CN111521531A - Aerosol concentration measuring device and method - Google Patents
Aerosol concentration measuring device and method Download PDFInfo
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- CN111521531A CN111521531A CN202010328311.6A CN202010328311A CN111521531A CN 111521531 A CN111521531 A CN 111521531A CN 202010328311 A CN202010328311 A CN 202010328311A CN 111521531 A CN111521531 A CN 111521531A
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- 239000000443 aerosol Substances 0.000 title claims abstract description 128
- 238000000034 method Methods 0.000 title claims abstract description 33
- 239000002245 particle Substances 0.000 claims abstract description 59
- 238000002156 mixing Methods 0.000 claims abstract description 38
- 238000005259 measurement Methods 0.000 claims abstract description 34
- 239000007788 liquid Substances 0.000 claims abstract description 23
- 239000012528 membrane Substances 0.000 claims abstract description 21
- 239000003595 mist Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 230000009471 action Effects 0.000 claims description 10
- 238000001914 filtration Methods 0.000 claims description 9
- 229920006395 saturated elastomer Polymers 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- 230000007423 decrease Effects 0.000 claims description 6
- 230000008033 biological extinction Effects 0.000 claims description 5
- 239000003960 organic solvent Substances 0.000 claims description 5
- 239000008213 purified water Substances 0.000 claims description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 230000008859 change Effects 0.000 claims description 3
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 239000012153 distilled water Substances 0.000 claims description 3
- 238000009413 insulation Methods 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- 230000003287 optical effect Effects 0.000 description 5
- 238000000149 argon plasma sintering Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010291 electrical method Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 238000012538 light obscuration Methods 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 239000013618 particulate matter Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/06—Investigating concentration of particle suspensions
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- G01N15/075—
Abstract
An aerosol concentration measuring device and a measuring method. The method comprises the following steps: the device comprises an aerosol inlet, a mixing cavity, a cloud chamber, a buffer cavity, a light source, a photosensitive device, a first valve, a second valve, a series of valves, a third valve, a microcontroller, a signal processing unit, a pressure sensor, a micro pump, a filter membrane, pure liquid and an aerosol outlet. The aerosol inlet, the first valve, the mixing cavity, the second valve, the cloud chamber, the series valves, the buffer cavity, the micropump and the aerosol outlet are sequentially connected, and the filter membrane, the third valve and the cloud chamber are sequentially connected. The pressure sensor, the light source and the photosensitive device are respectively arranged in the cloud chamber. The first valve, the second valve, the series valve, the third valve and the micropump are respectively connected with the microcontroller; the photosensitive device is connected with the signal processing unit, and the signal processing unit is connected with the microcontroller. The pure liquid is located in the mixing chamber. The series valve comprises at least one sub-valve, one end of the sub-valve is connected with the cloud chamber, and the other end of the sub-valve is connected with the buffer cavity. The invention can realize the measurement of aerosol particles with extremely small particle size and wide concentration range, and is easy to miniaturize.
Description
Technical Field
The invention relates to the technical field of aerosol measurement, in particular to an aerosol concentration measuring device and a measuring method.
Background
An aerosol is a suspension system formed by suspending liquid or solid particles in a gas medium, wherein the characteristic particle size of a particle phase is generally 1nm to 100 μm, but since particles with the particle size of more than 1 μm are easy to settle, the stable suspension time is short, and particles with the particle size of less than 10nm are difficult to detect, the general real-time aerosol measurement only aims at aerosol particles with the range of 10nm to 1 μm.
Concentration is one of important indexes for characterizing aerosol characteristics, and the existing real-time measurement method for aerosol concentration mainly comprises an optical method based on a light scattering and extinction principle and an electrical method based on a diffusion charge principle. Conventional optical-principle-based instruments mainly include optical particle counters and laser particle counters, and since light scattering of fine particles having a size smaller than the wavelength of light is very weak, a simple optical method is generally effective only for particles having a particle size greater than 0.3 μm. Measuring instruments based on electrical principles mostly need to be used in combination with particle counters to get the size distribution of aerosol particles.
In the prior art, the real-time aerosol measuring instrument with extremely small particle size and wide concentration range is almost large instrument equipment with complex structure, and cannot meet the requirements of multipoint and distributed application in a limited space environment and the measurement requirements of aerosol occasions with wide concentration range.
