Optical interference methane detector absorption cell assembly

Abstract

This utility model relates to the field of gas detection technology, specifically to an absorption tube assembly for an optical interference methane detector, comprising a tube body, a first end cap, a second end cap, and a flow guiding structure. The threaded connection of the first and second end caps ensures a reliable seal at both ends of the tube body and facilitates disassembly for replacement of expired reagents within the storage chamber. The flow guiding structure optimizes the airflow path by setting a first distribution plate and a second distribution plate, with several first and second air holes respectively formed on them. This design forces the incoming mixed gas to pass uniformly through the entire reagent layer of the storage chamber, significantly extending the effective contact time and contact area between the gas and the reagent, reducing refractive index measurement deviations caused by residual impurity gases, and ultimately improving the accuracy and reliability of the methane volume fraction determination results.

Description

Technical Field

[0001] This utility model relates to the field of gas detection technology, and more specifically, to an absorption tube assembly for an optical interference methane detector. Background Technology

[0002] An optical interferometric methane analyzer is an instrument that quantitatively analyzes gas composition by measuring changes in the refractive index of a gas. The calibration of the optical interferometric methane analyzer uses a pressure method. According to the operating principle of the analyzer, when there is no methane gas in the test environment, both the gas sample chamber and the air chamber of the analyzer are filled with air, resulting in the same refractive index and optical path length, and the interference fringes in the analyzer do not shift. When methane gas is present in the test environment, the refractive index changes due to the change in gas composition in the gas sample chamber, and the optical path length of the gas sample chamber also changes accordingly, causing the interference fringes to shift. The amount of shift in the interference fringes is proportional to the volume fraction of methane. Measuring this shift allows for the measurement of the volume fraction of methane in the air. Since the gas mixture to be measured usually contains water vapor and carbon dioxide, and the refractive index of water vapor Z1≈1.33 is much higher than that of dry air Z0≈1.0003, if the moisture content of the gas mixture to be measured is high, it will significantly change the refractive index, leading to an inflated methane concentration reading. The refractive index of carbon dioxide, Z3≈1.00044, is close to that of methane, Z4≈1.00045. When the gas being measured contains carbon dioxide, its refractive index is superimposed on that of methane, causing the interference fringe shift to deviate from the theoretical value of a pure methane-air system, resulting in an overestimation or underestimation of the methane concentration. Therefore, when using an optical interferometric methane detector, it is necessary to remove water vapor and carbon dioxide from the gas mixture being measured.

[0003] Existing optical interferometric methane detectors typically have a drying tube at the sampling tube, which is filled with a reagent to remove impurities such as water vapor and carbon dioxide from the gas mixture to be measured. Due to its relatively simple structure, it cannot fully remove impurities from the gas mixture to be measured, resulting in inaccurate measurement results. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an absorption tube assembly for an optical interference methane detector, designed to effectively remove impurity gases from the mixed gas to be measured, thereby improving the accuracy of the measurement results.

[0005] An absorption tube assembly for an optical interference methane detector according to an embodiment of the present invention includes: The tube body has a storage cavity inside, and the storage cavity has openings at both ends; A first end cap is threaded to one end of the tube body; an air inlet pipe is provided on the first end cap. A second end cap is threaded to the other end of the tube body; an exhaust pipe is provided on the second end cap. The flow guiding structure has a first distribution plate and a second distribution plate respectively provided at both ends of the pipe body. The first distribution plate is provided with a plurality of first air holes, and the second distribution plate is provided with a plurality of second air holes. The air inlet pipe is connected to the storage cavity through the first air holes, and the air outlet pipe is connected to the storage cavity through the second air holes.

[0006] According to some embodiments of the present invention, the first pore and the second pore are radially and uniformly distributed on the first distribution plate and the second distribution plate; the diameter of the first pore and the second pore gradually increases radially.

[0007] According to some embodiments of the present invention, the first air hole of the first distribution plate and the second air hole of the second distribution plate are arranged in an axially offset manner.

[0008] According to some embodiments of the present invention, a first slot is provided on the first distribution plate, a second slot is provided on the second distribution plate, a first locking post is provided on the tube body corresponding to the first slot, and a second locking post is provided on the tube body corresponding to the second slot.

[0009] According to some embodiments of this utility model, the tube body is made of a transparent material.

[0010] According to some embodiments of this utility model, a color matching card is provided on the outer peripheral wall of the tube.

[0011] According to some embodiments of this utility model, the outer peripheral walls of the intake pipe and the exhaust pipe are respectively provided with a pagoda structure.

