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

Abstract

The bubble-generating nozzle (100) defines a gas flow path (110). The gas flow path (110) discharges bubbles (FB) formed by gas introduced from one end (110a) into the stationary liquid (LQ) from the other end (110b). When the length from one end (110a) to the other end (110b) of the gas flow path (110) is L [m], the equivalent diameter of the gas flow path (110) is D [m], and the kinematic viscosity of the gas is v [m2 / s], the bubble-generating nozzle (100) satisfies the relationship L > 24.0 * (D2 / 4v).

Description

Technical Field

[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. Background Art

[0002] As tubular nozzles for discharging bubbles into liquid, there are known nozzles used to atomize bubbles (hereinafter referred to as bubble atomizing nozzles) and nozzles used to generate bubbles (hereinafter referred to as bubble generating nozzles).

[0003] The bubble miniaturization nozzle is used in a so-called dynamic bubble generating device that miniaturizes bubbles by dissolving, shearing, and other processes. A gas-liquid mixed fluid in which bubbles are pre-mixed in a liquid is introduced into the bubble miniaturization nozzle. In the dynamic bubble generating device, a pressure mechanism such as a bubble miniaturization nozzle and a liquid pump that forcibly flows the liquid is used to locally pressurize or depressurize the gas-liquid mixed fluid. Thus, bubbles contained in the gas-liquid mixed fluid are dissolved or sheared, thereby miniaturizing them.

[0004] On the other hand, a gas is introduced into the bubble generating nozzle instead of a gas-liquid mixed fluid. The gas introduced into the bubble generating nozzle is discharged from the front end of the bubble generating nozzle into the liquid as bubbles. As disclosed in Patent Document 1, a bubble generating device using a bubble generating nozzle can also be realized by a simple structure that connects the bubble generating nozzle to a gas supply source.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-136638

[0006] In the above-mentioned dynamic bubble generating device, the size of the obtained bubbles is prone to deviation, and due to the operation of the above-mentioned pressurizing mechanism, contamination is easily generated, and the temperature of the liquid is easily increased. Therefore, it is sometimes desired to use a bubble generating nozzle to generate bubbles in a so-called static bubble generating device that does not use the above-mentioned pressurizing mechanism.

[0007] However, even in this case, it is not easy to generate bubbles of uniform size. In addition, it is not easy to generate bubbles stably using a bubble generating nozzle, that is, to generate bubbles under the condition of suppressing the generation of pulsation. Therefore, it is a major issue to establish a design method for a bubble generating nozzle that can discharge bubbles of uniform size and does not easily generate pulsation when discharging bubbles. Summary of the invention

[0008] The object of the present invention is to provide a bubble generating nozzle which can discharge bubbles of uniform size and is not prone to pulsation when discharging bubbles, a bubble generating device and a bubble generating method using the bubble generating nozzle, and a bubble generating nozzle manufacturing method suitable for manufacturing the bubble generating nozzle.

[0009] The bubble generating nozzle of the present invention defines a gas flow path for introducing gas from one end and discharging bubbles formed by the gas into a stationary liquid from the other end, and is characterized in that:

[0010] 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], satisfying L>24.0×(D 2 / 4ν).

[0011] The length L of the gas flow path may also be 0.3×10 －3 [m] or above.

[0012] The length L of the gas flow path may also be 1×10 －3 [m] or above.

[0013] The length L of the gas flow path may also be 100×10 －3 [m] or less.

[0014] The equivalent diameter D of the gas flow path can also be 1×10 －6 [m] or more and 100×10 －6 [m] or less.

[0015] The bubble generating device according to the present invention comprises:

[0016] The bubble generating nozzle according to the present invention;

[0017] a gas storage chamber defining a cavity portion communicating with the gas flow path of the bubble generating nozzle, wherein the volume of the cavity portion is larger than the volume of the gas flow path; and

[0018] The gas supply source supplies the gas to the cavity portion of the gas storage chamber.

