On-line measurement system for particle size and component of fogdrop

Abstract

The utility model discloses a fogdrop particle size and component on-line measurement system, which relates to the technical field of fogdrop on-line measurement and comprises a laser, a scattered light receiving component, a light trap and a fogdrop sampling channel cylinder. The laser is used for emitting laser, and scattered light is obtained after the laser is scattered by fogdrops in the fogdrop sampling channel cylinder; the four independently-arranged scattered light receiving assemblies are arranged on the outer side of the fogdrop sampling channel cylinder in a surrounding mode in the axial direction of the fogdrop sampling channel cylinder so as to receive scattered light, the detectors in all the scattered light receiving assemblies and laser beams emitted by the lasers are located on the same plane A, and the movement direction of fogdrops in the fogdrop sampling channel cylinder is perpendicular to the plane A; light beam focuses of scattered light received by all the scattered light receiving assemblies are located at the central position of the fogdrop sampling channel cylinder on the plane A; the light trap is used for absorbing laser directly penetrating through the fog drop sampling channel cylinder; according to the online measurement system and method, real-time non-contact measurement of the particle size and the chemical components of a single fog drop can be realized at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of droplet online measurement, in particular to an online measurement system for droplet particle size and composition. Background Art

[0002] Fog is a natural weather phenomenon. It is an aerosol system composed of a large number of small water droplets or ice crystals with a particle size distribution of 2-100 μm. Continuous fog can harm people's health and affect social and economic development, mainly in the following aspects:

[0003] (1) Heavy fog can significantly reduce air visibility, causing traffic accidents on land, flight delays at airports, and ship suspensions at sea, seriously affecting traffic safety and operational efficiency;

[0004] (2) Pollutant particles in fog will shorten the sunshine time and affect the photosynthesis of crops, thus greatly increasing the probability of crop diseases and insect pests, affecting the quality of crops and causing food production reduction;

[0005] (3) Some harmful substances will combine with water vapor in foggy weather, making the harmful substances more toxic. The particles that make up the fog will be inhaled and retained in the human body, causing upper respiratory tract infections and seriously damaging human health.

[0006] (4) In dense fog, the insulation level of insulators is greatly reduced, which may cause short circuits in transmission lines and power outages in the power grid, affecting the normal electricity use of people in all walks of life and causing serious economic losses;

[0007] (5) Fog can also affect satellite and microwave communications, causing a sharp drop in signals and reduced communication quality.

[0008] The spectral distribution of fog droplets is an important parameter of fog. Research on the spectrum of fog droplets helps people understand the physical and chemical changes in the atmosphere and the mechanisms and laws of fog generation, improves human ability to predict fog, and enhances people's defense capabilities against fog damage, thereby reducing the losses caused by fog damage.

[0009] In addition, the composition of fog droplets is complex and diverse, and is not just composed of water. They are affected by geographical location, seasonal changes, and a variety of environmental factors, resulting in significant differences in composition. In arid and desert areas, dust is one of the common components of fog droplets. These dust particles can be blown up by the wind and captured by fog droplets. Due to the influence of seawater evaporation in coastal areas, the content of chloride salts (such as sodium chloride) in sea fog is significantly higher than that in inland fog. Dust generated by industrial activities, such as coal smoke and industrial dust, is also one of the components of fog droplets, especially near industrial areas. In addition, fog droplets may also contain salts, which may come from seawater evaporation, salt in the soil, and industrial emissions.

[0010] In addition to the aforementioned components, fog droplets may also contain sand, sea salt, industrial dust, nitrates, ammonium salts, and carbon black. These components come from a variety of sources, including waste gas and soot emitted by human life and production, sulfates ejected from volcanic eruptions, and gases emitted by microbial metabolism. The chemical composition of fog droplets is related to the location of the fog. For example, the chloride content in sea fog is significantly higher than that in inland fog, while sulfate is ubiquitous in fog in different regions, with similar levels. Furthermore, the concentration of ions in small and large droplets varies, with small droplets generally containing higher concentrations of ions than large droplets. However, the concentration of acetate in large droplets is higher than in small droplets.

