Fine bubble generation device and plant growth promotion system

Abstract

To enable fine bubbles to be easily and stably generated.SOLUTION: A fine bubble generation device 1 includes: a liquid swirling flow part 2 which generates a swirling fluid H by swirling introduced liquid; a first tapered flow path 32 as an acceleration part to which the swirling fluid H is introduced and which accelerates the flow speed and swirling speed of the swirling fluid H by narrowing the flow path in a tapered shape in the flow direction of the swirling fluid H; a space 34 as a gas introduction part which is located on the downstream side in the flow direction (X positive direction) of the swirling fluid from the first tapered flow path 32, and in which gas is introduced to the swirling fluid to perform gas-liquid mixture; and a second tapered flow path 33 as a fine bubble generation part to which the gas-liquid mixed fluid K obtained through the gas-liquid mixture in the space 34 is introduced and which generates fine bubbles in the gas-liquid mixed fluid K by widening the flow path in a reverse-tapered shape with respect to the flow direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fine bubble generator and a plant growth promotion system.

Background Art

[0002] In recent years, due to the deterioration of the global environment, technologies for reducing environmental load have been demanded. In cleaning, waste liquid treatment, etc., a large amount of organic solvents are used, and there is also a current situation where chemicals are used for the wastewater treatment. Many technologies using fine bubbles have been reported as cleaning methods that do not use these organic solvents and chemicals.

[0003] For example, in Patent Document 1, the refinement of bubbles as a gas component is achieved using a very thin Venturi tube.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology of generating fine bubbles using a conventional Venturi tube disclosed in Patent Document 1 and the like, when there are large foreign matters or residues in the liquid, the Venturi tube may be clogged, and it may be difficult to continuously generate fine bubbles.

[0005] An object of the present invention is to enable the generation of fine bubbles simply and stably.

Means for Solving the Problems

[0006] In order to solve the above problems, a fine bubble generator according to an aspect of the present invention includes a liquid swirling flow section that swirls the introduced liquid to generate a swirling fluid, an acceleration section into which the swirling fluid is introduced and that accelerates the flow velocity and swirling speed of the swirling fluid by narrowing the flow path in a tapered shape with respect to the flow direction of the swirling fluid, a gas introduction section that introduces gas into the swirling fluid on the downstream side in the flow direction from the acceleration section to mix the gas and liquid, and a fine bubble generation section into which the gas-liquid mixed fluid mixed with gas and liquid in the gas introduction section is introduced and that generates fine bubbles in the gas-liquid mixed fluid by widening the flow path in an inverse tapered shape with respect to the flow direction.

Advantages of the Invention

[0007] Fine bubbles can be generated simply and stably.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] Embodiments will be described below with reference to the accompanying drawings. To facilitate understanding of the description, the same reference numerals are used for the same components in each drawing as much as possible, and duplicate descriptions are omitted.

[0010] In the following description, the X direction, Y direction, and Z direction are perpendicular to each other. The X direction is the arrangement direction of the liquid swirling flow portion 2 and the gas-liquid mixing portion 3. Also, the X direction is the flow direction of the liquid in the gas-liquid mixing portion 3. The X negative direction side is the upstream side of the flow direction (the liquid inlet 4 side), and the X positive direction side is the downstream side of the flow direction (the discharge port 6 side). The Z direction is the extending direction of the liquid inlet 4 and the gas inlet 5. The Z positive direction side is the upstream side of the flow directions of the liquid and gas at the liquid inlet 4 and the gas inlet 5, and the Z negative direction side is the downstream side of the flow directions of the liquid and gas. The Y direction is the radial direction of the circular housing 21 of the liquid swirling flow portion 2.

[0011] <Microbubble generator> With reference to FIGS. 1 to 7, the microbubble generator 1 according to the embodiment will be described. FIG. 1 is a longitudinal sectional view of the microbubble generator 1 according to the embodiment.

[0012] As shown in FIG. 1, the microbubble generator 1 generates a gas-liquid mixed fluid K having microbubbles by mixing the liquid flowing in from the liquid inlet 4 and the gas flowing in from the gas inlet 5, and discharges the gas-liquid mixed fluid K from the discharge port 6. The microbubble generator 1 includes a liquid swirling flow portion 2 and a gas-liquid mixing portion 3. The liquid inlet 4 is provided in the liquid swirling flow portion 2, and the gas inlet 5 and the discharge port 6 are provided in the gas-liquid mixing portion 3. The liquid swirling flow portion 2 and the gas-liquid mixing portion 3 are in communication. That is, the microbubble generator 1 introduces the liquid flowing in from the liquid inlet 4 from the liquid swirling flow portion 2 into the gas-liquid mixing portion 3, mixes it with the gas flowing in from the gas inlet 5 in the gas-liquid mixing portion 3 to generate a gas-liquid mixed fluid K having microbubbles, and discharges the generated gas-liquid mixed fluid K having microbubbles from the discharge port 6.

[0013] The liquid swirling flow section 2 swirls the liquid flowing in from the liquid inlet 4 to generate a swirling flow. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and shows the internal structure when the liquid swirling flow section 2 is viewed from the discharge port 6 side (the positive X direction side). As shown in FIGS. 1 and 2, the liquid swirling flow section 2 has a circular housing 21, an inner peripheral wall 22, and a communication hole 23.

