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Combustion, Explosion and Shock Waves

2016 year, number 5

Solid Propellant Combustion in High-Velocity Gas Flow (Review)

V. A. Arkhipov1, V. E. Zarko2, I. K. Zharova1, A. S. Zhukov1, E. A. Kozlov1, D. D. Aksenenko3, A. V. Kurbatov3
1Tomsk State University, Tomsk, 634050 Russia
2Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 Russia
3Altai Federal Research and Production Center, Biisk, 659323 Russia
Keywords: твердое топливо, эрозионное горение, коэффициент эрозии, сверхзвуковой поток, параметр Победоносцева, параметр Вилюнова, solid fuel, erosive burning, erosion coefficient , supersonic flow, Pobedonostsev parameter, Vilyunov parameter

Abstract >>
Combustion of solid propellant charges in rocket propulsion systems usually occurs under conditions of intense flow of combustion products (solid rocket motor), gaseous oxidizer (hybrid rocket motor) or air (ramjets and air-breathers).This causes the so-called erosive burning effects, resulting in a change in the burning law under the influence of the gas flow. The main approaches to modeling the erosive burning of solid fuels in high-velocity gas flow are considered. Methods for the criterial description of the results of experimental studies of the erosive burning of solid fuels under transonic and supersonic flow conditions are analyzed.

Stabilization of Diffusion Flames of Impacting and Opposing Fuel Jets

V. K. Baev, A. N. Bazhaikin
Khristianovich Institute of Theoretical and Applied Mechanics, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: диффузионное горение, встречные струи, срыв горения, стабилизация пламени, критерий гомохронности, балластирование топлива углекислым газом, diffusion combustion, opposing jets, combustion failure, flame stabilization, homochronicity criterion, fuel ballasting by carbon dioxide

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Stability of diffusion combustion of fuel jets impacting on targets and interaction of two jets (pure propane-butane and the same fuel with addition of carbon dioxide) are experimentally studied. Data on combustion failure are obtained for various variants of jet interaction, as well as information about the composition of combustion products, air-to-fuel ratio, and completeness of combustion before combustion failure. It is shown that the domain of stable combustion of impacting and opposing jets is expanded by more than an order of magnitude as compared to combustion of individual free jets.

Combustion and Detonation of Propane-Air Composition in Large-Scale Experiments

V. I. Tarzhanov, V. G. Vil'danov, V. I. Sdobnov, I. V. Telichko, A. D. Zinchenko, A. E. Makarov, I. A. Litvinenko, V. A. Ogarkov, V. V. Vlasov, A. V. Vorob'ev, I. G. Koretskii, S. L. Mukhin, A.F. Khanin, A. N. Grachev, V. A. Matkin, V. A. Potashnikov
Zababakhin Russian Federal Nuclear Center, Institute of Technical Physics, Snezhinsk, 456770 Russia
Keywords: горение, детонация, переход горения в детонацию, пропановоздушные составы, крупномасштабные опыты, combustion, detonation, deflagration to detonation transition, propane-air compositions, large-scale experiments

Abstract >>
This paper presents the results of two large-scale tests performed to clarify the conditions for the detonation of propane-air compositions in model surface clouds in the absence and in the presence of confining rigid walls. Model clouds with sizes of 15 x 6 x 4.2 and 15 x 6 x 2 m were confined by plastic tents. A mixture of starting reactants in the cloud was ignited by the hot detonation products propagating along a perforated 0.82 x 23 m tube passing through the space of the tent. Hot detonation products were injected from the tube through holes of 20 and 40 mm diameters. Detonation of the propane-air mixture in the tube was initiated by explosion of an explosive charge placed at the tube end. Detonation occurred in the propane-air cloud bounded on one side by a rigid vertical wall, and no detonation was observed in the cloud with similar injection of hot products without a rigid wall. It is concluded that the divergence or convergence of the flows of hot detonation products play a key role in the process, being responsible for the presence or absence of detonation in the mixing region, respectively.

Catalytic Oxidation of Methane on Ceramic-Metal Catalysts CuO CuO/Al$2O3/FeAlO/FeAl

S. F. Tikhov1, Yu. N. Bespalko1, V. A. Sadykov1,2, A. N. Salanov1, S. I. Reshetnikov1
1Boreskov Institute of Catalysis, SB RAS, Novosibisk 630090, Russia
2Novosibirsk State University, Novosibirsk 630090 Russia
Keywords: каталитическое окисление метана, керамометаллические катализаторы, catalytic oxidation of methane, ceramic-metal catalysts

Abstract >>
The activity of plates of CuO/Al2O3/FeAlO/FeAl ceramic metal structured catalysts is compared by varying the alumina content in them. The catalysts were prepared by impregnation of the ceramic metal carriers obtained by mechanochemical activation of powder mixtures of an alumina precursor (20-50% (wt.)), iron and aluminum, followed by hydrothermal treatment and calcination. It is shown that with increasing content of the alumina precursor (product of thermal activation of hydrargillite) increases the specific surface area of the carrier and meso- and macropore volume and reduces its mechanical strength. The content of the active component (CuO) also increases, resulting in an increase in the specific activity of the catalyst despite a reduction in the effectiveness of using the active component. The activity of catalysts with a medium concentration of alumina is sufficient to initiate oxidation of methane.

