Air-bubble generator

Abstract

To provide an air-bubble generator that is able to generate more air bubbles than a conventional one.SOLUTION: In an air-bubble generator 1 including a cylindrical body 2 in which a swirling flow passage 10 through which liquid flows while swirling is formed, the swirling flow passage 10 has: a constricted portion 11 formed along a vertical surface perpendicular to a flowing direction of the liquid; and a pair of facing surface portions 12 disposed to face each other so as to sandwich the constricted portion 11 as viewed from the flowing direction of the liquid. A flow-passage cross section, obtained by cutting the swirling flow passage 10 along the vertical surface is formed in such a shape that rotates along the vertical surface as it advances in the flowing direction of the liquid. An area (S1) of a flow-passage cross section on an outlet side of the swirling flow passage 10 is set to be larger than an area (S2) of a flow-passage cross section on an inlet side of the swirling flow passage 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a bubble generator including a cylindrical body in which a swirling flow path through which a liquid flows while swirling is formed.

Background Art

[0002] For example, a bubble generator is known as a device for generating fine bubbles called so-called fine bubbles having a diameter of 100 μm or less in a liquid (see Patent Document 1).

[0003] The bubble generator described in Patent Document 1 is configured to generate bubbles by providing a through-hole through which a liquid flows while swirling and reducing the pressure by utilizing the centrifugal force when the liquid swirls. In this device, the area of the flow path cross-section on the outlet side of the through-hole is set smaller than the area of the flow path cross-section on the inlet side of the through-hole.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the device described in Patent Document 1, when the liquid flowing through the through-hole is discharged from the through-hole, it collides with the already discharged liquid, so that the liquid near the outlet of the through-hole is pressurized and the pressure rises. Further, in this device, since the area of the flow path cross-section on the outlet side of the through-hole is set smaller than the area of the flow path cross-section on the inlet side of the through-hole, the liquid flowing through the through-hole is accelerated and discharged. When the accelerated liquid is discharged from the through-hole, it is impossible to suppress the pressure increase due to the collision with the already discharged liquid, and the pressure reduction effect in the through-hole decreases in proportion to this pressure increase, and the generation of bubbles is suppressed. Therefore, there is room for improvement in terms of generating more bubbles.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a bubble generator that can generate more bubbles than in the prior art.

Means for Solving the Problems

[0007] The characteristic configuration of the bubble generator according to the present invention for solving the above problems is a bubble generator including a cylindrical body in which a swirling flow path through which a liquid flows while swirling is formed, wherein the swirling flow path has a constricted portion constricted along a vertical plane perpendicular to the flow direction of the liquid, and a pair of opposing surfaces disposed to face each other so as to sandwich the constricted portion when viewed from the flow direction of the liquid, and a cross-section of the flow path obtained by cutting the swirling flow path along the vertical plane is formed in a shape that rotates along the vertical plane as it advances in the flow direction of the liquid, and the area (S1) of the cross-section of the flow path on the outlet side of the swirling flow path is set to be larger than the area (S2) of the cross-section of the flow path on the inlet side of the swirling flow path.

[0008] In the bubble generator of this configuration, centrifugal force acts on the liquid flowing while swirling in the swirling flow path, and a pressure difference is generated between the liquid flowing through the constricted portion and the liquid flowing near the pair of opposing surfaces. As a result, the liquid flowing through the constricted portion is decompressed, and bubbles are generated in the liquid flowing through the constricted portion. According to the bubble generator of this configuration, the area (S1) of the cross-section of the flow path on the outlet side of the swirling flow path is set to be larger than the area (S2) of the cross-section of the flow path on the inlet side of the swirling flow path. Thereby, the liquid flowing through the swirling flow path is decelerated and discharged. In this way, even if the decelerated liquid collides with the liquid containing the bubbles already discharged from the swirling flow path, the collision energy is small, so that an increase in the pressure of the liquid containing the bubbles already discharged can be suppressed, and in addition to suppressing a decrease in the decompression effect in the swirling flow path, more bubbles can be generated than in the prior art (Patent Document 1).

[0009] In the bubble generator according to the present invention, It is preferable that the swirling flow path is formed such that the distance between the pair of opposing surfaces increases and the area of the flow path cross section increases as the liquid flows in the flow direction.

