JP2023113278A - fine bubble generator - Google Patents

Abstract

To provide a fine bubble generator where a mechanism automatically dissolving an air reservoir generated at the startup of a conventional air self-suctioning bubble generator is provided and operations at the startup and the re-supplying of a liquid are made easy without increasing components.SOLUTION: In a fine bubble generator,: in addition to a main flow passage filling a liquid at the inside of the fine bubble generator liquid, a sub flow passage is provided around the main flow passage and an air reservoir is dissolved by flowing the liquid from the sub flow passage toward a suction part; and air can be self-supplied by flowing liquids jetted from the main flow passage and the sub flow passage into a confluence chamber to form a vortex in the confluence chamber.SELECTED DRAWING: Figure 2

Description

The present invention relates to fine bubble generators.

Bubbles have various names depending on their size, but in the present specification, all bubbles with a diameter of 100 micrometers or less are included as "fine bubbles", and "fine bubbles" with a diameter of 1 micrometer or more (1 to 100 micrometers) are referred to as "microbubbles", those less than 1 micrometer from the observable lower limit are referred to as "ultra-fine bubbles", and bubbles or bubbles when there is no need to distinguish between them.

In the field of machine tools, by generating bubbles in the liquid (coolant) used in processing, it is possible to extend the life of tools (drills, grindstones, etc.), reduce warpage of workpieces, and improve productivity. known to contribute to improvement.

Methods for generating bubbles in a liquid are broadly classified into those that do not involve liquid flow and those that involve liquid flow. As an example of the former, a micropore method is known, and as an example of the latter, a cavitation method is known.

Patent Literature 1 describes a microporous bubble generator. In this document, a fine bubble generator having a cylindrical main body, a channel through which a liquid to be provided with bubbles passes, an air receiving portion for receiving compressed gas, and a porous body separating the channel and the air receiving portion is disclosed. This fine bubble generator generates a large number of fine bubbles by supplying a compressed gas to the porous body and releasing the compressed gas from the surface of the porous body into the liquid.

Patent Document 2 describes a cavitation-type bubble generator. This bubble generator includes a gas-liquid loop flow stirring and mixing chamber for stirring and mixing liquid and air by a loop-shaped flow, a liquid supply hole, a jet hole, one or more air inlet holes into which air flows, It consists of an air supply chamber. When the inside of the gas-liquid loop flow stirring and mixing chamber becomes negative pressure, the bubble generator can naturally suck air from the outside (hereinafter referred to as self-suction) to generate microbubbles.

JP 2021-118994 A JP 2009-189984 A

The microporous method of US Pat. Therefore, it is necessary to provide a compressed air generator (compressor, etc.) or a pressure vessel (cylinder, etc.). In addition, the porous body used in Patent Document 1 also has a problem that fine bubble generation efficiency decreases due to clogging after multiple uses.

In the cavitation-type bubble generator described in Patent Document 2, it is possible to self-suck air by forming a vortex of liquid without using compressed air. Fine air bubbles can be obtained by shearing and stirring the sucked air in the gas-liquid mixing chamber. However, there is no recognition of the troublesomeness of the operator when using it in a machine tool.

FIG. 1 shows a schematic diagram of the bubble generator described in Patent Document 2. As shown in FIG. In the bubble generator disclosed in Patent Document 2, piping resistance and pressure loss are less likely to occur inside the gas-liquid loop flow stirring and mixing chamber.

Therefore, when the inside is already full of water as shown in Fig. 1a) and there is no air pocket from the initial state, the bubble can be self-sucked by supplying liquid as shown in Fig. 1b), but Fig. 1c) In the initial state where the interior is empty as shown in FIG.

In this way, when the inside of the gas-liquid loop flow type stirring and mixing chamber is once empty, an air pool is formed around the air inflow hole, which is the intake part, and even if the liquid is supplied again, the air will be automatically replenished. can't breathe

Here, when the inventors conducted an experiment using only the main channel as in the bubble generator of Patent Document 2, no bubbles were generated in the supplied liquid. It was thought that the bubble could not be generated because the air pool was too large to generate a vortex of the liquid inside the bubble generator.

As a means for eliminating air pockets, there is a method of priming the inside of the gas-liquid mixing chamber. For example, the outlet of the bubble generator may be valved off and the valve may be opened after priming is completed. By doing so, the inside of the gas-liquid mixing chamber is filled with water, and air pockets are eliminated.