Transformation of Thermal Regimes of Exothermic Reaction in the Case of Harmonic Perturbations of the Velocity and Temperature of the Reagent at the Entrance of the Adiabatic Reactor

A. A. Butakov, E. N. Shatunova, A. Yu. Kostin
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: адиабатический реактор, математическое моделирование, тепловые режимы, периодические возмущения, стабилизация неустойчивых режимов, adiabatic reactor, mathematical modeling, thermal conditions, periodic perturbations, stabilization of unstable regimes

Abstract >>
On the basis of physical concepts and the results of thermal theory of combustion, the qualitative analysis and mathematical simulation of transformation of steady temperature distributions along the length of the adiabatic reactor. It is revealed that, with a certain amplitude and a frequency of harmonic perturbations of the velocity of reagents, it is possible to increase the thermal stability of the process (obtain the pre-explosion heating).

Initiation of Combustion of Coal Particles Coated with a Water Film in a High-Temperature Air Flow

A. V. Zakharevich1, G. V. Kuznetsov1, V. V. Salomatov2, P. A. Strizhak1, S. V. Syrodoi1
1Tomsk Polytechnical University, Tomsk, 6340050 Russia
2Kutateladze Institute of Thermophysics, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: водоугольное топливо, зажигание, тепло- и массоперенос, термическое разложение, испарение, водяная пленка, время задержки зажигания, время испарения, water-coal fuel, ignition, heat and mass transfer, thermal decomposition, evaporation, water film, ignition delay time, evaporation time

Abstract >>
Results of an experimental study of ignition of a water-coal fuel in a high-temperature air flow are presented. The fuel is obtained on the basis of the mark D coal or filtrational cake of the Severnaya dressing plant. Based on the experimental results, physical and mathematical models of the processes of thermal preparation and ignition of water-coal fuel particles are formulated, which take into account the joint proceeding of the most relevant physical and chemical transformations (which exert an essential effect on the ignition condition) and the processes of heat and mass transfer during the induction period. A comparison of the basic ignition characteristics (ignition delay time and limiting values of the gas medium temperature), which are obtained experimentally and theoretically (based on results of numerical simulations), leads to a conclusion that the water film affects the dynamics of the ignition process.

Combustion of Carbonized Coal Residue in Water-Oxygen Supercritical Fluid

A. A. Vostrikov, O. N. Fedyaeva, D. Yu. Dubov, A. V. Shishkin, M. Ya. Sokol
Kutateladze Institute of Thermal Physics, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: горение, газификация, уголь, водокислородный сверхкритический флюид, combustion, gasification, coal, water-oxygen supercritical fluid

Abstract >>
The first mode is implemented partial oxidation carbonized residue in coal vodokislorodnogo fluid stream at a temperature of 923 K and a pressure ~30 MPa. Detected flow coupled processes of oxidation and carbon balance formation of inflammable gases (hydrogen content in the products increase by 26 % its relative amount in the original sample) due to the participation of the molecules H2O in redox reactions.

On the Mechanism of Thermal Decomposition of Ammonium Dinitramide (Review)

N. E. Ermolin, V. M. Fomin
Khristianovich Institute of Theoretical and Applied Mechanics, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: динитрамид аммония, конденсированная фаза, термическое разложение, механизм, ammonium dinitramide, condensed phase, thermal decomposition, mechanism

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Despite significant progress in studying thermal decomposition of ammonium dinitramide (ADN), the kinetics of the process at the level of elementary stages has not been adequately studied. The aim of this review is to summarize various published data, which are of interest for studying and simulating the processes of thermal decomposition and combustion of ADN. Considerable attention is paid to physical and chemical properties of ADN, dinitramide and its anion N(NO2)2-, which play a key role in ADN decomposition. Various channels of decomposition of ADN, dinitramide, and N(NO2)2- are discussed. Results illustrating alternative points of view on the decomposition process are presented.

