JP2007144394A - Bubble-generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bubble-generating device which is applicable to any equipment, improves efficiency in generating bubbles, and reduces a pressure loss of a liquid. <P>SOLUTION: The bubble-generating device is provided with; a bubble-generating part 4 which generates bubbles in a liquid in a Venturi tube 100; a liquid-inflow part 3 which makes a liquid flow into the bubble-generating part 4; and a liquid-outflow part 6 through which a liquid passing through the bubble-generating part 4 flows. In the bubble-generating part 4, bubbles are generated due to cavitation. Further, the bubble-generating part 4 is provided with a slipstream generating member 5 which generates a slipstream in a liquid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bubble generating device that generates bubbles in a liquid.

2. Description of the Related Art Conventionally, a bubble generating device that generates bubbles in a liquid using cavitation generated in a narrow tube portion of a venturi tube has been developed. For example, Japanese Patent Application Laid-Open No. 2003-230824 discloses a technique in which a surfactant is added to a bubble generating device to reduce the friction coefficient of the inner surface of a narrow tube path, thereby reducing the pressure loss of the liquid. Japanese Patent Laying-Open No. 2005-28305 discloses a technique for reducing the static pressure of a liquid in a narrow tube portion where cavitation occurs.
Japanese Patent Laid-Open No. 2003-230824 JP 2005-28305 A

  In general, the pressure loss of a liquid increases in proportion to the square of the liquid flow velocity. Therefore, when the flow rate of the liquid in the narrow tube portion is increased, the static pressure of the liquid is lowered, but there is a problem that the pressure loss of the liquid is increased.

  On the other hand, in order to generate bubbles efficiently, it is necessary to generate cavitation in the narrow tube portion of the venturi tube. Cavitation is a phenomenon in which a gas dissolved in a liquid is precipitated due to the static pressure of the fluid reaching a pressure equal to or lower than the saturated vapor pressure.

  According to the technique described in Japanese Patent Application Laid-Open No. 2003-230824, a decrease in pressure loss of the liquid is suppressed. However, the technique described in Japanese Patent Application Laid-Open No. 2003-230824 cannot be applied to a device to which a surfactant cannot be added, for example, a dishwasher that cleans tableware using salt.

  In the technique described in Japanese Patent Application Laid-Open No. 2005-28305, it is possible to reduce the static pressure of the liquid in the narrow tube portion where cavitation occurs and efficiently generate bubbles, but the liquid in the narrow tube portion No measures have been taken to reduce the pressure loss.

  The present invention has been made in view of the above-described problems, and the object thereof can be applied to any device, and reduces the pressure loss of liquid while improving the efficiency of bubble generation. It is an object of the present invention to provide a bubble generating device capable of

  The bubble generator of the present invention includes a venturi tube. The venturi tube includes a bubble generation unit that generates bubbles in the liquid, a liquid introduction unit that guides the liquid to the bubble generation unit, a liquid outlet unit through which the liquid that has passed through the bubble generation unit flows, and a liquid in or near the bubble generation unit. And a wake generating member that is provided in the introduction portion and generates a wake in the liquid.

  According to said structure, the pressure loss of the liquid which contains a bubble can be reduced, generating a bubble efficiently. In addition, the bubble generating apparatus of the present invention can be applied to any device because it is not necessary to add a surfactant to the liquid in order to reduce the pressure loss.

  Further, if the shape of the wake generating member is a cylindrical shape extending substantially perpendicular to the direction of liquid flow in the bubble generating portion, the Reynolds number is in the range from Re = 10 to 100,000 downstream of the wake generating member. The Karman vortex inside can be generated.

  In addition, if the shape of the wake generating member is a streamline that causes the liquid to flow along the stream line, the liquid along the stream line around the wake generating member while generating a vortex downstream of the wake generating member. Can be generated. Therefore, the flow of the liquid can be made smooth while efficiently generating bubbles.

