Development of the temperature fields in an electric arc struck on a point electrode in a homogeneous gas stream

A study is made of the problem of a point electric source in a homogeneous gas stream and operating in the arc discharge regime. The development of an electric arc struck on a point cathode in a medium which moves without deformation is studied. The stationary problem of a two-dimensional electric arc that develops in a medium with piecewise constant electrical conductivity is solved. Expressions are obtained for the temperature fields, the thickness of the arc, the current-voltage characteristics, and the power in the arc. The stability of this stationary state with respect to short-wavelength perturbations is investigated. The critical electrical current at which instability commences is determined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 91–99, March–April, 1981.I thank O. N. Sinkevich and I. M. Rutkevich for discussing the work, and also V. I. Grabovskii and V. A. Mareev for making some calculations.     

Investigation of a dense,chemically reacting plasma by the high-frequency probe potential modulation method

A method is proposed for investigating a chemically reacting plasma by means of an electric probe whose potential is modulated by a high-frequency sinusoidal voltage. The method is based on the use of a numerical solution of the problem of an electric probe introduced under negative potential into a steady-state low-temperature plasma formed in a mixture of chemically reacting molecular gases. The conditions under which the charged particle concentration in the region undisturbed by the probe is constant as a result of equilibrium between the ionization and recombination rates are examined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 114–119, November–December, 1987.     

“Bunched” model of corona discharge in a gas-dynamical flow

In the present paper, a theoretical model of corona discharge is proposed for the case when electric charge transport is implemented by means of the motion of discrete charged bunches of finite dimensions. A system of equations and boundary conditions is formulated for the study of unsteady cyclic processes in a corona discharge. The electric field induced by the space charge of bunches and the presence of an external electric circuit are taken into account. A solution of the formulated system of equations for corona discharge with spherical geometry is obtained. The integrated (current-voltage) characteristics and the amplitude-frequency characteristics of the corona discharge are found. The proposed theory is generalized to the case of a corona discharge in a moving gas. The unsteady characteristics of corona discharge with spherical geometry for gas motion in a radial direction are found.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 153–160, January–February, 1986.The authors wish to express their gratitude to V. A. Likhter and V. I. Shul'gin for their useful discussions and valuable observations.     

Electric characteristics of a probe in a subsonic plasma flow

Lam [1] and Su [2] have formulated and given some results of the solution to the problem of the concentration distributions of the charged particles and electric field in a weakly ionized plasma that flows past a conducting body (an electric probe) under the condition that the Reynolds number of the oncoming flow is high. In the present paper, this problem is solved by the method of exterior and interior asymptotic expansions with respect to a small parameter [3]. The form of the current-voltage characteristics of the probe is found as a function of the determining parameters of the problem. Data of an experimental verification of the obtained results for the case of a cold probe in a flowing air plasma containing added potassium are given.     

Effect of the wall on the ionic saturation current of a cylindrical probe

The hydrodynamic theory of electrostatic probes in a weakly ionized gas has been developed considerably (for example, [1–5]). However, the results obtained relate to cases of a single probe in the form of a plane, a sphere, or a cylinder. Only recently have investigations been made of such questions as the effect of the walls bounding a plasma on the characteristics of a probe, edge effects, etc. [6, 7], which is explained by the considerable difficulties in the solution of problems with sharply changing values along the boundaries, which includes also the problem of a probe in a dense plasma. In the present article it is shown that the investigation of three-dimensional and edge effects can be considerably simplified if we consider limiting conditions of the saturation currents. The article gives the results of a numerical solution of the problem of a cylinderical probe around a wall.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 182–185, September–October, 1976.     

Plasma density and electeic field strength distributions at a boundary with an electrode

Close to the cathode in an arc discharge, or to the surface of a probe operating on the ionic branch of its characteristic, conditions are obtained under which the Langmuir layer freely passes ions coming from the plasma, while the reverse ion flow is virtually zero. The plasma density, ion distribution, and electric fieid-strength close to the electrode are found in the present paper. The extrapolated length is evaluated for the plasma density. The absolute value of the electric field strength increases logarithmically at the boundary with the electrode.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 11, No, 2, pp. 4–6, March–April, 1970.     