[0012] According to some embodiments of the present invention, a first sealing gasket is provided between the first end cap and the tube body, and a second sealing gasket is provided between the second end cap and the tube body.

[0013] According to some embodiments of the present invention, both the first end cap and the second end cap are made of brass.

[0014] According to some embodiments of the present invention, anti-slip textures are respectively provided on the outer peripheral walls of the first end cap and the second end cap.

[0015] An absorption tube assembly of an optical interference type methane detector according to an embodiment of the present invention has at least the following beneficial effects: According to the present invention, the absorption tube assembly of the optical interference methane detector includes a tube body, a first end cap, a second end cap, and a flow guiding structure. A storage chamber is provided within the tube body, with openings at both ends. The first end cap is threaded to one end of the tube body; an inlet pipe is provided on the first end cap; the second end cap is threaded to the other end of the tube body; an exhaust pipe is provided on the second end cap; the flow guiding structure has a first distribution plate and a second distribution plate at each end of the tube body, with a plurality of first air holes on the first distribution plate and a plurality of second air holes on the second distribution plate; the inlet pipe communicates with the storage chamber through the first air holes; and the exhaust pipe communicates with the storage chamber through the second air holes. Through this structural design, the threaded connection of the first and second end caps ensures reliable sealing of the openings at both ends of the tube body, while facilitating disassembly for replacement of expired reagents in the storage chamber. The flow guiding structure optimizes and controls the airflow path by providing the first and second distribution plates, each with a plurality of first and second air holes. This design forces the incoming mixed gas to pass uniformly through the reagent layer throughout the storage chamber, significantly extending the effective contact time and contact area between the gas and the reagent. This overcomes the problems of localized airflow short-circuiting or insufficient contact that may exist in traditional simple drying tubes. Consequently, it significantly improves the removal efficiency of interfering impurity gases, especially water vapor and carbon dioxide, making the gas composition entering the main body of the analyzer closer to a pure methane-air mixture. This reduces refractive index measurement deviations caused by residual impurity gases at the source, ultimately improving the accuracy and reliability of methane volume fraction determination results. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a cross-sectional structural diagram of the present invention; Figure 3 This is a schematic diagram of an exploded structure of the present invention; Figure 4 This is a schematic diagram of the flow guiding structure and gas passage of this utility model.

[0017] In the picture: 100 - Tube body, 110 - Storage cavity, 120 - First retaining post, 130 - Second retaining post, 140 - Color matching card; 200-First end cap, 210-Intake pipe, 211-Pagoda structure, 220-First sealing gasket, 230-Anti-slip texture; 300 - Second end cap, 310 - Exhaust pipe, 320 - Second sealing gasket; 400 - Flow guiding structure, 410 - First distribution plate, 411 - First air hole, 412 - First slot, 420 - Second distribution plate, 421 - Second air hole, 422 - Second slot, 500 - Flexible hose. Detailed Implementation

[0018] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0019] In the description of this utility model, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this utility model 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, they should not be construed as limitations on this utility model.

[0020] In the description of this utility model, "multiple" refers to two or more. The use of "first" and "second" is for distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features or their sequential relationship.

[0021] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0022] Reference Figures 1 to 4As shown, this utility model discloses an absorption tube assembly for an optical interference methane detector. The absorption tube assembly includes a tube body 100, a first end cap 200, a second end cap 300, and a flow guiding structure 400. A storage cavity 110 is provided inside the tube body 100, with openings at both ends. The first end cap 200 is threadedly connected to one end of the tube body 100. An air inlet pipe 210 is provided on the first end cap 200. The second end cap 300 is threadedly connected to the other end of the tube body 100. The tube body 100 is connected by a threaded connection at one end; an exhaust pipe 310 is provided on the second end cap 300; a first distribution plate 410 and a second distribution plate 420 are respectively provided at both ends of the flow guiding structure 400. The first distribution plate 410 is provided with a plurality of first air holes 411, and the second distribution plate 420 is provided with a plurality of second air holes 421; the inlet pipe 210 is connected to the storage chamber 110 through the first air holes 411; the exhaust pipe 310 is connected to the storage chamber 110 through the second air holes 421. Specifically, in this embodiment, the mixed gas to be measured first enters the absorption tube assembly through the inlet pipe 210 on the first end cap 200. The mixed gas is evenly dispersed through the plurality of first air holes 411 on the first distribution plate 410 of the flow guiding structure 400 and then enters the storage chamber 110 of the tube body 100. The storage chamber 110 is filled with a chemical agent specifically used to remove water vapor and carbon dioxide. When the mixed gas flows through the storage chamber 110, the water vapor and carbon dioxide molecules inside react chemically or are physically adsorbed with the reagent, thus being effectively removed. The purified gas then flows to the other end of the storage chamber 110 and is collected through several second vents 421 on the second distribution plate 420 of the flow guiding structure 400. Finally, it flows out of the absorption tube assembly through the exhaust pipe 310 on the second end cover 300 and enters the subsequent optical interference methane detector body for refractive index measurement.

