Submersible aeration apparatus

Abstract

A submersible aeration apparatus (100) includes an air passage (10) formed on an upper side of a pump chamber (20) to draw air into the pump chamber (20); a suction port (30) formed on a lower side of the pump chamber (20) to draw liquid into the pump chamber (20); an impeller (5) configured to draw air through the air passage (10) and liquid through the suction port (30); and an ejection passage (21) formed to eject the air and liquid to the outside. The impeller (5) includes a main plate portion (50) arranged to cover a connection port (22a) connecting the air passage (10) to the pump chamber (20), and a vane portion protruding downward from a lower surface of the main plate portion (50) on the suction port (30) side; and the main plate portion (50) has a cut-out part connecting the air passage (10) and the pump chamber (20) to each other, and a groove part (54) recessed from an upper surface of the main plate portion (50) toward the lower surface and extending from an inner peripheral side toward an outer peripheral side of the main plate portion (50).

Description

Underwater aeration device

[0001] The present invention relates to a submerged aeration device.

[0002] A submerged aeration device has been known in the past, and is disclosed, for example, in Japanese Patent Publication No. 56-11080.

[0003] The above-mentioned Japanese Patent Publication No. 56-11080 discloses an aeration device that includes an air suction impeller for sucking air from the atmosphere, a water pumping impeller for sucking liquid, and a motor that drives the air suction impeller and the water pumping impeller via a single rotating shaft. This aeration device is configured to mix liquid and air inside and discharge the mixture into the external liquid.

[0004] Special Publication No. 56-11080

[0005] Although not explicitly stated in the above-mentioned Japanese Patent Publication No. 56-11080, in the field of underwater aeration devices, it has been desirable to improve the amount of air suction (suction pressure) by the impeller for a given amount of liquid to be introduced in order to perform aeration more efficiently. However, the above-mentioned Japanese Patent Publication No. 56-11080 does not take into consideration improving the amount of air suction (suction pressure) by the impeller for a given amount of liquid to be introduced.

[0006] This invention has been made to solve the above-mentioned problems, and one object of this invention is to provide an underwater aeration device that can improve the amount of air suction (suction pressure) for a given amount of liquid to be introduced.

[0007] In order to achieve the above object, one aspect of the present invention provides an underwater aeration device comprising: an air passage provided above a pump chamber through which air flows in; an inlet provided below the pump chamber through which liquid flows in; an impeller disposed in the pump chamber that rotates to allow air to flow in through the air passage and liquid to flow in through the inlet; and a discharge passage through which the air and liquid that have flowed into the pump chamber are discharged to the outside, wherein the impeller includes a main plate portion that is disposed so as to cover the connection port between the air passage and the pump chamber, and blade portions that protrude downward from the underside of the main plate portion on the inlet side, and the main plate portion is provided with a cutout portion that connects the air passage to the pump chamber, and a concave groove portion that is recessed from the upper surface of the main plate portion toward the underside and extends from the inner side to the outer side of the main plate portion.

[0008] In one aspect of the submersible aeration device of the present invention, as described above, the main plate of the impeller is provided with a notch that connects the air passage to the pump chamber, and a concave groove that is recessed from the upper surface of the main plate toward the underside and extends from the inner periphery to the outer periphery of the main plate. This allows air to flow into the pump chamber through the notch, and the groove generates negative pressure when the impeller rotates, which effectively draws air into the air passage from the atmosphere. In other words, the shape of the impeller, which includes the groove, can improve the amount of air suction (suction pressure). Therefore, the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device can be improved (increased).

[0009] In the submersible aeration device according to the above aspect, preferably, a plurality of grooves are provided at predetermined intervals around the circumferential direction of the impeller. This configuration allows negative pressure to be generated at multiple locations on the impeller by the multiple grooves, thereby allowing air to flow more effectively from the atmosphere into the ventilation passage due to the negative pressure generated at multiple locations. This allows for a greater increase in the amount of air suction (suction pressure) for a given amount of liquid to be introduced into the submersible aeration device.

