Aerosol scattering measurement device and method

Abstract

The invention discloses an aerosol scattering measurement device and method. The device comprises an aerosol scattering cavity, a plurality of light sources, a motor, a photoelectric detector bracket and a photoelectric detector, a cylindrical aerosol scattering cavity with a hollow interior is enclosed by an upper cover plate, a lower bottom plate and a cavity body; the upper cover plate and the lower bottom plate are respectively provided with an aerosol inflow hole and an aerosol outflow hole; the light source adopts lasers with different wavebands, and the emergent end of each laser is correspondingly connected with a laser input hole site of the cavity; the side surface of the cavity is provided with a plurality of probe holes, and each probe hole is provided with an optical attenuation sheet. The photoelectric detector bracket is arranged on the outer side of a cavity body of the aerosol scattering cavity, and the motor drives the photoelectric detector bracket to rotate and drives the photoelectric detector to collect scattering signals of all detection holes corresponding to the lasers of all wavebands. According to the invention, scattering signals of multiple angles can be fully automatically measured in a 360-degree range, and in-situ measurement and accurate identification of the scattering signals in aerosol optical characteristics are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of light scattering measurement, and in particular to an aerosol scattering measurement device and method. Background Art

[0002] Aerosols are tiny droplets and particles present in the atmosphere, which come from natural sources (such as fog, mist and dust) and anthropogenic sources (such as haze, smog and air particle pollutants). Aerosols participate in various atmospheric processes, such as ice nucleation, precipitation and global climate effects, and can also absorb and scatter solar radiation, thus having a significant impact on the Earth's radiation budget and atmospheric visibility. Therefore, the scattering and absorption measurement technology of aerosol particles is of great significance to the study of atmospheric science.

[0003] Using light scattering to characterize small particles in the air is an important analytical tool in aerosol science. This technology is divided into angle-resolved light scattering, polarized light scattering, and scattering profile measurement. These methods calculate the size and shape of particles by inverting the angle, intensity, and particle depolarization ratio of scattered light, and can detect aerosol particles quickly and with high resolution.

[0004] Sorensen summarized the application potential of light scattering technology in detecting and measuring aerosol particles, calculated the scattering intensity, anisotropy and intensity correlation time of light scattering measurement, and provided reference for some specific experiments; in terms of experiments, researchers have established a variety of optical systems for aerosol scattering measurement. For example, Guo et al. used 5 photomultiplier tubes (PMT) to measure the angular scattering signals of 10°, 30°, 60°, 85° and 115° to obtain the aerosol particle size distribution; Ding et al. built an experimental device combining aerodynamic and light scattering technology to solve the problem of simultaneous measurement of particle size and shape; and some researchers designed a measurement device combining polarized light scattering and angle-resolved light scattering to achieve shape recognition of single aerosol particles, which can effectively distinguish spherical, rod-shaped and other irregular aerosol particles. In addition, by measuring the characteristic time of the fluctuation of the light intensity of Brownian particles to calculate the diffusion coefficient, dynamic light scattering technology was developed, which has become a standard method for measuring the particle size and distribution of submicron and nanoparticles.

[0005] In general, the light scattering measurement technology of aerosols has been widely studied. However, this technology has long suffered from problems such as a large number of detectors, high cost, small scattering measurement angle, and single light source wavelength.

[0006] Most light scattering methods can only measure scattered signals within a small angle range. On the one hand, this is limited by the design of the optical system, and it is difficult to provide detection ports for scattered signals at more angles; on the other hand, it is limited by the manufacturing cost of the device. Each additional angle measurement may mean adding one more detector. The scattered light intensity is usually weak, which requires the use of high-sensitivity photodetectors for scattered light detection, which will greatly increase the cost. In addition, some old-fashioned aerosol scattering measurement instruments are not very intelligent. The equipment requires human intervention or monitoring of the instrument's working process, and the measurement efficiency is low. Moreover, most scattering devices usually only measure single-wavelength scattering signals, because it is not easy to coordinate the detection timing of the laser when there are multiple light sources, or it is impossible to effectively distinguish multi-dimensional signals during data processing. This leads to a lack of multi-wavelength and multi-angle information in scattering measurements, which limits the relevant research on aerosol optical properties. Summary of the invention

