Trace gas concentration measuring system based on hollow-core optical fiber

Abstract

The utility model discloses a trace gas concentration measuring system based on a hollow-core optical fiber. The trace gas concentration measuring system comprises a laser source, a gas cavity, the hollow-core optical fiber, a spectrograph and a data processing device, a first optical window and a second optical window are symmetrically arranged on the two sides of the gas cavity, and a ventilation window is arranged on any side, except the two sides where the first optical window and the second optical window are located, of the gas cavity; the hollow-core optical fiber is located in the gas cavity, and the two ends of the hollow-core optical fiber are in sealed connection with the first optical window and the second optical window respectively; the ventilation window is connected with an air inlet pipeline and a vacuum pipeline in a multi-way mode, the air inlet pipeline is connected with an air source, and the vacuum pipeline is connected with a vacuum pump. According to the invention, the optical window and the ventilation window are arranged at different sides of the gas cavity, so that the influence of airflow impact on the hollow-core optical fiber is reduced; the air inlet pipeline, the air source, the vacuum pipeline and the vacuum pump are arranged on the ventilation window in a multi-way mode, and the convenience of airflow control is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of gas concentration measurement, in particular to a trace gas concentration measurement system based on hollow core optical fiber. Background Art

[0002] Trace gas concentration measurement has important applications in environmental monitoring, respiratory diagnosis, industrial production safety monitoring, pollution emission management, etc. Currently, the light absorption method based on hollow-core optical fiber is generally used to measure the trace gas concentration in the gas.

[0003] In the prior art, the patent publication number CN116124696A "Gas Concentration Detection Device Based on Hollow-core Fiber" includes: a laser output module, an air chamber, an air box, a collimator and a photoelectric detector. The gas to be measured is filled into the hollow-core fiber through the through holes on the end face and side of the fiber. The laser emitted by the laser output module is coupled into the hollow-core fiber placed in the air box through the air chamber. The output laser of the fiber is collimated by the collimator and then received by the photoelectric detector. The concentration information of the trace gas is obtained by processing the signal processing device.

[0004] In the above-mentioned prior art, when the gas to be tested is filled into the hollow-core optical fiber through the end face of the optical fiber, since the first air chamber is directly in contact with the end face of the hollow-core optical fiber, that is, in this path, the airflow directly passes through the first air chamber into the end face of the hollow-core optical fiber, the impact of the airflow may cause damage to the hollow-core optical fiber; in addition, the air box of the above-mentioned prior art is provided with two air inlets and two air outlets, and the sealing of multiple air inlets and outlets and the air pressure in the air box need to be considered, and the convenience of airflow control is poor. Utility Model Content

[0005] The utility model provides a trace gas concentration measurement system based on hollow core optical fiber, which is used to solve the problems in the prior art that there is no reliable method for damaging the hollow core optical fiber due to airflow impact, and the airflow control convenience is poor.

[0006] On the one hand, the utility model provides a trace gas concentration measurement system based on hollow-core optical fiber, comprising: a laser source, a gas cavity, a hollow-core optical fiber, a spectrometer and a data processing device.

[0007] The first optical window and the second optical window are symmetrically arranged on both sides of the gas cavity, and a ventilation window is arranged on any side of the gas cavity except the two sides where the first optical window and the second optical window are located.

[0008] The hollow-core optical fiber is located inside the gas cavity, and two ends of the hollow-core optical fiber are sealed and connected to the first optical window and the second optical window respectively.

[0009] The ventilation window is multi-way connected to an air intake pipe and a vacuum pipe, the air intake pipe is connected to a gas source, and the vacuum pipe is connected to a vacuum pump.

[0010] The output optical path of the laser source starts from the laser source and is output to the hollow-core optical fiber through the first optical window. The input optical path of the spectrometer starts from the hollow-core optical fiber and is input to the spectrometer through the second optical window.

[0011] A plurality of vent holes are arranged on the side of the hollow core optical fiber.

[0012] The vacuum pump is used to evacuate the gas chamber.

[0013] The gas source is used to introduce the gas to be tested into the gas cavity.

[0014] The spectrometer is used to send spectrum data to the data processing device.

[0015] The data processing device is used to analyze the spectrum data to obtain the trace gas concentration in the gas to be measured.

[0016] In a possible implementation, the vent holes are symmetrically arranged in two rows along the side of the hollow-core optical fiber, with the central axis of the hollow-core optical fiber as the axis of symmetry.

