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Combustion, Explosion and Shock Waves

2018 year, number 1

Experimental Study of a Cellular Ethanol Flame Evaporating "On the Ceiling"

R. Kh. Abdrakhmanov, B. F. Boyarshinov
Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: диффузионное пламя, ячейки, смешанная конвекция, грибовидные структуры, PIV, массоперенос, неустойчивость Рэлея-Тейлора, diffusion flame, cells, mixed convection, mushroom-shaped structures, mass transfer, Rayleigh-Taylor instability

Abstract >>
This paper describes the study of evaporation and combustion of ethanol under a horizontal wall in a stratified shear gas layer in the case of the Rayleigh - Taylor instability. The data on the nature of flow are obtained with the use of particle image velocimetry (PIV), and temperature profiles are recorded by a thermocouple. It is shown that the formation of cells occurs in a narrow range of air velocity of 0.6±0.05 m/s and does not depend on the height of the obstacle (backward step or an edge is 0-7 mm in height). The flow between the wall and flame front is an alternation of mushroom-shaped structures moving from one wall to another. In the cellular flame, the flow of substance (with respect to the air flow) exceeds its level in a standard laminar boundary layer three times. The averaged transverse velocity is directed away from the wall in the boundary layer with combustion without cells, and it is reduced and directed toward the wall in the cellular flame between the wall and flame front.

Quantum-Chemical Calculations of Primary Reactions of Cyclopentadienone Thermolysis

A. R. Gildina1,2, A. M. Mebe3, Ya. A. Medvedko1, V. N. Azyazov1,2
1Samara National Research University named after Academician S. P. Korolev, Samara, 443086 Russia
2Lebedev Physical Institute, Russian Academy of Sciences, Samara, 443011 Russia
3Florida International University, 33199 Miami, USA
Keywords: горение, пиролиз, полициклические ароматические углеводороды, циклопентадиенон, винилацетилен, ацетилен, пропадиенал, реакционный путь, метод функционала плотности, метод ab initio, combustion, pyrolysis, polycyclic aromatic hydrocarbons, cyclopentadienone, vinylacetylene, acetylene, propadienal, reaction path, density functional method, ab initio method

Abstract >>
Quantum-chemical calculations by the CCSD(T)-F12/vtz-f12В method are used to find the geometric structure and determining the frequency of oscillations and the energy of reactants, products, transitional states, and reactions of decomposition of C5H4O. The calculated energy barriers for two most probable paths of the C5H4O pyrolysis reaction, which are equal to 96.3 and 96.5 kcal/mole, confirm that pyrolysis proceeds at a high temperature, and the most probable decomposition products are vinylacetylene and carbon monoxide. The formation of such products as cyclobutadiene, acetylene, and propadienal can be explained by realization of the energetically beneficial path.

Assessment of Maximum Efficiency of a Burner with Heat Recovery

I. A. Terletskii
Far Eastern Federal University, Vladivostok, 690950 Russia
Keywords: горение, термоэлектричество, микросистемы, combustion, thermoelectricity, Microsystems

Abstract >>
Estimates are obtained the maximum efficiency of a system consisting of a burner with heat recovery connected to an ideal heat engine operating according to the Carnot cycle. The burner serves as a heater of the ideal machine, and the cold side is at the ambient temperature. The combustion products heat the hot wall of the ideal machine and then transfer the heat of the combustible mixture supplied to the combustion chamber. Recovery of the heat of the combustible mixture through a heat-conducting wall of a countercurrent heat exchanger, in which the combustion products and the combustible mixture move toward each other in the channels separated by a heat-conducting partition. An estimate is obtained for the total efficiency of the system, which is determined as the ratio of the useful power of the ideal machine to the chemical energy flux reaching the burner device. It is shown that the total performance of the system can approach the Carnot-cycle efficiency with the maximum possible temperature of the hot side of the ideal machine.