[0010] According to the bubble generator of this configuration, as the liquid flows in the flow direction, the distance between the pair of opposing surfaces increases, so that the swirling radius of the liquid flowing through the swirling flow path increases as the liquid flows in the flow direction. Although this increase in the swirling radius is accompanied by a decrease in the swirling speed of the liquid, the centrifugal force acting on the liquid is compensated by the increase in the swirling radius. Further, since the area of the flow path cross section of the swirling flow path increases as the liquid flows in the flow direction, the centrifugal force acting on the liquid is strengthened. Furthermore, the liquid flowing through the swirling flow path becomes a turbulent state in which the swirling flow is disturbed as the liquid flows in the flow direction due to the interaction between the increase in the swirling radius and the increase in the area of the flow path cross section as described above, and the stirring action increases. Thus, by strengthening the centrifugal force acting on the liquid and increasing the stirring action, more bubbles can be efficiently generated and the generated bubbles can be efficiently diffused in the liquid.

[0011] In the bubble generator according to the present invention, The area ratio (S1 / S2) of the area (S1) to the area (S2) is preferably 1.1 to 1.5.

[0012] Since the speed of the liquid discharged from the swirling flow path is related to the momentum of the liquid, if the speed is excessively reduced in the swirling flow path, the momentum of the liquid becomes too weak to be suitable for use. In the bubble generator of this configuration, the area ratio (S1 / S2) of the area (S1) of the flow path cross section on the outlet side of the swirling flow path to the area (S2) of the flow path cross section on the inlet side of the swirling flow path is set to 1.1 to 1.5. Thereby, the balance between the area (S1) and the area (S2) is improved, and while generating more bubbles than before, the momentum of the liquid can be made suitable for use.

[0013] In the bubble generator according to the present invention, It is preferable that an inclined portion that inclines radially outward of the cylindrical body in the direction of the liquid flow is formed at the opening edge on the outlet side of the swirling flow path in the cylindrical body.

[0014] According to the bubble generator of this configuration, a part of the liquid discharged from the outlet of the swirling flow path flows along the inclined portion that inclines radially outward of the cylindrical body in the direction of the liquid flow, so that bubbles can be efficiently dispersed.

[0015] In the bubble generator according to the present invention, The angle formed by the inclined portion with respect to the liquid flow direction is preferably 20 to 70°.

[0016] When the angle formed by the inclined portion with respect to the liquid flow direction is too small, most of the liquid discharged from the outlet of the swirling flow path advances straight in the direction of the liquid flow, so that bubbles cannot be efficiently dispersed. On the other hand, when the angle formed by the inclined portion with respect to the liquid flow direction is too large, the liquid is excessively decelerated near the outlet of the swirling flow path, and the momentum of the liquid becomes too weak to be suitable for use. In the bubble generator of this configuration, the angle formed by the inclined portion with respect to the liquid flow direction is set to 20 to 70°. Thereby, the angle formed by the inclined portion with respect to the liquid flow direction becomes appropriate, bubbles can be efficiently dispersed, and the momentum of the liquid can be made suitable for use.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Best Mode for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described with reference to the drawings. However, the present invention is not intended to be limited to the embodiments described below or the configurations described in the drawings.

[0019] <Usage Example of the Bubble Generator> FIG. 1 is a diagram showing a usage example of a bubble generator 1 according to an embodiment of the present invention. FIG. 1(a) is a perspective view of a state where the bubble generator 1 is incorporated in a shower head 100. FIG. 1(b) is an exploded perspective view showing the connection relationship of the shower head 100, the connector 104, and the hose 102 and the arrangement relationship of the bubble generator 1. In FIG. 1(a), a liquid such as cold water or warm water flows in the direction indicated by the arrow in the figure. As shown in FIG. 1(b), a hollow shaft-shaped male screw portion 101 through which the liquid can flow is formed at the base end portion (lower end portion) of the shower head 100. A connector 104 having a female screw portion 103 that can be screwed into the male screw portion 101 is attached to the tip end portion of a hose 102 for supplying the liquid to the shower head 100. Inside the connector 104, a hollow disk-shaped pedestal portion 105 through which the liquid can flow is incorporated.

