Device for researching wall surface impact vibration law of liquid drops and method for obtaining parameters

Abstract

The invention discloses a device for researching a wall surface impact vibration rule of liquid drops. The device comprises a substrate optical platform, a lifting assembly, a liquid drop generation assembly, a vibration experiment table assembly, an image acquisition assembly and a data post-processing assembly, the lifting assembly is installed on the substrate optical platform and controls the falling speed of liquid drops. The liquid drop generation assembly is located at the central position above the vibration experiment assembly and is used for generating liquid drops impacting the vibration wall surface; the vibration experiment table assembly is used for controlling the wall surface to vibrate; the image acquisition assembly is used for observing the dynamic process of the liquid drop impacting the vibration wall surface in real time; and the data post-processing assembly is used for processing the acquired image and obtaining related parameters. The device provided by the invention observes the dynamic process that the liquid drop impacts the vibration wall surface, and provides a basis for the relationship between the dynamic characteristics of the liquid drop and the vibration parameters.

Description

Technical Field

[0001] The present invention belongs to the field of fluid mechanics and relates to a device for studying the law of droplet impact on a vibrating wall surface and a method for obtaining parameters therefrom. Background Art

[0002] The interaction between droplets and solid surfaces is a complex and important physical process that widely exists in nature and industrial production, such as spray cooling, minimum quantity lubrication, pesticide spraying, inkjet printing, etc. In recent years, with the rapid development of fields such as micro-nano technology and biomedical engineering, it has become particularly important to deeply understand the interaction mechanism between droplets and vibrating surfaces. Especially when the wall surface is in a vibrating state, the impact behavior of droplets will be significantly affected, showing more complex and diverse characteristics. Therefore, in-depth experimental research on the dynamic behavior of droplets impacting vibrating wall surfaces at different phases helps to reveal the physical mechanism of the interaction between droplets and vibrating wall surfaces, providing new ideas and a basis for theoretical research and technological applications in related fields.

[0003] Chinese Patent CN220780380 (publication date: April 16, 2024) discloses a droplet vibration device that uses a microfluidic chip and a signal generating device to achieve droplet vibration, where the electrodes in the microfluidic chip are of a left-right structure. Chinese Patent CN213684208 U (publication date: July 13,

[0003] 2021) discloses a fragmentation and atomization device for droplets impacting an ultrasonic vibrating wall surface. The disadvantages of the above two patents are as follows: First, only specific vibration devices or fragmentation and atomization devices are provided, and the entire experimental device is not disclosed. Second, a method for processing and analyzing the collected data images is not provided, especially a method for calculating parameters such as the collision phase angle based on sine signals and through high-speed photography technology.

[0004] The experimental device for droplets impacting vibrating wall surfaces and the method for post-processing the collected data are of great significance for industrial production and aerospace: For example, in an internal combustion engine using direct injection technology, fuel is sprayed into the cylinder in the form of droplets and will impact wall surfaces such as the top surface of the piston, and the wall surface will vibrate during the operation of the engine; for example, when an aircraft is flying in a high-altitude low-temperature environment, supercooled droplets will impact vibrating wall surfaces such as the intake duct and the fuselage surface of the moving aircraft, which will affect the safety of the aircraft. Therefore, there is an urgent need for an experimental device for droplets impacting vibrating wall surfaces and a method for analyzing droplet dynamics data throughout the process. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a device for studying the law of droplet impact on a vibrating wall surface, which is used to observe the dynamic process of droplet impact on the vibrating wall surface and provide a basis for the relationship between the dynamic characteristics of the droplet and the vibration parameters. At the same time, the present invention also provides a method for obtaining kinetic parameters based on this device, from which dynamic characteristic parameters such as droplet collision phase angle, droplet spreading time, maximum spreading factor, oscillation stabilization time, and maximum oscillation height factor can be obtained.

