阅读说明：本技术 微泡产生装置及水处理装置 (Microbubble generator and water treatment device ) 是由 柴田芳树 花村厚次 于 2020-07-22 设计创作，主要内容包括：在使柱状部突出到筒状构件的节流孔的结构的微泡产生装置中,由于柱状部的存在会阻碍流体的流动,因此限制了产生微泡的流体的流量。另外,有时在柱状部间会夹卡住异物。制造柱状部费工费时。进一步而言,在将柱状部以悬臂梁的状态进行支承时难以确保机械刚性,耐久性的确保变得困难。本发明涉及一种微泡产生装置,其依次形成有使直径从筒状主体的入口起逐渐减小的入口部、与该入口部连续的节流孔、以及与该节流孔连续的扩径部,其中,优选节流孔与所述扩径部之间的边界形成为径向立面,扩径部的直径是所述节流孔的直径的3～10倍。在出口周壁形成凹部。(In the microbubble generator having a structure in which the columnar portion protrudes to the orifice of the cylindrical member, the flow rate of the fluid for generating microbubbles is restricted because the presence of the columnar portion obstructs the flow of the fluid. In addition, foreign matter may be caught between the columnar portions. The columnar portion is labor-and time-consuming to manufacture. Further, when the columnar portion is supported in a cantilever state, it is difficult to ensure mechanical rigidity, and it is difficult to ensure durability. The present invention relates to a microbubble generator having an inlet portion whose diameter is gradually reduced from an inlet of a cylindrical body, an orifice continuous with the inlet portion, and an expanded diameter portion continuous with the orifice, wherein a boundary between the orifice and the expanded diameter portion is preferably formed as a radial vertical surface, and the diameter of the expanded diameter portion is 3 to 10 times the diameter of the orifice. A recess is formed in the peripheral wall of the outlet.)

1. A microbubble generator having a cylindrical shape with an orifice, wherein,

a recess is formed in the peripheral wall of the outlet of the orifice.

2. A microbubble generation device in which the concave portions are equally distributed in the circumferential direction and the radial direction at the peripheral wall of the outlet of the orifice with the center of the orifice as the center.

3. The microbubble generation apparatus according to claim 1 or 2, wherein an outlet peripheral wall of the orifice is formed in a direction perpendicular with respect to an axis of the orifice.

4. A microbubble generator according to any one of claims 1 to 3, wherein an inlet portion having a diameter that gradually decreases toward the inlet of the orifice is formed on the inlet side of the orifice, an expanded diameter portion is formed on the outlet side of the orifice, and second concave portions or convex portions that are continuous or discontinuous in the circumferential direction are formed on the inner circumferential surface of the expanded diameter portion.

5. A microbubble generator having an inlet portion whose diameter is gradually reduced from an inlet of a cylindrical body, an orifice continuous with the inlet portion, and an expanded diameter portion continuous with the orifice, wherein,

the boundary between the orifice and the enlarged diameter portion is formed as a radial vertical surface,

the diameter of the diameter-expanding portion is 3 to 10 times the diameter of the orifice,

the expanded diameter portion is expanded only at the outlet.

6. A microbubble generation apparatus according to claim 5, wherein the boundary is constituted by an orifice outlet peripheral wall formed in a direction (± 20 degrees) perpendicular to an axis of the orifice.

7. The microbubble generation apparatus according to claim 5 or 6, wherein a concave portion is formed at the outlet peripheral wall.

8. The microbubble generation device according to any one of claims 5 or 7, wherein second concave or convex portions that are continuous or intermittent in the circumferential direction are formed on an inner circumferential surface of the diameter-expanded portion.

9. A water treatment apparatus comprising the microbubble generator according to any one of claims 1 to 8 and a water supply unit that supplies water to the microbubble generator.

10. A water treatment apparatus further comprises a microbubble remover for removing the microbubbles generated by the microbubble generator.

11. A method for treating water, wherein,

the water treatment method comprises the following steps:

preparing a microbubble generation device according to any one of claims 1 to 8; and

water is supplied to an inlet side of the orifice.

12. The water treatment method according to claim 11, wherein microbubbles contained in the water discharged from the outlet side of the orifice are removed.

13. A method for producing micro-bubble water, wherein,

the manufacturing method of the micro-bubble water comprises the following steps:

preparing water; and

treating the water by a microbubble generation device as defined in any one of claims 1 to 8.