[0020] When using the shower head 100, insert the cylindrical body 2 (described later in the bubble generator 1) into the male screw portion 101, and abut the flange portion 3 (described later in the bubble generator 1) against the pedestal portion 105. Then, thread the female screw portion 103 onto the male screw portion 101 and tighten it. Connect the hose 102 to the shower head 100 via the connector 104. Here, the flange portion 3 of the bubble generator 1 is smaller than the outer diameter of the male screw portion 101 and can abut against the end face of the male screw portion 101, and its outer diameter is set to be incorporable inside the connector 104. Thereby, when liquid is supplied to the shower head 100 via the hose 102, the flange portion 3 is pressed against and adhered to the end face of the male screw portion 101 by the supply pressure of the liquid. It is preferable to attach an annular backup material (not shown), which is an arbitrary configuration, to the flange portion 3 so that no gap is generated between the flange portion 3 and the pedestal portion 105.

[0021] <Overall configuration of the bubble generator> FIG. 2 is a perspective view of the bubble generator 1 according to an embodiment of the present invention. FIG. 2(a) is a perspective view seen from the front side in the liquid flow direction, and FIG. 2(b) is a perspective view seen from the rear side in the liquid flow direction. The bubble generator 1 shown in FIGS. 1(a) and (b) generates minute bubbles, so-called fine bubbles, in a liquid such as water in which a gas such as air is dissolved. Here, fine bubbles refer to minute bubbles of 100 μm or less. Those of 1 μm to 100 μm are microbubbles, and those of several tens of nm to 1 μm (1000 nm) are called ultrafine bubbles (also referred to as "nanobubbles"). However, the fine bubbles in this specification include both of them.

[0022] As shown in FIGS. 2(a) and (b), the bubble generator 1 includes a cylindrical body 2 in which a swirling flow path 10 through which a liquid flows while swirling is formed, and a flange portion 3 formed to project outward in an annular shape at the base end portion (the rear end portion in the liquid flow direction) of the cylindrical body 2. The bubble generator 1 is made of resin and its size is not particularly limited. For example, when used in a shower head 100 as shown in FIG. 1, a faucet in the kitchen, or various other cleaning appliances, etc., it is preferable to set the length of the cylindrical body 2 to 10 to 20 mm and the diameter to 5 to 10 mm. Further, it is preferable to set the diameter of the flange portion 3 to 12 to 20 mm and the thickness to 1 to 3 mm.

[0023] <cylindrical body> The cylindrical body 2 is formed such that the contour of its cross-section is circular and it extends in the axial direction of the central axis with a virtual axis extending in the liquid flow direction (hereinafter referred to as the "liquid flow direction") as the central axis. In FIGS. 2(a) and (b), the liquid flow direction is indicated by a white arrow, and the central axis that coincides with the central axis of the cylindrical body 2 is indicated by a dashed-dotted line with the symbol "CL".

[0024] <swirling flow path> As shown in FIG. 2(a), the swirling flow path 10 has a constricted portion 11 and a pair of opposing surface portions 12. The constricted portion 11 is formed in a constricted shape along a vertical plane perpendicular to the liquid flow direction. That is, the constricted portion 11 includes a pair of curved shape portions 13 that are curved inward so as to approach the central axis line CL, and these curved shape portions 13 are arranged so as to sandwich the central axis line CL in a direction perpendicular to the central axis line CL. The pair of opposing surface portions 12 are arranged to face each other with the constricted portion 11 therebetween when viewed from the liquid flow direction, and are formed to extend in an arc shape along the circumferential direction with the central axis line CL as a reference.

[0025] The swirling flow path 10 further has a pair of expanding portions 14 arranged to connect between the constricted portion 11 (a pair of curved-shaped portions 13) and the pair of opposing faces 12. The pair of expanding portions 14 are formed in a trumpet shape that flares out such that the distance between them increases as they proceed from the pair of curved-shaped portions 13 toward the pair of opposing faces 12. In this way, the swirling flow path 10 is defined and formed by the pair of curved-shaped portions 13, the pair of expanding portions 14, and the pair of opposing faces 12.

[0026] In the present embodiment, the cross-section of the swirling flow path 10 cut along a vertical plane perpendicular to the liquid flow direction is formed in a constricted shape where the central portion is narrower than both end portions in the radial direction of the cylindrical body 2. In this example, the constricted shape appears as a continuous shape of the pair of curved-shaped portions 13, the pair of expanding portions 14, and the pair of opposing faces 12 in a vertical plane perpendicular to the liquid flow direction. Hereinafter, unless otherwise specified, the "radial direction" refers to the radial direction of the cylindrical body 2.

