阅读说明：本技术 一种布放式气体检测装置及其工作方法 (Distributed gas detection device and working method thereof ) 是由 钱玮 徐骏 盛道斌 于 2021-08-16 设计创作，主要内容包括：本发明提供一种布放式气体检测装置,包括装置主体单元、装置外延单元、以及用于连接装置主体单元和装置外延单元的光纤,所述装置主体单元包括激光控制器、激光器、至少三个光纤转接器、光纤隔离器、光电探测器和数据采集系统,所述装置外延单元包括依次设置的光纤整形器、衰荡腔和光纤收集器。本发明采用光纤器件,具体包括布放光纤、光纤隔离器、光纤整形器、光纤收集器、光纤转接器,连接微/小型衰荡腔,可以在距离装置主体较远的位置对气体浓度进行精确测量。(The invention provides a distributed gas detection device which comprises a device main body unit, a device extension unit and optical fibers for connecting the device main body unit and the device extension unit, wherein the device main body unit comprises a laser controller, a laser, at least three optical fiber adapters, an optical fiber isolator, a photoelectric detector and a data acquisition system, and the device extension unit comprises an optical fiber shaper, a ring-down cavity and an optical fiber collector which are sequentially arranged. The invention adopts an optical fiber device, which specifically comprises a distribution optical fiber, an optical fiber isolator, an optical fiber shaper, an optical fiber collector and an optical fiber adapter, is connected with the micro/small ring-down cavity, and can accurately measure the gas concentration at a position far away from the main body of the device.)

1. The distributed gas detection device is characterized by comprising a device main body unit, a device extension unit and optical fibers for connecting the device main body unit and the device extension unit, wherein the device main body unit comprises a laser controller, a laser, at least three optical fiber adapters, an optical fiber isolator, a photoelectric detector and a data acquisition system;

one end of one optical fiber is sequentially connected with a laser, a first optical fiber adapter, an optical fiber isolator and a second optical fiber adapter in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper, and the laser controller is connected with the laser in a control mode;

one end of the other optical fiber is sequentially connected with the photoelectric detector and the third optical fiber adapter in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector, and the data acquisition system is connected with the photoelectric detector in a data transmission mode.

2. The deployed gas detection apparatus of claim 1, wherein the laser is a tunable quantum cascade laser.

3. The deployed gas detection apparatus of claim 1, wherein the photodetector is an indium antimonide detector.

4. The deployed gas detection apparatus of claim 1, wherein the ring down cavity is comprised of a first cavity mirror, a second cavity mirror, and a support mesh disposed between the first cavity mirror and the second cavity mirror.

5. The deployed gas detection apparatus of claim 4, wherein the first cavity mirror and the second cavity mirror are high reflectivity mirrors with the same size and radius of curvature.

6. A method of operating a deployment gas detection apparatus as claimed in any one of claims 1 to 5, comprising the steps of:

s1, constructing and distributing type gas detection device

The distributed gas detection device comprises a device main body unit, a device extension unit and optical fibers for connecting the device main body unit and the device extension unit, wherein the device main body unit comprises a laser controller, a laser, at least three optical fiber adapters, an optical fiber isolator, a photoelectric detector and a data acquisition system, and the device extension unit comprises an optical fiber shaper, a ring-down cavity and an optical fiber collector which are sequentially arranged;

one end of one optical fiber is sequentially connected with a laser, a first optical fiber adapter, an optical fiber isolator and a second optical fiber adapter in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper, and the laser controller is connected with the laser in a control mode;

one end of the other optical fiber is sequentially connected with a photoelectric detector and a third optical fiber adapter in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector, and the data acquisition system is connected with the photoelectric detector in a data transmission way;

