A greenhouse gas content rapid detection device

Abstract

This invention discloses a rapid greenhouse gas content detection device, comprising an optical frequency comb laser, a ring-down cavity, and a photodetector. The ring-down cavity includes a cavity body with an inlet and an outlet. One end of the cavity body has a fixed end plate, and the other end has an adjustable end plate. Both the fixed and adjustable end plates are equipped with cavity mirrors. An adjustment mechanism is provided between the adjustable end plate and the cavity body to adjust the installation angle of the adjustable end plate. The ring-down cavity also includes an optical path detection mechanism. During detection, the gas to be detected enters through the inlet of the ring-down cavity and exits through the outlet. The laser emitted by the optical frequency comb laser is received by the photodetector after passing through the ring-down cavity. In this invention, the adjustment mechanism and the optical path detection mechanism on the ring-down cavity can adjust and calibrate the installation angle of the cavity mirrors, improving the installation accuracy between the cavity mirrors.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and in particular to a rapid detection device for greenhouse gas content. Background Technology

[0002] The concentrations of trace gases in the air, such as carbon oxides, nitrogen oxides, and nitrogen hydrides, are limited to the ppm and ppb levels, making them important indicators for environmental monitoring. Among atmospheric trace gases, major gaseous pollutants include SO2, NO, CO, CO2, O3, total oxidants, hydrogen halides, and hydrocarbons. The increase in atmospheric greenhouse gases, ozone, methane, and other trace gases is a significant factor contributing to the greenhouse effect. Greenhouse gases effectively absorb infrared radiation, contributing to the greenhouse effect. Carbon dioxide is the most prevalent and emitted greenhouse gas, while methane is present in relatively smaller quantities. Greenhouse gas analysis and monitoring systems not only provide reliable data for studying global climate change but also offer fundamental technological means for promoting energy conservation and emission reduction.

[0003] Spectroscopic analysis is a rapid and effective method for detecting greenhouse gas content. For example, an existing invention patent, publication number CN108398393A, entitled "A Cavity Ring-down Spectrometer and Measurement Method for Rapidly Measuring Greenhouse Gas Content," describes a method where the gas to be detected is passed into a ring-down cavity. A laser beam generated by a laser passes through the ring-down cavity, interacts with the gas inside, and is emitted from the other end, where it is received by a photodetector. Analysis of the absorption peak spectral signal allows the determination of the greenhouse gas content.

[0004] The ring-down cavity is a crucial component of the entire detection device. Existing ring-down cavities consist of a cavity body and cavity mirrors positioned at both ends. After the laser enters the ring-down cavity, it is reflected back and forth between the two cavity mirrors, extending the laser's absorption path and increasing the interaction length between the laser and the gas being detected, thus significantly improving detection accuracy. However, the cavity mirrors at both ends require very high installation precision. Traditional ring-down cavities cannot calibrate the installation angle of the cavity mirrors, making them prone to significant installation errors that affect actual detection. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies and provide a rapid detection device for greenhouse gas content.

[0006] The objective of this invention is achieved through the following technical solution: a rapid greenhouse gas content detection device, comprising an optical frequency comb laser, a ring-down cavity, and a photodetector. The ring-down cavity includes a cavity body with an inlet and an outlet. One end of the cavity body has a fixed end plate, and the other end has an adjustable end plate. Both the fixed and adjustable end plates are equipped with cavity mirrors. An adjustment mechanism is provided between the adjustable end plate and the cavity body to adjust the installation angle of the adjustable end plate. The ring-down cavity also includes an optical path detection mechanism. During detection, the gas to be detected enters through the inlet of the ring-down cavity and exits through the outlet. The laser emitted by the optical frequency comb laser is received by the photodetector after passing through the ring-down cavity.

