JP2006231304A - Method and apparatus for generating microbubble - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of generating microbubbles that can steadily generate microbubbles having small diameters and less variation in the diameter, and an apparatus for generating microbubbles. <P>SOLUTION: The apparatus A for generating microbubbles has a device 10 for supplying a gas mixture liquid such as an aspirator and a pump device, a tube body 2 through which the gas mixture liquid flows, an ultrasonic vibration generater 3, and a plurality of mesh plates 4 disposed inside the tube body 2. When the gas mixture liquid which is prepared by mixing liquid with gas is made to pass through the porous body 4, ultrasonic vibrations are imparted to the porous body 4 to generate microbubbles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microbubble generating method and a microbubble generating device for generating fine bubbles (hereinafter referred to as microbubbles) in a liquid.

Devices equipped with microbubble generators have been proposed as facial instruments, water purifiers, washing machines, washing machines, etc., and as devices that can be used as such microbubble generators, for example, in liquid stored in a tank When a gas is blown through a porous body, a structure has been devised in which microbubbles are generated by applying ultrasonic vibration to the porous body (Patent Document 1).
JP 2003-93858 A

  However, in the microbubble generator described in Patent Document 1, when a gas is blown into the liquid through the porous body, it is a method of applying ultrasonic vibration to the porous body to crush and release the bubbles. There is a problem that the diameter of the bubble is large and the variation in the diameter is large.

  In view of the above problems, an object of the present invention is to propose a microbubble generating method and a microbubble generating apparatus capable of regularly generating microbubbles having a small diameter and a small variation in diameter.

  In order to solve the above problems, the microbubble generation method according to the present invention is characterized in that a gas mixture obtained by mixing a gas with a liquid is passed through the porous body and ultrasonic vibration is applied to the porous body. To do.

  In the present invention, when a gas is blown into a liquid through the porous body, unlike a method of crushing bubbles by applying ultrasonic vibration to the porous body, a gas mixed liquid in which a gas is mixed with the liquid is formed into the porous body. When passing, since the microbubbles are generated by applying ultrasonic vibration to the porous body, the microbubbles having a small diameter and a small variation in the diameter can be generated. The reason for this is that microbubbles are generated by applying ultrasonic vibrations while gas is mixed with the liquid in advance and the gas mixture is constantly passed through the porous body. Since it is maintained in a steady state, it is considered that the diameter of the microbubbles generated from the gas mixture is small and the variation in diameter is small. In addition, since the ultrasonic vibration causes not only the porous body but also the surrounding liquid to be ultrasonically vibrated, it is considered that the bubbles are crushed not only when passing through the porous body but also before and after that. Further, it is considered that the ultrasonic vibration is equally applied to the gas through the liquid because the ultrasonic vibration is applied to the gas mixed with the liquid, instead of directly applying the ultrasonic vibration to the bubbles.

  The microbubble generator according to the present invention includes a tubular body through which a gas mixed liquid obtained by mixing a gas with a liquid passes, a porous body that is fixed in the tubular body and through which the gas mixed liquid passes, and the porous body And an ultrasonic vibration generating device for applying ultrasonic vibration to the head.

  In the present invention, the ultrasonic vibration generator is fixed coaxially to the portion where the porous body is fixed on the upstream side of the portion where the porous body is fixed. It is preferable that If comprised in this way, size reduction of a microbubble generator can be achieved.

  In this invention, the said porous body is arrange | positioned in the said 2nd pipe part located downstream among the 1st pipe part and 2nd pipe part which comprise an L-shaped part in the said pipe body. In this case, the ultrasonic vibration generator employs a configuration in which the L-shaped portion and the bent portion of the tubular body are fixed coaxially with the second tube portion so as to form the L-shaped portion and the T-shape. be able to.

  In the present invention, when the porous body is disposed in the straight portion of the tubular body, the ultrasonic vibration generating device is located upstream of the ultrasonic vibration generating device in the straight portion, and the inner side is a flow path. It is possible to adopt a configuration in which the ring shape is fixed coaxially to the straight portion.

