A criterion of similarity and transition to turbulence for electric arc flows

A method is suggested for determining the similarity criterion and the criterion of transition of an electric arc flow in a plasmatron channel from a laminar regime to a turbulent one (equivalent Reynolds number) that does not require using any reference temperature. Application of this method to the available experimental data on the transition to turbulence demonstrates its correctness and efficiency. The critical value of the proposed similarity criterion corresponding to the boundary of the transition from a laminar regime to a turbulent one has been revealed. A marginal curve separating the regions of the laminar and turbulent regimes of the plasma flow has been plotted in the space of the operating plasmatron parameters. A phenomenon of a double change of the electric arc flow regime with electric current rise upon constant plasma-forming gas flow rate has been discovered.     

Multicriterial Optimization of the Operation and Design Parameters of Electric-Arc Plasmatrons of Linear Circuits

A new method of design synthesis of electric arc heaters by prescribed characteristics is suggested. The method has been applied for multicriterial optimization of the conditions of burning an arc with longitudinal eddy stabilization by an air flow in a plasmatron channel.     

The Shunting of Current and the Resultant Variation of Voltage in Channels of Plasmatrons with Self-Adjusting Length of Electric Arc

The characteristics of pulsation processes in dc plasmatrons with the cathode located in the channel center and the anode in the form of a cylindrical or a conical channel wall are investigated in plasmas of argon and nitrogen at atmospheric pressure. The fast Fourier transform of signals and their subsequent computer processing are used to obtain the dependences of the frequency of fluctuations of the arcing voltage on the working parameters of the plasmatron, namely, the electric arc current, the flow rate of plasma-forming gas, and the channel diameter. For plasmatrons with the self-adjusting length of the electric arc, analysis is performed of the mechanism of reclosing of the anode region of the arc, i.e., of the electric arc shunting associated with the stretching of the current filament by a flow of gas and with the electrodynamic interaction of different filament regions. A formula is derived which defines the dependence of the characteristic frequency of fluctuations of the arcing voltage on the external parameters of the problem, namely, the arc current, the flow rate of the working gas, and the characteristic channel diameter. It is demonstrated that the pattern of the dependence of the frequency of voltage fluctuations on the gas flow rate may vary with the values of the parameter of magnetohydrodynamic interaction. The formula generalizes the experimental results of numerous researchers obtained in a wide range of variation of the external parameters.     

Heat loss in the channel of a plasmatron

A mathematical model is constructed and a computational experiment is carried out to determine the characteristics of a longitudinally blown electric arc in the channel of a plasmatron under conditions of local thermal equilibrium. A feature of the model is that it makes allowance for radiation transfer in the real spectrum of an electric- arc plasma. An algorithm for solving the problem is presented and the effect of radiation reabsorption on the radiation and conductive heat loss in the plasmatron channel is shown.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 3, pp. 505–511, March, 1990.     

The effect of a diaphragm on the vortex thermoinsulation of arc in a plasmatron channel

The pattern of gas (argon) flow and heating in a diaphragmed plasmatron channel is calculated within the framework of an equilibrium magnetogasdynamic model, depending on the diaphragm position and hole size and on the gas flow rate and twist momentum. Special features of the arc characteristics in a channel of variable cross section are established for streams with and without twist.     

Flow turbulence in a cylindrical channel encompassing an electric arc

The effect of an electric arc on the gas flow in a cylindrical channel is investigated. It is shown that the striking of an arc in a laminar flow leads to its turbulence at the boundary of the arc column. Within the arc column, the flow is rendered laminar by the high viscosity of the arc plasma. However, thermal turbulence may develop in the central part of the arc.Academic Scientific Combine A. V. Lykov institute of Heat and Mass Exchange, Academy of Sciences of Belarus', Minsk. Translated from Inzhenerno-Fizicheski Zhurnal, Vol. 62, No. 4, pp. 601–607, April, 1992.     

Experimental investigation of the spatial displacements of an arc-heated plasma

Oscillations of an electric arc in a plasmatron with the fixed arc in wide ranges of currents and air flow rates have been investigated. The distribution functions of arc oscillations have been obtained for various currents, gas flow rates, and distances from a cathode.     

The volt-ampere characteristics of a DC arc plasmatron with a distributed anode spot

A new DC plasmatron with a hot rod cathode and cold nozzle anode was proposed and tested at atmospheric pressure, generating nearly spectrally clean plasmas of air, air/diesel fuel mixture, oxygen, and CF₄. The arc Volt-Ampere characteristic (VAC) is an integral indicator reflecting the general behavior of all the arc parts, among which the most important are the by-electrode layers and positive column. The sensitivity of the VAC to the gas flow velocity in the technologic channel confirmed the external vortex nature of the anode arc spot, which does not hide inside the anode orifice, but exits it and interacts with the gas flow.     

Calculation of the Characteristics of the Initial Section of the Plasma Generator Channel

An equilibrium magnetogasdynamic model of plasma is used to calculate the flow and heating of gas in the initial section of the plasma generator channel. The gas is heated by an electric arc. The distribution of the electric field intensity, temperature, velocity, and pressure drop is obtained depending on changes in the current strength, gas flow rate, and the wall thickness of the electrode nozzle. It is found that axial zones of return flow are formed in the vicinity of the initial section of the channel. The calculation results are compared to the experimental data.     