s2 calibration distribution type gas detection device

The power supply of the device is turned on, the laser outputs laser, and the output wavelength lambda of the laser is adjusted by the laser controller₀Making the output wavelength be the non-absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₁At the moment, the laser controller turns off the current of the laser, the output light intensity of the laser is instantaneously reduced to zero at the moment, the received light intensity of the photoelectric detector is exponentially attenuated by e, and the light intensity is t₁₁The light is attenuated to 1/e of the maximum light intensity at any moment;

s3 arrangement device extension unit

Arranging the device extension unit of the arrangement type gas detection device to a position to be detected, and ensuring that the optical fiber is in a loose state;

s4, measuring the concentration of the gas to be measured

Adjusting the output wavelength of the laser by the laser controller such that the output wavelength λ₁Is the absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₂At the moment, the laser controller turns off the current of the laser, the output light intensity of the laser is instantaneously reduced to zero at the moment, the received light intensity of the photoelectric detector is exponentially attenuated by e, and the light intensity is t₁₂The light is attenuated to 1/e of the maximum light intensity at any moment;

s5, calculating the gas concentration

In the calibration process of step S2, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the cavity ring-down time is represented as t₁₁-t₀₁(ii) a During the measurement process of step S4, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the sample ring-down time is represented as t₁₂-t₀₂；

The concentration of the gas to be measured Conc is expressed as:

Conc＝c^-1·[(t₁₂-t₀₂)^-1-(t₁₁-t₀₁)^-1]·σ(λ₁)^-1；

where c is the speed of light, σ (λ)₁) For the gas to be measured at the absorption wavelength lambda₁The absorption cross section of (a).

Technical Field

The invention relates to a gas detection device, in particular to a distributed gas detection device and a working method thereof.

Background

In the fields of urban environmental monitoring and oil gas chemical engineering safety, trace gas detection is very important. The cavity ring-down spectroscopy technology is an absorption spectroscopy technology with high sensitivity and high precision, and an optical resonant cavity with high fineness is utilized, so that the measurement optical path can be greatly improved, and the cavity ring-down spectroscopy technology is very suitable for measuring trace gas. However, the gas detection device based on the technology adopts a space beam coupling mode, so that the whole device can only measure the gas concentration near an operator, and if a longer gas inlet pipe is used for collecting gas samples, the sampling time can be prolonged, and the measurement efficiency is reduced.

Disclosure of Invention

The invention aims to provide a distributed gas detection device and a working method thereof, and solves the problem that the conventional gas detection device based on the cavity ring-down spectroscopy technology cannot carry out remote measurement and can only carry out measurement near the device.

In order to solve the above technical problems, an embodiment of the present invention provides a distributed gas detection apparatus, including an apparatus main unit, an apparatus extension unit, and an optical fiber for connecting the apparatus main unit and the apparatus extension unit, where the apparatus main unit includes a laser controller, a laser, at least three optical fiber adapters, an optical fiber isolator, a photodetector, and a data acquisition system, and the apparatus extension unit includes an optical fiber shaper, a ring-down cavity, and an optical fiber collector, which are sequentially arranged;

one end of one optical fiber is sequentially connected with a laser, a first optical fiber adapter, an optical fiber isolator and a second optical fiber adapter in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper, and the laser controller is connected with the laser in a control mode;

one end of the other optical fiber is sequentially connected with the photoelectric detector and the third optical fiber adapter in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector, and the data acquisition system is connected with the photoelectric detector in a data transmission mode.

The laser adopts a tunable quantum cascade laser.

Preferably, the photoelectric detector is an indium antimonide detector.

The ring-down cavity consists of a first cavity mirror, a second cavity mirror and a supporting net, wherein the supporting net is arranged between the first cavity mirror and the second cavity mirror.

Preferably, the first cavity mirror and the second cavity mirror are high-reflectivity lenses with the same size and curvature radius.

