AU2020100794A4 - System and method for use in freezing and coating after impact of micron-sized droplets onto spherical surfaces - Google Patents

System and method for use in freezing and coating after impact of micron-sized droplets onto spherical surfaces Download PDF

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AU2020100794A4
AU2020100794A4 AU2020100794A AU2020100794A AU2020100794A4 AU 2020100794 A4 AU2020100794 A4 AU 2020100794A4 AU 2020100794 A AU2020100794 A AU 2020100794A AU 2020100794 A AU2020100794 A AU 2020100794A AU 2020100794 A4 AU2020100794 A4 AU 2020100794A4
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low temperature
temperature control
control system
distribution plate
micron
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AU2020100794A
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Zhanyong LI
Xiusheng WU
Jun Xu
Qing Xu
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Tianjin University of Science and Technology
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Tianjin University of Science and Technology
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Abstract

The present invention relates to a system for solving frozen coating of micron-size droplets impacting a spherical surface, comprising a droplet collision experiment table and an image acquisition visualization system. The droplet collision experiment table is composed of a low temperature control system, an electrostatic atomizer, a particle distribution plate and a lifting table; the electrostatic atomizer is placed on the upper end of the low temperature control system; spherical particles are arranged on the particle distribution plate; the particle distribution plate is arranged on a rib plate of the lifting table and placed in the same vertical position as a nozzle in the low temperature control system; the image acquisition visualization system is composed of a high-speed camera, an LED light source and a PC; the PC is connected with a port of the high-speed camera; the high-speed camera and the LED light source are placed symmetrically on both ends of the lifting table; and a lens and the light source are adjusted to the same height as the spherical centers of the spherical particles. The experimental working conditions of the method are low temperature conditions; and the method can clearly acquire the images of frozen coating of the droplets impacting the spherical particles, has an image processing method with a visualization system, and is suitable for the research of frozen coating of the droplets impacting solid surfaces. F-33