[0014] The circular housing 21 is a hollow housing with a cylindrical appearance. As shown in FIG. 1, the circular housing 21 has a cylindrical wall 21A corresponding to the peripheral surface of the cylindrical shape, a first circular wall 21B corresponding to the top surface of the cylindrical shape, and a second circular wall 21C corresponding to the bottom surface of the cylindrical shape. The cylindrical wall 21A is arranged such that the direction of the central axis O is parallel to the X direction. The outer edge of the first circular wall 21B is connected along the circular edge end portion on the positive X direction side of the cylindrical wall 21A. Similarly, the outer edge of the second circular wall 21C is connected along the circular edge end portion on the negative X direction side of the cylindrical wall 21A. Thereby, the hollow circular housing 21 is formed.

[0015] As shown in FIG. 1, the liquid inlet 4 is connected to communicate with the cylindrical wall 21A of the circular housing 21 at a position on the positive Z direction side of the cylindrical wall 21A with the Z direction as the extending direction, thereby enabling the introduction of liquid into the inside of the liquid swirling flow section 2. Further, in the X direction, the liquid inlet 4 is arranged at the end portion of the cylindrical wall 21A of the circular housing 21 on the side of the second circular wall 21C. Also, as shown in FIG. 2, the liquid inlet 4 is linearly formed along the tangent in the Z direction of the circular cross-section of the cylindrical wall 21A at the end position on the negative Y direction side of the cylindrical wall 21A.

[0016] The inner peripheral wall 22 is a cylindrical member provided inside the circular housing 21. As shown in FIG. 1, the inner peripheral wall 22 stands upright from the second circular wall 21C toward the positive X direction side. The tip end portion on the positive X direction side of the inner peripheral wall 22 does not reach the first circular wall 21B, and a flow path is formed between the inner peripheral wall 22 and the first circular wall 21B. Also, as shown in FIG. 2, the inner peripheral wall 22 has a circular cross-sectional shape when viewed in the X direction and is arranged concentrically with the cylindrical wall 21A. That is, the central axis of the inner peripheral wall 22 is the same as the central axis O of the cylindrical wall 21A of the circular housing 21.

[0017] As shown in Fig. 1, the communication hole 23 is a cylindrical member that stands upright on the X negative direction side from the first circular wall 21B inside the circular housing 21. The tip of the communication hole 23 on the X negative direction side does not reach the second circular wall 21C, and a flow path is formed between the communication hole 23 and the second circular wall 21C. Further, as shown in Fig. 2, the communication hole 23 has a circular cross-sectional shape when viewed in the X direction and is arranged concentrically with the cylindrical wall 21A and the inner peripheral wall 22. That is, the central axis of the communication hole 23 is also the same as the central axis O of the cylindrical wall 21A of the circular housing. Further, the communication hole 23 is formed to have a smaller diameter than the inner peripheral wall 22 and is arranged on the center side of the concentric circle from the inner peripheral wall 22. The portion of the first circular wall 21B on the center side from the communication hole 23 is opened in a circular shape along the inner peripheral surface of the communication hole 23, whereby the liquid swirling flow portion 2 and the gas-liquid mixing portion 3 are communicated through the communication hole 23.

[0018] In this way, in the liquid swirling flow portion 2, the liquid is introduced into the inside from the outer edge portion of the circular housing 21 through the liquid inlet 4. Then, while swirling along the circumferential direction of the cylindrical shape that gradually decreases in diameter in the order of the cylindrical wall 21A, the inner peripheral wall 22, and the communication hole 23 and gradually moving toward the central axis O side, the swirling radius of the liquid gradually decreases, so the swirling speed is gradually accelerated. As a result, finally, a swirling fluid H (see Fig. 3) of the liquid swirling at a desired swirling speed is generated from the communication hole 23 and supplied to the gas-liquid mixing portion 3.

[0019] The gas-liquid mixing portion 3 mixes the swirling fluid of the liquid whose flow velocity has been accelerated in the liquid swirling flow portion 2 with the gas to generate a gas-liquid mixed fluid L having fine bubbles. As shown in Fig. 1, the gas-liquid mixing portion 3 includes a cylindrical housing 31, a first tapered flow path 32 (acceleration portion), and a second tapered flow path 33 (fine bubble generation portion).

[0020] The cylindrical housing 31 is integrally formed with, for example, the communication hole 23 of the liquid swirling flow portion 2 and is formed in a cylindrical shape that continuously extends in the X positive direction from the communication hole 23. That is, the central axis of the cylindrical housing 31 is also the same as the central axis O of the cylindrical wall 21A of the circular housing 21. The discharge port 6 is an opening at the end of the cylindrical shape of the gas-liquid mixing portion 3 on the X positive direction side.

[0021] The first tapered flow path 32 and the second tapered flow path 33 are installed inside the cylindrical housing 31 and are flow paths for flowing the liquid introduced from the liquid swirling flow portion 2. The first tapered flow path 32 and the second tapered flow path 33 are arranged in series along the flow direction of the liquid flowing through the cylindrical housing 31, and the first tapered flow path 32 is arranged on the upstream side (X negative direction side) of the second tapered flow path 33.

