A method to measure the velocity of subsonic submerged plasma jets with unstable flows based on an analysis of the motion of optical inhomogeneities introduced into the jet is considered. A source of these inhomogeneities in the form of a heat-resistant thin rod is placed in a diametrical direction of a chosen cross section of the jet flowing from the output channel of a high-current DC plasmatron into ambient air under atmospheric pressure. The plasma-forming gas is a mixture of argon and nitrogen, and the characteristic Reynolds numbers of the studied flows are ReD = 50–300. The perturbation effect of the body introduced into the plasma jet on the two most important characteristics (plasma temperature and velocity) was studied. Specific features of laminar and pulsating flows of submerged plasma jets were studied via two-site, high-speed, synchronous visualization. It is shown that the length of the continuity restoration part of the jet flowing around the rod at a temperature of 10–12 kK and a velocity of 100–500 m/s is very small (several millimeters) under these conditions. The plasma temperature in the region of the strongest thermal perturbation caused by the introduction of the rod was measured with spectral methods. The observed plasma cooling is compared with the calculated decrease in the enthalpy due to expenditures for the heating and ablation of the rod material.

With the aim of studying nitrogen plasma flow impacting graphite surfaces, we investigated the evolution of a plasma jet moving from the nozzle of the plasma torch to the target. The motion is accompanied by a decrease in temperature from 10 to 7 kK with a loss of ≈ 60% of the deposited energy and an increase in the density of carbon-containing impurities with partial preservation of the local thermodynamic equilibrium. The main reactions are thermal processes of the formation and decomposition of molecules, dissociative recombination and recharging of nitrogen ions. In the presence of carbon impurities, this set is supplemented with the substitution reaction C + N 2 ↔ CN + N, electron-collision processes of stepwise ionization and recombination, and a whole ion-molecular cascades of reloads and substitutions. It has been established that a small admixture of carbon (∼ 0.1%) manifests itself only in ion-molecular kinetics, increasing the electron concentration, determining the ionic composition of the plasma, and thereby violating the equilibrium between its neutral and charged components. This leads, in particular, to the recombination nonequilibrium distribution of carbon atoms over electronic states. Other carbon-containing impurities (CN and C 2 ) are not significant.

A study was performed to investigate the transfer of organic compounds and water from an aqueous solution to the gas phase under the action of a direct current discharge, in which an aqueous solution that contains organic compounds plays the role of a cathode. The effect of the area of the free surface of a liquid in various reactors, as well as the effect of the stirring mode of a solution near the surface of a liquid on the rate of transfer of water and organic compounds under the action of a discharge of this type, have been investigated. It is shown that a change in the area of the free surface of a liquid has no significant effect on the rate of transfer of water and organic compounds from solution to the gas phase under the action of a direct current discharge with a liquid cathode. It is shown that the stirring mode and the temperature of the solution, on the contrary, have a very significant effect on the rate of nonequilibrium transfer of both water and organic compounds from solution to the gas phase under the action of a discharge with a liquid cathode.

A cold atmospheric-pressure plasma jet was studied using the novel microwave plasmatron recently developed. Cold plasma jet was generated in Ar flow by electrode 2.45 GHz discharge of up to 200 W power in the portable plasmatron burner (torch) with 2.5 cm diameter outlet. Oscillograms and floating potential dependences on distance from the torch outlet were measured by planar electric probe. Axial and radial distributions of gas temperature in a cold plasma jet were obtained by means of thermocouple method.

Dynamics of the discharge with a liquid cathode was studied using the method of high-speed visualization. The video data was compared with the emission spectra of the discharge plasma. Electrical parameters of the discharge were measured. The effect of organic impurities in the solution on the discharge parameters was investigated.

We present results of spectroscopic measurement of electron temperature in submerged nitrogen and argon mixture plasma jet for cases of free flow and introduction of thin graphite rod into the jet. The observed cooling of plasma caused by rod introduction agrees with the calculated enthalpy decrease from graphite rod heating and ablation. In this experiment, a marker was used to create artificial optical inhomogeneities in the flow, which allowed us to determine flow velocity from the analysis of their movement. In this case, we aim to determine the degree of influence of rod introduction into the plasma on its parameters. Upon introduction into the plasma, the rod was heated and partially destroyed by the plasma flow, reducing its temperature by 8-20% depending on the flow rate of the plasma-forming gas. The observed plasma cooling was compared with the calculated decrease in enthalpy caused by the cost of heating and ablation of the rod material.

This work presents the results of numerical simulation and experimental studies of a weakly conducting fluid motion in a system of two electrodes “wire above the plane”.

Abstract In this work the detailed structure of a direct current discharge with a liquid cathode was studied by high-speed imaging and emission spectroscopy. The movement of filaments into which the discharge channel is divided is studied. The processes of formation and destruction of filaments are investigated. Spectra were recorded at different distances from the liquids surface on the discharge axis. The dependences of the luminescence intensity of the main spectral lines and bands on the distance to the liquid surface at different discharge currents are found.

