Bubble generating device, bubble generating method, and method for manufacturing a member for bubble generation

Abstract

A nozzle (100) for bubble formation demarcates a gas channel (110). The gas channel (110) ejects bubbles (FB) of a gas introduced through one end (110a), from the other end (110b) into a static liquid (LQ). When the length of the gas channel (110) from the one end (110a) to the other end (110b) is expressed by L [m], the equivalent diameter of the gas channel (110) is expressed by D [m], and the dynamic viscosity of the gas is expressed by ν [m2 / s], then the nozzle (100) for bubble formation satisfies the relationship L>24.0×(D2 / 4ν).

Description

Bubble generating nozzle, bubble generating device, bubble generating method, and bubble generating nozzle manufacturing method

[0001] The present invention relates to a bubble generating nozzle, a bubble generating device, a bubble generating method, and a method for manufacturing a bubble generating nozzle.

[0002] Known tubular nozzles for ejecting bubbles into a liquid include those used to atomize bubbles (hereinafter referred to as bubble atomization nozzles) and those used to generate bubbles (hereinafter referred to as bubble generation nozzles).

[0003] Bubble atomization nozzles are used in so-called dynamic bubble generation devices that atomize bubbles through processes such as dissolution and shearing. A gas-liquid mixture fluid in which bubbles have been mixed with the liquid in advance is introduced into the bubble atomization nozzle. In dynamic bubble generation devices, the gas-liquid mixture fluid is locally pressurized or depressurized using the bubble atomization nozzle and a pressurizing means such as a liquid pump that forcibly flows the liquid. This causes the bubbles contained in the gas-liquid mixture fluid to be atomized by dissolving or shearing.

[0004] On the other hand, a gas, not a gas-liquid mixture fluid, is introduced into the bubble generating nozzle. The gas introduced into the bubble generating nozzle is discharged as bubbles from the tip of the bubble generating nozzle into the liquid. As disclosed in Patent Document 1, a bubble generating device using a bubble generating nozzle can also be realized by a simple configuration in which the bubble generating nozzle is connected to a gas supply source.

[0005] Japanese Patent Application Laid-Open No. 2019-136638

[0006] In the dynamic bubble generators described above, the size of the bubbles produced tends to vary, and the operation of the pressurizing means tends to cause contamination and increase the temperature of the liquid. Therefore, there are cases where it is desirable to generate bubbles using a bubble generating nozzle in a so-called static bubble generator that does not use the pressurizing means.

[0007] However, even in this case, it is not easy to generate bubbles of uniform size. Furthermore, it is also not easy to steadily generate bubbles using a bubble-generating nozzle, that is, to generate bubbles under conditions that suppress the generation of pulsation. Therefore, establishing a design method for a bubble-generating nozzle that can eject bubbles of uniform size and that minimizes pulsation during the ejection of bubbles is an important issue.

[0008] The object of the present invention is to provide a bubble generating nozzle that can eject bubbles of uniform size and that is less likely to cause pulsation when ejecting the bubbles, a bubble generating device and bubble generating method that use the bubble generating nozzle, and a bubble generating nozzle manufacturing method that is suitable for manufacturing the bubble generating nozzle.

[0009] The bubble generating nozzle according to the present invention is a bubble generating nozzle that defines a gas flow path into which a gas is introduced from one end and into which bubbles of the gas are discharged from the other end into a still liquid, wherein the length from one end of the gas flow path to the other end is L [m], the equivalent diameter of the gas flow path is D [m], and the kinetic viscosity of the gas is ν [m ２ / s], L > 24.0 × (D ２ / 4ν) satisfies the relationship:

[0010] The length L of the gas flow path is 0.3×10 －３ It may be more than [m].

[0011] The length L of the gas flow path is 1×10 －３ It may be more than [m].

[0012] The length L of the gas flow path is 100×10 －３ It may be less than [m].

