Том 54, № 5 (2016)

A kinetic model of nonequilibrium chemical processes in gas mixtures of Si, O, H, and Ar and a model of the calculation of the main parameters of plasma facilities for the implementation of the plasma-chemical method of the direct preparation of silicon from quartz in argon–hydrogen gas-plasma flows have been formulated. The criteria and general conditions at which the maximal yield of silicon is achieved were determined. The main mode and construction parameters of plasma facilities were determined. It is shown that at the consumed electrical power of a stationary plasmatron of 100 kW the calculated efficiency of the facility (over vapor Si) could be on the order of 10^–2 g/s.

According to the results of a numerical experiment, we show the possibility of control of the glow discharge parameters and structure by means of creating a supersonic gas flow in the selected section of the interelectrode spacing.

We present the results of investigation of a discharge with a current of 15–200 A between graphite electrodes at argon pressure of 10–90 kPa after long-term specimen heating by the DC at a temperature of about 3 kK. The change in the electrode shape is evidence of the existence of a melt film on the electrode surfaces at the temperature of 3.3–3.5 kK. The anode vaporization velocity is in agreement with the data on the pressure of the saturated vapor of the atomic carbon.

To provide shock-wave experiments with the metrological characteristics of fused quartz applied as a window material, we measure the free surface velocity history and the particle velocity history under dynamic compression in different experimental arrangements. From these measurements, we obtain data on the material compressibility within the tensile stress domain and at elevated temperatures. We show that the anomalous compressibility of the fused quartz takes place not only under compression but also under tension. We measure the elastic compression adiabats within the temperature range from 20 to 340°C.

The behavior of multicomponent mixtures and alloys, including bismuth, under high dynamic loads is described by the thermodynamically equilibrium (TEC) model. For condensed phases, the Mie–Grüneisen-type equation of state with regard to the Grüneisen coefficient depending on temperature is used, and gas in pores is among the main environmental components. The model used makes it possible to calculate the behavior of bismuth and materials based on this element (mixtures and alloys) for pressures higher than 6 GPa in one-velocity and one-temperature approximations on the assumption that the pressure is identical for all phases. The calculation results have been compared with the known experimental data and the model calculations performed by different researchers for porosity values varying from 1 to 3. It has been indicated that the model reliably describes shock loading of solid and porous bismuth as well as multicomponent alloys containing bismuth.

Stepwise heating of a mercury film on graphene with Stone–Wales defects and hydrogenated edges is studied by the molecular dynamics methods at 800 K. Transformation of the film into a drop and its detachment from graphene is observed at a temperature of ∼700 K. The phonon spectra determined by horizontal and vertical atomic vibrations, the mobility coefficients of Hg atoms separated in directions, the density profile and radial distribution function of mercury, the angular distribution of nearest geometrical neighbors, the stress tensor of graphene, and the roughness of a graphene sheet are calculated.

Based on the boiling shock concept, a physical model of discharge from orifices and short nozzles of the flashing liquid with temperatures reaching the critical thermodynamic temperature has been constructed. The mechanism of formation of “daisy-shaped” jets that accompany the discharge modes with the radial jet expansion has been investigated. It has been shown that in the case under consideration the flow separates into two areas not connected with each other, viz., the central core in the vicinity of the flow axis and the peripheral liquid expansion region. The geometry of shock wave formations that occur during discharge of a high-temperature liquid has been studied. Comparison with experimental data shows a good agreement. The effect of a stepwise drop in the reactive force to zero upon onset of discharge modes with a jet radial expantion has been explained.

The effect of a sand protective screen on attenuation of the shock wave reflected from the screen has been studied experimentally and numerically. The measurements are compared with the data on the effect of the screen thickness on the attenuation of the reflected wave.

A new approach to calculate the process of vapor condensation from a gas–vapor mixture based on the superposition method is developed. Analytical parametric analysis of the problem is performed, which makes it possible to determine the influence of the governing parameters. A modification of the phenomenological model, which allows one to perform correct calculations in a previously uninvestigated range of high gas contents, is proposed for the first time. The calculation results, experimental data, and results of numerical computations are compared.

Disperse systems consisting of a liquid and gas bubbles located in it are considered. Two possible versions of evolution of bubbles under the conditions studied are assessed. In simple liquids, contact between two bubbles causes them to merge, as the separating film breaks. In the case of complex organic liquids, amphiphilic film is formed on the surface of bubbles, and the lifetime of bubbles in contact increases with their size. Under an external electric field, chains of bubbles are formed, lined up along the electric field potential lines. The presence of bubbles in liquid greatly lowers the breakdown threshold, as the critical parameters of the breakdown field in liquids are two to three orders of magnitude higher than those in gases at atmospheric pressure. Various breakdown mechanisms in liquids are discussed from the viewpoint of formation of the gas phase during the passage of an electric current through a liquid medium. The character of propagating a streamer in separate bubbles is studied with their random distribution in liquid and in the case of formation of some structures of bubbles; the critical parameters of disperse systems, that can lead to their electrical breakdown, are presented. Along with the general concepts of electrical breakdown in dispersed systems, experimental studies of these processes are considered, and the nature of electrical breakdown in liquid dielectrics, including transformer oil, is discussed.

The development of a fine-dispersed droplet sheet of optimal structure for frameless space lowtemperature heat rejection systems is considered. The possibility of an optimal combination of the thermal capacity rejected by a droplet radiative cooler and the predicted efficiency of the space power unit is substantiated. The dependences of the basic thermal characteristics on the number of droplet planes used have been derived for low- and medium-temperature radiators with an ionic-liquid-based heat carrier.