Tubular member, bubble generating device, and bubble generating method

Abstract

This invention provides a technology that can generate fine bubbles with a sufficient number density in a liquid, and can also sufficiently dissolve gaseous components in that liquid. [Solution] The tubular member 100 is formed in a tubular shape that defines a flow path 200 for a gas-liquid mixed fluid containing a liquid and a gaseous component mixed with the liquid. The gas-liquid mixed fluid is injected under pressure from one end of the tubular member 100 and flows out from the other end of the tubular member 100. The tubular member 100 has a first constricted portion 110, a second constricted portion 120 closer to the other end than the first constricted portion 110, an intermediate portion 130, and an outside air introduction portion 140. The first narrowed flow path portion 210 is the portion of the flow path 200 that is narrowed at the first constricted portion 110. The second narrowed flow path portion 220 is the portion of the flow path 200 that is narrowed at the second constricted portion 120. The outside air introduction portion 140 guides outside air to the first narrowed flow path portion 210. The area of ​​the cross-section of the second narrow channel section 220 is larger than the area of ​​the cross-section of the first narrow channel section 210.

Description

Technical Field

[0001] The present invention relates to a tubular member, a bubble generator, and a bubble generation method.

Background Art

[0002] As disclosed in Patent Document 1, there is known a bubble generator including a pump that pumps a fluid (hereinafter referred to as a gas-liquid mixed fluid) containing a liquid and a gas component mixed in the liquid, and a tubular member into which the gas-liquid mixed fluid pumped by the pump flows.

[0003] In this bubble generator, the tubular member has a first throttle portion and a second throttle portion arranged in series at intervals in the length direction of the tubular member. In each of the first throttle portion and the second throttle portion, the gas component contained in the gas-liquid mixed fluid is dissolved in the liquid by pressurization, and the dissolved gas component is precipitated as bubbles by decompression.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the above bubble generator, fine bubbles can be generated in a liquid at a high number density. However, since the gas component dissolved in the liquid is precipitated as bubbles, the concentration of the gas component dissolved at the molecular level in the liquid (hereinafter referred to as the dissolved concentration) in the liquid decreases. Therefore, there has been a limit to improving the dissolved concentration of the gas component in the liquid.

[0006] However, not only gaseous components existing in the form of bubbles in a liquid, but also gaseous components dissolved at the molecular level in the liquid can contribute to various reactions. Therefore, depending on the application of the gas-liquid mixed fluid obtained from a bubble generator, it may be desirable to achieve both an increase in the number density of bubbles and an increase in the dissolved concentration of gaseous components.

[0007] The object of the present invention is to provide a technology that can generate fine bubbles with a sufficient number density in a liquid and can sufficiently dissolve gaseous components in that liquid. [Means for solving the problem]

[0008] The tubular member according to the present invention is A tubular member formed in the shape of a tube that defines a flow path for a gas-liquid mixed fluid containing a liquid and a gaseous component mixed with the liquid, wherein the gas-liquid mixed fluid is injected under pressure from one end and the injected gas-liquid mixed fluid flows out from the other end, By locally narrowing the area of ​​the cross-sectional surface perpendicular to the longitudinal direction of the tubular member of the flow path, a first throttling section is formed that restricts the flow of the gas-liquid mixed fluid, A second throttling portion is located adjacent to the first throttling portion at a position closer to the other end than the first throttling portion, and by locally narrowing the area of ​​the cross-sectional surface of the flow path, the second throttling portion restricts the flow of the gas-liquid mixed fluid that has passed through the first throttling portion. The intermediate portion defines the intermediate flow path, which is the portion of the flow path that is narrowed in the first constricted flow path section and the portion that is narrowed in the second constricted flow path section. An outside air introduction section that guides outside air into the first narrow flow channel section, It has, The area of ​​the cross-section of the second narrow channel is larger than the area of ​​the cross-section of the first narrow channel.

[0009] The first narrow cross section, which is the cross-section of the first narrow channel, has a shape in which the longitudinal direction is the U1 axis parallel to the first narrow cross section, The second narrow cross-section, which is the cross-section of the second narrow channel portion, has a shape in which the V1 axis parallel to the second narrow cross-section is the longitudinal direction. The dimension of the first narrow section in the U1 axial direction is equal to the dimension of the second narrow section in the V1 axial direction. The dimension of the second narrow cross-section in the direction of the V2 axis, which is parallel to the second narrow cross-section and perpendicular to the direction of the V1 axis, may be larger than the dimension of the first narrow cross-section in the direction of the U2 axis, which is parallel to the first narrow cross-section and perpendicular to the direction of the U1 axis.

[0010] Let LA be the dimension of the first narrow cross-section in the U2 axial direction. When the dimension of the second narrow cross-section in the V2 axial direction is LB, The relationship 1.5 × LA ≤ LB ≤ 6.5 × LA may also be satisfied.

[0011] When the equivalent diameter of the intermediate flow channel is denoted as LC, The relationship 8 × LA ≤ LC ≤ 32 × LA may also be satisfied.

[0012] The following relationships may also be satisfied: 0.8[mm]≦LA<3[mm], LA+2[mm]≦LB, and 3[mm]≦LB≦5[mm].

[0013] The distance in the longitudinal direction between the first narrow channel and the second narrow channel may be shorter than the interval at which the longitudinal flow velocity of the gas-liquid mixed fluid that passes through the first constriction and flows through the intermediate channel returns to the longitudinal flow velocity of the gas-liquid mixed fluid when it is pressed into the tubular member from one end.

[0014] Let LZ be the distance in the longitudinal direction between the first narrow channel section and the second narrow channel section. When the equivalent diameter of the intermediate flow channel is denoted as LC, The relationship 1.5 × LC ≤ LZ ≤ 3 × LC may also be satisfied.

[0015] The direction of the V1 axis may be parallel to the direction of the U1 axis.

[0016] The V1-axis direction may be a direction in which the U1-axis direction is rotated around a virtual central axis parallel to the length direction.

[0017] The bubble generating device according to the present invention the tubular member according to the present invention described above, a feeder for press-fitting the gas-liquid mixed fluid into the tubular member, and includes.

[0018] The bubble generating device according to the present invention a liquid tank in which the gas-liquid mixed fluid is stored, a return pipe connecting the inside of the liquid tank and the other end of the tubular member, a supply pipe connecting the inside of the liquid tank and the feeder, further includes, the feeder sucks the gas-liquid mixed fluid from the inside of the liquid tank through the supply pipe, and pumps the sucked gas-liquid mixed fluid together with gas into the tubular member, and the gas-liquid mixed fluid flowing out from the other end of the tubular member may return to the inside of the liquid tank through the return pipe. <0000O95>

[0019] The bubble generating method according to the present invention is a bubble generating method using a tubular member formed in a tube that defines a flow path of a gas-liquid mixed fluid containing a liquid and a gas component mixed with the liquid, wherein the gas-liquid mixed fluid is press-fitted from one end and the press-fitted gas-liquid mixed fluid flows out from the other end, wherein the tubular member a first throttle portion that locally narrows the area of a cross section perpendicular to the length direction of the tubular member of the flow path to throttle the flow of the gas-liquid mixed fluid, is adjacent to the first throttle portion at a position closer to the other end than the first throttle portion, and locally narrows the area of the cross section of the flow path to throttle the flow of the gas-liquid mixed fluid that has passed through the first throttle portion, a second throttle portion, The intermediate portion defines the intermediate flow path, which is the portion of the flow path that is narrowed in the first constricted flow path section and the portion that is narrowed in the second constricted flow path section. An outside air introduction section that guides outside air into the first narrow flow channel section, It has, The area of ​​the cross-section of the second narrow channel is larger than the area of ​​the cross-section of the first narrow channel. A precipitate bubble generation step is performed in which precipitate bubbles are generated by the precipitation of the gaseous component dissolved in the liquid in the first narrow channel section, An air-derived bubble generation step is performed in which the outside air is guided to the first narrow channel through the outside air introduction section by the negative pressure generated in the first narrow channel section, thereby generating outside air-derived bubbles, which are bubbles originating from the outside air. A stirring step in which the bubbles originating from the outside air and the precipitated bubbles are stirred in the intermediate channel by the turbulence generated in the intermediate channel, Includes. [Effects of the Invention]

[0020] According to the tubular member of the present invention, dissolved gaseous components precipitate in the first narrow channel, generating precipitated bubbles. Furthermore, the negative pressure generated in the first narrow channel leads outside air into the first narrow channel through the outside air introduction section, generating outside air-derived bubbles. In addition, turbulence generated in the intermediate channel stirs the outside air-derived bubbles and precipitated bubbles in the intermediate channel.

