Microbubble generation device

Abstract

To provide a microbubble generating device that can increase the number of microbubbles generated. [Solution] The microbubble generating device 1 comprises a flow path 52 through which a target liquid containing gas flows, a bubble generating nozzle 20 arranged in the flow path 52 and having a plurality of bubble generating holes 21a, 21b, 22a, 22b, which generates microbubbles downstream, and an upstream flow control plate 30 arranged upstream of the bubble generating nozzle 20 in the flow path 52.

Description

Technical Field

[0001] The present invention relates to a microbubble generating device.

Background Art

[0002] Devices that generate fine bubbles, including microbubbles and ultra-fine bubbles, are known. Fine bubbles are utilized in various applications such as beauty, cleaning, promoting the growth of agricultural and livestock products and aquatic products, and maintaining the freshness of food.

[0003] Patent Document 1 discloses an ultra-fine bubble generating device. The device includes a Venturi core that generates ultra-fine bubbles. Further, a buffer cavity is formed between the Venturi core and the barrier mesh. It is disclosed that the water flow ejected from the Venturi channel impacts and shears the water in the buffer cavity, thereby improving the cavitation effect and causing a large amount of ultra-fine bubbles to be contained in the drainage.

[0004] Patent Document 2 discloses a microbubble generating device. The device includes a flow path and a negative pressure generating chamber that is connected to the flow path adjacent to the side wall of the flow path. The flow path is disclosed to include a flow velocity accelerating portion where the diameter of the flow path is smaller than that at the supply port, and a flow velocity decelerating portion where the diameter is larger than that of the flow velocity accelerating portion on the discharge port side of the flow velocity accelerating portion. Thereby, it is said that the content of microbubbles can be increased. Further, the device includes a filter for adjusting the flow of the fluid on the discharge port side.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] In microbubble generation devices, there is a need to increase the number of microbubbles generated by the nozzle. Conventional methods have already been used to increase the number of microbubbles generated.

[0007] This invention was made in view of the above background, and aims to provide a microbubble generating device that can increase the number of microbubbles generated by a new method. [Means for solving the problem]

[0008] One aspect of the present invention is, A flow path through which a target liquid containing gas is circulated, A bubble generating nozzle is arranged in the aforementioned flow path and has multiple bubble generating holes, generating fine bubbles downstream, The microbubble generating apparatus includes an upstream flow control plate positioned upstream of the bubble generating nozzle in the aforementioned flow path. [Effects of the Invention]

[0009] It was found that the flow velocity of the target liquid flowing into the bubble generation pores affects the number of microbubbles generated in those pores. When a bubble generation nozzle contains multiple bubble generation pores, it is necessary to increase the number of microbubbles generated in each of the pores. Through diligent research, we discovered that the number of microbubbles generated increases when the flow velocity of the target liquid flowing into each of the pores is uniform, compared to when the flow velocity of the target liquid flowing into each of the pores is non-uniform.

[0010] The microbubble generating apparatus includes an upstream flow control plate. The upstream flow control plate makes it possible to reduce the flow velocity difference in the flow velocity distribution of a second flow channel cross-section located between the upstream flow control plate and the bubble generating nozzle compared to the flow velocity difference in the flow velocity distribution of a first flow channel cross-section located upstream of the upstream flow control plate. The flow velocity difference in the flow velocity distribution of a predetermined flow channel cross-section refers to the difference between the minimum and maximum values ​​of the flow velocity distribution of the target liquid in that predetermined flow channel cross-section.

[0011] If the microbubble generation device does not include an upstream flow control plate, the target liquid with a large velocity difference in the velocity distribution of the first channel cross-section will reach the bubble generation nozzle. This would result in a large variation in the velocity of the target liquid flowing into each of the multiple bubble generation holes.

[0012] On the other hand, if the microbubble generation device includes an upstream flow control plate, the target liquid having a velocity difference in the velocity distribution of the second channel cross-section can reach the bubble generation nozzle. The velocity difference in the velocity distribution of the second channel cross-section is smaller than the velocity difference in the velocity distribution of the first channel cross-section. In other words, the variation in the velocity of the target liquid flowing into each of the multiple bubble generation holes can be reduced. Consequently, the number of bubbles generated by each of the multiple bubble generation holes can be increased. As a result, the number of bubbles generated by the bubble generation nozzle can be increased.

[0013] Therefore, according to the above embodiment, it is possible to provide a microbubble generating apparatus that can increase the number of microbubbles generated. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows an axial cross-sectional view of the microbubble generating apparatus in Example 1, and the flow velocity of the target liquid in each channel cross-section. [Figure 2] Figure 2 is an enlarged cross-sectional view taken along line II-II in Figure 1. [Figure 3] Figure 3 is an enlarged cross-sectional view taken along line III-III in Figure 1. [Figure 4] Figure 4 is an enlarged view of the first bubble generation nozzle, which constitutes the microbubble generation apparatus in Example 1, as seen from the inlet of the microbubble generation apparatus. [Figure 5] Figure 5 is an enlarged view of the upstream flow control plate, which constitutes the microbubble generation apparatus in Example 1, as seen from the inlet of the microbubble generation apparatus. [Figure 6]FIG. 6 is an enlarged view of the downstream flow control plate that constitutes the fine bubble generator in Example 1, as seen from the outlet of the fine bubble generator. [Figure 7] FIG. 7 is an enlarged view of the upstream flow control plate that constitutes the fine bubble generator in Example 2, as seen from the inlet of the fine bubble generator. [Figure 8] FIG. 8 is an axial cross-sectional view of the fine bubble generator in Example 3. [Figure 9] FIG. 9 is an axial cross-sectional view of the fine bubble generator in the comparative example, and a diagram showing the flow velocity of the target liquid in each flow path cross-section.

MODE FOR CARRYING OUT THE INVENTION

[0015] The fine bubble generator is used in a flow path through which a target liquid containing gas flows. The target liquid includes water, chemical liquid, cosmetic liquid, etc. The gas is mainly air, but can be a gas species according to the purpose. The target liquid containing gas is particularly preferably tap water, industrial water, or agricultural water, that is, water containing air.

[0016] The fine bubble generator is preferably installed in a water pipe through which tap water, industrial water, or agricultural water flows. The fine bubble generator is used in water pipes installed in commercial, industrial, and agricultural facilities such as residential buildings, office buildings, factories, and farms.

[0017] When the fine bubble generator is used in a residential building, for example, it may be installed in a water pipe for introducing tap water into the residential building, or it may be installed in each residential facility such as a kitchen, washroom, bathroom, or toilet. When the fine bubble generator is installed in a water pipe for introducing tap water into a residential building, fine bubbles can be supplied to all residential facilities connected downstream of the water pipe.

[0018] The microbubbles include at least fine bubbles. Fine bubbles are defined in ISO 20480-1 and JIS B 8741-1. Fine bubbles include microbubbles and ultrafine bubbles. Microbubbles have a diameter of 1 μm or more and less than 100 μm, while ultrafine bubbles have a diameter of less than 1 μm. The microbubble generating device is preferably a device that generates ultrafine bubbles.

[0019] The microbubble generating device includes a flow path. The microbubble generating device also includes a cylindrical body that forms at least a portion of the flow path. Here, the flow path is a flow path for circulating a target liquid containing gas. In other words, the cylindrical body is configured to be connected to an upstream cylindrical section for forming an upstream flow path. The cylindrical body is also configured to be connected to a downstream cylindrical section for forming a downstream flow path.

[0020] The cylindrical body may be formed in the shape of a straight pipe or a bent pipe. Furthermore, the cylindrical body may be formed from a single cylindrical member or from multiple cylindrical members of different diameters, such as a multi-tube structure. Each of the multiple cylindrical members may be made of the same material or different materials.

[0021] The microbubble generation device includes a bubble generation nozzle. The bubble generation nozzle is configured to generate microbubbles. Below, examples of bubble generation nozzles are described, specifically a configuration for generating microbubbles and a configuration for generating ultrafine bubbles.