The invention also provides a working method of the distributed gas detection device, which comprises the following steps:

s1, constructing and distributing type gas detection device

The distributed gas detection device comprises a device main body unit, a device extension unit and optical fibers for connecting the device main body unit and the device extension unit, wherein the device main body unit comprises a laser controller, a laser, at least three optical fiber adapters, an optical fiber isolator, a photoelectric detector and a data acquisition system, and the device extension unit comprises an optical fiber shaper, a ring-down cavity and an optical fiber collector which are sequentially arranged;

one end of one optical fiber is sequentially connected with a laser, a first optical fiber adapter, an optical fiber isolator and a second optical fiber adapter in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper, and the laser controller is connected with the laser in a control mode;

one end of the other optical fiber is sequentially connected with a photoelectric detector and a third optical fiber adapter in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector, and the data acquisition system is connected with the photoelectric detector in a data transmission way;

s2 calibration distribution type gas detection device

The power supply of the device is turned on, the laser outputs laser, and the output wavelength lambda of the laser is adjusted by the laser controller₀Making the output wavelength be the non-absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₁When the laser controller cuts off the current of the laser, the output light intensity of the laser is instantaneously reduced to zero, the received light intensity of the photoelectric detector is exponentially attenuated by e, and the light intensity is t₁₁The light is attenuated to 1/e of the maximum light intensity at any moment;

s3 arrangement device extension unit

Arranging the device extension unit of the arrangement type gas detection device to a position to be detected, and ensuring that the optical fiber is in a loose state;

s4, measuring the concentration of the gas to be measured

Adjusting the output wavelength of the laser by the laser controller such that the output wavelength λ₁Is the absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₂When the laser controller cuts off the current of the laser, the output light intensity of the laser is instantaneously reduced to zero, the received light intensity of the photoelectric detector is exponentially attenuated by e, and the light intensity is t₁₂The light is attenuated to 1/e of the maximum light intensity at any moment;

s5, calculating the gas concentration

In the calibration process of step S2, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the cavity ring-down time is represented as t₁₁-t₀₁(ii) a During the measurement process of step S4, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the sample ring-down time is represented as t₁₂-t₀₂；

The concentration of the gas to be measured Conc is expressed as:

Conc＝c^-1·[(t₁₂-t₀₂)^-1-(t₁₁-t₀₁)^-1]·σ(λ₁)^-1；

where c is the speed of light, σ (λ)₁) For the gas to be measured at the absorption wavelength lambda₁The absorption cross section of (a).

The technical scheme of the invention has the following beneficial effects:

the invention utilizes the optical fiber device to realize that the distributed gas detection device based on the cavity ring-down spectroscopy technology can carry out real-time online concentration measurement on trace gas at a position far away from operators or a remote position. Compared with the traditional device, the device has certain advantages in remote measurement, and the device extension unit is formed by passive devices, so that the device is particularly suitable for the field with potential safety hazards of gas leakage in petrochemical coal and the like.

Drawings

FIG. 1 is a schematic diagram of the optical path of the present invention;

FIG. 2 is a schematic diagram showing the variation of the output light intensity of the laser and the received light intensity of the detector with time according to the present invention.

Description of reference numerals:

1. a laser controller; 2. a laser; 3. a first optical fiber adapter; 4. a fiber isolator; 5. a second optical fiber adapter; 6. a third optical fiber adapter; 7. a photodetector; 8. a data acquisition system; 9. a device main body unit; 10. an optical fiber; 11. an optical fiber shaper; 12. a first cavity mirror; 13. a ring down cavity; 14. a second cavity mirror; 15. an optical fiber collector; 16. the device extends the unit.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1, the distributed gas detection device includes a device main unit 9, a device extension unit 16, and an optical fiber 10 for connecting the device main unit 9 and the device extension unit 16, where the device main unit 9 includes a laser controller 1, a laser 2, at least three optical fiber adapters, an optical fiber isolator 4, a photodetector 7, and a data acquisition system 8, and the device extension unit 16 includes an optical fiber shaper 11, a ring-down cavity 13, and an optical fiber collector 15, which are sequentially disposed.