[0021] In this way, by generating precipitated bubbles and bubbles derived from the outside air, and by stirring in the intermediate channel between the generated precipitated bubbles and the bubbles derived from the outside air, it is possible to generate fine bubbles with a sufficient number density in the liquid.

[0022] Furthermore, even though the gaseous components dissolved in the liquid precipitate as precipitated bubbles, stirring in the intermediate channel promotes the dissolution of bubbles originating from the outside air into the liquid. Therefore, it is possible to sufficiently dissolve the gaseous components in the liquid. [Brief explanation of the drawing]

[0023] [Figure 1] A conceptual diagram showing the configuration of a bubble generating device according to the first embodiment. [Figure 2] A cross-sectional view showing a cross-section parallel to the longitudinal direction of a tubular member according to the first embodiment. [Figure 3] A schematic perspective view showing the three-dimensional shape of the inner surface of a tubular member according to the first embodiment. [Figure 4] A side view of the tubular member according to the first embodiment, viewed in the longitudinal direction. [Figure 5] A side view of the tubular member according to the second embodiment, viewed in the longitudinal direction. [Figure 6] A graph showing the mode diameter of red tide control agents pulverized using the bubble generating apparatus described in the examples and comparative examples. [Figure 7] A graph showing the distribution of the number density of bubbles generated using the bubble generating apparatus according to the example, with respect to bubble diameter. [Modes for carrying out the invention]

[0024] The bubble generating apparatus according to an embodiment will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0025] [First Embodiment] As shown in Figure 1, the bubble generating apparatus 700 according to this embodiment includes a liquid tank 500. A gas-liquid mixed fluid 600 is stored inside the liquid tank 500.

[0026] The gas-liquid mixed fluid 600 refers to a fluid containing a liquid 610 and a gaseous component mixed in the liquid 610. In this specification, "a gaseous component is mixed" means not only that the gaseous component exists in the liquid 610 in the form of bubbles 620, but also that it exists in a form dissolved in the liquid 610 at the molecular level without forming bubbles 620.

[0027] Furthermore, the bubble generating device 700 includes a pump 300 for pumping the gas-liquid mixed fluid 600 stored in the liquid tank 500, a tubular member 100 into which the gas-liquid mixed fluid 600 pumped by the pump 300 is injected, and piping 400 that defines the flow path of the gas-liquid mixed fluid 600 from inside the liquid tank 500 through the pump 300 to the tubular member 100.

[0028] The piping 400 includes a supply pipe 410 connecting the inside of the liquid tank 500 to the pump 300, and an intermediate pipe 420 connecting the pump 300 to the tubular member 100.

[0029] The pumping unit 300 includes a liquid pump 310 and a first outside air inlet 320. The liquid pump 310 draws in the gas-liquid mixed fluid 600 stored in the liquid tank 500 through the supply pipe 410 and sends the drawn-in gas-liquid mixed fluid 600 to the tubular member 100 through the intermediate pipe 420.

[0030] The first outside air inlet 320 is provided in the supply piping 410. The first outside air inlet 320 connects the inside of the supply piping 410 to the outside in order to introduce outside air into the supply piping 410. That is, the action of the liquid pump 310 in drawing in the gas-liquid mixed fluid 600 creates a negative pressure inside the supply piping 410 that is lower than the external atmospheric pressure (typically atmospheric pressure). Due to this negative pressure, outside air naturally flows into the supply piping 410 through the first outside air inlet 320.

[0031] In this way, the gas-liquid mixed fluid 600, which is drawn out from the liquid tank 500 by the liquid pump 310, is sent to the tubular member 100 through the intermediate piping 420 together with the outside air taken in through the first outside air introduction section 320.

[0032] The tubular member 100 is formed in a tubular shape that defines the flow path for the gas-liquid mixed fluid 600. The gas-liquid mixed fluid 600, which is pumped by the pumper 300, flows into the tubular member 100 from one end (hereinafter referred to as the inlet end) 101, and the flowing gas-liquid mixed fluid 600 flows out from the other end (hereinafter referred to as the outlet end) 102 of the tubular member 100.

[0033] The tubular member 100, like the pressure pump 300, has the function of taking in outside air into the gas-liquid mixed fluid 600. Specifically, the tubular member 100 has a second outside air inlet 140. Due to the negative pressure generated inside the tubular member 100, outside air naturally flows into the tubular member 100 through the second outside air inlet 140. The second outside air inlet 140 is an example of an outside air inlet according to the present invention.

[0034] The tubular member 100 primarily plays the roles of increasing the number density of bubbles 620 in the liquid 610 of the gas-liquid mixed fluid 600, refining the bubbles 620, and increasing the dissolved concentration of gaseous components dissolved at the molecular level in the liquid 610.

[0035] Furthermore, the piping 400 according to this embodiment also includes a return pipe 430 that connects the outlet end 102 of the tubular member 100 to the inside of the liquid tank 500. That is, the gas-liquid mixed fluid 600 that flows out from the outlet end 102 of the tubular member 100 returns to the inside of the liquid tank 500 through the return pipe 430.

[0036] Therefore, the gas-liquid mixed fluid 600, which was sucked out of the liquid tank 500 by the liquid pump 310 and then returned to the liquid tank 500 via the tubular member 100, is then sucked out of the liquid tank 500 again by the liquid pump 310.

[0037] In this way, the gas-liquid mixed fluid 600 circulates through a closed circuit comprising the piping 400 and the liquid tank 500. Each time the circulation of the gas-liquid mixed fluid 600 is repeated, the number density of bubbles 620 in the tubular member 100 is increased, the bubbles 620 become finer, and the dissolved concentration of gaseous components in the liquid 610 is increased.

[0038] Before starting the liquid pump 310, the liquid tank 500 may contain a liquid 610 with a gaseous content that is negligible. In the pump 300 having the first outside air inlet 320, a gas-liquid mixed fluid 600 is formed to be injected into the tubular member 100.

[0039] The bubble generating apparatus 700 according to this embodiment has its most distinctive feature in the configuration of the tubular member 100. Therefore, the configuration of the tubular member 100 will be described in detail below.

[0040] As shown in Figure 2, the tubular member 100 is formed in a straight tubular shape and defines a flow path 200 inside, extending from the inlet end 101 to the outlet end 102. A gas-liquid mixed fluid 600, pressurized by the pump 300 shown in Figure 1, flows through the flow path 200.

[0041] In the following, the end of the tubular member 100 closer to the outlet end 102 in the longitudinal direction will be referred to as the "rear end". The tubular member 100 has a configuration in which a first constriction section 110, an intermediate section 130, and a second constriction section 120 are arranged in that order towards the rear between the inlet end 101 and the outlet end 102.

