Extraction type full-wave-band multi-component gas detection system and method

Abstract

The invention provides an extraction type full-wave-band multi-component gas detection system and method. The extraction type full-wave-band multi-component gas detection system comprises an upper computer, a lock-in amplifier, a detector, a gas pool, an optical fiber beam combiner, an intermediate infrared measuring device and a near infrared measuring device, wherein the intermediate infrared measuring device and the near infrared measuring device are respectively connected with the lock-in amplifier and the optical fiber beam combiner; the mid-infrared measuring device comprises a mid-infrared laser driver, a spatial light-optical fiber coupling mechanism connected with the first laser driver, and a sealing device for preventing an exposed spatial light path from being influenced by air components. By adopting the extraction type full-wave band detection technology, the problems of light beam transmission and coupling in the prior art are solved, simultaneous detection of hydrogen sulfide and carbon monoxide multi-component gas is realized, and the detection efficiency and accuracy are remarkably improved. By optimizing the structural design of the detection system, the detection wave band range is expanded, the detection flexibility is improved, and the interference of air components on measurement is avoided, so that the detection sensitivity is improved, and errors are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, in particular to an extractive full-band multi-component gas detection system and method. Background Art

[0002] SF6 (sulfur hexafluoride), as an excellent insulating medium, is widely used in high-voltage electrical equipment, such as GIS (gas-insulated switchgear) and transformers. However, when SF6 insulation equipment experiences faults such as partial discharge, overheating, or arcing, SF6 molecules decompose and react with moisture and oxygen in the environment to produce a variety of decomposition products. National standards have clearly stipulated the need for real-time monitoring of decomposition products in SF6 gas-insulated electrical equipment, such as SO2, H2S, CF4, and CO, to determine the equipment's operating status. Among the many SF6 decomposition products, H2S (hydrogen sulfide) is a toxic gas, and changes in its concentration can serve as a key diagnostic indicator for SF6 insulation equipment faults. For example, a low concentration of sulfur-containing decomposition products and an abnormally high CO concentration may indicate a low-temperature overheating fault in the equipment; the presence of H2S is often associated with a discharge fault. Therefore, gas monitoring of H2S and CO is necessary.

[0003] Traditional detection methods such as electrochemical sensors and conventional infrared spectroscopy, while suitable in certain scenarios, face challenges in detecting SF6 decomposition products: insufficient sensitivity to capture low-concentration H2S, limited selectivity to distinguish H2S in complex gas mixtures, and long response times that prevent real-time monitoring. Therefore, H2S detection methods based on mid-infrared laser technology have become the preferred option. Mid-infrared laser technology has attracted considerable attention in recent years due to its superior sensitivity and selectivity. Despite this, current technology still faces challenges in using mid-infrared lasers for low-concentration and high-precision H2S measurement. First, spatial optical transmission is susceptible to interference from environmental factors, while fiber optic transmission in the mid-infrared band is limited by the development of single-mode fiber technology. Second, the adsorption properties of hydrogen sulfide significantly affect detection sensitivity. Hydrogen sulfide molecules tend to adsorb on material surfaces, reducing the amount of detectable gas in the optical path, leading to signal attenuation and errors. In particular, adsorption issues within the gas cell significantly interfere with detection sensitivity. Finally, current mid-infrared laser technology for H2S detection has limited the simultaneous detection of other gas components. Summary of the Invention

[0004] One of the purposes of the present invention is to provide an extractive full-band multi-component gas detection system to solve the problem that existing detection devices cannot achieve full-band multi-component gas detection.

[0005] The present invention is implemented as follows: an extractive full-band multi-component gas detection system includes: a host computer, a phase-locked amplifier, a detector, a gas pool with a function of extracting the gas to be measured, and a fiber optic combiner connected in sequence; also includes a mid-infrared measurement device and a near-infrared measurement device connected to the phase-locked amplifier and the fiber optic combiner, respectively; the mid-infrared measurement device includes a mid-infrared laser driver and a spatial light-fiber coupling mechanism connected to the mid-infrared laser; the near-infrared measurement device includes a near-infrared laser driver and a near-infrared laser driven by the near-infrared laser driver.

[0006] Furthermore, one of the objectives of the present invention can be achieved by the following technical solution:

[0007] The spatial light-fiber coupling mechanism includes a mid-infrared laser driven by a mid-infrared laser driver, a coupling lens for absorbing laser light emitted by the mid-infrared laser, and a single-mode optical fiber connected to the coupling lens and transmitting optical information.