[0022] At the upstream end in the liquid flow direction, the diameter of the first tapered flow path 32 is the same as the inner diameter of the cylindrical housing 31. As it proceeds in the downstream direction (X positive direction) of the liquid flow direction, the diameter gradually decreases, and it is formed such that the diameter is the smallest at the downstream end. That is, the first tapered flow path 32 is formed in a tapered shape with respect to the liquid flow direction. The X-direction position of the upstream end of the first tapered flow path 32 is arranged at the upstream end of the cylindrical housing 31, that is, at the position of the first circular wall 21B of the liquid swirling flow portion 2, as shown in FIG. 1 for example.

[0023] At the upstream end in the liquid flow direction, the diameter of the second tapered flow path 33 is the smallest. As it proceeds in the downstream direction (X positive direction) of the liquid flow direction, the diameter gradually increases, and it is formed such that the diameter is the largest at the downstream end and becomes the same as the inner diameter of the cylindrical housing 31. That is, the second tapered flow path 33 is formed in an inverse tapered shape with respect to the liquid flow direction. The X-direction position of the downstream end of the second tapered flow path 33 is arranged at the downstream end of the cylindrical housing 31, that is, at the position of the discharge port 6, as shown in FIG. 1 for example.

[0024] The first tapered flow path 32 and the second tapered flow path 33 are arranged coaxially with the cylindrical housing 31. That is, the central axes of the first tapered flow path 32 and the second tapered flow path 33 are also the same as the central axis O of the cylindrical wall 21A of the circular housing 21.

[0025] The position of the downstream end of the first tapered flow path 32 in the X direction is arranged upstream of the position of the upstream end of the second tapered flow path 33 in the X direction. That is, between the first tapered flow path 32 and the second tapered flow path 33, there is a space 34 (gas introduction part) that is larger than the minimum diameter of the downstream end of the first tapered flow path 32 and the minimum diameter of the upstream end of the second tapered flow path 33 and has the same diameter as the inner diameter of the cylindrical housing 31. The cross-sectional area of the cross-section orthogonal to the X direction of this space 34 is larger than the cross-sectional area of the downstream end of the first tapered flow path 32 and the cross-sectional area of the upstream end of the second tapered flow path 33.

[0026] In the example of FIG. 1, the minimum diameter of the downstream end of the first tapered flow path 32 is formed smaller than the minimum diameter of the upstream end of the second tapered flow path 33. In other words, the cross-sectional area of the minimum diameter portion of the first tapered flow path 32 is different from the cross-sectional area of the minimum diameter portion of the second tapered flow path 33, and it is preferable that the cross-sectional area of the minimum diameter portion of the first tapered flow path 32 is smaller. With this configuration, the gas-liquid mixed fluid K (see FIG. 3) generated in the space 34 can easily flow into the second tapered flow path 33.

[0027] The gas inlet 5 is connected to communicate with the cylindrical housing 31 at a position on the positive Z-direction side of the peripheral wall of the cylindrical housing 31 with the Z direction as the extending direction, so that gas can be introduced into the inside of the gas-liquid mixing section 3. Further, the connection position of the gas inlet 5 in the X direction is arranged at the downstream end position of the first tapered flow path 32 or at an arbitrary position upstream of the downstream end position. That is, as shown in the examples of FIGS. 1 and 3, it is preferable that the connection position of the gas inlet 5 is arranged at a position upstream of the space 34 between the first tapered flow path 32 and the second tapered flow path 33.

[0028] Next, the operation of the fine bubble generator 1 will be described.

[0029] First, as shown by arrow A in FIGS. 1 and 2, the liquid flowing into the liquid swirling flow portion 2 from the liquid inlet 4 in the Z negative direction rotates along the inner peripheral surface of the cylindrical wall 21A of the circular housing 21 as shown by arrow B in FIG. 2, and moves in the X positive direction in the space between the inner peripheral surface of the cylindrical wall 21A and the outer peripheral surface of the inner peripheral wall 22 as shown by arrow C in FIG. 1. Then, when it reaches the first circular wall 21B at the X positive direction end of the circular housing 21, it flows from the gap between the first circular wall 21B and the inner peripheral wall 22 to the center side of the inner peripheral wall 22, rotates in the same direction as arrow B along the inner peripheral surface of the inner peripheral wall 22 as shown by arrow D in FIG. 2, and moves in the X negative direction in the space between the inner peripheral surface of the inner peripheral wall 22 and the outer peripheral surface of the communication hole 23 as shown by arrow E in FIG. 1. Then, when it reaches the second circular wall 21C at the X negative direction end of the circular housing 21, it flows from the gap between the second circular wall 21C and the communication hole 23 to the center side of the communication hole 23, rotates in the same direction as arrows B and D along the inner peripheral surface of the communication hole 23 as shown by arrow F in FIG. 2, and moves through the communication hole 23 in the X positive direction as shown by arrow G in FIG. 1. As a result, the liquid becomes a swirling fluid H (see FIG. 3) and is introduced into the gas-liquid mixing portion 3.

[0030] FIG. 3 is a diagram schematically showing the flow of liquid and gas in the gas-liquid mixing portion 3. As shown in FIG. 3, the liquid (swirling fluid H) that has become a swirling flow due to the rotation in the liquid swirling flow portion 2 is introduced from the communication hole 23 of the liquid swirling flow portion 2 into the cylindrical housing 31 of the gas-liquid mixing portion 3 and flows toward the discharge port 6 on the X positive direction side. Then, the swirling fluid H enters the first tapered flow path 32, and the flow velocity increases at the portion where the flow path narrows in a tapered shape in the first tapered flow path 32, and it becomes a swirling fluid with a higher circumferential speed (swirling speed) while rotating longitudinally. That is, the first tapered flow path 32 functions as an "acceleration portion for accelerating the flow velocity and swirling speed of the introduced liquid swirling fluid H".

