System and method for observing bubble motion characteristics

Abstract

The invention provides an observation system for bubble motion characteristics. The observation system comprises an experiment water tank; the gas power generation device is used for pumping gas under different power conditions into the experimental water tank to form bubbles, and the gas power generation device is provided with a gas incidence section extending below the liquid level in the experimental water tank; the observation device comprises a camera platform, a continuous laser and a light uniformizing plate, the camera platform comprises a plurality of side high-speed cameras arranged in an array mode and an upper high-speed camera located above a gas incidence section, and the gas incidence section should be located in an observation area of the camera platform; and the data acquisition and control unit is used for controlling the observation device and pre-processing and analyzing the obtained original data to obtain bubble motion characteristics under different experiment conditions, interaction between bubbles caused by bubble motion and influence of the bubble motion on the flow field. According to the invention, the whole process of bubble generation, development, maturation and formation of a boil-vortex structure on the water surface can be observed.

Description

Technical Field

[0001] The invention belongs to the technical field of gas-liquid two-phase flow measurement, and in particular relates to an observation system and method for bubble motion characteristics. Background Art

[0002] Two-phase flow observation has always been one of the important research contents in fluid dynamics. The behavior characteristics of bubbles and the liquid flow field movement caused by them are of great significance to production and life. The study of the process mechanism of bubbles from the initial development stage to the final breakup at the gas-liquid interface has always been one of the hot topics of relevant researchers. With the continuous development of measurement technology, the two-phase flow motion characteristics of bubbles at different development stages have been widely observed, which has greatly improved the theoretical development level and practical application field of two-phase flow. However, the observation of two-phase flow is often only focused on a certain section. The overall observation and research on the motion characteristics of bubbles from the development of liquid to the arrival of the gas-liquid interface and even the formation of bubble vortexes on the water surface is still insufficient. The continuous movement of bubbles still requires detailed observation data to clarify the gas-liquid two-phase flow motion mechanism. The observation of bubble motion characteristics at different development stages, the interaction between bubbles, and the interaction between bubbles and water bodies have all been improved. Summary of the invention

[0003] The present invention aims to solve, at least to some extent, one of the technical problems of insufficient observation of bubble motion characteristics.

[0004] To this end, the present invention provides a bubble motion characteristics observation system and method, which can observe the entire process of bubble generation, development, maturation to the formation of bubble vortex structure on the water surface, and enhance the understanding and analysis of gas-liquid motion characteristics and interactions at each stage.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a bubble motion characteristic observation system, comprising:

[0007] The experimental water tank is a transparent box with an open top and filled with liquid;

[0008] A gas power generating device, used for pumping gas with different power conditions into the experimental water tank to form bubbles, the gas power generating device having a gas incident section extending below the liquid surface in the experimental water tank, the gas incident section consisting of an air pipe with a bent section and an injection needle located at the end of the bent section of the air pipe;

[0009] An observation device, comprising a camera platform, a continuous laser and a homogenizing plate; the camera platform comprises a plurality of side high-speed cameras arranged in an array on one side of the outside of the experimental water tank and an upper high-speed camera located above the gas incident section, the gas incident section of the gas power generating device should be within the observation area of ​​the camera platform, and the original data of the bubble movement and flow field movement at each stage in the experimental water tank are continuously obtained through the camera platform; the continuous laser emitted by the continuous laser should cover the entire vertical plane where the bubble movement is located, providing a light source for the observation of the flow field movement caused by the bubble movement; the homogenizing plate is located on the periphery of the experimental water tank, and is used to provide a stable and uniform light source for the camera platform;

[0010] The data acquisition and control unit is used to control the observation device and pre-process and analyze the raw data obtained by the observation device to obtain the bubble movement characteristics under different experimental conditions, the interaction between bubbles caused by bubble movement, and the influence of bubble movement on the flow field.

[0011] In some embodiments, the gas power generating device includes an air compressor, an air filter, a gas storage tank, a digital gas mass flow meter and the gas incident section which are connected in sequence through a gas pipeline, and the top of the gas incident section is installed on a three-axis gantry platform.

