JP2006061817A - Aeration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aeration device which can reduce a pressure loss due to aeration by generating fine bubbles, has high durability, and allows an easy maintenance and inspection. <P>SOLUTION: The aeration device is equipped with an aeration member with metal sheet having a number of fine pores or slits. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to a mass transfer technique from a gas phase to a liquid phase by gas-liquid contact, and more particularly to an air diffuser for efficiently transferring oxygen to a water treatment tank using an aerobic biological reaction.

  Various types of diffuser devices have been proposed for efficiently performing oxygen transfer to a water treatment tank using an aerobic biological reaction.

  For example, Patent Document 1 relates to an improvement of a membrane aeration apparatus in which a membrane having a large number of small holes is attached to a holder to which compressed air is supplied. In order to suppress excessive expansion of the membrane due to compressed air, It is disclosed that a partition frame having 2 to 25 openings is attached at a position slightly above the membrane.

  However, since the air diffuser of Patent Document 1 uses a stretchable synthetic resin or synthetic rubber membrane provided with a large number of small holes as the air diffuser surface, the following (1) to (4) There were drawbacks.

(1) A membrane using a synthetic resin or a synthetic rubber as a material has low durability and is likely to deteriorate when actually used in wastewater.

(2) Since the membrane is inflated by supplying air and the small holes closed by the water pressure are expanded and diffused by the atmospheric pressure, the air chamber pressure rises and the pressure loss due to the diffusion increases.

(3) The resin material for the membrane is weak and easily damaged by construction work during maintenance and inspection.

(4) Since synthetic resins and synthetic rubbers, which are membrane materials, do not have hydrophilic properties, the ability to remove bubbles from the membrane is poor, and fine bubbles cannot be obtained.
JP 2003-320388 A

  It is an object of the present invention to provide an air diffusing device that can generate fine bubbles to reduce pressure loss due to air diffusing, has high durability, and is easy to maintain and inspect.

  The air diffuser according to the present invention includes an air diffuser provided with a thin metal plate having a large number of fine holes or slits.

  The metal thin plate is preferably a pure titanium plate.

  The metal sheet preferably has a superhydrophilic film formed on the surface.

  The super hydrophilic coating is preferably a titanium dioxide coating.

  It is preferable that the diffuser member is formed by stacking two metal thin plates having a plurality of slits arranged in parallel at predetermined intervals so that the slits of the respective metal thin plates intersect.

  It is preferable that the air diffusion member is formed by forming the metal thin plate into a cylindrical shape.

  The cylindrical air diffusion member preferably has an elliptical or streamline cross section.

  It is preferable that the apparatus further includes a water flow generating device that generates a water flow along the air diffusion side surface of the thin metal plate.

  It is preferable to further include a vibration device that vibrates the air diffuser using an air flow.

  It is preferable that the vibration exciter is a whistle that emits a sound having substantially the same frequency as the natural frequency of the air diffuser during air diffusion.

  According to the present invention, it is possible to provide an air diffuser that can generate fine bubbles to reduce pressure loss due to air diffusion, has high durability, and can be easily maintained and inspected.

  Hereinafter, an embodiment of an air diffuser according to the present invention will be described with reference to the drawings.

(First embodiment)
The air diffusion device 10 of the first embodiment includes an air diffusion member made of a porous metal thin plate. In the example of FIG. 1, the air diffusing member (hereinafter referred to as the air diffusing plate 1) is plate-shaped, but it may be cylindrical as shown in FIG.

  As shown in FIGS. 1A and 1B, the disc-shaped diffuser plate 1 is mounted on the upper portion of the casing 4 communicating with the air supply pipe 3 by the diffuser plate pressing ring 2. . As shown in FIG. 1C, a number of fine holes 6 are opened on the upper surface of the diffuser plate 1. These holes 6 are arranged in a lattice shape at equal pitch intervals, and the shape of the openings is circular. A check valve 5 is provided at a connection portion between the air supply pipe 3 and the casing 4 in order to prevent a reverse flow of water to the air supply pipe 3 side.

  When this air diffuser 10 is used, for example, the air diffuser 1 is directed upward in a liquid such as water (including sewage), and a gas such as air is supplied from the air supply pipe 3 to diffuse the air. By passing it through the plate 1, fine bubbles can be generated from the holes 6 provided in the diffuser plate 1 and diffused. Hereinafter, the surface of the diffuser plate 1 on which air bubbles are generated (surface on the diffuser side) is referred to as the diffuser surface.

  For example, when this air diffuser 10 is used in a water treatment tank that utilizes an aerobic biological reaction, fine bubbles can be generated. Therefore, when the same amount of air is supplied, contact between air and sewage The area (area of the gas-liquid contact interface) increases, and the oxygen transfer efficiency can be improved. Hereinafter, an example in which the liquid to be diffused is water and the gas to be supplied is air will be described. However, the present invention is not limited to this example. For example, pure oxygen gas or other gas such as a mixed gas in which two or more of oxygen, nitrogen, hydrogen, and carbon dioxide gas are mixed can be supplied. .

Examples of the metal thin plate include a titanium plate coated with a titanium dioxide film in addition to a stainless steel plate and a pure titanium plate. In general, a metal thin plate has higher strength than a resin or rubber film and plate, and has excellent durability and hydrophilicity. However, a stainless steel plate or a pure titanium plate is particularly excellent in durability in sewage. It has the advantage of being excellent. Among these, it is preferable to use a pure titanium plate as the metal thin plate. This is because titanium has a higher hydrophilicity than other metal materials, so that a liquid phase easily enters between the gas phase and the solid surface (aeration surface), and promotes the detachment of bubbles from the edge of the hole. This is because there is an effect. Due to this effect, the diffuser plate using the pure titanium plate can obtain finer bubbles than the diffuser plate of the same shape using another metal material. The refinement of bubbles leads to a decrease in pressure loss due to aeration. In the air diffuser, when the air supply amount is in the range of 5 to 50 Nm ³ / h / m ² , the pressure loss head for air to form bubbles through the fine holes of the air diffuser plate is 1 It is preferable to be in a range of about ˜5 KPa. This is because by setting the pressure loss head within this range, a sufficient amount of fine bubbles can be generated without increasing the distortion and deflection of the diffuser plate.

