AU3801099A

AU3801099A - Swirling type micro-bubble generating system

Info

Publication number: AU3801099A
Application number: AU38010/99A
Authority: AU
Inventors: Hirofumi Ohnari
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-07-07
Filing date: 1999-07-07
Publication date: 2001-01-18
Anticipated expiration: 2019-07-07
Also published as: AU770174B2

Description

50677 AWT:PFB P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

HIROFUMI OHNARI Address for Service: COLLISON CO., 117 King William Street, Adelaide, S.A. 5000 Invention Title: SWIRLING TYPE MICRO-BUBBLE GENERATING SYSTEM The following statement is a full description of this invention, including the best method of performing it known to me: Acua Invetor o* FROM MRMipi F999Y 71 1843/WU11 :42.'X"4q420139971 0 P 4

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SPECIFICATION

SWIRLING TYPE MICRO-BUBBLE GENERATING SYSTEM FIELD OF THE INVENTION The present invention relates to a micro-bubble generating system for efficiently dissolving gas such as the air, oxygen gas, etc. into liquid such as city water, river water, etc., for purifying polluted water and for effectively utilizing the water for reconditioning and renewal of water environment.

BACKGROUND ART In conventional type aeration systems, e.g. in most of aeration systems using micro-bubble generating system installed for culture and growth of aquatic animals, air •c bubbles are generated by injecting the air under pressure into water through fine pores of tubular or planar microbubble generating system installed in the tank, or air .bubbles are generated by introducing the air into water flow with shearing force or by vaporizing the air dissolved in water by rapidly reducing pressure of the pressurized water.

In the aeration process using the micro-bubble generating system with the above functions, operation is basically controlled by adjusting the air supply quantity or r MVM YzAPzq1tWTJ)FJT IU u TY Thrn fil Od 1A i j:14 041d Z,'3YED-t2 1 599 7 1 F the number of the micro-bubble generating 3ystem3 to be installed, while it is necessary to efficiently dissolve gas such as air, carbon dioxide, etc. into water and further to promote circulation of the water.

However, the aeration system usinq the conventional type micro-bubble generating system, e.g. diffusion system based on injection, even when fine cores are provided, when air bubbles are injected under pressure through pores, volume of each of the air bubbles is expanded, and diameter of each air bubble is increased to several millimeters due to surface tension of the air bubbles during injection.

Thus, it is difficult to generate air bubbles of smaller diameter. Also, there are problems such as clogging of the pores or increase of power consumption caused by the operation for long time.

In the system to generate the air bubbles by introducing the air into water flow with shearing force using vanes and air bubble jet stream, it is necessary to have higher number of revolutions to generate cavitation.

Also, there are problems of power consumption increase and the problem of corrosion of vanes or vibration caused by generation of cavitation. Further, there are problems ir that only a small amount of micro-bubbles can be generated.

In the system where gas-liquid two-phase flow collides with the moving vane or projection, fishes or small aquatic 1~ Q D= ,w0 6:qL/3fl69-t4 1 99710 P 6 animals in natural lakes or culture tanks may be injured, and this causes trouble in the development and maintenance of the environmental condition necessary for the growth of fishes and other aquatic animals.

Further, in the pressurizing system, the system must be designed in larger size and requires higher cost, and operation cost is also high.

In none of the prior art in this field as described above, it has been possible to generate micro-bubbles with diameter of not more than 20 pm in industrial scale.

SUMMARY OF THE INVENTION After fervent study efforts, the present inventors have successfully developed the present invention, by which it is possible to generate micro-bubbles with diameter of not more than 20 pm in industrial scale.

As shown in Fig. 12, which indicates the principle of the system according to the present invention, a microbubble generating system is provided, which comprises a conical space 100 in a container, a pressure liquid inlet 500 provided in tangential direction on a part of circumferential surface of inner wall of the space, a gas introducing hole 80 opened at the center of the bottom 300 of the conical space, and a swirling gas-liquid outlet 101 near the top of the conical space.

r\l nv/fi /w)r'ywl ME(X 1 8 44,' I 42/"24442CJi 39971 G P 7 The entire system or at least the swirling gas-liquid outlet 101 is submerged in the liquid, and by sending pressure liquid from the pressure liquid inlet 500 into the conical space 100, a swirling flow is formed inside, and negative pressure is generated along the axis of the conical tube. By this negative pressure, the gas is sucked through the gas introducing hole 80. As the gas passes along the axis of the tube where the pressure is at the lowest, a narrow swirling gas cavity 60 is generated.