[0006] A device for studying the law of droplet impact on a vibrating wall surface according to the present invention includes a base optical platform, a lifting assembly, a droplet generation assembly, a vibration test bench assembly, an image acquisition assembly, and a data post-processing assembly; the lifting assembly is installed on the base optical platform and is used to adjust the falling height required by the droplet generation assembly to control the falling speed of the droplet; the droplet generation assembly is located at the upper center position of the vibration test assembly and is used to generate droplets that impact the vibrating wall surface; the vibration test bench assembly is arranged on the base optical platform and is used to control the vibration of the wall surface impacted by the droplet; the image acquisition assembly is used to observe the dynamic process of droplet impact on the vibrating wall surface in real time; the data post-processing assembly is used to process the acquired images and obtain relevant parameters.

[0007] Further, the lifting assembly includes a stepping motor and a lifting device, and the droplet generation assembly includes a micro-flow injection pump, a syringe, and an injection pump controller; the lifting frame is installed on the base optical platform, and the stepping motor is fixed at the top of the lifting device; the micro-flow injection pump is connected to the sliding seat of the lifting device, the injection pump controller is fixed on the base optical platform and is connected to the micro-flow injection pump, and the syringe is connected below the micro-flow injection pump.

[0008] Further, the vibration test bench assembly includes a vibration table, a support, an acrylic plate, and a vibration signal generator. The support and the vibration signal generator are both fixed on the base optical platform. The vibration table is placed on the support and is located directly below the syringe. The vibration signal generator is electrically connected to the vibration table, and the acrylic plate is connected to the top of the vibration table.

[0009] Further, the image acquisition assembly includes a background light source, a light source filter screen, a high-speed camera, a height lifting platform, and a hydraulic pump; the hydraulic pump and the height lifting platform are both placed on the base optical platform. The hydraulic pump is connected to the height lifting platform. The high-speed camera is placed on the height lifting platform. The background light source and the light source filter screen are both placed on the base optical platform. The background light source is opposite to the center of the high-speed camera lens, and the light source filter screen is located in front of the background light source. The top of the vibration table is flush with the center of the high-speed camera lens; the data analysis assembly includes a workstation and a data network cable, and the workstation is connected to the high-speed camera through the data network cable.

[0010] A method for obtaining the law parameters of a droplet impacting a vibrating wall surface, and its specific steps are as follows: ①. Add deionized water into the syringe, and discharge the excess gas in the syringe. Install the syringe on the card slot of the micro-droplet injection pump. The micro-droplet injection pump is connected to the sliding seat of the lifting device. By controlling the stepping motor, the micro-injector is moved to a suitable position through the sliding seat; ②. Adjust the illumination intensity and light source mode of the background light source of the high-speed camera, adjust the direction of the background light source and the position of the high-speed camera, and focus on the top of the vibration table; ③. Use the injection pump controller to adjust the feeding amount of the droplets. The micro-droplet injection pump pushes the syringe to generate colliding water droplets. After the droplets reach the required volume, use the injection pump controller to pause the liquid discharge operation; ④. Adjust the optical lifting platform through the hydraulic pump. Observe through the high-speed camera and the image acquisition component, and adjust the focal length of the high-speed camera so that a clear image of the upper end surface of the vibration table appears in the center of the workstation screen; ⑤. Adjust the sine parameters (amplitude, frequency) input by the vibration signal generator so that the upper surface of the vibration table generates vibration, which drives the acrylic plate to vibrate. Then trigger the injection pump controller to generate droplets. During this period, use the high-speed camera to shoot the dynamic process of the droplets impacting the vibrating wall surface, and transmit the captured pictures to the workstation for storage; ⑥. Use the workstation to identify the images collected by the high-speed camera, and obtain the dynamic parameters of the droplets impacting the vibrating wall surface, including the collision phase angle θ of the droplets on the vibration table, the spreading time t 铺 , the maximum spreading factor βmax, the oscillation stabilization time t 稳 , the maximum oscillation height factor hmax.

[0011] Among them, in step ⑤: The specific operation of the vibration signal generator is: select the output mode, the output signal is a sine signal, rotate the left end knob to adjust the input amplitude, and then rotate the right end knob to adjust the input frequency. Connect it to the vibration table through a wire, and the vibration table generates vibration.

