Aeration device

Abstract

To make a flow of water inside an aeration device smoother, thereby enabling aeration water to be released over a wider area.SOLUTION: An aeration device 1 is moored in water and circulates deep seawater by aeration. The aeration device 1 includes: an inner cylinder 10 in which an upward flow is formed by air lift; an outer cylinder 12 disposed on an outer periphery of the inner cylinder 10 in which a downward flow is formed in a gap between the inner cylinder 10 and the outer cylinder; and a first upper guide portion 20 disposed above the inner cylinder 10 and configured to guide the upward flow so as to convert the upward flow into the downward flow. The first upper guide portion 20 has a conical guide surface 20a whose diameter gradually increases from bottom to top.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an aeration device for supplying oxygen mainly to deep water such as a dam lake for the purpose of improving water quality. [Background technology]

[0002] BACKGROUND ART Aeration devices are known that are moored to the bottom of a reservoir lake or the like and supply oxygen by aeration while absorbing deep water near the bottom of the lake.

[0003] For example, Patent Document 1 discloses an aeration device comprising an air diffuser moored to the lake bottom and a device main body that circulates the upward flow generated by the air released from the air diffuser. The device main body has a double-tube structure and includes an inner tube in which the upward flow is formed and an outer tube in which a downward flow is formed. Straightening plates are provided above the outer and inner tubes, and the upward flow flowing inside the inner tube is converted into a downward flow by moving along the straightening plates from the inner tube to the outer tube (the gap between the inner and outer tubes) at the top of the device main body. A discharge port that opens outward is provided at the lower end of the outer tube, and the downward flow flowing through the outer tube is released into the water through this discharge port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-048616 Summary of the Invention [Problem to be solved by the invention]

[0005] In the aeration device described above, for example, deep seawater is drawn into the inner cylinder from its lower end, rises inside the inner cylinder, changes direction at the upper end of the inner cylinder, descends into the outer cylinder, and is then released into the water from a discharge port at the lower end of the outer cylinder. In this case, the upward flow formed in the inner cylinder can be turbulent, in order to enhance the aeration effect. On the other hand, it is desirable for the downward flow formed in the outer cylinder to be as close to laminar as possible. In other words, it is desirable to suppress a decrease in the flow rate of the downward flow by creating a laminar flow, allowing aerated water with increased dissolved oxygen content to be released (supplied) over a wider area.

[0006] However, since the above-mentioned conventional aeration device is configured to convert an ascending flow into a descending flow by causing the ascending flow to collide with a plate-shaped straightening plate from below, turbulence tends to remain in the descending flow, and it is thought that it is difficult to make the descending flow a laminar flow. Therefore, there is still room for improvement in order to be able to release aerated water over a wider area.

[0007] The present invention has been made in consideration of the above circumstances, and aims to make the flow of water inside an aeration device smoother, and thereby enable the aeration water to be released over a wider area. [Means for solving the problem]

[0008] In order to solve the above problems, an aeration device according to one aspect of the present invention is an aeration device that is moored underwater and circulates mainly deep water by aeration, and includes an inner cylinder in which an ascending current is formed inside by air lift, an outer cylinder that is disposed on the outer periphery of the inner cylinder and in which a descending current is formed in the gap between the inner cylinder and the outer cylinder, and an upper guide portion that is disposed above the inner cylinder and guides the ascending current to convert it into the descending current, and the upper guide portion has a conical guide surface whose diameter gradually increases from bottom to top.

[0009] This aeration device allows the upward flow formed inside the inner cylinder to be smoothly guided from the center of the inner cylinder to the outside (radially outward) along the conical guide surface of the upper guide section. This allows the upward flow to be converted into a downward flow without significant flow disturbance, contributing to the laminarization of the downward flow formed inside the outer cylinder (the gap). As a result, a decrease in the flow velocity of the downward flow is suppressed, making it possible to release the aerated water over a wider area.

[0010] In the above configuration, when the upper guide portion is defined as a first upper guide portion, it is preferable that the configuration further includes a second upper guide portion having a circular ring shape that surrounds the first upper guide portion, and that the second upper guide portion has a guide surface with a V-shaped cross section whose diameter gradually increases from top to bottom.

[0011] With this configuration, the upward flow guided from the center of the inner cylinder to the outside (radially outward) along the conical guide surface of the first upper guide section can be further smoothly guided downward along the guide surface of the second upper guide section. In other words, the flow that converts (reverses) from an upward flow to a downward flow (reverse flow) can be smoothly guided into the outer cylinder. As a result, the laminarization of the downward flow formed inside the outer cylinder is promoted.