[0027] Examples of the above-mentioned "constricted shape" include, for example, a balance pattern type in which both end portions in the radial direction are formed in the shape of ginkgo leaves, a gourd type in which both end portions in the radial direction are formed in a circular shape, an I-shaped type in which both end portions in the radial direction are formed in an elliptical shape or a rounded square shape, a deformed type in which one end portion in the radial direction is formed in the shape of a ginkgo leaf and the other end portion is formed in a circular shape, an elliptical shape, or a rounded square shape. Thus, by making the central portion in the radial direction narrower and both end portions in the radial direction wider in the cross-section of the swirling flow path 10, the centrifugal force when the liquid swirls in the swirling flow path 10 becomes larger, and the central portion is significantly depressurized. The size of the constricted shape is not particularly limited. For example, when the outer diameter of the cylindrical body 2 is 5 to 10 mm, it is preferable to set the longitudinal length of the constricted shape to 3 to 8 mm and the width of the narrowest portion in the central portion in the radial direction to 1 to 3 mm. From the viewpoint of ensuring the liquid flow velocity necessary to obtain a desired centrifugal force, the area of the cross-section of the swirling flow path 10 on the inlet side is preferably 1 / 15 to 1 / 5, and more preferably 1 / 10 to 1 / 7, of the area of the cross-section of the liquid supply flow path (in this example, the flow path extending from the connector 104 to the male screw portion 101) where the bubble generator 1 is arranged.

[0028] FIG. 3 is an explanatory view of the structure of the swirling flow path 10. As shown in FIG. 3, in the swirling flow path 10, the cross-sectional shape of the flow path, which is a constricted shape obtained by cutting the swirling flow path 10 along a vertical plane perpendicular to the liquid flow direction, is formed in a shape that rotates around the central axis CL along the vertical plane as it advances in the liquid flow direction. Further, in the swirling flow path 10, the distance D between the pair of opposing surfaces 12 is set to increase and the area of the constricted cross-sectional shape of the flow path is set to increase as it advances in the liquid flow direction.

[0029] The degree of rotation of the constricted cross-sectional shape of the flow path can be indicated by the rotation angle of the constricted cross-sectional shape of the flow path with respect to the length of the swirling flow path 10. When advancing 10 mm in the liquid flow direction (the direction in which the central axis CL extends), it is preferably rotated 90 to 180°, and more preferably rotated 90 to 120°. In this example, when advancing 10 mm in the liquid flow direction, the constricted cross-sectional shape of the flow path is set to rotate 90° around the central axis CL. Note that the degree of rotation of the constricted cross-sectional shape of the flow path is also determined by the balance with the liquid pressure of the liquid. When the liquid pressure is relatively high and the flow velocity is large, the rotation angle per 10 mm of the length of the swirling flow path 10 may be relatively small. The above numerical range is suitable when the liquid pressure is 1 to 2 kgf / cm 2 (≈0.1 to 0.2 Mpa: the outlet pressure level of general tap water).

[0030] FIG. 4 is an explanatory view of the cross-sectional area of the swirling flow path 10. FIG. 4(a) is a view showing the cross-section of the bubble generator 1 when viewed from the front side (the outlet side of the swirling flow path 10), and FIG. 4(b) is a view showing the cross-section of the bubble generator 1 when viewed from the back side (the inlet side of the swirling flow path 10). In FIG. 4(a), the cross-section of the swirling flow path 10 on the outlet side is the area indicated by the shaded hatching, and the area of this area is denoted as S1. In FIG. 4(b), the cross-section of the swirling flow path 10 on the inlet side is the area indicated by the shaded hatching, and the area of this area is denoted as S2. In the bubble generator 1 of the present embodiment, the area (S1) is set to be larger than the area (S2).