Determination of the constants of electrochemical reactions and the ion mobility coefficients in weakly conducting liquids from an analysis of the current—voltage characteristics

The problem is considered of the passage of a direct current through a solution of a weak electrolyte in a two-dimensional cell. Allowance is made for the electrochemical reactions of dissociation and reconbination which take place in the electrolyte when the rate of dissociation of the molecules is regarded as dependent on the electric field intensity [1–3]. For electrolytes whose recombination coefficient is of the order of magnitude of the Langevin coefficient, theoretical current—voltage characteristics are given for the limiting cases of large and small values of the characteristic times for the ion concentrations to be changed by electrochemical reactions and the transport of ions by the electric field. A method of determining the dissociation rate, the recombination coefficient, and the ion mobility coefficients is proposed on the basis of comparison of the theoretical and experimental current—voltage characteristics.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6. pp. 113–120, November–December, 1984.     

Electrode region of a weakly ionized plasma in chemical equilibrium

The paper is devoted to an analysis of the wall (electrode) region of disturbance of the electric parameters of a weakly ionized plasma, i.e., the region in which the concentrations of the charged particles and the values of the electric field change from the distributions corresponding to the conditions in the undisturbed plasma to the values determined by the boundary conditions on the wall.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 142–153, January–February, 1982.I thank G. A. Lyubimov and G. A. Tirskii for interest in the work and valuable discussions.     

Theory of plasma acceleration in electric and magnetic fields

The problem of the acceleration of a plasma in crossed electric and magnetic fields under the simplest physical conditions suitable for comparison with experiment is considered. Analytical expressions are obtained for the velocity of the electrons, the value of the resonance acceleration zone, and the increment of the potential of the accelerated plasma.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 14–17, November–December, 1972.     

Effect of an electric field on the nitrogen oxide emission and structure of a laminar propane diffusion flame

The effect of an electric field E on the structure and nitrogen oxide NO_x emission of an individual laminar propane diffusion flame is experimentally investigated. The current-voltage characteristics of the flame, its deformation, the fuel-air ratio and the NO_x emission are determined for positive and negative burner polarities. A reduction in NO_x emission (up to 30% with respect to the emission index) is demonstrated in the case of negative burner polarity. A cause-and-effect relationship between the processes in the flame is proposed: the presence in the flame of positively charged ions and soot particles; the motion of the ions in the E field and the onset of an induced electrohydrodynamic flow directed towards the negatively charged burner; the retention and increase in the concentration of soot particles in the lower region of the flame, which leads to an increase in soot particle radiation and hence to a decrease in the temperature of the flame front and a corresponding reduction in NO_x emission. The electrohydrodynamic aspects of the problem are subjected to a qualitative analysis.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 13–23, March–April, 1995.     

The influence of radiation on the temperature profile of an induced discharge in argon at atmospheric pressure

This study presents a quantitative evaluation of the influence of radiation upon the parameters of a long induced discharge in argon at atmospheric pressure. Radiation heat transfer in the optically transparent tin plasma layers with thickness of the order of several centimeters) and reabsorption spectral intervals is examined. Experimental error produced by inaccurate knowledge of the transfer and optical characteristics of the plasma is evaluated. The effect of convection on radial temperature profile is evaluated.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiztki, No. 6, pp. 35–43, November–December, 1971.     

Effect of surface and volume ionization on the electrode potential drop

We consider the change in the potential of the electric field in the free fall layer at the electrodes as a function of the characteristics of the surface and the volume ionization. Systematic calculations are made of the electrode potential drop for a tungsten cathode and anode in a lithium and cesium plasma. The potential of the electric field is obtained as a function of the plasma pressure, the degree of volume ionization, the electron temperature, the electrode temperature, and the current density.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 137–139, July–August, 1970.     

Investigation of the aerothermochemical process in a fixed-bed catalytic reactor

The transport processes in a fixed-bed catalytic reactor are investigated numerically with allowance for the interaction of the thermal and hydrodynamic effects. The problem is solved in the two-dimensional formulation over the entire interval of laminar viscous gas flow. The effect of voidage nonuniformities near the wall on the aerodynamic, temperature and concentration patterns is studied. The possible coexistence of different heterogeneous catalysis regimes over the cross section of the apparatus, depending on the gas dynamic and thermophysical parameters, is demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 116–123, March–April, 1991.     

Theory of the temperature relaxation of an electron-ion plasma in a high-frequency electric and constant magnetic field

The effective collision frequency of electrons and ions which leads to temperature equalization in a plasma in a constant magnetic field and a weak high-frequency electric field when the gyroscopic radius of the electrons is less than the Debye screening radius is determined. The corresponding values of the relaxation time are determined over a wide range of values of the ratio between the electron and ion temperatures, over a wide range of values of the magnetic and electric fields, and also as a function of the frequency of the external electric field.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 41–48, November–December, 1970.     

