Vol 56, No 5 (2018)

The excitation rate constants of the lower excited states of inert gas atoms by electron impact in the gas-discharge plasma are determined with taking into account the self-consistent character of this process and the rates of similar processes in the plasma of alkali metals. The rate constants of the stepwise ionization in a uniform gas-discharge plasma of inert gases are determined. They are also determined in a nonunifom plasma if the nonuniformity is a result of the passage of a gas-discharge current. Based on the rates of these processes, the populations of lower excited levels are calculated in the case where the equilibrium in the gas-discharge plasma of inert gases is determined by inelastic collisions of electrons with atoms.

An analytical solution is obtained for the linearized problem on the behavior of collisionless nondegenerate electron plasma in a layer located in an external alternating electric field. It is assumed that the electrons are mirror-reflected from the plasma boundary. The expansion of the solution in eigenfunctions of the corresponding characteristic system is established. The value of the absorption of the electric field energy in the layer is calculated. A case in which the frequency of the external field is close to the plasma frequency is investigated. It is shown that oscillations are observed in the dependence of the absorption on the frequency at frequencies above that of the plasma. These oscillations are associated with the excitation of plasma oscillations in the layer.

In the context of the development of the IVTANTHERMO information and reference system, heat capacity equations have been derived for solid and liquid stoichiometric uranium dioxide in the temperature ranges of 298.15–3130 K and 3130–8000 K, respectively, on the basis of an analysis of experimental data available in the literature. The appearance of new experimental data on the UO₂ enthalpy and heat capacity up to 8000 K made it necessary to recalculate the temperature dependences of the heat capacity. The refined values of thermodynamic functions (heat capacities, entropy, enthalpy increments, and the reduced Gibbs energy) obtained by numerical integration of these equations in a range of 100–8000 K have been entered into the IVTANTHERMO database.

X-ray diffraction studies of boron carbide В₁₃С₂ crystals were performed within a temperature range of 25–700°C. The thermal expansion coefficeint of boron carbide В₁₃С₂ crystals was determined. The temperature dependence of the thermal expansion coefficient was established to have a kink in the temperature region of 420–465°C. The change of thermal expansion anisotropy was revealed. The results of X-ray diffraction indirectly confirm the literature data on the existence of a phase transition in boron carbide in the region of 439–444°C.

A technique for measuring the specific heat of conducting substances (metals, zirconium carbide and nitride, and graphite) in conditions of pulsed heating with a microsecond current pulse at a constant and increasing pressure is considered. The reliability of the detection of a steep increase in specific heat before melting, which is presumably associated with the emergence of Frenkel defects, is shown. An estimate of the errors in the measurements of the specific heat is given.

We used the impulse-temporal method to measure the speed of sound in NaCl–NaBr, NaCl–NaI, and NaBr–NaI binary molten mixtures with respect to temperature and composition. Using the literature data on density, we calculated the adiabatic compressibility of these systems. We obtained the negative deviations of the speed of sound and the positive deviations for the compressibility from the additive values; the deviation values depend on the size ratio of the mixed anions.

The separated flows taking place in different-geometry diffusers and in a high velocity inlet have been studied by the Reynolds Averaged Navier-Stokes–Implicit Large Eddy Simulation (RANS/ILES) method. The presented modified method makes it possible to increase the computation accuracy of separated areas and attached boundary layers. The flows in a model inlet of mixed compression with a rectangle cross section are calculated for incoming flow Mach number of 5.9 on a grid with 4.13 × 10⁶ cells, beginning with a mode without throttling and finishing with buzz mode. The boundary where the inlet becomes unstable, if throttling is increased, is determined. The relationship of the pressure on time at the upper wall of the inlet isolator channel for all modes, including the buzz mode, is compared with the experimental one. The correlation between inlet throttling and buzz frequency is revealed. The performance curve is determined. The experimental and calculated results are in good agreement for all available experimental parameters for the examined inlet. The presented method demonstrates higher accuracy with respect to the calculations performed by the LES method on the fine grid of the examined inlet.

