A device and method for accurate and rapid measurement of aerosol size-dependent activation rate

Abstract

The present application relates to aerosol particle size activation rate accurate and fast measuring device, including: differential electrical mobility analyzer, used to obtain 10 nanometer to 550 nanometer particle size range monodisperse aerosol;Aerodynamic sizing instrument, used to obtain 90 nanometer to 800 nanometer particle size range monodisperse aerosol;Condensation nucleus counter, used to obtain the number of monodisperse aerosol particles screened by differential electrical mobility analyzer, and used to obtain the number of monodisperse aerosol particles screened by aerodynamic sizing instrument;Cloud condensation nucleus counter, used to obtain the number of cloud condensation nuclei in monodisperse aerosol screened by differential electrical mobility analyzer and aerodynamic sizing instrument.The present application also relates to aerosol particle size activation rate accurate and fast measuring method, the present application can realize accurate and fast measurement of aerosol particle size activation rate under multiple supersaturation conditions, belongs to the field of aerosol detection and the field of cloud microphysics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerosol detection and the field of cloud microphysics, and particularly relates to a device and method for accurately and rapidly measuring aerosol particle size activation rate. BACKGROUND

[0002] The interaction between aerosols and clouds is an important source of uncertainty in climate change assessment and extreme weather prediction. Cloud condensation nuclei, i.e. aerosols that can be activated into clouds under a certain supersaturation, are the key parameters that affect the interaction between aerosols and clouds. The ability of aerosol particles to absorb moisture and activate to form cloud condensation nuclei under a certain supersaturation depends on their particle size and chemical composition. Among them, the particle size of aerosol is an important factor affecting its activation characteristics. The parameter for accurately quantifying this ability is the aerosol activation rate under a certain supersaturation, i.e. the aerosol particle size activation rate. In order to obtain the aerosol particle size activation rate, the particle size of the aerosol needs to be measured and screened. Therefore, continuous flow thermal gradient cloud condensation nucleus counters and aerosol particle size analyzers are mainly used to measure this parameter. In the existing research on the activation characteristics of aerosols, the method of using a differential mobility analyzer, a condensation nucleus counter and a cloud condensation nucleus counter is usually adopted. However, the method of using a differential mobility analyzer to screen aerosol particles is affected by the multiple charging of particles, i.e. smaller particles carrying a single charge and larger particles carrying multiple charges have the same electrical mobility, so that particles with different particle sizes but the same electrical mobility are screened out at the same time. Therefore, the aerosol obtained by this method is not of a single particle size. In addition, the commonly used centrifugal particle mass analyzer also has a similar problem.

[0003] Generally, to study the activation characteristics of aerosols, experiments need to be conducted under a variety of supersaturation conditions. However, in the observation process, we mainly adjust the supersaturation by changing the temperature difference, which requires a long temperature stabilization time, and thus leads to a decrease in the measurement time precision. In the actual atmospheric environment, the supersaturation conditions vary greatly. For example, the supersaturation in fog and low-level clouds can be less than 0.1%, while the supersaturation in deep convective clouds can be as high as 1%. In the cloud condensation nucleus counter, it can take up to ten minutes to reach a stable state when the supersaturation changes between 0.1% and 1%. Generally, the observation time precision of the aerosol particle size activation rate requires to be within 1 hour, so the stabilization time of the cloud condensation nucleus counter will have a significant impact on the measurement time precision of the aerosol particle size activation rate. In addition, the supersaturation in the cloud condensation nucleus counter can also be quickly changed by changing the flow rate. However, the flow rate under low supersaturation conditions is low, which leads to a low number of cloud condensation nuclei in the counter. Considering that the number of cloud condensation nuclei under low supersaturation conditions is already low (especially in clean areas and background areas with light aerosol pollution), the measurement efficiency under low supersaturation conditions is low, so this method is not suitable for low supersaturation measurements.

[0004] In addition, the cloud condensation nucleus counter may have a large identification bias under low supersaturation conditions. Its working principle is to activate and grow cloud condensation nuclei into several microns of droplets in the cloud chamber, while aerosols that cannot be activated into cloud condensation nuclei (interstitial aerosols, usually less than 1 micron) have a significant difference in particle size from cloud condensation nuclei. By measuring the number concentration of droplets with an optical particle counter, the number concentration of cloud condensation nuclei can be calculated. However, under lower supersaturation conditions (less than 0.15%), the droplets grown from cloud condensation nuclei in the cloud condensation nucleus counter can be less than 2 microns, while some hygroscopic interstitial aerosols can grow to more than 1 micron by hygroscopic growth. Therefore, under such conditions, it is difficult for the cloud condensation nucleus counter to effectively distinguish between cloud condensation nuclei and interstitial aerosols, resulting in an overestimation of the number of cloud condensation nuclei measured by the cloud condensation nucleus counter. To solve this problem, a method for accurately distinguishing cloud condensation nuclei under low supersaturation conditions has been proposed in the prior art. This method requires analysis of the droplet spectrum in the cloud condensation nucleus counter. However, considering the measurement uncertainty of the optical particle counter in the cloud condensation nucleus counter, the screening efficiency of the currently used differential mobility analyzer is difficult to meet the requirements of this correction method. In order to accurately measure the aerosol particle size activation rate under low supersaturation conditions, it is necessary to use an aerosol classifier with higher screening efficiency. SUMMARY