[0011] When droplets contain organic matter, their surface tension is reduced, leading to more droplets being formed under conditions of water vapor supersaturation. Conversely, when droplets contain inorganic matter, their surface tension increases, resulting in a decrease in droplet concentration. The diversity and complexity of these components make the study of droplets an interdisciplinary field, encompassing multiple disciplines, including environmental science and meteorology, and crucial for understanding atmospheric chemical processes, climate change, and its impact on human health.

[0012] With the advancement of optical technology, light scattering has become a fast, non-contact measurement technique for droplets, gradually becoming one of the mainstream measurement methods for laser particle counters. American companies like DMT have also launched commercial instruments. With the development of laser measurement technology in the 1970s, laser technology was applied to droplet measurement. Digital signal processing was used to calculate droplet size and distribution information, significantly improving the accuracy of droplet size measurement and simplifying the measurement process. Laser methods for droplet measurement employ two principles: laser holography, which uses laser film to record a spatial holographic image of the droplets being measured. This allows for precise measurement of droplet size and concentration, and can even perform dynamic measurements of droplets within a certain velocity range. Light scattering: Based on the Mie scattering principle, optical droplet spectrometers have been successfully developed in Europe and the United States. These spectrometers infer droplet size based on the intensity of incident light scattered by particles, with a measurement range of 2μm to 50μm.

[0013] At present, light scattering technology still has the following problems and shortcomings in the online monitoring of droplets:

[0014] (1) The droplet sampling system must determine whether the sampled droplets pass through the sampling point in order to accurately perform subsequent scattered light calculations. Existing droplet sampling systems are difficult to implement the sampling method of a single droplet passing through, that is, the method of a group of droplets passing through the sampling channel tube. Therefore, it is difficult to accurately obtain the position of the droplet passing through the sampling channel, which makes it difficult to locate the sampling single particle.

[0015] Although the FM120 of the American DMT Instrument Company uses a method to calculate the splitting ratio of the scattered light beam after passing through the beam-splitting cemented prism to determine whether the particles are within the system depth of field and determine the specific location of the droplets, the optical path is complex and the error is large in actual application.

[0016] (2) The existing technology only measures the particle size and number concentration of droplets, but it is difficult to obtain information such as the chemical composition of the droplets;

[0017] (3) The existing light scattering particle size measurement results are easily affected by parameters such as the refractive index and particle shape of the particles, thereby reducing the accuracy of the particle size measurement. Utility Model Content

[0018] Based on the technical problems existing in the background technology, the utility model proposes an online measurement system for droplet size and composition, which can simultaneously realize real-time non-contact measurement of the particle size and chemical composition of a single droplet.

[0019] The utility model proposes an online measurement system for droplet size and composition, comprising a laser, a scattered light receiving component, a light trap and a droplet sampling channel cylinder;

[0020] The laser is used to emit laser light, and the laser light is scattered by the droplets in the droplet sampling channel to obtain scattered light;

[0021] Four independently arranged scattered light receiving assemblies are arranged around the outside of the droplet sampling channel barrel along the axial direction of the droplet sampling channel barrel to receive scattered light, and the detectors in all scattered light receiving assemblies and the laser beam emitted by the laser are on the same plane A. The movement direction of the droplets in the droplet sampling channel barrel is perpendicular to the plane A. The focus of the scattered light beam received by all scattered light receiving assemblies is located at the center of the droplet sampling channel barrel on the plane A.

[0022] The light trap is used to absorb the laser light that directly passes through the droplet sampling channel.

[0023] Furthermore, each scattered light receiving assembly includes a detector, a signal processing circuit and a computer, wherein the input of the signal processing circuit is connected to the output of the detector, and the output is connected to the input of the computer;

[0024] The receiving ends of the four detectors are respectively at 15 degrees, 30 degrees, 140 degrees, and 160 degrees to the laser emission direction to receive scattered light from different directions.