[0007] In order to overcome the defects and shortcomings of the prior art, the present invention provides an aerosol scattering measurement device and method. The present invention adopts lasers of different bands, and the laser output end is incident into a hollow cylindrical aerosol scattering cavity. A plurality of detection holes are provided on the side of the cavity to provide aerosol scattering signal collection of different bands and angles, thereby solving the long-standing problems of aerosol scattering measurement devices, such as small measurement range, low precision, single light source and low intelligence. In addition, a motor and a photoelectric detector bracket are used to drive the photoelectric detector to collect scattering signals of each detection hole corresponding to the laser of each band, thereby achieving the purpose of measuring multi-angle scattering signals with a single photoelectric detector, thereby solving the problems of complex structure, high cost and complex wiring caused by a large number of detectors in aerosol angle-resolved light scattering measurement, and realizing multi-wavelength and multi-angle fully automatic aerosol angle-resolved scattering intensity detection.

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

[0009] The present invention provides an aerosol scattering measurement device, comprising: an aerosol scattering cavity, a plurality of light sources, a motor, a photoelectric detector bracket, and a photoelectric detector;

[0010] The aerosol scattering cavity comprises an upper cover plate, a lower bottom plate and a cavity body, wherein the upper cover plate, the lower bottom plate and the cavity body enclose an aerosol scattering cavity with a hollow cylindrical shape inside;

[0011] The upper cover plate is provided with an aerosol inflow hole, and the lower base plate is provided with an aerosol outflow hole;

[0012] The cavity is provided with a plurality of laser input holes and a plurality of laser output holes at both ends along the central axis, the light source adopts lasers of different wavelength bands, and the output end of each laser is connected to the laser input hole correspondingly;

[0013] The side of the cavity is provided with a plurality of detection holes, and each detection hole is provided with an optical attenuation sheet;

[0014] The photoelectric detector is connected to a photoelectric detector bracket, and the photoelectric detector bracket is connected to a motor. The photoelectric detector bracket is arranged outside the aerosol scattering cavity, and the photoelectric detector is aligned with the detection hole on the side of the cavity. The motor drives the photoelectric detector bracket to rotate, and the photoelectric detector bracket drives the photoelectric detector to collect scattering signals of each detection hole corresponding to the laser of each band.

[0015] As a preferred technical solution, the laser input holes correspond to the laser output holes one by one, and the laser input holes are equidistantly distributed from top to bottom, wherein the center hole is located at half the height of the aerosol scattering cavity, and the output ends of each laser are incident in parallel into the aerosol scattering cavity.

[0016] As a preferred technical solution, the detection holes are located in the same plane and at half the height of the aerosol scattering cavity.

[0017] As a preferred technical solution, the detection holes include side scattering detection holes, forward scattering detection holes and backscattering detection holes, wherein the detection holes with an angle less than 90° with the laser emission direction are forward scattering detection holes, the detection holes with an angle greater than 90° with the laser emission direction are backscattering detection holes, and the holes with the two angles closest to vertical are side scattering detection holes;

[0018] And / or the forward scattering detection hole adopts an optical attenuation plate with a high attenuation coefficient, and the side scattering detection hole and the back scattering detection hole adopt optical attenuation plates with a low attenuation coefficient.

[0019] As a preferred technical solution, the motor is also provided with a motor drag platform, a flange, and a motor connecting rod;

[0020] One end of the motor platform is used to connect to the loading platform, the other end of the motor platform is connected to the motor, the output shaft of the motor is connected to the flange, one end of the motor connecting rod is connected to the flange, and the other end of the motor connecting rod is connected to the photoelectric detector bracket.