[0005] In view of the technical problems existing in the prior art, the purpose of the present application is to provide an accurate and rapid measurement device for aerosol particle size activation rate, to realize accurate and rapid measurement of aerosol particle size activation rate under multiple supersaturation conditions, and to solve the limitations of existing aerosol particle size activation rate measurement methods, especially the measurement accuracy of aerosol particle size activation rate under low supersaturation conditions at extremely low aerosol concentration.

[0006] Another purpose of the present application is to provide an accurate and rapid measurement method for aerosol particle size activation rate, to realize accurate measurement of aerosol particle size activation rate under low supersaturation conditions at low aerosol concentration.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions:

[0008] An accurate and rapid measurement device for aerosol particle size activation rate comprises: a differential electrical mobility analyzer for screening dry aerosol by electrical mobility particle size to obtain monodisperse aerosol in the particle size range of 10 nm to 550 nm; an aerodynamic sizing instrument for screening dry aerosol by aerodynamic particle size to obtain monodisperse aerosol in the particle size range of 90 nm to 800 nm; a condensation nucleus counter for obtaining the number of monodisperse aerosol particles screened by the differential electrical mobility analyzer, and for obtaining the number of monodisperse aerosol particles screened by the aerodynamic sizing instrument; and a cloud condensation nucleus counter for obtaining the number of cloud condensation nuclei in the monodisperse aerosol screened by the differential electrical mobility analyzer and the aerodynamic sizing instrument.

[0009] As a preferred, the measurement device further comprises a switching system for switching the condensation nucleus counter to obtain the number of monodisperse aerosol particles screened by the differential electrical mobility analyzer or the aerodynamic sizing instrument.

[0010] As a preferred, the switching system comprises a main gas path, an air inlet branch, an electromagnetic valve and an electromagnetic valve switching control circuit board; the number of electromagnetic valves and air inlet branches is two; the two electromagnetic valves are connected with the differential electrical mobility analyzer and the aerodynamic sizing instrument through connecting pipelines respectively, the two electromagnetic valves are connected with the main gas path through two air inlet branches respectively, the main gas path is connected with the condensation nucleus counter, and the two electromagnetic valves are connected with the electromagnetic valve switching control circuit board.

[0011] As a preferred, the measurement device further comprises an industrial computer for controlling the differential electrical mobility analyzer, the aerodynamic sizing instrument and the switching system to run, and for reading the measurement results of the cloud condensation nucleus counter and the condensation nucleus counter in real time.

[0012] As a preferred, the measurement device further comprises a dryer for dehumidifying and drying the aerosol.

[0013] As a preferred, the aerosol dried by the dryer is generated by an aerosol generator or obtained by a sampling head, part of the aerosol generated by the aerosol generator or obtained by the sampling head flows through the dryer for dehumidification drying, and the rest of the aerosol is filtered by the filter and discharged into the air.

[0014] As a preferred, the connecting pipe, the main gas path and the gas inlet branch are all prepared by using conductive black rubber pipes.

[0015] An accurate and rapid measurement method of aerosol particle size activation rate, the method adopts an accurate and rapid measurement device of aerosol particle size activation rate, and the method comprises the following steps:

[0016] S1: collecting or producing aerosol;

[0017] S2: drying the aerosol;

[0018] S3: screening the dried aerosol to obtain monodisperse aerosol of 10-800 nanometers;

[0019] S4: obtaining the number of monodisperse aerosol particles after screening by using a condensation nucleus counter;

[0020] S5: obtaining the number of cloud condensation nuclei of monodisperse aerosol under the condition of 0.05%-0.8% supersaturation ratio by using a cloud condensation nucleus counter;

[0021] S6: calculating the ratio of the number of monodisperse cloud condensation nuclei and the number of aerosol particles according to the obtained number of monodisperse cloud condensation nuclei and the number of aerosol particles, and obtaining the distribution of the ratio of the number of monodisperse cloud condensation nuclei and the number of aerosol particles with particle size, that is, the aerosol particle size activation rate.

[0022] As a preferred, in step S3, the method for obtaining monodisperse aerosol of 10-800 nanometers is that the dried aerosol flows to a differential electrical mobility analyzer and an aerodynamic size classifier respectively, the differential electrical mobility analyzer screens the dried aerosol to obtain monodisperse aerosol in the particle size range of 10-550 nanometers, and the aerodynamic size classifier screens the dried aerosol to obtain monodisperse aerosol in the particle size range of 90-800 nanometers.