[0025] Furthermore, the four detectors convert the scattered light signals I1, I2, I3, and I4 received at the four angles into electrical signals and input them into the signal processing circuits connected to them respectively. The signal processing circuit amplifies the signal change and inputs the obtained signal peaks P1, P2, P3, and P4 at the four angles into the computer respectively. The computer compares the peak P4 with the standard light intensity-particle size relationship curve to obtain the droplet particle size, and compares the ratios of P1 / P4, P2 / P4, and P3 / P4 with the standard peak ratio-chemical composition database to obtain the chemical composition information of the droplets; among them, I1 is received by the detector at an angle of 160 degrees to the laser emission direction, I2 is received by the detector at an angle of 140 degrees to the laser emission direction, I3 is received by the detector at an angle of 30 degrees to the laser emission direction, and I4 is received by the detector at an angle of 15 degrees to the laser emission direction.

[0026] Furthermore, the receiving angle of the detectors in all scattered light receiving assemblies is less than ±4 degrees to ensure the spatial resolution and validity of each measurement value.

[0027] Furthermore, the online measurement system also includes a collimating lens and an aperture. The laser light emitted by the laser passes through the collimating lens and the aperture in sequence and is collimated and incident on the droplets in the droplet sampling channel tube to obtain scattered light.

[0028] Furthermore, the collimating lens is an aspheric collimating lens, and the absorption efficiency of the light trap to the laser is greater than 0.99.

[0029] A method for online measurement of droplet size and composition. Each scattered light receiving assembly includes a detector, a signal processing circuit, and a computer. The input of the signal processing circuit is connected to the output of the detector, and the output is connected to the input of the computer. The measurement method includes the following steps:

[0030] Step 1, four detectors receive scattered light after the laser emitted by the laser is scattered by the droplets in the droplet sampling channel tube, and convert the scattered light signals I1, I2, I3, and I4 at four angles into electrical signals and input them into the signal processing circuits connected to them respectively. The signal processing circuit amplifies the signal change and inputs the obtained signal peaks P1, P2, P3, and P4 at the four angles into the computer respectively, wherein I1 is received by the detector at an angle of 160 degrees to the laser emission direction, I2 is received by the detector at an angle of 140 degrees to the laser emission direction, I3 is received by the detector at an angle of 30 degrees to the laser emission direction, and I4 is received by the detector at an angle of 15 degrees to the laser emission direction;

[0031] Step 2: After preprocessing the signal peaks P1, P2, P3, and P4, if all the preprocessed signal peaks are greater than the preset signal strength threshold, the droplet has passed through the center of the droplet sampling channel tube, and the process proceeds to step 3. If all the preprocessed signal peaks have a signal peak less than or equal to the preset signal strength threshold, the droplet has not passed through the center of the droplet sampling channel tube, and the process returns to step 1.

[0032] Step 3: Measure the relationship between the standard particle size and the signal peak P4 under the same droplet sampling environment, and obtain the standard light intensity-particle size relationship curve through third-order linear fitting;

[0033] Step 4: Measure the direct relationship between the standard particle composition and the P1 / P4, P2 / P4, and P3 / P4 ratios under the same droplet sampling environment to obtain a standard peak ratio-chemical composition database;

[0034] Step 5: The scattered light receiving component measures the scattered light signal of a single droplet passing through the laser spot during the sampling process, and compares the signal peak value P4 with the standard light intensity-particle size relationship curve to obtain the required droplet size information;

[0035] Step 6: The scattered light receiving component measures the scattered light signal of a single droplet passing through the laser spot during the sampling process, and compares the signal peak ratios P1 / P4, P2 / P4, and P3 / P4 with the standard peak ratio-chemical composition database to obtain the chemical composition information of the required droplets.

[0036] Furthermore, in step 3, the standard light intensity-particle size relationship curve is obtained by third-order linear fitting. The third-order linear fitting formula is as follows:

[0037] y=B0+B1*x+B2*x 2 +B3*x 3

[0038] Among them, y is the standard light intensity, x is the standard particle size, and B0, B1, B2, and B3 are fitting parameters.

[0039] Furthermore, in step 2, the comparison process of the signal peak values ​​P1, P2, P3, and P4 with the preset signal strength threshold is as follows:

[0040] The computer obtains the signal strength S1, S2, S3, and S4 of each detector based on the acquired signal peaks P1, P2, P3, and P4;

[0041] The signal strengths S1, S2, S3, and S4 are smoothed to reduce noise and thus normalize the signal strengths;

[0042] Set the signal strength threshold T to determine whether the droplets pass through the center of the droplet sampling channel;

[0043] Compare the signal intensities after each normalization and determine the detector with the minimum signal intensity.