However, the method of opening and closing the outlet of the bubble generator with a valve is troublesome for the operator. Furthermore, installation of the valve requires space. Since space is often limited near the grindstone or grinding point, it may not be possible to install the bubble generator. Even if a valve is installed, the inside of the bubble generator will be filled with water while the outlet is blocked, so there will be a problem that the water will flow back from the air supply part and leak outside. sell.

The problem to be solved by the present invention is to provide a cavitation-type bubble generator disclosed in Patent Document 2 with a mechanism that automatically eliminates the air pool that occurs at the time of start-up, and at the time of start-up and re-supply of liquid without increasing the number of parts. It is to simplify the work.

The present invention has the following configurations.
at least one inlet into which liquid flows;
an outlet for discharging liquid;
A confluence chamber is provided between the inlet and the outlet,
a main flow path that is linearly connected from the inlet to the outlet via the confluence chamber;
at least one or more sub-channels arranged around the main channel and connected from the inlet to the confluence chamber;
At least one suction unit is provided around a location where the secondary flow path joins the merging chamber, and sucks gas from the outside.
A fine bubble generator that creates fine bubbles in the liquid that passes through it.

As described above, in the invention disclosed in Patent Document 2, since the liquid is supplied only through the main flow path, the liquid can be sufficiently supplied to the vicinity of the intake section provided on the side as shown in FIG. 1d). unsatisfactory.

As a mechanism for eliminating the side air pools, the inventors considered arranging a sub-flow path separately from the main flow path. This air pool can be eliminated by causing the liquid to flow from this secondary flow path toward the periphery of the intake section.

The fine bubble generator of the present invention solves the above-described problems by arranging the liquid flowing from the sub-channel and the main channel to merge in the confluence chamber and fill the interior of the fine-bubble generator.

The fine bubble generator of the present invention uses not only the main flow path but also the sub-flow path, so that the periphery of the intake section communicating with the outside can be filled with water, without increasing the number of parts or performing complicated operations. It became possible to self-suck air from the outside.

The present invention has the following configurations.
at least one inlet into which liquid flows;
an outlet for discharging liquid;
A confluence chamber is provided between the inlet and the outlet,
a main flow path that is linearly connected from the inlet to the outlet via the confluence chamber;
at least one or more sub-channels arranged around the main channel and connected to a confluence chamber;
At least one suction unit is provided around a location where the secondary flow path joins the merging chamber, and sucks gas from the outside.
A fine bubble generator that creates fine bubbles in the liquid that passes through it.
Details of the components are shown below.

The liquid L enters from the inflow port 11 (on the right side in both FIGS. 2 to 6) and is discharged from the discharge port 12 (on the left side in FIG. 2 to FIG. 6) in a state in which fine bubbles are generated. Either or one of the inlet 11 and the outlet 12 may be provided with a threaded portion 25 for a hose for supplying the liquid L.

The fine bubble generator of the invention has a main channel 16 and a secondary channel 17 .

The main flow path 16 is a flow path through which the liquid flowing from the inlet 11 is linearly supplied to the confluence chamber 14 . The main flow path 16 can take the flow path that is generally the shortest path inside the generator from the inlet 11 to the outlet.

The secondary flow path 17 is a flow path that supplies the liquid to the vicinity of the intake section 15 that is provided at the location where the fluids merge into the confluence chamber 14 . If the liquid is supplied only from the main flow path, as shown in Fig. 1d), an air pool occurs around the intake section and the air cannot be sucked by itself. The secondary flow path 17 can supply the liquid to the portion where the air pool is generated, eliminate the air pool, and fill the inside of the fine bubble generator with the liquid without performing any special work.

The secondary channel 17 is arranged around the main channel 16 inside the fine bubble generator. The sub-channel 17 may be formed by branching into the main channel and the sub-channel at the tip of the inlet 11 (FIGS. 2 to 4). Good (Fig. 5). Alternatively, it may be formed by branching from the middle of the main flow path 16 leading from the inlet 11 to the confluence chamber 14 (FIG. 6).

The secondary flow path 17 does not have to be the shortest path from the inlet 11 to the outlet 12. For example, the angle may be parallel to the main flow path 16 or at another angle. If they are not parallel, when viewed from the inlet, the sub-channel 17 may be a channel in which a plurality of straight lines spread radially toward the downstream side, or may be a channel in which a plurality of straight lines spread concentrically.

The cross-sectional areas of the main channel and the sub-channel may be different or the same. By making the sub-channel narrower than the main channel, when the liquid passes through the sub-channel, the flow velocity of the liquid becomes faster than in the other parts, so according to Bernoulli's theorem, air can be more automatically distributed. easier to inhale.

