Fine bubble generation device

Abstract

To provide a fine bubble generation device capable of efficiently generating nano-order fine bubbles.SOLUTION: There is provided a fine bubble generation device 1 in which an inlet part 10 whose diameter gradually decreases from an inlet of a cylindrical main body, an orifice 15 continuous with the inlet part, and an enlarged-diameter part 20 continuous with the orifice are sequentially formed, an outlet peripheral wall 8 of the orifice is formed as a radial vertical surface, the enlarged-diameter part is opened only at an outlet located on an extension of a center line of the orifice, the diameter of the enlarged-diameter part is 3 to 10 times the diameter of the orifice, the orifice includes a straight-tube portion, the length of the straight-tube portion is 0.5 to 2.0 times the length of the outlet diameter of the orifice, and the outlet peripheral wall is within ±20 degrees around the vertical line with respect to the axis of the orifice.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fine bubble generator. [Background technology]

[0002] One method for generating fine bubbles is to use the cavitation effect. Patent Documents 1 and 2 disclose a fine bubble generator in which a columnar part protrudes into an orifice in a tubular main body, generating nano-sized fine bubbles in the water flow passing through this orifice. When tap water is introduced into this fine bubble generator, the water flow is throttled by the throttle section formed between the opposing pillars, increasing its flow rate. As a result, a negative pressure area is created in the throttle section (and downstream of it) according to Bernoulli's principle, and the resulting cavitation (decompression) effect causes dissolved gases in the water to separate out, generating fine bubbles. For micron-order fine bubbles, it is sufficient to simply provide a small-diameter portion (orifice) in the cylindrical member (Patent Document 3). That is, micron-order fine bubbles can be generated by a device equipped with an inlet portion whose inner diameter gradually narrows from the inlet end to the center of the cylindrical member, an orifice connected to this inlet portion, and an expanding diameter portion connected to this orifice whose inner diameter gradually widens toward the other outlet end of the cylindrical member. For other details, see Patent Documents 4 to 12. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5712292 [Patent Document 2] Patent No. 6279179 [Patent Document 3] Patent No. 6369879 [Patent Document 4] Japanese Patent Application Publication No. 2018-51561 [Patent Document 5] Korean Patent Publication No. 10-2018-0114665 [Patent Document 6] International Publication No. 2018 / 02070 [Patent Document 7] Japanese Patent Application Laid-Open No. 2008-296096 [Patent Document 8] Japanese Patent Application Laid-Open No. 2013-146714 [Patent Document 9] Japanese Patent Application Laid-Open No. 2008-161826 [Patent Document 10] Japanese Patent Application Laid-Open No. 2011-83772 [Patent Document 11] Japanese Patent Application Laid-Open No. 2008-290050 [Patent Document 12] Japanese Patent Application Laid-Open No. 2013-146714 Summary of the Invention [Problem to be solved by the invention]

[0004] To generate nano-order fine bubbles, a columnar part was provided protruding from the orifice of the cylindrical member. The presence of such pillars hinders the flow of fluid, limiting the flow rate of the fluid that generates fine bubbles. Furthermore, foreign matter may become trapped between the pillars. Furthermore, it is time-consuming to manufacture the columnar portion, and when the columnar portion is supported in a cantilevered state, it is difficult to ensure mechanical rigidity and durability. [Means for solving the problem]

[0005] The present invention has been made to achieve the above object and is defined as follows: A cylindrical fine bubble generator having an orifice, A fine bubble generator in which a recess is formed in the peripheral wall of the orifice outlet.

[0006] Here, the orifice refers to a portion of the cylindrical member that is reduced in diameter and has a predetermined length. In other words, the cylindrical member is connected to the inlet side and outlet side of the orifice by an inlet portion and an outlet portion (expanded diameter portion) having a diameter larger than that of the orifice. The orifice preferably has a flat inner surface of the same diameter to stabilize the flow. The diameter of the orifice can be designed arbitrarily based on the relationship between the desired compression ratio (for the fluid) and the amount of fluid to be processed. To achieve the cavity effect, it is important to adjust the difference in diameter between the orifice outlet and the subsequent expanded diameter section.

[0007] The length of the orifice can be designed arbitrarily as long as the fluid flowing through the orifice is stable, that is, the flow is aligned in the axial direction. Of course, the diameter of the orifice is not limited to being uniform in the axial direction, but the diameter of the orifice may be varied gradually, or a spiral groove may be formed on the inner peripheral surface.

