An experimental device for controlling co-axial collision of double droplets
By designing an experimental device that includes a dual-droplet generator, a power unit, and an image acquisition module, high-precision collision of two droplets in the same direction along a straight line was achieved. This solves the problems of complex structure and difficult parameter control in existing devices and provides highly automated experimental analysis capabilities.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2023-08-15
- Publication Date
- 2026-05-29
AI Technical Summary
Existing droplet collision devices are complex in structure, expensive, and difficult to control droplet parameters precisely. They also cannot achieve collisions of two droplets in the same direction along a straight line, resulting in a low collision probability.
An experimental device was designed, comprising a dual droplet generator, a power unit, an image acquisition and processing module, and a pressure chamber module. The position and velocity of the droplets are precisely controlled by a servo motor and an electric displacement platform to achieve collisions in the same direction along a straight line. The gas phase environment and droplet type can also be adjusted.
It realizes a high-precision and highly automated two-droplet co-directional collision experiment, which can accurately control droplet parameters under various working conditions, reduce human operation errors, capture the droplet collision process, and is suitable for experimental analysis of various gas phase environments and droplet types.
Smart Images
Figure CN117073977B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of droplet collision technology and relates to an experimental device for controlling the collision of two droplets in the same direction. Specifically, it relates to an experimental device for controlling the gas phase environment, droplet type, velocity, particle size, and eccentricity of two droplets in the same direction. Background Technology
[0002] Droplet collisions are common phenomena in various fluid dynamics processes in nature and engineering, occurring in processes such as rain and snow formation, spray combustion in internal combustion engines, and interactions between condensed droplets in solid rocket motors. Research on collisions between single droplets has significant theoretical and practical implications. Droplet type, size, collision velocity, eccentricity, and gaseous environment all have a crucial impact on the collision outcome.
[0003] Invention patent CN 110201812A discloses "a droplet collision generating device". The experimental device can achieve controllable speed, particle size and angle of two droplets. In this experimental device, the droplet generating device moves obliquely towards the center position and collides. However, the collision speed is still difficult to control precisely, the collision probability is low, and it is difficult to achieve precise control of droplet parameters. Invention patent CN110006792B discloses "an experimental system and method for droplet-particle collision coagulation test". It can realize the study of collision between free-moving solid particles and droplets under different conditions. However, this experimental device is not suitable for collision between droplets, and it cannot achieve the goal of collision between two droplets in the same direction along a straight line.
[0004] In summary, most existing droplet collision devices are complex in structure and costly to implement. Furthermore, the collision velocities of the droplets are often intersecting, making it difficult to control the droplet parameters and resulting in a low collision probability. Currently, there is no experimental device capable of achieving collisions of two droplets in a straight line. Summary of the Invention
[0005] The purpose of this invention is to provide an experimental apparatus for co-directional collisions of two droplets, enabling different types of droplets to collide in the same direction along a straight line at predetermined positions under various gaseous environments with different velocities, particle sizes, and eccentricities. This invention offers advantages such as high precision and a high degree of automation.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] This invention discloses an experimental apparatus for controlling the co-directional collision of two droplets, comprising a dual-droplet generator and power unit module, an image acquisition and processing module, and a pressure chamber module. The dual-droplet generator and power unit module is the core module of the experimental apparatus; the dual-droplet generator is used to generate a single droplet, and the power unit is used to control the movement of the droplet generator.
[0008] It is necessary to ensure that the needles of the two droplet generators are on the same straight line. By controlling the distance between the two droplet generators and the droplet ejection time, the position and velocity of the two droplets upon collision are controlled. When a droplet with velocity v1 collides with a droplet with velocity v2, the expressions for the distance between the droplet generators and the droplet motion time are:
[0009]
[0010] △t=t1-t2 (2)
[0011] In the formula, the height of the plane at the collision location is set to 0, h1 is the distance from the tip of the needle of the higher-position droplet generator to the collision plane, h2 is the distance from the tip of the needle of the lower-position droplet generator to the collision plane, v1 is the velocity of the droplet generated by the higher-position droplet generator, v2 is the velocity of the droplet generated by the lower-position droplet generator, t1 is the time taken from the generation of the higher-position droplet to the collision, t2 is the time taken from the generation of the lower-position droplet to the collision, Δt is the time difference between the generation of droplets by the two droplet generators, and g is the acceleration due to gravity.