[0023] In this embodiment, the threaded first end cap 200 and second end cap 300 ensure a reliable seal between the openings at both ends of the tube body 100, while facilitating disassembly for replacement of expired reagents in the storage chamber 110. The flow guiding structure 400 optimizes the airflow path by setting a first distribution plate 410 and a second distribution plate 420, with several first air holes 411 and several second air holes 421 respectively on them. This design forces the incoming mixed gas to pass uniformly through the entire reagent layer of the storage chamber 110, greatly extending the effective contact time and contact area between the gas and the reagent, overcoming the problems of local airflow short-circuiting or insufficient contact that may exist in traditional simple drying tubes. This significantly improves the removal efficiency of interfering impurity gases, especially water vapor and carbon dioxide, making the gas composition that finally enters the main body of the measuring instrument closer to a pure methane and air mixture, reducing the refractive index measurement deviation caused by residual impurity gases at the source, and ultimately improving the accuracy and reliability of the methane volume fraction measurement results.

[0024] In some embodiments of this invention, the first vent 411 and the second vent 421 are radially and uniformly distributed on the first distribution plate 410 and the second distribution plate 420; the diameters of the first vent 411 and the second vent 421 gradually increase radially. Specifically, in this embodiment, after the gas mixture to be tested enters from the inlet pipe 210 of the first end cap 200, it first contacts the first distribution plate 410 of the guide structure 400. Since the first vent 411 is radially and uniformly distributed on the first distribution plate 410, and the vent diameter gradually increases radially, the gas obtains differentiated channel resistance when flowing through different radial positions. The small-diameter first vent 411 near the center of the plate forms a higher flow resistance, forcing some gas to diffuse towards the edge region of the plate; while the large-diameter first vent 411 far from the center of the plate provides a lower flow resistance, allowing more gas to pass through. This gradient distribution of vent diameter promotes the gas to naturally form a uniform radial flow pattern, avoiding gas concentration through the center or edge region of the distribution plate. The gas then enters the storage chamber 110 of the tube 100 uniformly through the first vent 411 and flows axially along the storage chamber 110. The impurity removal agent filled in the storage chamber 110 comes into full contact with the gas, and water vapor and carbon dioxide are efficiently removed. When the purified gas reaches the other end of the storage chamber 110, it gathers at the second distribution plate 420 of the guide structure 400. The second vent 421 is also radially and uniformly distributed with its diameter gradually increasing radially. This structure ensures that the gas maintains a uniform flow velocity distribution during the outflow process, avoiding local gas stagnation or short circuits. Finally, the gas is smoothly output from the exhaust pipe 310 of the second end cap 300 through the second vent 421 and enters the methane detector body for refractive index detection. The radially and uniformly distributed first vent 411 and second vent 421 ensure that the gas is fully covered across the cross-section of the storage chamber 110, eliminating the airflow dead zone problem common in traditional simple drying tubes. The gradient design with gradually increasing orifice diameter along the radial direction creates a self-regulating flow resistance: the small orifice diameter in the central region suppresses center penetration caused by high-speed airflow impact, forcing the gas to diffuse outwards; the large orifice diameter in the outer peripheral region reduces flow resistance and prevents gas accumulation at the cavity edge. This synergistic effect allows the gas to automatically form a uniform axial laminar flow as it passes through the storage cavity 110, ensuring that all gas molecules can fully contact the reagent layer and maximize the effective adsorption capacity of the reagent. Simultaneously, the radial flow velocity equalization characteristic significantly extends the interaction time between the gas and the reagent, completely eliminating insufficient contact caused by excessively high local airflow velocities. This structure fundamentally solves the technical defect of low impurity removal efficiency in traditional drying tubes, bringing the removal rates of water vapor and carbon dioxide close to the theoretical limit. Ultimately, it ensures that the change in refractive index of the gas entering the methane analyzer only reflects the change in methane concentration, fundamentally eliminating the interference of impurity gases on the displacement of interference fringes and achieving high-precision measurement of methane volume fraction.

