CN114047136A - High-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system and method - Google Patents

Abstract

The invention provides a high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system and method, and belongs to the technical field of gas detection. Laser is incited to the optoacoustic cell from the aperture of trompil concave surface speculum, makes laser produce multiple reflection in order to increase the gas absorption journey between trompil concave surface speculum and the plane reflecting mirror of installing on the light filter switching wheel, and the reflection number of times can exceed 20 times to optoacoustic signal has been strengthened by a wide margin, adopts trompil concave surface speculum to hardly destroy the optical path of infrared thermal radiation light source's axial incident light sum reverberation simultaneously, thereby makes middle infrared thermal radiation light form the double pass in the optoacoustic cell and absorbs in order to strengthen optoacoustic signal. The invention fully utilizes the advantages of the photoacoustic spectrometry and the laser photoacoustic spectrometry based on the mid-infrared thermal radiation light source, which are respectively suitable for measuring multi-component gas and have high detection precision, realizes technical complementation and provides a technical scheme with strong competitiveness for the high-sensitivity detection of multi-component trace gas.

Description

High-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system and method

Technical Field

The invention belongs to the technical field of gas detection, and relates to a high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system and method.

Background

The photoacoustic spectrometry gas detection technology has the remarkable advantages of high sensitivity, more measurement components, no gas consumption, small sampling amount and the like, and plays an important role in the analysis of dissolved gas in transformer oil and other applications. Power transformer for connecting different powerThe operation reliability of the core component of the pressure class is directly related to the stable and safe operation of the power system. At present, oil-immersed transformers are generally adopted in large-scale power transformers, insulating oil is a mixture composed of hydrocarbon molecules with different molecular weights, and during long-term operation, faults such as overheating and discharging cause the insulating oil and insulating paper to crack so as to generate various characteristic gases (mainly comprising CH)₄、C₂H₆、C₂H₄、C₂H₂CO and CO₂) Most of these gases are dissolved in oil. The analysis of the components and the content of the dissolved gas in the oil can judge the type and the severity of the latent insulation fault in the transformer, so that the real-time monitoring of the dissolved gas in the oil has important significance for the reliable operation of a power grid.

Photoacoustic spectroscopy is a spectral calorimetry technique that directly measures the heat generated by a gas due to the absorption of light energy, and is a background-free absorption spectroscopy technique. The photoacoustic spectroscopy is mainly classified into photoacoustic spectroscopy based on a mid-infrared thermal radiation light source and laser photoacoustic spectroscopy according to different photoacoustic excitation light sources. The mid-infrared thermal radiation light source has a wide spectral emission range and covers the characteristic absorption band of most polar gas molecules. The photoacoustic spectrometer based on the mid-infrared thermal radiation light source can detect various gas components by selecting optical filters with different central wavelengths, but has the problems of low detection sensitivity and large cross interference. British Kelman corporation first developed a photoacoustic spectroscopy analysis device for gas dissolved in oil based on a blackbody radiation infrared broad spectrum light source, and can perform online monitoring on various characteristic gases in oil. The laser has the characteristics of narrow line width, large spectral power density and the like, the signal-to-noise ratio of photoacoustic measurement can be greatly improved by adopting a second harmonic detection technology, and meanwhile, the measurement error caused by the overlapping of spectral lines of multi-component gas is reduced. However, laser light sources, particularly mid-infrared lasers, are expensive, and the existing laser photoacoustic spectrometers only have great advantages in detection of trace gases with few components. In the analysis application of the dissolved gas in the transformer oil, the photoacoustic spectrometer based on the mid-infrared thermal radiation light source which is commonly adopted at present has the following problems: acetylene and methane, etc. due to cross-interference and background absorptionThe detection sensitivity of the gas is not high enough. The document Chen K, Gong Z, Yu Q.Fiber-amplified photosynthetic sensor for sub-ppb level acetyl ethylene detection [ J]Sensors and Actuators A: Physical,2018,274:184-₄gas detection[J]Optical Express,2021,29(9): 13600-. The patent 'an optoacoustic spectrum multi-component trace gas detection instrument and method' can realize the measurement of multi-component gas by utilizing a mid-infrared thermal radiation light source and a laser light source, but is influenced by factors with short absorption range, and the sensitivity is still required to be improved. Therefore, the high-sensitivity photoacoustic spectroscopy system has important application value in multi-component trace gas detection.

