Volume 91, №2
INFLUENCE OF SORET EFFECT ON REDISTRIBUTION OF ALLOYING ELEMENTS BETWEEN THE COATING AND SUBSTRATE UNDER CONDITIONS OF EXTERNAL HEATING
An analytical solution has been obtained for a conjugate problem on redistribution of alloying elements between a coating and a substrate with account for the Soret effect caused by a temperature gradient under conditions of external heating and of the difference between the thermophysical and diffusional properties of conjugate layers. It is shown that the Soret effect can accelerate the diffusion of elements between the coating and substrate (when the thermal diffusion coeffi cient of a coating element is higher than that in the substrate) and retard it (in the opposite case), as well as lead to the leakage of the diffusant from the coating surface deep into the material.
Author: M. V. Chepak-Gizbrekht and A. G. Knyazeva
Keywords: diffusion, Soret effect, surface heating, interface between layers, operational method, asymptotic expansion
DETERMINATION OF THE TEMPERATURE DEPENDENCE OF HEAT CAPACITY FOR SOME MOLECULAR CRYSTALS OF NITRO COMPOUNDS
An analysis of the existing approximations used for describing the dependence of heat capacity at a constant volume on the temperature of a molecular crystal has been carried out. It is shown that the considered Debye and Einstein approximations do not enable one to adequately describe the dependence of heat capacity at a constant volume on the temperature of the molecular crystals of nitro compounds. This inference requires the development of special approximations that would describe both low-frequency and high-frequency parts of the vibrational spectra of molecular crystals. This work presents a universal dependence allowing one to describe the dependence of heat capacity at a constant volume on temperature for a number of molecular crystals of nitro compounds.
Author: Yu. M. Kovalev and V. F. Kuropatenko
Keywords: equation of state, molecular crystal, Helmholtz energy, Planck constant, Boltzmann constant, Debye approximation, Einstein approximation
INTERACTION OF A GAS FLOW CARRYING NONSPHERICAL MICROPARTICLES WITH A CROSS CYLINDER
A model of the dynamics of the particles-spheroids carried by a gas fl ow over a cross cylindrical body and rebounding from it has been developed. In this model, the gas fl ow around the particles is assumed to be viscous, and the reverse action of the particles on the gas and the collisions between them are not taken into account. The coeffi cients of recovery of the velocity components of the particles rebounded from the cylinder were determined on the basis of the heuristic theory in which the physical and mechanical properties of colliding bodies are considered. The infl uence of the ratio between the axes of particles-spheroids on the coeffi cient of wetting of the cylinder by them, the distributions of the mass-fl ow density of the particles and their velocity components over the cylinder surface, and the spatial distribution of the indicated quantities of the rotating particles rebounded from the cylinder was investigated numerically. The model proposed can be used for estimating the action of ice microcrystals and particles of volcanic ash emissions and dust storms on the structural elements of aircraft engines and small-size fl ying vehicles.
Author: I. A. Amelyushkin and A. L. Stasenko
Keywords: spheroid, eccentricity, recovery coeffi cient, mass-fl ow density, ice crystals
HIGH-VISCOSITY OIL FILTRATION IN THE POOL UNDER THERMAL ACTION
We have developed a mathematical model and constructed numerical solutions of the problem of heating a highviscosity oil pool through one horizontal well or a system of wells and have shown the possibility of their further operation until the limiting profi table discharge of oil is attained. The expenditure of heat in heating the oil pool, the evolution of discharge of oil, and the mass of extracted oil over the considered period have been considered.