[0012] In some embodiments, the gas power generating device is equipped with digital gas mass flow meters with different ranges for providing gas under different power conditions.

[0013] In some embodiments, the observation system is equipped with a plurality of air tubes with different bending angles for studying the rising efficiency of bubble movement under different incident angles, the bending angle of the air tube is α, α∈(0,90°], and the positions of the bending sections of the air tubes with different bending angles should satisfy the position of the bubble generating end in the experimental water tank remains unchanged; the observation system is equipped with a plurality of injection needles with different apertures for analyzing the bubble movement characteristics under different incident apertures.

[0014] In some embodiments, the bending angle of the trachea is set to 15°, 30°, 45°, 60°, 75°, 90°, and the aperture of the injection needle is set to 0.1 mm-5 mm.

[0015] In some embodiments, the observation device also includes a camera mounting platform, which includes a frame composed of an aluminum alloy profile and a plurality of camera mounting positions mounted on the frame, each camera mounting position respectively includes a connected optical plate and a three-axis motion platform, each high-speed camera is mounted on a corresponding three-axis motion platform, and the optical plate is used to keep the observation planes of each side high-speed camera consistent in the horizontal direction.

[0016] In some embodiments, the observation device is equipped with two light averaging plates, the first light averaging plate is located on the other side of the outside of the experimental water tank opposite to the side high-speed camera, and the second light averaging plate is located near the upper high-speed camera.

[0017] In some embodiments, the data acquisition and control unit includes a computer, a switch and a synchronizer, and the computer is loaded with a camera data acquisition module and a data processing module; each high-speed camera is connected to the computer through the switch, and communication is achieved through a local area network constructed by Ethernet; the computer controls the observation frequency of each high-speed camera through the synchronizer to achieve simultaneous and same-frequency observation of each high-speed camera, and controls the opening and closing time of the homogenizing plate and the continuous laser; the camera data acquisition module is used to set the camera's acquisition parameters, including acquisition frame, number of acquisitions, exposure conditions and image storage location; the data processing module is used to pre-process the raw data observed by the camera platform, and then use a pre-trained deep learning model to detect bubbles in gas-liquid two-phase flow, so as to obtain the bubble motion characteristics under different experimental conditions, the interaction between bubbles caused by bubble motion, and the influence of bubble motion on the flow field.

[0018] In some embodiments, according to different gas incident dynamics, the computer assigns different observation frequencies to the camera platform through the synchronizer;

[0019] In one working cycle, the computer uses the synchronizer to shoot the first frame image with the homogenizing plate as the light source, so as to analyze the movement characteristics of the bubbles; the computer uses the synchronizer to shoot the second frame image under the irradiation of the continuous laser, so as to analyze the movement characteristics of the flow field under the influence of the bubbles, thereby realizing the synchronous measurement of the bubble movement and the liquid flow field.

[0020] The second aspect of the present invention provides an observation method based on the observation system described in any embodiment of the first aspect of the present invention, comprising the following steps:

[0021] Step 1: determine the test section of the experimental water tank to be observed, place a camera mounting platform for carrying a camera platform at an appropriate position near the experimental water tank, and connect a side high-speed camera for observing the vertical movement characteristics of bubbles to the camera mounting platform;

[0022] Step 2: Build the pneumatic generating device and set the initial conditions of bubble movement. Place the gas incident section into the center of the experimental water tank through a three-axis gantry platform installed above the experimental water tank, and place it within the observation area of ​​the side high-speed camera. Then, place the upper high-speed camera for observing the bubble vortex movement characteristics at an appropriate position above the injection needle through a camera installation platform.

