Microbubble generator

Abstract

To provide a microbubble generator having simple and inexpensive structure and generating a large quantity of microbubbles.SOLUTION: A microbubble generator 1 comprises: a tubular flow path F (flow path tank 2) that causes liquid introduced from an inlet 200 at one end to pass therethrough and discharges the liquid from an outlet 201 at the other end; a swirling flow generation section 4 that is disposed on an upstream side of the flow path F; a first orifice 5 that is disposed on the downstream side of the swirling flow generation section 4 in the flow path F; a gas supply pipe 6 that has an upper end 61 disposed outside the flow path F and a lower end 62 disposed between the first orifice 5 and the inlet 200 within the flow path tank 2, and supplies gas from outside the flow path F into the flow path tank 2; and a static mixer 7 that is disposed between the arrangement position of the lower end 62 of the gas supply pipe 6 and the outlet 201 in the flow path F.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a microbubble generator that generates microbubbles such as microbubbles and nanobubbles in a liquid. [Background technology]

[0002] In recent years, microbubbles, nanobubbles, and other fine bubbles have been used in industrial fields. Microbubbles are bubbles (air bubbles) with diameters ranging from 1 μm to several tens of μm, and nanobubbles are bubbles with diameters ranging from 1 nm to 1000 nm (1 μm). Industrial applications include, for example, fisheries and agriculture.

[0003] There are various types of devices for generating microbubbles (microbubble generators) as described above, including the swirling flow type, pressurized dissolution type, orifice-venturi tube type, ultrasonic type, and microporous filter type. Of these, the swirling flow type generates microbubbles by crushing air bubbles using a high-speed liquid swirling flow, and Patent Document 1 discloses a swirling flow type microbubble generator (microbubble generator). The microporous filter type generates microbubbles by passing gas through a microporous filter, and Patent Document 2 discloses a microbubble generator using a microporous filter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4652478 [Patent Document 2] Patent No. 6809671 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to increase the amount of microbubbles generated using a single method such as the one described above, the device configuration is complex and expensive. For example, the microbubble generator of the above-mentioned Patent Document 1 has a dual structure of a gas-liquid generation tank and an outer shell tank, and liquid is supplied to the inside of the gas-liquid generation tank from the outside of the gas-liquid generation tank using multiple liquid supply ports, thereby generating a strong swirling flow and efficiently generating microbubbles. As such, because it has a dual structure of a generation tank and an outer shell tank, the configuration is complex and it is difficult to manufacture inexpensively.

[0006] The microbubble generator of Patent Document 2 includes a gas storage tube that receives gas and a shell tank that covers the gas storage tube and receives liquid. A porous member is formed midway through the gas storage tube. A gap is formed between the porous member and the shell tank. Liquid fed into the shell tank is passed through the gap at high speed to create a reduced pressure in the gap, causing the gas in the gas storage tube to be released into the gap through the porous member. The liquid flowing through the gap at high speed separates the bubbles from the surface of the porous member, and the pressure of the liquid flow is immediately released rapidly, generating micro- or nano-sized microbubbles. Thus, the microbubble generator of Patent Document 2 requires a gas storage tube with a porous member formed midway and a shell tank. Furthermore, a spiral current control plate is required to create a high-speed swirling flow in the shell tank. This makes the configuration of the generator complex and difficult to manufacture inexpensively.

[0007] Therefore, an object of the present invention is to provide a microbubble generator that is inexpensive, has a simple configuration, and generates a large amount of microbubbles. [Means for solving the problem]

[0008] (1) In order to solve the above problems, the micro-bubble generator according to the present invention is a micro-bubble generator having a tubular flow path through which a liquid flows in from an inlet at one end and is discharged from an outlet at the other end, the micro-bubble generator comprising: a swirling flow generating unit arranged upstream of the flow path; an orifice arranged in the flow path downstream of the swirling flow generating unit 4; a gas supply pipe having one end arranged outside the flow path and the other end arranged between the orifice and the outlet in the flow path, for supplying a gas from outside the flow path to the flow path; and a static mixer arranged between the position of the other end of the gas supply pipe and the outlet, wherein the swirling flow generating section comprises a laminate in which plate-like members having a plurality of flow path through holes formed on concentric circles centered on a center point thereof are stacked in the direction of passage of the liquid in the flow path so that corresponding flow path through holes in each of the plate-like members are connected to each other, and each of the plate-like members is arranged to rotate in a predetermined direction based on an axis connecting the center points of each of the plate-like members, relative to the plate-like member adjacent to it on the upstream side of the flow path.

[0009] (2) The stack may function as a static mixer, with plate-shaped interposing members disposed between adjacent plate-shaped members so as not to block the plurality of flow path through holes.

[0010] (3) The micro-bubble generator may comprise a first cylindrical body, a second cylindrical body, and a third cylindrical body that constitute the flow path and are arranged in a line from the upstream side to the downstream side of the liquid. The first cylindrical body has a first protruding portion that protrudes inward on its inner surface, and the swirl flow generating portion is arranged to abut against the downstream end of the first protruding portion. The second cylindrical body has an upstream end attached to the downstream end of the first cylindrical body, and has a second protruding portion that protrudes inward on its inner surface at a position midway in the direction of passage of the liquid, and the first orifice is arranged at the downstream end of the second protruding portion. The third cylinder has an upstream end attached to a downstream end of the second cylinder, a small-diameter section formed at a midpoint in the liquid passage direction, the small-diameter section having a smaller inner diameter than the upstream and downstream sides of the midpoint, a second orifice disposed at an upstream edge of the small-diameter section, the static mixer disposed at a downstream edge of the small-diameter section, and the gas supply pipe inserted into the small-diameter section.Furthermore, the micro-bubble generator may further include: a first internal cylinder inserted into the first cylinder and the second cylinder and extending from the downstream end of the swirl flow generating section to the second protruding section, a second internal cylinder inserted into the second cylinder and the third cylinder and extending from the downstream end of the first orifice to the upstream end of the second orifice, and a third internal cylinder inserted into the third cylinder and extending from the downstream end of the static mixer in the liquid passage direction.

[0011] (4) The microbubble generator may be of a circulation type that circulates the liquid discharged from the outlet to the inlet, and may generate a microbubble-containing liquid to be supplied to agricultural or marine products. [Effects of the Invention]