The cross-section of the shape of the main channel 16 and the sub-channel 17 may be, for example, circular, rectangular, or other shapes.

The width of the intake portion 15 is appropriately selected according to the flow rate and flow velocity. If the width of the intake section is wider than the desired range, the liquid that has passed through the secondary flow path 17 will leak from the inside of the intake section to the outside. When the air intake portion 15 has a slit shape, particularly when the width of the air intake portion is more than 0 to 0.3 mm, microbubbles are generated efficiently, which is preferable. The air intake portion 15 is adjusted by a washer as a typical adjustment method, but other methods may be used. As an example, a method may be used in which four equally spaced holes are provided in the downstream end surface of the sub-flow path so that an intake portion can be obtained without a washer.

The position of the suction unit 15 may be near the point where the secondary flow path flows into the confluence chamber. In the surrounding area where the liquid flows into the merging chamber 14, the liquid ejected from the secondary flow path forms a vortex, and the air can be self-sucked from the intake section. It may be the boundary between the sub-channel 17 and the merging chamber 14, or it may be on the merging chamber side.

The intake part 15 may be configured to be exposed to the outside of the fine bubble generator and directly contact the surrounding space, or may be surrounded by a case and provided with an air chamber 20 for containing an arbitrary gas. good.

The confluence chamber 14 is a confluence portion of the liquid sent from the main channel 16 and the sub-channel 17, and is a portion that supplies gas. Since it is necessary to generate a vortex inside in order to self-prime the gas, it should be the part with the widest cross-sectional area in the fine bubble generator. The shape of the interior of the confluence chamber 14 is preferably such that the pressure loss decreases toward the discharge port. Further, if the liquid has a shape that easily causes a vortex, the self-suction of the air is promoted, which is preferable. For example, as shown in FIGS. 2 to 6, the walls may be tapered toward the outlet.

Furthermore, as shown in FIG. 3, a concave portion 27 can be formed in the wall surface of the confluence chamber on the extension line of the sub-flow passage 17 . The concave portion 27 allows the liquid that joins from the secondary flow path to flow into the vicinity of the intake section, thereby facilitating elimination of air stagnation.
The gas introduced from the intake section 15 is typically air. Other gases, such as nitrogen, oxygen, carbon dioxide, argon, etc., may also be used. Similarly, the liquid L may be fresh water, distilled water, pure water, or sea water. It may be an acidic or alkaline solution, or a processing coolant (emulsion type, chemical type, chemical solution type, solution type, soluble type, etc.).

The material of the fine bubble generator is not particularly limited. Select from materials including steel, aluminum, wood and plastic. Any material can be used as long as it does not corrode with liquid, does not deteriorate in function due to dimensional change due to swelling, and exhibits and maintains the performance of forming a flow path.

The main body forming the inlet 11, the main flow path 16, and the sub flow path 17 (hereinafter referred to as the main body) and the confluence chamber 14 may be connected by bolts or by welding. The portion where the main body and the merging chamber are in contact may be formed into a thin lip shape and press-fitted, or may be fastened with a retaining ring.

(Example 1)
As shown in FIG. 2, the fine bubble generator in Example 1 consists of two parts: a main body having an inlet 11 and a main channel 16 and a secondary channel 17; The two parts were joined by a weld 21 . The intake part 15 was provided at the boundary between the main body having the inlet, the main flow path and the sub flow path, and the confluence chamber. As the air intake portion 15, a slit serving as the air intake portion 15 was provided between the main body and the merging chamber 14, and the width was set to 0.05 mm. An air chamber 20 is provided outside the intake portion 15 . The main flow path 16 and the sub-flow path 17 are formed as paths that go straight from the inlet 11 toward the confluence chamber 14 . Four sub-channels 17 were provided at intervals of 90 degrees. The cross-sections of the shape of the main channel 16 and the sub-channel 17 are circular.

The main body was made of SUS304, and threaded portions 25 by tapered pipe screws were provided on the inlet side and the outlet side of the main body, respectively, and connected to flexible hoses (not shown). The liquid supplied from the flexible hose reached the inflow port 11 and branched into the main channel 16 and the sub-channel 17 . The liquid L branched to the secondary flow path generated a whirlpool at the stage of entering the merging chamber, automatically sucked air from the intake section 15, and was able to be used as it was.