  The air diffuser plate may be formed from a single metal thin plate, or a laminate in which a plurality of metal thin plates are stacked may be used as the air diffuser plate. When using a laminate of thin metal plates as the diffuser plate, the thin metal plates may be joined with an adhesive or the like, or may not be joined. In the case of using a laminate that is not joined, for example, it is preferable to prevent the air from leaking out from the periphery by using the above-described diffuser plate pressing ring.

  The thickness of the diffuser plate 1 (the thickness of the metal thin plate when using a single metal plate, the thickness of the laminate when using a laminate of metal thin plates) varies depending on the size of the diffuser. However, it is preferable to make it into the range of 0.3-1 mm. This is because if the thickness of the diffuser plate exceeds 1 mm, it becomes heavy and not only is inconvenient to handle and transport, but also the flow path becomes longer, and the pressure loss may increase. On the other hand, if the thickness of the diffuser plate is less than 0.3 mm, the rigidity is insufficient, so that there is a risk of deformation when air is supplied. Moreover, if the deformation at the time of air supply becomes excessively large, the pressure loss may increase as in the case of conventional products made of resin or rubber.

  The hole can be formed by punching by machining, for example. When a laminate of thin metal plates is used as the diffuser plate, the thin metal plates with holes can be overlapped so that the positions of the holes coincide with each other. it can.

  The hole diameter is determined according to the use conditions and the size of the diffuser plate, but is preferably in the range of 0.01 to 0.3 mm. This is because if the hole diameter is less than 0.01 mm, the pressure loss becomes excessive and bubbles may not come out. On the other hand, if the hole diameter exceeds 0.3 mm, the bubbles may be coarsened. In FIG. 1C, the hole 6 opening in a circular shape is shown, but the opening shape of the hole can be an ellipse, a rectangle, a triangle, a hexagon, other polygons, or an indefinite shape.

  It is preferable that each hole has a uniform size and is formed at uniform intervals. This is because if the pore size and the distance between the holes are made uniform, a uniform mesh can be formed, and a diffused surface like when a sintered metal or a resin porous plate is used as the diffuser plate. This is because it is possible not only to make it difficult for the airflow resistance to be biased but also to prevent bubble polymerization. As a result, uniform and fine bubbles can be generated and diffused from the entire surface of the diffuser surface. In a uniform mesh, all of the adjacent holes are preferably arranged at an equal distance, and the distance between the holes at this time is preferably in the range of 1 mm or more and 5 mm or less. If the distance between the holes is less than 1 mm, the bubbles that have just been generated will be polymerized immediately above the diffuser surface, and fine bubbles may not be formed, and the rigidity of the diffuser plate will be reduced and the durability will deteriorate. Because there is a fear. On the other hand, if the distance between the holes exceeds 5 mm, the amount of bubbles generated may be insufficient.

  As the diffuser plate, a thin metal plate having a large number of slits or a laminate thereof may be used instead of the holes. The slits are preferably formed in parallel at equal intervals.

  The slit width is preferably in the range of 0.02 to 0.2 mm. This is because if the slit width exceeds 0.2 mm, fine bubbles may not be obtained. On the other hand, not only is it difficult to form a slit having a width of less than 0.02 mm, but pressure loss due to air diffusion may increase. In addition, the more preferable range of the slit width is 0.04 to 0.1 mm.

  The slit can be continuous or intermittent. The slits can also be arranged in a staggered manner. When the slits are arranged in a staggered manner, it is preferable that the pitch interval between the adjacent slits facing each other is in the range of 1.5 to 5 mm. If the pitch interval is less than 1.5 mm, the generated bubbles may be polymerized and coarsened, and the rigidity of the diffuser plate may be reduced to deteriorate durability. On the other hand, if the pitch interval exceeds 5 mm, a desired amount of bubbles may not be generated. The most preferable range of the pitch interval of the slit is 2 to 3.5 mm. Within this range, a desired amount of fine bubbles can be generated and necessary rigidity can be ensured.

  Such a slit can be formed by machining, for example. As the diffuser plate, a thin metal plate in which both holes and slits are formed can be used, or a thin metal plate in which holes are formed and a thin metal plate in which slits are formed can be used in an overlapping manner.

  As the diffuser plate, a metal thin plate on which a super-hydrophilic film is formed can be used, and this diffuser plate will be described with reference to FIG. Here, a thin metal plate having holes will be described, but the present invention can also be applied to a thin metal plate having slits.

  The diffuser plate 21 is formed of a thin metal plate 23 coated with a superhydrophilic film 22. The super hydrophilic coating 22 is formed on both surfaces (including the inner surface of the hole) of the thin metal plate 23. This superhydrophilic coating makes it easier for the liquid phase 26 to enter between the gas phase (gas particles 25) and the superhydrophilic coating 22, and the bubbles can be made finer. In FIG. 2, the arrows indicate the direction of air supply. Examples of superhydrophilic materials include various titanium oxides. Of these, titanium dioxide is preferred because of its very high hydrophilicity.

  The diffuser plate 21 is obtained, for example, by coating a thin metal plate or a laminate 23 of a thin metal plate with a superhydrophilic material such as titanium dioxide by vapor deposition or the like. The thickness of the coating 22 is preferably in the range of 1 μm to 20 μm per thin metal plate. If the thickness of the coating exceeds 20 μm, the pore size may decrease and the pressure loss may increase. On the other hand, if the coating thickness is less than 1 μm, the coating may be peeled off during use. is there.

  When a pure titanium plate is used as the metal thin plate, a titanium oxide (eg, titanium dioxide) film can be formed by subjecting the perforated pure titanium plate to heat treatment or oxidation treatment. Since titanium oxide has a higher hydrophilicity than pure titanium, it is possible to achieve further bubble miniaturization. In particular, when heat treatment or oxidation treatment is used, a titanium oxide film can be formed thick, so that high hydrophilicity can be maintained over a long period of time, which is preferable.

  When a laminate of thin metal plates is used as the diffuser plate, holes may be made in the laminate of thin metal plates first, and then a superhydrophilic film may be formed on the surface of the laminate. Alternatively, a superhydrophilic film may be formed on a thin metal plate having holes previously formed, and thereafter, the thin metal plates may be overlapped so that the positions of the holes coincide with each other.

(Second embodiment)
In the example shown in FIG. 1, the diffuser plate having a circular diffuser surface has been described. However, the shape of the diffuser plate is not limited to this, and the disk has various polygonal shapes and an open central portion. And other shapes such as ellipse and gourd. The air diffusing device of the second embodiment will be described with reference to FIG.

