High-frequency Induction Discharge Research Articles

Investigation of Heat Transfer Regimes in Subsonic Dissociated-Nitrogen Jets of a High-Frequency Induction Plasmatron under Additional Surface Heating by Laser Radiation

The heat transfer to a cylindrical water-cooled copper model was experimentally investigated in an induction VGU-4 high-frequency (HF) plasmatron of the Institute for Problems in Mechanics of the Russian Academy of Sciences. The model, 30 mm in diameter, equipped with a calorimetric transducer with a heat-adsorbing graphite surface, 13.8 mm in diameter, was exposed to the surface heating in the combined regime by nitrogen plasma and laser radiation and in the cases of the heating with only laser radiation or a nitrogen plasma jet. The experiments in the HF-plasmatron jets were performed at the pressure in the setup low-pressure chamber p = 1 × 104 Pa, nitrogen mass flow rate G = 2.4 g/s, and the plasmatron HF-generator anode power Na.p. = 22 kW. It is established that in the chosen experimental regimes the dissociated-nitrogen jet and the high-frequency induction discharge do not produce a considerable effect on the laser beam passing through them. The values of the heat flux density are obtained as functions of the laser radiation power delivered. The subsonic nitrogen plasma flow in the quartz discharge channel and in the low-pressure chamber of the VGU-4 setup is numerically modeled under the experimental conditions basing on the solution of the complete Navier–Stokes equations using the Patankar–Spalding method.

Spectral and emission characteristics of XeCl-excilamps of high-frequency induction discharge for ultraviolet disinfection

The object of study is a XeCl-excilamp with excitation by a high-frequency inductive discharge. The relevance of the work is due to the need to improve the spectral-emission characteristics of excilamps and methods for their excitation for wide practical application. The aim of the study is to optimize the spectral and emission characteristics of wide-aperture XeCl-exisilamp with electrode-free induction high-frequency discharge excitation for ultraviolet disinfection of municipal and industrial premises. The introduction briefly notes the positive effects of disinfection with ultraviolet radiation. Advantages and problems of excimer lamps and methods of their excitation as sources of ultraviolet radiation for disinfection are described. The main part presents the results of the development of a working model of an excilamp with induction high-frequency discharge excitation and the experimental study of its spectral-emission characteristics. The maximum output power of ~11 W on a mixture of HCl : Xe : He = 1 : 20 : 20 at its pressure of ~1 Torr is obtained. The maximum efficiency of the XeCl-excilamp from the high-frequency field energy invested in the discharge was ~8%, which is close to the typical values of the efficiency of excilamps with excitation by capacitive discharge. The spectral composition of the radiation was studied. It was shown that more than 90 % of the excimer lamp energy is concentrated in the ultraviolet region of the spectrum in the B-X band (maximum wavelength ~308 nm). A characteristic feature of the observed spectrum of the excimer lamp with induction high-frequency discharge excitation is the broadening of the radiation bands as compared to the spectra of the radiation of barrier or capacitive discharge excilamps. The obtained results make excitation of excilamps by high-frequency induction discharge attractive for further study and practical application. The main conclusions about the work done are formulated in the conclusion.

Влияние плазменного высокочастотного индукционного разряда на физико-химические свойства дисперсной системы Ti – Fe – Ni, полученной электрохимическим способом

The Ti – Fe – Ni dispersed system was synthesized by the method of contact exchange on the surface of dispersed titanium in an aqueous chloride-containing solution of iron and nickel. The morphology and composition of the surface, as well as the actual phase composition of the Ti – Fe – Ni dispersed system before and after plasma treatment, have been studied by X-ray phase analysis, scanning electron microscopy and Auger spectroscopy. It is shown that on the surface of titanium microparticles, separate spherical subindividuals and their agglomerates are formed, characterized by nanosizes (100 – 200 nm). It was also found that the Ti – Fe – Ni system contains highly distorted metallic phases of iron and nickel, as well as a hydride phase of TiH2, which practically do not undergo phase transformations as a result of the passage of low-pressure argon through an inductively coupled plasma discharge. It is shown that the metallic phases of titanium, iron, and nickel are characterized by the presence of a thin oxide film on the particle surface, and the total content of the oxide phase in the samples does not exceed 1.5 wt. %. The treatment of the Ti – Fe – Ni system microparticles by high frequency induction discharge in low-pressureargon leads to small changes in the content of phases, the lattice constant and the microstructure of the system under study.It indicates a certain solubility of elements in each other and a greater crystallinity of the phases relative to those in particles untreated by plasma.

