An aerosol mass concentration detection system

Abstract

The present invention discloses an aerosol mass concentration detection system, which includes a sheath flow device, an optical detection module, a zero calibration gas path module, and an air extraction power module; when performing mass concentration detection, the aerosol entering the shunt cavity of the sheath flow device from the aerosol inlet is divided into two paths. One path flows into the optical chamber through the sample gas pipe, and the other path becomes clean gas after passing through the first gas path and the second gas path, and then flows into the optical chamber through the sheath gas cavity and the gas flow gap to form a sheath flow protection for the sample gas; during zero calibration, the air extraction flow rate of the zero calibration gas path module is greater than that of the air extraction power module. All the aerosol entering the shunt cavity from the aerosol inlet flows into the first gas path. The external clean gas is divided into two paths after flowing into the optical chamber through the second gas path, the sheath gas cavity, and the gas flow gap. One path flows into the first gas path through the sample gas pipe, and the other path is discharged through the air outlet of the optical chamber, realizing automatic zero calibration, overcoming the disadvantage of low efficiency of manual zero calibration, and solving the problem of aerosol interception during zero calibration of the two-way three-way solenoid valve of the traditional photometer.

Description

Technical Field

[0001] The present invention relates to the field of gas detection, and particularly to an aerosol mass concentration detection system. Background Art

[0002] An aerosol is a colloidal dispersion system formed by dispersing and suspending solid or liquid small particles in a gas medium, also known as a gas dispersion system. Its dispersed phase is solid or liquid small particles with a size of (0.001 - 10) micrometers, and the dispersion medium is a gas. Aerosols have great applications in medicine, environmental science, military science, etc.

[0003] In many particulate matter measurements and particulate matter concentration studies in the air, an aerosol photometer is used to detect the particulate matter mass concentration in the monitored environment. Currently, in the production and detection of filter materials such as masks and meltblown cloth, aerosol particles are used to detect the filtration efficiency of the filter materials. An aerosol photometer is a simple optical measurement system. By establishing the relationship between the aerosol mass concentration and the photoelectric signal of a photodetector, real-time detection of the aerosol mass concentration can be achieved.

[0004] The structure of a traditional photometer is as Figure 9 shown. The traditional photometer does not have a sheath flow device. When measuring, the aerosol will fill the entire detection chamber after entering the detection chamber. On the one hand, it will affect the stability of the detection. On the other hand, the aerosol will deposit on the optical lens in the detection chamber, and the detection accuracy of the instrument will decrease after long-term sampling.

[0005] In addition, for zero calibration of the traditional photometer, there are two methods: manual zero calibration and automatic zero calibration. When using manual zero calibration, generally there is no Figure 1 two-way three-way solenoid valve 1 and zero calibration filter 2 in it. Manually insert the zero calibration filter at the aerosol inlet of the photometer detection module 3, and then start the zero calibration program; for a photometer with an automatic zero calibration function, a two-way three-way valve 1 and a zero calibration filter 2 are connected at the inlet of the aerosol photometer. When starting the zero calibration program, the A end and the S end of the two-way three-way valve 1 are connected, and the S end is connected to the zero calibration filter 2 to achieve zero calibration; however, when the photometer starts to detect, the A end and the B end of the two-way three-way valve 1 are connected. But due to the structure problem of the two-way three-way valve 1, the aerosol will be intercepted when passing through the solenoid valve, which results in a large difference between the actual aerosol concentration and the aerosol concentration entering the photometer detection module 3, thus leading to an incorrect aerosol concentration value.

[0006] The above information disclosed in this background art is only used to increase the understanding of the background art of the present application. Therefore, it may include prior art that is not known to those of ordinary skill in the art. Summary of the Invention

[0007] In response to the problems pointed out in the background technology, the present invention proposes an aerosol mass concentration detection system. On the one hand, a sheath gas system is used to isolate the aerosol in the aerosol detection cavity to prevent the aerosol from diffusing after entering the aerosol detection cavity, thereby keeping the optical devices in the detection cavity clean; on the other hand, the self-zeroing sheath flow meter can realize automatic zeroing, overcome the shortcoming of low efficiency of manual zeroing, and solve the problem of aerosol retention during automatic zeroing of the two-position three-way solenoid valve of the traditional photometer.