[0012] Among them, in step ⑥: To obtain the collision phase angle θ of the droplets, the following steps are included:

[0013] Ⅰ. Record the pixel coordinates of the maximum displacement and minimum displacement of the upper end surface of the vibration table in the vertical direction, which are Ymax and Ymin respectively. Define the pixel coordinate of Ymax as the reference coordinate of the phase angle 90°; Ⅱ. The moment before the droplet impacts the wall surface is defined as the collision moment 0. Record the vertical coordinate Y0 of the upper end surface of the vibration table at this time. Calculate the collision phase angle θ1 preliminarily through the formula: Observe the movement direction of the wall surface to determine the specific range of θ1

[0014] Ⅲ. Record the number of photos n1 at the collision moment 0, record the number of photos n2 when Y0 moves to Ymax, and then use the formula to obtain a more accurate collision phase angle Among them: f 壁is the wall vibration frequency at the top of the shaker controlled by the signal generator, T 壁 is its vibration period, f 相 is the refresh rate of the camera.

[0015] Among them, in step ⑥: Obtaining the spreading time and the maximum spreading factor between the droplet and the wall during the droplet impacting the vibrating wall includes the following steps: Ⅰ. Recording the spreading process of the droplet impacting the vibrating wall, converting the collision video into pictures, and recording the camera refresh rate; Ⅱ. Recording the number of photos n1 at the moment of collision 0, and recording the number of photos n3 at the moment of the maximum spreading diameter of the droplet: Ⅲ. The spreading time t 铺 and the calculation formula of the maximum spreading factor β is as follows: where X1 and X2 are the pixel coordinates in the horizontal axis direction on the left and right boundaries of the droplet in the photo respectively, R is the ratio of the actual length to the pixel length, and D0 is the actual diameter length of the droplet before collision.

[0016] Among them, in step ⑥: Obtaining the oscillation stable time and the maximum oscillation height factor of the droplet on the vibrating wall after the droplet impacts the vibrating wall includes the following steps: Ⅰ. Recording the oscillation process of the droplet impacting the vibrating wall, converting the collision video into pictures, and recording the camera refresh rate; Ⅱ. Calculating the center height of the droplet according to the pixels of the photographed droplet. When the maximum value of the center height of the droplet is basically unchanged within the oscillation period, recording the number of photos n4 when the center height of the droplet first reaches this value; Ⅲ. The oscillation stable time t 稳 and the calculation formula of the maximum oscillation height factor hmax is as follows: where Y x1 and Y x1 are the pixel coordinates in the vertical axis y direction on the left and right boundaries of the droplet in the photo at the bottom of the droplet during the oscillation process of the droplet, Y1 is the result calculated by the midpoint coordinate formula of the two, Y2 is the pixel coordinate of Y1 in the vertical axis y direction, R is the ratio of the actual length to the pixel length, and D0 is the actual diameter length of the collision before the droplet collides.

[0017] The advantages of the device and method of the present invention are as follows: First, the device of the present invention can record the whole process of a droplet impacting a vibrating wall surface, and quantitatively study the dynamic evolution process and phase change process of the droplet morphology when the droplet impacts the vibrating wall surface with different vibration parameters through this device, so as to obtain dynamic parameters such as the collision phase angle, spreading time, maximum spreading factor, oscillation stabilization time, and maximum oscillation height factor of the droplet on the vibrating wall surface, in order to master the mechanism, variation law, and control method of the droplet impacting the vibrating wall surface, etc.; Second, the device of the present invention changes the output signal of the vibration signal generator and the vibration frequency and vibration amplitude of the input sine signal, so as to master the influence of the wall surface on the dynamic characteristics of the droplet under different vibration conditions; Third, the research on the droplet impacting the vibrating wall surface helps to optimize the design of fuel injection components and combustion chambers, make the fuel atomize, mix, and burn better, improve the combustion efficiency, reduce fuel consumption and pollutant emissions; The research on the droplet impacting the vibrating wall surface helps to develop effective anti-icing and de-icing technologies to prevent water droplets from freezing and affecting the aerodynamic shape, flight performance, and safety of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a perspective view of the experimental device for a droplet impacting a vibrating wall surface of the present invention;

[0019] Figure 2 is a front view of the experimental device for a droplet impacting a vibrating wall surface of the present invention;

[0020] Figure 3 is a schematic diagram of the coordinates of the collision position between the droplet and the wall surface;

[0021] Figure 4 is a schematic diagram of the spreading and oscillation of a droplet impacting a vibrating wall surface.

