Volume 94, №3
SELECTIVE MASS TRANSFER OF BORON ISOTOPES IN THE OPTIMAL CASCADES OF STRAIGHT-THROUGH GAS CENTRIFUGES
A method of numerical-analytical optimization of the cascades of straight-through gas centrifuges for separating boron isotopes in the form of trifl uoride BF3 has been developed. As a criterion, the minimum of the total number of gas centrifuges at the given external parameters of the scheme of cascades was adopted. The method is based on the analytical relations obtained for fl ows of stages in the approximation of total feed fl ow minimization. The calculations involve estimates of the effi ciency of separation of boron isotopes in a straight-through centerbody centrifuge that determine the optimal operating regime of the latter. Two schemes of cascades for obtaining BF3 with enrichment by 95% 10B on selection and 0.001% at the dump are considered, which is equivalent to 99.999% enrichment with 11B. It is shown that the optimum total number of centrifuges is the same for both schemes.
Author: V. A. Palkin, S. S. Lubnin, and V. I. Tokmantsev
Keywords: isotope separation, boron isotopes, separation cascade, straight-through centrifuge, optimization
ON THE POTENTIAL OF THE MIE THEORY AND THE SIMULATION APPROACH IN INVESTIGATING SPECTRAL-KINETIC COEFFICIENTS OF ULTRAPOROUS THERMAL PROTECTIVE MATERIALS
Certain capabilities of the original combined statistical simulation mathematical model covering the structure and physical properties of fi brous and reticulated high-temperature materials have been shown. An important element of the model is a "virtual scanner" developed earlier, i.e., a software tool making it possible to investigate the pattern of interaction between electromagnetic radiation and orthogonal representative elements of materials. Free parameters have been described and tests of both the spectral part of the model based on the Mie theory and the joint model, which confi rm their adequacy, have been presented. The behavior of local spectra of transmission, absorption, and scattering of electromagnetic radiation of a number of the existing and hypothetical materials has been studied. In certain reticulated materials, the authors recorded an "order catastrophe" in the absorption spectrum: an abrupt and strong, of several orders of magnitude, change in the spectral absorption coeffi cients, that is not associated with resonance phenomena in absorption. The presence of a fairly wide resonance region was recorded in the transmission spectrum of an amorphous-quartz-based fi brous material and the parameter affecting the location of this region was found.
Author: V. V. Cherepanov and O. M. Alifanov
Keywords: high-temperature porous materials, radiation spectral-kinetic coeffi cients, modeling, phase transitions
MODELING THE PROCESS OF LIQUID FLOW IN THE SYSTEM "FORMATION–PIPELINE"
A model of the process of nonstationary motion of a liquid in the conjugate system "formation–pipeline" has been constructed, and coupled equations have been solved. An analytical expression has been obtained that makes it possible to determine the infl uence of the law of variation in the pressure at the end of the pipeline and in connections to it on the pressure at the wellbore. Numerical calculations have been carried out at different values of the system′s parameters.
Author: É. M. Abbasov and N. A. Agaeva
Keywords: fi ltration, Laplace transformation, motion of a liquid, continuity equation, Volterra integral equation
ON THE THERMAL STATE OF A CONDENSATION HEAT EXCHANGER
Within the framework of a model of a heat-releasing structured granular bed, simulation has been conducted of the heat-transfer processes in a gas-tube heat exchanger in the presence of water vapor condensation in the vapor–gas mixture. A functional dependence of the heat fl ux used for heating water on the geometric and hydraulic parameters of the heat exchanger has been established.