[0044] If the minimum signal strength is greater than the preset signal strength threshold, the droplet passes through the center of the droplet sampling channel;

[0045] If the minimum signal strength is less than or equal to the preset signal strength threshold, the droplet has not passed through the center position of the droplet sampling channel cylinder.

[0046] The advantages of the online measurement system for droplet size and composition provided by the present invention are as follows: the online measurement system for droplet size and composition provided in the present invention structure, (1) adopts a method of jointly detecting the sampling point position by four detectors, which can accurately determine the droplets passing through the sampling point. This method can calculate the actual position by intensity by utilizing the distribution model of the light signals of the four detectors, thereby improving the accuracy of droplet sampling. The offset can be calculated by the output current of the four detectors, thereby achieving center positioning. This method can improve the positioning accuracy of a single sampled droplet, and helps to solve the problem of incorrect measurement and positioning of a single droplet particle caused by a group of droplets passing through the sampling channel in the prior art; (2) utilizing the characteristics that the scattering signal of the droplet is positively correlated with the particle size under small-angle light scattering and the scattering signal is correlated with the chemical composition of the particulate matter under specific multi-angle light scattering, the particle size spectrum and chemical composition of a single droplet can be measured online at the same time; it plays a good technical support role in the change characteristics and source analysis of fine particulate matter in the atmosphere; (3) it is simple, does not require membrane sampling and offline analysis, and effectively expands the real-time online sensing method of multiple physical and chemical parameters of droplets based on the light scattering principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural diagram of the utility model;

[0048] Figure 2 This is the distribution structure diagram of the four detectors;

[0049] Figure 3 This is a graph showing the relationship between the scattering signal intensity and scattering angle of sand, sea salt, industrial dust, salt, and water;

[0050] Among them, 1-laser, 2-scattered light receiving component, 3-light trap, 4-droplet sampling channel tube, 5-straight lens, 6-aperture, 7-droplet, 21-detector, 22-signal processing circuit, 23-computer, 211-first detector, 212-second detector, 213-third detector, 214-fourth detector. DETAILED DESCRIPTION

[0051] The following describes the technical solution of the present invention in detail through specific embodiments. Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0052] like Figures 1 to 3 As shown, the utility model proposes an online measurement system for droplet particle size and composition, including a laser 1, a scattered light receiving component 2, a light trap 3 and a droplet sampling channel tube 4; the laser 1 is used to emit laser, and the laser is scattered by the droplets 7 in the droplet sampling channel tube 4 to obtain scattered light; four independently arranged scattered light receiving components 2 are arranged along the axial direction of the droplet sampling channel tube 4 around the outside of the droplet sampling channel tube 4 to receive scattered light, and the detectors 21 in all scattered light receiving components 2 are in the same plane A as the laser beam emitted by the laser 1, the movement direction of the droplets 7 in the droplet sampling channel tube 4 is perpendicular to the plane A, and the focus of the scattered light beam received by all scattered light receiving components 2 is located at the center position of the droplet sampling channel tube 4 on the plane A; the light trap 3 is used to absorb the laser that directly passes through the droplet sampling channel tube 4.

[0053] In this embodiment, each scattered light receiving component 2 includes a detector 21, a signal processing circuit 22 and a computer 23. The input of the signal processing circuit 22 is connected to the output of the detector 21, and the output is connected to the input of the computer 23; the receiving ends of the four detectors 21 are respectively at 15 degrees, 30 degrees, 140 degrees and 160 degrees to the laser emission direction to receive scattered light in different directions.

[0054] This embodiment uses a method in which four detectors 21 jointly detect the sampling point position (the sampling point is located at the center of the droplet sampling channel barrel on plane A), which can accurately determine the droplets passing through the sampling point. This method uses the structural distribution of scattered light received by the four detectors 21 to calculate the actual position from the intensity, thereby improving the accuracy of droplet sampling. The offset can be calculated using the output current of the four detectors, thereby achieving center positioning. This method can improve the positioning accuracy of a single sampled droplet, helping to solve the accuracy problem caused by the passage of a group of droplets through the droplet sampling channel barrel 4 in the prior art.