Description

SYSTEM AND METHOD FOR USE IN FREEZING AND COATING AFTER IMPACT OF MICRON-SIZED DROPLETS ONTO SPHERICAL SURFACES
TECHNICAL FIELD
[0001] The present invention belongs to the technical field of spray-freeze drying, relates to a microscopic dynamic observation technology of morphological change during frozen coating of micron-size droplets impacting the surfaces of spherical particles, and particularly relates to a system and method for solving frozen coating of micron-size droplets impacting spherical surface to analyze dynamic change during frozen coating of micron-size droplets impacting low temperature spherical surfaces.
BACKGROUND OF THE PRESENT INVENTION
[0002] The research on the impacting of a single droplet on the surface of a spherical particle has attracted more and more attentions of researchers in recent years. The collision problem of the droplet mainly involves the spray-freeze drying technology in industry and the solution of natural disaster problems in real life. For example, in the drying industry, the spray freeze drying technology is used to improve the quality of powder products. By researching the coating phenomenon of droplets on carrier particles, powder particles with a porous structure on the surface are prepared to improve the instant solubility and size uniformity of the powder. The icing phenomenon of fog droplets on transmission wires in winter is researched, and the transmission wires are prevented from collapsing due to icing problems by researching the icing mechanism. In order to further research the freezing mechanism of atomized droplets after impacting the carrier particles, the freezing behavior of the droplets in the process that the droplets hit the spherical particles needs to be researched experimentally.
[0003] According to the previous research, the impacting phenomenon between the droplets and walls mostly involves planes, and rarely involves the collision phenomenon of curved surfaces. Moreover, most experiments research physical changes such as droplet spreading and breaking at room temperature. Most researches on the freezing behavior in the droplet collision process involve large millimeter-size droplets.
[0004] Therefore, the method solves the research on the dynamic behavior of the i
2020100794 20 May 2020 frozen coating process of micron-size droplet impacting spherical particle surfaces, and has an image processing method with a visualization system.
SUMMARY OF PRESENT INVENTION
[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a visualization system and method for solving frozen coating of micron-size droplets impacting a spherical surface, belongs to a microscopic observation method, and provides a reliable research method for researching a series of dynamic behaviors and the freezing mechanism of atomized droplets after impacting the particles.
[0006] The present invention solves the technical problem by the following technical solution:
[0007] A system for solving frozen coating of micron-size droplets impacting a spherical surface comprises a droplet collision experiment table and an image acquisition visualization system, wherein the droplet collision experiment table is composed of a low temperature control system, an electrostatic atomizer, a particle distribution plate and a lifting table; the electrostatic atomizer is placed on the upper end of the low temperature control system; spherical particles are arranged on the particle distribution plate; the particle distribution plate is arranged on the upper end of the lifting table and placed in the same vertical position of a nozzle in the low temperature control system; the image acquisition visualization system is composed of a high-speed camera, an LED light source and a PC; the PC is connected with a port of the high-speed camera; the high-speed camera and the LED light source are placed symmetrically on both ends of the lifting table; and a lens and the light source are adjusted to the same height as the spherical centers of the spherical particles.
[0008] Moreover, the low temperature control system can manually set the temperature, and a droplet entry hole and a hand hole for adjusting the particle distribution plate are formed in an upper cover of the low temperature control system.
[0009] Moreover, the electrostatic atomizer generates micron-size droplets through electrostatic atomization, and can adjust flow rate, electrostatic pressure and frequency; and nozzles of different sizes can be installed.
[0010] Moreover, the particle distribution plate is a strip-shaped aluminum plate with a column of hemispherical grooves on a surface.
2020100794 20 May 2020
[0011] Moreover, the high-speed camera is supported by a tripod, and a data output port is connected to the PC through a data cable; and a thermal insulation layer is arranged outside a body of the high-speed camera.
[0012] Moreover, the upper end of the lifting table is provided with a rectangular pipeline for placing the particle distribution plate; and a rectangular notch is formed in the center of the pipeline.
[0013] A method for solving frozen coating of the micron-size droplets impacting the spherical surface comprises the following steps:
[0014] 1) particle precooling: arranging the spherical particles on the particle distribution plate; placing the distribution plate on the upper end of the lifting table; placing the lifting table in the low temperature control system; aligning the spherical centers of the spherical particles with the center of a circle of the droplet entry hole; and setting the temperature of the low temperature control system as -30°C for precooling;
