JPH11345699A - Liquid plasma generating method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the initial stage of plasma jet generation by forming liquid in a liquid housing part in liquid drops with an element for converting alternating electric energy into mechanical vibration, and supplying the liquid drops to an arc generating portion. SOLUTION: Water 24 is put onto a container 6, voltage is applied to an anode 2, a button 16 is pushed to move a cathode holder 3, a cathode 4 is brought into contact with the anode 2, pushing of the button 16 is stopped, the cathode holder 3 is returned together with the button 16, the cathode 4 is separated from the anode 2, and arc discharge is conducted in a discharge chamber 11. When the button 16 is pushed down, a piezo element 28 driving circuit is also started to generate ultrasonic vibration, water 24 is converted into mist, the mist is supplied to a gap between the outer circumferential surface of a porous heat conducting material 8 and the inner circumferential surface of a torch main body 1 through a heat resistant pipe 30 to form water vapor. Excess pressure is generated, the water vapor is supplied to the discharge chamber 11 through the outer circumferential path of a ring 9 and a path 10 of a tip tapered part, plasma is generated, plasma is jetted from the center hole of the anode 2, and an arc pillar is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for generating thermal plasma, and more particularly, to a plasma jet or plasma arc by ionizing vapor generated by evaporating a liquid with an arc generated between a cathode and an anode. The present invention relates to a liquid plasma generation method and an apparatus therefor.

[0002]

2. Description of the Related Art Thermal plasma generators are used in processes for melting and refining in the steel industry, treating toxic waste in the chemical industry, and synthesizing gas such as acetylene. It is also used in processes such as fine particle synthesis, thermal spraying, and sintering. Most of the thermal plasma generators put into practical use are so-called gas plasma devices using a gas such as argon, hydrogen, or nitrogen as a plasma source or a working medium (hereinafter referred to as a working medium). Liquid plasma devices using such liquids have also been proposed, and some have been put to practical use. For example, a water plasma spraying apparatus using water as a liquid and using a plasma jet for spraying is known. Further, an apparatus using water as a liquid and using a plasma jet for welding is also known.

FIG. 3 is a schematic structural view of a plasma torch using a liquid proposed in US Pat. No. 5,609,777. The plasma torch includes a plasma torch main body 1 having a discharge chamber 11 and a working fluid container 6. The main body 1 has an anode 2 having a discharge port formed thereon, and a rod-shaped cathode 4 coaxial with the discharge port. This card 4 is fixed to the holder 3. The holder 3 is surrounded by an electrically insulating tube 12, which is further surrounded by a thermally conductive tube 13. The main body 1 has a ring 9 made of a heat conductive material. The ring 9 is in contact with the anode 2 and has a passage 10 to the discharge chamber 11 tangentially formed at a contact portion with the anode 2. This passage is slightly inclined (for example, about 3 to 10 degrees) in a circumferential direction about the center of the ring 9.

[0004] The container 6 is provided with a sleeve 5 on the main body 1 side.
And the inside thereof is filled with a moisture absorbing material 7. As the moisture absorbing material 7, for example, kaolin wool or glass wool can be used.

The gap between the main body 1 and the container 6 is filled with a porous heat conductive material 8. The porous heat conductive material 8 is in contact with the ring 9 on the main body 1 side, and is in contact with the moisture absorbing material 7 on the container 6 side. As the porous heat conductive material 8, a sintered copper shot, a copper chip, or the like can be used.

The cathode holder 3, the electrically insulating tube 12, and the thermally conductive tube 13 extend to the rear end side through the porous thermally conductive material 8 and the moisture absorbing material 7.
The rear ends of the tubes 12 and 13 are fixed to the structure 21. The cathode holder 3 is movable in the axial direction in the electrically insulating tube 12, and a button 16 is attached to a rear end thereof. This button 1
6 is a cover 14 whose tip is attached to the structure 22.
Through the center hole and is exposed to the outside, and the flange portion 20 on the base end side is arranged so as to abut the inner peripheral edge of the hole. The spring 15 urges the rear end side. A voltage from an external power supply (not shown) can be applied to the anode 2 and the cathode 4.