[0022] Wherein: 1 - high-speed camera background light source, 2 - light source filter screen, 3 - lifting device, 4 - stepping motor, 5 - micro-flow injection pump, 6 - syringe, 7 - high-speed camera, 8 - height lifting platform, 9 - hydraulic pump, 10 - workstation, 11 - micro-flow injection pump controller, 12 - vibration table, 13 - bracket, 14 - droplet, 15 - acrylic plate, 16 - vibration signal generator, 17 - base optical platform, 18 - data network cable. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0024] Embodiment 1

[0025] From Figure 1 、 Figure 2It can be seen that a device for studying the law of droplet impact on a vibrating wall surface according to the present invention includes a base optical platform 17, a lifting assembly, a droplet generation assembly, a vibration test bench assembly, an image acquisition assembly, and a data post-processing assembly; the lifting assembly is installed on the base optical platform 17 and is used to adjust the falling height required by the droplet generation assembly to control the falling speed of the droplet; the droplet generation assembly is located at the upper center position of the vibration experiment assembly and is used to generate droplets that impact the vibrating wall surface; the vibration test bench assembly is arranged on the base optical platform 17 and is used to control the vibration of the droplet impacting the wall surface; the image acquisition assembly is used to observe the dynamic process of the droplet impacting the vibrating wall surface in real time; the data post-processing assembly is used to process the acquired images and obtain relevant parameters.

[0026] The device of the present invention can record the whole process of a droplet impacting a vibrating wall surface with different amplitudes, frequencies, and phase angles, and calculate and analyze through the image data recorded by the device to obtain relevant parameters of the droplet collision.

[0027] Embodiment 2

[0028] From Figure 1 、 Figure 2 It can be seen that for the device of the present invention: the lifting assembly includes a stepping motor 4 and a lifting device 3, and the droplet generation assembly includes a micro-flow injection pump 5, a syringe 6, and an injection pump controller 11; the lifting frame 3 is installed on the base optical platform 17, and the stepping motor 4 is fixed at the top of the lifting device 3; the micro-flow injection pump 5 is connected to the sliding seat of the lifting device 3, the injection pump controller 11 is fixed on the base optical platform 17 and is connected to the micro-flow injection pump 5, and the syringe 6 is connected below the micro-flow injection pump 5.

[0029] When the stepping motor 4 works, the micro-injection pump 5 moves up and down with the sliding seat of the lifting device 3 to control the distance from the droplet to the specimen. The distance change range is 0 - 50 cm, and the corresponding droplet speed range is 1 - 2.5 m / s. The injection pump controller 11 controls the moment of droplet impact.

[0030] Embodiment 3

[0031] From [[ID=Z3]] Figure 1 、 Figure 2 It can be seen that for the device of the present invention: the vibration test bench assembly includes a vibration table 12, a bracket 13, an acrylic plate 14, and a vibration signal generator 16. The bracket 13 and the vibration signal generator 15 are both fixed on the base optical platform 17. The vibration table 12 is placed on the bracket 13 and is located directly below the syringe 5. The vibration signal generator 16 is electrically connected to the vibration table 12, and the acrylic plate 14 is connected to the upper surface of the vibration table 12.

[0032] The vibration table 12 receives the vibration signal from the vibration signal generator 16, and the upper surface of the vibration table 12 drives the acrylic plate 14 to displace according to the vibration signal such as amplitude and frequency, so that the liquid droplets impact the wall surface of the vibrating acrylic plate 14 to obtain relevant data.

[0033] Example 4

[0034] From Figure 1 、 Figure 2 It can be seen that for the device of the present invention: the image acquisition component includes a background light source 1, a light source filter screen 2, a high-speed camera 7, a height lifting platform 8, and a hydraulic pump 9; the hydraulic pump 9 and the height lifting platform 8 are both placed on the base optical platform 17, the hydraulic pump 9 is connected to the height lifting platform 8, the high-speed camera 7 is placed on the height lifting platform 8, the background light source 1 and the light source filter screen 2 are both placed on the base optical platform 17, the background light source 1 is opposite to the center of the lens of the high-speed camera 7, the light source filter screen 2 is located in front of the background light source 1, and the top of the vibration table 12 is flush with the center of the lens of the high-speed camera 7; the data analysis component includes a workstation 10 and a data network cable 18, and the workstation 10 is connected to the high-speed camera 7 through the data network cable 18.