[0023] As a preferred, during the measurement process, part of the monodisperse aerosol after the aerodynamic classifier is sent to the cloud condensation nucleus counter A column, and the other part is sent to the cloud condensation nucleus counter B column; part of the monodisperse aerosol after the differential mobility analyzer is sent to the cloud condensation nucleus counter A column, and the other part is sent to the cloud condensation nucleus counter B column; wherein, according to the time period when the supersaturation ratio of the cloud condensation nucleus counter A column reaches stability, or the time period when the supersaturation ratio of the cloud condensation nucleus counter B column reaches stability, the switching system switches the cloud condensation nucleus counter to cooperate with the A column or the B column which has reached stability to alternately measure the aerosol particle size activation rate.

[0024] Overall, the present application has the following advantages:

[0025] 1. The present application mainly uses an aerodynamic classifier, a differential mobility analyzer and a cloud condensation nucleus counter to accurately measure the aerosol particle size activation rate under different supersaturation ratios. This method is particularly suitable for measuring the aerosol particle size activation rate under low supersaturation ratios in low aerosol concentration conditions, and solves the problems of aerodynamic particle size correction and cloud condensation nucleus identification. Due to the existence of multiple charge problems, particles with the same mass nucleus ratio can be screened out at the same time when screening large particles, so there is a multiple charge error, and the screening efficiency of the differential mobility analyzer decreases as the particle size increases. Under low supersaturation ratios (less than 0.15%), the cloud condensation nucleus counter cannot accurately distinguish cloud condensation nuclei and interstitial aerosols, resulting in overestimation of the number of cloud condensation nuclei measured by the cloud condensation nucleus counter. On the other hand, the aerodynamic classifier has a large uncertainty when screening small particles (less than 100 nanometers), and for aerosols with different densities and shapes, the monodisperse particles screened by the aerodynamic classifier have different volume equivalent particle sizes, and their corresponding electrical mobility diameters are different. Using the aerodynamic classifier alone to screen aerosol particles has a large deviation. In order to solve these problems, the aerodynamic classifier is used in combination with the cloud condensation nucleus counter to accurately identify cloud condensation nuclei under low supersaturation ratios, and the actual particle size of the aerosol screened by the aerodynamic classifier is determined by comparing the particle size screening results of the aerodynamic classifier and the differential mobility analyzer, thereby solving the problem of aerodynamic particle size screening by the aerodynamic classifier. This method realizes the screening of monodisperse aerosols in different particle size ranges in the measurement of aerosol particle size activation rate under different supersaturation ratios, thereby facilitating the cloud condensation nucleus counter and the cloud condensation nucleus counter to obtain corresponding data, and ultimately obtaining the measurement results of aerosol particle size activation rate under different supersaturation ratios.

[0026] 2. The present application can ensure high-precision measurement time by optimizing technical means and using only one cloud condensation nucleus counter. In the conventional method, two cloud condensation nucleus counters are needed to be connected at the same time, one with the differential electrical mobility analyzer and the other with the aerodynamic particle sizer, to measure the aerosol particle number filtered by the differential electrical mobility analyzer and the aerodynamic particle sizer, respectively. However, due to the need for a certain stabilization time when switching the supersaturation ratio of the cloud condensation nucleus counter, the traditional method has a time period in the measurement time cycle that cannot be used for effective measurement. The present application designs a switching system to switch the cloud condensation nucleus counter to cooperate with another stabilized cloud chamber to measure the aerosol size distribution activation rate during the period when the supersaturation ratio of the cloud chamber of the cloud condensation nucleus counter reaches stability. By alternating operation in this way, only one cloud condensation nucleus counter is needed to achieve the same time resolution measurement effect as two cloud condensation nucleus counters in the conventional method. Through this improvement, not only the equipment cost is reduced, but also the measurement efficiency is improved. In addition, since the measurement method of the present application only needs to use one cloud condensation nucleus counter, the error caused by the difference between different cloud condensation nucleus counters can be reduced, and the measurement accuracy is also improved to some extent. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of an aerosol size distribution activation rate accurate and rapid measurement device in an embodiment of the present application.

[0028] Figure 2 is a schematic diagram of a supersaturation ratio setting scheme in a cloud condensation nucleus counter in an embodiment of the present application.

[0029] Figure 3 is a schematic diagram of the measured curve of aerosol size distribution activation rate and sampling points in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below in conjunction with the specific embodiments.

