Oxygen dissolving device and oxygen dissolving method using the same

Abstract

To provide a technology which enables oxygen in air to be dissolved into a liquid efficiently with a simple structure.SOLUTION: An oxygen dissolution device 1 includes: an upper tank 4 having an upper surface 4c into which a liquid is injected and a bottom part 4b provided with a falling hole 9 in which the liquid falls rolling air thereinto; and a cylindrical tube 8 which extends downward from the bottom part 4 and communicates with the falling hole 9. The cylindrical tube 8 has: a cylindrical body 10; and multiple cylindrical projections 12 which are provided on an inner peripheral surface 10a of the cylindrical body 10 and generate Karman vortexes in the liquid passing through the cylinder body 10.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an oxygen dissolving device and an oxygen dissolving method using the same. [Background technology]

[0002] Conventionally, techniques for increasing the amount of dissolved oxygen in water have been used to improve the water quality of purification facilities, lakes, reservoirs, dams, and the like. Examples of such techniques include a method of supplying compressed air to a porous air diffuser pipe placed underwater, a method of forming a shear flow using a rotating blade or the like placed underwater and supplying compressed air into the flow, and a method of generating microbubbles or nanobubbles underwater. However, the above-mentioned conventional method requires a compressor for compressing the gas, which makes the apparatus large-scale.

[0003] Therefore, the applicant of the present application has proposed an apparatus with a simple configuration that promotes dissolution of oxygen into a liquid and increases the amount of dissolved oxygen in the liquid (see Patent Document 1). Patent Document 1 filed by the applicant of the present application discloses an apparatus for promoting dissolution of oxygen into a liquid and increasing the amount of dissolved oxygen in the liquid. 9, this device comprises a cylindrical pipe 100 extending in the vertical direction and an outer pipe 102 disposed outside the cylindrical pipe 100. A plurality of air intake holes 104 are provided on the side surface of the cylindrical pipe 100.

[0004] A liquid such as water is supplied into the cylindrical pipe 100. The liquid supplied into the cylindrical pipe 100 passes through the cylindrical pipe 100 from top to bottom. At this time, negative pressure is generated between the liquid passing through the cylindrical pipe 100 as a fluid and the inner circumferential surface 100a of the cylindrical pipe 100, causing air outside the cylindrical pipe 100 to pass through the air intake holes 104 and be introduced into the cylindrical pipe 100. The air introduced into the cylindrical pipe 100 is taken into the liquid as air bubbles. In the device of Patent Document 1, air is introduced into the liquid as bubbles, thereby efficiently dissolving oxygen from the air into the liquid, and the amount of dissolved oxygen in the liquid can be increased with a simple configuration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6281927 Summary of the Invention [Problem to be solved by the invention]

[0006] The inventors of the present application have conducted extensive research into a device with a simple configuration that can efficiently dissolve oxygen from the air into a liquid, and as a result have invented a new configuration that differs from the device described in Patent Document 1 above, which can efficiently dissolve oxygen from the air into a liquid.

[0007] That is, an object of the present invention is to provide a new technology that can efficiently dissolve oxygen in the air into a liquid with a simple configuration. [Means for solving the problem]

[0008] (1) The oxygen dissolution device of the present invention comprises an upper tank having a bottom provided with an opening through which a liquid is poured and a drop hole through which the liquid falls while entraining air, and a cylindrical pipe extending downward from the bottom and communicating with the drop hole, the cylindrical pipe having a tube body and a plurality of cylindrical protrusions provided on the inner surface of the tube body that generate Karman vortices in the liquid passing through the tube body.

[0009] According to the above configuration, when liquid containing entrained air is introduced into the cylindrical pipe through the drop hole, the air that falls along with the liquid is entrained in the liquid as air bubbles. The liquid passes through the cylindrical pipe with the entrained air bubbles. The liquid with the entrained air bubbles passes around the cylindrical protrusions inside the cylindrical pipe. At this time, Karman vortices are generated in the liquid that has passed around the cylindrical protrusions. These Karman vortices agitate and mix the entrained air bubbles with the liquid, accelerating the dissolution of oxygen into the liquid. As a result, oxygen from the air can be efficiently dissolved into the liquid. Thus, with the above-described configuration, oxygen in the air can be efficiently dissolved into the liquid with a simple configuration in which a plurality of cylindrical protrusions are provided on the inner peripheral surface of the tube body.

[0010] (2) In the oxygen dissolving device, the diameter of the cylindrical protrusions is preferably equal to or less than 1 / 4 of the inner diameter of the cylindrical body. If the diameter of the multiple cylindrical protrusions is larger than 1 / 4 of the inner diameter of the cylindrical body, the cross section of the flow path inside the cylindrical body will be smaller than necessary, which may hinder the flow of liquid when it is introduced into the cylindrical body, and may prevent the required flow rate from being obtained. By setting the diameter of the cylindrical protrusions to ¼ or less of the inner diameter of the cylindrical body, the liquid inside the cylindrical body can pass through at a required flow rate.