[0021] As a preferred technical solution, the motor, the motor platform and the flange plate have a completely penetrating structure on the central axis of the air inlet and the air outlet of the scattering cavity.

[0022] As a preferred technical solution, the photoelectric detector bracket is provided with a plurality of photoelectric detector slots, and the hole position distribution of the photoelectric detector slots is the same as the hole position distribution of the detection holes of the aerosol scattering cavity.

[0023] As a preferred technical solution, the laser uses lasers in the ultraviolet, visible and infrared bands.

[0024] As a preferred technical solution, the aerosol scattering cavity is further provided with a plurality of fixing frames for fixing the aerosol scattering cavity to the optical platform, the fixing frames are provided with an arc adaptation structure and a through hole, the arc of the arc adaptation structure is the same as that of the scattering cavity, and is used to be close to the aerosol scattering cavity, and the through hole is connected to the optical platform;

[0025] And / or a gasket is provided at the junction of the lower bottom plate of the aerosol scattering cavity and the cavity body.

[0026] The present invention also provides a control method for an aerosol scattering measurement device, comprising the following steps:

[0027] Introduce aerosol into the aerosol scattering cavity, turn on the laser and set the laser emission intensity;

[0028] Mark the starting detection hole. Starting from the starting detection hole, the motor drives the photoelectric detector bracket to rotate. The photoelectric detector bracket drives the photoelectric detector to rotate, and the photoelectric detector is aligned with each detection hole.

[0029] When reaching a certain detection hole, the motor stops and returns to the angle where the current photoelectric detector is located. The photoelectric detector returns the scattered signal of the detection hole, and the scattered signal is analyzed to obtain the detection hole information and scattering intensity information;

[0030] Switch lasers of different bands, measure the scattering signals of the corresponding bands in the same detection hole, and the photoelectric detector bracket drives the photoelectric detector to rotate to the next detection hole until the scattering signal collection of all detection holes is completed.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) The present invention adopts lasers of different wavelength bands. The laser output end is incident into a hollow cylindrical aerosol scattering cavity. A plurality of detection holes are arranged on the side of the cavity to provide aerosol scattering signal collection of different wavelength bands and angles, thereby solving the long-standing problems of aerosol scattering measurement devices, such as small measurement range, low precision, single light source and low intelligence. The present invention can automatically measure scattering signals at multiple angles within a range of 360°, thereby realizing in-situ measurement and accurate identification of scattering signals in aerosol optical properties.

[0033] (2) The present invention uses a motor and a photodetector bracket to drive the photodetector to collect scattering signals from each detection hole corresponding to the laser of each band, thereby achieving the purpose of measuring multi-angle scattering signals with a single photodetector, thereby solving the problems of complex structure, high cost and complex wiring caused by a large number of detectors in aerosol angle-resolved light scattering measurement, and realizing fast, accurate, multi-wavelength, multi-angle and fully automatic aerosol angle-resolved scattering signal measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the overall structure of the aerosol scattering measurement device of the present invention;

[0035] Figure 2 Schematic diagram of the structure of the aerosol scattering cavity of the present invention;

[0036] Figure 3 It is a schematic diagram of the upper cover structure of the aerosol scattering cavity of the present invention;

[0037] Figure 4 Schematic diagram of the cavity structure of the aerosol scattering cavity of the present invention;

[0038] Figure 5 Schematic diagram of the fixing frame structure of the aerosol scattering chamber of the present invention

[0039] Figure 6 Schematic diagram of the control flow of the aerosol scattering measurement device of the present invention.