[0031] The swirling fluid H whose peripheral velocity has increased due to the first tapered flow path 32 flows out into the space 34 between the first tapered flow path 32 and the second tapered flow path 33. This space 34 is a space wider than the cross-sectional area of the downstream end of the first tapered flow path 32 and the cross-sectional area of the upstream end of the second tapered flow path 33. The swirling fluid I passing through this space 34 causes the fluid filling this space 34 to also perform a rotational motion. Inside this space 34, it is at a negative pressure with respect to the atmospheric pressure, and as shown by the arrow J in FIGS. 1 and 3, gas flows in from the gas inlet 5. As a result, gas is introduced into the liquid of the swirling fluid I and gas-liquid mixing occurs, resulting in a gas-liquid mixed fluid K. That is, the space 34 functions as a "gas introduction part that introduces gas into the swirling fluid accelerated by the acceleration part (the first tapered flow path 32) and performs gas-liquid mixing".

[0032] The gas-liquid mixed fluid K generated in the space 34 as the gas introduction part enters the second tapered flow path 33 and flows toward the discharge port 6 where the reverse tapered flow path of the second tapered flow path 33 widens. At the discharge port 6 side of the second tapered flow path 33 with a reverse taper, a shear force is generated at the interface or boundary surface between the gas and the liquid, efficiently generating nano-order bubbles and causing the liquid to be mixed with fine gas to contain fine bubbles. Then, the gas-liquid mixed fluid L having the generated fine bubbles is output from the discharge port 6. That is, the second tapered flow path 33 functions as a "fine bubble generation part that generates fine bubbles in the gas-liquid mixed fluid K introduced from the space 34".

[0033] Thus, the fine bubble generator 1 of the present embodiment includes a liquid swirling flow part 2 that swirls the introduced liquid to generate a swirling fluid H, a first tapered flow path 32 as an acceleration part that introduces the swirling fluid H and accelerates the flow velocity and swirling speed of the swirling fluid H by narrowing the flow path in a tapered shape with respect to the flow direction of the swirling fluid H, a space 34 as a gas introduction part that introduces gas into the swirling fluid on the downstream side in the flow direction (X positive direction) of the swirling fluid from the first tapered flow path 32 and performs gas-liquid mixing, and a second tapered flow path 33 as a fine bubble generation part that introduces the gas-liquid mixed fluid K gas-liquid mixed in the space 34 and generates fine bubbles in the gas-liquid mixed fluid K by widening the flow path in a reverse tapered shape with respect to the flow direction.

[0034] With this configuration, since the space 34 as the gas introduction part is arranged immediately after the outlet of the first tapered flow path 32 as the acceleration part for accelerating the swirling fluid H of the liquid, the gas having a relatively low specific gravity and a slow flow velocity with respect to the liquid is once condensed near the center of the axial flow of the swirling fluid of the liquid and then gas-liquid mixed. The gas-liquid mixed fluid K thus gas-liquid mixed is introduced into the second tapered flow path 33 as the microbubble generation part. On the outlet 6 side where the flow path widens in the second tapered flow path 33, a shearing force is generated at the interface or boundary surface between the gas and the liquid of the gas-liquid mixed fluid K, and the gas can be atomized by this shearing force. As a result, nano-order bubbles can be efficiently generated, and it becomes possible to generate and output a gas-liquid mixed fluid L containing microbubbles in which the liquid and the fine gas are mixed. Further, since microbubbles can be generated without using a very thin Venturi tube described in Patent Document 1, for example, like the conventional microbubble generation method, problems such as clogging of the Venturi tube can be avoided, and microbubbles can be generated more stably. Also, in other conventional microbubble generation methods, a configuration using a high-pressure liquid delivery pump for generating microbubbles is known, but in this embodiment, microbubbles can be generated without using such a high-pressure liquid delivery pump, so a micro mechanism can be generated with a simpler configuration than before. Thus, according to the microbubble generator 1 of this embodiment, microbubbles can be generated simply and stably.

[0035] FIG. 4 is a plan view showing an example of the configuration of the second tapered flow path 33. As shown in FIG. 4, as shown in FIG. 4, the second tapered flow path 33 is preferably configured to be movable along the X direction and can be arranged at an arbitrary position. With this configuration, the interval d1 in the X direction of the space 34 between the first tapered flow path 32 and the second tapered flow path 33 can be adjusted to an arbitrary dimension.

[0036] In the case of the configuration of Fig. 4, after aligning the end position on the negative X-direction side of the second tapered flow path 33 to a desired position in the X direction, for example, by fixing the end on the positive X-direction side with the fixing ring 35, the interval d1 in the X direction of the space 34 can be fixed at an arbitrary dimension. Note that, in order to draw gas from the gas inlet 5 into the inside of the gas-liquid mixing section 3, the interval d1 between the first tapered flow path 32 and the second tapered flow path 33 (i.e., the dimension in the X direction of the space 34) is preferably about 5 mm to 10 mm. When the interval d1 between the first tapered flow path 32 and the second tapered flow path 33 is too narrow or too wide compared to the above dimensions, a reverse flow phenomenon may occur where the fluid flows back into the gas inlet 5.