The invention patent (CN 101375149A) provides a real-time particulate matter measuring system applying an evaporation-condensation-measuring method, the system integrates the existing method, especially the measuring part directly uses the existing particle counter, which is not beneficial to the miniaturization of the system. Patents [ CN101960288A ] and [ CN104181084B ] respectively propose particle measurement methods based on the electrical principle. The pure electrical method usually needs to pretreat the sample because the charged characteristic of the particles is sensitive to the concentration, which causes great loss of the original sample. Patent [ CN105466822A ] describes an aerosol real-time measuring instrument based on the light scattering principle, and patent [ CN108426808A ] utilizes the extinction characteristic of the aerosol to measure the mass concentration of particles. The optical method has good real-time performance, but the lower limit of the particle size of the detectable particles is relatively high, generally 300 nanometers.
Disclosure of Invention
The invention provides an aerosol concentration measuring device and an aerosol concentration measuring method, which can realize the measurement of aerosol particles with extremely small particle size and wide concentration range and are easy to miniaturize.
The invention provides an aerosol concentration measuring device, comprising:
the system comprises an aerosol inlet, a mixing cavity, a cloud chamber, a buffer cavity, a light source, a photosensitive device, a first valve, a second valve, a series valve, a third valve, a microcontroller, a signal processing unit, a pressure sensor, a micro pump, a filter membrane, pure liquid and an aerosol outlet;
the aerosol inlet, the first valve, the mixing cavity, the second valve, the cloud chamber, the series of valves, the buffer cavity, the micropump and the aerosol outlet are sequentially connected, the filter membrane, the third valve and the cloud chamber are sequentially connected, the pressure sensor, the light source and the photosensitive device are respectively installed in the cloud chamber, the cloud chamber is installed in the buffer cavity, the first valve, the second valve, the series of valves, the third valve and the micropump are respectively connected with the microcontroller, the photosensitive device is connected with the signal processing unit, the signal processing unit is connected with the microcontroller, and the pure liquid is located in the mixing cavity;
the serial valves comprise at least one sub valve, one end of each sub valve is connected with the cloud chamber, the other end of each sub valve is connected with the buffer cavity, and each sub valve is respectively connected with the microcontroller;
or the cloud chamber and the buffer cavity are arranged side by side, and the cloud chamber is connected with the buffer cavity through the series of valves;
the light source and the photosensitive device are respectively arranged on two opposite wall surfaces in the cloud chamber.
Further, the photosensitive device is a semiconductor photosensitive element, including: photoelectric tube, photomultiplier, photo resistance, phototriode.
Further, the cloud chamber is made of black plastic; the cloud chamber is cylindrical, and the light source and the photosensitive device are respectively arranged at two ends of the cylinder.
Further, the first valve, the second valve, the third valve and the series of valves are micro electromagnetic valves; the micropump is a micro vacuum pump.
Further, the series of valves consists of a first sub-valve and a second sub-valve; one end of the first sub-valve is connected with the cloud chamber, and the other end of the first sub-valve is connected with the buffer cavity; one end of the second sub-valve is connected with the cloud chamber, and the other end of the second sub-valve is connected with the buffer cavity; the first sub-valve and the second sub-valve are respectively connected with the microcontroller.
Further, the measuring device further includes: and the filter membrane is arranged at the inlet of the aerosol and is used for filtering out larger particles with the particle size exceeding a certain value in the aerosol.