[0008] The spatial light-fiber coupling mechanism is arranged in a sealing device capable of evacuating a vacuum.

[0009] The mid-infrared laser is a laser emitting light at 2.5 to 10 μm, and the near-infrared laser is a laser emitting light at 0.76 to 2.5 μm.

[0010] The mid-infrared laser is a laser emitting at 2.639 μm, and the near-infrared laser is a laser emitting at 2.334 μm.

[0011] The gas pool and the optical fiber combiner, the near-infrared measurement device and the optical fiber combiner, and the mid-infrared measurement device and the optical fiber combiner are all connected through single-mode optical fibers; the host computer and the phase-locked amplifier, the phase-locked amplifier and the detector, the phase-locked amplifier and the mid-infrared laser driver, and the phase-locked amplifier and the near-infrared laser driver are all electrically connected.

[0012] The optical path of the gas pool is 0.1 to 100 m, and the gas pool is connected to an air pump for extracting the gas to be measured.

[0013] The second purpose of the present invention is to provide an extractive full-band multi-component gas detection method to solve the problem that existing detection methods cannot achieve full-band multi-component gas detection.

[0014] The second object of the present invention is achieved as follows: an extractive full-band multi-component gas detection method, applied to the above-mentioned extractive full-band multi-component gas detection system, comprises the following steps:

[0015] S1: The host computer controls the lock-in amplifier using LabVIEW to set the driving signal to a low-frequency sawtooth superimposed high-frequency sine signal, and inputs it to the first laser driving circuit and the second laser driving circuit respectively;

[0016] S2: The mid-infrared laser driver converts the received signal into a current signal, then drives the mid-infrared laser to emit a 2.639μm wavelength laser, which is then transmitted to the fiber combiner through a coupling lens and a single-mode fiber. At the same time, the near-infrared laser driver converts the received signal into a current signal, then drives the near-infrared laser to emit a corresponding 2.334μm wavelength laser, which is then transmitted to the fiber combiner through a single-mode fiber.

[0017] S3: The fiber combiner combines the two laser beams into one optical signal, which enters the gas pool containing the gas to be detected and is then transmitted to the detector.

[0018] S4: The detector converts the optical signal into an electrical signal, which is input into a phase-locked amplifier for demodulation. The demodulated signal is input into the host computer for signal processing and concentration inversion through LabVIEW to obtain the concentrations of hydrogen sulfide and carbon monoxide.

[0019] Before step S1, the gas pool is purged with high-purity nitrogen, and the host computer controls the mid-infrared laser driver through a phase-locked amplifier to control the temperature of the mid-infrared laser, and controls the temperature at 45°C; the host computer controls the near-infrared laser driver through a phase-locked amplifier to control the temperature of the near-infrared laser, and controls the temperature at 15°C.

[0020] In step S1 , the driving signal of the mid-infrared laser driver is a sawtooth scanning range of 79-119 mA superimposed on a 24 mA sine wave, and the driving signal of the near-infrared laser driver is a sawtooth scanning range of 80-155 mA superimposed on a 29 mA sine wave.

[0021] This invention utilizes extractive full-band detection technology, overcoming the existing challenges of beam transmission and coupling. It achieves simultaneous detection of hydrogen sulfide and carbon monoxide, significantly improving detection efficiency and accuracy. By optimizing the structural design of the detection system, it reduces gas adsorption and loss during the detection process, thereby increasing detection sensitivity and reducing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0024] Example 1

[0025] An extractive full-band multi-component gas detection system, such as Figure 1 As shown, the system includes a host computer, a lock-in amplifier, a detector, a gas cell with a function for extracting the gas to be measured, and a fiber combiner, which are connected in sequence. It also includes a mid-infrared measurement device and a near-infrared measurement device, which are connected to the lock-in amplifier and the fiber combiner, respectively. The mid-infrared measurement device includes a mid-infrared laser driver and a spatial light-to-fiber coupling mechanism connected to the mid-infrared laser driver. The near-infrared measurement device includes a near-infrared laser driver, a near-infrared laser, and a single-mode fiber connected to the fiber combiner. The detector is fixed to the gas cell or connected to the gas cell via a single-mode fiber. Single-mode fibers connect the detector and the gas cell, the gas cell and the fiber combiner, the near-infrared measurement device and the fiber combiner, and the mid-infrared measurement device and the fiber combiner. Electrical connections are made between the host computer and the lock-in amplifier, between the lock-in amplifier and the detector, between the lock-in amplifier and the mid-infrared laser driver, and between the lock-in amplifier and the near-infrared laser driver.