[0007] Preferably, the adjustment mechanism includes an inner fixing ring plate and an outer fixing ring plate disposed on the cavity. The inner fixing ring plate is located inside the adjustable end plate, and the outer fixing ring plate is located outside the adjustable end plate. An elastic sealing ring is provided between the inner fixing ring plate and the adjustable end plate. At least three adjusting screws are connected to the outer fixing ring plate, and the front end of the adjusting screws abuts against the adjustable end plate.

[0008] Preferably, four adjusting screws are provided, and the four adjusting screws are arranged in a circular array on the outer fixing ring plate.

[0009] Preferably, the optical path detection mechanism includes a calibration mirror mounted on an adjustable end plate, and a calibration laser corresponding to the calibration mirror is provided at one end of the cavity near the adjustable end plate; a transmission window is provided on the fixed end plate, and a calibration positioning plate is provided on the transmission window, with calibration marks provided on the calibration positioning plate; the laser emitted by the calibration laser is reflected by the calibration mirror and then projected onto the calibration positioning plate.

[0010] Preferably, the calibration mark is a cross mark.

[0011] Preferably, the calibration positioning plate is made of a transparent or translucent material.

[0012] Preferably, the elastic sealing ring includes an elastic curved portion located in the middle, the cross-section of the elastic curved portion is U-shaped, the elastic curved portion protrudes towards the center of the elastic sealing ring, the two ends of the elastic curved portion are provided with thrust end faces, the sides of the two ends of the elastic curved portion are provided with sealing contact portions, the adjustable end plate and the inner fixed ring plate are respectively provided with a first wedge-shaped ring groove and a second wedge-shaped ring groove, the cross-section of the first wedge-shaped ring groove and the second wedge-shaped ring groove are right-angled triangles, the first wedge-shaped ring groove and the second wedge-shaped ring groove are both provided with a conical surface and a stop surface, the sealing contact portions at both ends of the elastic curved portion are respectively located in the first wedge-shaped ring groove and the second wedge-shaped ring groove, the sealing contact portion contacts the conical surface, the thrust end face is provided with a contact protrusion ring, the contact protrusion ring contacts the stop surface.

[0013] Preferably, the inner side of the elastic bending portion is provided with a first buffer ring groove, and the outer side of the elastic bending portion is provided with a second buffer ring groove; the bottom surfaces of the first buffer ring groove and the second buffer ring groove are arc surfaces.

[0014] Preferably, the elastic sealing ring is made of nitrile rubber.

[0015] The beneficial effects of the present invention are as follows: In the present invention, the ring-down cavity is provided with an adjustment mechanism and an optical path detection mechanism, which can adjust and calibrate the installation angle of the cavity mirror, thereby improving the installation accuracy between the cavity mirrors. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a ring-down optical cavity.

[0017] Figure 2 This is a schematic diagram of the structure of the calibration positioning plate.

[0018] Figure 3 for Figure 1 Enlarged view of section A.

[0019] Figure 4 This is a cross-sectional view of the elastic sealing ring.

[0020] Figure 5 for Figure 4 Enlarged view of section B in the middle.

[0021] Figure 6 This is a schematic diagram of the modulation principle of an optical frequency comb laser.

[0022] In the diagram: 1. Cavity; 2. Fixed end plate; 3. Adjustable end plate; 4. Endoscope; 5. Air inlet; 6. Air outlet; 7. Calibration laser; 8. Calibration mirror; 9. Transmission window; 10. Calibration positioning plate; 11. Outer fixed ring plate; 12. Adjusting screw; 13. Inner fixed ring plate; 14. Pressure sensor; 16. Cross mark; 17. Elastic sealing ring; 18. First wedge-shaped ring groove; 19. Second wedge-shaped ring groove; 20. Elastic bending part; 21. Sealing contact part; 22. Thrust end face; 23. Contact protrusion ring; 24. First buffer ring groove; 25. Second buffer ring groove. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0024] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0025] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0026] like Figure 1-6 As shown, a rapid greenhouse gas content detection device includes an optical frequency comb laser, a ring-down cavity, and a photodetector. The ring-down cavity includes a cylindrical cavity 1. The cavity 1 has an inlet 5 and an outlet 6. One end of the cavity 1 has a fixed end plate 2, and the other end has an adjustable end plate 3. Both the fixed end plate 2 and the adjustable end plate 3 are equipped with cavity mirrors 4. The fixed end plate 2 is perpendicular to the central axis of the cavity 1. The cavity mirror 4 is a plano-concave mirror, with a concave surface on the side facing inwards from the cavity 1. During detection, the gas to be detected enters through the inlet of the ring-down cavity and exits through the outlet. The laser emitted by the optical frequency comb laser passes through the ring-down cavity and is received by the photodetector, obtaining the absorption peak spectral signal.