  In the present invention, the porous body is preferably attached in multiple stages along the flow-down direction of the gas mixture. If comprised in this way, the microbubble produced | generated by the porous body of the front | former stage can be made finer by the porous body of a back | latter stage, and the diameter can be arrange | equalized.

  In the present invention, it is preferable that the porous body is fixed at an intermediate position in the tubular body with the outer peripheral portion being sandwiched by the tubular member from both sides.

  In the microbubble generating method and the microbubble generating device of the present invention, when a gas is blown into the liquid through the porous body, unlike the method in which bubbles are crushed by applying ultrasonic vibration to the porous body, the gas is injected into the liquid. When the mixed gas mixture is passed through the porous body, the microbubbles are generated by applying ultrasonic vibration to the porous body. Therefore, it is possible to generate microbubbles having a small diameter and a small variation in diameter. .

  Hereinafter, an example of a microbubble generator to which the present invention is applied will be described with reference to the drawings.

[Embodiment 1]
(overall structure)
FIG. 1 is a schematic cross-sectional view of a microbubble generator according to Embodiment 1 of the present invention. As shown in FIG. 1, the microbubble generator 1 of the present embodiment includes a gas mixture supply device 10 that mixes a gas with a liquid and supplies the mixture as a gas mixture, and an L-shaped tube 2 through which the gas mixture flows. And an ultrasonic vibration generator 3 and a plurality of mesh plates 4 (porous bodies) disposed inside the tube body 2. The end portions 21 and 22 of the tube body 2 are respectively connected to the outside, and the end portion 21 is connected to a gas mixture supply device 10 such as an aspirator or a pump device. The supplied gas mixture flows in the tube body 2 toward the end 22.

  In the tube body 2, the first tube portion 210 and the second tube portion 220 are bent at a right angle to form the L-shaped portion 20. Of the first tube portion 210 and the second tube portion 220, A plurality of mesh plates 4 are fixed to the second pipe portion 220 located on the downstream side.

  The mesh plate 4 is a metal hard porous body and has a three-stage configuration in which three mesh plates are attached along the flow direction of the gas mixture. The mesh plate 4 has an outer diameter larger than the inner diameter of the tube body 2. In the pipe body 2, the second pipe portion 220 is configured by connecting three pipe members 26, 27, and 28. The mesh plate 4 is fixed to the inside of the tube body 2 by sandwiching the outer peripheral side of the mesh plate 4. Note that the space between the pipe members 26, 27, and 28 is sealed by the rubber packing 9. Here, the mesh diameter of the mesh plate 4 is appropriately set according to the viscosity of the liquid, the diameter of bubbles to be generated, and the like.

  In the microbubble generator 1 of this embodiment, the round bar-shaped ultrasonic vibration generator 3 is fixed to the bent portion of the tube body 2 so as to form a T-shape with the L-shaped portion 20 of the tube body 2. The ultrasonic vibration generating device 3 is in a state of being fixed coaxially with the second tube portion 220. As the ultrasonic vibration generating device 3, a well-known device used in an ultrasonic cleaning device or the like can be used, and a detailed description thereof is omitted, but the piezoelectric ceramic vibrator 6 and the piezoelectric element 6 are sandwiched. A pair of electrodes 7a and 7b is provided. In addition, since the screw hole 311 is formed in the end surface 31 of the ultrasonic vibration generator 3, the ultrasonic vibration generator 3 is connected to the tube body by the fixing screw shaft 8 protruding from the end surface 201 of the tube body 2. 2 can be fixed.

  Such an ultrasonic vibration generator 3 oscillates ultrasonic waves that vibrate parallel to the out-of-plane direction of the end face 31. The vibration direction is indicated by an arrow C. Therefore, the vibration direction C of the ultrasonic vibration oscillated from the ultrasonic vibration generator 3 is parallel to the flow direction of the gas mixture and is perpendicular to the mesh plate 4, that is, the gas mixture on the mesh plate 4. Parallel to the passing direction. Here, the frequency of the ultrasonic vibration oscillated from the ultrasonic vibration generator 3 is set in the range of 20 Hz to 1 MHz, although it depends on the viscosity of the liquid and the diameter of the bubble to be generated.