[0010] In the underwater aeration device according to the above aspect, preferably, a plurality of cutouts and grooves are provided, and the plurality of cutouts and grooves are alternately arranged in the circumferential direction of the impeller. With this configuration, the cutouts and grooves are alternately arranged in the circumferential direction of the impeller, so that air can be introduced into the pump chamber in a balanced manner in the circumferential direction of the impeller, and negative pressure can be generated in a balanced manner in the circumferential direction of the impeller. Therefore, it is possible to suppress the application of uneven force to the impeller in the circumferential direction of the impeller, and the impeller can be rotated efficiently.

[0011] The submersible aeration device according to the above aspect preferably further includes a casing having a pump chamber formed therein, the outer peripheral end of the groove extending to the outer peripheral end face of the main plate, and the impeller configured to allow air to flow from the air passage into the pump chamber through the cutout and into the groove, which then flows into the pump chamber from the groove through a gap between the casing and the outer peripheral end face of the main plate. This configuration allows air to flow into the pump chamber not only through the cutout but also through the gap between the casing and the outer peripheral end face of the main plate. This further improves the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device.

[0012] In this case, it is preferable that a chamfer be provided at the outer peripheral end of the groove. With this configuration, the chamfer allows the air flow path to be gradually reduced in size between the groove and the gap. Therefore, the chamfer can prevent a sudden change in the size of the air flow path, thereby reducing pressure loss when air flows from the groove into the gap.

[0013] In the submersible aeration device according to the above aspect, the depth of the groove is preferably between 1 / 3 and 2 / 3 times the thickness of the main plate. This configuration can prevent a decrease in the strength of the main plate, which would otherwise occur if the depth of the groove were greater than 2 / 3 times the thickness of the main plate. Furthermore, it can prevent the negative pressure generated by the groove from becoming too small, which would otherwise occur if the depth of the groove were less than 1 / 3 of the thickness of the main plate.

[0014] The submersible aeration device according to the above aspect preferably further includes a rotating shaft supporting an impeller, the impeller further including a boss portion coaxial with the rotating shaft and disposed on the inner periphery of the main plate portion, and the inner periphery end of the groove extends to the boss portion. With this configuration, the inner periphery end of the groove can be formed to the boss portion, allowing the groove portion to generate a large negative pressure when the impeller rotates. This allows air to be more effectively introduced into the ventilation passage from the atmosphere. This further improves the amount of air suction (suction pressure) for a given amount of liquid introduced into the submersible aeration device.

[0015] In the underwater aeration device according to the above aspect, the width of the groove is preferably greater than the depth of the groove in the circumferential direction of the main plate. With this configuration, the width of the groove that forms the opening on the air inflow side can be made relatively large, so that air can efficiently flow into the groove.

[0016] In the above-described configuration including a casing having a pump chamber formed therein, the connection port is preferably circularly formed on the inner end surface of the casing, the casing is disposed above the main plate so as to cover the main plate, and includes an annular portion facing the upper surface of the main plate, and in plan view, the outer peripheral portion of the groove is positioned to overlap the annular portion, and the inner peripheral portion of the groove is positioned to overlap the connection port. With this configuration, air can be introduced into the groove from directly above the main plate on the inner peripheral side of the impeller that is outside the annular portion, rather than from above the entire groove. This allows an air flow from the inner peripheral side to the outer peripheral side to be generated in the groove, thereby allowing air to efficiently flow from the groove into the pump chamber via the outer peripheral end of the impeller (groove).

[0017] In the submersible aeration device according to the above aspect, the grooves are preferably curved in an arc shape in plan view. By configuring the grooves in this way, the grooves can be made longer than when they are formed linearly, thereby generating negative pressure over a larger area. This allows for a greater increase in the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device.

[0018] According to the present invention, as described above, it is possible to improve the amount of air suction (suction pressure) for a given amount of liquid to be introduced.

[0019] 1 is a cross-sectional view showing the overall configuration of a submersible aeration device according to an embodiment; FIG. 2 is a perspective view of an impeller of a submersible aeration device according to an embodiment, shown from above; FIG. 3 is a perspective view of an impeller of a submersible aeration device according to an embodiment, shown from below; FIG. 4 is a plan view of an impeller of a submersible aeration device according to an embodiment; FIG. 5 is a partial enlarged view of part A of FIG. 1; FIG. 6 is a graph showing the relationship between water depth and air volume in examples and comparative examples; FIG. 7 is a table showing the relationship between water depth and air volume in examples and comparative examples; FIG. 8 is a plan view of an impeller according to a first modified example; FIG. 9 is a plan view of an impeller according to a second modified example.

