A SF6 gas sensing and detecting system and method based on a CO2 laser hollow core fiber

Abstract

The application relates to an SF6 gas sensing and detecting system and method based on a CO2 laser hollow-core optical fiber, which comprises a CO2 laser, a coupling joint, a flexible hollow-core optical fiber, an outlet connecting piece, a power detector and a computer. Light emitted by the CO2 laser enters a flexible hollow-core optical fiber gas chamber through the coupling joint and is absorbed by the to-be-detected gas, and an output light signal after absorption is output. The power detector receives the output light signal at an output port of the outlet connecting piece and converts the output light signal into an electric signal for real-time detection. The application has the advantages that CO2 laser is used as a light source, gas concentration is directly reflected by measuring optical fiber output power, operation is easy, data processing is simple, limit detection concentration is low, gas response time is short, miniaturization is realized, the optical fiber gas chamber is easy to couple and manufacture, and the like, and the application can be used for qualitative and quantitative analysis and detection of trace SF6 gas.

Description

Technical Field

[0001] This invention relates to the field of gas sensing technology, and in particular to an SF6 gas detection system and method based on CO2 laser hollow fiber. Background Technology

[0002] SF6 gas has excellent insulating properties and is often used to insulate high-voltage power equipment. However, SF6 gas strongly absorbs infrared radiation energy, leading to an increase in ambient temperature. It is one of the six major greenhouse gases. Therefore, while widely using SF6, it is even more important to prevent SF6 gas leaks and accurately detect even trace leaks to prevent potential problems.

[0003] Currently, commonly used methods for SF6 gas detection include gas chromatography, infrared imaging, photoacoustic spectroscopy, and infrared absorption spectroscopy. In recent years, SF6 gas detection technology has indeed made significant progress. SF6 gas exhibits strong characteristic absorption in the mid-infrared region at a wavelength of 10.6 μm, with very little cross-reactivity with the absorption wavelengths of most other gases, thus infrared spectroscopy has received widespread attention. However, developing an SF6 sensing system that is simple in structure, easy to operate, and has high sensing performance still faces considerable challenges. Summary of the Invention

[0004] The purpose of this invention is to provide an SF6 gas sensing and detection system based on CO2 laser hollow fiber. Its advantages include ease of operation, simple data processing, low detection limit concentration, short gas response time, miniaturization, easy coupling of the fiber optic gas cell, and low manufacturing cost. It directly reflects the gas concentration through output power, enabling qualitative and quantitative analysis and detection of SF6 gas.

[0005] The specific technical solution for achieving the objective of this invention is as follows:

[0006] An SF6 gas sensing and detection system based on CO2 laser hollow fiber uses a CO2 laser as the light source and a flexible hollow fiber as the laser transmission channel and gas chamber for SF6 gas concentration sensing and detection. The system includes: a CO2 laser, a coupling connector, a flexible hollow fiber, an outlet connector, a power detector, a gas bag, a gas pump, and a computer. The coupling connector includes an inlet connector and a sleeve, connecting the gas path and the optical path. The inlet connector is a three-way structure, fitted with a sleeve to adjust the focus. One horizontal end of the inlet connector is connected to the CO2 laser, and the other... One end is connected to a flexible hollow optical fiber, and the other end is connected to a gas pump. The outlet connector is a three-way structure, with one horizontal end connected to the flexible hollow optical fiber and the other end aligned with a power detector, and the other vertical end connected to a gas bag to discharge gas. The gas bag is connected to the gas pump. The power detector and CO2 laser are connected to a computer. The flexible hollow optical fiber is used for optical path transmission and as a gas detection chamber. The power detector is used to receive the light signal absorbed by the gas to be tested and convert it into an electrical signal. The computer is used to control the laser and record real-time gas detection data.

[0007] A focusing lens is added inside the sleeve of the coupling connector, and the light inlet window of the inlet connector is sealed by a sealing ring.

[0008] The output connector is horizontally aligned with the light outlet of the power detector, which is equipped with a window and sealed by a sealing ring, and is directly aligned with the power detector for detection.