Author: V. Sh. Shagapov, Yu. A. Yumagulova, and A. A. Gizzatullina
Keywords: high-viscosity oil, oil pool heating, oil filtration
MODELING OF THE TEMPERATURE FIELD RECOVERY IN THE OIL POOL
This paper considers the problem on mathematical modeling of the temperature fi eld recovery in the oil pool upon termination of injection of water into the pool. The problem is broken down into two stages: injection of water and temperature and pressure recovery upon termination of injection. A review of the existing mathematical models is presented, analytical solutions for a number of cases have been constructed, and a comparison of the analytical solutions of different models has been made. In the general form, the expression has been obtained that permits determining the temperature change in the oil pool upon termination of injection of water (recovery of the temperature fi eld).
Author: I. L. Khabibullin, A. Ya. Davtetbaev, D. F. Mar′in, and A. A. Khisamov
Keywords: mathematical modeling, oil pool, fi ltration, temperature distribution, termination of injection, temperature fi eld recovery
MATHEMATICAL SIMULATION OF THE PROCESS OF AEROBIC TREATMENT OF WASTEWATER UNDER CONDITIONS OF DIFFUSION AND MASS TRANSFER PERTURBATIONS
A mathematical model of the process of aerobic treatment of wastewater has been refi ned. It takes into account the interaction of bacteria, as well as of organic and biologically nonoxidizing substances under conditions of diffusion and mass transfer perturbations. An algorithm of the solution of the corresponding nonlinear perturbed problem of convection–diffusion–mass transfer type has been constructed, with a computer experiment carried out based on it. The infl uence of the concentration of oxygen and of activated sludge on the quality of treatment is shown. Within the framework of the model suggested, a possibility of automated control of the process of deposition of impurities in a biological fi lter depending on the initial parameters of the water medium is suggested.
Author: A. Ya. Bomba and A. P. Safonik
Keywords: aerobic treatment, wastewater, organic and biologically nonoxidizing substance, diffusion and mass transfer perturbations
DETERMINATION OF THE FLOW FIELD IN THE PROPELLANT TANK OF A ROCKET ENGINE ON COMPLETION OF THE MISSION
In the present work, a method of mathematical simulation is employed to describe processes occurring in the specimens of new equipment and using the remaining propellant in rocket-engine tanks. Within the framework of certain turbulence models, the authors perform a calculation of the fl ow fi eld in the volume of the tank of the launch-vehicle stage when a hot gas jet is injected into it. A vortex fl ow structure is revealed; the characteristics of heat transfer for different angles of injection of the jet are determined. The obtained correlation Nu = Nu(Re) satisfactorily describes experimental data.
Author: A. V. Fedorov, I. A. Bedarev, S. A. Lavruk, V. I. Trushlyakov, and V. Yu. Kudentsov
Keywords: spent vehicle stages, physicomathematical simulation, heat transfer
INTEGRAL MODEL OF NOISE OF AN ENGINE-PROPELLER POWER PLANT
A semiempirical model is proposed for estimation of the noise levels produced by aircraft piston power plants in the far acoustic fi eld, which takes account of the main sources of noise. The acoustic fi eld is considered as a superposition of fi elds formed by the radiations from a propeller and a piston engine. For calculation estimation of the levels of tonal noise of the propeller, it is proposed that a semiempirical method developed by the authors earlier be used. To determine the levels of vortex propeller noise which is presumably dominant in the broad-band noise of tractor propellers, it is proposed that one analytical model of trailing-edge noise be used. An empirical model of noise is proposed for calculation of the acoustic characteristics of a piston engine. Good agreement is shown between calculated and experimental data on the noise of power plants with tractor propellers. The data have been derived in acoustic testing of light aircraft of the An-2, Yak-18T, MAI-223M, and F30 type under static conditions at the aviabase of the Moscow Aviation Institute. Lines of further research are formulated for improvement of this procedure and expansion of the fi eld of its application
Author: P. A. Moshkov and V. F. Samokhin
Keywords: propeller, noise of a propeller, noise of a piston engine, noise of a power plant, aeroacoustics, noise of an aircraft, noise of an unmanned fl ying vehicle
EXPERIMENTAL AND COMPUTATIONAL MODELING OF THE PROCESSES OF SUPERSONIC OUTFLOW FROM A HALF-CLOSED CHANNEL
This article is devoted to the investigation of the thermo-gas-dynamic processes in half-closed channels, into which air is fed through holes focused on the axis. We have investigated the infl uence of the size of holes, their arrangement, and the orientation of jets fl owing out through them, as well as of the settling chamber pressure on the pressure at various points of the channel wall and on the fi elds of fl ow parameters (the fi eld of Mach numbers and the pressure and temperature fi elds). Experimental investigations were accompanied by numerical 2D and 3D calculations.
