K. L. Stepanov

Thermodynamic and optical properties of gases in a wide range of parameters

Abstract This work describes calculational methods and the results of systematic calculations of the thermodynamic properties, composition, spectral and mean absorption coefficients for air, water, silicon dioxide and the atmosphere of Mars (0.965 CO 2 + 0.035 N 2 ). The range of the considered temperatures from 0.1 to 10 3 eV includes the molecular state of the substances, dissociative gas, low temperature plasma and multicharge plasma. The selected density range ϱ = 10 −9 -10 −2 g cm −3 includes the most interesting states for applications. The main mechanisms which determine the absorption coefficients of gases and plasma (inverse bremsstrahlung; photoionization from the ground and excited states of particles; photodissociation of molecules; photoionization from internal particle shells; electronic-vibrational transitions in molecules; line absorption by atoms and ions) were taken into account. Absorption coefficients were determined for photon energies e = 3 × 10 −2 -10 4 eV.

Bank of optical and physical characteristics for solving problems of radiative plasma dynamics

A bank of data on the thermophysical and optical properties of the plasma of a number of elements and their mixtures is presented, which is the basis for simulating the problems of radiative plasma dynamics. For a substance in the state of thermodynamic equilibrium, this bank contains information on the equations of state, thermodynamic functions, shock adiabatics, and also spectral, group, and mean absorption coefficients. In the state of shock-radiative equilibrium, using a radiational-collisional model, the steady states of an optically transparent plasma and its spectral and integral radiative losses are determined, and evaluations of the role of self-radiation reabsorption are given. The rates of the processes of ionization and recombination in an unsteady plasma are discussed.

Radiation of Strong Shock Waves in Air: Part II

This paper is a continuation of [1], in which the structure of a radiating shock wave propagating in air with real thermodynamic and optical properties at an altitude ofH ≤ 50 km with a velocity ofD = 10–50 km/s is studied. A converging iteration process is constructed that enables one to use the distribution of the gasdynamic parameters and radiant fluxes along the mean optical variable, found in the first part of the paper ([1 ]), to determine the structure of radiating strong shock waves and the spectral and integral characteristics of radiation generated by a shock wave.

Databank on thermodynamic and optical properties of plasma

Methods of evaluation of thermodynamic and optical properties of multicomponent gases within a wide range of conditions are discussed. A databank on component composition, thermodynamic functions, spectral and group absorption coefficients, and Planck and Rosseland mean free paths of radiation for plasmas of air, water, silicon dioxide, and the Martian atmosphere (0.965 CO2+0.035 N2) is composed based on calculations.

The effect of electron density on the kinetics of fullerene formation in carbon plasma

The influence of the carbon cluster charge on their coagulation kinetics has been studied. The equations of kinetics have been solved and it is established that allowance for the cluster charging leads to an increase in the rate of fullerene formation under otherwise equal conditions. In connection with this, the role of minor impurities with a low ionization potential in carbon-containing plasma is discussed.

Determination of the Local Parameters of a Cascade‐Arc Plasma by the Profiles of the Lines in the Radiation Spectrum

The transverse distribution of the plasma temperature in the positive column of a d.c. cascade arc in argon at atmospheric pressure has been measured. The measurements have been carried out by the conventional method involving the determination of the emissivity of plasma as well as directly from the radiation spectrum of the arc without recourse to the Abelian inversion. A theoretical and model justification of the applicability of the second method is given. The results of the determination of the temperature profile in the observation direction by the width and shift of the ArI 425.9‐nm line selected for the diagnostics are presented. An analysis of the data obtained supports the possibility of determining the temperature of an inhomogeneous, optically thin plasma from the profiles of lines in the emission spectrum.

LINE RADIATION SPECTRA OF INHOMOGENEOUS FLUCTUATING PLASMA VOLUMES

The influence of spatial inhomogeneity and temporal fluctuations of the parameters of equilibrium plasma on the intensity and shape of the lines in the spectrum of its radiation was investigated. A closed mathematical model based on the solution of the radiation transfer equation, which describes the formation of the emission spectrum of the plasma volume with given characteristics, has been constructed. A semianalytical approximation that permits adequate description of the line radiation spectra of optically transparent plasma has been developed. The laws of formation of the line radiation spectra of inhomogeneous fluctuating plasma volumes and the relations relating the characteristics of these spectra to the emissivity and local parameters of the plasma have been found. For the presentation of the results, we have chosen atmospheric‐pressure argon plasma.

Integral transfer of radiation of the actual spectrum in problems of radiative plasmadynamics

Radiative energy transfer in plasma is investigated with account for its actual optical properties. Consideration is based on the spectrum-integral method of partial characteristics. Databanks on integral partial characteristics of a number of substances are composed on the basis of data on optical properties that include the molecular state of matter, weakly ionized plasma, and plasma with multicharge ions and the main processes that determine absorption of thermal radiation (bound-bound, free-free, and bound-free transitions in molecules, atoms, and ions). Calculations of plasma radiation by this method are compared with results of spectral description. Some generalizations of the given method for solving problems of radiative plasmadynamics are considered.

Radiant Heat Transfer in Propagation of Nonlinear Waves in a Plasma. Integral Approximation for a Real Spectrum

Using the spectrum‐integral method of partial characteristics, we investigated radiative transfer of energy in a plasma, taking into account the actual optical properties of the plasma. The method is based on the representation of the plasma radiation flux (in the case of a plane layer) or its intensity (for an arbitrary geometry) in terms of the spectrum‐integral quantities. Usually an assumption on continuous (linear or parabolic) distribution of thermodynamic parameters of the plasma between the points of radiation generation and of its observation is used. This approximation provides a good description of radiation transfer in a plasma with small gradients of the parameters. In the case of a sharp change in the plasma parameters due to the propagation of nonlinear waves in it, the method of partial characteristics is generalized by introducing discontinuity solutions into consideration. Results are given confirming the high efficiency of the approach described.

Radiation of strong shock waves propagating in the earth’s atmosphere

Radiation of a strong shock wave propagating in air at heights H ≤ 50 km with velocity D=20–50 km/sec is investigated. From the solution of a self-consistent radiation-gasdynamic problem with real thermodynamic and optical properties of air the distributions of gasdynamic parameters and radiant fluxes in the heating region ahead of the front and in the relaxation zone behind a viscous shock are obtained. The characteristics of radiation generated by the shock wave and going to “infinity” are determined. Calculations of integral and spectral radiation fluxes on the earth’s surface at different stages of the motion of a large asteroid in the atmosphere are given.