[0017] In a possible implementation, the air intake pipe is provided with an air intake valve, and the vacuum pipe is provided with a vacuum valve.

[0018] In a possible implementation, the ventilation window is further connected to an air outlet pipe, and the air outlet pipe is provided with an air outlet valve.

[0019] In a possible implementation manner, the gas chamber is provided with a barometer.

[0020] In a possible implementation manner, a laser attenuation plate, a narrow-band filter, and a first focusing lens are sequentially arranged on an output light path between the laser source and the first optical window.

[0021] In a possible implementation manner, a second focusing lens, a cutoff filter, and a third focusing lens are sequentially arranged on the input light path between the second optical window and the spectrometer.

[0022] In a possible implementation, the ventilation window is further connected to a buffer pipe.

[0023] The buffer pipe extends from the ventilation window into the gas cavity and is split to both sides along the inner wall of the gas cavity.

[0024] The trace gas concentration measurement system based on hollow core optical fiber in the utility model has the following advantages:

[0025] By arranging the optical window and the ventilation window on different sides of the gas cavity, the impact of airflow shock on the hollow-core optical fiber is reduced; by arranging multiple air inlet pipes, gas sources, vacuum pipes and vacuum pumps on the ventilation window, the convenience of airflow control is improved.

[0026] The proposed hollow-core optical fiber is provided with a plurality of ventilation holes on its side, which improves the air pressure stability inside and outside the hollow-core optical fiber; the proposed ventilation holes are symmetrically arranged in two rows along the side of the hollow-core optical fiber with the central axis of the hollow-core optical fiber as the symmetry axis, which improves the smoothness of air flow.

[0027] A laser attenuation plate, a narrowband filter and a first focusing lens are sequentially arranged on the output light path between the proposed laser source and the first optical window, and a second focusing lens, a cutoff filter and a third focusing lens are sequentially arranged on the input light path between the second optical window and the spectrometer, thereby improving the adjustability of the laser.

[0028] The proposed ventilation window is also connected to a buffer pipe, which extends from the ventilation window into the gas cavity and diverts air to both sides along the inner wall of the gas cavity, thereby buffering the airflow entering the gas cavity, thereby improving the safety of the gap optical fiber and the uniformity of air pressure distribution without reducing the airflow velocity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of the structure of a trace gas concentration measurement system based on hollow core optical fiber provided in an embodiment of the utility model;

[0031] Figure 2 A side schematic diagram of a hollow core optical fiber provided in an embodiment of the utility model.

[0032] Description of reference numerals:

[0033] 1-laser source, 2-gas cavity, 3-hollow core optical fiber, 4-spectrometer, 5-data processing device, 11-laser attenuation plate, 12-narrow band filter, 13-first focusing lens, 21-first optical window, 22-second optical window, 23-ventilation window, 231-inlet pipe, 232-gas source, 233-inlet valve, 234-vacuum pipe, 235-vacuum pump, 236-vacuum valve, 237-outlet pipe, 238-outlet valve, 239-buffer pipe, 24-barometer, 31-vent, 41-second focusing lens, 42-cut-off filter, 43-third focusing lens. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0035] Embodiment 1:

[0036] like Figure 1 to Figure 2 As shown, an embodiment of the utility model provides a trace gas concentration measurement system based on hollow-core optical fiber, comprising: a laser source 1, a gas cavity 2, a hollow-core optical fiber 3, a spectrometer 4 and a data processing device 5.

[0037] The gas cavity 2 is symmetrically provided with a first optical window 21 and a second optical window 22 on both sides thereof, and a ventilation window 23 is provided on any side of the gas cavity 2 except for the first optical window 21 and the second optical window 22 .

[0038] The hollow-core optical fiber 3 is located inside the gas cavity 2 , and two ends of the hollow-core optical fiber 3 are sealed and connected to the first optical window 21 and the second optical window 22 , respectively.

[0039] The ventilation window 23 is multi-way connected to an air intake pipe 231 and a vacuum pipe 234 . The air intake pipe 231 is connected to a gas source 232 , and the vacuum pipe 234 is connected to a vacuum pump 235 .

[0040] The output optical path of the laser source 1 starts from the laser source 1 and is output to the hollow core optical fiber 3 through the first optical window 21 . The input optical path of the spectrometer 4 starts from the hollow core optical fiber 3 and is input to the spectrometer 4 through the second optical window 22 .

[0041] A plurality of vent holes 31 are disposed on the side of the hollow core optical fiber 3 .