The three-dimensional problem of conjugate heat and mass transfer upon the motion of a spherically blunted cone at various angles of attack along a set trajectory is theoretically explored. Thermal protection materials, including carbon materials with high heat-conducting properties, conventional carbon fiber-reinforced plastic coatings, and promising nondestructible ceramic materials, are analyzed. It is shown that the application of the latter makes it possible to preserve the initial geometry of the body and to attain a considerable temperature decrease in the coating surface upon the development of new materials with high thermal conductivity.

A model has been developed for the formation of a porous layer of nanoparticles (nanolayers) on the surface of a heater during the boiling of a nanofluid. From a practical point of view, the properties and the process of the formation of a nanolayer on the heater surface are of interest. Modification of the heating surfaces in power equipment via the formation of a porous layer on them is more promising than the use of a nanofluid as a coolant. The study of the formation of a nanolayer during boiling provides insight into its properties and aids in the study of its effect on heat transfer during boiling and boiling crisis. The main goal of theoretical simulation at this stage is to obtain a calculation expression to calculate the time of the formation of a layer of a certain thickness on the surface.

In this paper, we analyze the hydrogen combustion and heat transfer in the combustion chamber in an oxygen environment with forced cooling of the combustion chamber. We simulated the combustion of a previously unmixed mixture of fuel and oxidizer with allowance for dissociation processes. The main parameters and composition of the combustion products are determined for different geometric dimensions of the combustion chamber and the excess oxidant coefficients. An increase in the internal diameter and length of the combustion chamber with an unchanged hydrogen consumption is shown to lead to a reduction in the actual underburning. In this case, the actual underburning is significant due to the dissociation of combustion products at high temperatures. The effect of oxidizer excess on underburning and the temperature of combustion products is studied.

The propagation of acoustic waves in gas mixtures with vapor, monodisperse drops, and solid particles of various materials and sizes has been studied. A mathematical model is presented; the dispersion relation, the equilibrium and frozen speeds of sound, and low- and high-frequency asymptotes for the linear attenuation coefficient are deduced; the dispersion curves are calculated. The influence of particle size and disperse phase parameters on dissipation and dispersion of acoustic waves is analyzed for a mixture of air with vapor, water drops, and aluminum and carbon black particles. Fast Fourier transform is used to calculate the pulse perturbations in the studied media.

Various methods are considered for the production of useful electric and thermal energy based the use of a steam–hydrogen mixture with parameters corresponding to the parameters upon the exit of hydrothermal oxidation of aluminum from an experimental reactor developed earlier at the Joint Institute for High Temperatures of the Russian Academy of Sciences. The appropriate types of basic power-generating equipment that operate on hydrogen are chosen. The main thermodynamic parameters of the schemes of thermal power plants are analyzed, and their thermodynamic efficiency is determined.

The appearance of modern sources and detectors of terahertz radiation (10¹¹–10¹³ Hz) stimulated the rapid development of practical applications for radiation in this frequency range. Therefore, the question of the safety of terahertz radiation for living objects was sharply raised. In this review, we present an analysis of research on this issue published from 2010 to the present. A brief description of the most significant works performed before 2010 is given. Particular attention is paid to the sources of terahertz radiation used in the studies and the results of experimental work on the study of possible bioeffects when such radiation is applied to both individual cell lines and microorganisms and animals generally.

We present the experimental results on thermograms and plots of temperature distributions along the streamer and spark discharges in a high-frequency capacitive field between solid and liquid electrodes for different electrode geometries.

We have studied the thermal diffusivity and thermal conductivity of Bi_{1 –x}Gd_xFeO₃ multiferroics within the high temperature range of 300–1200 K. We consider the dominant mechanisms of the heat transfer of phonons within the domain of ferroelectric and antiferromagnetic phase transitions and determine the temperature dependence of the mean free path of the phonons.

Heterogeneous nucleation in extended states of liquid argon with a solid particle is studied with molecular dynamics methods. The rupture strength of cavitation in the liquid is determined as a function of the energy of interaction between molecules of liquid and those of solid inclusion. The influence of solid particle sizes on the nucleation process is explored.