[0035] Adjust the height lifting platform 8 so that the center of the lens of the high-speed camera 7 is flush with the top of the vibration table 12. After the image of the vibration table 12 is completely displayed in the center of the screen of the workstation 10, then adjust the focal length of the high-speed camera 7 so that a clear image of the vibration table 12 can be observed in the center of the screen of the workstation 10.

[0036] The refresh rate of the high-speed camera 7 is 1000 frames per second, and the resolution of the acquisition window is 1240x1280. It is used to observe the initial collision phase of the liquid droplets impacting the vibrating surface, the movement change of the liquid droplets hitting the wall, the spreading of the liquid droplets, and the oscillation behavior of the liquid droplets, and completely and detailedly record the dynamic process of the liquid droplets impacting the vibrating wall surface and spreading, retracting, and oscillating on the wall surface; after the high-speed camera 7 takes the photos, they are imported into the workstation 10 through the data network cable 18. In the workstation 10, use the pictures to observe the morphological dynamic evolution process and phase change process of the liquid droplets impacting the vibrating wall surface with different vibration parameters, and obtain dynamic parameters such as the collision phase of the liquid droplets on the vibrating wall surface.

[0037] Example 5

[0038] For the device of the present invention: the liquid droplet material in the syringe 6 is deionized water.

[0039] Example 6

[0040] A method for obtaining the law parameters of a droplet impacting a vibrating wall surface according to the present invention, and the specific steps are as follows: ①. Add deionized water into the syringe, and discharge the excess gas in the syringe. Install the syringe on the card slot of the micro-droplet injection pump, and the micro-droplet injection pump is connected to the sliding seat of the lifting device. By controlling the stepping motor, the micro-syringe is moved to a suitable position through the sliding seat; ②. Adjust the illumination intensity and light source mode of the background light source of the high-speed camera, adjust the direction of the background light source and the position of the high-speed camera, and focus on the top of the vibration table; ③. Use the injection pump controller to adjust the feeding amount of the droplets. The micro-droplet injection pump pushes the syringe to generate collision water droplets. After the droplets reach the required volume, use the injection pump controller to pause the liquid discharging operation; ④. Adjust the optical lifting platform through the hydraulic pump. Observe through the high-speed camera and the image acquisition component, and adjust the focal length of the high-speed camera so that a clear picture of the upper end surface of the vibration table appears in the center of the workstation screen; ⑤. Adjust the sine parameters (amplitude, frequency) input by the vibration signal generator so that the upper surface of the vibration table generates vibration, thereby driving the acrylic plate to vibrate, and then trigger the injection pump controller to generate droplets. During this period, use the high-speed camera to shoot the dynamic process of the droplet impacting the vibrating wall surface, and transmit the captured pictures to the workstation for storage; ⑥. Use the workstation to identify the images collected by the high-speed camera, and obtain the dynamic parameters of the droplet impacting the vibrating wall surface, including the collision phase angle θ of the droplet on the vibration table, the spreading time t 铺 ., the maximum spreading factor βmax, the oscillation stabilization time t 稳 ., and the maximum oscillation height factor hmax.

[0041] Example 7

[0042] The method of the present invention: In step ⑤: The specific operation of the vibration signal generator is as follows: Select the output mode, the output signal is a sine signal, rotate the left end knob to adjust the input amplitude, and then rotate the right end knob to adjust the input frequency. Connect to the vibration table through the wire, and the vibration table generates vibration.

[0043] Example 8

[0044] The method of the present invention: In step ⑥: Obtaining the collision phase angle θ of the droplet includes the following steps: As Figure 3 shown, Ⅰ. Record the pixel coordinates of the maximum displacement and the minimum displacement of the upper end surface of the vibration table in the vertical direction, which are Ymax and Ymin respectively. Define the pixel coordinate of Ymax as the reference coordinate of the phase angle 90°; Ⅱ. The moment before the droplet impacts the wall surface is regarded as the collision moment 0, and record the vertical coordinate Y0 of the upper end surface of the vibration table at this time. Calculate the collision phase angle θ1 preliminarily through the formula: Observe the movement direction of the wall surface to determine the specific range of θ1,

[0045] Ⅲ. Record the number of photos \(n_1\) at the moment of collision \(0\), record the number of photos \(n_2\) when \(Y_0\) moves to \(Y_{max}\), and then use the formula to obtain a more accurate collision phase angle \(\theta_2\).