In the conical space 100, a swirling flow is generated from the inlet (pressure liquid inlet) 500 toward the outlet (swirling gas-liquid outlet) 101. As cross-sectional area of the space 100 is gradually reduced toward the swirling gas-liquid outlet 101, both the swirling velocity and velocity of the flow directed toward the outlet are increased at the same time.

eooo In association with this swirling, centrifugal force is applied on the liquid and centripetal force is applied on the air at the same time because of the difference of specific gravity between the liquid and the gas. As a result, the liquid portion and the gas portion become *separable from each other, and the gas is turned to a narrow thread-like gas swirling cavity 60, which is narrowed down and runs continuously up to the outlet 101 and is then injected through the outlet. At the same time as the

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injection, swirling is rapidly weakened by the surrounding stationary water. Then, radical difference in swirling velocity occurs before and after that point. Because of the difference of swirling velocity, the thread-like gas cavity 60 is cut off in continuous and stable manner. As a result, a large amount of micro-bubbles, e.g. micro-bubbles of 10 to 20pm in diameter, are generated near the outlet 101 and are discharged.

Specifically, the present invention provides: a swirling type micro-bubble generating system, comprising a container main unit having a conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the conical space, and a swirling gas-liquid outlet arranged at the top of the conical space; a swirling type micro-bubble generating system, comprising a container main unit having a truncated conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the truncated conical space, and a swirling gas-liquid outlet arranged in the upper portion of the truncated conical space; a swirling type micro-bubble eneratng system, a swirling type micro-bubble generating system, comprising a container main unit having a space of bottlelike shape, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the bottle-like space, and a swirling gas-liquid outlet arranged at the top of the bottle-like space; a swirling type micro-bubble generating system according to one of to above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having the same radius of curvature on inner wall of the space; a swirling type micro-bubble generating system according to one of to above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having different radii of curvature on inner wall of the space; a swirling type micro-bubble generating system according to one of to above, wherein the pressure liquid inlet is provided on a part of circumferential surface of inner wall near the bottom of the space; a swirling type micro-bubble generating system according to cne of to above, wherein the pressure liquid inlet is provided on a part of circumferential FROM XWMWiFmNi TYYY 7fl 69(X) 18:45 "WES:42,/"4201399710 P i0 surface of inner wall near a point halfway down of the space; and a swirling type micro-bubble generating system according to one of to above, wherein a baffle plate is arranged immediately before the swirling gas-liquid outlet.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view of a swirling type micro-bubble generating system of an embodiment according to the present invention; Fig. 2 is a plan view of the above; Fig. 3 is a longitudinal sectional view at the center along the line B B in Fig. 2; Fig. 4 is a lateral sectional view of a lower flow base gee' along the line A A in Fig. 1; Fig. 5 is a drawing to explain triple swirling flows on 99 a cross-section of inner space of a covered cylinder along Sthe line X X; Fig. 6 is a drawing to explain swirling ascending flow 9 9 and descending flow and a gas vortex flow in the above embodiment along the line Y Y; Fig. 7 is a drawing to explain generation of microbubbles in the gas vortex flow; Fig. 8 is a drawing to explain a micro-bubble r MUM JwmPrII i tlvvzM M7W ffl bU iU: ,'U'IiB:q2/UD44201 39q71u P ii generating mechanism having four lateral discharge ports on a central reflux outlet; Fig. 9 is a drawing to explain the micro-bubble generating mechanism at a first lateral discharge port of Fig. 8; Fig. 10 is a drawing to explain the micro-bubble generating mechanism as seen on a side wall adjacent to the first lateral discharge port of Fig. 8; Fig. 11 is" a drawing to explain the micro-bubble generating mechanism as seen on a second lateral discharge port of Fig. 8; Fig. 12 is to explain a system of another embodiment, also serving to explain the principle of the present invention; Fig. 13 is to explain a system of another improved embodiment of the present invention; Fig. 14 is to explain a system of still another

S.

embodiment of the present invention; Fig. 15 is a graphic representation of the results, showing diameter of each of the air bubbles and distribution o of air bubble generation frequency, when a medium type system according to the present invention was submerged into water and micro-bubbles were generated using the air as the gas; and Fig. 16 is a drawing to explain the system of an Fig. 16 is a drawing to explain the system of an r M PLT npn*^n IF] Ot 'A 0 W4L 0 q, Z' xz"4 efj 1 399-11 Q F 1 2 embodiment of the present invention when it is installed in a water tank.

BEST MODE FOR CARRYING OUT THE INVENTION As shown in the drawing to explain the principle of the present invention in Fig. 12, a micro-bubble generating system comprises a conical space 100 formed in a container of the system, a pressure liquid inlet 500 provided in tangential direction on a part of circumferential surface of inner wall of the space, a gas introducing hole 80 arranged at the center of a bottom 300 of the conical space, and a swirling gas-liquid outlet 101 arranged near the top of the conical space.