[0023] Step 3: connect all high-speed cameras in the camera platform to the data acquisition and control unit, use the calibration board to focus each high-speed camera and determine the observation range of each high-speed camera;

[0024] Step 4: Set up the light homogenizing plate and the continuous laser, and connect them to the data acquisition and control unit;

[0025] Step 5: triggering the high-speed cameras in the camera platform to take pictures at the same time and frequency through the data acquisition and control unit, and obtaining the original data of the bubble movement and flow field movement of a sufficient number of bubbles in the liquid from generation, development, and maturation to the formation of a bubble vortex structure on the water surface according to the initial conditions of the bubble movement set in step 2;

[0026] Step 6: Based on the original data obtained in step 5, the data acquisition and control unit is used to analyze the bubble motion characteristics under different experimental conditions, the interaction between bubbles caused by the bubble motion, and the influence of the bubble motion on the flow field.

[0027] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0028] The present invention uses a mature digital gas mass flowmeter on the market to accurately adjust the pneumatic flow rate, ensuring the precise control and repeatability of the initial conditions of the observation indicators; an array-type synchronous measurement system established by multiple high-speed cameras can observe and characterize the movement characteristics of the gas-liquid two-phase flow in different bubble rising stages in detail and accurately; the high-speed camera arranged just above the water tank captures the bubble vortex effect caused by different initial conditions, which can be used to establish the correlation between the initial development of bubbles and the bubble vortex on the water surface. In general, the present invention has intuitive observation objects, complete observation elements, high experimental efficiency, strong scalability, operability and repeatability, and strong use prospects and scientific research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of an observation system for bubble motion characteristics provided by an embodiment of the first aspect of the present invention;

[0030] Figure 2 The second aspect of the present invention provides an embodiment based on Figure 1 A flow chart of the observation method of the observation system shown;

[0031] Figure 3 is to use Figure 1 A diagram showing some of the observation results obtained by the observation system shown.

[0032] In the figure:

[0033] 1. Experimental water tank;

[0034] 21. Trachea; 22. Injection needle; 23. Air compressor; 24. Gas storage tank; 25. Air filter; 26. Digital gas mass flow meter;

[0035] 31. Side high-speed camera; 32. Upper high-speed camera; 33. First light averaging plate; 34. Second light averaging plate;

[0036] 4. Data acquisition and control unit. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0038] On the contrary, the present application covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present application as defined by the claims. Further, in order to make the public have a better understanding of the present application, some specific details are described in detail in the detailed description of the present application below. Those skilled in the art can fully understand the present application without the description of these details.

[0039] The first aspect of the present invention provides an observation system for bubble motion characteristics, which can realize the observation of the size, position, shape, speed, etc. of bubbles in the whole process of gas-liquid two-phase flow under aerodynamic conditions from the initial stage to the water surface, and realizes the measurement of the liquid phase flow field structure under the influence of aerodynamics, and can also realize accurate measurement of the bubble vortex structure above the water surface. The following is a detailed description in conjunction with the accompanying drawings and specific embodiments.

[0040] See also Figure 1 , a bubble motion characteristic observation system provided by an embodiment of the first aspect of the present invention comprises:

[0041] The experimental water tank 1 is a transparent box with an open top, and the box is filled with liquid;

[0042] A gas power generating device is used to pump gases with different power conditions into the experimental water tank 1 to form bubbles. The gas power generating device has a gas incident section extending below the liquid level in the experimental water tank 1. The gas incident section is composed of a gas pipe 21 with a bent section and an injection needle 22 located at the end of the bent section of the gas pipe 21;

[0043] The observation device includes a camera platform, a continuous laser (the continuous laser is not shown in the figure) and a light scattering plate; the camera platform includes a plurality of side high-speed cameras 31 arranged in an array on one side of the experimental water tank 1 and an upper high-speed camera 32 located above the gas incident section. The gas incident section of the gas power generating device should be within the observation area of ​​the camera platform, and the original data of the bubble movement and flow field movement at each stage in the experimental water tank 1 are continuously obtained through the camera platform; the continuous laser emitted by the continuous laser should cover the entire vertical plane where the bubble movement is located, so as to provide a light source for the observation of the flow field movement caused by the bubble movement; the light scattering plate is located on the periphery of the experimental water tank 1, and is used to provide a stable and uniform light source for the camera platform;

[0044] The data acquisition and control unit 4 is used to control the observation device and pre-process and analyze the raw data obtained by the observation device to obtain the bubble movement characteristics under different experimental conditions, the interaction between bubbles caused by bubble movement, and the influence of bubble movement on the flow field.