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0009] The present invention provides an aerosol mass concentration detection system, comprising:

[0010] A sheath flow device, wherein a mutually isolated shunt cavity and a sheath air cavity are provided in its inner cavity, an aerosol inlet and a sheath air outlet communicated with the shunt cavity, and a sheath air inlet and a mounting hole communicated with the sheath air cavity are provided on the wall of the sheath flow device, a sample gas tube is provided in the inner cavity of the sheath flow device, one end of the sample gas tube is communicated with the shunt cavity, and the other end of the sample gas tube passes through the sheath air cavity and enters the mounting hole, a sheath gas tube is provided in the mounting hole, the sheath gas tube is sleeved on the outer periphery of the sample gas tube, and a gas flow gap communicated with the sheath air cavity is formed between the sheath gas tube and the sample gas tube;

[0011] An optical detection module connected to the sheath flow device, wherein the gas outlet end of the sample gas tube and the gas outlet end of the sheath gas tube are both in communication with the optical chamber in the optical detection module;

[0012] A zeroing gas path module, comprising a first gas path and a second gas path, wherein the first gas path is connected to the sheath gas outlet, the second gas path is connected to the sheath gas inlet, and a first pump is provided on the first gas path;

[0013] An air pumping power module connected to the air outlet of the light chamber, and the air pumping power module is provided with a second pump;

[0014] When the detection system performs aerosol mass concentration detection, the first pump is turned off, the second pump is turned on, the first gas path is connected to the second gas path, the second gas path is disconnected from the atmosphere, and the aerosol entering the diversion cavity from the aerosol inlet is divided into two paths, one path flows into the optical chamber through the sample gas pipe, and the other path is converted into clean gas through the first gas path and the second gas path and then flows into the optical chamber through the sheath gas cavity and the gas flow gap;

[0015] When the detection system is calibrated, the air extraction flow rate of the first pump is greater than that of the second pump. The first gas path is disconnected from the second gas path, and the second gas path is communicated with the atmosphere. All the aerosol entering the shunt cavity from the aerosol inlet flows into the first gas path. The external clean gas enters the optical chamber through the second gas path, the sheath gas cavity, and the gas flow gap and is divided into two paths. One path flows into the first gas path through the sample gas pipe, and the other path is discharged through the air outlet of the optical chamber.

[0016] In some embodiments of the present application, a first filter, a second switching valve, a first switching valve, and the first pump are sequentially arranged on the first gas path along the gas flow direction;

[0017] A second filter and a third switching valve are sequentially arranged on the second gas path along the gas flow direction;

[0018] One port of the second switching valve is connected to one port of the third switching valve through a pipeline, and one port of the first switching valve is connected through a pipeline between the second filter and the third switching valve.

[0019] In some embodiments of the present application, a first orifice flowmeter, a first differential pressure sensor, and a first temperature sensor are arranged between the first pump and the first switching valve;

[0020] A second orifice flowmeter, a second differential pressure sensor, and a second temperature sensor are arranged between the third switching valve and the sheath gas inlet.

[0021] In some embodiments of the present application, a fourth differential pressure sensor is arranged between the first gas path and the second gas path. One end of the fourth differential pressure sensor is connected between the first filter and the sheath gas outlet, and the other end is connected between the second orifice flowmeter and the sheath gas inlet.

[0022] In some embodiments of the present application, a third filter and the second pump are sequentially arranged on the air extraction power module along the gas flow direction. A third orifice flowmeter, a third differential pressure sensor, and a third temperature sensor are arranged between the third filter and the second pump.

[0023] In some embodiments of the present application, a fifth differential pressure sensor is arranged between the air extraction power module and the second gas path. One end of the fifth differential pressure sensor is connected between the second orifice flowmeter and the sheath gas inlet, and the other end is connected between the third filter and the air outlet of the optical chamber.

[0024] In some embodiments of the present application, the sheath flow cell includes an upper shell, a lower shell, and a partition portion. The upper shell and the lower shell are connected up and down to form the inner cavity of the sheath flow cell. The partition portion is disposed in the inner cavity to divide the inner cavity into the shunt cavity and the sheath gas cavity arranged up and down. The sample gas tube passes through the partition portion;

[0025] The aerosol inlet is provided at the top of the upper shell, and the sheath gas outlet is provided on the side wall of the upper shell;

[0026] The mounting hole is provided at the bottom of the lower shell, and the sheath gas inlet is provided on the side wall of the lower shell.

[0027] In some embodiments of the present application, the partition portion includes a partition main body portion and a circumferentially extending portion. The circumferentially extending portion extends circumferentially along the middle position of the outer peripheral wall of the partition main body portion. The partition main body portion located above the circumferentially extending portion is connected to the bottom opening of the upper shell, and the partition main body portion located below the circumferentially extending portion is connected to the top opening of the lower shell. The bottom end of the upper shell and the top of the lower shell respectively abut against the circumferentially extending portion.