[0031] Compared with the existing method for detecting aerosol size distribution activation rate, the monodisperse aerosol filtered by the differential electrical mobility analyzer is difficult to meet the accurate and rapid detection of aerosol size distribution activation rate, therefore, the present application proposes a set of measurement device based on differential electrical mobility analyzer, aerodynamic particle sizer and cloud condensation nucleus counter, which realizes accurate identification of cloud condensation nucleus at low supersaturation ratio by using aerodynamic particle sizer, and corrects the aerodynamic particle size by simultaneous measurement of differential electrical mobility analyzer and aerodynamic particle sizer, without increasing the number of cloud condensation nucleus counters and reducing the time resolution of measurement, so as to realize accurate and rapid measurement of aerosol size distribution activation rate at multiple supersaturation ratios. Please see the following embodiments for details:

[0032] Embodiment One

[0033] In this embodiment, Figure 1 A schematic diagram of a device for accurate and rapid measurement of aerosol activation diameter under multiple supersaturation conditions is shown, which is based on the cooperation of a differential electrical mobility analyzer, an aerodynamic particle sizer and a cloud condensation nucleus counter. In Figure 1 In the device, a polydisperse aerosol is introduced into the device through a conductive black rubber tube. Part of the flow passes through a dryer for drying treatment, and the other part of the excess aerosol is filtered through a filter and discharged. The dried aerosol is divided into two paths through a Y-type shunt tube (made of conductive black rubber tube) to flow to the aerodynamic particle sizer and the differential electrical mobility analyzer, respectively. The monodisperse aerosol filtered by the differential electrical mobility analyzer flows to the condensation nucleus counter in one path and to the B column of the cloud condensation nucleus counter in the other path. The monodisperse aerosol filtered by the aerodynamic particle sizer flows to the condensation nucleus counter in one path and to the A column of the cloud condensation nucleus counter in the other path. The monodisperse aerosol filtered by the differential electrical mobility analyzer and the aerodynamic particle sizer flows to the same condensation nucleus counter through a switching system. The instruments used in the device and their related settings will be described in detail below.

[0034] An aerosol generator is used only when calibrating the instrument, which can generate a polydisperse aerosol of known composition, and is used for the calibration of the supersaturation ratio in the cloud condensation nucleus counter. The flow rate of the aerosol generator should be slightly greater than the sum of the flow rates of the downstream instruments.

[0035] In some embodiments, the aerosol in the environment can also be sampled by a sampling head.

[0036] A dryer is used to dehumidify and dry the generated or sampled aerosol.

[0037] A cloud condensation nucleus counter is used to obtain the number of cloud condensation nuclei in the monodisperse aerosol filtered by the differential electrical mobility analyzer / aerodynamic particle sizer. The flow rates of the A column and the B column of the cloud condensation nucleus counter are both set to 0.4 Lpm. The supersaturation ratio sequence of the A column is set to 0.2%, 0.14%, 0.1% and 0.05%, and the supersaturation ratio sequence of the B column is set to 0.8%, 0.4%, 0.2% and 0.14%. The running time of the four supersaturation ratios of the A column and the B column is set to 15 minutes. A complete measurement cycle is one hour, and the cloud condensation nucleus activation diameters corresponding to different hygroscopic aerosols are shown in Table 2.

[0038] Table 2, Aerosol activation critical diameter (nm) corresponding to different hygroscopic parameters under each supersaturation ratio

[0039]

[0040] It is important to note that the supersaturation ratio shows a decreasing trend rather than an increasing trend during the supersaturation ratio scanning cycle for cloud condensation nuclei. Meanwhile, the time used for each supersaturation ratio in the two cloud chambers (Column A and Column B) involved in the measurement is the same, which is 15 minutes. According to the characteristics of the instrument, the cloud condensation nuclei counter needs a certain stabilization time when the supersaturation ratio is switched, and the greater the difference in supersaturation ratio, the longer the stabilization time required. In addition, the stabilization time required during the cooling process is faster than that during the heating process. For the differential mobility analyzer, the time for completing a complete particle size screening cycle is short, which can be set to 5 minutes. However, the stabilization time corresponding to a high supersaturation ratio is longer, which needs to be set to 10 minutes. For the aerodynamic sizer, the time for completing a complete particle size screening cycle is longer, which needs to be set to 10 minutes. However, the stabilization time corresponding to a low supersaturation ratio is shorter, which can be set to 5 minutes. Figure 2 The supersaturation ratio settings for Column A and Column B, the duration of each supersaturation ratio, and the arrangement of the measurement time are shown. Each small section in the figure represents five minutes, and every three small sections (i.e., 15 minutes) correspond to the time of one supersaturation ratio. The solid line section represents the time for measurement after the supersaturation ratio reaches stability, and the dashed line section is used for the time required for the supersaturation ratio to switch and reach stability. For the 15 minutes of each supersaturation ratio of Column A, the first 5 minutes are used for the switching of the supersaturation ratio of Column A, and the last 10 minutes are used for the scanning of the aerodynamic sizer. Similarly, for the supersaturation ratio of Column B, the duration of the first supersaturation ratio (0.8%) is set to 5 minutes. Within these 5 minutes, the supersaturation ratio is stable for each hour cycle after the first scan at startup, except for the first scan. These 5 minutes are used for the scanning of the differential mobility analyzer. The duration of the second to fourth supersaturation ratios is set to 15 minutes. Within these 15 minutes, the first 10 minutes are used for the switching of the supersaturation ratio of Column B to a stable state, and the last 5 minutes are used for the scanning of the differential mobility analyzer. Finally, it is important to note that the last 10 minutes of each hour cycle of Column B are connected to the first 5 minutes in actual operation, and the supersaturation ratio setting is consistent, and these 10 minutes are mainly used for the time required for the supersaturation ratio to switch and reach stability.