[0019] The bubble generating method of the present invention comprises the following steps:

[0020] a preparation step of preparing a bubble generating nozzle defining a gas flow path; and

[0021] a bubble discharge step of introducing gas into the gas flow path from one end of the gas flow path and repeatedly discharging bubbles formed by the introduced gas into the stationary liquid from the other end of the gas flow path,

[0022] 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], use the condition that satisfies L>24.0×(D 2 / 4ν) is used as the nozzle for generating bubbles.

[0023] In the bubble exhausting step, the gas may be introduced into the gas flow path via a gas storage chamber connected to one end of the gas flow path of the bubble generating nozzle, the one end of the gas flow path being open.

[0024] The method for manufacturing a bubble generating nozzle according to the present invention manufactures a bubble generating nozzle that defines a gas flow path for introducing gas from one end and discharging bubbles formed by the gas into a stationary liquid from the other end.

[0025] It is characterized by having the following steps:

[0026] a preparation step of preparing a workpiece as a blank of the bubble generating nozzle; and

[0027] a removing process step of performing a removing process on the workpiece to remove a portion of the workpiece, thereby forming the gas flow path in the workpiece;

[0028] In the removal process, 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], through the above removal process, a material satisfying L>24.0×(D 2 / 4ν) in the above-mentioned gas flow path.

[0029] In the removal process, the gas flow path may be formed by wire discharge machining as the removal process.

[0030] According to the bubble generating nozzle of the present invention, bubbles of uniform size can be discharged, and pulsation is unlikely to occur when the bubbles are discharged. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a cross-sectional view of the bubble generating nozzle according to the first embodiment.

[0032] Figure 2 This is a conceptual diagram showing the structure of the bubble generating device according to the first embodiment.

[0033] Figure 3 is the relationship between the length L of the gas flow path in the bubble generation nozzle involved in Experimental Example 1-15 and the physical quantity R 2 Scatter plot of the relationship between .

[0034] Figure 4 This is a flowchart of the method for manufacturing the bubble generating nozzle according to the first embodiment.

[0035] Figure 5 It is a cross-sectional view of a bubble generating nozzle and a gas storage chamber according to a second embodiment. DETAILED DESCRIPTION

[0036] Hereinafter, a bubble generation nozzle and a bubble generation device according to an embodiment will be described with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0037] [First embodiment]

[0038] Figure 1 The sectional view of the bubble generating nozzle 100 according to the present embodiment is shown. The bubble generating nozzle 100 defines a gas flow path 110 through which gas passes.

[0039] Gas is introduced from one end (hereinafter referred to as the gas introduction end) 110a of the gas flow path 110. The other end (hereinafter referred to as the bubble discharge end) 110b of the gas flow path 110 is arranged in the liquid. The gas introduced from the gas introduction end 110a passes through the gas flow path 110, and bubbles formed by the gas are discharged from the bubble discharge end 110b.

[0040] In this embodiment, the gas flow path 110 is defined as a straight column, specifically, a right cylindrical shape. The bubble generation nozzle 100 defining the right cylindrical gas flow path 110 is composed of a straight tubular body with openings at both ends. That is, one opening of the tubular body is a gas inlet end 110a, and the other opening is a bubble discharge end 110b.

[0041] Hereinafter, the manner of using the bubble generating nozzle 100 will be described in detail.

[0042] Figure 2The structure of the bubble generating device 500 having the above-mentioned bubble generating nozzle 100 is shown. The bubble generating device 500 comprises: a liquid tank 400 storing the liquid LQ, a straight tube-shaped bubble generating nozzle 100 that discharges bubbles FB into the liquid LQ in the liquid tank 400, a gas storage chamber 200 connected to the bubble generating nozzle 100, and a gas supply source 300 that supplies gas to the gas storage chamber 200.

[0043] The gas storage chamber 200 defines a cavity 210. The cavity 210 is connected to the gas flow path 110 of the bubble generating nozzle 100. The volume of the cavity 210 is larger than the volume of the gas flow path 110. In addition, in this specification, the concept of "gas storage chamber" does not include a gas pipe for conveying gas. The gas storage chamber is a space for storing gas defined at the end or midway of the gas pipe.

