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Combustion, Explosion and Shock Waves

2020 year, number 2

Extension of the Laminar Flame in a Weak Electric Field

A. V. Tupikin1, V. V. Zamashchikov2,3
1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
2Voevodskii Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
3Novosibirsk State University, Novosibirsk, 630090 Russia
Keywords: ламинарное пламя, электрическое поле, PIV, спектрозональная регистрация, нормальная скорость пламени, растяжение пламени, laminar flame, electric field, spectral zonal registration, normal velocity of the flame, flame extension

Abstract >>
An approach to studying the influence of the electric field on the flame with separate consideration of the effects of curving and extending of the plane flame is proposed. The degree of deformation can be used as a factor determining the action efficiency. Based on the results obtained by combined application of particle image velocimetry and spectral zonal registration, the change in the degree of deformation of the flame of a Bunsen-type burner located between flat electrodes is estimated.

On the Structure of an Impinging Jet with Flow Swirl and Burning

D. K. Sharaborin1,2, R. V. Tolstoguzov1,2, V. M. Dulin1,2, D. M. Markovich1,2
1Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
2Novosibirsk State University, Novosibirsk, 630090 Russia
Keywords: закрученная струя, горение в вихревом потоке, импактная струя, пристенное горение, swirled jet, vortex burning, impinging jet, wall burning

Abstract >>
The PIV and PLIF OH methods were used to experimentally study the structure of a jet impinging on a flat surface with swirl and combustion of a propane-air mixture with an equivalence ratio of 0.7 at distances between the nozzle and the surface H / d = 1 and 3 and in the absence of the impinged surface. The swirl parameter was 0.41 and 1.0, and the Reynolds number was 5000. It is concluded that for both values of the swirl parameter, the presence of the surface leads to the formation of an extended central cone-shaped recirculation zones. For H / d = 3 and 2, the intensity of OH fluorescence near the impinged surface and inside the recirculation zone significantly reduced. This effect is presumably caused by a decrease in the temperature of combustion products in the recirculation zone, including in the neighborhood of the flame front.

Combustion of Ferrotitanium in Nitrogen

A. A. Glazunov1, Yu. M. Maksimov2, L. N. Chukhlomina2, B. Sh. Braverman2, A. N. Avramchik2
1Tomsk State University, Tomsk, 634050 Russsia
2Tomsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055 Russia
Keywords: ферротитан, горение, нитрид титана, глубина превращения, фазовый состав, ferrotitanium, combustion, titanium nitride, depth of conversion, phase composition

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Combustion of FTi70 industrial ferrotitanium containing 65.9% of Ti and a model alloy of iron with 30.6% of Ti in nitrogen is described. It is shown that the degree of nitriding of the combustion products of industrial ferrotitanium is low. The distribution of nitrogen along the sample diameter is uneven. The dilution of the alloy with the final product increases in the degree of nitriding. The study of the combustion of the model alloy concludes that the degree of nitriding increases along with the melting point of the initial alloy. The composition of the combustion products of ferrotitanium is described.

Discrete Model of Combustion of a Donor-Acceptor Mixture

V. G. Prokof'ev1,2
1Tomsk State University, Tomsk, 634050 Russia
2Tomsk Scientific Center, Siberian Branch, Russian Academy of Science, Tomsk, 634021 Russia
Keywords: гетерогенная система, элементарная ячейка, безгазовое горение, heterogeneous system, unit cell, gasless combustion

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The numerical simulation method is used to analyze the influence of a unit cell size on the burning rate of a donor-acceptor system. The cell size determines the fragmentation of a combustion wave. It is determined during calculations that, with an increase in the unit cell size, the average burning rate of the sample decreases. The combustion limits of a cellular system with external heat removal from the sample surface are determined: an increase in the unit cell size contributes to expansion of the combustion limits of the sample. The principal possibility of the synthesis in a chemical furnace for the cellular formation of the structure of the reacting system is shown.

Prospects of usinsg Boron Powders as Fuel. II. Influence of Aluminum and Magnesium Additives and their Compounds on the Thermal Behavior of Boron Oxide

A. N. Pivkina, D. B. Meerov, K. A. Monogarov, Yu. V. Frolov, N. V. Murav'ev
Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia
Keywords: частицы бора, оксид бора, испарение, термическая стабильность, термический анализ, boron particles, boron oxide, evaporation, thermal stability, thermal analysis