[0027] An adjustment mechanism is provided between the adjustable end plate 3 and the cavity 1 to adjust the installation angle of the adjustable end plate. Specifically, the adjustment mechanism includes an inner fixing ring plate 13 and an outer fixing ring plate 11 disposed on the cavity 1, both of which are circular ring-shaped structures. The inner fixing ring plate 13 is located inside the adjustable end plate 3, and the outer fixing ring plate 11 is located outside the adjustable end plate 3. An elastic sealing ring 17 is provided between the inner fixing ring plate and the adjustable end plate. At least three adjusting screws 12 are connected to the outer fixing ring plate 11, and the front end of the adjusting screws 12 abuts against the adjustable end plate 3. In this application, four adjusting screws 12 are provided, and the four adjusting screws 12 are arranged in a circular array on the outer fixing ring plate 11. The elastic sealing ring 17 is made of a flexible material such as rubber. The angle of the adjustable end plate is adjusted by adjusting the screws 12. The elastic sealing ring 17 has the following two functions: 1. The elastic sealing ring 17 acts as a seal to prevent gas leakage in the decaying optical cavity; 2. The elastic sealing ring 17 has a certain elasticity, which allows the adjustable end plate 3 to be tightened against the front end of the adjustable screw 12. Preferably, the elastic sealing ring 17 is made of nitrile rubber.

[0028] Furthermore, the elastic sealing ring includes an elastic bending portion 20 located in the middle. The cross-section of the elastic bending portion 20 is U-shaped and protrudes towards the center of the elastic sealing ring. Both ends of the elastic bending portion 20 are provided with thrust end faces 22. The sides of both ends of the elastic bending portion 20 are provided with sealing contact portions 21. The adjustable end plate 3 and the inner fixed ring plate 13 are respectively provided with a first wedge-shaped ring groove 18 and a second wedge-shaped ring groove 19. The cross-section of the first wedge-shaped ring groove 18 and the second wedge-shaped ring groove 18 is a right-angled triangle. Both the first wedge-shaped ring groove 18 and the second wedge-shaped ring groove 19 include a conical surface and a stop surface. The sealing contact portions 21 at both ends of the elastic bending portion 20 are located in the first wedge-shaped ring groove 18 and the second wedge-shaped ring groove 19, respectively. The sealing contact portions 21 are in contact with the conical surface. The thrust end face 22 is provided with a contact protrusion ring 23, which is in contact with the stop surface.

[0029] The elastic bending portion 20 is bent into a "U" shape. After being bent, the elastic bending portion 20 stores a certain amount of elastic potential energy. Both ends of the elastic bending portion 20 tend to open outwards, so the sealing contact portions 21 at both ends of the elastic bending portion can tightly fit against the conical surface. The contact position between the sealing contact portion 21 and the conical surface achieves the first seal. Since the sealing contact portion 21 is located in the first and second wedge-shaped annular grooves, under the action of the conical surface, the end of the elastic bending portion 20 tends to move towards the stop surface, thereby causing the contact protrusion 23 on the thrust end face 22 to tightly fit against the stop surface, thus achieving the second seal and effectively improving the sealing effect. Under the action of the elastic potential energy of the elastic bending portion 20, the adjustable end plate 3 can firmly press against the front end of the adjusting screw, so that the adjustable end plate can remain stable in the non-adjusted state.