Author: V. M. Abashev, I. N. Eremkin, N. P. Zhivotov, V. P. Zamuraev, A. P. Kalinina, P. K. Tret′tyakov, and A. V. Tupikin
Keywords: supersonic flow, half-closed channel, cold and hot jets, experiment, computational modeling, Euler equation, temperature distribution
AERODYNAMIC RESISTANCE OF A BALL-TUBE MILL DURING TRANSPORT OF A POLYDISPERSE COAL GAS SUSPENSION
Analysis of experimental data on aerodynamic resistance of a ball-tube mill is given. It is shown that this resistance has two components brought about by the pressure losses resulting from the injection of dust particles into the main fl ow after coal grinding and from the transport of homogeneous gas suspension fl ow. A dimensionless equation has been obtained for the dependence of the pressure loss in flow of a homogeneous dust–air mixture on Reynolds number. Functional dependences of the mean-square velocity of the fl oating of coal particles and of their average diameter on the polydispersity parameters of coal dust have been found. An empirical dependence of pressure loss due to the injection of a polydisperse coal gas suspension into the main fl ow on the average velocity of fl oating of coal particles, their average size, and on the size of the mill has been obtained.
Author: S. D. Ivanov, A. N. Kudryashov, and V. V. Oshchepkov
Keywords: ball-tube mill, aerodynamic resistance, gas suspension, coal dust, grinding, floating velocity, pressure loss
MATHEMATICAL MODEL OF TRANSFER AND DEPOSITION OF FINELY DISPERSED PARTICLES IN A TURBULENT FLOW OF EMULSIONS AND SUSPENSIONS
The problem of modeling turbulent transfer of fi nely dispersed particles in liquids has been considered. An approach is used where the transport of particles is represented in the form of a variety of the diffusion process with the coeffi cient of turbulent transfer to the wall. Differential equations of transfer are written for different cases, and a solution of the cell model is obtained for calculating the effi ciency of separation in a channel. Based on the theory of turbulent transfer of particles and of the boundary layer model, an expression has been obtained for calculating the rate of turbulent deposition of fi nely dispersed particles. The application of this expression in determining the effi ciency of physical coagulation of emulsions in different channels and on the surface of chaotic packings is shown.
Author: A. G. Laptev and M. M. Basharov
Keywords: mass transfer of particles, turbulent diffusion, structure of fl ow, cellular model, physical coagulation
HYDRAULIC RESISTANCE TO A WATER FLOW IN TUBES WITH TWISTED RIBBED STRIPS
Results of experimental investigations of the hydraulic resistance to a water fl ow in tubes with twisted ribbed strips are presented. Ribs were positioned discretely on the surface of these strips at an angle to their axis. The strips were turned through 180o with a relative twist of 2.5 and 4. The ribs had a height of 0.5–1.5 mm and were positioned with a step of 40–120 mm. The angle of positioning of ribs relative to the axis of a strip was varied from 40 to 50o . General relations for calculating the hydraulic-resistance coeffi cient of the indicated tubes at Re = 8000–100,000 have been obtained.