Deactivation of Mechanically Activated Micronized Coal

A. P. Burdukov1, E. B. Butakov1, A. V. Kuznetsov1, M. Yu. Chernetskii1,2
1Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
2Siberian Federal University, Krasnoyarsk, 660074 Russia
Keywords: уголь, микропомол, механоактивация, деактивация, воспламенение, химическая активность, дезинтегратор, coal, microgrinding, mechanical activation, deactivation, ignition, chemical activity, disintegrator

Abstract >>
The effect of mechanically activated grinding of coal on their flammability has been studied. Coal treated in a ball pulverizer and mechanically activated coal cured for some time were compared in experiments. The experiments showed a decrease in the chemical activity of mechanically activated coal.

Effect of Melting of an Inert Component and Melt Spreading on Nonstationary Combustion Regimes of Gasless Systems

V. G. Prokof'ev1, V. K. Smolyakov2,3
1Tomsk State University, Tomsk, 634050 Russia
2Tomsk State University, Tomsk, 634021 Russia
3Tomsk Scientific Center, Russian Academy of Sciences
Keywords: безгазовое горение, спиновый режим, плавление, термокапиллярное течение, gasless combustion, spin mode, melting, thermocapillary flow

Abstract >>
The effect of the thermocapillary flow of the melting of an inert component of a gasless mixture on the spin combustion regimes of a cylindrical sample has been studied numerically. The change in the structure of the wave of spin combustion due to a change in the radius of the sample has been discussed, and new spin combustion modes has been found. Increasing the melt flow velocity leas to stabilization of the combustion - transition from spin modes to the stationary propagation of the combustion wave.

Burning of Mixtures of Copper Oxide with Titanium

Yu. M. Mikhailov1, V. V. Alyoshin1, V. I. Vershinnikov2, T. I. Ignat'eva2
1Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
2Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: оксид меди, титан, смесь, горение, режимы, copper oxide, titanium, mixture, burning, regimes

Abstract >>
This paper describes the study of the effect of physical and chemical properties of powder titanium and ratio of the original components on the burning parameters of its mixtures with copper oxide. It is shown that the linear burning rate of such mixtures is significantly dependent on the brand of used titanium. Under normal conditions, the mixtures can stably burn with the content of copper oxide of not smaller than 13%. With an increase in the content of copper oxide to a stoichiometric ratio, there is a change of burning regimes: multifocal, multifocal with detachment of solid residue, combination of convective and multifocal, multifocal with melt formation, fiery torch, and fireball. It is determined that, in this system, there may be convective burning under atmospheric pressure in the absence of outer reinforcement.

Mathematical Modeling of the Combustion of an Overfueled Aluminum-Air Mixture Based on the Nonequilibrium Thermodynamics of the Processes

A. Yu. Kryukov, V. I. Malinin
Perm Polytechnic University, Perm, 14990 Russia
Keywords: математическое моделирование, горение, аэровзвесь, алюминий, субоксиды, кинетика, равновесная и неравновесная термодинамика, mathematical modeling, burning, air-particle mixtures, aluminum, suboxides, kinetics, equilibrium and nonequilibrium thermodynamics

Abstract >>
This paper presents the results of mathematical modeling of the combustion of flow of a polyfractional micture of an aluminum powder in air taking into account the nonequilibrium nature of the process. The calculations were performed for values of the air-to-fuel ratio &alpha; = 0.1 - 0.5. Time dependences of thermodynamic parameters, the completeness of combustion of the metal particles, relative fractions of the residence time of the stream were obtained. The adequacy of the nonequilibrium model for describing thermodynamic processes is justified by comparing with the equilibrium model for time tending to ¥. The necessity of taking into account the formation of A2O suboxide present in the range of the air-to-fuel ratio was analyzed and proved. The need to include nitriding reactions in the mathematical modeling for 0.1 ≤ &alpha; < 0.4 shown by comparing the results of calculations based on equilibrium and nonequilibrium thermodynamics.