[0037] As described with reference to Fig. 4, by adopting a configuration in which the reverse tapered second tapered flow path 33 can be arbitrarily moved along the flow direction (X direction) of the swirling fluid, the dimension in the X direction of the space 34 as the gas introduction section can be adjusted to an appropriate dimension that can promote gas-liquid mixing.

[0038] Fig. 5 is a plan view showing an example of the position adjustment structure of the gas inlet 5. As shown in Fig. 5, a position adjustment structure that can adjust the position of the gas inlet 5 in the X direction to an arbitrary position may be provided in the gas-liquid mixing section 3. As the position adjustment structure, for example, as shown in Fig. 5, it has a slide plate 36 to which the gas inlet 5 is communicatively connected, and a pair of guides 37 that slidably sandwich the slide plate 36 from both sides in the Y direction. In this configuration, an opening 38 with the X direction as the longitudinal direction is provided in the region of the cylindrical housing 31 where the gas inlet 5 can be arranged, and the slide plate 36 is installed so as to cover this opening 38 from the outside of the outer peripheral surface of the cylindrical housing 31. The gap between the slide plate 36 and the outer peripheral surface of the cylindrical housing 31 is processed to ensure watertightness, thereby preventing liquid leakage from the opening 38.

[0039] In the example of Fig. 5, since the slide plate 36 is movable in the X direction along the guide 37 with respect to the cylindrical housing 31 of the gas-liquid mixing section 3, the gas inlet 5 can be arranged at any position in the X direction of the cylindrical housing 31 by moving the slide plate 36 to an arbitrary position in the X direction. The gas inlet 5 can communicate with the inside of the gas-liquid mixing section 3 through an opening provided in the cylindrical housing 31.

[0040] Fig. 6 is a plan view showing another example of the position adjustment structure of the gas inlet 5. As shown in Fig. 6, a plurality of mounting holes 39 to which the gas inlet 5 can be connected may be provided in the cylindrical housing 31 of the gas-liquid mixing section 3. The position of the gas inlet 5 is preferably arranged at the same position as the discharge-side tip (the end on the X positive direction side) of the first tapered flow path 32 or on the inflow side (the X negative direction side) from the tip. In the example of Fig. 6, any one of the plurality of mounting holes 39 that satisfies this condition may be selected and the gas inlet 5 may be connected. The remaining mounting holes 39 can be sealed by a sealing element such as a screw, etc., to ensure the watertightness of the gas-liquid mixing section 3. Although Fig. 6 illustrates a configuration in which five mounting holes 39 are provided, the number of mounting holes 39 may be other than five.

[0041] As described with reference to Figs. 5 and 6, by configuring the gas inlet 5 to be movable arbitrarily along the flow direction (X direction) of the swirling fluid, even when the position of the space 34 in the X direction changes according to the arrangement of the first tapered flow path 32 and the second tapered flow path 33, the introduction position of the gas into the gas-liquid mixing section 3 by the gas inlet 5 can be adjusted to an arbitrary position that can promote gas-liquid mixing. Examples of such an introduction position include the same position as the discharge-side tip (the end on the X positive direction side) of the first tapered flow path 32 or a position on the inflow side (the X negative direction side) from the tip.

[0042] The action of gas-liquid mixing in the gas introduction section (space 34) will be further described with reference to Fig. 7. Fig. 7 is an image showing the state of gas-liquid mixing in the gas introduction section (space 34).

[0043] As described with reference to FIG. 3, the gas J that has flowed into the gas-liquid mixing section 3, for example, is affected by the rotational motion of the swirling fluid I in the space 34, and becomes a swirling flow with a gradually increasing peripheral velocity while rotating in the outer peripheral space of the first tapered flow path 32. Then, as shown in FIG. 7, the swirling flow of the gas J is collected in the central portion of the swirling fluid I in the space 34 and becomes a thin streak-like swirling flow M. Then, the gas-liquid mixed fluid K in which the swirling flow M of this gas and the swirling fluid I of the liquid are gas-liquid mixed is introduced into the second tapered flow path 33. Further, at the discharge port side of the second tapered flow path 33 having an inverse taper, a shearing force is generated at the interface or boundary surface between the gas and the liquid of the gas-liquid mixed fluid K, efficiently generating nano-order bubbles, and becoming a gas-liquid mixed fluid L in which the liquid and the fine gas are mixed. The gas-liquid mixed fluid L having fine bubbles is discharged from the discharge port 6.

[0044] <Plant growth promotion system> With reference to FIGS. 8 and 9, the plant growth promotion system 10 according to the embodiment will be described. FIG. 8 is a diagram showing an example of the schematic configuration of the plant growth promotion system 10 according to the embodiment.

[0045] As shown in FIG. 8, the plant growth promotion system 10 is obtained by applying the fine bubble generator 1 according to this embodiment to a so-called hydroponic cultivation device, and includes a cultivation shelf 11, a water tank 12, and an LED lamp 13. A solution S mixed with liquid fertilizer is stored in the water tank 12. A first submersible pump 14 is installed in the water tank 12, and when the first submersible pump 14 operates, the solution S in the water tank 12 is supplied to the cultivation shelf 11 via a pipe 15 or the like. In the cultivation shelf 11, the plant P is cultivated with the solution S supplied from the water tank 12. Further, the solution S that has passed through the cultivation shelf 11 is returned to the water tank 12 again via a pipe 16 or the like. The LED lamp 13 irradiates the plant P cultivated in the cultivation shelf 11 with light R.