14. A method for producing water, wherein,

the method for producing water includes the steps of:

preparing micro bubble water manufactured by the method for manufacturing micro bubble water according to claim 13; and

removing a portion or all of the microbubbles from the microbubble water.

15. A cleaning agent, a bactericide, a disinfectant, a medicinal material, a food material, or a decorative material, wherein the cleaning agent, the bactericide, the disinfectant, the medicinal material, the food material, or the decorative material contains the micro-bubble water produced by the method for producing micro-bubble water according to claim 13.

16. A solvent for a cleaning agent, a bactericide, a disinfectant, a medicinal material, a food material, a decorative material, a building agent, a fertilizer material, or an emulsion, wherein the solvent for a cleaning agent, a bactericide, a disinfectant, a medicinal material, a food material, a decorative material, a building agent, a fertilizer material, or an emulsion comprises water produced by the method for producing water according to claim 14.

Technical Field

The present invention relates to a microbubble generator and a water treatment apparatus.

Background

As one method of forming microbubbles, cavitation effect is utilized. Patent documents 1 and 2 disclose microbubble generators as follows: the columnar portion is projected into the orifice of the tubular body portion, and the water flow passing through the orifice generates nano-scale microbubbles.

When tap water is introduced into the microbubble generator, the constricted portion of the water flow formed between the opposing columns is constricted and the flow rate thereof increases. As a result, a negative pressure region is formed in the constricted part (and downstream side thereof) according to the bernoulli principle, and dissolved gas in water is precipitated by the cavitation (pressure reduction) effect to generate microbubbles.

In the case of micro-bubbles of micron order, the cylindrical member may be provided with only a small diameter portion (orifice) (patent document 3). That is, the micron-order microbubbles can be formed by an apparatus including an inlet portion having an inner diameter gradually narrowed from an inlet-side end portion to a center portion of the cylindrical member, an orifice connected to the inlet portion, and an enlarged diameter portion connected to the orifice and having an inner diameter gradually widened toward the other end of the cylindrical member on the outlet side.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5712292

Patent document 2: japanese patent No. 6279179

Patent document 3: japanese patent No. 6369879

Disclosure of Invention

Problems to be solved by the invention

In order to generate microbubbles of nanometer order, the columnar portion protrudes to the orifice of the cylindrical member.

Since the presence of the columnar portion obstructs the flow of the fluid, the flow rate of the fluid that generates the microbubbles is restricted. In addition, foreign matter may be caught between the columnar portions.

In addition, it takes much time and labor to manufacture the columnar portion. Further, when the columnar portion is supported in a cantilever state, it is difficult to ensure mechanical rigidity, and it is difficult to ensure durability.

Means for solving the problems

The present invention is defined as follows to solve the above-described problems. Namely:

a microbubble generator having a cylindrical shape with an orifice, wherein,

a recess is formed in the peripheral wall of the outlet of the orifice.

Here, the orifice refers to a portion of the cylindrical member having a predetermined length and having a diameter reduced.

In other words, an inlet portion and an outlet portion (diameter-enlarged portion) having a larger diameter than the orifice are continuously formed on the inlet side and the outlet side of the orifice in the tubular member, respectively.

In order to stabilize the flow, it is preferable that the orifice has a flat inner circumferential surface having the same diameter. The diameter of the orifice can be designed arbitrarily by the relationship between the desired compression ratio (with respect to the fluid) and the throughput of the fluid. In order to exhibit the cavitation effect, it is important to adjust the difference between the diameter of the orifice outlet and the diameter of the enlarged diameter portion continuous therewith.

The length of the orifice can be designed arbitrarily as long as the fluid flowing through the orifice is stable, that is, as long as the flow converges in the axial direction of the orifice.

Of course, the diameter of the orifice is not limited to be uniform in the axial direction. The diameter of the orifice may be gradually changed, and a spiral groove may be formed in the inner circumferential surface of the orifice.

Preferably, the inlet portion continuing to the orifice is gradually reduced in diameter as it goes toward the orifice. This is to smoothly introduce the fluid into the orifice. This can sufficiently compress the fluid while ensuring a high flow rate.

