Methane concentration analyzer

Abstract

The methane concentration analyzer comprises a shell, a laser, a photoelectric detector, a laser driving circuit and an acquisition processing circuit are arranged in the shell, a lower end cover is arranged at the top of the shell, and the upper portion of the lower end cover is connected with an upper end cover through a supporting rod. 10 self-focusing lenses are mounted on the opposite surfaces of the upper end cover and the lower end cover, the 10 lenses are circumferentially and uniformly arranged clockwise, and the lenses with the same serial number on the upper end cover and the lower end cover are oppositely arranged; the lenses on the upper end cover and the lower end cover are connected through optical fibers at intervals of two lenses, the first lens on the lower end cover is connected with a laser through an incident optical fiber, and the eighth lens on the lower end cover is connected with a photoelectric detector through an emergent optical fiber. According to the analyzer disclosed by the utility model, the characteristic that the end face of the self-focusing lens is focused is utilized, the self-focusing lens is used as the collimating lens, the multi-time long-optical-path absorption gas chamber is designed, the length of an absorption path is increased, and the measurement accuracy is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of gas detection devices, in particular to a kind of methane concentration analyzers. BACKGROUND

[0002] Methane is the second largest greenhouse gas in the atmosphere after carbon dioxide, and its greenhouse effect is much higher than that of carbon dioxide. According to estimates by the International Organization of Climate Scientists, unit mass of methane contributes about 28 to 36 times more to the greenhouse effect than carbon dioxide on a time scale of about 20 years. The ocean is one of the important sources of atmospheric methane, and measuring the concentration of oceanic atmospheric methane helps to more accurately assess the contribution of methane to global climate change.

[0003] Currently, the measurement of oceanic atmospheric methane concentration generally uses tunable laser absorption spectroscopy (TDLAS). Although this method has the advantages of high sensitivity, high precision, high selectivity and fast response speed, it still faces some challenges, especially when the methane content in the oceanic atmosphere is very low.

[0004] Currently, the use of multiple reflection absorption cells to increase the absorption path length is a common means to improve the accuracy of atmospheric methane measurement, among which the Herriott absorption cell is the most widely used. However, the Herriott absorption cell still has some problems in practical application, mainly including:

[0005] 1. The design of Herriott absorption cell usually requires the laser beam to enter the absorption cell at a specific angle and position to achieve the best light path reflection and optical path utilization. However, due to the complexity of the internal structure of the absorption cell, the collimation of the laser becomes relatively difficult. The light path design inside the Herriott absorption cell is relatively complex, and the beam undergoes multiple reflections in the cell, forming a long optical path. Although this complex light path design improves the optical path utilization, it also increases the difficulty of light path adjustment and maintenance.

[0006] 2. In the Herriott absorption cell, after multiple reflections of the laser beam, the return light power may be significantly reduced due to the loss of mirrors, absorption and other loss factors in the light path. This will affect the sensitivity and accuracy of spectral measurement.

[0007] 3. The Herriott absorption cell has very high requirements for mechanical structural stability, and small deformations caused by environmental temperature changes or equipment vibration will have a serious impact on the incident and exit angles and the number of light reflections, thus causing the device to malfunction. INVENTION CONTENTS

[0008] In order to solve the above technical problems, the utility model provides a kind of methane concentration analyzer, utilize the characteristics of self-focusing lens end face focusing, it is used as collimating lens, design multiple long optical path absorption gas chamber, enhance the length of absorption path, improve measurement accuracy.

[0009] To achieve the above object, the technical scheme of the utility model is as follows:

[0010] A kind of methane concentration analyzer, including shell, the lower end cover is arranged at the top of the shell, laser, photoelectric detector, laser driver circuit and acquisition processing circuit are arranged in the shell, the cable is connected at the bottom of the shell;The upper end cover is connected by support rod above the lower end cover, 10 self-focusing lenses are mounted on the opposite face of the upper end cover and the lower end cover, 10 lenses are evenly arranged in clockwise direction, and the lens with same number is oppositely arranged on the upper end cover and the lower end cover;No.

[0011] In the above scheme, the upper end cover and the lower end cover are connected with dust screen periphery.

