Method and device for measuring greenhouse gas in real time through cross circulation of multiple measurement boxes

Abstract

The invention provides a method and a device for real-time measurement of cross circulation of greenhouse gas with multiple measurement boxes. The method comprises the following steps: using a set of gas analyzer, a multi-path controller and multiple measurement boxes; the top covers of the multiple measuring boxes are sequentially closed according to a set sequence, gas is extracted, the gas concentration is detected, the gas is circularly extracted and detected for multiple times according to the set sequence, and finally the measuring boxes are sequentially opened; the time required for each time of air exhaust detection is controlled within 10-30 seconds, and the time required for completing one cycle of air exhaust detection is controlled within 30 minutes; and after each cycle measurement is finished, the measurement boxes are opened in sequence. According to the method disclosed by the invention, the efficiency of monitoring the greenhouse gas flux is remarkably improved, and the device disclosed by the invention can be used for manufacturing a full-automatic multi-channel farmland greenhouse gas monitoring system, can be used for measuring greenhouse gas emission of farmland plants and is used for evaluating and screening carbon sequestration of crops.

Description

Technical Field

[0001] The present invention relates to the technical field of detecting the greenhouse gas emission flux of vegetation. Specifically, it relates to a method and device for real-time measurement of cross-circulation of greenhouse gases in multiple measurement chambers. Background Art

[0002] As an important part of the Earth's ecosystem, the greenhouse gas emissions of vegetation (mainly carbon dioxide and methane) are a key link in the global carbon cycle. Through flux detection, scientists can more accurately understand the carbon exchange process between vegetation and the atmosphere, thereby deeply understanding the mechanism and rate of the global carbon cycle. This is crucial for predicting and responding to climate change because even small changes in the carbon cycle can have a significant impact on the global climate; the data and information provided by flux detection can provide a scientific basis for policymakers to help formulate more reasonable and effective environmental policies; for example, in formulating emission reduction targets, evaluating emission reduction effects, and formulating carbon trading rules, flux detection data has important reference value.

[0003] Most of the existing detection methods are to draw gas from the sampling chamber into the gas bag, and then transport the gas bag to the laboratory for analyzing the gas concentration using a gas chromatograph. On the one hand, this technology requires manual closing of the measurement chamber and manual connection of multiple gas bags for each sampling, and after sampling, it is necessary to manually retrieve the gas bag. Therefore, continuous long-term monitoring of a sample plot cannot be carried out; on the other hand, the sample gas bag of this method also needs to be sent back to the laboratory for analysis, and the measurement data cannot be analyzed in real time. Therefore, we have made improvements to this and proposed a method and device for real-time measurement of cross-circulation of greenhouse gases in multiple measurement chambers. Summary of the Invention

[0004] In view of the above defects of the existing method and device for real-time measurement of cross-circulation of greenhouse gases in multiple measurement chambers, considering the specific feasibility and economy of farmland greenhouse gas monitoring work, and combining the experimental data of specific crop carbon sink assessment and screening, we have improved the method and device for real-time measurement of cross-circulation of greenhouse gases in multiple measurement chambers. Specifically, the present invention provides the following technical solutions.

[0005] A method for real-time measurement of cross-circulation of greenhouse gases in multiple measurement chambers, comprising:

[0006] Using a set of gas analyzers, a multi-channel controller, and several measurement chambers, where the number of measurement chambers ranges from 2 to 60;

[0007] Closing the top covers of several measurement chambers in a set order, extracting gas and detecting the gas concentration, circulating the gas extraction and detection several times in a set order, and finally opening the measurement chambers in turn;

[0008] The time required for each air extraction detection is controlled within 10 - 30 seconds, and the time required for completing one cycle of air extraction detection is controlled within 30 minutes; to reduce the data error caused by time differences between measurement chambers; after each cycle of measurement is completed, the measurement chambers are opened in sequence,

[0009] The objects and indicators detected and analyzed by the measurement chamber and the main body of the gas analyzer include: carbon dioxide, methane, nitrous oxide, ammonia, etc. in the air.

[0010] Furthermore, other sensors can be integrated into the above method to detect air temperature, air humidity, soil temperature, soil humidity, atmospheric pressure, light intensity, wind speed and direction, etc., for assisting in analyzing gas concentration, emission rate and related influencing factors.

[0011] The above term "a plurality of" means two or more, three or more, four or more, or more, and can be set according to actual needs. For the convenience of description, "a plurality of" can be expressed as "multiple".

[0012] The above term "a number of times" means two or more times, three or more times, four or more times, five or more times, or more, and can be set according to actual needs. For the convenience of description, "a number of times" can be expressed as "several times" or "a few times".

[0013] As a preferred implementation mode of the method of the present invention, the total number of measurement chambers is N, it is stipulated that the measurement chamber number k is equal to 1 to N, the initial value of the measurement chamber number is 1, the total number of cycles included in one batch of monitoring is M, the cycle number p is equal to 1 to M, and the initial value of the cycle number is 1. After power-on, first set the values of N and M, and set the initial values of k and p to 1. Then, start closing and air extraction detection from the No. 1 measurement chamber; after the detection is completed, judge whether the current cycle number p is the set total number of cycles M. If it is equal to M, open the current measurement chamber. Otherwise, continue to judge whether the current measurement chamber number k is less than the set total number of measurement chambers N. If it is less than N, increase the measurement chamber number by 1 and continue to detect the next measurement chamber; if k = N, continue to judge whether p is less than M. If it is less than M, increase p by 1, and set k to 1; if p is equal to M, it means that one batch of monitoring has been completed. At this time, judge whether it is continuous monitoring. If it is continuous monitoring, set both k and p to 1 and perform cyclic measurement again; if it is not continuous monitoring, end.

[0014] The second aspect of the present invention provides a multi-measurement box greenhouse gas cross-circulation real-time measurement device for implementing the above method. The device includes a gas analyzer main body, on which a multi-way controller main body is arranged. The gas analyzer main body is connected with two first connecting pipes, and several base structures are arranged between the two first connecting pipes. The base structures and the gas analyzer main body form a gas circuit through the two first connecting pipes, and a measurement box structure is detachably connected to each base structure.