The degree of diameter reduction (the angle of inclination with respect to the axial direction) can be arbitrarily selected depending on the type of fluid, the flow velocity, and the desired compression ratio.

The inner peripheral surface of the inlet portion is preferably formed as a flat surface, but a spiral groove or the like may be provided inside thereof.

The diameter of the hole outlet is increased as compared with the diameter of the hole outlet. As a result, the fluid compressed by the orifice is released to form a negative pressure when being discharged to the enlarged diameter portion, and a cavitation effect is exerted.

The difference (ratio) between the diameter of the orifice outlet and the maximum diameter of the enlarged diameter portion is arbitrarily designed according to the desired average particle diameter, the number of particles, and the like of the microbubbles.

A technique of forming micro-bubbles on a micron scale by releasing a fluid compressed by an orifice at an enlarged diameter portion to generate a negative pressure is known (see patent document 3).

In the present invention, by providing the concave portion in the peripheral wall of the outlet of the orifice, the microbubbles formed can be brought to the nanometer level without providing any pillar portion in the orifice.

By being able to omit the pillar portion, resistance in the orifice becomes small, and therefore the amount of fluid that can be handled increases. In addition, since the structure is simplified, manufacturing becomes easy and durability and maintenance convenience are improved.

Preferably, the recesses are equally distributed in the circumferential direction and the radial direction at the peripheral wall of the outlet of the orifice with the center of the orifice as the center thereof. This is for stable formation of microbubbles.

Preferably, the peripheral wall of the outlet of the orifice is formed in a direction perpendicular to the axis of the orifice, and the depth direction of the recess formed therein is set in the same direction as the axis of the orifice. The recess is provided with the same diameter along the depth direction from the part opening to the peripheral wall, or the recess is reduced in diameter along the depth direction. This is to avoid fluid retention in the recess. In addition, from the viewpoint of moldability (ease of mold release), it is also preferable to form the concave portion in the above-described manner.

The shape of the recess is arbitrary. For example, the recess may be provided so as to be separated from the orifice or to be close to the orifice as the recess becomes deeper.

The distance from the outlet peripheral edge of the orifice to the peripheral edge of the recess (the gap therebetween) is preferably short. However, if the thickness is too close to the above range, the thickness of the outlet peripheral edge becomes too thin to ensure mechanical strength. According to the study of the inventors of the present invention, when the device is made of resin, the distance between the two is set to 0.1mm or more.

From the viewpoint of bringing the peripheral edge of the outlet of the orifice close to the peripheral edge of the recess, the peripheral wall of the outlet of the orifice is preferably provided in a direction perpendicular to the central axis of the orifice.

According to the study of the inventors of the present invention, it is found that a large negative pressure is generated in the concave portion. According to the simulation result, negative pressure of 1/10-1/100 is generated compared with the center of the diameter-expanding part. Further, the negative pressure in the recess portion changes periodically due to the interaction with the water flow.

If the negative pressure in the recess becomes large, a large cavitation effect is generated accordingly. It is also considered that the periodic change in the negative pressure produces an effect equivalent to that of applying the ultrasonic wave to the fluid.

It is considered that the microbubble nanoscales are an interaction of a large negative pressure in the concave portion and its periodic variation due to the presence of the concave portion.

It is considered that the average particle diameter and the particle diameter distribution of microbubbles generated in the fluid can be controlled by controlling the values of these negative pressures and the frequency of changes thereof.

The following can be mentioned as parameters for controlling the value of the negative pressure in the recess and the frequency thereof.

The ratio of the outlet diameter of the orifice to the diameter of the enlarged diameter portion

Aspect ratio of the recess (ratio of area to depth of opening)

Velocity and viscosity of fluid discharged from outlet of orifice

Area ratio of concave portion to peripheral wall of throttle hole

Distance between outlet peripheral edge of orifice and peripheral edge of recess

The ratio of the outlet area of the orifice to the area of the recess, etc

The orifice is not particularly limited as long as it has a shape that constricts and compresses the water flow sent from the inlet to increase the flow velocity thereof, but it is preferably provided with a shape having a space with a circular cross section from the viewpoint of minimizing resistance to the water flow.

The diameter of the orifice can be arbitrarily selected according to the amount of water to be treated, and the like.