[0046] And particularly in the plant growth promotion system 10, the fine bubble generator 1 is installed in the water tank 12. Further, a second submersible pump 17 is installed in the fine bubble generator 1. When the second submersible pump 17 operates, the solution S in the water tank 12 is introduced into the liquid swirling flow section 2 of the fine bubble generator 1. Further, as shown in FIG. 8 for example, the gas inlet 5 of the fine bubble generator 1 is arranged such that the upper end opening protrudes from above the water tank 12 to the outside, and is preferably installed so that gas can always be introduced into the gas-liquid mixing section 3 of the fine bubble generator 1 regardless of the water level of the solution S in the water tank 12. Thereby, the fine bubble generator 1 generates a gas-liquid mixed fluid L having fine bubbles using the solution S in the water tank 12. That is, the fine bubble generator 1 can further generate fine bubbles in the solution S in which the liquid fertilizer is mixed with water. Therefore, the above-described first submersible pump 14 can supply the solution S' having fine bubbles to the cultivation shelf 11, and the plants P are cultivated by the solution S' having fine bubbles on the cultivation shelf 11.

[0047] In the example of FIG. 8, the second submersible pump 17 is integrally connected to the fine bubble generator 1. However, the second submersible pump 17 only needs to be connected to at least the liquid inlet 4 of the fine bubble generator 1, and the solution S may be introduced into the liquid swirling flow section 2 through the liquid inlet 4. For example, a configuration in which the second submersible pump 17 is installed at a position away from the fine bubble generator 1 in the water tank 12 and connected to the liquid inlet 4 via a tube or the like may be used. Further, the second submersible pump 17 only needs to be able to output power sufficient to suck up the solution S in the water tank 12 and send it to the liquid inlet 4, and does not need to be a high-pressure liquid feed pump like the pump used for generating fine bubbles in a conventional fine bubble generator.

[0048] The fine bubble generator 1 according to the present embodiment has an advantage that it is possible to simply generate a large number of nano-level fine bubbles without using a high-pressure liquid feed pump for liquid feeding.

[0049] Generally, the temperature of the solution rises when a high-pressure liquid delivery pump is used. In a solution circulation type hydroponic cultivation device as shown in Fig. 8, although it also takes into account the outside air temperature, since the solution S circulates, when a high-pressure liquid delivery pump is used to generate fine bubbles, the solution temperature continues to rise. When the temperature of the solution S rises, the roots of the plant P weaken in the cultivation shelf 11, and there is a risk that the growth rate decreases. That is, when a fine bubble generator using a conventional high-pressure liquid delivery pump is applied to a hydroponic cultivation device, even if fine bubbles are generated to promote the growth of the plant P, there is a risk that the promotion of growth is inhibited due to factors such as the temperature rise of the solution S.

[0050] In response to such a conventional problem, in the plant growth promotion system 10 according to the present embodiment, as described above, the fine bubble generator 1 can generate fine bubbles without using a high-pressure liquid delivery pump. As a result, while suppressing the temperature rise of the solution S, it is possible to supply the solution S' containing a large number of nano-level fine air bubbles, so that the growth promotion of the plant P can be more surely promoted.

[0051] Fig. 9 is a diagram showing another example 10A of the schematic configuration of the plant growth promotion system according to the embodiment. As shown in Fig. 9, the plant growth promotion system according to the present embodiment is also applicable to a multi-stage hydroponic cultivation device. In the example of Fig. 9, the plant growth promotion system 10A includes a first cultivation shelf 11A and a second cultivation shelf 11B. The first cultivation shelf 11A is arranged above the second cultivation shelf 11B, and the solution S' discharged from the first cultivation shelf 11A is supplied to the lower second cultivation shelf 11B via a pipe 18 or the like, and the solution S' discharged from the second cultivation shelf 11B is returned to the water tank 12 via a pipe 16 or the like. The plant growth promotion system 10A includes a first LED lamp 13A and a second LED lamp 13B that irradiate light on each of the first cultivation shelf 11A and the second cultivation shelf 11B.

[0052] Even in the plant growth promotion system 10A shown in FIG. 9, it is possible to generate fine bubbles in the solution S while suppressing the temperature rise of the solution S, and the solution S' having fine bubbles can be supplied to both the first cultivation shelf 11A and the second cultivation shelf 11B. Therefore, similar to the plant growth promotion system 10 shown in FIG. 8, the growth of the plant P can be more surely promoted.

[0053] In the example of FIG. 9, a configuration including a two-stage cultivation shelf of the first cultivation shelf 11A and the second cultivation shelf 11B is illustrated, but the number of stages of the cultivation shelf may be three or more.

Example

[0054] Next, examples of the present invention will be specifically described.

[0055] <Setting of the First Test> Example 1, Comparative Examples 1 and 2 were set as follows, and a first test was conducted to verify the effects of the fine bubble generator 1 according to the above embodiment.

[0056] <Example 1> The fine bubble generator 1 shown in FIGS. 1 and 2 was created.

[0057] The created fine bubble generator 1 was installed in an acrylic water tank, and a gas-liquid mixed fluid L having fine bubbles was generated in the water in the water tank. The amount of water stored in the water tank was 180 liters. A submersible pump was used to send the fluid to the fine bubble generator 1. The flow rate of the submersible pump was 30 liters per minute. The operating time of the fine bubble generator 1 was set to 6 minutes assuming that all the water in the acrylic water tank passed through the pump.

