Bubble generator and bubble generation method

Abstract

To stably supply bubbles by suppressing the adhesion of the bubbles to the inner wall surface of a pipe.SOLUTION: The bubble generator (1) includes a pipe (2) through which a liquid flows, a reduced-diameter portion having a smaller inner radius than the pipe (2), a bubble generating portion (3) configured to cause cavitation in the liquid to generate bubbles, and a plate-shaped guide member (10) disposed inside the pipe (2) downstream of the bubble generating portion (3) at a predetermined interval so as to connect an inner wall surface 2a of the pipe (2) in a radial direction and having a curved surface protruding in a plate thickness direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bubble generator and a bubble generating method. [Background technology]

[0002] Conventionally, as in Patent Document 1, for example, a bubble generation mechanism has been known in which a flow path is formed in a penetrating form connecting an inlet opening at the inlet end and an outlet opening at the outlet end of a component body having a defined inlet end on the liquid inlet side and an outlet end on the liquid outlet side, and a throttle section having a smaller flow cross-sectional area than the inlet is formed midway through the flow path, and the throttle section divides the axial cross-section of the flow path into three or more segment regions, and a collision section is arranged to further reduce the flow cross-sectional area of ​​the throttle section, and the flow of gas-dissolved liquid supplied to the inlet end of the component body is made to collide with the collision section, and then distributed to each segment region while passing through at an increased speed, and the reduced pressure effect causes the dissolved gas to precipitate out, turning it into a bubble-containing liquid, which then flows out from the outlet.

[0003] Also, as shown in Patent Document 2, there is known a nanobubble-producing device comprising a pipe for passing a liquid, a branch pipe that branches off a part of the liquid at a branching section on the upstream side of the pipe and returns it to a junction on the downstream side of the pipe, a gas-liquid mixing section provided midway through the branching pipe that mixes a gas with a part of the liquid, a microbubble-producing section that generates microbubbles in the range of 4 to 100 μm in the liquid, and a nanobubble-producing section that comprises a nanobubble-producing section main body connected to the downstream end of the pipe, a perforated plate provided in the main body, and an impingement plate provided downstream of and adjacent to the perforated plate, and that generates nanobubbles in the range of 100 nm or less in the liquid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5712292 [Patent Document 2] Japanese Patent Publication No. 2022-137446 Summary of the Invention [Problem to be solved by the invention]

[0005] Bubbles, being hydrophobic (water-repellent), tend to adhere to the surface of hydrophobic materials such as fluororesin. Furthermore, after bubbles are generated, the water or aqueous solution spreads inside the pipe, bringing the bubble-laden water or aqueous solution into contact with the inner wall surface of the pipe. If the piping material is a hydrophobic material, the generated bubbles will adhere to the inner wall surface of the pipe over a wide area, which is a problem. Similarly, if the liquid is oil, when a gas that is not easily soluble in oil is bubbled, the bubbles will tend to adhere to the surface of an oil-repellent material. Furthermore, after bubbles are generated, the oil will spread inside the pipe, bringing the bubble-laden oil into contact with the inner wall surface of the pipe. If the piping material is an oil-repellent material, the generated bubbles will adhere to the inner wall surface of the pipe over a wide area, which is a problem.

[0006] The present invention has been made in view of the above points, and its object is to suppress adhesion of bubbles to the inner wall surface of a pipe and to supply bubbles stably. [Means for solving the problem]

[0007] In order to achieve the above object, in the present invention, the jet is extended further downstream.

[0008] Specifically, in the first invention, A tube through which a liquid flows; a reduced diameter portion provided inside the pipe and having a diameter smaller than the inner diameter of the pipe; a bubble generating unit that generates bubbles in the liquid; The configuration includes a plate-shaped guide member arranged inside the pipe at a predetermined distance downstream of the reduced diameter section, so as to connect the inner wall surface of the pipe in the radial direction, and having a curved surface protruding in the plate thickness direction.

[0009] According to the above configuration, by providing a guide member having a curved surface protruding in the thickness direction immediately after the diameter-reducing portion, the Coanda effect causes the jet to extend further downstream, allowing bubbles to be collected at the center of the pipe over a longer distance. This reduces the possibility of bubbles adhering to the pipe wall surface, allowing the bubbles to be stably transported downstream. Here, the term "liquid" includes oil, water, aqueous solutions, etc. In addition, in systems that do not introduce outside air, the diameter-reducing portion and the bubble-generating portion may be located in the same place. In systems that do introduce outside air, such as ejector systems, the bubble-generating portion may be located at a different position from the diameter-reducing portion.

[0010] In the second invention, in the first invention, The guide member is configured so that the jet of water from the bubble generating section flows along the guide member, causing the bubbles to flow downstream while being separated from the inner wall surface of the pipe.

[0011] According to the above configuration, it is possible to effectively reduce the possibility of bubbles adhering to the pipe wall surface, and to stably transport the bubbles downstream.

[0012] In a third aspect of the present invention, in the first or second aspect of the present invention, The guide member has a streamlined cross section when viewed along a direction perpendicular to the radial direction of the pipe and the thickness direction.

