Volume 98, №3

DEVELOPMENT AND METROLOGICAL INVESTIGATIONS OF THE CHARACTERISTICS OF A PRIMARY TRANSDUCER OF MOISTURE OF MATERIALS

The author has proposed a structure of the facility for measuring the moisture of materials, that contains the case, the cover, capacitive electrodes, the measuring resonant circuit, inductance coils, capacitors, the alternating-volt- age source, and the indicator device. Metrological properties have been investigated from the results of the con- ducted experiment within the measurement scale. Here, two capacitive electrodes located at the base of the cylin- drical case were manufactured from copper foil in the form of a "double circle" and were connected, via the switch, in parallel with the reference capacitor and with one adjacent capacitor of the ferroresonant bridge circuit, and the other two adjacent inductance arms of the ferroresonant bridge circuit were manufactured in the form of two aiding-connected coils wound onto the shared core in the form of a toroid. Here, the ferroresonant bridge circuit at the output is connected to the threshold voltage indicator, and at the input, to an a.c. circuit with a frequency of 50 Hz via the autotransformer the handler of whose arm is jointed to the pointer of an arc scale in units of humidity of food and other loose materials.
Author:  Sh. M. Masharipov
Keywords:  moisture of a material, capacitive method, electrode, measuring resonant circuit, inductance coil, alternating-voltage source, indicator device, ferroresonant bridge circuit

EXACT SOLUTIONS OF SOME HEAT AND MASS TRANSFER PROBLEMS IN FISSURED-POROUS MEDIA WITH REFERENCE TO KARST AND THERMOKARST MODELS

Exact solutions of some problems of heat and mass transfer in fissured-porous media with a dissolving or partially melting skeleton are obtained in relation to karst and thermokarst models, as well as an expression for the depth of development of karstified areas of rocks
Author:  M. G. Khramchenkov
Keywords:  fissured porous media, rocks, dissolution, melting, filtration, phase transition, mass exchange, heat and mass transfer, karst, thermokarst, mathematical modeling
Page:  583

ON THE TRANSFER OF INERTIAL PARTICLES UNDER SHARP ACCELERATIONS OF THE MEDIUM

The nonlinear problem on the acceleration of a massive particle picked up by fast flow in a gravity field has been investigated analytically. This problem is of interest, in particular, in connection with hazardous convective phenomena in the lower atmosphere (squally gusts of wind, tornadoes). Heavy particles/objects transferred by intense winds represent one basic factor of hazard associated with such phenomena. Relevant theoretical problems are complicated by the linear dependence of the hydrodynamic resistance on the particle velocity with respect to the medium and have been investigated by numerical methods as a rule. In the work, consideration has been given to the analytical model enabling us to establish certain general regularities of acceleration of particles in nonstationary flows. Emphasis was placed upon situations with short-duration pulse changes in the medium′s velocity
Author:  L. Kh. Ingel′
Keywords:  nonstationary flow, inertial particle, hydrodynamic resistance, acceleration, transfer
Page:  588

INVESTIGATION OF THE FILTRATION OF VISCOUS HYDROCARBON LIQUIDS IN THE PRESENCE OF AN ELECTROMAGNETIC FIELD

An investigation has been made into the characteristic properties of filtration of hydrocarbon fluids (oils) having various physicochemical properties in the presence of low-power electromagnetic fields. A procedure for physical and mathematical modeling of oil filtration in an electromagnetic field is provided. The paper presents the results of experimental investigations indicating the dependence of oil filtration parameters on the content of high-molecular polar components. It is shown that the dielectrophoretic forces acting in a direction perpendicular to the direction of oil filtration change the isolines of pressure distribution in the oil system, which results in a reduction of the oil flow rate in its filtration under the action of an electromagnetic field. The intensity of these forces is the higher, the higher is the content of polar components in the oil and the higher is the strength of the field applied
Author:  R. R. Zinnatullin and A. A. Musin
Keywords:  filtration, electromagnetic action, polar components, dielectric parameters
Page:  593

SIMULATION OF PRESSURE EVOLUTION BETWEEN THE DISTURBING AND LISTENING WELLS IN A LOW-PERMEABLE FORMATION

Based on the previously proposed law of filtration with a limit gradient, the problem of interaction of wells in a low- permeable formation determined by the method of hydraulic listening is solved. The possibility of determining the filtration properties of the formation by the shape of the response curves is established. It is shown that the analysis of such a curve allows one to identify the deviation of the filtration law in the formation from the linear Darcy law
Author:  O. V. Dudareva
Keywords:  ultra-low permeability, nonlinear filtration, limiting pressure gradient, hydraulic listening method, finite difference method
Page:  599