[0012] In this case, it is preferable that the first upper guide portion and the second upper guide portion are arranged inside and outside with a gap therebetween.

[0013] With this configuration, excess air separated in the process of converting the ascending flow into a descending flow along the first and second upper guide parts can be easily released upward through the gap between the first and second upper guide parts. In other words, even with the first and second upper guide parts, it is possible to easily move the separated air to an air reservoir or the like provided in the upper part of the device.

[0014] In the aeration device of each of the above aspects, the guide surface of the upper guide portion may be a curved surface that is concave upward.

[0015] According to this configuration, the upward flow is guided along the curved guide surface, and the upward flow can be converted into a downward flow without being disturbed.

[0016] In the aeration device of each of the above aspects, an annular guide portion having a circular cross section may be provided at the upper end of the inner cylinder, which, together with the first upper guide portion, forms a flow path for diverting the upward flow.

[0017] This configuration suppresses the generation of vortexes when the ascending flow is converted into a descending flow at the upper end of the inner cylinder, thereby contributing to laminarization of the descending flow formed inside the outer cylinder.

[0018] In addition, in each of the above-mentioned aspects of the aeration device, a lower guide portion is provided at the lower end of the inner cylinder to guide water that is absorbed into the inner cylinder from the lower end as the upward flow is formed, and the lower guide portion may have a conical guide surface whose diameter gradually decreases from bottom to top.

[0019] With this configuration, as an upward flow is formed by the air lift, water around the lower end of the inner cylinder is sucked along the guide surface of the downstream guide section. In other words, water is prevented from being sucked in from directly below the inner cylinder. This makes it difficult for mud from the bottom of the water to be sucked into the inner cylinder, and prevents an increase in flow resistance of the upward flow due to the sucking of mud. [Effects of the Invention]

[0020] According to the present invention as described above, in the aeration device, it is possible to make the flow of water inside the device smoother, and in turn to release the aerated water over a wider area. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view of an aeration device of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the upper part of the device main body. [Figure 3]3 is a cross-sectional view of the device main body (a cross-sectional view taken along line III-III in FIG. 2) mainly showing the first upper guide portion and the second upper guide portion. FIG. [Figure 4] FIG. 2 is a cross-sectional view of the device body, mainly showing the emission section. [Figure 5] FIG. 2 is a cross-sectional view of the lower end portion of the device main body. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0023] 1 is a longitudinal cross-sectional view of an aeration apparatus 1 according to the present invention, showing the aeration apparatus 1 installed in a dam lake. The aeration apparatus 1 can also be applied to bodies of water where hypoxic water occurs in the lower layers, such as lakes, marshes, bays, aquaculture fishing ports, fish pens, and aquariums, and is not limited to reservoirs such as dam lakes and reservoirs.

[0024] The aeration device 1 is a submerged device installed below the lake surface (water surface), and comprises a device main body 2 moored to the lake bottom (bottom) BL, an aeration device 4 that supplies air into the device main body 2, and an exhaust device 36 that exhausts excess air from the device main body 2. The aeration device 1 is a facility that prevents anaerobic conditions in the deep layers by drawing deep water near the lake bottom BL into the device main body 2 using air lift caused by air (air bubbles) released from the aeration device 4, forming an upward current, and then aerating the water (aerated water) to increase the amount of dissolved oxygen, and releasing this water back into the water.

[0025] The device body 2 is roughly cylindrical overall, and is moored to a sinker 6 installed on the lake bottom BL by a chain 7 connected to its lower end. More specifically, the buoyancy of a float 8 provided on the device body 2 causes it to rise above the lake bottom BL by the connecting length of the chain 7, thereby mooring it in an upright position in the water, i.e., in a vertical, self-supporting state.

[0026] The device body 2 has a double-tube structure including an inner tube 10 that extends vertically and has a circular cross section, and an outer tube 12 that is also circular in cross section and is located outside (radially outward from) the inner tube 10 and extends vertically. The inner tube 10 and the outer tube 12 are concentrically arranged and fixed to each other via a spacer (not shown). A gap is formed between the outer peripheral surface of the inner tube 10 and the inner peripheral surface of the outer tube 12. Within the device body 2, the interior of the inner tube 10 is the passage for the upward flow, and the gap between the inner tube 10 and the outer tube 12 (hereinafter, for convenience, may be referred to as the interior of the outer tube 12) is the passage for the downward flow, i.e., the passage for water that has passed through the upper end of the inner tube 10 and has been converted (reversed) from an upward flow to a downward flow.