Author: A. A. Giniyatullin, S. É. Tarasevich, and A. B. Yakovlev
Keywords: hydraulic resistance, swirling flow, twisted ribbed strip
NUMERICAL SIMULATION OF THE INTERACTION OF AN AIR SHOCK WAVE WITH A SURFACE GAS–DUST LAYER
Within the framework of the one-velocity and multivelocity models of a dust-laden gas with the use of the Godunov method with a linearized Riemann solver, the problem of the interaction of a shock wave with a dust-laden gas layer located along a solid plane surface has been studied
Author: V. S. Surov
Keywords: dust-laden gas, hyperbolic models of gas suspension, Godunov′s method, mathematical simulation
EXACT SOLUTION OF THE TWO-DIMENSIONAL PROBLEM ON AN IMPACT IDEAL-LIQUID JET
The two-dimensional problem on the collision of a potential ideal-liquid jet, outfl owing from a reservoir through a nozzle, with an infi nite plane obstacle was considered for the case where the distance between the nozzle exit section and the obstacle is fi nite. An exact solution of this problem has been found using methods of the complex-variable function theory. Simple analytical expressions for the complex velocity of the liquid, its fl ow rate, and the force of action of the jet on the obstacle have been obtained. The velocity distributions of the liquid at the nozzle exit section, in the region of spreading of the jet, and at the obstacle have been constructed for different distances between the nozzle exit section and the obstacle. Analytical expressions for the thickness of the boundary layer and the Nusselt number at the point of stagnation of the jet have been obtained. A number of distributions of the local friction coeffi cient and the Nusselt number of the indicated jet are presented.
Author: V. D. Belik
Keywords: impact jet, obstacle, exact solution, two-dimensional problem, boundary layer, friction coeffi cient, Nusselt number
MICROWAVE HEATING OF A LIQUID STABLY FLOWING IN A CIRCULAR CHANNEL UNDER THE CONDITIONS OF NONSTATIONARY RADIATIVE-CONVECTIVE HEAT TRANSFER
A class of nonlinear problems of nonstationary radiative-convective heat transfer under the microwave action with a small penetration depth is considered in a stabilized coolant fl ow in a circular channel. The solutions to these problems are obtained, using asymptotic procedures at the stages of nonstationary and stationary convective heat transfer on the heat-radiating channel surface. The nonstationary and stationary stages of the solution are matched, using the "longitudinal coordinate–time" characteristic. The approximate solutions constructed on such principles correlate reliably with the exact ones at the limiting values of the operation parameters, as well as with numerical and experimental data of other researchers. An important advantage of these solutions is that they allow the determination of the main regularities of the microwave and thermal radiation infl uence on convective heat transfer in a channel even before performing cumbersome calculations. It is shown that, irrespective of the heat exchange regime (nonstationary or stationary), the Nusselt number decreases and the rate of the surface temperature change increases with increase in the intensity of thermal action.
Author: V. V. Salomatov, E. M. Puzyrev, and A. V. Salomatov
Keywords: microwave radiation, heat radiation, nonstationary heat transfer, stationary heat transfer, round channel, stabilized fl ow, radiative-convective heat transfer, Nusselt number, Stark number
ON APPLICATION OF THE OSTWALD–DE WAELE MODEL TO DESCRIPTION OF NON-NEWTONIAN FLUID FLOW IN THE NIP OF COUNTER-ROTATING ROLL
The accuracy of the Ostwald–de Waele model in solving the problem of roll fl ow has been assessed by comparing with the "reference" solution for an Ellis fl uid. As a result of the analysis, it has been shown that the model based on a power-law equation leads to substantial distortions of the fl ow pattern
Author: V. M. Shapovalov
Keywords: mathematical modeling, non-Newtonian fl uid, rolls, Ostwald–de Waele model, Ellis model, pressure, shear stress, velocity