Author: Yu. S. Teplitskii, E. A. Pitsukha, A. R. Roslik, É. K. Buchilko
Keywords: forward (direct) fl ow, counterfl ow, heat exchanger, heat fl ux, water, vapor–gas mixture, condensation
INVESTIGATION INTO THE PYROLYSIS OF MEDICAL WASTE IN A FIXED-BED REACTOR
An experimental investigation has been conducted into the pyrolysis of typical medical waste components in a fi xedbed reactor with a view to obtaining detailed information on the process characteristics. It is shown that the main loss of the mass of the mixture of chlorine-containing medical wastes occurs in two stages. The fi rst stage which fi nishes at a temperature of about 400o C is characterized by the discharge of pyrolysis water and gas which contains hydrogen chlorine. At the second stage, at a temperature from 400 to 500o C, there is a discharge of the main part of volatile substances that are largely made up of pyrolytic oil. An environmentally safe and cost-effective method of solving the problem of medical waste disposal based on its two-stage pyrolysis has been proposed. The method includes the removal of chlorine-containing components from medical waste before the thermal degradation of their organic part, which, in practice, excludes the possibility of formation of highly toxic chlorine-containing substances
Author: V. V. Khaskhachikh, V. F. Kornil′eva, G. Ya. Gerasimov
Keywords: medical waste, pyrolysis, fi xed-bed reactor, chlorine-containing pollutants
IDENTIFYING THE PERMEABILITY FIELD OF A THREE-DIMENSIONAL LAYERED BED WITH ALLOWANCE FOR A PRIORI INFORMATION ON WELLS UNDER STEADY-STATE SINGLE-PHASE FILTRATION CONDITIONS
Consideration is given to the coeffi cient problem on determining the permeability fi eld of a three-dimensional layered bed under the conditions of steady-state single-phase fi ltration of the liquid. This problem is reduced to the problem of minimizing the residual function, which is constructed from the known values of pressure at the wellbore. An algorithm to solve this problem is proposed, whose distinctive feature is allowance for additional a priori information on the identifi ed parameters. It is assumed that the proportionality coeffi cients of permeability of the layers on the wells are known. On the model problem, the solution stability to errors in measurements of pressure at the wellbore is investigated
Author: A. V. Elesin, A. Sh. Kadyrova, and A. I. Nikiforov
Keywords: inverse coeffi cient problem, identifying the permeability fi eld, residual function
MATHEMATICAL MODELING OF THE PROCESS OF STEAM-ASSISTED GRAVITY DRAINAGE DURING THE EXTRACTION OF HIGH-VISCOSITY OIL
The paper is devoted to the development of models and methods to describe and predict the process of steam-assisted gravity drainage during the extraction of high-viscosity oil. On the basis of the original physicomathematical model, the authors have considered the problems of circulation of a steam in the injection well for preheating the stratum, the stratum sweep by the action of the steam, and methods to increase it. The presence of the optimum spacing between pairs of reactive wells or the optimum density of the network of wells has been established. From an analysis of basic mechanisms of the process, the authors have identifi ed the causes of the maximum value of the oil recovery factor for the optimum network of wells. The possibility has been shown of raising the economic effi ciency of the process of passage from the injection of a steam to the injection of unheated water in the fi nal stage of the process.
Author: A. Ya. Gil′manov, K. M. Fedorov, A. P. Shevelev
Keywords: engineering problems of extraction of high-viscosity oil, steam chamber, injection well, producing well, steam-assisted gravity drainage, integral model based on mass and heat balances, steam-oil ratio, sweep effi ciency, oil recovery factor
PRODUCTION OF FERROMAGNETIC ADSORBENTS FROM SOLID PRODUCTS OF BIOWASTE CARBONIZATION IN A FLUIDIZED BED IN A MEDIUM OF SUPERHEATED WATER VAPOR
Consideration has been given to problems of chemical activation of a solid product of hydrothermal carbonization (hydrochar) of biomass. Pellets from a mixture of poultry litter and straw subjected to carbonization in a fl uidized bed in a medium of superheated water vapor at a temperature of 300o C were impregnated with water solution of ferric nitrate, dried in the air at a temperature of 100o C, and held for 2 h at a temperature of 300o C for degradation of iron(III) nitrate and its transformation into iron oxides. The pellets were activated at a temperature of 700–800o C in a horizontal tube furnace in an inert argon atmosphere. The obtained ferromagnetic sorbents have a rather developed system of micro- and mesopores. Furthermore, a twofold increase in the duration of activation results in an 18% increase of the pore specifi c surface, and the rise in the temperature of the activation process leads to an increase in this surface by 45%
Author: N. S. Muratova, S. N. Kuz′min, O. Yu. Milovanov, A. V. Melezhik
Keywords: hydrothermal carbonization, hydrocoke, chemical activation, ferromagnetic sorbent