[0015] 2) arranging the image acquisition visualization system: after precooling is completed, arranging the high-speed camera and the LED light source symmetrically on both sides of the spherical particles; adjusting the lens and the light source to the same height as the spherical centers of the spherical particles; connecting the PC with the high-speed camera; positioning shooting speed at 5000 frames/second; using image pixels of 1024*512 when shooting; adjusting the light source intensity until the PC acquires a clear particle image; and closing the low temperature control system for another short precooling;
[0016] 3) arranging the electrostatic atomizer: using a syringe to suck 50ml of spray liquid; installing the syringe on the top end of the electrostatic atomizer; adjusting the flow rate and electrostatic pressure and frequency; placing the electrostatic atomizer on the upper cover of the low temperature control system; and keeping the nozzle, the center of the circle of the droplet entry hole and the spherical centers of the particles on one line;
[0017] 4) droplet impacting: simultaneously starting image acquisition software and the electrostatic atomizer to shoot a frozen coating process of the droplet impacting the spherical particle; after image acquisition is completed, moving the particle distribution plate through the hand hole of the low temperature control system to conduct experiments on other spherical particles; and repeating the above operation until the experiments of all the particles are completed;
2020100794 20 May 2020
[0018] 5) image processing: conducting grey processing on the images; extracting boundaries between a liquid film and the spherical particles in the images; then, fitting particle contours to obtain a morphological image of the liquid film; calibrating by taking the particles as reference objects because the diameter of the particles is a fixed value; and finally scanning the morphological image to obtain the thickness, spreading length and other parameters of the liquid film.
[0019] The present invention has the advantages and beneficial effects:
[0020] 1. In the visualization system and method for solving frozen coating of the micron-size droplets impacting the spherical surface in the present invention, the electrostatic atomizer can add different spray liquids; different feed flows are set; and different nozzles can be installed to produce micron-size droplets (80-2000 pm), to adapt to various experimental researches.
[0021] 2. In the visualization system and method for solving frozen coating of the micron-size droplets impacting the spherical surface in the present invention, the high-speed camera and the LED light source are placed on both sides of the particles; the LED light source adopts parallel light; and backlight is used for shooting, thereby greatly improving image clarity.
[0022] 3. In the visualization system and method for solving frozen coating of the micron-size droplets impacting the spherical surface in the present invention, the particle distribution plate has a column of hemispherical grooves on which multiple spherical particles of different sizes can be placed, thereby greatly improving the use continuity of the visualization system, avoiding multiple switching of the low temperature control system, and saving energy consumption.
[0023] 4. In the visualization system and method for solving frozen coating of the micron-size droplets impacting the spherical surface in the present invention, the lifting table can be adjusted to different heights; the upper end of the lifting table is provided with a rectangular pipeline for placing the particle distribution plate; and a rectangular notch is formed in the pipeline, to avoid the influences of the droplets on other particles on the distribution plate and improve the accuracy of the experiment. [0024] 5. In the visualization system and method for solving frozen coating of the micron-size droplets impacting the spherical surface in the present invention, the image processing visualization system used in the method can obtain the dynamic changes of the droplets, and obtain the parameters such as the thickness and spreading length of the liquid film of the droplet after programming, thereby
2020100794 20 May 2020 providing sufficient data for the mechanism research.
DESCRIPTION OF THE DRAWINGS
[0025] Fig. 1 is a structural schematic diagram of a visualization system of the present invention;
[0026] Fig. 2 is a left view of a lifting table of a visualization system of the present invention;
[0027] Fig. 3 is a top view of a particle distribution plate of a visualization system of the present invention;
[0028] Fig. 4 is a schematic diagram of morphological change of a liquid film of a droplet collision process of the present invention; and
[0029] Fig. 5 is a schematic diagram of an image processing process.
[0030] List of reference numerals
[0031] 1-low temperature control system; 2-high-speed camera; 3-rectangular pipeline; 4-PC; 5-hand hole; 6-electrostatic atomizer; 7-syringe; 8-nozzle; 9-droplet entry hole; 10-spherical particle; 11-particle distribution plate; 12-LED light source; and 13-lifting table.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] The present invention will be further described below in detail through specific embodiments. The following embodiments are only descriptive, not limiting, and shall not limit the protection scope of the present invention.