  Also, if the shape of the wake generating member has a corner that becomes narrower from the downstream side toward the upstream side, a so-called stagnation point is formed in which there is no velocity boundary layer thickness at the most upstream end of the corner portion. Is done. A new velocity boundary layer grows from this stagnation point. This velocity boundary layer is an unstable boundary layer and is unstable. Therefore, the liquid flow is likely to be peeled off, and vortices are likely to be generated. As a result, cavitation is likely to occur. Further, if the corner portion has a sharp cross-sectional shape, the generation efficiency of cavitation increases.

  Further, if the wake generating member has a mirror-symmetric shape with respect to a predetermined plane along the liquid flow direction, the resistance generated in the liquid flowing in the vicinity of the wake generating member is reduced.

  The cross-sectional shape of the wake generating member may be a polygon. However, what is important for generating cavitation is the corner located most upstream and the corner located next, that is, the second corner, and the corner located downstream of these corners. Since the portion is downstream of the position where cavitation occurs, it does not contribute much to the occurrence of cavitation. Rather, the corner located downstream of the second corner is a factor that complicates the liquid flow. As a result, pressure loss increases. Therefore, it is desirable that there is no corner other than the corner located on the most upstream side and the corner located next. Therefore, it is desirable that the shape of the wake generating member in the predetermined cross section along the liquid flowing direction is a triangle rather than a polygon other than the triangle.

  In addition, when the wake generating member has a spiral groove like a drill blade, even if the wake generating member rotates around the axis, any part of the spiral groove always causes a liquid flow. Accept. Therefore, a vortex is always generated downstream of that part. That is, there is no problem that cavitation does not occur due to the rotation of the wake generating member around the axis. As a result, a structure for preventing the wake generating member from rotating about the axis becomes unnecessary.

  The bubble generating device of the present invention further includes a gas introducing unit connected to the bubble generating unit or the liquid introducing unit in the vicinity thereof so as to guide the gas to the bubble generating unit or the liquid introducing unit in the vicinity thereof. Is desirable. According to this, it becomes possible to generate more bubbles in the bubble generation unit.

  Further, the gas introduction part and the bubble generation part or the liquid introduction part in the vicinity thereof are connected so that the gas flows toward the bubble generation part located upstream of the wake generation member or the liquid introduction part in the vicinity thereof. It is desirable. In the above bubble generating device, the negative pressure portion is also formed in the bubble generating portion upstream of the wake generating member or the liquid introducing portion in the vicinity thereof. Therefore, the gas may be guided upstream of the wake generating member. In this case, the gas passes through the portion where the vortex is generated downstream of the wake generating member. As a result, the gas can be split by the shearing force caused by the vortex. Therefore, the bubbles can be made finer.

  Further, it is desirable that the gas introduction part and the bubble generation part or the liquid introduction part in the vicinity thereof are connected so that the gas flows toward the wake generation member in the bubble generation part or the liquid introduction part in the vicinity thereof. According to this configuration, since the pressure in the vicinity of the wake generating member is particularly low, it becomes easier to guide more gas to the bubble generating unit. As a result, a large amount of bubbles can be miniaturized.

  In addition, the ratio of the area of the wake generating member projected onto the above-described vertical surface to the area of the bubble generating portion projected onto the surface perpendicular to the liquid flow direction in the bubble generating portion is greater than 0 and It is desirable that it is 4 or less. According to this configuration, it is possible to obtain a bubble generating device having a pressure loss smaller than the pressure loss of the conventional bubble generating device.

Hereinafter, a bubble generating device according to an embodiment of the present invention will be described with reference to the drawings.
(Embodiment 1)
First, the bubble generator of Embodiment 1 is demonstrated using FIGS.