[0045] In some embodiments, the experimental water tank 1 is a transparent box with an open top, 1.0 m high, 0.8 m wide, and 6.0 m long, which ensures that the floating process of bubbles after entering the liquid is fully developed, and also avoids the interference of the water tank wall on the water surface bubble vortex and even the underwater bubble movement and liquid flow field movement. The liquid filled in the experimental water tank 1 is water or other transparent liquid. In addition, liquids of different depths can be set according to experimental conditions to explore the influence of water depth on the movement of bubbles in the liquid and the movement of the liquid flow field.

[0046] In some embodiments, the gas power generating device includes an air compressor 23, an air filter 25, a gas storage tank 24, a digital gas mass flow meter 26 and a gas incident section which are sequentially connected through a gas pipeline. Among them, the air compressor 23 and the gas storage tank 24 constitute a pneumatic supply device, which ensures the stability and uniformity of the input airflow; the air filter 25 is used to filter impurities such as oil and water in the output airflow of the air compressor 23 to ensure the cleanliness of the observed air, and at the same time plays a role in stabilizing the pressure, ensuring the stability and repeatability of the experiment; the digital gas mass flow meter 26 is used to accurately control the gas power size of the liquid input into the experimental water tank 1 (the gas flow rate can be used to measure the gas power size of the liquid entering the experimental water tank), which ensures the operability and repeatability of the observation system of this embodiment, and adds The credibility of the gas-liquid two-phase flow observation data is enhanced; in the gas incident section, the air pipe 21 and the injection needle 22 are connected by an air pipe adapter of the same size, and are wrapped with raw tape to ensure airtightness; in this embodiment, a plurality of air pipes 21 with different bending angles are provided, and the adjustment of the gas incident angle is achieved by selecting the air pipes 21 with corresponding bending angles, which is used to study the rising efficiency of bubble movement under different incident angles, and the top of the air pipe 21, that is, the top of the gas incident section, is installed on a three-axis gantry platform, and the three-axis gantry platform is used to facilitate the adjustment of the gas incident section and the experimental water tank 1 The relative position between them is adjusted to adjust the observation position. The gas incident section is placed in the center of the experimental water tank 1 in the span direction and is within the observation area of ​​the camera platform. The material of the air pipe 21 should be smooth enough and airtight. A stainless steel conduit is preferably used. The air pipe 21 consists of a vertical section and a bending section at its end. The angle α between the extension line of the vertical section and the bending section is the bending angle of the air pipe 21, α∈(0,90°], and the bending section positions of the air pipes 21 with different bending angles are different to ensure that the position of the bubble generating end in the experimental water tank 1 remains unchanged and the stability of the experimental equipment is ensured. ; In this embodiment, the end of the injection needle 22 equipped with different apertures is used as the bubble generating end, which is used to analyze the bubble movement characteristics under different incident apertures. Since the surface area of ​​the needle is significantly smaller than that of the common nozzle, at a certain inclination angle, the bubble generation and floating stages will not be affected by the nozzle edge profile. Therefore, compared with the commonly used nozzles, the injection needle 22 reduces the influence of the bubble generating device on the initial shape of the bubble; the position of the needle end from the bottom of the experimental water tank 1 can be set to 10cm, 20cm, 30cm, etc., which is used to analyze the bubble movement characteristics under different pressures.

[0047] Optionally, the maximum gas power that the air compressor 23 can provide is 0.8Mpa, which can meet the laboratory gas power requirements; the digital gas mass flowmeter 26 can adopt two ranges of 0-1L / min and 0-25L / min, which are used to observe the bubble movement characteristics under trace power and high power respectively, and realize the study of the bubble's own movement and the interaction between bubbles.

[0048] Optionally, the bending angle of the stainless steel catheter is set to 15°, 30°, 45°, 60°, 75°, 90°, and the aperture of the injection needle 22 is set to vary from 0.1 mm to 5 mm.

