Fine bubble generating device

Abstract

To provide a fine bubble generating device that can stably generate sufficient quantity of fine bubble continuously.SOLUTION: A size suppression gas mixing part 60 constituting a fine bubble generating device includes an ultrasonic wave irradiator 61 and an air pump 62. The air pump 62 mixes air in water 2 flowing through piping 5. The ultrasonic wave irradiator 61 irradiates the water 2 flowing in an ultrasonic wave irradiation tank 610 with an ultrasonic wave UW, so as to suppress increase of a size of maximum bubble by energy generated by the ultrasonic wave UW of irradiation. A ball valve 67 arranged in front of the ultrasonic wave irradiation tank 610 mechanically suppresses increase of the size of the maximum bubble in the water 2 flowing therethrough.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a microbubble generating device. [Background technology]

[0002] Fine bubbles generated in liquids such as water, more specifically microbubbles or nanobubbles, are said to reach several thousand degrees and several thousand atmospheric pressures when they disappear, and it is possible to forcibly decompose the gas molecules inside. As a result, they generate free radicals with strong oxidizing power. Since these free radicals have strong bactericidal power, liquids containing fine bubbles, such as water, are also used for sterilizing food ingredients. Note that microbubbles are defined as bubbles with a diameter of 1 to 100 μm according to the ISO (International Organization for Standardization) standard. Although the exact definition of nanobubbles varies depending on the application field and the generation method, they are generally defined as bubbles with a diameter of 1 μm or less.

[0003] It has also been confirmed that microbubbles contained in liquids can adsorb and separate dirt from the surface of objects, while also preventing reattachment. As a result, liquids containing microbubbles can also be used as cleaning liquids. Microbubbles are also expected to be used in a wide range of other fields, including environmental purification, medicine, and health.

[0004] One method for generating microscopic bubbles in liquid is the pressurization / decompression method, which combines pressurization and decompression. This pressurization / decompression method applies high pressure to the liquid, and then applies a lower pressure to the liquid, generating microscopic bubbles by this pressure change. Some microscopic bubble generating devices that employ this pressurization / decompression method mix a gas into the liquid supplied to a pump that pressurizes the liquid, thereby more efficiently generating microscopic bubbles in the liquid after decompression (see, for example, Patent Documents 1 and 2).

[0005] In order to increase the amount of fine bubbles generated, it is desirable to mix a larger amount of gas into the liquid. However, when a large amount of gas is mixed into the liquid, large bubbles are more likely to exist in the liquid. Large bubbles make it easier for the gas and liquid to separate, or for gas to accumulate. This makes it easier for air entrapment to occur, a phenomenon that reduces the pump's capacity (performance) so that sufficient discharge pressure or flow rate cannot be obtained. As the pump's capacity decreases, the amount of fine bubbles generated also decreases. In some cases, this may lead to the need for maintenance. For this reason, it is important to be able to stably maintain a sufficient amount of fine bubbles generated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-20005 A [Patent Document 2] Patent No. 7202584 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention proposes a fine bubble generating device that can stably maintain a sufficient amount of fine bubbles generated. [Means for solving the problem]

[0008] A fine-bubble generating device according to one embodiment of the present disclosure includes a pump capable of applying pressure to a liquid being supplied, a gas mixing section that mixes gas into the liquid being supplied to the pump, and a suppression section that suppresses the size of maximum bubbles that are the largest of the bubbles present in the liquid after the gas has been mixed by the gas mixing section. Effect of the Invention

[0009] In the present invention, a sufficient amount of fine bubbles can be stably generated. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an example of a positive displacement pump. [Diagram 3] 11A and 11B are diagrams illustrating an example of concentration change depending on the size of air bubbles present in cleaning water. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to a second embodiment of the present invention. [Diagram 5] FIG. 11 is a diagram for explaining an example of concentration change depending on the size of air bubbles present in cleaning water in the second embodiment. [Figure 6] FIG. 11 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to a third embodiment of the present invention. [Figure 7] FIG. 4 is a diagram illustrating a configuration example of a size suppression gas mixer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example, including modified examples, and the technical scope of the present invention is not limited to this. Various modified examples are also included in the technical scope of the present invention.

