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2014 year, number 3

Skeletal Mechanism of Inhibition and Suppression of a Hydrogen Flame by Addition of Trimethylphosphate

O. P. Korobeinicheva, V. M. Shvartsberga, A. G. Shmakova,b
a Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences
Novosibirsk, 630090 Russia
b Novosibirsk State University
Novosibirsk, 630090 Russia
Keywords: skeletal mechanism, inhibition, fire suppression, trimethylphosphate, burning velocity

Abstract >>
A skeletal mechanism of inhibition and suppression of H2/O2/N2 by addition of trimethylphosphate was developed. It includes a mechanism of hydrogen oxidation (13 elementary steps involving 7 species) and two elementary reactions involving trimethylphosphate and its conversion products. This skeletal mechanism adequately predicts the burning velocity of flames with added inhibitor in the range of equivalence ratios studied, and can be used to model fire suppression.

Model for Filtration Combustion of Carbon: Approximation of a Thermodynamically Equilibrium Composition of Combustion Products

E. V. Polianczyk and S. V. Glazov
Institute of Problems of Chemical Physics, Russian Academy of Sciences
Chernogolovka, 142432 Russia
Keywords: filtration combustion, modeling, carbon combustion

Abstract >>
A model for stationary filtration combustion of mixtures of carbon with a solid incombustible material in a counterflow a gas containing oxygen and a chemically inert gas is proposed. If the rates of chemical reactions in the combustion zone are sufficiently high, the ratio of carbon monoxide and dioxide in combustion products is assumed to be thermodynamically equilibrium at the combustion temperature. This assumption provides a closure for the balance equations for carbon, oxygen, and energy in the combustion front and gives explicit analytical expressions for the combustion temperature and composition of the products as functions of the composition of the carbon/inert mixture and of the gaseous oxidizer in stoichiometric regimes. Combustion modes are numerically calculated for a wide variation of the compositions. The upper limit of the reagent supply rate until which equilibrium relations can be used is found. A comparison of model predictions with experimental results shows their reasonable qualitative agreement.

Kinetic Model of Single Boron Particle Ignition Based upon Both Oxygen and (BO)n Diffusion Mechanism

W. Ao, J. H. Zhou, J. Z. Liu, W. J. Yang, Y. Wang, and H. P. Li
Zhejiang University
Hangzhou, 310027 China
Keywords: boron, ignition, diffusion, kinetic, model

Abstract >>
A comprehensive ignition model for single boron particles in an oxygenated environment containing O2 and H2O is developed. Microcharacteristics of the boron oxide layer on the surface of boron particles at elevated temperatures are studied. Two typical distributions of species inside the surface oxide layer are detected. One is composed of three layers [B2O3, (BO)n, and B2O3], while the other is composed of two layers [(BO)n and B2O3], both according to the order from the internal to external side of the layer. In the model development, two submodels, submodel I and submodel II, are developed with regard to two different observed species distributions in the surface oxide layer. For submodel I, it is assumed that both (BO)n and O2 are the governing species diffusing into the liquid oxide layer. For submodel II, only (BO)n is the governing species. These two submodels are combined into a new bi-directional model consisting of four key kinetic processes: evaporation of the liquid oxide layer, global surface reaction between oxygen from the environment and boron, reaction between the inner boron core and oxygen, and global reaction of boron with water vapor. The ignition time predicted by the model is in good agreement with previous experimental data.

Effect of Stochasticity of the Spatial Distribution of Particles in a Gas Suspension on Combustion Front Propagation

P. S. Grinchuk
Lykov Institute of Heat and Mass Transfer, National Academy of Sciences of Belarus
Minsk, 220072 Belarus
Keywords: gas suspension, combustion wave, random spatial structure, BoseEinstein distribution

Abstract >>
A statistical model of combustion of a gas suspension of solid particles is proposed. The model takes into account the influence of the stochastic spatial distribution of particles on the combustion front velocity. The BoseEinstein distribution in the presentation of occupation numbers is used as the basic mathematical apparatus of the model. The model offers an explanation for the effect observed in some experiments, which is associated with the shift of the combustion front velocity peak to the range of fuel-rich gas suspensions. The limits of applicability of the proposed statistical model to real gas suspensions are estimated.