Disclosure of Invention

The invention aims to provide a high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system and method, aims to solve the problems that individual gas detection precision is low and mid-infrared thermal radiation light and laser are difficult to be simultaneously and efficiently coupled to a photoacoustic cell in a photoacoustic spectroscopy based on a mid-infrared thermal radiation light source, and expands a larger space for the application of a photoacoustic spectroscopy multi-component trace gas detection technology in the trace gas detection field.

The technical scheme of the invention is as follows:

a high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system comprises a mid-infrared thermal radiation light source 1, a collimating lens 2, achopper 3, an opticalfilter switching wheel 4, awindow sheet 5, aphotoacoustic cell 6, a laserlight source module 7, anoptical fiber coupler 8, anoptical fiber collimator 9, an open-holeconcave reflector 10, anair inlet valve 11, anair outlet valve 12, amicrophone 13, a control andsignal processing circuit 14 and acomputer 15; after wide spectrum light emitted by the intermediate infrared thermal radiation light source 1 is focused by the collimating lens 2, the wide spectrum light is modulated by thechopper 3; the control andsignal processing circuit 14 controls the opticalfilter switching wheel 4, modulated light penetrates through one optical filter in the opticalfilter switching wheel 4, then enters thephotoacoustic cell 6 through thewindow sheet 5, and is reflected by the perforated concave reflectingmirror 10 to generate double-pass absorption enhancement in the photoacoustic cell; the modulation signal output by the control andsignal processing circuit 14 modulates the wavelength of the laserlight source module 7; two beams of laser in thelaser source module 7 pass through theoptical fiber coupler 8 and then pass through theoptical fiber collimator 9 to be collimated, and then are incident into thephotoacoustic cell 6 from the small hole of the perforatedconcave reflector 10; thephotoacoustic cell 6 is provided with anair inlet valve 11 and anair outlet valve 12 which are used for controlling the inlet and the outlet of the gas to be measured; amicrophone 13 is mounted on thephotoacoustic cell 6 for detecting photoacoustic signals generated in thephotoacoustic cell 6; the signal input end of the control andsignal processing circuit 14 is connected with themicrophone 13, and digital signal processing is carried out after photoacoustic signals are collected; thecomputer 15 is connected with the control andsignal processing circuit 14 and is used for setting the working parameters of the control andsignal processing circuit 14 and displaying the output photoacoustic signal measured value.

A high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection method is characterized in that mid-infrared thermal radiation light and laser are efficiently coupled into the same small-volume photoacoustic cell, and high-sensitivity detection of multi-component gas is realized through multiple reflection and absorption enhancement; the method comprises the following specific steps:

firstly, after receiving a control instruction input by acomputer 15, a control andsignal processing circuit 14 opens anair inlet valve 11 and anair outlet valve 12 to make the gas to be measured fill thephotoacoustic cell 6 and set working parameters; after wide spectrum light emitted by the intermediate infrared thermal radiation light source 1 is converged by the collimating lens 2, the light intensity is modulated by thechopper 3; the control andsignal processing circuit 14 controls the opticalfilter switching wheel 4, and the different component gases are respectively measured by switching the optical filters in the opticalfilter switching wheel 4; modulated light penetrates through one optical filter in the opticalfilter switching wheel 4, then enters thephotoacoustic cell 6 through thewindow piece 5, is reflected by the perforated concave reflectingmirror 10, and then generates double-pass absorption enhancement in the photoacoustic cell.