  The air diffuser 30 of the second embodiment has a rectangular air diffuser plate 31, and the diffuser plate pressing ring 32 and the casing 33 are adapted to the shape of the air diffuser plate 31, The configuration is the same as that of the air diffuser 10 of FIG. The metal thin plate, the hole, and the slit can be the same as those described with reference to FIGS.

(Third embodiment)
Next, an air diffuser according to a third embodiment of the present invention will be described with reference to FIGS. 4 and 5.

  The air diffusion device 40 of the third embodiment includes an air diffusion plate 41 made of a laminate in which two metal thin plates having a plurality of slits are overlapped. As is clear from FIG. 5 (a), a plurality of parallel slits 42a are formed at a predetermined pitch interval on the thin metal plate (hereinafter referred to as the upper metal thin plate 41a) located on the upper stage of the diffuser plate 41. ing. On the lower surface of the upper metal thin plate 41a, there is a metal thin plate (hereinafter referred to as the lower metal thin plate 41b) having a slit 42b similar to the metal thin plate 41a, and a slit 42a of the metal thin plate 41a and a slit 42b of the metal thin plate 41b. They are arranged so as to be substantially orthogonal. In this manner, the diffuser plate 41 is formed with a square hole having a substantially slit width (hereinafter referred to as an assembly hole 43) at the intersection of the slit 42a and the slit 42b, and the bubbles 44 are scattered from the assembly hole 43. I care. In FIG. 5, the arrow indicates the direction of bubble movement. Except as described above, the air diffuser 40 of FIG. 4 has the same configuration as the air diffuser 10 of FIG. The slit width, pitch interval, and inter-slit distance are preferably within the above ranges for the same reason as described above. The metal thin plate can be the same as that described with reference to FIGS.

  The assembly holes formed in this way can be made smaller in size than the round holes formed by machining when the thickness of the diffuser plate is the same, so that finer bubbles are generated. Has the advantage of being able to. In addition, since the bubble polymerization can be suppressed as compared with the case where a thin metal plate having a slit is used alone, there is an effect that finer bubbles can be generated.

  In the example of FIG. 5, the case where the slits 42 a and 42 b of the upper and lower metal thin plates 41 a and 41 b are intersected at 90 ° and the assembly holes are square has been described, but the assembly hole shape is not limited to this, The shape of the assembly hole can be changed to a rhombus or a parallelogram by variously changing the crossing angle between the slit of the upper metal sheet and the slit of the lower metal sheet other than 90 °. This crossing angle is preferably in the range of 60 ° to 90 °. This is because if the crossing angle is less than 60 °, the diagonal width of the assembly hole becomes too large even if the slit width is within the above range, and fine bubbles may not be obtained. As the crossing angle is closer to 90 °, finer bubbles can be obtained.

  In the example of FIGS. 4 and 5, the case where two metal thin plates are overlapped has been described. However, the number of metal thin plates is not limited to this, and an assembly hole shape can be formed by overlapping three or more metal thin plates. The strength of the diffuser plate can be increased. Here, by forming a plurality of parallel slits on the front and back surfaces of one sheet of metal so as to have an intersecting angle in the range of 60 ° to 90 °, the front side slit and the back side slit Assembly holes can also be formed at the intersections.

(Fourth embodiment)
As shown to (a) and (b) of FIG. 6, the diffuser 60 of 4th embodiment has the shape of the diffuser plate 61 (what overlapped the upper metal thin plate 61a and the lower metal thin plate 61b). Except that the diffuser plate holding ring 62 and the casing 63 are rectangular and conform to the shape of the diffuser plate 61, the configuration is the same as that of the diffuser 40 of FIGS. 4 and 5. . The thin metal plate and the assembly hole can be the same as those described with reference to FIGS.

(Fifth embodiment)
A diffuser according to a fifth embodiment will be described with reference to FIG.

  The air diffuser 70 according to the fifth embodiment includes a diffuser cylinder 71. As shown in (a) of FIG. 7, the scattering cylinder 71 is formed by cylindrically forming a thin metal plate having a large number of fine holes 76. An air supply pipe 73 is connected to the tip of the dust cylinder 71 through a connector 72. A check valve 75 is provided at a connecting portion between the air supply pipe 73 and the connector 72. The other end of the dust cylinder 71 is fitted with a dust cylinder end plate 74 so that the air supplied from the pipe 73 does not leak from the end opening of the dust cylinder 71. Except as described above, the air diffuser 70 of FIG. 7 has the same configuration as the air diffuser 10 of FIG. The metal thin plate, the hole, and the slit can be the same as those described with reference to FIGS.

  In the case of using this air diffuser 70, for example, as shown in FIG. 7A, the air diffuser 71 is disposed in water so that the longitudinal direction of the air diffuser 71 is substantially horizontal, and air is supplied from the air supply pipe 73. Then, fine air bubbles can be generated from the holes 76 by ventilating the diffuser cylinder 71 and diffused.

  Such a scattering cylinder can be produced by first forming a through hole in a thin metal plate and then forming the thin metal plate into a cylindrical shape, or forming the thin metal plate into a cylindrical shape. It can also be produced by perforating thereafter. The same applies to the case where the through slit is formed. In any case, it is preferable that the side portions where the metal thin plates are overlapped are mechanically joined using, for example, welding or using bolts or rivets so that the gas does not leak out.

(Sixth embodiment)
In the example of FIG. 7, the air diffuser having a diffuser cylinder having a simple through hole has been described. However, as shown in FIG. 8, a diffuser cylinder having an assembly hole can also be used.

  As shown in FIGS. 8A and 8B, the air diffuser 80 according to the sixth embodiment is different from the air diffuser 81 shown in FIG. 7 except that the air diffuser 81 has an assembly hole 82. The configuration is the same as that of 70. Such a diffusion cylinder can be produced by, for example, forming the diffusion plate described in FIG. 6 into a cylindrical shape. The scattering cylinder 81 has two large and small cylinders 81a and 81b formed by cylindrically forming a thin metal plate in which a plurality of parallel slits are formed, and the small diameter cylinder 81b is placed in the large diameter cylinder 81a. It can also be produced by insertion.