[0042] The first throttling section 110 locally narrows the area of ​​the cross-section (hereinafter referred to as the cross-section) of the flow path 200 perpendicular to the longitudinal direction of the tubular member 100 (hereinafter also simply referred to as the cross-sectional area). As a result, the flow of the gas-liquid mixed fluid 600 injected under pressure from the inlet end 101 is restricted at the first throttling section 110.

[0043] Specifically, the first constriction section 110 includes a narrowing tapered section 111 that gradually decreases the cross-sectional area of ​​the flow path 200 toward the rear, a widening tapered section 113 that gradually increases the cross-sectional area of ​​the flow path 200 toward the rear, and a throat section 112 located between the narrowing tapered section 111 and the widening tapered section 113.

[0044] In the first constricted section 110, the cross-sectional area of ​​the flow path 200 is smallest at the throat section 112. Hereinafter, the portion of the flow path 200 that is narrowed at the throat section 112 of the first constricted section 110 will be referred to as the "first narrowed flow path section 210".

[0045] The second throttling section 120 is located closer to the outlet end 102 than the first throttling section 110. The second throttling section 120 is adjacent to the first throttling section 110. Like the first throttling section 110, the second throttling section 120 also locally narrows the cross-sectional area of ​​the flow path 200. As a result, the flow of the gas-liquid mixed fluid 600 that has passed through the first throttling section 110 is throttled at the second throttling section 120.

[0046] Specifically, the second constriction section 120 includes a narrowing tapered section 121 that gradually decreases the cross-sectional area of ​​the flow path 200 toward the rear, a widening tapered section 123 that gradually increases the cross-sectional area of ​​the flow path 200 toward the rear, and a throat section 122 located between the narrowing tapered section 121 and the widening tapered section 123.

[0047] In the second constriction section 120, the cross-sectional area of ​​the flow path 200 is smallest at the throat section 122. Hereinafter, the portion of the flow path 200 that is narrowed at the throat section 122 of the second constriction section 120 will be referred to as the "second narrowed flow path section 220".

[0048] The intermediate section 130 is located between the first throttling section 110 and the second throttling section 120. The intermediate section 130 defines the intermediate flow path section 230, which is the portion of the flow path 200 between the first throttling section 110 and the second throttling section 120. The cross-sectional area of ​​the intermediate flow path section 230 is constant in the longitudinal direction of the tubular member 100.

[0049] In the following, the portion of the flow path 200 between the inlet end 101 and the first throttling section 110 will be referred to as the "inlet end flow path section 240". Also, the portion of the flow path 200 between the second throttling section 120 and the outlet end 102 will be referred to as the "outlet end flow path section 250".

[0050] The cross-sectional areas of the inlet end channel section 240 and the outlet end channel section 250 are constant in the longitudinal direction of the tubular member 100. The cross-sectional area of ​​the inlet end channel section 240 is equal to the cross-sectional area of ​​the outlet end channel section 250. Also, the cross-sectional area of ​​the intermediate channel section 230 is equal to the cross-sectional area of ​​the inlet end channel section 240.

[0051] Furthermore, in the following, the distance in the longitudinal direction of the tubular member 100 between the first narrow channel section 210 and the second narrow channel section 220 (hereinafter simply referred to as the distance) will be denoted as LZ. Specifically, the distance LZ refers to the distance in the longitudinal direction of the tubular member 100 between the midpoint of the throat section 122 of the first constriction section 110 and the midpoint of the throat section 222 of the second constriction section 120.

[0052] Due to the flow resistance at the first throttling section 110, the longitudinal flow velocity of the gas-liquid mixed fluid 600 in the tubular member 100 (hereinafter simply referred to as the longitudinal flow velocity) may decrease at the first throttling section 110. However, depending on the length of the gap LZ, the longitudinal flow velocity of the gas-liquid mixed fluid 600 flowing through the intermediate flow channel section 230 may return to the longitudinal flow velocity of the gas-liquid mixed fluid 600 when it was injected into the tubular member 100 from the inlet end 101 (hereinafter referred to as the initial flow velocity).

[0053] However, in this embodiment, the interval LZ is designed to be shorter than the interval at which the longitudinal flow velocity of the gas-liquid mixed fluid 600 flowing through the intermediate flow channel 230 returns to its initial flow velocity. As a result, turbulence occurs in the portion of the flow channel 200 that includes the intermediate flow channel 230, from the first narrow flow channel 210 to the second narrow flow channel 220.

[0054] Furthermore, as previously described, the tubular member 100 is equipped with a second outside air inlet 140, as shown in Figure 1. The second outside air inlet 140 guides outside air to the first narrow channel section 210. Specifically, the second outside air inlet 140 defines a ventilation passage 141 that connects the first narrow channel section 210 to the outside of the tubular member 100. The ventilation passage 141 extends perpendicular to the length direction of the tubular member 100.

[0055] To facilitate the following explanation, we define an XYZ Cartesian coordinate system in which the longitudinal direction of the tubular member 100 is the Z-axis direction, the extending direction of the ventilation passage 141 defined by the second outside air introduction section 140 is the Y-axis direction, and the direction perpendicular to the Z-axis and Y-axis directions is the X-axis direction.

[0056] Figure 3 is a schematic perspective view showing only the inner surface of the tubular member 100 in order to represent the three-dimensional shape of the flow path 200 defined by the tubular member 100. As shown in Figure 3, multiple ventilation passages 141 are arranged in the X-axis direction. Each ventilation passage 141 connects the first narrow flow path section 210 to the outside of the tubular member 100.

[0057] When the diameter of each ventilation passage 141 is P, the distance between adjacent ventilation passages 141 in the X-axis direction is greater than or equal to P. This prevents bubbles 620 discharged from one ventilation passage 141 into the first narrow channel section 210 from coming into contact with or merging with bubbles 620 discharged from an adjacent ventilation passage 141 into the first narrow channel section 210 in the channel 200 beyond the first narrow channel section 210.

[0058] Next, the shape of the first narrow channel section 210 will be described. Hereafter, the cross-section of the first narrow channel section 210 will be referred to as the "first narrow section".

[0059] The first narrow section has a shape where the longitudinal direction is in one direction parallel to the first narrow section (hereinafter referred to as the U1 axis direction) and the short direction is in a direction parallel to the first narrow section and perpendicular to the U1 axis direction (hereinafter referred to as the U2 axis direction), specifically forming a rectangle. In other words, the dimension of the first narrow section in the U2 axis direction is smaller than the dimension of the first narrow section in the U1 axis direction.

[0060] Next, the shape of the second narrow channel section 220 will be described. In the following, the cross-section of the second narrow channel section 220 will be referred to as the "second narrow section".

[0061] The second narrow section, like the first narrow section, has a shape where the longitudinal direction is in one direction parallel to the second narrow section (hereinafter referred to as the V1 axis direction) and the short direction is in a direction parallel to the second narrow section and perpendicular to the V1 axis direction (hereinafter referred to as the V2 axis direction), specifically forming a rectangle. In other words, the dimension of the second narrow section in the V2 axis direction is smaller than the dimension of the second narrow section in the V1 axis direction.

[0062] As shown in Figure 4, in this embodiment, the V1 axis direction, which is the longitudinal direction of the second narrow section, is parallel to the U1 axis direction, which is the longitudinal direction of the first narrow section. Furthermore, the U1 axis direction and the V1 axis direction are parallel to the X axis direction. Consequently, the U2 axis direction, which is the short direction of the first narrow section, and the V2 axis direction, which is the short direction of the second narrow section, are parallel to the Y axis direction.

