can be adopted, allowing the cantilever beam to vibrate in the photoacoustic cell. When the gas concentration in the photoacoustic cell changes, the vibration frequency of the π-shaped cantilever beam changes accordingly, and the phase of the interference signal changes. The gas concentration information can be inverted through the laser demodulation system. In actual application scenarios, the π-shaped cantilever beam produced by the present invention has demonstrated extremely high sensitivity in detecting trace acetylene gas, effectively detecting acetylene gas concentration changes as low as 0.1ppm.

[0057] 3) The π-shaped composite cantilever beam of the present invention has been optimized in terms of structure and material selection, significantly improving the accuracy and sensitivity of acetylene gas detection; compared with traditional metal cantilever beams, its smaller Young's modulus makes the cantilever beam more sensitive to the pressure waves generated by acetylene gas; the π-shaped structural design increases the effective force-bearing area and structural flexibility of the cantilever beam, further improving the sensitivity; during the manufacturing process, the raw material ratio and processing accuracy are strictly controlled to ensure the consistency and stability of the cantilever beam performance; at the same time, the FP cavity formed in combination with the optical fiber provides a reliable physical basis for accurately monitoring the change in cavity length and thus detecting acetylene concentration, greatly improving the accuracy and reliability of detection compared with traditional detection structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A schematic diagram of the process of applying an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam provided by the present invention to comprehensive monitoring of transformer body faults;

[0059] Figure 2 A schematic diagram of the structure of a photoacoustic cell in an acetylene optical fiber photoacoustic detection system based on a π-shaped cantilever beam provided by the present invention;

[0060] Figure 3 A schematic diagram of the process of an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam provided by the present invention;

[0061] Figure 4 This is a dimensional diagram of a π-shaped cantilever beam in an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam provided by the present invention. DETAILED DESCRIPTION

[0062] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Example

[0063] like Figures 1 to 2 As shown, an embodiment of the present invention provides an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam, comprising: a photoacoustic cell, an excitation light source, a superluminescent diode, a single-mode optical fiber, an optical fiber circulator, a spectrometer, a data acquisition and control circuit module, a data analysis and computer module, and a π-shaped cantilever beam;

[0064] Specifically, in this embodiment, an air inlet and an air outlet are provided in the photoacoustic cell for the inlet and outlet of the gas to be measured; wherein, the photoacoustic cell of this embodiment is made of stainless steel, which has good sealing and corrosion resistance;

[0065] In addition, the gas flow path and multi-reflection mirror wall inside the photoacoustic cell are carefully designed to increase the effective light absorption length. The air inlet and outlet of the photoacoustic cell are sealed to ensure smooth inflow and outflow of the gas to be tested without leakage.

[0066] In actual use, the gas to be tested first passes through a pre-treatment device to remove impurities and moisture to avoid interference with the test results;

[0067] The pretreated gas slowly enters the photoacoustic cell through the gas inlet and is fully mixed in the photoacoustic cell.

[0068] In one implementation of this embodiment, in an experiment simulating acetylene gas detection in transformer oil, the photoacoustic cell that has undergone pretreatment and optimized gas flow channel design can effectively improve the detection efficiency of acetylene gas, enabling the system to detect changes in acetylene gas concentration more quickly and accurately.

[0069] Specifically, the photoacoustic cell of this embodiment has been innovatively designed in terms of structure and gas guiding method to improve the efficiency and accuracy of acetylene gas detection; the multiple reflection mirror wall design increases the action path of gas and light, thereby improving the photoacoustic conversion efficiency; the sealed air inlet and outlet ensure the sealing of the photoacoustic cell, prevent external gas from mixing in and internal gas from leaking, and ensure the stability of the detection environment; the gas pretreatment process effectively removes interfering substances, reduces background noise, and improves the sensitivity and reliability of detection; through these optimization measures, the photoacoustic cell can provide a more stable and efficient environment for acetylene gas detection, thereby improving the performance of the entire detection system.