Ignition of Filtration Gas Combustion Waves by the Flame of the Filtered Gas

N. A. Kakutkinaa, A. A. Korzhavina, E. V. Manzhosa, A. D. Rychkovb
a Voevodskii Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences
Novosibirsk, 630090 Russia
b Institute of Computational Technologies, Siberian Branch, Russian Academy of Sciences
Novosibirsk, 630090 Russia
Keywords: filtration combustion, combustion of gases, ignition

Abstract >>
Mathematical modeling of ignition of filtration gas combustion waves in a porous medium with external initiation of combustion by the filtered gas is performed. It is shown that the surface temperature of the porous medium at which the flame enters the latter is a function of system parameters. The existence of the lower and upper flammability limits in terms of the gas filtration rate is found. Dependences of the ignition time on parameters of the porous medium are obtained, and their interpretation is given.

Applicability Analysis of Mathematical Models for the Combustion Characteristics in the Pool Fire

Zh. Chena, X.-N. Wub, W.-H. Songa, L.-Yu. Lva, and X.-D. Wangc
a Environment and Chemistry College, Tianjin Polytechnic University
300387 Tianjin, China
b School of Environment Science and Engineering, Tianjin University
300110 Tianjin, China
c Poly Explosives Group Co., Ltd.
100038 Beijing, China

Keywords: pool fire, combustion characteristics, heat radiation flux, mathematical model, FDS

Abstract >>
A pool fire characterized by high temperature and heat radiation, is a common accident in chemical industry. The important combustion characteristic parameters are the heat radiation flux, the burning rate, the flame height, etc., but the most significant one is the heat radiation flux. The calculation model of the pool fire has an important role to assess the accident. There are three types of widely used pool fire models, the Shokri and Beyler model, the Mudan model, and the point source model. The models are used to calculate the combustion parameters of three different kinds of oils in tanks of different scales. The predictions of three models are compared with the simulation results. The analysis shows that the point source model has a large error for pool fires with the diameter greater than 10 m and the thermal radiation flux smaller than 5 kW/m2, and the model is more applicable to heavy crude pool fires. The scope of application of the Mudan model is broader, and this model ensures higher accuracy if the thermal radiation flux is smaller than 5 kW/m2. The Shokri and Beyler model is more suitable for the case where the pool fire diameter is greater than 40~m and the thermal radiation flux is above 5 kW/m2, and the results for the light crude pool fire based on this model are more reasonable.

Combustion Behavior of a Ti + TiC Mixture in a Nitrogen Coflow

B. S. Seplyarsky, A. G. Tarasov, R. A. Kochetkov, I. D. Kovalev
Institute of Structural Macrokinetics and Materials Science (ISMAN), Russian Academy of Sciences
Chernogolovka, 142432 Russia
Keywords: SHS, TiC + Ti mixtures, granulation

Abstract >>
Combustion of powder and granular mixtures of TiC + Ti in a quartz tube purged with nitrogen was studied. Mixtures based on fine and coarse-grained TiC were used. It is found that purging of a powder mixture of bulk density with fine titanium carbide with nitrogen coflow does not lead to the spread of the flame front, whereas granular mixtures burn at the same pressure difference. Mixtures based on coarse-grained titanium carbide powder burn in both powder and granular form. The burning rate of a granular mixture of TiC + Ti with coarse-grained titanium carbide is significantly higher than when using fine titanium carbide. It is shown that in the case of a coarse-grained TiC, granulation of the mixture of TiC + Ti significantly improves the degree of nitriding of the synthesis products compared to the powder mixture. During combustion of granular mixtures of TiC + Ti, in contrast to powder mixtures of the same composition, a single-phase product of approximate composition TiC0.5N0.44 is formed as a result of synthesis.