[0027] The upper end of the outer cylinder 12 is located higher than the upper end of the inner cylinder 10. The upper end of the outer cylinder 12 is closed by a dome-shaped ceiling 14, and as a result, an air reservoir chamber 15 is formed in the upper end region of the device main body 2. The air reservoir chamber 15 is a space that stores excess air released from the upward flow.

[0028] An inverted water surface is set in the air reservoir chamber 15. By maintaining the position (height) of the inverted water surface at an appropriate level, it becomes possible to switch from an ascending flow to a descending flow, and ultimately to release aerated water from the device main body 2. An exhaust pipe 16 for adjusting the position of the inverted water surface is provided on the ceiling portion 14. The exhaust pipe 16 is connected via a hose 18 to an exhaust device 36 that floats on the lake surface due to the buoyancy of a float 35. The hose 18 is connected to a valve 36a provided on the exhaust device 36. In other words, the pressure in the air reservoir chamber 15 is adjusted by opening and closing the valve 36a so that the position of the inverted water surface is maintained at an appropriate level.

[0029] Reference numeral 17 in Fig. 1 denotes an emergency exhaust pipe 17 equipped with a valve not shown. The emergency exhaust pipe 17 is an emergency device that releases air from the air reservoir chamber 15 into the water if the pressure in the air reservoir chamber 15 rises abnormally (above a set pressure) due to, for example, a problem with the exhaust device 36.

[0030] A first upper guide portion 20 and a second upper guide portion 22 are provided above the inner cylinder 10. These upper guide portions 20, 22 guide the upward flow in the upper part of the inner cylinder 10, thereby converting the upward flow into a downward flow and guiding it into the outer cylinder 12.

[0031] Figure 2 is a vertical cross-sectional view of the upper part of the device main body 2, and Figure 3 is a horizontal cross-sectional view of the device main body 2 (cross-sectional view along line III-III in Figure 2) mainly showing the first upper guide portion and the second upper guide portion.

[0032] 2 and 3, the first upper guide portion 20 has a conical guide surface 20a whose diameter gradually increases from bottom to top. The center of the first upper guide portion 20 is located on the center line O of the inner cylinder 10. The cross-sectional shape of the guide surface 20a is an upwardly concave curved surface (sometimes referred to as a curved surface), preferably an arc-shaped surface (sometimes referred to as an arc surface), as shown in FIG. 2. When the guide surface 20a is an arc-shaped surface, it is preferable that the radius of curvature is approximately the same as the radius of the inner cylinder 10, in which case the center of the radius of curvature is set at the upper end of the inner cylinder 10 or a position nearby.

[0033] The second upper guide portion 22 has an annular shape in a plan view, and is provided concentrically with the first upper guide portion 20 so as to surround the first upper guide portion 20.

[0034] The second upper guide portion 22 has a guide surface 22a with a V-shaped cross section whose diameter gradually increases from top to bottom. The cross section of the guide surface 22a is a curved surface concave upward, preferably an arc-shaped surface, as shown in Figure 2. The height position of the inner edge of the guide surface 22a of the second upper guide portion 22 and the height position of the outer edge of the guide surface 20a of the first upper guide portion 20 are approximately the same.

[0035] The first upper guide portion 20 and the second upper guide portion 22 are disposed inside and outside with a gap therebetween and are connected to each other by connecting portions 24 at multiple different positions in the circumferential direction. In this example, as shown in FIG. 3 , the first upper guide portion 20 and the second upper guide portion 22 are connected to each other at positions spaced 90° apart in the circumferential direction. As a result, multiple arc-shaped openings 25 are formed between the first upper guide portion 20 and the second upper guide portion 22, lined up intermittently in the circumferential direction and each penetrating in the vertical direction. Each opening 25 functions as a passage for allowing excess air released from the upward flow to escape to the air reservoir chamber 15.

