Bubble formation device and bubble formation method

Abstract

A bubble formation device includes a first porous body (11) and a second porous body (12). The first porous body (11) has an array of first through-holes (11a). Gas is injected from ends of the first through-holes (11a) at a first surface (S1) to generate fine bubbles (B) at ends thereof at a second surface (S2) that is in contact with a liquid (L). The second porous body (12) has an array of second through-holes (12a) through which the fine bubbles (B) and the liquid (L) can pass, and is disposed in the liquid (L) so as to deform the fine bubbles (B) growing from the ends of the first through-holes (11a) at the first surface (S1). The second porous body (12) is disposed with a gap (E), through which the fine bubbles (B) and the liquid (L) can pass, with respect to the first porous body (11) such that the direction of the second through-holes (12a) is the same as that of the first through-holes (11a).

Description

Air bubble forming device and air bubble forming method

[0001] The present invention relates to an air bubble forming device and an air bubble forming method.

[0002] Many bubble-forming devices that generate fine bubbles (microscopic bubbles) use a liquid pump to create a liquid flow using mechanical power, and then use the energy of the liquid flow to make the bubbles finer. However, because this type of device requires a liquid pump, it has high operating costs, the overall device configuration is large, handling is complicated, and it is difficult to avoid contamination from the liquid pump, etc. (hereinafter simply referred to as "contamination").

[0003] Therefore, bubble-generating devices that do not require a liquid pump have been proposed (for example, Patent Document 1). This device can generate fine bubbles in a state closed off from the outside world, and is therefore expected to be used in a contamination-free environment. However, this device is also a dynamic bubble-generating device that uses power to create a liquid flow, so the overall configuration is large-scale and handling is complicated, just like devices that use a liquid pump.

[0004] Patent No. 6755035

[0005] Therefore, devices have been proposed that generate fine bubbles quasi-statically using sound waves, ultrasonic waves, or high voltage, but these devices also tend to be large-scale and difficult to handle.

[0006] Furthermore, static bubble-forming devices have also been proposed that generate microbubbles without using a power source to create a liquid flow. In these devices, microbubbles are generated from a nozzle or porous body with a constriction. However, even with these devices, in order to generate a large amount of microbubbles with a uniform bubble diameter, measures such as adding a surfactant to the surface of the nozzle or porous body to make it hydrophilic are required. Furthermore, there is a limit to how much the size of the microbubbles formed can be reduced, and the size of the microbubbles also varies.

[0007] The present invention has been made in light of the above-mentioned circumstances, and aims to provide an air bubble-forming device and an air bubble-forming method that can generate a large amount of fine bubbles of uniform size without using power to create a liquid flow.

[0008] In order to achieve the above object, the bubble formation device according to a first aspect of the present invention comprises: a first porous body having an array of first through holes formed therein, in which gas is injected from one end of the first through holes to generate microbubbles at the other end in contact with the liquid; and a second porous body having an array of second through holes formed therein, through which microbubbles and liquid can pass, and disposed in the liquid so as to deform microbubbles growing from the other end of the first through holes, wherein the second porous body is disposed with a gap between it and the first porous body so that the orientation of the second through holes is the same as that of the first through holes.

[0009] In the arrangement of the first through holes, each of the first through holes may have a uniform shape and size in a cross section perpendicular to the direction of penetration, and may be arranged at a constant pitch.

[0010] The first through holes and the second through holes may be arranged at a constant pitch, and the arrangement pitch of the first through holes may be at least twice the arrangement pitch of the second through holes.

[0011] The second porous body may be a mesh structure in which the second through holes are formed by a mesh of mesh fibers.

[0012] The shape of the inner wall when the second through hole is cut along a cutting plane including a center line of the second through hole extending in the penetration direction may be bent or curved.

[0013] The cross-sectional shape of the second through hole as viewed in the penetration direction may be polygonal.

[0014] The device may further include an adjustment unit that can adjust the size of the gap.