The wall surface of the merging chamber 14 is inclined at 15 degrees on one side so as to taper from the intake side toward the discharge port 12 . The liquid coming out of the confluence chamber 14 contained fine bubbles B and was supplied to the workpiece through the discharge port 12 .

As the coolant, a JIS A3 class water-soluble cutting fluid diluted 20 times with tap water was used. The total volume of coolant generating microbubbles was 100 liters. A centrifugal pump was used as a pump for sending coolant to the fine bubble generator.

Microbubbles were measured with Particle Insight (manufactured by Shimadzu Corporation). During that time, the fine bubble generator was left running. The number density of microbubbles was 224,000 per milliliter. Ultra fine bubbles were not measured.

(Example 2)
FIG. 3 shows a fine bubble generator in Example 2. As shown in FIG. As in the first embodiment, it is composed of two parts, the main body side and the confluence chamber 14 side. formed to be The cross-sections of the shape of the main channel 16 and the sub-channel 17 are circular. The intake part 15 was provided on the wall surface on the side of the confluence chamber 14 where one sub flow path 17 merges. An air chamber 20 was provided outside the intake portion 15, and an air tube with a diameter of 6 mm was connected with a joint 26. In the confluence chamber, a recess 27 was provided in the wall on the extension line of the sub-channel.

At the time of assembly, the main body and the confluence chamber 14 were fastened using a snap ring 23 so that they were fixed at a fixed position. An O-ring 22 was provided between the main body and the confluence chamber 14 to prevent liquid leakage. A counterbored hole with a depth of 0.05 mm provided on the surface where the merging chamber 14 comes into contact with the main body and has a smaller inner diameter than the O-ring 22 is provided in the intake section 15. and

The liquid L branched to the sub-flow path 17 hits the concave portion provided in the wall surface of the merging chamber 14, changes the flow, and effectively eliminates the air pool around the intake section 15. - 特許庁It was confirmed that the liquid discharged from the discharge port 12 contained microbubbles and was cloudy, and the air was automatically sucked from the suction unit 15 . Other conditions for generating and measuring microbubbles were the same as in Example 1. At this time, the number density of microbubbles was 300,000 per milliliter.

(Example 3)
FIG. 4 shows a fine bubble generator in Example 3. As shown in FIG. As in Example 1, the main flow passage 16 and the sub flow passage 17 were provided at four locations at intervals of 90 degrees. The angle formed by the sub-channel 16 and the central axis of the main channel 17 was set to 22.5 degrees. The cross-sections of the shape of the main channel 16 and the sub-channel 17 are circular.

At the time of assembly, the main body and the confluence chamber 14 were fastened using a snap ring 23 so that they were fixed at a fixed position. An O-ring 22 was provided between the main body and the confluence chamber 14 to prevent liquid leakage. A counterbore with a depth of 0.05 mm provided in a portion of the surface where the merging chamber 14 contacts the main body and has an inner diameter smaller than that of the O-ring 22 is used as the intake portion. did. The suction part 15 was provided at a position where the liquid was ejected from the secondary flow path 17 . An air chamber 20 was provided outside the intake portion 15, and an air tube with a diameter of 6 mm was connected with a joint 26. As in Example 1, the liquid L branched into the secondary flow path 17 generated a vortex when entering the confluence chamber 14 , and automatically sucked air from the intake section 15 .

Other conditions for generating and measuring microbubbles were the same as in Example 1. At this time, the number density of microbubbles was 332,000 per milliliter.

(Example 4)
FIG. 5 shows a schematic diagram of a fine bubble generator in Example 4. As shown in FIG. A hole serving as the main flow path 16 and four holes serving as the sub-flow path 17 were provided at intervals of 90 degrees. The cross-sections of the shape of the main channel 16 and the sub-channel 17 are rectangular. The sub-flow path 17 is formed radially widening toward the intake portion 15 . In Example 4, the inlets 11 of the main channel 16 and the sub-channels 17 are separated from each other. Also in this form, the liquid L branched into the secondary flow path 17 generated a vortex when it entered the merging chamber 14 , and automatically sucked the air G from the intake section 15 .

Other conditions for generating and measuring microbubbles were the same as in Example 1.
The number density of microbubbles was 711,000 per milliliter. Ultra fine bubbles were not measured.