[0015] Preferably, the above base structure includes two second connecting pipes, which are respectively communicated with the two first connecting pipes. A base main body is fixedly communicated between the two second connecting pipes. Solenoid valves are connected to both of the two second connecting pipes. A socket ring is fixedly connected to the bottom of the base main body, and a retaining ring is fixedly connected to the top of the base main body. A sealing ring is fixedly sleeved on the outer surface of the retaining ring.

[0016] In an implementation manner, the measurement box structure is a first measurement component. The first measurement component includes a first measurement box inserted into the outer surface of the sealing ring. A lid assembly that can be opened and closed is arranged on the top of the first measurement box.

[0017] The lid assembly includes a fixed seat fixedly installed on one side of the first measurement box and a protective cover located above the first measurement box. A first connecting plate is fixedly installed on the top of the fixed seat, and a second connecting plate is fixedly installed on the top of the protective cover. A first connecting shaft is inserted between the second connecting plate and the first connecting plate. The first connecting shaft is fixedly connected to the second connecting plate and rotatably connected to the first connecting plate. A first motor is fixedly installed on one side of the fixed seat, and the output shaft of the first motor is fixedly connected to the first connecting shaft.

[0018] Further, the measurement box structure is a second measurement component. The second measurement component includes a second measurement box inserted into the outer surface of the sealing ring. A lifting ring is sleeved on the outer surface of the second measurement box. A plurality of electric push rods are installed between the bottom of the lifting ring and the side surface of the second measurement box. Ventilation openings are respectively opened on both sides of the second measurement box, and two sealing baffles located above the ventilation openings are respectively slidably connected to both sides of the second measurement box.

[0019] A second rack is fixedly installed on the top of the sealing baffle, a first rack is fixedly installed on the bottom of the lifting ring, the first rack meshes with a first gear, the second rack meshes with a second gear, the second gear meshes with the first gear, and both the second gear and the first gear are connected to the side surface of the second measurement box through a rotating shaft.

[0020] As a preferred solution, both ends of the sealing baffle are fixedly connected with linear sliders, the inner walls of the linear sliders are slidably connected with linear guide rails, and the linear guide rails are fixedly connected with the side surface of the second measuring box.

[0021] Preferably, a connecting cylinder is arranged above the second measuring box, a toothed ring is fixedly sleeved on the outer surface of the connecting cylinder, an annular groove is formed on the outer side surface of the toothed ring, a plurality of connecting frames are fixedly connected to the top of the lifting ring, pulleys are arranged on the plurality of connecting frames, and the plurality of pulleys are all slidably connected with the inner wall of the annular groove;

[0022] A second motor is fixedly installed on the side surface of the lifting ring, an output shaft of the second motor is fixedly connected with a third gear, and the third gear meshes with the outer side of the toothed ring.

[0023] Preferably, an annular guide rail is fixedly installed on the top of the second measuring box, a plurality of annular sliders are slidably connected to the outer surface of the lifting ring, third racks are fixedly connected to the tops of the plurality of annular sliders, the tops of the third racks penetrate through the toothed ring, and a limiting seat is slidably connected to the outer surface of the third rack, and the limiting seat is fixedly installed on the top of the toothed ring.

[0024] In an implementation scheme, a connecting seat is arranged in the middle of the connecting cylinder, a plurality of second connecting shafts are rotatably connected to the outer side surface of the connecting seat through bearings, a vane is fixedly connected to one end of each second connecting shaft, a third connecting shaft is fixedly connected to each vane, one end of each third connecting shaft penetrates through the connecting cylinder and is fixedly connected with a fourth gear, the fourth gear meshes with the third rack, and a sealing bearing is arranged at the connection between the outer surface of the third connecting shaft and the connecting cylinder; an elastic sealing sleeve is arranged on the outer surface of the vane, and the elastic sealing sleeve is in contact with the connecting seat and the connecting cylinder.

[0025] The method and device for real-time measurement of cross-circulation of greenhouse gases in multiple measuring boxes of the present invention are used to manufacture a full-automatic multi-channel farmland greenhouse gas monitoring system, which can measure the greenhouse gas emissions of farmland plants and is used for crop carbon sink assessment and screening. Compared with the existing technology, the method provided by the present invention can monitor up to 60 measuring boxes, improving the monitoring throughput; the device provided by the present invention is a full-automatic measurement system, reducing the manual time for manual greenhouse gas sampling. The device system of the present invention has a simple structure, is provided with a gas storage device, can perform real-time detection, can ensure the internal and external air pressure balance during the detection process, and reduce the error caused by gas circulation due to the change of internal and external air pressure caused by gas extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of the device for real-time measurement of cross-circulation of greenhouse gases in multiple measuring boxes provided by the present invention;

[0027] Figure 2 Structural schematic diagram of the base structure provided by the present invention;

[0028] Figure 3 Structural schematic diagram of the base structure and the first measurement component provided by the present invention;

[0029] Figure 4 Structural schematic diagram of the base structure provided by the present invention;

[0030] Figure 5 Structural schematic diagram after the protective cover provided by the present invention is opened;

[0031] Figure 6 Structural schematic diagram of the multi-measurement box greenhouse gas cross-circulation real-time measurement device provided by the present invention;

[0032] Figure 7 Structural schematic diagram of the base structure and the second measurement component provided by the present invention;

[0033] Figure 8 Structural schematic diagram of the first gear provided by the present invention;

[0034] Figure 9 Structural schematic diagram of the fourth gear provided by the present invention;

[0035] Figure 10 Schematic diagram of the method for multi-measurement box greenhouse gas cross-circulation real-time measurement provided by the present invention;

[0036] Figure 11 Control logic diagram of cross-circulation real-time measurement provided by the present invention;

[0037] Figure 12 Time-axis schematic diagram of the operation of the air extraction detection event provided by the present invention;

[0038] Figure 13 Schematic diagram of the events of closing and opening the measurement box during the monitoring period of multiple measurement boxes provided by the present invention.

[0039] Figure 14 Shows the change curve of the methane concentration in the measurement box monitored by the multi-measurement box greenhouse gas cross-circulation real-time measurement device of the present invention in the rice test field of the Shanghai Songjiang Experimental Base of the Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences. From 0 second to 2000 seconds, the methane concentration in the measurement box gradually increases.