[0049] In some embodiments, the observation device mainly includes: a continuous laser, a uniform light, an array camera platform composed of multiple high-speed cameras, and a camera mounting platform. The observation range of the observation device covers the entire process from the underwater generation stage of the bubble to the bubble reaching the gas-liquid interface and the bubble vortex structure formed when the bubble bursts above the water surface. The camera mounting platform (the camera mounting platform is not shown in the figure) includes a skeleton composed of aluminum alloy profiles and a number of camera mounting positions assembled on the skeleton. Each camera mounting position includes a connected optical plate and a three-axis motion platform. The optical plate ensures that the observation planes of the multiple side high-speed cameras 31 used are consistent in the horizontal direction, realizing the continuous observation of the bubble movement and ensuring the complete shooting of each stage of the bubble movement; the high-speed camera is set up on the optical plate using a three-axis motion platform, and the observation height of different high-speed cameras can be adjusted, providing sufficient freedom to ensure the diversity of the observation system. The multiple high-speed cameras used are of the same model and consistent parameters. They all have the characteristics of high frequency, high precision and high resolution. The highest resolution is 1920×1080 pixels, which ensures full-frame shooting of the bubble development stage. All high-speed cameras are connected to the data acquisition and control unit 4 and transmit data with the data acquisition and control unit 4. The side high-speed cameras 31 in the camera platform are arranged at intervals along the height direction of the experimental water tank 1 through the camera mounting platform to observe the movement characteristics of the bubbles in the vertical direction. The upper high-speed camera 32 is arranged at an appropriate position above the gas incident section through the camera mounting platform to observe the water surface bubble vortex movement characteristics of the bubbles. In the embodiment of the present invention, two light-homogenizing plates are provided. The first light-homogenizing plate 33 is located on the other side of the experimental water tank 1 and is arranged opposite to the side high-speed camera 31 to provide a light source for the movement of the bubbles in the vertical direction. The second light-homogenizing plate 34 is located near the upper high-speed camera 32 to provide a light source for the bubble vortex movement of the bubbles on the water surface. The continuous laser is used to provide a light source for observing the influence of bubble movement on the liquid flow field. It should be noted that two light sources are used in the present invention. When used to study bubble movement, only a homogenizing plate is used for supplementary lighting, while when observing the movement of liquid flow field under the influence of bubbles, only laser is used for supplementary lighting.

[0050] Optionally, the size of the first light homogenizing plate 33 and the second light homogenizing plate 34 are both 0.8m×0.8m, and the power is both 88W; the maximum power of the continuous laser is 20W, which can meet the experimental requirements.

[0051] Optionally, before using the camera platform for observation, it is necessary to use a calibration plate to focus each high-speed camera to ensure the acquisition of the clearest raw data of bubble movement and flow field movement. At the same time, the calibration plate is used to determine the observation range of each high-speed camera to ensure that the shooting range of each high-speed camera is consistent, the shooting sections are consistent in the horizontal direction, and the shooting sections are connected in the vertical direction. The calibration plate can be a black and white chessboard.

[0052] Optionally, by default, the long frame of the height camera is set to the horizontal direction. The camera can be rotated and the vertical direction can be set to the maximum frame of the high-speed camera. At the same time, the aluminum alloy profile skeleton of the camera platform can be adjusted, and the position of each side high-speed camera 31 can be fine-tuned using a three-axis motion platform, so that the overlapping area between adjacent side high-speed cameras 31 is smaller, which can save camera resources and computing resources.

[0053] In some embodiments, the data acquisition and control unit 4 includes a computer, a switch and a synchronizer. The computer is loaded with a camera data acquisition module and a data processing module. The high-speed cameras in the camera platform are connected to the computer through the switch, and communication is achieved through a local area network built by Ethernet. The computer controls the observation frequency of each high-speed camera through the synchronizer to achieve simultaneous and frequency observation of each high-speed camera, as well as control the opening and closing time of the homogenizer and the continuous laser.