[0055] In this embodiment, laser 1 is a semiconductor laser that outputs laser light of stable light intensity to improve the accuracy of droplet size measurement. The receiving angle of the detector 21 in all scattered light receiving components 2 is less than ±4 degrees to ensure the spatial resolution and validity of each measurement value. The absorption efficiency of the light trap 3 for laser light is greater than 0.99 to avoid stray light interference with the signal measurement results of each detector. Light trap 3 adopts a Brewster light trap.

[0056] It should also be noted that the droplet 7 at the measurement point should ensure that the focus of the scattered light beam received by the four detectors is at the center of the droplet sampling channel tube on plane A, so as to achieve real-time measurement and analysis of single droplet information.

[0057] It can be understood that in order to improve the ability of the laser to be collimated and incident on the droplet sampling channel tube 4, the present embodiment further provides a collimating lens 5 and an aperture 6. The laser emitted by the laser 1 passes through the collimating lens 5 and the aperture 6 in sequence and is collimated and incident on the droplets 7 in the droplet sampling channel tube 4 to obtain scattered light. The collimating lens 5 adopts an aspheric collimating lens to achieve the best laser collimation effect.

[0058] For ease of explanation, the four detectors 21 are respectively a first detector 211, a second detector 212, a third detector 213, and a fourth detector 214, wherein the first detector 211 is at an angle of 160 degrees to the laser emission direction to receive the scattered light signal I1; the second detector 212 is at an angle of 140 degrees to the laser emission direction to receive the scattered light signal I2; the third detector 213 is at an angle of 30 degrees to the laser emission direction to receive the scattered light signal I3; and the fourth detector 214 is at an angle of 15 degrees to the laser emission direction to receive the scattered light signal I4.

[0059] According to the attached Figure 2 In this embodiment, the first detector 211 and the third detector 213 are preferably disposed on one side of the laser emission direction, designated as side B, and the second detector 212 and the fourth detector 214 are disposed on the other side of the laser emission direction, designated as side C. On side B, with the laser emission direction as a reference, the direction of the scattered light received by the first detector 211 is 160 degrees to the laser emission direction, and the direction of the scattered light received by the third detector 213 is 30 degrees to the laser emission direction. On side C, with the laser emission direction as a reference, the direction of the scattered light received by the second detector 212 is 140 degrees to the laser emission direction, and the direction of the scattered light received by the fourth detector 214 is 15 degrees to the laser emission direction. Thus, scattered light from four directions is received by the four detectors 21.

[0060] A method for online measurement of droplet size and composition comprises the following steps:

[0061] Step 1: Four detectors 21 receive scattered light emitted by the laser 1 after being scattered by the droplets 7 in the droplet sampling channel tube 4, and convert the scattered light signals I1, I2, I3, and I4 at four angles into electrical signals and input them into the signal processing circuits 22 connected to them respectively. The signal processing circuit 22 amplifies the signal change and inputs the obtained signal peak values ​​P1, P2, P3, and P4 at the four angles into the computer 23 respectively, wherein I1 is received by the first detector 211, I2 is received by the second detector 212, I3 is received by the third detector 213, and I4 is received by the fourth detector 214.

[0062] Step 2: After preprocessing the signal peaks P1, P2, P3, and P4, if all the preprocessed signal peaks are greater than the preset signal strength threshold, the droplet 7 passes through the center of the droplet sampling channel tube 4, and the process proceeds to step 3. If all the preprocessed signal peaks have a signal peak less than or equal to the preset signal strength threshold, the droplet 7 does not pass through the center of the droplet sampling channel tube 4, and the process returns to step 1.

[0063] The comparison process of the signal peak values ​​P1, P2, P3, and P4 with the preset signal strength threshold values ​​is as follows: the computer 23 obtains the signal strength S1, S2, S3, and S4 of each detector 21 based on the obtained signal peak values ​​P1, P2, P3, and P4; the signal strengths S1, S2, S3, and S4 are smoothed respectively to reduce noise, thereby standardizing the signal strength; a signal strength threshold T is set to determine whether the droplet 7 passes through the center position of the droplet sampling channel tube 4; each standardized signal strength is compared to determine the detector 21 corresponding to the minimum signal strength; if the minimum signal strength is greater than the preset signal strength threshold value, the droplet 7 passes through the center position of the droplet sampling channel tube 4; if the minimum signal strength is less than or equal to the preset signal strength threshold value, the droplet 7 does not pass through the center position of the droplet sampling channel tube 4.