  As shown in FIGS. 1 and 2, the bubble generation device of the present embodiment includes a venturi tube 100. In the venturi tube 100, a bubble generating unit 4 that generates bubbles in the liquid, a liquid introducing unit 3 that guides the liquid to the bubble generating unit 4, and a liquid outlet unit 6 through which the liquid that has passed through the bubble generating unit 4 flows are formed. ing. The cross-sectional area of the flow path of the bubble generation unit 4, that is, the projected area of the bubble generation unit 4 in a plane perpendicular to the direction in which the liquid flows is larger than the cross-sectional areas of the flow paths of the liquid introduction unit 3 and the liquid discharge unit 6. It is getting smaller.

  More specifically, the cross-sectional area of the liquid introduction part 3 gradually decreases toward the bubble generation part 4. That is, the liquid introduction part 3 is a conical space. In addition, the cross-sectional area of the liquid outlet 6 gradually increases as the distance from the bubble generator 4 increases. That is, the liquid outlet 6 is also a conical space. The bubble generating unit 4 is a cylindrical space that is continuous with the smallest cross section of the liquid introducing unit 3 and the liquid outlet unit 6. Further, in the bubble generating device of the present embodiment, as shown in FIG. 2, the wake generating member 5 that causes the bubble generating unit 4 to generate a wake in the liquid is provided.

  According to the above configuration, the stagnation point of the liquid is formed at a predetermined position upstream of the wake generation member 5. A boundary layer extends along the flow of liquid from the stagnation point. However, the boundary layer peels from the wake generating member 5 at a predetermined position downstream of the wake generating member 5. When separation of the boundary layer occurs, a slow flow portion and a fast flow portion are formed downstream of the boundary layer. Therefore, a backflow occurs. This reverse flow is a so-called vortex. That is, when the wake generating member 5 is provided in the bubble generating unit 4, the vortex 10 is generated in the wake as shown in FIG. The pressure at the center of the vortex 10 is lower than the pressure upstream of the wake generating member 5. Therefore, a portion having a pressure lower than the pressure of the surrounding liquid locally is formed downstream of the wake generating member 5.

  On the other hand, cavitation is a phenomenon in which bubbles are generated due to a boiling phenomenon of a liquid when the static pressure of the liquid reaches a pressure equal to or lower than a saturated vapor pressure. The portion with the lowest static pressure is the portion with the smallest cross-sectional area of the flow path. For this reason, in the bubble generating unit 4 having a small cross-sectional area of the flow path of the bubble generating device, the pressure is considerably low, and cavitation is likely to occur. As a result, bubbles are easily generated in the bubble generation unit 4. Therefore, if the wake generating member 5 is not of a size that greatly reduces the liquid flow velocity, the portion below the saturated vapor pressure will hardly cause a decrease in the liquid flow velocity that causes the liquid pressure loss. Formed and cavitation occurs efficiently. In other words, since the wake generating member 5 is provided in the bubble generation unit 4, it is possible to reduce the pressure loss of the liquid containing the bubbles while efficiently generating the bubbles. In addition, the bubble generating device of this embodiment can be applied to any device because it is not necessary to add a surfactant to the liquid in order to suppress a decrease in pressure loss.

  Further, in the present embodiment, as can be seen from FIGS. 1 and 2, the shape of the wake generating member 5 is a cylindrical shape that extends substantially perpendicularly to the direction in which the liquid flows in the bubble generating unit 4. Therefore, as shown in FIG. 3, Karman vortices having Reynolds numbers in the range from Re = 10 to 100,000 can be generated downstream of the wake generating member 5.

  In the present embodiment, as shown in FIG. 4, even if the wake generating member 5 is provided in the liquid introducing portion 3 in the vicinity of the bubble generating portion 4, the effect obtained by the structure shown in FIG. And almost the same effect can be obtained. In the structure shown in FIG. 4, the vicinity of the bubble generating unit 4 means a position where the same effect as the above-described effect obtained by the bubble generating device having the structure shown in FIG. 2 can be obtained.