[0012] (First embodiment) FIG. 1 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to a first embodiment of the present invention. The micro-bubble generator shown in Fig. 1 is designed to generate micro-bubbles for cleaning, sterilization, etc. In other words, it is designed to be used mainly as a cleaning machine that generates cleaning liquid.

[0013] As shown in Fig. 1, the micro-bubble generator is configured such that water 2 present in a water source 1 is supplied to a pump 3 via a pipe 5 to apply pressure, and the water 2 discharged from the pump 3 is caused to flow into a pipe 6 and discharged from an outlet 4 connected to the pipe 6. For this purpose, one end of the pipe 5 is located in the water 2 of the water source 1, and the other end is connected to an inlet 31 of the pump 3. One end of the pipe 6 is connected to an outlet 32 ​​of the pump 3, and the other end is connected to the outlet 4. The arrows shown in Fig. 1 represent the flow of the water 2.

[0014] In addition, both the piping 5 and 6 are one or more pipes, tubes, or hoses. They may be a combination of multiple types of members. In other words, the piping 5 may be any pipe capable of supplying the water 2 from the water source 1 to the suction port 31 of the pump 3. Similarly, the piping 6 may be any pipe capable of supplying the water 2 from the discharge port 32 of the pump 3 to the discharge port 4, and the type and combination of the pipes are not particularly limited. The discharge port 4 is not particularly limited as long as it can discharge the water 2 in the piping 5 to the outside. In other words, the discharge port 4 may be a nozzle, a valve, or the like. The water 2 is selected as a liquid that generates fine bubbles. The liquid to be selected may be any liquid capable of generating fine bubbles. For example, the liquid may be alcohol.

[0015] The pump 3 is a positive displacement pump. A positive displacement pump is a type of pump that pressurizes a liquid present in a certain volume and conveys the liquid by imparting energy to the liquid. Positive displacement pumps include piston pumps, plunger pumps, and diaphragm pumps.

[0016] FIG. 2 is a diagram illustrating an example of a positive displacement pump. The positive displacement pump shown in Fig. 2 is a piston pump. As the piston 302 moves in the cylinder 301, the water 2 is sucked in through the suction port 31 or discharged through the discharge port 32. As the piston 302 approaches the suction port 31 and the discharge port 32, the pressure applied to the water 2 present in the space formed by the cylinder 301 and the piston 302 increases. Conversely, as the piston 302 moves away from the suction port 31 and the discharge port 32, the pressure in the space formed by the cylinder 301 and the piston 302 decreases. This pressure decrease allows the water 2 to flow into the space.

[0017] The high pressure applied by the movement of the piston 302 acts to dissolve the large and small air bubbles 21 present in the water 2 in the water 2. This is because the greater the pressure applied, the greater the amount of gas dissolved in the saturated state. The reciprocating movement of the piston 302 also generates complex movements in the water 2 within the cylinder 301. These movements cause the air bubbles 21 to become smaller. Relatively large air bubbles 21 are split into multiple smaller air bubbles 21. As a result, the gas present as the air bubbles 21 becomes more soluble in the water 2.

[0018] For this reason, it is expected that a larger amount of gas will be dissolved in the water 2 after high pressure is applied by the pump 3. This is why a positive displacement pump is used as the pump 3. There is no particular limitation on the type. Note that the suction port 31 and the discharge port 32 are provided with a mechanism for preventing backflow of the water 2, such as a check valve. Therefore, the arrows representing the flow of the water 2 at the suction port 31 and the discharge port 32 are unidirectional.

[0019] The water 2 discharged from the pump 3 flows through the pipe 6 due to the kinetic energy imparted by the pump 3, and is discharged from the outlet 4. When the water 2 is discharged to the outside from the outlet 4, the water 2 is discharged at a shape and speed that depend on the speed at which it flows through the pipe 6, the pressure (static pressure) within the pipe 6, and the shape of the outlet 4.