[0012] According to the above configuration, it is possible to provide a microbubble generator that is inexpensive, has a simple configuration, and generates a large amount of microbubbles. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a front view of a microbubble generator according to an embodiment of the present invention. [Figure 2] 2 is a cutaway view of the front portion of the flow path tank and the front portions of the first to third internal cylindrical bodies in the micro-bubble generator of FIG. 1. FIG. [Figure 3] FIG. 2 is a left side view of the microbubble generator shown in FIG. 1. [Figure 4] 2 is a cross-sectional view of the fine bubble generator shown in FIG. 1 taken along the line AA. [Figure 5] FIG. 2 is an explanatory diagram of the configurations and dimensions of an orifice, a plate-like member, and a static mixer. [Figure 6] FIG. [Figure 7] (A) is a right side view of the plate-shaped member at the most upstream side, (B) is a right side view of the plate-shaped member adjacent to the downstream side of the plate-shaped member in (A), (C) is a right side view of the plate-shaped member adjacent to the downstream side of the plate-shaped member in (B), (D) is a right side view of the plate-shaped member adjacent to the downstream side of the plate-shaped member in (C), and (E) is a right side view of the plate-shaped member adjacent to the downstream side of the plate-shaped member in (D). [Figure 8] FIG. 2 is an explanatory diagram showing an example of a method of using the microbubble generator shown in FIG. [Figure 9] 10 is a table showing the experimental results of a non-circulating type using the experimental device a. [Figure 10] 10 is a graph showing the experimental results of FIG. 9. [Figure 11] 10 is a table showing the experimental results of a non-circulating type using experimental apparatus b. [Figure 12] 12 is a graph showing the experimental results of FIG. 11. [Figure 13] 10 is a table showing the experimental results of a non-circulating type using experimental apparatus c. [Figure 14] 14 is a graph showing the experimental results of FIG. 13. [Figure 15] 10 is a table showing the experimental results of a non-circulating type using experimental device d. [Figure 16] 16 is a graph showing the experimental results of FIG. 15. [Figure 17] 10 is a table showing experimental results of a circulation type using experimental apparatus d. [Figure 18]18 is a graph showing the experimental results of FIG. 17. [Figure 19A] 1 is a graph showing the cumulative number of fruits in a strawberry harvesting experiment. [Figure 19B] 1 is a graph showing the sugar content of fruits harvested in a strawberry harvesting experiment. [Figure 19C] This is a graph showing the monthly harvest yield from fiscal year 2018 to fiscal year 2021 in the tomato harvesting experiment. [Figure 20] This is a photo of Nishikigoi carp being raised in a Nishikigoi breeding experiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] A micro-bubble generator according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 7. FIG. 1 is a front view of the micro-bubble generator according to this embodiment. FIG. 2 is a cutaway view of the micro-bubble generator shown in FIG. 1, showing the front portion of the flow channel tank and the front portions of the first to third internal cylinders. FIG. 3 is a left side view of the micro-bubble generator shown in FIG. 1. Note that the gas supply pipe 6 and the pipe insertion section 232 are omitted in FIG. 3 for ease of viewing. FIG. 4 is a cross-sectional view of the drawstring bag shown in FIG. 1, taken along the line A-A. Note that the configuration upstream of the intermediate portion 22A is omitted in FIG. 4 for ease of viewing. FIG. 5 is an explanatory diagram of the configuration and dimensions of the orifice and the plate-like member. FIG. 6 is a front view of the swirl flow generating section. FIG. 7(A) is a right side view of the uppermost downstream plate-like member. FIG. 7(B) is a right side view of the plate-like member adjacent to the downstream side of the plate-like member shown in FIG. 7(A). Fig. 7(C) is a right side view of a plate-shaped member adjacent to the downstream side of the plate-shaped member in Fig. 7(B). Fig. 7(D) is a right side view of a plate-shaped member adjacent to the downstream side of the plate-shaped member in Fig. 7(C). Fig. 7(E) is a right side view of a plate-shaped member adjacent to the downstream side (most downstream side) of the plate-shaped member in Fig. 7(D). In this embodiment, the upper side in Fig. 1 will be referred to as the upper side of the micro-bubble generator, the lower side in Fig. 1 will be referred to as the lower side of the micro-bubble generator, the left side in Fig. 1 will be referred to as the left side of the micro-bubble generator, the right side in Fig. 1 will be referred to as the right side of the micro-bubble generator, the front side in Fig. 1 will be referred to as the front side of the micro-bubble generator, and the back side in Fig. 1 will be referred to as the rear side of the micro-bubble generator.

[0015] The microbubble generator 1 according to this embodiment is a device that generates microbubbles such as microbubbles and nanobubbles. The definitions of microbubbles and nanobubbles are as described above. First, the configuration of the microbubble generator 1 will be described. In this embodiment, bubbles may be referred to as air bubbles.

[0016] (Configuration of the fine bubble generator) The micro-bubble generator 1 includes a tubular flow channel tank 2 through which a liquid introduced through an inlet 200 at one end (left end) passes and is discharged from an outlet 201 at the other end (right end). That is, the inside of the flow channel tank 2 forms a flow channel F for the liquid. The micro-bubble generator 1 also includes a swirling flow generating unit 4 arranged upstream (left side) of the flow channel F, a first orifice 5 arranged downstream (right side) of the swirling flow generating unit 4 in the flow channel F, a gas supply pipe 6 having one end (upper end 61) arranged outside the flow channel F and the other end (lower end 62) arranged in the flow channel F between the first orifice 5 and the outlet 201, for supplying gas (air) to the flow channel F from outside the flow channel F, and a static mixer 7 arranged in the flow channel F between the position of the lower end 62 of the gas supply pipe 6 and the outlet 201. According to the micro-bubble generator 1, the amount of micro-bubbles generated is significantly increased due to the interaction of each micro-bubble generating section (swirl flow generating section 4, first orifice 5, gas supply pipe 6, static mixer 7). The components of the micro-bubble generator 1 will be described in detail below.

[0017] (Configuration of the micro-bubble generator: flow channel tank) 1 and 2, the flow path tank 2 includes a first cylindrical body 21, a second cylindrical body 22, and a third cylindrical body 23 that form a flow path F and are arranged side by side from the upstream side to the downstream side of the liquid. Specifically, the first cylindrical body 21, the first cylindrical body 22, and the third cylindrical body 23 are arranged side by side in this order from left to right, and the right edge (downstream end) of the first cylindrical body 21 is connected (attached) to the left edge (upstream end) of the second cylindrical body 22, and the right edge (downstream end) of the second cylindrical body 22 is connected (attached) to the left edge (upstream end) of the third cylindrical body 23, thereby communicating the internal spaces of the first cylindrical body 21, the second cylindrical body 22, and the third cylindrical body 23. Note that this connection may be made via a member.

[0018] In the first cylindrical body 21 and the second cylindrical body 22, the diameters (inner and outer diameters) of the upstream portions are larger than those of the downstream portions, based on the left-right midpoints 21A and 22A. The outer diameters of the midpoints 21A and 22A continuously decrease toward the right. The diameters (inner and outer diameters) of the downstream portion of the first cylindrical body 21 and the diameters (inner and outer diameters) of the upstream portion of the second cylindrical body 22 are substantially constant and substantially identical. This allows the right edge of the first cylindrical body 21 and the left edge of the second cylindrical body 22 to be connected with substantially constant and flush inner and outer surfaces.

[0019] Furthermore, the third cylindrical body 23 has a small inner diameter portion 231 formed on its inner surface at a midpoint in the liquid flow direction, the small inner diameter portion 231 having a smaller inner diameter than the upstream and downstream sides of the midpoint. The downstream and upstream sides of the small inner diameter portion 231 have substantially constant diameters (outer and inner diameters) and are substantially the same as the diameters (outer and inner diameters) of the second cylindrical body 22 on the downstream side. This allows the right edge of the second cylindrical body 22 and the left edge of the third cylindrical body 23 to be connected flush with each other on both the inner and outer surfaces. The flow path tank 2 does not necessarily have to be formed of the first to third cylindrical bodies 21, 22, and 23, and may be formed of a single cylindrical body. The shape of the flow path tank 2 can also be modified as appropriate. The configurations of the first cylindrical body 21, the second cylindrical body 22, and the third cylindrical body will be described in more detail below.

[0020] The first cylindrical body 21 has a first protruding portion 21B that protrudes inward from the inner surface of the midway portion 21A. The first protruding portion 21B is formed around the inner circumference, and its diameter continuously reduces in the downstream portion. The swirl flow generating portion 4 is arranged to abut against the downstream end of the first protruding portion 21B. The detailed configuration of the swirl flow generating portion 4 will be described later. A water faucet socket insert is attached to the inner surface of the first cylindrical body 21 upstream of the first protruding portion 21B, allowing the insertion of piping for a pump (not shown). The second cylindrical body 22 has a second protruding portion 22B that protrudes inward from the inner surface at a midway position in the direction of liquid flow (midway portion 22A). The second protruding portion 22B is formed around the inner circumference, and its inner diameter gradually reduces in the upstream portion, forming a reduced diameter portion 221. The first orifice 5 is disposed so as to abut against the downstream end (end face) of the second protruding portion 22 B. The detailed configuration of the first orifice 5 will be described later.