ANALYSIS AND DETERMINATION OF THE OPTIMAL PROCESS PARAMETERS OF ELECTRODIALYSIS PURIFICATION OF SOME CHEMICAL-INDUSTRY SOLUTIONS

The problem of determining the optimal parameters of the process of electrodialysis purification of wastewater generated during the production of printed circuit boards is considered. To increase the completeness of separation, the choice of the maximum current density and the thickness of the diffusion boundary layer in the ionite membrane system is substantiated. The problem is choosing the optimal parameters of the electrodialysis separation process is formulated. An example of calculating the optimal separation parameters for a single-component copper sulfate solution is presented. A graph of the flow region with optimal operating parameters of the electrodialysis unit is constructed depending on the sizes of the membranes
Author:  S. I. Lazarev, K. V. Shestakov, O. V. Dolgova, O. A. Abonosimov, and K. K. Polyanskii
Keywords:  electrodialysis, maximum current density, diffusion layer, purification of industrial solutions
Page:  606

METHOD OF PROCESSING FORMATION PULSE TESTING DATA

A new method is presented for processing data of productive formation pulse testing, based on the use of specially modified pressure recovery functions, with the pressure measured in the observation well of the formation. The functions are constructed by subtracting from real pressure recovery functions the second highest members of the asymptotic series of an integral exponential function representing an exact analytical solution of the diffusivity equation describing the dynamics of pressure variation in the well during formation pulse testing. The performed analysis has shown that the Bourdet derivatives of pressure recovery functions modified by the suggested method are much faster in approaching horizontal asymptotes whose height is used to determine the formation parameters. This allows the use of a time-logarithmic part of the pressure recovery function, with the pressure measured in the formation observation wells, to process formation pulse testing data, which ensures an improvement in the accuracy and validity of determining its parameters. In processing real field pulse test data, modified pressure recovery functions should be constructed by an exhaustive method of searching multipliers before the second members of the asymptotic series with a view to identifying optimum values of these multipliers ensuring the fastest way for the Bourdet derivatives to approach a horizontal asymptote.
Author:  A. M. Svalov
Keywords:  formation, pulse testing, integral exponential function, Bourdet derivatives
Page:  614

FORECASTING TECHNOLOGICAL INDICATORS OF OIL AND GAS CONDENSATE FORMATION DEVELOPMENT BY HORIZONTAL WELLS WITH CRITICAL GAS-FREE PRODUCTION RATE

Based on a three-phase multicomponent filtration model, the possibilities of efficient exploitation of the oil rim of a gas condensate formation by a horizontal well with a gas-free production rate were investigated. It was found that the regime of critical gas-free production rates, as applied to horizontal wells, allows one to avoid a breakthrough of the gas and water cones and, by adjusting the distance between wells and their initial oil flow rates, to significantly increase the final oil recovery factor
Author:  R. R. Nazaraliev and K. S. Mamedov
Keywords:  wells, critical gas-free production rates, gas and water cones, oil rim, gas condensate formation, horizontal wel
Page:  620

ELECTRICAL STABILIZATION OF A CARBON NANOMATERIAL IN AN AQUEOUS SUSPENSION

Consideration has been given to the technique of improving the settling (sedimentation) resistance of an aqueous suspension of a carbon nanomaterial due to electrical stabilization through the impact of a gas electric discharge. It has been shown that the solid-phase charging (and discharging) used enables us to promptly change the state of the suspension and to reduce the treatment time without surfactants. A comparison has been made with the functionalization of the carbon nanomaterial by ozonization by the criterion of energy cost reduction
Author:  S. A. Zhdanok, a, A. V. Krauklis, E. A. Kazei, A. V. Pavlov, and S. V. Shushkov
Keywords:  carbon nanomaterial, nanosize particles, sedimentation, stability of a suspension, electrical stabilization, gas discharge
Page:  626

SYNTHESIS AND OPTICAL CHARACTERIZATION OF POLYANILINE–TIN-OXIDE NANOCOMPOSITES

Polyaniline–tin-oxide nanocomposites have been successfully synthesized by the in situ polymerization method and their optical properties were investigated. It was established that the absorbance and transmittance of these nanocomposites decrease with increase in the amount, of tin-oxide nanoparticles in them and that their reflectance in the UV, VIS, and NIR regions of the electromagnetic spectrum is very low
Author:  L. U. Okafor and A. A. Okafor
Keywords:  polyaniline–tin-oxide nanocomposites, nanoparticles, optical properties
Page:  634