[0030] Because the surface of the elastic bending portion 20 is subjected to significant tension during bending, it is prone to cracking. In this application, a first buffer ring groove 24 is provided on the inner side of the elastic bending portion 20, and a second buffer ring groove 25 is provided on the outer side. Both the first and second buffer ring grooves 24 and 25 are arranged circumferentially along the elastic sealing ring 17. The bottom surfaces of the first and second buffer ring grooves 24 and 25 are arc-shaped. By providing the first and second buffer ring grooves 24 on the surface of the elastic bending portion 20, the surface tension of the elastic bending portion 20 during bending is effectively reduced, lowering the risk of cracking and improving the service life of the elastic sealing ring 17.

[0031] The ring-down cavity also includes an optical path detection mechanism. Specifically, the optical path detection mechanism includes a calibration mirror 8 mounted on the adjustable end plate 3. The calibration mirror 8 is a 45-degree mirror, and its reflective surface forms a 45-degree angle with the adjustable end plate. A calibration laser 7, corresponding to the calibration mirror, is located at one end of the cavity 1 near the adjustable end plate. A transmission window 9 is provided on the fixed end plate 2, and a calibration positioning plate 10 is provided on the transmission window 9. The calibration positioning plate 10 has a calibration mark 16. The calibration positioning plate 10 is made of transparent or semi-transparent material. The calibration mark 16 is a cross mark located at the center of the calibration positioning plate 10. The installation error between the two cavity mirrors is detected by the optical path detection mechanism. During detection, the laser emitted by the calibration laser 7 is reflected by the calibration mirror 8 and projected onto the calibration positioning plate 10. If the spot of the laser 7 hits the calibration mark 16 at the center of the calibration positioning plate 10, it indicates that the installation accuracy between the two cavity mirrors meets the requirements and the two cavity mirrors are parallel. If the spot of the calibration laser 7 deviates from the calibration mark 16 at the center of the calibration positioning plate 10, it indicates that there is an installation angle error between the two cavity mirrors. Adjust the angle of the adjustable end plate 3 by adjusting the screw until the spot of the calibration laser 7 is located on the calibration mark 16 of the calibration positioning plate 10.

[0032] The cavity 1 is also equipped with a pressure sensor 14, which can monitor the pressure of the gas filling the cavity.

[0033] In this invention, the ring-down cavity is equipped with an adjustment mechanism and an optical path detection mechanism, which can adjust and calibrate the installation angle of the cavity mirror, thereby improving the installation accuracy between the cavity mirrors.

[0034] During detection, a ring-down optical cavity is used as a sample cell to study cavity ring-down-dissipation (UFS-CRDS) technology based on ultrafast spectroscopy, which can be used to achieve high-precision measurement of greenhouse gases, especially CO2.

[0035] When the ring-down cavity is filled with gas, the change in the intensity of transmitted light after passing through the ring-down cavity is shown in the following equation:

[0036] ;

[0037] According to Lambert-Beer's law, after light interacts with a sample, the intensity of transmitted light is related to the sample's absorption coefficient. related:

[0038] ;

[0039] Where L is the sample length. It is the intensity of the incident light. It is the absorption coefficient, and the absorption signal is proportional to the sample length. When the probe light mode resonates with the cavity mode, the effective interaction length can be increased, thus improving the sensitivity of the cavity spectrum.