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Physicochemical changes occurring in an oxide shell of boron particles during heating are extremely important for the oxidation and combustion of boron, including those in solid propellant compositions. The Al2O3, MgO, MgF2, Al, and Mg impurities were experimentally discovered in an oxide layer on boron particles obtained by various methods. The goal of this work is to determine the effect of these impurities on the thermal behavior of boron oxide, with particular attention paid to evaporation of B2O3. The temperature and thermal effects of reactions between the components are thermoanalytically determined, and the processes of dehydration, melting, and evaporation of boron oxide are analyzed in detail. The enthalpy of evaporation of boron oxide, starting at a temperature above 1 300oC is experimentally determined, and is equal to 347 ± 3 kJ/mol. An interaction is observed between magnesium fluoride and boron oxide at a temperature of about 1 000oC with a mass loss corresponding to the content of magnesium fluoride and the formation of gas-phase boron fluoride. It is established that boron dissolved in oxide has virtually no effect on the evaporation of the boron oxide melt, while the addition of Al2O3 or MgO significantly increases its thermal stability. Based on the analysis of the results obtained, an assumption is made about the effect of impurities on boron activity in the processes of boron ignition and combustion.

Influence of the Amount of a Fe2O3 Modifier on the Oxidation Rate of ASD-4 Micron-Sized Powder

V. G. Shevchenko1, V. N. Krasil'nikov1, D. A. Eselevich1, A. V. Konyukova1, Z. S. Vinokurov2,3, A. I. Ancharov3,4, B. P. Tolochko4,5
1Institute of Solid State Chemistry, Ural Branch of Russian Academy of Sciences, Ekaterinburg, 620990 Russia
2Boreskov Institute of Catalysis, 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 Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630128 Russia
Keywords: алюминий, порошок, модификация, основной формиат железа, оксиды железа, окисление, фазовый анализ, aluminum, powder, modification, basic iron formate, iron oxides, oxidation, phase analysis

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The effect of the modification of ASD-4 micron-sized aluminum powder with iron oxide on its oxidation in air is investigated. The modification consisted of coating the surface of metal particles with gel based on Fe(OH)(HCOO)2 and ethylene glycol monomethyl ether, CH3OC2H4OH, followed by heat treatment in air. It was found that the presence of iron oxide generally has a positive effect on the dynamics of oxidation ASD-4 powder when heated in air. The oxidation rate of modified powders increases with increasing content of iron oxide in them. X-ray diffraction analysis using a synchrotron radiation source under heating to 1 000 oC showed that the samples contained only the main phases γ-Al2O3 and α-Al2O3, γ-Fe2O3 and α-Fe2O3, and other iron oxides or intermetallic compounds were not found. At a mass concentration of 10 % Fe, an earlier appearance of the phase α-Al2O3 is observed and the exothermic peak of maximum heat release is shifted to lower temperatures (893 oC) compared to the unmodified ASD-4 powder (1 045 oC).

Suppression Characteristics of Flame Combustion and Thermal Decomposition of Forest Fuels

D. V. Antonov, A. O. Zhdanova, G. V. Kuznetsov
Tomsk Polytechnic University, Tomsk, 634050 Russia
Keywords: пламенное горение, термическое разложение, подавление, лесной горючий материал, теплофизические свойства, пористость, flame combustion, thermal decomposition, suppression, forest combustible material, thermophysical properties, porosity

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An approach to the mathematical modeling of the suppression of thermal decomposition and flame burning of forest fuels is proposed which is different from the well-known approaches in that a pyrolyzed FF layer is represented as a heterogeneous structure with high porosity and the thermophysical characteristics of this layer are described within the framework of additive mathematical models of thermal conductivity, heat capacity, and density. Experimental studies of the main thermophysical characteristics (thermal conductivity, heat capacity, thermal diffusivity) of typical FFs were performed. Mathematical modeling of heat- and mass-transfer processes under the conditions considered was performed, and the suppression characteristics of the destruction reaction of a typical FF were determined using the values of thermophysical characteristics established in the experiments. The ranges of the integral characteristics of FF flame suppression while varying the thermophysical characteristics of FF within the permissible limits were identified.

On the Efficiency of Using a Real Pressure Dependence of the Solid Propellant Burning Rate in a Solid Rocket Motor

A. M. Lipanov1,2, L. N. Kolesnikova2, A. Yu. Leshchev3
1Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Moscow, 125047 Russia
2Kalashnikov Izhevsk State Technical University, Izhevsk, 426069 Russia
3Udmurt Federal Research Center, Ural Branch, Russian Academy of Sciences, Izhevsk, 426067 Russia
Keywords: твердое топливо, заряд, двигатель, давление, скорость горения, закон скорости горения, solid propellant, charge, engine, pressure, burning rate, burning rate-pressure dependence

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A comparative analysis of maximum pressures in a solid rocket motor obtained using exponential and real pressure dependences of the solid propellant burning rate on was performed. It is shown that at high exponents in the burning law, there is a large (tens of percent) difference between the maximum motor pressure obtained by the above two methods. In the case where the exponent is in the range of 0.3–0.4, the exponential pressure dependence of the burning rate overestimates motor pressure only by 2–3%.

