JP2019057477A - Plasma generator - Google Patents

Abstract

To provide a plasma generator capable of stabilizing discharge.SOLUTION: A plasma generator 100 comprises: a first electrode 110 and a second electrode 120, at least their part being arranged in a flow passage 180 for making liquid 101 flow; a cylindrical insulation body 130 that has, on its end surface, an aperture positioned in the flow passage 180 and is arranged so as to surround a side surface of the first electrode 110 via a space for allowing gas to pass; and a power supply 140 for applying voltage between the first electrode 110 and the second electrode 120 to generate plasma. The liquid 101 flows outside the insulation body 130 along a direction in which the gas passes through the aperture.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a plasma generator.

  Patent Document 1 and Patent Document 2 describe a liquid processing apparatus that supplies a gas into a liquid and generates plasma in the supplied gas.

Japanese Patent Laid-Open No. 2015-33694 Japanese Patent Laying-Open No. 2015-136644

  However, in the conventional liquid processing apparatus, Karman vortex or water entrainment occurs around the cylinder for introducing the gas into the liquid. For this reason, there is a problem that the discharge is not stable due to variations in the size of bubbles formed by the introduced gas.

  The present disclosure provides a plasma generator that can stabilize discharge.

  A plasma generator according to one embodiment of the present disclosure includes a first electrode and a second electrode at least a part of which are disposed in a flow channel for flowing a liquid, and an opening located in the flow channel at an end surface. A cylindrical insulator disposed so as to surround the side surface of the first electrode with a space for allowing gas to pass between the first electrode and the second electrode. And a power source that generates plasma by applying a voltage, and the liquid flows outside the insulator along a direction in which the gas passes through the opening.

  According to the present disclosure, it is possible to provide a plasma generator that can stabilize discharge.

FIG. 1 is a block diagram illustrating a configuration example of a plasma generator according to an embodiment. FIG. 2 is a cross-sectional view showing a configuration in the vicinity of the first electrode of the plasma generator according to the embodiment. FIG. 3 is a cross-sectional view showing a configuration in the vicinity of the first electrode taken along line III-III in FIG. FIG. 4 is a graph showing a change in power consumption over time when the plasma generator according to the embodiment is operated. FIG. 5 is a block diagram illustrating a configuration example of the plasma generator according to the first modification of the embodiment. FIG. 6 is a cross-sectional view showing a configuration in the vicinity of the first electrode of the plasma generator according to Modification 1 of the embodiment. FIG. 7 is a cross-sectional view showing a configuration in the vicinity of the first electrode of the plasma generating apparatus according to Modification 2 of the embodiment.

(Knowledge that became the basis of this disclosure)
Conventionally, in a liquid processing apparatus, a gas is supplied into a cylindrical insulator covering an electrode, and plasma is generated in the liquid by discharging in a bubble formed by the supplied gas. In such a gas introduction type underwater plasma device, a cylinder for introducing a gas is installed in a direction to block the flow of water. For this reason, when gas is discharged from the cylinder into the water, Karman vortex or water entrainment occurs. As a result, the discharge is not stable due to variations in the size of the bubbles. Specifically, when the bubble size varies, the distance from the electrode to the gas-liquid interface is not stable, and the discharge is not stable by changing the discharge distance.

  Therefore, the present inventors have intensively studied to provide a plasma generator capable of stabilizing discharge. As a result, it was found that the discharge is stabilized by making the direction of the gas discharged from the cylindrical insulator substantially the same as the direction of flow of the liquid.

  Specifically, the gas is released without interruption by making the direction of the gas released from the cylindrical insulator substantially the same as the direction in which the liquid flows. For this reason, it can suppress that the distance from an electrode to a gas-liquid interface changes greatly. Thus, the discharge can be stabilized by making the direction of the gas discharged from the cylindrical insulator substantially the same as the direction in which the liquid flows.

  Therefore, a plasma generation device according to one embodiment of the present disclosure includes a first electrode and a second electrode that are at least partially disposed in a flow channel for flowing a liquid, and an opening located in the flow channel. A cylindrical insulator disposed on an end face so as to surround a side surface of the first electrode with a space for allowing gas to pass therethrough, and the first electrode and the second electrode. A power source for generating plasma by applying a voltage therebetween, and the liquid flows outside the insulator along a direction in which the gas passes through the opening.

  According to this, since the direction of the gas discharged from the opening of the cylindrical first insulator and the direction in which the liquid flows can be made substantially the same, the stabilization of the discharge can be realized. The effect is the same whether the second electrode is installed upstream or downstream of the first electrode.

  Here, the plasma generation device according to an aspect of the present disclosure may further include a supply device that discharges the gas from the opening into the liquid by supplying the gas to the space.