On Mixing of the Products of Detonation of Composite Explosives in the Chemical Reaction Region

V. V. Mitrofanov, V. M. Titov
Lavrentyev Institute of Hydrodynamics,Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: ультрадисперсный алмаз (УДА), детонация, смешение, диффузия, изотопный метод, ultrafine diamond (UFD), detonation, mixing, diffusion, isotope technique

Abstract >>
The problem of mixing of the products of detonation of composite explosives is of principal importance for the synthesis of ultrafine diamond from composite mixtures and also for chemistry of detonation processes as a whole. An analysis of mixing in the chemical reaction region due to molecular diffusion shows that this mechanism may be important only for grain sizes of several micrometers. If the grain sizes reach tens or hundreds of micrometers, only partial mixing on the grain boundaries is possible. Investigations of the hydrodynamic mechanism of mixing shows that it may occur owing to a nonuniform velocity field behind the detonation wave front in the mixture and to the development of turbulence and cumulative processes during pore implosion. In mixtures with grain sizes of the order of 30 m, these processes can lead to appreciable mixing during the time of »0.5\s and longer. Theoretical estimates are compared with the results of experiments performed at the Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences and at the Altai scientific and industrial enterprise (Biisk) for studying the synthesis of ultrafine diamond with the use of the isotope technique.

Laser Initiation of PETN-Based Compositions with Submicron Coal Particles

B. P. Aduev, D. R. Nurmukhametov, N. V. Nelyubina, R. Yu. Kovalev, A. P. Nikitin, A. N. Zaostrovskii, Z. R. Ismagilov
Institute of Coal Chemistry and Material Science, Russian Academy of Sciences, Kemerovo, 650000 Russia
Keywords: взрыв, лазерное инициирование, тэн, бурый уголь, низкометаморфизованный уголь, лазер, оптоакустика, летучие вещества, коксовый остаток, explosion, laser initiation, PETN, brown coal, low-metamorphized coal, laser, optoacoustics, volatiles, carbon residue

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This paper describes the results of experiments on laser initiation of composites based on PETN and inclusions of submicron coal particles. The thresholds and kinetic characteristics of explosion of mixed compositions based on PETN and inclusions of submicron coal particles (B and DG) are studied under the influence of neodymium laser (1064nm, 12 ns), depending on the mass concentration of inclusions in the range of 0-5%. It is shown that the minimum threshold of explosive decomposition of PETN equal to 1.1 J/cm2 can be achieved if the concentration of both types of inclusions is 0.5%.

Numerical Simulation of the Formation of Shaped-Charge Jets from Hemispherical Liners of Degressive Thickness

S. V. Fedorov
Bauman Moscow State Technical University, Moscow, 105005 Russai
Keywords: кумулятивный заряд, кумулятивная струя, полусферическая облицовка дегрессивной толщины, массово-скоростное распределение, распределение предельная длина струи - скорость, shaped charge, shaped-charge jet, hemispherical liner, degressive thickness, mass-velocity distribution, ultimate jet length-velocity distribution

Abstract >>
The formation of shaped-charge jets from hemispherical copper liners of degressive (decreasing from top to bottom) thickness is analyzed by numerical simulation of a two-dimensional axisymmetric problem of continuum mechanics. The basis for the comparison was taken to be the parameters of the jet formed from a modern standard shaped charge with a conical liner which provides penetration of a steel target to a depth equal to 10 charge diameters. In the comparative analysis, we used calculated mass-velocity distributions and the ultimate jet length-velocity distributions obtained on the their basis, from which the potential penetrability of jets was evaluated. It is shown that the use of hemispherical cumulative liners of degressive thickness makes it possible to form shaped-charge jets that are not inferior in head velocity and penetrability to the jets from conical liners.

Specific Features of the Transformation of Spall Cracks to Localized Shear Bands

S. N. Buravova, E. V. Petrov, A. S. Shchukin
Institute of Structural Macrokinetics and Material Science Problems, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: ударная волна, разгрузка, интерференция, локализация, адиабатические полосы сдвига, откольное разрушение, shock wave, unloading, interference, localization, adiabatic shear bands, spall fracture

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Investigations of specific features of the microstructure of the region where a spall crack transforms to an adiabatic shear band are based on a spall model of strain localization, which implies that adiabatic shear bands are induced by interference of unloading waves, and the value of the negative stress in the expansion region of these waves does not exceed the dynamic strength of the material. It is shown that the transition region contains a tremendous number of dislocation ensembles, which is much greater than the number of dislocation ensembles generated by a shock wave. Detection of micrometer-sized fracture sites in the region of interference of unloading waves implies that small fracture sites are formed in a polycrystalline material on dislocations arising in the course of dynamic tension.