[0020] Hereinafter, an embodiment will be described with reference to the drawings.

[0021] 1 to 5, an embodiment of a submersible aeration device 100 will be described. In each figure, the Z1 direction indicates the upper side, the Z2 direction indicates the lower side, and the R direction indicates the circumferential direction of the impeller 5.

[0022] As shown in Figure 1, the submersible aeration device 100 is installed on the bottom of a water storage area such as an aeration tank, and is a device for aerating the water storage area. The submersible aeration device 100 is installed at a relatively deep portion of the water storage area, and is capable of performing deep tank aeration.

[0023] The submerged aeration device 100 is configured to generate negative pressure in the pump chamber (gas-liquid mixing chamber) 20 by rotating the impeller 5 in the pump chamber 20. As a result, the submerged aeration device 100 is configured to allow air to flow in from the atmosphere above the liquid surface in the aeration tank and to allow the liquid in the aeration tank to flow in. The submerged aeration device 100 is configured to mix the air and liquid by rotating the impeller 5 in the pump chamber 20, and then discharge the air and liquid (gas-liquid mixture) into the liquid in the aeration tank. The gas-liquid mixture discharged from the submerged aeration device 100 has a higher amount of dissolved oxygen than the liquid flowing into the submerged aeration device 100.

[0024] The submersible aeration device 100 comprises an aeration chamber (housing) 1, a guide casing 2, and a suction cover 3. The guide casing 2 has a pump chamber 20 formed therein in which an impeller 5 is disposed. The guide casing 2 is an example of the "casing" in the claims.

[0025] The submersible aeration device 100 also includes a motor 4 including a rotating shaft (output shaft) 40 and an impeller 5 .

[0026] (Configuration of the "aeration chamber" of the submersible aeration device) The aeration chamber (housing) 1 is provided with an aeration passage (air chamber) 10 above the pump chamber 20, through which air flows in. The aeration chamber 1 is also provided with an air inlet 11 at the upstream end of the aeration passage 10, which allows air to flow into the interior of the submersible aeration device 100. An aeration conduit P is connected to the air inlet 11 from above. One downstream end of the aeration conduit P is connected to the air inlet 11, and the other upstream end is disposed in the atmosphere above the liquid surface of the aeration tank so that air can flow in. Note that a blower device (air blower) that sends air into the aeration conduit P may be installed at the other upstream end of the aeration conduit P.

[0027] (Configuration of the "guide casing" of the submersible aeration device) The guide casing 2 is attached directly from below to the aeration chamber (housing) 1. In plan view, the guide casing 2 is provided with a plurality of discharge paths 21 extending radially from a central pump chamber (gas-liquid mixing chamber) 20. The discharge paths 21 are paths for discharging the air and liquid (gas-liquid mixture) that flows into the pump chamber 20 and is mixed in the pump chamber 20 into the liquid in the aeration tank.

[0028] The guide casing 2 also includes an annular portion 22 at its upper portion (on the ventilation chamber 1 side). The annular portion 22 is disposed above the main plate portion 50 of the impeller 5 so as to cover the main plate portion 50, and faces the upper surface 50b of the main plate portion 50 from above. The annular portion 22 is disposed apart from the upper surface 50b of the main plate portion 50 by a small gap whose width is in the vertical direction (see FIG. 5). As an example, the size of this gap is 0.5 mm.

[0029] The guide casing 2 (annular portion 22) is provided with a connection port 22a that connects the air passage (air chamber) 10 and the pump chamber 20. The connection port 22a is a circular hole formed in the inner peripheral end surface of the guide casing 2. The circular connection port 22a is located inside the arc-shaped outer edge of the impeller 5 in a plan view. Therefore, the connection port 22a is located directly above the impeller 5. The center position of the connection port 22a substantially coincides with the central rotation axis α of the rotating shaft 40.

[0030] (Configuration of the "suction cover" of the underwater aeration device) The suction cover 3 is attached directly to the guide casing 2 from below. The suction cover 3 is removed from the guide casing 2 when the impeller 5 is attached to or removed from the rotating shaft 40. A pump chamber 20 is arranged above the suction cover 3. The suction cover 3 has a suction port 30, through which liquid flows, below the pump chamber 20. The suction port 30 is a circular hole formed in the inner peripheral end face of the suction cover 3. The suction port 30 is arranged directly below the impeller 5. The center position of the suction port 30 approximately coincides with the central rotation axis α of the rotating shaft 40.