SYNTHESIS AND OPTICAL CHARACTERIZATION OF POLYANILINE–TIN-OXIDE NANOCOMPOSITES

Polyaniline–tin-oxide nanocomposites have been successfully synthesized by the in situ polymerization method and their optical properties were investigated. It was established that the absorbance and transmittance of these nanocomposites decrease with increase in the amount, of tin-oxide nanoparticles in them and that their reflectance in the UV, VIS, and NIR regions of the electromagnetic spectrum is very low
Author:  L. U. Okafor and A. A. Okafor
Keywords:  polyaniline–tin-oxide nanocomposites, nanoparticles, optical properties
Page:  634

INFLUENCE OF THE MACH NUMBER OF FLOW PAST A SPHERICALLY BLUNTED CONE MADE OF COMBINED MATERIALS ON ITS HEAT EXCHANGE CHARACTERISTICS

The influence of the Mach number of a supersonic flow past a spherically blunted cone on the temperature of its surface made of combined materials with high thermal conductivity is investigated. Simple methods for estimating the reduction of maximum temperatures of such a surface are proposed
Author:  V. I. Zinchenko and V. D. Gol'din
Keywords:  supersonic flow, thermal protection, Mach number, conjugate heat exchange
Page:  638

ACCURATE ANALYTICAL SOLUTIONS OF THE VELOCITY PROFILE IN THE BOUNDARY LAYER ON A PLATE (BLASIUS PROBLEM)

A classical problem in the theory of a viscous laminar boundary layer on a flat thin plate (the Blasius problem) is considered. Using the nonlinear least squares method, accurate correlation dependences for the longitudinal velocity have been found, which can be used further in numerical simulation of plane and three-dimensional flows in the boundary layer. A comparison of the calculated and analytical profiles of velocity u with known data is carried out.
Author:  V. M. Zubarev
Keywords:  laminar boundary layer, incompressible Newtonian fluid, thin flat plate, Blasius problem, analytical approximations, nonlinear least squares method
Page:  644

GAS-DYNAMIC FEATURES OF STATIONARY AIR FLOW ADMISSION INTO A CYLINDER THROUGH A POPPET VALVE AND CROSS PROFILED CHANNELS

The paper presents experimental data on velocity fields of a steady flow in the cylinder as it is filled with air through a poppet valve and channels in a cylinder head (CH) with cylinders of various cross section shapes (a circle, a square, and a triangle). The investigations were carried out on a laboratory stand simulating the main elements of the intake system of a reciprocating engine. A steady-state motion in the gas-dynamic system was created using a compressor settling the air from the cylinder. The average air flow velocity in the intake manifold was from 2 to 5 m / s. The investigations into the structure of the flow in the cylinder were carried out using a 2D PIV system. It has been established that the shape of the CH channel cross section has a substantial effect in the air flow distribution in the reciprocating engine cylinder. It is shown that in using a round cannel, there is a flow motion in CH along the side walls and there is virtually no flow in the center of the cylinder. The use of a square channel results in a more uniform filling of the entire cylinder volume with air. The installation of a CH with a triangular channel leads to the formation of a large-scale flow swirl inside the cylinder. The obtained data create a scientific foundation for designing intake systems with improved gas exchange quality indicators and promising characteristics of recipro- cating engines
Author:  L. V. Plotnikov, D. A. Davydov, D. N. Krasil′nikov, and V. A. Shurupov
Keywords:  cylinder admission, cylinder head channel, poppet valve, steady air flow, velocity field, reciprocating engine, PIV method
Page:  655

SINGLE-PRESSURE MODEL OF A MULTIVELOCITY HETEROGENEOUS MEDIUM WITH A GASDYNAMIC KERNEL

A nonconservative model of a shared-pressure multivelocity multicomponent heterogeneous medium with com- pressible and incompressible fractions has been proposed whose differential equations are based on the laws of conservation of mass, momentum, and energy for the entire mixture and its individual components. To exclude the "parasitic" smearing of contact boundaries, the parameter ξ has been introduced into the equations of the mix- ture′s model; it is proposed that this parameter be selected small and nearly zero. The characteristic analysis has been made of the equations of the model and its hyperbolicity has been shown at the parametric values ξ  (0, 1]. In integrating the model′s equations, use has been made of the multidimensional nodal method of characteristics which is based on the splitting of the initial system of equations by coordinate directions into a number of one-di- mensional subsystems, each being solved with the inverse method of characteristics. Using this method, a number of one-dimensional and two-dimensional model problems have been calculated
Author:  V. S. Surov
Keywords:  nonconservative one-parameter model, shared-pressure multivelocity heterogeneous medium, multidimensional nodal method of characteristics
Page:  662