  Further, in the bubble generation device of the present embodiment, if the gas introduction unit 7 is connected to the bubble generation unit 4 so as to guide the gas to the bubble generation unit 4, more gas is efficiently generated in the bubble generation unit 4. Therefore, it is possible to generate more bubbles in the bubble generation unit 4. However, since the bubble generation device of the embodiment has a function of generating bubbles using cavitation generated in the bubble generation unit 4, the configuration of the gas introduction unit 7 is essential for the bubble generation device of the present embodiment. Is not a component of As shown in FIG. 5, the bubble generating device of the present embodiment is configured so that the gas is introduced into the liquid introducing unit 3 in the vicinity of the bubble generating unit 4 so as to guide the gas to the liquid introducing unit 3 in the vicinity of the bubble generating unit 4. Even if the introduction part 7 is connected, the same effects as those described above obtained by the structure shown in FIG. 2 can be obtained. In the structure shown in FIG. 5, the vicinity of the bubble generation unit 4 means a position where an effect substantially similar to the above-described effect obtained by the bubble generation device having the structure shown in FIG. 2 can be obtained. Further, the structure shown in FIG. 6 can provide substantially the same effect as that obtained by the structures shown in FIGS. 2, 4, and 5. The positions where the wake generating member 5 and the gas introducing unit 7 shown in FIG. 6 are provided are the above-described effects obtained by the wake generating member 5 and the gas introducing unit 7 shown in FIG. If it is a position where the same effect as can be obtained, it may be slightly away from the bubble generating unit 4.

  In the bubble generating device of the present embodiment, as shown in FIG. 5 or FIG. 6, the gas flows toward the bubble generating unit 4 positioned upstream of the wake generating member 5 or the liquid introducing unit 3 in the vicinity thereof. Thus, since the gas introduction part 7 and the bubble generation part 4 or the liquid introduction part 3 in the vicinity thereof are connected, the following effects are obtained.

  In the bubble generating device of the present embodiment, a negative pressure portion is also formed upstream of the bubble generating portion 4 or the wake generating member 5 in the vicinity of the liquid introducing portion 3. Therefore, the gas may be guided upstream of the wake generating member 5. In this case, as shown in FIG. 3, the gas passes through a portion where the vortex 10 is generated downstream of the wake generating member 5. As a result, the bubbles can be broken by the shearing force caused by the vortex 10. Therefore, the bubbles can be made finer.

  Further, in the bubble generating device of the present embodiment, as described above, as shown in FIG. 2, the gas introducing unit 7 and the bubbles are arranged so that the gas flows toward the wake generating member 5 in the bubble generating unit 4. The generator 4 is connected. According to this, since the pressure in the vicinity of the wake generating member 5 is particularly low, more gas can be easily guided to the bubble generating unit 4. As a result, a large amount of fine bubbles are generated. However, in order to obtain this effect, as shown in FIG. 6, the gas introduction unit 7 and the bubble generation so that the gas flows toward the wake generation member 5 in the liquid introduction unit 3 in the vicinity of the bubble generation unit 4. The liquid introduction part 3 in the vicinity of the part 4 may be connected.

  Next, the effect | action which arises in the bubble generator of this Embodiment is demonstrated. First, the effect | action which arises in the bubble generator in which the gas introduction part 7 is not provided is demonstrated.

  In the bubble generator shown in FIGS. 1 and 2 (considered that the gas introduction part 7 is not provided), the liquid pressurized by a pressurizing device such as a pump (not shown), as indicated by an arrow 1, The liquid is introduced from the liquid inlet 2 into the liquid inlet 3. Thereafter, the liquid flow becomes a contracted flow in the liquid introduction part 3. In this process, the liquid flow rate increases and its static pressure decreases.

  The liquid that reaches the liquid introduction part 3 reaches the bubble generation part 4 as a narrow tube part having the smallest cross-sectional area next. In the process of reaching the bubble generating unit 4, the liquid flow rate further increases and the static pressure further decreases.