[0044] In this embodiment, the gas storage chamber 200 is connected to the end of the gas introduction end 110a of the bubble generating nozzle 100. However, a gas pipe that connects the cavity 210 and the gas flow path 110 may be interposed between the gas storage chamber 200 and the bubble generating nozzle 100.

[0045] 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 into the gas flow path 110 of the bubble generating nozzle 100 from the gas introduction end 110a.

[0046] The gas flowing into the gas flow path 110 passes through the gas flow path 110 and is discharged one by one from the bubble discharge end 110b into the liquid LQ as bubbles FB. The bubble generating device 500 can form bubbles FB having a diameter of, for example, less than 300 μm, more specifically, a diameter of 100 μm or less.

[0047] As described above, in the so-called dynamic bubble generating device (not shown), a pressure field of local pressure increase or pressure decrease is formed in the liquid by a pressurizing mechanism such as a liquid pump, and the bubbles are forcibly dissolved or sheared in the pressure field to make them fine. Figure 2 The static bubble generating device 500 is shown. That is, the bubble generating device 500 according to the present embodiment does not use the above-mentioned pressurizing mechanism for forming a local pressure field.

[0048] The bubble generating device 500 according to the present embodiment can be used in a manner of repeatedly discharging bubbles FB one by one into a macroscopically static liquid (hereinafter referred to as a static liquid) LQ without substantially disturbing the liquid LQ in the liquid tank 400. Here, "macroscopically static" means that the pressure is considered to be uniform and the flow velocity is zero from a macroscopic perspective in space and time, and specifically, it means that the pressure field described above for actively miniaturizing the bubbles FB is not formed.

[0049] Furthermore, in particular, in such a static usage, it may be desirable to suppress variations in the size of the air bubbles FB and to always discharge the air bubbles FB stably.

[0050] However, conventionally, it is difficult to make the size of the bubbles FB uniform, and pulsation may occur when the bubbles FB are discharged. In particular, in a structure including the gas storage chamber 200, there are problems such as the size of the bubbles FB being varied and pulsation being easily generated due to changes in the pressure of the gas in the cavity 210 and local non-uniformity of the pressure.

[0051] Therefore, the inventors of the present application have attempted to solve the above-mentioned problems by optimizing the shape of the bubble generating nozzle 100 with respect to the gas used. Hereinafter, an experimental example in which the optimal shape of the bubble generating nozzle 100 is searched for in order to solve the above-mentioned problems will be described.

[0052] [Experimental example]

[0053] First, the main factors that determine the length of the gas flow path 110 required to solve the above-mentioned problems were studied. Figure 1 As shown, here, the "length of the gas flow path 110" refers to the length L from the gas introduction end 110a to the bubble discharge end 110b.

[0054] It can be considered that the cross-sectional area of ​​the gas flow path 110 is the first factor that determines the required length of the gas flow path 110. Figure 1 As shown in FIG. 1 , 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). When the radius of the gas flow path 110 perpendicular to the length direction is set to R, the cross-sectional area of ​​the gas flow path 110 can be written as A∝R 2 .

[0055] It can be considered that the cross-sectional area A of the gas flow path 110 is equal to R 2 The larger the value, the easier it is for the density or pressure of the gas to become locally non-uniform in the gas flow path 110. Therefore, it can be considered that the cross-sectional area A of the gas flow path 110 is equal to R. 2 The larger the value, the longer the length L of the gas flow path 110 needs to be in order to achieve uniformity of the size of the bubbles FB and suppression of pulsation.

[0056] In addition, the kinematic viscosity v of the gas used can be considered to be the second factor that determines the required length of the gas flow path 110. It can be considered that the larger the kinematic viscosity v of the gas, the less likely it is that the density or pressure of the gas will be locally non-uniform in the gas flow path 110. Therefore, it can be considered that the larger the kinematic viscosity v of the gas, the shorter the length L of the gas flow path 110 can be for achieving uniformity of the size of the bubbles FB and suppression of pulsation.