[0040] Figure 15 Shows the change curve of the carbon dioxide concentration in the paddy field measurement box monitored by the multi-measurement box greenhouse gas cross-circulation real-time measurement device of the present invention. From 0 second to 2000 seconds, the carbon dioxide concentration in the measurement box gradually decreases.

[0041] Figure 16 It shows the full - growth - period change curves of the greenhouse gas methane emission fluxes of two rice varieties planted in the rice experimental field of the Shanghai Songjiang experimental base, monitored by the multi - measurement - box greenhouse gas cross - cycle real - time measurement device of the present invention. From 60 days after transplanting to 115 days after transplanting, it first gradually increases and then decreases. Different - shaped markers represent different rice varieties, including two varieties: N0 - W - D and N0 - W - d. Among them, different numbers represent the plot numbers for measurement. The numbers are the repeated plot numbers, and the d and D numbers correspond.

[0042] Figure 17 It shows the full - growth - period change curves of the greenhouse gas methane emission fluxes of two rice varieties planted in the rice experimental field of the Shanghai Songjiang experimental base, monitored by the multi - measurement - box greenhouse gas cross - cycle real - time measurement device of the present invention. From 60 days after transplanting to 115 days after transplanting, it first gradually increases and then decreases. Different - shaped markers represent different rice varieties, including two varieties: N0 - 9 - D and N0 - 9 - d. Among them, different numbers represent the plot numbers for measurement. The numbers are the repeated plot numbers, and the d and D numbers correspond.

[0043] Figure 18 It shows the daily change curves of the greenhouse gas methane emission fluxes of four rice varieties planted in the rice experimental field of the Shanghai Songjiang experimental base, monitored by the multi - measurement - box greenhouse gas cross - cycle real - time measurement device of the present invention. It gradually increases from morning to around 2 pm and then gradually decreases. Different - shaped markers represent different rice varieties, including four varieties: N2 - 9 - D, N2 - 9 - d, N2 - W - D, and N2 - W - d.

[0044] Figure 19 It shows the statistical bar chart of the methane emission fluxes of two rice varieties 9311 - D and 9311 - d planted in the rice experimental field of the Shanghai Songjiang experimental base under four different nitrogen - fertilizer application treatment conditions (N0, N1, N2, N3) at multiple growth - period stages. DFT66 - 70 represents 66 - 70 days after rice transplanting. * indicates statistical significance (p < 0.05).

[0045] The description of the reference numerals is as follows:

[0046] 1. Multi - way controller main body; 2. Gas analyzer main body; 3. First connecting pipe;

[0047] 4. Base structure; 401. Base main body; 402. Sealing ring; 403. Retaining ring; 404. Insert ring; 405. Second connecting pipe; 406. Solenoid valve;

[0048] 5. First measurement component; 501. First measurement box; 502. Fixed seat; 503. First connecting plate; 504. First connecting shaft; 505. Second connecting plate; 506. First motor; 507. Protective cover;

[0049] 6. Second measurement component; 601. Second measurement box; 602. Lifting ring; 603. Electric push rod; 604. First rack; 605. Second rack; 606. Second gear; 607. First gear; 608. Ventilation opening; 609. Linear slider; 610. Linear guide rail; 611. Connecting frame; 612. Pulley; 613. Sealing baffle; 614. First protective cover; 615. Connecting cylinder; 616. Tooth ring; 617. Ring groove; 618. Second motor; 619. Third gear; 620. Annular guide rail; 621. Annular slider; 622. Third rack; 623. Fourth gear; 624. Limit seat; 625. Connecting seat; 626. Second connecting shaft; 627. Third connecting shaft; 628. Blade; 629. Second protective cover. Detailed implementation manner

[0050] When the multi-measurement box greenhouse gas cross-circulation real-time measurement device of the present invention is used for monitoring farmland greenhouse gases, it can be called a "multi-channel farmland greenhouse gas monitoring system". This multi-channel farmland greenhouse gas monitoring system solves the problems in the prior art that using a sampling box to pump gas into an air bag cannot perform long-term monitoring and real-time analysis and measurement. By connecting a set of analyzers to multiple measurement boxes, and using a multi-channel controller to perform cross-circulation gas sampling on multiple measurement boxes and conduct long-term real-time measurement, the efficiency of monitoring greenhouse gas flux is greatly improved.

[0051] The farmland greenhouse gas detection methods in the prior art are divided into two categories.

[0052] The first category: Pump gas from a sampling box into an air bag, and then transport the air bag to a laboratory to analyze the gas concentration using a gas chromatograph. The disadvantages are as follows: On the one hand, for each sampling of this technology, it is necessary to manually close the measurement box and manually connect multiple air bags, and after sampling, it is necessary to manually retrieve the air bags. Therefore, continuous long-term monitoring of a sample plot cannot be carried out. On the other hand, the sample air bag of this method also needs to be sent back to the laboratory for analysis, and the measurement data cannot be analyzed and measured in real time.

[0053] Category 2: Measuring boxes with multiple top lids that can automatically open and close. Through pipelines, multi-way switching valves, an automatic control unit, an on-line gas analyzer, etc., the multiple measuring boxes are sequentially detected. Each time, only one of the measuring boxes is closed, and a loop is formed with the gas analyzer through the pipeline and the multi-way switching valve to continuously monitor the gas concentration in the measuring box. The disadvantages are as follows: Since the greenhouse gas emission rate is low, the detection time for each measuring box is relatively long, generally 10 - 30 minutes. Also, because the greenhouse gas emission rate varies greatly with the time of day, direct comparison between different plots needs to be controlled within a relatively short time period, generally considered optimal within 1 hour. Therefore, for this method of sequentially measuring multiple measuring boxes, the number of measuring boxes that each set of equipment can include is small. If all the measuring boxes are measured within 1 hour, there can only be 2 - 6 measuring boxes.

[0054] The device of the present invention uses a set of analyzers to connect multiple measuring boxes, and can perform cross - cyclic gas sampling on multiple measuring boxes through a multi - way controller and continuously measure in real time, significantly improving the efficiency of monitoring the greenhouse gas flux of crops.