  The liquid reaching the bubble generating unit 4 collides with the wake generating member 5. Thereafter, a wake is generated, and a vortex 10 shown in FIG. 3 is formed in the liquid downstream of the wake generating member 5. In the portion where the vortex 10 is formed, the static pressure of the liquid is lower than that of the surrounding liquid. Therefore, the pressure of the liquid in the portion where the vortex 10 is generated becomes a pressure equal to or lower than the saturated vapor pressure. Therefore, cavitation occurs. Bubbles are generated by cavitation. The bubbles are divided by the turbulent flow in the bubble generating unit 4 and reach the liquid outlet 6 together with the liquid.

  The liquid that has reached the liquid outlet 6 has a rapid increase in static pressure and a rapid decrease in flow velocity because the cross-sectional area of the flow path increases rapidly. At this time, a turbulent flow is generated in the liquid outlet 6 and the separated bubbles are further subdivided by the turbulent shear force. As a result, fine bubbles are formed. The fine bubbles and the liquid that have reached the liquid outlet 6 are discharged from the liquid outlet 9 as a gas-liquid mixture into a pipe outside the bubble generator or the surrounding fluid, as indicated by an arrow 8.

  Next, the effect | action which arises in the bubble generator provided with the gas introduction part 7 is demonstrated. Even in this case, the same action as that produced in the bubble generating device in which the gas introduction part 7 is not provided is produced. However, the bubble generating device provided with the gas introducing unit 7 is capable of sucking the surrounding gas into the bubble generating unit 4 or the liquid introducing unit 3 in the vicinity thereof using the negative pressure of the liquid. This is different from the bubble generating device in which the part 7 is not provided. The gas sucked from the gas introducing part 7 into the bubble generating part 4 or the liquid introducing part 3 in the vicinity thereof is divided by the turbulent flow generated in the bubble generating part 4 as in the case where the gas introducing part 7 is not provided. Bubbles are formed and refined in the liquid outlet 6 where the bubbles are rapidly expanding. At this time, a larger amount of fine bubbles are generated in comparison with the bubble generation device in which the gas introduction part 7 is not provided.

In general, the presence / absence of cavitation is determined using a cavitation coefficient K = 0.5 × (P1−P0) / (ρ × V ² ). Further, it is considered that cavitation occurs when the cavitation coefficient K is about 1 to 0.7.

  Here, P1 is the static pressure of the liquid in the bubble generating unit 4, P0 is the saturated vapor pressure, V is the fluid velocity of the bubble generating unit 4, and ρ is the density of the fluid.

  FIG. 7 shows the relationship between the pressure loss and the cavitation coefficient K when the wake generating member 5 is not provided in the bubble generating unit 4. FIG. 7 shows that the pressure loss when the cavitation coefficient K = 1 is as much as 8 MPa. On the other hand, FIG. 8 shows the relationship between the pressure loss and the cavitation coefficient K when the wake generating member 5 is provided. FIG. 8 shows that the pressure loss when the cavitation coefficient K = 1 is only about 1 MPa.

  From the comparison between the graph shown in FIG. 7 and the graph shown in FIG. 8, the pressure loss in the case where the wake generating member 5 is provided in the bubble generating unit 4 is that the wake generating member 5 is provided in the bubble generating unit 4. Obviously, it is much lower than the pressure loss in the absence.

  However, if the wake generating member 5 becomes too large, the increase in the channel resistance due to the wake generating member 5 becomes too large, and therefore the pressure when the wake generating member 5 is provided in the bubble generating unit 4 The loss becomes larger than the pressure loss when the wake generation member 5 is not provided in the bubble generation unit 4.

  From this point of view, the size of the wake generating member 5 is a surface perpendicular to the direction in which the liquid flows in the bubble generating unit 4 as can be understood by comparing the graph shown in FIG. 7 and the graph shown in FIG. The area of the resistor projected on the surface is 0.4 times or less (excluding zero) the area of the bubble generating unit 4 projected on a plane perpendicular to the liquid flow direction in the bubble generating unit 4. desirable. In FIG. 9, m is perpendicular to the direction in which the liquid flows in the bubble generation unit 4 with respect to the area of the bubble generation unit 4 projected onto the plane perpendicular to the direction in which the liquid flows in the bubble generation unit 4. It is the ratio of the area of the wake generating member 5 projected onto the surface. As shown in FIG. 9, if m is 0.1 or more and 0.4 or less, the wake generation member 5 is provided in the bubble generation unit 4, thereby reducing pressure loss and cavitation. It has been confirmed by simulation that bubbles can be generated.