[0057] As mentioned above, the first factor A∝R 2 The first factor A∝R has an influence in the direction of increasing the required length L of the gas flow path 110, and the second factor ν has an influence in the direction of decreasing the required length L of the gas flow path 110. Therefore, as a formula including these first factors A∝R 2 The physical quantity f(A∝R 2 ,ν), assuming that R 2 / ν.

[0058] Then, the length L of the gas flow path 110 and the physical quantity R 2 The uniformity of the size of the bubbles FB generated and the stability of the discharge of the bubbles FB (hereinafter collectively referred to as bubble generation characteristics) were investigated for various combinations of / ν in each structure.

[0059] The straight tube-shaped bubble generating nozzle 100 involved in Experimental Example 1-15 was produced in which the combination of the length L of the gas flow path 110 and the radius R of the gas flow path 110 was different from each other. Then, the bubble generating nozzle 100 involved in Experimental Example 1-15 was used to actually generate bubbles FB, and the bubble generating characteristics were confirmed. In addition, in Experimental Examples 1-15, air was used as the gas constituting the bubbles FB. In addition, the static liquid LQ was formed of water.

[0060] Table 1 shows the length L of the gas flow path 110 and the radius R of the gas flow path 110 in the bubble generation nozzle 100 according to Experimental Examples 1 to 15, and the results of confirming the bubble generation characteristics.

[0061] [Table 1]

[0062]

[0063] In Table 1, "0" 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 always discharged stably without pulsation. On the other hand, "×" means that there are problems in the bubble generation characteristics, specifically, the size of the bubbles FB is not uniform or pulsation occurs during the discharge of the bubbles FB.

[0064] Experimental Examples 1 to 13 showed excellent bubble generation characteristics, corresponding to the examples. On the other hand, Experimental Examples 14 and 15 had problems in bubble generation characteristics, corresponding to the comparative examples.

[0065] The kinematic viscosity ν of air used as gas in Experimental Example 1-15 is 15.12×10 －6 [m 2 / S]. Using this value and the value of radius R shown in Table 1, the above-mentioned physical quantity R was calculated. 2 / ν.

[0066] Figure 3 is to depict the physical quantity R calculated by this 2 The scatter plot of 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 represents the length L of the gas flow path 110 in [m]. The horizontal axis represents the physical quantity R in [s]. 2 That is, when the radius R of the gas flow path 110 is expressed in [m], 2 / S] when the unit represents kinematic viscosity, the physical quantity R 2 The dimension of / ν is [s]. In addition, both the vertical axis and the horizontal axis are expressed in logarithmic scales.

[0067] like Figure 3 As shown, by comparing the length L of the gas flow path 110 with the physical quantity R 2 As can be seen from the results of the scatter plot of the combinations of ν / ν, there is a boundary line BL that distinguishes Experimental Examples 1 to 13 as embodiments and Experimental Examples 14 and 15 as comparative examples. Figure 3 Among them, preferred bubble generation characteristics can be obtained in a region above the boundary line BL, that is, in a region where the length L is larger than the boundary line BL.

[0068] The dividing line BL is Figure 3 The two logarithmic scales are shown as straight lines on the scatter plot. Figure 3 The slope of the straight line and the intercept with respect to the vertical axis are read from , and it is found that the slope is 1 and the intercept is log(24.0). That is, the boundary line BL is represented by the following formula (1).

[0069] log(L)=log(R 2 / ν)+log(24.0)···(1)

[0070] therefore, Figure 3 The area above the boundary line BL is expressed by the following inequality (2).

[0071] log(L)>log(R 2 / ν)+log(24.0)···(2)

[0072] Furthermore, if the above inequality (2) is expressed in antilog form, the following inequality (3) can be obtained.

[0073] L>24.0×(R 2 / ν)···(3)

[0074] That is, as long as inequality (3) is satisfied, a preferable bubble generation characteristic can be obtained.

[0075] In Experimental Example 1-15, a nozzle having a circular cross section of the gas flow path 110 was used as the bubble generating nozzle 100, and R 2 / ν is the above-mentioned physical quantity. However, it is considered 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.