[0040] Among them, 1-aerosol scattering cavity, 2-photoelectric detector bracket, 3-motor connecting rod, 4-motor, 5-motor drag platform, 6-photoelectric detector, 7-upper cover plate, 8-cylindrical scattering cavity, and 9-fixed frame. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] like Figure 1 As shown, this embodiment provides an aerosol scattering measurement device, including: an aerosol scattering cavity 1, a plurality of light sources, a motor 4, a photoelectric detector bracket 2, and a photoelectric detector 6;

[0043] like Figure 2-Figure 5 As shown, the overall structure of the aerosol scattering cavity 1 includes an upper cover plate 7, a cylindrical scattering cavity 8, a lower base plate and a fixing frame 9. The upper cover plate 7, the lower base plate and the cylindrical scattering cavity 8 enclose an aerosol scattering cavity with a hollow interior and a cylindrical shape. The wall thickness of the cavity can meet the needs of conventional threaded holes. The size design of the scattering cavity takes into account the sensitivity of the photoelectric detector and the attenuation coefficient of the aerosol scattering intensity with distance, thereby ensuring the measurement effectiveness of the detector at each detection hole position.

[0044] On the side (curved surface) of the cylindrical scattering cavity, a total of 42 through-threaded holes are arranged in this embodiment, and each threaded hole is adapted to the thread of the core-inserted multi-mode quartz optical fiber and the installation thread of the optical attenuation plate.

[0045] In this embodiment, three laser input holes are designed at one end of the central axis (angle 180°) of the cylindrical scattering cavity and are equidistantly distributed from top to bottom, wherein the central hole is located at half the height of the cylindrical scattering cavity.

[0046] In this embodiment, the light source uses three high-power lasers in the ultraviolet, visible and infrared bands. The output end of each laser is coupled to a multimode optical fiber, and the optical fiber output end is threadedly mounted to the three laser input holes of the scattering cavity to ensure parallel incidence.

[0047] On the opposite side of the laser input hole (the other end of the central axis), three corresponding laser output holes are designed, and a black box-type light trap is designed at the rear end of the output hole to collect the output laser. In addition, 36 detection holes are designed between 3° and 355° on the side of the scattering cavity, and all holes are located in the same plane, that is, at half the height of the cylindrical scattering cavity. Among them, 18 holes are used to detect the backscattering of aerosols, 16 holes are used to detect the forward scattering of aerosols, and the remaining 2 holes are used to detect side scattering of about 90°.

[0048] In this embodiment, the holes in the scattering cavity that are closest to the two vertical angles are side scattering detection holes; for other holes, along the laser emission direction, the detection holes whose angles with the laser emission direction are less than 90° are forward scattering detection holes, and the detection holes whose angles with the laser emission direction are greater than 90° are back scattering detection holes;

[0049] In this embodiment, the inner surface of the scattering cavity is blackened to ensure that the scattered light is not reflected by the cavity wall for the second time and affects the detection quality. An optical attenuation plate is installed on the inner side of the scattering cavity for each detection hole to achieve proportional attenuation of the scattering intensity. The forward scattering intensity is high, so a high OD (Optical Density) attenuation plate with a larger attenuation coefficient is used, while the side and backward scattering holes are installed with low OD attenuation plates. The optical attenuation plate can not only regulate the intensity of the scattered light, but also ensure the airtightness inside the scattering cavity and achieve complete sealing inside the cavity. The scattering cavity is made of stainless steel, and the overall surface should be smooth and flat. Finally, a plurality of equidistant threaded holes are designed on the upper and lower surfaces of the cavity wall for mounting the bottom plates of the upper and lower surfaces.

[0050] Specifically, the light intensity of backscatter and sidescatter is relatively low, so the attenuation sheet with higher light transmittance (e.g., 80%-90% light transmittance) is generally added. The purpose of adding attenuation sheets to the backscatter and sidescatter holes with low scattering intensity in this embodiment is twofold: 1. To achieve the sealing of the cavity; 2. To ensure that the hole position is the same as the forward scattering, that is, to control the variables to avoid the hole position without attenuation sheet being different from the hole position with attenuation sheet installed. The analysis of the measurement results requires the identification of different scattering directions, and the final value is obtained based on the attenuation coefficient of the direction and the measured value.