Then, the control andsignal processing circuit 14 controls the optical filter switchingwheel 4, and rotates theplane mirror 16 installed on the opticalfilter switching wheel 4 to the front of thewindow piece 5; the output modulation signal of the control andsignal processing circuit 14 is formed by superposing a sine signal with fixed frequency and a sawtooth wave signal, and the modulation signal is input into the laserlight source module 7 to change the working current of the laser so as to realize the modulation and scanning of the laser wavelength; two bundles of laser in thelaser source module 7 pass through theoptical fiber coupler 8, and then pass through theoptical fiber collimator 9 to carry out beam collimation, and the aperture from the trompilconcave surface reflector 10 is incited to theoptoacoustic cell 6, and laser light sees throughwindow piece 5 and produces multiple reflection at trompilconcave surface reflector 10 andplane mirror 16, and the number of reflection exceeds 20, increases substantially the gas to laser energy's absorption journey.

After the gas molecules to be measured in thephotoacoustic cell 6 absorb light energy, part of the molecules are excited to an excited state and return to a ground state after radiationless transition, and the energy of the molecules is converted into periodic temperature change of the gas in the form of translation energy, so that photoacoustic signals are generated in thephotoacoustic cell 6; themicrophone 13 converts the detected photoacoustic signal into an electrical signal and inputs the electrical signal to the signal input end of the control andsignal processing circuit 14, the photoacoustic signal excited by the mid-infrared thermal radiation light source 1 adopts an intensity modulation-fundamental wave detection method, and the photoacoustic signal excited by the laserlight source module 7 adopts a wavelength modulation-second harmonic detection method; the control andsignal processing circuit 14 respectively processes fundamental wave and second harmonic wave signals, and then displays the measured concentration value of the multi-component gas on thecomputer 15; finally, the control andsignal processing circuit 14 controls the opening of theinlet valve 11 and theoutlet valve 12 to discharge the gas.

The wavelength of the emission spectrum of the intermediate infrared thermal radiation light source 1 is 3-12 μm, and the infrared absorption spectrum wave band of ethane, ethylene, carbon monoxide and carbon dioxide gas molecules is covered.

The working frequency of thechopper 3 is 20-200 Hz.

The optical filter switchingwheel 4 is provided with 1 plane reflector and 4 band-pass infrared optical filters. The plane mirror is used for enhancing laser photoacoustic signals through multiple reflection when methane and acetylene are measured; the center wavelengths of the 4 bandpass infrared filters correspond to the absorption peaks of ethane, ethylene, carbon monoxide and carbon dioxide, respectively.

The transmission wavelength range of thewindow sheet 5 is 1.5-12 μm, and both the mid-infrared light and the near-infrared light emitted by the mid-infrared thermal radiation light source 1 and the laserlight source module 7 can penetrate through thewindow sheet 5.

Thephotoacoustic cell 6 is a non-resonant photoacoustic cell, and the diameter of an internal air chamber is 10mm, and the length of the internal air chamber is 30 mm.

The laserlight source module 7 is composed of two near-infrared tunable lasers and is used for measuring acetylene and methane respectively.

The splitting ratio of theoptical fiber coupler 8 is 50: 50.

The middle of the perforatedconcave reflector 10 is provided with a small hole with the aperture of 0.5 mm.

The control andsignal processing circuit 14 extracts fundamental and second harmonic photoacoustic signals simultaneously.

The principle of the invention is as follows: the middle infrared thermal radiation light and the laser are simultaneously and efficiently coupled to a specially designed cylindrical photoacoustic cell, wherein the middle infrared thermal radiation light is condensed and then enters the photoacoustic cell from a window sheet through an infrared band-pass filter, and after being reflected by an open-hole concave reflector, the middle infrared thermal radiation light generates double-pass absorption enhancement in the photoacoustic cell, and the photoacoustic signal is measured by adopting an intensity modulation-fundamental wave detection technology, so that the high-sensitivity detection of ethane, ethylene, carbon monoxide and carbon dioxide gas is realized; laser is emitted to the photoacoustic cell from the small hole of the perforated concave reflecting mirror through the optical fiber collimator, multiple reflection is generated between the perforated concave reflecting mirror and the plane reflecting mirror arranged on the optical filter switching wheel by the laser, the photoacoustic signal is measured by adopting a wavelength modulation-second harmonic detection technology, the interference of the fundamental frequency photoacoustic signal generated by the solid photoacoustic effect due to the multiple reflection on the surface of the cell wall is eliminated, background-free detection is realized, and high-sensitivity detection on methane and acetylene gas is realized.