  According to this, since gas can be supplied to space by supply devices, such as an airflow pump, a bubble can be generated continuously.

  Here, the plasma generator according to one embodiment of the present disclosure may further include a structure that forms the flow path.

  According to this, since the positional relationship between the first electrode and the insulator and the flow path can be fixed in advance, the discharge can be easily stabilized.

  Here, the flow path may include a first flow path that extends along an imaginary straight line, and the opening may be located in the first flow path.

  According to this, since the first flow path where the opening is located extends along a straight line, the flow of the liquid is stabilized in the vicinity of the opening. Therefore, since the bubble shape is further stabilized, the distance from the electrode to the gas-liquid interface is stabilized, and the discharge can be further stabilized.

  Here, the opening may be orthogonal to the straight line.

  According to this, since the direction of the gas discharged from the opening and the direction in which the liquid flows are parallel, the released gas is less likely to disturb the flow of the liquid. Thereby, the distance from an electrode to a gas-liquid interface is stabilized, and discharge can be further stabilized.

  Here, the liquid flowing through the first flow path and the gas passing through the opening may flow downward with respect to a horizontal plane.

  According to this, the influence of gravity can be made to act positively by setting the direction of the gas discharged from the opening of the first insulator and the direction of the flow of the liquid downward with respect to the horizontal plane. Therefore, even if it does not install the airflow pump which sends out gas, gas can be flowed by drawing in by the flow of water flow. Thereby, size reduction and weight reduction of a plasma generator are realizable.

  Here, the cross-sectional shape of the first flow path when cut along a plane parallel to the straight line may be line symmetric.

  According to this, since the shape of the first flow path is axisymmetric, it is sufficiently suppressed that the insulator prevents the liquid flow. For this reason, gas can be sent out smoothly, the distance from an electrode to a gas-liquid interface can be stabilized, and discharge can be stabilized.

  Here, the cross-sectional shape of the first flow path when cut along a plane orthogonal to the straight line may be circular or annular.

  According to this, the first flow path is formed without unevenness around the cylindrical insulator. Specifically, since the cross section of the first flow path in a plane orthogonal to the direction in which the first flow path extends is circular, the liquid flow can be stabilized. Therefore, the distance from the electrode to the gas-liquid interface is stabilized, and the discharge can be stabilized.

  Here, the flow path may further include a bent second flow path connected to the upstream side of the first flow path.

  According to this, the flow of the liquid can be suppressed by the bent second flow path, and the liquid flowing through the first flow path can be stabilized. Thereby, since it can suppress that a turbulent flow generate | occur | produces in the vicinity of opening, the distance from an electrode to a gas-liquid interface is stabilized, and discharge can be stabilized.

  Here, the second flow path may be bent in an S shape.

  According to this, since the liquid flowing through the first flow path can be further stabilized, the discharge can be further stabilized.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. Numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of constituent elements, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present disclosure will be described as arbitrary constituent elements that constitute a more desirable form.

  Moreover, each figure is a schematic diagram and does not necessarily represent a strict dimension. Accordingly, the scales and the like do not necessarily match in each drawing. Moreover, in each figure, the same code | symbol is attached | subjected about the substantially same structure, The overlapping description is abbreviate | omitted or simplified.

(Embodiment)
[1. Overview]
First, an outline of a plasma generator according to an embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration example of a plasma generator 100 according to the present embodiment.

As shown in FIG. 1, the plasma generator 100 generates a plasma 103 in a bubble 102 formed by a gas supplied into a liquid 101. As a result, the plasma generator 100 generates active species in the liquid 101. The liquid 101 is, for example, water (H ₂ O) or an aqueous solution such as pure water, tap water, rain water, or well water, but is not limited thereto.

Examples of the active species include hydroxyl radical (OH), hydrogen radical (H), oxygen radical (O), superoxide anion (O ²⁻ ), monovalent oxygen ion (O ⁻ ) or hydrogen peroxide (H ₂ O). ₂ ) and the like. With these active species, the harmful substances contained in the liquid 101 can be decomposed or sterilized. Further, the liquid 101 containing active species can be used for decomposition or sterilization of other substances.

[2. Constitution]
Next, the configuration of the plasma generator 100 will be described with reference to FIGS. 1 and 2. FIG. 2 is a cross-sectional view showing a configuration in the vicinity of the first electrode 110 according to the present embodiment. Specifically, FIG. 2 shows a cross section passing through the central axis of the first electrode 110.

  As shown in FIG. 1, the plasma generator 100 includes a first electrode 110, a second electrode 120, an insulator 130, a power source 140, a supply pump 150, a structure 160, a circulation pump 170, and the like. And a control circuit 190. The structure 160 forms a flow path 180 for flowing the liquid 101. As shown in FIG. 1, the structure 160 includes a reaction tank 161, a processing tank 162, and a pipe 163.