[0011] (3) In the oxygen dissolving device, the height of the cylindrical protrusions is preferably not less than (1 / 2)d and not more than d, where d is the diameter of the cylindrical protrusions. If the height of the cylindrical protrusions is smaller than (2 / 3)d, there is a risk that the stirring effect of Karman vortices will not be sufficiently obtained. If the height of the cylindrical protrusions is greater than the diameter d of the cylindrical protrusions, the cross section of the flow path inside the cylindrical body becomes smaller than necessary, which may hinder the flow of liquid when it is introduced into the cylindrical body, making it difficult to obtain the required flow rate.Furthermore, there is a risk that foreign matter may get caught on the cylindrical protrusions. By making the height of the multiple cylindrical protrusions smaller than (2 / 3)d and equal to or less than d, it is possible to obtain the stirring effect of the Karman vortex while preventing foreign matter mixed in the liquid from getting caught on the multiple cylindrical protrusions.

[0012] (4) In the oxygen dissolving device, the plurality of cylindrical protrusions preferably include a plurality of first cylindrical protrusions arranged circumferentially at a first height position in the vertical direction and a plurality of second cylindrical protrusions arranged circumferentially at a second height position lower than the first height position, and the circumferential positions of the plurality of first cylindrical protrusions and the circumferential positions of the plurality of second cylindrical protrusions are different from each other. In this case, it is possible to prevent the Karman vortex generated downstream of the plurality of first cylindrical projections from interfering with the plurality of second cylindrical projections, thereby preventing a decrease in the stirring effect. Furthermore, by providing a large number of cylindrical protrusions at the same height position, the cross section of the flow path inside the cylindrical pipe is not narrowed, and more cylindrical protrusions can be provided inside the cylindrical pipe overall while limiting the number of cylindrical protrusions at the same height position.

[0013] (5) In the oxygen dissolution device, when the diameter of the plurality of cylindrical protrusions is d, it is preferable that the circumferential distance on the inner surface between a pair of adjacent second cylindrical protrusions among the plurality of second cylindrical protrusions is 6.2d or more, and the circumferential distance on the inner surface between a reference first cylindrical protrusion which is one of the plurality of first cylindrical protrusions and a target second cylindrical protrusion which is located next to the reference first cylindrical protrusion in the circumferential direction among the plurality of second cylindrical protrusions is 3.1d or more. In this case, it is possible to prevent the Karman vortex generated downstream of the reference first cylindrical projection and the Karman flow generated downstream of the target second cylindrical projection from interfering with each other.

[0014] (6) From another perspective, the oxygen dissolving method according to the present disclosure includes the steps of injecting a liquid into an upper tank having a bottom provided with an opening through which the liquid is injected and a drop hole through which the liquid falls while entraining air, and introducing the liquid into a cylindrical tube extending downward from the bottom and communicating with the drop hole. The cylindrical pipe has a cylindrical body and a plurality of cylindrical protrusions provided on the inner peripheral surface of the cylindrical body to generate Karman vortices in the liquid passing through the cylindrical body. According to this method, oxygen in the air can be efficiently dissolved into the liquid with a simple configuration. [Effects of the Invention]

[0015] According to the present disclosure, oxygen in the air can be efficiently dissolved in the liquid. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a configuration diagram of an oxygen dissolving device according to this embodiment. [Figure 2] FIG. 2(a) is a cross-sectional view of the upper tank, and FIG. 2(b) is a plan view of the upper tank. [Figure 3] FIG. 3(a) is a cross-sectional view including the central axis of the cylindrical tube, and FIG. 3(b) is a cross-sectional view taken along line BB in FIG. 3(a). [Figure 4] FIG. 4 is a plan view of the inner circumferential surface of the tube main body when unfolded. [Figure 5] FIG. 5(a) is a partial cross-sectional view of a cylindrical pipe according to a modified example, and FIG. 5(b) is a partial cross-sectional view of a cylindrical pipe according to another modified example. [Figure 6] FIG. 6 is a model diagram for explaining the state in which Karman vortices are generated by a cylindrical protrusion. [Figure 7] FIG. 7 is a schematic plan view showing the state of Karman vortices generated by the first cylindrical projection and the second cylindrical projection according to the embodiment. [Figure 8] FIG. 8 is a graph showing the change in oxygen saturation over time. [Figure 9] FIG. 9 is a cross-sectional view showing a conventional oxygen dissolving device. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments will now be described with reference to the drawings. [Regarding the embodiment] FIG. 1 is a configuration diagram of an oxygen dissolving device according to this embodiment. In FIG. 1, the oxygen dissolving device 1 includes an injection mechanism 2 , an upper tank 4 , a lower tank 6 , and a cylindrical pipe 8 . The oxygen dissolving device 1 is a device for promoting dissolution of oxygen in the air into the liquid injected into the upper tank 4 by the injection mechanism 2, thereby increasing the amount of dissolved oxygen. The liquid may be tap water, water stored in lakes, reservoirs, dams, etc., or wastewater treated in a wastewater treatment facility, but may also be other liquids. Wastewater treated in wastewater treatment facilities may contain foreign matter. Foreign matter includes fine particles such as fiber waste, paper fiber waste, wheat flour particles, rice flour particles, bean husk waste, peanut shell waste, metal powder, and microbial carcasses, as well as relatively large debris. Wastewater containing such fine particles has a higher viscosity than water that does not contain such fine particles.