When using this plasma torch,
First, the stopper 17 is removed, and water as a working fluid is put into the container 6 through the working fluid replenishing hole 18 so that the moisture absorbing material in the container contains water. Thereafter, the stopper 17 is attached. In this state, the external power supply is turned on to start applying a voltage to the anode 2 and the like. Then, the user pushes the button 16 to move the cathode holder 3, and the cathode 4 at the tip thereof is connected to the anode 2.
Contact. Then, the pressing of the button 16 is stopped. When the pushing is stopped, the button 16 is pushed back by the urging force of the spring 15, and accordingly, the cathode holder 3 also returns to the initial position. With this return, arc discharge starts in the discharge chamber 11 when the cathode 4 separates from the anode 2.

The heat generated by the current flowing by the arc discharge is transmitted to the water contained in the porous heat conductive material 8 through the heat conductive link 9. As a result, the water becomes steam. Then, an excess pressure is generated, and this vapor passes through the tangential flow path 10 of the ring 9 and enters the discharge chamber 11. Here, the water vapor is turned into plasma. Then, it is blown out through a hole in the center axis of the anode 2. Thereby, the arc column is stabilized, and at the same time, the anode 2 and the cathode 4 are cooled. When the water vapor passes through the passage 10, the thrust in the spiral direction is obtained by the above-described circumferential inclination. This propulsive force is inherited even if it is turned into plasma, and further stabilizes the arc and stabilizes the plasma blown out from the hole in the central axis of the anode 2.

It is said that this plasma torch consumes about 70 ml of water when continuously operated for 25 minutes at an input power of 1 KW.

[0010]

In this known plasma torch, water as a working liquid is turned into steam by the heat generated by the arc discharge, and is moved to the discharge chamber by its vapor pressure. Instability of the plasma jet in the early stage of the generation of the gas, or a structure that can transfer the heat generated by the arc discharge to the main container of water or its vicinity, etc. There are restrictions.

The present invention has been made in view of the above background, and an object of the present invention is to provide a liquid plasma generating method and a device using a novel working liquid transport system.

[0012]

In order to achieve the above object, the present invention is directed to a liquid plasma generating method for generating plasma by ionizing liquid vapor with an arc generated between a cathode and an anode. The liquid in the liquid storage section for storing the liquid is converted into liquid droplets by an element that converts alternating electric energy into mechanical vibration and supplied to the arc generating portion side.

According to a second aspect of the present invention, there is provided a liquid plasma apparatus for generating plasma by ionizing a liquid vapor with an arc generated between a cathode and an anode, wherein the liquid in the liquid storage section for storing the liquid is It is characterized in that the electric energy is converted into liquid droplets by an element that converts the electric energy into mechanical vibration and supplied to the arc generating site side.

Here, the element for converting alternating electric energy into mechanical vibration may be either a magnetostrictive element or a piezoelectric element. Particularly, an ultrasonic transducer that converts alternating current energy of 20 kHz or more into mechanical vibration having the same frequency is preferable.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a plasma torch using water as a working liquid, which is a liquid plasma apparatus, will be described below with reference to FIGS. The plasma torch of the present embodiment is obtained by improving the known plasma torch shown in FIG. In FIG. 1, the same reference numerals are given to portions corresponding to the configuration of the known plasma torch.

In FIG. 1, the plasma torch of the present embodiment differs from the above-described known plasma torch in the following points. (1) The moisture absorbing material 7 was taken out of the working fluid container 6 and the inside of the container was partitioned by the partition member 25, thereby forming a water storage chamber for directly storing the water 24 in the internal space on the rear end side. (2) A mist chamber for converting water into mist by ultrasonic vibration is formed on the side of the torch main body 1 from the water storage chamber by the additionally provided partition walls 26 and 27, and a piezoelectric element, for example, ultrasonic vibration For example, a piezo element 28 is arranged as a child. An external drive circuit and a switch (not shown) for applying a voltage from an external power supply were connected to the piezo element 28. (3) In order to supply the water in the water storage chamber to the mist generation chamber, a felt 29 as a water transmission member is disposed so as to straddle both chambers. The end of the felt 29 on the mist forming chamber side was positioned so as to be in contact with the piezo element 28. (4) The porous heat conductive material 8 was made shorter, and the shape was changed as described later. Further, with this shape change, the link 9
Also changed the shape. (5) The gap between the outer peripheral surface of the porous thermoconductive material 8 and the inner peripheral surface of the torch main body 1 and the above-mentioned mist forming chamber were connected by a plurality of heat-resistant pipes 30. (6) The anode 2 and the cathode 4 may be used as the cathode 2 and the anode 4 by reversing the voltage.

