Regimes of gasification of lean coal layers

Based on a generalized volume-average model, the regimes of filtration combustion in gasification of lean coal layers, which are of interest for evaluation of the parameters and realization of underground gasification of brown Belarusian coals, have been analyzed. The existence of two basic regimes — those of cocurrent and countercurrent gasification waves — has been established. Data on the characteristics of the regimes and the conditions of their existence have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 2, pp. 56–61, March–April, 2006.     

Methane-to-hydrogen conversion in the filtration-combustion wave of rich methane-air mixtures

The superadiabatic-effect-based process of noncatalytic conversion of methane to a hydrogenous synthesis gas in a cocurrent filtration-combustion wave has been considered. The influence of the composition and specific flow rate of the working mixture on the basic parameters of conversion — the maximum temperature in the filtration-combustion wave, the wave’s propagation velocity, and the composition of the reaction products — has been investigated. Filtration-combustion regimes optimum from the viewpoint of the most efficient conversion of methane to a hydrogenous synthesis gas have been found from the experimental data obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 90–95, March–April, 2007.     

Simulation of the turbulent mixing of a passive impurity in a jet mixer

Results of numerical simulation of the mixing of a turbulent jet with a cocurrent incompressible-fluid flow (Schmidt number Sc ≈ 1000) in a cylindrical channel of circular cross section (axisymmetric mixer) with the use of the standard k-ε turbulence model and different models for the averaged value of the mixture fraction and its variance have been given. For the problem of mixing of an inert passive impurity, two regimes of flow — the regime with the formation of a recirculation zone and that without its formation — have been considered. The formulated statistical model has been verified with the use of experimental data and results of calculation by large-eddy simulation. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 666–681, July–August, 2008.     

Analysis of the process of mixing of a passive impurity in a jet mixer

The experimental results for two regimes of mixing of a passive impurity in an axisymmetric jet mixer — the mixing of a turbulent jet and a cocurrent flow to form a recirculation zone behind the nozzle and an analogous mixing without the formation of a recirculation zone (Re_d = 10,000) — have been presented. The velocity field has been measured in the mixer cross sections at different distances from the nozzle (0.1 < x/D < 9.1) with a one-component Doppler laser anemometer, whereas the scalar field (concentration of the passive impurity) has been diagnosed by the laser-induced fluorescence method. Based on the scalar distributions obtained, the autocorrelation function and the integral scale have been computed, the form of the probability density function has been restored, and the distributions of the asymmetry and excess coefficients have been constructed. Visualization of flow in the mixer has been carried out. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 46–59, March–April, 2007.     

Testing of numerical methods,convective schemes,algorithms for approximation of flows,and grid structures by the example of a supersonic flow in a step-shaped channel with the use of the CFX and fluent packages

An unsteady supersonic flow of a nonviscous gas with a Mach number M = 3 in a step-shaped channel has been calculated. The accuracy of the forecasts made has been analyzed on the basis of the Roe dissipation model and the advective upwind splitting method with the use of convective schemes of the second and third orders of accuracy and algorithms for approximation of flows. Triangular and polyhedral grids have been tested. The mechanism of formation of an artificial physical instability on grid structures with a local-gradient adaptation has been considered. It is shown that the existence of a singular point — a right corner — in the computational region causes a large phase change in the evolution of the flow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 326–330, March–April, 2009.     

Rheological behavior of oils in a magnetic field

The influence of magnetic treatment parameters on the rheological properties of oils has been investigated. It has been noted that the strongest effect on these properties is produced by the regime of magnetic treatment — steady-state or flowing, the volume rate of oil flow, and the induction value of the magnetoactivator magnetic field. The optimal regimes of magnetic treatment have been determined. It has been shown that treatment of oil with a magnetic field promotes a decrease in the solidification temperature and the amount of asphalt-resin deposits. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 102–109, January–February, 2006.     