SUPPRESSION OF THE THERMAL DECOMPOSITION REACTION OF FOREST COMBUSTIBLE MATERIALS IN LARGE-AREA FIRES
Experimental investigations on the characteristic time of suppression of the thermal decomposition reaction of typical forest combustible materials (aspen twigs, birch leaves, spruce needles, pine chips, and a mixture of these materials) and the volume of water required for this purpose have been performed for model fi re hotbeds of different areas: SFCM = 0.0003–0.007 m2 and SFCM = 0.045–0.245 m2 . In the experiments, aerosol water fl ows with droplets of size 0.01–0.25 mm were used for the spraying of model fi re hotbeds, and the density of spraying was 0.02 L/(m2 ·s). It was established that the characteristics of suppression of a fi re by an aerosol water fl ow are mainly determined by the sizes of the droplets in this fl ow. Prognostic estimates of changes in the dispersivity of a droplet cloud, formed from large (as large as 0.5 L) "drops" (water agglomerates) thrown down from a height, have been made. It is shown that these changes can infl uence the conditions and characteristics of suppression of a forest fi re. Dependences, allowing one to forecast the characteristics of suppression of the thermal decomposition of forest combustible materials with the use of large water agglomerates thrown down from an aircraft and aerosol clouds formed from these agglomerates in the process of their movement to the earth, are presented
Author: R. S. Volkov, A. O. Zhdanova, G. V. Kuznetsov, and P. A. Strizhak
Keywords: forest combustible materials, thermal decomposition, hotbed of fi re, aerosol fl ow, water mass
EXPERIMENTAL ASSESSMENT OF THE MASS OF ASH RESIDUE DURING THE BURNING OF DROPLETS OF A COMPOSITE LIQUID FUEL
An experimental study has been made of the regularities of burning of single droplets of typical compositions of a composite liquid fuel during the heating by an air fl ow with a varied temperature (600–900 K). As the basic components of the compositions of the composite liquid fuel, use was made of the: waste of processing (fi lter cakes) of bituminous coals of ranks K, C, and T, waste motor, turbine, and transformer oils, process mixture of mazut and oil, heavy crude, and plasticizer. The weight fraction of a liquid combustible component (petroleum) product) ranged within 0–15%. Consideration has been given to droplets of a composite liquid fuel with dimensions (radius) of 0.5 to 2 mm. Conditions of low-temperature initiation of combustion to ensure a minimum possible mass of solid incombustible residue have been determined. Petroleum products have been singled out whose addition to the composition of the composite liquid fuel tends to increase the ash mass (compared to the corresponding composition without a liquid combustible component). Approximation dependences have been obtained which permit predicting the infl uence of the concentration of the liquid petroleum product as part of the composite liquid fuel on the ash-residue mass
Author: D. O. Glushkov, A. V. Zakharevich, P. A. Strizhak, and S. V. Syrodoi
Keywords: composite liquid fuel, coal-processing waste, waste petroleum products, low-temperature ignition, ash
SOLUTION OF A NONLINEAR HEAT CONDUCTION EQUATION FOR A CURVILINEAR REGION WITH DIRICHLET CONDITIONS BY THE FAST-EXPANSION METHOD
The analytical solution of the nonlinear heat conduction problem for a curvilinear region is obtained with the use of the fast-expansion method together with the method of extension of boundaries and pointwise technique of computing Fourier coeffi cients
Author: A. D. Chernyshov
Keywords: nonlinear heat conduction equation, curvilinear region, fast-expansion method, analytical solution
INTEGRAL METHOD OF BOUNDARY CHARACTERISTICS: NEUMANN CONDITION
A new algorithm, based on systems of identical equalities with integral and differential boundary characteristics, is proposed for solving boundary-value problems on the heat conduction in bodies canonical in shape at a Neumann boundary condition. Results of a numerical analysis of the accuracy of solving heat-conduction problems with variable boundary conditions with the use of this algorithm are presented. The solutions obtained with it can be considered as exact because their errors comprise hundredths and ten-thousandths of a persent for a wide range of change in the parameters of a problem