[0070] In this embodiment, a π-shaped cantilever beam is arranged in the photoacoustic cell, wherein one end of the π-shaped cantilever beam is fixed, and the other end is combined with a single-mode optical fiber to form an FP cavity (Fabry-Perot cavity);

[0071] It should be further explained that the π-shaped cantilever beam of this embodiment is a π-shaped composite cantilever beam, which is made of a carbon fiber and epoxy resin composite material; wherein the volume fraction of the carbon fiber is 60%-70%, and the volume fraction of the epoxy resin is 30%-40%;

[0072] In this embodiment, the preparation method of the π-shaped composite cantilever beam is as follows:

[0073] S101. Select carbon fiber and epoxy resin as raw materials, with the volume fraction of carbon fiber controlled at 60%-70% and the volume fraction of epoxy resin controlled at 30%-40%;

[0074] S102, mixing the carbon fiber and epoxy resin raw materials uniformly;

[0075] S103, using a compression molding process, in a mold, the carbon fiber and epoxy resin, which are evenly mixed, are cured and molded under a preset temperature and pressure.

[0076] As a further solution of this embodiment, please refer to Figure 4 The beam length L1 of the completed π-shaped composite cantilever beam is 1 mm, the beam width W1 is 0.5 mm, the π-shaped head width W2 is 1.5 mm, the length L2 is 4 mm, and the thickness t is 0.2 mm.

[0077] The π-shaped composite cantilever beam is combined with the single-mode optical fiber via a fiber-optic ceramic sleeve. It can be explained that after the π-shaped composite cantilever beam is manufactured, it is combined with the single-mode optical fiber via the fiber-optic ceramic sleeve to form an FP cavity.

[0078] Specifically, during the bonding process, high-precision optical alignment equipment is used to ensure the precise alignment of the cantilever beam and the single-mode optical fiber, and the FP cavity length is adjusted by the optical equipment so that the FP cavity length is stabilized at about 10 microns. It should be noted that the optical alignment equipment can use a multi-axis Picomotor device to align the translation stage. This embodiment does not limit its specific model, so as to meet the actual requirements for precise alignment of the cantilever beam and the optical fiber.

[0079] The cantilever beam can usually work in a dynamic mode. For the π-shaped cantilever beam in this embodiment working in the dynamic mode, the resonant frequency f of the cantilever beam is:

[0080] Where: λ is the wavelength; E is the Young's modulus; t is the thickness of the cantilever beam; ρ is the density; L is the length of the cantilever beam head;

[0081] Based on this, it can be seen that the resonant frequency of the π-shaped cantilever is related to the parameters in the above formula. For trace gas detection, a dynamic working mode can be adopted to allow the cantilever to vibrate in the photoacoustic cell. When the gas concentration in the photoacoustic cell changes, the vibration frequency of the π-shaped cantilever changes accordingly, and the phase of the interference signal changes. The gas concentration information can be inverted through the laser demodulation system.

[0082] In practical applications, the π-shaped composite cantilever beam of this embodiment is integrated into an optical sensor system. Standard acetylene gas samples of varying concentrations are introduced under a controlled environment. The vibration signal generated by the photoacoustic effect of the gas is received by an optical fiber and converted into a recordable voltage signal by a photoelectric converter.

[0083] The test results are shown in the following table:

[0084]

[0085] It can be seen that the π-shaped cantilever beam produced in this embodiment shows extremely high sensitivity when detecting trace acetylene gas, effectively detecting changes in acetylene gas concentration as low as 0.1ppm, and has comprehensive advantages in anti-electromagnetic interference (the shortcoming of electric microphones) and structural stability (compared with rectangular cantilever beams).

[0086] In this embodiment, the π-shaped composite cantilever beam is optimized in structure and material selection, which significantly improves the accuracy and sensitivity of acetylene gas detection; compared with the traditional metal cantilever beam, its smaller Young's modulus makes the cantilever beam more sensitive to the pressure wave generated by acetylene gas; the π-shaped structural design increases the effective force-bearing area and structural flexibility of the cantilever beam, further improving the sensitivity; during the manufacturing process, the raw material ratio and processing accuracy are strictly controlled to ensure the consistency and stability of the cantilever beam performance; at the same time, the FP cavity formed in combination with the optical fiber provides a reliable physical basis for accurately monitoring the change in cavity length and thus detecting acetylene concentration, greatly improving the accuracy and reliability of detection compared with traditional detection structures.

[0087] In this embodiment, the excitation light source is used to illuminate the gas to be measured entering the photoacoustic cell;

[0088] It should be further explained that the excitation light source is a semiconductor laser with a central wavelength of 1532.83 nm and a power of 100 mW.

[0089] The superluminescent diode is used to couple the emitted broadband light into the FP cavity through a single-mode fiber and a fiber circulator to generate an interference spectrum.