2 (a) and 2 (b), the porous heat conductive material 8 is different from the porous heat conductive material of FIG. 3 except for a portion facing the inner peripheral surface of the torch main body 1. The rear end side was cut into a shape. In addition, countless projections 31 are provided spirally on the outer peripheral surface. Further, a taper is provided at a contact end portion with the link 9, and a tangential groove passage 32 is formed in the taper portion.
Were formed. Then, the shape of the rear end face of the link 9 is
An inverted tapered shape was formed so as to contact the tapered portion. A plurality of links (8 in the illustrated example) are provided on the outer peripheral surface of the link 9.
The groove passage 10a of the present invention was formed. In addition, only a part (three in the illustrated example) of the plurality of grooves 10a on the outer peripheral surface is continuous with a tapered end portion of the link 9 that comes into contact with the note 2, thereby forming a groove groove 10 for a passage. .

In FIG. 2C, a flat piezo element 28 was used as the piezo element, and the felt ends were overlapped so as to be in contact with the surface. A square hole 33 was formed at the felt end. In place of such a shape, FIG.
A plurality of round holes 34 may be formed as shown in FIG. Further, one end of the heat resistant pipe may be connected to the round hole 34 as shown by a virtual line in FIG.

In the above configuration, when using the plasma torch of this embodiment, first, the stopper 17 is removed, and water as a working fluid is poured into the water storage chamber in the container 6 from the working fluid replenishing hole 18. The water 24 in the water storage chamber is supplied to the mist forming chamber through the felt 29, water is held at the felt end overlapping the upper surface of the piezo element 27, and the inside of the hole 33 formed in the felt 29 is also filled with water. It is. Thereafter, the stopper 17 is attached. In this state, the external power supply is turned on to start applying a voltage to the anode 2 and the like. And
The button 16 is pressed to move the cathode holder 3, and the cathode 4 at the tip thereof is brought into contact with the anode 2. Then, the pressing of the button 16 is stopped. When the push is stopped, the button 16 is pushed back by the urging force of the spring 15,
Accordingly, the cathode holder 3 also returns to the initial position. With this return, when the cathode 4 separates from the anode 2, an arc discharge starts in the discharge chamber 10. The contact portion between the lid 14 and the plastic cover 19 is a screw. By turning the screw by hand, the positional relationship between the lid 14 and the plastic cover 19 can be adjusted. Thereby, the distance between the anode 2 and the cathode 4 can be adjusted. Therefore, an optimal length of the arc can be obtained.

In this embodiment, when the external power supply is turned on, the button 16
As the key is pressed, a voltage is also applied to the driving circuit of the piezo element 28, and the piezo element 28 starts ultrasonic vibration. By this ultrasonic vibration, water held at the felt end on the piezo element is turned into mist. In particular, the water filled in the hole 33 formed at the felt end is efficiently misted. And the mist of water is heat resistant pipe 3
0 and the outer peripheral surface of the porous heat conductive material 8 and the torch body 1
Is supplied to the gap between the inner peripheral surface and the inner peripheral surface.