By forcibly sending the pressure liquid into the conical space 100 through the pressure liquid inlet 500, a swirling flow is formed within the conical space, and negative pressure is generated along the axis of the conical tube. By the negative pressure thus generated, the gas is sucked into the gas introducing hole 80, and the gas passes along the tube axis where the pressure is at the lowest.

As a result, a narrow swirling gas cavity 60 is generated.

In the conical space 100, a swirling flow is formed from the inlet (pressure liquid inlet) 500 toward the outlet (swirling gas-liquid outlet). As the cross-sectional area of the space 10 is gradually reduced tcward the swirling *9 *°oooo r UM PIYPOMPiT I 'JJ0 /A 68 1 P:46/W413H42, XM442U 39710 P !3 gas-liquid outlet U11, swirling flow velocity and velocity of the flow directed toward the outlet are increased at L.= same time.

In association with the swirling, due to the difference of specific gravity between the liquid and the gas, centrifugal force is applied on the liquid and centripetal force is applied on the gas at the same time. As a result, the liquid portion and the gas portion become separable from each other. The gas is turned to a narrow thread-like gas swirling cavity 60 with its diameter gradually reduced toward the outlet 101, and the gas is injected through the outlet. At the same time as this injection, the swirling is rapidly weakened by the surrounding stationary liquid.

Thus, radical difference of swirling velocity occurs. By the occurrence of the swirling velocity difference, the thread-like gas cavity 60 is cut off in continuous and stable manner. As a result, a large amount of microbubbles, e.g. micro-bubbles with diameter of 10 20 um, are generated near the outlet 101 and are discharged.

S According to another aspect of the invention, as shown in Fig. 6 for example, in a covered cylinder 4 in shape of an inverted circular cone (truncated circular cone) with its diameter gradually increased toward the top, there occur triple swirling flows, i.e. a swirling ascending liquid flow 20 running up along peripheral portion 4a, a swirling rnUM RIZI-WJIRMI I KUM /11 6- B(XI1:4//,'111 'I4/3MV"ZU139Y71U P14 descending liquid flow 22 running down inside the peripheral portion and a swirling cavity 23 under negative pressure in the central portion. In the swirling cavity 23 under negative pressure, self-sucking gas component 26 and dissolving gas component 27 are accumulated, and a gas vortex flow 24 is formed, which descends and swirls while being extended and narrowed down. When this vortex flow is discharged through the central reflux port 6 in the lower portion, it undergoes resistance from the discharge passage.

Then, difference of swirling velocity occurs, and the gas vortex flow itself is forcibly cut off and broken down, and micro-bubbles are generated.

Fig. 12 is a drawing to explain the principle of the system of the present invention. Fig. 12 is a side view and Fig. 12 is a sectional view along the line A A in Fig. 12 A micro-bubble generating system comprises a conical space 100 formed in a container of the system of the present •g invention, a pressure liquid inlet 500 provided in tangential direction on a part of circumferential surface of inner wall of the space, a gas introducing hole 80 arranged at the center of a bottom 300 of the conical space, and a swirling gas-liquid outlet 101 arranged near the top of the conical space.

Normally, the main unit of the system of the present 11 o FROM PMV+fiWf Hi F1999v 7,9 68W 1:47,11II! :42,K5044201399710 F invention is installed under the water surface.

There are two cases: the case where the main unit of the system is installed under the water surface and the case where it is installed outside and in contact with a water tank.

According to the present invention, water is normally used as the liquid and the air is used as the gas. In addition, the liquid may include solvent such as toluene, acetone, alcohol, etc., fuel such as petroleum, gasoline, etc., foodstuff such as edible oil, butter, ice cream, beer, etc., drug preparation such as drug-containing beverage, health care product such as bath liquid, environmental water such as water of lake or marsh, or polluted water from sewage purifier, etc. Further, the gas may include inert gas such as hydrogen, argon, radon, etc., oxidizing agent such as oxygen, ozone, etc., acidic gas such as carbon dioxide, hydrogen chloride, sulfurous acid gas, nitrogen oxide, hydrogen sulfide, etc., and alkaline gas such as ammonia.

In Fig. 12, reference symbol Pa indicates pressure in *the swirling liquid flow inside the conical space, Pb represents pressure in the swirling gas flow, Pc represents pressure in the swirling gas flow near the gas inlet, Pd is pressure in the swirling gas flow near the outlet, and Pe represents pressure in the swirling liquid flow at the rKuM wywFfSH M Y999T 7F1 68 001 7,W il9 42./"'44201 39710 P 16 outlet.

In the conical space 100, pressure liquid is sent under pressure in tanqential direction through the liquid inlet 500. Then, a swirling flow is generated from the inlet 500 toward the swirling gas-liquid outlet 101. Because crosssectional area is gradually reduced toward the outlet 101, both the swirling flow velocity and the velocity of the flow directed toward the outlet are increased at the same time.