BROWNIAN COAGULATION OF NANODROPLETS IN A VAPOR–GAS MIXTURE AND THEIR WEIBULL DISTRIBUTION
A nonlinear Brownian coagulation of nanodroplets in a vapor–gas mixture was investigated with the use of their Weibull distribution having a maximum information entropy. An iteration method is proposed for determining the parameters of this distribution which, for the Brownian coagulation, is self-similar in character. The evolution of a system of nanodroplets as a result of their coagulation with retention of the total mass of the liquid in them was calculated. It is shown that, as a result of the coagulation of nanodroplets in a vapor–gas mixture, their number in a unit volume of the mixture can decrease by several orders of magnitude for several milliseconds
Author: S. P. Fisenko
Keywords: free molecular regime, coagulation kernel, average cube of the droplet radius, characteristic time of coagulation
EXPERIMENTAL STUDY OF THE EFFECT OF THE HELICAL RIBS IN A SPIRALLY COILED TUBE ON THE FRICTION REACTOR AND THE NUSSELT NUMBER OF A NANOFLUID FLOW IN IT
The effect of the centrifugal force arising in a spirally coiled tube with helical ribs on the heat transfer in the fl uid fl ow in it was investigated. It is shown that, due to this force, the rate of heat transfer in the fl uid fl ow in a spirally coiled tube with helical ribs is larger than that in an analogous tube with no ribs. It was established that, in the case where nanoparticles are added to the base fl uid fl owing in a spirally coiled tube with helical ribs, its transport properties change, with the result that the Nusselt number of the fl uid fl ow increases. Moreover, an increase in the nanofl uid concentration leads to an increase in the rate of heat transfer in the fl uid fl ow in the tube depending on the direction of its helical ribs, and the friction factor of the fl uid fl ow in the tube insignifi cantly increases in this case.
Author: P. Naphon, S. Wiriyasart, A. Srichat
Keywords: nanofl uid, spirally coiled tube, helical rib
Page: 614 -621
SEPARATION OF A GAS MIXTURE IN NANOSIZE POROUS MEMBRANES. EFFECT OF ADSORPTION AND SURFACE DIFFUSION
The authors have studied the infl uence of the adsorption and surface diffusion of one component of a binary gas mixture on pore walls on the effect of separation of the gas mixture during its fl ow through a nanosize porous membrane in a free molecular regime. A capillary porous-medium model obtained by the momentum-balance method was taken as a basis for analysis. Expressions have been determined for the separation factor and the concentration jump of the adsorbed component for an assigned pressure difference on the membrane, which make it possible to analyze the infl uence of the initial concentration of the adsorbable component and of the temperature on the separation effect. Calculations have been performed of the concentration jump for a number of commercial gas mixtures (CO2/H2, CO/H2, CH4/H2, and N2/He). It has been shown that taking account of surface diffusion may lead to appreciable variations (of several tens of percent) of the obtained values from Knudsen values of the effect in the absence of adsorption.
Author: V. M. Zhdanov A. A. Stepanenko
Keywords: nanoporous membranes, Knudsen fl ow, adsorption, surface diffusion, capillary model, separation of a gas mixture, separation factor, concentration jump
INFLUENCE OF IONIZING RADIATION ON THE CORROSION RESISTANCE OF ZnNi/SiO2 COMPOSITE COATINGS
The infl uence of x-ray radiation on the protective properties of ZnNi/SiO2 composite coatings has been investigated experimentally, and the optimal regimes of their electrodeposition on irradiation by the method of complete factor experiment have been revealed. It is shown that the action of x-ray radiation on the electrolytes used for electrodeposition of ZnNi/SiO2 leads to an increase in their dispersive power, which makes it possible to form composite coatings with the metal uniformly distributed over the surface and, correspondingly, with elevated corrosion resistance. It has been found that the action of x-ray radiation on the process of electric deposition of ZnNi/SiO2 coatings promotes formation of layers with enhanced anticorrosion properties. Based on experimental data and according to the method of complete factor experiment, the infl uence of variations in the x-ray radiation exposure dose power and concentration of SiO2 nanoparticles in the electrolyte on the dispersive power of electrolytes and corrosion resistance of ZnNi/SiO2 coatings has been considered. Regression equations have been obtained, an analysis of the coeffi cients of which allowed the conclusion that a maximum increase in the dispersive power and a decrease in the rate of appearance of corrosion products on ZnNi/SiO2 coatings are achieved on combination of two factors: addition of SiO2 nanoparticles to the electrolyte and irradiation of the electrolyte by x-ray radiation in the process of coating deposition. The developed statistical model allows one to adequately determine the optimal concentrations of SiO2 nanoparticles in an electrolyte and the regime of x-ray irradiation for obtaining coatings with enhanced anticorrosive properties.