[0015] A bubble formation method according to a second aspect of the present invention includes passing gas through one end of first through holes arranged in a first porous body into the first through holes to generate microbubbles at the other end of the first through holes that contacts the liquid, placing a second porous body having an array of second through holes formed therein, through which the microbubbles and liquid can pass, in the liquid so that the orientation of the second through holes is the same as that of the first through holes and so that a gap is formed between the second through holes and the first porous body, through which the microbubbles and liquid can pass, and deforming the microbubbles growing from the other end of the first through holes.

[0016] According to the present invention, a large amount of fine bubbles of uniform size can be generated without using power to create a liquid flow.

[0017] 1A is a perspective view showing the overall configuration of an air bubble formation device according to an embodiment of the present invention; FIG. 1B is a cross-sectional view showing the configuration of the air bubble generation unit of FIG. 1A; FIG. 1C is a schematic view showing an enlarged configuration of the air bubble generation unit; FIG. 1D is a schematic view of a mesh structure when viewed in the penetration direction of second through-holes; FIG. 1E is a first schematic view showing microbubbles from generation to departure; FIG. 1F is a second schematic view showing microbubbles from generation to departure; FIG. 1G is a schematic view showing microbubbles from generation to departure; FIG. 1H is a schematic view showing a state in which a plurality of microbubbles are simultaneously formed; FIG. 1I is a schematic view of second through-holes when viewed from the penetration direction; FIG. 1J is a schematic view showing a state in which microbubbles join together; FIG. 1K is a schematic view showing a modified example of a second porous body; FIG. 1L is a flowchart showing a bubble formation method according to an embodiment of the present invention; FIG. 1L is a graph showing a comparison of the size and variation of the Sauter diameter of microbubbles formed by the air bubble formation device of FIG. 1A with the size and variation of the Sauter diameter of microbubbles formed by other types of air bubble formation devices; 1 is a graph showing a comparison of the characteristics of the volumetric mass transfer coefficient with respect to the gas superficial velocity in the bubble formation device of FIG. 1 and that of other types of bubble formation devices. FIG. 2 is a graph showing a comparison of the characteristics of the volumetric mass transfer coefficient with respect to the required power in the bubble formation device of FIG. 1 and that of other types of bubble formation devices.

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are denoted by the same reference numerals. In the following embodiments, the terms "have," "include," or "contain" also mean "consist of" or "consist of."

[0019] 1A and 1B, the overall configuration of an air bubble formation device 100 according to this embodiment will be described. As shown in Fig. 1A, the air bubble formation device 100 according to this embodiment forms fine bubbles B. The air bubble formation device 100 includes an air bubble generation unit 1, a first container 2, and a second container 3.

[0020] The interior of the first container 2, i.e., the first region Ar1 (see FIG. 1B ), is filled with gas G. The first container 2 is an air storage chamber that temporarily stores the gas G. The interior of the second container 3, i.e., the second region Ar2 (see FIG. 1B ), is filled with liquid L. The bubble generation unit 1 forms the top surface of the first container 2 and also forms part of the bottom surface of the second container 3.

[0021] The bubble generating unit 1 is disposed at the boundary between the first area Ar1 and the second area Ar2, and defines the boundary. The bubble generating unit 1 takes in gas G from the bottom of the first container 2 and discharges fine bubbles B into the liquid L in the second container 3.

[0022] 1A , the bubble-forming device 100 includes a gas supply source 4, a gas supply pipe 5, a regulator 6, a flow meter 7, a pressure gauge 8, and a control unit 10. In this embodiment, the gas supply source 4 is a supply source of gas G that is the source of fine bubbles B. The gas supply pipe 5 supplies the gas G supplied from the gas supply source 4 to a first region Ar1 in the first container 2.

[0023] The regulator 6 adjusts the amount of gas G supplied from the gas supply source 4 through the gas supply pipe 5. The flow meter 7 measures the flow rate of the gas G supplied from the gas supply source 4 through the gas supply pipe 5. The pressure meter 8 measures the air pressure of the gas G supplied from the gas supply source 4 through the gas supply pipe 5.

[0024] The control unit 10 adjusts the regulator 6 based on the flow rate of the gas G measured by the flow meter 7 and the air pressure of the gas G measured by the pressure meter 8 to control the flow rate and pressure of the gas G.

[0025] 1B, the bubble generating section 1 includes a first porous body 11 and a second porous body 12. The first porous body 11 and the second porous body 12 are both plate-shaped members.