[0012] After the droplet generator at the lower position emits droplets, the lower droplet generator is moved by a power device to prevent the droplets at the higher position from colliding with the needle of the lower droplet generator when they fall.
[0013] The droplet generator includes: a droplet generating servo motor, a droplet generating screw, a droplet generating fixing device, a mechanical piston, a metal syringe, liquid, a syringe, and a needle. Under the control of the droplet generating servo motor and the transmission of the droplet generating screw, the mechanical piston moves, squeezing the liquid in the metal syringe into the syringe and dripping it from the needle, producing single droplets of a preset particle size.
[0014] Preferably, the inner diameter of the needle is less than 1 mm, and the droplet size can be changed by changing the inner diameter of the needle.
[0015] Preferably, in the droplet generator, a servo motor controls and drives a mechanical piston to move precisely. The movement speed of the mechanical piston should be kept extremely low, with a propulsion speed of less than 1 mm / min, to ensure that the liquid falls from the tip of the needle in the form of a single droplet with an initial velocity of zero.
[0016] The power unit includes an XY-direction electric displacement platform, a Z-direction electric displacement platform, a scale, and a controller. The XY-direction electric displacement platform consists of two unidirectional electric displacement platforms. Each unidirectional electric displacement platform includes a displacement servo motor, a base plate, a coupling, a bearing seat, a movable base, an X-direction displacement screw, a guide rail, and a slider. The Z-direction electric displacement platform consists of a Z-direction displacement servo motor, a Z-direction displacement screw, and a support platform.
[0017] The unidirectional electric displacement platform enables adjustable and controllable movement of the moving base in one direction. The base plate serves as a fixed connection, and the displacement servo motor is connected to the controller, receiving signals from the controller and issuing action commands. When a forward / backward command is issued, the rotation of the X-direction displacement servo motor is converted by the coupling and bearing housing into the movement of the slider on the X-direction displacement screw. The slider is fixed to the base, and the movement of the slider drives the movement of the moving base, achieving precise control of the movement process of the moving base. A unidirectional electric displacement platform is formed by vertically fixing one unidirectional electric displacement platform onto the moving base of another unidirectional electric displacement platform. The dual servo motors, under the control of the controller, can achieve precise control and position feedback of XY plane motion. The Z-axis moving platform is driven by the rotation of the Z-direction displacement servo motor, which drives the Z-direction displacement screw to achieve the translation of the support platform. By connecting the Z-direction displacement servo motor to the controller, the support platform can be moved precisely in the Z-direction, thereby controlling the position of the droplet generator in the Z-direction. The controller controls the movement of multiple servo motors and makes the next instruction based on the position feedback of each motor, so as to complete the instruction with high precision within a predetermined time sequence. The scale provides position feedback information for each servo motor and obtains the spatial coordinates of the needle.
[0018] The image acquisition and processing module includes a high-intensity light source, a three-way displacement platform for the high-intensity light source, a high-speed camera, a camera tripod, and a computer. The three-way displacement platform is used to adjust the spatial position of the high-intensity light source; the camera tripod is used to adjust the spatial position of the high-speed camera; the principle for adjusting the spatial position is to keep the light-emitting center of the high-intensity light source and the shooting center of the high-speed camera aligned in a straight line; the computer and the high-speed camera are connected via ports; the high-intensity light source can illuminate the shooting area of the high-speed camera in high frame rate shooting mode, while the location of the two droplets is in darkness; the shooting method is the shadow method, which can more clearly capture the droplet collision process.
[0019] As a preferred option, the high-intensity light source three-way displacement platform uses an electric displacement platform to achieve three-way movement of the high-intensity light source.
[0020] Preferably, the center of the strong light source and the center of the high-speed camera are precisely measured using a ruler.
[0021] As a preferred option, the high-speed camera is equipped with a macro microscope lens.