[0012] In the above scheme, heating module and temperature and humidity probe are arranged on the lower end cover, starting heating module can prevent the influence of condensate on the end face of optical fiber and self-focusing lens, and the temperature and humidity value in the air chamber between the upper end cover and the lower end cover can be monitored by temperature and humidity probe.

[0013] In the above scheme, the laser is electrically connected with the laser driver circuit.

[0014] In the above scheme, the photoelectric detector, temperature and humidity probe and heating module are electrically connected with the acquisition processing circuit.

[0015] In the above scheme, a circular groove is arranged at the edge of the upper end cover and the lower end cover, the dust screen is embedded in the circular groove, and a detachable structure is formed.

[0016] In the above scheme, the laser is VCSEL laser with near-infrared 1654nm waveband tail fiber.

[0017] In the further technical scheme, the dust screen is stainless steel sintered screen.

[0018] By the technical scheme, the methane concentration analyzer has the following beneficial effects:

[0019] 1、The utility model discloses a plurality of self -focusing lens series connection's mode improves the length of absorption light path, makes the spectral absorption intensity increase, improves the accuracy and the lower limit of measurement of the methane concentration measurement in the ocean atmosphere,

[0020] 2, the self -focusing lens is a kind of optical lens with refractive index distribution gradually changing along radial direction, with good focusing performance.The material used by self-focusing lens can refract the light transmitted along the axis, and the refractive index is distributed according to the law of gradually decreasing along the radial direction. The self-focusing lens can make the outgoing light rays converge smoothly and continuously to a point. The diameter of the self-focusing lens is very small, which can make the structure of the optical system more miniaturized. Moreover, the end face of the self-focusing lens is a plane, which is more convenient for optical processing compared with traditional lenses. The utility model utilizes the focusing characteristics of the end face of the self-focusing lens as a collimating lens, which can improve the aggregation performance and make the light transmission direction more accurate and controllable.

[0021] 3、The utility model discloses the dustproof net of connecting in the periphery of upper end cover and lower end cover, the dustproof net is stainless steel sintered mesh, this sintered mesh can make the gas to be measured enter the air chamber between upper end cover and lower end cover, and the stainless steel sintered mesh is used as filter element, blocks the impurity such as dust, particulate matter and enters the air chamber inside, reduces the influence of dust, particulate matter and the like on laser propagation;

[0022] 4、The utility model discloses the plurality of self -focusing lens series connection's mode does not connect adjacent lens, but connects two lenses, which can avoid the external noise caused by too small bending radius of optical fiber and the weakening of optical fiber transmission performance caused by too narrow bending.

[0023] 5、The utility model discloses the plurality of self -focusing lens series connection's mode makes the light path only transmit once between each self -focusing lens, greatly reduces the difficulty of light path design and mechanical processing, so that the influence of equipment deformation caused by temperature change, vibration and the like on light path is very small.

[0024] 6、The utility model discloses heating module and temperature and humidity probe on lower end cover, can prevent condensate from influencing optical fiber end face and self -focusing lens by starting heating module, and the temperature and humidity value in the air chamber between upper end cover and lower end cover can be monitored through temperature and humidity probe. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0026] Figure 1The utility model discloses a kind of methane concentration analyzers schematic diagram disclosed in the embodiment of the utility model.

[0027] Figure 2 It is the distribution and connection schematic diagram of self-focusing lens on lower end cover and upper end cover, (a) lower end cover, (b) upper end cover.

[0028] Figure 3 It is optical path transmission schematic diagram.

[0029] In the drawing, 1, shell; 2, laser; 3, photoelectric detector; 4, laser driver circuit; 5, acquisition processing circuit; 6, cable; 7, lower end cover; 8, upper end cover; 9, support rod; 10, dust screen; 11, heating module; 12, temperature and humidity probe; 13, incident optical fiber; 14, outgoing optical fiber; the number of first to tenth lens on lower end cover is 71-79, 70 respectively; the number of first to tenth lens on upper end cover is 81-89, 80 respectively. DETAILED DESCRIPTION

[0030] The technical scheme in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model.

[0031] The utility model provides a kind of methane concentration analyzers, including shell 1, laser 2 is arranged in shell 1 inside, photoelectric detector 3, laser driver circuit 4 and acquisition processing circuit 5, the cable 6 of shell 1 bottom is connected, for equipment power supply and communication.Laser 2 is the VCSEL laser 2 of near infrared 1654nm wave band tail fiber.Laser 2 is electrically connected with laser driver circuit 4.Photoelectric detector 3 and acquisition processing circuit 5 are electrically connected.