[0090] It should be further explained that the superluminescent diode is a broad-spectrum light source with an output power of 10 mW. Specifically, an SLED detection light source tube can be used.

[0091] In this embodiment, during the installation process, a precise optical path calibration device is used to ensure that the laser emitted by the excitation light source accurately irradiates the gas area to be measured in the photoacoustic cell. To ensure the stable operation of the laser, a heat dissipation device and a power supply voltage stabilization module are provided on one side of the excitation light source. The heat dissipation device uses an efficient heat sink and fan combination to promptly dissipate the heat generated by the laser operation. The power supply voltage stabilization module ensures the stability of the voltage input to the laser, avoiding the impact of voltage fluctuations on the output power and wavelength stability of the laser. Among them, the superluminescent diode is used as a broadband light source. When connected to the optical fiber circulator, low-loss optical fiber fusion technology is used to ensure efficient transmission of optical signals.

[0092] As an implementation method of this embodiment, in the actual detection system, the excitation light source after optical path calibration and stabilization device optimization can continuously and stably provide energy for the photoacoustic excitation of acetylene gas, and the superluminescent diode can also stably output broadband light, ensuring the accuracy and stability of interference spectrum acquisition.

[0093] As another implementation method, the excitation light source and superluminescent diode are optimized in terms of selection, installation and connection methods to ensure the stability and reliability of the light source part of the system; optical path calibration ensures the effective utilization of the excitation light, and the heat dissipation device and power supply voltage stabilization module extend the service life of the laser and improve its operating stability; low-loss fiber fusion technology reduces the loss of optical signals during transmission, ensuring that broadband light can smoothly enter the FP cavity and produce a stable interference spectrum; these optimization measures provide a stable and reliable light source foundation for subsequent acetylene gas concentration detection, improving the performance and detection accuracy of the entire detection system.

[0094] In this embodiment, the spectrometer is used to collect interference spectra;

[0095] It should also be noted that the fiber circulator is used to transmit the broadband light of the superluminescent diode through the FP cavity formed by the single-mode optical fiber and the π-shaped composite cantilever beam, and transmit the interference light output by the FP cavity to the spectrometer.

[0096] The fiber circulator is selected to have low insertion loss and high isolation. During installation, it is firmly fixed on the optical platform and connected to the single-mode optical fiber using a high-precision fiber alignment fixture to ensure that the optical signal transmission path within the fiber circulator is accurate and reduce signal reflection and loss.

[0097] In addition, the spectrometer of this embodiment is equipped with a high-resolution detector and a precision optical dispersion element, which can accurately collect the interference spectrum output by the FP cavity. Before use, the spectrometer is calibrated. The calibration process includes wavelength calibration and intensity calibration. The wavelength accuracy and intensity measurement accuracy of the spectrometer are calibrated by using a standard spectral source to ensure the accuracy of the collected data.

[0098] In this embodiment, the data acquisition and control circuit module is used to transmit the interference spectrum data collected by the spectrometer to the data analysis and computer module;

[0099] The data analysis and computer module is used to analyze the change in the length of the FP cavity and obtain the acetylene concentration after calibration;

[0100] It should be further explained that the data acquisition and control circuit module includes a control circuit, and the data analysis and computer module includes a computer; wherein the control circuit module is used to control the working state of the spectrometer and transmit the collected interference spectrum data to the computer; the computer demodulates the cavity length change of the FP cavity in the interference spectrum through a white light interference signal demodulation algorithm.

[0101] Specifically, the white-light interferometric signal demodulation algorithm can extract information about changes in the FP cavity length from the interference spectrum collected by the spectrometer. The system responds to changes in acetylene concentration within a few milliseconds, with a minimum detection limit of 0.1 ppm.

[0102] The data acquisition and control circuit module also includes a microcontroller and a data acquisition chip. The microcontroller is responsible for controlling the working parameters of the spectrometer, such as acquisition frequency and integration time. The data acquisition chip is used to convert the analog signal output by the spectrometer into a digital signal and transmit the data to the computer through a high-speed data transmission interface.

[0103] In one implementation of this embodiment, in a laboratory, an installed and calibrated optical fiber circulator, a spectrometer, and a data acquisition and control circuit module are used to collect and transmit interference spectrum data to provide data support for subsequent analysis and processing by a computer.