[0028] In some embodiments of the present application, the mounting hole includes a first-stage mounting hole and a second-stage mounting hole that are vertically aligned and communicate with each other. The inner diameter of the first-stage mounting hole is smaller than the inner diameter of the second-stage mounting hole. The sheath gas tube is disposed in the second-stage mounting hole, and the gap between the first-stage mounting hole and the sample gas tube is used for gas flow.

[0029] In some embodiments of the present application, a first lock nut and a first sealing ferrule are sleeved on the top of the sample gas tube, and both the first lock nut and the first sealing ferrule are connected to the partition portion;

[0030] A fixed flange is provided at the bottom of the lower shell. A second lock nut and a second sealing ferrule are sleeved on the bottom of the sample gas tube, and both the second lock nut and the second sealing ferrule are connected to the fixed flange.

[0031] Compared with the prior art, the advantages and positive effects of the present invention are:

[0032] (1) The sheath gas can prevent the aerosol from diffusing after entering the aerosol detection chamber, keep the optical devices in the detection chamber clean, and improve the accuracy and service life of the instrument.

[0033] (2) The self-zeroing sheath flow cell overcomes the low efficiency of manual zeroing and solves the problem of aerosol interception during the automatic zeroing of the two-way three-way solenoid valve of the traditional photometer.

[0034] (3) The method for accurately measuring the aerosol mass concentration of the aerosol concentration detection module 500 can effectively eliminate the signal drift caused by temperature changes and the noise interference of the circuit itself, and the measurement result is more accurate.

[0035] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more apparent. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0037] Figure 1 Structural schematic diagram of an aerosol mass concentration detection system according to an embodiment;

[0038] Figure 2 Structural schematic diagram of a sheath flow device according to an embodiment;

[0039] Figure 3 Structural schematic diagram of an aerosol mass concentration detection module according to an embodiment;

[0040] Figure 4 is Figure 3 Cross-sectional view taken along line A-A in ;

[0041] Figure 5 Gas path connection diagram when the aerosol mass concentration detection system according to an embodiment performs aerosol mass concentration detection;

[0042] Figure 6 is Figure 5 Schematic diagram of the air flow inside the aerosol mass concentration detection module in the working state shown;

[0043] Figure 7 Gas path connection diagram when the aerosol mass concentration detection system according to an embodiment performs self-zero calibration;

[0044] Figure 8 is Figure 7 Schematic diagram of the air flow inside the aerosol mass concentration detection module in the working state shown;

[0045] Figure 9 Structural schematic diagram of a traditional photometer;

[0046] Reference numerals:

[0047] 100 - Zero - calibration gas path module, 101 - First pump, 102 - First orifice flowmeter, 103 - First differential pressure sensor, 104 - First temperature - measuring sensor, 105 - Second filter, 106 - First switching valve, 107 - Second switching valve, 108 - Third switching valve, 109 - First filter, 110 - Fourth differential pressure sensor, 111 - Second orifice flowmeter, 112 - Second temperature - measuring sensor, 113 - Second differential pressure sensor, 114 - First gas path, 115 - Second gas path;

[0048] 200 - Sheath flow device, 201 - Aerosol inlet, 202 - Shunt chamber, 203 - Sheath gas outlet, 204 - Partition part, 2041 - Partition main body part, 2042 - Circumferential extension part, 205 - Sheath gas inlet, 206 - Fixed flange, 207 - Sheath gas pipe, 208 - First lock nut, 209 - Sample gas pipe, 210 - First sealing ferrule, 211 - Sheath gas chamber, 212 - Second sealing ferrule, 213 - Second lock nut, 214 - Gas flow gap, 215 - First section of mounting hole, 216 - Upper shell, 217 - Lower shell;

[0049] 300 - Optical detection module, 301 - Light chamber, 302 - Diaphragm, 303 - Laser diode, 304 - Collimating lens, 305 - Cylindrical lens, 306 - Gas outlet, 307 - Light trap Ⅰ, 308 - Light trap Ⅱ, 309 - Spherical mirror Ⅰ, 310 - Photo - diode Ⅰ, 311 - Spherical mirror Ⅱ, 312 - Photo - diode Ⅱ, 313 - Light - shielding plate, 314 - Aerosol detection area.

[0050] 400 - Air - extraction power module, 401 - Second pump, 402 - Third orifice flowmeter, 403 - Third differential pressure sensor, 404 - Third temperature - measuring sensor, 405 - Fifth differential pressure sensor, 406 - Third filter;

[0051] 500 - Aerosol mass concentration detection module. Detailed implementation manners

[0052] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0053] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0054] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0055] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected to" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0056] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0057] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0058] This embodiment discloses an aerosol mass concentration detection system, which mainly includes a sheath flow device 200, an optical detection module 300, a zero calibration gas path module 100, a pumping power module 400, etc. Among them, the sheath flow device 200 and the optical detection module 300 constitute an aerosol mass concentration detection module 500.