[0064] The formula for normalized signal strength is as follows:

[0065]

[0066] Among them, S norm is the normalized signal intensity, S i is the signal strength, i∈[1,4], μ is the mean of the signal strength, and σ is the standard deviation of the signal strength.

[0067] Step 3: Measure the relationship between the standard particle size and the signal peak P4 under the same droplet 7 sampling environment, and obtain the standard light intensity-particle size relationship curve through third-order linear fitting;

[0068] The third-order linear fitting formula is as follows:

[0069] y=B0+B1*x+B2*x 2 +B3*x 3

[0070] Among them, y is the standard light intensity, x is the standard particle size, and B0, B1, B2, and B3 are fitting parameters.

[0071] Step 4: Measure the direct relationship between the standard particle composition and the P1 / P4, P2 / P4, and P3 / P4 ratios under the same droplet 7 sampling environment to obtain a standard peak ratio-chemical composition database;

[0072] Step 5: The scattered light receiving component 2 measures the scattered light signal of a single droplet passing through the laser spot during the sampling process, and compares the signal peak value P4 with the standard light intensity-particle size relationship curve to obtain the required particle size information of the droplet 7;

[0073] Step 6: The scattered light receiving component 2 measures the scattered light signal of a single droplet passing through the laser spot during the sampling process, and compares the signal peak ratios P1 / P4, P2 / P4, and P3 / P4 with the standard peak ratio-chemical composition database to obtain the chemical composition information of the required droplet 7.

[0074] The basic principle of mist droplet composition discrimination in this embodiment is:

[0075] The scattered light intensity I at point P in the droplet scattered light field S :

[0076]

[0077] Among them, r is the distance from the center of the droplet to the field point P, λ is the wavelength of the incident light, I0 is the incident light intensity, I HH is the relative intensity of polarized light parallel to the direction of incident light; I VV is the relative intensity of polarized light perpendicular to the direction of the incident light;

[0078] I HH =i1(θ)=|D1(θ)| 2 ;I VV =i2(θ)=|S2(θ)| 2 ;

[0079] Among them, S1(θ) and S2(θ) are two amplitude functions related to the scattering angle, and θ is the angle between the scattered light and the incident light. It can be expressed as:

[0080]

[0081] in:

[0082] Among them, πn , τ n is an auxiliary angle function related to the scattering angle, used to describe the scattering directionality of light, P n 、P n (1) are Legendre function and first-order associated Legendre function, respectively, and the Mie scattering coefficient a n 、b n It can be expressed as

[0083]

[0084] Where:

[0085] Among them, φ n (x)ξ n ,ξ' n (x) represents φ n (x) and ξ n The derivatives of (x) with respect to x represent the rate of change of these two functions at a specific point, and are usually used to calculate the relative changes in the scattering or transmission process. n+1 / 2 (x) and are the half-integer order Bessel function of the first kind and the half-integer order Hankel function of the second kind, φ n (x),ξ n (x), J n+1 / 2 (x), It is usually used to describe the propagation of spherical waves, where m is the relative complex refractive index, that is, the ratio of the refractive index of the scatterer to the refractive index of the surrounding medium.

[0086] That is, when the composition of the droplets 7 is different, their complex refractive index is also different. When the droplet scattering phase function distribution is calculated according to the Mie scattering theory, there is a certain correlation between the scattered light intensity ratio at different angles and the droplet composition, so the droplet composition can be distinguished.

[0087] As an example:

[0088] The online measurement system includes a laser 1, a light trap 3, a droplet sampling channel tube 4, a collimating lens 5 and an aperture 6, a first detector 211, a second detector 212, a third detector 213, a fourth detector 214, a signal processing circuit 22 and a computer 23.