In association with the swirling, due to the difference of specific gravity between the liquid and the gas, centrifugal force is applied on the liquid and centripetal force is applied on the gas at the same time. As a result, the liquid portion and the gas portion become separable from each other. The gas is turned to a narrow thread-like gas swirling cavity 60, and the gas flow in thread-like shape under negative pressure is continuously sent to the outlet 101.

Then, the qas is automatically sucked (self-sucked) into the gas introducing hole 80. The gas is then cut off and broken down and sent into the swirling flow with the pressure Pc, i.e. it is turned to air bubbles, and is incorporated in the swirling flow.

As a result, the narrow thread-like gas swirling cavity 60 in the central portion and the liquid swirling flow around the cavity are injected through the outlet 101. At 13 FHUM RIePBFMII 1 9992P 71 6b(X)1 8: 4 U1 8:42/3§420139 971 P 17 the same time as the injection, the swirling flow is rapidly weakened by the surrounding stationary water. Thus, radical difference in swirling velocity occurs. Because of this difference of swirling velocity, the thread-like gas cavity 60 at the center of the swirling flow is cut off in continuous and stable manner. Then, a large amount of micro-bubbles, e.g. micro-bubbles of 10 20 pm in diameter, are generated near the outlet 101.

In this figure, the following correlation exists: d,/di 10 to L 1.5 to 2.0 x d2 where d, is diameter of the swirling gas-liquid cutlet 101, d 2 is diameter of the bottom 300 of the conical space, d3 is diameter of the gas introducing hole 80, and L stands for the distance between the swirling gas-liquid outlet 101 and the bottom 300 of the conical space. The range of numerical values for each type of the system is as given below: d, d, d, L Large-size 1.3 2.5 cm 22 35 cm 2.6 3.5 mm 38 70 ci system Medium-size 55 12.0 mm 10 21 cm 1.3 2.5 mm 15 36 ci system Small-size 2.0 4.5 mm 2.0 5.0 cm 0.7 1.2 nm 3.5 10.0 *o system Mini-size Not more than 3 0 mm 1.2 S e50.7 21.5 mm 0.3 1.0 mm 1.2 system 1.5 mm r Kum yo"i-OMPIT L V'J'J I I] Ud I K) I d: !J :'4Z,'XM9q#4,1(J I JV 9 f F IS In case of a medLum-siZe system, tor example, a pump of 2 kW, 200 liters/min., arid with head of water of 40 mn is used. By the use of this system, a large amount of microbubbles can be generated. A layer of micro-bubbles of about 1 cm in thickness can be accumulated over the entire water surface in a water tank with volume of 5 in'. This system can be applied for purification of water in a pond with volume of 2000 m' or more.

In case of a small-size system, e.g. with a pump of about 30 W and 20 liters/min., the system can be used in a water tank with volume of about 1 to 30 Mn 3 When the present invention is applied to seawater, micro-bubbles can be very easily generated, and the conditions for application can be further extended.

Fig. 15 is a graphic representation of the results, i.e.

diameter of air bubbles and distribution of aeneration frequency of air bubbles, when micro-bubbles were generatedi by installing a medium-size system as shown in Fig. 12 under boo* 00*0.water surface and using the air as the gas. The results when air suction quantity through the gas introducing hole 0 0 HO8 was adjusted are also shown. In this case, when suction was set to 0 cm 3 air bubbles Of 10 20 Mrn in diameter *were generated. This may be attributed to the fact that the air dissolved in water was separated and was turned to air bubbles. In this respect, the system according to the FR(0M PWTiiPhM R 9 9 19 Y '1T1 68() F 849 present invention can also be used as a deaerator for the dissolved gas.

When the system according to the present invention is installed in the liquid, and pressure liquid water under pressure) is supplied into the conical space 100 through the pressure liquid inlet 500 via the pressure liquid introducing pipe 50 using storage pump, it is possible to easily generate and supply micro-bubbles of 10 im in diameter in the liquid water) by simply connecting the gas introducing pipe air pipe) from outside to the gas introducing hole The above space may not always be in conical shape and may be designed in cylindrical shape with its diameter gradually increased (or gradually decreased). For example, it may be designed in shape of a bottle as shown in Fig. 14.

The generating condition of the air bubbles can be controlled by adjusting a valve (not shown) for gas flow rate control connected to the forward end of the gas introducing hole 80, and generation of optimal micro-bubbles can be easily controlled as desired. Further, it is possible to generate air bubbles having diameter of larger than 10 20 im by such adjustment.

By the control of diameter ofair bubbles to be generated, it is possible to generate micro-bubbles in size of several hundreds of pm without extremely reducing the 16 FROM XVMT-"ffi~ 1999Y 7P 69 i8:49/ 71 :42/XRa4420 13Y9970 P amount of micro-bubbles with diameter of 10 20 Mm.