[0009] The focusing lens and window are made of ZnSe, Ge, ZnS, NaCl, or KBr.

[0010] The flexible hollow-core optical fiber has a hollow structure, which includes a plastic tube, a glass tube, and a metal tube. The inner surface of the structural tube is coated with a metal layer, which includes a high-reflectivity Ag, Cu, Au, Ni, or Zn coating. The inner surface of the structural tube also has a metal compound dielectric layer for adjusting the low-loss transmission window, which includes GeO2, AgI, CaF2, or Ge. The flexible hollow-core optical fiber can be bent and integrated on a substrate. The optical fiber is wrapped and protected by an outer tube, and interfaces are installed at the optical fiber inlet and outlet for easy connection between the two ends.

[0011] The plastic tube includes polypropylene, polyetheretherketone, polyimide, ABS plastic, or polycarbonate tube; the interface includes SMA connector, FC connector, TA connector, or TB connector.

[0012] The CO2 laser selected is a CO2 laser capable of outputting wavelengths corresponding to the characteristic absorption peaks of SF6.

[0013] A method for detecting SF6 gas concentration based on the above system, the method comprising the following specific steps:

[0014] Step 1: The gas to be tested is pumped into the flexible hollow fiber gas cell through the inlet connector of the coupling connector using an air pump, and then discharged through the outlet connector.

[0015] Step 2: The light emitted by the CO2 laser enters the flexible hollow fiber gas cell through the coupling connector and is absorbed by the gas to be tested, and the absorbed light signal is output.

[0016] Step 3: The power detector converts the absorbed optical signal into a corresponding electrical signal;

[0017] Step 4: The computer receives the electrical signal output from the power detector and then calculates the concentration of SF6 to be measured; specifically:

[0018] An inert single background gas is introduced into the hollow fiber optic chamber. Then, a set of standard SF6 gases is introduced into the flexible hollow fiber optic chamber through the inlet connector. The standard SF6 gases contain known concentrations, and a relationship between standard concentration and absorbance is established. When detecting SF6 to be tested, the SF6 gas to be tested is pumped into the flexible hollow fiber optic chamber. The absorption power of the gas to be tested is recorded by a computer and compared with the established relationship between standard concentration and absorbance to obtain the concentration of the detected SF6 gas.

[0019] The advantages of this invention include low detection limit concentration, short gas response time, miniaturization, easy coupling of the fiber optic gas cell, and low manufacturing cost. It enables qualitative and quantitative analysis and detection of SF6 gas. The gas concentration can be directly reflected by the output power, and the operation is simple, making it suitable for industrial online detection. Attached Figure Description

[0020] Figure 1 This is an overall structural diagram of the gas detection system provided by the present invention;

[0021] Figure 2 A schematic diagram of the longitudinal section of the coupling joint provided by the present invention;

[0022] Figure 3 This is a schematic diagram of an integrated hollow fiber optic substrate provided by the present invention. Implementation

[0023] To make the objectives, technical solutions, and key points of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0024] See Figure 1 and Figure 3This embodiment of the SF6 gas sensing and detection system based on CO2 laser hollow fiber includes: a coupling connector 1, a CO2 laser 2, a flexible hollow fiber 3, an outlet connector 4, a power detector 5, a gas bag 6, a gas pump 7, and a computer 8. The coupling connector 1 is used for coupling the CO2 laser 2 with the flexible hollow fiber 3 and for pumping in the sulfur hexafluoride (SF6) gas to be measured. The outlet connector 4 is connected to the flexible hollow fiber 3 at one end, allowing the laser to pass through while preventing gas leakage. The horizontal end of the outlet connector 4 is aligned with the power detector 5, and the vertical end is connected to the gas bag 6 to discharge the gas. The flexible hollow fiber 3 serves as the transmission channel for the optical path and the gas detection chamber, and is integrated into a substrate 9 for miniaturization. The power detector 5 is used to receive the optical signal absorbed by the gas to be measured and convert it into an electrical signal. The computer 8 is used to control the CO2 laser 2 and record real-time gas detection data. The coupling connector includes an inlet connector and a sleeve, connecting the gas path and the optical path. The inlet connector is a three-way structure, fitted with a sleeve to adjust the focus. One horizontal end of the inlet connector is connected to the CO2 laser, and the other end is connected to the flexible hollow optical fiber. The vertical end is connected to the gas pump.