[0013] The equivalent diameter D of the gas flow path is 1×10 －６ [m] or more, 100×10 －６ It may be less than [m].

[0014] The bubble generation device of the present invention comprises the bubble generation nozzle of the present invention described above, an air storage chamber that defines a hollow portion that communicates with the gas flow path of the bubble generation nozzle and has a volume of the hollow portion that is larger than the volume of the gas flow path, and a gas supply source that supplies the gas to the hollow portion of the air storage chamber.

[0015] The bubble generating method according to the present invention comprises: a preparation step of preparing a bubble generating nozzle defining a gas flow path; and a bubble discharging step of introducing gas into the gas flow path from one end thereof, and repeatedly discharging bubbles of the introduced gas from the other end thereof into a still liquid, wherein the length from one end to the other end of the gas flow path is L [m], the equivalent diameter of the gas flow path is D [m], and the kinetic viscosity of the gas is ν [m ２ / s], the bubble generating nozzle has a value of L>24.0×(D ２ / 4ν) is used.

[0016] In the bubble discharging step, the gas may be introduced into the gas flow path through an air storage chamber connected to an end of the bubble generating nozzle where the one end of the gas flow path is open.

[0017] A method for manufacturing a bubble generating nozzle according to the present invention is a method for manufacturing a bubble generating nozzle defining a gas flow path into which a gas is introduced from one end and which discharges bubbles of the gas from the other end into a still liquid, the method comprising: a preparation step of preparing a workpiece that will form the bubble generating nozzle; and a removal step of forming the gas flow path in the workpiece by subjecting the workpiece to a removal process of removing a part of the workpiece, wherein in the removal process, the length from the one end to the other end of the gas flow path is defined as L [m], the equivalent diameter of the gas flow path is defined as D [m], and the kinetic viscosity of the gas is defined as ν [m]. ２ / s], L > 24.0 × (D ２ The gas flow passages that satisfy the relationship of (v / 4ν) are formed by the removal process.

[0018] In the removal processing step, the gas flow passage may be formed by wire electric discharge machining as the removal processing.

[0019] The bubble generating nozzle according to the present invention can eject bubbles of uniform size, and is less likely to cause pulsation when the bubbles are ejected.

[0020] 1 is a cross-sectional view of a bubble generating nozzle according to the first embodiment; FIG. 2 is a conceptual diagram showing the configuration of a bubble generating device according to the first embodiment; FIG. 3 is a graph showing the length L of a gas flow path and the physical quantity R in a bubble generating nozzle according to Experimental Example 1-15; ２ 10 is a scatter diagram showing the relationship between the air pressure and the air density of the air bubble generating nozzle according to the first embodiment;

[0021] Hereinafter, a bubble generating nozzle and a bubble generating device according to an embodiment will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0022] 1 shows a cross-sectional view of a bubble generation nozzle 100 according to this embodiment. The bubble generation nozzle 100 defines a gas flow path 110 through which a gas passes.

[0023] Gas is introduced from one end 110a (hereinafter referred to as the gas inlet end) of the gas flow path 110. The other end 110b (hereinafter referred to as the bubble outlet end) of the gas flow path 110 is placed in the liquid. The gas introduced from the gas inlet end 110a passes through the gas flow path 110, and bubbles made of the gas are discharged from the bubble outlet end 110b.

[0024] In this embodiment, the gas flow path 110 is defined in the shape of a right column, specifically, a right circular cylinder. The bubble generating nozzle 100 defining the right circular cylinder-shaped gas flow path 110 is configured as a straight tubular body with both ends open. That is, one opening of the tubular body is the gas inlet end 110a, and the other opening is the bubble outlet end 110b.

[0025] The manner in which the bubble generating nozzle 100 is used will now be described in detail.