Study of heat and mass transfer process in the interaction zone between subsonic plasma jet and surface of sublimating heat-resistant sample us one of current interest topics of contemporary thermophysics and physics of heterogeneous plasma. Despite a large number of works being performed in recent years, many fundamental problems have yet to get an adequate solution or even to be tackled yet. The challenge of determining plasma parameters in the boundary region of plasma jet wrapping around the solid surface is one of these problems. This work presents first results of experimental determination of electron, atomic and molecular plasma component temperature fields in the deceleration area of the plasma jet hitting the surface of sublimating heat-resistant sample. One of the important aspects of this work is selection and rational of spectral diagnostics methods with high spatial and temporal resolution based on analysis of nonequilibrium atomic-molecular plasma kinetics.

An experimental unit is described for effective alloying of steel with nitrogen by plasma arc remelting. Production regimes are developed for unit operation making it possible to obtain a super-equilibrium content of nitrogen (up to 0.22%) in remelted metal with action of a plasma flow at a temperature of ≈ 7000 K in molten metal with the metal temperature in the arc-binding zone of up to ≈ 2700 K. The technology of remelting of 55Kh20G9N4 steel facilitates grain refinement, an increase in strength properties, ductility, and overall energy for failure, wear resistance under dry friction conditions and a reduction in the corrosion rate.

The paper presents the experimental results on plasma heating of fired periclase-carbonaceous refractory material. A high heating rate of more than 1000∘C/h was achieved. The thermophysical properties of the fired refractory were refined. It was shown that fired periclase-carbon has a lower thermal conductivity than unfired (9.5 and 25 W/(m·K), respectively), as well as higher emissivity (0.6 and 0.3, respectively). Using the obtained data, the parameters of the CFD model of the plasma heating process of periclase-carbonaceous refractory were refined, which will enable a more accurate simulation of this process in the future.

In an automated measuring complex using optical and spectral methods the spatial and temporal changes in the parameters and composition of nitrogen plasma jet were investigated. The plasma jet was flowing out of the nozzle of the plasma torch with 10-12 kK temperature and acting on the sample of MPG-6 graphite. Due to the heating of the sample to the temperatures of 2.5-3 kK the influence of the sublimating material of the sample on the plasma composition and temperature in the near-surface region of the sample was investigated. An original method based on the analysis of movement of optical inhomogeneities in the plasma flow was used to estimate the plasma jet velocity in the region where it interacts with the sample. The combined analysis of the results of two-positioning video recordings opens up the possibility of determining spatial-temporal distributions of the plasma jet velocities, in medium and high pressure environments, in the ranges from few to thousands of m/s and 3-15 kK temperatures.

To study the interacting system “heat-resistant sample – an incident plasma stream” a setup of synchronized measurement equipment was developed and tested that recorded the main parameters of such interaction. Heat resistance tests were carried out on the samples of MPG-6 grade isotropic graphite, and samples of pyrolytic graphite that were subjected to a long (60 … 100 s) exposure to nitrogen, argon and air plasma streams at atmospheric pressure. As plasma generators a series of plasma torches with a vortex stabilization of the stream and an expanding anode channels was used. The temperature and composition of the plasma in the jet and near the sample were determined using two AvaSpec2048 and AvaSpec3648 scanning optical spectrometers and the MS5402i spectrograph with the Andor matrix at its outlet. The surface temperature of the sample was determined in real time using three independent ways: two pyrometric systems - a high-speed micro-pyrometer FMP1001 and a two-position visualization of the heated sample by high-speed Motion Pro X3 and VS-FAST cameras, and the spectral analysis of the wide-range thermal radiation of the samples. The main method for determining the rate of material loss during the action of a plasma jet on it was to analyze a two-position synchronous visualization of the “jet-sample” system. When a crater was formed on the surface of the sample under the “dagger” effect of a plasma jet, a video recording system of the crater zone was used, backlit using the “laser knife” method.

An experimental automated system was designed and constructed for studying the parameters and characteristics of non-stationary interacting system high-enthalpy-plasma stream investigated sample: enthalpy of plasma in the incident stream; speed and temperature of plasma stream; temperature of electrons and heavy particles, ionic composition and their spatial distribution; heat flux incident on the sample (kW/cm(2)); surface temperature of the sample; ablation of the sample material, and others. Measurements of achievable plasma heat flux levels are carried out by calorimetry of plasma streams incident on the surface of multi section copper calorimeter. Determination of acceleration characteristics for profiled plasma torch nozzle, as well as the gas flow rate is produced by measuring the total pressure using the Pitot tube. Video visualization of interacting system is carried out using synchronized high-speed cameras. Micropyrometry of the selected zone on the sample surface is carried out by high-speed, three-wavelength pyrometer. To measure the rate of mass loss of the sample, in addition to the weighing method of evaluation the methods of laser knife and two-position stereoscopy are used. Plasma and sample emission characteristics are performed with two separate spectrometers.