[0031] (Configuration of the "motor including a rotating shaft" of the underwater aeration device) The rotating shaft 40 rotatably supports the impeller 5. More specifically, the impeller 5 is attached to the lower end of the rotating shaft 40 by a fixing member F. The fixing member F is, for example, a bolt. The fixing member F is disposed inside the boss portion 52 of the impeller 5. The rotation direction (RO direction) of the rotating shaft 40 is clockwise (RO direction) in a plan view. The motor 4 has a stator and a rotor that rotatably supports the rotating shaft 40. The motor 4 is configured to drive the impeller 5 to rotate via the rotating shaft 40 to which the impeller 5 is attached.

[0032] An oil chamber 6 in which a mechanical seal 6a is installed is provided along the rotation shaft 40 between the motor 4 and the pump chamber 20 (air passage 10). The mechanical seal 6a has the function of preventing (suppressing) the liquid in the pump chamber 20 (air passage 10) from flowing into the motor 4 side.

[0033] (Configuration of the "Impeller" of the Submersible Aeration Device) The impeller 5 shown in Figures 2 to 4 has the function of introducing liquid and air into the interior of the submersible aeration device 100. The impeller 5 also has the function of mixing the liquid and air inside the submersible aeration device 100. In other words, the impeller 5 has the function of generating a gas-liquid mixture. The impeller 5 also has the function of discharging the mixed liquid and air (gas-liquid mixture) into the liquid outside the submersible aeration device 100.

[0034] The impeller 5 includes a main plate portion (shroud) 50 arranged to cover the connection port 22a between the air passage 10 and the pump chamber 20, multiple (five) blade portions (vanes) 51 protruding downward from the lower surface 50a on the suction port 30 side of the main plate portion 50, and a boss portion 52.

[0035] The main plate 50 extends horizontally and is formed in a disk shape with its thickness generally in the up-down direction. The blades 51 are arranged at equal angular intervals in the circumferential direction (R direction) of the impeller 5. When viewed from below, each blade 51 is formed by a U-shaped curved surface and a flat surface located at the lower end of the U-shaped curved surface.

[0036] The boss portion 52 protrudes upward from the upper surface 50b of the main plate portion 50. The boss portion 52 is arranged coaxially with the rotary shaft 40 and on the inner peripheral side of the main plate portion 50. The boss portion 52 is formed in a hollow cylindrical shape that is open on the lower side. As described above, the fixing member F that attaches the impeller 5 to the rotary shaft 40 is arranged inside the boss portion 52.

[0037] Here, the main plate portion 50 is provided with a plurality of (five) notches 53 and a plurality of (five) grooves 54 .

[0038] The plurality of cutouts 53 are arranged at equal angular intervals in the circumferential direction of the impeller 5. The plurality of grooves 54 are also arranged at equal angular intervals in the circumferential direction of the impeller 5. The plurality of cutouts 53 and the plurality of grooves 54 are arranged alternately in the circumferential direction of the impeller 5.

[0039] (Configuration of "cutout portion" in main plate portion) The cutout portion 53 connects the air passage 10 and the pump chamber 20. The cutout portion 53 cuts out the main plate portion 50 in a U-shape in plan view (viewed from below). The cutout portion 53 extends linearly in the radial direction of the blade portion 51. A portion of the cutout portion 53 is located inside the blade portion 51. The cutout portion 53 is connected to the pump chamber 20 at the end face on the outer periphery of the blade portion 51. The inner peripheral end portion 53a of the cutout portion 53 extends to the boss portion 52. The inner peripheral end portion 53a of the cutout portion 53 is formed in a semicircular shape in plan view.

[0040] (Configuration of "groove" of main plate portion) The groove portion 54 is formed in a concave shape recessed from the upper surface 50b of the main plate portion 50 toward the lower surface 50a of the main plate portion 50. The groove portion 54 extends from the inner periphery side to the outer periphery side of the main plate portion 50.