[0026] 2 shows the configuration of a bubble generation device 500 that includes the above-described bubble generation nozzle 100. The bubble generation device 500 includes a liquid tank 400 that stores the liquid LQ, a straight-tube-shaped bubble generation nozzle 100 that discharges bubbles FB into the liquid LQ in the liquid tank 400, an air storage chamber 200 that is connected to the bubble generation nozzle 100, and a gas supply source 300 that supplies gas to the air storage chamber 200.

[0027] The air storage chamber 200 defines a hollow portion 210. The hollow portion 210 is in communication with the gas flow path 110 of the bubble generation nozzle 100. The volume of the hollow portion 210 is larger than the volume of the gas flow path 110. In this specification, the concept of "air storage chamber" excludes a gas pipe for transporting gas. An air storage chamber is an end or intermediate portion of a gas pipe that defines a space for accumulating gas.

[0028] In this embodiment, the air storage chamber 200 is connected to the end of the bubble generation nozzle 100 where the gas inlet end 110a is open. However, a gas pipe that connects the hollow portion 210 and the gas flow path 110 may be interposed between the air storage chamber 200 and the bubble generation nozzle 100.

[0029] The gas supply source 300 is configured using a gas pump, a gas cylinder, etc. The gas supply source 300 supplies gas to the cavity 210 of the gas storage chamber 200. The gas supplied to the cavity 210 flows from the gas inlet end 110 a into the gas flow path 110 of the bubble generation nozzle 100.

[0030] The gas that has flowed into the gas flow path 110 passes through the gas flow path 110 and is successively discharged as bubbles FB from the bubble discharge end 110b into the liquid LQ. The bubble generation device 500 can form bubbles FB that are so-called fine bubbles, for example, with a diameter of less than 300 μm, more specifically, with a diameter of 100 μm or less.

[0031] As mentioned above, in a so-called dynamic bubble generation device (not shown), a pressure field in which local pressure is increased or decreased is created in a liquid by a pressurizing means such as a liquid pump, and bubbles are forcibly dissolved or sheared in the pressure field to break them down into finer bubbles. In contrast, the device shown in Figure 2 is a static bubble generation device 500. That is, the bubble generation device 500 according to this embodiment does not use a pressurizing means for creating the above-mentioned local pressure field.

[0032] The bubble generation device 500 according to this embodiment can be used in a manner in which bubbles FB are repeatedly ejected one by one into a macroscopically static liquid (hereinafter referred to as the "static liquid") LQ, without substantially disturbing the liquid LQ in the liquid tank 400. Here, "macroscopically static" means that, from a spatial and temporal perspective, the pressure can be considered to be uniform and the flow rate to be zero; specifically, the above-mentioned pressure field for actively breaking down the bubbles FB into finer particles is not formed.

[0033] In particular, in such a static use mode, it may be desirable to suppress variations in the size of the bubbles FB and to steadily and stably discharge the bubbles FB.

[0034] However, conventionally, it has been difficult to make the size of the bubbles FB uniform, and there has been a problem that pulsation may occur when the bubbles FB are discharged. In particular, in a configuration including the air accumulation chamber 200, there has been a problem that variations in the size of the bubbles FB and pulsation are likely to occur due to changes in the gas pressure in the cavity 210, localized non-uniformity in the pressure, etc.

[0035] Therefore, the inventors of the present application attempted to solve this problem by optimizing the shape of the bubble generation nozzle 100 for the gas used. Below, we will describe an experimental example in which the optimal shape of the bubble generation nozzle 100 was sought to solve the above problem.

[0036] [Experimental Example] First, we investigated the main factors that determine the length of the gas flow path 110 necessary to solve the above problem. Here, the "length of the gas flow path 110" refers to the length L from the gas inlet end 110a to the bubble discharge end 110b, as shown in Figure 1.