DEPENDENCE OF FLOW BEHAVIOR AND AERODYNAMIC CHARACTERISTICS ON THE SIZE OF SQUARE CYLINDERS IN VEE-ARRANGEMENT

A two-dimensional finite volume method and a full multi-grid technique are used to scrutinize the influence of the arrangement of three cylinders, which are placed in four different configurations, and their corresponding dimensions on the characteristics of flow. Four main combinations are adopted in terms of the cylinder positions while the influence of various parameters, namely, the cylinder with their corresponding dimensions and the Reynolds number (Re) variation on the flow behavior is discussed. The flow patterns, critical Reynolds number, and force coefficients are computed for the four arrangements in terms of streamlines, iso-vortices, and drag coefficient (CD) evolutions. Of great interest is the analysis of the combined effect of the Reynolds number and of the adopted arrangements on the bifurcation emergence phenomenon and the CD evolution profiles. The numerical outcomes demonstrate that Re values, different arrangements of cylinders, and dimension variations of each square cylinder have a prominent influence on the flow characteristics.
Author:  Salwa Fezai, Fakher Oueslati, and Brahim Ben-Beya c
Keywords:  vee-arrangement, size of square obstacle, incompressible fluid flow, Reynolds number, vortex shedding, regimes of flow, aerodynamic forces
Page:  677

THEORETICAL ASPECTS OF CENTRIFUGAL INDUCTION DEPOSITION OF FUNCTIONAL COATINGS

The theoretical aspects of calculating temperature–time parameters for single-layer, multilayer, and thick-layer functional coatings obtained by the method of centrifugal induction surfacing with account for geometric, ther- mophysical, and electrophysical parameters of the workpiece and the layer being applied, and also convective and radiative heating of the outer workpiece surface. A system has been developed for control of the workpiece temperature in the process of centrifugal induction surfacing, and also a mathematical model has been developed for the movement of the melt front in the coating material, differing from the existing models in that the surface tem- perature from which the heat transfer occurs is variable and changes in time according to a linear law. Using this model, we determined the minimum time of coating deposition onto the workpiece making it possible to minimize the negative effect of the thermal impact on the formation of its structure, to raise the technological process pro- ductivity, to reduce energy consumption, and to save nonferrous and high alloys due to a reduction in the allowance for mechanical treatment of the workpiece
Author:  M. A. Belotserkovsky, I. A. Sosnovsky, A. A. Kurilyonok, and V. V. Shkurko
Keywords:  centrifugal induction surfacing, functional coating, mathematical model, heat transfer, melt front, temperature control system
Page:  694

DETERMINATION OF THE PARAMETERS OF NEON PLASMA WITH ACCOUNT FOR COLLISIONS OF CHARGED PARTICLES

Judging by publications dedicated to investigating plasma using probes, investigators are constantly confronted with problems of calculating plasma parameters. There is now a certain tendency to criticize classical methods of diagnostics. True, it should be said that authors criticizing the Langmuir theory and some other methods of diagnostics sometimes do not perform gas-kinetic assessments and do not compare them with the characteristic dimensions of the space-charge layer (SCL) surrounding the probe (a.k.a charge sheath). Certainly, in this case, they very often go beyond the conditions which underlie the theory. The most acute problem of plasma diagnos- tics and determination of its parameters occurs in the case of 1–2 collisions of charged particles taking place in the probe SCL. In such diagnostics, questions arise about the way of determining the temperature of charged particles, about the mass of charged particles, the area of application of techniques and, certainly, about the SCL thickness
Author:  M. A. Gasilov, S. A. Gutzev, N. B. Kosykh, and S. S. Kutcakov
Keywords:  discharge in neon, plasma, probe, space-charge layer (charge sheath), electric field
Page:  707

SYNTHESIS OF TURBOSTRATIC GRAPHENE UNDER THE CONDITIONS OF FLASH PLASMA-CHEMICAL PYROLYSIS OF CARBON-CONTAINING RAW MATERIALS