[0041] The aerodynamic classifier is used to size the dried aerosol by aerodynamic diameter to obtain monodisperse aerosols in the 90 nm to 800 nm diameter range. Since the aerodynamic classifier does not require the aerosol to carry a certain amount of charge, it is not affected by aerosols carrying multiple charges. In addition, the aerodynamic classifier performs significantly better than the differential mobility analyzer in sizing large diameter aerosols (typically greater than 300 nm), but the minimum diameter is typically 100 nm for small diameter aerosols. Given the importance of large diameter aerosols in the activation characteristics of aerosol cloud condensation nuclei, especially at low supersaturation ratios, and the contribution of small diameter aerosols to the activation characteristics of cloud condensation nuclei primarily at high supersaturation ratios, this instrument can be used to measure the activation rate of aerosols with a supersaturation ratio of 0.2% or less. During operation, the sheath gas flow rate of the aerodynamic classifier is set to about 10 Lpm, while the sample gas flow rate is set to 1 Lpm, ensuring that the ratio of the sheath gas flow rate to the sample gas flow rate of the aerodynamic classifier is in the range of 10:1. The corresponding particle sizing accuracy parameter value is set to about 10. The particle size settings are run by the control program according to the particle sizes and residence times in Tables 3 and 4. During the operation of the aerodynamic classifier, the aerosol particle size gradually increases, and the corresponding rotational speed gradually decreases. Since the acceleration process of the aerodynamic classifier takes longer than the deceleration process, the particle size settings gradually change in the order from small to large, i.e., the rotational speed gradually changes from high to low. In addition, when the aerodynamic classifier switches from one rotational speed to another rotational speed set point, there is a transmission time and a stabilization (delay) time. When the aerosol particle size is continuously operated, the aerodynamic classifier requires a transmission time of 9.5 s and a stabilization time of 5 s. Increasing the stabilization interval time can improve the repeatability of particle counting, thereby reducing the uncertainty of particle diffusion.

[0042] Table 1, Figure 2 corresponding supersaturation ratio setting value

[0043]

[0044] In the scanning cycle of the aerodynamic classifier, the first 5 minutes do not measure. During these 5 minutes, since the supersaturation ratio is not yet stable, a rough scan of the aerodynamic classifier can be performed. Although the rough scan particle size settings are too large to completely show the process of the rise in aerosol activation rate, the particle size range that must be scanned can be reduced to perform a fine scan with higher particle size resolution. The specific operation can be seen in Table 3.

[0045] Table 3 Aerodynamic classifier rough scan particle size settings

[0046]

[0047] The coarse sizing range of the aerodynamic sizer is determined and set according to the temperature change of the cloud condensation nuclei counter, and then the activation range is roughly determined within the coarse sizing range. When the aerodynamic sizer is used for coarse sizing, aerosols with smaller particle sizes are not activated, and when the particle size increases to a certain value, cloud condensation nuclei begin to exist. For example, the particle size that starts to activate at 0.2% supersaturation ratio is 100 nm. When the particle size increases to a certain extent, and the ratio of cloud condensation nuclei to aerosol particle number remains unchanged, it is known that the aerosol is substantially completely activated. Further, smaller particle size intervals are set in the stage where the number of cloud condensation nuclei rises rapidly, and larger particle size intervals can be appropriately set in the stage where the number of cloud condensation nuclei rises slowly. In Table 4, the particle size interval is 10 nm in the range of 90 to 160 nm, and the particle size interval is 20 nm or more than 30 nm when the particle size exceeds 160 nm at a supersaturation ratio of 0.2%. Similarly, at a supersaturation ratio of 0.14%, 0.1%, and 0.15%, the particle size interval is 10 nm in the stage where the activation rate rises, and the particle size interval is set to 20 nm or more in other stages. In addition, it should be noted that 1-2 points are taken before and after the activation range of the aerosol to ensure that the particle size of the aerosol is measured before and after the activation range, so that the complete particle size activation rate curve of the rising section is obtained. See Figure 3 When the aerodynamic sizer is used for fine sizing of particle size, the detailed characteristics of the aerosol particle size activation rate changing with particle size can be measured.

