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Combustion, Explosion and Shock Waves

2015 year, number 5

1.
On the Flame Shape in Diffusion Combustion of a Liquid Fuel Film on a Substrate

A. A. Korzhavin, I. G. Namyatov
Voevodskii Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk, Russia
Keywords: горение, диффузионное пламя, задача Бурке-Шумана, combustion, diffusion flame, Burke-Schumann problem

Abstract >>
In this paper, we consider the classical Burke-Schumann problem as applied to the construction of a mathematical model of a diffusion flame spreading over a fuel film deposited on a thin substrate. This formulation is used to model the combustion of a gaseous fuel flowing from a thin slot (half-width xin and mixed with oxidizer flowing from a parallel slot (with the outer boundary xout). The key parameters determining the position of the flame front in the space are identified: the Peclet number Pe, the stoichiometric parameter A dependent on the equivalence ratio, and the geometric parameter Xin = xin/xout. The dependences of the flame length on these parameters, including xout → 8, are analyzed. Comparison shows good agreement between calculated and experimental
																								



2.
On the Correlation of Inverted Flame Blow-Off Limits with the Boundary Velocity Gradient at the Flame Holder Surface

Y. Shoshin, L. P. H. Goey
Eindhoven University of Technology, 5600MB Eindhoven, The Netherlands
Keywords: обращенное пламя, стабилизация пламени, срыв пламени, градиент скорости, inverted flame, flame stabilization, blow-off, boundary velocity gradient

Abstract >>
Conductive heat losses from the base of a lean methane--air inverted flame stabilized behind the trailing edge of a thin rod have been experimentally evaluated. The results favor the view that the heat losses to the flame holder play a crucial role in the inverted flame stabilization and blow-off. Simple estimations have been performed, which indicate that the well-established correlation between the mixture composition and the boundary velocity gradient at the flame holder, usually considered as a proof of the flame stretch theory of blow-off, can be explained without involving the flame stretch concept. The suggested explanation of this correlation is based on the assumption that the heat loss to the flame holder is the main factor that determines the inverted flame blow-off behavior and on the similarity between the mechanisms of energy and momentum diffusion in gases (Pr ≈ 1).
																								



3.
Application of Detailed and Reduced Kinetic Schemes for the Description of Detonation of Diluted Hydrogen-Air Mixtures

I. A. Bedarev1,2, K. V. Rylova1,3, A. V. Fedorov1,2
1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
2Novosibirsk State University of Architecture and Civil Engineering, Novosibirsk, 630008 Russia
3Novosibirsk State Technical University, Novosibirsk, 630073 Russia
Keywords: подавление детонации, математическое моделирование, смесь реагирующих газов и инертных частиц, detonation suppression, mathematical modeling, mixture of reactive gases and inert particles

Abstract >>
A possibility of using some kinetic models for the description of detonation of a gaseous hydrogen-air mixture is justified. A hierarchy of mathematical models from the simplest model of combustion under static conditions to the model of unsteady nonequilibrium gas dynamics is numerically constructed. Verification is performed on the basis of experimental data on the ignition delay time as a function of temperature and on the detonation wave velocity as a function of dilution of the mixture by argon or nitrogen. A mathematical technology for the description of cellular detonation propagation in channels of various engineering devices is developed on the basis of detailed and reduced kinetic mechanisms of nonequilibrium chemical transformations within the framework of the ANSYS Fluent commercial software system. It is demonstrated that the cell size in a mixture diluted by argon by 92% in a channel 30 mm wide is in good agreement with experimental data.
																								



4.
Filtration Combustion of Carbon in the Presence of Endothermic Oxidizers

S. V. Glazov, E. V. Polianczyk
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
Keywords: фильтрационное горение, углеродное топливо, моделирование, противоток, эндотермический окислитель, Filtration combustion, carbon fuel, modeling, opposed flow, endothermic oxidizer

Abstract >>
This paper presents a model for the steady-state filtration combustion of carbon mixtures with a solid incombustible material in opposed gas flow containing an endothermic oxidizer such as steam and/or carbon dioxide. A computation scheme for calculating the characteristics of the process (combustion temperature and composition of the products) is proposed for the case where the product composition is determined by the thermodynamic equilibrium in the high-temperature zone. For stoichiometric regimes, finite analytical expressions are obtained that relate the combustion temperature and the composition of the products with the oxidizer gas composition and the proportion of carbon in the carbon/solid inert material mixture. Predictions of the model are in qualitative agreement with published experimental data.
																								