[0022] The pressure chamber module includes a pressure chamber, a Z-axis scale, a laser, a gas inlet, gas pipelines, a pressure reducing valve, a high-pressure gas source, fixtures, a gas outlet, a solenoid valve, a vacuum pump, a collection dish, and observation windows. There are two observation windows: one is a channel for strong light signals to enter the pressure chamber, and the other is a channel for light signals to enter a high-speed camera. The gas inlet is the channel for high-pressure gas to enter the pressure chamber; the gas outlet is the channel for gas to leave the pressure chamber. The high-pressure gas source is connected to the gas inlet of the pressure chamber via a gas pipeline and a pressure reducing valve to pressurize the pressure chamber. The inlet is connected to the outside via a gas pipeline and a solenoid valve for depressurizing the gas inside the pressure chamber; the vacuum pump is used to create a low-pressure or even vacuum environment inside the pressure chamber; the laser is connected and fixed to the top of the pressure chamber via threads, and the laser emits a laser beam vertically downward to determine the XY position of the droplet generator needle tip; the collecting dish is located at the bottom of the pressure chamber directly opposite the laser and is used to collect the droplets after collision; there are two fixing components, which are square metal parts with multiple threaded through holes, both welded to the pressure chamber, with high structural strength, and their Z-axis position is higher than the upper part of the observation window.
[0023] As a preferred option, a high-brightness, thin, straight green laser is selected;
[0024] Preferably, the thickness of the fastener is ≥20mm.
[0025] The gaseous environment is altered by changing the gas composition and pressure within the pressure chamber module.
[0026] The type of droplet can be changed by altering the liquid inside the metal syringe.
[0027] The droplet velocity is changed by altering the Z-axis position of the droplet generator.
[0028] The droplet size can be changed by altering the needle diameter.
[0029] The collision eccentricity is achieved by precisely adjusting the distance from the tip of the droplet generator needle to the laser. That is, the distance from the needle tip to the laser is zero during a center collision, and the distance is increased when there is eccentricity.
[0030] Beneficial effects:
[0031] 1. The present invention discloses an experimental device for controlling the collision of two droplets in the same direction, which can realize the behavior of two droplets moving along a vertical line at a predetermined speed and colliding at a predetermined position, providing an experimental device for analyzing the collision behavior of droplets moving along the same straight line.
[0032] 2. The present invention discloses an experimental device for controlling the collision of two droplets in the same direction. The droplet generator and the power device are both connected to the controller. With the help of the position feedback of the servo motor, the controller can complete the command with high precision within a predetermined time sequence. It has high integration, convenient control, and high degree of automation, which greatly avoids the errors and uncertainties of manual operation.
[0033] 3. The present invention discloses an experimental device for controlling the collision of two droplets in the same direction. The device changes the gas phase environment by changing the gas composition and pressure in the pressure chamber module; changes the droplet type by changing the liquid in the metal syringe; changes the droplet velocity by changing the Z-axis position of the two droplet generator; changes the droplet size by changing the needle diameter; and obtains collisions with different eccentricities by adjusting the position of the droplet generator needle, thereby realizing adjustable and controllable parameters of droplet collision under various working conditions.
[0034] 4. The present invention discloses an experimental device for controlling the collision of two droplets in the same direction. The device obtains the dynamic process of droplet collision through an image acquisition and processing system, and captures the processes such as droplet aggregation and rebound after collision. It can be applied to the experimental analysis of the collision of two droplets in the same direction. Attached Figure Description
[0035] Figure 1 This is a schematic diagram of the experimental device for controlling the collision of two droplets in the same direction according to the present invention.
[0036] Figure 2 This is a schematic diagram of the image acquisition and processing module.
[0037] Figure 3 This is a schematic diagram of the pressure chamber module structure.
[0038] Figure 4 This is a schematic diagram of the droplet generator and power unit module.
[0039] Figure 5 This is a structural diagram of the electric displacement platform in the X direction.
[0040] Figure 6 This is a structural diagram of the displacement platform in the XY direction.
[0041] Figure 7 This is a schematic diagram of a droplet generator.