Oxidation of Aluminum in Mixtures with Polyethylene after Plastic Straining at High Pressures

V. A. Zhorin1, M. R. Kiselev2, A. V. Grachev1, T. A. Ladygina1
1Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia
2Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119991 Russia
Keywords: высокое давление, пластическая деформация, полиэтилен, металлополимерные смеси, термогравиметрический анализ, окисление алюминия, high pressure, plastic strain, polyethylene, metal-polymer mixtures, thermogravimetric analysis, aluminum oxidation

Abstract >>
Powder mixtures of low-density polyethylene and aluminum with the 20-80% weight ratio of the species are subjected to plastic straining at pressures of 1 and 4 GPa in a high-pressure devices of the Bridgman anvil type. Mass changes in the strained mixtures in the temperature range from 30 to 800oC are studied by the method of thermal gravimetry. A decrease in mass associated with polymer decomposition occurs in the temperature range from 30 to 450oC, which is always smaller than the polymer content in the mixtures. A possible reason is the formation of heat-resistant products due to aluminum interaction with polymer decomposition products. In the temperature range from 450 to 800oC, the mass of the specimens increases, which is caused by aluminum oxidation and nitride hardening. The mass change depends on the strain magnitude and strain pressure. To separate the oxidation and nitride hardening processes, the thermogravimetric measurements are performed in air, in nitrogen, and in argon. The thermal effects of aluminum interaction both with the polymer decomposition products and with oxygen and nitrogen are analyzed by the method of differential scanning calorimetry.

Oxidation of ASD-4 Powder Modified by V2O5

V. G. Shevchenko1, D. A. Eselevich1, N. A. Popov1, V. N. Krasilnikov1, Z. S. Vinokurov2, A. I. Ancharov3,4, B. P. Tolochko4,5
1Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, Ekaterinburg, 620990 Russia
2Boreskov Institute of Catalysis.Г  Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
3Novosibirsk State University, Novosibirsk, 630090 Russia
4Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
5Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, 630128 Russia
Keywords: алюминий, порошок, поверхность, модификация, пентоксид ванадия, окисление, фазовый анализ, aluminum, powder, surface, modification, vanadium pentoxide, oxidation, phase analysis

Abstract >>
The sequence of phase formation during ASD-4 aluminum powder modified by vanadium pentoxide during heating in air in the temperature range 873-1073 K was studied by synchrotron radiation X-ray diffraction. It was shown that the sharp acceleration of the oxidation of the modified powder was associated with the loss of the protective properties of the oxide shell on the particle surface due to the polyvalence of vanadium, which provides structural and phase changes on the surface and in the depth of oxidized metal.

Investigation of Nickel Aluminide Formed due to Shock Loading of Aluminum-Nickel Mixtures in Flat Recovery Ampoules

A. N. Zhukov1, V. A. Yakushev1, S. Yu. Anan'ev2, V. V. Dobrygin1,3, A. Yu. Dolgoborodov2,4
1Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
2Joint Institute of High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia
3Lomonosov Moscow State University, Moscow, 119991 Russia
4National Research Nuclear University “MePhI”, Moscow, 115409 Russia
Keywords: ударные волны, алюминий, никель, алюминид никеля, получение, механоактивация, микроискажения решетки, размер кристаллитов, shock waves, aluminum, nickel, nickel aluminide, obtaining, mechanical activation, lattice microdistortions, crystallite size

Abstract >>
Detailed results of an X-ray diffraction analysis of equimolar mixtures of nickel and aluminum with different particle sizes before and after shock loading in flat recovery ampoules are reported.

Exit of a Heterogeneous Detonation Wave into a Channel with Linear Expansion. II. Critical Propagation Condition

A. V. Fedorov, T. A. Khmel, S. A. Lavruk
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: газовзвеси алюминия, гетерогенная детонация, расширяющийся канал, численное моделирование, карты распространения детонации, suspension of aluminum particles in a gas, heterogeneous detonation, expanding channel, numerical simulation, detonation propagation chart

Abstract >>
Propagation of a detonation wave in monodisperse suspensions of reacting particles (based on the model of the suspension of aluminum particles in oxygen) in channels with a linearly expanding section is studied within the framework of mechanics of heterogeneous reacting media. Reduced kinetics is described with allowance for the transitional (from diffusion to kinetic) regime of combustion of micron-sized and submicron-sized spherical aluminum particles. The effects of the channel width, particle diameter, and wall angle on propagation conditions and detonation regimes are determined. The critical channel width is found to be a nonmonotonic function of the expansion angle, which is associated with qualitatively different wave patterns behind an oblique step. Flow charts are constructed, and the results are compared with solutions of problems of heterogeneous detonation wave propagation in channels with a step and with sudden expansion.