(Example 5)
FIG. 6 shows a schematic diagram of a fine bubble generator in Example 5. As shown in FIG. The fine bubble generator has a shape in which the sub-channel 17 branches from the main channel 16 . Further, the secondary flow path 17 is provided by a gap between the main body and a middle piece 19 fixed by a jig (not shown), and is a flow path extending concentrically from the main flow path 16 . A slit serving as an intake portion 15 was provided between the main body and the merging chamber 14, the width of the intake portion 15 was set to 0.05 mm, and the main body and the merging chamber 14 were fastened with bolts. A threaded portion 25 (not shown) is provided in the main flow path 16 for supplying the liquid L to the main body and in the liquid discharge port 12 provided at the other end. The diameter of the main channel 16 was 2 millimeters. As in the other embodiments, the liquid branched to the secondary flow path 17 generated a vortex when entering the merging chamber 14 and automatically sucked the air G from the intake section 15 .

Other conditions for generating and measuring microbubbles were the same as in Example 1. The number density of microbubbles was 690,000 per milliliter. FIG. 7 shows the measurement results of microbubbles in Example 5. As shown in FIG.

Using the form of Example 5, ultra-fine bubbles were measured using tap water. The results are shown in FIGS. 8 and 9. FIG. Tap water was circulated through a fine bubble generator for 6 hours. Zeta View (manufactured by Microtrack Bell) was used for the measurement. The bubble number density measurement range is greater than the lower limit of detection and less than 1 micrometer. The volume of tap water for generating ultra-fine bubbles was 100 liters, and the temperature was 24 degrees. A centrifugal pump was used as a pump for sending tap water to the fine bubble generator. Its flow rate was 8 liters per minute. An interval of 24 hours or more was provided from the sampling of tap water to the measurement.

When the fine bubble generator was running for 0 minutes, the bubble number density was about 20 million bubbles per milliliter. Since ultra-fine bubbles should not have been generated yet, it was presumed that this was the result of detection of foreign matter originally contained in the tap water. After that, the number density of ultra-fine bubbles increased with the lapse of operation time, and increased to 150 million bubbles per milliliter after 6 hours.

The bubble diameter distribution of ultra-fine bubbles after 6 hours was as shown in FIG. A sharp peak appears in the vicinity of 100 nm, indicating that fine bubbles are obtained.
The fine bubble generator of the present invention was able to generate both microbubbles and ultrafine bubbles.

In any of the examples, even when the fine bubble generator was operated from an empty state, a sufficient amount of microbubbles could be generated.

11 inlet port 12 outlet port 13 branching portion 14 confluence chamber 15 intake portion 16 main channel 17 sub-channel 18 main body 19 middle piece 20 air chamber (or intake portion)
21 Welded portion 22 O-ring 23 Retaining ring 24 Taper 25 Threaded portion 26 Joint position (or intake portion)
27 recess G air L liquid B bubble

Schematic diagram of generation of air pool in bubble generator in prior art Schematic diagram of the fine bubble generator in Example 1 Schematic diagram of a fine bubble generator in Example 2 Schematic diagram of fine bubble generator in Example 3 Schematic diagram of fine bubble generator in Example 4 Schematic diagram of the fine bubble generator in Example 5 Bubble density and bubble diameter distribution in coolant in Example 5 Change in operating time and bubble density of fine bubble generator in Example 5 Ultra-fine bubble bubble density and bubble diameter distribution in tap water in Example 5

Claims (8)

at least one inlet into which liquid flows;
an outlet for discharging liquid;
A confluence chamber is provided between the inlet and the outlet,
a main flow path that is linearly connected from the inlet to the outlet via the confluence chamber;
at least one or more sub-channels arranged around the main channel and connected to a confluence chamber;
At least one suction unit is provided around a location where the secondary flow path joins the merging chamber, and sucks gas from the outside.
A fine bubble generator that creates fine bubbles in the liquid that passes through it. 2. The fine bubble generator according to claim 1, wherein the secondary flow path branches off from the main flow path beyond the inlet. 2. The fine bubble generator according to claim 1, wherein the secondary flow path branches between the inlet and the confluence chamber. 2. The fine bubble generator according to claim 1, wherein the inlet of said secondary channel is different from the inlet of said main channel. The fine bubble generator according to any one of claims 1 to 4, wherein the confluence chamber tapers toward the outlet. The fine bubble generator according to any one of claims 1 to 5, wherein a wall surface of said confluence chamber on an extension line of said sub-channel has a recess. 7. The fine bubble generator according to any one of claims 1 to 6, wherein the sub-channel extends radially outward from the central axis of the main channel. A fine bubble generator according to any one of claims 1 to 7, wherein the cross-sectional area of the secondary channel is smaller than the cross-sectional area of the main channel.

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