[0025] In some embodiments of this utility model, the first vent 411 of the first distribution plate 410 and the second vent 421 of the second distribution plate 420 are arranged in a staggered manner along the axial direction. Specifically, in this embodiment, after the gas mixture to be tested enters the flow guiding structure 400 from the inlet pipe 210 of the first end cover 200, it first passes through the first vent 411 on the first distribution plate 410, which is radially and uniformly distributed and whose diameter gradually increases radially. Because the first vent 411 and the second vent 421 are arranged in a staggered manner along the axial direction, the gas cannot flow straight to the second vent 421 of the second distribution plate 420 after entering the storage cavity 110 through the first vent 411. This staggered design forces the gas to generate multi-directional deflection flow in the storage cavity 110. When the gas flows through the first distribution plate 410, the small-diameter first vent 411 in the central region forms high resistance, causing the gas to diffuse outward, while the large-diameter first vent 411 in the outer peripheral region guides the gas to enter the cross-section of the storage cavity 110 uniformly. Due to the axial positional deviation between the first vent 411 and the second vent 421, the gas entering the storage chamber 110 must migrate along a non-linear path towards the second distribution plate 420. During this migration, the gas is forced to repeatedly change its flow direction, passing through the impurity removal agent layer filled in the storage chamber 110. This multi-directional turning flow mode significantly increases the contact frequency between gas molecules and agent particles, and prolongs the residence time of the gas in the storage chamber 110. Finally, after reaching the second distribution plate 420, the gas converges through the second vent 421, which is also radially distributed and has a radially increased aperture, and is smoothly output to the methane detector body through the exhaust pipe 310 of the second end cap 300.

[0026] In some embodiments of this utility model, a first slot 412 is provided on the first distribution plate 410, a second slot 422 is provided on the second distribution plate 420, a first locking post 120 is provided on the pipe body 100 corresponding to the first slot 412, and a second locking post 130 is provided on the pipe body 100 corresponding to the second slot 422. Specifically, in this embodiment, during installation, the first distribution plate 410 is assembled first using the first locking post 120, and then the second distribution plate 420 is assembled using the second locking post 130. In the assembly design, the positions of the first locking post 120 and the second locking post 130 can ensure the installation angle of the first distribution plate 410 and the second distribution plate 420. This ensures that the first air hole 411 of the first distribution plate 410 and the second air hole 421 of the second distribution plate 420 are arranged axially offset.

[0027] In some embodiments of this utility model, the tube body 100 is made of a transparent material. Specifically, in this embodiment, the tube body 100 is made of transparent acrylic material, which has advantages such as impact resistance, ease of processing, and the ability to observe the state of the internal desiccant.

[0028] In some embodiments of this invention, a color comparison chart 140 is provided on the outer peripheral wall of the tube 100. Specifically, in this embodiment, during the verification process, the operator can directly observe the state changes of the reagent in the storage cavity 110 through the transparent tube 100, and simultaneously use the color comparison chart 140 on the outer peripheral wall of the tube 100 to assess the remaining effective volume of the reagent in real time. When the color change of the reagent reaches the critical threshold marked on the color chart, it indicates that the reagent needs to be replaced. The combination design of the transparent tube 100 and the color comparison chart 140 innovatively realizes real-time visual monitoring of the reagent's efficacy. The transparent material allows the operator to intuitively grasp the reagent consumption process, avoiding the problem of reagent overuse or premature replacement caused by the inability to observe the internal state in traditional opaque tubes 100. The color comparison chart 140 fixed on the outer peripheral wall provides a standardized colorimetric reference, and its color gradation blocks marked according to the percentage of effective volume of the reagent enable the operator to accurately determine the current remaining adsorption capacity of the reagent. When the observed color change of the reagent reaches 50% of the color chart area, it indicates that the remaining reagent can only maintain half-load processing capacity and needs to be replaced. When it reaches 20% of the calibrated color level on the color chart, immediate replacement of the reagent is mandatory to prevent impurities from penetrating. This design eliminates the risk of decreased impurity removal rate due to reagent failure at the source, ensuring continuous and efficient removal of water vapor and carbon dioxide. At the same time, visual monitoring greatly reduces maintenance blindness, avoiding measurement errors caused by untimely replacement and preventing reagent waste due to excessive replacement. This self-diagnostic function works synergistically with the original airflow optimization characteristics of the flow guidance system to maintain stable gas purification performance throughout the entire life cycle of the absorption tube assembly, providing dual reliability assurance for the optical interferometry methane concentration detection.