Author: D. V. Lavysh, N. G. Val′ko, V. M. Anishchik, R. R. Korennoi, Milan Šebok
Keywords: electrocrystallization, x-ray radiation, current effi ciency, regression equations, factor, criteria, adequacy
NUMERICAL SIMULATION OF THE INTERACTION OF A SHOCK WAVE WITH A DENSE LAYER OF PARTICLES
A numerical simulation of a nonstationary fl ow of a gas containing inert particle in a shock tube has been perfumed on the basis of the model of mutually penetrating continua, in which the gaseous and dispersed phases are defi ned by sets of mass, momentum, and energy conservation equations and the equation for the evolution of the dispersedphase volume fraction. The main equations are hyperbolic, and they are solved using the Godunov-type method of increased accuracy. The shock-wave structure of the gas fl ow in the working section of the shock tube and the space and time dependences of this fl ow were determined. The numerical-simulation results are compared with available experimental and calculation data
Author: K. N. Volkov, V. N. Emel′yanov, A. V. Efremov
Keywords: numerical simulation, shock wave, inert particles, dense layer, shock tube, supersonic two-phase fl ow.
INITIATION OF VORTEX FLOWS INDUCED BY DOUBLE DIFFUSION
The convection that owes its origin to double (differential) diffusion in a rotating medium in the gravity force fi eld may lead, generally speaking, to transfer of vorticity, and, in particular, to its concentration. As a rule, this is not considered in geophysical applications, since the spatial and time scales of such a convection and of rotation effects differ greatly — the period of planetary rotation is many orders of magnitude larger that the characteristic time of the existence of the corresponding convective structures in seawater. It is shown in the work that in the atmosphere the occurrence of the processes is possible, in which a noticeable transfer of the vorticity of such convection is more real. The effects of the type of double diffusion in air are possible in principle due to some difference in the rates of the transfer of heat, steam, and (or) of a heavy impurity. A linear model of the convection caused by double diffusion in a rotating medium is considered. In elaboration of the previous work of the author, a much more complex problem is considered with account for the temperature stratifi cation of the medium. Differential diffusion makes possible the vertical motions and concentration of vorticity despite the negative feedbacks, caused by the background stable stratifi cation of density.
Author: L. Kh. Ingel
Keywords: double (differential) diffusion, convection, rotating stratifi ed medium, heavy impurity, linear model, vorticity, concentration, atmosphere, whirlwind
Page: 648 -652
INTENSIFICATION OF THE MAGNETIC FIELD IN JET FLOWS OF CONDUCTING MATERIALS: COLLISION OF TWO SUCH FLOWS
In the context of the one-dimensional problem of magnetic hydrodynamics on the collision and spread of plane jets of an incompressible conducting material in which a transverse magnetic fi eld was created before the collision of its jets, the intensifi cation of the magnetic fi eld in the material of such a jet under an extensional strain with elongation of its fi bers in the direction of the magnetic fl ux lines was investigated. With the use of the time integral Laplace transform, the asymptotics of the intensifi cation of the magnetic fi eld in a jet of a metal was determined as a function of the magnetic Reynolds number of the jet. It is shown that in the case of deformation of a metal, in which a magnetic fi eld was preliminarily created at a fast rate under an explosive or an impact load, the magnetic fi eld in the metal can be intensifi ed to the level at which the effects accompanying the generation of this fi eld will substantially infl uence the behavior of the metal. The results obtained explain the substantial decrease in the penetrating ability of a cumulative charge in the case where an axial magnetic fi eld is created in the coat of the charge before its detonation.
Author: S. V. Fedorov
Keywords: magnetic hydrodynamics, conducting material, jet fl ow, magnetic fi eld, rapid deformation, cumulative charge, cumulative jet
Page: 654 -664
ON THE STRUCTURE OF THE SOUND FIELD NEAR A TURBULENT JET EMANATING FROM A NOZZLE IN THE CASE WHERE PERTURBATIONS EXIST IN ITS PRECHAMBER
Results of investigation of the structure of the sound fi eld near a supersonic isothermal air jet emanating from the nozzle of a jet engine under the conditions of existence of perturbations in its jet-edge generator by the direct shadow method are presented.