[0063] Furthermore, the Y-axis positions of the first narrow channel section 210 and the second narrow channel section 220 are the same. That is, the Y-axis center position of the first narrow section and the Y-axis center position of the second narrow section are the same. And the longitudinal dimension, i.e., the X-axis dimension, of the first narrow section and the longitudinal dimension, i.e., the X-axis dimension, of the second narrow section are equal to LC.

[0064] However, when the dimension of the second narrow section in the direction of its shorter side, the V2 axis direction, i.e., the Y axis direction, is LB, and the dimension of the first narrow section in the direction of its shorter side, the U2 axis direction, i.e., the Y axis direction, is LA, then LB > LA. For this reason, the cross-sectional area of ​​the second narrow channel section 220 is larger than the cross-sectional area of ​​the first narrow channel section 210.

[0065] As shown in Figure 4, the tubular member 100 according to this embodiment is formed in a circular shape when viewed in the Z-axis direction. In Figure 2, the cross-sections of the intermediate flow channel 230, the inlet end flow channel 240, and the outlet end flow channel 250 are circular. The longitudinal dimension LC of the first narrow flow channel 210 and the second narrow flow channel 220 shown in Figure 4 is equal to the diameter LC of the cross-section of the intermediate flow channel 230, the inlet end flow channel 240, and the outlet end flow channel 250 shown in Figure 2.

[0066] Referring to Figure 2, the manner in which bubbles 620 are generated in the tubular member 100 will be described below.

[0067] As previously described, a gas-liquid mixed fluid 600 flows into the tubular member 100 from the inlet end 101. The water pressure of the incoming gas-liquid mixed fluid 600 gradually increases towards the rear as the cross-sectional area of ​​the flow path 200 decreases in the narrowing tapered section 111. As a result, during the process of the gas-liquid mixed fluid 600 passing through the narrowing tapered section 111, the gas bubbles 620 contained in the gas-liquid mixed fluid 600 dissolve into the liquid 610 due to the pressurization.

[0068] On the other hand, the flow velocity of the gas-liquid mixed fluid 600 gradually increases towards the throat 112. The flow velocity of the gas-liquid mixed fluid 600 is maximum in the first narrow channel section 210 defined by the throat 112. As this dynamic pressure increases, the static pressure of the gas-liquid mixed fluid 600 becomes minimum in the first narrow channel section 210, and a negative pressure lower than atmospheric pressure is generated in the first narrow channel section 210.

[0069] As a result, the gaseous components dissolved in the liquid 610 of the gas-liquid mixed fluid 600 precipitate in the first narrow channel section 210. In this specification, "precipitation" refers to the appearance of gaseous components dissolved in the liquid 610 as bubbles 620. That is, in the first narrow channel section 210, precipitated bubbles 621 are generated by the precipitation of gaseous components dissolved in the liquid 610 (precipitated bubble generation step). The precipitation of precipitated bubbles 621 also occurs in the intermediate channel section 230.

[0070] Furthermore, the negative pressure generated in the first narrow channel section 210 guides outside air into the first narrow channel section 210 through the second outside air introduction section 140. As a result, outside air-derived bubbles 622, which are bubbles 620 originating from the outside air introduced through the second outside air introduction section 140, are generated separately from the precipitated bubbles 621 (outside air-derived bubble generation process).

[0071] As previously described, the distance LZ between the first narrow channel section 210 and the second narrow channel section 220 is shorter than the interval at which the longitudinal flow velocity of the gas-liquid mixed fluid 600 that has passed through the first throttling section 110 returns to its initial flow velocity. As a result, turbulence is generated throughout the entire intermediate channel section 230. This turbulence in the intermediate channel section 230 then agitates the precipitated bubbles 621 and the bubbles 622 originating from the outside air (agitation step).

[0072] This stirring causes the precipitated bubbles 621 and the bubbles 622 originating from the outside air to be broken up or crushed in the intermediate channel section 230. In this way, the generation of precipitated bubbles 621 and bubbles 622 originating from the outside air, along with the stirring in the intermediate channel section 230, allows for the generation of bubbles 620 with a sufficient number density in the liquid 610.

[0073] Furthermore, even though the gaseous components dissolved in the liquid 610 precipitate as precipitated bubbles 621, stirring in the intermediate channel 230 promotes the dissolution of air-derived bubbles 622 into the liquid. As a result, sufficient gaseous components can be dissolved in the liquid 610.

[0074] Furthermore, stirring of the precipitated bubbles 621 and the bubbles 622 originating from the outside air in the intermediate channel section 230 also contributes to the refinement of the bubbles 620. According to this embodiment, it is possible to generate bubbles 620 with a diameter of 300 [μm] or less, more specifically, bubbles 620 with a diameter of 100 [μm] or less, which are called so-called fine bubbles, and even bubbles 620 with a diameter of 1 [μm] or less, which are called so-called ultrafine bubbles.

[0075] Furthermore, as previously described, the cross-sectional area of ​​the second narrow channel section 220 is larger than that of the first narrow channel section 210. This mainly contributes to ensuring sufficient turbulence in the intermediate channel section 230 by moderately suppressing the resistance experienced by the flow of the gas-liquid mixed fluid 600 in the second throttling section 120.

[0076] Furthermore, the more intense the turbulence generated in the intermediate flow channel 230, the greater the number density of the bubbles 620, the greater the dissolved concentration of gaseous components in the liquid 610, and the finer the bubbles 620 become.

[0077] Furthermore, the configuration in which the cross-sectional area of ​​the second narrow channel section 220 is larger than that of the first narrow channel section 210 contributes to promoting the precipitation of precipitated bubbles 621 in the intermediate channel section 230 by appropriately suppressing the pressure in the intermediate channel section 230.

[0078] Furthermore, if the cross-sectional area of ​​the second narrow channel section 220 is less than or equal to the cross-sectional area of ​​the first narrow channel section 210, the pressure loss in the second throttling section 120 becomes too large, making it impossible to form sufficiently violent turbulence in the intermediate channel section 230. Also, because the pressure in the intermediate channel section 230 becomes too high, it becomes difficult for precipitated bubbles 621 to precipitate sufficiently in the intermediate channel section 230.

[0079] Furthermore, according to this embodiment, since the pressure loss in the second throttling section 120 can be moderately suppressed, a strong turbulent flow can be formed in the intermediate flow path section 230 without setting the pressure of the gas-liquid mixed fluid 600 at the discharge position of the liquid pump 310 shown in Figure 1, i.e., the discharge pressure of the liquid pump 310, to a very high level.

[0080] As an example, the discharge pressure of the liquid pump 310 can be kept below 1.0 MPa, preferably below 0.4 MPa. However, the discharge pressure of the liquid pump 310 is not particularly limited, and a higher discharge pressure may create more intense turbulence in the intermediate flow channel 230.

[0081] The following describes particularly preferred dimensional conditions for the tubular member 100.

[0082] Refer to Figure 2 again. As previously described, the dimension of the first narrow section in the short direction (U2 axis direction) is LA, and the dimension of the second narrow section in the short direction (V2 axis direction) is LB. It is preferable that the tubular member 100 satisfies the relationship 1.5 × LA ≤ LB ≤ 6.5 × LA.

[0083] By setting the dimension LB to 1.5 × LA or greater, the water pressure in the intermediate channel section 230 can be appropriately suppressed. As a result, precipitated bubbles 621 with a higher number density can be generated not only in the first narrow channel section 210 but also in the intermediate channel section 230.