[0008] It is preferable that the diameter of the inlet leading to the orifice gradually decreases toward the orifice in order to smoothly introduce the fluid into the orifice, thereby ensuring a high flow rate and sufficiently compressing the fluid. The degree of diameter reduction (angle of inclination relative to the axial direction) can be selected arbitrarily depending on the type of fluid, flow rate, and desired compression ratio. The inner peripheral surface of the inlet portion is preferably flat, but a spiral groove or the like may be provided inside.

[0009] The expanded diameter section following the orifice outlet is larger in diameter than the orifice outlet, so that when the fluid compressed in the orifice is discharged into the expanded diameter section, it is released and becomes negative pressure, thereby exerting the cavity effect. The difference (ratio) between the diameter of the orifice outlet and the maximum diameter of the expanded diameter section is designed arbitrarily depending on the desired average particle size and number of particles of the fine bubbles.

[0010] It is widely known that micro-order fine bubbles are formed by releasing a fluid compressed in an orifice at an expanded diameter section to create a negative pressure (see Patent Document 3). In this invention, by providing a recess in the peripheral wall of the orifice outlet, the fine bubbles formed can be made nano-order without providing any pillar parts in the orifice. By eliminating the pillar portion, the resistance in the orifice is reduced, thereby increasing the amount of fluid that can be processed. In addition, the structure is simplified, which makes it easier to manufacture and improves durability and maintainability.

[0011] The recesses are preferably distributed uniformly in the circumferential and radial directions on the peripheral wall of the orifice outlet, with the center of the orifice as their center, in order to stably generate fine bubbles. The peripheral wall of the orifice outlet is formed perpendicular to the axis of the orifice, and the depth direction of the recess formed there is preferably in the same direction as the axis of the orifice. This recess has the same diameter from the opening in the peripheral wall in the depth direction, or the diameter decreases in the depth direction. This is to prevent fluid from stagnating in the recess. Also, from the viewpoint of moldability (ease of demolding), it is preferable to form the recess as described above.

[0012] The recess may have any shape. For example, the recess may be formed so that the deeper it is, the further away or closer it becomes to the orifice. The closer the distance between the orifice outlet periphery and the recess periphery (the gap between the two), the better. However, if the distance is too close, the wall thickness around the outlet becomes too thin and mechanical strength cannot be ensured. According to the inventors' research, when the device is made of resin, the distance between the two should be 0.1 mm or more. From the viewpoint of bringing the periphery of the orifice outlet and the periphery of the recess closer to each other, it is preferable that the peripheral wall of the orifice outlet be perpendicular to the central axis of the orifice.

[0013] The inventors' investigations revealed that a large negative pressure is generated within the recess. Simulation results show that the negative pressure generated is 1 / 10 to 1 / 100 of that at the center of the expanded diameter section. Furthermore, the negative pressure within the recess changes periodically due to interaction with the water flow. The larger the negative pressure in the recess, the larger the cavity effect that will occur there. It is also believed that the periodic change in negative pressure will have the same effect as applying ultrasonic waves to a fluid. The nano-sized fine bubbles caused by the presence of the recesses is thought to be the result of an interaction between the large negative pressure within the recesses and their periodic changes. It is believed that by controlling the value of these negative pressures and the frequency of their changes, it is possible to control the average particle size and particle size distribution of the fine bubbles generated in the fluid.

[0014] The following parameters control the value of the negative pressure in the recess and its frequency: Ratio of orifice outlet diameter to the diameter of the expanded portion Aspect ratio of the recess (ratio of the area of ​​the opening to its depth) The velocity and viscosity of the fluid discharged from the orifice outlet Ratio of the area of ​​the recess to the peripheral wall of the orifice Distance between the orifice outlet periphery and the recess periphery Ratio of the orifice exit area to the area of ​​the recess, etc.

[0015] The orifice is not particularly limited in shape as long as it narrows and compresses the water flow sent from the inlet and increases its flow rate, but from the standpoint of minimizing resistance to the water flow, it is preferable that it has a space with a circular cross section. The diameter of the orifice can be selected arbitrarily depending on the amount of water to be treated, etc. To achieve this flow rate, the flow rate and pressure of the fluid and the texture (material, surface roughness) of the inner circumferential surface of the orifice are adjusted. To stabilize the flow rate, it is preferable to provide a section with the same diameter (straight pipe section). The length of the straight pipe section is preferably 0.5 to 2.0 times, more preferably 1.0 to 1.5 times, the length of the outlet diameter of the orifice.