[0042] Wherein: 1—Image acquisition and processing module, 1.1—Computer, 1.2—High-speed camera, 1.3—High-intensity light source, 1.4—High-intensity light source three-way displacement platform, 1.5—Camera tripod;
[0043] 2—Pressure chamber module, 2.1—Pressure chamber, 2.2—Z-axis direction scale, 2.3—Laser, 2.4—Gas inlet, 2.5—Gas pipeline, 2.6—Pressure reducing valve, 2.7—High-pressure gas source, 2.8—Fixed component, 2.9—Gas outlet, 2.10—Solenoid valve, 2.11—Vacuum pump, 2.12—Collection dish, 2.13—Observation window;
[0044] 3—Droplet generator and power unit module; 3.1—Controller; 3.2—Droplet generator; 3.3—XY direction moving base; 3.4—XY direction moving displacement platform; 3.5—Support platform; 3.6—XY axis direction scale; 3.7—Z direction displacement screw; 3.8—Z direction displacement servo motor; 3.9—Servo motor port; 3.10—Hex bolt; 3.11—Base; 3.6.1—X direction electric displacement platform; 3.6.1.1—X direction displacement servo motor; 3.6.1.2—Base plate; 3.6 3.6.1.3—Coupling; 3.6.1.4—Bearing seat; 3.6.1.5—X-direction moving base; 3.6.1.6—X-direction displacement screw; 3.6.1.7—Slider; 3.6.1.8—Guide rail; 3.6.2—Y-direction electric displacement platform; 3.2.1—Droplet generating servo motor; 3.2.2—Droplet generating screw; 3.2.3—Droplet generating fixing device; 3.2.4—Mechanical piston; 3.2.5—Metal syringe; 3.2.6—Liquid; 3.2.7—Needle; 3.2.8—Needle. Detailed Implementation
[0045] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0046] Example:
[0047] In this embodiment, a 200-micrometer water droplet was subjected to a unidirectional collision experiment in a vacuum environment. The velocity of the high-speed droplet was 6 m / s and the velocity of the low-speed droplet was 4 m / s when the collision occurred. The eccentricity of the two droplets was 0, that is, a head-on collision occurred.
[0048] Calculated from equations (1) and (2), the value of h1 is 1.8367m, the value of h2 is 0.8163m, t1 is 0.6122s, and t2 is 0.4082s.
[0049] To achieve unidirectional collision of the two droplets, firstly, two droplet generators are fixed at a predetermined height; secondly, the positions of the droplet generator needles on the horizontal plane are controlled so that the two needles are aligned with the vertically downward laser; then, the droplets are controlled to fall freely at a predetermined time. After the droplet is emitted from the lower droplet generator, a servo motor is controlled by a controller to move the droplet generator, preventing the droplet at the higher position from colliding with the needle of the lower droplet generator; finally, the position of the droplet generator is estimated, and a high-speed camera system is fixed in advance to record the entire droplet collision process.
[0050] The experimental apparatus for controlling the co-directional collision of two droplets is as follows: Figure 1 As shown, the experimental setup can be divided into three modules: image acquisition and processing module 1, pressure chamber module 2, and droplet generator and power unit module 3. The main function of image acquisition and processing module 1 is to start high-frequency recording at a predetermined time to completely record the experimental process of droplet collision. The main function of pressure chamber module 2 is to provide the experimental working environment and prepare for the normal operation of droplet generator and power unit module 3. Droplet generator and power unit module 3 is the core of the experimental setup, and its main functions are to generate droplets and control the movement of the droplet generator, ensuring the droplets are generated at predetermined times and positions, and to quickly move the droplet generator position after the low-speed droplets are generated to avoid affecting the movement of the high-speed droplets.
[0051] Figure 2 This is a schematic diagram of the image acquisition and processing module. Before the experiment, the position of the droplet collision is first estimated based on the position of the droplet generator 3.2. Then, the positions of the strong light source displacement platform 1.4 and the high-speed camera tripod 1.5 are adjusted so that the center of the strong light source 1.3 and the center of the high-speed camera 1.2 are consistent with the droplet collision position. The strong light source 1.3 serves as a strong backlight during the shooting process. The shooting frame rate of the high-speed camera 1.2 is set to 10,000 frames / s, and the exposure time is 80μs. The shadow method is used for shooting. The high-speed camera 1.2 is connected to the computer 1.1, and the camera shooting signal trigger time is preset in advance to ensure complete recording of the collision process.