[0084] By setting the dimension LB to 6.5 × LA or less, more intense turbulence can be formed in the intermediate channel section 230, allowing the precipitated bubbles 621 and the bubbles 622 originating from the outside air to be vigorously stirred at high speed in the intermediate channel section 230. In particular, the vigorous stirring of the bubbles 622 originating from the outside air at high speed further promotes their dissolution into the liquid 610, leading to a further improvement in the dissolved concentration of gaseous components in the liquid 610.

[0085] In one specific example, the value of dimension LA satisfies the relationship 0.8 [mm] ≤ LA < 3 [mm]. By setting dimension LA to 0.8 [mm] or more, a sufficient amount of outside air can be drawn into the first narrow channel section 210 through the ventilation passage 141. Furthermore, by setting dimension LA to 3 [mm] or less, precipitated bubbles 621 with a higher number density can be made to appear in the first narrow channel section 210.

[0086] Furthermore, when determining the specific value of dimension LA in this manner, it is preferable that, in addition to the above relationship, the following relationships are also satisfied: LA + 2 [mm] ≤ LB and 3 [mm] ≤ LB ≤ 5 [mm].

[0087] Furthermore, it is preferable that the diameter LC of the intermediate flow channel 230 satisfies the relationship 8 × LA ≤ LC ≤ 32 × LA.

[0088] By setting the diameter LC of the intermediate channel section 230 to 8 × LA or more, more intense turbulence can be formed in the intermediate channel section 230, and sufficient space can be secured for stirring the precipitated bubbles 621 and bubbles 622 originating from the outside air. Alternatively, by setting the diameter LC of the intermediate channel section 230 to 32 × LA or less, the occurrence of flow stagnation can be suppressed, and more intense turbulence can be formed throughout the entire intermediate channel section 230.

[0089] In this embodiment, a configuration in which the cross-section of the intermediate channel section 230 is circular is illustrated. However, the influence of the "shape" of the cross-section of the intermediate channel section 230 on the characteristics of bubble 620 generation is considered to be almost negligible. That is, the shape of the cross-section of the intermediate channel section 230 is not limited to a circle, but may be non-circular, such as an ellipse, triangle, or polygon with four or more sides. The same applies to the shape of the cross-sections of the inlet end channel section 240 and the outlet end channel section 250.

[0090] Therefore, the above-mentioned "diameter LC" can be generalized to "equivalent diameter LC" to include not only cases where the cross-section of the intermediate flow channel 230 is circular, but also cases where it is not circular. In this specification, "equivalent diameter of the flow channel" refers to a value defined as D = 4A / W, where A is the area of ​​the cross-section of the flow channel and W is the circumference of the cross-section. When the cross-section of the flow channel is circular, the equivalent diameter is equal to the diameter of the circle formed by the cross-section of the flow channel.

[0091] Furthermore, as previously described, the distance LZ between the first narrow channel section 210 and the second narrow channel section 220 is shorter than the interval at which the longitudinal flow velocity of the gas-liquid mixed fluid 600 in the intermediate channel section 230 returns to its initial flow velocity. To satisfy this requirement, it is preferable that the distance LZ satisfies the relationship 1.5 × LC ≤ LZ ≤ 3 × LC. Here, LC represents the equivalent diameter of the intermediate channel section 230, as described above.

[0092] [Second Embodiment] Figure 4 illustrates a configuration in which the V1 axis direction, which is the longitudinal direction of the second narrow section, is parallel to the U1 axis direction, which is the longitudinal direction of the first narrow section. The V1 axis direction and the U1 axis direction do not have to be parallel to each other. Specific examples are described below.

[0093] As shown in Figure 5, a virtual central axis CL is defined parallel to the longitudinal direction of the tubular member 100, i.e., the Z-axis direction. The virtual central axis CL passes through the centroid of the cross-section of the tubular member 100.

[0094] In this embodiment, the V1 axis direction, which is the longitudinal direction of the second narrow section, is rotated by an angle θ around the virtual central axis CL relative to the U1 axis direction, which is the longitudinal direction of the first narrow section. Figure 5 illustrates the case where angle θ = 90°. However, angle θ may be any value greater than 0° and less than or equal to 90°.

[0095] Furthermore, the fact that the longitudinal direction of the first narrow cross-section, the U1 axis direction, coincides with the X axis direction is the same as in the first embodiment. Therefore, when the angle θ = 90°, the longitudinal direction of the second narrow cross-section, the V1 axis direction, coincides with the Y axis direction. In addition, other configurations, including the spacing LZ shown in Figures 2 and 3, are the same as in the first embodiment. According to this embodiment, more intense turbulence can be formed in the intermediate flow channel 230.

[0096] [Third Embodiment] In the following, a structure that restricts the flow of the gas-liquid mixed fluid 600 will be generally referred to as a "restriction section," and the narrowest part of the flow path of the gas-liquid mixed fluid 600 defined by the restriction section will be referred to as a "narrow flow path section." The concept of a restriction section includes the first restriction section 110 and the second restriction section 120 described above. The concept of a narrow flow path section also includes the first narrow flow path section 210 and the second narrow flow path section 220 described above.

[0097] The first and second embodiments of the tubular member 100 have been described, which have two throttling portions, a first throttling portion 110 and a second throttling portion 120. The tubular member 100 may have other throttling portions (hereinafter referred to as additional throttling portions), as long as it has the first throttling portion 110 and the second throttling portion 120 which defines an intermediate flow path portion 230 between the first throttling portion 110 and the second throttling portion 120.

[0098] Therefore, the tubular member 100 according to this embodiment further comprises an additional throttling portion. The additional throttling portion may be located behind the second throttling portion 120 or in front of the first throttling portion 110. Here, "rear" refers to the side closer to the outlet end 102 with respect to the Z-axis direction, as previously described. "Front" refers to the side closer to the inlet end 101 with respect to the Z-axis direction.

[0099] Furthermore, multiple additional aperture sections may be arranged in series behind the second aperture section 120 or in front of the first aperture section 110, or one or more additional aperture sections may be arranged both behind the second aperture section 120 and in front of the first aperture section 110. The area of ​​the cross-section of the narrow flow path defined by the additional aperture section is not particularly limited.

[0100] [Example A] To explore a preferred configuration for the diaphragm, experiments were conducted with various configurations of the diaphragm. In all experiments, the cross-sectional shape of the narrow channel defined by the diaphragm was rectangular. Table 1 below shows the conditions of this experiment.

[0101] [Table 1]

[0102] In Table 1, “A[mm]-B[mm]” represents a configuration in which two aperture sections are arranged in series, with the width of the narrow channel defined by the front aperture section being A[mm] (hereinafter also referred to as the width of the aperture section), and the width of the rear aperture section being B[mm]. Similarly, “A[mm]-B[mm]-C[mm]” represents a configuration in which three aperture sections are arranged in series, with the width of the foremost aperture section being A[mm], the width of the rearmost aperture section being C[mm], and the width of the central aperture section being B[mm]. Furthermore, “A[mm]” represents a configuration in which only one aperture section is arranged, and the width of that aperture section is A[mm].

[0103] In all of the experimental examples A1-A14, a circular pipe with an inner diameter of 25 mm was used as the object to which the constriction section was provided. A tubular member is a circular pipe to which a constriction section has been provided. That is, in the tubular member relating to any of the experimental examples A1-A14, the inner diameter of the portion between the constriction section adjacent to the inlet end and the inlet end, and the inner diameter of the portion between the constriction section adjacent to the outlet end and the outlet end, are 25 mm.

[0104] Furthermore, in experimental examples A1-A5, A7, A9, A11, A13, and A14, where multiple aperture sections are arranged in series, the inner diameter of the tubular member between adjacent aperture sections in the Z-axis direction is also 25 mm. In addition, the distance in the Z-axis direction between adjacent aperture sections was set to 50 mm.