[0021] As described above, the third cylinder 23 has a small inner diameter section 231 formed midway along the direction of liquid flow, with the inner diameter gradually increasing in its upstream section and gradually decreasing in its downstream section. This gradually increasing section will be referred to as the "expanding section," and the gradually decreasing section will be referred to as the "constricting section." The second orifice 5A is disposed so as to abut against the upstream edge (expanding section) of the small inner diameter section 231, and the static mixer 7 is disposed so as to abut against the downstream edge (constricting section) of the small inner diameter section 231. The configurations of the second orifice 5A and the static mixer 7 will be described in detail below. A cylindrical tube insertion section 232 protruding from the upper outer surface of the third cylinder 23 at the midway position is provided on the upper side of the outer surface. The pipe insertion portion 232 has a flange 232A formed midway in the height direction, and a through-hole formed in the height direction that reaches the small inner diameter portion 231. The gas supply pipe 6 is inserted into the through-hole from the lower end 62, thereby inserting the gas supply pipe 6 into the small inner diameter portion 231. A sealant or the like may be attached between the gas supply pipe 6 and the pipe insertion portion 232. The region between the second orifice 5A and the static mixer 7 (the region where the gas supply pipe 6 is inserted) is referred to as the gas supply region 70.

[0022] A first internal cylinder 3A is inserted into the first cylinder 21 and the second cylinder 22. The first internal cylinder 3A extends from the downstream end (right end) of the swirl flow generating section 4 to the upstream end (left end) of the second protruding portion 22B. This allows the swirl flow generating section 4 to be sandwiched and fixed between the first protruding portion 21B and the first internal cylinder 3A. The outer diameter of the first internal cylinder 3A is preferably such that it can be fitted into the first cylinder 21 and the second cylinder 22 without any gaps. The first internal cylinder 3A may be bonded to the first cylinder 21 and the second cylinder 22 with an adhesive or the like.

[0023] The second internal cylinder 3B is inserted into the second cylinder 22 and the third cylinder 23. The second internal cylinder 3B extends from the downstream end of the first orifice 5 to the upstream end of the second orifice 5A. This allows the first orifice 5 to be sandwiched and fixed between the second protruding portion 22B and the second internal cylinder 3B, and the first orifice 5A to be sandwiched and fixed between the small inner diameter portion 231 and the second internal cylinder 3B. The outer diameter of the second internal cylinder 3B is preferably such that it can be fitted into the second cylinder 22 and the third cylinder 23 without any gaps. The second internal cylinder 3B may be bonded to the second cylinder 22 and the third cylinder 23 with an adhesive or the like.

[0024] Furthermore, a third internal cylinder 3C is inserted into the third cylinder 23, and the third internal cylinder 3C extends from the downstream end of the static mixer 7 in the direction in which the liquid passes and protrudes to the outside of the third cylinder 23. The downstream end of the third internal cylinder 3C serves as the outlet 201 of the flow path F. The outer diameter of the third internal cylinder 3C is preferably a size that allows it to be fitted into the third cylinder 23 without any gaps. The third internal cylinder 3C may be adhered to the inside of the third cylinder 23 with an adhesive or the like.

[0025] (Configuration of the micro-bubble generator: swirl flow generating section) Next, the configuration of the swirl flow generating unit 4 will be described. With reference to FIGS. 2, 3, 5, 6, and 7, the swirl flow generating unit 4 includes a stack 40 in which a plurality of (five in this embodiment) plate-like members 41 are stacked in the flow direction (from left to right) of the liquid in the flow channel tank 2 (flow channel F). The plate-like members 41 are circular in side view, have a thickness in the left-right direction, and have a through-hole 43 for screw fastening formed in the center. The diameter of the plate-like members 41 is preferably slightly smaller than the inner diameter of the first cylindrical body 21, and is preferably a dimension such that the stack 40 can be fitted into the first cylindrical body 21 without any gaps. The number of plate-like members 41 is not limited to five, and may be more or less than five. The plurality of plate-like members 41 are formed to have substantially the same shape and dimensions. The plate-like members 41 have a plurality of through holes 411 formed on concentric circles centered on the central point, and are stacked so that corresponding through holes 411 in each plate-like member 41 communicate with each other. With the plate-like members 41 stacked, screws 44 are inserted through the screw-fastening through holes 43, and screw fasteners 45 are fixed to the lower ends of the screws 44. Note that the method of fixing the plate-like members 41 to each other is not limited to screw fastening. Furthermore, in this embodiment, the through holes 411 are circular in side view, but are not limited to this configuration and may have other shapes.

[0026] In this embodiment, four flow path through holes 411 are formed on the same circle centered on the central point in the plate-like member 41. Specifically, the flow path through holes 411 are formed at positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees on this same circle. Note that "corresponding flow path through holes 411 in each plate-like member 41" refers to flow path through holes 411 formed at the same position, specifically, flow path through holes 411 formed at the position of 0 degrees on the same circle, flow path through holes 411 formed at the position of 90 degrees on the same circle, flow path through holes 411 formed at the position of 180 degrees on the same circle, and flow path through holes 411 formed at the position of 270 degrees on the same circle. In this embodiment, the flow path through holes 411 are formed on the same circle, but they do not necessarily have to be formed on the same circle as long as they are formed on concentric circles. Furthermore, the number of flow path through holes 411 is not limited to four, and a smaller or larger number of through holes may be formed.

[0027] As shown in FIG. 7 , each plate-like member 41 is arranged so as to rotate in a predetermined direction (i.e., counterclockwise) around an axis connecting the center points of the plate-like members (point O in FIG. 7 ) relative to the adjacent plate-like member 41 on the upstream side of the flow path tank 2 (flow path F). As a result, when liquid passes through the corresponding flow path through-holes 411 in each plate-like member 41 of the stack 40, the liquid flows into the downstream side of the stack 40 from four locations at oblique angles (e.g., 30 to 40 degrees), generating a swirling flow. The generation of this swirling flow can pulverize gas contained in the liquid, generating microbubbles. Furthermore, the liquid that has passed through the swirling flow generating unit 4 is prevented from flowing back upstream of the swirling flow generating unit 4. Furthermore, the plate-like members 41 are easy to mold and can be manufactured inexpensively, and since the swirling flow generating section 4 is formed by stacking such plate-like members 41, the swirling flow generating section 4 can be manufactured inexpensively with a simple configuration.

[0028] As shown in FIG. 6 , in the stack 40, plate-shaped interposing members 42 are disposed between adjacent plate-shaped members 41 so as not to block the multiple flow path through-holes 411. This allows the stack 40 to function as a stacked static mixer. That is, in this embodiment, four interposing members 42 are disposed between adjacent plate-shaped members 41. Furthermore, one interposing member 42 is disposed to the right of the most upstream interposing member 42, but this interposing member 42 is not necessarily disposed. The number of plate-shaped members 42 is not limited to five and may be more or less than five. The interposing member 42 is a circular plate-shaped member having a thickness in the left-right direction in a side view. A screw-fastening through-hole 421 having the same dimensions and shape as the screw-fastening through-hole 43 is formed in the center. The thickness of the interposing member 42 is, for example, 0.2 mm or more but less than 1.0 mm, more preferably 0.2 mm or more but 0.5 mm or less, but this is not limited thereto. The interposing member 42 is configured so that a screw 44 is inserted into the plate-like member 41 via the screw-fastening through-hole 421, and the interposing member 42 is fixed with a screw fixing tool 45. Here, the diameter of the interposing member 42 is formed to be smaller than the distance from the center point of the plate-like member 41 to the innermost position of the flow path through-holes 411, so that the plurality of flow path through-holes 411 are not blocked.