[0052] Figure 3This is a schematic diagram of the pressure chamber module. Before the experiment begins, preparations are made according to the experimental requirements for the gas phase environment. In this embodiment, the gas inlet 2.4, gas outlet 2.9, and pressure reducing valve 2.6 are closed; the vacuum pump 2.11 is turned on to evacuate the pressure chamber to a vacuum; the vacuum pump is then turned off, and the pressure chamber 2.1 is sealed. Additionally, the laser 2.3 on top of the pressure chamber 2.1 is remotely activated to emit a vertically downward laser beam. If the experimental environment is high-pressure, the high-pressure gas source 2.7 is introduced into the pressure chamber 2.1 through the gas pipeline 2.5 from the gas inlet 2.4. All valves except the gas inlet 2.4 are closed, and the pressure reducing valve 2.6 is controlled to increase the pressure at its low-pressure end to a predetermined pressure. Once the pressure is reached, the pressure reducing valve 2.6 is closed, preparing for the experiment. The Z-axis direction scale 2.2 is marked on the pressure chamber 2.1 to prepare for the droplet generator and power unit module 3; the collection dish 2.12 is for collecting droplets after the collision; the observation window 2.13 is for the normal operation of the image acquisition and processing module 1; the solenoid valve 2.10 is for releasing the pressure in the pressure chamber after the experiment.
[0053] Figure 4 For the droplet generator and power unit module 3, before the experiment, the Z-axis coordinates of the two droplet generators 3.2 were first calculated according to the droplet velocity and predetermined collision position in the experimental requirements. Then, the Z-direction electric displacement platform was adjusted to the predetermined position by the controller 3.1. The controller 3.1 controlled the rotation of the Z-direction displacement servo motor 3.8 and the Z-direction lead screw 3.7 to drive the support platform 3.5 to move up and down. Next, the controller 3.1 controlled the movement of the XY-direction electric displacement platform 3.4 so that the position of the needle 3.2.8 in the two droplet generators 3.2 was completely consistent with the position of the laser beam. Then, the lower droplet generator 3.2 was set to move the X-direction servo motor 3.8 to ensure that it moves quickly to the left after generating the droplet, so as to avoid the collision of the higher droplet with the needle 3.2.8 during the fall. Finally, the timing signal was connected to the trigger end of the high-speed camera 1.2 to ensure complete recording of the collision process of the two droplets. The Z-axis servo motor 3.8 is connected to the controller 3.1 via the servo motor port 3.9, and is connected to the fixture 2.8 via a hex bolt 3.10 in a threaded connection. The XY-axis scale 3.6 and the Z-axis scale 2.2 provide a scale reference for the movement of the droplet generator 3.2.
[0054] Figure 5 and Figure 6The diagram shows the structure of the X / XY direction electric displacement platform. The platform consists of an X-direction displacement servo motor (3.6.1.1), a base plate (3.6.1.2), a coupling (3.6.1.3), a bearing seat (3.6.1.4), an X-direction moving base (3.6.1.5), an X-direction displacement lead screw (3.6.1.6), a slider (3.6.1.7), and a guide rail (3.6.1.8). The base plate (3.6.1.2) provides a fixed connection. During operation, the X-direction servo motor (3.6.1.1) controls the movement of the X-direction moving base (3.6.1.5). Connected to controller 3.1, the X-direction displacement servo motor 3.1.1 receives signals from controller 3.1 and issues action commands. When a forward / backward command is issued, the rotation of the X-direction displacement servo motor 3.6.1.1 is converted by coupling 3.6.1.3 and bearing housing 3.6.1.4 into the movement of slider 3.6.1.7 on the X-direction displacement screw 3.6.1.6. Slider 3.6.1.7 is fixedly connected to the X-direction moving base 3.6.1.5. The movement of slider 3.6.1.7 drives the movement of X-direction moving base 3.6.1.5, realizing precise control of the movement process of X-direction moving base 3.6.1.5. Connecting the two unidirectional electric displacement platforms, X-direction electric displacement platform 3.6.1 and Y-direction electric displacement platform 3.6.2, forms the XY-direction electric displacement platform 3.4. Under the control of controller 3.1, the dual servo motors can realize precise control and position feedback of the movement of the XY-direction base 3.3 in the XY plane.