[0026] [First Porous Body] The first porous body 11 has a first surface S1 and a second surface S2 facing in the opposite direction to the first surface S1. The first surface S1 is disposed so as to contact the first region Ar1 filled with gas in the first container 2. The second surface S2 is disposed so as to contact the second region Ar2 filled with liquid L. The areas of the first surface S1 and the second surface S2 of the first porous body 11 may be any size. For example, the area may be 1.0 cm × 1.0 cm, but is not limited to this.

[0027] The first porous body 11 has an array of first through holes 11a that penetrate between the first surface S1 and the second surface S2. In this embodiment, each of the first through holes 11a functions as a bubble-generating nozzle that discharges fine bubbles B. The end of each first through hole 11a on the first surface S1 is a gas inlet end through which gas G is introduced, and the end of each first through hole 11a on the second surface S2 is a bubble outlet end through which fine bubbles B are discharged. As shown in FIG. 2 , the first porous body 11 generates fine bubbles B at the end of the second surface S2 that comes into contact with the liquid L into which gas has been injected from the gas inlet end of the first through hole 11a.

[0028] The first through hole 11 a connects the gas inlet end and the bubble outlet end in a straight line. The first through hole 11 a has a shape of a right column, such as a right circular cylinder or a right-angled prism. However, the shape of the first through hole 11 a may be an oblique cylinder, a curved shape, or a shape in which the size of a cross section perpendicular to the through hole direction changes along the through hole direction.

[0029] 2, in the first porous body 11, each of the first through-holes 11a through which the gas G is introduced from the same first container 2 has a uniform cross-sectional shape and size (diameter D) perpendicular to the penetration direction, and is arranged at a constant arrangement pitch P1. Therefore, the size of the fine bubbles B generated in each of the multiple first through-holes 11a is uniform (see FIG. 5).

[0030] The diameter D of the first through holes 11a can be, for example, 2 μm, but can be changed depending on the size of the microbubbles B to be formed and can be, for example, 10 μm or less. The arrangement pitch P1 of the first through holes 11a can be 1250 μm. The number of the first through holes 11a can be approximately 36. However, the diameter, hole pitch, and number of the first through holes 11a are not limited to these.

[0031] The first porous body 11 can be, for example, a silicon substrate that has been subjected to a hydrophilic treatment, which involves treating the surface without applying a surfactant. This hydrophilic treatment reduces the water repellency of the surface, for example, by surface processing. The material for the first porous body 11 is not limited to silicon; a material that is highly rigid and resistant to deformation, such as metal or ceramic, can also be selected. However, if the first porous body 11 is a silicon substrate, it is possible to form minute first through-holes 11a of desired sizes in desired locations with high precision using semiconductor manufacturing technology.

[0032] [Second Porous Body] As shown in Fig. 1B, the second porous body 12 is disposed in the liquid L in the second region Ar2. The second porous body 12 has a third surface S3 and a fourth surface S4 facing in the opposite direction from the third surface S3, and is disposed so that the third surface S3 faces the second surface S2 of the first porous body 11. As shown in Fig. 2, the second porous body 12 is disposed in a direction in which microbubbles B generated at the ends of the second surface S2 of the first through holes 11a grow. The second porous body 12 has an array of second through holes 12a penetrating between the third surface S3 and the fourth surface S4.

[0033] The second through holes 12a have a size that allows the passage of micro-bubbles B and liquid L. In Fig. 2, the shortest distance between the opposing inner walls of the second through holes 12a is indicated as L2. The second through holes 12a are arranged at a constant arrangement pitch P2. In the horizontal direction, the positions of the second through holes 12a may coincide with the positions of the first through holes 11a, but in consideration of the release of micro-bubbles B, it is generally desirable that the first through holes 11a and the second through holes 12a be arranged offset from each other.

[0034] In the second porous body 12, the circle-equivalent diameter L2 of the second through holes 12a can be, for example, 0.18 mm, but can be adjusted as appropriate. The circle-equivalent diameter L2 of the second through holes 12a may be greater than 0.1 mm. The arrangement pitch P2 of the second through holes 12a can be, for example, 254 μm. However, the circle-equivalent diameter L2 and the arrangement pitch P2 of the second through holes 12a can be changed as appropriate.