[0018] The upper tank 4 stores the liquid injected from the injection mechanism 2. FIG. 2(a) is a cross-sectional view of the upper tank 4, and FIG. 2(b) is a plan view of the upper tank 4. As shown in Figures 1, 2(a), and 2(b), the upper tank 4 has a cylindrical peripheral wall 4a and a bottom 4b. The bottom 4b is a disk-shaped member made of stainless steel or the like. The peripheral wall 4a is a cylindrical member made of stainless steel or the like, and is erected on the periphery of the bottom 4b. The upper surface 4c of the upper tank 4 is open. The liquid from the injection mechanism 2 is injected through the opening in the upper surface 4c. In other words, the upper surface 4c forms an opening through which the liquid is injected.

[0019] The bottom 4b is provided with a drop hole 9. The drop hole 9 is a circular hole for dropping the liquid stored inside the upper tank 4 downward. The center of the drop hole 9 coincides with the central axis C of the peripheral wall 4a and the bottom 4b.

[0020] The cylindrical pipe 8 is provided on the lower surface 4b1 of the bottom portion 4b. The cylindrical pipe 8 is a cylindrical tubular member that extends downward from the lower surface 4b1. The cylindrical pipe 8 is provided along the edge of the drop hole 9 on the lower surface 4b1. In this way, the cylindrical pipe 8 is in communication with the drop hole 9. The central axis of the cylindrical tube 8 in the longitudinal direction coincides with the central axis C.

[0021] As shown in Fig. 1, the injection mechanism 2 has a first injection pipe 2a and a second injection pipe 2b. The first injection pipe 2a and the second injection pipe 2b are connected to a liquid storage tank (not shown). Liquid is supplied to the first injection pipe 2a and the second injection pipe 2b from the liquid storage tank. The liquid passes through the first injection pipe 2a and the second injection pipe 2b and is injected into the upper tank 4.

[0022] The first injection pipe 2a has a pipe main body 2a1 and a flow rate regulator 2a2. The pipe main body 2a1 is provided above the upper tank 4 and injects liquid into the upper tank 4. The flow rate regulator 2a2 has a function of regulating the flow rate of the liquid passing through the pipe main body 2a1. 2(b), a line parallel to the vertical direction that passes through point x1 on bottom 4b passes through the central axis of pipe body 2a1. In other words, first injection pipe 2a is provided directly above point x1 on bottom 4b. Therefore, the liquid injected from first injection pipe 2a collides near point x1 on bottom 4b.

[0023] 1, second injection pipe 2b has pipe body 2b1 and flow rate regulator 2b2. Pipe body 2b1 is provided above upper tank 4 and injects liquid into upper tank 4. Flow rate regulator 2b2 has the function of regulating the flow rate of liquid passing through pipe body 2b1. In Figure 2(b), a line parallel to the vertical direction that passes through point x2 on the edge of drop hole 9 in bottom portion 4b passes through the central axis of pipe body 2b1. In other words, second injection pipe 2b is provided directly above point x2 on bottom portion 4b. Therefore, the liquid injected from second injection pipe 2b collides near point x2 on bottom portion 4b. The points x1 and x2 are located on a straight line H (FIG. 2(b)) that passes through the central axis C.

[0024] Since point x2 is on the edge of drop hole 9, most of the liquid injected from second injection pipe 2b is introduced directly into drop hole 9. On the other hand, the liquid injected from first injection pipe 2a is not introduced directly into drop hole 9, but flows so as to spread over bottom 4b, and then falls from the periphery of drop hole 9 towards drop hole 9. For this reason, a difference occurs in the falling speed (flow rate) between the liquid introduced directly into drop hole 9 from second injection pipe 2b and the liquid injected by first injection pipe 2a and dropping from the periphery of drop hole 9. As a result, negative pressure is generated around the liquid introduced directly into drop hole 9 from second injection pipe 2b, and the surrounding air is sucked into drop hole 9. As a result, the liquid introduced into the drop hole 9 falls downward while drawing in surrounding air. The liquid introduced into the drop hole 9 falls downward while drawing in the surrounding air, and is then introduced into the cylindrical tube 8. The flow rate of the first injection pipe 2a and the flow rate of the second injection pipe 2b are adjusted appropriately so that the liquid introduced into the drop hole 9 falls downward while entraining the surrounding air.