[0089] Laser 1 uses a 650nm, 30mW semiconductor laser; light trap 3 uses a Brewster light trap; all detectors use high-sensitivity avalanche photodiodes; collimating lens 5 uses an aspheric collimating lens that matches the divergence angle of laser 1; light trap 3 should achieve an absorption efficiency of the emitted laser greater than 0.99 to prevent stray light from interfering with the signal measurement results of each detector. Fog droplets 7 should pass through the laser beam individually to achieve real-time measurement and analysis of individual droplet information.

[0090] The laser light emitted by the laser 1 is collimated and incident on the mist droplet 7 after passing through the collimating lens 5 and the aperture 6. The scattered light is received by the fourth detector 214, the third detector 213, the second detector 212, and the first detector 211, which are respectively received at angles of approximately 15 degrees, 30 degrees, 140 degrees, and 160 degrees to the laser emission angle. The receiving angles of the first detector 211, the second detector 212, the third detector 213, and the fourth detector 214 are less than ±4 degrees to ensure the spatial resolution and validity of each measurement value. The directly transmitted laser light is absorbed by the light trap 3. The first detector 211, the second detector 212, the third detector 213, and the fourth detector 214 convert the light signals I1, I2, I3, and I4 received at various angles into electrical signals and input them into the signal processing circuit 9. The signal processing circuit 9 amplifies the signal variation and inputs the signal peak values ​​P1, P2, P3, and P4 into the computer 23, respectively. P4 is substituted into the standard light intensity-particle size relationship fitting function to obtain the measured particle size. The P1 / P4, P2 / P4, and P3 / P4 ratios are compared with the standard peak value ratio-chemical composition database to determine the chemical composition information of the droplets.

[0091] like Figure 3 As shown, sand, sea salt, industrial dust, and salts all have specific light scattering phase functions, meaning a specific relationship between scattered signal intensity and scattering angle. Scattered light at around 15 degrees is less affected by droplet composition and serves as a signal for measuring particle size. However, different ratios exist at 30, 140, and 160 degrees, serving as signals for analyzing particle composition.

[0092] Then, the required droplet size information and chemical composition information are obtained through steps one to six.

[0093] This embodiment uses a single laser 1 and four detectors 21, and performs data comparison and analysis to achieve simultaneous online measurement of individual droplet particle size and chemical composition signals. This embodiment is simple, does not require membrane sampling and offline analysis, and effectively expands the online sensing method for multiple physical and chemical parameters of droplets based on the principle of light scattering, especially providing reliable data for real-time monitoring and source analysis of droplets. The spectral distribution and composition analysis of droplets are key parameters for studying fog. In-depth exploration of the spectral distribution and composition of droplets not only helps deepen understanding of atmospheric physical and chemical changes, but also promotes understanding of the formation mechanisms and laws of fog. By improving the ability to predict fog, this embodiment enhances human defense capabilities against fog damage, thereby helping to reduce losses caused by fog damage, and has important practical application value and scientific significance.

[0094] Therefore, this embodiment also has the following advantages:

[0095] (1) It makes up for the deficiency of ordinary droplet sampling system in determining whether the sampled droplets pass through the sampling point;

[0096] Droplet sampling systems must determine whether a sampled droplet has passed through a sampling point in order to accurately perform subsequent scattered light calculations. Existing droplet sampling systems struggle to sample a single droplet as it passes through. Instead, they rely on a cluster of droplets passing through the sampling channel. This makes it difficult to accurately determine the location of a droplet as it passes through the sampling channel, making it difficult to locate a single sampled particle.

[0097] Although the American instrument FM120 uses the method of calculating the splitting ratio of the scattered light beam after passing through the beam-splitting cemented prism to determine whether the particles are within the system depth of field and determine the specific location of the droplets, the optical path is complex and the error is large in actual application.

[0098] This embodiment uses four detectors to jointly detect the sampling point location, accurately identifying droplets passing through the sampling point. This method utilizes the distribution model of the optical signals from the four detectors to determine the actual location from the intensity, thereby improving droplet sampling accuracy. The output currents of the four detectors can be used to calculate the offset, thereby achieving center positioning. This method improves the accuracy of locating individual sampled droplets, helping to address the accuracy issues caused by clusters of droplets passing through the sampling channel in existing technologies.