[0051] In this embodiment, the diameters of the upper cover plate and the lower base plate are the same as the outer diameter of the aerosol scattering cavity, and are designed as two solid stainless steel thin discs. The discs are installed on the upper and lower surfaces of the cylindrical scattering cavity to seal the interior of the scattering cavity. An internal threaded through hole adapted to the external thread quick-tightening is designed at the center of the base plate. The hole in the upper cover plate is used for aerosol inflow, and the hole in the lower base plate is used for aerosol outflow. In order to ensure the airtightness of the base plate during installation, this embodiment designs two gaskets to be installed at the junction of the lower base plate and the scattering cavity. The gasket is a soft material with good airtightness, such as NBR (nitrile rubber), fluororubber, and asbestos-free. The gasket, base plate, and upper and lower surfaces of the scattering cavity are designed with threaded holes of the same position and size for the installation of the three.

[0052] In this embodiment, the scattering cavity as a whole needs to be installed on an optical platform to facilitate optical path adjustment. Therefore, this embodiment designs a fixing frame 9 to fix the above-mentioned cylindrical scattering cavity on the optical platform. The fixing frame 9 is designed with a curved arc adaptation structure. The curvature of the structure is the same as that of the scattering cavity, so as to facilitate close contact with the cylindrical wall. The front end of the bottom of the fixing frame 9 is used to support the scattering cavity, and a through hole is designed at the rear end to be fixed on the optical platform. This embodiment designs three fixing frames, which are at an angle of 120° to achieve triangular fixation of the aerosol scattering cavity.

[0053] In this embodiment, aerosol particles are input from top to bottom, and the scattered signals generated by three lasers irradiating the aerosol particle group are collected by 36 detection holes around the cavity. This design satisfies multi-wavelength and multi-angle aerosol scattering measurements;

[0054] In this embodiment, a high-precision motor rotation structure is set to realize a single photoelectric detector to measure the aerosol scattering signal at 36 angles. Considering that the high-precision rotating motor is difficult to bear the weight of the scattering cavity as a whole, a structure based on a suspended rotating motor is adopted to separate the motor rotation and the aerosol scattering cavity. Figure 1 As shown, the motor 4 is also provided with a motor platform 5, a flange, and a motor connecting rod 3. One end of the motor platform 5 is used to connect to the loading platform, and the other end of the motor platform 5 is connected to the motor. The output shaft of the motor 4 is connected to the flange, one end of the motor connecting rod 3 is connected to the flange, and the other end of the motor connecting rod 3 is connected to the photoelectric detector bracket 2. The photoelectric detector of this embodiment can adopt a high-sensitivity photodiode module;

[0055] Among them, the motor platform is used to suspend the entire motor rotating structure on the upper loading platform. In this embodiment, the motor platform is designed as a stainless steel whole with flat plates at both ends and a hollow cylindrical channel in the middle. Four through holes are made on the top of the platform to fix it on the loading platform, and four screw holes are made on the bottom to install the rotating motor. Compared with the connection with a connecting rod, the motor platform as an integral connecting piece has stronger stability. The motor connecting rod is used to fix the flange of the rotating motor and the photoelectric detector bracket. The fixed end of the flange adopts a slotted hole design so that each connecting rod can be installed on multiple screw holes of the flange, thereby increasing stability. The photoelectric detector bracket is a hollow disk made of aluminum alloy, in which the inner diameter is slightly larger than the outer diameter of the scattering cavity, so that it is easy to effectively install it on the periphery of the scattering cavity. The inner circle of the photoelectric detector bracket is distributed with multiple countersunk slots from bottom to top for fixing the motor connecting rod, and the outer circle is distributed with 36 countersunk fixing slots for the photoelectric detector from top to bottom. The detector slot hole distribution of the photoelectric detector bracket is exactly the same as that of the scattering cavity, so that it is easy to install the photoelectric detector at any position. The high-precision photodiode module used in this embodiment is in the shape of a rectangular parallelepiped. In actual application, the fixed position of the photodiode module is adjusted through the slot hole so that its photosensitive surface is almost close to the side of the scattering cavity. In addition, this embodiment uses a threaded gasket to adjust the height of the photodiode module so that the center of its photosensitive surface is on the same plane as the center of the scattering cavity detection hole.