[0059] Figure 1 It is a schematic structural diagram of the aerosol mass concentration detection system. Figure 2 It is a schematic structural diagram of the sheath flow device 200. Figure 3 It is a schematic structural diagram of the aerosol mass concentration detection module 500. Figure 4 For Figure 3 The sectional view taken along the A-A direction in Figure 5 It is a gas path connection diagram when the aerosol mass concentration detection system detects the aerosol mass concentration. Figure 6 For Figure 5 The schematic diagram of the air flow in the aerosol mass concentration detection module 500 in the working state shown. Figure 7 It is a gas path connection diagram when the aerosol mass concentration detection system performs self-zero calibration. Figure 8 For Figure 7 The schematic diagram of the air flow in the aerosol mass concentration detection module 500 in the working state shown.

[0060] Among them, Figure 6 In , in the aerosol concentration detection module 500, Q1 is the aerosol flow direction, and Q2 is the sheath gas flow direction. Figure 7 In , in the aerosol concentration detection module 500, Q1 is the aerosol flow direction, and Q2 and Q3 are the sheath gas flow directions.

[0061] The structure of the sheath flow device 200 refers to Figure 2, a mutually isolated diverter cavity 202 and a sheath air cavity 211 are provided in its inner cavity, the diverter cavity 202 is located above the sheath air cavity 211, an aerosol inlet 201 and a sheath air outlet 203 connected with the diverter cavity 202 are provided on the wall of the sheath flow device 200, the aerosol inlet 201 is located at the top of the diverter cavity 202, the sheath air outlet 203 is located at the side of the diverter cavity 202, a sheath air inlet 205 and a mounting hole (not marked) connected with the sheath air cavity 211 are also provided on the wall of the sheath flow device 200, the sheath air inlet 205 is located at the side of the sheath air cavity 211, the mounting hole is located at the bottom of the sheath air cavity 211, and the sheath air outlet 203 and the sheath air inlet 205 are located on the same side of the sheath flow device 200. A sample gas tube 209 is provided in the inner cavity of the sheath flow device 200. The sample gas tube 209 passes through the shunt cavity 202 and the sheath gas cavity 211. One end (top end) of the sample gas tube 209 is connected with the shunt cavity 202, and the other end (top end) of the sample gas tube 209 passes through the sheath gas cavity 211 and enters the mounting hole. A sheath gas tube 207 is provided in the mounting hole. The sheath gas tube 207 is sleeved on the outer circumference of the sample gas tube 209. The inner diameter of the sheath gas tube 207 is larger than the inner diameter of the sample gas tube 209. A gas flow gap 214 connected with the sheath gas cavity 211 is formed between the sheath gas tube 207 and the sample gas tube 209.

[0062] Reference Figure 3 The optical detection module 300 is connected to the sheath flow device 200 , and the outlet end of the sample gas tube 209 and the outlet end of the sheath gas tube 207 are both connected to the optical chamber in the optical detection module 300 .

[0063] Reference Figure 1 The zeroing gas path module 100 includes a first gas path 114 and a second gas path 115 . The first gas path 114 is connected to the sheath gas outlet 203 , the second gas path 115 is connected to the sheath gas inlet 205 , and a first pump 101 is disposed on the first gas path 114 .

[0064] The air pumping power module 400 is connected to the air outlet 306 of the light chamber, and a second pump 401 is provided on the air pumping power module 400 .

[0065] Reference Figure 5 and Figure 6 When the detection system performs aerosol mass concentration detection, the first pump 101 is turned off, the second pump 401 is turned on, the first gas path 114 is connected to the second gas path 115, and the second gas path 115 is disconnected from the atmosphere. The aerosol entering the diversion cavity 202 from the aerosol inlet 201 is divided into two paths, one path flows into the optical chamber through the sample gas pipe 209, and the other path is converted into clean gas through the first gas path 114 and the second gas path 115 and then flows into the optical chamber through the sheath gas cavity 211 and the gas flow gap 214.

[0066] The sheath gas can prevent the aerosol from diffusing after entering the aerosol detection chamber, keep the optical devices in the detection chamber clean, and improve the accuracy and service life of the instrument.

[0067] Referring to Figure 7 and Figure 8 , when the detection system is calibrated to zero, both the first pump 101 and the second pump 401 are turned on. The air extraction flow rate of the first pump 101 is greater than that of the second pump 401. The first gas path 114 is disconnected from the second gas path 115, and the second gas path 115 is in communication with the atmosphere. All the aerosol entering the shunt chamber 202 from the aerosol inlet 201 flows into the first gas path 114. The outside clean gas enters the light chamber through the second gas path 115, the sheath gas chamber 211, and the gas flow gap 214 and is divided into two paths. One path flows into the first gas path 114 through the sample gas pipe 209, and the other path is discharged through the air outlet 306 of the light chamber.