[0029] As described above, by disposing the plate-shaped interposing members 42 between adjacent plate-shaped members 41, the stack 40 can function as a stack-type static mixer. Therefore, when a liquid passes through the stack 40, not only is a swirling flow generated, but the static mixer function can also generate fine bubbles, making it possible to generate a large number of fine bubbles in the swirling flow generating section 4. However, the stack 40 may be configured to have only a plurality of plate-shaped members 41 without including the interposing members 42.

[0030] (Configuration of the fine bubble generator: First and second orifices) The first and second orifices 5, 5A will be described with reference to FIGS. 2 and 5. The first and second orifices 5, 5A are disk-shaped, with a through-hole that is approximately circular in side view formed in the center as a water flow section 51, 51A. The first orifice 5 is arranged so that its plate surface faces the left-right direction, and as described above, is sandwiched between the second protruding portion 22B and the second internal cylinder 3B within the second cylinder 22. The first orifice 5 is formed to have a larger inner diameter than the inner diameter of the downstream end (right edge) of the second protruding portion 22B and the second internal cylinder 3B, but smaller than the inner diameter downstream of the midpoint 22A of the second internal cylinder 3B. This allows the first orifice 5 to be sandwiched and fixed between the second protruding portion 22B and the second internal cylinder 3B within the second internal cylinder 3B downstream of the midpoint 22A. Furthermore, the liquid is allowed to pass through the water flow section 51 of the first orifice 5 without leakage and flow into the second internal cylinder 3B. The first orifice 5 may be connected to the second protruding portion 22B or the second internal cylinder 3B with an adhesive or the like.

[0031] The second orifice 5A is disposed with its plate surface facing the left-right direction and is sandwiched between the upstream end (left end) of the small inner diameter portion 231 and the downstream end (right end) of the second internal cylinder 3B, as described above. The second orifice 5A is formed to have a larger inner diameter than the small inner diameter portion 231 and the inner diameter of the second internal cylinder 3B, but is smaller than the inner diameter of the third cylinder 23 upstream of the small inner diameter portion 231. This allows the second orifice 5A to be sandwiched and fixed between the small inner diameter portion 231 and the first internal cylinder 3B. Liquid is allowed to pass through the flow section 51A of the second orifice 5A without leakage and flow into the gas supply region 70. The second orifice 5A may be connected to the second internal cylinder 3B and the small inner diameter portion 231 with an adhesive or the like.

[0032] The flow passage sections 51, 51A of the first and second orifices 5, 5A have a smaller cross-sectional area than the area immediately upstream thereof. As the liquid passes through the flow passage sections 51, 51A, the sudden change in pressure caused by the change in cross-sectional area causes air bubbles in the liquid to collapse. This generates microbubbles. Furthermore, the pressure is reduced immediately downstream of the first and second orifices 5, 5A. This reduced pressure immediately downstream of the first and second orifices 5, 5A automatically supplies air from the outside through the gas supply pipe 6 located downstream of the first and second orifices 5, 5A.

[0033] (Configuration of the fine bubble generator: gas supply area and static mixer) As described above, the second orifice 5A is disposed at the upstream end of the small inner diameter portion 231, the static mixer 7 is attached to the downstream end, and the gas supply pipe 6 is inserted into the gas supply region 70 between the second orifice 5A and the static mixer 7. The static mixer 7 and the small inner diameter portion 231 may be connected with an adhesive or the like.

[0034] Due to the decompression effect immediately downstream of the first and second orifices 5, 5A, air is automatically supplied via the gas supply pipe 6 located downstream of the first and second orifices 5, 5A. As a result, air from the outside is supplied into the gas supply region 70 and is sheared by the liquid that has flowed into the gas supply region 70 through the second orifice 5A, causing cavitation and generating a large amount of fine bubbles. These fine bubbles flow into the static mixer 7. Here, the flow velocity of the liquid flowing into the gas supply region 70 is increased by passing through the second orifice 5A. Furthermore, the liquid flows into the gas supply region 70 as a swirling flow. These factors also increase the amount of fine bubbles generated.

[0035] 4 and 5, the static mixer 7 is a disk-shaped member with its plate surface facing left and right. A through-hole, which is generally circular in side view, is formed in the center of the static mixer 7, and multiple blades 71 extending inward from the edge of the through-hole are formed at predetermined intervals. In this embodiment, nine blades are formed, each tapering inward and having a flat tip. However, the shape, number, and arrangement of the blades 71 of the static mixer 7 are not limited to this and can be changed as appropriate. The static mixer 7 does not necessarily have to be plate-shaped, but a plate-shaped configuration is preferred for ease of installation. When liquid passes through the static mixer 7, the blades 71 crush air bubbles, generating microbubbles. The liquid containing these microbubbles flows through the third internal cylinder 3C to the outlet 201 and is discharged.

[0036] (Materials for micro-bubble generators) In this embodiment, the micro-bubble generator 1 is made of the following materials. The flow path tank 2, the first internal cylinder 33A, the second internal cylinder 33B, and the third internal cylinder 33C are made of resin (for example, vinyl chloride). The flow path tank 2, the first internal cylinder 33A, the second internal cylinder 33B, and the third internal cylinder 33C can be made of commercially available "vinyl chloride pipe fittings." Furthermore, the third cylinder 23 of the flow path tank 2 can be made of commercially available "vinyl chloride sprinkler nozzles."

[0037] The swirl flow generating section 4 (plate-shaped member 41, interposing member 44), first orifice 5, and second orifice 5A are made of metal (for example, stainless steel). These members 4, 5, and 5A can be made of so-called stainless steel washers (for example, an inner diameter of 6.5 mm). The plate-shaped member 41 can be made by forming a plurality of flow path through-holes 411 in the stainless steel washer. The gas supply pipe 6 is made of metal (for example, stainless steel), and a commercially available product called a "stainless steel pipe" can be used. The static mixer 7 is made of metal (for example, stainless steel), and a commercially available product called an "internal tooth washer" can be used.

[0038] (Method of manufacturing a microbubble generator) An example of a method for manufacturing the micro-bubble generator 1 will be described below with reference to FIGS. The first cylindrical body 21, the second cylindrical body 22, and the third cylindrical body 23 are manufactured by molding or the like. A pipe insertion portion 232 is formed in the third cylindrical body 23, and a through hole is formed in the pipe insertion portion 232. The first to third inner cylindrical bodies 3A to 3C are manufactured by molding or the like. Then, the swirl flow generating portion 4 is manufactured. Specifically, five plate-like members 41 and five interposing members 42 are alternately stacked, and screws 44 are inserted through the screw-fastening through holes 43, 421 and fixed with screw fixing devices 45. In this way, the swirl flow generating portion 4 is manufactured.