[0032] Shell 1 top is provided with lower end cover 7, and lower end cover 7 is connected with upper end cover 8 through three support rods 9 above lower end cover 7, and inner air chamber is formed between upper end cover 8 and lower end cover 7, and dust screen 10 is connected to the periphery of upper end cover 8 and lower end cover 7.The dust screen 10 is a stainless steel sintered screen, which allows the measured gas to enter the air chamber, and the stainless steel sintered screen acts as a filter element to block dust, particulate matter and other impurities from entering the air chamber, reducing the impact of dust, particulate matter and other impurities on laser propagation.Each of the edges of the upper end cover 8 and the lower end cover 7 is provided with a circular groove, and the dust screen 10 is embedded in the circular groove to form a detachable structure.The sintered screen can be removed from the device periodically, cleaned using a dedicated ultrasonic cleaning machine, or flushed with inert gases such as nitrogen gas from the opposite direction to make it have good gas permeability.

[0033] The upper end cover 8 is arranged in parallel with the lower end cover 7, and the distance between the two is L. The upper end cover 8 and the lower end cover 7 are both provided with 10 self-focusing lenses (hereinafter referred to as lenses for short) on the opposite surfaces, and the 10 lenses are arranged in a circumferential direction uniformly, and the same numbered lenses on the upper end cover 8 and the lower end cover 7 are arranged oppositely. The lenses on the upper end cover 8 and the lower end cover 7 are all connected by optical fibers with an interval of two lenses, specifically: the first lens 81 on the upper end cover 8 is connected to the fourth lens 84 by an optical fiber, the second lens 82 is connected to the ninth lens 89 by an optical fiber, the third lens 83 is connected to the sixth lens 86 by an optical fiber, the fifth lens 85 is connected to the eighth lens 88 by an optical fiber, and the seventh lens 87 is connected to the tenth lens 80 by an optical fiber; the second lens 72 on the lower end cover 7 is connected to the fifth lens 75 by an optical fiber, the third lens 73 is connected to the tenth lens 70 by an optical fiber, the fourth lens 74 is connected to the seventh lens 77 by an optical fiber, the sixth lens 76 is connected to the ninth lens 79 by an optical fiber, and the first lens 71 is connected to the laser 2 by an incident optical fiber 13, and the eighth lens 78 is connected to the photoelectric detector 3 by an emission optical fiber 14.

[0034] The light transmission process is as follows:

[0035] The light emitted by the laser 2 enters the first lens 71 on the lower end cover 7 through the incident optical fiber 13, and the light becomes parallel light after passing through the first lens 71. The parallel light produces spectral absorption in the gas chamber, and then enters the corresponding first lens 81 on the upper end cover 8, completing a spectral absorption. The first lens 81 on the upper end cover 8 converges and couples the light into the optical fiber, enters the fourth lens 84 on the upper end cover 8, and the light emitted from the fourth lens 84 passes through the gas chamber, enters the fourth lens 74 on the lower end cover 7, and completes a spectral absorption. Then repeat the above process, and the last time is that the eighth lens 88 on the upper end cover 8 changes the light into parallel light, and the parallel light produces spectral absorption in the absorption gas chamber, and the convergence of the light is completed by the eighth lens 78 on the lower end cover 7, and then transmitted to the photoelectric detector 3 through the emission optical fiber 14.

[0036] In the gas chamber, since 10 pairs of self-focusing lenses are arranged, the light emitted by the light source passes through the absorption gas chamber for 10 times, and therefore the absorption light path length is 10L. Since the outer shape of the absorption gas chamber is small, the spacing between each self-focusing lens is small, and if the self-focusing lenses are connected in sequence, the bending radius of the optical fiber is too small, which can cause external noise and weakening of the transmission performance of the optical fiber due to too narrow bending. Therefore, in the utility model, in the upper end cover 8, the tail fiber of the first lens 81 is not connected to the second lens 82, but is connected to the fourth lens 84, forming a cross-connection mode. The emitted light passes through the first lens group, the fourth lens group, the seventh lens group, the tenth lens group, the third lens group, the sixth lens group, the ninth lens group, the second lens group, the fifth lens group and the eighth lens group, and is converged by the eighth lens 78 on the lower end cover 7 into the outgoing optical fiber 14 and finally enters the photoelectric detector 3. The optical fiber connection mode effectively increases the bending radius of the self-focusing lens connected optical fiber, and can effectively avoid the problems of external noise and weakening of the transmission performance of the optical fiber due to too narrow bending.