One end of one optical fiber 10 is sequentially connected with a laser 2, a first optical fiber adapter 3, an optical fiber isolator 4 and a second optical fiber adapter 5 in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper 11, and the laser controller 1 is connected with the laser 2 in a control mode.

One end of the other optical fiber 10 is sequentially connected with the photoelectric detector 7 and the third optical fiber adapter 6 in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector 15, and the data acquisition system 8 is connected with the photoelectric detector 7 in a data transmission mode.

The laser 2 adopts a tunable quantum cascade laser, and the output wavelength of the laser is adjusted by changing the temperature of the laser through the laser controller 1.

The first fiber adapter 3, the second fiber adapter 5 and the third fiber adapter 6 are used for connection of different fiber devices, and FC/APC joints can be adopted.

The optical fiber isolator 4 is used for inhibiting the ring-down cavity 13 from generating an optical feedback effect and reducing the adverse effect of feedback laser on the laser 2.

The photoelectric detector 7 is used for collecting the transmitted light intensity after passing through the ring-down cavity 13, and an indium antimonide detector can be adopted.

The optical fiber shaper 11 is used for output laser collimation and spot shaping (adjusting spot size and position), and can be realized by adopting a plurality of spherical lenses or aspheric lenses.

The ring-down cavity 13 is composed of a first cavity mirror 12, a second cavity mirror 14 and a support net, and the support net is arranged between the first cavity mirror 12 and the second cavity mirror 14. The first cavity mirror 12 and the second cavity mirror 14 are high-reflectivity lenses with the same size and curvature radius, and the reflectivity is better than 0.9995 near 4.6 mu m. The supporting net is made of polytetrafluoroethylene materials and rigid metal materials, and is used for filtering suspended particles in air.

The fiber collector 15 is used for collecting the transmitted light intensity and converging the light into the optical fiber.

The invention also provides a working method of the distributed gas detection device, which comprises the following steps:

s1, constructing and distributing type gas detection device

The distributed gas detection device comprises a device main body unit, a device extension unit and optical fibers for connecting the device main body unit and the device extension unit, wherein the device main body unit comprises a laser controller 1, a laser 2, at least three optical fiber adapters, an optical fiber isolator 4, a photoelectric detector 7 and a data acquisition system 8, and the device extension unit comprises an optical fiber shaper 11, a ring-down cavity 13 and an optical fiber collector 15 which are sequentially arranged;

one end of one optical fiber is sequentially connected with a laser 2, a first optical fiber adapter 3, an optical fiber isolator 4 and a second optical fiber adapter 5 in series, the other end of the optical fiber is connected with the end part of an optical fiber shaper 11, and the laser controller 1 is connected with the laser 2 in a control mode;

one end of the other optical fiber is sequentially connected with the photoelectric detector 7 and the third optical fiber adapter 6 in series, the other end of the other optical fiber is connected with the end part of the optical fiber collector 15, and the data acquisition system 8 is connected with the photoelectric detector 7 in a data transmission mode.

S2 calibration distribution type gas detection device

The power supply of the device is turned on, the laser 2 outputs laser, and the output wavelength lambda of the laser 2 is adjusted by the laser controller 1₀Making the output wavelength be the non-absorption peak of the gas to be measured; the photoelectric detector 7 receives the laser, and the data acquisition system 8 displays a light intensity signal received by the photoelectric detector 7; when the light intensity signal reaches the trigger threshold, it is counted as t₀₁At the moment, the laser controller 1 turns off the current of the laser 2, the light intensity output by the laser 2 is instantaneously reduced to zero at the moment, the light intensity received by the photoelectric detector 7 is exponentially attenuated by e, and the light intensity is t₁₁The time instant decays to 1/e of the maximum light intensity.

S3 arrangement device extension unit

And arranging the device extension unit of the arrangement type gas detection device to a position to be detected, and ensuring that the optical fiber is in a loose state.