Consideration has been given to the energy-efficient process of synthesis of graphene with a turbostratic structure via flash plasma-chemical pyrolysis (flash-pyrolysis) from technical carbon and electrode graphite in a pulsed spark discharge with a duration from 20 to 500 ms. A setup is suggested that, compared to the prototype, is distinguished by increased energy efficiency and the possibility to conduct the process in an energy-saving regime due to the use of a condenser battery discharge in the circuit instead of a nonlinear condenser resistor and a diod voltage multiplier. The formation of a graphene structure is confirmed by the Raman spectroscopy (RS) using the intensity peaks in the range of 2424 cm –1 . The yield of turbostratic graphene was determined by the integral characteristics of the attenuated total reflectance of the radiation in the infrared region. The investigations of the carbon product (graphene soot) obtained in the process of flash plasma-chemical synthesis showed a content of turbostratic graphene of up to 15–20 wt.%. The obtained results are substantiated by the methods of RS- and FT-IR spectroscopy and also by the new method of qualitative control of the graphene content using integral transmission coefficients determined with the help of IR-spectroscopy of attenuated total reflectance
Author:  M. Yu. Dolomatov, O. L. Ryzhikov, V. R. Subkankulov, S. S. Vershinin, and V. V. Lazarev
Keywords:  plasma-chemical pyrolysis, turbostratic graphene, modified plasma-chemical flash-pyrolysis plant, IR spectrum, RS spectrum
Page:  713

METHOD FOR DETERMINING THE ENERGY OF IONS FROM THERMAL VISUALIZATION PICTURES OF ION JETS

A method for determining the ion energy from thermal patterns of jets issuing from an ion source is proposed. Thermal experimental studies and numerical modeling are performed for a jet of ionized nitrogen losing energy in a gas target of its own gas. It is shown that the method of thermal visualization of ion jets together with their numerical modeling can be used to obtain the energy level of bombarding ions, which allows determining the magnitude of the thrust. The method can be used in studies of accelerating high-frequency ion engines with an unknown level of accelerating voltage.
Author:  I. S. Vavilov, K. I. Zharikov, P. S. Yachmenev, V. V. Fedyanin, A. I. Luk′yanchik, P. V. Stepen′
Keywords:  accelerating ion microengine, ion-optical system, thermovizualization, numerical modeling, target, ion range
Page:  718

ON THE BURNOUT OF PARTICLES MOVING ON THE GRATE

Within the framework of the combustion model, the main qualitative features of the process of evolution of a fuel particle moving on a grate are determined. The limiting form of the dependence of the particle combustion time on its initial diameter at elevated Damköhler numbers is established. A generalized dependence of the Fourier number on the determining factors is obtained
Author:  Yu. S. Teplitskii, E. A. Pitsukha, V. A. Dubina, and A. R. Roslik
Keywords:  grate, combustion model, fuel particle, combustion time, speed of a particle, kinetic and diffusion regimes, Damköhler number, Fourier number, combustion rate coefficient
Page:  730

MATHEMATICAL AND ALGORITHMIC SUPPORT FOR PROCESSING EXPERIMENTAL DATA OBTAINED BY THE METHOD OF A FLAT PULSE HEAT SOURCE FOR MEASURING THERMOPHYSICAL PROPERTIES OF PLANT TISSUES OF FRUITS AND ROOT CROPS

To study the thermophysical characteristics of plant tissues of fruits and root crops, flat samples of which can be obtained by mechanical cutting methods, a method of a flat pulsed heat source is proposed. A mathematical model of the heat transfer process in a measuring cell is developed, and an algorithm for processing experimental data on the change in temperature difference over time, recorded during the experiment, is proposed. It is proven that the use of the proposed algorithm for processing experimental data allows reducing the errors in measuring thermophysical characteristics.
Author:  P. V. Balabanov, S. S. Baranov, A. G. Divin, A. S. Egorov, S. V. Ponomarev, and G. V. Shishkina
Keywords:  thermal diffusivity coefficient, thermal conductivity, measurement, relative errors, minimization, data processing, optimization
Page:  738

INTENSIFICATION OF A COMPLEX OF THERMOPHYSICAL CHARACTERISTICS OF A HIGH-ENTHALPY THERMALLY DECOMPOSABLE HEAT PROTECTION ON JOULE CONTACT HEATING UNDER HIGH VACUUM CONDITIONS