The invention has the advantages that: by adopting the scheme of fusing the intermediate infrared thermal radiation light source and the laser light source, the advantages of high measurement precision and high detection precision of multi-component gas respectively possessed by the photoacoustic spectrometry and the laser photoacoustic spectrometry based on the intermediate infrared thermal radiation light source are fully utilized, and technical complementation is realized. Laser is incited to the optoacoustic cell from the aperture of trompil concave surface speculum, makes laser produce multiple reflection in order to increase the gas absorption journey between trompil concave surface speculum and the plane reflecting mirror of installing on the light filter switching wheel, and the reflection number of times can exceed 20 times to optoacoustic signal has been strengthened by a wide margin, adopts trompil concave surface speculum to hardly destroy the optical path of infrared thermal radiation light source's axial incident light sum reverberation simultaneously, thereby makes middle infrared thermal radiation light form the double pass in the optoacoustic cell and absorbs in order to strengthen optoacoustic signal. The structure can enable two kinds of photoacoustic excitation light to be efficiently coupled at the same time, and compared with a scheme that one photoacoustic cell is matched with one light source, the structure of the system is effectively simplified, and the requirement on the gas sample amount is reduced. The invention provides a very competitive technical scheme for high-sensitivity detection of multi-component trace gas.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a schematic structural diagram of the filter switching wheel.

In the figure: 1 a mid-infrared thermal radiation light source; 2 a collimating lens; 3, a chopper; 4 optical filter switching wheel;

5 window sheets; 6, a photoacoustic cell; 7 laser light source module; 8, a fiber coupler; 9 a fiber collimator;

10 opening a concave reflector; 11 an intake valve; 12 an air outlet valve; 13 a microphone;

14 control and signal processing circuitry; 15 a computer; 16 plane mirrors;

17 mid-infrared bandpass filters for ethane measurement;

18 a mid-infrared bandpass filter for measuring ethylene;

19 a mid-infrared band pass filter for measuring carbon monoxide;

20 mid-infrared band pass filters for measuring carbon dioxide.

Detailed Description

The following detailed description of the invention refers to the accompanying drawings.

A high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection system mainly comprises a mid-infrared thermal radiation light source 1, a collimating lens 2, achopper 3, an opticalfilter switching wheel 4, awindow sheet 5, aphotoacoustic cell 6, a laserlight source module 7, anoptical fiber coupler 8, anoptical fiber collimator 9, an open-holeconcave reflector 10, anair inlet valve 11, anair outlet valve 12, amicrophone 13, a control andsignal processing circuit 14 and acomputer 15. After receiving a control instruction input by thecomputer 15, the control andsignal processing circuit 14 opens theair inlet valve 11 and theair outlet valve 12 to make the gas to be measured fill thephotoacoustic cell 6 and set working parameters; after wide spectrum light emitted by the intermediate infrared thermal radiation light source 1 is converged by the collimating lens 2, the light intensity is modulated by thechopper 3; the control andsignal processing circuit 14 controls the opticalfilter switching wheel 4, and the different component gases are respectively measured by switching the optical filters in the opticalfilter switching wheel 4; modulated light penetrates through one optical filter in the opticalfilter switching wheel 4, is incident into thephotoacoustic cell 6 through thewindow sheet 5, is reflected by the perforated concave reflectingmirror 10, and then generates double-pass absorption enhancement in the photoacoustic cell; the control andsignal processing circuit 14 controls the opticalfilter switching wheel 4, and rotates theplane mirror 16 arranged on the opticalfilter switching wheel 4 to the front of thewindow piece 5; the output modulation signal of the control andsignal processing circuit 14 is formed by superposing a sine signal with fixed frequency and a sawtooth wave signal, and the modulation signal is input into the laserlight source module 7 to change the working current of the laser so as to realize the modulation and scanning of the laser wavelength; two beams of laser in thelaser source module 7 pass through theoptical fiber coupler 8 and then pass through theoptical fiber collimator 9 to be collimated, the laser beams are incident into thephotoacoustic cell 6 from the small hole of the perforatedconcave reflector 10, and the laser beams are reflected for multiple times on the perforatedconcave reflector 10 and theplane reflector 16 through thewindow sheet 5, so that the absorption range of the gas to the laser energy is greatly improved; after the gas molecules to be measured in thephotoacoustic cell 6 absorb light energy, part of the molecules are excited to an excited state and return to a ground state after radiationless transition, and the energy of the molecules is converted into periodic temperature change of the gas in the form of translation energy, so that photoacoustic signals are generated in thephotoacoustic cell 6; themicrophone 13 converts the detected photoacoustic signal into an electrical signal and inputs the electrical signal to the signal input end of the control andsignal processing circuit 14, the photoacoustic signal excited by the mid-infrared thermal radiation light source 1 adopts an intensity modulation-fundamental wave detection method, and the photoacoustic signal excited by the laserlight source module 7 adopts a wavelength modulation-second harmonic detection method; the control andsignal processing circuit 14 respectively processes fundamental wave and second harmonic wave signals, and then displays the measured concentration value of the multi-component gas on thecomputer 15; the control andsignal processing circuit 14 controls the opening of theinlet valve 11 and theoutlet valve 12 to discharge the gas.