[0054] Optionally, according to different gas incident dynamics, the computer assigns different observation frequencies to the high-speed camera through a synchronizer. For example, when observing the movement of a single bubble, the observation frequency is set to 400Hz, and when observing the movement of a larger dynamic bubble such as 5L / min, the observation frequency is set to 2000Hz, which not only ensures the accurate capture of the instantaneous characteristics of the bubble movement, but also avoids the waste of observation resources. In addition, the opening and closing time of the homogenizer and the continuous laser can also be controlled by the synchronizer. In one working cycle, the first frame of the image is taken with the homogenizer as the light source, which is used to analyze the movement characteristics of the bubble; the second frame of the image is taken under the irradiation of the continuous laser, which is used to analyze the flow field movement characteristics under the influence of the bubble, and realize the synchronous measurement of the bubble movement and the liquid flow field.

[0055] Optionally, the camera data acquisition module loaded in the computer is used to set the camera acquisition frame, the number of acquisitions, the exposure conditions and the storage location, etc. The camera data acquisition module can continuously take tens of thousands of pictures for the same working condition, avoiding the systematic errors of the bubble and liquid movement characteristics under pneumatic conditions, and providing detailed experimental analysis data, which is highly representative and can be used for subsequent data processing.

[0056] Optionally, a data processing module loaded in the computer is used to pre-process the raw data observed by the camera platform through Python and Matlab, and then use a pre-trained deep learning model to detect bubbles in the gas-liquid two-phase flow, providing a basis for the subsequent analysis of the geometric morphology and motion characteristics of the bubbles in different rising stages, so as to obtain the bubble motion characteristics under different experimental conditions, the interaction between bubbles caused by bubble motion, and the impact of bubble motion on the flow field.

[0057] Optionally, the deep learning model uses Mask R-CNN, which can automatically realize bubble detection and mask extraction in gas-liquid two-phase flow.

[0058] Optionally, in order to improve the operating stability of the camera data acquisition module and the data processing module and the storage speed of the captured images during experimental observation, multiple computers can respectively and evenly control a certain number of high-speed cameras to improve experimental efficiency.

[0059] See also Figure 2 The second aspect of the present invention provides an observation method based on the above observation system, comprising the following steps:

[0060] Step 1: determine the test section of the experimental water tank 1 to be observed, place a camera mounting platform for carrying the camera platform at an appropriate position near the experimental water tank 1, and connect the side high-speed camera 31 for observing the vertical movement characteristics of bubbles to the corresponding camera mounting position on the camera mounting platform;

[0061] Step 2: Connect the air compressor 23, the gas storage tank 24, the air filter 25, the digital gas mass flowmeter 26 and the gas incident section through a rubber tube to build a pneumatic generating device 2, use the digital gas mass flowmeter 26 to set the initial conditions of bubble movement, and place the gas incident section into the center of the experimental water tank 1 through a three-axis gantry platform erected above the experimental water tank 1, and at the same time be within the observation area of ​​the side high-speed camera 31, and then arrange the upper high-speed camera 32 for observing the bubble vortex movement characteristics of the air bubble at an appropriate position above the injection needle 22 through the camera mounting platform;

[0062] Step 3: Connect all high-speed cameras in the camera platform to the computer through the switch, use the calibration board to focus each high-speed camera to ensure the acquisition of the clearest raw data of bubble motion and flow field motion, and use the calibration board to determine the observation range of each high-speed camera. Through the external trigger control of the synchronizer, all high-speed cameras in the camera platform can be measured at the same time and at the same frequency;

[0063] Step 4: Set up a first light-homogenizing plate 33 on the other side of the experimental water tank 1 of the side high-speed camera 31 for observing the vertical movement of bubbles, and set up a second light-homogenizing plate 34 directly above the upper high-speed camera 31 for observing the bubble vortex movement characteristics of bubbles, to provide a stable and uniform light source for capturing the full-process motion characteristics of bubbles, set up a continuous laser on the vertical surface of the water tank where the side high-speed camera 31 is located, and use a three-axis gantry platform to ensure that the continuous laser emitted by the continuous laser covers the entire vertical surface where the bubble moves, to provide a light source for observing the flow field motion caused by the bubble motion, and connect the light-homogenizing plate and the continuous laser to the synchronizer to control the opening and closing time of the light-homogenizing plate and the continuous laser.