[0058] A sample of the gas-liquid mixed fluid L generated under the above conditions was collected, and the bubble diameter and number were measured by the dynamic light scattering method.

[0059] <Comparative Example 1> In Comparative Example 1, measurements were performed under the same conditions as in Example 1 except that a fine bubble generator using a pressurized dissolution method was used. The pressurized dissolution method is known as a fine bubble generation method using a pressurized pump.

[0060] <Comparative Example 2> In Comparative Example 2, measurements were carried out under the same conditions as in Example 1, except that a microbubble generator using a Venturi tube method was used. The Venturi tube method is a technique disclosed in, for example, Patent Document 1.

[0061] <Results of the First Test> The results of the first test are shown in Table 1.

Table 1

[0062] As shown in Table 1, in Example 1, it was confirmed that the average particle diameter and the number of microbubbles were both able to obtain performance equivalent to that of the pressure dissolution method of Comparative Example 1.

[0063] In the pressure dissolution method of Comparative Example 1, since a pressure pump is used for generating microbubbles, the system becomes expensive and the structure becomes complicated. Further, in the pressure dissolution method, there are secondary effects such as heat generation during continuous operation and an increase in the water temperature, and intermittent operation is recommended for systems sensitive to the water temperature. For this reason, in Comparative Example 1, there may be cases where the performance shown in Table 1 cannot be exhibited depending on the usage conditions.

[0064] On the other hand, in Example 1, it is not necessary to use a pressure pump for generating microbubbles. Therefore, the microbubble generator 1 according to the present embodiment used in Example 1 has a low cost and a simple configuration, and can exhibit performance equivalent to that of Comparative Example 1. Further, since there is no influence such as heat generation, it can stably exhibit performance equivalent to the results in Table 1 regardless of the usage conditions.

[0065] Also, as shown in Table 1, in Example 1, it was confirmed that, with respect to the Venturi tube method of Comparative Example 2, the average particle diameter was the same, but 10 times more microbubbles could be generated in terms of the number of microbubbles.

[0066] Thus, from the results of the first test, it was shown that the microbubble generator 1 according to the present embodiment can generate microbubbles simply and stably as compared with the conventional pressure dissolution method and Venturi tube method.

[0067] <Settings of the Second Test> First, as a preliminary test of the second test, the plant growth promotion system 10 according to the present embodiment shown in FIG. 8 was created, and an appropriate liquid fertilizer was selected using the created plant growth promotion system 10.

[0068] As the light source 13 for photosynthesis, plant-growing LEDs having peaks at 450 nm and 660 nm were used. 50 liters of tap water and a liquid fertilizer were put into a water tank 12 with a capacity of 60 liters, and a fine bubble generator 1 and a liquid feed water pump 14 with a liquid feed rate of 30 liters per minute were installed. The cultivation shelf 11 has a structure in which a diluted aqueous solution of the liquid fertilizer (solution S' in FIG. 8) circulates.

[0069] As candidates for the liquid fertilizer, liquid fertilizers A, B, and C, which are products of three companies, were selected. The plant P cultivated on the cultivation shelf 11 was Komatsuna.

[0070] For the solution S in the water tank 12, those obtained by diluting each of the liquid fertilizers A to C 250 times and 500 times with ion-exchanged water were used. On the cultivation shelf 11, the solution S' was poured into a 500-cc plastic container, and Komatsuna that had been germinated on a 2-cm square cube-shaped sponge in advance was planted so as to be immersed. The photosynthetic photon flux density of the LED 13 corresponding to Komatsuna was adjusted to 100 (μmol / m 2 ·s). Cultivation was carried out under these conditions, and the state and size of Komatsuna 14 days after the start were measured.

[0071] Table 2 shows the results of the preliminary test.

Table 2

[0072] As shown in Table 2, it was confirmed that among the candidates of the three types of liquid fertilizers A to C, the liquid fertilizer B diluted 250 times and 500 times with ion-exchanged water showed the best growth results. Therefore, in the following second test, the liquid fertilizer B diluted 500 times with ion-exchanged water was used as the solution S.

[0073] Example 2, Comparative Examples 3 and 4 were set up as follows, and a second test was conducted to verify the effects of the plant growth promotion system 10 according to the above embodiment.

[0074] <Example 2> The multi-stage plant growth promotion system 10A according to this embodiment shown in FIG. 9 was created.

[0075] In the created plant growth promotion system 10A, for the light sources 13A and 13B for photosynthesis, plant-growing LEDs having peaks at 450 nm and 660 nm were used. Among the 24 hours of a day, the irradiation time of the plant-growing LEDs was set to 24 hours.

[0076] Into the water tank 12, liquid fertilizer B diluted 500-fold with tap water was introduced as the solution S so that the total circulating water volume would be 110 liters, and a fine bubble generator 1 and a liquid feed water pump 14 for 60 liters per minute were installed.

[0077] The cultivation shelves 11A and 11B have a structure in which the diluted liquid fertilizer aqueous solution S circulates as a solution S' processed to have fine bubbles by the fine bubble generator 1. Cultivation was carried out under these conditions, and the growth degree of Komatsuna after 20 days was measured. As indicators of the growth degree, the average length (cm), average weight (g), and sugar content (%) were selected.