[0036] A flow straightening guide 26 (annular guide portion of the present invention) is disposed at the upper end of the inner cylinder 10. The flow straightening guide 26 is a member that has a circular cross section and is annular in plan view, and is integrally joined to the upper end of the inner cylinder 10. The upward flow inside the inner cylinder 10 is converted into a downward flow while passing through a flow path formed between the upper guide portions 20, 22 and the flow straightening guide 26. In other words, the flow straightening guide 26, together with the upper guide portions 20, 22, forms a flow path for converting the upward flow into a downward flow.

[0037] The inner peripheral surface of the flow straightening guide 26 faces the inside of the inner cylinder 10, and the outer peripheral surface faces the outside of the inner cylinder 10. Here, as shown in FIG. 2, the flow straightening guide 26 is provided so that the projection dimension PI of the flow straightening guide 26 toward the inside of the inner cylinder 10 is larger than the projection dimension PO of the flow straightening guide 26 toward the outside. In addition, an auxiliary guide 27 having a triangular cross section is provided at the upper end of the outer peripheral surface of the inner cylinder 10. The auxiliary guide 27 is a member that forms a linear (linear in the cross section) guide surface connecting the position of the maximum diameter of the flow straightening guide 26 and a predetermined position on the outer peripheral surface of the inner cylinder 10 below the position of the maximum diameter of the outer peripheral surface of the flow straightening guide 26, as shown in FIG. 2. By providing such flow straightening guide 26 and auxiliary guide 27 at the upper end of the inner cylinder 10, the generation of a vortex is suppressed in the process of converting an ascending flow into a descending flow.

[0038] As shown in Fig. 1, the inner cylinder 10 extends downward below the lower end of the outer cylinder 12. A discharge portion 28 is provided at the lower end of the outer cylinder 12 as shown in Fig. 4. Fig. 4 is a vertical cross-sectional view of the device main body 2, mainly showing the discharge portion 28.

[0039] The discharge section 28 is a passage that redirects the downward flow formed inside the outer cylinder 12 radially outward from the device body 2 and discharges it into the water. Specifically, a skirt section 12a that widens downward is formed at the lower end of the outer cylinder 12, and a truncated cone-shaped annular member 13 that corresponds to the skirt section 12a is disposed below the skirt section 12a and faces the skirt section 12a. This forms the discharge section 28 that opens radially outward from the device body 2 and has an omnidirectional discharge port 28c that is continuous around the entire circumference. The annular member 13 is joined to the outer peripheral surface of the inner cylinder 10 while being supported from below by a bracket 29.

[0040] 4, the discharge section 28 includes a curved section 28a that is connected to the gap between the inner cylinder 10 and the outer cylinder 12 and is concave downward, and a horizontal section 28b that is continuous with the curved section 28a, extends in a direction perpendicular to the center line O, and has the discharge port 28c at its end. With this configuration, the downward flow that is formed inside the outer cylinder 12, i.e., in the gap between the inner cylinder 10 and the outer cylinder 12, is converted into a radially outward flow and is discharged into the water from the discharge port 28c.

[0041] In order to avoid abrupt changes in the discharge shape and minimize the form resistance of the flow, discharge section 28 is formed so that the water flow passage width (the width in the direction perpendicular to the water flow direction in the cross-sectional view of FIG. 4) is approximately constant from one end to the other. That is, the passage width G2 of curved section 28a and the passage width G3 of the horizontal section are approximately equal, and these passage widths G2 and G3 are formed so that they are approximately equal to the passage width G1 inside outer cylinder 12 (the radial width dimension of the gap between inner cylinder 10 and outer cylinder 12). This configuration minimizes form resistance and makes it possible to discharge water into water from discharge port 28c without disturbing the downward flow inside outer cylinder 12.

[0042] As described above, the inner cylinder 10 extends downward below the lower end (i.e., the discharge portion 28) of the outer cylinder 12. The lower end 10a of the inner cylinder 10 is the receiving portion for deep sea water, and is formed in the shape of an inverted funnel with the inner diameter gradually increasing from top to bottom, as shown in Figure 5. Note that Figure 5 is a vertical cross-sectional view of the lower end of the device main body 2.

[0043] An air diffuser 4 is disposed inside this lower end portion 10a. The air diffuser 4 releases (i.e., diffuses) air (air bubbles) into the interior of the inner cylinder 10. The air diffuser 4 is disposed in the center of the lower end portion 10a of the inner cylinder 10, and is supported by the lower end portion 10a via a bracket (not shown).