A method for measuring the concentration of an aerosol using a device as described above,
the pure liquid is used for volatilizing steam to ensure that the steam reaches a saturated state in the mixing cavity;
the mixing cavity is used for mixing the incoming aerosol particles with saturated vapor of the pure liquid and outputting aerosol-saturated vapor mixture;
the micropump is used for pumping out part of aerosol in the buffer cavity to enable the buffer cavity to reach a certain vacuum degree;
the buffer cavity is used for forming a certain vacuum degree and forming a certain pressure difference with the cloud chamber;
the cloud chamber is used for forming a certain pressure difference with the buffer cavity and enabling inflow aerosol to expand towards the buffer cavity in a heat insulation mode, so that the temperature in the cloud chamber is reduced, the aerosol-steam mixture reaches a supersaturated state, and steam is condensed on aerosol particles to enable the particle volume to be increased to form cloud mist; the larger the concentration of particles in the aerosol is, the denser the cloud formed in the cloud chamber is, the stronger the extinction characteristic is, and the weaker the light intensity reaching the photosensitive device is;
the volume of the space in the mixing cavity is at least 8 times larger than the volume of the space in the cloud chamber;
the light source is used for emitting light with a certain wavelength;
the photosensitive device is used for sensing the light intensity change caused by aerosol fog in the cloud chamber;
the pressure sensor is used for measuring the pressure in the cloud chamber in real time;
the signal processing unit is used for filtering, amplifying and the like of the sensing electric signal of the photosensitive device and outputting the processed electric signal to the microcontroller;
the first valve is used for controlling the on-off of the aerosol flowing into the mixing cavity path;
the second valve is used for controlling the on-off of the aerosol circulation path between the mixing cavity and the cloud chamber;
the series of valves are used for controlling the on-off of an aerosol circulation path between the cloud chamber and the buffer cavity;
the third valve is used for controlling the on-off of a gas flow path between the cloud chamber and the filter membrane;
the filter membrane is used for filtering particles in the aerosol to obtain pure gas; the pure gas enters the cloud chamber through the third valve, disperses the cloud mist in the cloud chamber after the measurement is finished, and discharges the cloud mist to the buffer cavity;
the microcontroller is used for controlling the on-off of the first valve, the second valve, the series of valves and the third valve according to a certain time sequence logic, starting and stopping the micropump, receiving a signal of the pressure sensor, receiving a signal of the signal processing unit, and calculating the quantity concentration of aerosol particles according to the signal output by the signal processing unit and an analytical expression, wherein the analytical expression is a polynomial between the signal output by the signal processing unit and the quantity concentration, and the polynomial meets the preset precision requirement.
Further, the sequential logic is: at the beginning of the measuring cycle, at t1At the moment, the micro pump and the series of valves are opened, and then the pressure in the cloud chamber and the buffer chamber is reduced under the action of the micro pump; when the pressure sensor detects that the pressure in the cloud chamber is reduced to P1When (t)2Moment), the first valve and the second valve are opened, the aerosol to be measured enters the mixing cavity through the aerosol inlet and the first valve, the aerosol is mixed with the vapor of the pure liquid in the mixing cavity and then enters the cloud chamber and the buffer cavity through the second valve and the series of valves, and the pressure in the cloud chamber and the buffer cavity rises; when the pressure sensor detects the cloudThe pressure in the chamber rises to P2When (t)3Time), the series of valves are closed, after which the pressure in the cloud chamber continues to rise and the pressure in the buffer chamber drops; when the pressure sensor detects that the pressure in the cloud chamber rises to P3When (at t)4Time), closing the first valve and the second valve; continuously running for a period of time T1Then at t5Closing the micropump and opening the series of valves, wherein the aerosol-steam mixture in the cloud chamber adiabatically expands to the buffer chamber due to the pressure difference between the cloud chamber and the buffer chamber, the pressure in the cloud chamber rapidly decreases, the temperature decreases, the steam in the cloud chamber reaches a supersaturated state, and aerosol particles increase to form cloud mist; expanding the aerosol and the steam in the cloud chamber for a period of time T2To t6Closing the series of valves at the moment, reading the measurement signal of the signal processing unit, and outputting or displaying the aerosol concentration measurement value; waiting for the system to stabilize for a period of time T3To t7Opening the series of valves and the third valve, allowing pure gas filtered by the filter membrane to enter the cloud chamber and the buffer cavity through the third valve under the action of pressure difference between the cloud chamber and the buffer cavity, and discharging expanded cloud mist out of the cloud chamber; a period of time T4And then closing the series of valves and the third valve to finish a measuring cycle.