Numerical Analysis of the Characteristics of an Arc in Laminar and Turbulent Gas Flows

The equations of magnetic gas dynamics are used to calculate the characteristics of an electric arc in a plasmotron channel versus the gas flow rate. The results obtained with the aid of the laminar and the two-parameter k– model of turbulence with allowance for deviations from equilibrium in the plasma and for the swirling of the gas are compared with experimental data. The stability of a laminar flow to the effect of weak hydrodynamic perturbations is investigated.     

Velocity of the electric arc in a plasmatron discharge chamber

An experimental investigation of the velocity of a high-current arc with air injection in the discharge chamber of a coaxial sectioned plasmatron is described. The experiments showed that the velocity of the cathode spot on the electrode surface depends on the arc current and on the external magnetic field strength. The air flow rate in the plasmatron chamber was 7.1 g/sec.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 3, pp. 570–574, September, 1969.     

Effect of the frequency of the external magnetic field on the behavior of the arc in a two-jet plasmatron

The results of studies of the frequency characteristics of an electric arc in a two-jet plasmatron in a transverse magnetic field are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 2, pp. 245–249, February, 1986.     

Intensification of a Laminar Flow in a Narrow Microchannel with Single-Row Inclined Oval-Trench Dimples

A fully developed laminar air flow in a plane-parallel channel of width 6 and height 1 with single-row inclined oval-trench dimples on the walls are calculated using multiblock computing technologies at Re = 10³. A periodic channel section of length 4 with one dimple of length 4.5, width 1, an angle of inclination to the flow of 45°, and a depth varying from 0 to 0.375 is considered. Intensification of a laminar flow in the flow core in a channel supplied with trench dimples of depth more than 0.25, such that the maximum velocity is 1.5 times higher than the maximum flow velocity in a smooth channel, is found.     

Electrical and thermal structure of the argon arc of a two-jet plasmatron

The thermal structure and the distribution of the axial electric field strength of the arc of a two-jet plasmatron were investigated experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 5, pp. 833–837, November, 1982.     

Two-mode model of flow in a plasmotron channel

The characteristics of an electric arc in a turbulent gas flow are calculated on the basis of the concept of laminar flow in the arc zone.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 5, pp. 830–835, November, 1986.     

Current-voltage characteristics of a three-phase one-chamber alternating current plasmatron

A method for the determination of the current-voltage characteristics of a one-chamber three-phase industrial-frequency plasmatron is considered. The form of the characteristics is set proceeding from general laws governing a gas flow past an arc; a numerical value of the coefficients entering these characteristics is calculated with account of the data obtained in the experiment.     

Comparison of the characteristics of a plasma generated by a d.c. arc plasmatron and a high-voltage a.c. plasmatron with rail-shaped electrodes (gliding arc) as applied to the synthesis of carbon nanomaterials

Comparative results of investigating the parameters of plasmas generated by atmospheric-pressure electric-arc plasmatrons of two types operating in the regime of simultaneous partial oxidation of hydrocarbons and their pyrolysis, have been given. It has been established by spectral and thermophysical measurements that the component composition of the plasma and its thermal characteristics at exit from a d.c. plasmatron significantly differ from the parameters of a plasmatron of the second type — an a.c. plasmatron with rail-shaped electrodes of the gliding-arc type. The temperature nonequilibrium and the presence of the carbon dimers C₂ in the plasma (in the absence of the monomer C) generated by the rail-shaped-electrode plasmatron point to the fact that realization of the synthesis of fullerene-containing particles and, probably, particles containing nanotubes is, in principle, possible in reactors based on it, just as in more energy-intensive reactors with low-voltage d.c. arc plasmatrons. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 3–11, July–August, 2006.     

Generalization of volt-ampere characteristics of the electric arc in a double-jet plasmatron with tubular single-chamber electrode units

On a double-jet plasmatron with cylindrical single-chamber electrode units, an experimental study of volt-ampere characteristics of the electric arc is conducted at current 105–550 A, voltage 400–1320 V, total flow rate of the plasma-forming gas (air) (0.76–9.83)∙10⁻³ kg ⁄ s, angle between the cathode and anode parts 45–62°, distance between the cathode and anode axes at the outlet from nozzles 0.07–0.2 m, and outlet pressure of ~0.1 MPa. Correlations for these characteristics are obtained.     

Calculating the parameters of electric-arc heaters with gas-stabilized arcs

We used a turbulent model of a longitudinally streamlined electric arc to derive an analytical solution for the problem of the distribution of the primary flow and discharge parameters in a cylindrical discharge channel of an electric-arc heater.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 17, No. 1, pp. 50–56, July, 1969.     

Transverse Electric Discharges in Supersonic Air Flows: Space-Time Structure and Current-Voltage Characteristics of Discharge

The space-time evolution of potential distribution in a pulsed transverse discharge in a supersonic jet of air is studied in a mode close to the current generator mode. The current dependences of the longitudinal electric field intensity and of the discharge channel diameter are measured for different values of pressure in the jet. It is demonstrated that the electric field intensity decreases with increasing discharge current by the power law, with the exponent being close to that for a highly contracted glow or arc discharge in the absence of flow. The increase in current is accompanied first of all by an increase in the discharge channel cross section. The characteristics of the oscillatory mode of discharge burning are studied for discharge power supplies, which are close to the current generator mode. The obtained dependences of the oscillation period on the external parameters of discharge, namely, current, pressure, and interelectrode spacing, are interpreted. An expression is derived which describes the maximal extent of discharge along the flow in the case of instability due to external electric circuit. This extent may increase further only in the case of transition to supplies close to current generators; in this case, the extent is restricted by the mechanism of repeated breakdown.