The flow rate and pressure of the fluid and the texture (material and surface roughness) of the inner peripheral surface of the orifice are adjusted to obtain the flow velocity. In order to stabilize the flow velocity, it is preferable to provide a portion (straight tube portion) having the same diameter. The length of the straight tube portion 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.

A large diameter portion is formed on the downstream side of the orifice, and water passing through the orifice is discharged to the large diameter portion. Thereby, the water flow compressed by the orifice is released and its pressure is lowered. Bubbles are formed by cavitation effects as a result of the reduced pressure.

The cross section of the enlarged diameter portion continuous with the outlet of the orifice is preferably circular, and the center portion thereof coincides with the center of the orifice. Thereby, the fluid discharged from the outlet of the orifice is uniformly diffused and decompressed. Therefore, microbubbles are formed equally.

In the present invention, the peripheral wall of the outlet of the orifice is perpendicular to the axis of the orifice, and as a result, the enlarged diameter portion is formed in a cylindrical shape and has a uniform diameter from the periphery of the orifice outlet.

By providing the peripheral wall of the outlet of the orifice with a vertical wall, the fluid discharged from the outlet of the orifice can be efficiently made into a negative pressure. In addition, it is conceivable to obtain a cycle of a large negative pressure and an appropriate negative pressure by bringing the recess portion close to the orifice outlet.

The shape of the inner peripheral surface of the enlarged diameter portion can be designed arbitrarily, and for example, the enlarged diameter portion continuous to the outlet of the orifice can be formed into an inverted funnel shape in which the diameter thereof is gradually enlarged as it separates from the outlet.

The pressure of the recess formed in the peripheral wall of the orifice outlet is 1/10-1/100 greater than the pressure of the central portion of the enlarged diameter portion. Since the pressure value cannot be directly measured, Simulation results using Simulation software (Simulation) relating to water flow are used. The results of the simulation are shown in FIG. 4.

In the concave portion formed with the negative pressure as described above, the density of the fluid is decreased, and a state of gas is basically formed. It is considered that when the fluid in the concave portion formed in the gas state is involved in the fluid in the liquid state, microbubbles are formed. Then, the fluid flowing through the diameter-enlarged portion interferes with the fluid gasified in the concave portion, and the negative pressure in the concave portion periodically changes. The frequency of the change and the magnitude of the negative pressure in the concave portion can be considered to interact with each other, thereby achieving the nano-scale formation of the microbubbles.

The second recess may be provided continuously or discontinuously in the circumferential wall of the enlarged diameter portion in the circumferential direction.

The generation of microbubbles in the second concave portion can also be promoted. The pressure in the second recess is set to be higher than the pressure in the first recess formed around the outlet of the orifice and lower than the pressure in the center of the enlarged diameter portion.

The fluid flowing through the enlarged diameter portion is agitated by the second recesses in the peripheral wall of the enlarged diameter portion. As a result, the cavitation effect in the first concave portion is promoted.

From the viewpoint of stirring, the second concave portion can be replaced with a convex portion.

According to the microbubble generator of the present invention, if a fluid such as water is once passed therethrough, microbubbles on the order of nanometers can be generated in a large amount therein. In other words, the fluid entering the recess has the property of a gas phase within the recess due to the large negative pressure generated in the recess. As a result, variations may occur in the characteristics of the fluid itself.

For example, it is conceivable that a so-called cluster (cluster) of fluid is broken although it cannot be metered. In other words, as the bundle becomes smaller, the permeability of the fluid itself becomes greater. The surface tension of the nano bubble water obtained by the present invention is the same as that of ordinary water. On the other hand, in nano bubble water of a type in which bubbles of air supplied to water are made fine by mechanical stirring or application of pressure from the outside, the surface tension is reduced, and the target substance is easily wetted.

Thus, the micro-bubble water produced by the micro-bubble generating apparatus of the present invention has new characteristics in its own right. Therefore, in other aspects of the present invention, microbubbles are removed from the microbubble water obtained by the method already described. The water treated by the micro bubble generating apparatus of the present invention has new characteristics even if micro bubbles are not present. In order to remove the microbubbles, ultrasonic waves are applied to grow the microbubbles of nanometer size into micron-sized microbubbles, and then the micron-sized microbubbles are naturally collapsed.

The microbubble water is not limited to the microbubble from which all of the microbubbles have been removed, and any part thereof may be removed.