[0016] A large diameter section is formed downstream of the orifice, and the water that passes through the orifice is released into this large diameter section. This releases the water flow that was compressed by the orifice, reducing its pressure. This pressure reduction creates a cavity effect, which causes bubbles to form.

[0017] The expanded diameter section following the orifice outlet preferably has a circular cross section, with its center coinciding with the center of the orifice. This allows the fluid discharged from the orifice outlet to be uniformly dispersed and decompressed, thereby uniformly forming fine bubbles. In this invention, the peripheral wall of the orifice outlet is perpendicular to the axis of the orifice, so that the expanded diameter portion is cylindrical with a uniform diameter from the orifice outlet periphery. By making the peripheral wall of the orifice outlet vertical, the fluid discharged from the orifice outlet can be efficiently subjected to negative pressure. Also, by placing the recess close to the orifice outlet, it is thought that a larger negative pressure and a suitable negative pressure period can be obtained. The shape of the inner peripheral surface of the expanded diameter portion can be designed arbitrarily. For example, the expanded diameter portion continuing to the outlet of the orifice can be shaped like an inverted funnel, with the diameter gradually increasing with increasing distance from the outlet.

[0018] The pressure in the recess formed on the peripheral wall of the orifice outlet is set to 1 / 10 to 1 / 100 of the pressure in the center of the expanded diameter section. Because the pressure value cannot be measured directly, the simulation results of a water flow simulation software (Simulation by SolidWorks) are used. See Figure 4 for specific simulation results. The density of the fluid in the recess under this negative pressure decreases, and the fluid becomes almost gaseous. It is believed that fine bubbles are formed when the gaseous fluid in the recess is mixed with the liquid fluid. The fluid flowing through the enlarged diameter section and the gaseous fluid in the recess then interfere with each other, causing the negative pressure in the recess to change periodically. It is believed that the frequency of this change, combined with the magnitude of the negative pressure in the recess, allows the fine bubbles to be made nano-sized.

[0019] The second recess may be provided in the peripheral wall of the enlarged diameter portion in a circumferentially continuous or discontinuous manner. The generation of fine bubbles can also be promoted in this second recess. The negative pressure in the second recess is greater than that in the first recess formed around the outlet of the orifice and less than that in the center of the expanded diameter portion. The second recess in the peripheral wall of the enlarged diameter portion agitates the fluid flowing through the enlarged diameter portion, thereby promoting the cavity effect in the first recess. From the standpoint of agitation, the second recess can be replaced by a protrusion.

[0020] The fine bubble generator of this invention can generate a large amount of nano-sized fine bubbles by passing a fluid such as water through an orifice once. In other words, because a large negative pressure is generated in the recess, the fluid that enters the recess takes on the properties of a gas phase within the recess. As a result, the properties of the fluid itself may change. For example, although it is not possible to measure this, it is thought that so-called fluid clusters are being destroyed. In other words, as the clusters become smaller, the permeability of the fluid itself increases. Furthermore, the surface tension of the nanobubble water obtained by this invention is the same as that of regular water. On the other hand, nanobubble water obtained by a method in which air bubbles supplied to water are made finer by mechanical stirring or applying external pressure has a lower surface tension, making it more likely to wet with other substances.

[0021] Thus, the fine bubble water produced by the fine bubble generator of the present invention possesses novel properties. Therefore, in another aspect of the present invention, fine bubbles are removed from the fine bubble water obtained by the method described above. Even if fine bubbles are not present, water treated with the fine bubble generator of the present invention possesses novel properties. To remove the fine bubbles, ultrasonic waves are applied to grow nano-sized fine bubbles into micro-sized bubbles, and then the micro-sized fine bubbles are allowed to disappear naturally. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view of a fine bubble generator according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the same seen from the exit side. [Figure 3] FIG. 3 is a chart showing the measurement results of the device of FIG. [Figure 4] Figure 4 also shows the simulation results. [Figure 5] FIG. 5 is a cross-sectional view of a fine bubble generator according to another embodiment. [Figure 6] FIG. 6 is a chart showing the measurement results of the device of FIG. [Figure 7] FIG. 7 is a cross-sectional view of a fine bubble generator according to another embodiment. [Figure 8] FIG. 8 is a chart showing the measurement results of the device of FIG. [Figure 9] FIG. 9 is a cross-sectional view of a fine bubble generator according to another embodiment. [Figure 10] FIG. 10 is a chart showing the measurement results of the device of FIG. [Figure 11] Figure 11 is a chart summarizing the results of Figures 3, 6, 9, and 10 on the same scale. DETAILED DESCRIPTION OF THE INVENTION