5.
Calculation of the Characteristics of Agglomerates during Combustion of High-Energy Composite Solid Propellants

V. A. Babuk, A. N. Ivonenko, A. A. Nizyaev
Ustinov Baltika State Technical University (Voenmekh), St. Petersburg, 190005 Russia
Keywords: агломерация, горение, топливо, конденсированные продукты, моделирование, agglomeration, combustion, propellant, condensation products, modeling

Abstract >>
The problem of calculating the characteristics of the agglomerates formed during combustion of high-energy composite solid propellants is considered. It is shown that the mathematical models developed by the authors can be used for different propellant formulations to evaluate not only the dispersion of agglomerates, but also their quantity, chemical composition, and structure. The rules (algorithm) of using the developed models for a wide range of propellant formulations are determined. Modeling results for a number of propellant formulations based on various components are analyzed.
																								



6.
Semi-Empirical Model of the Combustion Wave in a Gas Suspension of Magnesium Particles

A. V. Fedorov, A. V. Shulgin, Yu. S. Korneeva
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: газовзвесь, воспламенение, горение, математическое моделирование, структура волны горения, gas suspension, ignition, combustion, mathematical modeling, combustion wave structure

Abstract >>
A physicomathematical model within the framework of the approach of mechanics of reacting heterogeneous media is proposed to describe the combustion wave in a mixture of a gas and fine magnesium particles. The model is verified on the basis of dependences of the limiting temperature of ignition and combustion wave velocity on the radius and volume concentration of particles. It is guaranteed that the model is valid in the range of particle radii from 7.5 to 35 μm and in the range of volume concentrations of particles (1.2–2.4)·10–4.
																								



7.
On the Theory of Multiple Repetitions of a Nonisothermal Wave Process

V. K. Smolyakov, O. V. Lapshin
Tomsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia
Keywords: метастабильная фаза, волны горения и разложения, metastable phase, combustion and decomposition waves

Abstract >>
An explanation for multiple repetitions of a nonisothermal wave process in one sample is proposed. The explanation is based on synthesis and decomposition of a metastable product. A mathematical model of this phenomenon is constructed and studied. The resultant characteristics of synthesis and decomposition waves are compared with available experimental data.
																								



8.
Effect of V2O5 on the Oxidation Mechanism of ASD-4 Powder

V. G. Shevchenko1, V. N. Krasil'nikov1, D. A. Eselevich1, A. V. Konyukova1, A. I. Ancharov2,3, B. P. Tolochko2
1Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences, Ekaterinburg, 620990 Russia
2Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch, Novosibirsk, 630128 Russia
3Novosibirsk State University, Novosibirsk, 630090 Russia
Keywords: порошкообразный алюминий, ванадийсодержащие гидрогели, активация окисления, полнота окисления, in-situ исследование структурного превращения, powdered aluminum, vanadium-containing hydrogels, activation of oxidation, completeness of oxidation, in-situ study of structural conversion

Abstract >>
Thermokinetic data on the oxidation of ASD-4 powder modified by impregnation with V2O5 gel were obtained by thermogravimetry and differential scanning calorimetry under heating in air to 1250 °C at a rate of 10 deg/min. The phase formation process directly during oxidation of the modified ASD-4 was studied by powder x-ray diffraction method using a synchrotron radiation source. A mechanism for the effect of V2O5 on the oxidation of ASD-4 is proposed on the basis of literature data and analysis of the results of the studies performed.
																								



9.
Thermal Explosion in Mechanically Activated Low-Calorific-Value Compositions

M. A. Korchagin1,2
1Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630128 Russia
2Tomsk State University, Tomsk, 634050 Russia
Keywords: механическая активация, тепловой взрыв, низкокалорийные составы, температура инициирования реакции, твердофазный синтез, mechanical activation, thermal explosion, low-calorific-value compositions, reaction initiation temperature, solid phase synthesis

Abstract >>
The effect of preliminary mechanical activation of low-calorific-value powdered formulations in a planetary ball mill on the main parameters of the subsequent thermal explosion has been studied. It has been found that in mechanically activated compositions, the initiation temperature of thermal explosion is reduced by hundreds of degrees. The maximum decrease (1300 °C) is observed for the Ti + 4 wt.% C system. Regimes of preliminary mechanical activation of reaction mixtures and the subsequent thermal explosion conditions producing Ti3Al and Ni3Al single-phase intermetallic compounds with nanometer grain size were determined. For the 3Ni + Al composition, the energy accumulated during mechanical activation was evaluated. It is shown that the initiation temperature of thermal explosion in the MA compositions studied can be used to estimate the temperature that develops in the mill drums.
																								