Combustion of Model Compositions Based on Furazanotetrazine Dioxide and Dinitrodiazapentane. I. Binary Systems

V. N. Simonenkoa, P. I. Kalmykovb, A. B. Kiskina, O. G. Glotova, V. E. Zarkoa, K. A. Sidorovb, B. V. Pevchenkob, R. G. Nikitinb
a Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Science
Novosibirsk, 630090 Russia
b Altai Federal Research and Production Center
Biisk, 659322 Russia
Keywords: furazano[3,4-e]tetrazine-4,6-dioxide (furazanotetrazine dioxide, FTDO), 2,4-dinitro-2,4-diazapentan (DNP), eutectics, [1FTDO1DNP] molecular compound, burning rate, deflagration-to-explosion transition, combustion-wave temperature

Abstract >>
The combustion behavior of high-energy systems based on furazano[3,4-e]tetrazine-4,6-dioxide and 2,4-dinitro-2,4-diazapentane with metal and energetic additives (Al, AlH3 ammonium perchlorate, ammonium dinitramide, and HMX) has been studied. The burning rate, combustion stability, and characteristic combustion temperatures with pressure variation are estimated. It is found that there is a critical burning rate above which a deflagration-to-explosion transition occurs. The critical conditions depend on the formulation of the compositions.

Acceleration and Heating of Powder Particle by Gas Detonation Products in Channels with a Conical Passage

I. S. Batraev, E. S. Prokhorov, V. Yu. Ul'yanitskii
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences
Novosibirsk, 630090 Russia
Keywords: gas detonation, particulates, detonation spraying

Abstract >>
The results of numerical modeling and experimental realization of the impact of a chemically reacting gas flow on powder particles during profiling (diameter increase while maintaining volume) of the barrel combustion chamber of a unit for detonation spraying are given. The passage from the combustion chamber into the barrel muzzle is made using connecting taper sleeves with a small narrowing angle. It is shown that such profiling can significantly reduce the barrel size without compromising the technological capabilities of the detonation unit.

Molecular Dynamics Simulation of Combustion Front Propagation in a PETN Single Crystal

O. V. Sergeev, A. V. Yanilkin
Dukhov All-Russian Research Institute of Automatics
Moscow, 127055 Russia
Keywords: molecular dynamics, PETN, hot spot, ReaxFF, burning rate

Abstract >>
The propagation velocity of the combustion front in PETN was calculated. The kinetics of the chemical reactions occurring during propagation of combustion and dependences of the burning rate on the direction in the crystal and external pressure are discussed. The pressure dependence is linear in the pressure range of up to 30 GPa. The results are compared with experimental data and ab initio calculations.

Influence of Laser Wavelength on the Critical Energy Density for Initiation of Energetic Materials

A. V. Kalenskiia, A. A. Zvekovb, M. V. Anan'evaa, I. Yu. Zykova, V. G. Krigera, and B. P. Adueva
a Kemerovo State University
Kemerovo, 650043 Russia
b Institute of Coal Chemistry and Chemical Materials Science
Kemerovo, 650000 Russia
Keywords: hot-spot model of thermal explosion, laser initiation, absorption efficiency, metal nanoparticles, PETN

Abstract >>
Critical densities of the energy of laser initiation of PETN containing nanoscale aluminum inclusions at radiation wavelengths of 1064 and 532 nm were measured experimentally. The critical initiation-energy density that corresponds to a 50%th probability of explosion was 1.15 J/cm2 for the first harmonic of a neodymium laser and 0.7 J/cm2 for the second. The dependence of the efficiency of radiation absorption by aluminum on the size of metal nanoparticles for the first and second harmonics of a neodymium laser is calculated. It is shown that the particle diameter corresponding to the absorption efficiency maximum and the amplitude of the maximum depend on the radiation wavelength. The absorption efficiency maximum for the first harmonic is observed in an inclusion 204 nm in diameter, and for the second, in an inclusion 96 nm in diameter. The amplitude of the maximum increases from 0.351 at a wavelength of 1064 nm to 0.490 at a wavelength of 532 nm. Dependences of the critical initiation energy density for energetic materials on the radius of metallic nanoparticles are calculated. Qualitative agreement between theoretical and experimental results is shown.