[0055] Figure 7 The diagram shows the structure of the droplet generator. It consists of a droplet generating servo motor 3.2.1, a droplet generating lead screw 3.2.2, a mechanical piston 3.2.4, a metal syringe 3.2.5, a needle tube 3.2.7, liquid 3.2.6, a needle tip 3.2.8, and a droplet generating fixing device 3.2.3. The droplet generating fixing device 3.2.3 is used to fix the various components. The droplet generating servo motor 3.2.1 is connected to the controller 3.1, and its movement is controlled by the controller 3.1. The droplet generating servo motor 3.2.1 drives the droplet generating lead screw 3.2.2. The droplet generating lead screw 3.2.2 is fixed to the mechanical piston 3.2.4, enabling it to precisely push the mechanical piston 3.2.4 at ultra-low speed. The mechanical piston 3.2.4 pushes the liquid 3.2.6 in the metal syringe 3.2.5, which drips along the needle tube 3.2.7 from the needle tip 3.2.8 with an initial velocity of zero.
[0056] This embodiment discloses an experimental apparatus for controlling the unidirectional collision of two droplets, comprising the following operating steps:
[0057] Step 1: Turn on the laser 2.3 so that the laser is vertically downward, and adjust the position of the collection dish 2.12 so that the laser is directly in front of it.
[0058] Step 2: Based on the experimental conditions, the Z-axis coordinate of the needle 3.2.8 in the lower droplet generator 3.2 is calculated to be 1.8367m, and the Z-axis coordinate of the needle in the higher droplet generator is 0.8163m. The Z-axis coordinate of the estimated collision position is 0. Based on the controller 3.1, the droplet generating servo motor 3.2.1 is adjusted to move the needle 3.2.8 to the predetermined position. Then, based on the controller 3.1, the two XY direction electric displacement platforms 3.6 are adjusted so that the outlets of the needles 3.2.8 of the two droplet generators 3.2 come into contact with the laser.
[0059] Step 3: Based on the controller 3.1, adjust the movement of the droplet generating servo motors 3.2.1 in the two droplet generators 3.2, thereby controlling the movement speed of the mechanical piston 3.2.4 to 0.5 mm / min, preset the start time of movement, and preset the lower droplet's falling time to lag behind the higher droplet by 0.204 s. Set the droplet generator 3.2 recovery command, that is, respond quickly after the droplet falls, move the droplet generator 3.2 to the left, and affect the falling process of the higher droplet on the wall.
[0060] Step 4: Close the high-pressure gas source valve 2.7, turn on the vacuum pump 2.11 to evacuate the gas in the pressure chamber 2.1 to a vacuum, turn off the vacuum pump 2.11 and close the vacuum pump valve, and keep the pressure chamber 2.1 sealed.
[0061] Step 5: The experiment begins with the higher droplet forming first. After it falls, the lower droplet forms. Then, the lower droplet generator moves, and the two droplets undergo free fall and collide at a predetermined position. The process before and after the collision is recorded by the high-speed camera 1.2.
[0062] Step Six: After the experiment, open the valve, turn off the laser 2.3, check the data acquisition results, analyze the results captured by the high-speed camera 1.2, obtain accurate parameters such as droplet collision velocity and particle size, and prepare for the next experiment.
[0063] The above description further details the purpose, method, apparatus, and advantages of the present invention. It should be understood that the above description is only a specific implementation process of the present invention and is used to explain the present invention. It is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the present invention.