[2-1. electrode]
The first electrode 110 is an electrode at least partially disposed in the flow path 180. The first electrode 110 is one of an electrode pair for generating the plasma 103. The first electrode 110 is used as a reaction electrode, and a plasma 103 is generated around it. The first electrode 110 functions as an anode. The first electrode 110 is, for example, a rod-shaped electrode.

  As shown in FIG. 2, the first electrode 110 includes an electrode portion 111 and a screw portion 112. The electrode portion 111 is a long cylindrical portion provided on the distal end side of the first electrode 110. The electrode unit 111 is a metal electrode formed from a metal material such as tungsten, for example. In addition, the electrode part 111 may be formed using metal materials, such as aluminum, iron, copper, or these alloys.

  In the present embodiment, the electrode portion 111 of the first electrode 110 is disposed in the flow path 180. As shown in FIG. 2, the electrode portion 111 is surrounded by a cylindrical insulator 130 with a space 132 interposed therebetween. The electrode unit 111 contacts the liquid 101 flowing from the opening 131 of the insulator 130 when the gas is not supplied by the supply pump 150. When the gas is supplied by the supply pump 150, the supplied gas fills the space 132, so that the electrode unit 111 is covered with the supplied gas and does not contact the liquid 101.

  In the present embodiment, the electrode part 111 and the insulator 130 are arranged coaxially. A space 132 is provided between the electrode portion 111 and the insulator 130 over the entire circumference. That is, the space 132 is a cylindrical space having a substantially uniform width d1. The width d1 is a distance between the side surface of the electrode part 111 of the first electrode 110 and the side surface of the insulator 130, and is 1 mm or more and 3 mm or less.

  The screw portion 112 is a metal member that supports the electrode portion 111. Specifically, the electrode portion 111 is fixed by being press-fitted into the screw portion 112. The screw part 112 is electrically connected to the electrode part 111 and transmits the power received from the power source 140 to the electrode part 111.

  The screw portion 112 is provided on the rear end side of the first electrode 110. The shape of the screw portion 112 is, for example, a long cylindrical shape. The diameter of the screw part 112 is larger than the diameter of the electrode part 111, for example, 3 mm. For example, the screw portion 112 is formed using a metal material that is easy to process, such as iron.

  The screw portion 112 is held by the holding portion 134. Specifically, a male screw is provided on the outer surface of the screw portion 112. The screw part 112 is held by the holding part 134 by screwing the male screw with the female screw provided in the holding part 134.

  The threaded portion 112 is provided with a through hole 114 connected to the supply pump 150. The through hole 114 communicates with the space 132. For this reason, the gas supplied from the supply pump 150 is released into the liquid 101 flowing through the flow path 180 from the opening 131 of the insulator 130 through the through hole 114 and the space 132.

  In the present embodiment, as shown in FIG. 2, the threaded portion 112 is provided with two through holes 114. Thereby, the pressure loss of the gas in the through-hole 114 is suppressed. The number of through holes 114 may be only one or three or more.

  As shown in FIG. 2, the end surface 113 of the first electrode 110 is recessed from the opening surface of the opening 131. The retreat amount d2 at this time is a range in which contact between the plasma 103 generated in the vicinity of the end surface 113 of the first electrode 110 and the inner surface of the insulator 130 is suppressed. Specifically, the retraction amount d2 of the end face 113 of the first electrode 110 is not less than 0 mm and not more than 3 mm.

  The retraction amount d2 can be adjusted by rotating the screw portion 112 around the axis. As the screw portion 112 rotates, the electrode portion 111 and the screw portion 112 move in an axial direction relative to the insulator 130 fixed to the holding portion 134. Thereby, the position of the end surface 113 can be made variable.

[2-2. Second electrode]
The second electrode 120 is an electrode at least partially disposed in the flow path 180. In addition, in the example shown in FIG. 1, although both the 1st electrode 110 and the 2nd electrode 120 are being fixed to the reaction tank 161, it is not restricted to this. For example, the second electrode 120 may be fixed to the treatment tank 162 or the pipe 163.

  The second electrode 120 is the other electrode pair for generating the plasma 103. The second electrode 120 functions as a cathode. The second electrode 120 is in contact with the liquid 101.

  The second electrode 120 is, for example, a rod-shaped electrode. The specific configuration of the second electrode 120 is, for example, the same as that of the first electrode 110, but is not limited thereto.

[2-3. Insulator]
The insulator 130 is disposed so as to surround the side surface of the first electrode 110 with the space 132 interposed therebetween. Specifically, the insulator 130 is attached to the reaction tank 161 so as to provide a ventilation space 132 on the outer periphery of the electrode portion 111 of the first electrode 110.