[0104] In addition, the fiber optic circulator, spectrometer, and data acquisition and control circuit module of this embodiment have been optimized in terms of selection, installation, and calibration, thereby improving the accuracy and stability of interference spectrum acquisition and data transmission. The low insertion loss and high isolation fiber optic circulator ensures the efficient transmission of optical signals, and the high-precision installation and alignment fixtures reduce signal loss and interference. The spectrometer's high-resolution detector and precision optical dispersion elements, as well as the calibration process, ensure the accuracy of interference spectrum acquisition. The microcontroller, dedicated data acquisition chip, and optimized data transmission interface enable precise control of the spectrometer and fast and stable data transmission. These optimization measures work together to improve the data acquisition and processing capabilities of the entire detection system, providing a strong guarantee for the accurate detection of acetylene gas concentration.

[0105] In a further preferred but non-limiting embodiment, the computer and the white light interference signal demodulation algorithm further include: data analysis software is set in the computer, and the data analysis software is integrated with the white light interference signal demodulation algorithm;

[0106] Specifically, in the process of algorithm implementation, advanced digital signal processing technologies such as fast Fourier transform and wavelet transform are used to process the collected interference spectrum data and calculate the concentration of acetylene gas. The calculation process is as follows:

[0107] Acetylene gas is excited in the photoacoustic cell by a semiconductor laser. Acetylene absorbs light energy and converts it into heat. By modulating the semiconductor laser to generate periodic light energy, the periodic heat generation generates pressure waves caused by thermal expansion and contraction. The specific formula is as follows:

[0108] Where: P PA is the photoacoustic pressure; is the gas adiabatic index; C is the acetylene gas concentration in the photoacoustic cell; P0 is the incident light power of the semiconductor laser; α is the acetylene gas absorption coefficient; is the optical path length in the photoacoustic cell; v is the volume of the photoacoustic cell; Modulate the angular frequency of the laser; is the gas damping time;

[0109] The photoacoustic pressure drives the cantilever beam to deflect, causing the FP cavity length to change. The specific formula is as follows:

[0110] Where: ΔL is the change in the FP cavity length; A is the cross-sectional area of ​​the cantilever beam; E is the elastic modulus of the cantilever beam material; t is the thickness of the cantilever beam. When the gas concentration in the photoacoustic cell changes, the deformation of the cantilever beam changes, which in turn causes the cavity length to change.

[0111] The change in cavity length causes the phase of the interference spectrum to shift, which can be expressed by the following specific formula:

[0112] Where: is the interference phase change; is the initial phase; n is the refractive index of the medium in the cavity; L0 is the initial cavity length; is the laser center wavelength; is the SLED interference light intensity; is the incident light intensity of SLED; r1, r2 are the reflectivity of the front and rear mirrors of FP cavity;

[0113] After obtaining the spectral signal using a spectrometer, the interference spectrum is Fourier transformed to obtain the frequency characteristic signal;

[0114] By combining the above formulas, the relationship between the phase and the acetylene gas concentration C can be obtained:

[0115] .

[0116] This example uses material and structural optimization (low Young's modulus composite materials and π-shaped enhanced sensitivity) to convert minute acetylene concentration changes into detectable phase changes, and then achieves quantitative analysis through high-precision optical demodulation.

[0117] In addition, in order to improve the adaptability and accuracy of the algorithm, the algorithm is regularly optimized and updated, and the algorithm parameters and processing procedures are adjusted according to the problems encountered in the actual detection process and new data characteristics;

[0118] For example, in practical applications, the algorithm-optimized detection system can quickly respond to changes in acetylene concentration within a few milliseconds, and the minimum detection limit can reach 0.1ppm, effectively achieving high-precision detection of trace acetylene gas.

[0119] In this embodiment, the computer and white-light interferometer signal demodulation algorithm are optimized in hardware configuration and algorithm design, ensuring that the system can quickly and accurately process interference spectrum data and obtain acetylene gas concentration; high-performance computer hardware can be used to provide powerful computing power and storage support for the operation of the algorithm, and advanced digital signal processing technology and optimized algorithm flow improve the accuracy and speed of data processing; regular algorithm optimization and updating enable the system to adapt to different detection environments and data characteristics, maintaining high detection accuracy and sensitivity; through these optimization measures, the computer and white-light interferometer signal demodulation algorithm become the core link for the entire detection system to achieve high-precision, real-time detection, effectively improving the system's monitoring ability for acetylene gas in transformer oil.