Influence of the concentration of a dispersed phase and of the magnetic field on the attenuation of ultrasonic waves in magnetic fluids

The regularities of the propagation of elastic waves of ultrasonic range in magnetic fluids have been experimentally established. The influence of relaxation processes — nonlocal heat exchange and viscous dissipation — on the coefficient of attenuation of sound has been revealed and a comparison to the existing theoretical data has been made. The dependences (anisotropic in form) of the attenuation of the wave’s amplitude on the value and direction of the magnetic field have been determined and an interpretation of the results obtained has been proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 133–140, September–October, 2007.     

New composite sorbents of water and ammonia for chemical and adsorption heat pumps

New sorbents of water and ammonia — “salt in porous matrix” composites and “salt on fiber” composites — have been reviewed. The possibility of “constructing” the sorption properties of the composites at the nanophase level by varying their composition, the size of the host-matrix pores, and synthesis conditions has been shown. The application of the new materials in adsorption refrigerating devices has been considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 160–175, November–December, 2006.     

Partially crystallized elastomer as a nanocomposite model

Data on the influence of crystallization on the mechanical properties of elastomers — the elastic modulus, the relaxation properties, in particular, restorability in compression, and the tensile strength — have been generalized. These data have been compared to those on the influence of active fillers and a much higher crystallization efficiency has been shown. The size of single crystals has been evaluated for most crystallizable rubbers. It has been inferred that the nanosize of single crystals of elastomers and their direct bond with the elastomer matrix influence the mechanical properties of elastomer materials. In considering a partially crystallized elastomer as a nanocomposite model, one can formulate requirements imposed on efficient nanofillers for elastomer materials. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 19–23, September–October, 2005.     

Simulation of the supersonic turbulent flow around a cylinder with coaxial disks

The turbulent axisymmetric flow around a stepped body — a cylinder with coaxial front and rear disks — has been calculated with the aid of a VP2/3 package based on multiblock computational technologies and the generalized procedure of pressure correction. The computational model has been tested with the example of a supersonic flow around a sphere. The numerical forecasts made with the use of Spalart–Allmares shear stress transfer and eddy viscosity transfer models have been compared with the data of the aeroballistic experiment, wind tunnel tests, and the results of the calculation of the flow around the disk–cylinder arrangement by a simplified zonal model in a wide range of variation of the incident flow Mach number (from 1.5 to 4). We have obtained a good agreement between the calculated transverse flow density distributions in the front stalling zone and those determined from the interferograms for the wave-drag-rational disk–cylinder arrangement. The influence of the rear disk on the drag of the disk–cylinder–disk arrangement has been estimated.     

Modeling of the sorption deformation of glassy polymer sorbents in interaction with gases in a high-pressure region

Based on the phenomenological-thermodynamics method, a model of sorption deformation of a glassy polymer sorbent — polycarbonate — in interaction with carbon dioxide in a high-pressure region has been proposed. The possibility of describing sorption equilibrium for this system has been analyzed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 175–179, September–October, 2006.     

Gas flow through a porous heat-releasing medium with allowance for the temperature dependence of gas viscosity

The gas flow through a porous heat-releasing medium is considered. It has been noted that account for the temperature dependence of the gas viscosity strongly influences the solution: the gas flow rate markedly decreases and a stronger heating occurs. Analysis of the flow of a gas with a temperature-dependent viscosity by the Sutherland formula has revealed two steady-state cooling regimes — stable and unstable ones. It has been shown that the possibility of the steady-state regime is determined not only by the problem parameters but by the initial conditions as well. The transient process from the state of rest in the absence of heat release to the state of the regime of induced filtration upon instantaneous switching-on of heat input is described. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 35–40, January–February, 2006.     

Influence of Optical and Thermophysical Characteristics of Biological Tissue on Its Thermal Conditions Under Laser Irradiation

On the basis of the developed analytical method of solving the heat conduction equation in a multicomponent biological tissue, its thermal conditions under laser irradiation have been investigated. Quantitative data on the temperature fields under a wide variation of the optical and thermophysical parameters in the tissue in the 400– 700-nm range of wavelengths are given. The steady-state regime of the field in the tissue at various depths has been investigated. Estimates of the possible use of the time dependence of temperature under tissue cooling to solve the inverse problem — determine the heat-conductivity coefficient, the parameter of heat exchange with the medium, and the depth attenuation coefficient of light — are given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 15–21, May–June, 2005.     