[0020] FIG. 1 also shows an example of the pressure (static pressure) applied to the water 2. In this example, the pump 3 is at its maximum pressure. As shown in Fig. 1, a maximum pressure (first pressure) is applied to the water 2 by the pump 3. In other words, the pump 3 applies a pressure to the supplied water 2 that is higher than the pressure of the water 2 before it is supplied to the pump 3. A pressure (second pressure) lower than the maximum pressure is applied to the water 2 discharged from the pump 3 and flowing through the pipe 6. This reduced pressure causes bubbles to be generated by gases dissolved in the water 2.

[0021] This pressure is not uniform inside the pipe 6, but gradually decreases due to losses that occur as the water 2 flows. The difference between the pressure applied to the water 2 at the outlet 4 and the external pressure, atmospheric pressure (third pressure), provides momentum to the water 2 discharged from the outlet 4. The pressure applied to the water 2 inside the pipe 5 is lower than atmospheric pressure so that the water 2 can be supplied to the pump 3. The water 2 that has been discharged or will be discharged from the outlet 4 is hereinafter also referred to as "washing water".

[0022] Figure 3 is a diagram explaining an example of the change in concentration depending on the size of bubbles present in the cleaning water. The concentration is the number of bubbles present per 1 ml. Figure 3 shows the measurement results obtained for cleaning water generated multiple times. As shown in Figure 3, the concentration tends to increase as the size decreases. Specifically, the concentration peaks at about 400 million bubbles / ml when the bubble size is about 60 nm.

[0023] Since such a concentration can be obtained with such a bubble size, it is understood that cleaning water can be generated without storing the water 2 discharged from the pump 3 in a tank or the like. By eliminating a tank or the like, the fine bubble generator can be made smaller and lighter. This makes it more portable. It can be more easily moved and installed wherever it is needed. This results in high convenience.

[0024] In this embodiment, the pump 3 is used as a power source that enables the transport of water 2 from a water source 1 to the pump 3 and the discharge of cleaning water from a discharge port 4. If a separate tank or the like is provided to enable the forceful discharge of cleaning water, it is necessary to prepare multiple such power sources. At least, a power source for moving the water 2 stored in the tank or the like is further required. Since the need for multiple power sources is avoided, the fine bubble generator can be made smaller and lighter, making it more portable.

[0025] In the example shown in FIG. 3, water 2 from the water source 1 contains microbubbles at a concentration of about 20 million bubbles / ml. The concentration of microbubbles in the cleaning water is 10 times higher than that of water 2. The reason for this result is thought to be that a relatively large number of microbubbles are generated in the water 2 while it is flowing through the pipe 6. The energy given to the water 2 by the pump 3 may contribute greatly to the generation of such microbubbles. In addition, it is thought that a significant number of microbubbles are generated in the water 2 after it is discharged from the pump 3 into the pipe 6, during the time it flows through the pipe 6 and is discharged from the outlet 4, due to the difference with the high pressure applied by the pump 3 and the pressure drop that occurs during that time.

[0026] Second embodiment FIG. 4 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to a second embodiment of the present invention. 4, in the second embodiment, a valve 11 and a Venturi tube 12 are arranged in the piping 5 from the water source 1 side. The Venturi tube 12 corresponds to the gas mixer in the second embodiment.

[0027] The Venturi tube 12 is provided to mix air with the water 2 flowing inside the Venturi tube 12. A check valve 13 is attached to the tube that leads the air to the water 2 to prevent backflow, that is, to prevent the water 2 from being discharged to the outside. A valve 14 is provided between the check valve 13 and the Venturi tube 12 to adjust the amount of gas (air) supplied to the Venturi tube 12.

[0028] Valve 11 is for adjusting the flow rate and speed of water 2 flowing through Venturi tube 12. In this embodiment, valves 11 and 14 make it possible to adjust both the amount of water 2 flowing through Venturi tube 12 and the amount of gas mixed with the water 2. Due to the presence of Venturi tube 12, the pressure (static pressure) applied to water 2 flowing through pipe 5 is lower only at the location where Venturi tube 12 exists than at other locations. The valve 11 may adjust the flow rate of the water 2 to be supplied by a pump (not shown) or the like from the water source 1. In other words, the water source 1 may be a facility capable of supplying the water 2, such as a water facility.