[0120] Among them, you can refer to Figure 3 , the working process of this embodiment is:

[0121] S201, introducing the gas to be measured into the photoacoustic cell through the gas inlet, and irradiating the gas to be measured with an exciting light source;

[0122] S202. When the gas to be measured contains acetylene, the acetylene absorbs the light of a specific wavelength from the excitation light source and generates a pressure wave. The pressure wave acts on the π-shaped composite cantilever beam, causing the cantilever beam to vibrate, thereby causing the length of the FP cavity to change.

[0123] S303, the broadband light emitted by the superluminescent diode is coupled into the FP cavity through the single-mode optical fiber and the optical fiber circulator to generate an interference spectrum;

[0124] S304, the spectrometer collects the interference spectrum and transmits the data to the data acquisition and control circuit module through the data acquisition and control circuit module;

[0125] S305 , the data acquisition and control circuit module demodulates the change in the FP cavity length using a white light interference signal demodulation algorithm, and obtains the acetylene concentration after calibration. Example

[0126] Based on Example 1, an application of an acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam in comprehensive monitoring of transformer body faults includes the following steps:

[0127] S401, preparing a π-shaped composite cantilever beam, and combining one end of the cantilever beam with a single-mode optical fiber to form an FP cavity;

[0128] S402, introducing the gas to be measured into the photoacoustic cell through the gas inlet of the photoacoustic cell, and irradiating the gas to be measured using a semiconductor laser with a central wavelength of 1530 nm and a power of 100 mW as an excitation light source;

[0129] The S403 and SLED detection light sources emit a broad spectrum light with an output power of 10mW, which enters the FP cavity through a fiber circulator. When acetylene absorbs the specific wavelength of the excitation light source and generates a pressure wave that acts on the cantilever beam, causing the FP cavity length to change, an interference spectrum carrying information about the cavity length change is generated.

[0130] S404, a spectrometer collects interference spectra;

[0131] S405, the data acquisition and control circuit module controls the operation of the spectrometer and transmits the collected data to the data analysis and computer module;

[0132] S406, the data analysis and computer module demodulates the FP cavity length change through the white light interference signal demodulation algorithm, obtains the acetylene concentration after calibration, and realizes the comprehensive monitoring of the transformer body fault.

[0133] The above disclosures are only a few specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. An acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam, characterized in that: include: The photoacoustic cell is provided with an air inlet and an air outlet for the inlet and outlet of the gas to be measured; A π-shaped cantilever beam is placed in the photoacoustic cell, one end of which is fixed and the other end is combined with a single-mode optical fiber to form an FP cavity; A semiconductor laser is used to irradiate the gas to be measured entering the photoacoustic cell; The SLED detection light source tube is a broadband light source, which is used to couple the emitted broadband light into the FP cavity through a single-mode optical fiber and a fiber circulator to generate an interference spectrum. A spectrometer for collecting interference spectra; The data acquisition and control circuit module is used to transmit the interference spectrum data collected by the spectrometer to the data analysis and computer module; Data analysis and computer module, used to analyze the change in FP cavity length and obtain the acetylene concentration after calibration; The π-shaped cantilever beam is a π-shaped composite material cantilever beam, which is made of carbon fiber and epoxy resin composite material; Wherein, the volume fraction of the carbon fiber is 60%-70%, and the volume fraction of the epoxy resin is 30%-40%; The preparation method of the π-shaped composite cantilever beam is as follows: Carbon fiber and epoxy resin are selected as raw materials, with the volume fraction of carbon fiber controlled at 60%-70% and the volume fraction of epoxy resin controlled at 30%-40%; Mix the carbon fiber and epoxy resin raw materials evenly; The compression molding process is used to solidify the carbon fiber and epoxy resin mixed evenly in the mold under the preset temperature and pressure. The π-shaped composite cantilever beam has a beam length L1 of 1 mm, a beam width W1 of 0.5 mm, a π-shaped head width W2 of 1.5 mm, a length L2 of 4 mm, and a thickness t of 0.2 mm.

2. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 1, characterized in that: The π-shaped composite material cantilever beam is combined with the single-mode optical fiber via an optical fiber ceramic sleeve to form the FP cavity.

3. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 1, characterized in that: The π-shaped cantilever beam works in a dynamic mode, and its cantilever beam resonant frequency f is: Where: λ is the wavelength; E is the Young's modulus; t is the cantilever beam thickness; ρ is the density; L is the cantilever beam head length.

4. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 1, characterized in that: The semiconductor laser has a central wavelength of 1532.83 nm and a power of 100 mW; Wherein, the output power of the SLED detection light source tube is 10mW.

5. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 1, characterized in that: The optical fiber circulator is used to transmit the broadband light of the superluminescent diode through the FP cavity formed by the single-mode optical fiber and the π-shaped composite material cantilever beam, and transmit the interference light output by the FP cavity to the spectrometer.

6. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 1, characterized in that: The data acquisition and control circuit module includes a control circuit, and the data analysis and computer module includes a computer; The control circuit module is used to control the working state of the spectrometer and transmit the collected interference spectrum data to the computer; The computer demodulates the cavity length change of the FP cavity in the interference spectrum through a white light interference signal demodulation algorithm.

7. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 6, characterized in that: The data acquisition and control circuit module also includes a microcontroller and a data acquisition chip, and the microcontroller is responsible for controlling the working parameters of the spectrometer; The data acquisition chip is used to convert the analog signal output by the spectrometer into a digital signal and transmit the data to the computer through a data transmission interface.

8. The acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam according to claim 7, characterized in that: The computer and white light interference signal demodulation algorithm also includes: Data analysis software is set up in the computer. The data analysis software integrates a white light interference signal demodulation algorithm to process the collected interference spectrum data and calculate the concentration of acetylene gas. The calculation process is as follows: Acetylene gas is excited in the photoacoustic cell by a semiconductor laser. Acetylene absorbs light energy and converts it into heat. By modulating the semiconductor laser to generate periodic light energy, the periodic heat generation generates pressure waves caused by thermal expansion and contraction. The specific formula is as follows: Where: P PA is the photoacoustic pressure; is the gas adiabatic index; C is the acetylene gas concentration in the photoacoustic cell; P0 is the incident light power of the semiconductor laser; α is the acetylene gas absorption coefficient; is the optical path length in the photoacoustic cell; v is the volume of the photoacoustic cell; Modulate the angular frequency of the laser; is the gas damping time; The photoacoustic pressure drives the cantilever beam to deflect, causing the FP cavity length to change. The specific formula is as follows: Where: ΔL is the change in the FP cavity length; A is the cross-sectional area of ​​the cantilever beam; E is the elastic modulus of the cantilever beam material; t is the thickness of the cantilever beam. When the gas concentration in the photoacoustic cell changes, the deformation of the cantilever beam changes, which in turn causes the cavity length to change. The change in cavity length causes the phase of the interference spectrum to shift, which can be expressed by the following specific formula: Where: is the interference phase change; is the initial phase; n is the refractive index of the medium in the cavity; L0 is the initial cavity length; is the laser center wavelength; is the SLED interference light intensity; is the incident light intensity of SLED; r1, r2 are the reflectivity of the front and rear mirrors of FP cavity; After obtaining the spectral signal using a spectrometer, the interference spectrum is Fourier transformed to obtain the frequency characteristic signal; By combining the above formulas, the relationship between the phase and the acetylene gas concentration C can be obtained: 。 9. An application of the acetylene fiber photoacoustic detection system based on a π-shaped cantilever beam as claimed in claim 1 in comprehensive monitoring of transformer body faults, characterized in that: The steps include: A π-shaped composite cantilever beam was prepared, and one end of the cantilever beam was combined with a single-mode optical fiber to form an FP cavity. The gas to be measured is introduced into the photoacoustic cell through the gas inlet of the photoacoustic cell, and a semiconductor laser is used as an excitation light source to irradiate the gas to be measured; The SLED detection light source tube emits a broad spectrum of light, which enters the FP cavity through a fiber circulator. When acetylene absorbs the specific wavelength of the excitation light source and generates a pressure wave that acts on the cantilever beam, causing the FP cavity length to change, an interference spectrum carrying information about the cavity length change is generated. The spectrometer collects interference spectra; The data acquisition and control circuit module controls the operation of the spectrometer and transmits the collected data to the data analysis and computer module; The data analysis and computer module demodulates the FP cavity length change through the white light interference signal demodulation algorithm, and obtains the acetylene concentration after calibration, thereby realizing comprehensive monitoring of transformer body faults.

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