[0023] FIG. 1 is a cross-sectional view showing the structure of a fiber optic generating device 1 according to an embodiment of the present invention. This fine bubble generator (hereinafter sometimes simply referred to as the "generator") 1 comprises a cylindrical casing 3, an inlet portion 10, an orifice 15, an expanded diameter portion 20, and a recess 40. The cylindrical housing 3 is composed of three pieces 4, 5, and 6. A fitting hole 7 is drilled at one end of the first piece 4 (the left side in the figure), and this fitting hole 7 has a flat bottom (the peripheral wall 8 of the opening of the orifice 15). The second and third pieces 5 and 6 are inserted into this fitting hole 7 without any gaps.

[0024] The other end (right side in the figure) of the first piece 4 has a conical inlet 10 that is connected to an orifice 15. The orifice 15 is a through hole of the same radius that opens into the fitting hole 7. The center lines of the orifice 15 and the inlet 10 are aligned with the center line of the first piece 4. In the first piece 4 , a first recess 40 is formed at the bottom of the fitting hole 7 , that is, in the peripheral wall 8 of the outlet of the orifice 15 .

[0025] As shown in FIG. 2, the first recesses 40 are radially opened at intervals of 90 degrees in the circumferential direction on the peripheral wall 8 with the center of the outlet of the orifice 15 as the center. In this example, the opening of the recess 40 is rectangular (oval) with rounded corners, and is drilled parallel to the orifice 15 while maintaining this opening shape.

[0026] The second piece 5 is a disk-shaped member that fits into the fitting hole 7, and is formed with a first enlarged diameter portion 21 that continues to the orifice 15. The diameter of this first enlarged diameter portion 21 gradually increases from around the center of the second piece 5, forming a second recess 23. In this example, the second recess 23 is formed continuously in the circumferential direction of the inner peripheral surface of the second piece 5, but this may also be formed intermittently.

[0027] The disk-shaped third piece 6 is placed on top of the second piece 5 and fitted into the fitting hole 7. The third piece 7 is formed with a second enlarged diameter portion 25, which combines with the first enlarged diameter portion 21 of the second piece 5 to form the enlarged diameter portion 20 of the fine bubble generator 1. In this example, the first expanded diameter portion 21 and the second expanded diameter portion 25 have the same diameter, but the diameter of the second expanded diameter portion 25 may be larger than that of the first expanded diameter portion 21.

[0028] The three pieces 4, 5 and 6 that make up the cylindrical housing 3 can all be made of synthetic resin, but of course they can also be made of metal or ceramics. In the above, the first recess 40 is entirely exposed to the first enlarged diameter portion 21 . The first recess 40 may be expanded in the radial direction as viewed from the peripheral wall 8 so that a portion of it is covered by the second piece 5 when the second piece 5 is fitted thereto. The first recesses 40 are preferably formed radially from the center of the outlet of the orifice 15, and are not limited to the four directions shown in Fig. 2, but may be formed in any direction within a range of, for example, 3 to 12. When viewed from the center of the outlet of the orifice 15, the first recesses 40 are preferably evenly distributed in the circumferential and radial directions.

[0029] A fine bubble generator having the following specifications was prepared for this example: The cylindrical housing 3 was made of ABS resin. Cylindrical housing 3: diameter 12.0 mm, length: 10 mm Inlet opening diameter: 8.0 mm Opening angle of the inlet slope: 90 degrees Orifice 15 diameter: 0.9 mm Orifice 15 length: 1.0 mm Vertical width of the first recess 40: 0.7 mm Width of the first recess 40: 0.4 mm Depth of the first recess 40: 0.5 mm Distance between the orifice 15 and the first recess 40: 0.1 mm Diameter of enlarged parts 21 and 25: 0.3 mm Inclination angle of second recess 23: 90 degrees Width of the second recess 23: 0.75 mm Fitting hole 7: diameter 10 mm, depth 4.0 mm Thickness of the third and fourth pieces: 2.0 mm each

[0030] Tap water was introduced into the inlet side of the fine bubble generator configured in this way at a pressure of 2.0 MPa, and the water discharged from the expanded diameter section 20 was collected and the particle size distribution of the fine bubbles contained therein was measured using a Shimadzu SALD-7500H. The results are shown in Figure 3. The average particle size was 93 nm, and there were over 370 million nano-sized fine bubbles per ml. Micro-sized fine bubbles were almost nonexistent. A simulation of the water flow in this example is shown in Figure 4. In Figure 4, the flow velocity is indicated by the shade of the arrow. The lighter the arrow, the faster the flow velocity. The pressure in the enlarged diameter portion was 31.7 kPa, whereas the pressure in the first recess was 2.1 kPa and the pressure in the second recess was 2.9 kPa.