(Seventh embodiment)
Next, an air diffuser according to a seventh embodiment of the present invention will be described with reference to FIGS. 9 and 10.

  As shown in FIG. 9A, the air diffuser 90 of the seventh embodiment is provided with an annular water flow generator 91 having a shape corresponding to the ring 2 on the upper part of the air diffuser plate pressing ring 2. Except for this, the configuration is the same as that of the air diffuser 10 of FIG. In FIG. 9, an arrow W indicates the direction of water flow. The water flow generator 91 communicates with an external ejection liquid supply source (not shown) via a pipe 96. As is clear from FIG. 9B, the annular water flow generator 91 has a plurality of nozzle holes (not shown) on the inner side surface, and water is ejected from the nozzle holes, so that the diffuser of the diffuser plate 1 is diffused. A water flow W from the outer periphery toward the center along the air surface can be generated. A liquid other than water can be ejected from the water flow generator 91, and this liquid is preferably the same as the liquid to be diffused.

  As shown in FIG. 10 (b), when air is supplied to the diffuser plate 1, gas particles 94 start to come out from the holes 6, and when the gas particles 94 reach a certain size, As a single bubble 95, it separates from the diffuser surface and rises. In FIG. 10, the arrow W indicates the water flow direction, and the arrow X indicates the air supply direction. As shown in FIG. 10 (a), when a flow along the diffuser surface is generated immediately above the diffuser surface of the diffuser plate 1, gas particles 92 before separation formed on the diffuser surface are formed. Resistance in the direction of water flow works. Due to this resistance, the gas particles 92 leave the diffuser surface more quickly than when there is no flow, so that finer bubbles 93 can be generated. This embodiment can also be applied to the air diffuser 40 of FIG.

(Eighth embodiment)
In the example of FIG. 9, although the case where the water flow which goes to the center part from the outer periphery of a diffuser plate was demonstrated was demonstrated, the water flow direction is not restricted only to this. An air diffuser according to an eighth embodiment will be described with reference to FIG.

  As shown in FIG. 11A, the air diffuser 110 according to the eighth embodiment is a disk-shaped air diffuser plate 111 having a circular opening at the center, and a cylindrical water flow generator 112. 1 is configured in the same manner as the air diffuser 10 of FIG. 1 except that is inserted into the central opening of the air diffuser plate 111. This water flow generator 112 communicates with an external ejection liquid supply source (not shown) via a pipe 113. For example, the pipe 113 extends from the water flow generator 112 to the inside of the casing 114 having the same structure as the casing 4 described with reference to FIG. 1, and is drawn out from the side surface of the casing 114 to the outside. As is clear from FIG. 11B, the water flow generator 112 has a plurality of nozzle holes (not shown) on the outer surface, and the air diffused surface of the diffuser plate 111 is formed by ejecting water from the nozzle holes. A water flow from the central part to the outer periphery can be generated along the line. In addition, in FIG. 11, the arrow has shown the water flow direction. This embodiment can also be applied to the air diffuser described with reference to FIGS. 4 and 9.

(Ninth embodiment)
The air diffusing device of the ninth embodiment will be described with reference to FIG.

  The air diffuser 120 of the ninth embodiment is the same as the air diffuser 90 of FIG. 9 except that the annular water flow generator 121 is semicircular as shown in FIG. It is configured. According to this water flow generator 121, it is possible to generate a water flow along the air diffusion surface from the water flow generator side toward the other side. In FIG. 12, the arrow indicates the direction of water flow. This embodiment can also be applied to the air diffuser described with reference to FIGS.

  9-12, although the air diffusing device provided with the disk-shaped air diffusing plate has been described, as shown in FIGS. 13-15, the air diffusing device provided with the rectangular air diffusing plate or the air diffusing cylinder may also be used. Each can be equipped with a water flow generator.

(Tenth embodiment)
As shown in FIGS. 13A and 13B, the air diffuser 130 of the tenth embodiment has a shape conforming to the ring 133 on one long side of the square air diffuser plate pressing ring 133. The configuration is the same as that of the air diffuser 30 in FIG. 3 except that an elongated rectangular column-shaped water flow generator 131 is fitted. The water flow generator 131 communicates with an external ejection liquid supply source (not shown) via a pipe 132. According to this water flow generation device 131, it is possible to generate a water flow along the air diffusion surface from the long side where the water flow generation device 131 is installed toward the other long side. In FIG. 13, the arrow indicates the direction of water flow. The water flow generator can be installed on both long sides of the diffuser plate pressing ring 32, or can be installed on one or both short sides. This embodiment can also be applied to the air diffuser 60 of FIG.

(Eleventh embodiment)
As shown in FIGS. 14A and 14B, the air diffuser 140 of the eleventh embodiment surrounds the outer periphery of the coupler 72 provided at the end of the diffuser cylinder 71 on the piping side. 7 except that the ring-shaped water flow generating device 141 is fitted. The water flow generator 141 communicates with an external ejection liquid supply source (not shown) via a pipe 142. In FIG. 14, the arrow indicates the direction of water flow. As is clear from FIG. 14B, the water flow generator 141 has a plurality of nozzle holes 143 that open to the side of the scattering cylinder, and by ejecting water from the nozzle holes 143, A longitudinal water flow can be generated along the outer peripheral surface. The water flow generator can also be provided on the end of the dust cylinder 71 opposite to the pipe side, for example, on the dust cylinder end plate 74. This embodiment can also be applied to the air diffuser 80 of FIG.

(Twelfth embodiment)
As shown in FIGS. 15 (a) and 15 (b), the air diffuser 150 of the twelfth embodiment has an elongated prismatic shape below the diffuser cylinder 71 arranged so that its longitudinal direction is substantially horizontal. The water flow generator 151 is provided in parallel with the scattering cylinder 71. This water flow generator 151 is disposed so as to have a gap between it and the diffuser cylinder 71, and communicates with an external ejection liquid supply source (not shown) via a pipe 152. Except as described above, the air diffuser 150 has the same configuration as the air diffuser 70 of FIG. As is clear from FIG. 15B, the water flow generator 151 has a plurality of upward nozzle holes (not shown), and can generate an upward water flow by ejecting water from the nozzle holes. In FIG. 15, the arrows indicate the direction of water flow. This water flow is divided into two flows when it hits the lower part of the scattering cylinder 71, and becomes a flow substantially perpendicular to the longitudinal direction of the scattering cylinder 71 along the outer peripheral surface of the scattering cylinder 71. This embodiment can also be applied to the air diffuser described with reference to FIGS.