Claims
1. An experimental apparatus for controlling the collision of two droplets in the same direction, characterized in that: include: Dual droplet generator and power unit (3); the dual droplet generator (3.2) is used to generate a single droplet; the power unit is used to control the movement of the droplet generator (3.2); The power unit must ensure that the needles (3.2.8) of the two droplet generators (3.2) are located on the same vertical line, and control the position and velocity of the two droplets when they collide by controlling the distance between the two droplet generators and the time of droplet ejection; when a droplet with velocity v1 collides with a droplet with velocity v2, the expressions for the distance between the droplet generators and the time of droplet motion are as follows: （1） （2） In the formula, the height of the plane at the collision location is set to 0, h1 is the distance from the tip of the needle of the higher-position droplet generator to the collision plane, h2 is the distance from the tip of the needle of the lower-position droplet generator to the collision plane, v1 is the velocity of the higher-position droplet during the collision, v2 is the velocity of the lower-position droplet during the collision, t1 is the time taken from the higher-position droplet's generation to the collision, t2 is the time taken from the lower-position droplet's generation to the collision, Δt is the time difference between the two droplet generators generating droplets, and g is the acceleration due to gravity. After the droplet generator (3.2) at a relatively low position emits a droplet, the lower droplet generator is moved by a power device to avoid the droplet at a higher position from colliding with the needle of the lower droplet generator when it falls.
2. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The droplet generator includes a droplet generating servo motor (3.2.1), a droplet generating lead screw (3.2.2), a droplet generating fixing device (3.2.3), a mechanical piston (3.2.4), a metal syringe (3.2.5), a liquid (3.2.6), a syringe (3.2.7), and a needle (3.2.8). The droplet generating fixing device (3.2.3) is used to fix the various components. The droplet generating servo motor (3.2.1) is connected to the controller (3.1), and the movement of the droplet generating servo motor (3.2.1) is controlled by the controller. (3.1) Control: The droplet generating servo motor (3.2.1) drives the droplet generating screw (3.2.2) to move. The droplet generating screw (3.2.2) is fixedly connected to the mechanical piston (3.2.4). Under the control of the droplet generating servo motor (3.2.1) and the transmission of the droplet generating screw (3.2.2), the mechanical piston (3.2.4) moves and squeezes the liquid in the metal syringe (3.2.5) into the needle tube (3.2.7) and drips from the needle tip (3.2.8) to generate a single droplet of preset particle size.
3. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The inner diameter of the needle is less than 1 mm, and the droplet size generated can be changed by changing the inner diameter of the needle.
4. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: In the droplet generator, a servo motor controls and drives a mechanical piston to move precisely. The speed at which the servo motor drives the mechanical piston in the droplet generator is less than 1 mm / min, ensuring that the liquid falls from the tip of the needle in the form of a single droplet with an initial velocity of zero.
5. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The power unit includes: an XY-direction electric displacement platform (3.4), a Z-direction electric displacement platform, a scale (3.6), and a controller (3.1); the XY-direction electric displacement platform (3.4) consists of two unidirectional electric displacement platforms, each unidirectional electric displacement platform including a displacement servo motor (3.6.1.1), a base plate (3.6.1.2), a coupling (3.6.1.3), a bearing seat (3.6.1.4), a movable base (3.6.1.5), an X-direction displacement screw (3.6.1.6), a guide rail (3.6.1.8), and a slider (3.6.1.7); the Z-direction electric displacement platform consists of a Z-direction displacement servo motor (3.8), a Z-direction displacement screw (3.7), and a support platform (3.5); The unidirectional electric displacement platform enables adjustable and controllable movement of the movable base (3.6.1.5) in one direction. The base plate (3.6.1.2) serves as a fixed connection. The displacement servo motor (3.6.1.1) is connected to the controller (3.1), receiving signals from the controller (3.1) and issuing action commands. When a forward / backward command is issued, the rotation of the X-direction displacement servo motor (3.6.1.1) is converted by the coupling (3.6.1.3) and bearing seat (3.6.1.4) into the movement of the slider (3.6.1.7) on the X-direction displacement screw (3.6.1.6). The slider (3.6.1.7) is fixedly connected to the base (3.6.1.2). The movement of the slider (3.6.1.7) drives the movement of the movable base (3.6.1.5), realizing precise control of the movement process of the movable base (3.6.1.5). A unidirectional electric displacement platform (3.6.2) is vertically The XY electric displacement platform (3.4) is formed by fixing a movable base (3.6.1.5) on another unidirectional electric displacement platform (3.6.1). Under the control of the controller (3.1), the dual servo motors can achieve precise control and position feedback of XY plane motion. The Z-direction electric displacement platform is driven by the Z-direction displacement servo motor (3.8) to rotate and drive the Z-direction displacement screw (3.7) to realize the translation of the support platform (3.5). By connecting the Z-direction displacement servo motor (3.8) to the controller (3.1), the support platform (3.5) can be accurately moved in the Z direction, thereby controlling the position of the droplet generator (3.2) in the Z direction. The controller (3.1) controls the movement of multiple servo motors and makes the next instruction according to the position feedback of each motor, so as to realize the high-precision completion of the instruction within the predetermined time sequence. The scale provides position feedback information for each servo motor and obtains the spatial coordinates of the needle.
6. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: It also includes an image acquisition and processing module (1); the image acquisition and processing module (1) includes a computer (1.1), a high-speed camera (1.2), a strong light source (1.3), a three-way displacement platform for the strong light source (1.4), and a camera tripod (1.5); the three-way displacement platform for the strong light source (1.4) is used to adjust the spatial position of the strong light source (1.3); the camera tripod (1.5) is used to adjust the spatial position of the high-speed camera (1.2); the principle of adjusting the spatial position is to keep the light emission center of the strong light source (1.3) and the shooting center of the high-speed camera (1.2) on a straight line; the computer (1.1) and the high-speed camera (1.2) are connected by ports; the strong light source (1.3) can illuminate the shooting area of the high-speed camera in high frame rate shooting mode, while the location of the two droplets is dark; the shooting method adopts the shadow method.
7. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The high-intensity light source three-way displacement platform uses an electric displacement platform to realize the three-way movement of the high-intensity light source; The positions of the center of the strong light source and the center of the high-speed camera were precisely measured using a ruler; The high-speed camera is equipped with a macro microscope lens.
8. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The experimental setup also includes a pressure chamber module (2); the pressure chamber module (2) includes a pressure chamber (2.1), a Z-axis direction scale (2.2), a laser (2.3), a gas inlet (2.4), a gas pipeline (2.5), a pressure reducing valve (2.6), a high-pressure gas source (2.7), a fixing component (2.8), a gas outlet (2.9), a solenoid valve (2.10), a vacuum pump (2.11), a collection dish (2.12), and an observation window (2.13); there are two observation windows (2.13), one is the channel for the strong light source signal to enter the pressure chamber (2.1), and the other is the channel for the light signal to enter the high-speed camera (1.2); the gas inlet (2.4) is the channel for high-pressure gas to enter the pressure chamber (2.1); the gas outlet (2.9) is the channel for gas to leave the pressure chamber; the high-pressure gas source (2.7) passes through the gas pipeline (2.5) and the pressure reducing valve (2.6) and the pressure chamber. The gas inlet (2.4) of the pressure chamber (2.1) is connected to pressurize the pressure chamber (2.1). The gas outlet (2.9) is connected to the outside through the gas pipeline (2.5) and the solenoid valve (2.10) for depressurizing the gas in the pressure chamber (2.1). The vacuum pump (2.11) is used to create a low-pressure or even vacuum environment in the pressure chamber (2.1). The laser (2.3) is connected and fixed to the top of the pressure chamber (2.1) by threads. The laser (2.3) emits laser light vertically downward to determine the XY position of the tip of the droplet generator needle. The collecting dish (2.12) is located at the bottom of the pressure chamber directly opposite the laser (2.3) and is used to collect the droplets after collision. There are two fixing parts (2.8), which are square metal parts with multiple threaded through holes. They are all welded to the pressure chamber (2.1) and have high structural strength. The Z-axis position is higher than the upper part of the observation window.
9. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The gas phase environment is changed by changing the gas composition and pressure in the pressure chamber module (2); the droplet type is changed by changing the liquid in the metal syringe (3.2.5); the droplet velocity is changed by changing the Z-axis position of the droplet generator (3.2); and the droplet size is changed by changing the diameter of the needle (3.2.8). The collision eccentricity is achieved by precisely adjusting the distance from the tip of the droplet generator needle (3.2.8) to the laser. That is, the distance from the needle to the laser is zero when there is a collision, and the distance is increased when there is eccentricity.
10. The experimental apparatus for controlling the unidirectional collision of two droplets as described in claim 1, characterized in that: The laser selected is a high-brightness, thin, straight green laser; the thickness of the fixing component is ≥20mm.