[0068] The above zero calibration method can overcome the low efficiency of manual zero calibration and solve the problem of aerosol interception during the automatic zero calibration of the traditional photometer's two-way three-way solenoid valve.

[0069] In some embodiments of the present application, referring to Figure 1 , along the gas flow direction on the first gas path 114, a first filter 109, a second switching valve 107, a first switching valve 106, and a first pump 101 are sequentially provided. Along the gas flow direction on the second gas path 115, a second filter 105 and a third switching valve 108 are sequentially provided. One port of the second switching valve 107 is connected to one port of the third switching valve 108 through a pipeline. One port of the first switching valve 16 is connected through a pipeline between the second filter 105 and the third switching valve 108.

[0070] A first orifice flowmeter 102, a first differential pressure sensor 103, and a first temperature measuring sensor 104 are provided between the first pump 101 and the first switching valve 106. The two ports of the first differential pressure sensor 103 are respectively connected to the front and rear ends of the orifice of the first orifice flowmeter 102 (it is stipulated that the direction opposite to the gas flow direction is the front), and the first temperature measuring sensor 103 is arranged at the front end of the orifice of the first orifice flowmeter 102.

[0071] A second orifice flowmeter 111, a second differential pressure sensor 113, and a second temperature measuring sensor 112 are provided between the third switching valve 108 and the sheath gas inlet 205. The two ports of the second differential pressure sensor 113 are respectively connected to the front and rear ends of the orifice of the second orifice flowmeter 111 (it is stipulated that the direction opposite to the gas flow direction is the front), and the second temperature measuring sensor 112 is arranged at the front end of the orifice of the second orifice flowmeter 111.

[0072] A fourth differential pressure sensor 110 is provided between the first gas path 114 and the second gas path 115. One end of the fourth differential pressure sensor 110 is connected between the first filter 109 and the sheath gas outlet 203, and the other end is connected between the second orifice flowmeter 111 and the sheath gas inlet 205.

[0073] The air extraction power module 400 is successively provided with a third filter 406 and a second pump 401 along the gas flow direction. A third orifice flowmeter 402, a third differential pressure sensor 403, and a third temperature measuring sensor 404 are provided between the third filter 406 and the second pump 401. Two ports of the third differential pressure sensor 403 are respectively connected to the front and rear ends of the orifice of the third orifice flowmeter 402 (it is stipulated that the reverse direction of the gas flow direction is the front), and a third temperature measuring sensor is provided at the front end of the orifice of the third orifice flowmeter 402.

[0074] A fifth differential pressure sensor 405 is provided between the air extraction power module 400 and the second gas path 115. One end of the fifth differential pressure sensor 405 is connected between the second orifice flowmeter 111 and the sheath gas inlet 205, and the other end is connected between the third filter 406 and the gas outlet 306 of the optical chamber.

[0075] Refer to Figure 5 and Figure 6 When the detection system performs aerosol mass concentration detection, the first pump 101 is closed and the second pump 401 is turned on. The aerosol passes through the aerosol inlet 201 under the action of negative pressure and reaches the shunt chamber 202. Part of the aerosol reaches the first filter 109 through the sheath gas outlet 203, and becomes clean air after being filtered by the first filter 109. The clean air passes through the second switching valve 107. At this time, the S2 port of the second switching valve 107 is connected to the A2 port, so that the first gas path 114 is connected to the second gas path 115, and then passes through the third switching valve 108. At this time, the A3 port of the third switching valve 108 is connected to S3, and then passes through the second orifice flowmeter 111 and the sheath gas inlet 205 to reach the sheath gas chamber 211, and then enters the optical detection module 300 through the sheath gas pipe 207; Another part of the aerosol in the shunt chamber 202 directly reaches the optical detection module 300 through the sample gas pipe 209.

[0076] As Figure 6 shown, the clean air coming out of the sheath gas pipe 207 will wrap the aerosol passing through the aerosol detection area 314 from the sample gas pipe 209, enter the gas outlet 306, and leave the optical detection module 300.

[0077] Detection principle of the optical detection module 300: Refer to Figure 3 and Figure 4, The sheath flow cell 200 is installed on the optical chamber 301 and forms an aerosol concentration detection module 500 together with the optical detection module 300. The laser diode 303 emits a divergent laser beam. The laser beam is collimated by the collimating lens 304. After collimation, the laser beam passes through the aperture 302 to eliminate stray light. Then, the laser beam is shaped by the cylindrical lens 305 so that the laser beam passes directly below the sample gas pipe 209 and then reaches the optical trap I 307 and is absorbed. The laser beam reflected on the surface of the optical trap I 307 will be absorbed by the optical trap II 308.

