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2013 year, number 6

Nanoparticles of Energetic Materials: Synthesis and Properties (Review)

M. K. Berner1, V. E. Zarko2, M. B. Talawar1
1Organizatsiya for the Prohibition of Chemical Weapons (OPCW), 2517 The Hague, Netherlands
2Institute of Chemical Kinetics and Combustion them V.V. Voevodsky SB RAS, 630090 Novosibirsk
Keywords: nanoparticles, gas-generating propellants, energetic materials

Abstract >>
The replacement of micrometer-sized metal fuel powders in gas-generating solid propellants with nanosized metal powders has become a common trend in the design of new types of propellants in recent decades. This trend has been motivated by the unique properties of propellants containing nanocomponents. The emergence of nanostructured gas-generating propellants suggests new directions for the development of highly concentrated and efficient energy sources. Technologies for large-scale production of nanometal powders and other nanostructured materials with tailored characteristics have also experienced an impetuous development in recent years. This paper presents a classification, description, and competitive analysis of the main methods of producing nanoscale and nanostructured materials used to produce gas-generating propellants. The main advantages and difficulties concomitant with the use of nanomaterials in propellant formulations are discussed. Specific issues related to the high reactivity and pyrophoricity of nanomaterials and related risks are analyzed. Methods for the preservation and passivation of the surface of nanomaterials are classified and discussed. The focus is on those methods that are most widely used, and those that are considered promising today.

Solving the Problem of Diffusion Combustion of a Droplet with Allowance for Several Independent Reactions

V. M. Guendugov, N. N. Smirnov, V. V. Tyurenkova
Moscow State University M.V. Lomonosov, 119992 Moscow
Keywords: gas, liquid, droplet, fuel, evaporation, combustion, diffusion

Abstract >>
Steady combustion of a liquid fuel droplet in a gaseous oxidizer environment with equilibrium or nonequilibrium evaporation from the surface is studied. As the fueloxidizer interaction is not limited to one reaction and usually proceeds in accordance with a multistage chain or non-chain mechanism, the SchwabZel'dovich method is extended to several reactions. The results obtained show that this solution method tested on two reactions can be effectively used to solve combustion problems.

Dynamic Characteristics of a Resonant Gas-Dynamic System for Ignition of a Fuel Mixture

K. Yu. Aref'ev1,2, A. V. Voronetskii2, M. A. Il'chenko1
1Tsentralny Institute of Aviation Motors Baranov, 111116 Moscow
2Moscow State Technical University Bauman, 105005 Moscow
Keywords: ignition system, pressure oscillations, gas-dynamic resonance, liquid-propellant thruster, Hartmann oscillator

Abstract >>
Results of an experimental study of specific features of operation of a resonant gas-dynamic ignition system, as applied to initiation of liquid-propellant thrusters, are reported. Dynamic characteristics of the initiation process are determined. The behavior of the spectral characteristics of pressure oscillations in the combustor of a testbench model of a liquid-propellant thruster with ignition of the fuel mixture by the gas-dynamic system is considered.

Theory of Combustion of Thin Film Structures

O. V. Lapshin, V. K. Smolyakov
Department of Structural Macrokinetics Tomsk Scientific Center, SB RAS, 634050, Tomsk
Keywords: boundary kinetics, diffusion, combustion modes

Abstract >>
The problem of combustion of thin film compositions is considered in view of the finite reaction rate at the interfaces. Formulas defining the combustion rate in the diffusion mode and the mode limited by the boundary kinetics are obtained. On the basis of these formulas, techniques for estimating the parameters of the diffusion and boundary kinetics are proposed. Unsteady combustion modes are studied, and features of the transition from the kinetic to the diffusion mode are revealed.