Further, the pressure P1Satisfies the following conditions: less than half of standard atmospheric pressure;
the pressure P2Satisfies the following conditions: p1+20kPa≤P2≤80kPa；
The pressure P3Satisfies the following conditions: p is more than or equal to 90kPa3≤100kPa；
The time period T1Satisfies the following conditions: after the period of time, the pressure in the buffer chamber drops below half the standard atmospheric pressure by the micro pump;
the time period T2Satisfies the following conditions: after the period of time, the pressure within the cloud chamber drops below half of standard atmospheric pressure;
the time period T3Satisfies the following conditions: in the time period, the signal processing unit completes measurement signal processing and outputs the measurement signal to the microprocessor, and the microprocessor completes calculation of aerosol quantity and concentration and displays a measurement result after receiving the measurement signal;
the time period T4Satisfies the following conditions: after the period of time, the pressure sensor detects that the pressure within the cloud chamber is about one standard atmosphere.
Further, the pure liquid is purified water or a volatile organic solvent, and the purified water comprises: deionized water and distilled water; the organic solvent includes: alcohol and n-butanol.
The aerosol concentration measuring method and the aerosol concentration measuring device provided by the invention can realize the measurement of aerosol particles with extremely small particle size and wide concentration range by rapidly expanding the aerosol and saturated steam in the cloud chamber and increasing the aerosol particles into fog and controlling the time sequence, and are easy to miniaturize.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of an aerosol concentration measuring device according to an embodiment of the present invention;
fig. 2 is a control timing chart of a method and an apparatus for measuring aerosol concentration according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention, and based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts belong to the scope of the present invention.
The invention provides an aerosol concentration measuring method and a device, and the method and the device are shown in figure 1 and comprise the following steps:
the device comprises an aerosol inlet 1, a mixing cavity 2, a cloud chamber 3, a buffer cavity 4, a light source 5, a photosensitive device 6, a first valve 7, a second valve 8, a series of valves 9, a third valve 10, a microcontroller 11, a signal processing unit 12, a pressure sensor 13, a micro pump 14, a filter membrane 15, pure liquid 16 and an aerosol outlet 17.
The aerosol inlet 1, the first valve 7, the mixing chamber 2, the second valve 8, the cloud chamber 3, the series of valves 9, the third valve 10, the buffer chamber 4, the micro pump 14, the aerosol outlet 17 connects gradually, the filter membrane 15, the third valve 10, the cloud chamber 3 connects gradually, the pressure sensor 13, the light source 5, the photosensitive device 6 is installed respectively in the cloud chamber 3, the cloud chamber 3 is installed in the buffer chamber 4, the first valve 7, the second valve 8, the series of valves 9, the third valve 10, the micro pump 14 respectively with microcontroller 11 links to each other, the photosensitive device 6 with signal processing unit 12 connects, signal processing unit 12 with microcontroller 11 connects, pure liquid 16 is located in the mixing chamber 2.
The series valve 9 comprises at least one sub-valve, the sub-valves are respectively positioned between the cloud chamber 3 and the buffer cavity 4, and each sub-valve is respectively connected with the microcontroller 11; sub-valves 91 to 9n are shown.
Or, the cloud chamber 3 and the buffer cavity 4 are arranged side by side, and the cloud chamber 3 is connected with the buffer cavity 4 through the series of valves 9.
The light source 5 and the photosensitive device 6 are respectively arranged on two opposite wall surfaces in the cloud chamber 3.
A method for measuring the aerosol concentration by adopting the device is characterized in that:
the pure liquid 16 is used to volatilize the vapor and to saturate the vapor in the mixing chamber 2.
The mixing chamber 2 is used for mixing the incoming aerosol with the volatile vapor of the pure liquid 16 and outputting the aerosol-vapor mixture.
In particular, after the aerosol flows through the mixing chamber 1, saturated vapor is mixed therein, the type of saturated vapor being related to the type of pure liquid 16.
The micro pump 14 is used for pumping out part of aerosol in the buffer cavity 4 to enable the buffer cavity 4 to reach a certain vacuum degree.
The buffer cavity 4 is used for forming a certain vacuum degree and forming a certain pressure difference with the cloud chamber 3.
The cloud chamber 3 is used for forming a certain pressure difference with the buffer cavity 4, enabling inflow aerosol to expand towards the buffer cavity 4 in a heat insulation mode under the action of the pressure difference, enabling the temperature in the cloud chamber 3 to be reduced, enabling the aerosol-steam mixture to reach a supersaturated state, enabling steam to be condensed on aerosol particles to enable the particle volume to be increased, and forming cloud mist. The greater the concentration of particles in the aerosol, the denser the cloud formed in the cloud chamber 3, the stronger the extinction characteristics, and the weaker the light intensity reaching the light-sensitive device 6.