[0099] (2) This embodiment makes up for the shortcomings of ordinary light scattering methods in measuring droplet parameters. For example, the single-angle light scattering method can only measure the particle (droplet) size. The previous multi-angle detection scheme was only based on the design of different particle shapes without in-depth analysis of the relationship between the chemical composition of the particles and the light scattering signals at different angles. This embodiment uses the characteristics of droplets that the scattering signal is positively correlated with the particle size under small-angle light scattering and the scattering signal is related to the chemical composition of the particles under specific multi-angle light scattering to achieve simultaneous online measurement of the particle size spectrum and chemical composition of a single droplet. This method plays a good technical support role in the analysis of the changing characteristics and sources of fine particulate matter in the atmosphere.

[0100] (3) The utility model is simple to implement, does not require membrane sampling and offline analysis, and effectively expands the real-time online sensing method of multiple physical and chemical parameters of droplets based on the principle of light scattering.

[0101] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An online measurement system for droplet size and composition, characterized in that: It comprises a laser (1), a scattered light receiving component (2), a light trap (3) and a droplet sampling channel tube (4); The laser (1) is used to emit laser light, and the laser light is scattered by the mist droplets (7) in the mist droplet sampling channel tube (4) to obtain scattered light; Four independently arranged scattered light receiving components (2) are arranged around the outside of the droplet sampling channel tube (4) along the axial direction of the droplet sampling channel tube (4) to receive scattered light, and the detectors (21) in all the scattered light receiving components (2) and the laser beam emitted by the laser (1) are on the same plane A, the movement direction of the droplet (7) in the droplet sampling channel tube (4) is perpendicular to the plane A, and the focus of the scattered light beam received by all the scattered light receiving components (2) is located at the center of the droplet sampling channel tube (4) on the plane A; The light trap (3) is used to absorb the laser light that directly passes through the mist droplet sampling channel cylinder (4).

2. The online measurement system for droplet size and composition according to claim 1, characterized in that: Each scattered light receiving assembly (2) includes a detector (21), a signal processing circuit (22) and a computer (23), wherein the input of the signal processing circuit (22) is connected to the output of the detector (21), and the output is connected to the input of the computer (23); The receiving ends of the four detectors (21) are respectively oriented at 15 degrees, 30 degrees, 140 degrees and 160 degrees to the laser emission direction so as to receive scattered light in different directions.

3. The online measurement system for droplet size and composition according to claim 2, characterized in that: The four detectors (21) convert the scattered light signals I1, I2, I3, and I4 received at four angles into electrical signals and input them into the signal processing circuits (22) connected to them. The signal processing circuits (22) amplify the signal variation and input the obtained signal peak values ​​P1, P2, P3, and P4 at the four angles into the computer (23). The computer (23) compares the peak value P4 with the standard light intensity-particle size relationship curve to obtain the particle size of the droplet (7). P1 / P 4. The ratios of P2 / P4 and P3 / P4 are compared with the standard peak ratio-chemical composition database to obtain the chemical composition information of the droplet (7); wherein I1 is received by the detector (21) at an angle of 160 degrees to the laser emission direction, I2 is received by the detector (21) at an angle of 140 degrees to the laser emission direction, I3 is received by the detector (21) at an angle of 30 degrees to the laser emission direction, and I4 is received by the detector (21) at an angle of 15 degrees to the laser emission direction.

4. The online measurement system for droplet size and composition according to claim 1, characterized in that: The receiving angles of the detectors (21) in all scattered light receiving components (2) are less than ±4 degrees, so as to ensure the spatial resolution and validity of each measurement value.

5. The online measurement system for droplet size and composition according to claim 1, characterized in that: The online measurement system further comprises a collimating lens (5) and an aperture (6). The laser light emitted by the laser (1) passes through the collimating lens (5) and the aperture (6) in sequence and is collimated and incident on the mist droplets (7) in the mist droplet sampling channel tube (4) to obtain scattered light.

6. The online measurement system for droplet size and composition according to claim 5, characterized in that: The collimating lens (5) is an aspheric collimating lens, and the absorption efficiency of the light trap (3) to laser light is greater than 0.99.

Images