[0026] The host computer is responsible for overall system control, data processing, and display. It sends control commands and receives back-end detection data, enabling real-time analysis and storage of hydrogen sulfide and carbon monoxide concentrations. The detector detects the laser signal after it passes through the gas cell and converts the optical signal into an electrical signal. Because the signal change caused by absorption is relatively weak, a lock-in amplifier is used to amplify the weak signal and improve the signal-to-noise ratio. The demodulated signal is then fed to the host computer. Finally, the host computer performs data acquisition and concentration calculation. Specifically, the host computer receives and processes the detection signal, calculates the H2S concentration in real time, stores and graphically displays the collected data, and generates instant alarms based on preset alarm thresholds. This enables comprehensive monitoring of the operating status and fault warnings of SF6 insulation equipment.

[0027] The spatial light-to-fiber coupling mechanism consists of a mid-infrared laser, a coupling lens that receives the laser light, and a single-mode fiber connected to the coupling lens and transmitting the optical information. The 2.639μm mid-infrared laser is securely mounted on the spatial light-to-fiber coupling mechanism via a cage structure. This structure not only ensures stable laser output but also effectively prevents external vibrations from interfering with the optical path. The spatial light output of the mid-infrared laser is collimated and focused before being efficiently coupled into the single-mode fiber. The relative positions of the collimation and coupling lenses in the spatial light-to-fiber coupling mechanism are adjusted to achieve optimal light energy coupling into the single-mode fiber. The spatial light-to-fiber coupling mechanism utilizes a Sorebo KT120 / M, with two cage systems on either side. Each cage system consists of four precision-ground stainless steel guide rods (6mm diameter) forming a spatial constraint frame. The laser output of the mid-infrared laser and the fiber input are locked at the confocal planes on either side of the coupling lens, achieving three-point coaxiality through geometric optical conjugation. The system also integrates a quick-release fiber optic interface, enabling rapid switching between multimode and single-mode fibers. The precision adjustment part uses ST1XY-D / M and SM1ZA to perform high-precision submicron adjustment on the X, Y and Z axes respectively, and can be locked by snaps for coarse / fine adjustment conversion.

[0028] The optical path of the gas pool can be selected in the range of 0.1 to 100m, and the most preferred one in this embodiment is 29m, which has good sealing performance and uniform airflow distribution. The gas pool is connected to an air pump for extracting the gas to be tested, and the air pump is connected to a sampling pipeline to ensure that the sampling device can be directly connected to the SF6 insulating equipment, and the fault decomposition products (hydrogen sulfide and carbon monoxide) in the SF6 insulating equipment are extracted into the gas pool. The gas pool is designed with an inlet pipeline and a filter device to ensure the purity of the extracted gas, and is closely connected with the subsequent gas pool to achieve continuous and stable gas delivery. The output end of the single-mode optical fiber is precisely fixed to the gas pool inlet, and the detector fixture is correctly installed at the gas pool outlet to ensure that the laser is output after a stable long optical path in the gas pool. The single-mode optical fiber introduces the laser into the long optical path gas pool of about 29m. The long optical path design enhances the optical interaction between the laser and H2S, and improves the detection sensitivity.

[0029] The spatial light-fiber coupling mechanism is set in a sealing device that can draw a vacuum. In the process of coupling mid-infrared spatial light to the optical fiber, due to the existence of a local free space optical path, environmental moisture such as water vapor may interfere with the spectral detection. In order to avoid the free space part being interfered with by moisture during the coupling process, ensure that the sealing device maintains a low-pressure environment during long-term use, and improve the stability and accuracy of the measurement, a sealing device is designed. Its main function is to form a local closed space in the coupling area and reduce the internal pressure to 0.005atm by vacuuming, significantly reducing the interference of water molecules, thereby ensuring the purity of the detection signal. The cavity of the sealing device has the following interfaces and functions: KF25 flange interface: used to connect the vacuum pump group to evacuate the closed cavity until the pressure in the cavity drops to about 0.005atm, effectively suppressing water vapor and other interferences from entering the optical path. The KF40 flange interface is used to expand or connect other optical fiber coupling parts to ensure the continuity and stability of beam transmission; the seven-pin aviation plug provides a reliable connection for the laser's driving power supply and temperature control module, ensuring the stability of the laser's operating parameters; the mechanical pressure gauge is integrated into the top of the sealed cavity and displays the internal vacuum degree in real time, allowing operators to monitor and adjust the vacuum state.