[0055] In a specific example of greenhouse gas detection, for example, the measurement method of carbon dioxide can use the non - dispersive infrared method, with a measurement range of 0 - 1% vol.%. The measurement methods of gases such as methane, nitrous oxide, and ammonia can use the non - dispersive infrared method or photo - feedback cavity - enhanced absorption spectroscopy, with measurement ranges such as: methane 0 - 100 ppm, nitrous oxide 0 - 10 ppm, ammonia 0 - 500 ppb. Further, other sensors can be integrated to detect air temperature, air humidity, soil temperature, soil humidity, atmospheric pressure, light intensity, wind speed and direction, etc., for assisting in analyzing gas concentration, emission rate, and related influencing factors.

[0056] After the device of the present invention is set at a specific location in the farmland, it continuously monitors the above - mentioned objects and indicators in the air, calculates parameters such as the greenhouse gas emission rate, greenhouse gas emission flux, respiration rate, and photosynthesis rate of crops or other vegetation. These data can help evaluate the carbon emission and absorption of the ecosystem and provide valuable data support for studying the carbon cycle. The present invention can also be used for screening and evaluating crop varieties with excellent carbon sink traits of high yield and low emission.

[0057] When the device is used for monitoring greenhouse gases in farmland and evaluating the carbon sink of crops, it has the following technical effects.

[0058] 1. Fully automatic measurement with a large measurement throughput. The present invention utilizes a set of analyzers connected to multiple measurement chambers. Through program control, cross-cyclic gas sampling is performed on multiple (up to 60 at most) measurement chambers and real-time measurement is carried out, greatly improving the efficiency of monitoring greenhouse gas fluxes. It can be used for simultaneous data comparison and analysis of multiple experimental plots in farmland, and further for the screening of multiple crop varieties. This method can achieve a measurement time deviation of no more than 15 minutes between different measurement chambers. This is currently the monitoring system with the largest number of measurement chambers, and the time deviation between different controlled measurement chambers is relatively small. Generally, it is considered that the change range of greenhouse gases is relatively small within half an hour. When measuring in the field and comparing the measurement data of multiple plots, a difference of half an hour is within the acceptable range.

[0059] 2. During the measurement process, the air pressure inside the measurement chamber is balanced, and no external gas is introduced to cause measurement errors. The method of the present invention, when monitoring the gas inside the measurement chamber, constructs a gas circuit between the measurement chamber and the analyzer. While extracting gas for measurement, the gas is also returned to the measurement chamber, which can ensure the air pressure balance inside the measurement chamber during the process of extracting gas for measurement, and prevent external air or gas in the soil from entering the measurement chamber due to the decrease in the internal air pressure of the measurement chamber. The existing manual sampling box method extracts about 100 ml of gas from the sampling box, continuously extracts 4 times at intervals of 10 minutes, and the gas extracted each time will cause a certain air pressure difference due to the reduction of internal gas, resulting in the flow of internal and external gases.

[0060] 3. This system is relatively simple and easy to deploy in the field farmland or other test areas. According to the measurement needs, the entire system can also be moved to different farmland locations for deployment. The system of the present invention includes multiple measurement chambers, 1 multiplexer switching controller, 1 gas analyzer, and pipelines. The measurement chambers can be conveniently carried, and both the multiplexer switching controller and the analyzer are placed in a metal cabinet suitable for field use, without the need for a gas storage device, etc.

[0061] 4. High measurement accuracy. The present invention uses the method of calibrating the time drift of the gas analyzer with standard gas at regular intervals. During the detection process, the gas in the standard gas cylinder is regularly introduced into the gas analyzer for detection and recording. By analyzing the drift change curve of the standard gas, fitting calculation is carried out, and then time drift calibration is performed on the sample gas measured at different times according to the fitting formula.

[0062] The technical solution of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments; and the structures shown in the drawings are only schematic and do not represent real objects. It should be noted that based on these embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention. Moreover, without conflict, the embodiments in the present invention and the features and technical solutions in the embodiments can be combined with each other.

[0063] It should be understood that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0064] Embodiment 1

[0065] Please refer to Figure 10 , a method for real-time measurement of cross-circulation of greenhouse gases in multiple measurement boxes, including the following steps:

[0066] Use a set of gas analyzers, a multi-channel controller, and multiple measurement boxes, where the number of measurement boxes ranges from 2 to 60;

[0067] The lids of multiple measurement boxes are sequentially closed in a set order, gas is extracted and the gas concentration is detected, and the gas is cyclically extracted and detected in a set order for several times, and finally the measurement boxes are opened in sequence;

[0068] The time required for each gas extraction and detection is controlled within 10 - 30 seconds, and the time required for completing a cycle of gas extraction and detection is controlled within 30 minutes; to reduce data errors caused by time differences between measurement boxes; the greenhouse gas emission flux fluctuates during the day, and the fluctuation amplitude within 1 hour is small, optimally 30 minutes, usually negligible. After each cycle of measurement is completed, the measurement boxes are opened in sequence,

[0069] The objects and indicators detected and analyzed by the measurement boxes and the main body of the gas analyzer include: carbon dioxide, methane, nitrous oxide, ammonia, etc. in the air.

[0070] Furthermore, the method can also integrate other sensors to detect air temperature, air humidity, soil temperature, soil humidity, atmospheric pressure, light intensity, wind speed and direction, etc., for assisting in analyzing gas concentration, emission rate, and related influencing factors.

[0071] A temperature sensor is installed inside the measurement box to measure the gas temperature inside the measurement box, and a humidity sensor, a barometric pressure sensor, and a photosynthetic photon sensor are also installed for analyzing influencing factors and emission laws of greenhouse gas fluxes, etc.

[0072] The method provided by the present invention can ensure that the measurement time deviation between different measurement boxes does not exceed 15 minutes. The time deviation between different measurement boxes controlled is relatively small. Generally, it is considered that the change range of greenhouse gases is relatively small within half an hour. When comparing the measurement data of multiple plots during measurement, a difference of half an hour is within the acceptable range.

[0073] Further, as Figure 11 shown, the total number of measurement boxes is N. It is stipulated that the measurement box number k ranges from 1 to N, and the initial value of the measurement box number is 1. The total number of cycles included in one batch of monitoring is M, and the cycle number p ranges from 1 to M, and the initial value of the cycle number is 1. After power-on, first set the values of N and M, and set the initial values of k and p to 1. Then, start closing and air extraction detection from the No. 1 measurement box; after the detection is completed, judge whether the current cycle number is the set total number of cycles M. If it is equal to M, open the current measurement box. Otherwise, continue to judge whether the current measurement box number k is less than the set total number of measurement boxes N. If it is less than N, increase the measurement box number by 1 and continue to detect the next measurement box; if k = N, continue to judge whether p is less than M. If it is less than M, increase p by 1, and set k to 1; if p is equal to M, it means that one batch of monitoring has been completed. At this time, judge whether it is continuous monitoring. If it is continuous monitoring, set both k and p to 1 and start the measurement cycle again; if it is not continuous monitoring, end.