[0048] Table 4, fine scanning particle size setting of the aerodynamic sizer

[0049]

[0050]

[0051] The differential mobility analyzer is responsible for the electrical mobility particle size screening of the dried aerosol to obtain monodisperse aerosols in the particle size range of 10 nm to 550 nm. It is mainly used to measure the aerosol particle size activation rate at a supersaturation ratio of more than 0.14%. In the operation process, the sheath gas flow is set to about 5 L / min, and the sample gas flow is set to 1 Lpm, so as to ensure that the ratio of the sheath gas flow to the sample gas flow of the differential mobility analyzer is in the range of 5:1. Since the differential mobility analyzer controls the particle size allowed to pass through by the electrode, the time required for switching the electrical mobility particle size is very short. The measurement of the aerosol particle size activation rate can be completed in the last 5 minutes of each supersaturation ratio in the B column.

[0052] The condensation nuclei counter is used to obtain the number of monodisperse aerosol particles dried and screened by the differential mobility analyzer / aerodynamic sizer, and the flow rate is set to 0.6 Lpm.

[0053] The switching system comprises a main gas path, an air inlet branch, an electromagnetic valve and an electromagnetic valve switching control circuit board; the number of the electromagnetic valve and the air inlet branch is two; the two electromagnetic valves are connected with the differential electrical mobility analyzer and the air dynamics sieve instrument through the connecting pipeline respectively; the two electromagnetic valves are connected with the main gas path through the two air inlet branches respectively; the main gas path is connected with the condensation nucleus counter; the two electromagnetic valves are connected with the electromagnetic valve switching control circuit board. The two electromagnetic valves are connected with the power supply system; the power supply system is connected with the electromagnetic valve switching control circuit board; the switching system is used for realizing the automatic opening and closing of the program-controlled electromagnetic valve according to the set time length.

[0054] In order to realize the automatic operation of the instrument, an industrial computer is further included, as shown in Figure 1 , the industrial computer is the computer in Figure 1 , and the computer program in Figure 1 is the existing conventional program used by the industrial computer to control the differential electrical mobility analyzer, the air dynamics sieve instrument and the switching system to run, and to read the measurement results of the cloud condensation nucleus counter and the condensation nucleus counter in real time.

[0055] In the embodiment, in order to realize the automatic operation of the instrument, the specific particle diameter of the aerosol is set and read, including setting and reading the sheath gas flow of the differential electrical mobility analyzer and the air dynamics sieve instrument, setting the start time of each particle diameter of the differential electrical mobility analyzer and the air dynamics sieve instrument, storing the measurement data of the condensation nucleus counter and the cloud condensation nucleus in real time, and adjusting the particle diameter setting of the air dynamics sieve instrument according to the data in real time, while outputting the measurement results in real time.

[0056] The working process of the switching system is as shown in Figure 2The over-saturation ratio is maintained for 15 minutes, and each cycle lasts for 1 hour. The switching system is used to switch the differential mobility analyzer and the cloud condensation nuclei counter first every 5 minutes, then every 10 minutes, and so on. Specifically, in the first 5 minutes of each cycle, the electromagnetic valve connecting the differential mobility analyzer and the cloud condensation nuclei counter is opened, while the electromagnetic valve connecting the aerodynamic sizer and the cloud condensation nuclei counter is closed. The 5 minutes are mainly used for the scanning of the differential mobility analyzer at an over-saturation ratio of 0.8%. Since the coarse scanning of the aerodynamic sizer does not need to be coupled with the cloud condensation nuclei counter, and the over-saturation ratio of column A is not stable, the coarse scanning of the aerodynamic sizer at an over-saturation ratio of 0.2% can be performed at the same time. In this way, the cloud condensation nuclei counter over-saturation ratio stabilization time is fully utilized without causing a decrease in the time resolution. When the coarse scanning is completed and the over-saturation ratio of column A is stabilized at 0.2%, the electromagnetic valve connecting the aerodynamic sizer and the cloud condensation nuclei counter is automatically opened by the switching system, and the electromagnetic valve connecting the differential mobility analyzer and the cloud condensation nuclei counter is automatically closed. The aerosol that has passed through the aerodynamic sizer is divided into two parts, one of which flows to the cloud condensation nuclei counter, and the other of which flows to the cloud condensation nuclei counter. Then, the aerodynamic sizer is used to scan according to the fine screening particle size and residence time set in Table 4 to obtain the aerosol particle size activation rate under the condition of a low over-saturation ratio. The fine screening lasts for 10 minutes, and at the same time, the 10 minutes are also given to the change of the over-saturation ratio of column B from 0.8% to 0.4%, which overlaps with the fine scanning time of the aerodynamic sizer of column A at an over-saturation ratio of 0.2%. When column A completes the fine screening of the aerodynamic sizer at an over-saturation ratio of 0.2%, the over-saturation ratio of column B is also stabilized at 0.4%. The electromagnetic valve connecting the differential mobility analyzer and the cloud condensation nuclei counter is automatically opened by the switching system, and the electromagnetic valve connecting the aerodynamic sizer and the cloud condensation nuclei counter is automatically closed. After 5 minutes, the differential mobility analyzer starts to scan according to the preset particle size and residence time to obtain the aerosol particle size activation rate under the condition of a high over-saturation ratio. In this way, switching is continuously performed to complete the measurement of the aerosol particle size activation rate under multiple over-saturation ratio conditions.