[0056] In this embodiment, the stage, the motor drag platform, and the rotary motor have a completely penetrating structure on the central axis of the scattering cavity air inlet and outlet, thereby ensuring that the gas can flow from the top of the stage into the scattering cavity through the connection of the pipeline. In actual operation, the rotation of the rotary motor is controlled by a computer, and at this time, the flange of the high-precision rotary motor rotates, driving the motor connecting rod and the photoelectric detector bracket to rotate, thereby realizing that the photodiode module is aligned with the scattering cavity detection hole at a certain angle.

[0057] like Figure 6As shown, this embodiment also provides a control method for an aerosol scattering measurement device, wherein the upper computer adopts a PC (Personal Computer), and the lower computer adopts a self-designed FPGA board (Field Programmable Gate Array), which includes a core board and a bottom board with an RS485 serial port and an RJ45 network port. First, aerosol is introduced into the scattering cavity, all devices are powered on, and the rotating motor and three lasers are connected to the PC through a serial cable; the relevant parameters of the rotating motor are set through serial port instructions on the PC, such as: rotation speed, rotation mode, return to zero speed, etc.; after the parameters are set, the PC sends a command to the serial port of the laser to turn on the laser and set the laser emission intensity; then, the system will automatically control the motor rotation to find the nearest detection hole position that can make the photodetector output the maximum signal, and mark the hole position as the starting position. Specifically, the output signal of the photodetector will be converted into a voltage, and the magnitude of this voltage corresponds to the value after AD conversion. The larger the voltage, the larger the value of AD conversion. The value range of AD conversion is 0-255, and the voltage range is 0-12V. The hole position with the largest output voltage and the largest AD conversion value is the hole position with the largest output signal.

[0058] In this embodiment, the angle data of each detector hole position in the scattering cavity has been solidified in the system background in advance, and the rotating motor returns to the current angle at any time, so the system can analyze in real time which hole position the current photodiode module is located in the scattering cavity. Based on this, starting from the initial position, the system can continuously drive the motor to rotate so that the photosensitive surface of the photodiode is aligned with each scattering detection hole with high precision. When reaching a certain measuring point, the system controls the motor to stop, and then the photodiode measures the scattering signal of the hole position and inputs it into the FPGA board in the form of an analog signal. The FPGA board designed in this embodiment includes an analog signal input terminal, an analog signal to digital signal module (A / D module) and a network transmission module. Therefore, the lower computer converts the analog signal into a digital signal, and packages it into network data, and transmits the scattering data of the hole to the upper computer through the RJ45 network port. After the upper computer receives the data, it parses the data header and itself, which contains scattering hole position information and scattering intensity information.

[0059] In this embodiment, the scattering signals collected are generated by three high-power lasers irradiating aerosol particle groups. When analyzing, it is necessary to distinguish which laser's scattering signal it is. The laser is turned on and off by software control, so the software always retains the index information of the current laser, for example, the state is 0 when there is no laser, the state is 1 when laser 1 is turned on, the state of laser 2 is 2, and the state of laser 3 is 3. Therefore, the collected data can correspond to the current laser state to identify which laser generated the scattering signal.

[0060] In this embodiment, since the scattering signals collected are at multiple angles, the backward, forward, and lateral scattering at different positions can be obtained based on the angle of the corresponding hole position, that is, the scattering signal intensity of the hole at a certain current angle, the scattering signals generated by three high-power lasers irradiating the aerosol particle group, and the scattering signals at multiple angles. The results can correspond one to one, and it can be clear which angle and which laser the scattering intensity is.