[0025] 3(a) is a cross-sectional view including the central axis of the cylindrical tube 8, and FIG. 3(b) is a cross-sectional view taken along the line BB in FIG. 3(a). As shown in FIGS. 3( a ) and 3 ( b ), the cylindrical tube 8 has a cylindrical main body 10 and a plurality of cylindrical protrusions 12 . The tube body 10 is a cylindrical member made of stainless steel or the like. The upper end of the tube body 10 is connected to the lower surface 4b1 of the bottom portion 4b. The tube body 10 is in communication with the drop hole 9. Therefore, the liquid dropping downward from the drop hole 9 is introduced into the tube body 10.

[0026] The plurality of cylindrical protrusions 12 are cylindrical members made of stainless steel or the like, and are provided on the inner peripheral surface 10a of the tube main body 10. The plurality of cylindrical protrusions 12 each have the same shape. The plurality of cylindrical protrusions 12 protrude radially inward from the inner circumferential surface 10a. The plurality of cylindrical protrusions 12 are provided by fixing cylindrical members to the inner circumferential surface 10a by welding or an adhesive layer.

[0027] In this embodiment, when liquid containing entrained air is introduced into the cylindrical tube 8 through the drop hole 9, the air that falls along with the liquid is entrained in the liquid as air bubbles. The liquid passes through the cylindrical tube 8 with the entrained air bubbles. The liquid with the entrained air bubbles passes around the cylindrical protrusions 12 inside the cylindrical tube 8. At this time, Karman vortices are generated in the liquid that has passed around the cylindrical protrusions 12. These Karman vortices agitate and mix the entrained air bubbles with the liquid, accelerating the dissolution of oxygen into the liquid. As a result, oxygen from the air can be efficiently dissolved into the liquid. As described above, according to this embodiment, with the simple configuration of providing a plurality of cylindrical protrusions 12 on the inner peripheral surface 10a of the cylindrical main body 10, oxygen in the air can be efficiently dissolved into the liquid.

[0028] When the above-mentioned conventional device is installed in a wastewater treatment facility and used to dissolve oxygen in wastewater, the wastewater is introduced into a cylindrical pipe. Wastewater can contain not only water but also various foreign matter such as fine particles and dust. When a liquid containing such foreign matter is introduced into a cylindrical pipe, the foreign matter can adhere to and block the intake hole of the cylindrical pipe, causing the intake hole to become clogged. When the intake hole becomes clogged, the amount of air introduced into the cylindrical pipe through the intake hole decreases, making it impossible to sufficiently incorporate air (air bubbles) into the liquid, which can reduce the efficiency of dissolving oxygen into the liquid.

[0029] In this regard, the present embodiment does not have an intake hole like the conventional device described above, so even if the liquid contains foreign matter, it is possible to prevent a decrease in the efficiency of dissolving oxygen into the liquid, and it is possible to efficiently dissolve oxygen in the air.

[0030] The liquid that has passed through the cylindrical pipe 8 falls into the lower tank 6 (FIG. 1) and is stored in the lower tank 6. The liquid stored in the lower tank 6 is drained into a drain tank (not shown) disposed below the lower tank 6 and is stored in the drain tank. The drain tank is equipped with a pump. The liquid stored in the drain tank is returned to the liquid storage tank by this pump, so that the liquid passes through the cylindrical pipe 8 repeatedly. This allows the oxygen dissolution device 1 to efficiently dissolve oxygen in the air into the liquid.

[0031] As shown in FIG. 3(a), the plurality of cylindrical protrusions 12 are provided in four vertical positions (height positions T1, T2, T3, T4) of the cylindrical tube 8, three at each position. The three cylindrical protrusions 12 at each height position are arranged at equal intervals in the circumferential direction.

[0032] Hereinafter, of the multiple cylindrical protrusions 12, the three cylindrical protrusions 12 arranged at height position T1 will also be referred to as first cylindrical protrusions 12A, the three cylindrical protrusions 12 arranged at height position T2 will also be referred to as second cylindrical protrusions 12B, the three cylindrical protrusions 12 arranged at height position T3 will also be referred to as third cylindrical protrusions 12C, and the three cylindrical protrusions 12 arranged at height position T4 will also be referred to as fourth cylindrical protrusions 12D.

[0033] The distance between the height position T1 and the height position T2, the distance between the height position T2 and the height position T3, and the distance between the height position T3 and the height position T4 are the same. The circumferential position of the first cylindrical protrusion 12A and the circumferential position of the third cylindrical protrusion 12C are the same. Furthermore, the circumferential position of the second cylindrical projection 12B and the circumferential position of the fourth cylindrical projection 12D are the same.