Wherein, the coverage wavelength range of the mid-infrared heat radiation light source 1 is 3-12 μm. The operating frequency of thechopper 3 is 40 Hz. The filter switchingwheel 4 is provided with 1 plane reflector and 4 band-pass infrared filters. Thewindow piece 5 is a film-coated zinc selenide window piece, and the transmission wavelength range is 1.5-12 mu m; thephotoacoustic cell 6 is a non-resonant photoacoustic cell, and the diameter of an internal air chamber is 10mm, and the length of the internal air chamber is 30 mm.

The laserlight source module 7 consists of two near-infrared narrow linewidth DFB lasers, the central wavelengths of which are 1532nm and 1653nm respectively, and the lasers are used for measuring acetylene and methane gas respectively. The splitting ratio of thefiber coupler 8 is 50: 50. The middle of the openconcave reflector 10 is provided with a small hole with the aperture of 0.5 mm. The control andsignal processing circuit 14 is a high performance digital lock-in amplifier that can extract both fundamental and second harmonic photoacoustic signals.

Fig. 2 is a schematic structural diagram of the filter switching wheel. Thefilter switching wheel 4 is provided with aplane mirror 16, a mid-infrared band-pass filter 17 for measuring ethane, a mid-infrared band-pass filter 18 for measuring ethylene, a mid-infrared band-pass filter 19 for measuring carbon monoxide and a mid-infrared band-pass filter 20 for measuring carbon dioxide. The central wavelength of the mid-infrared band-pass filter 17 for ethane measurement was 3.3 μm, the central wavelength of the mid-infrared band-pass filter 18 for ethylene measurement was 10.5 μm, the central wavelength of the mid-infrared band-pass filter 19 for carbon monoxide measurement was 4.6 μm, and the central wavelength of the mid-infrared band-pass filter 20 for carbon dioxide measurement was 4.3 μm.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