  As shown in FIG. 2, the insulator 130 is a cylindrical insulator in which an opening 131 is provided in an end surface 133 in contact with the liquid 101. In the present embodiment, the insulator 130 is a long cylindrical body surrounding the side surface of the electrode portion 111 of the first electrode 110. The insulator 130 is fixed to the reaction tank 161 so as to penetrate the side wall of the reaction tank 161 and the opening 131 is located in the flow path 180. Specifically, the insulator 130 is fixed by the holding portion 134. For example, the insulator 130 and the first electrode 110 are arranged so that the axial direction thereof is parallel to the vertical direction.

  The inner diameter of the insulator 130 is larger than the outer diameter of the electrode part 111. Moreover, the electrode part 111 and the insulator 130 are arrange | positioned coaxially. For this reason, the space 132 is formed in a cylindrical shape over the entire circumference of the electrode portion 111. Due to the space 132, the electrode portion 111 does not contact the insulator 130. For example, the inner diameter of the insulator 130 is 3 mm, and the outer diameter of the electrode part 111 is 0.8 mm. As a result, the width d1 of the space 132 is 1.1 mm.

  The gas supplied to the space 132 is discharged into the liquid 101 in the reaction tank 161 through the opening 131. The released gas becomes bubbles 102 and diffuses into the liquid 101. At this time, the opening 131 has a function of determining the upper limit of the bubble size.

  The insulator 130 is made of alumina ceramic, for example. Alternatively, the insulator 130 may be made of magnesia, zirconia, quartz, yttrium oxide, or the like.

  The insulator 130 is not limited to a cylindrical body, but may be a rectangular tube. In addition, the insulator 130 is held by the holding unit 134, but may be directly fixed to the wall surface of the reaction tank 161.

[2-4. Power supply]
The power source 140 includes a step-up transformer that applies a predetermined voltage between an electrode pair including the first electrode 110 and the second electrode 120. By applying a voltage between the step-up transformer and the electrode pair, a plasma 103 is generated between the electrode pair. Generation of the plasma 103 generates various active species such as OH radicals in the liquid 101. Specifically, the power source 140 applies a pulse voltage or an AC voltage between the first electrode 110 and the second electrode 120.

  For example, the applied voltage is a positive high voltage pulse of 2 kV / cm to 50 kV / cm and 1 Hz to 100 kHz. The voltage waveform may be, for example, a pulse shape, a sine half waveform, or a sine waveform. Moreover, the value of the current flowing between the first electrode 110 and the second electrode 120 is, for example, 1 mA to 3A. Here, as an example, the power supply 140 applies a positive pulse voltage having a frequency of 30 kHz and a peak voltage of 4 kV.

[2-5. Supply pump]
The supply pump 150 is an example of a supply device that discharges gas from the opening 131 into the liquid 101 by supplying gas to the space 132 between the first electrode 110 and the insulator 130. Thereby, bubbles 102 are continuously generated at the tip portions of the insulator 130 and the first electrode 110. For example, the supply pump 150 takes in ambient air and supplies the air to the space 132 through the through hole 114 of the screw portion 112. Note that the supply pump 150 may supply not only air but also argon, helium, nitrogen gas, oxygen gas, or the like.

  Note that the plasma 103 is generated between the electrode pair without the bubble 102, but the presence of the bubble 102 can increase the generation efficiency of the active species by the plasma 103. Further, when the gap between the electrode pair including the first electrode 110 and the second electrode 120 is disposed in the liquid 101 without supplying gas, the electrode pair becomes a resistive load. When at least one of the first electrode 110 and the second electrode 120 is in a bubble in the liquid 101, the electrode pair becomes a capacitive load.

[2-6. Channel and structure]
The structure 160 forms a flow path 180 for flowing the liquid 101. The structure 160 includes a reaction tank 161, a processing tank 162, and a pipe 163. The flow path 180 is formed by a reaction tank 161, a processing tank 162, and a pipe 163.

  In the present embodiment, the flow path 180 is formed in an annular shape. The liquid 101 circulates in the flow path 180. Specifically, the liquid 101 flows through the reaction tank 161, the processing tank 162, and the pipe 163 in order. In FIG. 1, the direction of the liquid 101 flowing through the flow path 180 is indicated by an arrow. The liquid 101 is circulated through the flow path 180 by the circulation pump 170.

  The channel 180 may be provided with a branch path. A valve that can be opened and closed is arranged in the branch path. By operating the valve, the liquid 101 flowing through the flow path 180 can be taken out as needed. Alternatively, a new liquid can be added in the flow path 180.