[0042] The vacuum pump 235 is used to evacuate the gas chamber 2 .

[0043] The gas source 232 is used to introduce the gas to be tested into the gas chamber 2 .

[0044] The spectrometer 4 is used to send spectrum data to the data processing device 5 .

[0045] The data processing device 5 is used to analyze the spectral data to obtain the trace gas concentration in the gas to be measured.

[0046] Specifically, the spectrometer 4 is electrically connected or communicatively connected to the data processing device 5. The data processing device 5 is a host computer.

[0047] In this embodiment, the vent hole 31 is configured to be a rectangle with a length of 150 μm and a width of 40 μm. In other possible embodiments, the vent hole 31 may be configured to be other shapes or sizes.

[0048] In this embodiment, the measurement process of the trace gas concentration measurement system is as follows: first, turn on the vacuum pump 235 to evacuate the gas cavity 2 (since a number of vents 31 are provided on the side of the hollow-core optical fiber 3, the air pressure changes inside and outside the hollow-core optical fiber 3 are basically synchronized, and the air pressure difference inside and outside is small or zero). Then turn off the vacuum pump 235, turn on the gas source 232, and the gas to be measured enters the gas cavity 2 through the ventilation window 23, and enters the hollow-core optical fiber 3 through the vent 31. After a period of time, the gas to be measured is evenly distributed in the gas cavity 2 and the hollow-core optical fiber 3, and the gas source 232 is turned off. Turn on the laser source 1, and the laser passes through the first optical window 21, the hollow-core optical fiber 3, and the second optical window 22 in turn to reach the spectrometer 4. The spectrometer 4 sends the spectral data to the data processing device 5, and the data processing device 5 analyzes the spectral data to obtain the trace gas concentration in the gas to be measured.

[0049] Exemplarily, the vent holes 31 are symmetrically arranged in two rows along the side of the hollow-core optical fiber 3 with the central axis of the hollow-core optical fiber 3 as the axis of symmetry.

[0050] Specifically, by symmetrically arranging two rows of vent holes 31 , the airflow inside and outside the hollow-core optical fiber 3 is made smoother, which helps the gas to be measured to diffuse quickly into the hollow-core optical fiber 3 .

[0051] Exemplarily, the air intake pipe 231 is provided with an air intake valve 233 , and the vacuum pipe 234 is provided with a vacuum valve 236 .

[0052] Specifically, when the gas source 232 needs to be opened or closed, the air intake valve 233 is opened or closed first; when the vacuum pump 235 needs to be opened or closed, the vacuum valve 236 is opened or closed first.

[0053] Embodiment 2:

[0054] Exemplarily, the gas chamber 2 is provided with a barometer 24 .

[0055] Exemplarily, the ventilation window 23 is also connected to an air outlet pipe 237 , and the air outlet pipe 237 is provided with an air outlet valve 238 .

[0056] Specifically, in this embodiment, the measurement process of the trace gas concentration measurement system adds a gas outlet step of the gas outlet pipe 237 and the gas outlet valve 238 on the basis of Example 1, including: before closing the gas source 232, the gas pressure inside the gas chamber 2 is also monitored by the barometer 24; when the gas pressure inside the gas chamber 2 is greater than the external air pressure, the gas source 232 is closed, and then the gas outlet valve 238 is opened; part of the gas to be measured leaves the gas chamber 2 through the gas outlet pipe 237 under the action of the pressure difference; when the gas pressure inside the gas chamber 2 is equal to the external air pressure, the gas outlet valve 238 is closed.

[0057] Embodiment 3:

[0058] Exemplarily, a laser attenuation plate 11 , a narrow-band filter 12 and a first focusing lens 13 are sequentially arranged on the output light path between the laser source 1 and the first optical window 21 .

[0059] Exemplarily, a second focusing lens 41 , a cutoff filter 42 and a third focusing lens 43 are sequentially arranged on the input light path between the second optical window 22 and the spectrometer 4 .

[0060] Specifically, in this embodiment, the measurement process of the trace gas concentration measurement system is the same as that of Embodiment 1, but the input optical path and the output optical path are optimized, wherein the laser attenuation plate 11 is used to adjust the intensity of the laser, the narrow-band filter 12 is used to adjust the monochromaticity of the laser, the first focusing lens 13 is used to focus the laser to the first optical window 21, the second focusing lens 41 is used to focus the laser output from the second optical window 22, the cutoff filter 42 is used to separate the Raman light in the laser, and the third focusing lens 43 is used to focus the Raman light to the spectrometer 4.