Development and Testing of the Laser System of Ignition of Rocket Engines

N. V. Pletnev1, N. B. Ponomarev2, G. A. Motalin2, V. F. Murashov2
1Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow, 119991 Russia
2Keldysh Research Center, Moscow, 125438 Russia
Keywords: жидкостные ракетные двигатели, камера сгорания, горючее, окислитель, факел, запальник, воспламенитель, форсунки, лазерное зажигание, оптическая свеча, лазер, кварцевое волокно, liquid rocket engines, combustion chamber, fuel, oxidizer, flame, igniter, flash fuse, nozzles, laser ignition, optical candle, laser, quartz fiber

Abstract >>
This paper describes an experimental study pertaining to laser ignition of igniters of liquid rocket engines operating on such fuels as O2g + kerosene, O2g + ethanol, and O2g + H2g, and to how they ignite the fuel of a model combustion chamber. A quartz fiber based optical spark plug is described, which allows for multiple ignition of the igniter and the combustion chamber without replacing the spark plug. This study also touches upon possible types of pulsed lasers used in the laser ignition system, a fiber-optic laser igniter that remain insulated and efficient at a combustion chamber pressure of up to 10 MPa and more than 100 ignition cycles.

Modeling of Cellular Detonation in Gas Suspensions of Two Fractions of Aluminum Nanoparticles

T. A. Khmel, S. A. Lavruk
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: газовзвеси, микро- и нанодисперсные порошки алюминия, ячеистая детонация, численное моделирование, gas suspensions, aluminum micro- and nanoparticles, cellular detonation, numerical simulation

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Cellular detonation in suspensions of two fractions of submicron and nano-sized aluminum particles is studied by numerical methods. Approaches of mechanics of heterogeneous media are used. The transition from the continuum to free-molecular regime of the flow around the particles is taken into account in the processes of interphase interaction. Particle combustion is described within the framework of the previously developed model of reduced kinetics. The results calculated for two-dimensional flows in a plane channel reveal significant differences from suspensions of two fractions of microparticles, where degeneration of transverse waves is observed. In the present study, weakly regular and irregular cellular structures are formed, which is also confirmed theoretically on the basis of the acoustic analysis based on the Barthel method.

Parameters of Continuous Detonation of Methane/Hydrogen-Air Mixtures with Addition of Air to Combustion Products

F. A. Bykovskii, S. A. Zhdan, E. F. Vedernikov
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: добавочная подача воздуха, непрерывная спиновая детонация, непрерывная многофронтовая детонация, метан, водород, воздух, поперечные детонационные волны, кольцевая камера сгорания, структура течения, удельный импульс, addition of air, continuous spin detonation, continuous multifront detonation, methane, hydrogen, air, transverse detonation waves, annular combustor, flow structure, specific impulse

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Results of experimental investigations in a flow-type annular cylindrical combustor with an outer diameter of 503 mm are reported. The influence of air addition to products of continuous spin detonation of CH4/mH2-air mixtures on the parameters of detonation waves, pressure in the combustor, and specific impulse is considered. It is demonstrated that addition of air to detonation products increases the velocity of continuous spin detonation, the pressure in the combustor, and the thrust, whereas the specific flow rate of the fuel decreases.

Modeling of Continuous Spin Detonation of a Hydrogen-Air Mixture in an Annular Cylindrical Combustor

S. A. Zhdan, A. I. Rybnikov, E. V. Simonov
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: непрерывная спиновая детонация, камера сгорания проточного типа, поперечные детонационные волны, водородовоздушная смесь, математическое моделирование, continuous spin detonation, flow-type combustor, transverse detonation waves, hydrogen-air mixture, mathematical modeling

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A closed mathematical model of continuous spin detonation with the chemical kinetics equation correlated with the second law of thermodynamics is developed for a hydrogen-air mixture within the framework of quasi-three-dimensional unsteady gas-dynamic formulation. The model takes into account the reverse influence of the oscillation processes in the combustor on the injection system of the mixture components. For comparisons with experimental data, the numerical simulations are performed for the geometric parameters of the flow-type annular combustor with an outer diameter of 306 mm used in the experiments. For the flow rates of the mixture varied in the interval 73.1-171.3 kg/(s·m2), the one-wave, two-wave, and three-wave regimes of continuous spin detonation are calculated, the flow structure is analyzed, the specific impulses are determined, and comparisons with experimental data are performed. It is shown that the use of a simplified single-stage kinetic scheme of hydrogen oxidation, which was used in some investigations, for simulating continuous spin detonation leads to results that differ from the experimental data by several times.