[0039] The swirl flow generating section 4 is inserted from the right side of the first cylinder 21 up to the first protruding portion 21B, and then the left side of the first internal cylinder 3A is inserted up to the swirl flow generating section 4. Then, the right side of the first internal cylinder 3A is inserted from the left side into the second cylinder 22. The right edge of the first cylinder 21 and the left edge of the second cylinder 22 are fixed together with an adhesive or the like. Next, the first orifice 5 is inserted from the right side of the second cylinder 22 up to the second protruding portion 22B, and then the left side of the second internal cylinder 3B is inserted up to the first orifice 5. Next, the second orifice 5A is inserted from the left side into the third cylinder 23 up to the small inner diameter portion 231, and then the right side of the second internal cylinder 3B is inserted. The right edge of the second cylinder 22 and the left edge of the third cylinder 23 are fixed together with an adhesive or the like. Next, the static mixer 7 is inserted into the third cylinder 23 from the right side up to the small inner diameter portion 231, and then the left side of the third inner cylinder 3C is inserted. Then, the gas supply pipe 6 manufactured by molding or the like is inserted from the through hole in the pipe insertion portion 232 of the third cylinder 23.

[0040] (How to use the fine bubbles of the fine bubble generator) An example of how to use the micro-bubble generator 1 will be described below with reference to FIG. 8. FIG. 8 is an explanatory diagram showing an example of how to use the micro-bubble generator shown in FIG. 1. The micro-bubble generator 1 according to this embodiment is placed in a water tank 100 that stores a liquid W, such as water. One end of a pipe 10 is inserted into the gas supply pipe 6, and the other end of the pipe 10 is positioned above the water surface. Alternatively, the upper end 61 of the gas supply pipe 6 may be positioned above the water surface without using the pipe 10. In this state, the liquid W stored in the water tank 100 is sent to the inlet 200 of the micro-bubble generator 1 using a pump P. As a result, the liquid W flowing in from the inlet 200 of the micro-bubble generator 1 passes through the outlet 201 and is discharged into the water storage area of ​​the water tank 100. As the liquid passes through the micro-bubble generator 1, micro-bubbles are generated in the liquid W and supplied to the water storage area. This method of use is a circulation type in which the liquid discharged from the outlet 201 is circulated to the inlet 200. Therefore, the liquid W containing bubbles discharged from the outlet 201 passes through the micro-bubble generator 1 repeatedly, and the amount of micro-bubbles contained in the stored liquid W can be further increased.

[0041] The microbubble-containing water generated by the microbubble generator 1 is particularly suitable for use in agriculture and the fisheries industry. Agriculture and the fisheries industry often use mineral-containing well water, river water, and lake water, rather than tap water. Since this water often has a reduced air content, it is preferable to supply a large amount of microbubbles. In agriculture and the fisheries industry, it is considered satisfactory if nanobubbles with a cumulative Q of approximately 100 million particles / mL are supplied. The microbubble generator 1 can easily generate a large amount of microbubbles simply by operating the microbubble generator 1 in the water tank 100. As will be described later in the "Demonstration Experiment of the Effect of the Microbubble Generator" section, nanobubbles with a cumulative Q of 600 million particles / mL or more can be generated by using the microbubble generator 1 to generate nanobubbles in a 10-minute circulation system.

[0042] We conducted a growth experiment in which we supplied nanobubbles with a cumulative Q of approximately 200 million bubbles / mL to koi and goldfish, and the results are shown in sample individuals a to e in Figure 20. The smaller fish were raised without the supply of fine bubbles, while the larger fish were raised with the supply of nanobubbles. As can be seen, the supply of nanobubbles significantly affected the growth rate. Here, we explain the general method of raising goldfish and koi. Goldfish and koi are primarily raised in outdoor ponds (such as reservoirs) and indoor ponds during the winter. From midsummer to autumn, fry are released into outdoor ponds (water temperature 16-25°C, DO 8-9 mg / L) to grow into koi. Only strong, beautiful, and marketable koi are then selected and kept. The selection process is carried out three times: once after hatching, and twice between July and September. In this rearing experiment, the number of surviving carp after this selection process increased by 18.7% (FY2022) after nanobubble supply. This was compared to the case without nanobubble supply. To prevent the carp from weakening in the winter cold, they are kept in wintering greenhouses where the water temperature is maintained at 18-20°C (DO 4-8 mg / L). The wintering yield is generally estimated to be 96-98%. Carp, such as koi, rapidly become sluggish and lose strength when the water temperature drops below 8°C, and they are known to develop fish diseases at water temperatures between 16 and 28°C. Therefore, it is necessary to maintain a constant water temperature (18-20°C). However, after nanobubble supply, the wintering yield increased to 98-100% even when water was supplied at 6-10°C without heating. Because the dissolved oxygen concentration (DO) of this water was increased to 8-11 mg / L, it is estimated that the number of standing carp after selection increased even when the water temperature was lower than the 18-20°C mentioned above. Thus, it can be seen that supplying marine products with nanobubbles having a cumulative Q of approximately 200 million / mL or more eliminates the need for a heater to heat the water and increases the number of standing carp after sorting. The microbubble generator 1 according to this embodiment can easily generate nanobubbles with a cumulative Q of approximately 200 million / mL or more, making it suitable for use in the marine products industry.

[0043] We also conducted experiments to measure sugar content, the number of normal and heterogeneous fruits, and other factors when nanobubbles with an integrated Q of approximately 200 million particles / mL were supplied to tomatoes and strawberries. The strawberry variety tested was Yotsuboshi. The cultivation environment was as follows: The light source was a white LED (190 ± 15 µmol m-2 s-1, 15 cm below the lamp) and a second LED (120 ± 20 µmol m-2 s-1, 15 cm below the lamp). The cultivation period was from late June to mid-August. The lamp provided 12 h of light and dark illumination, and the room temperature was 21°C. The DFT cultivation method was used, with partial changes of the nutrient solution weekly. The EC (electrical conductivity) from planting was 0.4 dS m-1. The test method involved supplying microbubbles from mid-June, harvesting once at the end of July, and counting the number of fruits and other factors at the end of August.

[0044] As shown in Figure 19A, the supply of nanobubbles tended to result in a higher cumulative number of normal fruits and fewer deformed fruits. Comparing the cumulative number of normal fruits on August 3rd, the number was just under 40 when nanobubbles were supplied, and just under 15 when nanobubbles were not supplied. Comparing the cumulative number of deformed fruits in early August, the number was 3 when nanobubbles were supplied, and 1 when nanobubbles were not supplied.

[0045] Furthermore, although the relationship between the supply of nanobubbles and the sugar content of fruit was unknown, measurements of fruit sugar content in this experiment revealed that supplying the nanobubbles increases the sugar content of fruit. As shown in Figure 19B, the sugar content (BRIX value) of Yotsuboshi apples was higher in fruits supplied with nanobubbles than in fruits not supplied with nanobubbles. Furthermore, when nanobubbles were supplied to tomatoes from March to June in fiscal year 2021 (July 2021 to June 2022), tomatoes with a sugar content of 10 or higher were harvested, whereas in fiscal year 2020 (July 2020 to June 2021), tomatoes with a sugar content of 10 to 12 were harvested. Figure 19C shows the monthly yield of regular-shaped fruits for fiscal years 2018, 2019, 2020, and 2021. In this figure, the yield of regular-shaped fruits was the highest in fiscal year 2021, which shows that the tomato harvest experiment also showed that supplying nanobubbles with a cumulative Q of approximately 200 million particles / mL to crops increased the number of regular-shaped fruits. Thus, the experimental results for both strawberries and tomatoes show that supplying nanobubbles with a cumulative Q of approximately 200 million particles / mL to crops can increase the number of regular-shaped fruits and the sugar content of the fruits.

[0046] As described above, the micro-bubble generator 1 according to this embodiment can easily generate nanobubbles with a cumulative Q of about 200 million / mL or more, and is therefore suitable for use in agriculture.