[0064] Step 5: Start shooting. Set the size, number, storage location, etc. of each set of working condition shooting pictures through the camera data acquisition module. The synchronizer controls the simultaneous and frequency shooting. According to the initial conditions of bubble movement set in step 2, obtain the original data of bubble movement and flow field movement of sufficient bubbles in the liquid from generation, development, maturity to the formation of bubble vortex structure on the water surface;

[0065] Step 6: Based on the raw data obtained in step 5, use the data processing module in the data acquisition and control unit to analyze the bubble motion characteristics under different incident angles, different incident apertures, different gas dynamics, and different water depths, the interaction between bubbles caused by bubble motion, and the impact of bubble motion on the flow field.

[0066] Alternatively, since the flow conditions and optical settings of different experiments vary greatly, simple image processing filters are not sufficient to process all bubble images with various geometric characteristics. Even in a single bubble flow image, the characteristics of the bubbles are different and cannot be easily distinguished by a single processing process. Therefore, machine learning methods can be used to analyze the obtained data.

[0067] Figure 3 An observation system for bubble motion characteristics using an embodiment of the present invention captures bubble motion images under different high-speed cameras and different dynamic conditions. Compared with the currently available observation systems, the images captured by the observation system based on the embodiment of the invention can clarify the geometric morphology and motion characteristics of bubbles at different depths under different incident angles and different incident apertures, and can also analyze the characteristics of single bubbles, bubble groups, and even different bubble flow types, and can also analyze the flow field characteristics caused by bubble motion under different initial conditions over a large range and long sequence. At the same time, the large sample data obtained by the observation system can be used to identify and predict bubble motion and flow field motion using existing machine learning and other algorithms.

[0068] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0069] Although examples of the present invention have been shown and described above, it is to be understood that the above examples are illustrative and are not to be construed as limitations of the present invention, and that a person skilled in the art may make changes, modifications, substitutions and variations to the above examples within the scope of the present invention.

Claims

1. An observation system for bubble motion characteristics, characterized in that: include: The experimental water tank is a transparent box with an open top and filled with liquid; A gas power generating device, used for pumping gas with different power conditions into the experimental water tank to form bubbles, the gas power generating device having a gas incident section extending below the liquid surface in the experimental water tank, the gas incident section consisting of an air pipe with a bent section and an injection needle located at the end of the bent section of the air pipe; An observation device, comprising a camera platform, a continuous laser and a homogenizing plate; the camera platform comprises a plurality of side high-speed cameras arranged in an array on one side of the outside of the experimental water tank and an upper high-speed camera located above the gas incident section, the gas incident section of the gas power generating device should be within the observation area of ​​the camera platform, and the original data of the bubble movement and flow field movement at each stage in the experimental water tank are continuously obtained through the camera platform; the continuous laser emitted by the continuous laser should cover the entire vertical plane where the bubble movement is located, providing a light source for the observation of the flow field movement caused by the bubble movement; the homogenizing plate is located on the periphery of the experimental water tank, and is used to provide a stable and uniform light source for the camera platform; The data acquisition and control unit is used to control the observation device and pre-process and analyze the raw data obtained by the observation device to obtain the bubble movement characteristics under different experimental conditions, the interaction between bubbles caused by bubble movement, and the influence of bubble movement on the flow field.

2. The observation system according to claim 1, characterized in that: The gas power generating device comprises an air compressor, an air filter, a gas storage tank, a digital gas mass flow meter and the gas incident section which are sequentially connected through a gas pipeline. The top end of the gas incident section is installed on a three-axis gantry platform.

3. The observation system according to claim 2, characterized in that: The gas power generating device is equipped with digital gas mass flow meters of different ranges for providing gas under different power conditions.