A method of parametric identification of a set of thermophysical characteristics (specific thermal conductivity, specific heat capacity, integral reflectivity and emissivity) of high-enthalpy thermally decomposable thermal protection under Joule heating in diffusion approximation is proposed. The problem of finding the extremum of the mean-square functional of the residual between the theoretical and experimental temperature fields at the locations of temperature sensors is solved with preliminary specifications of the basis functions that take into account the dependence of the characteristics under consideration on temperature. Optimization of the thermal protection parameters is performed using the conjugate gradient method as the most accurate algorithm of the first order of convergence. For its implementation, three conjugate heat exchange problems are preliminarily solved to determine the sensitivity coefficients necessary to calculate the gradient of the residual functional under study.
Author:  N. O. Borshchev and M. I. Losev
Keywords:  Joule heating, iterative regularization method, conjugate gradient method, Arrhenius equation
Page:  746

INFLUENCE OF ZINC ON THE THERMOPHYSICAL PROPERTIES AND THERMODYNAMIC FUNCTIONS OF LEAD BABBITT B(PbSb15Sn10)

Lead-based babbitt, which has high thermal conductivity and excellent compliance with requirements, is com- monly used by manufacturers in applications for systems that will be subjected to impact loads. Some lead-based babbitt products have a uniform grain structure, so they can be used for heavy loads at low constant speeds. In addition, lead-based babbitt is an economical alloy, therefore it can be used for general-purpose machinery, line shafts, and machine shops. It can also be used in agricultural machinery, cement equipment, conveyors, elevators, and metallurgical equipment. The thermodynamic and thermophysical properties of lead and its alloys are the subject of numerous ex- perimental and theoretical studies. Available experimental data include measurements of heat capacity, enthalpy, entropy, and Gibbs energy at normal pressure in the temperature range 298.15–550 K. The paper presents the results of experimental determination of the heat capacity of lead babbitt B(PbSb15Sn10), alloyed with zinc, and calculation of the temperature dependence of changes in the thermodynamic functions of this al- loy. The studies of the temperature dependence of the heat capacity of lead babbitt B(PbSb15Sn10), alloyed with zinc, were carried out in the "cooling" mode using computer technology and the Sigma Plot 10.0 program. Polynomials of the temperature dependence of the heat capacity and changes in the thermodynamic functions (enthalpy, entropy, and Gibbs energy) of lead babbitt B(PbSb15Sn10), alloyed with zinc, and the standard (Pb grade C00) were established, which with the correlation coefficient Rcor = 0.999 describe these changes. It is shown that with an increase in the zinc content, the heat capacity of the original alloy increases. The enthalpy and entropy of lead babbitt B(PbSb15Sn10), alloyed with zinc, increase with the temperature and zinc content, and the value of the Gibbs energy decreases.
Author:  I. N. Ganiev, M. B. Jumaeva, Kh. M. Khojanazarov, H. O. Odinazoda, and S. U. Khudoyberdizoda
Keywords:  lead babbitt B(PbSb15Sn10), zinc, "cooling" mode, temperature dependence, heat capacity, heat emission coefficient, enthalpy, entropy, Gibbs energy
Page:  757

TEMPERATURE DEPENDENCE OF HEAT CAPACITY AND THERMODYNAMIC FUNCTIONS OF ALUMINUM ALLOY AlMg5.5Li2.1Zr0.15 OF DURALUMIN TYPE ALLOYED WITH PRASEODYMIUM

The specific heat capacity of the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin type with praseodymium was investigated in the "cooling" mode using the known heat capacity of the reference sample of aluminum grade A5. Using the experimentally found values of the rates of cooling alloy samples and a standard, knowing their masses, the polynomials of the temperature dependence of the heat capacity of the alloys were established, which are described by a four-term equation. Using the integrals of the specific heat capacity, the polynomials of the temperature dependence of changes in enthalpy, entropy, and Gibbs energy for the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin with praseodymium type were determined. The obtained dependences show that with increasing temperature, the heat capacity, enthalpy, and entropy of the alloys increase, and the value of the Gibbs energy decreases. An increase in the praseodymium content reduces the heat capacity, heat emission coefficient, enthalpy, and entropy of the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin type.
Author:  I. N. Ganiev, S. U. Khudoyberdizoda, S. S. Savdulloeva, J. H. Jayloev, and Kh. M. Khojanazarov
Keywords:  aluminum alloy AlMg5.5Li2.1Zr0.15 of duralumin type, praseodymium, "cooling" mode, specific heat capacity, heat emission coefficient, thermodynamic functions
Page:  764

TEMPERATURE DEPENDENCE OF HEAT CAPACITY AND THERMODYNAMIC FUNCTIONS OF ALUMINUM ALLOY AlMg5.5Li2.1Zr0.15 OF DURALUMIN TYPE ALLOYED WITH PRASEODYMIUM