[0037] The first factor that determines the required length of the gas flow path 110 is the cross-sectional area of ​​the gas flow path 110. Here, the "cross-sectional area of ​​the gas flow path 110" refers to the cross-sectional area A of the gas flow path 110 perpendicular to the direction in which the gas passes (hereinafter referred to as the length direction), as shown in Figure 1. The cross-sectional area A of the gas flow path 110 is expressed as A ∝ R, where R is the radius of the gas flow path 110 perpendicular to the length direction. ２ It can be written as:

[0038] Cross-sectional area A∝R of the gas flow path 110 ２ It is considered that the larger the cross-sectional area A∝R of the gas flow passage 110, the more likely it is that local non-uniformity in the density or pressure of the gas will occur. ２ It is considered that the larger the value of φ, the longer the length L of the gas flow path 110 needs to be in order to achieve uniformity in the size of the bubbles FB and suppression of pulsation.

[0039] The kinetic viscosity v of the gas used is considered to be a second factor that determines the required length of the gas flow path 110. It is considered that the greater the kinetic viscosity v of the gas, the less likely it is that local non-uniformity in the density or pressure of the gas will occur in the gas flow path 110. For this reason, it is considered that the greater the kinetic viscosity v of the gas, the shorter the length L of the gas flow path 110 that is required to achieve uniform size of the bubbles FB and suppress pulsation.

[0040] As described above, the first factor A∝R ２ The first factor A∝R has an effect in a direction that increases the required length L of the gas flow path 110, and conversely, the second factor ν has an effect in a direction that decreases the required length L of the gas flow path 110. ２ and a second factor ν, and determines the required length L of the gas flow path 110. ２ , v) as R ２ / ν was assumed.

[0041] The length L of the gas flow path 110 and the physical quantity R ２ Various combinations of / ν were actually constructed, and for each construction, the uniformity of the size of the generated bubbles FB and the stability of the discharge of the bubbles FB (hereinafter collectively referred to as bubble generation characteristics) were investigated.

[0042] Straight-tube bubble-generating nozzles 100 according to Experimental Examples 1-15 were manufactured, each having a different combination of the length L of the gas flow path 110 and the radius R of the gas flow path 110. Bubbles FB were actually generated using the bubble-generating nozzles 100 according to Experimental Examples 1-15, and the bubble generation characteristics were confirmed. Note that air was used as the gas that constitutes the bubbles FB in all of Experimental Examples 1-15. Furthermore, the still liquid LQ was made of water.

[0043] Table 1 shows the length L and radius R of the gas flow path 110 in the bubble generating nozzle 100 according to Experimental Example 1-15, as well as the results of confirmation of the bubble generation characteristics.

[0044]

[0045] In Table 1, "◯" means that the bubble generation characteristics are excellent, that is, the size of the bubbles FB is sufficiently uniform and the bubbles FB can be steadily and steadily ejected without pulsation. On the other hand, "×" means that the bubble generation characteristics are poor, specifically, the size of the bubbles FB is non-uniform or pulsation occurs when the bubbles FB are ejected.

[0046] Experimental Examples 1-13 exhibited excellent bubble generation characteristics and correspond to Examples, whereas Experimental Examples 14 and 15 had poor bubble generation characteristics and correspond to Comparative Examples.

[0047] The kinematic viscosity ν of the air used as the gas in Experimental Example 1-15 was 15.12 × 10 －６ [m ２ / S]. Using this value and the value of the radius R shown in Table 1, the physical quantity R ２ / ν was calculated.

[0048] FIG. 3 shows the calculated physical quantity R ２ 1 is a scatter diagram plotting data points determined by the combination of / ν and the length L of the gas flow path 110 shown in Table 1. The vertical axis indicates the length L of the gas flow path 110 in units of [m]. The horizontal axis indicates the physical quantity R ２ / ν is expressed in units of [s]. That is, the radius R of the gas flow path 110 is expressed in units of [m], and the kinematic viscosity is expressed in units of [m ２ / S], the physical quantity R２ The dimension of / ν is [s]. The vertical and horizontal axes are both shown in logarithmic scales.