[0105] In the tubular member relating to Experimental Example A1, the 4 mm wide constricted section corresponds to the second constricted section 120 described above, and the 1 mm wide constricted section corresponds to the first constricted section 110 described above. Therefore, the tubular member relating to Experimental Example A1 corresponds to the embodiment in terms of the arrangement of the constricted sections.

[0106] In the tubular members of experimental examples A2-A5, the 4 mm wide constricted section corresponds to the second constricted section 120 described above, and the 1 mm wide constricted section located in front of that constricted section corresponds to the first constricted section 110 described above. Therefore, the tubular members of experimental examples A2-A5 also correspond to the embodiment in terms of the arrangement of the constricted sections.

[0107] In addition, in the tubular members of experimental examples A2 and A3, the 1 mm wide diaphragm located behind the second diaphragm 120 corresponds to the additional diaphragm described above. Furthermore, in the tubular members of experimental examples A4 and A5, the 1 mm wide diaphragm located in front of the first diaphragm 110 corresponds to the additional diaphragm described above.

[0108] The tubular members in experimental examples A6, A8, A10, and A12 are comparative examples in terms of the arrangement of the constricted portion, as they have only one constricted portion.

[0109] The tubular members in experimental examples A7, A9, A11, and A13, although having two constricted sections, qualify as comparative examples in terms of the arrangement of the constricted sections, as the cross-sectional areas of the narrow flow channels defined by these constricted sections are equal to each other.

[0110] Although the tubular member in experimental example A14 has two constricted sections, the cross-sectional area of ​​the narrow channel defined by the front constricted section is larger than the cross-sectional area of ​​the narrow channel defined by the rear constricted section, and therefore it falls under the comparative example in terms of the arrangement of the constricted sections.

[0111] Furthermore, in Table 1, "gas" refers to the type of gaseous component to be included in the gas-liquid mixed fluid. In all of the experimental examples A1-A14, the outside air inlet for introducing outside air into the tubular member, i.e., the second outside air inlet 140 shown in Figure 2, was omitted, and the "gas" listed in Table 1 were introduced only from the first outside air inlet 320 upstream of the liquid pump 310 shown in Figure 1.

[0112] Then, in order to evaluate each of the tubular members related to experimental examples A1-A14, the red tide control agent was added to seawater (liquid 610) in the liquid tank 500, and the liquid pump 310 was operated to pulverize the red tide control agent through the stirring action caused by the turbulence generated in the tubular members. The discharge pressure of the liquid pump 310 was adjusted to 0.35 [MPa] or less.

[0113] The red tide control agent used was primarily composed of clay containing montmorillonite. Al ions leached from the clay into seawater destroy plankton cells. The bubbles 620 generated in the tubular member enhance the red tide control function by dispersing the red tide control agent.

[0114] Figure 6 shows the measurement results of the mode diameter of the red tide control agent crushed using the tubular member described in Experimental Examples A1-A14, according to the procedure described above. The smaller the mode diameter of the red tide control agent, the more vigorously the gas-liquid mixed fluid 600 containing the red tide control agent was agitated in the tubular member. Therefore, the smaller the mode diameter of the red tide control agent, the more favorable the arrangement of the constriction portion in the tubular member used to crush the red tide control agent is.

[0115] As shown in Figure 6, experimental examples A1-A5, which correspond to the examples, yielded experimental results showing that the mode diameter of the red tide control agent was smaller compared to experimental examples A6-A14, which correspond to the comparative examples. In other words, experimental examples A1-A5, which correspond to the examples, were able to sufficiently dissolve viscous aggregated particles, which are ultrafine powders with a particle size of about 10 [μm] or less, without using a dispersant.

[0116] The results of this experiment showed that a configuration having at least two adjacent diaphragm sections, where the cross-sectional area of ​​the narrow channel defined by the rear diaphragm section is larger than the cross-sectional area of ​​the narrow channel defined by the front diaphragm section, is preferable.

[0117] In the tubular members of experimental examples A6, A8, A10, and A12, there is only one constricted section, so the red tide control agent cannot be sufficiently crushed.

[0118] Although the tubular member in experimental example A14 has two constricted sections, the cross-sectional area of ​​the narrow channel defined by the front constricted section is larger than the cross-sectional area of ​​the narrow channel defined by the rear constricted section. As a result, the flow resistance in the rear constricted section is too great, and it is not possible to form high-speed, sufficiently violent turbulence in the intermediate channel between the two constricted sections, resulting in insufficient pulverization of the red tide control agent.

[0119] Although the tubular members in experimental examples A7, A9, A11, and A13 also have two constricted sections, the cross-sectional areas of the narrow channel sections defined by these constricted sections are equal. Even if the cross-sectional areas of the two narrow channel sections are equal, the intensity of the turbulence generated in the intermediate channel section is not sufficient, and the red tide control agent cannot be sufficiently crushed.

[0120] [Example B] One of the objectives of this experiment was to investigate the relationship between the method of introducing gas into liquid 610 and the dissolved concentration of the gaseous component in the resulting gas-liquid mixed fluid 600. Experiments were conducted by changing various methods of introducing the gas. Air was used as the gas. The conditions for this experiment are shown in Table 2 below.

[0121] [Table 2]

[0122] In Table 2, experimental examples B1-B5 correspond to the examples in terms of the method of introducing the gas and the arrangement of the throttling section. In experimental examples B1-B5, the configuration shown in Figure 1 is adopted, and outside air is introduced into the gas-liquid mixed fluid 600 from the first outside air introduction section 320 and the second outside air introduction section 140, respectively.

[0123] The "two-stage cross" configuration of the tubular member 100 in experimental examples B1 and B2 refers to a configuration in which, as shown in Figure 5, the longitudinal direction of the second narrow channel section 220 crosses the longitudinal direction of the first narrow channel section 210 when viewed in the Z-axis direction, specifically a configuration where the angle θ shown in Figure 5 is 90°.

[0124] Furthermore, the term "two-stage parallel" used to describe the configuration of the tubular member 100 in experimental examples B3-B5 means a configuration in which the longitudinal direction of the second narrow channel section 220 is parallel to the longitudinal direction of the first narrow channel section 210, as shown in Figure 4.

[0125] In experimental examples B1-B5, as in experimental example A1 described above, the shapes of both the first and second narrow cross-sections were rectangular, the dimension of the first narrow channel section 210 in the short direction was 1 mm, the dimension of the second narrow channel section 220 in the short direction was 4 mm, and the distance between the first narrow channel section 210 and the second narrow channel section 220 in the Z-axis direction was 50 mm. Furthermore, a circular pipe with an inner diameter of 25 mm was used as the object to which the first and second constriction sections 110 and 120 were provided.

[0126] In Table 2, experimental examples B6-B9 correspond to comparative examples in terms of the gas introduction method and the arrangement of the throttling section. The term "single stage" used to describe the configuration of the tubular member in experimental examples B6-B9 means that there is only one throttling section. The dimension in the short direction of the narrow flow path defined by this single throttling section was set to 1 mm.

[0127] The term "pressurized dissolution type," which describes the configuration of the tubular member in Experimental Example B6, means that the only point where outside air is drawn in by negative pressure is the first outside air inlet 320 located upstream of the liquid pump 310 shown in Figure 1. In Experimental Example B6, the second outside air inlet 140 and the second throttling section 120 shown in Figure 2 are omitted. The other configurations are the same as those in Experimental Examples B1-B5.