Modeling of an Electrothermal Explosion in Gasless Systems Placed into an Electroconducting Medium

S. A. Bostandzhiyan, I. S. Gordopolova, V. A. Shcherbakov
Institute of Structural Macrokinetics RAS, 142432 Chernogolovka
Keywords: electrothermal explosion, modeling, inert heating, ignition

Abstract >>
An electrothermal explosion in cylindrical specimens surrounded by an annular layer of an electroconducting material is simulated. The entire system is located in a cylindrical metallic casing, which is electrically insulated from the electroconducting medium. Heat exchange with the ambient medium proceeds in accordance with Newton's law. An analytical solution of the problem of determining stationary temperature fields under inert heating in the absence of chemical heat sources is obtained. Critical conditions of the electrothermal explosion (power of electric heat release) are determined. Ignition on the specimen axis occurs in the supercritical regime in a certain range of the power of electric heat release. At greater values of the power of electric heat release, ignition occurs on the specimen surface.

Acoustic Emission during Self-Propagating High-Temperature Synthesis

A. I. Kirdyashkin, R. M. Gabbassov, Yu. M. Maksimov, V. G. Salamatov
Department of Structural Macrokinetics Tomsk Scientific Center, Russian Academy of Sciences, 634021 Tomsk
Keywords: combustion, heterogeneous system, acoustic emission

Abstract >>
It was established experimentally that during SHS, reaction systems (NiAl, TiB, MoB, etc.) generated acoustic oscilations in the frequency range from 5 Hz to 1.1 MHz with a pulse power of up to 17 W. It was found that the combustion of different systems is characterized by an individual set of dynamic parameters of acoustic emission in the modes of low ordered discrete pulses and highly ordered self-oscillations. It is shown that the spatial zone of acoustic emission is localized near the combustion wave. Analysis of the acoustic emission mechanisms of SHS is performed.

Unsteadiness in a Ramjet Model

V. M. Levin1, V. N. Karasev1, L. L. Kartovitskii1, E. A. Krymov2, O. A. Skachkov2
1Moscow Aviation Institute, 125993 Moscow
2Central Research Institute of Ferrous Metallurgy Bardin, 105005 Moscow
Keywords: ramjet, two-section combustor, aviation kerosene, working process, instability

Abstract >>
The process of combustion of a hydrocarbon fuel in a pulsed mode is discussed on the basis of results of ramjet testing in an external flow modeling a Mach 5 flight.

Analytical Calculation of the Negative Erosive Burning Rate

K. O. Sabdenov, M. Erzada
Eurasian National University L.N. Gumileva, 010008 Astana, Kazakhstan
Keywords: negative erosive effect, critical Vilyunov number, BulgakovLipanov number, kinetic energy of gas flow, initial combustion temperature of solid propellant

Abstract >>
The rate of negative erosive combustion is calculated using analytical methods and a simple model of the gas-phase chemical reactions A → B. The conversion of part of the thermal energy into the kinetic energy of motion of gaseous combustion products along the propellant gasification surface is taken into account within the model. Solutions are obtained for the cases where the thickness of the laminar sublayer is larger or smaller than the width of the combustion zone in the gas phase. The calculation results confirm the author's previous conclusion: manifestation reduction in the negative erosive effect with decreasing initial temperature of the propellant is caused by narrowing of the region of its occurrence.

Underwater Combustion of Ballistite Propellant in the Centrifugal Force Field with the Gasification Front Moving Toward the Acceleration Vector

V. D. Barsukov, S. V. Goldaev, N. P. Min'kova, S. A. Basalaev
Institute of Applied Mathematics and Mechanics, Tomsk State University, 634050 Tomsk
Keywords: ballistite propellant, acceleration, water medium, mobile localizer of the combustion zone, gasification front

Abstract >>
This paper discusses the results of experiments on the underwater combustion of ballistite propellant in a centrifugal force field where the gasification front moves in the direction of acceleration. The necessary conditions for the combustion were provided using a mobile localizer of the combustion zone, which was a shell of a heat-resistant material put on the test sample of the propellant.