[0013] According to the above configuration, if the guide member has a streamlined shape, the jet flow emitted from the bubble generating section flows along the surface of the guide member, and therefore the jet flow is more likely to extend downstream.

[0014] In addition, in the fourth invention, A tube through which a liquid flows; a reduced diameter section provided inside the pipe with a diameter smaller than the inner diameter of the pipe; and a bubble generating section that generates bubbles in the liquid. a plate-like guide member disposed inside the pipe at a predetermined distance downstream of the reduced diameter portion so as to radially connect the inner wall surface of the pipe, the plate-like guide member having a curved surface protruding in a plate thickness direction; A liquid is caused to flow through the pipe at a predetermined flow rate and a predetermined flow rate, and bubbles are generated in the bubble generating unit. The jet of water from the reduced diameter portion flows along the guide member, causing the bubbles to flow downstream while being separated from the inner wall surface of the pipe.

[0015] According to the above configuration, by providing a guide member with a curved surface that protrudes in the thickness direction immediately after the reduced diameter section, the Coanda effect causes the jet to extend further downstream, allowing the bubbles to be collected at the center of the pipe for a longer distance. This reduces the possibility of bubbles adhering to the pipe wall surface, and enables the bubbles to be transported downstream in a stable manner. [Effects of the Invention]

[0016] As described above, according to the present invention, by providing a guide member immediately after the reduced diameter section, the Coanda effect causes the jet to extend further downstream, allowing bubbles to be collected at the center of the pipe over a longer distance. This effectively reduces the possibility of bubbles adhering to the inner wall surface of the pipe, allowing for a stable supply of bubbles. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is an enlarged cross-sectional view of a portion of a bubble generator according to an embodiment of the present invention. FIG. [Figure 2] 1A and 1B are enlarged views of the guide member and its surroundings, in which FIG. 1A is a plan view and FIG. 1B is a side view. [Figure 3] FIG. 4 is an enlarged cross-sectional view showing a guide member. [Figure 4] 10A and 10B are graphs showing flow velocity contours in the analysis results according to the example, where (a) is the flow velocity contour in the xy cross section, and (b) is the flow velocity contour in the zx cross section. [Figure 5]10 is a graph showing flow velocity contours on an xy cross section in the analysis results according to the comparative example. [Figure 6] 10 is a graph showing flow velocity distributions in xy cross sections in the analysis results according to an example and a comparative example. [Figure 7] 10 is a graph showing the flow velocity distribution in the zx cross section in the analysis results according to the example and the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] 1 shows a schematic cross section of a bubble generator 1 according to an embodiment of the present invention, from an inlet 2b to an outlet 2c and the surrounding area. This bubble generator includes a pipe 2 through which water or an aqueous solution flows as a liquid, and includes a bubble generating unit 3 therein, which has a reduced diameter section 31 whose diameter is smaller than the inner diameter of the pipe 2 and generates bubbles by causing cavitation in the water or aqueous solution. In this embodiment, the fluid flowing inside the pipe 2 is referred to as "water or an aqueous solution," but this means water or a hydrophilic liquid, excluding hydrophobic liquids such as oil.

[0020] Furthermore, bubbles generated in the bubble generating section 3 may be generated by a known generating method other than cavitation.

[0021] As shown in Figure 2, a plate-shaped guide member 10 having a curved surface protruding in the thickness direction is provided inside the pipe 2 at a predetermined distance downstream of the reduced diameter section 31, so as to connect the inner wall surface 2a of the pipe 2 in the radial direction.

[0022] The bubble generator 1 of this embodiment is configured so that the jet from the reduced diameter section 31 flows along the guide member 10, causing the bubbles to flow downstream while being separated from the inner wall surface 2a of the tube 2.

[0023] As shown in the enlarged view in Fig. 3, the guide member 10 has a streamline-shaped cross-section. In the present embodiment, when viewed along the radial direction of the pipe 2 and the longitudinal direction of the guide member 10, the cross-section at the upstream side is semi-elliptical, and the cross-section at the downstream side is a shape in which semi-elliptical shapes with a major diameter longer than the major diameter (2A) of the upstream side are continuous. As shown in Fig. 3, the length B of the rear cross-section is longer than the length A of the front cross-section (B > A), and the plate thickness t of the guide member 10 satisfies t < A, and it has a thin plate shape. It is desirable that the downstream end is pointed, but it does not have to be pointed as in the present embodiment.

[0024] -Fluid Analysis- Next, a three-dimensional fluid analysis was performed on the behavior of the jet in the bubble generator 1 according to the present embodiment using water as the working fluid. The analysis conditions were a steady-state analysis using a turbulent flow model, the flow rate on the inflow side was set to 1 L / min, and the outflow pressure was fixed. In this analysis, a single-phase flow model (a model in which cavitation does not occur) was adopted for confirming the effect of the jet.