  The reaction tank 161 is a part of the structure 160 that forms the flow path 180 of the liquid 101. At least a part of the first electrode 110 and the second electrode 120 is disposed inside the reaction tank 161. The reaction tank 161 is, for example, a U-shaped tube. The first electrode 110 and the insulator 130 are disposed on the right portion (left side in FIG. 1) of the U-shape, and the second electrode 120 is disposed on the left portion (right side in FIG. 1).

  The processing tank 162 is a part of the structure 160 that forms the flow path 180 and is, for example, a container for storing the liquid 101. The outer shape of the processing tank 162 may be any shape such as a rectangular parallelepiped, a cylinder, or a sphere. The processing tank 162 may be, for example, a tray with an open top.

  The treatment tank 162 stores pure water as a plasma liquid stock solution as the liquid 101 before applying a voltage. The treatment tank 162 stores the plasma-treated liquid 101 after the plasma 103 is generated by applying a voltage.

  The pipe 163 is a part of the structure 160 that forms the flow path 180, and connects the reaction tank 161 and the processing tank 162. The pipe 163 is formed from, for example, a tubular member such as a pipe, a tube, or a hose. Alternatively, the pipe 163 may be a groove having a U-shaped cross section.

  Each of the reaction tank 161, the processing tank 162, and the pipe 163 is formed of, for example, an acid-resistant resin material. For example, the reaction tank 161 is formed of a fluororesin such as polytetrafluoroethylene, silicon rubber, polyvinyl chloride, stainless steel, or ceramic.

[2-7. Circulation pump]
The circulation pump 170 is an example of a liquid feeding device that circulates the liquid 101 between the reaction tank 161 and the processing tank 162 via the pipe 163. In the present embodiment, circulation pump 170 is arranged in the middle of pipe 163.

[2-8. Control circuit]
The control circuit 190 controls the entire plasma generator 100 by executing a program recorded in a memory, for example. The control circuit 190 is realized by an integrated circuit such as a central processing unit (CPU) or a microcomputer, for example.

  Specifically, the control circuit 190 controls the power supply 140, the supply pump 150, and the circulation pump 170. For example, the control circuit 190 operates the power supply 140, the supply pump 150, and the circulation pump 170, the magnitude and frequency of the voltage applied by the power supply 140, the amount of gas supplied by the supply pump 150, and the circulation pump 170. The flow rate of the liquid 101 is adjusted.

  For example, the control circuit 190 operates the power supply 140, the supply pump 150, and the circulation pump 170 when a start operation from a user is received or when a start time indicated by predetermined schedule information is reached. Let Alternatively, the control circuit 190 may always circulate the liquid 101, and may operate the supply pump 150 and the power supply 140 in this order when starting the plasma processing.

[3. Operation]
Subsequently, the operation of the plasma generating apparatus 100 according to the present embodiment will be described.

  In plasma generator 100 according to the present embodiment, supply pump 150 supplies gas while circulation pump 170 circulates liquid 101. The gas supplied by the supply pump 150 is supplied to the space 132 through the through hole 114 of the screw portion 112. The liquid 101 that has filled the space 132 before the gas is supplied is discharged into the liquid 101 in the reaction tank 161 through the opening 131. For example, the gas flow rate is 0.8 L / min. The gas fills the space 132 and covers the electrode part 111 of the first electrode 110. As a result, the first electrode 110 is insulated from the liquid 101.

  The power source 140 applies a voltage between the first electrode 110 and the second electrode 120. For example, a positive pulse voltage having a frequency of 30 kHz and a peak voltage of 4 kV is applied. As a result, a discharge is generated between the end face 113 of the first electrode 110 and the gas-liquid interface, and plasma 103 is generated in the bubble 102 covering the electrode portion 111 of the first electrode 110. Active species are generated by the plasma 103, and the generated active species are taken into the liquid 101. Since the liquid 101 circulates, the active species can be spread throughout the liquid 101.

[4. Flow path shape and insulator arrangement]
Here, the shape of the flow path 180 and the arrangement of the insulator 130 with respect to the flow path 180 will be described.

  The flow path 180 includes a first flow path 181 extending along an axis P indicated by a one-dot chain line in FIG. The axis P is an axis extending along a virtual straight line, and extends, for example, vertically downward. An opening 131 of the insulator 130 is located in the first flow path 181. The opening 131 is orthogonal to the axis P.

  In the present embodiment, the liquid 101 flows outside the insulator 130 along the direction in which the gas passes through the opening 131 of the insulator 130. In FIG. 2, the flowing direction of the liquid 101 is indicated by a solid arrow, and the direction in which the gas passes through the opening 131 is indicated by a broken arrow.