Continuous Spin Detonation of a CoalAir Mixture in a Flow-Type PlaneRadial Combustor

F. A. Bykovskii1, S. A. Zhdan1,2, E. F. Vedernikov1, Yu. A. Zholobov2
1Institute of Hydrodynamics M.A. Lavrentiev SB RAS, 630090 Novosibirsk
2Novosibirsk State University, 630090 Novosibirsk
Keywords: continuous spin detonation, planeradial vortex combustor, coal, flow structure

Abstract >>
Regimes of continuous spin detonation of coal particles in an air flow in a flow-type plane–radial combustor 500 mm in diameter are studied. The tested substance is fine-grained cannel coal from Kuzbass having a particle size of 17 mm and containing 24.7% of volatiles, 14.2% of ashes, and 5.1% of moisture. A certain amount of hydrogen is added for coal transportation into the combustor and promotion of the chemical reaction on the surface of solid particles. To reduce air pressure losses in channels connecting the manifold and the combustor, their cross section is increased to limiting values (25 cm2), whereas the combustor exit diameter is reduced. The angle of the air flow direction and the combustor geometry are also varied. The minimum pressure difference in the air injection channels (16%) is reached with stability of continuous spin detonation in the combustor being retained. The domain of continuous spin detonation regimes in the coordinates of the fuel flow rate and specific flow rate of the mixture is constructed. The results of studying detonation burning of solid fuels can find applications in power engineering, chemical industry, and environmental science, in particular, contamination by combustion products.

Ab initio Crystal Structure and Charge Density Distribution of a Highly Energetic 2,4-dinitrobenzoic Acid Molecule

P. Srinivasan1, S. N. Asthana2, P. Kumaradhas1
1University Periyar, Salem 636011, India
2Laboratory of high energy materials, 411021 Pune, India
Keywords: energetic material, crystal structure prediction, electron density, Laplacian of electron density, electrostatic potential, impact sensitivity

Abstract >>
The energetic parameters, such as density, bond strength, and sensitivity of explosives/propellants decide their detonation power and safety. Experimentally, optimization of these parameters is found to be a difficult task; therefore, prior to synthesis, it makes sense to estimate these parameters by computational techniques, ab initio crystal structure prediction, and quantum chemical calculation coupled with the AIM analysis. Here, we predict the density of an energetic 2,4-dinitrobenzoic acid (DNBA) molecule from different ab initio crystal structure models and validate the results through comparisons with experimental data. The bond topological characterization reveals that the C—NO2 bonds are the weakest bonds and are identified as sensitive bonds in the molecule. The bond sensitivity is estimated from Murray's method. The impact sensitivity of this molecule is also calculated. Large negative electrostatic potential regions are found near the NO2 and carboxylic groups, which are the reactive sites of the molecule.

Detonation Parameters of Pressed Charges of Benzotrifuroxane

A. Yu. Dolgoborodov, M. A. Brajnikov, M. N. Makhov, N. E. Safronov, V. G. Kirilenko
Institute of Chemical Physics N.N. Semenova RAS, 119991 Moscow
Keywords: benzotrifuroxane, detonation, optical pyrometer, temperature, heat of explosion, propellant performance

Abstract >>
The brightness temperature and pressure profiles of the detonation products of pressed charges of benzotrifuroxane were determined by a pyrometric method, and the heat of explosion and propellant performance were experimentally determined. The temperature of the detonation products (4100150 K) was significantly lower than the calculated values reported in most theoretical papers. Compared to HMX, benzotrifuroxane has a higher heat of explosion but lower expansion velocity of the shell T-20) method and Gurney energy.

Equation of State of Polytetrafluoroethylene for Calculating Shock Compression Parameters at Megabar Pressures

A. M. Molodets, D. V. Shakhrai, A. S. Savinykh, A. A. Golyshev, V. V. Kim
Institute of Problems of Chemical Physics, 142432 Chernogolovka
Keywords: shock-wave compression, polymers, Grneisen coefficient, equation of state

Abstract >>
Semi-empirical equations of state (thermal and caloric) are obtained to calculate not only the kinematic parameters (shock wave velocity, particle velocity, reverberation of waves) but also the thermodynamic parameters (temperature, pressure, compression) of monolithic and porous polytetrafluoroethylene at high shock pressures. The equations of state are used to model wave interaction in shock-wave experiments using the developed hydrocode. The equations are verified by comparison simulation results with published results of experiments and the data of our shock compression tests of solid and porous samples of PTFE in the range of 10170 GPa.