[0022] Configurations for generating microbubbles include, for example, (1) bubble disruption by liquid shearing, (2) precipitation of dissolved gas in the liquid, and (3) rapid condensation of vapor bubbles. (1) Bubble disruption by liquid shearing includes (1-1) the "swirling flow liquid type" which disrupts bubbles by high-speed liquid swirling flow, (1-2) the "ejector type or Venturi type" which disrupts bubbles by rapid pressure changes in the gas-liquid flow path, (1-3) the "micropore type" which refines bubbles by fine gas dispersion holes, and (1-4) the "static mixer type" which shears bubbles by obstacles in the gas-liquid flow path. (2) Precipitation of dissolved gas in the liquid includes (2-1) the "pressurized precipitation type" which precipitates bubbles by rapidly depressurizing a saturated solution under pressure, and (2-2) the "heated precipitation type" which precipitates bubbles by rapidly heating a saturated solution at room temperature. (3) Rapid condensation of vapor bubbles includes (3-1) the "direct vapor contact condensation method," which refines the mixed gas bubbles by direct contact condensation of vapor.

[0023] Configurations for generating ultrafine bubbles include, for example, (4) a method using microbubbles as a raw material, and (5) a method for directly generating ultrafine bubbles.

[0024] (4) Methods using microbubbles as a raw material include (4-1) the "high-speed swirling liquid flow method," in which bubbles are crushed by a high-speed swirling liquid flow to generate microbubbles and ultrafine bubbles in the liquid, and after the microbubbles float and separate, only the ultrafine bubbles remain in the liquid; and (4-2) the "pressurized dissolution method," in which gas is pressurized and dissolved in the liquid to a supersaturated state, and then the liquid is rapidly depressurized to generate microbubbles and ultrafine bubbles, and after the microbubbles float and separate, only the ultrafine bubbles remain in the liquid.

[0025] (5) Methods for directly generating ultrafine bubbles include (5-1) the "surfactant-added micropore method," in which a sufficient amount of surfactant is added to the liquid to reduce the gas-liquid interfacial tension and disperse ultrafine bubbles from very small gas dispersion pores, and (5-2) "ultrasonic cavitation," in which ultrafine bubbles are generated from dissolved gas in the liquid by cavitation.

[0026] The bubble generating nozzle can use at least one of the generating means described above. The bubble generating nozzle may include only one nozzle or may include multiple nozzles. The multiple nozzles may be arranged in series in the direction of the flow path. The multiple nozzles may have the same structure or different structures.

[0027] The microbubble generating device includes an upstream flow control plate. The upstream flow control plate is positioned upstream of the bubble generation nozzle in the flow path formed by the cylindrical body. The upstream flow control plate is configured to make the velocity difference in the flow velocity distribution of the second flow path cross-section located between the upstream flow control plate and the bubble generation nozzle smaller than the velocity difference in the flow velocity distribution of the first flow path cross-section located upstream of the upstream flow control plate.

[0028] The second flow channel cross-section may be positioned closer to the bubble generation nozzle than the midpoint between the upstream flow control plate and the bubble generation nozzle. The midpoint between the upstream flow control plate and the bubble generation nozzle is the midpoint in the flow channel direction between the downstream surface of the upstream flow control plate and the upstream surface of the bubble generation nozzle.

[0029] The flow velocity of the target liquid in the first channel cross-section may be configured to be greatest at the center of the first channel cross-section. For example, in a channel without flow obstructions, the flow velocity is greatest at the center of the channel cross-section and decreases radially outward. The fact that the flow velocity of the target liquid is greatest at the center of the first channel cross-section includes the case where there are no flow obstructions in a predetermined range upstream of the first channel cross-section.

[0030] Furthermore, the upstream flow control plate may include a wall portion located closer to the center than the radial midpoint, which blocks the flow of the target liquid, and a plurality of through-holes located radially outside the wall portion and extending along the circumferential direction. As a result, the flow velocity of the target liquid near the center, where the flow velocity is high in the first flow channel cross-section, is reduced by the wall portion. On the other hand, the target liquid at radial positions where the flow velocity is lower than the center in the first flow channel cross-section can flow through the through-holes. Therefore, the flow velocity difference of the target liquid can be reduced in the flow velocity distribution of the second flow channel cross-section located downstream of the upstream flow control plate.

[0031] The wall portion of the upstream flow deflector may be positioned to include the center of the flow channel cross-section. In other words, the wall portion of the upstream flow deflector is formed in the radial direction from the center to the inner diameter edge of the through hole.

[0032] Furthermore, the wall portion of the upstream flow control plate may be positioned radially outward from the center of the flow channel cross-section, so as not to be located at the center. In this case, a central hole is formed at the center of the flow channel cross-section of the upstream flow control plate.

[0033] The opening area of ​​each of the multiple through-holes in the upstream flow control plate may be larger than the opening area of ​​each of the bubble-generating holes. The flow velocity of the target liquid that has passed through the upstream flow control plate can be set to a desired range. In other words, the flow velocity of the target liquid in the second flow channel cross-section can be set to a desired range.

[0034] The multiple through-holes in the upstream flow control plate may be formed in an arc shape, for example, when viewed from the central axis direction of the flow path. By forming the through-holes in an arc shape, the fluid flowing in a predetermined radial range can be allowed to flow smoothly. As a result, the flow velocity of the fluid flowing in that radial range can be maintained as much as possible. In other words, the velocity difference in the flow velocity distribution of the second flow path cross-section can be set to a desired value.

[0035] The number of arc-shaped through holes can be set arbitrarily. For example, if two through holes are formed, each through hole may have a semi-circular shape. If four through holes are formed, each through hole may have an arc shape of approximately 90°.

[0036] The distance between the upstream flow control plate and the bubble generation nozzle should be set to 0.7 to 2 times the diameter of the inner circumference of the cylinder body. If the diameter of the inner circumference of the cylinder body changes, the average diameter of the portion of the inner circumference of the cylinder body located between the upstream flow control plate and the bubble generation nozzle should be used as the reference. The flow velocity of the target liquid in the second flow channel cross-section can be set to a desired range.

[0037] The upstream flow control plate has the function of blocking foreign matter during transport before installation and during the installed state. By adjusting the shape and size of the multiple through holes, it is possible to block foreign matter that may enter. By blocking foreign matter with the upstream flow control plate, clogging of the bubble generation holes of the bubble generation nozzle can be suppressed, and the number of bubbles generated can be maintained.

[0038] The upstream flow deflector can be seen from the inlet of the cylinder body. Therefore, from a design standpoint, the position and shape of the multiple through-holes in the upstream flow deflector may be set. Also, since the upstream flow deflector is located upstream of the bubble generation nozzle, it may be designed to function as a screen for the bubble generation nozzle. In this case, the position and shape of the multiple through-holes in the upstream flow deflector may be set to effectively act as a screen.

[0039] Multiple bubble-generating pores may be positioned at different locations in the radial direction of the flow path. For example, in the cross-section of the flow path, one bubble-generating pore may be formed at the center, and another bubble-generating pore may be formed at a position offset from the center. Alternatively, in the cross-section of the flow path, one bubble-generating pore may be formed at a position offset by a first distance from the center, and another bubble-generating pore may be formed at a position offset by a second distance (a distance different from the first distance) from the center.

[0040] Even if multiple bubble-generating pores are positioned at different radial locations, the upstream flow control plate can reduce variations in the flow velocity of the target liquid flowing into the multiple bubble-generating pores. Therefore, even if multiple bubble-generating pores are positioned at different radial locations, the number of microbubbles generated by each bubble-generating pore can be increased.

[0041] Multiple bubble-generating holes may have the same channel cross-sectional shape and the same channel length. When multiple bubble-generating holes have the same channel cross-sectional shape and channel length, the number of microbubbles generated by the multiple bubble-generating holes can be increased by reducing the variation in the flow velocity of the target liquid flowing into the multiple bubble-generating holes. Therefore, when multiple bubble-generating holes have the same channel cross-sectional shape and channel length, the number of microbubbles generated can be increased by arranging an upstream flow control plate.