Author: V. A. Kot
Keywords: heat-conduction equation, integral method of heat balance, thermal-disturbance front
NUMERICAL INVESTIGATION OF THE THERMAL REGIME OF UNDERGROUND CHANNEL HEAT PIPELINES UNDER FLOODING CONDITIONS WITH THE USE OF A CONDUCTIVE-CONVECTIVE HEAT TRANSFER MODEL
This paper presents the results of numerical analysis of thermal regimes and heat losses of underground channel heating systems under fl ooding conditions with the use of a convective-conductive heat transfer model with the example of the confi guration of the heat pipeline widely used in the Russian Federation — a nonpassage ferroconcrete channel (crawlway) and pipelines insulated with mineral wool and a protective covering layer. It has been shown that convective motion of water in the channel cavity of the heat pipeline under fl ooding conditions has no marked effect on the intensifi cation of heat losses. It has been established that for the case under consideration, heat losses of the heat pipeline under fl ooding conditions increase from 0.75 to 52.39% due to the sharp increase in the effective thermal characteristics of the covering layer and the heat insulator caused by their moistening
Author: V. Yu. Polovnikov
Keywords: heating system, heat losses, heat line, insulator humidifi cation, fl ooding
DECREASING THE THERMAL LOAD ON THE ENVIRONMENT WITH THE HELP OF THERMAL PUMPS IN THE SEWAGE TREATMENT SYSTEM
We propose designs for practical use of residual heat of sewage by means of thermal-pump transformation of thermal energy in plants operating on inverse Rankine and Lorentz cycles, as well as a method for sewage heat removal in drainage canals of water removal systems based on the application of double-pipe heat exchangers known as Field tubes.
Author: V. V. Lozovetskii, V. V. Lebedev, V. M. Cherkina, and M. S. Ivanchuk
Keywords: sewage, thermal-pump transformation of heat, Rankine and Lorentz cycles, double-pipe heat exchangers, Field tubes, sewage heat recovery, power-and-heat supply
ENGINEERING ANALYSIS OF THERMAL-LOAD COMPONENTS IN THE PROCESS OF HEATING OF PET PREFORMS
The infl uence of thermal-load components (convection, collimated and uncollimated components of infrared radiation) in the process of production of PET packaging on the heating of PET preforms has been assessed. It has been established that the collimated component of infrared radiation ensures most (up to 70%) of the thermal energy in the process of heating of a PET preform
Author: D. É. Sidorov, A. E. Kolosov, I. A. Kazak, and A. V. Pogorelyi
Keywords: polyethylene therephthalate, preform, convection, thermal load
IMPROVEMENT OF THE PROCESSES OF LIQUID-PHASE EPITAXIAL GROWTH OF NANOHETEROEPITAXIAL STRUCTURES
We have revealed the shortcomings of equipment and technological approaches in growing nanoheteroepitaxial structures with quantum dots by liquid-phase epitaxy. We have developed and fabricated a new vertical barreltype cassette for growing quantum dots and epitaxial layers of various thicknesses in one technological process. A physico-mathematical simulation has been carried out of the processes of liquid-phase epitaxial growth of quantumdimensional structures with the use of the program product SolidWorks (FlowSimulation program). Analysis has revealed the presence of negative factors infl uencing the growth process of the above structures. The mathematical model has been optimized, and the equipment has been modernized without additional experiments and measurements. The fl ow dynamics of the process gas in the reactor at various fl ow rates has been investigated. A method for tuning the thermal equipment has been developed. The calculated and experimental temperature distributions in the process of growing structures with high reproducibility are in good agreement, which confi rms the validity of the modernization made.