[0046] T 壁 = 1 / f 壁

[0047]

[0048] where: f 壁 is the vibration frequency of the wall surface at the top of the vibration table controlled by the signal generator, T 壁 is its vibration period, and f 相 is the frame rate of the camera.

[0049] Example 9

[0050] The method of the present invention: In step ⑥: Obtain the spreading time and the maximum spreading factor between the droplet and the wall surface during the process of the droplet impacting the vibrating wall surface, including the following steps: Ⅰ. Record the spreading process of the droplet impacting the vibrating wall surface, convert the collision video into pictures, and record the frame rate of the camera; Ⅱ. Record the number of photos \(n_1\) at the moment of collision \(0\), and record the number of photos \(n_3\) when the droplet reaches the maximum spreading diameter (as shown in the left figure below); Ⅲ. The spreading time \(t\) Figure 4 and the calculation formulas for the maximum spreading factor \(\beta\) are as follows: 铺

[0051] β max =(X2 - X1)*R / D0

[0052] t 铺 [[ID=3S]]=(n3 - n1) / f 相

[0053] where \(X_1\) and \(X_2\) are the pixel coordinates in the horizontal axis direction on the left and right boundaries of the droplet in the photo respectively, \(R\) is the ratio of the actual length to the pixel length, and \(D_0\) is the actual diameter length of the droplet before collision.

[0054] Example 10

[0055] The method of the present invention: In step ⑥: Obtain the oscillation stabilization time and the maximum oscillation height factor of the droplet on the vibrating wall surface after the droplet impacts the vibrating wall surface, including the following steps: Ⅰ. Record the oscillation process of the droplet impacting the vibrating wall surface, convert the collision video into pictures, and record the frame rate of the camera; Ⅱ. Calculate the height of the droplet center according to the pixels of the captured droplet. When the maximum value of the center height of the droplet remains basically unchanged within the oscillation period (as shown in the right figure below), record the number of photos \(n_4\) when the center height of the droplet first reaches this value; Ⅲ. The oscillation stabilization time \(t\) Figure 4 and the calculation formulas for the maximum oscillation height factor \(h_{max}\) are as follows: 稳

[0056] ​Y1 = (Y x1 + Y x2 ) / 2

[0057] h max = (Y2 - Y1) * R / D0

[0058] t 稳 = (n4 - n1) / f 相

[0059] where Y x1 , Y x1 are the pixel coordinates in the y-axis direction of the left and right boundaries of the droplet in the bottom photo of the droplet during the oscillation process. Y1 is the result calculated by the midpoint coordinate formula for the two, Y2 is the pixel coordinate of Y1 in the y-axis direction, R is the ratio of the actual length to the pixel length, and D0 is the actual diameter length of the collision before the droplet collision.

[0060] The advantages of the device and method of the present invention are as follows: First, the device of the present invention can record the whole process of the droplet impacting the vibrating wall surface, and quantitatively study the dynamic evolution process and phase change process of the droplet morphology when the droplet impacts the vibrating wall surface with different vibration parameters through this device, and obtain dynamic parameters such as the collision phase angle, spreading time, maximum spreading factor, oscillation stable time, and maximum oscillation height factor of the droplet on the vibrating wall surface, so as to master the mechanism, change law, and control method of the droplet impacting the vibrating wall surface, etc.; Second, the device of the present invention changes the output signal of the vibration signal generator and changes the vibration frequency and vibration amplitude of the input sine signal, so as to master the influence of the wall surface on the dynamic characteristics of the droplet under different vibration conditions; Third, the research on the droplet impacting the vibrating wall surface helps to optimize the design of the fuel injection component and the combustion chamber, make the fuel better atomized, mixed, and burned, improve the combustion efficiency, reduce fuel consumption and pollutant emissions; the research on the droplet impacting the vibrating wall surface helps to develop effective anti-icing and de-icing technologies to prevent water droplets from freezing and affecting the aerodynamic shape, flight performance, and safety of the aircraft.