[0040] In this application, the laser emitted by an optical frequency comb laser is modulated. The modulation principle is shown in Figure 7, and includes a computer, a preamplifier, a lock-in amplifier, a signal generator, a photodetector, and a laser controller. The photodetector detects the emitted laser light from the decaying optical cavity. The preamplifier amplifies the electrical signal detected by the photodetector and converts the amplified current signal into a voltage signal, which is then output to the lock-in amplifier for harmonic detection. The lock-in amplifier module generates a high-frequency sinusoidal modulation signal. This signal serves as a reference signal, which, along with the voltage signal from the photodetector, is demodulated by phase-sensitive detection to obtain the second harmonic signal. It also serves as the input signal to the laser controller, transmitted via the computer to the signal generator. The signal generator then generates a high-frequency sinusoidal modulation signal, which is transmitted to the laser controller to drive the optical frequency comb laser to output low-frequency scanning and high-frequency modulated laser light. The high-frequency sinusoidal modulation signal is also input to the lock-in amplifier as a reference signal. This process completes the modulation of the laser.

[0041] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A device for rapid detection of greenhouse gas content, characterized in that, The system includes an optical frequency comb laser, a ring-down cavity, and a photodetector. The ring-down cavity includes a cavity body with an inlet and an outlet. One end of the cavity body has a fixed end plate, and the other end has an adjustable end plate. Both the fixed and adjustable end plates are equipped with cavity mirrors. An adjustment mechanism is provided between the adjustable end plate and the cavity body to adjust the installation angle of the adjustable end plate. The ring-down cavity also includes an optical path detection mechanism. During detection, the gas to be detected enters through the inlet of the ring-down cavity and exits through the outlet. The laser emitted by the optical frequency comb laser is received by the photodetector after passing through the ring-down cavity. The adjustment mechanism includes an inner fixed ring plate and an outer fixed ring plate disposed on the cavity. The inner fixed ring plate is located inside the adjustable end plate, and the outer fixed ring plate is located outside the adjustable end plate. An elastic sealing ring is provided between the inner fixed ring plate and the adjustable end plate. At least three adjusting screws are connected to the outer fixed ring plate, and the front end of the adjusting screws abuts against the adjustable end plate. The optical path detection mechanism includes a calibration mirror mounted on an adjustable end plate, and a calibration laser corresponding to the calibration mirror is mounted on one end of the cavity near the adjustable end plate; a transmission window is mounted on the fixed end plate, and a calibration positioning plate is mounted on the transmission window, with calibration marks on the calibration positioning plate; the laser emitted by the calibration laser is reflected by the calibration mirror and then projected onto the calibration positioning plate. The elastic sealing ring includes an elastic curved portion located in the middle. The cross-section of the elastic curved portion is U-shaped and protrudes towards the center of the elastic sealing ring. Both ends of the elastic curved portion are provided with thrust end faces, and the sides of both ends of the elastic curved portion are provided with sealing contact portions. The adjustable end plate and the inner fixed ring plate are respectively provided with a first wedge-shaped ring groove and a second wedge-shaped ring groove. The cross-section of the first wedge-shaped ring groove and the second wedge-shaped ring groove are right-angled triangles. Both the first wedge-shaped ring groove and the second wedge-shaped ring groove include a conical surface and a stop surface. The sealing contact portions at both ends of the elastic curved portion are located in the first wedge-shaped ring groove and the second wedge-shaped ring groove, respectively. The sealing contact portions contact the conical surface. A contact protrusion is provided on the thrust end face, and the contact protrusion contacts the stop surface. The inner side of the elastic curved portion is provided with a first buffer ring groove, and the outer side of the elastic curved portion is provided with a second buffer ring groove. The bottom surfaces of the first buffer ring groove and the second buffer ring groove are arc surfaces.

2. The device for rapid detection of greenhouse gas content according to claim 1, characterized in that, The calibration mark is a cross mark.

3. The device for rapid detection of greenhouse gas content according to claim 1, characterized in that, The calibration positioning plate is made of transparent or translucent material.

4. The device for rapid detection of greenhouse gas content according to claim 1, characterized in that, The elastic sealing ring is made of nitrile rubber.

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