  As shown in FIG. 2, the direction in which the liquid 101 flows through the first flow path 181 (solid arrow) is the same as the direction in which gas passes through the opening 131 (broken arrow). Specifically, the inner wall of the reaction tank 161 forming the first flow path 181 and the insulator 130 are arranged in parallel to each other. As shown in FIG. 2, the first channel 181 has a line-symmetric cross section when cut along a plane parallel to the axis P. The axis of symmetry of line symmetry is an axis P indicated by a one-dot chain line in FIG.

  Here, the first flow path 181 is formed in the right portion of the U-shaped reaction tank 161. Specifically, the shape of the part forming the first flow path 181 of the reaction tank 161 is a cylindrical shape having the axis P as the central axis.

  3 is a cross-sectional view of the vicinity of the first electrode 110 taken along the line III-III in FIG. As shown in FIG. 3, the central axis of the cylindrical insulator 130 and the central axis of the cylindrical portion of the reaction tank 161 coincide with the axis P. As a result, a first channel 181 having an annular cross section when cut by a plane orthogonal to the axis P is formed outside the insulator 130. The cross-sectional shape of the first flow path 181 is uniform around the axis P. For this reason, the flow of the liquid 101 flowing through the first flow path 181 is stabilized.

  Note that the central axis of the cylindrical insulator 130 and the central axis of the columnar electrode portion 111 are coincident with the axis P. Thereby, the flow of the gas flowing through the space 132 along the side surface of the electrode part 111 is stabilized.

  Further, the gas passing through the opening 131 travels in the first flow path 181 along the flow of the liquid 101. For this reason, as shown in FIG. 2, the gas that has passed through the opening 131 and the liquid 101 proceed side by side in the same direction, so that turbulent flow is less likely to occur in the liquid 101.

  In the present embodiment, the liquid 101 flowing through the first flow path 181 and the gas passing through the opening 131 flow downward with respect to the horizontal plane. For example, both the liquid 101 and the gas flow vertically downward. That is, the axis P corresponds to the vertical direction. Thereby, since the liquid can flow smoothly using gravity, the entrainment of the liquid 101 into the insulator 130 is suppressed, and the occurrence of turbulence can be reduced.

[5. Effect etc.]
FIG. 4 is a graph showing a change in power consumption over time when the plasma generating apparatus 100 according to the present embodiment is operated. In FIG. 4, the horizontal axis indicates the elapsed time [seconds] from the generation of plasma by applying a voltage to the electrode pair. The vertical axis indicates the power consumption [W] consumed by the power supply 140.

  In FIG. 4, the time change of each power consumption of an Example and a comparative example is shown. In the embodiment, as shown in FIGS. 2 and 3, the direction in which the gas passes through the opening 131 and the direction in which the liquid 101 flows in the vicinity of the opening 131 are substantially the same. In the embodiment, the central axis of the cylindrical insulator 130 and the extending direction of the first flow path 181 are substantially parallel.

  In the comparative example, the direction in which the gas passes through the opening 131 and the direction in which the liquid 101 flows in the vicinity of the opening 131 are substantially orthogonal. In the comparative example, the central axis of the cylindrical insulator 130 and the direction in which the first flow path 181 extends are substantially orthogonal. In the example and the comparative example, other operating conditions are the same except that the positional relationship between the insulator 130 and the first flow path 181 is different.

  As shown in FIG. 4, when the operation time is the same time, the power consumption is suppressed in the embodiment as compared with the comparative example. In addition, the fluctuation range x of the power consumption in the example is suppressed to be smaller than the fluctuation range y of the power consumption according to the comparative example. Further, in the comparative example, the power consumption gradually increases as time elapses. On the other hand, in the embodiment, an increase in power consumption when time elapses is suppressed.

  As described above, according to the plasma generation apparatus 100 according to the present embodiment, the bubbles 102 emitted from the opening 131 of the cylindrical insulator 130 are not easily interrupted and can easily flow along the flow of the liquid 101. Further, according to the plasma generator 100, it is difficult for the turbulent flow of the liquid 101 to occur near the opening 131. Thereby, since the distance from the 1st electrode 110 to a gas-liquid interface is stabilized, as shown in FIG. 4, discharge can be stabilized.

(Modification)
Subsequently, two modifications 1 and 2 of the embodiment will be described. In the modified examples 1 and 2, the shape of the flow path in the vicinity of the opening 131 of the insulator 130 is different from that in the embodiment. In the following description, differences from the embodiment will be mainly described, and description of common points will be omitted or simplified.

[Modification 1]
First, Modification 1 will be described with reference to FIGS. 5 and 6.

  FIG. 5 is a block diagram showing a configuration example of the plasma generating apparatus 200 according to this modification. FIG. 6 is a cross-sectional view showing a configuration in the vicinity of the first electrode 110 of the plasma generating apparatus 200 according to this modification.