[0029] Fig. 5 is a diagram for explaining an example of concentration change depending on the size of bubbles present in cleaning water in the second embodiment. As in Fig. 3, Fig. 5 also shows measurement results obtained for cleaning water generated multiple times. As shown in FIG. 5, the concentration tends to increase as the size decreases, as in the first embodiment. Specifically, the concentration peaks at about 650 million bubbles / ml when the bubble size is about 60 nm. Water 2 does not generate fine bubbles. It is considered tap water.

[0030] In this way, in the second embodiment, a higher concentration can be obtained than in the first embodiment. This can be said to be the effect of mixing the air (gas) with the water 2 by the Venturi tube 12. As described above, the gas mixed into the water 2 is given high pressure by the movement of the piston 302 of the pump 3 (see FIG. 2), and is effectively dissolved in the water 2. Even if the air does not dissolve in the water 2, the air will be mixed as fine bubbles by adjusting the water volume and gas volume by the valves 11 and 14. When discharged from the pump 3, the air will be dissolved in the water 2 or will exist in the form of fine bubbles. As a result of a larger amount of air being dissolved in the water 2 and a large amount of fine bubbles being present, it is considered that the second embodiment can generate a larger amount of fine bubbles in the cleaning water compared to the first embodiment.

[0031] In this embodiment, the Venturi tube 12 is used to mix the gas into the water 2, because the valves 11 and 14 allow the necessary amount of gas to be mixed into the necessary amount of water 2. This allows the configuration to be simpler. However, the gas may be mixed using equipment other than the Venturi tube 12. The gas may be forcibly discharged into the water 2 using some kind of power source.

[0032] (Third embodiment) FIG. 6 is a diagram illustrating an example of the configuration of a micro-bubble generating device according to the third embodiment of the present invention. In the third embodiment, as shown in Fig. 6, a size suppression gas mixer 60 is disposed between the valve 11 and the pump 3. A speed reducer 80 that reduces the flow rate of the cleaning water discharged from the exhaust port 4 is connected to the exhaust port 4. The cleaning water that has been reduced in speed by the speed reducer 80 can be discharged to the outside from an exhaust port 81. This exhaust port 81 is also, for example, a nozzle or a valve. The speed reducer 80 is, for example, a hose for generating a pressure loss and slowing down the flow rate of the wash water, or equipment including a tank, etc. The configuration of the speed reducer 80 is not particularly limited.

[0033] This speed reducer 80 significantly reduces the flow rate of the wash water that is finally discharged. By reducing the flow rate, it is also possible to prevent the fine bubbles present in the wash water from being destroyed by impact when the water is discharged. As the destruction of the fine bubbles is prevented, the wash water can be stored in good condition. As a result, the speed reducer 80 is useful for enabling the wash water to be used primarily for purposes other than washing.

[0034] In order to suppress the flow rate of the cleaning water, it is desirable to make the flow area of ​​the cleaning water in the speed reducer 80 larger than the flow area of ​​the outlet 4. The flow area of ​​the speed reducer 80 must be determined taking into consideration the volumetric flow rate of the water 2 discharged from the pump 3 per unit time, the flow area of ​​the pipe 6, the flow area of ​​the outlet 4, the flow rate of the cleaning water discharged from the speed reducer 80, and the like. However, a high flow rate is required for the cleaning water. In consideration of this, it is desirable to make the flow area of ​​the speed reducer 80 9 times or more the flow area of ​​the outlet 4. It has also been confirmed that a member having elasticity is desirable as a member constituting the speed reducer 80. This is considered to be because the elasticity of the wall surface of the flow path suppresses the impact on the cleaning water. In this embodiment, the speed reducer 80 is attached to the outlet 4, but the speed reducer 80 may be attached directly to the pipe 6.