The volume of the mixing chamber 2 is at least 8 times larger than the volume of the cloud chamber 3.
The light source 5 is used for emitting light with a certain wavelength.
The photosensitive device 6 is used for sensing the light intensity change caused by aerosol fog in the cloud chamber 3.
The pressure sensor 13 is used for measuring the pressure in the cloud chamber 3 in real time.
The signal processing unit 12 is configured to perform processing such as filtering and amplification on the sensing electrical signal of the photosensitive device 6, and input the processed electrical signal to the microcontroller 11.
The first valve 7 is used for controlling the on-off of the path of the aerosol flowing into the mixing cavity 2.
And the second valve 8 is used for controlling the on-off of the aerosol circulation path between the mixing cavity 2 and the cloud chamber 3.
The series of valves 9 are used for controlling the on-off of the aerosol circulation path between the cloud chamber 3 and the buffer cavity 4.
And the third valve 10 is used for controlling the on-off of a gas flow path between the cloud chamber 3 and the filter membrane 6.
The filter membrane 6 is used for filtering particles in the aerosol to enable the aerosol flowing through the filter membrane to become pure gas; after the measurement is finished, the purified gas enters the cloud chamber 3 through the third valve 10 under the driving of the pressure difference between the buffer chamber 4 and the cloud chamber 3, disperses the cloud mist in the cloud chamber 3, and is discharged to the buffer chamber 4.
The microcontroller 11 is configured to control on/off of the first valve 7, the second valve 8, the series of valves 9, and the third valve 10, and on/off of the micropump 14 according to a certain sequential logic, receive an electrical signal from the pressure sensor 13, receive a signal from the signal processing unit 12, and calculate a quantity concentration of aerosol particles according to the signal output by the signal processing unit 12 and an analytical expression, where the analytical expression is a polynomial between the electrical signal and the quantity concentration that meets a preset precision requirement;
wherein the sequential logic is: at the beginning of the measuring cycle, at t1At the moment, the micro pump 14 and the series of valves 9 are opened, and then the pressure in the cloud chamber 3 and the buffer chamber 4 is reduced under the action of the micro pump 14; when the pressure sensor 13 detects that the pressure in the cloud chamber 3 drops to P1When (t)2At the moment), the first valve 7 and the second valve 8 are opened, then the aerosol to be measured enters the mixing cavity 2 through the aerosol inlet 1 and the first valve 7, the aerosol is mixed with the steam of the pure liquid 16 in the mixing cavity 2 and then enters the cloud chamber 3 and the buffer cavity 4 through the second valve 8 and the series of valves 9, and the pressure in the cloud chamber 3 and the buffer cavity 4 rises; when the pressure sensor 13 detects that the pressure in the cloud chamber 3 rises to P2When (t)3Time), the series of valves 9 is closed, after which the pressure in the cloud chamber 3 continues to rise and the pressure in the buffer chamber 4 falls; when in useThe pressure sensor 13 detects that the pressure in the cloud chamber 3 rises to P3When (at t)4Time), the first valve 7 and the second valve 8 are closed; continuously running for a period of time T1Then at t5At the moment, the micro pump 14 is closed, the series of valves 9 are opened, and then due to the pressure difference between the cloud chamber 3 and the buffer chamber 4, the aerosol-steam mixed gas in the cloud chamber 3 adiabatically expands to the buffer chamber 4, the pressure in the cloud chamber 3 rapidly decreases, the temperature decreases, the steam in the cloud chamber 3 reaches a supersaturated state, and aerosol particles increase to form cloud mist; the aerosol and steam in the cloud chamber 3 expand for a period of time T2To t6At the moment, the series of valves 9 are closed, the measurement signal of the signal processing unit 12 is read, and the aerosol concentration measurement value is output or displayed; waiting for the system to stabilize for a period of time T3To t7At the moment, the series of valves 9 and the third valve 10 are opened, and then under the action of the pressure difference between the cloud chamber 3 and the buffer chamber 4, pure gas filtered by the filter membrane 15 enters the cloud chamber 3 and the buffer chamber 4 through the third valve 10, and expanded cloud mist is discharged out of the cloud chamber; a period of time T4Then closing the series of valves 9 and the third valve 10 to finish a measurement cycle;
wherein the pressure P1Satisfies the following conditions: less than half of standard atmospheric pressure;
wherein the pressure P2Satisfies the following conditions: p1+20kPa≤P2≤80kPa；
Wherein the pressure P3Satisfies the following conditions: p is more than or equal to 90kPa3≤100kPa；