[0035] As shown in Figure 3, the second porous body 12 can be a mesh structure 21 in which the second through holes 12a are formed by a mesh of mesh fibers 20. The mesh fibers 20 can be, for example, stainless steel fibers that have been subjected to a hydrophilic treatment to increase the wettability of their surfaces without using a surfactant. However, the material of the mesh fibers 20 is not limited to this. Furthermore, the mesh fibers 20 can have only one layer. This is because multiple layers increase the flow resistance of the liquid L when it tries to flow through the second through holes 12a in the plate thickness direction.

[0036] 2, the second porous body 12 is disposed relative to the first porous body 11 with the second through-holes 12a oriented in the same direction as the first through-holes 11a, and with a gap E (distance L1) that allows the passage of microbubbles B and liquid L. The gap E can be, for example, 100 μm, but is generally desirably 0.1 mm to 0.4 mm.

[0037] 1B, a spacer 13 is provided between the first porous body 11 and the second porous body 12. The spacer 13 may be configured so that its vertical length can be adjusted. In this case, the spacer 13 functions as an adjusting unit that can adjust the size of the gap E. The adjusting unit adjusts the gap E to a size that will allow fine bubbles B of a desired size to be obtained.

[0038] When the second porous body 12 is a mesh structure 21, the mesh structure 21 may be floated by the buoyancy of the generated microbubbles B, thereby creating a gap E between the first porous body 11 and the mesh structure 21. In this case, the outer edges of the first porous body 11 and the second porous body 12 may be connected to each other without the interposition of the spacer 13.

[0039] 4A , the first porous body 11 generates microbubbles B at the ends of the first through-holes 11a on the second surface S2. The microbubbles B gradually grow and become larger. In this case, because a gap E is provided between the first porous body 11 and the second porous body 12, the liquid L present in the gap E can move horizontally as the microbubbles B grow. This promotes the growth of the microbubbles B.

[0040] Since a gap E is provided between the first porous body 11 and the second porous body 12, the liquid L can move freely in the horizontal direction through the gap E and pass between them. This makes it easier for the micro-bubbles B to grow in the horizontal direction as well.

[0041] As the microbubbles B continue to grow, their growth is hindered by the second porous body 12, causing the microbubbles B to deform in a direction toward the second through-holes 12a, as shown in Fig. 4B. In response to this deformation, some of the liquid L in the second through-holes 12a escapes toward the gaps E. This further promotes the growth of the microbubbles B from the ends of the first through-holes 11a.

[0042] When the second through-holes 12a grow further, as shown in FIG. 4C, the micro-bubbles B leave the first through-holes 11a and rise as independent micro-bubbles B through the second through-holes 12a.

[0043] In this way, in the bubble generating unit 1, a gap E is provided between the first porous body 11 and the second porous body 12, and the second through-holes 12a are provided in the second porous body 12, so that as the micro-bubbles B grow, the liquid L can easily pass through the gap E and the second through-holes 12a. This not only makes it easier for the micro-bubbles B to grow, but also makes it easier for the micro-bubbles B to escape from the ends of the first through-holes 11a. When the micro-bubbles B escape from the ends of the first through-holes 11a, new micro-bubbles B are generated at those ends. In this way, in the bubble generating unit 1, micro-bubbles B are continuously generated.

[0044] As described above, the second porous body 12 is positioned to hinder the growth of the micro-bubbles B generated at the end of the first through hole 11a, deforming them, and promoting the escape of the micro-bubbles from the other end of the first through hole.

[0045] 5, the generation, growth, and detachment of micro-bubbles B are simultaneously and intermittently repeated from the plurality of first through-holes 11a of the first porous body 11, resulting in the generation of a large number of micro-bubbles B of uniform size in the liquid L. This allows the micro-bubbles B to be monodispersed.

[0046] In this embodiment, as shown in Figures 2, 4A to 4C, and 5, the cross section of the mesh fiber 20 perpendicular to the longitudinal direction has a circular shape. In other words, in this embodiment, as shown in Figure 4A, when the second through hole 12a is cut along a cutting plane including the center line CL of the second through hole 12a extending in the penetration direction, the shape of the inner wall is curved. This reduces the flow resistance of the inner wall of the second through hole 12a to the liquid L, making it easier for the liquid L to move and promoting the growth and release of microbubbles B.

