Methods for generating microbubbles using superhydrophobic networks on open walls

Abstract

This invention relates to a method for generating microbubbles using a superhydrophobic network on an open wall surface. The invention involves creating a superhydrophobic network by spraying a superhydrophobic material onto a substrate plane. When a liquid fluid immerses the superhydrophobic tracks, a gas film ranging from several micrometers to hundreds of micrometers is formed on the network surface. Bubbles, under their own buoyancy or the upward drag force of the fluid, touch the superhydrophobic tracks, becoming stably adsorbed and moving upwards along the network tracks. When a single track branches into multiple tracks, a rapid change in capillary force causes the original bubble to quickly disperse into smaller sub-bubbles downstream. This invention effectively controls the upward movement of bubbles along the tracks and generates a large number of micro-scale sub-millimeter bubbles by controlling the width of the tracks and the diameter of the initial bubbles. Furthermore, no additional energy input is required during the generation of these microbubbles, allowing for control of bubble upward movement and the size of bubbles generated during splitting.

Description

Technical Field

[0001] This invention belongs to the field of multiphase flow and relates to a method for generating microbubbles using a superhydrophobic network on an open wall surface. Background Technology

[0002] Gas-liquid two-phase flow is a common phenomenon in nature and is widely used in many fields such as thermal power engineering, nuclear power engineering, cryogenic engineering, and aerospace, making it a current research hotspot in fluid mechanics. Superhydrophobic materials are a new type of material defined as having a stable contact angle greater than 150° and a rolling contact angle less than 10°. With their superior properties and strong hydrophobic capabilities, superhydrophobic materials have become a focus of scientific attention.

[0003] On the other hand, as a discrete phase in gas-liquid two-phase flow, microbubbles have the characteristics of long residence time and large specific surface area in fluids. Therefore, microbubbles show significant advantages over large-scale bubbles in applications such as wastewater treatment, chemical industry, and fuel electromagnetics.

[0004] Currently, most domestic and international technologies for generating microbubbles involve specialized bubble generators or generation within microchannels. The former results in poor monodispersity of the microbubbles and difficulty in control, while the latter is generally costly, has limited throughput, and is difficult to commercialize. This invention proposes a method for generating microbubbles using superhydrophobic networks on open walls. This method requires simple equipment and can rapidly generate a large number of sub-millimeter-scale microbubbles without requiring energy input. Summary of the Invention

[0005] The purpose of this invention is to address the current difficulty in generating microscale sub-millimeter-sized bubbles under conditions of no energy input, and to provide a method for generating microbubbles using a superhydrophobic network on an open wall surface.

[0006] To achieve the above objectives, this invention creates a superhydrophobic network by spraying a superhydrophobic material onto a substrate plane. The network has a binary tree structure, and apart from the superhydrophobic network region, the other planar regions are non-hydrophobic surfaces.

[0007] When a liquid fluid is submerged in a superhydrophobic orbital, a gas film ranging from several micrometers to hundreds of micrometers will form on the surface of the superhydrophobic network due to its superaerophilicity. The bubbles touch the superhydrophobic orbital under the action of their own buoyancy or the upward drag force of the fluid. Due to the superaerophilicity of the superhydrophobic orbital, the bubbles are stably adsorbed on the orbital and move upward along the orbital of the network.

[0008] When the movement reaches the bifurcation structure where a single track branches into multiple tracks, the capillary force changes drastically, causing the original bubble to rapidly disperse into smaller sub-bubbles in the downstream branches. These sub-bubbles continue to move in a straight line along their respective superhydrophobic branches. When they touch the bifurcation structure again, the above splitting process is repeated, producing even smaller sub-bubbles. This process continues until microbubbles that meet the size requirements are produced.

[0009] The initial bubble is a sub-millimeter-sized bubble.

[0010] The width W of the superhydrophobic track is 0.1 to 5D.

[0011] The superhydrophobic track has a droplet contact angle of 150–180°.