  As shown in FIG. 5, plasma generation apparatus 200 includes structure 260 having reaction tank 261 instead of structure 160 having reaction tank 161 as compared with plasma generation apparatus 100 according to the first embodiment. The point is different. The reaction tank 261 is different from the reaction tank 161 in the shape of the U-shaped right portion.

  In the present embodiment, the liquid 101 flows outside the insulator 130 along the direction in which gas passes through the opening 131 of the insulator 130. In FIG. 6, the flowing direction of the liquid 101 is indicated by a solid arrow, and the direction in which the gas passes through the opening 131 is indicated by a broken arrow.

  The flow path 280 includes a first flow path 281 that extends along an axis P indicated by a one-dot chain line in FIG. The opening 131 of the insulator 130 is located in the first flow path 281. The opening 131 is orthogonal to the axis P.

  As shown in FIG. 6, the liquid 101 flowing through the first flow path 281 and the gas passing through the opening 131 flow in a direction along the axis P. The first channel 281 has a line-symmetric cross section when cut along a plane parallel to the axis P. The axis of symmetry of line symmetry is an axis P indicated by a one-dot chain line in FIG.

  Here, the first flow path 281 is formed in the right portion of the U-shaped reaction tank 261. Specifically, the shape of the part forming the first flow path 281 of the reaction tank 261 is a truncated cone.

  The central axis of the cylindrical insulator 130 and the central axis of the truncated cone portion of the reaction vessel 261 coincide with the axis P. As a result, a first channel 281 having a circular cross section when cut by a plane orthogonal to the axis P is formed outside the insulator 130. The cross section taken along line III-III in FIG. 6 is the same as the cross section shown in FIG. The cross-sectional shape of the first flow path 281 is uniform around the axis P. For this reason, the flow of the liquid 101 flowing through the first flow path 281 is stabilized.

  Further, the gas passing through the opening 131 travels in the first flow path 281 along the flow of the liquid 101. For this reason, as shown in FIG. 6, the gas that has passed through the opening 131 and the liquid 101 proceed side by side in the same direction, so that turbulence is unlikely to occur in the liquid 101.

  As described above, according to the plasma generation device 200 according to this modification, it is difficult for the turbulent flow of the liquid 101 to occur near the opening 131. Thereby, since the distance from the 1st electrode 110 to a gas-liquid interface is stabilized, discharge can be stabilized.

[Modification 2]
Next, Modification 2 will be described with reference to FIG. FIG. 7 is a cross-sectional view showing the configuration in the vicinity of the first electrode 110 of the plasma generator according to this modification. In FIG. 7, the direction in which the liquid 101 flows is represented by a solid arrow, and the direction in which the gas flows is represented by a dashed arrow.

  In the plasma generating apparatus according to this modification, the first electrode 110 and the insulator 130 are arranged in a reaction vessel 360 having the shape shown in FIG. The reaction tank 360 is an example of a structure that forms the flow path 380 of the liquid 101. The reaction tank 360 is connected to, for example, the processing tank 162 and the pipe 163 shown in FIG. 1 and the like, and forms a circulation path for the liquid 101.

  A flow path 380 formed by the reaction tank 360 includes a first flow path 381 and a second flow path 382. The second flow path 382 is connected to the upstream side of the first flow path 381.

  The first flow path 381 extends along an imaginary straight line. Specifically, the first flow path 381 is the same as the first flow path 181 according to the embodiment. For example, the cross section taken along line III-III in FIG. 7 is the same as the cross section shown in FIG.

  The second flow path 382 is bent. Specifically, the second flow path 382 is bent in an S shape. The shape of the cross section of the second flow path 382 when cut along a plane orthogonal to the direction in which the liquid 101 flows is circular and has substantially the same area at an arbitrary position. For example, the second flow path 382 is formed by bending a cylindrical pipe into an S shape.

  According to the plasma generator according to this modification, the second flow path 382 bent is connected to the upstream side of the linear first flow path 381. For this reason, when the liquid 101 flows in the flow path 380, the liquid 101 passes through the second flow path 382 before reaching the first flow path 381 where the opening 131 of the insulator 130 is located. Since the second flow path 382 is bent, the flow of the liquid 101 is stabilized. As a result, the liquid 101 flows through the first flow path 381 at an equal speed, so that it is possible to suppress the occurrence of turbulent flow in the vicinity of the opening 131 of the insulator 130.

  From the above, according to the plasma generator according to this modification, the discharge can be further stabilized.