[0025] See Figure 2 The coupling connector 1 includes an inlet connector 102 and a sleeve 107. A lens 106 is added inside the sleeve 107. The CO2 laser 2 is connected to the sleeve 107 by a front adapter block 105. The beginning of the inlet connector 102 is equipped with a window 101 and sealed by a sealing ring. The inlet connector 102 can be adjusted to find the focal length. The position of the inlet connector 102 inside the sleeve 107 is fixed by an external positioning stud 104. The end of the inlet connector 102 is an SMA threaded interface 103, which is convenient for connecting the flexible hollow fiber 3 air chamber.

[0026] Preferably, both the window 101 and the lens 106 are made of ZnSe material that can transmit laser light with a wavelength of 10.6 μm.

[0027] Optionally, the end of the outlet connector 4 is fitted with a window 101 of the same specification and sealed by a sealing ring, and the position is supported and adjusted by a support clamp to ensure that the output end of the outlet connector 4 is parallel to the signal receiving plane of the power detector 5.

[0028] Preferably, the flexible hollow optical fiber 3 has a hollow structure and can be bent and integrated on a substrate 9 with a specific shape. Figure 3 As shown, the inner wall of the hollow fiber is coated with a reflective film layer and a dielectric layer. The fiber can be protected by being wrapped in an armored tube. SMA interfaces 103 are installed at the fiber inlet and outlet, which facilitates the connection of both ends to the inlet connector 102 and the outlet connector 4, respectively.

[0029] Optionally, the power detector 5 can receive laser signals and convert them into electrical signals for output, and connect to the computer 8 for real-time continuous monitoring.

[0030] Preferably, the CO2 laser 2 is a CO2 laser that can output a wavelength of 10.6 μm corresponding to the characteristic absorption peak of SF6.

[0031] Preferably, the computer 8 is connected to the CO2 laser 2 and the power detector 5, which facilitates the control of laser output and the real-time detection, recording and concentration value conversion of optical signals. Example 2

[0032] See Figure 1 and Figure 2 This embodiment of the SF6 gas sensing and detection method based on the flexible hollow-core optical fiber of the system of Embodiment 1 specifically includes:

[0033] S1: Based on Beer-Lambert law, that is, using the relationship between the strength of gas absorption of characteristic wavelength light and the concentration of light-absorbing substance, the gas to be tested is first introduced into the flexible hollow optical fiber 3 gas chamber through the inlet connector 102 by the air pump 7, and then discharged through the outlet connector 4.

[0034] S2: The light emitted by CO2 laser 2 passes through the flexible hollow fiber 3 gas chamber and is absorbed by the gas to be tested, thus obtaining the absorbed light signal.

[0035] S3: Power detector 5 converts the absorbed optical signal into a corresponding electrical signal;

[0036] S4: Signal processing. The computer 8 receives the electrical signal output by the power detector 5 and then calculates the concentration of the gas to be measured.

[0037] Specifically, step S4 includes: introducing an inert gas such as nitrogen or argon into the flexible hollow fiber 3 gas chamber as a single background gas; then introducing a set of standard SF6 gases into the flexible hollow fiber 3 gas chamber through the inlet connector 102, wherein the set of standard SF6 gases contains a known concentration; activating the gas detection system, using the computer 8 to record the standard absorption power parameters of the background gas and the set of standard SF6 gases, and calculating and converting the correspondence between standard concentration and absorbance to obtain a standard absorption power versus concentration relationship spectrum; when detecting the SF6 to be tested, the SF6 gas to be tested, loaded into the dual-valve gas bag 6, is pumped into the gas chamber through the gas pump 7, and then flows out of the outlet connector 4 back to the gas bag 6, forming a closed and environmentally friendly test environment; then the computer 8 records the absorption power of the gas to be tested and compares it with the established relationship between standard concentration and absorbance to obtain the concentration of the detected SF6 gas.