[0061] In this embodiment, since the acquisition frequency of the A / D module is extremely high, each detection hole position usually collects multiple frames of signals. Therefore, this embodiment also designs a data filtering method to remove high and low data values, and use the average value of the remaining data as the scattering intensity measurement result of the hole. The collected data will be stored in the hard disk and plotted at the corresponding angle of the aerosol scattering phase function and displayed on the PC. Every time the data is transmitted, the header of the network data will contain the scattering hole position information and the scattering intensity information. When the data is analyzed, the obtained scattering intensity can be corresponded to a specific scattering angle value, so the scattering intensity can be corresponded to the angle. The scattering phase function is a line graph drawing process, with the scattering angle as the horizontal coordinate and the scattering intensity as the vertical coordinate. The measured data is input and the line graph can be drawn using the software.

[0062] In this embodiment, the average value is used as the scattering intensity measurement result of the hole. The average value is taken because the acquisition frequency of AD conversion is very high. Therefore, when collecting data for each scattering hole position, a lot of data for this hole position will be collected (for example, if the current laser is an ultraviolet laser, then the data currently detecting the hole position are all ultraviolet laser data). However, this embodiment only requires one scattering intensity data for each hole position, so the average value of these data is taken as the scattering intensity measurement result of the hole position.

[0063] In addition, the light source can be switched arbitrarily during the detection process, and the same hole position can measure the scattered signals of three wavelengths. At this point, the measurement of one hole position is completed, and the PC drives the motor to rotate to the next measurement point, and this reciprocating process realizes non-intervention and fully automatic aerosol scattering measurement.

[0064] The aerosol scattering measurement device of this embodiment can realize multi-wavelength, multi-angle fully automatic aerosol angle-resolved scattering intensity detection. For the aerosol scattering cavity, most of the existing ones are designed as a single light source input and a small number of scattering detection holes. In addition, most angle-resolved scattering measurement technologies install a high-sensitivity photodetector at each scattering hole, such as APD (Avalanche Photo Diode) and PMT (Photomultiplier Tube). This is because the device lacks a certain mechanical motion design, and because the size of its scattering cavity is usually large, the scattering signal at the measuring point is often very weak, forcing researchers to use detectors with higher sensitivity. In order to avoid installing multiple high-cost detectors, some researchers use a highly sensitive camera to collect scattering signals. However, due to the size of the camera's field of view, the range of scattering angles that can be measured by this method is very limited, usually within 1°. The present invention designs a scattering cavity with 36 measurement angles, and realizes multi-angle measurement of a single detector through a high-precision motor rotation structure. This greatly saves costs while providing richer aerosol scattering information, solving the long-standing problems of aerosol scattering measurement devices such as small measurement range, low accuracy, single light source and low intelligence.

[0065] In addition, the size of the scattering cavity designed by the present invention effectively improves the intensity of the scattered signal at the detection hole position. Specifically, the intensity of the scattered signal is negatively correlated with the distance of the scatterer (or the length of the propagation path). The scattering cavity of the present invention is relatively small in size, which can effectively improve the scattering intensity, and there are more scattering holes, which can meet the measurement requirements of the photodiode module. The optical attenuation plate is used to further adjust the scattered light intensity after the size of the scattering cavity is fixed. In addition, another very important function of the optical attenuation plate screwed on the scattering hole position is to seal the gas inside the scattering cavity. The present invention can use a high-sensitivity photodiode module as a detector, which also improves universality and stability to a certain extent.

[0066] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An aerosol scattering measurement device, characterized in that: include: Aerosol scattering cavity, multiple light sources, motor, photodetector bracket, photodetector; The aerosol scattering cavity comprises an upper cover plate, a lower bottom plate and a cavity body, wherein the upper cover plate, the lower bottom plate and the cavity body enclose an aerosol scattering cavity with a hollow cylindrical shape inside; The upper cover plate is provided with an aerosol inflow hole, and the lower base plate is provided with an aerosol outflow hole; The cavity is provided with a plurality of laser input holes and a plurality of laser output holes at both ends along the central axis, the light source adopts lasers of different wavelength bands, and the output end of each laser is connected to the laser input hole correspondingly; The side of the cavity is provided with a plurality of detection holes, and each detection hole is provided with an optical attenuation sheet; The photoelectric detector is connected to a photoelectric detector bracket, the photoelectric detector bracket is connected to a motor, the photoelectric detector bracket is arranged outside the aerosol scattering cavity, the photoelectric detector is aligned with the detection hole on the side of the cavity, the motor drives the photoelectric detector bracket to rotate, and the photoelectric detector bracket drives the photoelectric detector to collect scattering signals of each detection hole corresponding to the laser of each band.