In an embodiment shown in Fig. 13, pressure liquid introducing pipes 50 and 50' are installed at two different points respectively, i.e. near the bottom 300 ot the conical space and at a point before the swirling gas-liquid outlet 101 two or more pipes may be installed in tangential direction with spacings between them on circumferential surface of inner wall having different radius of curvature).

When the liquid is supplied by extensively increasing the liquid introducing pressure from the pressure liquid inlet 500' on the left side to a value higher than the introducing pressure through the pressure liquid inlet 500 on the right side. As a result, number of revolutions of the liquid on the left side can be extensively increased, and air bubbles can be generated.

By adjusting the pressure of the pressure water sent through the pressure liquid inlets 500 and 500', air bubbles having any diameter can be generated. Reference numeral 200 represents a baffle plate, and this is helpful in promoting generation and diffusion of micro-bubbles.

In the following, description will be given on a microbubble generating system according to another embodiment of the present invention.

Fig. 1 is a front view of a swirling type micro-bubble generating system of an embodiment according to the present 17 o*o FROM IWBPTWiT RO9IY 7A 69(W, 18:4/Wa8I842/XgO'42013997IO P 2.

invention; Fig. 2 is a plan view of the above; Fig. 3 is a longitudinal sectional view at the center along the line B B in Fig. 2; Fig. 4 is a lateral sectional view of a lower flow base along the line A A in Fig. 1; Fig. 5 is a drawing to explain triple swirling flows on a cross-section of inner space of a covered cylinder along the line X X; Fig. 6 is a drawing to explain swirlinq ascending flow and descending flow and a gas vortex flow in the above embodiment along the line Y Y; Fig. 7 is a drawing to explain generation of micro-bubbles in the gas vortex flow; Fig. 8 is a drawing to explain a micro-bubble generating mechanism having four lateral discharge ports on a central reflux outlet; Fig. 9 is a drawing to explain the microbubble generating mechanism at a first lateral discharge port of Fig. 8; Fig. 10 is a drawing to explain the microbubble generating mechanism as seen on a side wall adjacent to the first lateral discharge port of Fig. 8; Fig. 11 is a drawing to explain the micro-bubble generating mechanism as seen on a second lateral discharge port of Fig. 8; Fig. 12 is to explain a system of another embodiment, also serving to explain the principle of the present invention; Fig. 13 is to explain a system of another improved embodiment of the present invention; Fig. 14 is to explain a system of still another embodiment of the present invention; Fig. 15 is a graphic representation of the results, showing diameter of 18 FROM YBITPWB*i 19991 71 68 )d8:5f),/W1.81 :42,'X3 420I3997O P 22 edch of the air bubbles and distribution of air bubble generation frequency, when a medium type system according to the present invention was submerged into water and microbubbles were generated using the air as the gas; and Fig. 16 is a drawing to explain the system of an embodiment of the present invention when it is installed in a water tank.

In the figures, reference numeral 1 is a swirling type micro-bubble generating system, 2 is a lower flow base, 3 is a circular accommodation chamber, 4 is a covered cylinder, is a liquid inlet, 6 is a central reflux port, 7 is a lateral discharge port, 8 is a gas self-sucking pipe, 20 is a swirling ascending liquid flow, 22 is a swirling descending liquid flow, 23 is a swirling cavity under negative pressure, 24 is a gas vortex flow, and 25 is a cutoff sector.

Structurally, the swirling type micro-bubble generating system 1 according to the present invention can be roughly divided to the following unit structures: a liquid swirling introducing structure where liquid flow is forcibly introduced and swirled into the circular accommodation chamber 3 of the lower flow base 2, a swirling ascending liquid flow forming structure positioned above the circular accommodation chamber 3 and formed in a peripheral portion 4a of a covered cylinder 4 designed in shape of an inverted circular cone with its diameter gradually increased upward, 19 o FROM rorow/"HP F y9y 711 69 18 50W9 42,1"'44201 399710 F 23 a swirling descending liquid flow forming structure provided on a portion 4b inside the peripheral portion 4a, a microbubble generating structure, comprising a swirling cavity 23 under negative pressure formed in the central portion 4c by centrifugal and centripetal forces of dual swirling flows, i.e. a swirling ascending liquid flow 20 and a swirling descending liquid flow 22, a unit for forming a gas vortex flow 24, which contains a self-sucking gas 26 and an eluted gas 27 in the swirling cavity 23 under negative pressure, descending and swirling while being extended and narrowed down, the gas vortex flow 24 undergoes resistance when entering the central reflux port 6, difference of swirling velocity occurs between the upper portion 24a and the lower portion 24b of the vortex flow, the vortex flow 24 is forcibly cut off and micro-bubbles are generated, and a swirling injection structure where the generated microbubbles are incorporated in the swirling descending liquid flow and it is discharged out of the system through the lateral discharge port 7 as a swirling injection flow.