[0057] Invention principle: first, the aerosol generated by the aerosol generator flows through the drying tube, and then flows to the aerodynamic sizing spectrometer and the differential mobility analyzer through a Y-shaped shunt. After being screened by the aerodynamic sizing spectrometer, part of the monodisperse aerosol flows to the condensation nucleus counter, and the other part flows to column A of the cloud condensation nucleus counter. After being screened by the differential mobility analyzer, part of the monodisperse aerosol flows to the condensation nucleus counter, and the other part flows to column B of the cloud condensation nucleus counter. The two gas paths (gas inlet branch) to the condensation nucleus counter are combined into one gas path (main gas path) to the condensation nucleus counter by the switching system, so that the aerodynamic sizing spectrometer and the differential mobility analyzer share one condensation nucleus counter. Then, the condensation nucleus counter obtains the number of monodisperse aerosol particles screened by the differential mobility analyzer and the number of monodisperse aerosol particles screened by the aerodynamic sizing spectrometer. The cloud condensation nucleus counter obtains the number of cloud condensation nuclei in the monodisperse aerosol screened by the differential mobility analyzer and the aerodynamic sizing spectrometer. Finally, the aerosol size activation rate is calculated based on the number of monodisperse aerosol particles and the number of cloud condensation nuclei. The aerosol size activation rate is the ratio of the number of cloud condensation nuclei to the number of aerosols.

[0058] In addition, the aerodynamic sizing spectrometer still has some uncertainty in particle size screening. The aerodynamic particle size on which the screening is based is not only related to the geometric size of the aerosol, but also affected by the dynamic shape factor and the effective density of the particle. The aerosol particle size measured by the differential mobility analyzer is mainly related to the geometric size of the aerosol. Therefore, by comparing the particle size distribution of the aerosol number at 0.14% and 0.2% supersaturation ratio between the differential mobility analyzer and the aerodynamic sizing spectrometer, the shape factor and the effective density of the particle can be calculated, and the aerodynamic particle size screened by the aerodynamic sizing spectrometer can be corrected.

[0059] According to the above instrument and connection operation mode, the device provided by the application can accurately and quickly measure the aerosol size activation rate under multiple supersaturation ratios, correct the aerodynamic particle size, and accurately identify the cloud condensation nuclei. It is especially suitable for accurate measurement of aerosol size activation rate under low aerosol concentration and low supersaturation ratio. At the same time, the system uses a switching system to use only one condensation nucleus counter to achieve high measurement time accuracy.

[0060] Example two

[0061] An accurate and rapid measurement method of aerosol size activation rate, which adopts an accurate and rapid measurement device of aerosol size activation rate, and includes the following steps:

[0062] S1: collect or produce aerosol; for example, collect by a sampling head or produce by an aerosol generator.

[0063] S2: drying the aerosol; for example, drying the aerosol by using a conventional dryer.

[0064] S3: screening the dried aerosol to obtain monodisperse aerosol with a particle size of 10-800 nm.

[0065] S4: using a condensation nucleus counter to obtain the number of monodisperse aerosol particles after screening.

[0066] S5: using a cloud condensation nucleus counter to obtain the number of cloud condensation nuclei of the monodisperse aerosol under a supersaturation ratio of 0.05%-0.8%.

[0067] S6: calculating the ratio of the number of cloud condensation nuclei to the number of aerosol particles with respect to the particle size, i.e., obtaining the aerosol particle size activation ratio, according to the obtained number of cloud condensation nuclei and the number of aerosol particles. Figure 3 As shown in the table, when the ratio of the number of cloud condensation nuclei to the number of aerosol particles is 0.4, the corresponding particle size is 220 nm.

[0068] In step S3, the method for obtaining the monodisperse aerosol with a particle size of 10-800 nm is as follows: the dried aerosol is respectively flowed to a differential mobility analyzer and an aerodynamic particle sizer, the dried aerosol is screened by the differential mobility analyzer to obtain monodisperse aerosol with a particle size of 10-550 nm, and the dried aerosol is screened by the aerodynamic particle sizer to obtain monodisperse aerosol with a particle size of 90-800 nm.

[0069] During the measurement process, part of the monodisperse aerosol screened by the aerodynamic particle sizer is flowed to the condensation nucleus counter, and the other part is flowed to the A column of the cloud condensation nucleus counter; part of the monodisperse aerosol screened by the differential mobility analyzer is flowed to the condensation nucleus counter, and the other part is flowed to the B column of the cloud condensation nucleus counter; wherein, according to the time period during which the supersaturation ratio of the A column of the cloud condensation nucleus counter reaches stability, or the time period during which the supersaturation ratio of the B column of the cloud condensation nucleus counter reaches stability, the switching system switches the condensation nucleus counter to cooperate with the A column or the B column which has reached stability to alternately measure the aerosol particle size activation ratio.