Разработка и исследование плазмохимической технологии получения смешанных оксидов урана и плутония из растворов

This paper presents the results of work on the application of plasma-chemical technology for producing uranium and plutonium oxides and their homogeneous mixtures from nitrate solutions of a given composition for the purpose of manufacturing fuel element cores. The technology is based on the process of high-temperature decomposition of aqueous solutions of salts by spraying them into a flow of the heat-transfer gas (air) heated to 5000 – 6000 K in a plasma torch. It is a highly productive short-stage process. No reagents are required for salt precipitation; there are no filtration and high-temperature treatment precipitation operations; the resulting powders are chemically active. It was found that the transformation time of salt solution drops to oxides is 0.05 – 0.10 s for the length of 0.5 – 0.7 m. The temperature in the reactor varies in the range of 1200 – 1800 K; no sintering and fusion of particles occurs. The apparatus-technological scheme of the plant has been developed. The technological equipment is made in a nuclear-safe design and installed in the exhaust boxes. The scheme includes a high-frequency induction plasmatron (plasma torch) with coaxial gas inlet into the discharge chamber. The high-frequency induction discharge is excited by inserting a grounded ignition electrode into the plasmatron discharge chamber. The plasmatron design provides the possibility of long continuous operation at high plasma temperatures with the creation of intensive plasma-jet processes for processing radioactive solutions. The reactor provides ways to prevent product accumulation on the walls (gas curtain method, electric pulse cleaning of cylindrical surfaces, vortex tangential gas supply at the level of the outlet holes of the injectors). Equipment for the separation of nanodispersed oxide powders from high-temperature steam- and powder-gas flows (vortex precipitators, filters with a metal-woven partition) has been developed and applied. The degree of oxide recovery in vortex precipitators is 88 – 92 % per stage, in filters with a metal-cloth partition the degree of purification reaches 105 – 108. Plasma-chemical oxides are nanocrystalline and nanoscale materials represented by crystalline and amorphous structures. Mixed powders are a homogeneous mixture of oxides in the form of solid solutions. The particle size does not exceed 3 μm; the crystallite size is about 10 nm. Fuel elements were manufactured from mixed powders at FGUP “Mayak”, which passed successful tests in the “Bor-60” reactor. Seven industrial fuel elements were manufactured for the BN-600 reactor, six of which were loaded into the reactor.

Analysis of the Equation of the Balance of Energy in the Field of Heating Limited to the Longitudinal Coordinate

The analysis of energy balance equation for viscous laminar flow of fluid or gas in the cylindrical channel in the area (zone) of warm up bounded along the longitudinal coordinate is made. It was found that at laminar flow of fluid or gas in a round pipe, in each warm up area bounded along the longitudinal coordinate there are the areas of direct and reverse flows separated by a plane that is a locus of points where temperature is maximal for each fixed value of radial coordinate r. The received results also explain occurrence of returnable currents in plasma of the high-frequency induction discharge of atmospheric pressure.

The phenomenon of bicyclones a high-frequency induction discharge and the related questions of flows in channels with the presence of zones of heating, bounded along the longitudinal coordinate

The phenomenon of a bicyclones in a high-frequency induction discharge is explained. It is shown that this phenomenon should be characteristic of a wider range of objects having an internal heat source, limited by the longitudinal coordinate. In the present work, this phenomenon is considered as peculiar to fairly wide class of flows in cylindrical channels if there are one or several heating zones (internal or external) inside these channels, limited by the longitudinal coordinate.