At the upper center of the lower flow base 2 designed in cubic shape, the circular accommodation chamber 3 is provided. On inner peripheral surface 3a of the circular accommodation chamber 3, a liquid inlet 5 is opened toward the inner peripheral surface 3a in tangential direction.

To a water pipe connection Sa mounted on outer intake sector 1 I)7. 1t .0tA~ 171, 1 mi. 4t 1XEW'-T I, r L' of the inlet 5, a water pipe 10 is connected, which has a pump 11 for water supply (Fig. 12) and a flow control valve 12 (may be mounted outside and not underwater) are mounted at the middle of the water pipe 10. Water flow is forcibly introduced to the inner peripheral surface 3a of the circular accommodation chamber 3 in tangential direction counterclockwise, and a swirling introducing flow running in the direction of an arrow D (counterclockwise) in the figure is formed.

On an opened step of the circular accommodation chamber 3, a cylindrical portion 42 at the lower end of the cylinder is engaged, and the covered cylinder 4 designed in inverted circular cone with its diameter gradually increased upward is erected. Reference numeral 41 is a flat upper cover of the cylinder. Along the central axis (C C) of the upper cover 41, a gas suction pipe 8 is inserted and directed downward, and the gas is automatically sucked into the swirling cavity 23 under negative pressure formed at the central portion 4c as to be described later.

As described above, the gas-liquid mixed flow introduced and swirled in the direction of D into the circular accommodation chamber 3 is sent into the covered cylinder 4 while maintaining its swirling force, and the flow ascends and swirls along inner peripheral portion 4a and forms a swirling ascending liquid flow 20. The rnv~m ydiw-^fwji1 I VYM II 6 (X)Jm nJ: qZ/f*4201 3 9971 P swirling ascending liquid flow runs along inner peripheral surface of the cylinder with its diameter gradually increased, and while gradually increasing the swirling velocity and it reaches upper end of the cylinder 4 Then, it flows back in the direction of an arrow 21 toward the inner portion 4b from the peripheral portion 4a and begins to descend while swirling, and the swirling descending liquid flow 22 is formed. Next, by centrifugal and centripetal forces of dual swirling flows, i.e. the swirling ascending liquid flow 20 and the swirling descending liquid flow 22, the swirling cavity 23 under negative pressure is formed at the central portion 4c of the cylinder 4.

Because the swirling descending flow area is gradually reduced along the central axis (C C) in shape of an inverted circular cone of the cylinder 4, the swirling velocity is increased, while internal pressure is reduced.

Therefore, the shape of the swirling cavity 23 at the central portion 4c is extended and narrowed down. With the extension of the swirling cavity, internal pressure is more r. and more reduced. Thus, from the swirling descending liquid flow 22 moving around the cavity, the air contained in the water flow is eluted.

On the other hand, into the swirling cavity 23 under negative pressure, which descends while swirling, the air is automatically sucked via the gas self-sucking pipe 8. The 22 FROM 3fOUIPflAM RMT -Y 7J1 68( (A :51PW1118:42/""4201399711 P 26 self-sucking gas 26 and the eluted gas 27 coming from the swirling flow are accumulated in the swirling cavity 23 under negative pressure, and a gas vortex flow 24 is formed, which swirls and descends while being extended and narrowed down.

Micro-bubbles cannot be generated only by the formation of the gas vortex flow 24, which swirls and descends along the central axis (C In the micro-bubble generating system 1 according to the present invention, as shown in Fig.

7, during the process where the flow is discharged through the central reflux port 6 with respect to the gas vortex flow 4, the flow undergoes the resistance in the discharge passage, and difference in swirling velocity is generated between the upper portion 24a and the lower portion 24b of the gas vortex flow 24. The gas vortex flow 24 is forcibly twisted and cut off, and micro-bubbles are generated.

The smaller the diameter of the cross-section of the gas vortex flow 24 is, the more favorable condition is obtained for generation of micro-bubbles. The diameter of the cross-section can be easily controlled by adjusting the self-sucking amount of the air from the gas self-sucking pipe 8 by the flow control valve 12 (Fig. 15). The more the self-sucking amount of the air is, the more the diameter of the cross-section of the gas vortex flow is increased.

When the amount of self-sucking reaches zero, the diameter 23 **o r n-VM wYjctIwMI i 'Jvv- /1 bd 1 8:52/-V11 8: 42/3CN9-4ZV1 Jb19 F 2-1 takes the minimal value. When the amount of the selfsucking gas is zero, the gas vortex flow 24 is formed only by the eluted gas 27 from the swirling descending liquid flow 22. In the purification of polluted water, which contains less amount of dissolved oxygen, special care must be taken on the ability of purification.