The specific heat capacity of the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin type with praseodymium was investigated in the "cooling" mode using the known heat capacity of the reference sample of aluminum grade A5. Using the experimentally found values of the rates of cooling alloy samples and a standard, knowing their masses, the polynomials of the temperature dependence of the heat capacity of the alloys were established, which are described by a four-term equation. Using the integrals of the specific heat capacity, the polynomials of the temperature dependence of changes in enthalpy, entropy, and Gibbs energy for the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin with praseodymium type were determined. The obtained dependences show that with increasing temperature, the heat capacity, enthalpy, and entropy of the alloys increase, and the value of the Gibbs energy decreases. An increase in the praseodymium content reduces the heat capacity, heat emission coefficient, enthalpy, and entropy of the aluminum alloy AlMg5.5Li2.1Zr0.15 of the duralumin type
Author:  I. N. Ganiev, S. U. Khudoyberdizoda, S. S. Savdulloeva, J. H. Jayloev, and Kh. M. Khojanazarov
Keywords:  aluminum alloy AlMg5.5Li2.1Zr0.15 of duralumin type, praseodymium, "cooling" mode, specific heat capacity, heat emission coefficient, thermodynamic functions
Page:  764

OSCILLATIONS OF A THREE-LAYER PLATE CAUSED BY A THERMAL SHOCK AND PULSE LOAD

The effect of thermal shock on forced oscillations caused by a pulse load on a circular three-layer plate is investigated. The plate is asymmetrical in thickness, its lower surface and contour are thermally insulated. The distribution of nonstationary temperature over the plate thickness is calculated using an approximate formula obtained by solving the heat conductivity problem with averaging the thermophysical properties of the materials of the three-layer package. Using Neumann′s hypothesis, forced oscillations from a pulse load are superimposed on free oscillations caused by a thermal shock (an instantaneous drop in a heat flux). The hypothesis of a broken line is used as a kinematic one: the Kirchhoff hypothesis for high-strength thin load-bearing layers; the Timoshenko hypothesis on the rectilinearity and incompressibility of the deformed normal, which rotates by a certain additional angle (shear), for a thicker filler incompressible in thickness. The formulation of the initial-boundary value problem includes partial differential equations of motion obtained by the Lagrange variational method, homogeneous initial conditions, and boundary conditions of the hinged contour of the plate. The sought functions are the defection of the plate, shear in the filler, and the radial displacement of the median plane of the filler. For the analytical solution of the initial-boundary value problem on the oscillations of a three-layer plate under the action of a pulse surface load in a nonstationary temperature field, a system of orthonormal eigenfunctions is constructed. The sought solution is written in series. Calculation formulas for displacements are given. A numerical parametric analysis of the plate deflection depending on the intensity and time of exposure to the heat flux is carried out.
Author:  É. I. Starovoitov, Yu. M. Pleskachevskii, and D. V. Leonenko
Keywords:  circular three-layer plate, heat flux, pulse load, forced oscillations
Page:  779

NONLINEAR PROBLEM ON CONVECTIVE HEAT EXCHANGE: ADVANCED SEMI-ANALYTICAL SOLUTION METHODS (REVIEW AND CRITICAL ANALYSIS)

A review and a critical analysis of modern advanced semi-analytical methods, such as the perturbation method, the homotopy perturbation method, the variational iteration method, the homotopy analysis method, the Taylor series method, the successive differentiation method, the differential transformation method, the Adomian decomposition method, and the optimal homotopy asymptotic method, are presented. These methods were investigated by the example of approximate solving a nonlinear initial-value problem on the convective cooling of a system with lumped parameters and a temperature-dependent heat capacity
Author:  V. A. Kot
Keywords:  nonlinear differential equation, nonlinear initial-value problem, nonlinear convection equations, methods PM, HPM, VIM, HAM, TSM, SDM, DTM, and OHAM
Page:  788

MODELING THE OPTIMUM HEAT REMOVAL IN THE SYSTEM OF COOLING OF SHELL BLADES OF A GAS-TURBINE ENGINE ON THE BASIS OF A DURABILITY CRITERION