[0074] As Figure 12 shown, in the figure, 8 measurement boxes are taken as an example, that is, N = 1 to N = 8. The measurement sequence is from the No. 1 measurement box to the No. 8 measurement box. The time t1 required for each measurement box to perform air extraction detection in turn. After the previous measurement box completes the air extraction detection, the next measurement box immediately starts the air extraction detection, and so on until the last measurement box. When the last measurement box completes the air extraction detection, one measurement cycle ends. After waiting for the time t2, start the second measurement cycle. The time t2 is generally 10 minutes, and the range of t2 can be set from 1 minute to 30 minutes according to the gas flux and detection accuracy requirements of the detection sample. When 4 measurement cycles are completed, the flux monitoring of one batch of multiple measurement boxes ends, and the total time required is t3.

[0075] As Figure 13 shown, during the monitoring period of multiple measurement boxes, for the events of closing and opening the measurement boxes, in order to reduce the measurement error caused by the difference in the box closing time between the measurement boxes, here, in the first measurement cycle, each measurement box is closed in turn, and then the air extraction detection of this measurement box is immediately started. In the last measurement cycle, each measurement box is opened when the air extraction detection ends. In this way, the closing time length and the air extraction detection event of each measurement box are the same relative to the time when the measurement box is closed. Therefore, there is no error caused by different closing times between the measurement boxes.

[0076] Example 2

[0077] Please refer to Figure 1 、 Figure 2 and Figure 6 ,a real-time measurement device for cross-circulation of greenhouse gases in multiple measurement boxes, which is applied to the method for real-time measurement of cross-circulation of greenhouse gases in multiple measurement boxes, includes a gas analyzer main body 2, a multi-channel controller main body 1 is arranged on the gas analyzer main body 2, and the gas analyzer main body 2 is connected with two first connecting pipes 3. A plurality of base structures 4 are arranged between the two first connecting pipes 3. The base structure 4 and the gas analyzer main body 2 form a gas circuit through the two first connecting pipes 3. A measurement box structure can be detachably connected to each base structure 4; the gas analyzer main body 2 mentioned in this embodiment is the gas analyzer in Embodiment 1, and the multi-channel controller main body 1 is the multi-channel controller main body in Embodiment 1. An electromagnetic valve group can also be arranged inside the gas analyzer main body to switch the on-off of the gas circuit between the main path and each measurement box. Each measurement box is directly connected to the gas analyzer main body through a separate pipeline. The gas guide pipe connected to the measurement box base can also be selected to be connected to the side wall or the top cover of the measurement box.

[0078] The setting of the gas circuit makes the air pressure balanced during the measurement process and does not introduce external gases to cause measurement errors. The method adopted in the present invention constructs a gas circuit between the measurement box structure and the gas analyzer main body 2 when monitoring the gas in the measurement box structure. While extracting and measuring the gas, the gas is also returned to the measurement box structure, which can ensure the air pressure balance in the measurement box structure during the process of extracting and measuring the gas, and will not cause external air or gas in the soil to enter the measurement box structure due to the decrease of the air pressure inside the measurement box structure.

[0079] Further, as shown in Figure 2 and Figure 4 ,the base structure 4 includes two second connecting pipes 405. The two second connecting pipes 405 are respectively communicated with the two first connecting pipes 3, and a base main body 401 is fixedly communicated between the two second connecting pipes 405. Solenoid valves 406 are connected to both of the two second connecting pipes 405. An insertion ring 404 is fixedly connected to the bottom of the base main body 401, and a retaining ring 403 is fixedly connected to the top of the base main body 401. A sealing ring 402 is fixedly sleeved on the outer surface of the retaining ring 403. The solenoid valve 406 is connected to the multi-channel controller main body 1, and the multi-channel controller main body 1 can control the solenoid valve 406. The insertion ring 404 is used for inserting into the soil.

[0080] The term "connection" includes mechanical connection, electrical connection, and / or communication connection (including data transmission). A person skilled in the art can unambiguously determine whether it is a mechanical connection, an electrical connection, or a communication connection based on the usage environment of this term. When "connection" represents a communication connection (i.e., a communication link, including data transmission), it includes wired connection and wireless connection.

[0081] Embodiment 3

[0082] The multi-measurement box greenhouse gas cross-cycle real-time measurement device provided in Embodiment 2 is further optimized. Specifically, as Figure 1 、 Figure 3 and Figure 5 shown, the measurement box structure is the first measurement component 5. The first measurement component 5 includes a first measurement box 501 inserted into the outer surface of the sealing ring 402. A lid assembly that can be opened and closed is provided at the top of the first measurement box 501. A temperature sensor is installed inside the first measurement box 501 to measure the gas temperature inside the box. A humidity sensor, a barometric pressure sensor, and a photon sensor are also installed to analyze factors affecting greenhouse gas flux and emission laws, etc.

[0083] The lid assembly includes a fixed seat 502 fixedly installed on one side of the first measurement box 501 and a protective cover 507 located above the first measurement box 501. A first connecting plate 503 is fixedly installed at the top of the fixed seat 502. A second connecting plate 505 is fixedly installed at the top of the protective cover 507. A first connecting shaft 504 is inserted and connected between the second connecting plate 505 and the first connecting plate 503. The first connecting shaft 504 is fixedly connected to the second connecting plate 505 and is rotatably connected to the first connecting plate 503. A first motor 506 is fixedly installed on one side of the fixed seat 502. The output shaft of the first motor 506 is fixedly connected to the first connecting shaft 504. The first motor 506 can drive the protective cover 507 to open and close through the first connecting shaft 504 and the second connecting plate 505, thereby realizing automatic detection. When the protective cover 507 is closed, it can seal the first measurement box 501, and can reduce the situation of external air entering during the air extraction detection process. The first motor 506 is also connected to the multi-channel controller main body 1.