  Next, an air diffusing device including a plurality of air diffusing plates or air diffusing cylinders will be described with reference to FIGS.

(Thirteenth embodiment)
As shown in FIG. 16, the air diffuser 160 of the thirteenth embodiment includes, for example, four air diffusers 161, 162, 163, and 164. These air diffusion units 161 to 164 have the same structure as the air diffusion device 10 of FIG. 1, and are arranged in parallel so that the air diffusion surfaces face upward and are substantially horizontal to each other. Yes. The air supply pipes of the air diffusion units 161 to 164 communicate with a common air supply pipe 165. A water flow generator 166 that communicates with an external jet liquid supply source (not shown) is installed on the side of the outermost air diffuser unit 161 among the air diffusers 161-164. The water flow generator 166 has an elongated discharge port 167 for ejecting liquid vigorously, and the discharge port 167 is disposed so as to be horizontal to the air diffusion surface. The water flow along the air diffusing surfaces of the air diffusing plates of the four air diffusing units 161 to 164 can be generated by the injection from the discharge ports. In FIG. 16, the arrow Y indicates the direction of movement of bubbles, and the arrow W indicates the direction of water flow. These air diffusion units 161 to 164 can be configured in the same manner as the air diffusion devices described in FIGS. 3, 4, 6, 9, and 11 to 13.

  A liquid other than water can be ejected from the water flow generator described above, and this liquid is preferably the same as the liquid to be diffused.

(14th embodiment)
As shown in FIG. 17, the air diffuser 170 of the fourteenth embodiment is different from the air diffuser 160 of FIG. 16 except that the water flow generator 171 generates a water flow by means of the liquid propeller 172. It has the same configuration. The water flow generator 171 can generate a water flow along the air diffusion surfaces of the air diffusion plates of the four air diffusion units 161 to 164 by rotating the sub propeller 172. In FIG. 17, the arrow Y indicates the direction of movement of the bubbles, and the arrow W indicates the direction of water flow and the range in which the water flow occurs (substantially the same range as the range having the entire length of the propeller).

(Fifteenth embodiment)
As shown in FIGS. 18A and 18B, the air diffuser 180 of the fifteenth embodiment includes, for example, five air diffusers 181, 182, 183, 184, and 185 each having a diffuser cylinder. . These air diffusers 181 to 185 have the same configuration as the air diffuser 70 of FIG. 7, and the air diffusers are arranged in parallel so that the longitudinal direction of the air diffuser is substantially horizontal. . The air supply pipes of the air diffusion units 181 to 185 communicate with the common pipe 186. A water flow generator 187 communicating with an external jet liquid supply source (not shown) is installed on the side of the outermost air diffuser unit 181 among the air diffusers 181 to 185. The water flow generator 187 has an elongated discharge port 188 that jets water vigorously, and the discharge port 188 is arranged so as to be horizontal to the scattering cylinder. As apparent from FIG. 18 (b), when the water flow hits the side of the diffuser cylinder of the air diffuser unit 181 closest to the discharge port 188 by the injection from the discharge port 188, the water flow is divided into two flows. It flows along the tangent of the diffuser surface outside the cylinders 181 to 185. In FIG. 18, the arrow Y indicates the direction of bubble generation, and the arrow W indicates the direction of water flow. A liquid other than water can be ejected from the water flow generator described above, and this liquid is preferably the same as the liquid to be diffused. The air diffusion units 181 to 185 may have the same configuration as that of the air diffusion device described with reference to FIGS.

(Sixteenth embodiment)
In the example of FIG. 7, the air diffusion device including a diffuser cylinder having a circular cross section has been described. However, as illustrated in FIGS. 19 and 20, the cross sectional shape of the diffuser cylinder can be elliptical or streamlined.

  As shown in FIGS. 19A and 19B, the air diffusing device 190 of the sixteenth embodiment includes five air diffusing units 191, 192, 193, 194, 195 each having a diffused cylinder. In each of the aeration units 191 to 195, the diffusion cylinders are arranged in parallel so that the longitudinal direction of the diffusion cylinders is substantially horizontal. The diffuser unit 191 has an elliptical cross section of the diffuser cylinder 196, and a connector 197 at the tip of the diffuser cylinder 196 and an end plate 198 for the other end of the diffuser cylinder 196 conform to the shape of the diffuser cylinder 196. Except for this, the configuration is the same as that of the air diffuser 70 of FIG. The air diffusers 192 to 195 have the same configuration as the air diffuser unit 191. In FIG. 19, arrow Y indicates the direction of bubble generation, and arrows W1 and W2 indicate the direction of water flow.

  As shown in FIG. 19B, in this air diffuser 190, bubbles released one after another in the direction of arrow Y from the surface of the diffused cylinder move upward due to buoyancy, and liquid (for example, , Water). By making the cross-sectional shape of the diffusion cylinder into an ellipse having a long axis in the rising direction of the bubbles, the upward flow can be changed into a flow W1 in the tangential direction on the surface of the diffusion cylinder and a flow W2 along the diffusion surface. it can. As a result, as described in FIG. 10A, shearing stress substantially parallel to the air diffused surface due to the water flow can be applied to the gas particles adhering to the air diffused surface due to surface tension. Compared to the case where there is no air, it can be removed from the diffuser surface more quickly. As a result, finer bubbles can be diffused at shorter intervals. The air diffusers 191 to 195 can also have the same configuration as the air diffuser described with reference to FIGS. 8, 14, and 15. This embodiment can also be applied to the air diffuser 180 of FIG.

(Seventeenth embodiment)
As shown in FIGS. 20A and 20B, the air diffuser 200 according to the seventeenth embodiment includes five air diffusers 201, 202, 203, 204, 205 each having a diffuser cylinder. In each of the aeration units 201 to 205, the diffusion cylinders are arranged in parallel so that the longitudinal direction of the diffusion cylinders is substantially horizontal. The air diffuser unit 201 is a streamline in which the cross section of the air diffuser 206 has a long axis in the rising direction of the bubbles, and the upper side is narrower, the connector 207 at the tip of the air diffuser 206 and the other end Except that the diffuser cylinder end plate 208 conforms to the shape of the diffuser cylinder 206, it has the same configuration as the diffuser 70 of FIG. The air diffusion units 202 to 205 have the same configuration as the air diffusion unit 201. In FIG. 20, the arrow Y indicates the direction of bubble movement, and the arrows W1 and W2 indicate the direction of water flow. Except for what has been described above, the air diffuser 200 has the same configuration as the air diffuser 190, and the same effects as the air diffuser 190 can be obtained.