Shock-Wave Initiation of a Thermite Mixture of Al + CuO

S. Yu. Anan'ev1, L. I. Grishin1,2, A. Yu. Dolgoborodov1,2,3, B. D. Yankovskii1
1Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia
2National Research Nuclear University MEPhI, Moscow, 115409 Russia
3Semenov Federal Research Center for Chemical Physics Russian Academy of Sciences, Moscow, 119991 Russia
Keywords: термитные составы, ударно-волновое инициирование, химическая реакция, детонация, thermite compositions, shock-wave initiation, chemical reaction, detonation

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Shock-wave initiation of chemical reaction in pressed pellets of a stoichiometric mixture of Al and CuO powders in a steel tube was studied. The dynamics of the chemical transformations in the heterogeneous flow of reaction products of the mixture during dispersion of the pressed pellet material in a rarefaction wave was investigated. From the results of pyrometric measurements, the maximum brightness temperature of chemical reaction products was ≈3 500 K.

Influence of the Density of PETN-Coal Composites on the Threshold Characteristics of Explosive Decomposition in Laser Initiation

B. P. Aduev, D. R. Nurmukhametov, G. M. Belokurov, Ya. V. Kraft, Z. R. Ismagilov
Institute of Coal Chemistry and Material Science, Siberian Branch, Russian Academy of Sciences, Kemerovo, 650000 Russia
Keywords: лазерное инициирование, тэн, бурый уголь, низкометаморфизованный уголь, лазер, оптоакустика, фотометрический шар, laser initiation, PETN, brown coal, low-metamorphosed coal, laser, optoacoustics, photometric ball

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This paper presents the results of measuring the thresholds of explosive decomposition of PETN-coal under the action of laser radiation pulses (λ= 1 064 nm and τ= 14 ns). Samples whose thickness is 1 mm and whose densities are 1.1 and 1.7 g/cm3 with inclusions of submicron particles of brown coal (750 nm) are investigated. A minimum explosive threshold of 1.8 J/cm2 is reached with a concentration of inclusions of 0.5 % (by weight). The explosion is adiabatic. Composites with a density of 1.1 g/cm3 have a scattering matrix. A minimum explosive threshold of 2.3 J/cm2 is obtained for a concentration of inclusions of 1 %. An extinction rate is estimated: kext = 135 cm-1. Radiation is absorbed at a depth of <0.1 mm. Explosive decomposition in an unirradiated section develops according to the shock-wave mechanism of explosive combustion.

Experimental Study of Deformation of Spheroplastic under Shock Compression

V. S. Ziborov, G. I. Kanel', T. A. Rostilov
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia
Keywords: сферопластик, микросферы, волна ударного сжатия, предвестник, средняя массовая скорость, ударная адиабата, VISAR, spheroplastic, microspheres, shock compression wave, precursor, average mass velocity, shock adiabat

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This paper describes an experimental study of the shock compression of samples simulating media with a given porosity using epoxy-based spheroplastics with filler made of glass microspheres with volume concentrations of 0.27 and 0.55. Shock adiabats in a pressure compression range of 0.1-1.2 GPa are obtained. The shock compression pressure at which the fracture of the used microspheres begins is estimated. The dependence between the nature of deformation and the concentration of microspheres in the sample is established.

Identification of Melting of Lead Samples Recovered after Shock-Wave Loading and Unloading by Metallographic Analysis

O. N. Ignatova, N. Yu. Ilyushkina, A. N. Malyshev, V. I. Skokov, A. V. Shimanov, A. B. Georgievskaya, A. S. Sokolova
RFNC, All-Russian Research Institute of Experimental Physics, Sarov, 607190 Russia
Keywords: ударно-волновое нагружение, разгрузка, сохраненные образцы, металлографический анализ, свинец, shock-wave loading, unloading, recovered samples, metallographic analysis, lead

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This paper presents the results of metallographic analysis of the melting of C1 lead under shock-wave loading and unloading. Loading of lead samples in a titanium capsule was carried out by a plane shock wave using an aluminum projectile 6 mm thick, which was accelerated by detonation products of an explosive. The results of metallographic analysis of samples in the initial state, subjected to heat treated under normal conditions, and recovered after shock-wave loading are given. Melting traces were found in lead after shock-wave loading by a pressure of 25.6 GPa and subsequent unloading.