(Embodiment 2)
The bubble generation device of the present embodiment is almost the same as the bubble generation device of the first embodiment. However, in the bubble generating device of the present embodiment, as shown in FIG. 10, the shape of the wake generating member 5 extending so as to cross the bubble generating unit 4 in the direction perpendicular to the flow of the liquid is liquid. It differs from the bubble generator of Embodiment 1 in that it is streamlined to flow along a streamline, for example, a wing shape. The bubble generating device of the present embodiment has the same configuration as that of the bubble generating device of the first embodiment except for the differences described above, and the action obtained by the bubble generating device of the first embodiment. The same effect as the effect can be obtained.

  According to the bubble generating device of the present embodiment, it is possible to generate a liquid flow along the streamline around the wake generating member 5 while generating the vortex 10 downstream of the wake generating member 5. Therefore, the flow of the liquid can be made smooth while efficiently generating bubbles. Therefore, pressure loss can be reduced as compared with the cylindrical wake generating member of the first embodiment. The streamline may have any shape as long as it is a generally-known shape that has a small resistance to the fluid and hardly generates turbulent flow.

  As a modification of the bubble generating device of the present embodiment, as shown in FIGS. 11 to 13, the wake generating member 5 is attached to the inner surface of the bubble generating unit 4 with a streamlined wing-shaped portion by a column 5 a. It may be done. Even in such a modified example, if the resistance due to the column 5a is small, substantially the same effect as that obtained by the wake generating member 5 having the structure shown in FIG. 10 can be obtained.

(Embodiment 3)
The bubble generator of this embodiment will be described with reference to FIGS.

  In the above-described first and second embodiments, the shape of the wake generating member 5 is a cylindrical shape and a streamline shape, but in the bubble generating device of the present embodiment, shown in FIGS. 14 and 15. Thus, the shape of the wake generating member 5 is a shape like a protrusion protruding from the inner peripheral surface of the pipe line surrounding the bubble generating part 4. Such a protruding wake generating member 5 can also promote the generation of bubbles due to cavitation.

  That is, the shape of the wake generating member 5 may be any shape as long as it can generate a wake and can promote the generation of bubbles by cavitation as described above.

  For example, if the wake generating member 5 has a corner portion 20 as shown in FIG. 16, generation of bubbles due to cavitation can be further promoted. This will be described in detail below.

  According to the above-described cylindrical and streamlined wake generating member 5, a stagnation point can be formed if a complete fluid that has no theoretical viscosity flows in the microbubble generator.

  However, since the actual fluid is a fluid having viscosity, if the flow velocity of the liquid flowing in the microbubble generator is small, in the microbubble generator provided with the wake generating member having no corners, It is difficult to form a complete stagnation point as compared to a fine bubble generator provided with a wake generating member having a corner. Therefore, a certain amount of boundary layer is formed even at the position where the stagnation point is to be formed. Therefore, if the wake generating member having no corner is used, a stable velocity boundary layer is formed as compared with the case where the wake generating member 5 shown in FIGS. 16 to 21 is used. That is, separation and turbulence in the liquid are difficult to occur.

  On the other hand, for example, as shown in FIG. 16, when the shape of the wake generating member 5 is a shape having a corner portion 20, even if viscous fluid flows in the vicinity of the corner portion 20, the velocity boundary The thickness of the layer is smaller than that in the case where the shape of the wake generating member 5 as described above is a cylinder and a streamline type. Thus, the velocity boundary layer grows from a thin velocity boundary layer to a thick velocity boundary layer. Therefore, the state of the velocity boundary layer is unstable. Therefore, separation and turbulence are likely to occur in the liquid flow. As a result, vortices and cavitation are likely to occur.