[0128] The term "ejector type," which describes the configuration of the tubular member in experimental examples B7-B9, means that the only point where outside air is drawn in by negative pressure is the second outside air inlet 140 shown in Figure 2. In experimental examples B7-B9, the first outside air inlet 320 shown in Figure 1 and the second throttling section 120 shown in Figure 2 are omitted. The other configurations are the same as those in experimental examples B1-B5.

[0129] In Table 2, "gas flow rate" refers to the flow rate of air introduced into the gas-liquid mixed fluid 600 by negative pressure. Specifically, in experimental example B6, which is a comparative example, "gas flow rate" refers to the flow rate of air introduced from the first outside air inlet 320. In experimental examples B7-B9, which are comparative examples, "gas flow rate" refers to the flow rate of air introduced from the second outside air inlet 140.

[0130] Furthermore, in experimental examples B1-B5, which are examples of the actual implementation, "gas flow rate" refers to the sum of the flow rate of air introduced from the first outside air inlet 320 and the flow rate of air introduced from the second outside air inlet 140. In all of experimental examples B1-B5, the flow rate of air introduced from the first outside air inlet 320 was 0.1 [L / min], and the flow rate of air introduced from the second outside air inlet 140 was 0.3 [L / min].

[0131] Furthermore, in Table 2, “liquid pump discharge pressure” refers to the pressure of the gas-liquid mixed fluid 600 at the discharge point of the liquid pump 310 shown in Figure 1. Also, in Table 2, “gas-liquid mixed fluid flow rate” refers to the flow rate of the gas-liquid mixed fluid 600 flowing through the tubular member.

[0132] Furthermore, in Table 2, the "overall mass transfer capacity coefficient" is an index that quantitatively evaluates the performance of dissolving gaseous components. A larger overall mass transfer capacity coefficient indicates that gaseous components can be dissolved efficiently in liquid 610, and that a larger amount of gaseous components are dissolved relative to liquid 610.

[0133] As shown in Table 1, experimental results obtained in experimental examples B1-B5, which correspond to the examples, showed a dramatic increase in the overall mass transfer capacity coefficient compared to experimental examples B6-B9, which correspond to the comparative examples. In other words, experimental examples B1-B5, which correspond to the examples, allow for the dissolution of a large amount of gaseous components in liquid 610.

[0134] The results of this experiment showed that, in the tubular member 100 into which a gas-liquid mixed fluid 600 containing liquid 610 and gaseous components is injected under pressure, a configuration in which outside air is further introduced from a second outside air introduction section 140 provided in the first throttling section 110 is preferable. With such a configuration, the dissolved concentration of gaseous components in liquid 610 can be dramatically increased.

[0135] In the configuration of Experimental Example B6, which corresponds to the comparative example, the same effect as in the example is obtained in which the gaseous component dissolved in liquid 610 precipitates as bubbles 620 in the constricted portion inside the tubular member. However, because the precipitation of the gaseous component as bubbles 620 reduces the dissolved concentration of the gaseous component in liquid 610, there is a limit to how much the overall mass transfer capacity coefficient can be increased.

[0136] In contrast, in the configurations of experimental examples B1-B5, which correspond to the embodiments, outside air is introduced not only in the preparation stage of preparing the gas-liquid mixed fluid 600 to be injected into the tubular member 100, but also in the second outside air introduction section 140 inside the tubular member 100.

[0137] Therefore, even though the gaseous components dissolved in the liquid 610 precipitate as precipitated bubbles 621 inside the tubular member 100, the outside air-derived bubbles 622, which originate from the outside air introduced from the second outside air introduction section 140, can be dissolved in the liquid 610 by stirring in the intermediate flow channel section 230. As a result, the gaseous components can be sufficiently dissolved in the liquid 610.

[0138] In the configurations of experimental examples B7-B9, which are comparative examples, outside air is introduced from the second outside air introduction section 140 inside the tubular member 100, but since there is only one constriction section, an intermediate flow path section 230 is not formed inside the tubular member. As a result, the outside air introduced from the second outside air introduction section 140 is not sufficiently agitated inside the tubular member. Consequently, the outside air cannot be sufficiently dissolved in the liquid 610, and there is a limit to how much the overall mass transfer capacity coefficient can be increased.

[0139] Figure 7 shows the number density distribution against diameter, i.e., bubble diameter, of 620 bubbles generated using the bubble generating apparatus according to Experimental Example B4, which corresponds to the examples. In the vertical axis of Figure 7, "E8" means 10 to the power of 8. That is, for example, "2.0E8" means 2.0 × 10⁸ 8 This means [units / mL]. In addition, in Figure 7, the bubble diameter at the location of the maximum point is noted near the maximum point of the curve representing the average of the number density measurement results.

[0140] As shown in Figure 7, the diameter of the bubbles 620 in the gas-liquid mixed fluid 600 is 500 nm or less. That is, it was confirmed that ultrafine bubbles with a bubble diameter of 1 μm or less could be formed. The mode diameter of the bubbles 620 in the gas-liquid mixed fluid 600 is 115.6 nm, and the number density at that mode diameter is 3.3 × 10⁻¹⁶. 8 The result was [bubbles / mL]. Here, mode diameter refers to the diameter of the most frequently occurring bubble.

[0141] The embodiments and experimental examples have been described above. The following modifications are also possible.

[0142] Figures 3-5 illustrate rectangular shapes as the cross-section of the first narrow channel section 210 and the second narrow channel section 220. While it is preferable that the first and second narrow channels have a longitudinal shape with one direction perpendicular to the Z-axis as the longitudinal direction (hereinafter referred to as the elongated shape), the elongated shape is not particularly limited to a rectangle. The elongated shape may be an ellipse with the aforementioned direction as the major axis, or a rectangle with its four corners rounded.

[0143] Furthermore, the shapes of the first and second narrow cross-sections do not necessarily have to be elongated. In short, it is sufficient that the area of ​​the second narrow flow cross-section is designed to be larger than the area of ​​the first narrow cross-section. This allows the flow resistance in the second constriction section 120 to be moderately suppressed, and intense turbulence to be formed in the intermediate flow channel section 230.

[0144] Figure 1 shows the return piping 430, but the return piping 430 may be omitted. If the return piping 430 is omitted, the gas-liquid mixed fluid 600 flowing out from the outlet end 102 of the tubular member 100 will be supplied to a liquid-tight container or other destination not shown. Also, the liquid tank 500 shown in Figure 1 is not essential. In short, any configuration in which the gas-liquid mixed fluid 600, containing liquid 610 and gaseous components, is injected into the tubular member 100 under pressure is sufficient.

[0145] Figure 1 illustrates a first outside air inlet 320 for preparing a gas-liquid mixed fluid 600 to be injected into the tubular member 100, but the configuration for preparing the gas-liquid mixed fluid 600 to be injected into the tubular member 100 is arbitrary. The gas-liquid mixed fluid 600 containing gaseous components may be prepared by a known method that does not use the first outside air inlet 320, and the gas-liquid mixed fluid 600 may be pumped into the tubular member 100 by a liquid pump 310 or other pressurizing means.

[0146] Figure 3 shows an example of four ventilation passages 141, but the number of ventilation passages 141 is not particularly limited. Only one ventilation passage 141 may be provided.

[0147] In the above embodiments and experimental examples, air was used as an example of the gaseous component contained in the gas-liquid mixed fluid 600, but the gaseous component is arbitrary. In addition to air, carbon dioxide, oxygen, ozone, nitrogen, etc. may be used as the gaseous component.

[0148] In the configuration shown in Figure 1, the outside air introduced from the first outside air introduction section 320 and the outside air introduced from the second outside air introduction section 140 may be the same or different. In this specification, "outside air" means gas present outside the tubular member 100 and is not limited to gas constituting the atmosphere surrounding the bubble generating device 700 (hereinafter referred to as atmosphere-constituting gas).