[0037] The lower end cover 7 is provided with a heating module 11 and a temperature and humidity probe 12. The heating module 11 is started to prevent the influence of condensed water on the end face of the optical fiber and the self-focusing lens, and the temperature and humidity value in the gas chamber between the upper end cover 8 and the lower end cover 7 can be monitored through the temperature and humidity probe 12. The temperature and humidity probe 12 and the heating module 11 are electrically connected with the acquisition and processing circuit 5.

[0038] The working process of the methane concentration analyzer of the utility model is as follows:

[0039] (1) The gas analyzer is powered on;

[0040] (2) The heating module 11 in the gas chamber of the gas analyzer is working to heat the gas chamber;

[0041] (3) When the temperature in the gas chamber reaches the preset temperature, the laser driver circuit 4 drives the VCSEL laser 2 to work, and the light emitted by the laser 2 is transmitted to the first lens 71 on the lower end cover 7 through the incident optical fiber 13. The first lens 71 collimates the light to make it output parallel light;

[0042] (4) The light is transmitted in each self-focusing lens group, and the absorption path length of the absorption gas chamber reaches 10 times the spacing of the upper and lower end covers 7;

[0043] (5) The light enters the eighth lens of the lower end cover 7, is converged into the outgoing optical fiber 14, and then enters the photoelectric detector 3, and the photoelectric detector 3 completes the photoelectric conversion;

[0044] (6) The acquisition and processing circuit 5 completes AD conversion and data processing, and outputs the methane concentration data.

[0045] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A methane concentration analyzer characterized by comprising: The application relates to a laser particle size analyzer, which comprises a shell, a laser, a photodetector, a laser driving circuit and a collection processing circuit arranged inside the shell, and a cable connected to the bottom of the shell; a lower end cover is arranged on the top of the shell, an upper end cover is connected to the lower end cover through a supporting rod, 10 self-focusing lenses are arranged on the opposite surfaces of the upper end cover and the lower end cover, the 10 lenses are arranged in a circumferential direction in a clockwise manner, and the lenses with the same number on the upper end cover and the lower end cover are arranged oppositely; a No.1 lens on the upper end cover is connected to a No.4 lens through an optical fiber, a No.2 lens is connected to a No.9 lens through an optical fiber, a No.3 lens is connected to a No.6 lens through an optical fiber, a No.5 lens is connected to a No.8 lens through an optical fiber, and a No.7 lens is connected to a No.10 lens through an optical fiber; a No.2 lens on the lower end cover is connected to a No.5 lens through an optical fiber, a No.3 lens is connected to a No.10 lens through an optical fiber, a No.4 lens is connected to a No.7 lens through an optical fiber, a No.6 lens is connected to a No.9 lens through an optical fiber, a No.1 lens is connected to the laser through an incident optical fiber, and a No.8 lens is connected to the photodetector through an emission optical fiber.

2. A methane concentration analyzer according to claim 1, wherein Dustproof nets are connected to the peripheries of the upper end cover and the lower end cover.

3. A methane concentration analyzer according to claim 1, wherein A heating module and a temperature and humidity probe are arranged on the lower end cover.

4. The methane concentration analyzer according to claim 1, wherein The laser is electrically connected to the laser driving circuit.

5. A methane concentration analyzer according to claim 3, wherein The photodetector, the temperature and humidity probe and the heating module are electrically connected to the collection processing circuit.

6. A methane concentration analyzer according to claim 2, wherein A circular groove is arranged on the edge of the upper end cover and the lower end cover, and the dustproof net is embedded in the circular groove.

7. A methane concentration analyzer according to claim 1, wherein The laser is a near-infrared 1654nm waveband tail fiber VCSEL laser.

8. A methane concentration analyzer according to claim 2, wherein The dustproof net is a stainless steel sintered net.

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