[0076] Therefore, not only when the cross section of the gas flow path 110 is circular, but also when it is non-circular such as an ellipse, a triangle, a polygon with more than four sides, generally speaking, when the equivalent diameter of the gas flow path 110 is set to D, D / 2 can be used instead of the above parameter R. In addition, when the cross-sectional area of ​​the gas flow path 110 is set to A and the perimeter of the cross section having the cross-sectional area A, that is, the perimeter of the gas flow path 110 in the imaginary plane perpendicular to the longitudinal direction is set to W, the equivalent diameter D is defined as D=4A / W. When the cross section of the gas flow path 110 is circular, the equivalent diameter D=2R.

[0077] That is, not only when the cross section of the gas flow path 110 is circular, but also when it is non-circular, generally speaking, (D / 2) can be used. 2 / ν to replace the above physical quantity R 2 / ν. In this case, inequality (3) can be rewritten as follows.

[0078] L>24.0×(D 2 / 4ν)···(4)

[0079] This inequality (4) holds true regardless of the shape of the cross section of the gas flow path 110. In inequality (4), the length L of the gas flow path 110 is expressed in [m], the equivalent diameter D is expressed in [m], and the kinematic viscosity ν is expressed in [m 2 / s]. Therefore, the scale factor 24.0 on the right has the dimension of velocity [m / s].

[0080] Based on the findings obtained from the experimental examples described above, the bubble generation method according to the present embodiment will be described below.

[0081] First, the bubble generation nozzle 100 defining the gas flow path 110 is prepared (preparation step). At least one end of the bubble generation nozzle 100 where the bubble discharge end 110b is opened is disposed in the static liquid LQ.

[0082] Next, gas is introduced into the gas flow path 110 from the gas introduction end 110a of the gas flow path 110, and bubbles FB formed by the introduced gas are repeatedly discharged one by one from the bubble discharge end 110b of the gas flow path 110 into the static liquid LQ (bubble discharge step). In addition, gas is introduced into the gas flow path 110 via the gas storage chamber 200 having a volume larger than that of the gas flow path 110.

[0083] The greatest feature of this embodiment is that a nozzle satisfying the above-mentioned inequality (4) is used as the bubble generating nozzle 100 according to the kinetic viscosity v of the gas used. This allows bubbles FB of uniform size to be discharged, and pulsation is less likely to occur when the bubbles FB are discharged.

[0084] In addition, since the size of the bubbles FB is uniform and pulsation is not easy to occur, the repetitive cycle of bubble FB generation, the specific size of the bubbles FB, etc. can be finely 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 gas pressure of the gas storage chamber 200, etc.

[0085] In addition, in this embodiment, a pressurizing mechanism such as a liquid pump is not used. In other words, the bubbles FB can be statically generated without going through dynamic processes such as dissolution, shearing, and cavitation. Therefore, when the bubbles FB are generated, contamination is not easily generated in the static liquid LQ, and the temperature of the static liquid LQ is not easily changed.

[0086] Hereinafter, preferred conditions for the length L and the equivalent diameter D of the gas flow path 110 will be described.

[0087] From the viewpoint of ensuring the structural strength of the bubble generating nozzle 100 particularly well and suppressing the difficulty in manufacturing the bubble generating nozzle 100, the length L of the gas flow path 110 is preferably 0.3×10 －3 [m] or more, more preferably 1×10 －3 [m] or above.

[0088] On the other hand, from the viewpoint of suppressing the pressure of the gas supply required for the discharge of the bubbles FB, the length L of the gas flow path 110 is preferably 100×10 －3 When a gas pump is used as the gas supply source 300, by satisfying this condition, the power required for the gas pump can be suppressed.

[0089] In addition, from the viewpoint of suppressing the difficulty in manufacturing the bubble generating nozzle 100, the equivalent diameter D of the gas flow path 110 is preferably 1×10 －6 On the other hand, in order to improve the reliability of generating bubbles FB as small as possible, specifically, bubbles FB with a diameter of 100 μm or less, which are called so-called micro bubbles, the equivalent diameter D of the gas flow path 110 is preferably 100×10 －6 [m] or less.