[0078] <Comparative Example 3> In Comparative Example 3, measurements were carried out under the same conditions as in Example 2, except that only tap water was used as the solution S.

[0079] <Comparative Example 4> In Comparative Example 4, measurements were carried out under the same conditions as in Example 2, except that a Venturi tube type fine bubble generator was used.

[0080] <Results of the Second Test> The results of the second test are shown in Table 3.

Table 3

[0081] As shown in Table 3, in Example 2, compared with Comparative Example 3 in which only tap water was used as the solution S, the sugar content of Komatsuna was equivalent, but it was confirmed that the average length of Komatsuna was promoted to grow to about 38 cm and the average weight was promoted to grow to about 36 g.

[0082] Also, in Example 2, compared with Comparative Example 4 in which a Venturi tube type microbubble generator was used, the average length and sugar content of Komatsuna were the same, but it was confirmed that the average weight of Komatsuna was promoted to grow to about 44 g.

[0083] Thus, from the results of the second test, it was shown that the plant growth promotion system 10A according to the present embodiment can more surely promote the growth of the plant P as compared with the case where only tap water is used as the solution S or the case where a conventional Venturi tube type microbubble generator is used.

[0084] As described above, the present embodiment has been described with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those obtained by appropriately making design changes by those skilled in the art to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each of the above-described specific examples and its arrangement, conditions, shape, etc. are not limited to those illustrated and can be changed as appropriate. Each element included in each of the above-described specific examples can be appropriately combined as long as no technical contradiction occurs.

[0085] In addition, in the above embodiment, as an application example of the microbubble generator 1, as shown in FIGS. 8 and 9, the plant growth promotion systems 10 and 10A related to the hydroponic cultivation device are exemplified, but the microbubble generator 1 according to the embodiment is also applicable to other cases. For example, a configuration in which microbubbles are mixed into the water sprayed in soil cultivation using the microbubble generator 1 according to the embodiment, or a configuration in which the microbubble generator 1 according to the embodiment is applied to a water circulation device in a system for breeding aquatic organisms in an aquarium and microbubbles are mixed into the water circulated by the water circulation device and supplied to the aquarium, and the like can be mentioned.

[0086] Aspects of the present invention are as follows, for example. <1> A liquid swirling flow section that swirls the introduced liquid to generate a swirling fluid, An acceleration section into which the swirling fluid is introduced and that accelerates the flow velocity and swirling speed of the swirling fluid by narrowing the flow path in a tapered shape with respect to the flow direction of the swirling fluid, A gas introduction section that introduces gas into the swirling fluid on the downstream side of the acceleration section in the flow direction to perform gas-liquid mixing, A fine bubble generation section into which the gas-liquid mixed fluid gas-liquid mixed in the gas introduction section is introduced and that generates fine bubbles in the gas-liquid mixed fluid by widening the flow path in an inverse tapered shape with respect to the flow direction, A fine bubble generator comprising the above. <2> The gas introduction section is provided with a gas inlet for introducing gas from the outside, The gas inlet is movable arbitrarily along the flow direction, The fine bubble generator according to <1> above. <3> The inverse tapered flow path of the fine bubble generation section is movable arbitrarily along the flow direction, The fine bubble generator according to <1> or <2> above. <4> The cross-sectional area of the minimum diameter portion of the tapered flow path of the acceleration section is different from the cross-sectional area of the minimum diameter portion of the inverse tapered flow path of the fine bubble generation section, The fine bubble generator according to any one of <1> to <3> above. <5> A plant growth promotion system including the fine bubble generator according to any one of <1> to <4> above.

Explanation of reference numerals

[0087] 1 Fine bubble generator 2 Liquid swirling flow section 3 Gas-liquid mixing section 32 First tapered flow path (acceleration section) 33 Second tapered flow path (fine bubble generation section) 34 Space (gas introduction section) 5 Gas inlet 10, 10A Plant growth promotion system

Prior Art Documents

Patent Documents

[0088]

Patent Document 1

Claims

1. A liquid swirling flow section that swirls the introduced liquid to generate a swirling fluid; An acceleration section into which the swirling fluid is introduced and that accelerates the flow velocity and swirling speed of the swirling fluid by narrowing the flow path in a tapered shape with respect to the flow direction of the swirling fluid; A gas introduction section that introduces gas into the swirling fluid on the downstream side of the acceleration section in the flow direction to mix gas and liquid; A fine bubble generation section into which the gas-liquid mixed fluid mixed with gas and liquid in the gas introduction section is introduced and that generates fine bubbles in the gas-liquid mixed fluid by widening the flow path in an inverse-tapered shape with respect to the flow direction; A fine bubble generator comprising the above.

2. The gas introduction section is provided with a gas inlet for introducing gas from the outside, The gas inlet is movable arbitrarily along the flow direction, The fine bubble generator according to Claim 1.

3. The inverse-tapered flow path of the fine bubble generation section is movable arbitrarily along the flow direction, The fine bubble generator according to Claim 1.

4. The cross-sectional area of the minimum diameter portion of the tapered flow path of the acceleration section is different from the cross-sectional area of the minimum diameter portion of the inverse-tapered flow path of the fine bubble generation section, The fine bubble generator according to Claim 1.

5. A plant growth promotion system including the fine bubble generator according to any one of Claims 1 to 4.

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