[0084] During use, when extracting the gas between the corresponding first measurement component 5 and the base structure 4, the multi-channel controller main body 1 controls the opening of the corresponding two solenoid valves 406, while the remaining solenoid valves 406 are closed, and the first motor 506 drives the protective cover 507 to close. The gas analyzer main body 2 sucks the air between the socket ring 404 and the first measurement box 501 into the gas analyzer main body 2 through one of the first connecting pipes 3 and the solenoid valve 406, and then transports it back to the first measurement box 501 through the other first connecting pipe 3 for detection by the gas analyzer main body 2. Then, the above steps are repeated to extract and detect the gas in the remaining first measurement components 5;

[0085] The first measurement box 501 mentioned in this embodiment is the measurement box in Embodiment 1.

[0086] Embodiment 4

[0087] The multi-measurement box greenhouse gas cross-circulation real-time measurement device provided in Embodiment 2 is further optimized. Specifically, as Figures 6 - 9 shown, the measurement box structure is the second measurement component 6. The second measurement component 6 includes a second measurement box 601 inserted into the outer surface of the sealing ring 402. A lifting ring 602 is sleeved on the outer surface of the second measurement box 601. A plurality of electric push rods 603 are installed between the bottom of the lifting ring 602 and the side surface of the second measurement box 601. Ventilation openings 608 are formed on both sides of the second measurement box 601. Two sealing baffles 613 located above the ventilation openings 608 are respectively slidably connected to both sides of the second measurement box 601. A temperature sensor is installed in the second measurement box 601 for measuring the gas temperature in the measurement box. A humidity sensor, a barometric pressure sensor, and a photon sensor are also installed for analyzing influencing factors and emission laws of greenhouse gas fluxes, etc. The second measurement box 601 mentioned in this embodiment is the measurement box in Embodiment 1;

[0088] A second rack 605 is fixedly installed at the top of the sealing baffle 613, and a first rack 604 is fixedly installed at the bottom of the lifting ring 602. The first rack 604 meshes with a first gear 607, and the second rack 605 meshes with a second gear 606. The second gear 606 meshes with the first gear 607, and both the second gear 606 and the first gear 607 are connected to the side of the second measuring box 601 through a rotating shaft. A first protective cover 614 is fixedly installed on the side of the second measuring box 601. The first rack 604, the second rack 605, the second gear 606, and the first gear 607 are all located in the first protective cover 614. During the process of the electric push rod 603 pushing the lifting ring 602 up and down, the first rack 604 can drive the second gear 606 to rotate through the first gear 607, and then the second gear 606 drives the second rack 605 to move up and down. The second rack 605 can drive the sealing baffle 613 to move up and down, and then the opening and closing of the air exchange port 608 can be controlled. The diameter of the first gear 607 is larger than the diameter of the second gear 606, so that the moving amplitude of the second rack 605 up and down is larger than the moving amplitude of the first rack 604 up and down.

[0089] Further, as Figure 7 shown, both ends of the sealing baffle 613 are fixedly connected with linear sliders 609. The inner wall of the linear slider 609 is slidably connected with a linear guide rail 610. The linear guide rail 610 is fixedly connected with the side of the second measuring box 601. The linear slider 609 and the linear guide rail 610 can limit the sealing baffle 613, so that the sealing baffle 613 can closely adhere to the second measuring box 601. After the sealing baffle 613 descends and corresponds to the position of the air exchange port 608, it can block the air exchange port 608.

[0090] Further, as Figure 7 and Figure 8 shown, a connecting cylinder 615 is arranged above the second measuring box 601. A toothed ring 616 is fixedly sleeved on the outer surface of the connecting cylinder 615. A ring groove 617 is formed on the outer side of the toothed ring 616. The top of the lifting ring 602 is fixedly connected with a plurality of connecting frames 611. A pulley 612 is arranged on each of the plurality of connecting frames 611. Each of the plurality of pulleys 612 is slidably connected with the inner wall of the ring groove 617. The cooperation between the connecting frame 611 and the pulley 612 can support the toothed ring 616;

[0091] A second motor 618 is fixedly installed on the side of the lifting ring 602. The output shaft of the second motor 618 is fixedly connected with a third gear 619. The third gear 619 meshes with the outer side of the toothed ring 616. The second motor 618 can drive the toothed ring 616 to rotate through the third gear 619. During the rotation of the toothed ring 616, the connecting cylinder 615 can be driven to rotate. After the connecting cylinder 615 descends, it can be inserted into the second measuring box 601. The second motor 618 and the electric push rod 603 are also connected to the multi-channel controller main body 1.

[0092] Furthermore, as shown in Figure 7 and Figure 9 , a circular guide rail 620 is fixedly installed on the top of the second measurement box 601. A plurality of annular sliders 621 are slidably connected to the outer surface of the lifting ring 602. The tops of the plurality of annular sliders 621 are fixedly connected to third racks 622. The top ends of the third racks 622 pass through the toothed ring 616. A limiting seat 624 is slidably connected to the outer surface of the third rack 622. The limiting seat 624 is fixedly installed on the top of the toothed ring 616. The cooperation between the annular slider 621 and the circular guide rail 620 can support the third rack 622.

[0093] Furthermore, as shown in Figure 7 and Figure 9 , a connection seat 625 is arranged in the middle of the connecting cylinder 615. A plurality of second connecting shafts 626 are rotatably connected to the outer side surface of the connection seat 625 through bearings. One end of each second connecting shaft 626 is fixedly connected to a blade 628. Each blade 628 is fixedly connected to a third connecting shaft 627. One end of each third connecting shaft 627 passes through the connecting cylinder 615 and is fixedly connected to a fourth gear 623. The fourth gear 623 meshes with the third rack 622. A sealing bearing is arranged at the connection between the outer surface of the third connecting shaft 627 and the connecting cylinder 615; the outer surface of the blade 628 has an elastic sealing sleeve, and the elastic sealing sleeve contacts the connection seat 625 and the connecting cylinder 615. A plurality of second protective covers 629 are installed on the side surface of the connecting cylinder 615. The fourth gear 623 and the third rack 622 are both located in the second protective cover 629. When the connecting cylinder 615 descends and is inserted into the second measurement box 601, the blade 628 rotates to the horizontal. At this time, the elastic sealing sleeves on adjacent blades 628 contact each other and contact the connecting cylinder 615 and the connection seat 625 to realize the sealing of the top of the connecting cylinder 615. In this way, the second measurement box 601 can be sealed during the air extraction detection process.