The microbubble water obtained by passing the microbubble generator of the present invention can have a high cleaning ability and other normal functions possessed by the microbubble water, while keeping the microbubble water as it is.

The fluid passing through the microbubble generation device is not limited to tap water. That is, any fluid may be used as long as it can pass through the microbubble generator and generate a negative pressure without blocking the orifice or the recess. Pure water and deionized water are not necessarily mentioned, and even sewage, seawater, and the like can be used as objects. Further, ethanol, gasoline, diesel oil, and the like can also be targeted.

The micro bubble water can be used as a raw material for cleaning materials, bactericides against viruses and bacteria, disinfection materials, medical materials, food materials, decorative materials, building agents, fertilizer materials, solvents for emulsions, and the like.

Similarly, water obtained by removing microbubbles from the microbubble water can also be used as a raw material for cleaning agents, bactericides, disinfectants, medical materials, food materials, decorative materials, building agents, fertilizer materials, solvents for emulsions, and the like.

Drawings

Fig. 1 is a sectional view of a microbubble generator according to an embodiment of the present invention.

Fig. 2 is a front view similarly viewed from the exit side.

Fig. 3 is a graph showing measurement results of the apparatus of fig. 1.

Fig. 4 is a diagram similarly showing the simulation result.

Fig. 5 is a sectional view of another embodiment of the microbubble generator.

Fig. 6 is a graph showing the measurement results of the apparatus of fig. 5.

Fig. 7 is a sectional view of another embodiment of the microbubble generator.

Fig. 8 is a graph showing the measurement results of the apparatus of fig. 7.

Fig. 9 is a sectional view of another embodiment of the microbubble generator.

Fig. 10 is a graph showing the measurement results of the apparatus of fig. 9.

Fig. 11 is a graph obtained by summarizing the results of fig. 3, 6, 9, and 10 on the same scale.

Detailed Description

Fig. 1 is a sectional view showing the structure of a microbubble generator 1 according to an embodiment of the present invention.

The microbubble generator (hereinafter, may be simply referred to as "generator") 1 includes an inlet 10, an orifice 15, an enlarged diameter portion 20, and a recess 40 in a cylindrical case 3.

The tubular case 3 is composed of three members 4, 5, and 6, and a fitting hole 7 is provided through one end side (left side in the drawing) of the first member 4, and the fitting hole 7 has a flat bottom surface (a peripheral wall 8 of an opening portion of the orifice 15). The second member 5 and the third member 6 are inserted into the fitting hole 7 without a gap.

An inlet 10 is formed at the other end (left side in the drawing) of the first member 4 to be inserted in a conical shape and connected to an orifice 15. The orifice 15 is a through hole having the same radius, and opens into the fitting hole 7. The orifice 15 and the inlet portion 10 are formed such that their center lines coincide with the center line of the first member 4.

In the first member 4, a first recess 40 is formed in the bottom surface of the fitting hole 7, i.e., in the peripheral wall 8 at the outlet of the orifice 15.

As shown in fig. 2, the first recesses 40 are radially opened in the circumferential wall 8 at intervals of 90 degrees in the circumferential direction around the center of the outlet of the orifice 15.

In this example, the opening of the recess 40 is formed in a rectangular shape (elliptical shape) with rounded corners. And is provided to penetrate in parallel with the orifice 15 while maintaining the shape of the opening.

The second member 5 is a disk-shaped member fitted into the fitting hole 7, and is formed with a first enlarged diameter portion 21 continuous with the orifice 15. The first enlarged diameter portion 21 is gradually enlarged in diameter from the vicinity of the center portion of the second member 5 to form a second recess 23.

In this example, the second recessed portions 23 are formed continuously in the circumferential direction of the inner circumferential surface of the second member 5, but may be formed intermittently.

The disc-shaped third member 6 is fitted into the fitting hole 7 so as to overlap the second member 5. The third member 6 is formed with a second enlarged diameter portion 25 which constitutes the enlarged diameter portion 20 of the microbubble generator 1 together with the first enlarged diameter portion 21 of the second member 5.

In this example, the first diameter-enlarged part 21 and the second diameter-enlarged part 25 are formed to have the same diameter, but the diameter of the second diameter-enlarged part 25 may be formed to be larger than the diameter of the first diameter-enlarged part 21.