[0047] As shown in Figure 6, the cross-sectional shape of the second through-hole 12a when viewed in the penetration direction is rectangular. Normally, micro-bubbles B tend to be round due to their surface tension. Therefore, when the cross-sectional shape of the second through-hole 12a is rectangular, paths for the liquid L are formed at the four corners of the second through-hole 12a. This makes it easier for the liquid L to move along these paths in the opposite direction to the micro-bubbles B, thereby promoting the growth and release of the micro-bubbles B.

[0048] The cross-sectional shape of the second through hole 12 a as viewed in the penetration direction is not limited to a quadrangle, but may be a triangle, or a shape with pentagons or more. In other words, the cross-sectional shape of the second through hole 12 a as viewed in the penetration direction may be any polygonal shape.

[0049] If the arrangement pitch P1 of the first through holes 11a and the arrangement pitch P2 of the second through holes 12a were the same as shown in FIG. 7, microbubbles B generated in two adjacent first through holes 11a would gather in one second through hole 12a and become a single large microbubble B. To prevent this, in this embodiment, as shown in FIG. 2, the arrangement pitch P1 of the first through holes 11a is twice the arrangement pitch P2 of the second through holes 12a. This ensures that microbubbles B escaping through the second through holes 12a are always generated in one of the first through holes 11a, thereby improving the uniformity of the microbubbles B. Basically, the arrangement pitch of the first through holes 11a should be at least twice the arrangement pitch of the second through holes 12a.

[0050] As shown in Fig. 8, the cross section perpendicular to the longitudinal direction of the mesh fiber 20 may be rectangular. In this case, the penetration direction of the second through holes 12a is along one diagonal of the rectangular cross section. In this case, when the second through holes 12a are cut along a cross section including a center line CL extending in the penetration direction, the shape of the inner wall of the second through holes 12a will be a bent shape. This reduces the flow resistance of the inner wall of the second through holes 12a to the liquid L, facilitating the movement of the liquid L and promoting the release of microbubbles B.

[0051] Next, a bubble formation method using the bubble formation device 100 according to this embodiment will be described. First, as shown in Fig. 9, a first porous body 11 and a second porous body are manufactured (step S1). Specifically, a silicon substrate is subjected to etching or the like to form a plurality of first through holes 11a, thereby manufacturing the first porous body 11.

[0052] Next, the bubble generating unit 1 is assembled (step S2). Specifically, the mesh structure 21, i.e., the second porous body 12, is attached to the first porous body 11 via the spacer 13, thereby assembling the bubble generating unit 1.

[0053] Next, the bubble-forming device 100 is set up (step S3). The first container 2, the second container 3, and the bubble-generating unit 1 are assembled as shown in Fig. 1, and the gas supply source 4, the gas supply pipe 5, the regulator 6, the pressure gauge 8, the flow meter 7, and the control unit 10 are attached to this assembly to assemble the entire bubble-forming device 100.

[0054] Next, bubbles are formed in the bubble-forming device 100 (step S4). Specifically, gas is supplied to the first region Ar1 of the first container 2, and liquid L is supplied to the second region Ar2 of the second container 3. The control unit 10 adjusts the air pressure of the gas in the first region Ar1 to be higher than the water pressure of the liquid L in the second region Ar2, and passes the gas through the first through-hole 11a.

[0055] In step S4, the bubble generating unit 1 performs the following operations (A) and (B): (A) Gas is passed through the first through holes 11a arranged in the first porous body 11 from the ends of the first surface S1 of the first through holes 11a to generate microbubbles B at the ends of the second surface S2 of the first through holes 11a that contact the liquid L. (B) A second porous body 12 having an array of second through holes 12a formed therein, through which the microbubbles B and the liquid L can pass, is placed in the liquid L so that the orientation of the second through holes 12a is the same as that of the first through holes 11a and a gap E through which the microbubbles B and the liquid L can pass is formed between the second porous body 12 and the first porous body 11, and the microbubbles B growing from the ends of the second surface S2 of the first through holes 11a is deformed.