As described above, the micro-bubble generating mechanism in the system according to the present invention comprises a first process where the swirling descending gas vortex flow 24 is formed in the covered cylinder 4 and a second process where swirling velocity difference occurs between the upper portion 24a and the lower portion 24b of the gas vortex flow 24, which swirls and descends while being extended and narrowed down, the flow undergoes resistance in the discharge passage, and micro-bubbles are generated when the gas vortex flow is forcibly twisted and cut off.

In the present system 1, a central reflux port 6 is formed, vertically along the central axis (C C) of the bottom 3b of the circular accommodation chamber 3, as a discharge passage to discharge the swirling descending S" liquid flow 22, which swirls and descends in the cylinder 4.

Further, four lateral discharge ports 7 are formed in radial :direction toward four lateral sides of the lower flow base 2 from the central reflux port 6.

24 rKUM PRwirzIIM i V1'yq /FI VT e(X !3:5Z/iil .:4.'XWWtq l Y9 11 0 Micro-bubbles are generated when the swirling and descending gas vortex flow 24 is twisted and cut off. The micro-bubbles are then discharged out of the system through four lateral discharge ports 7 via the central reflux port 6 together with the swirling descending liquid flow 22. When discharged, the water flow is sent out as a discharge injection flow 28 while maintaining its swirling force.

There may be only one lateral discharge port 7 instead of a plurality of discharge ports. Or, the lateral discharge port 7 may not be provided, and the central reflux port 6 may be narrowed down, and the micro-bubbles, which are generated by cutting and twisting of the swirling descending gas vortex flow 24 and the swirling descending liquid flow 22, may be discharged directly from the central reflux port. By the latter method, micro-bubbles can also be generated.

Referring to Figs. 8 to 11, description will be given now on micro-bubble generating mechanism when the central reflux port 6 is provided with four lateral discharge ports *o 71, 72, 73 and 74.

The gas vortex flow 24 swirls and descends in the central portion 4c of the covered cylinder 4. The vortex flow 24 is sent toward the four lateral discharge ports 71, 72, 73 and 74 through the central reflux port 6 together with the swirling descending liquid flow 22 in the direction r P 28 "Lv'~~7rlY r I~ of the arrow D. Fig. 9 shows the condition where the vortex flow is discharged into a first lateral discharge port 71. The lower portion 24b of the gas vortex flow undergoes resistance when it is sent and the swirling velocity is decreased. Then, difference in swirling velocity occurs between the lower portion 24b and the upper portion 24a of the gas vortex flow. The vortex flow is twisted and cut off, and micro-bubbles are generated.

Reference numeral 25 indicates a sector where the vortex flow is cut off.

Fig. 10 shows the condition where the gas vortex flow 24 undergoes resistance as it collides with an adjacent reflux port side wall 6a while the vortex flow is advancing toward a second lateral discharge port 72. When collided with the side wall 6a, the lower portion 24b of the vortex flow changes its swirling velocity, and micro-bubbles are generated at the cutting sector Fig. 11 shows the condition where the gas vortex flow 24 is discharged into the second discharge port 72. With a swirling velocity different from that of Fig. 10, the cutting sector 25 occurs, and micro-bubbles are generated.

As described above, while the vortex flow is revolved by one turn, it is discharged into each of the four lateral discharge ports 71, 72, 73, and 74 and repeatedly and alternately collided with adjacent side wall 6a. Each time, ft a 26 *ft o swirling velocity diCference occurs between the upper portion 24a and the lower portion 24b of the vortex flow.

Thus, the vortex flow is cut off and a large amount of micro-bubbles are generated.

The number of the lateral discharge ports 7 is related to the number of swirling of the swirling flow 22 and the gas vortex flow 24 and the number of cutting sectors In order to increase the number of swirling, it is necessary to induce the swirling of the liquid in early stage using high pressure pump. The more the number of the swirling is increased, the smaller the cutting sector (area) 25 becomes.

As a result, elution of the gas due to negative pressure is promoted, and a larger amount of smaller micro-bubbles can be generated. When the number of the lateral discharge ports 7 is increased, the number of micro-bubbles is increased. The results of the experiment reveal that, if the number of revolutions is at constant level, the number of optimal discharge ports is related to the amount of the introduced liquid. Under the condition where a pump of .0 liters/min. and with head of water of about 15 m is used, the optimal number of discharge ports is four.