Author: V. G. Pimshtein
Keywords: Results of investigation of the structure of the sound fi eld near a supersonic isothermal air jet emanating from the nozzle of a jet engine under the conditions of existence of perturbations in its jet-edge generator by the direct shadow method are presented.
EFFECTS OF RELATIVE MASS FLUX OVER THE RECESSED PART OF THE NOZZLE ON THE DISCHARGE COEFFICIENT
To evaluate the effi ciency (perfection) of the processes of discharge from a recessed nozzle of a solid rocket motor (solid-propellant rocket engine), the parameter of relative mass fl ux has been introduced instead of the mass fl ow ratio. Advanced methods of computational fl uid dynamics have been used to conduct investigations into the effects of relative mass fl ux over the recessed part of the inlet portion of the nozzle on the discharge coeffi cient. Consideration has been given to versions of the nozzle inlet portion of ellipsoid shape and of a shape constructed using the Vitoshinsky formula. The effects of relative mass fl ux on the nozzle metering characteristics have been determined with account for the changes in the geometric parameters of its recessed part and for the recess depth. A comparison is presented of the obtained results with the results of earlier investigations into radius-shaped nozzle inlet portions. Additionally, investigations have been conducted into the effects of the gas infl ow from the surface of the charge over the recessed part of the nozzle at constant geometry of its ellipsoid- or radius-shaped inlet portion on the nozzle discharge coeffi cient at different recess depths. Basic recommendations have been formulated for designing inlet portions of recessed nozzles.
Author: A. N. Sabirzyanov, A. N. Kirillova
Keywords: solid rocket motor, recessed nozzle, discharge coeffi cient, mass fl ux, computational fl uid dynamics
DYNAMICS OF PULSED SIGNALS IN A PIPELINE FILLED WITH A METHANE–VAPOR–DROPLET MIXTURE AND AFFECTED BY GAS–HYDRATE DEPOSITS
A study is made of the evolution of pulsed pressure perturbations in a pipeline fi lled with a gas–droplet medium, which represents "moist" methane at a below-dewpoint temperature, and having a portion in the form of an extended channel constriction. For this process, the authors have adopted a theoretical model of propagation of acoustic waves in the longwave range in the gas–droplet medium. The problem of propagation and refl ection of pulsed pressure perturbations in a horizontal pipeline having a portion of constriction because of hydrate deposits is solved by the method of fast Fourier transformation. Results of dispersion analysis of acoustic equations in a vapor–gas–droplet system are presented. Based on them, for real values of the parameters of pipelines, and also of the parameters of vapor–gas–droplet systems in them, the authors have obtained dependences of the phase velocity and the attenuation coeffi cient on the frequency of perturbation of an acoustic wave and the volume content of a suspended phase (water droplets). Also, an analysis has been made of the manifestation of viscosity and heat conduction in the wall pipeline layer saturated with water droplets. For the coeffi cients of refl ection and transmission of acoustic signals at the sites of constriction of the pipeline because of hydrate deposits, use has been made of the existing formulas. Results of numerical calculations have been presented, which illustrate the evolution of pulsed signals of varying duration and show the infl uence of the thickness of a gas–hydrate layer on the interior pipeline wall. It has been shown that growth in the thickness of the hydrate deposits on the wall and increase in the duration of the pulsed signal cause the amplitude of the returned signals (echo) to grow.
Author: V. Sh. Shagapov, É. V. Galiakbarova, and Z. R. Khakimova
Keywords: gas–droplet medium, hydrate plug, pressure pulse
CHARACTERISTIC FEATURES OF THE THERMOMECHANICS OF GAS FLOWS IN THE PISTON ENGINE OUTLET UNDER VARIOUS GAS-DYNAMICAL CONDITIONS
A comparative analysis of the thermomechanical characteristics of a gas in the internal combustion piston engine outlet in the case of stationary and pulsating gas fl ow regimes was carried out. An estimate of the effect of external turbulence (of the presence of a turbocompressor) in the engine outlet on the thermomechanics of fl ows pulsating in it has been carried out. It has been established that in the engine outlet the change-over of fl ow regime from a stationary to a pulsating one leads to an 8–10-fold increase in the turbulence degree, as well as to a change in the heat transfer coeffi cient by ±25%. It is shown that mounting of a turbocompressor in the engine outlet leads to a 1.5–2.5-fold increase in the hydraulic resistance of the system, to a decrease in the rate of air fl ow though the system on the average by 11%, and to a 1.5–3.0-fold increase in the turbulence degree at a low fl ow velocity, as well as to heat transfer intensifi cation by 33% at a high pressure at the output.