[0035] The size-reducing gas mixing section 60 mixes air into the water 2 flowing through the pipe 5, while further reducing the size of the maximum air bubbles that will be the largest among the air bubbles in the water 2 after the air has been mixed in. Therefore, the size-reducing gas mixing section 60 corresponds to the gas mixing section and the suppression section in this embodiment.

[0036] FIG. 7 is a diagram illustrating a configuration example of the size suppression gas mixer. As shown in FIG. 7, the size suppression gas mixer 60 includes an ultrasonic irradiator 61 and an air pump 62. The air pump 62 is for mixing air into the water 2 flowing through the pipe 5. As the air pump 62, for example, a diaphragm pump may be adopted. Air from the air pump 62 is supplied into the piping 5 via a pressure tank 63. A check valve 64 for preventing backflow is disposed between the air pump 62 and the pressure tank 63, and a needle valve 65 is disposed between the pressure tank 63 and the piping 5.

[0037] The pressure tank 63 stabilizes the supply of air into the piping 5. The needle valve 65 makes it possible to adjust the amount of air supplied from the pressure tank 63 to the piping 5. As the amount of air is adjusted, the amount of air supplied from the air pump 62 that is actually supplied into the piping 5 changes. The pressure tank 63 also functions as a buffer that absorbs pressure changes that accompany these changes.

[0038] In the third embodiment, a tap 66 provided with guide vanes is disposed closer to the valve 11 than the point where air is supplied to the pipe 5. The guide vanes provided on the tap 66 cause the water 2 to form a swirling flow inside the pipe 5. In Fig. 7, the flow of the water 2 is indicated by dashed arrows. Since the tap 66 is provided, in the third embodiment, it is assumed that the water source 1 is a facility capable of supplying water 2, or that a facility such as a pump is provided that enables the water source 1 to supply water 2.

[0039] The swirling flow of the water 2 increases the flow rate of the water 2 flowing through the pipe 5. Therefore, the air supplied into the pipe 5 through the needle valve 65 mixes with the water 2 in a more desirable manner. This is expected to further reduce the size of the maximum air bubbles in the water 2.

[0040] The ultrasonic irradiation device 61 is roughly divided into an ultrasonic irradiation tank 610 and an oscillator 620. The oscillator 620 and the ultrasonic irradiation tank 610 are electrically connected by a cable 630. The water 2 mixed with air is supplied to the ultrasonic irradiation tank 610. A ball valve 67 is disposed in front of the ultrasonic irradiation tank 610. This ball valve 67 is capable of adjusting the size of the flow path through which the water 2 passes. In this embodiment, the size of the flow path of the ball valve 67 is made small.

[0041] By reducing the size of the flow path, the size of the largest air bubble in the water 2 is mechanically suppressed. As the size of the flow path is reduced, the flow rate of the water 2 passing through the ball valve 67 becomes faster and the pressure (static pressure) decreases. On the other hand, on the front side of the ball valve 67, that is, on the valve 11 side, the pressure (static pressure) increases conversely, and the mixed air becomes more easily dissolved in the water 2, and actually dissolves. Therefore, the reduction in pressure at the ball valve 67 makes it easier to generate fine air bubbles. However, the generated fine air bubbles do not function to increase the size of the largest air bubble in the water 2.

[0042] The ball valve 67, together with the ultrasonic irradiation tank 610 described later, corresponds to the suppression unit in this embodiment. In this embodiment, the two suppression units are arranged in series, so that the maximum bubble size can be more reliably suppressed. Note that, in this embodiment, the ball valve 67 is used to make the size of the flow path adjustable, but the type of valve to be used is not particularly limited. The suppression unit may be one that cannot adjust the size of the flow path. For example, it may be something like a plate with holes.