Author: I. I. Maronchuk, D. D. Sanikovich, P. V. Potapkov, and A. A. Vel′chenko
Keywords: liquid-phase epitaxy, pulsed cooling, nanoheteroepitaxial structures, quantum dots, germanium, silicon, substrate, surface, solar cell
EXPERIMENTAL INVESTIGATION OF THE THERMOPHYSICAL PROPERTIES OF TIO2/PROPYLENE GLYCOL–WATER NANOFLUIDS FOR HEAT-TRANSFER APPLICATIONS
Nanofl uids have been prepared by dispersing TiO2 nanoparticles in 70:30% (by weight) water–propylene glycol mixture. The thermal conductivity and viscosity were found experimentally at various temperatures with the volume concentrations 0.1–0.8%. The results indicate that the thermal conductivity of the nanofl uids increases with the volume concentration and temperature. Similarly, the viscosity of the nanofl uids increases with the volume concentration but decreases with increase in the temperature. Correlations have been proposed for estimating the thermal conductivity and viscosity of the nanofl uids. The potential heat transfer benefi ts of their use in laminar and turbulent fl ow conditions has been explained.
Author: М. Leena and S. Srinivasan
Keywords: TiO2 nanofl uids, thermal conductivity enhancement, viscosity, density, volume concentration
EXPERIMENTAL STUDY AND A MATHEMATICAL MODEL OF THE PROCESSES IN FROZEN SOIL UNDER A RESERVOIR WITH A HOT HEAT-TRANSFER AGENT
On an experimental setup, the authors have measured temperature fi elds in frozen soil during the fi lling of a reservoir with hot heat-transfer agent (oil), and also the change in the shape and position of the front of ice melting (isotherms T = 0o C) with time. The approximate solution of a two-dimensional Stefan problem on thawing of frozen soil has been given; it has been shown that satisfactory agreement with experimental results can only be obtained with account taken of the convective transfer of heat due to the water motion in the region of thawed soil
Author: A. A. Kislitsyn, U. Yu. Shastunova, and Yu. F. Yanbikova
Keywords: Stefan problem, convective transfer of heat, hot reservoir, temperature fi eld, thawing front, frozen soil
INFLUENCE OF THE KINETICS OF HEAT AND MASS TRANSFER IN A BINARY-RECTIFICATION COLUMN ON THE REALIZABILITY RANGE OF ITS REGIMES
The range of realizable rates of fl ows in a binary-rectifi cation column in which heat is supplied into the boiler and is removed from the dephlegmator was investigated. It is shown that this range is determined by two characteristic parameters related to the kinetics of heat and mass transfer in the column and the composition of the mixture subjected to separation. The limiting capabilities of a cascade of two binary-rectifi cation columns for the separation of a ternary mixture in it were considered. The conditions for an optimum sequence of separation of a mixture in this cascade and for a consistent arrangement of its heat and mass exchange surfaces and the relation between the ultimate production rate of the cascade and the total heat losses in it were determined.
Author: M. A. Zaeva, A.M. Tsirlin, and I. A. Sukin
Keywords: rectifi cation, heat and mass exchange, separation, multicomponent mixture
NANOSECOND SURFACE MICRODISCHARGES IN MULTILAYER STRUCTURES
Multilayer structures in which nanosecond surface microdischarges are generated have been developed, fabricated, and investigated. In these structures, layers are made in the form of thin transparent fi lms, and a plasma discharge channel is formed in thin spacings between the layers. Passage of the discharge channel from one layer into the neighboring layer is implemented via pre-fabricated microholes. Images of microdischarges were obtained which confi rmed that their plasma channels are formed according to the route assigned by the holes. The route may follow a fairly complex scheme and have self-intersection points and portions in which the electrons are bound to move in opposition to the electric fi eld. In studying the shape of channels in multilayer strictures, the authors have found a new physical effect which lies in the azimuthal self-orientation of the discharge channel as it passes from one microhole to another
Author: A. E. Dubinov and V. A. Lyubimtseva