[0049] As shown in FIG. 3, the length L of the gas flow path 110 and the physical quantity R ２ / ν combinations were plotted on a scatter diagram, and it was found that there was a boundary line BL that distinguished Experimental Examples 1-13 as working examples from Experimental Examples 14 and 15 as comparative examples. In other words, in Figure 3, preferable bubble generation characteristics were obtained above the boundary line BL, i.e., in the region where the length L was greater than the boundary line BL.

[0050] The boundary line BL is expressed as a straight line on the double logarithmic scale scatter diagram shown in FIG. 3. The slope of the line and its intercept on the vertical axis were read from FIG. 3, and the slope was found to be 1 and the intercept was log(24.0). That is, the boundary line BL is expressed by the following formula (1): log(L)=log(R ２ / ν) + log(24.0) ... (1)

[0051] Therefore, the region above the boundary line BL in FIG. 3 is expressed by the following inequality (2): log(L)>log(R ２ / ν) + log(24.0) ... (2)

[0052] Furthermore, when the above inequality (2) is expressed in antilogarithms, the following inequality (3) is obtained: L>24.0×(R ２ / ν) (3) That is, if inequality (3) is satisfied, desirable bubble generation characteristics can be obtained.

[0053] In this experimental example 1-15, a bubble generating nozzle 100 having a circular cross section of the gas flow path 110 was used, and the physical quantity R ２ However, it is believed that the influence of the "shape" of the cross section of the gas flow path 110 on the bubble generation characteristics can be almost ignored.

[0054] Therefore, when the equivalent diameter of the gas flow path 110 is D, not only when the cross section of the gas flow path 110 is circular but also when the cross section is non-circular, such as an ellipse, a triangle, or a polygon having more than one side, it may be possible to use D / 2 instead of the above-mentioned parameter R. The equivalent diameter D is defined as D=4A / W, where A is the cross-sectional area of ​​the gas flow path 110 and W is the perimeter of the cross section having the cross-sectional area A, i.e., the perimeter of the gas flow path 110 in an imaginary plane perpendicular to the length direction. When the cross section of the gas flow path 110 is circular, the equivalent diameter D=2R.

[0055] That is, in general, the above-mentioned physical quantity R ２ / ν, (D / 2) ２ / ν may be used. In this case, inequality (3) can be rewritten as follows: L>24.0×(D ２ / 4ν) ...(4)

[0056] This inequality (4) holds regardless of the cross-sectional shape of the gas flow path 110. In inequality (4), the length L of the gas flow path 110 is expressed in units of [m], the equivalent diameter D is expressed in units of [m], and the kinematic viscosity ν is expressed in units of [m ２ / s]. Therefore, the proportionality coefficient 24.0 on the right side has the dimension of speed [m / s].

[0057] Based on the findings obtained from the experimental examples described above, the bubble generating method according to this embodiment will be described below.

[0058] First, a bubble generation nozzle 100 is prepared, which defines a gas flow path 110 (preparation step). At least the end of the bubble generation nozzle 100, where the bubble discharge end 110b is open, is placed in the still liquid LQ.

[0059] Next, gas is introduced into the gas flow path 110 from the gas inlet end 110a of the gas flow path 110, and bubbles FB made of the introduced gas are repeatedly discharged one by one from the bubble discharge end 110b of the gas flow path 110 into the still liquid LQ (bubble discharge process). The gas is introduced into the gas flow path 110 via a gas storage chamber 200 having a volume larger than the volume of the gas flow path 110.

[0060] The greatest feature of this embodiment is that the bubble generating nozzle 100 satisfies the above inequality (4) depending on the kinetic viscosity v of the gas used. This makes it possible to eject bubbles FB of uniform size, and reduces the risk of pulsation when the bubbles FB are ejected.