Optical Radiation from Shock-Compressed Epoxy with Glass Microspheres

S. A. Bordzilovskii, S. M. Karakhanov, V. V. Sil'vestrov
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences
Novosibirsk, 630090 Russia
Keywords: optical radiation, shock compression, microsphere, monolayer, viscoplastic deformation

Abstract >>
Hot-spot temperature in shock compression of a mixture of epoxy resins with glass hollow microspheres is estimated. The obtained hot-spot temperature of 3200 K at a shock pressure of 20 GPa significantly exceeds the temperature of shock-loaded homogeneous epoxy resin, which at this pressure is in the range of 11001400 K. The time characteristics of the radiation generated during viscoplastic compression of a monolayer of hollow microspheres in an epoxy matrix at a pressure of 9, 20, and 29 GPa were determined by an optical pyrometer. Experimental data are shown to be in good agreement with estimates based on the viscoplastic deformation model.

Phase Transitions in Shock-Loaded Titanium at Pressures up to 150 GPa

V. A. Borisenoka, M. V. Zhernokletova, b, A. E. Kovalevb, A. M. Poduretsa, b, V. G. Simakova, b, M. I. Tkachenkob
a Sarov Physical-Technical Institute of National Research Nuclear University MEPhI
Sarov, 607186 Russia
b Institute of Physics of Explosion, Institute of Experimental Physics (VNIIEF), Federal Nuclear Center
Sarov, 607188 Russia
Keywords: titanium, Hugoniot, phase transition, melting, speed of sound

Abstract >>
Phase transformations in VT1-0 titanium were studied. Shock profiles in the pressure range of 10–26 GPa were recorded by polyvinylidene fluoride sensors. Sound velocities in shock-compressed titanium samples were measured by two methods. At a pressure less than 30 GPa, the speed of sound in titanium was determined by the counter unloading method using Manganin gauges, and at a pressure of 30150 GPa, it was determined by the overtaking unloading method using indicator liquids. At a pressure of 2040 and 6090 GPa, the pressure dependences of the speed of sound have breaks, the first of which is apparently associated with the α → ω conversion, and the second with melting. X-ray analysis revealed the presence of the ω phase in the samples in steel capsules recovered after loading at a pressure of 923 GPa. The dependence of the yield of the ω phase on the loading pressure has the form of a curve with a maximum at ≈15 GPa.

Pressure Transmission in Aluminum Foams Impacted by Underwater Explosion Waves

Z.-Q. Fan, H.-H. Ma, Z.-W. Shen, M.-J. Lin
Department of Modern Mechanics, University of Science and Technology of China
Hefei, 230027 China
Keywords: underwater explosion wave, transmitted wave, aluminum foam, negative pressure, frequency

Abstract >>
The interaction of underwater explosion waves with aluminum foam plates with different cell types is investigated. It is shown that the transmitted wave that passed through a closed-cell sample can be decomposed into two parts, one with a low-frequency content, which corresponds to the gas pressure in the pores, and one with a high-frequency content, which is argued to be a coupling of waves transmitted by the matrix and wave interactions between the fluid and the matrix of the medium.

Methodology for Simulation of the Jet Formation Process in an Elongated Shaped Charge

A. Wojewdka, T. Witkowski
Faculty of Chemistry, Silesian University of Technology
44-100 Gliwice, Poland
Keywords: explosives, LS-DYNA, elongated shaped charge

Abstract >>
The performance of linear shaped charges depends on several different parameters. The density, the detonation velocity of the explosive, the shape of the detonation wave, the shape and wall thickness of the liner, and the distance of the shaped charge from the target are among the parameters that can be optimized by using computer simulation methods. In this paper, the jet formation process in a linear shaped charge and its action on an obstacle are simulated by using the LS-DYNA software. The results obtained are compared with experimental data.