S4, measuring the concentration of the gas to be measured

The output wavelength of the laser 2 is adjusted by the laser controller 1 such that the output wavelength λ₁Is the absorption peak of the gas to be measured; the photoelectric detector 7 receives the laser, and the data acquisition system 8 displays a light intensity signal received by the photoelectric detector 7; when the light intensity signal reaches the trigger threshold, it is counted as t₀₂At the moment, the laser controller 1 turns off the current of the laser 2, the light intensity output by the laser 2 is instantaneously reduced to zero at the moment, the light intensity received by the photoelectric detector 7 is exponentially attenuated by e, and the light intensity is t₁₂The time instant decays to 1/e of the maximum light intensity.

S5, calculating the gas concentration

In the calibration process of step S2, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the cavity ring-down time is represented by (t)₁₁-t₀₁) (ii) a During the measurement process of step S4, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the sample ring-down time is expressed as (t)₁₂-t₀₂)；

The concentration of the gas to be measured Conc is expressed as:

Conc＝c^-1·[(t₁₂-t₀₂)^-1-(t₁₁-t₀₁)^-1]·σ(λ₁)^-1；

where c is the speed of light, σ (λ)₁) For the gas to be measured at the absorption wavelength lambda₁The absorption cross section of (a).

The following further illustrates the technical solution of the present invention by taking the measurement of carbon monoxide gas concentration as an example.

The detection steps are as follows:

step one, building and arranging type gas detection device

The set-up gas detection device was constructed as described in step S1, wherein the laser center wavelength was about 4.6 μm.

Step two, calibrating the distribution type gas detection device

The power supply of the device is turned on, the laser outputs laser, and the output wavelength lambda of the laser is adjusted by the laser controller₀(4.67 μm) such that the output wavelength is the non-absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₁At the moment, the laser controller turns off the current of the laser, the output light intensity of the laser is instantaneously reduced to zero at the moment, the received light intensity of the photoelectric detector is exponentially attenuated by e, and the light intensity is t₁₁The time instant decays to 1/e of the maximum light intensity.

Step three, arranging the epitaxial unit of the device

And arranging the device extension unit of the arrangement type gas detection device to a position to be detected, and ensuring that the optical fiber is in a loose state.

Step four, measuring the concentration of the gas to be measured

Adjusting the output wavelength of the laser by the laser controller such that the output wavelength λ₁(4.61 μm) is the absorption peak of the gas to be measured; the photoelectric detector receives the laser, and the data acquisition system displays a light intensity signal received by the photoelectric detector; when the light intensity signal reaches the trigger threshold, it is counted as t₀₂At the moment, the laser controller turns off the current of the laser, the output light intensity of the laser is instantly reduced to zero at the moment, and the photoelectric detector receives the light intensityDecays exponentially with e and the light intensity is t₁₂The time instant decays to 1/e of the maximum light intensity.

Step five, calculating the gas concentration

In the calibration process of step S2, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the cavity ring-down time is represented by (t)₁₁-t₀₁) (ii) a During the measurement process of step S4, a ring-down curve formed by receiving the light intensity by the photodetector can be obtained, and the sample ring-down time is expressed as (t)₁₂-t₀₂)；

The concentration of the gas to be measured Conc is expressed as:

Conc＝c^-1·[(t₁₂-t₀₂)^-1-(t₁₁-t₀₁)^-1]·σ(λ₁)^-1；

where c is the speed of light, σ (λ)₁) For the gas to be measured at the absorption wavelength lambda₁The absorption cross section of (a).

In this embodiment, the gas to be measured is carbon monoxide gas, λ₀＝4.67μm，λ₁The time-dependent changes of the laser output intensity and the detector received intensity are shown in fig. 2, which is 4.61 μm. Wherein, in FIG. 2(a), t is₀₁The light intensity at the time t is shown in FIG. 2(b)₁₁The light intensity at the time, t in FIG. 2(c)₀₂The light intensity at the time t is shown in FIG. 2(d)₁₂The light intensity at the moment.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.