[0033] A visualization system and method for solving frozen coating of micron-size droplets impacting a spherical surface comprise a droplet collision experiment table and an image acquisition visualization system. The droplet collision experiment table comprises a low temperature control system 1, an electrostatic atomizer 6, a particle distribution plate 11 and a lifting table 13. Spherical particles 10 are arranged on the particle distribution plate 11; the particle distribution plate 11 is inserted into a rectangular pipeline 3; the lifting table 13 is arranged in the low temperature control system 1; the spherical particles 10 and a droplet entry hole 9 are kept in the same vertical position; the electrostatic atomizer 6 is placed on the upper end of the low temperature control system 1; and a nozzle 7 and the spherical particles 10 are kept in the same vertical position. The image acquisition visualization system comprises a high-speed camera 2, a PC 4 and an LED light source 12. The high-speed camera 2 and the LED light source 12 are placed on both sides of the lifting table 13; and the
2020100794 20 May 2020 spherical particles 10, the high-speed camera 2 and the LED light source 12 are kept in the same horizontal position.
[0034] A low temperature environment is provided by the low temperature control system 1, and an upper cover of the low temperature control system is provided with a hand hole 5 and a droplet entry hole 9. The hand hole 5 is used to move the particle distribution plate 11 to increase an experiment repetition rate and reduce the switching frequency of the low temperature control system 1.
[0035] A droplet generation visualization system generates micron-size droplets by the electrostatic atomizer 6; a syringe 7 and the nozzle 8 are installed on the electrostatic atomizer 6; and a specific flow rate, electrostatic pressure and frequency are set to generate micron-size tiny droplets.
[0036] The visualization system and method for solving frozen coating of micron-size droplets impacting a spherical surface comprise the following steps by using 10% pullulan polysaccharide solution as spray droplet material and adopting steel balls (5 mm) as spherical particles and cold storage temperature of -30°C as an example:
[0037] 1) steel ball precooling: arranging the steel balls on the particle distribution plate; placing the distribution plate on the upper end of the lifting table; placing the lifting table in the low temperature control system; aligning the spherical centers of the steel balls with the center of a circle of the droplet entry hole; and setting the temperature of the low temperature control system as -30°C for precooling;
[0038] 2) arranging the image acquisition visualization system: after precooling is completed, starting the low temperature control system and arranging the high-speed camera and the LED light source symmetrically on both sides of the spherical particles; adjusting the lens and the light source to the same height as the spherical centers of the spherical particles; connecting the PC with the high-speed camera; positioning shooting speed at 5000 frames/second; using image pixels of 1024*512 when shooting; adjusting the light source intensity until the PC acquires a clear particle image; and closing the low temperature control system for another short precooling;
[0039] 3) arranging the electrostatic atomizer: using a syringe to suck 50ml of 10% pullulan polysaccharide solution; installing the nozzles (240, 400 and 600 pm) and the syringe on the top end of the electrostatic atomizer; adjusting the flow rate and electrostatic pressure and frequency; placing the electrostatic atomizer on the upper
2020100794 20 May 2020 cover of the low temperature control system; and keeping the nozzles, the center of the circle of the droplet entry hole and the spherical centers of the steel balls on one line;
[0040] 4) droplet impacting: simultaneously starting image acquisition software and the electrostatic atomizer to shoot a frozen coating process of the droplet impacting the spherical particle; after image acquisition is completed, moving the particle distribution plate through the hand hole of the low temperature control system to conduct experiments on other steel balls; and repeating the above operation until the experiments of all the steel balls are completed;
[0041] 5) image processing: firstly conducting grey processing on the images; extracting boundaries between a liquid film and the steel balls in the images; then, fitting the contours of the steel balls to obtain a morphological image of the liquid film; calibrating by taking the steel balls as reference objects because the diameter of the steel balls is a fixed value (5 mm); and finally scanning the morphological image to obtain the thickness, spreading length and other parameters of the liquid film. Fig. 4 shows morphological change of the liquid film of a droplet collision process (experimental conditions: temperature of -30°C, droplet diameter of 600 pm and steel ball diameter of 5 mm); and Fig. 5 shows an image processing process.
[0042] Experimental conclusion: it can be seen from Fig. 4 that the image obtained by using the observation method for frozen coating of the micron-size droplets impacting the spherical surface designed by the patent is clear, and the dynamic change of the entire process of the droplets can be collected. It can be seen from Fig. 5 that the image processing method designed by the patent can accurately obtain the thickness and the spreading length of the film. It indicates that the method significantly improves the feasibility of the research on the impacting of the droplets on the surfaces of the spherical particles, and the obtained images and data are accurate and reliable.
[0043] Although the embodiments and the drawings of the present invention are disclosed for the illustrative purpose, those skilled in the art can understand that various replacements, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the disclosure in the embodiments and the drawings.