Relationship between the Critical Temperature of Thermal Explosion and the Thickness of a Lead Azide Plane Crystal

A. V. Khaneft1,2
1Tomsk Polytechnic University, Tomsk, 634050 Russia
2Kemerovo State University, Kemerovo, 650043 Russia
Keywords: азид свинца, тепловой взрыв, размерный эффект, критерий Семенова, уравнение теплового баланса, lead azide, thermal explosion, size effect, the Semenov criterion, heat balance equation

Abstract >>
This paper describes the calculation of the relationship of the critical ambient temperature at which lead -azide is ignited and the relationship of the critical temperature of self-heating with the thickness of plane crystals with the use of the Semenov criteria and numerical solution of the differential equation of heat balance. The heat balance equation is analyzed for sustainability. Analytical expressions for the determination of critical ambient temperatures and self-heating temperatures. The calculations are carried out with the parameters of the heterogeneous reaction of thermal decomposition of lead azide in the mode of decreasing volume. The calculations results are in good agreement with the known experimental data. It is shown that the larger the activation energy of the exothermic reaction, the stronger the relationship of the critical temperature of ignition of lead -azide with the thickness of plane crystals.

Standard Enthalpy of Formation of a CL-20 Bimolecular Crystal with Tris-Oxadiazol-Azepin and its Thermal Stability

A. I. Kazakov, T. K. Goncharov, D. B. Lempert, N. A. Plishkin, K. V. Bozhenko, A. N. Utenyshev, D. V. Dashko, A. I. Stepanov, S. M. Aldoshin
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: энтальпия сгорания, энтальпия образования, сокристаллизация, Оі-полиморфа CL-20, 7H-трис([1,2,5]оксадиазоло)[3,4-b:3',4'-d:3'',4''-f]азепин, бимолекулярные кристаллы, термическая стабильность, enthalpy of combustion, enthalpy of formation, cocrystallization, polymorph of CL-20, bimolecular crystals, thermal stability

Abstract >>
The standard enthalpies of combustion and formation of 7 H -tris([1,2,5]oxadiazol)[3,4-b:3',4'-d:3',4'-f]azepin, its bimolecular crystal with the &gamma;-polymorph (CL-20), and &gamma;-polymorphs of CL-20 are experimentally determined. The standard enthalpies of formation of the bimolecular crystal and the equimolecular mechanical mixture of &gamma;-CL-20 with azepin are found to differ by less than 12.8 kJ/mol. This small difference is validated by quantum-chemical calculations. It is experimentally observed that the presence of azepin in the bimolecular crystal inhibits thermal decomposition of &gamma;-CL-20 and increases the thermal stability of &gamma;-CL-20 in the bimolecular crystal as compared to &gamma;-CL-20 in the initial state.

Laser Initiation of the Decomposition of a Semi-Transparent Mixture of Energetic Materials

A. G. Knyazeva1,2, V. E. Zarko3
1Tomsk Polytechnic University, Tomsk, 634050 Russia
2Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia
3Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: инициирование, энергетические материалы, импульс лазерного излучения, двухкомпонентная смесь, двухфазная зона, initiation, energetic materials, laser radiation pulse, two-component mixture, two-phase zone

Abstract >>
In this paper, we propose a model for the heating and decomposition of a two-component mixture of energetic materials by a short laser pulse which takes into account melting and formation of a two-phase zone and the decomposition reaction of the individual components of the mixture. A binary solution of furazanotetrazine-dioxide (C2N6O3) and dinitrazapentane (C3H8N4O4) was studied. The pressure change in the reaction zone was calculated, and the effect of pressure on the rate of decomposition reactions was examined. Numerical investigations were performed to study the dynamics of the process and determine the main stages of the process: melting, the propagation of reaction zones in the mixture, the rapid development of an explosion or the termination of reactions, depending on the amount of stored energy. The influence of the optical properties of the mixture on the dynamics of initiation process was demonstrated.