Translated fromChinese

1.一种高灵敏度组合光源式光声光谱多组分气体检测系统，其特征在于，该高灵敏度组合光源式光声光谱多组分气体检测系统包括中红外热辐射光源(1)、准直透镜(2)、斩波器(3)、滤光片切换轮(4)、窗口片(5)、光声池(6)、激光光源模块(7)、光纤耦合器(8)、光纤准直器(9)、开孔凹面反射镜(10)、进气阀门(11)、出气阀门(12)、传声器(13)、控制与信号处理电路(14)和计算机(15)；中红外热辐射光源(1)发出的宽谱光经准直透镜(2)聚焦后，再经过斩波器(3)进行光调制；控制与信号处理电路(14)对滤光片切换轮(4)进行控制，调制光透过滤光片切换轮(4)中的一个滤光片后，经过设置在光声池(6)一端的窗口片(5)入射到光声池(6)中，再被设置在光声池(6)另一端的开孔凹面反射镜(10)反射后在光声池(6)中产生双程吸收增强；控制与信号处理电路(14)输出的调制信号对激光光源模块(7)进行波长调制；激光光源模块(7)中的两束激光经光纤耦合器(8)后，再经过光纤准直器(9)进行光束准直，从开孔凹面反射镜(10)的小孔入射到光声池(6)中；光声池(6)上设有进气阀门(11)和出气阀门(12)，用于控制待测气体的进入和排出；传声器(13)安装在光声池(6)上，用于探测光声池(6)内产生的光声信号；控制与信号处理电路(14)的信号输入端与传声器(13)相连，采集光声信号后进行数字信号处理；计算机(15)与控制与信号处理电路(14)相连，用于设置控制与信号处理电路(14)的工作参数并对输出的光声信号测量值进行显示。1. a high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection system is characterized in that, this high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection system comprises a mid-infrared thermal radiation light source (1), a collimation Lens (2), chopper (3), filter switching wheel (4), window (5), photoacoustic cell (6), laser light source module (7), fiber coupler (8), fiber collimator Straight device (9), perforated concave mirror (10), intake valve (11), exhaust valve (12), microphone (13), control and signal processing circuit (14) and computer (15); mid-infrared heat After the broad-spectrum light emitted by the radiation light source (1) is focused by the collimating lens (2), the light is modulated by the chopper (3); Control, after the modulated light passes through a filter in the filter switching wheel (4), it is incident into the photoacoustic cell (6) through the window (5) arranged at one end of the photoacoustic cell (6), and then is After reflection by the apertured concave mirror (10) disposed at the other end of the photoacoustic cell (6), two-way absorption enhancement is generated in the photoacoustic cell (6); the modulation signal output by the control and signal processing circuit (14) is used for the laser light source. The module (7) performs wavelength modulation; the two laser beams in the laser light source module (7) pass through the optical fiber coupler (8), and then pass through the optical fiber collimator (9) for beam collimation, and the beams are collimated from the perforated concave mirror (10). ) is incident into the photoacoustic cell (6); the photoacoustic cell (6) is provided with an air inlet valve (11) and an air outlet valve (12) for controlling the entry and discharge of the gas to be measured; the microphone (13) ) is installed on the photoacoustic cell (6) for detecting the photoacoustic signal generated in the photoacoustic cell (6); the signal input end of the control and signal processing circuit (14) is connected with the microphone (13) to collect the photoacoustic signal Then digital signal processing is performed; the computer (15) is connected to the control and signal processing circuit (14) for setting the working parameters of the control and signal processing circuit (14) and displaying the measured value of the output photoacoustic signal.2.根据权利要求1所述的高灵敏度组合光源式光声光谱多组分气体检测系统，其特征在于，所述的开孔凹面反射镜(10)的中间开有小孔，孔径为0.5mm。2. The high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection system according to claim 1, characterized in that, a small hole is opened in the middle of the apertured concave mirror (10), and the aperture is 0.5mm .3.根据权利要求1或2所述的高灵敏度组合光源式光声光谱多组分气体检测系统，其特征在于，所述的光声池(6)是非共振式光声池，内部气室直径为10mm，长度为30mm。3. The high-sensitivity combined light source type photoacoustic spectrum multicomponent gas detection system according to claim 1 or 2, wherein the photoacoustic cell (6) is a non-resonant photoacoustic cell, and the inner gas chamber diameter is 10mm and the length is 30mm.4.