Claims (5)

  1. We claim:
    1. A system for solving frozen coating of micron-size droplets impacting a spherical surface, comprising a droplet collision experiment table and an image acquisition visualization system, wherein the droplet collision experiment table is composed of a low temperature control system, an electrostatic atomizer, a particle distribution plate and a lifting table; the electrostatic atomizer is placed on the upper end of the low temperature control system; spherical particles are arranged on the particle distribution plate; the particle distribution plate is arranged on the upper end of the lifting table and placed in the same vertical position of a nozzle in the low temperature control system; the image acquisition visualization system is composed of a high-speed camera, an LED light source and a PC; the PC is connected with a port of the high-speed camera; the high-speed camera and the LED light source are placed symmetrically on both ends of the lifting table; and a lens and the light source are adjusted to the same height as the spherical centers of the spherical particles.
    2. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the low temperature control system can manually set the temperature, and a droplet entry hole and a hand hole for adjusting the particle distribution plate are formed in an upper cover of the low temperature control system.
    3. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the electrostatic atomizer generates micron-size droplets through electrostatic atomization, and can adjust flow rate, electrostatic pressure and frequency; and nozzles of different sizes can be installed.
    4. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the particle distribution plate is a strip-shaped aluminum plate with a column of hemispherical grooves on a surface.
    5. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the high-speed camera is supported by a tripod, and a data output port is connected to the PC through a data cable; and a thermal insulation layer is arranged outside a body of the high-speed
    2020100794 20 May 2020 camera.
    6. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the upper end of the lifting table is provided with a rectangular pipeline for placing the particle distribution plate; and a rectangular notch is formed in the center of the pipeline.
    7. The system for solving frozen coating of the micron-size droplets impacting the spherical surface according to claim 1, wherein the LED light source is a parallel light source with power of 60W, and the light intensity can be adjusted.
    8. A method for solving frozen coating of the micron-size droplets impacting the spherical surface according to any one of claims 1-7, comprising the following steps:
    1) particle precooling: arranging the spherical particles on the particle distribution plate; placing the distribution plate on the upper end of the lifting table; placing the lifting table in the low temperature control system; aligning the spherical centers of the particles with the center of a circle of the droplet entry hole; and setting the temperature of the low temperature control system as -50 to 0°C;
  2. 2) arranging the image acquisition visualization system: starting the low temperature control system after precooling is completed; arranging the high-speed camera and the LED light source symmetrically on both sides of the spherical particles; adjusting the lens and the light source to the same height as the particle distribution plate; connecting the PC with the high-speed camera; positioning shooting speed at 5000 frames/second; using image pixels of 1024*512 when shooting; adjusting the light source intensity until the PC acquires a clear particle image; and closing the low temperature control system;
  3. 3) arranging the electrostatic atomizer: using a syringe to suck 50ml of spray liquid; installing the syringe on the top end of the electrostatic atomizer; adjusting the flow rate and electrostatic pressure and frequency; placing the electrostatic atomizer on the upper cover of the low temperature control system; and aligning the nozzle with the center of the circle of the droplet entry hole;
    2020100794 20 May 2020
  4. 4) droplet impacting: simultaneously starting image acquisition software and the electrostatic atomizer to shoot a frozen coating process of the droplet impacting the spherical particle; after image acquisition is completed, moving the particle distribution plate through the hand hole of the low temperature control system to conduct experiments on other spherical particles; and repeating the above operation until the experiments of all the particles are completed;
  5. 5) image processing: conducting grey processing on the images; extracting boundaries between a liquid film and the spherical particles in the images; then, fitting particle contours to obtain a morphological image of the liquid film; calibrating by taking the particles as reference objects because the diameter of the particles is a fixed value; and finally scanning the morphological image to obtain the thickness, spreading length and other parameters of the liquid film.
AU2020100794A 2017-12-27 2020-05-20 System and method for use in freezing and coating after impact of micron-sized droplets onto spherical surfaces Active AU2020100794A4 (en)

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PCT/CN2018/116697 WO2019128557A1 (en) 2017-12-27 2018-11-21 System and method for use in freezing and coating after impact of micron-sized droplets onto spherical surfaces
AU2020100794A AU2020100794A4 (en) 2017-12-27 2020-05-20 System and method for use in freezing and coating after impact of micron-sized droplets onto spherical surfaces

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114397231A (en) * 2022-01-21 2022-04-26 中国矿业大学 Visual test device and method for adhesion and desorption of wet particles in gas-solid two-phase flow

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114397231A (en) * 2022-01-21 2022-04-26 中国矿业大学 Visual test device and method for adhesion and desorption of wet particles in gas-solid two-phase flow
CN114397231B (en) * 2022-01-21 2024-04-16 中国矿业大学 Visual test device and method for adhesion and desorption of wet particles in gas-solid two-phase flow

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