[0056] As described above, the air bubble generation device 100 according to the present embodiment can generate a large amount of fine bubbles B having a uniform desired size without using mechanical power. Smaller fine bubbles B rise slowly and have a smaller inertial force. Furthermore, while smaller fine bubbles B tend to be absorbed by larger ones when the sizes of the fine bubbles B are different, the fine bubbles B formed by the air bubble generation device 100 are uniform in size and therefore can exist in balance without being absorbed by each other. When a group of monodispersed fine bubbles B having an average bubble diameter of 200 μm or less is formed, the fine bubbles B can float and dissolve and shrink in the liquid L without coalescing, even when generated at a high density.

[0057] [Evaluation Test] The results of the evaluation test of the air bubble generation device 100 according to this embodiment will be described.

[0058] The Sauter diameter (surface area to volume ratio) of the generated microbubbles B was measured when the mesh diameter of the second through-holes 12a, i.e., the mesh structure 21, was set to 2.4 mm, 0.74 mm, 0.36 mm, and 0.18 mm. The measurement results are shown in FIG. 10. As shown in FIG. 10, the smaller the mesh diameter, the smaller the Sauter diameter of the microbubbles B, and the smaller the variation in the Sauter diameter. In particular, when the mesh diameter (circle equivalent diameter) was set to 0.36 mm and 0.18 mm, the size of the microbubbles B was found to be uniform. When the mesh diameter was set to 0.18 mm, the average Sauter diameter of the microbubbles B was approximately 198 μm, and the coefficient of variation (CV value) was 18.4%.

[0059] 10 shows, for comparison, the Sauter diameters of microbubbles B in another air bubble generation device that uses the first porous body 11 to create a steady flow field in the liquid L and generates microbubbles B using that flow field, as well as the Sauter diameters of microbubbles B in another air bubble generation device that generates microbubbles B by vibrating the first porous body 11. As shown in FIG. 10 , when microbubbles B were generated using mesh diameters of 0.36 mm and 0.18 mm in the air bubble generation device 100 according to this embodiment, the variation in the Sauter diameters of the microbubbles B was reduced compared to when microbubbles B of similar diameters were generated using a steady flow field and a vibrating flow field. This evaluation experiment revealed that the air bubble generation device 100 according to this embodiment can reduce the size and monodispersity of microbubbles B.

[0060] Furthermore, the mass transfer coefficient K of the fine bubbles B in the liquid L when the fine bubbles B are formed using the bubble-forming device 100 according to this embodiment is Ｌ a is evaluated. Ｌ a is an index showing how many fine bubbles B can be dissolved in the same volume.

[0061] FIG. 11 shows the mass transfer coefficient K Ｌ This graph shows the mass transfer capacity coefficient K a versus the change in gas superficial velocity [cm / s] in the bubble formation device 100 according to the present embodiment, as well as in a laminated slit type bubble formation device that generates bubbles using laminated slits, a sintered ball type bubble formation device that generates bubbles using sintered balls, and a single-hole nozzle type bubble formation device that generates bubbles using a single-hole nozzle. Ｌ The change in a is plotted.

[0062] As shown in FIG. 11, in the bubble generation device 100 according to the present embodiment, the mass transfer capacity coefficient K Ｌ a is dramatically improved by 85 times compared to when the second porous body 12 is not provided. This indicates that the air bubble generation device 100 has high gas dissolving ability at a low gas flow rate. Conversely, this indicates that the air bubble generation device 100 according to this embodiment can be made compact and portable.

[0063] FIG. 12 shows the mass transfer capacity coefficient K Ｌ 12 shows the mass transfer capacity coefficient K a when the second porous body 12 without a mesh (second through-holes) is used in the air bubble formation device 100 according to the present embodiment and when the mesh hole diameters are 0.74 mm, 0.36 mm, and 0.18 mm. Ｌ As shown in Figure 12, the Venturi type, pressurized dissolution type, swirling liquid flow type, and ejector type bubble-forming devices require a large amount of power to create a liquid flow, while even devices using a perforated plate or a constant flow nozzle have a low mass transfer capacity coefficient K Ｌ In order to increase a, it is necessary to increase the required power. In contrast, it has been revealed that the air bubble generation device 100 according to this embodiment can obtain a high gas dissolving ability with an extremely small power required to supply gas at a predetermined atmospheric pressure. In the air bubble generation device 100 according to this embodiment, the smaller the mesh diameter, the lower the mass transfer capacity coefficient K Ｌ It has also been shown that a can be increased.