Wherein the time period T1Satisfies the following conditions: after this period of time, the pressure in the buffer chamber 4 drops below half the standard atmospheric pressure by the micro pump 14;
wherein the time period T2Satisfies the following conditions: after this period of time, the pressure inside the cloud chamber 3 drops below half the standard atmospheric pressure;
wherein the time period T3Satisfies the following conditions: during this time period, the signal processing unit 12 is finishedProcessing the measurement signal and outputting the measurement signal to the microprocessor 11, wherein the microprocessor 11 completes calculation of aerosol quantity and concentration and displays the measurement result after receiving the measurement signal;
wherein the time period T4Satisfies the following conditions: after the period of time, the pressure sensor 13 detects that the pressure in the cloud chamber 3 is about a standard atmospheric pressure;
wherein, the analytic expression can be obtained by the following method:
s11: acquiring photoelectric signals obtained by measuring the calibrated aerosol by the aerosol concentration measuring device, wherein the quantity and concentration of the calibrated aerosol are known;
s12: setting a polynomial between the photoelectric signal and the number concentration;
s13: fitting the polynomial by a least square method to obtain parameters of the polynomial;
s14: and comparing the quantity concentration of the polynomial output with the quantity concentration of the particles of the calibration aerosol, if the error between the quantity concentration of the polynomial output and the quantity concentration of the particles in the calibration aerosol is less than or equal to a preset threshold value, finishing the fitting, otherwise, correcting the times of the polynomial and returning to S13.
In a possible implementation, the series of valves 9 consists of a first sub-valve and a second sub-valve; one end of the first sub-valve is connected with the cloud chamber 3, and the other end of the first sub-valve is connected with the buffer cavity 4; one end of the second sub-valve is connected with the cloud chamber 3, and the other end of the second sub-valve is connected with the buffer cavity 4; the first sub-valve and the second sub-valve are respectively connected with the microcontroller 11.
According to the aerosol concentration measuring method provided by the embodiment, the aerosol and steam in the cloud chamber are rapidly expanded by simultaneously opening the two or more sub-valves, and a certain supersaturation degree is achieved in a very short time, so that aerosol particles can be sufficiently atomized, the measurement of the aerosol particles with extremely small particle size and wide concentration range can be realized, and the miniaturization is easy.
In one possible implementation, the pure liquid 16 is purified water, which includes: deionized water, distilled water.
Alternatively, the pure liquid 16 is a volatile organic solvent comprising: alcohol and n-butanol.
In one possible implementation, the photosensitive device 6 is a semiconductor photosensitive element comprising: photoelectric tube, photomultiplier, photo resistance, phototriode.
In a possible implementation, the material of the cloud chamber 3 is black plastic.
In a possible implementation manner, the mixing chamber 2, the cloud chamber 3 and the buffer chamber 4 are integrally manufactured, which is beneficial to miniaturization.
In a possible implementation, the cloud chamber 3 is cylindrical in shape, and the light source 5 and the light sensor 6 are respectively mounted at both ends of the cylinder.
In a possible implementation, the first valve 7, the second valve 8, the third valve 10, and the series of valves 9 are micro solenoid valves.
In one possible implementation, the micro-pump 14 is a micro-vacuum pump.
In addition, the aerosol concentration measuring device further includes: and the filter membrane is arranged at the inlet of the aerosol and is used for filtering out larger particles with the particle size exceeding a certain value in the aerosol.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other similar elements in a process, method, article, or apparatus that comprises the element.
Those skilled in the art will appreciate that all or part of the steps of implementing the above method embodiments may be implemented by hardware associated with program instructions, and the program may be stored in a computer-readable storage medium, and when executed, the program performs the steps comprising the above method embodiments, and the storage medium comprises: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it is to be noted that: the above description is only a preferred embodiment of the present invention, and is only used to illustrate the technical solutions of the present invention, and not to limit the protection scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.