[0047] (The principle of how microbubbles are generated by the microbubble generator) The principle of microbubble generation in the microbubble generator 1 will be described in detail with reference to Figures 2, 5, 6, and 8. A liquid (e.g., water) is introduced into the flow path F (flow path tank 2) of the microbubble generator 1 from its inlet 200 by a pump P or the like. The introduced liquid passes through the swirl flow generating section 4. As described above, in the swirl flow generating section 4, each plate-like member 41 is arranged so as to rotate in a predetermined direction (the direction indicated by arrow X in Figure 7, i.e., counterclockwise) around an axis connecting the center points of each plate-like member (point O in Figure 7) relative to the adjacent plate-like member 41 on the upstream side of the flow path tank 2 (flow path F). Therefore, when the liquid passes through the swirl flow generating section 4, the liquid flows into the downstream side of the stack 40 from four oblique angles, generating a swirl flow in the liquid. Here, the swirl flow generating section 4 not only generates a swirl flow as described above, but also functions as a stacked static mixer. Therefore, these two functions can pulverize the gas (air, etc.) contained in the liquid and generate a large amount of fine bubbles.

[0048] Furthermore, as described above, since each of the plurality of plate-like members 41 is arranged so as to rotate more than the adjacent plate-like member 41 on the upstream side of the flow path tank 2 (flow path F), the edges of the flow path through holes 411 of each plate-like member 41 are overlapped in a stepped manner, and this overlapping portion prevents the generated micro-bubbles from flowing back upstream of the swirl flow generating section 4. Therefore, most of the large amount of generated micro-bubbles pass through the diameter reduction section 221 and reach the first orifice 5.

[0049] The liquid that reaches the first orifice 5 passes through the flowing water section 51 and flows downstream of the first orifice 5. Here, the flowing water section 51 has a smaller cross-sectional area than the section immediately upstream thereof. Therefore, as the liquid passes through the flowing water section 51, a sudden change in pressure occurs immediately downstream of the flowing water section 51 due to the change in the cross-sectional area of ​​the flow path. This causes bubbles in the liquid to further collapse and generate fine bubbles. The reduced diameter section 221 is formed to adjust the change in the cross-sectional area of ​​the flow path to a suitable level. Here, a swirling flow generated by the swirling flow generating section 4 flows into the first orifice 5. The swirling flow passing through the flowing water section 51 produces a more effective microbubble generation. In addition, the large amount of bubbles generated by the swirling flow generating section 4 can be further collapsed, thereby generating even more fine bubbles.

[0050] The liquid that has passed through the flow section 51 of the first orifice 5 passes through the flow section 51A of the second orifice 5A and flows into the gas supply region 70. The second orifice 5A has the same function as the first orifice 5, and is therefore capable of generating even more microbubbles. A gas supply pipe 6 is inserted into the gas supply region 70. The upper end 61 of the gas supply pipe 6 is located outside the flow channel vessel 2. As described above, the pressure is reduced immediately downstream of the flow sections 51, 51A of the first and second orifices 5, 5A. This pressure reduction automatically supplies air from the outside through the gas supply pipe 6 located downstream of the first and second orifices 5, 5A. The air from the outside is supplied to the gas supply region 70 and is sheared by the liquid that has flowed into the gas supply region 70 through the second orifice 5A, causing cavitation.

[0051] Here, the liquid flowing into the gas supply region 70 has a higher flow velocity as it passes through the second orifice 5A, thereby enhancing the micro-bubble generation effect. Furthermore, because the liquid flows into the gas supply region 70 as a swirling flow, the air from the gas supply pipe 6 is compressed and sheared, and the micro-bubble-containing liquid becomes a jet flow that flows into the static mixer 7. The jet flow that has passed through the gas supply region 70 passes through the static mixer 7 and is discharged from the outlet 201. Because the micro-bubble-containing liquid flows into the static mixer 7 as a jet flow, the amount of micro-bubbles generated by shearing in the static mixer 7 increases. Furthermore, by providing components with static mixer function (the swirling flow generating unit 4 and the static mixer 7) on both the inlet 200 side and the outlet 201 side, the amount of micro-bubbles generated can be further increased. The reasons for this are as follows. By arranging the swirl flow generating section 4, which is a stacked static mixer, near the inlet 200, the efficiency of fine bubble generation by the fine bubble generating mechanism (first and second orifices 5, 5A, gas supply region 70) located downstream of the swirl flow generating section 4 is improved, and by arranging the static mixer 7 also near the outlet 201, it is possible to further shear the fine bubbles generated upstream of the static mixer 7. In this way, the fine bubble generator 1 combines multiple bubble generation methods such as the swirl flow method, the orifice-venturi tube method, and aeration, and this is the optimal configuration that the inventors came up with after trial and error in order to increase the amount of fine bubbles generated.

[0052] The effects of the micro-bubble generator 1 according to this embodiment will be described below. (1) As described above, the micro-bubble generator 1 includes a tubular flow path F (flow path tank 2) through which a liquid introduced through the inlet 200 at one end passes and is discharged from the inlet 200 at the other end. The micro-bubble generator 1 also includes a swirl flow generating unit 4 arranged upstream of the flow path tank 2, a first orifice 5 arranged within the flow path tank 2 downstream of the swirl flow generating unit 4, a gas supply pipe 6 having an upper end 61 arranged outside the flow path tank 2 and a lower end 62 arranged within the flow path tank 2 at a position between the first orifice 5 and the inlet 200, for supplying gas from outside the flow path tank 2 into the flow path tank 2, and a static mixer 7 arranged within the flow path tank 2 between the position of the lower end 62 of the gas supply pipe 6 and the inlet 200. The swirling flow generating section 4 comprises a laminate 40 in which a plurality of plate-like members 41, each having a plurality of through holes formed on concentric circles centered on the center point, are stacked in the direction of liquid passage in the flow path tank 2 so that corresponding flow path through holes 411 in each plate-like member 41 are connected to each other, and each plate-like member 41 is arranged to rotate in a predetermined direction based on an axis connecting the center points of each plate-like member 41, relative to the adjacent plate-like member 41 on the upstream side of the flow path tank 2.

[0053] According to the above configuration, the interaction between the fine bubble generating units (swirl flow generating unit 4, first orifice 5, gas supply pipe 6, static mixer 7) described in the "Principle of Fine Bubble Generation in the Fine Bubble Generator" section significantly increases the amount of fine bubbles generated. This amount of fine bubbles will be described later in the "Demonstration Experiment of the Effect of the Fine Bubble Generator" section. Furthermore, since the main components of the fine bubble generator 1 are a tubular member (flow path vessel 2, gas supply pipe 6), a plate-like member with a through-hole (first orifice 5, static mixer 7), and a combination of a plate-like member with a through-hole (swirl flow generating unit 4), the structure is very simple and can be manufactured inexpensively. Furthermore, since the configuration can be manufactured using a combination of inexpensive commercially available products, using such commercially available products can further reduce manufacturing costs.

[0054] (2) Furthermore, the stack 40 of the swirl flow generating unit 4 functions as a static mixer by disposing plate-shaped interposing members 42 between adjacent plate-shaped members 41 so as not to block the multiple flow path through-holes 411. That is, each of the multiple plate-shaped members 41 is disposed so as to rotate more than the adjacent plate-shaped member 41 on the upstream side of the flow path tank 2 (flow path F), so that the edges of the flow path through-holes 411 of the multiple plate-shaped members 41 are spaced apart and form a stepped shape. This causes the liquid to collide with the edges of the flow path through-holes 411, forming a static mixer. By disposing the swirl flow generating unit 4, which is a stacked static mixer, near the inlet 200 and generating microbubbles near the inlet 200, the amount of microbubbles generated by the microbubble generating mechanism (first orifices 5, 5A, gas supply region 70) downstream of the swirl flow generating unit 4 can be increased.

