RU2082284C1 - Microwave cyclone-type plasma gun - Google Patents

Abstract

FIELD: microwave devices. SUBSTANCE: device has waveguide with power input, cylindrical discharge chamber which runs through waveguide in perpendicular to its wider wall, vortex generator, which is located in lower part of discharge chamber, field application unit, output nozzle, which is made integral with vortex generator and is located in lower part of discharge chamber. EFFECT: increased functional capabilities. 1 dwg

Description

 The present invention relates to the field of electrical engineering, namely to plasmatrons in which a plasma is produced by the action of a microwave field on a gas stream. It can find application in plasma technology of mechanical engineering, in chemical-technological processes.

 Known microwave plasmatron [1] containing a coaxial waveguide transition and a discharge chamber coaxial to it. The plasma torch is equipped with a disk mounted on the central conductor and a cover covering it with a uniform gap with central holes on opposite walls.

 Known microwave plasmatron for spectral analysis of solutions [2] The plasma torch consists of a discharge chamber made in the form of a double coaxial tube connected through a waveguide-coaxial transition with a waveguide line. The inner conductor has an axial channel with a conical extension at the exit to enter the aerosol of the sample.

 Known microwave plasmatron [3] containing a waveguide with energy input located along its axis, and a cylindrical discharge chamber passing through the waveguide perpendicular to its wide wall, the waveguide in the plane of its wide wall is circular, and the discharge chamber is located on the axis from the side of the waveguide, opposite to the input of energy.

 Known plasmatron with gas-vortex stabilization of the arc [4] Contains cathode and anode nodes, and the cathode node contains a housing with a swirl, a cathode insert, a pipe for supplying gas to the swirl.

 Known vortex plasmatron [5] containing a discharge chamber, electrode, nozzle and a supply system of the working fluid with a vortex formation system.

 The closest analogue is a microwave plasma reactor for chemical processes [6]. It contains a metal discharge chamber in the form of a cylinder with end faces, to the side surface of which at least two rectangular waveguides are connected through windows evenly spaced around the perimeter, a swirling gas flow input shaper installed at one of the bottoms, and exit nozzles passing through the second bottom. The wide walls of the waveguides are parallel to the axis of the chamber, the number of nozzles is selected at least four, one of the nozzles is located along the axis of the chamber, and the rest along the periphery at a uniform distance from the axis.

 The disadvantage of the prototype and the above plasmatrons is that the axial method of stabilizing the microwave discharge requires a poorly streamlined metal body, in which a discharge is burning, where electrical breakdowns are possible between the discharge and the poorly streamlined body, leading to erosion of the poorly flowing body, plasma pollution and a decrease in the operating life plasmatron. The tangential method of stabilization of the discharge does not require a poorly streamlined body, but the introduction of dispersed material into the plasma due to the action of centripetal forces leads to the ejection of particles onto the walls of the discharge chamber and, accordingly, the cessation of the microwave power supply and the discharge disruption.

 The aim of the proposed invention is to increase the service life of the plasma torch by creating gas-dynamic conditions for the effective entry of particles into the discharge, obtaining plasma electrodes not contaminated with materials, and increasing the gas heating efficiency.

 This goal is achieved by the fact that in a plasmatron containing a waveguide with energy input, a cylindrical discharge chamber passing through the waveguide perpendicular to its wide wall, a swirler located in the lower part of the discharge chamber, a sol supply unit, an output nozzle, and an output nozzle are built into the swirl and are located at the bottom of the discharge chamber.

 It is known that cyclone chambers designed to purify fine particles from gas flows only work efficiently up to a certain particle size (30 microns). Part of the finely dispersed material enters the exhaust pipe, which is a negative quality of the cyclone. In the cyclone-type microwave plasmatron, this phenomenon is positive and allows the introduction of a finely dispersed sol into the microwave plasma. When particles are introduced along the axis of the cyclone discharge chamber, large particles> 30 μm do not have time to change the trajectory of motion and fall into the exhaust nozzle passing through a microwave plasma. Small particles <30 μm stabilize in the plasma region and also exit through the exhaust nozzle, passing through the plasma. This ensures, on the one hand, the stable operation of the plasma torch due to the tangential stability of the microwave plasma, and on the other hand, a high coefficient of entry of fine particles into the plasma in the absence of ejection onto the walls.

 The drawing shows the proposed plasmatron, section.

 The microwave plasmatron contains: a waveguide, through which microwave power 1 is supplied, a cylindrical discharge chamber 2 made of quartz, which passes through the waveguide 1 in a wide wall, a swirler 3 located in the lower part of the discharge chamber. The swirler has a tangential air inlet 4. An exhaust nozzle output 5, which is located in the lower part of the discharge chamber, is built into the swirl 3, as is the swirl. At the top of the discharge chamber there is a sol feed unit 6. The sol is a finely divided powder or sprayed liquid.

 The device operates as follows.

 The microwave power supplied by the waveguide 1, supports the atmospheric pressure microwave discharge in the discharge chamber 2, formed by a cylindrical quartz tube, a sol supply unit 6, a swirler 3 and an output nozzle 5. The plasma-forming gas is supplied through the nozzles of the swirler 4 and exits into the output nozzle 5 heating up in microwave plasma. Stabilization of the microwave discharge is achieved by the tangential supply of a plasma-forming gas, which additionally acts as a cooler for the walls of the discharge chamber and the outlet nozzle. The sol is fed through a supply unit 6, located in the upper part of the discharge chamber, passes through heating, through a microwave plasma and goes to the output nozzle 5.

 The principle of operation of the microwave cyclone plasmatron is that due to the formation of a swirling flow in the lower part of the chamber having a radial component of the gas velocity directed to the axis of the discharge chamber, finely dispersed particles stabilize in the plasma region and are not ejected onto the walls.

 Unlike plasmatrons with axial discharge stabilization, this plasmatron can be made entirely of non-metallic parts, which allows initiating an electrodeless microwave discharge of atmospheric pressure for a wide range of parameters.

Parameters of stable operation of the plasma torch:
microwave field frequency 2450 MHz;
plasma-forming gas flow rate 20 60 l / min.

 The minimum diameter of the discharge chamber is determined by the size of the contracted microwave discharge at atmospheric pressure and is 10 mm. The maximum diameter is determined by the flow rate of the plasma-forming gas and the dimensions of the waveguide.

 The minimum size of the output nozzle is also determined by the size of the contracted microwave discharge and is 10 mm.

 The maximum diameter of the exhaust nozzle must be less than the internal dimensions of the discharge chamber.

 The depth of immersion of the exhaust nozzle is determined by the height of the swirl and should ensure the formation of an upward flow of gas and exclude the direct penetration of plasma-forming gas into the exhaust nozzle.

 The length of the discharge chamber is determined by the electrodeless combustion regime of the microwave discharge.

 The proposed cyclotron plasmatron can be used in the production of pure substances in the electronic, chemical and metallurgical industries, in coating, for gas heating, spheroidization of particles, in spectral analysis as a shock absorber or a source of excitation of spectra.

Claims (1)

 A microwave plasmatron containing an energy input waveguide, a cylindrical discharge chamber passing through the waveguide perpendicular to its wide wall, a swirler located in the lower part of the discharge chamber, a sol supply unit, an output nozzle, characterized in that the output nozzle is built into the swirl and is located in bottom of the discharge chamber.