[0041] The inner peripheral end 54a of the groove 54 extends to the boss 52. The inner peripheral end 54a of the groove 54 is formed in a semicircular shape in a plan view. The outer peripheral end 54b of the groove 54 extends to the outer peripheral end face 50c of the main plate 50. A chamfered portion 54c is provided at the outer peripheral end 54b of the groove 54. The chamfered portion 54c is a so-called C-chamfer. The chamfered portion may have another chamfered shape, such as an R-chamfer.

[0042] Groove 54 is curved in an arc shape in plan view. More specifically, groove 54 is curved such that the portion between inner circumferential end 54 a and outer circumferential end 54 b of groove 54 is positioned closer to the rotation direction (RO direction) of rotating shaft 40 than inner circumferential end 54 a and outer circumferential end 54 b of groove 54 in plan view.

[0043] As an example, the width L1 of the groove 54 shown in Fig. 4 is substantially constant in the circumferential direction (R direction) of the impeller 5. Furthermore, the width L1 of the groove 54 in the circumferential direction of the impeller 5 is greater than the depth L2 (see Fig. 5) of the groove 54 (L1 > L2). As a more specific example, the width L1 of the groove 54 in the circumferential direction of the impeller 5 is substantially equal to the width L10 of the cutout 53 (L1 ≈ L10).

[0044] Also, as an example, the depth L2 of the groove portion 54 shown in Figure 5 is greater than or equal to 1 / 3 and less than or equal to 2 / 3 times the thickness L3 of the main plate portion 50 (L3 x 1 / 3 ≤ L2 ≤ L3 x 2 / 3).

[0045] In plan view, the outer circumferential portion of the groove 54 is positioned so as to overlap with the annular portion 22 of the guide casing 2, and the inner circumferential portion of the groove 54 is positioned so as to overlap with the connection port 22a. In other words, the submersible aeration device 100 is configured to allow air to flow into the pump chamber 20 from a position directly above the impeller 5 on the inner circumferential side of the impeller 5.

[0046] When the impeller 5 rotates, there are two paths through which air flows from the air passage 10 into the pump chamber 20. In detail, the impeller 5 is configured to allow air to flow from the air passage 10 into the pump chamber 20 via the cutout portion 53, and also to allow air to flow from the air passage 10 into the groove portion 54, and then to allow air to flow from the groove portion 54 into the pump chamber 20 via the gap C (see FIG. 5 ) between the guide casing 2 and the outer peripheral end face 50 c of the main plate portion 50.

[0047] In detail, as the impeller 5 rotates, negative pressure is generated inside the groove 54, and air flows from the air passage 10 into the groove 54. The air that has flowed into the groove 54 then flows into the pump chamber 20 through the gap C. As an example, the size of the gap C is 0.5 mm.

[0048] Because the submersible aeration device 100 allows air to flow from the ventilation path 10 into the pump chamber 20 through the cutout 53 and the gap C, the amount of air relative to the amount of liquid flowing into the submersible aeration device 100 can be increased compared to when the impeller is formed without a groove so that air flows into the pump chamber only through the cutout. Therefore, the submersible aeration device 100 can effectively take in air. Therefore, the submersible aeration device 100 can effectively increase the amount of air discharged into the liquid in the aeration tank and the amount of dissolved oxygen in the liquid (gas-liquid mixture).

[0049] (Effects of the embodiment) In the present embodiment, the following effects can be obtained.

[0050] In this embodiment, as described above, the main plate 50 of the impeller 5 is provided with a notch 53 that connects the air passage 10 and the pump chamber 20, and a concave groove 54 that is recessed from the upper surface 50b of the main plate 50 toward the lower surface 50a and extends from the inner periphery to the outer periphery of the main plate 50. This notch 53 allows air to flow into the pump chamber 20, and the groove 54 generates negative pressure when the impeller 5 rotates. This negative pressure effectively draws air from the atmosphere into the air passage 10. In other words, the shape of the impeller 5, i.e., the groove 54, can improve the amount of air suction (suction pressure). Therefore, the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device 100 can be improved (increased).

[0051] In this embodiment, as described above, a plurality of grooves 54 are provided at predetermined intervals around the circumferential direction of the impeller 5. This allows negative pressure to be generated at multiple locations on the impeller 5 by the multiple grooves 54, and the negative pressure generated at multiple locations allows air to flow more effectively from the atmosphere into the ventilation path 10. This makes it possible to further improve the amount of air suction (suction pressure) for a given amount of liquid to be flowed into the submersible aeration device 100.