[0061] Furthermore, since the size of the bubbles FB is uniform and pulsation is unlikely to occur, the repetition period of the generation of the bubbles FB, the specific size of the bubbles FB, etc. can be precisely controlled by the equivalent diameter D of the bubble generating nozzle 100, the supply pressure of the gas from the gas supply source 300, the air pressure in the air storage chamber 200, etc.

[0062] Furthermore, in this embodiment, no pressurizing means such as a liquid pump is used. In other words, the bubbles FB can be generated statically without going through dynamic processes such as dissolution, shearing, and cavitation. For this reason, when the bubbles FB are generated, contamination is unlikely to occur in the still liquid LQ, and the temperature of the still liquid LQ is unlikely to change.

[0063] The following describes the preferred conditions for the length L and equivalent diameter D of the gas flow passage 110.

[0064] From the viewpoint of particularly ensuring the structural strength of the bubble generation nozzle 100 and suppressing the difficulty of manufacturing the bubble generation nozzle 100, the length L of the gas flow path 110 is set to 0.3×10 －３ [m] or more, and 1 × 10 －３ It is more preferable that it is [m] or more.

[0065] On the other hand, from the viewpoint of suppressing the pressure of the gas supply required for discharging the bubble FB, the length L of the gas flow path 110 is set to 100×10 －３ When a gas pump is used as the gas supply source 300, satisfying this condition can reduce the power required for the gas pump.

[0066] In order to prevent the difficulty of manufacturing the bubble generating nozzle 100, the equivalent diameter D of the gas flow passage 110 is set to 1×10 －６On the other hand, in order to increase the reliability of the generation of bubbles FB that are as small as possible, specifically bubbles FB that are so-called fine bubbles with a diameter of 100 μm or less, the equivalent diameter D of the gas flow path 110 is preferably 100×10 －６ It is preferable that the length is [m] or less.

[0067] Next, a method for manufacturing a bubble-generating nozzle according to this embodiment will be described.

[0068] As shown in Fig. 4, first, a workpiece that will become the base of the bubble generating nozzle 100 is prepared (preparation step S1). The workpiece preferably has a rectangular cylindrical shape. The material of the workpiece is not particularly limited. Examples of the material of the workpiece include metal and ceramics.

[0069] Next, the workpiece is subjected to a removal process to remove a portion of the workpiece, thereby forming the gas flow passage 110 in the workpiece (removal process step S2). In this removal process step S2, the gas flow passage 110 that satisfies the above-described inequality (4) is formed by the removal process.

[0070] Wire electric discharge machining is preferred as the removal process. When performing wire electric discharge machining, a linearly extending start hole is first drilled into the workpiece. A wire is then passed through the start hole, and with the wire as one electrode and the workpiece as the other electrode, the workpiece is moved two-dimensionally relative to the wire in an imaginary plane perpendicular to the direction of extension of the wire.

[0071] This cuts out a portion (hereinafter referred to as the "removed portion") from the workpiece, the portion having the same shape as the gas flow path 110. The length direction of the linear gas flow path 110 defined by cutting out the removed portion is parallel to the depth direction of the start hole and the extension direction of the wire described above. The start hole is formed in the removed portion.

[0072] However, the removal process is not limited to wire electric discharge machining. Hole-making using a drill or other rotating cutting tool may also be used as the removal process. In this case, the gas flow passage 110 having a right cylindrical shape is formed.

[0073] Furthermore, after the removal processing step S2, an outer shaping process may be performed to adjust the outer shape of the workpiece in which the gas flow path 110 has been formed. However, for example, if the workpiece prepared in the preparation step S1 has a rectangular columnar shape and the removal processing step S2 forms the gas flow path 110 that extends parallel to the height direction of the rectangular column, the outer shaping process is not necessary.

[0074] 1 and 2 illustrate an example of a bubble generating nozzle 100 that defines only one gas flow path 110. The bubble generating nozzle 100 may define a plurality of gas flow paths 110. A specific example thereof will be described below.