Then, the heat generated by the current flowing by the arc discharge is transmitted to the porous heat conductive material 8 through the heat conductive link 9. As a result, the mist of water supplied to the gap between the outer peripheral surface of the porous thermoconductive material 8 and the inner peripheral surface of the torch main body 1 becomes steam. As a result, excessive steam is generated, and this steam is supplied to the passage 10a on the outer peripheral surface of the link 9 and the groove passage 10 in the tapered end portion, as shown by reference numeral A in FIG.
Through the discharge chamber 11. In addition, of the plurality of passages 10a on the outer peripheral surface of the link 9, the passage
The vapor that has entered the non-continuous stream flows back. At the excess pressure, a part of the vapor passes directly to the discharge chamber 11 through the passage 32 at the tapered end of the porous thermoconductive material 9 as shown by the symbol B in FIG. enter in. The part of the backflow also directly enters the discharge chamber 11 through the passage 32. Then, the vapor that has entered the discharge chamber 11 is turned into plasma, and blows out to the outside through a hole in the central axis of the anode 2. Thereby, the arc column is stabilized, and at the same time, the anode 2 and the cathode 4 are cooled.

According to the plasma torch according to the above embodiment, the water mist generated by the ultrasonic vibrator is supplied to the torch main body 1 side, so that the water supply to the torch main body is controlled by controlling the ultrasonic vibrator. Can control. Thus, for example, stable water supply can be performed by continuous driving. Further, a stable jet of the plasma jet can be performed immediately after the start of the operation. On the other hand, in the known plasma torch shown in FIG. 3 described above, the state of water supply to the torch main body 1 side and the state of steam generation due to heating are affected by the state of water in the container 9 that fluctuates depending on the environment and use history. In particular, the plasma jet flow tends to be unstable immediately after the start of operation.

Also, in the plasma torch of the present embodiment,
Since the water is stored directly in the water storage chamber instead of being absorbed by the moisture absorbing material 7, a large amount of water can be secured because the moisture absorbing material 7 is not used. Therefore, the internal capacity of the entire plasma torch can be reduced, or the capacity of the contained water can be increased.

Although the liquid plasma device according to the above embodiment can be handled by hand, the present invention can also be applied to a fixed type liquid plasma device. In addition, the plasma device according to the above embodiment is of a plasma jet type ejecting as a plasma jet stream or a non-transitional arc generation type, but the present invention can also be applied to a type of generating a transitional arc. Further, the above-described embodiment employs a method of causing a current to flow by bringing the cathode and the anode into contact with each other and then separating the electrodes in order to cause an arc discharge. Instead, a high-frequency high voltage is applied between the electrodes. The method of applying gas to ionize the gas between the electrodes, the method of short-circuiting between the electrodes with a thin wire, and the method of using the arc when the wire is melted and blown off by the current as seed plasma,
The present invention is applicable.

[0025]

According to the present invention, it is possible to provide a liquid plasma generation method and apparatus using a novel working liquid transfer system.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a plasma torch according to an embodiment.

FIGS. 2A to 2D are partial explanatory views of the plasma torch.

FIG. 3 is a schematic configuration diagram of a plasma torch according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma torch main body 6 Container for working fluid 2 Anode with discharge port formed 3 Cathode holder 4 Card 5 Container sleeve 8 Porous heat conductive material 9 Heat conductive ring 10 Tangent passage 11 Discharge chamber 12 Electricity Insulating tube 13 Thermally conductive tube 14 Lid 15 Spring 16 Button 17 Plug 18 Working fluid refill hole 19 Plastic cover 20 Button flange 25 Partition member 26 Partition member 27 Partition member 28 Piezo element 29 Felt 30 Heat resistant pipe 31 projection 32 groove passage 33 hole 34 hole

Claims (2)

[Claims] In a liquid plasma generation method for generating plasma by ionizing vapor generated by evaporating a liquid by an arc generated between a cathode and an anode, a liquid in a liquid storage section for storing the liquid is formed by alternating electric power. A liquid plasma generation method, wherein a liquid is converted into droplets by an element that converts energy into mechanical vibration and supplied to an arc generation site side. 2. A liquid plasma apparatus for generating plasma by ionizing liquid vapor with an arc generated between a cathode and an anode, wherein the liquid in a liquid storage section for storing the liquid is subjected to alternating mechanical energy to mechanical vibration. A liquid plasma generator, wherein liquid is converted into droplets by an element to be converted and supplied to an arc generation site side.