[0052] In the present embodiment, as described above, a plurality of cutouts 53 and a plurality of grooves 54 are provided, and the plurality of cutouts 53 and the plurality of grooves 54 are arranged alternately in the circumferential direction of the impeller 5. As a result, the cutouts 53 and the grooves 54 are arranged alternately in the circumferential direction of the impeller 5, so that air can be caused to flow into the pump chamber 20 in a balanced manner in the circumferential direction of the impeller 5, and negative pressure can be generated in a balanced manner. Therefore, it is possible to suppress the application of a biased force to the impeller 5 in the circumferential direction of the impeller 5, and the impeller 5 can be rotated efficiently.

[0053] As described above, this embodiment further includes a guide casing 2 having a pump chamber 20 formed therein, and the outer peripheral end 54b of the groove 54 extends to the outer peripheral end face 50c of the main plate 50. The impeller 5 is configured to allow air to flow from the air passage 10 into the pump chamber 20 through the cutout 53, and also to allow air to flow into the groove 54 and into the pump chamber 20 from the groove 54 through the gap C between the guide casing 2 and the outer peripheral end face 50c of the main plate 50. This allows air to flow into the pump chamber 20 not only through the cutout 53 but also through the gap C between the guide casing 2 and the outer peripheral end face 50c of the main plate 50. This allows the air to flow into the pump chamber 20 through the cutout 53 and the gap C between the guide casing 2 and the outer peripheral end face 50c of the main plate 50. This further improves the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device 100.

[0054] In this embodiment, as described above, the outer peripheral end 54b of the groove 54 is provided with a chamfered portion 54c. This allows the chamfered portion 54c to form an air flow path that gradually becomes smaller between the groove 54 and the gap C. Therefore, the chamfered portion 54c can suppress a sudden change in the size of the air flow path, thereby reducing pressure loss when air flows from the groove 54 into the gap C.

[0055] In the present embodiment, as described above, the depth L2 of the groove 54 is greater than or equal to ⅓ and less than or equal to ⅔ times the thickness L3 of the main plate 50. This prevents a decrease in the strength of the main plate 50, which would occur if the depth L2 of the groove 54 were greater than ⅔ times the thickness L3 of the main plate 50. Furthermore, the depth L2 of the groove 54 is less than ⅓ times the thickness L3 of the main plate 50, which would prevent the negative pressure generated by the groove 54 from becoming too small.

[0056] As described above, this embodiment further includes a rotating shaft 40 that supports the impeller 5. The impeller 5 further includes a boss 52 that is coaxial with the rotating shaft 40 and disposed on the inner periphery of the main plate 50, and the inner end 54a of the groove 54 extends to the boss 52. This allows the inner end 54a of the groove 54 to be formed up to the boss 52, allowing the groove 54 to generate a large negative pressure when the impeller 5 rotates. This allows air to flow more effectively from the atmosphere into the ventilation path 10. This therefore further improves the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device 100.

[0057] In the present embodiment, as described above, the width L1 of the groove 54 in the circumferential direction of the main plate 50 is greater than the depth L2 of the groove 54. This allows the width of the groove 54, which forms the opening on the air inflow side, to be relatively large, allowing air to flow into the groove 54 efficiently.

[0058] In the present embodiment, as described above, the connection port 22a is formed in a circular shape on the inner end surface of the guide casing 2, the guide casing 2 is disposed above the main plate 50 so as to cover the main plate 50, and includes the annular portion 22 that is annular and faces the upper surface 50b of the main plate 50, and in a plan view, the outer peripheral portion of the groove 54 is disposed in a position overlapping with the annular portion 22, and the inner peripheral portion of the groove 54 is disposed in a position overlapping with the connection port 22a. This allows air to flow into the groove 54 from directly above the main plate 50 on the inner peripheral side of the impeller 5 that is outside the annular portion 22, rather than from above the entire groove 54. Therefore, an air flow from the inner peripheral side to the outer peripheral side can be generated in the groove 54, and air can efficiently flow from the groove 54 into the pump chamber 20 via the outer peripheral end of the impeller 5 (groove 54).