[0031] Since the speed of the liquid discharged from the swirling flow path 10 is related to the momentum of the liquid, if it is excessively decelerated in the swirling flow path 10, the momentum of the liquid will become too weak to be suitable for use. Therefore, the area ratio (S1 / S2) of the area (S1) to the area (S2) is preferably set to 1.1 to 1.5, and more preferably set to 1.2 to 1.4. Thereby, the balance between the area (S1) and the area (S2) is improved, and while generating more bubbles than in the conventional case (Patent Document 1), the momentum of the liquid can be made suitable for use. In this example, S1 is 20 mm 2 , S2 is 15.4 mm 2 , and the area ratio (S1 / S2) is set to 1.3.

[0032] FIG. 5 is a cross-sectional view taken along the line X-X of FIG. 4(a). As shown in FIG. 5, a pair of inclined portions 15 that incline radially outward of the cylindrical body 2 in the liquid flow direction are formed at the opening edge on the outlet side of the swirling flow path 10 in the cylindrical body 2. The angle formed by the inclined portion 15 with respect to the liquid flow direction, in other words, the angle formed by the inclined portion 15 with respect to the central axis CL, is preferably 20 to 70°, and more preferably 30 to 60°. In this example, the angle is set to 45°. As shown in FIG. 5, the swirling flow path 10 is in the swirling flow path formation region R K between the inclined portion formation region R where the pair of inclined portions 15 are formed in the cylindrical body 2 F and the flange portion formation region R where the flange portion 3 is formed S in the cylindrical body 2. In the present embodiment, the flow path cross-section on the outlet side of the swirling flow path 10 is a cross-section cut along a vertical plane perpendicular to the central axis CL at the boundary position (the position indicated by the arrow marked with the symbol "A" in FIG. 5) between the inclined portion formation region R K and the swirling flow path formation region R S , and the area of this cross-section is S1. Further, the flow path cross-section on the inlet side of the swirling flow path 10 is a cross-section cut along a vertical plane perpendicular to the central axis CL at the boundary position (the position indicated by the arrow marked with the symbol "B" in FIG. 5) between the flange portion formation region R F and the swirling flow path formation region R S , and the area of this cross-section is S2.

[0033] When the angle formed by the inclined portion 15 with respect to the liquid flow direction is too small, most of the liquid discharged from the outlet of the swirling flow path 10 flows straight toward the liquid flow direction, so that bubbles cannot be efficiently dispersed. On the other hand, when the angle formed by the inclined portion 15 with respect to the liquid flow direction is too large, the liquid is excessively decelerated near the outlet of the swirling flow path 10, and the momentum of the liquid becomes too weak to be suitable for use. Therefore, by setting the angle formed by the inclined portion 15 with respect to the liquid flow direction within the above numerical range, the angle formed by the inclined portion 15 with respect to the liquid flow direction becomes appropriate, and bubbles can be efficiently dispersed, and the momentum of the liquid can be made suitable for use.

[0034] Regarding the generation of bubbles by the bubble generator 1 configured as described above, the case where the bubble generator 1 is applied to the shower head 100 shown in Fig. 1(a) will be described as an example. When a liquid (tap water) such as cold water or hot water is supplied to the shower head 100 through the hose 102, the connector 104, and the bubble generator 1, the liquid flows while swirling in the swirling flow path 10 in the bubble generator 1. A centrifugal force acts on the liquid flowing while swirling in the swirling flow path 10, and a pressure difference is generated between the liquid flowing through the constricted portion 11 shown in Fig. 2(a) and the liquid flowing near the pair of opposing surfaces 12. As a result, the liquid flowing through the constricted portion 11 is depressurized. Usually, air is dissolved in tap water, but since it is always in contact with air at atmospheric pressure, it is almost saturated. When such a saturated liquid is depressurized, the solubility decreases, and the amount of gas (air) that can be dissolved decreases. Then, in the liquid flowing through the constricted portion 11, the gas that could not be dissolved is generated as bubbles.

[0035] Incidentally, when the liquid flowing through the swirling flow path 10 is discharged from the swirling flow path 10, the liquid near the outlet of the swirling flow path 10 is pressurized and the pressure increases by colliding with the already discharged liquid. In the bubble generator 1 of the present embodiment, the area (S1: the area of the shaded hatched portion in FIG. 4(a)) of the flow path cross section on the outlet side of the swirling flow path 10 is set larger than the area (S2: the area of the shaded hatched portion in FIG. 4(b)) of the flow path cross section on the inlet side of the swirling flow path 10. As a result, the liquid flowing through the swirling flow path 10 is decelerated and discharged. In this way, even if the decelerated liquid collides with the liquid containing the bubbles already discharged from the swirling flow path 10, the collision energy is small, so that the pressure increase of the liquid containing the bubbles already discharged can be suppressed, and the decrease in the pressure reducing action in the swirling flow path 10 can be suppressed. In addition, more bubbles can be generated than in the conventional case (Patent Document 1).