[0055] (3) The micro-bubble generator 1 comprises a first cylindrical body 21, a second cylindrical body 22, and a third cylindrical body 23, which constitute a flow path F and are arranged in a line from the upstream side to the downstream side of the liquid. The first cylindrical body 21 has a first protruding portion 21B that protrudes inward on its inner surface, and a swirl flow generating unit 4 is arranged so as to abut against the downstream end of this first protruding portion 21B. The second cylindrical body 22 has its upstream end attached to the downstream end of the first cylindrical body 21, and has a second protruding portion 22B that protrudes inward on its inner surface at a position midway in the direction of passage of the liquid, and a first orifice 5 is arranged at the downstream end of this second protruding portion 22B. The third cylinder 23 has its upstream end attached to the downstream end of the second cylinder 22, and a small inner diameter section 231 formed midway in the liquid flow direction, with the small inner diameter section 231 having a smaller inner diameter than the upstream and downstream sides of this midway position. A second orifice 5A is disposed at the upstream edge of this small inner diameter section 231, and a static mixer 7 is disposed at the downstream edge of the small inner diameter section 231, and a gas supply pipe 6 is inserted into the small inner diameter section 231. The fine bubble generator 1 further includes a first inner cylinder 3A, a second inner cylinder 3B, and a third inner cylinder 3C. The first inner cylinder 3A is inserted into the first cylinder 21 and the second cylinder 22, and extends from the downstream end of the swirl flow generating section 4 to the second protruding section 22B. The second internal cylinder 3B is inserted into the second cylinder 22 and the third cylinder 23, and extends from the downstream end of the first orifice 5 to the upstream end of the second orifice 5A. The third internal cylinder 3C is inserted into the third cylinder 23, and extends from the downstream end of the static mixer 7 in the direction in which the liquid passes.

[0056] According to the above configuration, the flow path vessel 2 is divided into the first cylinder 21, the second cylinder 22, and the third cylinder 23, which makes it easy to insert components such as the swirl flow generating unit 4, the orifice 5, the orifice 5A, and the static mixer 7 into the flow path vessel 2. Furthermore, because the first inner cylinder 3A is inserted into the first cylinder 21 and the second cylinder 22, and the second inner cylinder 3B is inserted into the second cylinder 22 and the third cylinder 23, the strength of the connection portion between the first cylinder 21 and the second cylinder 22 and the connection portion between the second cylinder 22 and the third cylinder 23 can be increased. Furthermore, the swirl flow generating section 4 can be fixed between the first internal cylinder 3A and the first protruding portion 21B, the first orifice 5 can be fixed between the second internal cylinder 3B and the second protruding portion 22B, the second orifice 5A can be fixed between the second internal cylinder 3B and the small inner diameter portion 231, and the static mixer 7 can be fixed between the third internal cylinder 3C and the small inner diameter portion 231. In this way, the swirl flow generating section 4, the orifice 5, the orifice 5A, and the static mixer 7 can be fixed with a simple configuration.

[0057] (Demonstration experiment of the effectiveness of a micro-bubble generator) Below, using Figures 9 to 18, a demonstration experiment that proves the effectiveness of the micro-bubble generator 1 will be explained. Figure 9 is a table showing the experimental results of a non-circulating type using experimental apparatus a. Figure 10 is a graph showing the experimental results of Figure 9. Figure 11 is a table showing the experimental results of a non-circulating type using experimental apparatus b. Figure 12 is a graph showing the experimental results of Figure 11. Figure 13 is a table showing the experimental results of a non-circulating type using experimental apparatus c. Figure 14 is a graph showing the experimental results of Figure 13. Figure 15 is a table showing the experimental results of a non-circulating type using experimental apparatus d. Figure 16 is a graph showing the experimental results of Figure 15. Figure 17 is a table showing the experimental results of a circulating type using experimental apparatus d. Figure 18 is a graph showing the experimental results of Figure 17.

[0058] In this experiment, four experimental devices for generating fine bubbles were prepared: experimental device a, experimental device b, experimental device c, and experimental device d. The particle size distribution of water (fine-bubble-containing water) passed through experimental device a to d was measured. This experiment was conducted using a nanoparticle size distribution measurement device (Shimadzu SALD-7500H Version 3.3.2) that employs SLIT optical systems based on scattered light intensity tracking technology, under conditions of room temperature of 22°C, water temperature of 15.3°C, and total dissolved solids of 57 ppm.

[0059] Figures 9, 11, 13, 15, and 17 show the particle sizes (μm) detected in the fine bubble-containing water in ascending order, along with the cumulative Q (particles / mL) and concentration (frequency q) associated with each particle size (μm). Here, cumulative Q (particles / mL) indicates the cumulative amount of all bubbles with a particle size (μm) or smaller. Furthermore, frequency q (particles / mL) indicates the amount contained within a predetermined range centered on the particle size (μm). The line graphs in Figures 10, 12, 14, 16, and 18 are cumulative graphs with particle size (μm) on the horizontal axis and concentration (cumulative Q) on the vertical axis. Furthermore, histograms are differential graphs with particle size (μm) on the horizontal axis and concentration (frequency q) on the vertical axis. The cumulative Q (particles / mL) in the line graphs indicates the cumulative amount of all particles with a particle size (μm) or smaller than the particle size displayed on the horizontal axis. The frequency q (particles / mL) in the difference graph indicates the amount included in the particle size range displayed on the horizontal axis.

[0060] 1 and 2, the experimental apparatus a has a configuration that is downstream of the first orifice 5 and upstream of the second orifice 5A. That is, it does not have the gas supply pipe 6 and static mixer 7 as a structure for generating micro bubbles, but has a swirl flow generating section 4 and the first orifice 5. Also, while the swirl flow generating section 4 of the fine bubble generator 1 has five plate-like members 41 and five interposing members 42 stacked alternately, the experimental apparatus a has three plate-like members 41 stacked without stacking the interposing members 42.

[0061] Experimental apparatus b differs from experimental apparatus a only in that it is equipped with a swirling flow generating section 4 in which five plate-like members 41 and five interposing members 42 are alternately stacked, similar to the micro-bubble generator 1. Here, the interposing members 42 used are 0.5 mm (washers), and the spacing between adjacent plate-like members 41 is approximately 0.5 mm. Experimental apparatus c differs from experimental apparatus b only in the interposing members 42 (washers) used, and the rest of the configuration is the same. The thickness of the interposing members 42 (washers) used in experimental apparatus c is 1.0 mm, and the spacing between adjacent plate-like members 41 is approximately 1.0 mm.

[0062] Experimental apparatus d has the same configuration as fine-bubble generator 1. That is, it is equipped with not only a swirl flow generating section 4 and a first orifice 5, but also a second orifice 5A, a gas supply pipe 6, and a static mixer 7. However, experimental apparatus d differs in configuration from fine-bubble generator 1 in that it is equipped with a swirl flow generating section in which three plate-like members 41 are stacked, instead of stacking an inserting member 42, as in experimental apparatus a.

[0063] 9 and 10 show the results of measuring the particle size distribution of water containing fine bubbles that was passed through experimental device a once (one pass). Specifically, water was pumped into the inlet (upstream end) of flow path F of experimental device a using a pump (installed in a water tank), and the particle size distribution of the water (water containing fine bubbles) discharged from the outlet (downstream end) of flow path F was measured. Note that outlet 201 (downstream end) was set outside the water storage area of ​​the water tank. The average diameter of the particles (air bubbles) detected in this experiment was 0.746 μm. Furthermore, fine bubbles with a particle diameter of less than 1 μm are considered nanobubbles, and the cumulative Q of particles with a particle diameter of 0.956 μm was 2,514,357 bubbles / mL.