(Other embodiments)
As mentioned above, although the plasma generator which concerns on the one or several aspect was demonstrated based on embodiment, this indication is not limited to these embodiment. Unless it deviates from the main point of this indication, the form which carried out various deformation | transformation which those skilled in the art thought to this embodiment, and the structure constructed | assembled combining the component in different embodiment is also included in the scope of this indication. It is.

  For example, in the above embodiment, an example in which the liquid flows vertically downward in the vicinity of the opening of the insulator has been described, but the present invention is not limited to this. The liquid may flow obliquely downward with respect to the horizontal plane. Specifically, the axis P corresponding to the insulator and the axis of the flow path may extend obliquely downward with respect to the horizontal plane. Alternatively, the liquid may flow in the horizontal direction, vertically upward, or obliquely upward with respect to the horizontal plane. By increasing the output of the liquid 101 by the circulation pump 170, the liquid can flow in an arbitrary direction. That is, the axis | shaft of an insulator and a flow path may face arbitrary directions.

  Further, for example, in the above-described embodiment, the example in which the opening of the insulator is orthogonal to the axis of the flow path that is a virtual straight line has been described, but the present invention is not limited thereto. The opening of the insulator may intersect obliquely with respect to the axis of the flow path. For example, the angle between the opening and the straight line may be in the range of 80 degrees to 90 degrees.

  For example, the cross-sectional shape of the flow path is not limited to a circular shape or an annular shape. The cross-sectional shape of the flow path may be square or oval.

  For example, the insulator may not be cylindrical. The electrode portion and the insulator of the first electrode, and the flow path in the vicinity of the insulator may be bent along the same axis. For example, in the cross section orthogonal to the said axis | shaft, it forms so that the area of a flow path may become equal.

  For example, the plasma generator may not include a structure that forms the flow path. For example, when the liquid flows along a predetermined direction, the insulator and the first electrode may be arranged in the liquid so as to be substantially parallel to the flow of the liquid. Further, the second electrode is similarly disposed in the liquid. In this state, plasma may be generated by applying a voltage between the first electrode and the second electrode.

  In each of the above embodiments, the control circuit of the plasma generator may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

  The present invention can be realized not only as a plasma generator, but also as a program including steps performed by each component of the plasma generator, and a computer-readable DVD (Digital Versatile Disc) recording the program. It can also be realized as a recording medium.

  That is, the comprehensive or specific aspect described above may be realized by a system, an apparatus, an integrated circuit, a computer program, or a computer-readable recording medium, and any of the system, the apparatus, the integrated circuit, the computer program, and the recording medium It may be realized by various combinations.

  Each of the above-described embodiments can be variously changed, replaced, added, omitted, etc. within the scope of the claims or an equivalent scope thereof.

  The present disclosure can be used for a plasma generation apparatus that generates a plasma liquid from water.

100, 200 Plasma generator 101 Liquid 102 Bubble 103 Plasma 110 First electrode 111 Electrode part 112 Screw part 113 End face 114 Through hole 120 Second electrode 130 Insulator 131 Opening 132 Space 133 End face 134 Holding part 140 Power supply 150 Supply pump 160, 260 Structure 161, 261, 360 Reaction tank 162 Processing tank 163 Pipe 170 Circulation pump 180, 280, 380 Flow path 181, 281, 381 First flow path 190 Control circuit 382 Second flow path

Claims (10)

A first electrode and a second electrode at least partially disposed in a flow path for flowing a liquid;
A cylindrical insulator having an opening located in the flow path at the end face, and surrounding the side surface of the first electrode through a space for allowing gas to pass through;
A power source for generating plasma by applying a voltage between the first electrode and the second electrode;
The liquid flows through the outside of the insulator along a direction in which the gas passes through the opening. The plasma generator according to claim 1, further comprising a supply device that discharges the gas into the liquid from the opening by supplying the gas to the space. The plasma generating apparatus according to claim 1, further comprising a structure that forms the flow path. The flow path includes a first flow path extending along a virtual straight line,
The plasma generating apparatus according to claim 3, wherein the opening is located in the first flow path. The plasma generator according to claim 4, wherein the opening is orthogonal to the straight line. The plasma generator according to claim 4 or 5, wherein the liquid flowing through the first flow path and the gas passing through the opening flow downward with respect to a horizontal plane. The plasma generator according to any one of claims 4 to 6, wherein a cross-sectional shape of the first flow path when cut along a plane parallel to the straight line is line symmetric. The plasma generating apparatus according to claim 7, wherein a cross-sectional shape of the first flow path when cut along a plane orthogonal to the straight line is a circular shape or an annular shape. The plasma generation apparatus according to any one of claims 4 to 8, wherein the flow path further includes a bent second flow path connected to an upstream side of the first flow path. The plasma generating apparatus according to claim 9, wherein the second flow path is bent in an S shape.

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