The focus of the study is raising the efficiency of heat removal in shell blades of a gas-turbine engine with the internal cooling system. A mathematical heat-removal model has been proposed that allows minimizing the mass flow rate of a cooling liquid due to the implementation of a thermally stressed state in the body of a turbine blade, which satisfies the durability criterion. The model makes it possible to reduce the nonuniformity of distribution of the durability life in the turbine-blade′s body, which results from the nonuniform stressed state and the nonuniform heating on the heat-supply surface of the blade. A mathematical formulation of the problem of the study was based on the equations of heat transfer under the conditions of steady-state heat transfer. A numerical model of calcu- lation of the pattern of coolant velocities and variable width of heat-removal channels was constructed with the finite-difference method. From the results of the study, the authors have analyzed the influence of the turbine-blade speed on the change in the geometry of heat-removal channels, at which a uniform thermally stressed state of the blade is ensured according to the durability criterion. The approach considered in the study may be used in cooling deflector-type blades of a gas-turbine engine. The proposed mathematical model will allow reducing the irrational mass flow rate of the coolant in less heat-loaded portions of the blade, and also raising the intensity of heat removal in more heat-loaded regions
Author:  I. K. Andrianov and E. K. Chepurnova
Keywords:  heat removal, turbine blade, durability, thermally stressed state
Page:  816

KINETICS OF MASS TRANSFER DURING THE ADSORPTION OF IONS OF HEAVY METALS BY NATURAL CLINOPTILOLITE

A mathematical model of mass transfer and diffusion during the adsorption of the ions of heavy metals Pb ²⁺ , Cd ²⁺ , Zn ²⁺ , and Ni ²⁺ from solutions has been developed. The isotherms and kinetic curves of adsorption of the indicated metals by natural clinoptilolite, and also the dependence of the adsorption of these ions on pH of the solution have been determined. It has been established that the process of separation is more intense at pH 6.2–7. The regularities of the influence of the concentration of the adsorptive in the solution on the total mass-transfer coefficient and the effective coefficient of diffusion in it have been determined
Author:  F. V. Yusubov and G. V. Veliyeva
Keywords:  mass transfer, diffusion, heavy metals, adsorption, isotherms, kinetics, mathematical model
Page:  827

A NONREFLECTIVE ELECTROMAGNETIC ABSORBER WITH GRADIENT DISTRIBUTION OVER THE LAYERS OF ABSORBING FILLERS

The conditions have been determined for nonreflective absorption of electromagnetic radiation by a two-layer dielectric–metal system with an exponential distribution of the content of absorbing fillers in the coating layers, which establish a functional relationship between the wavelength of electromagnetic radiation incident on the coat- ing, the complex dielectric constant of the coating layers and the parameter determining the layer-by-layer content of absorbing filers in the coating.
Author:  S. R. Kasimova
Keywords:  electromagnetic wave, nonreflective absorber, dielectric–metal system, coating
Page:  837

DEVELOPING THE TECHNOLOGY FOR MANUFACTURING OHMIC CONTACTS AND SEALING SEMICONDUCTOR TEMPERATURE CONVERTERS

It has been studied and established that the formation of ohmic contacts is one of the final and most important
operations in the technological process of manufacturing semiconductor temperature converters, since the change
in the characteristics of the device and its performance as a whole depend on the quality of the contacts. The
specific resistance of the contact depends exponentially on the ratio of the height of the potential barrier of the
contact to the root of the doping concentration of the region on which the contact is formed. At N > 10 17 cm –3 the
specific contact resistance ρ is determined mainly by tunneling processes and decreases rapidly as the degree of
doping increases. Therefore, to obtain small values of ρ, a high degree of doping or a small barrier height h b is
necessary. When manufacturing ohmic contacts, it should also be taken into account that the height of the energy
barrier h b is very sensitive to heat treatment of the sample before and after spraying
Author:  A. T. Rakhmanov and G. G. Boboev
Keywords:  semiconductor, ohmic contacts, single crystal, doping, specific resistance, silicon, converter, temperature, sputtering
Page:  841

ON THE FUNDAMENTAL AND PLANE WAVE SOLUTIONS OF THE EQUATIONS OF THE LORD–SHULMAN THEORY OF THERMOELASTICITY WITH MICROTEMPERATURES

The work deals with the fundamental solution of the equations of steady oscillations in the Lord–Shulman theory of thermoelasticity with microtemperatures recently proposed by Bazarra et al. (2020). In addition, the propagation of plane harmonic waves in an isotropic infinite thermoelastic medium under the Lord–Shulman theory of thermoelasticity with microtemperatures is studied. A dispersion relation is derived and obtained for three sets of coupled longitudinal waves. Characterizations of the wave profile, like phase velocity, penetration depth, and specific loss are examined numerically
Author:  Satyam Sachan, Roushan Kumar, and Amit Kumar
Keywords:  thermoelasticity, microtemperatures, fundamental solution, plane harmonic wave, Lord–Shulman thermoelasticity theory
Page:  846

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