[0070] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement modes, and all shall be included in the protection scope of the present application.

Claims

1. A device for accurate and rapid measurement of the size- resolved activation rate of aerosols, characterized in that, It comprises: a differential mobility analyzer for screening the dried aerosol by electric mobility particle size to obtain monodisperse aerosol in the particle size range of 10-550 nm; an aerodynamic sizing instrument for screening the dried aerosol by aerodynamic particle size to obtain monodisperse aerosol in the particle size range of 90-800 nm; a condensation nucleus counter for obtaining the number of monodisperse aerosol particles screened by the differential mobility analyzer, and for obtaining the number of monodisperse aerosol particles screened by the aerodynamic sizing instrument; a cloud condensation nucleus counter for obtaining the number of cloud condensation nuclei in the monodisperse aerosol screened by the differential mobility analyzer and the aerodynamic sizing instrument; a switching system for switching the condensation nucleus counter to obtain the number of monodisperse aerosol particles screened by the differential mobility analyzer or the aerodynamic sizing instrument; The switching system comprises a main gas path, an air inlet branch, an electromagnetic valve and an electromagnetic valve switching control circuit board; the number of electromagnetic valves and air inlet branches is two; the two electromagnetic valves are connected with the differential mobility analyzer and the aerodynamic sizing instrument through connecting pipes, respectively; the two electromagnetic valves are connected with the main gas path through two air inlet branches, respectively; the main gas path is connected with the condensation nucleus counter; and the two electromagnetic valves are connected with the electromagnetic valve switching control circuit board; During the measurement process, part of the monodisperse aerosol screened by the aerodynamic sizing instrument flows to the condensation nucleus counter, and the other part flows to the A column of the cloud condensation nucleus counter; part of the monodisperse aerosol screened by the differential mobility analyzer flows to the condensation nucleus counter, and the other part flows to the B column of the cloud condensation nucleus counter; wherein, according to the time period when the supersaturation ratio of the A column of the cloud condensation nucleus counter reaches stability, or the time period when the supersaturation ratio of the B column of the cloud condensation nucleus counter reaches stability, the switching system switches the condensation nucleus counter to cooperate with the already stable A column or B column to alternately measure the aerosol particle size activation rate.

2. The apparatus for accurate and rapid measurement of size-fractionated aerosol activation rates according to claim 1, wherein: It also comprises an industrial computer for controlling the differential mobility analyzer, the aerodynamic sizing instrument and the switching system to run, and for reading the measurement results of the cloud condensation nucleus counter and the condensation nucleus counter in real time.

3. The apparatus for accurate and rapid measurement of size-fractionated aerosol activation rates according to claim 1, wherein: It also comprises a dryer for dehumidifying and drying the aerosol.

4. The apparatus for accurate and rapid measurement of size-fractionated aerosol activation rates according to claim 3, wherein: The aerosol dried by the dryer is generated by an aerosol generator or collected by a sampling head; part of the aerosol generated by the aerosol generator or collected by the sampling head is dehumidified and dried by the dryer, and the remaining aerosol is filtered by a filter and discharged into the air.

5. The apparatus for accurate and rapid measurement of size-fractionated aerosol activation rates according to claim 1, wherein: The connecting pipes, the main gas path and the air inlet branches are prepared by using conductive black rubber pipes.

6. A method for accurate and rapid measurement of the size- resolved activation rate of aerosols, characterized in that, The method adopts the accurate and rapid aerosol particle size activation rate measurement device of any one of claims 1-5, and comprises the following steps: S1: collecting or producing aerosol; S2: drying the aerosol; S3: screening the dried aerosol to obtain monodisperse aerosol in the particle size range of 10-800 nm; In step S3, the method for obtaining monodisperse aerosol of 10-800 nm is as follows: the dried aerosol is respectively flowed to a differential electrical mobility analyzer and an aerodynamic particle sizer, the dried aerosol is screened by the differential electrical mobility analyzer to obtain monodisperse aerosol in the particle size range of 10-550 nm, and the dried aerosol is screened by the aerodynamic particle sizer to obtain monodisperse aerosol in the particle size range of 90-800 nm; S4: obtaining the number of screened monodisperse aerosol particles by using a condensation nucleus counter; S5: obtaining the number of cloud condensation nuclei of monodisperse aerosol under the condition of 0.05%-0.8% supersaturation ratio by using a cloud condensation nucleus counter; S6: calculating the distribution of the ratio of the number of monodisperse cloud condensation nuclei and the number of aerosol particles with the particle size, that is, obtaining the aerosol particle size activation rate.

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