[0075] 5, the bubble generating nozzle 100 according to this embodiment defines multiple, specifically five, gas flow paths 110. Each gas flow path 110 satisfies the above-described inequality (4) in relation to the gas used. Therefore, bubbles FB of uniform size can be ejected from each gas flow path 110, and pulsation is unlikely to occur when the bubbles FB are ejected.

[0076] In this embodiment, the gas accumulation chamber 200 is shared by all the gas flow paths 110. That is, all the gas flow paths 110 communicate with a common cavity 210. The volume of the cavity 210 is larger than the volume of each gas flow path 110 and is larger than the total volume of all the gas flow paths 110. As in the first embodiment, the gas accumulation chamber 200 is connected to the end of the bubble generation nozzle 100.

[0077] The first and second embodiments have been described above. The following modifications are also possible.

[0078] 2 and 4 illustrate a configuration in which gas is supplied to the bubble generating nozzle 100 via the air storage chamber 200, but the use of the air storage chamber 200 is not essential. That is, gas may be sent to the gas flow path 110 through a gas pipe connected directly to the bubble generating nozzle 100, without passing through the air storage chamber 200. The gas pipe typically has a cross-sectional area larger than the cross-sectional area A of the gas flow path 110.

[0079] 1 illustrates the gas flow path 110 extending linearly and straight, but the gas flow path 110 may have a bent portion. In this case, the length L of the gas flow path 110 substituted into inequality (4) refers to the length along the gas flow path 110 from the gas inlet end 110 a to the bubble discharge end 110 b.

[0080] 1 illustrates a gas flow path 110 in the shape of a straight cylinder having a constant cross-sectional area A in the longitudinal direction of the gas flow path 110. The cross-sectional area of ​​the gas flow path 110 (hereinafter referred to as local cross-sectional area) may vary depending on the position in the longitudinal direction of the gas flow path 110. For example, the gas flow path 110 may be defined in the shape of a truncated cone. In this case, the cross-sectional area A of the gas flow path 110 refers to the average value of the local cross-sectional area of ​​the gas flow path 110 from the gas inlet end 110a to the bubble discharge end 110b. The equivalent diameter D is also defined as a similar average value.

[0081] 2 shows a structure in which the gas inlet end 110a is directly connected to the gas storage chamber 200, but the gas inlet end 110a and the gas storage chamber 200 may be connected by a flexible pipe serving as a gas piping. In particular in such a case, that is, in a structure in which the cross-sectional shape or cross-sectional area of ​​the gas flow path 110 changes, the equivalent diameter D may be a circle-equivalent diameter. In this case, a segment section ΔL is taken from the upper end of the nozzle, and L / (R ２ / ν) to find L and L / (R ２ By examining the relationship between the length L and the length V, the length L can be defined.

[0082] The bubble-generating nozzle 100 and the bubble-generating device 500 according to this embodiment can be used to produce functional materials, for example, in the fields of food, cosmetics, medicine, etc. Specifically, by synthesizing microparticles having a hollow structure using the bubble-generating nozzle 100 and the bubble-generating device 500 according to this embodiment, it becomes possible to produce biomaterials such as three-dimensional porous structure scaffolds for cell culture, to produce protective films that suppress light absorption, and to produce semiconductor materials using hollow spacer particles.

[0083] The present invention can be modified in various ways without departing from its broad spirit and scope. The above-described embodiments are intended to illustrate the present invention and are not intended to limit the scope of the present invention. The scope of the present invention is defined not by the embodiments but by the claims. Various modifications made within the scope of the claims and within the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

[0084] This application is based on Japanese Patent Application No. 2022-146253 filed in Japan on September 14, 2022. The entire specification, claims, and drawings of Japanese Patent Application No. 2022-146253 are incorporated herein by reference.