Rheology of gelating systems

Two different types of physical gels — thermoreversible gels based on ultrahigh-molecular-weight polyethylene and thixotropic ones based on cysteine and silver nitrate — have been investigated using viscosimetric methods. Structural methods (IR and Raman spectroscopy and dynamic light scattering) have been used in interpretation of the rheological data obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 118–122, September–October, 2005.     

A kinetic approach to the rheology of inhomogeneous systems with account for the interaction of disperse-phase particles

By measuring the optical characteristics of a flow the rheology of a viscous non-Newtonian fluid — an aqueous solution of hydrolyzed polyacrylonitrile — has been studied. The loss of stability by the system with chaotic fluctuations of transparency has been established. A kinetic model, as well as kinetic equations that describe the flow of heterogeneous systems, have been suggested. It is expected that this approach will be used in calculations in oil-and gas production and filtration of non-Newtonian systems in porous media. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 90–97, November–December, 2006.     

Investigation of cutting forces by the method of statistical planning of the experiment

With the method of mathematical planning, the character and the degree of influence of the parameters of cutting regimes of the corresponding cutting forces in machining steels and alloys differing in physicochemical properties have been investigated. The dependence of the corresponding cutting forces on the change in the cutting regimes has been obtained. The optimum force characteristics have been found experimentally as a result of choosing the most favorable cutting regimes. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 190–195, September–October, 2005.     

Investigation of regimes of thermogravitational convection of a fluid between coaxial semicylinders with a heat-conducting shell in the presence of a local energy source

A numerical analysis has been made of the thermodynamic regimes of natural convection of a Newtonian fluid satisfying the Boussinesq approximation in the gap between coaxial semicylinders with finitely-thick walls in the presence of the heat-release source under the conditions of convective heat exchange with the environment. A mathematical model has been formulated in the dimensionless variables current function–velocity vorticity vector–temperature in polar coordinates. Streamlines and velocity and temperature fields reflecting the influence of the Prandtl number Pr = 0.7 and 7.0, the nonstationarity factor 0 < τ ≤ 300, the dimensions of the energy source, and of the relative thermal conductivity on the flow regimes and heat transfer have been obtained.     

Concerning the filtrational cooling of a heat-releasing granular bed in the presence of a first-order phase transition

Within the framework of a two-temperature approximation, mathematical simulation of the process of filtrational evaporative cooling of a heat-releasing bed is performed. Based on this, an engineering method for calculating the cooling of a granular bed has been developed; it allows one to determine the position and size of the evaporation zone and pressure drops in the system. The conditions for the existence of various regimes of evaporative cooling (the presence of one, two, or three zones of heating and evaporation of a heat carrier) have been obtained in dimensionless form. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 96–104, March–April, 2007.     

Engineering calculation of the characteristics of a filtration-combustion wave based on a one-dimensional two-temperature model

The authors present a method for determining the characteristics of a filtration-combustion wave that uses physically substantiated simplifications of a one-dimensional two-temperature model of filtration flow with Arrhenius kinetics. Explicit, physically transparent dependences for the ignition temperature, wave velocity, and maximum skeleton temperature are obtained. A brief review of and a comparison with other one-dimensional methods and with a numerical calculation are given. This method is shown to be superior to more cumbersome analytical two-temperature methods in accuracy. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 424–432, May–June, 1998.     

Capabilities of the dynamic quartz-resonator method for determining the viscoelastic parameters of thin liquid layers

The capabilities of the dynamic quartz-resonator method for determining the viscoelastic properties of liquids in thin layers (to 1 μm) have been studied. Aqueous solutions of glycerin of different concentrations and motor oils of different manufacturers have been used. The process of polymerization of éD-22 epoxy adhesive in the presence of a hardener — polyethylene polyamine — has been investigated as the model experiment. It has been shown that the broadening of the resonant curve and the shift of the resonant frequency plotted as functions of the thickness of a liquid layer enable one to single out the elastic and viscous components; this makes it possible to judge the change in the structure of boundary layers with processes that may occur at the interphase boundary. __________ Translated From Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, Pp. 193–200, January–February, 2007.