[0036] Further, in the bubble generator 1 of the present embodiment, as the liquid advances in the liquid flow direction, the distance D (see FIG. 3) between the pair of opposing surfaces 12 increases. Therefore, as the liquid advances in the liquid flow direction, the turning radius of the liquid flowing through the swirling flow path 10 increases. Although this increase in the turning radius is accompanied by a decrease in the turning speed of the liquid, the centrifugal force acting on the liquid is compensated by the increase in the turning radius. In addition, since the area of the flow path cross section of the swirling flow path 10 increases as the liquid advances in the liquid flow direction, the centrifugal force acting on the liquid is strengthened. Furthermore, the liquid flowing through the swirling flow path 10 becomes a turbulent flow state in which the swirling flow is disturbed as the liquid advances in the liquid flow direction due to the interaction between the increase in the turning radius and the increase in the area of the flow path cross section as described above, and the stirring action increases. Thus, by strengthening the centrifugal force acting on the liquid and increasing the stirring action, more bubbles can be efficiently generated and the generated bubbles can be efficiently diffused in the liquid.

[0037] In the swirling flow path 10, as it proceeds in the flowing direction of the liquid, it is formed into a swirling radius and flow path cross-section expanding structure in which the distance between the pair of opposing surface portions 12 increases and the area of the constricted-shaped flow path cross-section increases. As described above, a turbulent flow state is achieved and the stirring action is increased, so that the following effects can be obtained.

[0038] (1) Bubbles can be combined with each other to grow larger. Thereby, for example, dirt substances that cannot float due to insufficient buoyancy in the case of bubbles having a size of about 100 nm in diameter can be floated and separated from the object to be cleaned, and the cleaning effect can be further enhanced. (2) Bubbles having negative ions on the surface can be brought into more efficient contact with Ca ions and Mg ions contained in the liquid (tap water). Thereby, the inactivation of Ca ions and Mg ions can be further promoted. (3) Degassed water can be generated more efficiently.

[0039] As described above, the bubble generator of the present invention has been described based on one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the configuration can be appropriately changed without departing from the gist thereof.

Industrial Applicability

[0040] The bubble generator of the present invention can be effectively used when incorporated into a faucet or a shower head of a water supply for generating fine bubbles so-called fine bubbles.

Explanation of Reference Numerals

[0041] 1 Bubble generator 2 Cylindrical body 10 Swirling flow path 11 Constricted portion 12 Opposing surface portion 15 Inclined portion

Claims

1. A bubble generator comprising a cylindrical body in which a swirling flow path through which a liquid flows while swirling is formed, wherein the swirling flow path has, a constricted portion constricted along a vertical plane perpendicular to the flow direction of the liquid, and a pair of opposing surfaces disposed to face each other so as to sandwich the constricted portion when viewed from the flow direction of the liquid, and a cross-sectional area of the flow path obtained by cutting the swirling flow path along the vertical plane is formed in a shape that rotates along the vertical plane as it advances in the flow direction of the liquid, and an area (S1) of the cross-sectional area of the flow path on the outlet side of the swirling flow path is set to be larger than an area (S2) of the cross-sectional area of the flow path on the inlet side of the swirling flow path.

2. The bubble generator according to claim 1, wherein the swirling flow path is formed such that a distance between the pair of opposing surfaces increases and a cross-sectional area of the flow path increases as the liquid advances in the flow direction.

3. The bubble generator according to claim 1 or 2, wherein an area ratio (S1 / S2) between the area (S1) and the area (S2) is 1.1 to 1.

5.

4. The bubble generator according to claim 1 or 2, wherein an inclined portion that inclines radially outward of the cylindrical body in the flow direction of the liquid is formed at an opening edge on the outlet side of the swirling flow path in the cylindrical body.

5. The bubble generator according to claim 4, wherein an angle formed by the inclined portion with respect to the flow direction of the liquid is 20 to 70°.

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