[0044] 1, the air diffuser 4 is connected via an air supply hose 5 to a compressor installed on the shore of the dam lake, and discharges compressed air supplied from the compressor into the inner cylinder 10. By discharging air from the air diffuser 4 in this way, an upward flow due to air lift is formed inside the inner cylinder 10.

[0045] A lower guide section 30 is provided below the air diffuser 4. The lower guide section 30 guides deep seawater that is sucked into the inner cylinder 10 from the lower end section 10a as an upward flow is formed by the air lift. The lower guide section 30, together with the air diffuser 4, is supported on the lower end section 10a of the inner cylinder 10 via the bracket.

[0046] 5, the lower guide portion 30 has a conical guide surface 30a whose diameter gradually decreases from the bottom to the top. The center of the lower guide portion 30 is located on the center line O of the inner cylinder 10.

[0047] The cross-sectional shape of the guide surface 30a of the lower guide portion 30 is a curved surface concave downward as shown in FIG. 5, preferably an arcuate surface.

[0048] [Action and effect] In the aeration device 1, air (air bubbles) released from the air diffuser 4 forms an upward flow inside the inner cylinder 10. This upward flow causes deep seawater near the lake bottom BL, i.e., hypoxic water, to be drawn into the inner cylinder 10 from the lower end 10a of the inner cylinder 10. Because the lower end 10a of the inner cylinder 10 is provided with a lower guide portion 30, deep seawater is drawn into the inner cylinder 10 mainly from the periphery of the lower end 10a along the conical guide surface 30a of the lower guide portion 30. This prevents deep seawater from being drawn into the inner cylinder 10 from directly below along the center line O. Therefore, mud from the lake bottom BL is less likely to be drawn into the inner cylinder 10, and an increase in flow resistance of the upward flow due to the suction of mud is suppressed. As a result, a favorable upward flow is formed inside the inner cylinder 10.

[0049] As deep-sea water rises inside the inner cylinder 10, the dissolved oxygen content is increased by aeration. Then, the ascending flow with increased dissolved oxygen content, i.e., aerated water, is converted into a downward flow at the upper end of the inner cylinder 10. At this time, the ascending flow is guided to the outside of the inner cylinder 10 along the conical guide surface of the first upper guide portion 20, specifically the guide surface 20a consisting of a curved surface, and is further guided downward along the V-shaped cross-sectional guide surface of the second upper guide portion 22, specifically the guide surface 22a consisting of a curved surface. Therefore, the ascending flow inside the inner cylinder 10 is smoothly converted into a downward flow and flows into the inside of the outer cylinder 12.

[0050] In this case, by providing the flow straightening guide 26 and auxiliary guide 27 as described above at the upper end of the inner cylinder 10, the upward flow along the inner wall surface of the inner cylinder 10 flows along the auxiliary guide 27 while wrapping around the outside of the inner cylinder 10 along the surface of the flow straightening guide 26, and is converted into a downward flow with almost no turbulence. Therefore, the generation of vortexes when the upward flow converts into a downward flow is suppressed, and the laminarization of the downward flow is promoted. In other words, a decrease in the flow velocity of the downward flow is suppressed.

[0051] When the downward flow reaches the lower end of the outer cylinder 12, it is converted into a horizontal flow along the discharge section 28, i.e., along the curved section 28a and the horizontal section 28b, and is then discharged into the water from the discharge port 28c. In this case, because the passage width of the discharge section 28 (passage width G2 of the curved section 28a and passage width G3 of the horizontal section 28b) is set to be approximately equal to the passage width G1 inside the outer cylinder 12, the downward flow is smoothly converted into a horizontal flow and is discharged from the discharge port 28c without turbulence.

[0052] As described above, the aeration device 1 allows deep seawater absorbed from the lower end 10a of the inner cylinder 10 to flow smoothly inside the device body 2. Therefore, compared to conventional aeration devices (aeration devices of the background art) that convert an ascending flow into a descending flow along a plate-shaped straightening plate, laminarization of the descending flow formed inside the outer cylinder 12 is particularly promoted, and as a result, it becomes possible to release the aerated water over a wider area.

[0053] [Modifications, etc.] The aeration device 1 described above is an example of a preferred embodiment of the present invention, and the specific configuration can be appropriately changed without departing from the gist of the present invention. For example, the following configurations (1) to (3) may be adopted.