[0078] When the aerosol passes through the aerosol detection area 314, the aerosol particles will scatter under the irradiation of the laser beam. The photodiode I 310 will receive this scattered light and the light reflected by the spherical mirror II 311. The photodiode I 310 will convert the received optical signal into an electrical signal. After weight calibration, the electrical signal can be related to the mass concentration of the aerosol. A photodiode II 312 (with the same parameters as the photodiode I 310) is set at the symmetrical position of the photodiode I 310. A light shield 313 is set on the photosensitive surface of the photodiode II 312. In this way, the scattered light of the particles and the light reflected by the spherical mirror I 309 are blocked by the light shield 313. In this way, the photodiode II 312 can only measure other signals except the optical signal, such as the signal drift caused by temperature change and the noise existing in the circuit itself.

[0079] Refer to Figure 7 and Figure 8 , when performing self-zero calibration, the first pump 101 and the second pump 401 are started simultaneously. At this time, the internal air flow direction of the aerosol concentration detection module 500 is as Figure 8 shown. The pumping flow rate of the first pump 101 is greater than the sampling flow rate of the second pump 401 (the pressure difference value measured by the fourth pressure difference sensor 110 is greater than the value measured by the fifth pressure difference sensor 405). In this way, all the aerosol (Q1) passes through the aerosol inlet 201, enters the shunt chamber 202, and is all filtered by the first filter 109 after passing through the sheath gas outlet 203. At this time, the S2 interface of the second switching valve 107 is connected to B2, and the S1 connection of the first switching valve 106 is connected to B1. The first gas path 114 is disconnected from the second gas path 115, and then after passing through the first orifice flowmeter 102, it is connected to the first pump 101; because the pressure difference value measured by the fourth pressure difference sensor 110 is much greater than the value measured by the fifth pressure difference sensor 405 at this time, the clean air filtered by the second filter 105 will pass through the third switching valve 108 (at this time, the B3 interface is connected to the S3 interface) and the second orifice flowmeter 111 and enter the aerosol concentration detection module 500 and is divided into two parts Q2 and Q3. The Q2 part will follow the sample gas pipe 209, be mixed with the aerosol in the shunt chamber 202 and then be pumped away by the first pump 101. The part of the clean air Q3 will pass through the aerosol detection area 314 and be pumped away by the second pump 401 through the air outlet 306.

[0080] The first orifice flowmeter 102, the second orifice flowmeter 111, and the third orifice flowmeter 402 calculate their respective flow rates through the number of the first differential pressure sensor 103, the second differential pressure sensor 113, and the third differential pressure sensor 403 according to Equation 1.

[0081] (Equation 1)

[0082] In the formula, c is the discharge coefficient, ε is the expansion coefficient of the medium, d is the orifice plate diameter, β is the diameter ratio, Δρ is the differential pressure before and after the orifice plate, and ρ is the medium density.

[0083] The precise measurement method of the aerosol concentration detection module 500 for the aerosol mass concentration: Suppose in the self-zero calibration mode, since only clean air passes through the aerosol detection area 314 at this time, the value measured by the photodiode I 310 is used as the zero value, denoted as A1, and the value measured by the photodiode II 312 is the signal drift and circuit noise caused by the temperature change at this time, denoted as B1; in the measurement mode, there is aerosol passing through the aerosol detection area 314. Suppose the value measured by the photodiode I 310 at this time is A2, and the value measured by the photodiode II 312 is B2. Then the value that can actually reflect the aerosol mass is m = A1 - A2 - (B2 - B1). Assuming that after weighing and calibration, a functional relationship can be established between the electrical signal and the aerosol mass concentration as y = f(x), where x is the measured electrical signal value, such as current or voltage value, and y is the actual aerosol concentration value. According to the different physical properties of the aerosol particles, this functional relationship can be a linear function or a quadratic function, etc. After the functional relationship is determined and the value m that reflects the aerosol mass is substituted, the aerosol mass concentration can be obtained.

[0084] In the sheath flow cell 200, the diameters and lengths of the sample gas pipe 209 and the sheath gas pipe 207 can be replaced according to different sampling flow rates. The zero calibration gas path module 100 and the sheath flow cell 200 form a self-zero calibration sheath flow cell, which can be installed in the optical detection module 300 with different structures and has good interchangeability.