The three members 4, 5, and 6 constituting the cylindrical housing 3 may be formed of synthetic resin. Of course, the metal or ceramic may be used.

In the above description, all of the first concave portions 40 are exposed to the first enlarged diameter portion 21.

The first recess 40 may be partially covered by the second member 5 when the peripheral wall 8 is radially widened and fitted to the second member 5.

The first recessed portions 40 are preferably formed radially about the center of the outlet of the orifice 15, and are not limited to the four directions shown in fig. 2, and may be formed arbitrarily in a range of 3 to 12 directions, for example. It is preferable that the first recesses 40 are equally distributed in the circumferential direction and the radial direction when viewed from the center of the outlet of the orifice 15.

As a microbubble generation device of the example, a device of the following model was prepared. The cylindrical case 3 is made of ABS resin.

Cylindrical case 3: diameter 12.0mm, length: 10mm

Opening diameter of inlet portion: 8.0mm

Opening angle of inclined surface of inlet portion: 90 degree

Diameter of the orifice 15: 0.9mm

Length of orifice 15: 1.0mm

Longitudinal width of the first recess 40: 0.7mm

Lateral width of the first recess 40: 0.4mm

Depth of the first recess 40: 0.5mm

Distance between the orifice 15 and the first recess 40: 0.1mm

Diameter of enlarged diameter portions 21, 25: 0.3mm

Inclination angle of the second concave portion 23: 90 degree

Width of the second concave portion 23: 0.75mm

Fitting hole 7: diameter of 10mm and depth of 4.0mm

Thickness of third member and fourth member: each 2.0mm

Tap water was introduced into the inlet side of the microbubble generator 1 having such a configuration at a pressure of 2.0MPs, and the water discharged from the diameter expanding section 20 side was extracted, and the particle size distribution of the microbubbles contained therein was measured using SALD-7500H manufactured by shimadzu corporation.

The results are shown in fig. 3.

The average particle size was 93nm, and 1ml equivalent of nano-sized microbubbles exceeded 3 hundred million and 7000 million. Micro-bubbles of micron size are almost absent.

Fig. 4 shows a simulation of the water flow of this example. In fig. 4, the flow rate is indicated by the shading of the arrow. The lighter the color of the arrow, the faster the flow rate.

While the pressure in the enlarged diameter portion was 31.7kPa, the pressure in the first concave portion was 2.1kPa, and the pressure in the second concave portion was 2.9 kPa.

Next, the same test was performed for the microbubble generator (see fig. 5) in which the second concave portion is omitted in the embodiment of fig. 1.

The results are shown in fig. 6.

The average particle size was 109nm, and 1ml equivalent of nano-sized microbubbles were about 1 hundred million and 3000 ten thousand.

Next, the same test was performed for the microbubble generator (see fig. 7) in which the first concave portion is omitted in the embodiment of fig. 5.

The results are shown in fig. 8.

The average particle size was 136nm, and 1ml equivalent of nano-sized microbubbles was about 7700 ten thousand.

Next, the same test was performed for the microbubble generator (see fig. 9) in which the second concave portion is omitted in the embodiment of fig. 7.

The results are shown in fig. 10.

The average particle size was 158nm, and about 4800 million microbubbles were present at 1ml equivalent.

According to the above results, many microbubbles were generated in the microbubble generator of the nanometer scale in which the first concave portion and the second concave portion were omitted.

Fig. 11 is a graph obtained by summarizing the results of fig. 3, 6, 8, and 10 on the same scale.

As is clear from the results of fig. 11, the first concave portion and the second concave portion are provided, whereby the particle diameter of the generated microbubbles is reduced. Further, it is found that the first concave portion and the second concave portion are present together, so that the particle diameter of the generated microbubbles becomes extremely small, and as a result, the number of generated microbubbles becomes extremely large.

Based on the above, the inventors of the present invention have obtained the following knowledge and findings.

A microbubble generator having an inlet portion whose diameter is gradually reduced from an inlet of a cylindrical body, an orifice continuous with the inlet portion, and an expanded diameter portion continuous with the orifice, wherein,

the boundary between the orifice and the enlarged diameter portion is formed as a radial vertical surface,

the diameter of the diameter-expanding portion is 3 to 10 times the diameter of the orifice,

the expanded diameter portion is expanded only at the outlet.