Estimation of the Fireball Size in an Ethyne-Air Cloud Explosion

Y. Huang1, Q. Zhang1, H. Yan1, W. Gao2,3
1State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing, 100081 China
2Institute of Fluid Science, Tohoku University, Sendai, Miyagi, 980-8577 Japan
3School of Chemical Machinery, Dalian University of Technology, Dalian, Liaoning, 116024 China
Keywords: численное моделирование, взрыв, ацетиленовоздушная смесь, исходное облако, numerical simulation, explosion, ethyne-air mixture, original cloud

Abstract >>
A gas explosion accident is often followed by a serious fire. In order to effectively prevent fire induced by a gas explosion accident, it is necessary to have some knowledge of the related explosion processes. The subject of the present study is to examine deflagration behaviors beyond the original cloud of the ethyne-air mixture and the fireball size in an ethyne-air explosion by means of numerical simulations. The explosion overpressure, flow velocity, and reaction rate distribution in an ethyne-air explosion are obtained. The peak explosion overpressure is found to reach its maximum beyond the original cloud for ethyne-air mixtures with ethyne concentrations greater than 13% (by volume). The explosion pressures beyond the original cloud may be higher than those within the cloud for these ethyne-air mixtures. The ratio of the combustion range to that of the original cloud is 1.4-2.7 in the radial direction on the ground and 1.5-4 along the axis of symmetry perpendicular to the ground.

Specific Features of Plate Acceleration under Conditions of Magnetic-Pulsed Welding

A. G. Anisimov, V. I. Mali
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: ускорение пластин магнитным полем, магнитно-импульсная сварка металлов, неустойчивость, plate acceleration by a magnetic field, magnetic-pulsed welding of metals, instability

Abstract >>
Magnetic-pulsed welding differs from explosive welding only by sources of energy for plate acceleration: magnetic field energy is used instead explosion energy. Magnetic field interaction with the plate has some specific features associated with the value of energy stored in the battery, the rate of heating to the melting point, and the possibility of plate buckling, which impose constraints on using magnetic-pulsed welding. These constraints are associated with geometric parameters of the welded plates and the gaps between them; the critical values of these parameters are obtained in the present study. A capacitor battery is used in the experiments for plate acceleration. A new pioneering scheme of magnetic-pulsed welding of more than two plates is developed.

Generation of the Hyper-Speed Streams of Particles in Explosive Clamps of Ceramic Tubes

I. A. Balaganskii1, A. Merzhievskii1,2, V. Yu. Ulyanitskii1,2, I.A. Bataev1, A. A. Bataev1, A. D. Matrosov2, I. A. Stadnichenko2, I. S. Batraev2, A. V. Vinogradov1
1Novosibirsk State Technical University, Novosibirsk, 630073 Russia
2Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Rissia
Keywords: дисперсные кумулятивные струи, гиперскоростное метание, высокомодульная керамика, dispersed shaped-charge jets, hypervelocity acceleration, high-modulus ceramics

Abstract >>
The compression of ceramic (corundum) tubes by the detonation products of explosives were studied experimentally and numerically. The formation of a shaped-charge flow of ceramic particles and its effect on steel witnesses targets was investigated. The tubes were produced by detonation spraying. Ceramic particles were deposited on substrates - copper tubes, which were then dissolved in a solution of iron chloride. The experiments showed a significant penetrating effect of the flow of ceramic particles. Metallographic analysis showed that during the interaction of the flow with the target, the target material was partially evaporated. Numerical analysis of the process demonstrates features of the formation of the discrete shaped-charge jet: the maximum velocity of the leading part of which was about 23 km/s, and the velocity of the main part of the jet was about 14 km/s.