[0031] Next, a similar test was carried out on a product with the above specifications but omitting the second recess (see FIG. 5). The results are shown in Figure 6. The average particle size was 109 nm, and there were approximately 130 million nano-order fine bubbles per ml.

[0032] Next, a similar test was carried out on a product with the above specifications but omitting the first recess (see FIG. 7). The results are shown in Figure 8. The average particle size was 136 nm, and there were approximately 77 million nano-order fine bubbles per ml.

[0033] Next, a similar test was carried out on a product with the above specifications but omitting the first recess (see FIG. 9). The results are shown in Figure 10. The average particle size was 158 nm, and there were approximately 48 million nano-order fine bubbles per ml.

[0034] The above results show that even when the first recess and the second recess are omitted, a large number of nano-order fine bubbles are generated. Figure 11 summarizes the results of Figures 3, 6, 8, and 10 on the same scale. The results in Figure 11 show that the particle size of the generated fine bubbles becomes smaller by providing the first recess and the second recess. Furthermore, by having both the first recess and the second recess, the particle size of the generated fine bubbles becomes significantly smaller, and as a result, the number of generated fan bubbles also increases significantly.

[0035] From the above, the present inventors have made the following findings. A fine bubble generator having an inlet section whose diameter gradually decreases from the inlet of a cylindrical body, an orifice continuous with the inlet section, and an expanded diameter section continuous with the orifice, a boundary between the orifice and the expanded diameter portion is a radially elevated surface; The diameter of the expanded diameter portion is 3 to 10 times the diameter of the orifice, A fine bubble generator in which the expanded diameter portion is released only at its outlet.

[0036] In the above description, the boundary between the orifice and the expanded diameter section corresponds to the peripheral wall of the orifice outlet. This peripheral wall of the outlet is preferably perpendicular to the axis of the orifice, but may be inclined at ±20 degrees or ±10 degrees from the perpendicular. Here, with the orifice outlet as the center, the expanded diameter section side is designated as + and the inlet side as -. If the inclination of the outlet wall exceeds +20 degrees, the stirring and mixing of bubbles formed by the cavity effect will be insufficient.On the other hand, if the inclination of the outlet wall exceeds -20 degrees, the water flow discharged from the orifice will be drawn toward the inclined outlet wall, making it impossible to ensure a sufficient flow velocity, resulting in insufficient pressure reduction.

[0037] Furthermore, if the diameter of the expanded diameter section is less than three times the diameter of the orifice, the pressure reduction will be insufficient. On the other hand, if the diameter of the expanded diameter section is more than ten times the diameter of the orifice, the water flow discharged from the orifice outlet will be too dispersed, hindering the water flow. As a result, a sufficient flow velocity cannot be ensured, and the pressure reduction will be insufficient. It is preferable that the expanded diameter portion has a uniform inner diameter as shown in the drawing, but it may also be in the shape of an inverted funnel within the above range. The enlarged diameter portion is open only at its outlet. In other words, no air or other gases are injected into the peripheral wall of the enlarged diameter portion from the outside. If the enlarged diameter portion communicates with the external environment at any point other than its outlet, the reduced pressure environment within the enlarged diameter portion may be disturbed, which is undesirable.

[0038] The second recess is formed at a position where it can efficiently agitate the water flow discharged from the orifice outlet. It can be arbitrarily designed depending on the flow rate, the ratio of the diameter of the orifice to the diameter of the expanded portion, the shape of the expanded portion, etc. According to the inventors' investigations, it is preferable to form the second recess in the range of 0.5 to 1.5 times the diameter of the expanded portion from the orifice outlet toward the downstream side in the axial direction of the orifice.