Keywords: internal combustion piston engine, turbocompressor, gas fl ow, thermomechanics, external turbulence
ON THE PROBLEM OF BOUNDARY CONDITIONS IN THE MULTIDIMENSIONAL NODAL METHOD OF CHARACTERISTICS
The setting of boundary conditions on curvilinear walls in application to the multidimensional nodal method of characteristics is discussed, which is based on splitting the initial system of equations into a number of one-dimensional subsystems along the coordinate directions. For the boundary points located on curvilinear impermeable surfaces, a calculation method based on the procedure of fi ctitious nodes is suggested, with the use of which a number of test problems with self-similar solutions have been calculated.
Author: V. S. Surov
Keywords: hyperbolic systems, multidimensional nodal method of characteristics, boundary conditions
HYDROMAGNETIC OSCILLATORY REACTIVE FLOW THROUGH A POROUS CHANNEL IN A ROTATING FRAME SUBJECT TO CONVECTIVE HEAT EXCHANGE UNDER ARRHENIUS KINETICS
This paper is aimed at studying an unsteady hydromagnetic fl ow of a viscous incompressible electrically conducting reactive fl uid in a permeable channel with asymmetrical convective boundary conditions in a rotating reference frame under the Arrhenius kinetics with neglect of the reactant consumption. Asymmetrical convective heat exchange with the surrounding medium at the channel surfaces follows the Newton law of cooling. A chemical reaction in the fl ow system is exothermic and assumed to follow the Arrhenius rate law. The heat transfer characteristics of the fl ow are considered with viscous and Joule dissipations taken into account. The expressions for the velocity components obtained in closed form are used to calculate the wall shear stresses. The energy equation is tackled numerically with using MATLAB. The effects of the pertinent parameters on the fl ow dynamics are analyzed graphically. The results reveal that the combined effects of magnetic fi eld, rotation, suction/injection, and convective heating substantially affect the fl ow characteristics in the channel.
Author: S. Das, R. R. Patra, R. N. Jana
Keywords: hydromagnetic reactive fl ow, permeable channel, suction/injection, convective boundary conditions, viscous and Joule heating, Arrhenius kinetics, rotating frame
EFFECTS OF ELECTROMAGNETIC TREATMENT ON RHEOLOGICAL PROPERTIES OF OIL: EXPERIMENT AND APPLICATION
Laboratory tests have been conducted on four grades of oils from different fi elds. The results of the conducted tests on the effects of electromagnetic radiation on oil rheology have been presented. An analysis has been made of the effects of electromagnetic treatment on the characteristics of transportation of high-viscosity oil using the example of the operation of an oil pumping station
Author: L. A. Kovaleva, G. I. Mukharyamova
Keywords: rheological properties, electromagnetic treatment, oil, dynamic viscosity
INTERPRETATIVE MODEL OF RADIAL THERMAL LOGGING
A mathematical model of the temperature fi eld of a fl uid moving in a well is presented. It can be used as the basic one for interpreting measurements of radial temperature distributions. The initial problem has been solved on the basis of an exact "on the average" asymptotic method. The analytical solutions that describe the temperature fi elds of a fl uid in a well shaft were obtained with the aid of the Laplace–Carson transformation. It is shown that the zero expansion coeffi cient describes the radius-averaged background values of the temperature fi eld in the well. The expression for the fi rst coeffi cient describes the radial temperature profi les. This means that the proposed interpretative model allows one to carry out fi ltration of useful temperature anomalies of the radial profi le against the background of considerably large global temperature perturbations caused by the fl uid fl ow in the shaft of an operating well and thereby to remove the problems associated with the incorrect realization of inverse problems. Based on numerical calculations, the infl uence of the temperature signal from the bed and of the thermophysical parameters of the fi lling fl uid has been analyzed, and major advantages and disadvantages of the proposed interpretative model have been established.