  As described above with reference to FIGS. 19 and 20, by making the cross section of the diffused cylinder elliptical or streamlined, it is possible to obtain the same effect as that of the diffuser including the water flow generator.

(Eighteenth embodiment)
As shown in FIGS. 21A and 21B, the air diffuser 210 according to the eighteenth embodiment is added to the downstream side of the check valve 5 at the connecting portion of the casing 4 and the air supply pipe 3. Except that a whistle 211 is provided as a vibration device, the configuration is the same as that of the air diffuser 10 of FIG.

  The whistle 211 can emit a sound having substantially the same frequency as the natural frequency when the diffuser plate 1 is diffused. When air is supplied from the intake pipe 5, the whistle 211 emits a sound, which can vibrate the diffuser plate 1 and the gas particles adhering to the diffuser plate 1 (non-detached bubbles). it can. By this vibration, it is possible to shorten the time until the gas particles are detached from the diffuser plate 1, and it is possible to diffuse finer bubbles at shorter intervals. In particular, when the thickness of the diffuser plate 1 is in the range of 0.1 to 1 mm, the natural frequency of the diffuser plate 1 is often within the frequency range of the audible sound. 210 is suitable for practical use. In FIG. 21, the arrows indicate the air supply direction. FIG. 21 illustrates an example in which the whistle 211 as a vibration device is provided inside the casing 4. However, the position of the vibration device is not limited to this, and for example, the whistle 211 is connected to the intake pipe 3. It can also be provided in the opening on the diffuser plate 1 side.

  FIG. 21 illustrates an example in which a whistle is used as the vibration device. However, the vibration device is not limited to this, and any device that can vibrate the diffuser member using an air current is used. May be used. FIG. 22 shows an air diffuser using a Karman vortex generator as a vibrating device.

(Nineteenth embodiment)
As shown in FIGS. 22A and 22B, the air diffuser 220 according to the nineteenth embodiment has a disk shape in which the air diffuser plate 221 has an opening at the center, and the vibration is applied to the opening. A Karman vortex generator 222 is fitted as a device. The Karman vortex generator 222 has a support member 223, which is fixed to the diffuser plate 221. The support member 223 is provided with two sets of columnar members 225 connected to a column 224 extending toward the air supply pipe 3 so as to be perpendicular to the airflow. In FIG. 22, the arrow indicates the direction of air supply. Except as described above, the air diffuser 220 has the same configuration as the air diffuser 10 in FIG.

  When the air diffuser 220 is supplied with air from the intake pipe 3, Karman vortices are generated on the downstream side of the columnar member 225 along with the air flow, thereby adhering to the air diffuser plate 221 and the air diffuser plate 221. The gas particles (undetached bubbles) can be vibrated. In the example of FIG. 22, the air diffusion device provided with two columnar members has been described. However, the present invention is not limited to this, and the number of columnar members may be one or three or more. Good. This embodiment can also be applied to the air diffuser described with reference to FIGS.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

[Example]
Embodiments of the present invention will be described below with reference to FIGS. 1, 4, 23, 24 and 25. FIG.

<Assembly of the diffuser>
(Example 1, Comparative Example 1)
Example 1
A circular stainless steel plate (steel type: SUS304) having a thickness of 0.3 mm and a diameter of 15 cm was mechanically punched to form a large number of round holes to obtain a diffuser plate. At this time, holes were formed so that all of the adjacent holes were arranged at regular triangle pitch intervals to obtain a uniform mesh diffuser plate. The hole diameter was 0.25 mm, and the distance between holes was about 1.5 mm.

  The obtained diffuser plate was fixed to the upper part of the stainless steel casing connected to the air supply pipe with a diffuser plate pressing ring, and the diffuser having the structure shown in FIG. 1 was assembled. At this time, the diameter of the diffuser surface was 13 cm.

(Comparative Example 1)
A diffuser was assembled in the same manner as in Example 1 except that a disc-shaped resin plate (material: hard nylon) having a thickness of about 1.2 mm and a diameter of 15 cm was used instead of the stainless steel plate.

<Performance test>
As will be described below, the bubble size distribution generated was confirmed using the air diffusers of Example 1 and Comparative Example 1.

  Taking a diffuser into the water with the diffuser surface facing upward, and taking a picture with a single flash in a dark place while supplying air from the intake pipe at a flow rate of 10 L / min. went. In the field of view of the obtained photographic image, a range corresponding to 3 cm each (6 cm in total) from right above the diffuser surface to 3 cm above and from the center of the diffuser surface is defined as the measurement range, and is reflected within this range. The diameter of all bubbles was measured, and the relative frequency for each bubble diameter was calculated. The result is shown in FIG. In FIG. 24, the horizontal axis indicates the range of bubble diameter (mm), and the vertical axis indicates the relative frequency (%) with respect to the total number of bubbles in the measurement range.

  As is clear from FIG. 24, in the air diffuser of Example 1, the relative frequency of the small diameter bubbles in the range of 0.5 to 1.5 mm among the generated bubbles is high, and finer bubbles. Could be generated.

  On the other hand, in the air diffuser of Comparative Example 1, the relative frequency of relatively large bubbles having a diameter in the range of 1.5 to 2.0 mm among the generated bubbles is high, and the diameter is 0.5 to 1.0 mm. Fine bubbles within the range of could not be generated.

  By the way, in the diffuser plate of the comparative example 1, since the resin plate is used, although durability is low compared with the diffuser plate of Example 1, durability is low. The air diffuser of Example 1 using a thin metal plate as the air diffuser can greatly improve the durability as compared with those made of resin or rubber. Moreover, since the thickness of the diffuser plate is thinner than that of Comparative Example 1, the air diffuser of Example 1 has a short flow path and can reduce pressure loss. Furthermore, since the holes formed in the diffuser plate are not closed by water pressure, pressure loss can be reduced even when compared with an air diffuser using a resin film. Furthermore, since the metal thin plate has sufficient mechanical strength, it is possible to greatly reduce the possibility of being damaged even in maintenance and inspection work.