[0038] This embodiment has advantages such as low detection limit concentration, short gas response time, miniaturization capability, easy coupling of fiber optic gas cells, and low manufacturing cost, enabling qualitative and quantitative analysis and detection of SF6 gas. Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0039] This invention is applicable to the field of hollow fiber gas sensing.

Claims

1. An SF6 gas sensing and detection system based on CO2 laser hollow fiber, using a CO2 laser as the light source and a flexible hollow fiber as the laser transmission channel and gas chamber, for sensing and detecting SF6 gas concentration, characterized in that... The system includes: a CO2 laser, a coupling connector, a flexible hollow fiber, an outlet connector, a power detector, a gas bag, a gas pump, and a computer. The coupling connector includes an inlet connector and a sleeve, connecting the gas path and the optical path. The inlet connector is a T-junction structure with a sleeve fitted on its outer side for adjusting the focus. One horizontal end of the inlet connector connects to the CO2 laser, the other to the flexible hollow fiber, and the vertical end connects to the gas pump. The outlet connector is also a T-junction structure, with one horizontal end connected to the flexible hollow fiber, the other aligned with the power detector, and the vertical end connected to the gas bag to discharge gas. The gas bag is connected to the gas pump. The power detector and the CO2 laser are respectively connected to the computer. The flexible hollow fiber is used for optical transmission and serves as a gas detection chamber. The power detector receives the light signal absorbed by the gas being tested and converts it into an electrical signal. The computer controls the laser and records real-time gas detection data. A focusing lens is added inside the sleeve of the coupling connector, and the light inlet window of the inlet connector is sealed by a sealing ring. The output connector is horizontally aligned with the light outlet of the power detector, which is equipped with a window and sealed by a sealing ring. The light outlet is directly aligned with the power detector for detection. The flexible hollow-core optical fiber has a hollow structure tube, which includes a plastic tube, a glass tube, and a metal tube. The inner surface of the structural tube is provided with a metal coating, which includes a high-reflectivity Ag, Cu, Au, Ni, or Zn coating. The inner surface of the structural tube also has a metal compound dielectric layer for adjusting the low-loss transmission window, which includes GeO2, AgI, CaF2, or Ge. The flexible hollow-core optical fiber can be bent and integrated on a substrate. The optical fiber is wrapped and protected by an outer tube, and interfaces are installed at the optical fiber inlet and outlet for easy connection between the two ends. The CO2 laser selected is a CO2 laser capable of outputting wavelengths corresponding to the characteristic absorption peaks of SF6.

2. The system of claim 1, wherein, The focusing lens and window are made of ZnSe, Ge, ZnS, NaCl, or KBr.

3. The system of claim 1, wherein, The plastic tube includes polypropylene, polyetheretherketone, polyimide, ABS plastic, or polycarbonate tube; the interface includes SMA connector, FC connector, TA connector, or TB connector.

4. A method for detecting SF6 gas concentration based on the system of claim 1, characterized in that, The method includes the following specific steps: Step 1: The gas to be tested is pumped into the flexible hollow fiber gas cell through the inlet connector of the coupling connector using an air pump, and then discharged through the outlet connector. Step 2: The light emitted by the CO2 laser enters the flexible hollow fiber gas cell through the coupling connector and is absorbed by the gas to be tested, and the absorbed light signal is output. Step 3: The power detector converts the absorbed optical signal into a corresponding electrical signal; Step 4: The computer receives the electrical signal output from the power detector and then calculates the concentration of SF6 to be measured; specifically: A single inert background gas is introduced into the hollow fiber optic chamber. Then, a set of standard SF6 gases with known concentrations are introduced into the flexible hollow fiber optic chamber through the inlet connector. A relationship between the standard concentration and absorbance is established. When testing the SF6 to be tested, the SF6 gas to be tested is pumped into the flexible hollow fiber optic chamber. The absorption power of the gas to be tested is recorded by a computer and compared with the established relationship between the standard concentration and absorbance to obtain the concentration of the SF6 gas to be tested.

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