[0039] The following items are disclosed below: (1) A fine bubble generator having an inlet section whose diameter gradually decreases from the inlet of a cylindrical body, an orifice continuous with the inlet section, and an expanded diameter section continuous with the orifice, a first recessed portion is formed in a radial elevation of the boundary between the orifice and the expanded diameter portion, the first recessed portion being uniformly distributed in the circumferential direction and the radial direction with the center of the orifice as its center; A fine bubble generator in which second recesses or protrusions are formed on the inner surface of the expanded diameter portion, which are continuous or discontinuous in the circumferential direction. (2) A water treatment device comprising: a water flow compression section having a peripheral wall that compresses the water flow evenly; and a water flow release section formed downstream of the water flow compression section and having a larger diameter than the water flow compression section, wherein the water flow release section has a first recess that is recessed in the opposite direction to the water flow, and the pressure within the first recess is smaller than the pressure of the water flow released from the water flow compression section to the water flow release section. (3) The water treatment device according to (2), wherein the pressure in the first recess is 1 / 10 to 1 / 100 of the pressure in the center of the water flow release portion. (4) The water treatment device according to (2), wherein a second recess is formed in the radial direction on the inner surface of the water flow release section, and the pressure in the second recess is greater than the pressure in the first recess and less than the pressure at the center of the water flow release section. (5) The water treatment device according to (2), wherein the inner circumferential surface of the water flow release section is formed with circumferentially continuous or discontinuous recesses or circumferentially continuous or discontinuous protrusions, which agitate the water flow released from the water flow compression section. (6) 6. The water treatment device according to claim 2, further comprising a device for removing fine bubbles from the water flow released from the water flow releasing section.

[0040] The present invention is not limited to the above-described embodiments of the invention, and various modifications within the scope of the claims and within the scope that can be easily conceived by a person skilled in the art are also included in the present invention.

[0041] Disclose the following: (Claim 1) A fine bubble generator having an inlet section whose diameter gradually decreases from the inlet of a cylindrical body, an orifice continuous with the inlet section, and an expanded diameter section continuous with the orifice, The orifice has an outlet peripheral wall formed as a radially elevated surface; the expanded diameter portion is open only at an outlet at a point beyond the center line of the orifice, A recess is formed in the outlet peripheral wall. Fine bubble generator. (Claim 2) 2. The fine bubble generator according to claim 1, wherein the outlet peripheral wall is formed in a direction perpendicular (±20 degrees) to the axis of the orifice. (Claim 3) 3. The fine bubble generator according to claim 1, wherein second recesses or protrusions are formed on the inner surface of the enlarged diameter portion in a circumferential direction, either continuously or intermittently. (Claim 4) 4. The fine bubble generator according to claim 1, wherein the recesses are uniformly distributed in the circumferential and radial directions on the peripheral wall of the outlet of the orifice, with the center of the orifice as their center. (Claim 5) 5. The fine bubble generator according to claim 1, wherein the diameter of the expanded diameter portion is 3 to 10 times the diameter of the orifice. (Claim 6) 6. A water treatment device comprising the fine bubble generator according to claim 1 and a water supply unit that supplies water to the fine bubble generator. (Claim 7) 7. The water treatment device according to claim 6, further comprising a fine bubble remover that removes the fine bubbles generated in the water treatment device. (Claim 8) A step of preparing a fine bubble generator according to any one of claims 1 to 5; supplying water to the inlet. (Claim 9) 9. The water treatment method according to claim 8, wherein fine bubbles contained in the water discharged from the outlet side of the orifice are removed. (Claim 10) preparing water; and treating the water with the fine bubble generator according to any one of claims 1 to 5. (Claim 11) preparing fine bubble water produced according to claim 10; and removing some or all of the fine bubbles from the fine bubble water. [Explanation of symbols]

[0042] 1, 101, 201, 301 Fine bubble generator 8 Orifice outlet wall 10 Entrance 15 Orifice 20 Expanded diameter part 23 Second recess 40 First recess

Claims

1. an inlet portion whose diameter gradually decreases from the inlet of the cylindrical body, an orifice continuous with the inlet portion, and an expanded diameter portion continuous with the orifice are sequentially formed; The orifice has an outlet peripheral wall formed as a radially elevated surface; In a fine bubble generator, the expanded diameter portion is opened only at an outlet located at an extension of the center line of the orifice, the diameter of the expanded diameter portion is 3 to 10 times the diameter of the orifice, the orifice has a straight pipe portion, and the length of the straight pipe portion is 0.5 to 2.0 times the length of the outlet diameter of the orifice; A fine bubble generator in which the outlet peripheral wall is at an angle of ±20 degrees from the center perpendicular to the axis of the orifice.

2. A method for producing water containing fine valves, in which water is introduced into the inlet of the fine bubble generator described in claim 1 at a pressure of 2.0 MPa, so that substantially all of the fine valves contained in the water released from the expanded diameter section are of nano-order size.

3. 4. The method for producing water containing fine bubbles according to claim 3, wherein 99.8% of the fine bubbles contained in the water are on the nano-order in terms of number ratio.

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