[0064] As described above in detail, according to the bubble-forming device 100 of this embodiment, a gap E is formed between the first porous body 11 and the second porous body 12 so that the liquid L in the area surrounding the microbubbles B can pass freely, and therefore a large amount of microbubbles of uniform size can be generated without creating a liquid flow using power.

[0065] According to the air bubble formation device 100 of this embodiment, the first through holes 11a have uniform cross-sectional shapes and sizes (diameters D) perpendicular to the penetration direction and are arranged at the same arrangement pitch P1. In this manner, a large amount of uniform-sized microbubbles B can be formed at once. However, the cross sections of the first through holes 11a in the first porous body 11 may vary, and the arrangement pitch of the first through holes 11a may also vary.

[0066] According to the air bubble formation device 100 of this embodiment, the arrangement pitch P1 of the first through holes 11a is at least twice the arrangement pitch P2 of the second through holes 12a. However, this is not limited to this. The first through holes 11a and the second through holes 12a may be arranged so that the microbubbles B generated in each of the multiple first through holes 11a do not gather in one second through hole 12a.

[0067] In the air bubble formation device 100 according to the present embodiment, the second porous body is a mesh structure 21 in which a mesh that forms the second through-holes 12a is formed by the mesh fibers 20. The mesh structure 21 is suitable for preventing the growth of the microbubbles B generated in the first through-holes 11a and for obtaining microbubbles B of a desired size. Furthermore, if the second porous body 12 is the mesh structure 21, as described above, the buoyancy of the microbubbles B generated in the first through-holes 11a can float the mesh structure 21, thereby forming a gap E between the mesh structure 21 and the first porous body 11.

[0068] According to the air bubble generation device 100 of this embodiment, when the second through hole 12a is cut along a cross section including the center line CL extending in the through-hole direction, the shape of the inner wall of the second through hole 12a is bent or curved. This reduces the flow resistance of the liquid L passing through the second through hole 12a, making it easier for the micro-bubbles B and the liquid L to pass through the second through hole 12a. This makes it easier for the micro-bubbles B to escape.

[0069] According to the air bubble generation device 100 of this embodiment, the cross-sectional shape of the second through hole 12 a as viewed in the penetration direction is polygonal. This makes it possible to ensure a flow path through which the liquid L passes within the second through hole 12 a. This makes it easier to release the fine bubbles B.

[0070] According to the air bubble formation device 100 of this embodiment, the spacer 13 functions as an adjustment unit that can adjust the size of the gap E. By changing the size of the gap E, it is possible to change the size of the fine air bubbles B to be formed.

[0071] In addition, the size of the escaping microbubbles B can be adjusted by adjusting the cross-sectional shape, size and number of holes of the first through holes 11a and the second through holes 12a, the cross-sectional shape of the mesh fibers, the ratio of the arrangement pitch between the first through holes 11a and the second through holes 12a, and the affinity of the first porous body 11 and the second porous body 12 with the liquid L (e.g., water).

[0072] In the air bubble formation device 100 according to the present embodiment, the second porous body 12 is a mesh structure 21. However, this is not limiting. For example, the second porous body 12 may be formed of a substrate similar to that of the first porous body 11.

[0073] In the air bubble generating device 100 according to the present embodiment, the air bubble generating unit 1 is disposed so that the second surface S2 and the fourth surface S4 face upward. However, this is not limiting. For example, the air bubble generating unit 1 may be disposed so that the second surface S2 and the fourth surface S4 face horizontally.

[0074] Furthermore, the air bubble formation device 100 according to this embodiment can be a completely sealed batch device. Therefore, a material with excellent pressure resistance and chemical resistance can be selected according to the experimental environment as the material for the air bubble formation device 100. Furthermore, the type of gas G to be supplied can be freely set.