(Micro bubble generation operation)
In the microbubble generator 1 configured as described above, when the ultrasonic vibration generator 3 is driven to oscillate ultrasonic vibration while the gas mixture is supplied to the tube body 2, the ultrasonic vibration is The vibration is transmitted through the body 2 and ultrasonic vibration is applied to the mesh plate 4. Further, ultrasonic vibration is also given to the gas mixture flowing in the tube body 2. As a result, micro bubbles are generated on the downstream side of the mesh plate 4 having a three-stage structure, and the liquid containing the micro bubbles is discharged.

(Main effects of this form)
As described above, in the microbubble generating method and the microbubble generating device 1 according to the present embodiment, when a gas mixed liquid obtained by mixing a gas with a liquid is passed through the porous body 4, ultrasonic vibration is applied to the porous body 4. To generate microbubbles. Therefore, when a gas is blown into the liquid through the porous body, unlike the method in which the ultrasonic vibration is applied to the porous body to crush the bubbles, the gas mixture obtained by mixing the gas with the liquid is passed through the porous body 4. At this time, since the ultrasonic vibration is applied to the porous body 4, microbubbles having a small diameter and a small variation in diameter can be generated.

  The reason is that gas is mixed with the liquid in advance, and the microbubbles are generated by applying ultrasonic vibration while constantly passing the gas mixture through the porous body 4. It is considered that the diameter of the microbubbles is small and the variation in diameter is small. In addition, since the ultrasonic vibration causes not only the porous body 4 but also the surrounding liquid to be ultrasonically vibrated, it is considered that bubbles are crushed not only when passing through the porous body 4 but also around the porous body 4. . Further, it is considered that the ultrasonic vibration is equally applied to the gas through the liquid because the ultrasonic vibration is applied to the gas mixed with the liquid, instead of directly applying the ultrasonic vibration to the bubbles.

  Moreover, in the microbubble generator 1 of this embodiment, the ultrasonic vibration generator 3 has the porous body 4 fixed on the upstream side of the portion of the tubular body 2 where the porous body 4 is fixed. It is fixed coaxially to the part. For this reason, size reduction of the microbubble generator 1 can be achieved.

  Furthermore, in the microbubble generator 1 of this embodiment, since the three porous bodies 4 are attached in multiple stages along the flow-down direction of the gas mixed liquid, the microbubbles generated in the porous body 4 in the preceding stage are separated from the latter stage. The porous body 4 can be made finer and the diameters thereof can be made uniform.

[Embodiment 2]
FIG. 2 is a schematic cross-sectional view of a microbubble generator according to Embodiment 2 of the present invention. Since the basic configuration of the microbubble generator of this embodiment is the same as that of Embodiment 1, the same reference numerals are given to portions having corresponding functions, and description thereof is omitted. In FIG. 2, the microbubble generator 1 </ b> A of this embodiment includes a gas mixture supply device 10 such as an aspirator or a pump device, a tube body 2 </ b> A through which the gas mixture flows, an ultrasonic vibration generator 3 </ b> A, and a tube body 2. It has a plurality of mesh plates 4 (hard porous body) arranged inside.

  In this embodiment, a straight structure is adopted as the tubular body 2A, and the first tubular member 23, the second tubular member 24, the third tubular member 26, The fourth pipe member 27 and the fifth pipe member 28 are connected in this order. The first tube member 23 and the second tube member 24 are connected by a connection tube 25. The three mesh plates 4 are respectively disposed between the second tube member 24 and the fifth tube member 28, and this embodiment also has a three-stage configuration.

  In this embodiment, the ultrasonic vibration generating device 3A is configured in an annular shape having a flow path on the inside, and generates ultrasonic waves that vibrate parallel to the axial direction. The vibration direction is indicated by an arrow D. The ultrasonic vibration generator 3A is fixed so as to surround the outer peripheral surface of the connection pipe 25 between the first pipe member 23 and the second pipe member 24, and the portion to which the porous body 4 is fixed It is in the state fixed to the same axis to. Accordingly, the vibration direction D of the ultrasonic vibration oscillated from the ultrasonic vibration generator 3A is parallel to the flow direction of the gas mixture and is perpendicular to the mesh plate 4, that is, the gas mixture on the mesh plate 4 Parallel to the passing direction.