[0012] The thickness of the superhydrophobic track is less than 1 mm.

[0013] The branching tree structure is a binary structure, with a branching angle α ranging from 0 to 180°.

[0014] The length L between each two adjacent nodes in the described branching tree structure is 1D to 20D.

[0015] The branching tree structure consists of one main path and two or more branch paths.

[0016] The fluid may be a Newtonian fluid or a non-Newtonian fluid.

[0017] Compared with the prior art, the beneficial effects of this invention are:

[0018] (1) In view of the current problem that it is difficult to generate a large number of micro-scale sub-millimeter-level bubbles under the condition of no energy input, this invention proposes a method for generating microbubbles on superhydrophobic networks. By utilizing the superhydrophobicity and super hydrophobicity of superhydrophobic materials and the binary tree structure, the bubbles increase exponentially, thereby achieving the purpose of effectively and rapidly generating a large number of microbubbles.

[0019] (2) This invention addresses the issue of bubble generators with generally high costs by proposing a method for generating microbubbles using a superhydrophobic network. It utilizes the low manufacturing cost of the superhydrophobic track and the long effective time of the superhydrophobic track, which can be reused multiple times, thus achieving the goal of rationally saving resources.

[0020] (3) In view of the problem that bubbles generated in microchannels are easily blocked, the present invention proposes a method for generating microbubbles by superhydrophobic networks on open walls. The open walls are simple to manufacture, low in cost, and can allow a large number of microbubbles to be generated without blockage.

[0021] (4) This invention proposes a method for generating microbubbles using a superhydrophobic network, which addresses the fixed-model bubble generators currently available on the market. By adjusting the width of the superhydrophobic track, the generation of different microbubbles can be controlled for different bubble sizes.

[0022] (5) In view of the shortcomings of the current method of controlling the upward trajectory of bubbles in water and the inability to adjust the upward speed, the present invention proposes a method for generating microbubbles by superhydrophobic network on open wall surface. The superhydrophobic and air-loving material is used to exert a strong adhesion force on the bubbles in water to achieve the purpose of controlling the bubbles to rise in a straight line and the upward speed. Attached Figure Description

[0023] Figure 1 Front view of an open-walled superhydrophobic track;

[0024] Figure 2 Side view of an open-walled superhydrophobic track;

[0025] Figure 3 This is a schematic diagram of bubble generation in a binary tree structure.

[0026] Figure 4 Frontal view of the early stage of bubble splitting at α = 10°;

[0027] Figure 5 This is a frontal view of the late stage of bubble splitting at α = 10°. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and examples.

[0029] like Figure 1 , Figure 2 As shown, substrate material 1 is selected, its surface is cleaned, and then the desired binary tree structure track is reserved on the surface of the substrate material. Superhydrophobic water solution is used for spraying to obtain superhydrophobic track 2 with a smooth surface and edges, which significantly improves the hydrophobic properties of its surface.

[0030] If the equivalent diameter of the controlled bubble volume is D, then the range of the drawn track width W is 0.1D to 5D of the equivalent diameter of the target bubble, that is, the track width range W = 0.1 to 5D. Within this width range, the stability of the bubble movement is good, and the track's ability to capture rising bubbles and control the actual floating speed of the bubbles is relatively ideal. Figure 3 , Figure 4 , Figure 5As shown, in order to obtain a large number of effective microbubbles 3, a binary tree structure track is adopted, and the bifurcation angle α of the two branches derived from the same node is controlled to be between 0 and 180°. The length L between each two adjacent nodes is controlled to be between 1D and 20D, which is the equivalent diameter of the target bubble. That is, the length of each branch is L = 1 to 20D. Within this angle and length range, a large number of microscale sub-millimeter-level bubbles can be effectively generated on the open wall surface without energy input.