[0034] Furthermore, the circumferential position of the first cylindrical projection 12A (third cylindrical projection 12C) and the circumferential position of the second cylindrical projection 12B (fourth cylindrical projection 12D) are different from each other. More specifically, the second cylindrical projection 12B (fourth cylindrical projection 12D) is provided at a circumferential center position between a pair of circumferentially adjacent first cylindrical projections 12A (third cylindrical projections 12C) of the first cylindrical projections 12A (third cylindrical projections 12C). This makes it possible to prevent the Karman vortex generated downstream of the first cylindrical projection 12A from interfering with the second cylindrical projection 12B and reducing the stirring effect. Furthermore, by providing a large number of cylindrical protrusions 12 at the same height position, the cross section of the flow path within the tube body 10 is not narrowed, and more cylindrical protrusions 12 can be provided overall within the tube body 10 while limiting the number of cylindrical protrusions 12 at the same height position.

[0035] The diameter d (FIG. 3(a)) of the cylindrical protrusions 12 is preferably ¼ or less of the inner diameter D (FIG. 3(a)) of the cylindrical main body 10. If the diameter d of the multiple cylindrical protrusions 12 is larger than 1 / 4 of the inner diameter D, the cross section of the flow path within the cylindrical body 10 will be smaller than necessary, and when liquid is introduced into the cylindrical body 10, the flow of the liquid will be obstructed, and the required flow rate may not be obtained. By setting the diameter d of the cylindrical protrusions 12 to ¼ or less of the inner diameter D of the cylindrical main body 10, the liquid inside the cylindrical main body 10 can pass through at a required flow rate.

[0036] Furthermore, the height t (FIG. 3(b)) of the plurality of cylindrical protrusions 12 is preferably equal to or greater than (1 / 2)d and equal to or less than d. If the height t of the cylindrical projections 12 is smaller than (1 / 2)d, there is a risk that the stirring effect of Karman vortices will not be sufficiently obtained. If the height t of the cylindrical protrusions 12 is greater than the diameter d of the cylindrical protrusions 12, the cross section of the flow path inside the cylindrical main body 10 becomes smaller than necessary, which may hinder the flow of the liquid when it is introduced into the cylindrical main body 10, making it difficult to obtain the required flow rate. Furthermore, there is a risk that foreign matter may get caught on the cylindrical protrusions 12. By making the height t of the multiple cylindrical protrusions 12 smaller than (1 / 2)d and equal to or less than d, it is possible to obtain the stirring effect of the Karman vortex while preventing foreign matter mixed in the liquid from getting caught on the multiple cylindrical protrusions 12.

[0037] 4 is a plan view of the inner peripheral surface 10a of the cylindrical main body 10 when unfolded. In FIG. 4, the left-right direction on the paper surface is the circumferential direction. 4, the circumferential distance S1 between a pair of adjacent cylindrical protrusions 12 on the inner circumferential surface 10a of each of the cylindrical protrusions 12A to 12D is a value obtained by dividing the circumferential length of the inner circumferential surface 10a into thirds, and is set to be 6.2d or more. Note that the distance S1 is the distance between the points where the central axes of the pair of adjacent cylindrical protrusions 12A to 12D intersect with the inner circumferential surface 10a.

[0038] 4, the distance S2 is the circumferential distance on the inner peripheral surface 10a between the first cylindrical projection 12A (reference first cylindrical projection) and the second cylindrical projection 12B (target second cylindrical projection) that is located adjacent to the first cylindrical projection 12A, which is the reference first cylindrical projection, in the circumferential direction. The distance S2 is set to 1 / 2 of the distance S1. In other words, the distance S2 is set to 3.1d or more.

[0039] If the distance S1 is smaller than 6.2d, the Karman vortex generated downstream of the first cylindrical projection 12A may interfere with the second cylindrical projection 12B (adjacent projection). Also, if the distance S2 is smaller than 3.1d, the Karman vortex generated downstream of the first cylindrical projection 12A may interfere with the second cylindrical projection 12B. By setting the spacing S1 to 6.2d or more and the spacing S2 to 3.1d or more, it is possible to prevent the Karman vortex generated downstream of the first cylindrical protrusion 12A, which is the reference first cylindrical protrusion, and the Karman flow generated downstream of the second cylindrical protrusion 12B, which is the target second cylindrical protrusion, from interfering with each other.

[0040] Furthermore, the vertical distance h between each of the cylindrical projections 12A to 12D is set to 11.2d or more, which prevents the interference of the Karman vortex generated downstream of the first cylindrical projection 12A with the third cylindrical projection 12C, thereby preventing the vortex from weakening and reducing the stirring effect.