2. The aerosol scattering measurement device according to claim 1, characterized in that: The laser input holes correspond to the laser output holes one by one, and the laser input holes are equidistantly distributed from top to bottom, wherein the center hole is located at half the height of the aerosol scattering cavity, and the output ends of each laser are incident in parallel into the aerosol scattering cavity.

3. The aerosol scattering measurement device according to claim 1, characterized in that: The detection holes are located in the same plane and at half the height of the aerosol scattering cavity.

4. The aerosol scattering measurement device according to claim 1, characterized in that: The detection holes include side scattering detection holes, forward scattering detection holes and backscattering detection holes, wherein the detection holes with an angle less than 90° with the laser emission direction are forward scattering detection holes, the detection holes with an angle greater than 90° with the laser emission direction are backscattering detection holes, and the holes with the two angles closest to vertical are side scattering detection holes; And / or the forward scattering detection hole adopts an optical attenuation plate with a high attenuation coefficient, and the side scattering detection hole and the back scattering detection hole adopt optical attenuation plates with a low attenuation coefficient.

5. The aerosol scattering measurement device according to claim 1, characterized in that: The motor is also provided with a motor drag platform, a flange, and a motor connecting rod; One end of the motor platform is used to connect to the loading platform, the other end of the motor platform is connected to the motor, the output shaft of the motor is connected to the flange, one end of the motor connecting rod is connected to the flange, and the other end of the motor connecting rod is connected to the photoelectric detector bracket.

6. The aerosol scattering measurement device according to claim 5, characterized in that: The motor, the motor platform and the flange plate have a completely penetrating structure on the central axis of the air inlet and the air outlet of the scattering cavity.

7. The aerosol scattering measurement device according to claim 1, characterized in that: The photoelectric detector bracket is provided with a plurality of photoelectric detector slots, and the hole position distribution of the photoelectric detector slots is the same as the hole position distribution of the detection holes of the aerosol scattering cavity.

8. The aerosol scattering measurement device according to claim 1, characterized in that: The laser uses lasers in the ultraviolet, visible and infrared bands.

9. The aerosol scattering measurement device according to claim 1, characterized in that: The aerosol scattering cavity is also provided with a plurality of fixing frames for fixing the aerosol scattering cavity to the optical platform, the fixing frames are provided with arc adaptation structures and through holes, the arc of the arc adaptation structure is the same as that of the scattering cavity, and is used to be close to the aerosol scattering cavity, and the through holes are connected to the optical platform; And / or a gasket is provided at the junction of the lower bottom plate of the aerosol scattering cavity and the cavity body.

10. The control method of the aerosol scattering measurement device according to any one of claims 1 to 9, characterized in that: The steps include: Introduce aerosol into the aerosol scattering cavity, turn on the laser and set the laser emission intensity; Mark the starting detection hole. Starting from the starting detection hole, the motor drives the photoelectric detector bracket to rotate. The photoelectric detector bracket drives the photoelectric detector to rotate, and the photoelectric detector is aligned with each detection hole. When reaching a certain detection hole, the motor stops and returns to the angle where the current photoelectric detector is located. The photoelectric detector returns the scattered signal of the detection hole, and the scattered signal is analyzed to obtain the detection hole information and scattering intensity information; Switch lasers of different bands, measure the scattering signals of the corresponding bands in the same detection hole, and the photoelectric detector bracket drives the photoelectric detector to rotate to the next detection hole until the scattering signal collection of all detection holes is completed.

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