[0030] The mid-infrared laser is a laser that emits light at 2.5 to 10 μm, and the near-infrared laser is a laser that emits light at 0.76 to 2.5 μm. More preferably, the mid-infrared laser emits a laser with a wavelength of 2.639 μm, and the near-infrared laser emits a laser with a wavelength of 2.334 μm. According to the detection of the present invention, the 2.639 μm laser covers the absorption line of H2S, which is more than 10 times stronger than the near-infrared laser, and avoids interference from other components to the greatest extent. The 2.334 μm laser covers the strong absorption line of CO and effectively avoids interference from other components of the gas in the measured environment, which is conducive to achieving highly sensitive and accurate detection.

[0031] The mid-infrared laser driver is equipped with a mid-infrared temperature controller, and the near-infrared laser driver is equipped with a near-infrared temperature controller. The host computer controls the mid-infrared temperature controller connected to the mid-infrared laser driver through a lock-in amplifier to control the temperature of the mid-infrared laser, keeping it at 40-50°C, with an optimal temperature of 45°C. The host computer controls the near-infrared temperature controller connected to the near-infrared laser driver through a lock-in amplifier to control the temperature of the near-infrared laser, keeping it at 10-20°C, with an optimal temperature of 15°C.

[0032] Example 2

[0033] An extractive full-band multi-component gas detection method, applied to the extractive full-band multi-component gas detection system in the above-mentioned embodiment 1, comprises the following steps:

[0034] The gas cell is purged with high-purity nitrogen, including gas filtration and flow control, to ensure that the sample entering the gas cell is pure and at an appropriate flow rate to facilitate subsequent absorption measurements. The host computer controls the temperature of the mid-infrared laser at 45°C by controlling the mid-infrared temperature controller connected to the mid-infrared laser driver via a lock-in amplifier. The host computer also controls the temperature of the near-infrared laser at 15°C by controlling the near-infrared temperature controller connected to the near-infrared laser driver via a lock-in amplifier.

[0035] The lock-in amplifier is controlled by the host computer and LabVIEW program is used to set the driving signal to a low-frequency sawtooth superimposed high-frequency sine signal, and the signals are input to the first laser driving circuit and the second laser driving circuit respectively;

[0036] The mid-infrared laser driver converts the received signal into a current signal, then drives the mid-infrared laser to emit a 2.639μm wavelength laser, which is then transmitted to the fiber combiner through a coupling lens and a single-mode optical fiber. At the same time, the near-infrared laser driver converts the received signal into a current signal, then drives the near-infrared laser to emit a corresponding 2.334μm wavelength laser, which is then transmitted to the fiber combiner through a single-mode optical fiber.

[0037] The mid-infrared laser driver stably drives the mid-infrared ICL laser, ensuring continuous and stable output at the target wavelength (2.639μm) by controlling the operating current and temperature. The near-infrared laser driver stably drives the near-infrared laser, ensuring continuous and stable output at the target wavelength (2.334μm) by controlling the operating current and temperature. The drive signal for the mid-infrared laser driver is a 24mA sine wave with a sawtooth scan range of 79-119mA. The drive signal for the near-infrared laser driver is a 29mA sine wave with a sawtooth scan range of 80-155mA.

[0038] After the fiber optic combiner combines the two lasers into one optical signal, it enters the gas pool containing the gas to be detected and is then transmitted to the detector; the detector converts the optical signal into an electrical signal, inputs it into a phase-locked amplifier for demodulation, and then inputs the demodulated signal into the host computer for signal processing and concentration inversion through LabVIEW to obtain the concentrations of hydrogen sulfide and carbon monoxide.

[0039] Specifically, the host computer receives the WMS-2f and 1f signals demodulated by a lock-in amplifier and processes them using SG filtering and multiple averaging to obtain a normalized signal. Based on the laser characteristics and spectral parameters, the normalized signal of the gas to be measured is simulated. The Levenberg-Marquardt algorithm is used to perform a nonlinear least squares fit between the measured WMS-2f / 1f signal and the simulated signal, calculating the sum of squared errors of the fit. This process is iterated continuously until the predetermined convergence condition is reached. Once the fit converges, the system further optimizes the signal using an adaptive Kalman filter algorithm and outputs the current gas concentration value. If the fit does not converge, the system returns to an initial concentration value and continues the simulation until convergence, outputting the final concentration.