Strengthening of PMS-1 Copper Powder by High-Frequency Induction-Discharge Plasma

The improvement in the mechanical properties of PMS-1 copper powder under the action of low-pressure high-frequency induction-discharge plasma is considered.

Modification of Textile Materials with Nanoparticles Using Low-Pressure High-Frequency Plasma

The possibility of modifying the surface of textile fibers with inorganic nanoparticles is experimentally established. The processes of fixing silver nanoparticles on the surface of nonwoven materials based on polypropylene fibers with preliminary modification in plasma of a high-frequency (HF) capacitive discharge of low pressure in order to impart stable antibacterial properties are studied. The processes of glass-fabric modification with the simultaneous deposition of silicon dioxide nanoparticles under plasma conditions of a low-pressure HF induction discharge to achieve the effects of adjustable wettability are considered.

Site of maxima of conductivity, temperatures, density of the current and specific capacity of the thermal emission in the HFI-discharge

On the basis of theoretical analysis of distributions of the conductivity, current density and specific power of heat release in the high-frequency induction discharge, a law of crowding of maxima of these values has been established.

Hardening of the surface plasma jet high-frequency induction discharge of low pressure

The work presents results of research on the hardening surfaces of the products and increase their roughness class of plasma jet of high-frequency induction discharge of low pressure. It is shown that such processing allows to clear at the same time a surface of all types of pollution, to remove a defective layer after its machining, to receive a uniform microstructure, to raise a roughness class on 2 - 3 units.

Electrophysical and Thermal Parameters of Thermal Plasma in a High-Frequency Induction Discharge

A semiempirical model is proposed for the calculation of electrical, magnetic and thermal parameters of the plasma of a high-frequency induction discharge. The model is based on solving a system of two-dimensional Maxwell equations written for a cylindrical coordinate system.

A Two-Temperature Heat Transfer Model of an Emitting Plasma of a High-Frequency Induction Discharge Dear the Plasmoid Axis

A Two-Temperature Heat Transfer Model of an Emitting Plasma of a High-Frequency Induction Discharge Dear the Plasmoid Axis

High-Frequency Induction Discharge in a Gas Flow

High-Frequency Induction Discharge in a Gas Flow

Two-temperature model of the energy balance for plasma of high-frequency induction discharge in the vicinity of the axis of a plasmoid

The results of analysis of a set of equations of energy balance in the axial region of the work coil of an HF plasma generator are used, within the framework of two-temperature model, to derive analytical dependences for the calculation of temperature fields in this region in a two-dimensional formulation of the problem.

Application of resonant Raman scattering of light for plasma diagnostics

An application of a diagnostics method based on the scattering of laser radiation by atoms in plasma is discussed. The high sensitivity of the method is due to resonant enhancement of the Raman scattering cross section with a small offset from the exact optical resonance with an intermediate level. The measurements of the spatial distribution of the excited argon atoms were performed in the plasma of a high-frequency induction discharge in a wide range of offsets from exact resonance under the conditions of linearity and with saturation of the scattering intensity. The results of the experiments are used to analyze the sensitivity of the method and to formulate the requirements for diagnostics so as to optimize the experimental conditions.

High-frequency induction discharge in emission spectral analysis

High-frequency induction discharge in emission spectral analysis

Application of high-frequency induction discharge for obtaining continuous mode laser generation

Application of high-frequency induction discharge for obtaining continuous mode laser generation

Variational approach to the calculation of a high-frequency induction discharge

We discuss a result, obtained in [1], that contradicts experiments. It is shown that the reason for the contradiction involves the nonapplicability of the principle of minimum entropy production to thermodynamical systems situated in an alternating electromagnetic field. For stationary regimes of high-frequency discharges we formulate a variational problem that is equivalent to the original system of equations. We give a solution of this problem in the “channel model” approximation of a discharge with and without taking account of radiation losses.