Ion distribution function at the boundary with an electrode

The ion distribution function is found in the case in which the Langmuir layer freely passes the ions incident from the plasma while the reverse ion flux is zero. These conditions are realized near the cathode in an arc discharge and at the surface of a probe operating on the ion branch of the characteristic. The electric field outside the Langmuir layer is assumed small. We obtain the connection between ion current and plasma density at the boundary with the electrode, the expressions for the ion mean kinetic energy and for the mean energy removed from the plasma by the ion, which differ markedly from the corresponding expressions in the Maxwellian distribution case.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 10, No. 3, pp. 47–54, May–June, 1969.     

Investigation of electrogasdynamic jet behind a source of charged particles

We have investigated theoretically and experimentally a submerged jet emerging from a source of charged particles (corona-producing system). Simplest scaling laws are established for the distribution of the electric parameters in a unipolarly charged gas jet in the case of grounded and insulated sources. It is shown that the current from a grounded source and the floating potential to which an insulated system is charged depend strongly on the ambient conditions. Methods of decreasing the floating potential were investiated experimentally. The distributions of the local electric parameters in the jet were measured using a probe method. The propagation of viscous unipolarly-charged jets and the phenomenon of electric wind formation were investigated in [1, 2] and [2–5], respectively. The distinguishing features of the flows considered in the article consisted of their organization (blowing of a jet of uncharged gas over the corona-producing system), absence of walls to limit the flow, and the weak influence of electrostatic forces on the gas motion. The developed setup has made it possible to simulate the processes of accumulation of electric charge on a body as a result of the escape of a jet stream.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 3–13, September–October, 1971.In conclusion, the authors thank G. M. Bam-Zelikovich for useful discussions.     

The boundary layers of a fully ionized two-temperature plasma with given component temperatures at an electrode

The flow of a plasma with different component temperatures in the boundary layers at the electrodes of an MHD channel is investigated without any assumptions as to self-similarity. For the calculation of the electron temperature, the full energy equation for an electron gas [1] is solved with allowance for the estimates given in [2]. In contrast to [3, 4], the calculation includes the change in temperature of electrons and ions along the channel caused by the collective transport of energy, the work done by the partial pressure forces, and the Joule heating and the energy exchange between the components. The problem of the boundary layers in the flow of a two-temperature, partially ionized plasma past an electrode is solved in simplified form by the local similarity method in [5–7]. In these papers, either the Kerrebrock equation is used [5, 6] or the collective terms are omitted from the electron energy equation [7].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 3–10, September–October, 1972.The author thanks V. V. Gogosov and A. E. Yakubenko for interest in this work.     

Thermoconcentration convection under uniform lateral heating

The fine structure of thermoconvective flow near an inclined- plane heat source within a fluid with a stable density stratification due to salinity gradient is investigated using optical and probe techniques. The time dependence of the parameters of optical refraction coefficient gradient, specific electric conductivity, velocity and temperature fields is determined for different values of the heat source inclination angle. The difference in the spatial scales of variation of the different variables is demonstrated. The Nusselt numbers range from 1.8 to 5.4 for the structures under the plate and from 1.8 to 10.6 for the structures above the plate for Rayleigh numbers on the range from 2·10⁵ to 2·10⁶.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 112–124, September–October, 1995.     

Investigation of transport processes in the high-temperature boundary layer on an ablating graphite surface

A study is made of the transport processes in the boundary layer on a graphite surface in a stream of dissociated air. The diffusion and sublimation ablation regimes of the grahite are considered. In contrast to earlier investigations [1, 3], allowance is made for a larger number of components in the boundary layer, the multicomponent nature of the diffusion, and the disequilibrium of the chemical reactions in the gas phase. On the basis of a critical analysis of the experimental and theoretical investigations of the intermolecular interaction potentials, a model is chosen that makes it possible to calculate the transport properties of gas mixtures containing ablation products with satisfactory accuracy. The results of the numerical investigation of the problem were used to obtain the dependences of the characteristics of heat and mass transfer on the stagnation parameters of the oncoming flow and the temperature of the surface. The influence of the extent to which the chemical reactions are in disequilibrium on these characteristics is estimated. The results of the calculations are presented in the form of approximation formulas. The method of numerical solution is described elsewhere [4, 5].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 97–103, May–June, 1983.     

The influence of the hall effect on the current structure in a plasma flow with a spatially periodic magnetic field

The structure of the electric fields and current is studied for stationary plasma flow in an axially symmetric, spatially periodic magnetic field. The problem is solved in the magnetohydrodynamic approximation with allowance for the Hall term in the generalized Ohm's law equation. It is assumed that the magnetic Reynolds number and the interaction parameter are small.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 11–16, September–October, 1972.The author thanks N. A. Khizhnyak and A. A. Kalmykov for useful discussions.