In the above, the boundary between the orifice and the enlarged diameter portion corresponds to the outlet peripheral wall of the orifice. The outlet peripheral wall is preferably perpendicular to the axis of the orifice, but may be inclined at ± 20 degrees or ± 10 degrees from the perpendicular direction. Here, the expanded diameter portion side is defined as + and the inlet portion side is defined as-with the outlet of the orifice as the center.

If the inclination of the outlet peripheral wall exceeds +20 degrees, the agitation and mixing of the bubbles formed by the cavitation effect may be insufficient. On the other hand, if the inclination of the outlet peripheral wall exceeds-20 degrees, the water flow discharged from the orifice is guided to the inclined outlet peripheral wall side, so that a sufficient flow velocity cannot be secured, and the pressure reduction becomes insufficient.

If the diameter of the enlarged diameter portion is less than three times the diameter of the orifice, the pressure reduction becomes insufficient. On the other hand, if the diameter of the enlarged diameter portion exceeds ten times the diameter of the orifice, the water flow discharged from the outlet of the orifice is excessively dispersed and interferes with the water flow. Therefore, a sufficient flow rate cannot be secured, and the pressure reduction becomes insufficient.

Although the diameter-enlarged portion preferably has a uniform inner diameter as shown in the drawing, it may be provided in an inverted funnel shape within the above range.

The diameter-expanding portion is provided so as to expand only at an outlet thereof. In other words, the peripheral wall of the enlarged diameter portion is free from any gas other than air injected from the outside. If the expanded diameter portion communicates with the external environment outside the outlet, the reduced pressure environment inside the expanded diameter portion may be broken, which is not preferable.

The second recess is formed at a position where the water flow discharged from the outlet of the orifice can be efficiently stirred. The flow velocity, the ratio of the diameters of the orifice and the expanded diameter portion, the shape of the expanded diameter portion, and the like can be arbitrarily designed. According to the study of the inventors of the present invention, it is preferable that the diameter of the enlarged diameter portion is formed in a range of 0.5 to 1.5 times as large as the diameter of the orifice from the outlet of the orifice toward the downstream side in the axial direction of the orifice.

The following is disclosed below.

(1) A microbubble generator having an inlet portion whose diameter is gradually reduced from an inlet of a cylindrical body, an orifice continuous with the inlet portion, and an expanded diameter portion continuous with the orifice, wherein,

first recesses are formed in a radial vertical surface of a boundary between the orifice and the enlarged diameter portion, the first recesses being evenly distributed in the circumferential direction and in the radial direction, with a center of the orifice as a center,

second recesses or second protrusions are formed on the inner circumferential surface of the expanded diameter portion, the second recesses or the second protrusions being continuous or intermittent in the circumferential direction.

(2) A water treatment device is provided with: a water flow compression part having a peripheral wall for uniformly compressing the water flow; and a water flow releasing part formed on a downstream side of the water flow compressing part and having a diameter larger than that of the water flow compressing part, wherein the water flow releasing part is formed with a first recess recessed in a direction opposite to the water flow, and a pressure in the first recess is smaller than a pressure of the water flow released from the water flow compressing part to the water flow releasing part.

(3) The water treatment apparatus 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 discharge part.

(4) The water treatment apparatus according to (2), wherein a second recess is formed in a radial circumferential direction on an inner circumferential surface of the water flow discharging portion, and a pressure in the second recess is higher than a pressure in the first recess and is lower than a pressure in a center of the water flow discharging portion.

(5) The water treatment apparatus according to (2), wherein a circumferentially continuous or intermittent concave portion or a circumferentially continuous or intermittent convex portion is formed on an inner peripheral surface of the water flow discharge portion, and the water flow discharged from the water flow compression portion is stirred.

(6) The water treatment apparatus according to any one of claims 2 to 5, further comprising a device for removing microbubbles from the water flow discharged from the water flow discharge unit.

The present invention is not limited to the description of the embodiments of the invention described above. Various modifications within the scope that can be easily conceived by those skilled in the art without departing from the description of the technical solution are also included in the present invention.

[ description of reference ]

1. 101, 201, 301: a microbubble generating device;

8: a peripheral wall of the orifice outlet;

10: an inlet portion;

15: an orifice;

20: an expanding portion;

23: a second recess;

40: a first recess.