[0094] During use: When extracting the gas between the corresponding second measurement assembly 6 and the base structure 4, refer to Figure 6 and Figure 7, the electric push rod 603 drives the lifting ring 602 to descend. During the descent of the lifting ring 602, the sealing baffle 613 is driven to descend through the first rack 604, the second rack 605, the second gear 606 and the first gear 607 to block the ventilation port 608. At the same time, the lifting ring 602 drives the gear ring 616 and the connecting tube 615 to descend through the connecting frame 611 and the pulley 612. During the descent of the connecting tube 615 and the gear ring 616, the fourth gear 623 descends and cooperates with the third rack 622 to drive the third connecting shaft 627 to rotate, so that the bottom of the connecting tube 615 is inserted into the second measuring box 601, and the blade 628 rotates to a horizontal position. At this time, the adjacent The elastic sealing sleeves on the blade 628 are in contact with each other and with the connecting tube 615 and the connecting seat 625 to achieve sealing of the top of the connecting tube 615. The multi-channel controller body 1 controls the corresponding two solenoid valves 406 to open, while the remaining solenoid valves 406 are closed. The gas analyzer body 2 draws the air between the insert ring 404 and the second measuring box 601 into the gas analyzer body 2 through one of the first connecting pipes 3 and the solenoid valve 406, and then transports it back to the second measuring box 601 through the other first connecting pipe 3. The gas analyzer body 2 performs detection, and then repeats the above steps to extract and detect the gas in the remaining first measuring components 5;

[0095] After the corresponding second measuring component 6 is exhausted for detection, the electric push rod 603 pushes the lifting ring 602 to rise. During the rising process of the lifting ring 602, the sealing baffle 613 is driven to rise through the first rack 604, the second rack 605, the second gear 606 and the first gear 607 to release the blockage of the ventilation port 608. At the same time, the lifting ring 602 drives the gear ring 616 and the connecting tube 615 to rise through the connecting frame 611 and the pulley 612. During the rising process of the connecting tube 615 and the gear ring 616, the fourth gear 623 rises and cooperates with the third rack 622 to drive the third connecting shaft 627 to rotate, so that the bottom of the connecting tube 615 is separated from the second measuring box 601, and the blade 628 rotates to tilt, and the second motor 618 drives the ring groove 617 to rotate through the third gear 619 to rotate the connecting tube 615, and the connecting tube 615 drives the blade 628 to rotate and cooperates with the ventilation port 608 to accelerate the exchange of the second measuring box 601 with the outside air for subsequent detection.

[0096] It should be understood that the terms “(first)”, “(second)”, etc., herein are only used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0097] Example 5

[0098] In the rice experimental fields of the Shanghai Songjiang Experimental Base of the Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, under different nitrogen fertilizer application treatments, the multi-measurement box greenhouse gas cross-circulation real-time measurement device of the present invention was used to monitor the greenhouse gas methane and carbon dioxide emissions of multiple rice variety plots all day long. By detecting the changes in methane concentration and / or carbon dioxide concentration in the paddy field measurement box during each growth period of rice, the corresponding curves were drawn, the methane and / or carbon dioxide emission fluxes were statistically analyzed, and the gas emission change rules were judged. These rice varieties in the plots include N0-W-D, N0-W-d, N0-9-D, N0-9-d, N2-9-D, N2-9-d, N2-W-D, N2-W-d, etc.

[0099] Figure 14 It shows the change curve of methane concentration in the measurement box in a paddy field. From 0 second to 2000 seconds, as time goes on, the methane concentration in the measurement box gradually increases. Figure 15 It shows the change curve of carbon dioxide concentration in the measurement box. From 0 second to 2000 seconds, the carbon dioxide concentration gradually decreases.

[0100] Figure 16 It shows the whole growth period change curves of greenhouse gas methane emission fluxes of plots of two rice varieties N0-W-D and N0-W-d. From 60 days after transplanting to 115 days after transplanting, it first gradually increases and then decreases.

[0101] Figure 17 It shows the whole growth period change curves of methane emission fluxes of plots of two rice varieties N0-9-D and N0-9-d. From 60 days after transplanting to 115 days after transplanting, it first gradually increases and then decreases.

[0102] Figure 18 It shows the daily change curves of methane emission fluxes of plots of four rice varieties N2-9-D, N2-9-d, N2-W-D and N2-W-d. It gradually increases from morning to around 2 pm and then gradually decreases.

[0103] Figure 19 It shows the methane emission fluxes of plots of two rice varieties 9311-D and 9311-d at multiple growth stages under four different nitrogen fertilizer application treatments (N0, N1, N2, N3). DFT66-70 represents 66 - 70 days after rice transplanting.

[0104] The detection data shown in these figures more accurately reflects the actual situation.

[0105] The statistical results of this usage example show that the multi-measurement box greenhouse gas cross-circulation real-time measurement device and method provided by the present invention can effectively monitor the greenhouse gas methane and carbon dioxide emissions, providing reliable technical support for crop carbon sink assessment and screening.

[0106] The above are only the preferred specific embodiments of the present invention; however, the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its improved concept, making equivalent substitutions or changes, should be covered by the protection scope of the present invention.

Claims

1. A method for real-time measurement of cross-circulation of greenhouse gases in a multi-measurement chamber, characterized in that, Including the following steps: Using a set of gas analyzers, a multi-channel controller and multiple measurement chambers; A number of measurement chambers sequentially close their top covers in a set order, extract gas and detect the gas concentration, cycle the gas extraction and detection several times in a set order, and finally open the measurement chambers in sequence; The time required for each gas extraction and detection is controlled within 10 - 30 seconds, and the time required to complete one cycle of gas extraction and detection is controlled within 30 minutes; after each cycle of measurement, open the measurement chambers in sequence, The objects and indicators detected and analyzed by the measurement chambers and gas analyzers include: carbon dioxide, methane, nitrous oxide and ammonia in the air.