[0042] The microbubble generating device may further include a downstream flow control plate. The downstream flow control plate is positioned downstream of the bubble generating nozzle in the flow path formed by the cylindrical body. Furthermore, the downstream flow control plate is configured to suppress the increase in flow velocity at the center of the third flow path cross-section located downstream of the downstream flow control plate.

[0043] Microbubbles are generated inside the bubble generation nozzle and downstream of the bubble generation nozzle. Downstream of the bubble generation nozzle, for example, after microbubbles are generated, they may be further refined into ultrafine bubbles. However, if there is a large difference in flow velocity in the flow velocity distribution of the channel cross-section in the region through which the target liquid containing microbubbles flows, the microbubbles may collide with each other and disappear. As a result, the amount of ultrafine bubbles generated may decrease.

[0044] Generally, in a flow channel without flow obstructions, the flow velocity is highest at the center of the channel cross-section and decreases radially outward. Therefore, if a downstream flow control plate is not provided, the flow velocity at the center of the channel cross-section increases rapidly at a short distance downstream from the bubble generation nozzle. In other words, the velocity difference in the flow velocity distribution of the channel cross-section becomes large at a short distance downstream from the bubble generation nozzle. As mentioned above, a large velocity difference can lead to a decrease in the amount of microbubbles generated.

[0045] Therefore, by arranging the downstream flow deflector, the increase in flow velocity at the center of the third channel cross-section located downstream of the downstream flow deflector can be suppressed. In other words, compared to the case without the downstream flow deflector, the expansion of the velocity difference in the flow velocity distribution of the channel cross-section can be suppressed in the region from the downstream flow deflector to before and after the third channel cross-section. Consequently, by making the region from the downstream flow deflector to before and after the third channel cross-section a region where microbubbles are generated, the number of microbubbles generated can be increased.

[0046] The flow velocity of the target liquid at the center of the flow channel cross-section may be configured to increase as it progresses from the third flow channel cross-section to the fourth flow channel cross-section located downstream of the third flow channel cross-section. In other words, this means that there are no flow obstructions between the third and fourth flow channel cross-sections.

[0047] Furthermore, the downstream flow control plate may include a wall portion located closer to the center than the radial midpoint, which blocks the flow of the target liquid, and a plurality of through-holes located radially outside the wall portion and extending along the circumferential direction. The wall portion of the downstream flow control plate can suppress the increase in flow velocity at the center of the third flow channel cross-section located downstream of the downstream flow control plate. On the other hand, the target liquid located radially outside the wall portion can flow through the through-holes. In other words, compared to the case without a downstream flow control plate, the expansion of the velocity difference in the flow velocity distribution of the flow channel cross-section can be suppressed in the region from the downstream flow control plate to before and after the third flow channel cross-section. Therefore, by making the region from the downstream flow control plate to before and after the third flow channel cross-section a region where microbubbles are generated, the number of microbubbles generated can be increased.

[0048] The opening area of ​​each of the multiple through holes in the downstream flow control plate may be larger than the opening area of ​​each of the bubble generation holes. The flow velocity of the target liquid that has passed through the downstream flow control plate can be set to a desired range. In other words, the flow velocity of the target liquid in the third flow channel cross-section can be set to a desired range.

[0049] The downstream flow control plate has the function of blocking foreign matter during transport before installation and during the installed state. By adjusting the shape and size of the multiple through holes, it is possible to block foreign matter that may enter. By blocking foreign matter with the downstream flow control plate, clogging of the bubble generation holes of the bubble generation nozzle can be suppressed, and the number of bubbles generated can be maintained.

[0050] The downstream flow deflector can be seen from the outlet of the cylinder body. Therefore, from a design standpoint, the position and shape of the multiple through holes in the downstream flow deflector may be set. Also, since the downstream flow deflector is located downstream of the bubble generation nozzle, it may be designed to function as a screen for the bubble generation nozzle. In this case, the position and shape of the multiple through holes in the downstream flow deflector may be set to effectively serve as a screen.

[0051] The upstream and downstream flow deflectors may be formed to the same shape. Even if the upstream and downstream flow deflectors are the same shape, they can still achieve their respective effects. Furthermore, since the upstream and downstream flow deflectors can be formed as a single component, costs can be reduced.

[0052] The upstream and downstream flow deflectors may be formed in different shapes. By forming the upstream and downstream flow deflectors in their respective optimal shapes, their respective effects can be maximized.

[0053] In particular, the multiple through-holes in the downstream flow control plate may be formed in an arc shape, for example, when viewed from the central axis direction of the flow path. By forming the through-holes in an arc shape, the fluid flowing in a predetermined radial range can be allowed to flow smoothly. As a result, the flow velocity of the fluid flowing in that radial range can be maintained as much as possible. In other words, the velocity difference in the flow velocity distribution of the third flow path cross-section can be made as desired.

[0054] The number of arc-shaped through holes can be set arbitrarily. For example, if two through holes are formed, each through hole may have a semi-circular shape. If four through holes are formed, each through hole may have an arc shape of approximately 90°.

[0055] The distance between the bubble-generating nozzle and the upstream flow deflector may be equal to the distance between the bubble-generating nozzle and the downstream flow deflector. The upstream and downstream flow deflector will have symmetry with respect to the bubble-generating nozzle. This is aesthetically pleasing. [Examples]

[0056] (Example 1) 1. Microbubble Generating Device 1 The microbubble generator 1 will be described with reference to Figures 1 to 6. An example of the microbubble generator 1 being installed in a water pipe that carries tap water will be given. For example, the microbubble generator 1 is installed downstream of the water meter and adjacent to it.

[0057] The microbubble generating device 1 includes a cylindrical body 10, a bubble generating nozzle 20, an upstream flow regulating plate 30, and a downstream flow regulating plate 40. The cylindrical body 10 forms at least a portion 52 of the flow path 50. In other words, the microbubble generating device 1 includes a flow path 52, a bubble generating nozzle 20, an upstream flow regulating plate 30, and a downstream flow regulating plate 40. The individual elements of the microbubble generating device 1 are described below.

[0058] The cylindrical body 10 is formed of a metal such as stainless steel, or a hard resin. The cylindrical body 10 is formed in a straight pipe shape and forms at least a portion 52 of the flow path 50. That is, the cylindrical body 10 has an inlet 11 at one end and an outlet 12 at the other end. One end of the cylindrical body 10 is connected to a member 2 that forms the upstream flow path 51 of the flow path 50, and the other end of the cylindrical body 10 is connected to a member 3 that forms the downstream flow path 53 of the flow path 50.

[0059] The inner circumferential surface 13 of the cylindrical body 10 has a circular flow channel cross-section. However, the flow channel cross-section of the cylindrical body 10 is not limited to a circle and can be of various shapes such as elliptical or rectangular. Furthermore, the inner circumferential surface 13 of the cylindrical body 10 has the same flow channel cross-section along its entire length. However, the flow channel cross-section of the inner circumferential surface 13 of the cylindrical body 10 may change along the central axis of the flow channel. In the following, unless otherwise specified, "flow channel cross-section" refers to the cross-section perpendicular to the central axis of the flow channel 52 formed by the cylindrical body 10.

[0060] The cylindrical body 10 allows a target liquid containing gas to flow through it. In this case, the microbubble generator 1 is installed in a water pipe that carries tap water. Therefore, the cylindrical body 10 allows water containing air to flow through it.

[0061] The bubble-generating nozzle 20 is positioned in the flow path 52 formed by the cylindrical body 10. Specifically, the bubble-generating nozzle 20 is positioned near the midpoint in the flow path 52 formed by the cylindrical body 10, in the direction of the central axis of the flow path. The bubble-generating nozzle 20 generates fine bubbles downstream. In particular, the bubble-generating nozzle 20 generates ultrafine bubbles.