[0043] As shown in FIG. 7, the ultrasonic irradiation tank 610 is of a type in which liquid flows inside. Inside the ultrasonic irradiation tank 610, a transducer 611 that generates ultrasonic waves UW is provided. Thus, the ultrasonic irradiation tank 610 is configured to irradiate the ultrasonic waves UW generated by the transducer 611 to the water 2 flowing inside. In FIG. 7, the ultrasonic waves UW generated by the transducer 611 are visually represented by a dashed curved line. An oscillator 620 connected by a cable 630 generates a signal for driving the transducer 611. Reference numeral 612 denotes an air vent valve for venting air in the ultrasonic irradiation tank 210.

[0044] When ultrasonic waves UW are irradiated into water 2, the negative pressure created by the irradiation causes dissolved gases to gather and generate bubbles. However, if ultrasonic waves UW are continuously irradiated, the bubbles to which energy is continuously applied gradually grow larger as they repeatedly expand and contract. However, once the bubbles grow to a certain stage, they become unstable and are no longer able to maintain their shape. As a result, the size of the largest bubbles in water 2 is suppressed. Because the size of the largest bubbles is suppressed by the action of ultrasonic waves UW, the size of the largest bubbles is stably suppressed.

[0045] The water 2 discharged from the ultrasonic irradiation tank 610 is supplied to the pump 3. Since the size of the maximum air bubbles in the discharged water 2 is stably suppressed, performance degradation due to air entrapment or the like caused by air bubbles in the water 2 supplied to the pump 3 can be avoided or further suppressed. This means that the amount of air that can be mixed with the water 2 flowing in the pipe 5 can be increased. Therefore, the amount of fine bubbles generated can be increased more easily and stably. The amount of fine bubbles generated can also be maximized.

[0046] In this embodiment, when the concentration was actually confirmed, it tended to be larger as the size became smaller, as in the first and second embodiments. However, the peak concentration was about 900 million / ml when the bubble size was about 60 nm, and more fine bubbles could be generated than in the second embodiment. Water 2 was tap water in which fine bubbles were not generated.

[0047] The configuration of the size-reducing gas mixer 60 as shown in FIG. 7 is one example. The size-reducing gas mixer 60 is not particularly limited in configuration as long as it can achieve two functions: mixing gas into liquid and suppressing the size of the maximum bubble in the liquid after mixing the gas. If the size of the maximum bubble can be stably suppressed, ultrasonic waves UW do not need to be used. Even if ultrasonic waves UW are irradiated, the irradiation method is not limited to the ultrasonic irradiation tank 210. For mixing the gas, it is possible to mix a larger amount of gas into the liquid, so it is desirable to adopt a device that can mix the gas into the liquid without depending on the pressure of the liquid. This is why the air pump 62 is adopted in this embodiment. [Explanation of symbols]

[0048] 1 water source, 2 water, 3 pump, 4 outlet, 5, 6 piping, 11, 14 valve, 12 venturi tube, 13, 64 check valve, 60 size suppression gas mixing section, 61 ultrasonic irradiation machine, 62 air pump, 63 pressure tank, 65 needle valve, 66 tap, 67 ball valve, 610 ultrasonic irradiation tank, 620 oscillator.

Claims

1. A pump capable of applying higher pressure to the liquid being supplied; a gas mixing unit that mixes a gas with the liquid supplied to the pump; a suppression unit that suppresses the size of a maximum bubble that is the largest among the bubbles present in the liquid after the gas is mixed by the gas mixing unit; A fine bubble generating device equipped with:

2. a swirling flow generating section that generates a swirling flow in the liquid supplied to the gas mixing section; The fine bubble generating device according to claim 1 , further comprising:

3. The suppression unit suppresses the size of the largest bubble by irradiating ultrasonic waves into the liquid. The fine bubble generating device according to claim 1.

4. The suppression portion mechanically limits the size of the largest air bubble in the liquid. The fine bubble generating device according to claim 1.

5. The pump is a positive displacement pump. The fine bubble generating device according to claim 1.

6. A pipe for passing the liquid discharged from the pump; a deceleration section to which the liquid that has flowed through the pipe is supplied and which reduces the flow velocity of the liquid; The fine bubble generating device according to any one of claims 1 to 5, further comprising:

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