[0041] [Regarding modified examples] FIG. 5(a) is a partial cross-sectional view of a cylindrical tube 8 according to a modified example. In the above embodiment, an example was given of a case where the cylindrical protrusion 12 is provided by fixing a cylindrical member to the inner surface 10a by welding or the like, but the cylindrical protrusion 12 may also be provided by providing a through hole 10c in the tube main body 10 and inserting a protrusion member 20 into the through hole 10c. The protruding member 20 has a flange portion 20a that abuts against the outer peripheral surface 10b of the cylindrical main body 10, and a cylindrical portion 20b that extends from the flange portion 20a. The cylindrical portion 20b of the protruding member 20 is inserted into the through-hole 10c from the outer circumferential surface 10b side of the cylindrical main body 10. The protruding member 20 is fixed in place with the flange portion 20a in contact with the outer circumferential surface 10b. At this time, the cylindrical portion 20b protrudes radially inward from the inner peripheral surface 10a, forming a cylindrical protrusion 12. According to this modification, the cylindrical protrusion 12 can be easily provided inside the cylindrical main body 10. Furthermore, by making the protrusion member 20 detachable from the cylindrical main body 10, the protrusion member 20 can be easily replaced. Furthermore, by preparing protrusion members 20 with different lengths and diameters of the cylindrical portions 20b, the height t and diameter d of the cylindrical protrusion 12 can be changed, and the height t and diameter d can be set to an appropriate value depending on the liquid passing through the interior.

[0042] FIG. 5(b) is a partial cross-sectional view of a cylindrical tube 8 according to another modified example. The other modified example differs from the above modified example in that the protruding member 20 is provided with a through-hole 20c that communicates between the inside and outside of the tube main body 10. In another modification, the protruding member 20 is provided with a through-hole 20c, so that when liquid passes through the cylindrical body 10, the negative pressure causes air outside the cylindrical body 10 to pass through the through-hole 20c and be introduced into the cylindrical body 10. The air introduced into the cylindrical body 10 is taken into the liquid as air bubbles.

[0043] In this modification, when liquid containing foreign matter such as wastewater is passed through, through-hole 20c is blocked, and the amount of air introduced through through-hole 20c into tube body 10 decreases, thereby reducing the effect of through-hole 20c in promoting the dissolution of oxygen into the liquid. However, when water that does not contain foreign matter is passed through as a liquid, the stirring effect of the cylindrical protrusions 12 and the introduction of air through the through holes 20c can more effectively promote the dissolution of oxygen into the liquid.

[0044] In addition, in the above embodiment, an example was given of using an injection mechanism 2 having a first injection pipe 2a and a second injection pipe 2b, but as long as the liquid can be dropped into the drop hole 9 while entraining air, the injection mechanism 2 may inject the liquid using a single injection pipe, or may have a greater number of injection pipes. [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. (Example) A cylindrical body 10 having an inner diameter D of 30 mm and a length of 210 mm was prepared, and cylindrical protrusions 12 having a diameter d of 5 mm and a height t of 3 mm were provided on the inner surface 10a in the arrangement shown in Figure 4, to obtain a cylindrical tube 8. In FIG. 4, the interval S1 was 31.4 mm, the interval S2 was 15.7 mm, and the interval h was 56 mm. The above cylindrical pipe 8 was used to constitute an oxygen dissolving device 1 .

[0046] (Comparative Example) A cylindrical body having an inner diameter D of 30 mm and a length of 210 mm was prepared, and an air intake hole (inner diameter 2 to 3 mm) that communicates the inside and outside of the cylindrical body 10 was provided at the position where the cylindrical protrusion 12 in the example was arranged, to obtain a cylindrical tube. This air intake hole is a hole that guides air outside the cylindrical tube into the cylindrical tube by the negative pressure generated between the water passing through the tube body and the inner surface of the cylindrical tube. The oxygen dissolving device was constructed using a cylindrical pipe having an intake hole. This comparative example is an oxygen dissolving device based on the above-mentioned prior art.

[0047] (Regarding Karman vortices caused by the cylindrical protrusion 12 in the embodiment) Fig. 6 is a model diagram for explaining the manner in which Karman vortices are generated by the cylindrical protrusion 12. In Fig. 6, the lower part shows a model in which Karman vortices are generated by the cylindrical protrusion 12, and schematically shows the flow of fluid (liquid) around the cylindrical protrusion 12. The upper part shows the pressure at a predetermined position in the model.

[0048] In Figure 6, the liquid flows from left to right on the page. The laminar flow of the liquid separates at separation point P1. Downstream of separation point P1, numerous vortices are generated, causing a drop in pressure.

[0049] The upper graph in FIG. 6 shows the pressure of the laminar flow at a position N1 slightly upstream of the separation point P1 and the pressure of the laminar flow at a position N2 downstream of the cylindrical protrusion 12. As shown in this graph, the pressure of the laminar flow at the position N2 is significantly lower than the pressure of the laminar flow at the position N1. As a result, negative pressure occurs at the position N2, and many vortices are generated downstream of the cylindrical protrusion 12. In order to create a large difference in pressure between the position N1 and the position N2, it is preferable that the outer peripheral surface of the cylindrical projection 12 is a smooth surface without any irregularities. The reason is that if there are unevenness on the outer surface of the cylindrical protrusion 12, this may hinder the flow of fluid passing along the outer surface of the cylindrical protrusion 12, and the difference in pressure between position N1 and position N2 may become small.