[0062] The bubble-generating nozzle 20 includes a first bubble-generating nozzle 21 and a second bubble-generating nozzle 22. The first bubble-generating nozzle 21 and the second bubble-generating nozzle 22 are formed from, for example, a metal such as stainless steel or a hard resin. However, the number of bubble-generating nozzles 20 can be set arbitrarily.

[0063] The first bubble-generating nozzle 21 has a predetermined thickness t21, as shown in Figure 1. The outer circumferential surface of the first bubble-generating nozzle 21 has a shape corresponding to the inner circumferential surface of the cylindrical body 10. The first bubble-generating nozzle 21 is attached to the inner circumferential surface of the cylindrical body 10.

[0064] As shown in Figures 1 to 4, the first bubble generation nozzle 21 has multiple bubble generation holes 21a, 21b for generating fine bubbles downstream. Figure 4 illustrates a case where the first bubble generation nozzle 21 has five bubble generation holes 21a, 21b. However, the number of bubble generation holes 21a, 21b can be set arbitrarily.

[0065] Multiple bubble-generating holes 21a and 21b have the same flow path cross-sectional shape and the same flow path length. At least some of the multiple bubble-generating holes 21a and 21b are located at different positions in the radial direction of the flow path. In Figure 4, in the first bubble-generating nozzle 21, one bubble-generating hole 21a is located at the center of the flow path cross-section, and four bubble-generating holes 21b are located radially away from the center of the flow path cross-section. The four bubble-generating holes 21b are located at equal intervals in the circumferential direction around the center of the flow path cross-section.

[0066] The second bubble generation nozzle 22 has the same shape as the first bubble generation nozzle 21. As shown in Figure 1, the second bubble generation nozzle 22 has a predetermined thickness t22 and has a plurality of bubble generation holes 22a, 22b. The plurality of bubble generation holes 22a, 22b are the same as the plurality of bubble generation holes 21a, 21b of the first bubble generation nozzle 21.

[0067] The upstream flow regulating plate 30 is positioned in the flow path 52 formed by the cylindrical body 10, and is located upstream of the bubble generation nozzle 20 in the flow path 52. The upstream flow regulating plate 30 is made of, for example, a metal such as stainless steel, or a hard resin. As shown in Figure 1, the upstream flow regulating plate 30 has a predetermined thickness t30. The thickness t30 of the upstream flow regulating plate 30 is thinner than the thickness t21 of the first bubble generation nozzle 21. By making the thickness t30 of the upstream flow regulating plate 30 thinner, the pressure loss can be reduced. By reducing the pressure loss, the decrease in the amount of bubbles generated by the bubble generation nozzle 20 can be suppressed.

[0068] As shown in Figures 2 and 5, the upstream flow deflector 30 includes a wall portion 31, an outer peripheral portion 32, and a plurality of connecting portions 33. The wall portion 31 is located closer to the center than the radial midpoint of the upstream flow deflector 30. The wall portion 31 has, for example, a circular outer peripheral surface. No holes are formed in the wall portion 31. The outer peripheral portion 32 is located around the entire outer edge of the upstream flow deflector 30 and is formed in an annular shape. The outer peripheral surface of the outer peripheral portion 32 has a shape corresponding to the inner peripheral surface of the cylindrical body 10.

[0069] Multiple connection points 33 connect the wall portion 31 and the outer periphery portion 32. The multiple connection points 33 are arranged at equal intervals in the circumferential direction. The upstream flow deflector plate 30 is to include an even number of connection points 33, and these connection points 33 are preferably arranged in pairs with respect to the center of the upstream flow deflector plate 30. As shown in Figures 2 and 5, the upstream flow deflector plate 30 includes four connection points 33. However, the number of connection points 33 may be odd.

[0070] Therefore, the upstream flow deflector plate 30 has a plurality of through holes 34 surrounded by the outer peripheral edge of the wall portion 31, the inner peripheral edge of the outer peripheral portion 32, and the connecting portion 33. In other words, the plurality of through holes 34 are located radially outward from the wall portion 31 and radially inward from the outer peripheral portion 32. Furthermore, the plurality of through holes 34 extend along the circumferential direction. In addition, the plurality of through holes 34 are formed at equal intervals in the circumferential direction. Moreover, an even number of through holes 34 are formed and are arranged in pairs with respect to the center of the upstream flow deflector plate 30.

[0071] Figures 2 and 5 illustrate an example where the upstream flow deflector plate 30 has four through holes 34. The four through holes 34 are formed, for example, in an arc shape and have an angle of approximately 90°. Also, the circumferential length of the through holes 34 is longer than the circumferential width of the connecting portion 33.

[0072] As shown in Figure 2, the opening area of ​​one through-hole 34 is formed to be larger than the opening area of ​​one bubble-generating hole 21b of the first bubble-generating nozzle 21. Also, the radial width of one through-hole 34 is shorter than, for example, the diameter of one bubble-generating hole 21b. However, the radial width of one through-hole 34 may be about the same as the diameter of one bubble-generating hole 21b, or it may be longer than the diameter of one bubble-generating hole 21b.

[0073] Furthermore, as shown in Figure 2, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, each of the four through holes 34 is positioned to overlap with each of the four bubble-generating holes 21b. In other words, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, a portion of the four bubble-generating holes 21b is located downstream of the four through holes 34. Alternatively, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, the entirety of one bubble-generating hole 21b may be located inside one of the through holes 34.

[0074] The distance between the upstream flow control plate 30 and the first bubble generation nozzle 21 is L30. The diameter of the inner circumferential surface 13 of the cylindrical body 10 is D13. Here, the distance L30 is set to 0.7 to 2 times the diameter D13.

[0075] The downstream flow deflector plate 40 is positioned in the flow path 52 formed by the cylindrical body 10, and is located downstream of the bubble generation nozzle 20 in the flow path 52. The downstream flow deflector plate 40 is made of, for example, a metal such as stainless steel, or a hard resin. As shown in Figure 1, the downstream flow deflector plate 40 has a predetermined thickness t40. The thickness t40 of the downstream flow deflector plate 40 is thinner than the thickness t21 of the first bubble generation nozzle 21. The thickness t40 of the downstream flow deflector plate 40 is the same as the thickness t30 of the upstream flow deflector plate 30. By making the thickness t40 of the downstream flow deflector plate 40 thinner, the pressure loss can be reduced. By reducing the pressure loss, the decrease in the amount of bubbles generated by the bubble generation nozzle 20 can be suppressed.

[0076] As shown in Figures 3 and 6, the downstream flow deflector 40 is formed in the same shape as the upstream flow deflector 30. The downstream flow deflector 40 includes a wall portion 41, an outer peripheral portion 42, and a plurality of connecting portions 43. The wall portion 41 is located closer to the center than the radial midpoint of the downstream flow deflector 40. The wall portion 41 has, for example, a circular outer peripheral surface. No holes are formed in the wall portion 41. The outer peripheral portion 42 is located around the entire circumference of the outer peripheral edge of the downstream flow deflector 40 and is formed in an annular shape. The outer peripheral surface of the outer peripheral portion 42 has a shape corresponding to the inner peripheral surface of the cylindrical body 10. The plurality of connecting portions 43 connect the wall portion 41 and the outer peripheral portion 42. The plurality of connecting portions 43 are arranged at equal intervals in the circumferential direction.

[0077] Therefore, the downstream flow deflector 40 has a plurality of through holes 44 surrounded by the outer peripheral edge of the wall portion 41, the inner peripheral edge of the outer peripheral portion 42, and the connecting portion 43. In other words, the plurality of through holes 44 are located radially outward from the wall portion 41 and radially inward from the outer peripheral portion 42. Also, the plurality of through holes 44 extend along the circumferential direction. Figures 3 and 6 illustrate an example where the downstream flow deflector 40 has four through holes 44. The four through holes 44 are formed, for example, in an arc shape and have an angle of approximately 90°.