[0031] A binary tree-structured track is placed parallel to the direction of gravity in the water, on the same horizontal plane as the bubble generation point. The bottom of the track is positioned within a range of 0 to 3 times the equivalent diameter of the bubble volume at the horizontal distance from the bubble generation point. This facilitates the capture of bubbles in the water, enabling the generation of a large number of micro-scale sub-millimeter bubbles on the open wall surface. The natural rising velocity of the bubbles in water is approximately 0.25–0.33 m / s. For the same bubble diameter D, changing the width W of the superhydrophobic track can effectively control the rising velocity of the bubbles. When the width of the binary tree track is greater than 0.1D but less than D / 3, the rising velocity of the bubbles decreases significantly to approximately 0.15–0.23 m / s; while when the width of the binary tree track is greater than D / 3 but less than 5D, the resistance decreases, and the rising velocity increases significantly to approximately 0.27–1.1 m / s.

[0032] The velocity of a single bubble in the orbit decreases with increasing bifurcation level; this is the main trend in velocity variation for a single bubble in a fractal tree-like orbit. However, due to the bifurcation structure, the shape change of the bubble at the bifurcation point creates a capillary pressure difference between the bubble's head and tail, resulting in an acceleration that causes an increase in bubble velocity; this is the local trend in velocity variation for the bubble in the fractal tree-like orbit. Keeping the width W of the superhydrophobic orbit and the bifurcation angle α constant, changing the initial equivalent bubble diameter D affects the symmetry and synchronicity of bubble flow splitting in the binary tree-like orbit. A larger initial equivalent bubble diameter D is more conducive to the symmetry and synchronicity of bubble flow splitting; when the equivalent bubble diameter D is small, asymmetrical and asynchronous flow splitting phenomena are more likely to occur. In addition, the bubble's buoyancy also affects the symmetry and synchronicity of bubble flow splitting in the binary tree-like orbit; bubbles with higher buoyancy velocities exhibit better symmetry and synchronicity in flow splitting.

[0033] In summary, by reasonably controlling the width of the binary tree structure track on the open wall and the diameter of the initial bubble, it is possible to effectively control the bubble to float along the track and generate a large number of micro-scale sub-millimeter-sized bubbles. Moreover, no additional energy input is required during the generation of these micro-bubbles, and the size of the bubbles during breakup can be controlled. Therefore, this invention has great application value in the fields of multiphase flow and energy-saving technology.

Claims

1. A method for generating microbubbles by open-walled superhydrophobic network, characterized in that: a superhydrophobic network is prepared by spraying superhydrophobic material on a substrate plane to form superhydrophobic tracks, the network is in a binary tree structure, and the plane area other than the superhydrophobic network area is a non-hydrophobic surface; when a liquid fluid is immersed in the superhydrophobic tracks, a gas film with a thickness of several microns to hundreds of microns is formed on the surface of the network due to the supergasophilic property of the superhydrophobic network; the bubble touches the superhydrophobic tracks under the action of its own buoyancy or the upward drag force of the fluid, and is stably adsorbed on the tracks and moves upward along the tracks due to the supergasophilic property of the superhydrophobic tracks; when the bubble moves to a bifurcation structure in which a single track is bifurcated into multiple tracks, the capillary force changes sharply, causing the original bubble to quickly disperse into smaller sub-bubbles along the downstream branches, and the sub-bubbles continue to move linearly along the respective superhydrophobic branches, and the process is repeated when the sub-bubbles touch the bifurcation structure again, to generate smaller sub-bubbles, and the process is repeated until microbubbles with a required size are generated. The width W of the superhydrophobic tracks is 0.1-5D, and D is the volume-equivalent diameter of the bubble. The bifurcation angle α of the binary tree structure is 0-180°. The length L between two adjacent nodes in the binary tree structure is 1D-20D. ​ 2. The method of claim 1, wherein the open-walled surface superhydrophobic network produces microbubbles. ​ 3. The method of claim 1, wherein the open-walled surface superhydrophobic network produces microbubbles. ​ 4. The method for generating microbubbles on an open wall surface using a superhydrophobic network according to claim 2, characterized in that: ​

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