Claims (10)
1. An aerosol concentration measurement device, comprising:
the system comprises an aerosol inlet, a mixing cavity, a cloud chamber, a buffer cavity, a light source, a photosensitive device, a first valve, a second valve, a series valve, a third valve, a microcontroller, a signal processing unit, a pressure sensor, a micro pump, a filter membrane, pure liquid and an aerosol outlet;
the aerosol inlet, the first valve, the mixing cavity, the second valve, the cloud chamber, the series of valves, the buffer cavity, the micropump and the aerosol outlet are sequentially connected, the filter membrane, the third valve and the cloud chamber are sequentially connected, the pressure sensor, the light source and the photosensitive device are respectively installed in the cloud chamber, the cloud chamber is installed in the buffer cavity, the first valve, the second valve, the series of valves, the third valve and the micropump are respectively connected with the microcontroller, the photosensitive device is connected with the signal processing unit, the signal processing unit is connected with the microcontroller, and the pure liquid is located in the mixing cavity;
the serial valves comprise at least one sub valve, one end of each sub valve is connected with the cloud chamber, the other end of each sub valve is connected with the buffer cavity, and each sub valve is respectively connected with the microcontroller;
or the cloud chamber and the buffer cavity are arranged side by side, and the cloud chamber is connected with the buffer cavity through the series of valves;
the light source and the photosensitive device are respectively arranged on two opposite wall surfaces in the cloud chamber.
2. The aerosol concentration measuring device of claim 1, wherein the light-sensitive device is a semiconductor light-sensitive element comprising: photoelectric tube, photomultiplier, photo resistance, phototriode.
3. The aerosol concentration measurement device of claim 1, wherein the material of the cloud chamber is black plastic; the cloud chamber is cylindrical, and the light source and the photosensitive device are respectively arranged at two ends of the cylinder.
4. The aerosol concentration measuring method and device according to claim 1, wherein the first valve, the second valve, the third valve, the series of valves are micro solenoid valves; the micropump is a micro vacuum pump.
5. The aerosol concentration measurement device of claim 1, wherein the series of valves consists of a first sub-valve and a second sub-valve; one end of the first sub-valve is connected with the cloud chamber, and the other end of the first sub-valve is connected with the buffer cavity; one end of the second sub-valve is connected with the cloud chamber, and the other end of the second sub-valve is connected with the buffer cavity; the first sub-valve and the second sub-valve are respectively connected with the microcontroller.
6. An aerosol concentration measurement device according to claim 1, wherein the measurement device further comprises: and the filter membrane is arranged at the inlet of the aerosol and is used for filtering out larger particles with the particle size exceeding a certain value in the aerosol.
7. A method of measuring the concentration of an aerosol using the device of claim 1,
the pure liquid is used for volatilizing steam to ensure that the steam reaches a saturated state in the mixing cavity;
the mixing cavity is used for mixing the incoming aerosol particles with saturated vapor of the pure liquid and outputting aerosol-saturated vapor mixture;
the micropump is used for pumping out part of aerosol in the buffer cavity to enable the buffer cavity to reach a certain vacuum degree;
the buffer cavity is used for forming a certain vacuum degree and forming a certain pressure difference with the cloud chamber;
the cloud chamber is used for forming a certain pressure difference with the buffer cavity and enabling inflow aerosol to expand towards the buffer cavity in a heat insulation mode, so that the temperature in the cloud chamber is reduced, the aerosol-steam mixture reaches a supersaturated state, and steam is condensed on aerosol particles to enable the particle volume to be increased to form cloud mist; the larger the concentration of particles in the aerosol is, the denser the cloud formed in the cloud chamber is, the stronger the extinction characteristic is, and the weaker the light intensity reaching the photosensitive device is;
the volume of the space in the mixing cavity is at least 8 times larger than the volume of the space in the cloud chamber;
the light source is used for emitting light with a certain wavelength;
the photosensitive device is used for sensing the light intensity change caused by aerosol fog in the cloud chamber;
the pressure sensor is used for measuring the pressure in the cloud chamber in real time;
the signal processing unit is used for filtering, amplifying and the like of the sensing electric signal of the photosensitive device and outputting the processed electric signal to the microcontroller;
the first valve is used for controlling the on-off of the aerosol flowing into the mixing cavity path;
the second valve is used for controlling the on-off of the aerosol circulation path between the mixing cavity and the cloud chamber;
the series of valves are used for controlling the on-off of an aerosol circulation path between the cloud chamber and the buffer cavity;
the third valve is used for controlling the on-off of a gas flow path between the cloud chamber and the filter membrane;
the filter membrane is used for filtering particles in the aerosol to obtain pure gas; the pure gas enters the cloud chamber through the third valve, disperses the cloud mist in the cloud chamber after the measurement is finished, and discharges the cloud mist to the buffer cavity;
the microcontroller is used for controlling the on-off of the first valve, the second valve, the series of valves and the third valve according to a certain time sequence logic, starting and stopping the micropump, receiving a signal of the pressure sensor, receiving a signal of the signal processing unit, and calculating the quantity concentration of aerosol particles according to the signal output by the signal processing unit and an analytical expression, wherein the analytical expression is a polynomial between the signal output by the signal processing unit and the quantity concentration, and the polynomial meets the preset precision requirement.