[0064] Figures 11 and 12 show the results of measuring the particle size distribution of water containing fine bubbles that was passed through experimental device b once. Here, the average diameter of particles (air bubbles) detected in this experiment was 0.520 μm. In addition, the cumulative Q for particles with a diameter of 0.956 μm was 14,969,376 particles / mL. Figures 13 and 14 show the results of measuring the particle size distribution of water containing fine bubbles that was passed through experimental device c once (one pass). Here, the average diameter of particles (air bubbles) detected in this experiment was 0.681 μm. In addition, fine bubbles with a diameter of less than 1 μm are called nanobubbles, and the cumulative Q for particles with a diameter of 0.956 μm was 5,910,634 particles / mL.

[0065] Comparing the experimental results of Figures 9 and 10 with those of Figures 11 and 12 and those of Figures 13 and 14, the experimental results of Figures 11 and 12 and those of Figures 13 and 14 are better than those of Figures 9 and 10 in terms of both the smaller average particle (bubble) diameter and the larger cumulative Q for particle diameters of 0.956 μm. As mentioned above, the major difference between experimental apparatus a and experimental apparatuses b and c is that experimental apparatus a uses a swirl flow generating unit consisting of three stacked plate-like members 41 without any interposing members 42, whereas experimental apparatuses b and c use a swirl flow generating unit 4 consisting of five plate-like members 41 and five interposing members 42 stacked alternately. This indicates that the use of a swirl flow generating unit 4 consisting of interposing members 42 stacked between multiple plate-like members 41 improves the efficiency of fine bubble generation.

[0066] 11 and 12 with those of Figures 13 and 14, the experimental results of Figures 11 and 12 are better than those of Figures 13 and 14 in terms of both the smaller average particle (air bubble) diameter and the larger cumulative Q for particle diameters of 0.956 μm. As mentioned above, experimental apparatus c differs from experimental apparatus b only in the interposing member 42 (washer) used; the interposing member 42 (washer) used in experimental apparatus b is 0.5 mm thick, while the interposing member 42 (washer) used in experimental apparatus c is 1.0 mm thick. This indicates that the thickness of the interposing member 42 (washer) is preferably less than 1.0 mm.

[0067] Figures 15 and 16 show the particle size distribution measurement results for water containing fine bubbles that passed through experimental device d once. The average particle size (air bubbles) detected in this experiment was 0.708 μm. The cumulative Q for particles with a diameter of 0.956 μm was 2,749,002 particles / mL. Comparing the experimental results shown in Figures 9 and 10 with those shown in Figures 15 and 16, the experimental results shown in Figures 15 and 16 are superior in both the average particle size (air bubbles) and the cumulative Q for particles with a diameter of 0.956 μm. Experimental device d differs in that it includes not only a swirl flow generator 4 and a first orifice 5, but also a second orifice 5A, a gas supply pipe 6, and a static mixer 7 as a structure for generating fine bubbles. This indicates that the inclusion of a second orifice 5A, a gas supply pipe 6, and a static mixer 7 increases the amount of fine bubbles generated.

[0068] Figures 17 and 18 show the measurement results of the particle size distribution of fine-bubble-containing water after circulating it for 10 minutes in the experimental device d. That is, the particle size distribution of fine-bubble-containing water is measured after circulating it for 10 minutes using the method shown in Figure 8. Here, the average diameter of particles (bubbles) detected in this experiment was 0.154 μm. Also, the cumulative Q of particles with a diameter of 0.956 μm was 679,958,796 particles / mL. Comparing the experimental results of Figures 15 and 16 with those of Figures 17 and 18, the experimental results of Figures 17 and 18 are significantly better in both the average diameter of particles (bubbles) and the cumulative Q of particles with a diameter of 0.956 μm. Furthermore, they are significantly better than any of the experimental results described above. This shows that using the fine-bubble generator 1 as a circulation-type fine-bubble generator significantly improves the efficiency of fine-bubble generation.

[0069] [Modification] The above-described embodiment is an example of an embodiment to which the present invention is applied, and the materials, number, arrangement, and other configurations can be changed as appropriate. [Explanation of symbols]

[0070] 1. Microbubble generator 2. Flow channel tank 21 First Cylinder 21B 1st protruding part 22 Second Cylinder 22B 2nd protruding part 23 Third Cylinder 231 Small inner diameter section 200 entrance 201 Exit 3A 1st internal cylinder 3B Second internal cylinder 3C Third internal cylinder 4 Swirl flow generation part 40 laminate 41 Plate-shaped member 411 Flow path through hole 42 Interposing member 5 First Orifice 5A Second orifice 6 Gas supply pipe 61 Upper end (upper end) 62 Bottom end (other end) 7 Static Mixer F flow path

Claims

1. A microbubble generator having a tubular flow path through which a liquid flows in from an inlet at one end thereof and is discharged from an outlet at the other end thereof, a swirl flow generating unit disposed upstream of the flow path; a first orifice disposed in the flow path downstream of the swirling flow generation portion; a gas supply pipe having one end disposed outside the flow path and the other end disposed in the flow path at a position between the first orifice and the outlet, for supplying gas from outside the flow path to the flow path; a static mixer disposed in the flow path between the outlet and a position where the other end of the gas supply pipe is disposed, The swirl flow generating section is a laminate in which a plurality of plate-like members, each having a plurality of flow path through holes formed on concentric circles centered on a central point thereof, are stacked in a direction in which the liquid passes through the flow path so that the corresponding flow path through holes in each of the plate-like members are in communication with each other; Each of the plate-like members is arranged to rotate in a predetermined direction relative to an adjacent plate-like member on the upstream side of the flow path, with an axis connecting center points of the plate-like members as a reference. A microbubble generator characterized by:

2. the stack functions as a static mixer, with plate-shaped interposing members disposed between adjacent plate-shaped members so as not to block the plurality of flow path through holes; 2. The microbubble generator according to claim 1,

3. The flow path is configured to include a first cylindrical body, a second cylindrical body, and a third cylindrical body that are arranged in a line from an upstream side to a downstream side of the liquid, the first cylindrical body has a first protruding portion that protrudes inward on its inner surface, and the swirl flow generating portion is disposed so as to abut against a downstream end of the first protruding portion; the second cylindrical body has an upstream end attached to the downstream end of the first cylindrical body, and is provided with a second protruding portion that protrudes inward on an inner surface at a midpoint in the direction of passage of the liquid, and the first orifice is disposed at the downstream end of this second protruding portion; The third cylinder has an upstream end attached to a downstream end of the second cylinder, and a small inner diameter portion is formed at a midpoint in the direction of passage of the liquid, the small inner diameter portion having an inner diameter smaller than that of the upstream and downstream sides of the midpoint, the second orifice is disposed at an upstream edge of the small inner diameter portion, the static mixer is disposed at a downstream edge of the small inner diameter portion, and the gas supply pipe is inserted into the small inner diameter portion, a first internal cylindrical body inserted into the first cylindrical body and the second cylindrical body and extending from the downstream end of the swirl flow generating portion to the second protruding portion; a second inner cylinder inserted into the second cylinder and the third cylinder and extending from a downstream end of the first orifice to an upstream end of the second orifice; a third internal cylinder inserted into the third cylinder and extending from the downstream end of the static mixer in the direction in which the liquid passes; 2. The microbubble generator according to claim 1,

4. A circulation type in which the liquid discharged from the outlet is circulated to the inlet, and a liquid containing fine bubbles to be supplied to agricultural or marine products is generated.

4. The microbubble generator according to claim 1, wherein the microbubble generator is a microbubble generator.

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