  Furthermore, when the corner portion 20 has an acute corner portion in a cross section including the liquid flow direction, the velocity boundary layer thickness tends to become zero at the tip portion of the corner portion 20. In this case, the velocity boundary layer gradually increases in thickness from zero. Therefore, the state of the velocity boundary layer becomes more unstable. Thereby, separation and turbulence are more likely to occur in the liquid flow. Therefore, the generation of bubbles due to cavitation is further promoted.

  FIG. 17 is a cross-sectional view taken along line XVII-XVII in FIG. 16 and 17, it can be seen that the wake generating member 5 has a mirror-symmetrical shape (vertical symmetry or left-right symmetry) with respect to the direction in which the liquid flows.

  Further, the cross-sectional shape of the wake generating member 5 may be a polygon having corners 20, 21 and 22 as shown in FIG. Further, the cross-sectional shape of the wake generating member 5 may be an isosceles triangle having corners 20 and 21, as shown in FIG. Furthermore, as shown in FIGS. 20 and 21, the cross-sectional shape of the wake generating member 5 may have a spiral groove 5 a like a drill having a corner portion 20.

  In FIG. 17 to FIG. 21, the liquid flow 1 is indicated by a dotted arrow, and the tip of the corner portion 20 as a stagnation point is indicated by a black circle. The vortex 10 is indicated by a solid arrow. Further, the interface of the velocity boundary layer 50 is indicated by a one-dot chain line.

  As shown in FIGS. 16 and 17, when the wake generating member 5 is arranged mirror-symmetrically (in this case, vertically or horizontally symmetrical) with respect to a predetermined plane along the direction 1 in which the liquid flows, A mirror-symmetric flow (in this case, vertical symmetry or left-right symmetry) is formed in the vicinity of the generating member 5, and no biased flow is generated. Therefore, fluid resistance is reduced. As a result, the fluid pressure loss caused by the wake generating member 5 is reduced.

  However, what is important for the occurrence of cavitation by the wake generating member 5 is that the corner 20 located on the most upstream side in the direction in which the liquid flows and the corner 20 located on the most upstream side in the direction in which the liquid flows. This is the next corner (second corner) 21. That is, the corner portion 22 on the third surface is a corner portion on the downstream side of the cavitation occurrence position, and therefore does not contribute much to the occurrence of cavitation. On the contrary, the corner portion 22 on the third surface complicates the flow of the liquid, and causes an increase in the pressure loss of the liquid. Therefore, it is desirable to use the wake generating member 5 in which the corner 22 of the third surface is not provided. Therefore, as shown in FIG. 19, it is desirable to use the wake generating member 5 having a cross-sectional shape of a triangle (isosceles triangle in the figure) that does not have the corner portion of the third face.

  Moreover, as shown in FIG. 20, the shape of the wake generation member 5 may have a spiral shape like a drill or a screw. That is, the wake generating member 5 has a spiral groove 5a. Also by this, since the wake generation member 5 has the corner portion 20, it is possible to obtain an effect that no separation occurs in the liquid flow.