[0061] In summary, the present invention can record the dynamic change process of the droplet impacting the vibrating wall surface, collect and obtain a series of kinematic parameters, thereby mastering the physical mechanism of the interaction between the droplet and the vibrating wall surface, and enabling the obtained impact law to be applied in actual production and processing, and providing technical support for the key to solving practical problems in the fields of energy, aviation, medical treatment, etc., so as to improve the equipment performance, safety, and energy utilization efficiency.

Claims

1. An apparatus for studying the law of droplet impinging on a vibrating wall, characterized in that: It includes a base optical platform (17), a lifting component, a droplet generation component, a vibration test bench component, an image acquisition component, and a data post-processing component; the lifting component is installed on the base optical platform (17) and is used to adjust the falling height required by the droplet generation component to control the falling speed of the droplets; the droplet generation component is located at the upper central position of the vibration experiment component and is used to generate droplets that impact the vibrating wall surface; the vibration test bench component is arranged on the base optical platform (17) and is used to control the vibration of the wall surface impacted by the droplets; the image acquisition component is used to observe the dynamic process of the droplets impacting the vibrating wall surface in real time; the data post-processing component is used to process the acquired images and obtain relevant parameters.

2. The device according to claim 1, characterized in that: The lifting component includes a stepping motor (4) and a lifting device (3), and the droplet generation component includes a micro-flow injection pump (5), a syringe (6), and an injection pump controller (11); the lifting frame (3) is installed on the base optical platform (17), and the stepping motor (4) is fixed at the top of the lifting device (3); the micro-flow injection pump (5) is connected to the sliding seat of the lifting device (3), the injection pump controller (11) is fixed on the base optical platform (17) and is connected to the micro-flow injection pump (5), and the syringe (6) is connected below the micro-flow injection pump (5).

3. The device according to claim 1, characterized in that: The vibration test bench component includes a vibration table (12), a bracket (13), an acrylic plate (14), and a vibration signal generator (16). The bracket (13) and the vibration signal generator (15) are both fixed on the base optical platform (17). The vibration table (12) is placed on the bracket (13) and is located directly below the syringe (5). The vibration signal generator (16) is electrically connected to the vibration table (12), and the acrylic plate (14) is connected to the upper surface of the vibration table (12).

4. The device according to claim 1, characterized in that: The image acquisition component includes a background light source (1), a light source filter screen (2), a high-speed camera (7), a height lifting platform (8), and a hydraulic pump (9); the hydraulic pump (9) and the height lifting platform (8) are both placed on the base optical platform (17). The hydraulic pump (9) is connected to the height lifting platform (8). The high-speed camera (7) is placed on the height lifting platform (8). The background light source (1) and the light source filter screen (2) are both placed on the base optical platform (17). The background light source (1) is opposite to the center of the lens of the high-speed camera (7). The light source filter screen (2) is located in front of the background light source (1). The top of the vibration table (12) is flush with the center of the lens of the high-speed camera (7); the data analysis component includes a workstation (10) and a data network cable (18). The workstation (10) is connected to the high-speed camera (7) through the data network cable (18).