[0029] In some embodiments of this utility model, the outer peripheral walls of the intake pipe 210 and the exhaust pipe 310 are respectively provided with a pagoda structure 211. Specifically, in this embodiment, the intake pipe 210 and the exhaust pipe 310 are respectively connected to the flexible hose 500 inside the optical interference methane detector. By designing the pagoda structure 211, not only can the installation efficiency be improved, but the sealing performance can also be improved.

[0030] In some embodiments of this utility model, a first sealing gasket 220 is provided between the first end cap 200 and the tube body 100, and a second sealing gasket 320 is provided between the second end cap 300 and the tube body 100. Specifically, in this embodiment, by providing the first sealing gasket 220 and the second sealing gasket 320, the sealing performance of the first end cap 200 and the second end cap 300 can be improved.

[0031] In some embodiments of this utility model, both the first end cap 200 and the second end cap 300 are made of brass. Specifically, in this embodiment, brass possesses excellent machinability, allowing for the formation of a high-precision threaded connection structure through precision turning. This ensures a complete and stress-free sealing assembly where the first end cap 200 is fully engaged with one end of the tube body 100, and the second end cap 300 is fully engaged with the other end of the tube body 100. Its inherent metallic ductility allows for controllable plastic deformation of the end caps during tightening.

[0032] In some embodiments of this utility model, anti-slip textures 230 are respectively provided on the outer peripheral walls of the first end cap 200 and the second end cap 300. Specifically, in this embodiment, the anti-slip textures 230 facilitate the installation or removal of the first end cap 200 or the second end cap 300 by the operator.

[0033] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. An absorption tube assembly for an optical interference type methane detector, characterized in that, include: A tube body (100) is provided inside the tube body (100), and the storage cavity (110) is open at both ends; A first end cap (200) is threaded to one end of the tube body (100); an air inlet pipe (210) is provided on the first end cap (200). The second end cap (300) is threaded to the other end of the tube body (100); an exhaust pipe (310) is provided on the second end cap (300). A flow guiding structure (400) is provided with a first distribution plate (410) and a second distribution plate (420) at both ends of the pipe body (100). The first distribution plate (410) is provided with a plurality of first air holes (411), and the second distribution plate (420) is provided with a plurality of second air holes (421). The air inlet pipe (210) is connected to the storage chamber (110) through the first air holes (411). The exhaust pipe (310) is connected to the storage chamber (110) through the second air holes (421).

2. The absorption tube assembly of the optical interference methane detector according to claim 1, characterized in that, The first pore (411) and the second pore (421) are radially and uniformly distributed on the first distribution plate (410) and the second distribution plate (420); the diameter of the first pore (411) and the second pore (421) gradually increases radially.

3. The absorption tube assembly of the optical interference methane detector according to claim 2, characterized in that, The first air hole (411) of the first distribution plate (410) and the second air hole (421) of the second distribution plate (420) are arranged in an axially offset manner.

4. The absorption tube assembly of the optical interference methane detector according to claim 3, characterized in that, The first distribution plate (410) is provided with a first slot (412), the second distribution plate (420) is provided with a second slot (422), the tube body (100) is provided with a first locking post (120) corresponding to the first slot (412), and the tube body (100) is provided with a second locking post (130) corresponding to the second slot (422).

5. The absorption tube assembly of the optical interference methane detector according to claim 1, characterized in that, The tube body (100) is made of transparent material.

6. The absorption tube assembly of the optical interference methane detector according to claim 5, characterized in that, The outer peripheral wall of the tube (100) is provided with a color matching card (140).

7. The absorption tube assembly of the optical interference methane detector according to claim 1, characterized in that, The outer peripheral walls of the intake pipe (210) and the exhaust pipe (310) are respectively provided with pagoda structures (211).

8. The absorption tube assembly of the optical interference methane detector according to claim 1, characterized in that, A first sealing gasket (220) is provided between the first end cap (200) and the tube body (100), and a second sealing gasket (320) is provided between the second end cap (300) and the tube body (100).

9. The absorption tube assembly of the optical interference methane detector according to claim 1, characterized in that, Both the first end cap (200) and the second end cap (300) are made of brass.

10. The absorption tube assembly of the optical interference methane detector according to claim 9, characterized in that, The outer peripheral walls of the first end cap (200) and the second end cap (300) are respectively provided with anti-slip texture (230).

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