[0059] In this embodiment, as described above, the grooves 54 are curved in an arc shape in plan view. By curving the grooves 54 in an arc shape, the grooves 54 can be formed longer than when they are formed linearly, thereby generating negative pressure over a larger range. This allows for a greater increase in the amount of air suction (suction pressure) for a given amount of liquid flowing into the submersible aeration device 100.

[0060] Next, an example will be described with reference to FIGS. 6 and 7. FIG.

[0061] In the examples, the installation depth of the submersible aeration device described in the above embodiment was changed in the range of 1.5 [m] to 4.0 [m], and the amount of air flowing in from the inlet of the aeration pipe placed in the atmosphere [Sm ３ / h] (amount of air suction) was measured. The operating conditions of the submerged aeration device of the example were set to an output value to the motor of 0.75 [kW] and a driving frequency of the motor of 60 [Hz]. As described above, the impeller of the submerged aeration device of the example was provided with both grooves and notches.

[0062] As a comparative example, a submersible aeration device with an impeller of a different shape from that of the above-mentioned example was installed at a depth ranging from 1.5 m to 4.0 m, and the amount of air flowing in from the inlet of the aeration pipe placed in the atmosphere was measured. The operating conditions of the submersible aeration device of the comparative example were the same as those of the above-mentioned example. The submersible aeration device of the comparative example has the same configuration as the submersible aeration device of the example, except for the impeller.

[0063] The impeller of the submersible aeration device of the comparative example does not have grooves. The impeller of the submersible aeration device of the comparative example has the same shape as the impeller of the submersible aeration device of the example, except that it does not have grooves.

[0064] <Measurement Results> As shown in Figures 6 and 7, the air volume of the Example was greater than that of the Comparative Example at all installation depths. In detail, at an installation depth of 1.5 m, the air volume of the Example was 10.9 [Sm ３ / h], and the air volume of the comparative example was 8.8 [Sm ３At an installation depth of 2.0 m, the air volume of the example was 10.6 Sm ３ / h], and the air volume of the comparative example was 8.6 [Sm ３ At an installation depth of 2.5 m, the air volume of the example was 8.9 Sm ３ / h], and the air volume of the comparative example was 8.2 [Sm ３ At an installation depth of 3.0 m, the air volume of the example was 7.6 Sm ３ / h], and the air volume of the comparative example is 6.6 [Sm ３ At an installation depth of 3.5 m, the air volume of the example was 6.5 Sm ３ / h], and the air volume of the comparative example was 4.8 [Sm ３ At an installation depth of 4.0 m, the air volume of the example was 5.4 Sm ３ / h], and the air volume of the comparative example was 3.8 [Sm ３ / h].

[0065] The measurement results for the above examples and comparative examples confirmed that providing grooves in addition to notches on the impeller increased the amount of air that flowed in. Furthermore, while the air volume decreased in both the examples and comparative examples as the installation depth increased, it was confirmed that the examples were able to introduce more air at deeper installation depths than the comparative examples. Furthermore, it was found that, at installation depths of 2.5 m or greater, the percentage increase in the air volume of the examples relative to the air volume of the comparative examples tended to increase as the installation depth increased.

[0066] [Modifications] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and further includes all modifications (modifications) within the meaning and scope of the claims.

[0067] For example, in the above embodiment, the grooves are curved so that the portions between the inner and outer circumferential ends of the grooves are positioned closer to the rotation direction (RO direction) of the rotating shaft 40 than the inner and outer circumferential ends of the grooves in a plan view. However, the present invention is not limited to this. In the present invention, for example, as in the impeller 205 shown in FIG. 8 , the grooves 254 may be curved so that the portions between the inner and outer circumferential ends 54 a and 54 b of the grooves 254 are positioned closer to the opposite side of the rotation direction (RO direction) of the rotating shaft 40 than the inner and outer circumferential ends 54 a and 54 b of the grooves 254 in a plan view. In other words, the grooves 254 may be curved in the opposite direction to that in the embodiment.

[0068] 9, the grooves 354 may be formed to extend linearly in the radial direction of the impeller 305. Although not shown, the grooves may be formed to extend linearly in a direction inclined relative to the radial direction of the impeller.

[0069] In the above embodiment, an example in which five grooves and five notches are provided is shown, but the present invention is not limited to this. In the present invention, the number of grooves and the number of notches may be different from five.