[0090] Next, a method for manufacturing the bubble generating nozzle according to the present embodiment will be described.

[0091] like Figure 4 As shown, first, a workpiece as a blank of the bubble generating nozzle 100 is prepared (preparation step S1). The workpiece preferably has a straight column shape. The material of the workpiece is not particularly limited. Examples of the material of the workpiece include metals and ceramics.

[0092] Next, the workpiece is subjected to a removal process to remove a portion of the workpiece, thereby forming a gas flow path 110 in the workpiece (removal process step S2). In this removal process step S2, the gas flow path 110 satisfying the above-mentioned inequality (4) is formed by the removal process.

[0093] As the removal process, wire discharge machining is preferred. In the case of wire discharge machining, a starting hole extending in a straight line is previously made to penetrate the workpiece. Then, a wire is made to communicate with the starting hole, the wire is used as one electrode, the workpiece is used as another electrode, and the workpiece is made to move two-dimensionally relative to the wire in an imaginary plane at right angles to the extension direction of the wire.

[0094] Thus, a portion (hereinafter referred to as a removed portion) having the same shape as the gas flow path 110 is dug out from the workpiece. The length direction of the linear gas flow path 110 defined by the dug out removed portion is parallel to the depth direction of the start hole and the extension direction of the above-mentioned line. In addition, the start hole is formed in the removed portion.

[0095] However, the removal process is not limited to the wire discharge machining. As the removal process, a hole opening process based on a drill or other rotating cutting tool can also be used. In this case, a straight cylindrical gas flow path 110 is formed.

[0096] In addition, after the removal process step S2, a contour forming process may be performed to adjust the contour of the workpiece on which the gas flow path 110 is formed. However, for example, when the workpiece prepared in the preparation process S1 has a straight column shape and the gas flow path 110 extending parallel to the height direction of the straight column is formed in the removal process step S2, the contour forming process is not required.

[0097] [Second embodiment]

[0098] Figure 1 and Figure 2 The bubble generating nozzle 100 is exemplified as defining 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.

[0099] like Figure 5 As shown, the bubble generating nozzle 100 according to the present embodiment defines a plurality of, specifically, five, gas flow paths 110. Each gas flow path 110 satisfies the above-mentioned inequality (4) in relation to the gas used. Therefore, in each gas flow path 110, bubbles FB of uniform size can be discharged, and pulsation is not likely to occur when the bubbles FB are discharged.

[0100] In addition, in the present embodiment, the gas storage chamber 200 is commonly used for all gas flow paths 110. That is, all gas flow paths 110 are connected to the common cavity portion 210. The volume of the cavity portion 210 is larger than the volume of each gas flow path 110, and larger than the total value of the volume of all gas flow paths 110. The point that the gas storage chamber 200 is connected to the end of the bubble generation nozzle 100 is the same as the first embodiment.

[0101] The first and second embodiments have been described above, but the following modifications are possible.

[0102] Figure 2 and Figure 4 The structure in which gas is supplied to the bubble generating nozzle 100 via the gas storage chamber 200 is illustrated, but the use of the gas storage chamber 200 is not essential. That is, the gas may be supplied to the gas flow path 110 through a gas pipe directly connected to the bubble generating nozzle 100 instead of the gas storage chamber 200. As the gas pipe, a gas pipe having a cross-sectional area larger than the cross-sectional area A of the gas flow path 110 is typically used.

[0103] Figure 1 The gas flow path 110 is shown as extending straightly in a straight line, 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 the inequality (4) refers to the length along the gas flow path 110 from the gas introduction end 110a to the bubble discharge end 110b.

[0104] Figure 1 The gas flow path 110 is illustrated as a straight column 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 the local cross-sectional area) may also be different depending on the position in the longitudinal direction of the gas flow path 110. For example, the gas flow path 110 may also be defined as a truncated cone shape. 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. In addition, the equivalent diameter D is also the same average value.