[0061] Embodiment 4:

[0062] Exemplarily, the ventilation window 23 is also connected to a buffer pipe 239 .

[0063] The buffer pipe 239 extends from the ventilation window 23 into the gas chamber 2 and is split to both sides along the inner wall of the gas chamber 2 .

[0064] Specifically, in this embodiment, the measurement process of the trace gas concentration measurement system is the same as that of Embodiment 1, but the airflow direction of the measuring gas entering the gas chamber 2 is optimized. By setting a buffer pipe 239, the buffer pipe 239 extends into the gas chamber 2 from the ventilation window 23 and is diverted to both sides along the inner wall of the gas chamber 2, so that the airflow direction of the measured gas changes after entering the gas chamber 2, further reducing the impact of the airflow impact on the hollow-core optical fiber 3, while ensuring the uniformity of the air pressure distribution on both sides of the hollow-core optical fiber 3.

[0065] The embodiment of the utility model reduces the impact of airflow impact on the hollow-core optical fiber by arranging the optical window and the ventilation window on different sides of the gas cavity; and improves the convenience of airflow control by arranging multiple air inlet pipes, gas sources, vacuum pipes and vacuum pumps on the ventilation window.

[0066] The proposed hollow-core optical fiber is provided with a plurality of ventilation holes on its side, which improves the air pressure stability inside and outside the hollow-core optical fiber; the proposed ventilation holes are symmetrically arranged in two rows along the side of the hollow-core optical fiber with the central axis of the hollow-core optical fiber as the symmetry axis, which improves the smoothness of air flow.

[0067] A laser attenuation plate, a narrowband filter and a first focusing lens are sequentially arranged on the output light path between the proposed laser source and the first optical window, and a second focusing lens, a cutoff filter and a third focusing lens are sequentially arranged on the input light path between the second optical window and the spectrometer, thereby improving the adjustability of the laser.

[0068] The proposed ventilation window is also connected to a buffer pipe, which extends from the ventilation window into the gas cavity and diverts flow to both sides along the inner wall of the gas cavity, thereby buffering the airflow entering the gas cavity, thereby improving the safety of the gap optical fiber and the uniformity of air pressure distribution without reducing the airflow velocity.

[0069] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A trace gas concentration measurement system based on hollow core optical fiber, characterized in that: include: Laser source, gas cavity, hollow-core fiber, spectrometer and data processing device; The first optical window and the second optical window are symmetrically arranged on both sides of the gas cavity, and a ventilation window is arranged on any side of the gas cavity except the two sides where the first optical window and the second optical window are located; The hollow-core optical fiber is located inside the gas cavity, and two ends of the hollow-core optical fiber are sealed and connected to the first optical window and the second optical window respectively; The ventilation window is multi-way connected to an air intake pipe and a vacuum pipe, the air intake pipe is connected to a gas source, and the vacuum pipe is connected to a vacuum pump; The output optical path of the laser source starts from the laser source and is output to the hollow-core optical fiber through the first optical window. The input optical path of the spectrometer starts from the hollow-core optical fiber and is input to the spectrometer through the second optical window. A plurality of vent holes are arranged on the side of the hollow core optical fiber; The vacuum pump is used to evacuate the gas chamber; The gas source is used to pass the gas to be tested into the gas cavity; The spectrometer is used to send spectral data to the data processing device; The data processing device is used to analyze the spectrum data to obtain the trace gas concentration in the gas to be measured.

2. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: The vent holes are symmetrically arranged in two rows along the side of the hollow-core optical fiber, with the central axis of the hollow-core optical fiber as the symmetry axis.

3. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: The air intake pipe is provided with an air intake valve, and the vacuum pipe is provided with a vacuum valve.

4. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: The ventilation window is also connected to an air outlet pipeline, and the air outlet pipeline is provided with an air outlet valve.

5. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: The gas chamber is provided with a barometer.

6. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: A laser attenuation plate, a narrow-band filter and a first focusing lens are sequentially arranged on the output light path between the laser source and the first optical window.

7. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: A second focusing lens, a cutoff filter and a third focusing lens are sequentially arranged on the input light path between the second optical window and the spectrometer.

8. The trace gas concentration measurement system based on hollow core optical fiber according to claim 1, characterized in that: The ventilation window is also connected to a buffer pipe; The buffer pipe extends from the ventilation window into the gas cavity and is split to both sides along the inner wall of the gas cavity.

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