[0070] Furthermore, the width of the groove is not limited to the configuration described in the above embodiment, and the width of the groove may be changed to a width different from that in the above embodiment.

[0071] Furthermore, the depth of the grooves is not limited to the configuration described in the above embodiment, and the depth of the grooves may be changed to a depth different from that in the above embodiment.

[0072] In addition, although the above embodiment shows an example in which the plurality of cutouts and the plurality of grooves are arranged alternately, the present invention is not limited to this. In the present invention, the plurality of cutouts and the plurality of grooves do not have to be arranged alternately.

[0073] In the above embodiment, the cutouts are formed on the inside of the blades, but the present invention is not limited to this. In the present invention, the blades and the cutouts may be formed separately.

[0074] 2 Guide casing (casing) 5, 205, 305 Impeller 10 Ventilation path 20 Pump chamber 21 Discharge path 22 Annular portion 22a Connection port 30 Suction port 40 Rotating shaft 50 Main plate portion 50a Lower surface (of main plate portion) 50b Upper surface (of main plate portion) 50c Outer peripheral end surface (of main plate portion) 51 Blade portion 52 Boss portion 53 Notch portion 54, 254, 354 Groove portion 54a Inner peripheral end portion (of groove portion) 54b Outer peripheral end portion (of groove portion) 54c Chamfered portion 100 Underwater aeration device C Gap L1 Width of groove portion L2 Depth of groove portion L3 Thickness of main plate portion

Claims

1. An underwater aeration device comprising: an air passage provided above a pump chamber and through which air flows in; an inlet provided below the pump chamber and through which liquid flows in; an impeller disposed in the pump chamber and rotating to allow air to flow in through the air passage and liquid to flow in from the inlet; and a discharge passage for discharging the air and liquid that have flowed into the pump chamber to the outside, wherein the impeller includes a main plate portion disposed so as to cover a connection port between the air passage and the pump chamber, and blade portions protruding downward from the underside of the main plate portion on the inlet side, and the main plate portion is provided with a notch portion communicating the air passage with the pump chamber, and a concave groove portion recessed from the upper surface of the main plate portion toward the underside and extending from the inner peripheral side to the outer peripheral side of the main plate portion.

2. The underwater aeration device according to claim 1, wherein the grooves are provided in a plurality at predetermined intervals around the circumference of the impeller.

3. An underwater aeration device as described in claim 1 or 2, wherein a plurality of the notches and grooves are provided, and the plurality of the notches and grooves are arranged alternately in the circumferential direction of the impeller.

4. An underwater aeration device as described in any one of claims 1 to 3, further comprising a casing inside which the pump chamber is formed, the outer peripheral end of the groove extending to the outer peripheral end face of the main plate, and the impeller configured to allow air to flow from the air passage into the pump chamber via the cutout, and to allow air to flow into the groove, causing air to flow from the groove into the pump chamber via the gap between the casing and the outer peripheral end face of the main plate.

5. The underwater aeration device according to claim 4, wherein the outer peripheral end of the groove is provided with a chamfered portion.

6. An underwater aeration device as described in any one of claims 1 to 5, wherein the depth of the groove portion is greater than or equal to 1 / 3 and less than or equal to 2 / 3 of the thickness of the main plate portion.

7. An underwater aeration device as claimed in any one of claims 1 to 6, further comprising a rotating shaft that supports the impeller, the impeller further comprising a boss portion that is coaxial with the rotating shaft and that is disposed on the inner periphery of the main plate portion, and the inner periphery end of the groove portion extends to the boss portion.

8. An underwater aeration device as described in any one of claims 1 to 7, wherein the width of the groove portion in the circumferential direction of the main plate portion is greater than the depth of the groove portion.

9. An underwater aeration device as described in claim 4 or 5, wherein the connection port is formed in a circular shape on the inner end surface of the casing, the casing is arranged above the main plate portion so as to cover the main plate portion and includes an annular portion shaped like a ring that faces the upper surface of the main plate portion, and in a plan view, the outer peripheral portion of the groove portion is arranged in a position overlapping with the ring portion, and the inner peripheral portion of the groove portion is arranged in a position overlapping with the connection port.

10. An underwater aeration device according to any one of claims 1 to 9, wherein the groove portion is curved in an arc shape when viewed in a plane.