根据权利要求1或2所述的高灵敏度组合光源式光声光谱多组分气体检测系统，其特征在于，所述的滤光片切换轮(4)上安装有1个平面反射镜和4个带通红外滤光片；所述的激光光源模块(7)由两个近红外可调谐激光器组成，分别用于测量乙炔和甲烷；所述的光纤耦合器(8)的分光比为50:50。4. The high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection system according to claim 1 or 2, wherein the filter switching wheel (4) is provided with a plane mirror and 4 band-pass infrared filters; the laser light source module (7) is composed of two near-infrared tunable lasers, which are respectively used to measure acetylene and methane; the optical fiber coupler (8) has a splitting ratio of 50 :50.5.根据权利要求3所述的高灵敏度组合光源式光声光谱多组分气体检测系统，其特征在于，所述的滤光片切换轮(4)上安装有1个平面反射镜和4个带通红外滤光片；所述的激光光源模块(7)由两个近红外可调谐激光器组成，分别用于测量乙炔和甲烷；所述的光纤耦合器(8)的分光比为50:50。5. The high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection system according to claim 3, wherein the filter switching wheel (4) is provided with 1 plane reflection mirror and 4 Band-pass infrared filter; the laser light source module (7) is composed of two near-infrared tunable lasers, which are respectively used to measure acetylene and methane; the optical fiber coupler (8) has a split ratio of 50:50 .6.一种高灵敏度组合光源式光声光谱多组分气体检测方法，将中红外热辐射光和激光高效耦合到同一个小体积光声池中，通过多次反射吸收增强实现对多组分气体的高灵敏度检测；其特征在于，步骤如下：6. A high-sensitivity combined light source photoacoustic spectroscopy multi-component gas detection method, which efficiently couples mid-infrared thermal radiation light and laser into the same small-volume photoacoustic cell, and realizes detection of multi-component gas through multiple reflection absorption enhancement. High-sensitivity detection of gas; it is characterized in that, the steps are as follows:首先，控制与信号处理电路(14)接收计算机(15)输入的控制指令后，打开进气阀门(11)和出气阀门(12)，使待测气体充满光声池(6)，并设置工作参数；中红外热辐射光源(1)发出的宽谱光经准直透镜(2)会聚后，再经过斩波器(3)进行光强度调制；控制与信号处理电路(14)对滤光片切换轮(4)进行控制，通过切换滤光片切换轮(4)中的滤光片，分别对不同组分气体进行测量；调制光透过滤光片切换轮(4)中的一个滤光片后，经过窗口片(5)入射到光声池(6)中，再被开孔凹面反射镜(10)反射后在光声池中产生双程吸收增强；First, the control and signal processing circuit (14) opens the air inlet valve (11) and the air outlet valve (12) after receiving the control command input by the computer (15), so that the gas to be tested fills the photoacoustic cell (6), and sets the working parameters; after the broad-spectrum light emitted by the mid-infrared thermal radiation light source (1) is condensed by the collimating lens (2), the light intensity is modulated by the chopper (3); the control and signal processing circuit (14) adjusts the filter The switching wheel (4) is used for control, and by switching the filters in the filter switching wheel (4), the gases of different components are respectively measured; the modulated light transmits through one of the filters in the filter switching wheel (4) After the film, it is incident into the photoacoustic cell (6) through the window sheet (5), and then reflected by the apertured concave mirror (10) to generate two-way absorption enhancement in the photoacoustic cell;然后，控制与信号处理电路(14)对滤光片切换轮(4)进行控制，将滤光片切换轮(4)上安装的平面反射镜(16)旋转到窗口片(5)前面；控制与信号处理电路(14)的输出调制信号由固定频率的正弦信号和锯齿波信号叠加而成，调制信号输入到激光光源模块(7)改变激光器的工作电流，实现对激光波长的调制和扫描；激光光源模块(7)中的两束激光经光纤耦合器(8)后，再经过光纤准直器(9)进行光束准直，从开孔凹面反射镜(10)的小孔入射到光声池(6)中，激光光线透过窗口片(5)在开孔凹面反射镜(10)和平面反射镜(16)产生超过20次反射，大幅度提高气体对激光能量的吸收程；Then, the control and signal processing circuit (14) controls the filter switching wheel (4) to rotate the plane mirror (16) installed on the filter switching wheel (4) to the front of the window sheet (5); control and the output modulation signal of the signal processing circuit (14) is formed by superimposing a sine signal and a sawtooth wave signal of a fixed frequency, and the modulation signal is input to the laser light source module (7) to change the working current of the laser, so as to realize modulation and scanning of the laser wavelength; The two laser beams in the laser light source module (7) pass through the