8. A method of measuring aerosol concentration according to claim 7,
the sequential logic is: at the beginning of the measuring cycle, at t1At the moment, the micro pump and the series of valves are opened, and then the pressure in the cloud chamber and the buffer chamber is reduced under the action of the micro pump; when the pressure sensor detects that the pressure in the cloud chamber is reduced to P1When (t)2Moment), the first valve and the second valve are opened, the aerosol to be measured enters the mixing cavity through the aerosol inlet and the first valve, the aerosol is mixed with the vapor of the pure liquid in the mixing cavity and then enters the cloud chamber and the buffer cavity through the second valve and the series of valves, and the pressure in the cloud chamber and the buffer cavity rises; when the pressure sensor detects that the pressure in the cloud chamber rises to P2When (t)3Time of day), closing the series of valves, thereafter within the cloud chamberThe pressure in the buffer chamber is reduced; when the pressure sensor detects that the pressure in the cloud chamber rises to P3When (at t)4Time), closing the first valve and the second valve; continuously running for a period of time T1Then at t5Closing the micropump and opening the series of valves, wherein the aerosol-steam mixture in the cloud chamber adiabatically expands to the buffer chamber due to the pressure difference between the cloud chamber and the buffer chamber, the pressure in the cloud chamber rapidly decreases, the temperature decreases, the steam in the cloud chamber reaches a supersaturated state, and aerosol particles increase to form cloud mist; expanding the aerosol and the steam in the cloud chamber for a period of time T2To t6Closing the series of valves at the moment, reading the measurement signal of the signal processing unit, and outputting or displaying the aerosol concentration measurement value; waiting for the system to stabilize for a period of time T3To t7Opening the series of valves and the third valve, allowing pure gas filtered by the filter membrane to enter the cloud chamber and the buffer cavity through the third valve under the action of pressure difference between the cloud chamber and the buffer cavity, and discharging expanded cloud mist out of the cloud chamber; a period of time T4And then closing the series of valves and the third valve to finish a measuring cycle.
9. A method of measuring aerosol concentration according to claim 8, wherein the pressure P1Satisfies the following conditions: less than half of standard atmospheric pressure;
the pressure P2Satisfies the following conditions: p1+20kPa≤P2≤80kPa；
The pressure P3Satisfies the following conditions: p is more than or equal to 90kPa3≤100kPa；
The time period T1Satisfies the following conditions: after the period of time, the pressure in the buffer chamber drops below half the standard atmospheric pressure by the micro pump;
the time period T2Satisfies the following conditions: after the period of time, the pressure within the cloud chamber drops below half of standard atmospheric pressure;
the time period T3Satisfies the following conditions: in the time period, the signal processing unit completes measurement signal processing and outputs the measurement signal to the microprocessor, and the microprocessor completes calculation of aerosol quantity and concentration and displays a measurement result after receiving the measurement signal;
the time period T4Satisfies the following conditions: after the time period, the pressure sensor detects that the pressure in the cloud chamber is a standard atmospheric pressure.
10. The method of measuring aerosol concentration of claim 7, wherein the pure liquid is purified water or a volatile organic solvent, the purified water comprising: deionized water and distilled water; the organic solvent includes: alcohol and n-butanol.
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