  Also in the microbubble generating device 1A configured as described above, the microbubble generating method is similar to the first embodiment when the gas mixture is mixed with the liquid when passing through the porous body 4. Microbubbles are generated by applying ultrasonic vibration. Therefore, when a gas is blown into a liquid through the porous body, unlike the method of crushing bubbles by applying ultrasonic vibration to the porous body, microbubbles having a small diameter and a small variation in diameter are generated. be able to.

  Moreover, in the microbubble generator 1 of this embodiment, the ultrasonic vibration generator 3 has the porous body 4 fixed on the upstream side of the portion of the tubular body 2 where the porous body 4 is fixed. Since it is fixed coaxially to the portion, the microbubble generator 1 can be reduced in size. Moreover, in the microbubble generator 1 of this embodiment, since the three porous bodies 4 are attached in multiple stages along the flow-down direction of the gas mixture, the microbubbles generated in the preceding porous body 4 are removed from the rear stage. The porous body 4 can be made finer and the diameters thereof can be made uniform, and the same effects as in the first embodiment can be obtained.

  Furthermore, since the microbubble generator 1A of this embodiment is easier to assemble than the first embodiment, it is suitable for mass production. In addition, the size in the length direction can be suppressed to about 200 mm, and the configuration can be made quite small.

[Other embodiments]
In the above embodiment, the mesh plate 4 has a three-stage configuration. However, the mesh plate 4 may have one, two, or four or more stages depending on the diameter of the microbubbles to be generated. Further, instead of the mesh plate 4, a porous sintered plate having a large number of holes can be used. Furthermore, if a plurality of microbubble generators 1 and 1A are connected and the vibration frequency of the devices located on the downstream side is increased sequentially, even finer microbubbles, specifically bubbles with a microbubble diameter or less, are generated. It becomes possible to make it.

[Measurement system for microbubble diameter and distribution]
The diameter and distribution amount of the microbubbles generated from the microbubble generators 1 and 1A described above can be measured by, for example, a measurement system described below.

This measurement system pays attention to the characteristic that when an ultrasonic wave is applied to a microbubble so that the bubble does not collapse, the microbubble having a diameter corresponding to the frequency range resonates. If the ratio between the constant pressure specific heat and the constant volume specific heat is κ (a constant of about 1.4 for oxygen and nitrogen), the pressure applied to the liquid is P, and the specific gravity of the liquid is ρ, the radius r of the microbubble (bubble) is Formula r = 1 / 2πf√ (3κP / ρ)
(Minnaert's formula).

  As can be seen from this equation, bubbles having a large diameter resonate in a low frequency range, and bubbles having a small diameter resonate in a high frequency range. Further, the amount of bubbles can be obtained by performing FFT (Fast Fourier Transform) analysis on the sound pressure in the resonated sound range (frequency range). Therefore, if the change in the sound pressure for each frequency can be captured, the diameter and distribution amount of the microbubbles can be obtained therefrom.

  FIG. 3 is a schematic block diagram showing a measurement system configured based on this theory. As shown in this figure, the measurement system 100 according to the present embodiment is mainly configured by a control device 101 composed of a personal computer. In the liquid stored in the tank 10, microbubble generators 1 and 1A are arranged, and an oscillator 102 and a receiver 103 are arranged so as to sandwich microbubbles generated therefrom. The oscillator 102 is connected to the output side of the personal computer 101 via an oscillator 104 and an output amplifier 105. The receiver 103 is connected to the input side of the personal computer 101 via an input amplifier 106 and an FFT analyzer 107. A pressure sensor 108 is connected to the input side of the personal computer 101. The pressure sensor 108 is for correcting the pressure (P) applied to the liquid in the tank 10.