[0085] In some embodiments of the present application, referring to Figure 2 , the sheath flow cell 200 includes an upper shell 216, a lower shell 217, and a partition portion 204. The upper shell 216 and the lower shell 217 are connected up and down to form the inner cavity of the sheath flow cell 200. The partition portion 204 is disposed in the inner cavity to divide the inner cavity into a shunt cavity 202 and a sheath gas cavity 211 arranged up and down. The sample gas pipe 209 passes through the partition portion 204. The top of the upper shell 216 is provided with an aerosol inlet 201, and the side wall of the upper shell 216 is provided with a sheath gas outlet 203. The bottom of the lower shell 217 is provided with a mounting hole, and the side wall of the lower shell 217 is provided with a sheath gas inlet 205. The split structure of the sheath flow cell 200 is convenient for assembly.

[0086] As a specific embodiment, the partition portion 204 includes a partition main body portion 2041 and a circumferential extension portion 2042. The circumferential extension portion 2042 extends horizontally in a circumferential direction at an intermediate position of the outer peripheral wall of the partition main body portion 2041. The partition main body portion 2041 located above the circumferential extension portion is connected to the bottom opening of the upper shell 216, and a sealing ring is provided at the connection. The partition main body portion 2041 located below the circumferential extension portion 2042 is connected to the top opening of the lower shell 217, and a sealing ring is provided at the connection. The bottom end of the upper shell 216 and the top of the lower shell 217 respectively abut against the circumferential extension portion 2042.

[0087] During installation, first install the sample gas pipe 209 onto the partition portion 204, and then install the upper shell 216 and the lower shell 214 onto the partition portion 204 respectively, which is convenient for assembly.

[0088] In some embodiments of the present application, the installation hole includes an installation hole section 215 and an installation hole section two (not labeled) that are vertically aligned and communicated. The inner diameter of the installation hole section 215 is smaller than the inner diameter of the installation hole section two. The sheath gas pipe 207 is arranged in the installation hole section two. The gap between the installation hole section 215 and the sample gas pipe 209 is used for gas flow.

[0089] A step is formed between the installation hole section 215 and the installation hole section two. The top end of the sheath gas pipe 207 abuts against this step to play an installation stop role. The installation hole section 215 also plays a role in gas flow. The gas in the sheath gas cavity 211 enters the gas flow gap 214 between the sheath gas pipe 207 and the sample gas pipe 209 through the installation hole section 215 and then is discharged.

[0090] In some embodiments of the present application, a first lock nut 208 and a first sealing collar 210 are sleeved on the top of the sample gas pipe 209. Both the first lock nut 208 and the first sealing collar 210 are connected to the partition portion 204.

[0091] A fixed flange 206 is provided at the bottom of the lower shell 217. A second lock nut 213 and a second sealing collar 212 are sleeved on the bottom of the sample gas pipe 209. Both the second lock nut 213 and the second sealing collar 212 are connected to the fixed flange 206.

[0092] With such a setting, the installation stability and sealing performance of the sample gas pipe 209 and the sheath gas pipe 207 are improved.

[0093] The aerosol mass concentration detection system of the present application can achieve the following beneficial effects:

[0094] (1) The sheath gas can prevent the aerosol from diffusing after entering the aerosol detection cavity, keep the optical devices in the detection cavity clean, and improve the accuracy and service life of the instrument.

[0095] (2) The self-zeroing sheath flow meter 200 overcomes the disadvantage of low efficiency of manual zeroing and solves the aerosol retention problem during automatic zeroing of the two-position three-way solenoid valve of the traditional photometer.

[0096] (3) The method for accurately measuring the aerosol mass concentration of the aerosol concentration detection module 500 can effectively eliminate the signal drift caused by temperature changes and the noise interference of the circuit itself, and the measurement result is more accurate.