5. A method for obtaining the law parameters of a droplet impinging on a vibrating wall surface, and the specific steps are as follows: ①. Add deionized water into the syringe, and discharge the excess gas in the syringe. Install the syringe on the card slot of the micro-droplet injection pump, and the micro-droplet injection pump is connected to the sliding seat of the lifting device. Control the stepping motor to move the micro-syringe to a suitable position through the sliding seat; ②. Adjust the illumination intensity and light source mode of the background light source of the high-speed camera, adjust the direction of the background light source and the position of the high-speed camera, and focus on the top of the vibration table; ③. Use the injection pump controller to adjust the feed rate of the droplets. The micro-droplet injection pump pushes the syringe to generate collision water droplets. After the droplets reach the required volume, use the injection pump controller to pause the liquid discharge operation; ④. Adjust the optical lifting platform through the hydraulic pump. Observe through the high-speed camera and the image acquisition component, and adjust the focal length of the high-speed camera so that a clear image of the upper end surface of the vibration table appears in the center of the workstation screen; ⑤. Adjust the sine parameters (amplitude, frequency) input by the vibration signal generator so that the upper surface of the vibration table generates vibration, which drives the acrylic plate to vibrate, and then trigger the injection pump controller to generate droplets. During this period, use the high-speed camera to shoot the dynamic process of the droplets impinging on the vibrating wall surface, and transmit the captured pictures to the workstation for storage; ⑥. Use the workstation to identify the images collected by the high-speed camera, and obtain the dynamic parameters of the droplets impinging on the vibrating wall surface, including the collision phase angle θ of the droplets on the vibration table, the spreading time t 铺 , the maximum spreading factor βmax, the oscillation stabilization time t 稳 , the maximum oscillation height factor hmax.

6. The method according to claim 5, wherein in step ⑤: the specific operation of the vibration signal generator is as follows: select the output mode, the output signal is a sine signal, rotate the left-end knob to adjust the input amplitude, and then rotate the right-end knob to adjust the input frequency. Connect it to the vibration table through a wire, and the vibration table generates vibration.

7. The method according to claim 5, wherein in step ⑥: obtaining the collision phase angle θ of the droplet includes the following steps: Ⅰ. Record the pixel coordinates of the maximum displacement and the minimum displacement of the upper end face of the shaker in the vertical direction, which are Ymax and Ymin respectively, and define the pixel coordinates of Ymax as the reference coordinates of the phase angle 90°. Ⅱ. Take the moment immediately before the droplet impacts the wall as the collision time 0, record the vertical coordinate Y0 of the upper end face of the shaker at this time, and preliminarily calculate the collision phase angle θ1 through the formula: Observe the movement direction of the wall surface to determine the specific range of θ1. Ⅲ. Record the number of photos n1 at the collision time 0, record the number of photos n2 when Y0 moves to Ymax, and then use the formula to obtain a more accurate collision phase angle θ2. where: f 壁 is the wall vibration frequency at the top of the vibration table controlled by the signal generator, T 壁 is its vibration period, f 相 is the refresh rate of the camera.

8. The method according to claim 5, Its characteristics are as follows: In step ⑥: Obtaining the spreading time and the maximum spreading factor between the droplet and the wall during the process of the droplet impacting the vibrating wall, including the following steps: Ⅰ. Recording the spreading process of the droplet impacting the vibrating wall, converting the collision video into pictures, and recording the camera refresh rate; Ⅱ. Recording the number of photos n1 at the moment of collision 0, and recording the number of photos n3 at the moment of the maximum spreading diameter of the droplet; Ⅲ. The spreading time t 铺 , and the calculation formulas for the maximum spreading factor β are as follows: where X1 and X2 are the pixel coordinates in the horizontal axis direction on the left and right boundaries of the droplet in the photo respectively, R is the ratio of the actual length to the pixel length, and D0 is the actual diameter length of the droplet before collision.

9. The method according to claim 5, Its characteristics are as follows: In step ⑥: Obtaining the oscillation stable time and the maximum oscillation height factor of the droplet on the vibrating wall surface after the droplet impacts the vibrating wall surface, including the following steps: Ⅰ. Recording the oscillation process of the droplet impacting the vibrating wall surface, converting the collision video into pictures, and recording the camera refresh rate; Ⅱ. Calculating the center height of the droplet according to the pixels of the photographed droplet. When the maximum value of the center height of the droplet remains basically unchanged within the oscillation period, recording the number of photos n4 when the center height of the droplet first reaches this value; Ⅲ. The oscillation stable time t 稳 , and the calculation formula for the maximum oscillation height factor hmax is as follows: Among them, Y x1 , Y x1 are the pixel coordinates in the y-axis direction on the left and right boundaries of the droplet in the bottom photo of the droplet during the oscillation process. Y1 is the result calculated by the midpoint coordinate formula for the two, Y2 is the pixel coordinate of Y1 in the y-axis direction, R is the ratio of the actual length to the pixel length, and D0 is the actual collision diameter length of the droplet before collision.

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