10.
Correction of PIV Data for Reconstruction of the Gas Velocity in a Supersonic Underexpanded Jet

V. M. Boiko, V. I. Zapryagaev, A. A. Pivovarova, S. V. Poplavski
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: ударные волны, струйные течения, PIV-диагностика, shock waves, jet flows, PIV diagnostics

Abstract >>
A method of correction of particle image velocimetry (PIV) data for reconstruction of the gas velocity based on the particle velocity in supersonic underexpanded jets is considered. The method is based on estimating the velocity lag of tracer particles on the basis of their velocity relaxation parameter as a correction to PIV data in the Newton approximation of interphase interaction. It is shown that the velocity relaxation parameter of tracer particles in flows with velocity jumps can be determined from the initial PIV data. Correction with the found parameter of velocity relaxation of the phases provides good accuracy.
																								



11.
Method of Shock Wave Overpressure Reconstruction

Y. Guo, Y. Han, L. Wang
National Key Laboratory of Electronic test Technology in North University of China, Taiyuan, Shanxi, 030051 China
Keywords: восстановление избыточного давления, оптимальная структура тестирующей системы, разбиение сетки на подобласти с ячейками разного масштаба, оптимальное расположение датчиков, обобщенное обратное преобразование, overpressure reconstruction, optimal design of the testing system, subregion and multiscale cell partition, optimal distribution of sensors, generalized inversion

Abstract >>
A method of shock wave overpressure reconstruction is presented, which allows overcoming the drawbacks of the previous approaches associated with the lack of shock wave velocity measurement points and the limitations of the empirical formula. An optimal design of the testing system is proposed. Based on the optimal system, the shock wave velocity field is inverted with the use of the generalized inversion theory, and the overpressure distribution is obtained. The inversion results are preferable to empirical results because the experimental data are confirmed in a limited area. Methods of overpressure computation and visualization are described.
																								



12.
Formation of Cubic Silicon Nitride from the Low-Pressure Phase by High-Temperature Shock Compression

V. V. Yakushev, A. N. Zhukov, A. V. Utkin, A. I. Rogacheva, V. A. Kudakina
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: нитрид кремния, ударная волна, фазовые превращения, высокотемпературное ударное сжатие, уравнение состояния, сверхтвердые материалы, Silicon nitride, shock wave, phase transformations, high-temperature shock compression, equation of state, superhard materials

Abstract >>
The effect of high-temperature shock compression conditions on the degree of transformation of silicon nitride into a cubic gamma-modification at pressures of 36 and 50 GPa in planar recovery ampoules is studied. The x-ray Rietveld method is used to determine the quantitative phase composition before and after shock compression. The temperature reached during compression and the residual temperature after unloading are calculated. It is shown that the use of high-temperature shock compression at 36 GPa provides a higher transformation level compared to the classical approach based on the addition of copper powder into the samples.
																								



13.
Experimental and Computational Study of Quasispherical Compression of a Copper Shell Loaded by the Detonation of a Plastic Explosive Layer

V. A. Arinin1, V. V. Burtsev1, A. L. Mikhailov1,2, A. M. Podurets1,2, A. V. Rudnev1, M. A. Syrunin1,2, I. A. Tereshkina1,2, B. I. Tkachenko1, M. I. Tkachenko1, I. R. Trunin1,2, A. P. Tsoi1, I. V. Shiberin1
1Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center, Sarov, 607190 Russia
2Sarov Physics and Technology Institute, the Branch of the National Research Nuclear University “MIPhI” Sarov, 607186 Russia
Keywords: оболочка, квазисферически-симметричное нагружение, протонографическая регистрация, микроструктура, откольное разрушение, shell, quasispherical symmetric loading, proton radiography, microstructure, spall fracture

Abstract >>
This work presents the results of experiments on the compression of a spherical copper shell loaded by the detonation of a plastic explosive layer. A U-70 accelerator is used for radiographic recording of the convergence of the shell to the center, and metallographic analysis of the copper shell preserved after the experiment is performed. The results of multiframe proton radiography of the convergence of the inner boundary of the copper shell to the center are compared with the results of numerical simulations.
																								



14.
Estimating the Mass of a Pyrotechnic Mixture for Burning the Launch Vehicle Nose Fairing

D. B. Lempert1, V. I. Trushlyakov2, V. E. Zarko3,4
1Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432, Russia
2Omsk State Technical University, Omsk, 644050 Russia
3Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
4Tomsk State University, Tomsk, 634050 Russia
Keywords: сжигание, головной обтекатель, ракета космического назначения, пиротехническая смесь, burning, fairing, launch vehicle, pyrotechnic mixture

Abstract >>
It is proposed to carry out burning of the launch vehicle nose fairing after it has completed its mission on the descent trajectory from the moment of separation to an altitude of 5-10 km. Burning is carried out in the Earth atmosphere with additional heating of the faring material due to the reaction of pyrotechnic mixtures. Various pyrotechnic mixtures for use in the nose fairing are discussed.