(Examples 2 to 6)
(Example 2)
A disk-shaped stainless steel plate (steel type: SUS304) having a thickness of 0.3 mm and a diameter of 15 cm was mechanically processed to form a number of parallel staggered slits to obtain a diffuser plate. At this time, the slit width is 0.1 mm, the pitch interval between adjacent slits is 3 mm, and the distance between the slits (the distance between the slit and the slit on the straight line obtained by extending the slit in the longitudinal direction) is The length was 3 to 4 mm (slit length was 3 mm). A diffuser was assembled in the same manner as in Example 1 except that this diffuser plate was used.

(Example 3)
An air diffuser was assembled in the same manner as in Example 2 except that a pure titanium plate (purity: 99.5%) was used instead of the stainless steel plate.

Example 4
A slit was formed on a pure titanium plate having the same thickness and diameter as the stainless steel plate used in Example 2, and then a titanium dioxide film was coated to obtain a diffuser plate. At this time, the coating of the titanium dioxide film was performed as described below.

The pure titanium plate on which the slit is formed is subjected to pretreatment washing and drying, and then attached to a jig and placed in a vacuum kettle, and the titanium dioxide (TiO ₂ ) particles are evaporated from the tungsten port of the vapor deposition apparatus at 1800 ° C. A titanium dioxide film was formed by vapor deposition on a pure titanium plate. The thickness of the titanium dioxide coating was about 2 μm.

  A diffuser was assembled in the same manner as in Example 2 except that the obtained diffuser plate was used.

(Example 5)
Two pure titanium plates having the same thickness and diameter as the stainless steel plate used in Example 2 were prepared, and slits were formed in the same manner as in Example 2. These pure titanium plates were coated with a titanium dioxide film in the same manner as in Example 4, and overlapped so that the slits were orthogonal to each other to obtain a diffuser plate. The obtained diffuser plate was fixed to the upper part of the stainless steel casing connected to the intake pipe with a diffuser plate pressing ring, thereby assembling the diffuser having the structure shown in FIG.

(Example 6)
An air diffuser having a structure described below was assembled using an air diffuser plate obtained in the same manner as in Example 5.

  As shown in FIGS. 23A and 23B, the air diffuser 230 according to the sixth embodiment includes an air diffuser unit 231 and a water flow generator 232. The air diffuser unit 231 has the same configuration as the air diffuser 210 in FIG. 21 except that the air diffuser plate 233 is obtained in the same manner as in the fifth embodiment. As the whistle 211, one that emits a sound having a frequency of about 500 Hz was used. The water flow generator 232 has a length substantially the same as the diameter of the diffuser plate 233, and has a discharge port 234 for jetting water vigorously, and this discharge port 234 is substantially horizontal to the diffuser surface. It installed so that it might become. This water flow generator 232 communicates with an external jet liquid supply source (not shown). In FIG. 23, an arrow W indicates a water flow direction, and an arrow X indicates an air supply direction.

<Performance test>
The distribution of the bubble diameter generated in the same manner as in the air diffuser of Example 1 was confirmed using the air diffuser of Examples 2 to 6. The result is shown in FIG. In FIG. 25, the horizontal axis indicates the range of bubble diameter (mm), and the vertical axis indicates the relative frequency (%) with respect to the total number of bubbles in the measurement range.

  As for Example 6, the water flow generator 232 is activated at the time of air diffusion and water is injected from the discharge port 234 at a flow velocity of about 0.5 m / second at the outlet of the water flow generator, so that the water is scattered just above the air diffuser plate 231. It was confirmed that the water flow along the air surface was generated, and also that the sound was emitted from the whistle 211.

  As is clear from FIG. 25, the air diffusers of Examples 2 to 6 have a high relative frequency of small diameter bubbles, and were able to generate finer bubbles.

  Moreover, the air diffuser of Example 3 using the pure titanium plate which has a slit exists in the range of 0.5-1.5 mm in diameter compared with the air diffuser of Example 2 using a stainless steel plate. The relative frequency of small diameter bubbles was high, and finer bubbles could be generated. This is considered to be due to the high hydrophilicity of pure titanium.

  The air diffuser of Example 4 in which a titanium dioxide film was formed on a pure titanium plate having a slit had a diameter of 0.5 to 1.5 mm as compared to the air diffuser of Example 3 in which no film was formed. The relative frequency of the small diameter bubbles in the range was high, and finer bubbles could be generated. This is probably because titanium dioxide has a very high hydrophilicity.

  The diffuser of Example 5 in which two pure titanium plates having slits are overlapped has a diameter of 0.5 to 5 compared to the diffuser of Example 4 using a pure titanium plate having slits alone. The relative frequency of the small diameter bubbles in the range of 1.5 mm was high, and finer bubbles could be generated. This is considered to be due to the fact that fine assembly holes can be formed by combining slits.

  The air diffuser of Example 6 equipped with the water flow generator and the vibration generator is a small-sized bubble having a diameter in the range of 0.5 to 1.0 mm compared to the air diffuser of Example 5 not equipped with these. The relative frequency of was high, and finer bubbles could be generated. This is considered due to the fact that the time for the bubbles to leave the diffuser plate can be shortened by the water flow and vibration.