[0078] As shown in Figure 3, the opening area of ​​one through-hole 44 is formed to be larger than the opening area of ​​one bubble-generating hole 22b of the second bubble-generating nozzle 22. Also, the radial width of one through-hole 44 is shorter than, for example, the diameter of one bubble-generating hole 22b. However, the radial width of one through-hole 44 may be about the same as that of one bubble-generating hole 22b, or it may be longer than that of one bubble-generating hole 22b.

[0079] Furthermore, as shown in Figure 3, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, each of the four through holes 44 is positioned to overlap with each of the four bubble-generating holes 22b. In other words, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, a portion of the four bubble-generating holes 22b is located downstream of the four through holes 44. Alternatively, when viewed from the central axis direction of the flow path 52 of the cylindrical body 10, the entirety of one bubble-generating hole 22b may be located inside one of the through holes 44.

[0080] The distance between the downstream flow control plate 40 and the second bubble generation nozzle 22 is L40. Distance L40 is equal to the distance L30 between the upstream flow control plate 30 and the first bubble generation nozzle 21. However, distances L30 and L40 may be different. Also, distance L40 is set to 0.7 to 2 times the diameter D13.

[0081] 2. Flow of the target liquid and generation of microbubbles The target liquid flowing through the flow path 50 flows into the flow path 52 of the cylindrical body 10 from the inlet 11 of the cylindrical body 10. In the flow path 52 formed by the cylindrical body 10, the target liquid passes through the upstream flow control plate 30, the first bubble generation nozzle 21, the second bubble generation nozzle 22, and the downstream flow control plate 40, and flows out from the outlet 12. The flow of the target liquid and the generation of fine bubbles will be described in detail below.

[0082] The target liquid that flows into the cylinder body 10 first reaches the position of the upstream flow regulating plate 30. The upstream flow regulating plate 30 has a plurality of through holes 34. Therefore, the target liquid passes through the plurality of through holes 34 and moves downstream of the upstream flow regulating plate 30. The upstream flow regulating plate 30 also has a wall portion 31, an outer circumference portion 32, and a plurality of connection portions 33. The wall portion 31, the outer circumference portion 32, and the plurality of connection portions 33 block the flow of the target liquid. The blocked target liquid moves towards the plurality of through holes 34 and flows through the plurality of through holes 34.

[0083] The target liquid, having passed through the upstream flow control plate 30, reaches the position of the first bubble generation nozzle 21. The first bubble generation nozzle 21 has multiple bubble generation holes 21a and 21b. Therefore, the target liquid passes through the multiple bubble generation holes 21a and 21b and moves downstream of the first bubble generation nozzle 21. At this time, the amount of gas that can be dissolved in the target liquid decreases, generating microbubbles or ultrafine bubbles. Furthermore, after passing through the first bubble generation nozzle 21, the microbubbles are sheared, which also generates smaller microbubbles or ultrafine bubbles.

[0084] The target liquid flowing downstream of the first bubble-generating nozzle 21 reaches the position of the second bubble-generating nozzle 22. The second bubble-generating nozzle 22 has multiple bubble-generating holes 22a and 22b. Therefore, the target liquid passes through the multiple bubble-generating holes 22a and 22b and moves downstream of the second bubble-generating nozzle 22. At this time, the amount of gas that can be dissolved in the target liquid decreases, generating microbubbles or ultrafine bubbles. Furthermore, after passing through the second bubble-generating nozzle 22, the microbubbles or ultrafine bubbles are sheared, generating even smaller microbubbles or even smaller ultrafine bubbles.

[0085] The target liquid that flows downstream of the second bubble generation nozzle 22 reaches the position of the downstream flow control plate 40. The downstream flow control plate 40 has a plurality of through holes 44. Therefore, the target liquid moves downstream of the downstream flow control plate 40 by passing through the plurality of through holes 44. The downstream flow control plate 40 also has a wall portion 41, an outer periphery portion 42, and a plurality of connection portions 43. The wall portion 41, the outer periphery portion 42, and the plurality of connection portions 43 block the flow of the target liquid. The blocked target liquid moves towards the plurality of through holes 44 and flows through the plurality of through holes 44.

[0086] Therefore, the target liquid containing the fine bubbles generated by the first bubble generation nozzle 21 and the second bubble generation nozzle 22 passes through the multiple through holes 44 of the downstream flow control plate 40 and flows out from the outlet 12 of the cylindrical body 10.

[0087] Here, most microbubbles or ultrafine bubbles are generated when the liquid passes through the first bubble generation nozzle 21 and the second bubble generation nozzle 22, and immediately after passing through them. However, microbubbles or ultrafine bubbles may also be generated after the target liquid has passed through the downstream flow control plate 40. For example, ultrafine bubbles may be generated downstream of the downstream flow control plate 40 when microbubbles are sheared.

[0088] (Comparative example) As a comparative example, the microbubble generating apparatus 100 will be described with reference to Figure 9. The microbubble generating apparatus 100 in the comparative example has a configuration that does not include the upstream flow control plate 30 and the downstream flow control plate 40 compared to the microbubble generating apparatus 1 in Example 1.

[0089] (Flow rate of the target liquid) Referring to Figure 1, the flow velocity of the target liquid in the first channel cross-section S1, the second channel cross-section S2, the third channel cross-section S3, and the fourth channel cross-section S4 of the channel 50 will be explained.

[0090] Refer to the flow velocity of the target liquid in the first channel cross-section S10, second channel cross-section S20, third channel cross-section S30, and fourth channel cross-section S40 of the microbubble generating device 100 in the comparative example shown in Figure 9, as appropriate. The first channel cross-section S10, second channel cross-section S20, third channel cross-section S30, and fourth channel cross-section S40 are located at the same positions as the first channel cross-section S1, second channel cross-section S2, third channel cross-section S3, and fourth channel cross-section S4.

[0091] The first channel cross-section S1 is located upstream of the upstream flow regulating plate 30 in the channel 50. For example, the first channel cross-section S1 is located upstream of the upstream flow regulating plate 30 in the channel 52 formed by the cylindrical body 10. In other words, the first channel cross-section S1 is upstream of the upstream flow regulating plate 30 and is in close proximity to the upstream flow regulating plate 30. Here, there are no flow obstructions between the first channel cross-section S1 and the upstream flow regulating plate 30. Flow obstructions include objects that protrude toward the center of the channel and walls that obstruct flow. Also, the channel cross-sectional area between the first channel cross-section S1 and the upstream flow regulating plate 30 is approximately the same.

[0092] The second flow channel cross-section S2 is located between the upstream flow control plate 30 and the first bubble generation nozzle 21. In particular, the second flow channel cross-section S2 is located closer to the first bubble generation nozzle 21 than midway between the upstream flow control plate 30 and the first bubble generation nozzle 21. Here, there are no flow obstructions between the upstream flow control plate 30 and the first bubble generation nozzle 21. Also, the flow channel cross-sectional area is approximately the same between the upstream flow control plate 30 and the first bubble generation nozzle 21.

[0093] The third flow channel cross-section S3 is located downstream of the downstream flow control plate 40 in the flow channel 50. Immediately after the target liquid passes the downstream flow control plate 40, the target liquid is in a turbulent state. There are no flow obstructions downstream of the downstream flow control plate 40. Furthermore, the flow channel cross-sectional area is approximately the same between the second bubble generation nozzle 22 and the downstream flow control plate 40. In other words, after passing the downstream flow control plate 40, the target liquid gradually changes to a laminar flow. The third flow channel cross-section S3 corresponds, for example, to the vicinity of the boundary between turbulent and laminar flow, or to the vicinity of a state where turbulent flow is approaching laminar flow.

[0094] The fourth channel cross-section S4 is located downstream of the third channel cross-section S3. In Figure 1, the fourth channel cross-section S4 is located at the member 3 that forms the downstream channel 53, but it may also be located at the channel 52 formed by the cylindrical body 10.