Author: A. I. Filippova, E. P. Shcheglova
Keywords: well, temperature fi eld, Laplace–Carson transformation, radial thermal logging
Page: 720 -729
HIGH-TEMPERATURE THERMOLYSIS OF ORGANIC RAW MATERIALS
On the basis of investigations into the high-temperature steam thermolysis of organic raw materials in the form of mixtures of wood, agricultural, and polymer waste, the authors have substantiated the possibility of obtaining analogs of liquid fuels, and also of sorptive materials. It has been shown that in the fi rst stage of steam thermolysis at temperatures of about 500o C, gaseous and liquid hydrocarbons are formed, as well as solid residues, that acquire adsorptive properties during heating to 1000o C in the second stage.
Author: G. I. Zhuravskii,V. V. Savchin
Keywords: high-temperature steam thermolysis, organic raw materials, analogs of liquid fuels, sorptive materials
OXIDATIVE TORREFACTION OF WOOD BIOMASS IN A LAYER OF MINERAL FILLER
Consideration is given to a promising approach to heat treatment of biofuel, viz. oxidative torrefaction in a layer of mineral fi ller. The key features of the proposed technique are the uniformity of heating up the specimen and the possibility of controlling oxidizing processes in the specimen by changing the height of the mineral fi ller. Based on design-theoretical analysis, an investigation has been made of the thermal and kinetic processes accompanying torrefaction in a layer of mineral fi ller. It is shown that the presence of the mineral layer ensures a high degree of uniformity for heating up a biofuel specimen in the process of torrefaction. The infl uence of the mineral fi ller layer on the diffusion fl ows of atmospheric oxygen and volatile compounds released during heating up the specimen is shown
Author: B. V. Kichatov,A. M. Korshunov,A. D. Kiverin, I. S. Yakovenko
Keywords: biofuel, oxidative torrefaction, torrefaction in a layer of mineral fi ller, numerical simulation.
Page: 738 -743
THREE-DIMENSIONAL SIMULATION OF HEAT AND MASS TRANSFER PROCESSES DURING SHF HEATING OF OIL FLOW IN A PIPELINE
This article considers mathematical simulation of heat and mass transfer processes in the course of SHF heating of fl ow of a viscous fl uid, oil included, in a pipeline. A specifi c feature of the mathematical model is account for threedimensional effects, for example, the dependence of volumetric and surface heat release sources on the polar density angle. A numerical solution is obtained by the method of fi nite differences. The results of calculations for a concrete problem of SHF heating of oil fl ow in a pipeline are given. The results of two-dimensional and three-dimensional models are compared, and the infl uence of a number of factors on the results of simulation is analyzed.
Author: R. V. Arutyunyan
Keywords: oil, pipeline, SHF heating, mathematical simulation, method of fi nite differences, three-dimensional model
MATHEMATICAL MODEL AND NUMERICAL INVESTIGATION OF COMBUSTION FRONT PROPAGATION VELOCITY IN AN AEROSOL OF AN ALUMINUM NANOPOWDER SUSPENSION IN KEROSENE
A mathematical model of combustion of an aerosol of an aluminum nanopowder suspension in kerosene is presented, in which the state parameters of aerosol are determined by solving the system of energy conservation equations of gas, droplets, and particles, mass conservation equations of gas suspension components, and of the equations of motion of droplets and particles. The rate of oxidation of aluminum nanoparticles and the associated rate of heat release have been determined, as well as the dependences of the velocity of combustion front propagation in the aerosol on the mass concentrations of kerosene and aluminum nanopowder and on the initial aerosol temperature
Author: A. Yu. Krainov, V. A. Poryazov, K. M. Moiseeva, D. A. Krainov
Keywords: kerosene, aluminum nanopowder, suspension, aerosol, combustion, mathematical simulation
MULTIFUEL COMBUSTIBLE MIXTURES: SYNTHESIS GAS (CO–H2)
The authors have presented new data on the parameters of combustion and detonation of biofuel mixtures of carbon oxide and hydrogen (synthesis gas) with oxygen and air with variation of the ratio between CO and H2 and between the fuel components and the oxidant alike, including data on the critical energies of initiation of detonation, the characteristic dimensions of detonation cells, velocities of detonation, and energy release in detonation waves.