[0075] The air bubble-forming device 100 according to this embodiment not only has the ability to produce fine bubbles and the ability to highly control the size of the fine bubbles B, but also realizes compactness and portability of the device, allowing it to be attached to bottles, small aquariums, etc. Therefore, in addition to use in primary industries such as aquariums and physiological activities, it can be widely applied in fields such as beauty and skin care, life sciences and pharmaceuticals that require small-lot production of a wide variety of products such as beverages and adding texture and flavor, as well as in household toilet cleaning.

[0076] Furthermore, the air bubble-generating device 100 according to this embodiment has an apparatus structure that generates fine bubbles in a bulk liquid simply by placing a second porous body (baffle plate) 12 having a mesh structure on a first porous body (perforated plate) 11 without applying an external force. Therefore, the perforated plate that has been used as the most common air bubble generating device in the conventional chemical industry can be replaced with the air bubble generating unit 1 according to this embodiment, and the air bubble generating ability can be dramatically improved, so the significance and value of the air bubble generating unit 1 is extremely great.

[0077] This invention allows various embodiments and modifications without departing from the broad spirit and scope of this invention. Furthermore, the above-described embodiments are intended to explain this invention and do not limit the scope of this invention. That is, the scope of this invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of this invention.

[0078] In addition, this application claims priority based on Japanese Patent Application No. 2023-169190 filed on September 29, 2023, and the specification, claims, and drawings of Japanese Patent Application No. 2023-169190 are incorporated herein by reference.

[0079] The present invention can be applied to forming fine bubbles.

[0080] REFERENCE SIGNS LIST 1 Bubble generating unit, 2 First container, 3 Second container, 4 Gas supply source, 5 Gas supply pipe, 6 Regulator, 7 Flow meter, 8 Pressure gauge, 10 Control unit, 11 First porous body, 11a First through-hole, 12 Second porous body, 12a Second through-hole, 13 Spacer, 20 Mesh fiber, 21 Mesh structure, 100 Bubble generating device, Ar1 First region, Ar2 Second region, B Fine bubbles, CL Center line, E Gap, G Gas, L Liquid, S1 First surface, S2 Second surface, S3 Third surface, S4 Fourth surface

Claims

1. A bubble generating device comprising: a first porous body having an array of first through holes formed therein, into which gas is injected from one end of the first through holes to generate microbubbles at the other end in contact with liquid; and a second porous body having an array of second through holes formed therein through which microbubbles and liquid can pass, the second porous body being disposed in liquid so as to deform microbubbles growing from the other end of the first through holes, the second porous body being disposed between the first porous body and the second through holes so that the orientation of the second through holes is the same as that of the first through holes, with a gap between the second porous body and the first porous body allowing the passage of microbubbles and liquid.

2. The bubble forming device as described in claim 1, wherein in the arrangement of the first through holes, each of the first through holes has a uniform shape and size of a cross section perpendicular to the penetration direction, and is arranged at a constant pitch.

3. The bubble forming device as described in claim 1, wherein the first through holes and the second through holes are arranged at a constant pitch, and the arrangement pitch of the first through holes is at least twice the arrangement pitch of the second through holes.

4. The bubble forming device according to claim 1, wherein the second porous body is a mesh structure in which the second through holes are formed by a mesh of mesh fibers.

5. The bubble forming device according to claim 1, wherein the shape of the inner wall when the second through hole is cut along a cutting plane including a center line of the second through hole extending in the through direction is folded or curved.

6. The bubble generating device according to claim 1, wherein the cross-sectional shape of the second through hole when viewed in the penetrating direction is polygonal.

7. The bubble forming device according to claim 1, further comprising an adjustment unit capable of adjusting the size of the gap.

8. A method for forming bubbles, comprising: passing a gas through one end of first through holes arranged in a first porous body into the first through holes to generate microbubbles at the other end of the first through holes in contact with liquid; placing a second porous body having an array of second through holes formed therein, through which the microbubbles and liquid can pass, in the liquid such that the orientation of the second through holes is the same as the first through holes and a gap is formed between the first porous body and the second through holes through which the microbubbles and liquid can pass; and deforming the microbubbles growing from the other end of the first through holes.

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