[0149] A gas different from the atmospheric gas may be prepared in a cylinder, gas bag, or other airtight container, and the gas in that airtight container may be introduced through the first outside air inlet 320 and the second outside air inlet 140 by negative pressure. Here, negative pressure means a pressure lower than the atmospheric pressure inside that airtight container.

[0150] In the embodiments and experimental examples described above, water was used as an example of the liquid 610 constituting the gas-liquid mixed fluid 600. In this specification, the concept of "water" includes tap water, ion-exchanged water, distilled water and other tap water, industrial water and other reclaimed water, sewage, seawater, lake water, river water, groundwater, etc. Furthermore, liquid 610 is not limited to water. Examples of liquid 610 at room temperature and atmospheric pressure include water, ethanol, organic solvents, etc. [Explanation of Symbols]

[0151] 100...Tubular member, 101...Inflow end (one end), 102...Outlet end (other end), 110...First aperture section, 111...Narrowing tapered section, 112...throat, 113... Widening tapered section, 120...Second aperture section, 121...Narrowing tapered section, 122...throat, 123... Widening tapered section, 130... Middle section, 140...Second outside air intake (outside air intake), 141... Ventilation channel, 200...flow channel, 210...first narrow channel section, 220...second narrow channel section, 230...Intermediate flow channel section, 240...Inflow end flow path section, 250...outflow end flow path section, 300... Pressure pump, 310... Liquid pump, 320...First outside air intake section, 400... Piping, 410... Supply piping, 420...Intermediate piping, 430...Return piping, 500...liquid tank, 600…Gas-liquid mixed fluid, 610...liquid, 620...bubbles, 621...Precipitated bubbles, 622...Air bubbles originating from outside air, 700... Bubble generating device, CL... Virtual central axis.

Claims

1. A tubular member formed in the shape of a tube that defines a flow path for a gas-liquid mixed fluid containing a liquid and a gaseous component mixed with the liquid, wherein the gas-liquid mixed fluid is injected under pressure from one end and the injected gas-liquid mixed fluid flows out from the other end, By locally narrowing the area of ​​the cross-sectional surface perpendicular to the longitudinal direction of the tubular member of the flow path, a first throttling section is formed that restricts the flow of the gas-liquid mixed fluid, A second throttling portion is located adjacent to the first throttling portion at a position closer to the other end than the first throttling portion, and by locally narrowing the area of ​​the cross-sectional surface of the flow path, the second throttling portion restricts the flow of the gas-liquid mixed fluid that has passed through the first throttling portion. An intermediate portion defines the intermediate flow path, which is the portion of the flow path that is narrowed in the first constricted flow path portion and the portion that is narrowed in the second constricted flow path portion. An outside air introduction section that guides outside air into the first narrow flow channel section, It has, The area of ​​the cross-section of the second narrow channel is larger than the area of ​​the cross-section of the first narrow channel. Tubular member.

2. The first narrow cross section, which is the cross-section of the first narrow channel, has a shape in which the longitudinal direction is the U1 axis parallel to the first narrow cross section, The second narrow cross-section, which is the cross-section of the second narrow channel portion, has a shape in which the V1 axis parallel to the second narrow cross-section is the longitudinal direction. The dimension of the first narrow section in the U1 axial direction is equal to the dimension of the second narrow section in the V1 axial direction. The dimension of the second narrow cross-section in the direction of the V2 axis, which is parallel to the second narrow cross-section and perpendicular to the direction of the V1 axis, is greater than the dimension of the first narrow cross-section in the direction of the U2 axis, which is parallel to the first narrow cross-section and perpendicular to the direction of the U1 axis. The tubular member according to claim 1.

3. Let LA be the dimension of the first narrow cross-section in the U2 axial direction. When the dimension of the second narrow cross-section in the V2 axial direction is denoted as LB, The relationship 1.5 × LA ≤ LB ≤ 6.5 × LA is satisfied. The tubular member according to claim 2.

4. When the equivalent diameter of the intermediate flow channel is LC, The relationship 8 × LA ≤ LC ≤ 32 × LA is satisfied. The tubular member according to claim 3.

5. The following relationships are further satisfied: 0.8 [mm] ≤ LA < 3 [mm], LA + 2 [mm] ≤ LB, and 3 [mm] ≤ LB ≤ 5 [mm]. The tubular member according to claim 3.

6. The distance in the longitudinal direction between the first narrow channel and the second narrow channel is shorter than the interval at which the longitudinal flow velocity of the gas-liquid mixed fluid flowing through the intermediate channel after passing through the first constriction returns to the longitudinal flow velocity of the gas-liquid mixed fluid when it is pressed into the tubular member from one end. The tubular member according to claim 1.

7. Let LZ be the distance in the longitudinal direction between the first narrow channel section and the second narrow channel section. When the equivalent diameter of the intermediate flow channel is LC, 1. Satisfy the relationship 1.5 × LC ≤ LZ ≤ 3 × LC. The tubular member according to claim 1.

8. The V1 axis direction is parallel to the U1 axis direction. The tubular member according to claim 2.

9. The V1 axis direction is the direction obtained by rotating the U1 axis direction around a virtual central axis parallel to the longitudinal direction. The tubular member according to claim 2.

10. A tubular member according to any one of claims 1 to 9, A pressurizer for injecting the gas-liquid mixed fluid into the tubular member, A bubble generating device equipped with the following features.

11. A liquid tank in which the gas-liquid mixed fluid is stored, A return pipe connecting the inside of the liquid tank and the other end of the tubular member, A supply pipe connecting the inside of the liquid tank and the pressure pump, Furthermore, The pump draws the gas-liquid mixture from the inside of the liquid tank through the supply pipe, and pumps the drawn-in gas-liquid mixture together with the gas to the tubular member, and the gas-liquid mixture that flows out from the other end of the tubular member returns to the inside of the liquid tank through the return pipe. The bubble generating apparatus according to claim 10.

12. A method for generating bubbles using a tubular member that is formed in the shape of a tube to define a flow path for a gas-liquid mixed fluid containing a liquid and a gaseous component mixed with the liquid, the gas-liquid mixed fluid being injected under pressure from one end and the injected gas-liquid mixed fluid being discharged from the other end, The tubular member is By locally narrowing the area of ​​the cross-sectional surface perpendicular to the longitudinal direction of the tubular member of the flow path, a first throttling section is formed that restricts the flow of the gas-liquid mixed fluid, A second throttling portion is located adjacent to the first throttling portion at a position closer to the other end than the first throttling portion, and by locally narrowing the area of ​​the cross-sectional surface of the flow path, the second throttling portion restricts the flow of the gas-liquid mixed fluid that has passed through the first throttling portion. An intermediate portion defines the intermediate flow path, which is the portion of the flow path that is narrowed in the first constricted flow path portion and the portion that is narrowed in the second constricted flow path portion. An outside air introduction section that guides outside air into the first narrow flow channel section, It has, The area of ​​the cross-section of the second narrow channel is larger than the area of ​​the cross-section of the first narrow channel. A precipitate bubble generation step is performed in which precipitate bubbles are generated by the precipitation of the gaseous component dissolved in the liquid in the first narrow channel section, An air-derived bubble generation step is performed in which the outside air is guided to the first narrow channel through the outside air introduction section by the negative pressure generated in the first narrow channel section, thereby generating outside air-derived bubbles, which are bubbles originating from the outside air. A stirring step in which the bubbles originating from the outside air and the precipitated bubbles are stirred in the intermediate channel by the turbulence generated in the intermediate channel, A method for generating bubbles, including the method described above.

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