[0095] There are no flow obstructions between the third channel cross-section S3 and the fourth channel cross-section S4. Furthermore, the channel cross-sectional areas are approximately the same between the third channel cross-section S3 and the fourth channel cross-section S4. In other words, after passing through the downstream flow control plate 40, the target liquid gradually changes to a laminar flow toward the third channel cross-section S3, and then changes to a laminar flow toward the fourth channel cross-section S4.

[0096] As shown in Figure 1, the flow velocity of the target liquid in the first channel cross-section S1 is highest at the center of the first channel cross-section S1 and decreases as it moves radially outward. In other words, the flow velocity of the target liquid in the first channel cross-section S1 has a shape that is roughly like a quadratic curve or a parabola.

[0097] As shown in Figure 9, the velocity distribution in the first channel cross-section S10 in the comparative example is the same as the velocity distribution in the first channel cross-section S1.

[0098] As shown in Figure 1, the flow velocity of the target liquid in the second channel cross-section S2 is highest near the center of the second channel cross-section S2 and decreases radially outward. However, the flow velocity at the center of the second channel cross-section S2 is lower than the flow velocity at the center of the first channel cross-section S1. Therefore, the velocity difference in the flow velocity distribution of the second channel cross-section S2 is smaller than the velocity difference in the flow velocity distribution of the first channel cross-section S1.

[0099] An upstream flow-regulating plate 30 is positioned between the first flow channel cross-section S1 and the second flow channel cross-section S2. The upstream flow-regulating plate 30 has a wall portion 31 closer to the center than the radial midpoint, and has a plurality of through holes 34 radially outward from the wall portion 31. In other words, the upstream flow-regulating plate 30 is configured to make the velocity difference in the velocity distribution of the second flow channel cross-section S2 smaller than the velocity difference in the velocity distribution of the first flow channel cross-section S1.

[0100] However, it is not necessary for the flow velocity of the target liquid to be highest near the center of the second channel cross-section S2. For example, the flow velocity may be highest at a position slightly radially outside the center of the second channel cross-section S2.

[0101] Ideally, the flow velocity of the target liquid in the second channel cross-section S2 should be uniform. Uniform flow velocity in the second channel cross-section S2 increases the number of microbubbles generated by the bubble generation nozzle 20. However, in practice, it is not easy to achieve perfectly uniform flow velocity in the second channel cross-section S2. Therefore, the objective is to increase the number of microbubbles generated by the bubble generation nozzle 20 by minimizing the variation in flow velocity in the second channel cross-section S2 as much as possible. In particular, it is desirable that the variation in flow velocity be small in the area where the bubble generation holes 21a and 21b of the first bubble generation nozzle 21 are located.

[0102] In other words, by positioning the upstream flow control plate 30 upstream of the bubble generation nozzle 20, the velocity difference in the velocity distribution of the second flow channel cross-section S2 can be reduced. As a result, the number of microbubbles generated by the bubble generation nozzle 20 can be increased.

[0103] In particular, in the upstream flow-regulating plate 30, the multiple through-holes 34 are formed in an arc shape. That is, the multiple through-holes 34 are formed in a predetermined radial range within the upstream flow-regulating plate 30. Therefore, when flowing through the upstream flow-regulating plate 30, the flow velocity of the fluid flowing in that radial range can be maintained. As a result, the flow velocity distribution in the second flow channel cross-section S2 can be made to a desired distribution.

[0104] Furthermore, the circumferential length of the arc shape of the through-hole 34 is longer than the circumferential width of the connecting portion 33. In other words, the circumferential length of the arc shape of the through-hole 34 is longer than the circumferential length of the distance between adjacent through-holes 34 (the portion between two adjacent through-holes 34). Here, the through-hole 34 functions as a portion through which fluid flows, while the connecting portion 33 functions to obstruct fluid flow. Due to the above relationship of circumferential lengths, the total circumferential length of the multiple through-holes 34 is longer than the total circumferential length of the multiple connecting portions 33. Therefore, the multiple through-holes 34 can improve the flow of fluid flowing over a predetermined radial range, and the flow velocity distribution in the second flow channel cross-section S2 can be set to a desired distribution.

[0105] Furthermore, the multiple through-holes 34 are arranged at equal intervals in the circumferential direction. This makes it possible to suppress variations in flow velocity depending on the circumferential position in the second flow channel cross-section S2. Therefore, the flow velocity distribution in the second flow channel cross-section S2 can be made to a desired distribution.

[0106] Furthermore, the multiple through holes 34 are formed in an even number and are arranged in pairs with respect to the center of the upstream flow control plate 30. This also helps to suppress variations in flow velocity depending on the circumferential position in the second flow channel cross-section S2. Therefore, the flow velocity distribution in the second flow channel cross-section S2 can be made to a desired distribution.

[0107] As shown in Figure 9, the velocity distribution in the second channel cross-section S20 in the comparative example is the same as the velocity distribution in the first channel cross-section S10. Therefore, the velocity difference in the velocity distribution of the second channel cross-section S20 in the comparative example is large, and the number of microbubbles generated by the bubble generation nozzle 20 is relatively low.

[0108] As shown in Figure 1, the flow velocity of the target liquid in the third channel cross-section S3 is highest near the center of the third channel cross-section S3 and decreases as it moves radially outward. However, it is not necessary for the flow velocity of the target liquid to be highest near the center of the third channel cross-section S3. For example, the flow velocity may be highest at a position slightly radially outward from the center of the third channel cross-section S3.

[0109] A downstream flow-regulating plate 40 is positioned upstream of the third flow channel cross-section S3. The downstream flow-regulating plate 40 has a wall portion 41 closer to the center than the radial midpoint, and has a plurality of through holes 44 radially outward from the wall portion 41. In other words, the downstream flow-regulating plate 40 is configured to suppress the increase in flow velocity at the center of the third flow channel cross-section S3.

[0110] If, as shown in the comparative example Figure 9, the downstream flow control plate 40 is not installed in the microbubble generation device 100, then downstream of the second bubble generation nozzle 22, the flow velocity at the center of the flow channel cross-section increases rapidly at a short distance downstream from the second bubble generation nozzle 22. In other words, the flow velocity difference in the flow velocity distribution of the flow channel cross-section becomes large at a short distance downstream from the second bubble generation nozzle 22.

[0111] However, as shown in Figure 1, since the microbubble generation device 1 is equipped with a downstream flow control plate 40, it is possible to suppress the increase in flow velocity at the center of the third flow channel cross-section S3 located downstream of the downstream flow control plate 40. In other words, compared to the case where the downstream flow control plate 40 is not provided, it is possible to suppress the expansion of the flow velocity difference in the flow velocity distribution of the flow channel cross-section in the region from the downstream flow control plate 40 to before and after the third flow channel cross-section S3.

[0112] Here, downstream of the second bubble generation nozzle 22, for example, after microbubbles are generated, they may be further refined into ultrafine bubbles. In other words, the region from the second bubble generation nozzle 22 to before and after the third channel cross-section S3 contributes to increasing the number of microbubbles generated.

[0113] However, as shown in Figure 9, if there is a large difference in flow velocity in the flow velocity distribution of the channel cross-section downstream of the second bubble generation nozzle 22, that is, in the region where the target liquid containing microbubbles flows, the microbubbles may collide with each other and disappear. As a result, the amount of ultrafine bubbles generated may decrease. In other words, if the downstream flow regulating plate 40 is not placed and there is a large difference in flow velocity before and after the third channel cross-section S3, it becomes difficult for ultrafine bubbles to be generated by the liquid flow.

[0114] However, as shown in Figure 1, the placement of the downstream flow deflector 40 suppresses the increase in flow velocity at the center of the third flow channel cross-section S3 located downstream of the downstream flow deflector 40. In other words, compared to the case where the downstream flow deflector 40 is not placed, the expansion of the velocity difference in the flow velocity distribution of the flow channel cross-section can be suppressed in the region from the downstream flow deflector 40 to before and after the third flow channel cross-section S3. Therefore, by making the region from the downstream flow deflector 40 to before and after the third flow channel cross-section S3 the region where microbubbles are generated, the number of microbubbles generated can be increased.