At the outlet 7a of the lateral discharge port 7 in the lower flow base 2, a connection pipe 9 for discharge is connected. Because discharge direction is deflected at an angle of 45° in the direction of the arrow D in association C. W. 4. I ft U r fl with the direction to form the swirling flow in the covered cylinder 4 (direction of the arrow when the swirling Lype micro-bubble generating system 1 of the present invention is installed in a water tank 13 (Fig. 15), a circulating fl.ow running in the direction of the arrow D is formed around the swirling type generating system 1 as it is discharged as a swirling injection flow from the discharge connection pipe 9 into the water tank 13. As a result, micro-bubbles containing oxygen are evenly distributed in the water tank 13.

In the micro-bubble generating system 1 according to the present invention as described above, water flow containing micro-bubbles with diameter of 10 20 Mm in an amount of more than 90% can be discharged through the discharge port.

When the system is installed in the water tank 13, it is preferable that a weighty material is used as the lower flow base 2. In case it is made of plastics, a heavy stainless steel plate may be attached on the bottom. if the covered cylinder 4 is made of a transparent material, it *is advantageous in that the formation of the swirling ascending liquid flow and the swirling descending liquid flow inside can be directly observed.

The system of the present invention may be made of the materials such as plastics, metal, glass, etc., and it is FROM 3BmiVif 199YW 7)I 69(k) 18:54./'WII3:42/"S#942O,)139971 I P 32 preferable that the components of the system are integrated together by bonding, screw connection, etc.

INDUSTRIAL APPLICABILITY By the swirling type micro-bubble generating system of the present invention, it is possible to readily generate micro-bubbles in industrial scale. Because the system is relatively small in size and has simple construction, it is easier to manufacture, and the system will contribute to purification of water in ponds, lakes, marshes, man-made lakes, rivers, etc., processing of polluted water using microorganisms, and culture of fishes and other aquatic animals.

Micro-bubbles generated by the system according to the present invention can be used in the following applications: Purification of water quality in man-made lakes, natural lakes, ponds, rivers, sea, etc. and preservation of natural environment through growth of animals and microorganisms.

Purification of man-made and natural waters such as biotope and promotion of growth of fireflies, water weeds, etc.

Industrial applications Diffusion of high temperature in steel manufacture.

-Promotion of acid cleaning of stainless steel plate 29 VV IU L/ III'~ I and wires.

-Removal of organic substances in ultra-pure water manufacturing factory.

Removal of organic substances in polluted water by micro-bubble formation of ozone, increase of dissolved oxygen, sterilization, manufacture of synthetic resin foam such as urethane foam product.

-Processing of various types of waste water and liquid.

Sterilization by ethylene oxide, promotion of mixing of ethylene oxide with water in sterilizer.

Emulsification of defoaming agent.

-Aeration of polluted water in activated sludge treatment method.

Agricultural applications Increase of oxygen and dissolved oxygen to be used in hydroponic culture, and improvement of production yield.

Fisheries S Culture of eel Maintenance of life in cuttlefish tank Culture of yellowtail Artificial development of seeweeds Promotion of growth of fishes -Prevention of red tide Medical applications Use of micro-bubbles in hot bath to promote blood circulation and to maintain hot water in bath

Claims

1. A swirling type micro-bubble generating system, comprising a container main unit having a conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of said space, a gas introducing hole opened on the bottom of said conical space, and a swirling gas-liquid outlet arranged at the top of said conical space.

2. A swirling type micro-bubble generating system, comprising a container main unit having a truncated conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of said space, a gas introducing hole opened on the bottom of said truncated conical space, and a swirling gas- liquid outlet arranged in the upper portion of said truncated conical space.

3. A swirling type micro-bubble generating system, comprising a container main unit having a space of bottle- like shape, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of said space, a gas introducing hole opened on the bottom of said bottle-like space, and a swirling gas-liquid outlet arranged at the top of said bottle-like space. A swirling type micro-bubble generating system accordina to one of claims 1 to 3, wherein a plurality of 32 II YY ;1\1 I D I' i Li L i I i V r ;IU pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having the same radius of curvature on inner wall of said space. A swirling type micro-bubble generating system according to one of claim 1 to 4, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having different radii of curvature on inner wall of said space.

6. A swirling type micro-bubble generating system according to one of claims 1 to 5, wherein said pressure liquid inlet is provided on a part of circumferential surface of inner wall near the bottom of said space.

7. A swirling type micro-bubble generating system according to one of claims 1 to 6, wherein said pressure liquid inlet is provided on a part of circumferential surface of inner wall near a point halfway down of said space.

8. A swirling type micro-bubble generating system according to one of claims 1 to 7, wherein a baffle plate is arranged immediately before the swirling gas-liquid outlet.

9. A swirling type micro-bubble generating system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. Dated this 7th day of July 1999 HIROFUMI OHNARI By his Patent Attorneys COLLISON CO. y y lc<i^^Pks°u