[0105] Figure 2 The structure in which the gas inlet end 110a is directly connected to the gas storage chamber 200 is shown, but the gas inlet end 110a and the gas storage chamber 200 may be connected via a flexible pipe as a gas pipe. In this case, in particular, in the case of a structure with a change in the cross-sectional shape and cross-sectional area of ​​the gas flow path 110, the circle equivalent diameter may be used as the equivalent diameter D. In this case, the segment interval ΔL is taken from the upper end of the nozzle, and L / (R 2 / ν), and investigate the relationship between L and L / (R 2 / ν), so that the length L can be defined.

[0106] The bubble generating nozzle 100 and the bubble generating device 500 according to the present embodiment can be used for manufacturing functional materials in the fields of food, cosmetics, medicine, etc. Specifically, the bubble generating nozzle 100 and the bubble generating device 500 according to the present embodiment can be used to synthesize microparticles having a hollow structure, thereby making biomaterials such as three-dimensional void structure scaffolds for cell culture, making protective films that suppress light absorption, and making semiconductor materials using hollow spacer particles.

[0107] The present invention can be modified in various ways without departing from its broad spirit and scope. The above embodiments are used to illustrate the present invention and do not limit the scope of the present invention. The scope of the present invention is not represented by the embodiments but by the claims. Various modifications implemented within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

[0108] 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.

[0109] Description of Reference Numerals

[0110] 100…nozzle for bubble generation; 110…gas flow path; 110a…gas inlet end (one end); 110b…bubble discharge end (the other end); 200…gas storage chamber; 210…cavity; 300…gas supply source; 400…liquid tank; 500…bubble generating device; BL…dividing line; FB…bubble; LQ…liquid (static liquid).

Claims

1. A nozzle for bubble generation, defining a gas flow path for introducing gas from one end and discharging bubbles formed by the gas into a stationary liquid from the other end, characterized in that: 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], satisfying L>24.0×(D 2 / 4ν).

2. The bubble generating nozzle according to claim 1, wherein: The length L of the gas flow path is 0.3×10 －3 [m] or above.

3. The bubble generating nozzle according to claim 2, wherein: The length L of the gas flow path is 1×10 －3 [m] or above.

4. The bubble generating nozzle according to claim 1, wherein: The length L of the gas flow path is 100×10 －3 [m] or less.

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

6. A bubble generating device, characterized in that: have: The bubble generating nozzle according to any one of claims 1 to 5; a gas storage chamber defining a cavity portion communicating with the gas flow path of the bubble generating nozzle, wherein the volume of the cavity portion is larger than the volume of the gas flow path; and A gas supply source supplies the gas to the cavity portion of the gas storage chamber.

7. A method for generating bubbles, characterized in that: It has the following processes: A preparation step of preparing a nozzle for bubble generation that defines a gas flow path; and a bubble discharge step of introducing gas into the gas flow path from one end of the gas flow path, and repeatedly discharging bubbles formed by the introduced gas into the stationary liquid from the other end of the gas flow path, 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], use the condition that satisfies L>24.0×(D 2 / 4ν) is used as the bubble generating nozzle.

8. The bubble generating method according to claim 7, characterized in that: In the bubble exhaust step, gas is introduced into the gas flow path via a gas storage chamber connected to one end of the gas flow path of the bubble generating nozzle, the one end of the gas flow path being open.

9. A method for manufacturing a bubble generating nozzle, the method comprising: manufacturing a bubble generating nozzle defining a gas flow path for introducing gas from one end and discharging bubbles formed by the gas into a stationary liquid from the other end; It is characterized in that It has the following processes: a preparation step of preparing a workpiece as a blank of the bubble generating nozzle; and a removing process step of performing a removing process on the workpiece to remove a portion of the workpiece, thereby forming the gas flow path in the workpiece, In the removal process, 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], through the removal process, a material satisfying L>24.0×(D 2 / 4ν) in the gas flow path.

10. The method for manufacturing a nozzle for bubble generation according to claim 9, wherein: In the removing process step, the gas flow path is formed by wire discharge machining as the removing process.

Images