[0050] When the Reynolds number Re, which will be described later, satisfies a predetermined condition, many vortices downstream of the cylindrical projection 12 become Karman vortices.

[0051] 7 is a schematic plan view showing the state of Karman vortices generated by the first cylindrical projection 12A and the second cylindrical projection 12B according to the embodiment. In FIG. 7, the inner circumferential surface 10a of the cylindrical main body 10 is shown as a developed plan view.

[0052] In FIG. 7, the liquid moves as a fluid from the top to the bottom of the paper as indicated by the arrow. 7, a Karman vortex street K1 is shown downstream of the first cylindrical projection 12A, which is generated by the first cylindrical projection 12A when a liquid as a fluid passes through it. The Karman vortex street K1 appears in two staggered rows parallel to the direction of the fluid flow. The Karman vortex street K1 includes at least Karman vortices K11, K12, and K13. 7, a Karman vortex street K2 is shown downstream of the second cylindrical projection 12B, which is generated by the second cylindrical projection 12B as the liquid passes through it. Similar to the Karman vortex street K1, the Karman vortex street K2 also appears in two staggered rows parallel to the direction of fluid flow. The Karman vortex street K2 includes at least Karman vortices K21, K22, and K23.

[0053] In this cylindrical pipe 8, when water is introduced from the upper tank 4 into the cylindrical body 10, the maximum flow rate is 1050 cm 3 / s, and the flow velocity is 148.5 cm / s. The Reynolds number Re of the water flowing around the cylindrical projection 12 is expressed by the following formula (1). Re = Vd / ν (1) In the formula (1), V is the flow velocity (cm / s), d is the diameter of the cylindrical projection 12 (cm), and ν is the dynamic viscosity coefficient of water at 20°C (cm 2 / s).

[0054] The dynamic viscosity of water at 20°C is 0.01 cm 2 / s, the Reynolds number Re of the water flowing around the cylindrical projection 12 is 7425 according to the above formula (1). Generally, the Reynolds number Re is 500 <Re<2×10 5 When the flow rate is in this range, Karman vortices are generated downstream of the cylindrical projection 12. Therefore, the cylindrical projection 12 of the cylindrical pipe 8 in this example generates Karman vortices downstream.

[0055] Next, the generation period f of the Karman vortexes that occur in this example and the interval between the generated Karman vortices are calculated. The generation period f of the Karman vortex is calculated from the Strouhal number St shown in the following equation (2). St = fd / V (2)

[0056] Reynolds number Re is 500 <Re<2×10 5 In the range of , the Strouhal number St is almost constant. In the case of a cylindrical shape, the Strouhal number St is approximately 0.18. Therefore, from the above formula (2), the generation period f is 53.5 Hz. From the generation period f and the flow velocity V, the spacing a (see Figure 5) between the Kármán vortices in the vertical direction (water flow direction) included in the Kármán vortex street is calculated to be 28 mm. Furthermore, there is a relationship of b / a=0.281 between the vertical spacing a of the Karman vortices included in the Karman vortex street and the spacing b (see FIG. 5) in the direction perpendicular to the vertical direction (circumferential direction). Therefore, the interval b is 8 mm. The distance c between the Karman vortex street K1 and the Karman vortex street K2 in the direction perpendicular to the up-down direction (circumferential direction) is 7.7 mm. Note that the intervals a, b, and c are the intervals between the Karman vortices when the center of the Karman vortex is used as the reference.

[0057] In this embodiment, by setting the spacing S1 to 31.4 mm (6.2d or more) and the spacing S2 to 15.7 mm (3.1d or more), it is possible to prevent the Karman vortex street K1 and the Karman vortex street K2 from interfering with each other. Furthermore, by setting the intervals S1 and S2 as described above, it is possible to prevent the Karman vortex generated downstream of the first cylindrical projection 12A from interfering with the second cylindrical projection 12B and reducing the stirring effect.

[0058] (Evaluation test) Using the oxygen dissolving device according to the example and the oxygen dissolving device according to the comparative example, oxygen was dissolved in water (tap water), and the changes in oxygen concentration were compared. 20 L (liters) of water was charged into each of the Example and Comparative Example, and the charged water was circulated between the upper tank and the lower tank. The oxygen concentration of the water was measured at predetermined time intervals after the start of water circulation, and the oxygen saturation (%) of the water was calculated using the following formula (3). Oxygen saturation (%) = measured dissolved oxygen (mg / L) / saturated oxygen (mg / L) ···(3) When calculating the oxygen saturation, the measured value and saturated oxygen amount were corrected according to the water temperature.