  In the measurement system 100 configured as described above, the personal computer 101 operates the oscillator 104 to set the frequency range of ultrasonic vibration oscillated from the oscillator 102. The frequency range is set, for example, between 500 kHz and 2 MHz so that the microbubbles are not crushed, and the signal is output to the oscillator 102 via the output amplifier 105. The ultrasonic vibration that is oscillated from the oscillator 102 and propagates in the liquid and reaches the receiver 103 is input to the FFT analyzer 107 via the input amplifier 106, where it is analyzed. The data is input to the personal computer 101. In addition, an input frequency other than the output frequency in the ultrasonic vibration reaching the receiver 103 is subjected to filtering processing and processed as data by the personal computer 101.

  Since the relationship between the frequency and intensity (sound pressure) of ultrasonic vibration can be obtained from the data collected by the personal computer 101, the radius of the bubble and the distribution amount of the bubble can be obtained therefrom.

  That is, in obtaining the bubble radius and the distribution amount of the bubble, first, measurement is performed in a state where the microbubbles in the state where the microbubble generators 1 and 1A are stopped are not generated, and FIG. Take static data as shown.

  Next, the microbubble generators 1 and 1A are driven to perform measurement in a state where the microbubbles are generated, and dynamic data as shown in FIG.

  Next, the difference calculation between the dynamic data and the static data is performed to obtain the difference data as shown in FIG. From this difference data, it can be seen that there are many microbubbles (bubbles) having a radius (r) resonating between 740 kHz and 1100 kHz in the liquid in the tank 10. The radius (r) of the microbubble can be easily obtained from the above formula. The amount of bubbles can be obtained from the intensity (sound pressure).

  As described above, in the measurement system 100 of this embodiment, the diameter and distribution amount of microbubbles can be accurately and easily measured. Therefore, according to the present embodiment, it is possible to accurately and easily perform the measurement of the diameter and distribution amount of microbubbles, which has not been performed so much in the past, and thus it is possible to expand the use for microbubble measurement. It is possible to construct an inexpensive system with excellent cost performance.

It is a schematic sectional drawing of the microbubble generator which concerns on Embodiment 1 of this invention. It is a schematic sectional drawing of the microbubble generator which concerns on Embodiment 2 of this invention. It is a schematic block diagram which shows the measuring system for measuring the diameter and distribution amount of a microbubble. (a) thru | or (c) is a figure which shows the measurement result in the measurement system shown in FIG.

Explanation of symbols

1, 1A Microbubble generator 2, 2A Tube 3, 3A Ultrasonic vibration generator 4 Mesh plate (porous body)
10 Gas mixture supply device

Claims (7)

  A method for generating microbubbles, comprising passing a gas mixture obtained by mixing a gas into a liquid through a porous body and applying ultrasonic vibration to the porous body.   A tubular body through which a gas mixture obtained by mixing a gas with a liquid passes, a porous body that is fixed in the tubular body and through which the gaseous mixture passes, and an ultrasonic wave that imparts ultrasonic vibrations to the porous body A microbubble generator comprising a vibration generator.   3. The ultrasonic vibration generating device according to claim 2, wherein the ultrasonic vibration generator is coaxial with respect to a portion where the porous body is fixed on an upstream side of the portion where the porous body is fixed. A microbubble generator characterized by being fixed. In Claim 3, the said porous body is arrange | positioned in the said 2nd pipe part located in the downstream among the 1st pipe part and 2nd pipe part which comprise an L-shaped part in the said pipe body,
The ultrasonic vibration generator is fixed to the bent portion of the tube coaxially with the second tube portion so as to form the L-shaped portion and the T-shape. Bubble generator. The porous body according to claim 3, wherein the porous body is disposed on a straight portion of the tubular body.
The ultrasonic vibration generating device is coaxially fixed to the straight portion with an annular shape having a flow path on the inner side of the straight portion upstream of the ultrasonic vibration generating device. Bubble generator.   6. The microbubble generator according to claim 2, wherein the porous body is attached in multiple stages along a flow-down direction of the gas mixture.   7. The microbubble generator according to any one of claims 2 to 6, wherein the porous body has an outer peripheral portion sandwiched between pipe members from both sides and fixed at an intermediate position in the pipe body.

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