[0115] As shown in Figure 1, the flow velocity of the target liquid in the fourth channel cross-section S4 is highest at the center of the fourth channel cross-section S4 and decreases radially outward. The flow velocity distribution in the fourth channel cross-section S4 is the same as that in the first channel cross-section S1. Also, as shown in Figure 9, the flow velocity distribution in the fourth channel cross-section S40 in the comparative example is the same as that in the fourth channel cross-section S4. Furthermore, as shown in Figure 9, the flow velocity distribution in the third channel cross-section S30 in the comparative example is the same as that in the fourth channel cross-section S40.

[0116] Here, in the downstream flow-regulating plate 40, the multiple through-holes 44 are formed in an arc shape. That is, the multiple through-holes 44 are formed in a predetermined radial range of the downstream flow-regulating plate 40. Therefore, when flowing through the downstream flow-regulating plate 40, the flow velocity of the fluid flowing in that radial range can be maintained. As a result, the flow velocity distribution in the third flow channel cross-section S3 can be made into a desired distribution.

[0117] Furthermore, the circumferential length of the arc shape of the through-hole 44 is longer than the circumferential width of the connecting portion 43. In other words, the circumferential length of the arc shape of the through-hole 44 is longer than the circumferential length of the distance between adjacent through-holes 44 (the portion between two adjacent through-holes 44). Here, the through-hole 44 functions as a portion through which fluid flows, while the connecting portion 43 functions to obstruct fluid flow. Due to the above relationship of circumferential lengths, the total circumferential length of the multiple through-holes 44 is longer than the total circumferential length of the multiple connecting portions 43. Therefore, the multiple through-holes 44 can improve the flow of fluid flowing over a predetermined radial range, and the flow velocity distribution in the third flow channel cross-section S3 can be set to a desired distribution.

[0118] Furthermore, the multiple through holes 44 are arranged at equal intervals in the circumferential direction. This makes it possible to suppress variations in flow velocity depending on the circumferential position in the third flow channel cross-section S3. Therefore, the flow velocity distribution in the third flow channel cross-section S3 can be made to a desired distribution.

[0119] Furthermore, the multiple through holes 44 are formed in an even number and are arranged in pairs with respect to the center of the downstream flow-regulating plate 40. This also helps to suppress variations in flow velocity depending on the circumferential position in the third flow channel cross-section S3. Therefore, the flow velocity distribution in the third flow channel cross-section S3 can be made to a desired distribution.

[0120] (Example 2) The microbubble generation apparatus 1 in Example 2 will be described with reference to Figure 7. The microbubble generation apparatus 1 in Example 2 differs from the microbubble generation apparatus 1 in Example 1 in its upstream flow control plate 60 and downstream flow control plate. The upstream flow control plate 60 and downstream flow control plate will be described below.

[0121] The upstream flow control plate 60 includes a wall portion 61, an outer peripheral portion 62, and a plurality of connecting portions 63. The wall portion 61 is located closer to the center than the radial midpoint of the upstream flow control plate 60. The wall portion 61 has, for example, a circular outer peripheral surface. The inner peripheral surface of the wall portion 61 is located at a distance radially outward from the center. In other words, a central hole 61a is formed at the center of the wall portion 61. The diameter of this central hole 61a is, for example, the same as or less than the bubble generation hole 21a of the first bubble generation nozzle 21.

[0122] The outer periphery 62 is located around the entire circumference of the outer edge of the upstream flow deflector plate 60 and is formed in an annular shape. The outer surface of the outer periphery 62 has a shape corresponding to the inner surface of the cylindrical body 10. Multiple connecting parts 63 connect the wall part 61 and the outer periphery 62. Multiple connecting parts 63 are arranged at equal intervals in the circumferential direction.

[0123] Therefore, the upstream flow deflector 60 has a plurality of through holes 64 surrounded by the outer peripheral edge of the wall portion 61, the inner peripheral edge of the outer peripheral portion 62, and the connecting portion 63. In other words, the plurality of through holes 64 are located radially outward from the wall portion 61 and radially inward from the outer peripheral portion 62. Also, the plurality of through holes 64 extend along the circumferential direction. An example is given where the upstream flow deflector 60 has four through holes 64. The four through holes 64 are formed, for example, in an arc shape and have an angle of approximately 90°.

[0124] The opening area of ​​one through-hole 64 is larger than the opening area of ​​the central hole 61a. Also, the radial width of one through-hole 64 is shorter than the diameter of the central hole 61a. However, the radial width of one through-hole 64 may be about the same as the diameter of the central hole 61a, or it may be longer than the diameter of the central hole 61a.

[0125] The downstream flow deflector is formed to have the same shape as the upstream flow deflector 60.

[0126] In Example 2, even if the upstream flow deflector 60 has a central hole 61a, the velocity distribution in the second flow channel cross-section S2 does not change significantly. Therefore, the upstream flow deflector 60 exhibits the same effect as the upstream flow deflector 30 in Example 1. The same applies to the downstream flow deflector.

[0127] (Example 3) The microbubble generating apparatus 100 in Example 3 will be described with reference to Figure 8. Note that, unless otherwise specified, the same reference numerals used in Example 3 as those used in Example 1 represent the same components, etc.

[0128] The microbubble generating device 100 includes a cylindrical body 110, a bubble generating nozzle 20, an upstream flow control plate 30, and a downstream flow control plate 40. The cylindrical body 110 has male threaded portions 110a and 110b on the outer circumferential surfaces of both ends. The male threaded portion 110a is screwed into the member 2 that forms the upstream flow path 51. The male threaded portion 110b is screwed into the member 3 that forms the downstream flow path 53.

[0129] The cylindrical body 110 has an upstream inner surface 13a, an intermediate inner surface 13b, and a downstream inner surface 13c. The diameter of the upstream inner surface 13a is D13a, the diameter of the intermediate inner surface 13b is D13b, and the diameter of the downstream inner surface 13c is D13c. The diameter D13b of the intermediate inner surface 13b is smaller than the diameters D13a of the upstream inner surface 13a and D13c of the downstream inner surface 13c. A tapered step surface 121 is formed between the upstream inner surface 13a and the intermediate inner surface 13b. A tapered step surface 122 is formed between the intermediate inner surface 13b and the downstream inner surface 13c.

[0130] Annular grooves 131, 132, and 133 are formed on the upstream inner surface 13a. The spacing between annular grooves 131 and 132 is approximately the same as the thickness of the upstream flow control plate 30. Annular groove 133 is formed near the intermediate inner surface 13b and is located downstream of annular grooves 131 and 132. The spacing between annular groove 133 and the tapered stepped surface 121 is approximately the same as the thickness of the first bubble generation nozzle 21.

[0131] Annular grooves 141, 142, and 143 are formed on the downstream inner circumferential surface 13c. Annular groove 141 is formed near the intermediate inner circumferential surface 13b. The distance between annular groove 141 and the tapered stepped surface 122 is approximately the same as the thickness of the second bubble generation nozzle 22. Annular grooves 142 and 143 are located downstream of annular groove 141. The distance between annular grooves 142 and 143 is approximately the same as the thickness of the downstream flow control plate 40.

[0132] The microbubble generating device 100 further includes C-type retaining rings 151, 152, 153 positioned on the upstream inner circumferential surface 13a, and C-type retaining rings 161, 162, 163 positioned on the downstream inner circumferential surface 13c. The C-type retaining rings 151, 152, 153 are fitted into annular grooves 131, 132, 133, respectively. The C-type retaining rings 161, 162, 163 are fitted into annular grooves 141, 142, 143, respectively.