[0025] In the cross-section shown in Fig. 1, the inner diameter of the inlet 2b was set to 6.35 mm, the inner diameter of the bubble generation part 3 was set to 1.5 mm, the inner diameter of the inner wall surface 2a continuous with the bubble generation part 3 was set to 6.35 mm, and the inner diameter of the outlet 2c was set to 10 mm.

[0026] In Fig. 3, the length A of the front cross-section of the guide member 10 was set to 1.7 mm, the length B of the rear cross-section was set to 4.3 mm, and the plate thickness t was set to 0.3 mm. The distance from the bubble generation part 3 to the guide member 10 was set to 1.5 mm. The average jet velocity U was set to 9.4 m / s, and the flow velocity measurement line was set to 10.6 mm from the bubble generation part 3.

[0027] As shown in Figs. 4 and 5, it can be seen that in the example, the jet extends further downstream compared to the comparative example.

[0028] Also, as shown in Figs. 6 and 7, in the xy cross-section and the zx cross-section, in the region surrounded by the broken-line ellipse, the velocity distribution in the case of the example has a higher convex shape compared to the comparative example, and it was found that the jet is maintained further downstream due to the Coanda effect.

[0029] In this embodiment, by providing a guide member 10 having a curved surface that is convex in the thickness direction immediately after the reduced diameter section 31, the Coanda effect causes the jet to extend further downstream, allowing the bubbles to be collected at the center of the pipe 2 for a longer distance. This reduces the possibility of bubbles adhering to the inner wall surface 2a of the pipe 2, and allows the bubbles to be transported downstream stably.

[0030] In this embodiment, the jet flow emitted from the reduced diameter portion 31 flows along the surface of the guide member 10, so that the jet flow is likely to extend further downstream.

[0031] Therefore, in the bubble generator 1 according to this embodiment, by providing the guide member 10 immediately after the reduced diameter section 31, the jet flows further downstream due to the Coanda effect, and the bubbles can be collected over a longer distance at the center of the pipe 2. This reduces the possibility that the bubbles will adhere to the inner wall surface 2a of the pipe 2, and ensures a stable supply of bubbles.

[0032] (Other embodiments) The above-described embodiments are essentially preferred examples, and are not intended to limit the scope of the present invention, its applications, or uses.

[0033] In the above embodiment, the liquid is water or a solvent, but oil may also be used. When the liquid is oil, bubbles easily adhere to the surface of a pipe made of an oil-repellent material when a gas that is not easily soluble in oil is bubbled. Furthermore, after bubbles are generated, the oil spreads within the pipe, causing the oil containing the bubbles to come into contact with the inner wall surface of the pipe. If the piping material is an oil-repellent material, the generated bubbles will adhere to the inner wall surface of the pipe over a wide area. However, the guide member of the present invention can reduce the likelihood of bubbles adhering to the inner wall surface of the pipe, even when the liquid is oil, thereby enabling stable bubble supply. Furthermore, in the above embodiment, the bubble-generating unit 3 and the diameter-reducing unit 31 are located in the same place. However, the bubble-generating unit and the diameter-reducing unit may be located in different positions as long as the diameter-reducing unit is located upstream of the guide member.

[0034] In the above embodiment, the guide member 10 has a streamlined cross section when viewed along a direction perpendicular to the radial direction and thickness direction of the tube 2, and an example shape is shown, but the shape constituting the streamlined shape may also be a wing shape, an elliptical shape, or an approximately elliptical shape. [Explanation of symbols]

[0035] 1. Bubble Generator 2 tubes 2a Internal wall 2b Inlet 2c Outlet 3 Bubble generating section 31 Reduced diameter part 10 Guide member

Claims

1. A tube through which a liquid flows; a reduced diameter portion provided inside the pipe and having a diameter smaller than the inner diameter of the pipe; a bubble generating unit that generates bubbles in the liquid; a plate-like guide member disposed inside the pipe at a predetermined distance downstream of the reduced diameter portion so as to connect the inner wall surface of the pipe in the radial direction, the plate-like guide member having a curved surface protruding in the plate thickness direction A bubble generator characterized by:

2. The guide member is configured so that the jet flow from the bubble generating section flows along the guide member, causing the bubbles to flow downstream while being separated from the inner wall surface of the pipe.

2. The bubble generator of claim 1.

3. The guide member has a streamlined cross section when viewed along a direction perpendicular to the radial direction of the pipe and the thickness direction.

3. A bubble generator according to claim 1 or 2.

4. A tube through which a liquid flows; a reduced diameter portion provided inside the pipe and having a diameter smaller than the inner diameter of the pipe; a bubble generating unit that generates bubbles in the liquid; a plate-like guide member disposed inside the pipe at a predetermined distance downstream of the reduced diameter portion so as to radially connect the inner wall surface of the pipe, the plate-like guide member having a curved surface protruding in a plate thickness direction; A liquid is caused to flow through the pipe at a predetermined flow rate and a predetermined flow rate, and bubbles are generated in the bubble generating unit. The jet of water from the reduced diameter portion flows along the guide member, causing the bubbles to flow downstream while being separated from the inner wall surface of the pipe. A bubble generating method.

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