2. The method according to claim 1, wherein The total number of measurement chambers is N, it is stipulated that the measurement chamber number k is equal to 1 to N, the initial value of the measurement chamber number is 1, the total number of cycles included in one batch of monitoring is M, the cycle number p is equal to 1 to M, the initial value of the cycle number is 1. After power-on, first set the values of N and M, and set the initial values of k and p to 1. Then, start closing and gas extraction and detection from the No. 1 measurement chamber; After the detection is completed, judge whether the current cycle number p is the set total number of cycles M. If it is equal to M, open the current measurement chamber. Otherwise, continue to judge whether the current measurement chamber number k is less than the set total number of measurement chambers N. If it is less than N, increase the measurement chamber number by 1 and continue to detect the next measurement chamber; if k = N, continue to judge whether p is less than M. If it is less than M, increase p by 1, and set k to 1; if p is equal to M, it means that one batch of monitoring has been completed. At this time, judge whether it is continuous monitoring. If it is continuous monitoring, set both k and p to 1 and cycle the measurement again; if it is not continuous monitoring, end.

3. A multi-measurement box greenhouse gas cross-circulation real-time measurement device for implementing the method as described in claim 2, characterized in that, Including a gas analyzer main body (2), a multi-channel controller main body (1) is arranged on the gas analyzer main body (2), and the gas analyzer main body (2) is connected with two first connecting pipes (3). A number of base structures (4) are arranged between the two first connecting pipes (3). The base structures (4) form a gas circuit with the gas analyzer main body (2) through the two first connecting pipes (3). A measurement chamber structure is detachably connected to each base structure (4).

4. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement chamber according to claim 3, characterized in that The base structure (4) includes two second connecting pipes (405), the two second connecting pipes (405) are respectively communicated with the two first connecting pipes (3), and a base main body (401) is fixedly communicated between the two second connecting pipes (405). Solenoid valves (406) are connected to both of the two second connecting pipes (405). The bottom of the base main body (401) is fixedly connected with an insertion ring (404), the top of the base main body (401) is fixedly connected with a retaining ring (403), and a sealing ring (402) is fixedly sleeved on the outer surface of the retaining ring (403).

5. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement box according to claim 4, characterized in that, The measurement chamber structure is a first measurement component (5), and the first measurement component (5) includes a first measurement chamber (501) inserted into the outer surface of the sealing ring (402). The top of the first measurement chamber (501) is provided with an openable lid assembly; The lid assembly includes a fixed seat (502) fixedly installed on one side of the first measuring box (501) and a protective cover (507) located above the first measuring box (501). A first connecting plate (503) is fixedly installed on the top of the fixed seat (502). A second connecting plate (505) is fixedly installed on the top of the protective cover (507). A first connecting shaft (504) is inserted and connected between the second connecting plate (505) and the first connecting plate (503). The first connecting shaft (504) is fixedly connected to the second connecting plate (505) and rotatably connected to the first connecting plate (503). A first motor (506) is fixedly installed on one side of the fixed seat (502), and the output shaft of the first motor (506) is fixedly connected to the first connecting shaft (504).

6. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement chamber according to claim 4, characterized in that, The structure of the measuring box is the second measuring component (6). The second measuring component (6) includes a second measuring box (601) inserted into the outer surface of the sealing ring (402). A lifting ring (602) is sleeved on the outer surface of the second measuring box (601). A plurality of electric push rods (603) are installed between the bottom of the lifting ring (602) and the side surface of the second measuring box (601). Ventilation openings (608) are also formed on both sides of the second measuring box (601). Two sealing baffles (613) located above the ventilation openings (608) are respectively slidably connected to both sides of the second measuring box (601); A second rack (605) is fixedly installed on the top of the sealing baffle (613). A first rack (604) is fixedly installed on the bottom of the lifting ring (602). The first rack (604) meshes with a first gear (607). The second rack (605) meshes with a second gear (606). The second gear (606) meshes with the first gear (607), and both the second gear (606) and the first gear (607) are connected to the side surface of the second measuring box (601) through rotating shafts.

7. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement chamber according to claim 6, characterized in that, Both ends of the sealing baffle (613) are fixedly connected with linear sliders (609). The inner walls of the linear sliders (609) are slidably connected with linear guide rails (610). The linear guide rails (610) are fixedly connected to the side surface of the second measuring box (601).

8. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement box according to claim 7, characterized in that, A connecting cylinder (615) is arranged above the second measuring box (601). A toothed ring (616) is fixedly sleeved on the outer surface of the connecting cylinder (615). A ring groove (617) is formed on the outer side surface of the toothed ring (616). A plurality of connecting frames (611) are fixedly connected to the top of the lifting ring (602). A pulley (612) is arranged on each of the plurality of connecting frames (611). All the pulleys (612) are slidably connected to the inner wall of the ring groove (617); A second motor (618) is fixedly installed on the side surface of the lifting ring (602). The output shaft of the second motor (618) is fixedly connected with a third gear (619). The third gear (619) meshes with the outer side of the toothed ring (616).

9. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement box according to claim 8, characterized in that, A circular guide rail (620) is fixedly installed at the top of the second measuring box (601). A plurality of circular sliders (621) are slidably connected to the outer surface of the lifting ring (602). The tops of the plurality of circular sliders (621) are fixedly connected with third racks (622). The top ends of the third racks (622) pass through the toothed ring (616). A limiting seat (624) is slidably connected to the outer surface of the third rack (622). The limiting seat (624) is fixedly installed at the top of the toothed ring (616).

10. The real-time measurement device for cross-circulation of greenhouse gases in a multi-measurement box according to claim 9, characterized in that, A connecting seat (625) is arranged in the middle of the connecting cylinder (615). A plurality of second connecting shafts (626) are rotatably connected to the outer side surface of the connecting seat (625) through bearings. One end of each second connecting shaft (626) is fixedly connected with a blade (628). Each blade (628) is fixedly connected with a third connecting shaft (627). One end of each third connecting shaft (627) passes through the connecting cylinder (615) and is fixedly connected with a fourth gear (623). The fourth gear (623) meshes with the third rack (622). A sealing bearing is arranged at the connection between the outer surface of the third connecting shaft (627) and the connecting cylinder (615). The outer surface of the blade (628) is provided with an elastic sealing sleeve, and the elastic sealing sleeve contacts the connecting seat (625) and the connecting cylinder (615).

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