1A is a plan view of the air diffuser according to the first embodiment of the present invention, and FIG. 1B is along the line Ib-Ib of the air diffuser of FIG. FIG. 1C is an enlarged view of part c of the air diffuser of FIG. 1A. The cross-sectional enlarged view of the diffuser board for demonstrating a super hydrophilic film. 3A is a plan view of the air diffuser according to the second embodiment of the present invention, and FIG. 3B is along the line IIIb-IIIb of the air diffuser of FIG. Side partial sectional view. 4A is a plan view of the air diffuser according to the third embodiment of the present invention, and FIG. 4B is along the line IVb-IVb of the air diffuser of FIG. 4A. Side partial sectional view. FIG. 5A is a perspective view of a diffuser plate for explaining the diffuser of FIG. 4, and FIG. 5B is an enlarged view of a portion b of the diffuser plate of FIG. . 6A is a plan view of the air diffuser according to the fourth embodiment of the present invention, and FIG. 6B is along the line VIb-VIb of the air diffuser of FIG. 6A. Side partial sectional view. FIG. 7A is a side view of the air diffuser according to the fifth embodiment of the present invention, and FIG. 7B is along the line VIIb-VIIb of the air diffuser of FIG. Sectional view. 8A is a side view of the air diffuser according to the sixth embodiment of the present invention, and FIG. 8B is along the line VIIIb-VIIIb of the air diffuser of FIG. 8A. Sectional view. FIG. 9A is a plan view of the air diffuser according to the seventh embodiment of the present invention, and FIG. 9B is along the line IXb-IXb of the air diffuser of FIG. 9A. Side partial sectional view. FIG. 10A is a schematic cross-sectional view of a diffuser plate for explaining the bubble generation mechanism of the diffuser (when there is a flow) in FIG. 9A, and FIG. The cross-sectional schematic diagram of the diffuser board for demonstrating the generation | occurrence | production mechanism of the bubble when there is no flow. 11A is a plan view of the air diffuser according to the eighth embodiment of the present invention, and FIG. 11B is along the line XIb-XIb of the air diffuser of FIG. 11A. Side partial sectional view. 12 (a) is a plan view of the air diffuser according to the ninth embodiment of the present invention, and FIG. 12 (b) is along the line XIIb-XIIb of the air diffuser of FIG. 12 (a). Side partial sectional view. FIG. 13A is a plan view of the air diffuser according to the tenth embodiment of the present invention, and FIG. 13B is along the line XIIIb-XIIIb of the air diffuser of FIG. Side partial sectional view. 14 (a) is a side view of the air diffuser according to the eleventh embodiment of the present invention, and FIG. 14 (b) is an XIVb-XIVb line of the air diffuser of FIG. 14 (a). The cross-sectional schematic diagram along. 15A is a side view of the air diffuser according to the twelfth embodiment of the present invention, and FIG. 15B is an XVb-XVb line of the air diffuser of FIG. 15A. The cross-sectional schematic diagram along. The side fragmentary sectional view of the diffuser which concerns on 13th embodiment of this invention. The side fragmentary sectional view of the aeration apparatus concerning a 14th embodiment of the present invention. 18A is a partial cross-sectional view of the air diffuser according to the fifteenth embodiment of the present invention when viewed from above, and FIG. 18B is the air diffuser of FIG. The partial cross section schematic diagram along the XVIIIb-XVIIIb line of an apparatus. 19 (a) is a side view of the air diffuser according to the sixteenth embodiment of the present invention, and FIG. 19 (b) is an XIXb-XIXb line of the air diffuser of FIG. 19 (a). The cross-sectional schematic diagram along. 20 (a) is a side view of the air diffuser according to the seventeenth embodiment of the present invention, and FIG. 20 (b) is a line XXb-XXb of the air diffuser of FIG. 20 (a). The cross-sectional schematic diagram along. FIG. 21A is a plan view of an air diffuser according to the eighteenth embodiment of the present invention, and FIG. 21B is an XXIb-XXIb line of the air diffuser of FIG. The side fragmentary sectional view which followed. FIG. 22 (a) is a side partial sectional view of an air diffuser according to the nineteenth embodiment of the present invention, and FIG. 22 (b) is an air diffuser orthogonal to FIG. 22 (a). FIG. FIG. 23A is a plan view of the air diffuser of the sixth embodiment, and FIG. 23B is a side partial cross-sectional view of the air diffuser of FIG. 23A taken along line XXIIIb-XXIIIb. . The bar graph figure which shows the performance test result of the diffuser of Example 1 and Comparative Example 1. The bar graph figure which shows the performance test result of the diffuser of Examples 2-6.

Explanation of symbols

  1, 21, 31, 41, 61, 111, 221, 233 ... diffuser plate, 2, 32, 62, 133 ... diffuser plate pressing ring, 3, 73 ... air supply pipe, 4, 33, 63, 114 ... casing, 75 ... check valve, 6, 24, 76 ... hole, 10, 30, 40, 60, 70, 80, 90, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230 ... diffuser, 22 ... super hydrophilic coating, 23 ... thin metal plate, 25, 44, 93, 95 ... air bubbles, 26 ... liquid phase, 41a, 61a ... upper metal thin plate, 41b 61b ... Lower metal thin plate, 42a, 42b ... Slit, 43,82 ... Assembly hole, 71,81,196,206 ... Spread cylinder, 72,197,207 ... Connector, 74,198,208 ... Spread cylinder end Plate, 81a ... Large diameter cylinder (upper metal sheet), 81b ... Small diameter cylinder (lower metal sheet), 91,112,121,131,141,151,166,171,187,232 ... Water flow Raw device, 92, 94 ... gas particles, 96, 113, 132, 142, 152, 165, 186 ... piping, 143 ... nozzle holes, 161, 162, 163, 164, 181, 182, 183, 184, 185, 191, 192, 193, 194, 195, 201, 202, 203, 204, 205, 231 ... Air diffuser unit, 167, 188, 234 ... Discharge port, 172 ... Propeller in liquid, 211 ... Whistle, 222 ... Karman vortex generation Device, 223 ... support member, 224 ... post, 225 ... columnar member.

Claims (10)

  An air diffuser comprising an air diffuser provided with a thin metal plate having a large number of fine holes or slits.   The air diffuser according to claim 1, wherein the metal thin plate is a pure titanium plate.   The air diffuser according to claim 1, wherein the thin metal plate has a superhydrophilic film formed on a surface thereof.   The diffuser according to claim 3, wherein the superhydrophilic film is a titanium dioxide film.   5. The diffuser member is formed by stacking two metal thin plates having a plurality of slits arranged in parallel at predetermined intervals so that the slits of the respective metal thin plates intersect each other. The aeration apparatus according to any one of the above.   The air diffuser according to any one of claims 1 to 5, wherein the air diffuser is formed by forming the metal thin plate into a cylindrical shape.   The diffuser according to claim 6, wherein the cylindrical diffuser has an elliptical or streamline cross section.   The air diffuser according to any one of claims 1 to 7, further comprising a water flow generator that generates a water flow along a surface on the air diffuser side of the thin metal plate.   The air diffuser according to claim 1, further comprising a vibration exciter that vibrates the air diffuser using an air flow.   10. The air diffuser according to claim 9, wherein the vibration exciter is a whistle that emits a sound having substantially the same frequency as the natural frequency of the air diffuser during the air diffuser.

Images