optical fiber coupler (8), and then pass through the optical fiber collimator (9) for beam collimation, and enter the photoacoustic from the small hole of the apertured concave mirror (10). In the pool (6), the laser light passes through the window (5) to generate more than 20 reflections on the apertured concave mirror (10) and the plane mirror (16), which greatly improves the absorption range of the laser energy by the gas;光声池(6)中的待测气体分子吸收光能后，部分分子被激励到激发态，经过无辐射跃迁后回到基态，分子的能量以平动能的形式转换为气体的周期性温度变化，使光声池(6)中产生光声信号；传声器(13)将探测的光声信号转换为电信号后输入到控制与信号处理电路(14)的信号输入端，中红外热辐射光源(1)激发的光声信号采用强度调制-基波检测法，激光光源模块(7)激发的光声信号则采用波长调制-二次谐波检测法；控制与信号处理电路(14)分别对基波和二次谐波信号进行处理后，将测量的多组分气体的浓度值显示于计算机(15)；最后，控制与信号处理电路(14)控制打开进气阀门(11)和出气阀门(12)将气体排出。After the gas molecules to be tested in the photoacoustic cell (6) absorb the light energy, some molecules are excited to the excited state, and then return to the ground state after a non-radiative transition, and the energy of the molecules is converted into the periodic temperature change of the gas in the form of translational energy. , so that a photoacoustic signal is generated in the photoacoustic cell (6); the microphone (13) converts the detected photoacoustic signal into an electrical signal and then inputs it to the signal input end of the control and signal processing circuit (14), the mid-infrared heat radiation light source ( 1) The excitation photoacoustic signal adopts the intensity modulation-fundamental wave detection method, and the photoacoustic signal excited by the laser light source module (7) adopts the wavelength modulation-second harmonic detection method; After the wave and the second harmonic signal are processed, the concentration value of the measured multi-component gas is displayed on the computer (15); finally, the control and signal processing circuit (14) controls the opening of the inlet valve (11) and the outlet valve ( 12) Expel the gas.7.根据权利要求6所述的高灵敏度组合光源式光声光谱多组分气体检测方法，其特征在于，所述的中红外热辐射光源(1)的发射光谱的波长为3-12μm，覆盖乙烷、乙烯、一氧化碳和二氧化碳气体分子的红外吸收光谱波段。7. The high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection method according to claim 6, wherein the wavelength of the emission spectrum of the mid-infrared thermal radiation light source (1) is 3-12 μm, covering Infrared absorption spectral bands of ethane, ethylene, carbon monoxide and carbon dioxide gas molecules.8.根据权利要求6或7所述的高灵敏度组合光源式光声光谱多组分气体检测方法，其特征在于，所述的斩波器(3)的工作频率为20-200Hz。8. The high-sensitivity combined light source photoacoustic spectroscopy multi-component gas detection method according to claim 6 or 7, characterized in that, the operating frequency of the chopper (3) is 20-200 Hz.9.根据权利要求6或7所述的高灵敏度组合光源式光声光谱多组分气体检测方法，其特征在于，所述的窗口片(5)的透射波长范围为1.5-12μm，中红外热辐射光源(1)和激光光源模块(7)发射的中红外光线和近红外光线均可透过窗口片(5)。9. The high-sensitivity combined light source type photoacoustic spectrum multi-component gas detection method according to claim 6 or 7, wherein the transmission wavelength range of the window (5) is 1.5-12 μm, and the mid-infrared heat Both the mid-infrared light and the near-infrared light emitted by the radiation light source (1) and the laser light source module (7) can pass through the window sheet (5).10.根据权利要求8所述的高灵敏度组合光源式光声光谱多组分气体检测方法，其特征在于，所述的窗口片(5)的透射波长范围为1.5-12μm，中红外热辐射光源(1)和激光光源模块(7)发射的中红外光线和近红外光线均可透过窗口片(5)。10. The high-sensitivity combined light source type photoacoustic spectroscopy multi-component gas detection method according to claim 8, characterized in that, the transmission wavelength range of the window (5) is 1.5-12 μm, and the mid-infrared thermal radiation light source Both the mid-infrared light and the near-infrared light emitted by (1) and the laser light source module (7) can pass through the window sheet (5).

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