[0059] FIG. 8 is a graph showing the change in oxygen saturation over time. In FIG. 8, the vertical axis indicates the oxygen saturation level, and the horizontal axis indicates the time elapsed since the start of water circulation. In FIG. 8, square marks indicate the oxygen saturation level according to the example, and circles indicate the oxygen saturation level according to the comparative example. As shown in FIG. 8, the change in oxygen saturation level over time in the example and the change in oxygen saturation level over time in the comparative example are almost the same, and no significant difference is observed. From these results, it can be seen that the oxygen dissolving device of the example and the oxygen dissolving device of the comparative example have similar performance in dissolving oxygen into water.

[0060] 〔others〕 The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configurations described in the claims. [Explanation of symbols]

[0061] 1. Oxygen dissolution device 2 Injection mechanism 2a 1st injection tube 2a1 tube body 2a2 flow regulator 2b 2nd injection tube 2b1 tube body 2b2 Flow regulator 4 Upper Tank 4a Peripheral wall 4b bottom 4b1 Bottom side 4c Top surface 6 Lower Tank 8 Cylindrical tube 9 Fallhole 10. Cylinder body 10a Inner surface 10b Outer surface 10c through hole 12 Cylindrical protrusion 12A First cylindrical protrusion 12B Second cylindrical protrusion 12C Third cylindrical protrusion 12D 4th cylindrical protrusion 20 Protruding member 20a Tsuba 20b Cylindrical part 20c through hole 100 Cylindrical tube 100a Inner surface 102 Outer tube 104 Air intake C center axis D Inner diameter H straight line K1 Karman vortex street K11 Karman vortex K12 Karman vortex K13 Karman vortex K2 Karman vortex street K21 Karman vortex K22 Karman vortex K23 Karman vortex N1 position N2 position P1 Peel point T1 height position T2 height position T3 height position T4 height position

Claims

1. a cylindrical upper tank having a bottom with an opening through which a liquid is poured and a drop hole at the center through which the liquid falls while entraining air; an injection mechanism that injects the liquid from the opening toward the bottom of the upper tank; a cylindrical pipe extending downward from the bottom and communicating with the drop hole; the injection mechanism is configured to have a first injection pipe that drops the liquid toward a bottom surface portion of the bottom other than the drop hole, and a second injection pipe that drops the liquid toward an edge portion of the bottom of the drop hole, thereby generating a difference between the drop speed of the liquid introduced directly from the second injection pipe into the drop hole and the drop speed of the liquid injected by the first injection pipe and dropping from the periphery of the drop hole into the drop hole, The cylindrical tube is A cylinder body, a plurality of cylindrical protrusions provided on the inner circumferential surface of the cylindrical body, which generate Karman vortices in the liquid passing through the cylindrical body; Oxygen dissolving device.

2. The diameter of the plurality of cylindrical protrusions is equal to or less than 1 / 4 of the inner diameter of the cylindrical body. The oxygen dissolving device according to claim 1.

3. When the diameter of the plurality of cylindrical protrusions is d, The height of the cylindrical protrusions is equal to or greater than (½)d and equal to or less than d. The oxygen dissolving device according to claim 1 or 2.

4. The plurality of cylindrical protrusions are a plurality of first cylindrical protrusions arranged along a circumferential direction at a first height position in the up-down direction; a plurality of second cylindrical protrusions arranged along the circumferential direction at a second height position that is lower than the first height position, The circumferential positions of the plurality of first cylindrical protrusions and the circumferential positions of the plurality of second cylindrical protrusions are different from each other. The oxygen dissolving device according to any one of claims 1 to 3.

5. When the diameter of the plurality of cylindrical protrusions is d, a circumferential distance between a pair of adjacent second cylindrical projections on the inner circumferential surface is 6.2d or more, A circumferential distance on the inner circumferential surface between a reference first cylindrical projection, which is one of the plurality of first cylindrical projections, and a target second cylindrical projection, which is one of the plurality of second cylindrical projections and is located adjacent to the reference first cylindrical projection in the circumferential direction, is 3.1d or more. The oxygen dissolving device according to claim 4.

6. the liquid is poured into a cylindrical upper tank having a bottom with an opening through which the liquid is poured and a drop hole at the center through which the liquid falls while entraining air, and the liquid is introduced into a cylindrical pipe extending downward from the bottom and communicating with the drop hole, The liquid is poured into the upper tank using a first injection pipe that causes the liquid to fall toward a bottom portion other than the drop hole in the bottom portion, and a second injection pipe that causes the liquid to fall toward an edge portion of the drop hole in the bottom portion, thereby generating a difference between the falling speed of the liquid introduced directly from the second injection pipe into the drop hole and the falling speed of the liquid poured by the first injection pipe and falling from the periphery of the drop hole into the drop hole, The cylindrical pipe has a cylindrical body and a plurality of cylindrical protrusions provided on an inner peripheral surface of the cylindrical body to generate Karman vortices in the liquid passing through the cylindrical body. Oxygen dissolution method.

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