[0085] REFERENCE SIGNS LIST 100... bubble generating nozzle, 110... gas flow path, 110a... gas introduction end (one end), 110b... bubble discharge end (other end), 200... air storage chamber, 210... cavity, 300... gas supply source, 400... liquid tank, 500... bubble generating device, BL... boundary line, FB... bubble, LQ... liquid (static liquid).

Claims

1. A gas flow path through which gas is introduced from one end and bubbles composed of the gas are discharged into a stationary liquid from the other end, Let the length from the one end to the other end of the gas flow path be L [m], the equivalent diameter of the gas flow path be D [m], and the kinematic viscosity of the gas be ν [m ２ / s]. When L > 24.0 × (D ２ / 4ν) The gas flow path satisfying the following relationship, A bubble generator comprising the same.

2. The length L of the gas flow path is 0.3 × 10 －３ [m] or more, The bubble generator according to Claim 1.

3. The length L of the gas flow path is 1 × 10 －３ [m] or more, The bubble generator according to Claim 2.

4. The length L of the gas flow path is 100×10 －３ [m] or less, The bubble generator according to Claim 1.

5. The equivalent diameter D of the gas flow path is 1×10 －６ [m] or more and 100×10 －６ [m] or less, The bubble generator according to Claim 1.

6. Comprising a plurality of the gas flow paths each satisfying the following relationship, The bubble generator according to any one of Claims 1 to 5.

7. Further comprising an air storage chamber defining a cavity communicating with the gas flow path, the volume of the cavity of the air storage chamber being larger than the volume of the gas flow path, And The gas is supplied to the cavity of the air storage chamber. The bubble generator according to any one of Claims 1 to 5.

8. Further comprising an air storage chamber defining a cavity communicating with a plurality of the gas flow paths, the volume of the cavity being larger than the volume of each of the gas flow paths, And The gas is supplied to the cavity of the air storage chamber. The bubble generator according to Claim 6.

9. A preparation step of preparing a bubble generation member defining a gas flow path, and A bubble discharge step in which gas is introduced into the gas flow path from one end of the gas flow path, and bubbles composed of the introduced gas are repeatedly discharged into a stationary liquid from the other end of the gas flow path, Having Let the length from the one end to the other end of the gas flow path be L [m], the equivalent diameter of the gas flow path be D [m], and the kinematic viscosity of the gas be ν [m ２ / s]. When this is the case, as the bubble generation member, L > 24.0 × (D ２ / 4ν) A bubble generation method using one satisfying the following relationship.

10. In the bubble discharge step, Gas is introduced into the gas flow path through an air storage chamber connected to an end of the bubble generation member where the one end of the gas flow path is open. The bubble generation method according to Claim 9.

11. The bubble generation member Defines a plurality of the gas flow paths each satisfying the following relationship, In the bubble discharge step, The gas is introduced from one end of each of the gas flow paths. The bubble generation method according to Claim 9 or 10.

12. A bubble generation member manufacturing method for manufacturing a bubble generation member defining a gas flow path through which gas is introduced from one end and bubbles composed of the gas are discharged into a stationary liquid from the other end, Comprising a preparation step of preparing a workpiece to be the bubble generation member, and A removal processing step of performing a removal process of removing a part of the workpiece on the workpiece to form the gas flow path in the workpiece, Having And forming the gas flow path satisfying the following relationship by the removal processing. In the removal process, when the length from the one end to the other end of the gas flow path is L [m], the equivalent diameter of the gas flow path is D [m], and the kinematic viscosity of the gas is ν [m ２ / s], L > 24.0 × (D ２ / 4ν) ​ Method for manufacturing a member for generating bubbles.

13. In the removal process, the gas flow path is formed by wire electrical discharge machining as the removal process, The method for manufacturing a member for generating bubbles according to claim 12.

14. In the removal process, a plurality of the gas flow paths each satisfying the relationship are formed in the workpiece by the removal process, The method for manufacturing a member for generating bubbles according to claim 12 or 13.