4. The observation system according to claim 1, characterized in that: The observation system is equipped with a plurality of air tubes with different bending angles, which are used to study the rising efficiency of bubble movement under different incident angles. The bending angle of the air tube is α, α∈)0,90°], and the positions of the bending sections of the air tubes with different bending angles should satisfy the position of the bubble generating end in the experimental water tank remains unchanged; The observation system is equipped with a plurality of injection needles with different apertures for analyzing bubble movement characteristics under different incident apertures.

5. The observation system according to claim 4, characterized in that: The bending angle of the trachea is set to 15°, 30°, 45°, 60°, 75°, and 90°, and the aperture of the injection needle is set to 0.1mm-5mm.

6. The observation system according to claim 1, characterized in that: The observation device also includes a camera mounting platform, which includes a frame composed of aluminum alloy profiles and a plurality of camera mounting positions assembled on the frame, each camera mounting position respectively includes a connected optical plate and a three-axis motion platform, each high-speed camera is installed on the corresponding three-axis motion platform, and the optical plate is used to keep the observation planes of each side high-speed camera consistent in the horizontal direction.

7. The observation system according to claim 1, characterized in that: The observation device is equipped with two light averaging plates, the first light averaging plate is located on the other side of the outside of the experimental water tank opposite to the side high-speed camera, and the second light averaging plate is located near the upper high-speed camera.

8. The observation system according to claim 1, characterized in that: The data acquisition and control unit includes a computer, a switch and a synchronizer, and the computer is loaded with a camera data acquisition module and a data processing module; each high-speed camera is connected to the computer through the switch, and communication is achieved through a local area network constructed by Ethernet; the computer controls the observation frequency of each high-speed camera through the synchronizer to achieve simultaneous and same-frequency observation of each high-speed camera, and controls the opening and closing time of the homogenizing plate and the continuous laser; the camera data acquisition module is used to set the camera's acquisition parameters, including acquisition frame, number of acquisitions, exposure conditions and image storage location; the data processing module is used to pre-process the raw data observed by the camera platform, and then use a pre-trained deep learning model to detect bubbles in gas-liquid two-phase flow, so as to obtain the bubble movement characteristics under different experimental conditions, the interaction between bubbles caused by bubble movement, and the influence of bubble movement on the flow field.

9. The observation system according to claim 8, characterized in that: According to different gas incident dynamics, the computer assigns different observation frequencies to the camera platform through the synchronizer; In one working cycle, the computer uses the synchronizer to shoot the first frame image with the homogenizing plate as the light source, so as to analyze the movement characteristics of the bubbles; the computer uses the synchronizer to shoot the second frame image under the irradiation of the continuous laser, so as to analyze the movement characteristics of the flow field under the influence of the bubbles, thereby realizing the synchronous measurement of the bubble movement and the liquid flow field.

10. An observation method based on the observation system according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: determine the test section of the experimental water tank to be observed, place a camera mounting platform for carrying a camera platform at an appropriate position near the experimental water tank, and connect a side high-speed camera for observing the vertical movement characteristics of bubbles to the camera mounting platform; Step 2: Build the pneumatic generating device and set the initial conditions of bubble movement. Place the gas incident section into the center of the experimental water tank through a three-axis gantry platform installed above the experimental water tank, and place it within the observation area of ​​the side high-speed camera. Then, place the upper high-speed camera for observing the bubble vortex movement characteristics at an appropriate position above the injection needle through a camera installation platform. Step 3: connect all high-speed cameras in the camera platform to the data acquisition and control unit, use the calibration board to focus each high-speed camera and determine the observation range of each high-speed camera; Step 4: Setting up the light homogenizing plate and the continuous laser, and connecting them to the data acquisition and control unit; Step 5: triggering the high-speed cameras in the camera platform to take pictures at the same time and frequency through the data acquisition and control unit, and obtaining the original data of the bubble movement and flow field movement of a sufficient number of bubbles in the liquid from generation, development, and maturation to the formation of a bubble vortex structure on the water surface according to the initial conditions of the bubble movement set in step 2; Step 6: Based on the original data obtained in step 5, the data acquisition and control unit is used to analyze the bubble motion characteristics under different experimental conditions, the interaction between bubbles caused by the bubble motion, and the influence of the bubble motion on the flow field.

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