[0097] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0098] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An aerosol mass concentration detection system, characterized in that, include: A sheath flow device, wherein a mutually isolated shunt cavity and a sheath air cavity are provided in its inner cavity, an aerosol inlet and a sheath air outlet communicated with the shunt cavity, and a sheath air inlet and a mounting hole communicated with the sheath air cavity are provided on the wall of the sheath flow device, a sample gas tube is provided in the inner cavity of the sheath flow device, one end of the sample gas tube is communicated with the shunt cavity, and the other end of the sample gas tube passes through the sheath air cavity and enters the mounting hole, a sheath gas tube is provided in the mounting hole, the sheath gas tube is sleeved on the outer periphery of the sample gas tube, and a gas flow gap communicated with the sheath air cavity is formed between the sheath gas tube and the sample gas tube; An optical detection module connected to the sheath flow device, wherein the gas outlet end of the sample gas tube and the gas outlet end of the sheath gas tube are both in communication with the optical chamber in the optical detection module; A zeroing gas path module, comprising a first gas path and a second gas path, wherein the first gas path is connected to the sheath gas outlet, the second gas path is connected to the sheath gas inlet, and a first pump is provided on the first gas path; An air pumping power module connected to the air outlet of the light chamber, and the air pumping power module is provided with a second pump; When the detection system performs aerosol mass concentration detection, the first pump is turned off, the second pump is turned on, the first gas path is connected to the second gas path, the second gas path is disconnected from the atmosphere, and the aerosol entering the diversion cavity from the aerosol inlet is divided into two paths, one path flows into the optical chamber through the sample gas pipe, and the other path is converted into clean gas through the first gas path and the second gas path and then flows into the optical chamber through the sheath gas cavity and the gas flow gap; When the detection system is zeroed, the air pumping flow rate of the first pump is greater than the air pumping flow rate of the second pump, the first gas path is disconnected from the second gas path, the second gas path is connected to the atmosphere, the aerosol entering the diversion cavity from the aerosol inlet all flows into the first gas path, and the external clean gas flows into the optical chamber through the second gas path, the sheath gas cavity, and the gas flow gap, and then is divided into two paths, one path flows into the first gas path through the sample gas pipe, and the other path is discharged through the gas outlet of the optical chamber; The first gas path is provided with a first filter, a second switching valve, a first switching valve, and the first pump in sequence along the gas flow direction; A second filter and a third switching valve are sequentially arranged along the gas flow direction on the second gas path; One port of the second switching valve is connected to one port of the third switching valve through a pipeline, and one port of the first switching valve is connected between the second filter and the third switching valve through a pipeline; A first orifice flow meter, a first differential pressure sensor, and a first temperature sensor are provided between the first pump and the first switching valve; A second orifice flow meter, a second differential pressure sensor, and a second temperature sensor are provided between the third switching valve and the sheath gas inlet.

2. The aerosol mass concentration detection system according to claim 1, characterized in that: A fourth differential pressure sensor is provided between the first gas path and the second gas path. One end of the fourth differential pressure sensor is connected between the first filter and the sheath gas outlet, and the other end is connected between the second orifice flowmeter and the sheath gas inlet.

3. The aerosol mass concentration detection system according to claim 1, wherein A third filter and the second pump are sequentially provided in the air extraction power module along the gas flow direction. A third orifice flowmeter, a third differential pressure sensor, and a third temperature measurement sensor are provided between the third filter and the second pump.

4. The aerosol mass concentration detection system according to claim 3, wherein A fifth differential pressure sensor is provided between the air extraction power module and the second gas path. One end of the fifth differential pressure sensor is connected between the second orifice flowmeter and the sheath gas inlet, and the other end is connected between the third filter and the air outlet of the optical chamber.

5. The aerosol mass concentration detection system according to any one of claims 1 to 4, wherein The sheath flow device includes an upper shell, a lower shell, and a partition portion. The upper shell and the lower shell are connected up and down to form the inner cavity of the sheath flow device. The partition portion is provided in the inner cavity to divide the inner cavity into the shunt cavity and the sheath gas cavity arranged up and down. The sample gas pipe passes through the partition portion; The aerosol inlet is provided at the top of the upper shell, and the sheath gas outlet is provided on the side wall of the upper shell; The mounting hole is provided at the bottom of the lower shell, and the sheath gas inlet is provided on the side wall of the lower shell.

6. The aerosol mass concentration detection system according to claim 5, wherein The partition portion includes a partition main body portion and a circumferentially extending portion. The circumferentially extending portion extends circumferentially at the middle position of the outer peripheral wall of the partition main body portion. The partition main body portion located above the circumferentially extending portion is connected to the bottom opening of the upper shell, and the partition main body portion located below the circumferentially extending portion is connected to the top opening of the lower shell. The bottom end of the upper shell and the top end of the lower shell respectively abut against the circumferentially extending portion.

7. The aerosol mass concentration detection system according to claim 5, wherein The mounting hole includes a first mounting hole section and a second mounting hole section that are vertically and oppositely communicated. The inner diameter of the first mounting hole section is smaller than the inner diameter of the second mounting hole section. The sheath gas pipe is provided in the second mounting hole section, and the gap between the first mounting hole section and the sample gas pipe is used for gas circulation.

8. The aerosol mass concentration detection system according to claim 5, wherein A first lock nut and a first sealing ferrule are sleeved on the top of the sample gas pipe, and both the first lock nut and the first sealing ferrule are connected to the partition portion; A fixed flange is provided at the bottom of the lower shell. A second lock nut and a second sealing ferrule are sleeved on the bottom of the sample gas pipe, and both the second lock nut and the second sealing ferrule are connected to the fixed flange.

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