  20 and 21, when the wake generating member 5 having a drill or screw shape is used, the wake generating member 5 rotates around the axis due to the flow of the liquid. However, any part of the spiral groove 5a always receives the liquid. Therefore, the rotation of the wake generating member 5 around the axis is prevented in order to prevent the occurrence of the problem that the effect due to the provision of the corner portion 20 is not obtained because the groove 5a does not accept liquid. There is no need to provide a structure. Therefore, the production of the bubble generating device is facilitated.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a cross-sectional view of a bubble generation device according to a first embodiment. It is the II-II sectional view taken on the line of FIG. It is a figure for demonstrating Karman vortex which arises in the wake of a wake generation member. FIG. 6 is a cross-sectional view of a bubble generation device according to a first modification of the first embodiment. FIG. 6 is a cross-sectional view of a bubble generation device according to a second modification of the first embodiment. FIG. 10 is a cross-sectional view of a bubble generation device according to a third modification of the first embodiment. It is a graph which shows the relationship between the relationship of a cavitation coefficient and a pressure loss in case the wake generation member is not provided in the bubble generation part. It is a graph which shows the relationship between the relationship of a cavitation coefficient and a pressure loss in case the wake generation member is provided in the bubble generation part. It is a graph which shows the relationship between the relationship between the cavitation coefficient and the pressure loss when the ratio of the projected area of the wake generating member to the projected area of the bubble generating portion is varied. It is sectional drawing of the bubble generator of Embodiment 2. FIG. 10 is a cross-sectional view of a bubble generating device according to a modification of the second embodiment. FIG. 6 is an enlarged view of a wake generating member according to Embodiment 2. It is the XIII-XIII sectional view taken on the line of FIG. FIG. 6 is a cross-sectional view of a bubble generating device according to a third embodiment. It is the XV-XV sectional view taken on the line of FIG. FIG. 10 is a cross-sectional view of a bubble generation device according to a modification of the third embodiment. It is the XVII-XVII sectional view taken on the line of FIG. It is a figure which shows the wake generation member which has a regular hexagonal cross-sectional shape. It is a figure which shows the wake generation member which has a cross-sectional shape of an isosceles triangle. It is a figure which shows the wake generation member which has a spiral shape like a drill. It is the XXI-XXI sectional view taken on the line of FIG.

Explanation of symbols

  2 liquid inlet, 3 liquid inlet, 4 bubble generator, 5 wake generating member, 5a strut, 6 liquid outlet, 7 gas inlet, 9 liquid outlet, 10 vortex, 100 venturi.

Claims (12)

A bubble generating section for generating bubbles in the liquid;
A liquid introduction part for guiding liquid to the bubble generation part;
A liquid outlet part through which the liquid that has passed through the bubble generating part flows;
A wake generating member provided in the gas generating part or the liquid introducing part in the vicinity thereof, and generating a wake in the liquid,
A bubble generating device equipped with a venturi tube.   The bubble generating device according to claim 1, wherein the shape of the wake generating member is a cylindrical shape extending substantially perpendicular to a direction in which the liquid flows in the bubble generating unit.   The bubble generating apparatus according to claim 1, wherein the shape of the wake generating member is a streamline that allows the liquid to flow along a streamline.   The bubble generating apparatus according to claim 1, wherein the wake generating member has a corner portion that becomes narrower from the downstream side toward the upstream side.   The bubble generating device according to claim 4, wherein the corner portion has an acute cross-sectional shape.   The bubble generating apparatus according to claim 1, wherein the wake generating member has a mirror-symmetric shape with respect to a predetermined surface along a flow direction of the liquid.   The bubble generating apparatus according to claim 1, wherein a shape of the wake generating member in a predetermined cross section along the liquid flowing direction is a triangle.   The bubble generating apparatus according to claim 1, wherein the wake generating member has a spiral groove like a drill blade.   The bubble according to claim 1, further comprising a gas introduction unit connected to the bubble generation unit or the liquid introduction unit in the vicinity thereof so as to guide gas to the bubble generation unit or the liquid introduction unit in the vicinity thereof. Generator.   The gas introducing part and the bubble generating part or the liquid introducing part in the vicinity thereof so that the gas flows toward the bubble generating part located upstream of the wake generating member or the liquid introducing part in the vicinity thereof. And the bubble generating device according to claim 9.   The gas introducing part and the bubble generating part or the liquid introducing part in the vicinity thereof are connected so that the gas flows toward the wake generating member in the bubble generating part or the liquid introducing part in the vicinity thereof. The bubble generating device according to claim 9.   The ratio of the area of the wake generating member projected on the vertical surface to the area of the bubble generating portion projected on the surface perpendicular to the flow direction of the liquid in the bubble generating portion is greater than 0 and 0 The bubble generating device according to claim 1, which is 4 or less.

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