Keywords: Multilayer structures in which nanosecond surface microdischarges are generated have been developed, fabricated, and investigated. In these structures, layers are made in the form of thin transparent fi lms, and a plasma discharge channel is formed in thin spacings between the layers. Passage of the discharge channel from one layer into the neighboring layer is implemented via pre-fabricated microholes. Images of microdischarges were obtained which confi rmed that their plasma channels are formed according to the route assigned by the holes. The route may follow a fairly complex scheme and have self-intersection points and portions in which the electrons are bound to move in opposition to the electric fi eld. In studying the shape of channels in multilayer strictures, the authors have found a new physical effect which lies in the azimuthal self-orientation of the discharge channel as it passes from one microhole to another
DYNAMIC STABILITY OF A CYLINDRICAL SHELL STIFFENED WITH A CYLINDER AND LONGITUDINAL DIAPHRAGMS AT EXTERNAL PRESSURE
A study has been made of the dynamic stability of a cylindrical orthotropic shell stiffened with a hollow cylinder and inhomogeneous longitudinal diaphragms under the action of axial forces and pulsating external pressure. The infl uence of the cylinder and diaphragms on the stability of the shell was taken account of in the form of elastic foundations whose moduli of subgrade reaction are determined from the equations of a three-dimensional theory of elasticity and the Timoshenko model respectively. A solution to the equation of motion of the shell has been found in the form of a trigonometric circumferential-coordinate series. To construct the principal region of instability of the shell, a binomial approximation was used in the obtained Mathieu–Hill equations. As a result, the problem was reduced to a system of two algebraic equations for normal displacement of the shell at diaphragm installation sites. For uniformly spaced identical diaphragms, a solution has been obtained in explicit form. The dependences of the principal region of instability of the shell on the number and rigidity of the diaphragms have been determined at different radii of the cylinder channel.
Author: V. N. Bakulin, E. V. Danilkin, and A. Ya. Nedbai
Keywords: dynamic stability, stiffened cylindrical shell, modulus of subgrade reaction, three-dimensional elasticity theory
ELECTROTHERMAL ACTION OF THE PULSE OF THE CURRENT OF A SHORT ARTIFICIAL-LIGHTNING STROKE ON TEST SPECIMENS OF WIRES AND CABLES OF ELECTRIC POWER OBJECTS
The authors have given results of investigations of the electrothermal action of aperiodic pulses of temporal shape 10/350 μs of the current of a short artifi cial-lightning stroke on test specimens of electric wires and cables with copper and aluminum cores and sheaths with polyvinylchloride and polyethylene insulations of power circuits of industrial electric power objects. It has been shown that the thermal stability of such wires and cables is determined by the action integral of the indicated current pulse. The authors have found the maximum permissible and critical densities of this pulse in copper and aluminum current-carrying parts of the wires and cables. High-current experiments conducted under high-voltage laboratory conditions on a unique generator of 10/350 μs pulses of an artifi cial-lightning current with amplitude–time parameters normalized according to the existing requirements of international and national standards and with tolerances on them have confi rmed the reliability of the proposed calculated estimate for thermal lightning resistance of cabling and wiring products.
Author: M. I. Baranov and S. V. Rudakov
Keywords: pulse current, short-stroke lightning, wires, cables, industrial electric power objects, thermal lightning resistance
FEATURES OF EXTRUSION PROCESSING OF ULTRAHIGH MOLECULAR WEIGHT POLYETHYLENE. EXPERIMENT AND THEORY
Experimental studies have been made of the permissible regimes of processing ultrahigh molecular weight polyethylene GUR 2122 with molecular mass of 4.5 million g/moles in a laboratory extruder with an auger diameter 32 mm and a ratio L/D = 20 at temperatures of 155–165o C. On the basis of rotational viscometry, the rheological properties of the melt are described. A mathematical model and a numerical method for calculating the motion of ultrahigh molecular weight polyethylene melt in the auger and in the moulding rigging are proposed. The velocity and stress fi elds have been determined
Author: O. I. Skul′skii and E. V. Slavnov
Keywords: ultrahigh molecular weight polyethylene, extrusion, mathematical model, fi nite element method, velocities, stresses, working points