Claims

1. An extractive full-band multi-component gas detection system, characterized in that it includes The invention comprises: a host computer, a phase-locked amplifier, a detector, a gas pool with a function of extracting the gas to be measured, and a fiber combiner connected in sequence; it also comprises a mid-infrared measurement device and a near-infrared measurement device connected to the phase-locked amplifier and the fiber combiner respectively; the mid-infrared measurement device comprises a mid-infrared laser driver and a spatial light-fiber coupling mechanism connected to the mid-infrared laser; the near-infrared measurement device comprises a near-infrared laser driver and a near-infrared laser driven by the near-infrared laser driver.

2. The extractable full-band multi-component gas detection system according to claim 1 is characterized in that: The spatial light-fiber coupling mechanism includes a mid-infrared laser driven by a mid-infrared laser driver, a coupling lens for absorbing laser light emitted by the mid-infrared laser, and a single-mode optical fiber connected to the coupling lens and transmitting optical information.

3. The extractable full-band multi-component gas detection system according to claim 2 is characterized in that: The spatial light-fiber coupling mechanism is arranged in a sealing device capable of evacuating a vacuum.

4. The extractable full-band multi-component gas detection system according to claim 2 is characterized in that: The mid-infrared laser is a laser emitting 2.5-10 μm, and the near-infrared laser is a laser emitting 0.76-2.5 μm.

5. The extractable full-band multi-component gas detection system according to claim 2 is characterized in that: The mid-infrared laser is a laser emitting at 2.639 μm, and the near-infrared laser is a laser emitting at 2.334 μm.

6. The extractive full-band multi-component gas detection system according to claim 2, characterized in that: The gas pool and the optical fiber combiner, the near-infrared measurement device and the optical fiber combiner, and the mid-infrared measurement device and the optical fiber combiner are all connected through single-mode optical fibers; the host computer and the phase-locked amplifier, the phase-locked amplifier and the detector, the phase-locked amplifier and the mid-infrared laser driver, and the phase-locked amplifier and the near-infrared laser driver are all electrically connected.

7. The extractive full-band multi-component gas detection system according to claim 2, characterized in that: The optical path of the gas pool is 0.1 to 100 m, and the gas pool is connected to an air pump for extracting the gas to be measured.

8. An extractive full-band multi-component gas detection method, characterized in that: The extractive full-band multi-component gas detection system according to claim 1 comprises the following steps: S1: The host computer controls the lock-in amplifier using LabVIEW to set the driving signal to a low-frequency sawtooth superimposed high-frequency sine signal, and inputs it to the first laser driving circuit and the second laser driving circuit respectively; S2: The mid-infrared laser driver converts the received signal into a current signal, then drives the mid-infrared laser to emit a 2.639μm wavelength laser, which is then transmitted to the fiber combiner through a coupling lens and a single-mode fiber. At the same time, the near-infrared laser driver converts the received signal into a current signal, then drives the near-infrared laser to emit a corresponding 2.334μm wavelength laser, which is then transmitted to the fiber combiner through a single-mode fiber. S3: The fiber combiner combines the two laser beams into one optical signal, which enters the gas pool containing the gas to be detected and is then transmitted to the detector. S4: The detector converts the optical signal into an electrical signal, which is input into a phase-locked amplifier for demodulation. The demodulated signal is input into the host computer for signal processing and concentration inversion through LabVIEW to obtain the concentrations of hydrogen sulfide and carbon monoxide.

9. The extractive full-band multi-component gas detection method according to claim 8, characterized in that Before step S1, the gas pool is purged with high-purity nitrogen, and the host computer controls the mid-infrared laser driver through a phase-locked amplifier to control the temperature of the mid-infrared laser, and controls the temperature at 45°C; the host computer controls the near-infrared laser driver through a phase-locked amplifier to control the temperature of the near-infrared laser, and controls the temperature at 15°C.

10. The extractive full-band multi-component gas detection method according to claim 8, wherein In step S1, the driving signal of the mid-infrared laser driver is a sawtooth scanning range of 79-119 mA superimposed on a 24 mA sine wave, and the driving signal of the near-infrared laser driver is a sawtooth scanning range of 80-155 mA superimposed on a 29 mA sine wave.

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