[0133] The first bubble-generating nozzle 21 is positioned on the upstream inner surface 13a, closer to the intermediate inner surface 13b. The first bubble-generating nozzle 21 abuts against the tapered stepped surface 121. The first bubble-generating nozzle 21 has a chamfer on its downstream outer surface. This chamfer abuts against the tapered stepped surface 121. The first bubble-generating nozzle 21 is positioned by a C-type retaining ring 153.

[0134] The second bubble-generating nozzle 22 is positioned on the downstream inner surface 13c, closer to the intermediate inner surface 13b. The second bubble-generating nozzle 22 abuts against the tapered stepped surface 122. The second bubble-generating nozzle 22 has a chamfer on its upstream outer surface. This chamfer abuts against the tapered stepped surface 122. The second bubble-generating nozzle 22 is positioned by a C-type retaining ring 161.

[0135] The upstream flow deflector 30 is positioned on the upstream inner circumferential surface 13a. The upstream flow deflector 30 is positioned between the annular grooves 131 and 132. The upstream flow deflector 30 is positioned by C-type retaining rings 151 and 152. The downstream flow deflector 40 is positioned on the downstream inner circumferential surface 13c. The downstream flow deflector 40 is positioned between the annular grooves 142 and 143. The downstream flow deflector 40 is positioned by C-type retaining rings 162 and 163.

[0136] The shapes of the inner circumferential surfaces 13a, 13b, and 13c of the cylindrical body 110, and the retaining rings 151, 152, 153, 161, 162, and 163, allow each element to be easily positioned on the cylindrical body 110.

[0137] The first channel cross-section S1 is located upstream of the upstream flow control plate 30 in the channel 50. The second channel cross-section S2 is located between the upstream flow control plate 30 and the first bubble generation nozzle 21. The third channel cross-section S3 is located downstream of the downstream flow control plate 40 in the channel 50. The fourth channel cross-section S4 is located downstream of the third channel cross-section S3.

[0138] The microbubble generating device 100 in Example 3 exhibits the same effects as the microbubble generating device 1 in Example 1.

[0139] In addition, the microbubble generating apparatus can take the following forms, for example: [1] to

[10] .

[0140] [1] A flow path through which a target liquid containing gas is circulated, A bubble generating nozzle is arranged in the aforementioned flow path and has multiple bubble generating holes, generating fine bubbles downstream, A microbubble generating apparatus comprising an upstream flow control plate positioned upstream of the bubble generating nozzle in the flow path. [2] A microbubble generating apparatus wherein the upstream flow control plate is configured to make the difference in the flow velocity distribution of the second flow channel cross section located between the upstream flow control plate and the bubble generating nozzle smaller than the difference in the flow velocity distribution of the first flow channel cross section located upstream of the upstream flow control plate.

[0141] [3] The microbubble generating apparatus according to [2], wherein the second flow channel cross section is located closer to the bubble generating nozzle than midway between the upstream flow control plate and the bubble generating nozzle. [4] The microbubble generating apparatus according to any one of [1] to [3], wherein the flow velocity of the target liquid in the first channel cross-section is greatest at the center of the first channel cross-section.

[0142] [5] The upstream flow control plate is A wall portion located closer to the center than the radial midpoint, which obstructs the flow of the target liquid, A microbubble generating apparatus according to any one of [1] to [4], comprising: a plurality of through holes located radially outward from the wall portion and extending along the circumferential direction.

[0143] [6] The microbubble generating apparatus according to [5], wherein the opening area of ​​each of the through holes in the upstream flow control plate is larger than the opening area of ​​each of the bubble generating holes. [7] The microbubble generating apparatus according to [5] or [6], wherein each of the through holes in the upstream flow control plate is formed in an arc shape.

[0144] [8] The microbubble generating apparatus according to any one of [1] to [7], wherein the plurality of bubble generating holes are arranged at different positions in the radial direction of the flow path. [9] The microbubble generating apparatus according to [8], wherein the plurality of bubble generating holes have the same channel cross-sectional shape and the same channel length.

[0145]

[10] The microbubble generating apparatus according to any one of [1] to [9], further comprising a downstream flow control plate positioned downstream of the bubble generating nozzle in the flow path.

[11] The microbubble generating apparatus according to

[10] , wherein the downstream flow control plate is configured to suppress an increase in flow velocity at the center of the third flow channel cross-section located downstream of the downstream flow control plate.

[0146]

[12] The microbubble generating apparatus according to

[10] or

[11] , wherein the flow velocity of the target liquid at the center of the channel cross-section is configured to increase as it moves from the third channel cross-section to a fourth channel cross-section located downstream of the third channel cross-section.

[0147]

[13] The downstream flow deflector plate is A wall portion located closer to the center than the radial midpoint, which obstructs the flow of the target liquid, A microbubble generating apparatus according to any one of

[10] to

[12] , comprising a plurality of through holes located radially outward from the wall portion and extending along the circumferential direction.

[0148]

[14] The microbubble generating apparatus according to

[13] , wherein the opening area of ​​each of the through holes in the downstream flow control plate is larger than the opening area of ​​each of the bubble generating holes.

[15] The microbubble generating apparatus according to

[13] or

[14] , wherein each of the through holes in the downstream flow control plate is formed in an arc shape.

[16] The microbubble generating apparatus according to any one of

[10] to

[15] , wherein the upstream flow control plate and the downstream flow control plate are formed to be the same shape.

[17] A microbubble generating apparatus according to any one of

[10] to

[16] , wherein the distance between the bubble generating nozzle and the upstream flow control plate is equal to the distance between the bubble generating nozzle and the downstream flow control plate. [Explanation of symbols]

[0149] 1. Microbubble Generating Device 10. Main body of cylinder 20 Bubble-generating nozzles 21a, 21b, 22a, 22b Bubble-generating pores 30,60 Upstream flow control plate 31,61 Wall 34,64 through holes 40 Downstream flow control plate 41 Wall 44 Through holes 50 flow channels 52 Flow channel formed by the cylindrical body S1 First channel cross-section S2 Second channel cross-section S3 Third channel cross-section S4 Fourth channel cross section

Claims

1. A flow path through which a target liquid containing gas is circulated, A bubble generating nozzle is arranged in the aforementioned flow path and has multiple bubble generating holes, generating fine bubbles downstream, A microbubble generating apparatus comprising an upstream flow control plate positioned upstream of the bubble generating nozzle in the flow path.

2. The microbubble generating apparatus according to claim 1, wherein the upstream flow control plate is configured to make the difference in the flow velocity distribution of the second flow channel cross-section located between the upstream flow control plate and the bubble generating nozzle smaller than the difference in the flow velocity distribution of the first flow channel cross-section located upstream of the upstream flow control plate.

3. The aforementioned upstream flow control plate is A wall portion located closer to the center than the radial midpoint, which obstructs the flow of the target liquid, The microbubble generating apparatus according to claim 1, comprising a plurality of through holes located radially outward from the wall portion and extending along the circumferential direction.

4. The microbubble generating apparatus according to claim 1, wherein the plurality of bubble generating holes are arranged at different positions in the radial direction of the flow path.

5. Furthermore, the microbubble generating apparatus according to any one of claims 1 to 4, comprising a downstream flow control plate positioned downstream of the bubble generating nozzle in the flow path.

6. The microbubble generating apparatus according to claim 5, wherein the downstream flow control plate is configured to suppress an increase in flow velocity at the center of the third flow channel cross-section located downstream of the downstream flow control plate.

7. The microbubble generating apparatus according to claim 6, wherein the flow velocity of the target liquid at the center of the flow channel cross-section is configured to increase as it moves from the third flow channel cross-section to the fourth flow channel cross-section located downstream of the third flow channel cross-section.

8. The downstream flow control plate is, A wall portion located closer to the center than the radial midpoint, which obstructs the flow of the target liquid, The microbubble generating apparatus according to claim 5, comprising a plurality of through holes located radially outward from the wall portion and extending along the circumferential direction.

9. The microbubble generating apparatus according to claim 5, wherein the upstream flow control plate and the downstream flow control plate are formed to be the same shape.

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