[0054] (1) In the above embodiment, the conical guide surface 20a of the first upper guide portion 20 is a curved surface (arcuate surface) having a cross-sectional shape concave upward, as shown in FIG. 2. However, the guide surface 20a may be a general conical surface, i.e., a surface having a linear cross-sectional shape. This also applies to the guide surface 30a of the lower guide portion 30. Furthermore, the cross-sectional shape of the guide surface 22a of the second upper guide portion 22 is not limited to a curved surface (arcuate surface) concave upward, and may also be a surface having a linear cross-sectional shape.

[0055] (2) In the above embodiment, as shown in FIG. 2, the guide surface 22a of the second upper guide portion 22 is smaller than the guide surface 20a of the first upper guide portion 20. That is, in the cross section shown in FIG. 2, the length of the guide surface 22a of the second upper guide portion 22 is shorter than the length of the guide surface 22a of the first upper guide portion 20. However, the sizes of both guide surfaces 20a, 22a may be approximately the same. In this case, the upper guide portions 20, 22 may be formed so that the cross-sectional shapes of the guide surfaces 20a, 22a facing each other on the inside and outside of the inner tube 10 are symmetrical. For example, if the cross-sectional shapes of both guide surfaces 20a, 22a are arcuate surfaces, the upper guide portions 20, 22 may be formed so that the radii of curvature of both guide surfaces 20a, 22a are the same and the lengths of both guide surfaces 20a, 22a are equal. In this case, the radii of curvature may be equal to the radius of the inner tube 10. According to this configuration, the upward flow can be converted more smoothly into a downward flow along both guide surfaces 20a, 22a, which is more advantageous in making the downward flow laminar.

[0056] (3) In the above embodiment, the device body 2 is configured to send excess air in the air reservoir chamber 15 to the exhaust device 36 floating on the lake surface, and exhaust the air from the exhaust device 36 to the atmosphere. However, the device body 2 may also be configured to exhaust the excess air in the air reservoir chamber 15 into the water. With this configuration, aeration by exhausting the air into the water can achieve an aeration effect in the water area between the device body 2 and the lake surface.

[0057] (4) In the above embodiment, the discharge portion 28 is formed so that the passage width (the width in the direction perpendicular to the water flow direction in the cross-sectional view of FIG. 4) is approximately constant, but the passage width of the water flow may be gradually narrowed to maintain the flow velocity of the downward flow. That is, the passage width G2 of the curved portion 28a and the passage width G3 of the horizontal portion 28c may be formed so as to continuously narrow toward the discharge port 28c. [Explanation of symbols]

[0058] 1 Aeration device 2. Device body 4 Air diffuser 10 Inner cylinder 12 outer cylinder 20 First upper guide part 20a, 22a, 30a Guideway 22 Second upper guide part 24 Connecting part 25 Aperture 26 Flow straightening guide section (annular guide section) 27 Auxiliary Guide 28 Emission part 30 Lower guide part

Claims

1. An aeration device that is moored in water and circulates mainly deep water by aeration, an inner cylinder in which an upward flow is formed by air lift; an outer cylinder disposed on the outer periphery of the inner cylinder, and a downward flow is formed in a gap between the outer cylinder and the inner cylinder; an upper guide portion disposed above the inner cylinder and configured to guide the ascending flow to convert the ascending flow into the descending flow; The aeration device is characterized in that the upper guide portion has a conical guide surface whose diameter gradually increases from bottom to top.

2. The aeration device according to claim 1, When the upper guide portion is defined as a first upper guide portion, the apparatus further includes a second upper guide portion having an annular shape and surrounding the first upper guide portion, The aeration device, wherein the second upper guide portion has a guide surface having a V-shaped cross section whose diameter gradually increases from top to bottom.

3. The aeration device according to claim 2, The aeration device, characterized in that the first upper guide portion and the second upper guide portion are arranged inside and outside with a gap between them.

4. The aeration device according to any one of claims 1 to 3, An aeration device, characterized in that the guide surface of the upper guide portion is a curved surface that is concave upward.

5. The aeration device according to any one of claims 1 to 3, An aeration device characterized in that an annular guide portion having a circular cross section is provided at the upper end of the inner cylinder, which forms a flow path for diverting the upward flow together with the first upper guide portion.

6. The aeration device according to any one of claims 1 to 3, a lower guide portion disposed at a lower end of the inner cylinder and configured to guide water drawn into the inner cylinder from the lower end thereof as the upward flow is formed; The aeration device is characterized in that the lower guide portion has a conical guide surface whose diameter gradually decreases from bottom to top.

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