Keywords: multifuel systems, synthesis gas, initiation, critical energy, combustion, detonation, limits, detonation cells
MECHANISMS OF HEAT AND MASS TRANSFER IN THE LOCALIZATION OF GROUND FOREST FIRES WITH THE USE OF BARRIER STRIPS
Results of fi eld experiments on determination of the macroscopic mechanisms of heat and mass transfer in the localization of a ground forest fi re with the use of a barrier strip in the form of a wetted layer of forest combustible materials (needles, leaves, twigs, and their mix), positioned upstream of the front of combustion of such materials, are presented. Most attention has been concentrated on the complex analysis of the infl uence of the dispersity of a water aerosol (the concentration of the water droplets in it and their sizes), used for the formation of a barrier strip, on the parameters of this strip. It is shown that the conditions of effective localization and suppression of the fl aming and thermal decomposition of forest combustible materials can be realized in the case where a group of barrier strips of different widths, wetted to different depths, is formed in front of a forest fi re. The parameters of barrier strips (the volume of water supplied to a strip, the width of the strip, the depth of its wetting, and the specifi c density of the water in it) necessary and suffi cient for the localization of ground forest fi res of different sizes were estimated.
Author: G. V. Kuznetsov, D. V. Antonov, I. S. Voitkov, A. G. Islamova, S. S. Kropotova, and N. E. Shlegel'
Keywords: ground forest fi re, forest combustible materials, pyrolysis, combustion, fi eld experiments, barrier strip
THERMAL PROPERTIES OF BIOLOGICAL TISSUE GEL-PHANTOMS IN A WIDE LOW-TEMPERATURE RANGE
It is often impossible or impractical to conduct experiments on cooling, freezing, and thawing during medical cryoexposures with using biological tissues. In such cases, gel-phantoms are used. Due to the lack of accurate data, the defi nition of the thermal properties of gel-phantoms is relevant. The current study presents the results of the thermal properties measurements with using the differential scanning calorimetry (DSC) and transient hot bridge (THB) methods and of their analysis for fi ve gel-phantoms: 1) 95% water and 5% gelatin; 2) 95% water and 5% agar-agar; 3) 94% water, 3% gelatin, 2.5% agar-agar, and 0.5% sodium chloride; 4 and 5) ultrasound gels. The values of the effective specifi c heat capacity from –160 to 40o C, thermal conductivity, moisture content, freezable water fraction, and of the initial melting and cryoscopic temperatures are determined. The obtained results are compared with the values of the thermal properties of biotissue and distilled water. The infl uence of the gelphantom type on the character of phase transition is shown. Adaptation of the experimental data for cryoexposure simulation software is proposed. Recommendations for selecting a phantom are given. The impact of simplifi cation of the thermal properties on the thermal diffusivity is estimated. The data for calculating the properties of phantoms of different composition are proposed.
Author: I. V. Agafonkina, A. G. Belozerov, Yu. M. Berezovsky, I. A. Korolev, A. V. Pushkarev, D. I. Tsiganov, A. V. Shakurov, A. A. Zherdev
Keywords: thermal properties, gel-phantom, ultrasound gel, agar, gelatin, biological tissue, DSC, THB
ENERGETIC METAL–ORGANIC FRAMEWORKS: THERMAL BEHAVIORS AND COMBUSTION OF NICKEL OXIDE (II) BASED ON ACTIVATED CARBON COMPOSITIONS
Ammonium nitrate (AN) extensively used as an oxidizer in energetic compositions is a promising compound as a propellant and gas generator. It is well known that metal oxides help to address some of the disadvantages of AN, such as the low stability and low burning rate. To investigate the effect of nickel oxide (II) (NiO) on thermal decomposition of AN mixtures, the thermal characteristics of AN, activated carbon C, and NiO mixtures as of metal– organic frameworks (MOFs) were measured using simultaneous differential scanning calorimetry. The compositions were burnt at the pressures 1, 2, 3, and 3.5 MPa in a combustion chamber, and the burning rates were determined. On addition of a metal oxide, the burning rate was shown to increase three–four times. Besides, the activation energy of the systems was calculated.
Author: Zh. K. Yelemessova, A. M. Imangazy, M. I. Tulepov, Z. A. Mansurov
Keywords: energetic materials, metal–organic frameworks, ammonium nitrate, activated carbon, nickel (II) oxide, burning rate, activation energy