Home – Home – Jornals – Combustion, Explosion and Shock Waves 2019 number 2

A non-catalytic reaction of hydrogen interaction with sulfur dioxide is studied. It is found that this reaction in fact is a chain reaction of hydrogen oxidation by sulfur dioxide resulting in the formation of elementary sulfur. A mechanism of this reaction is proposed. The reaction is studied under static conditions in the temperature interval from 350 to 500oC at a pressure of the reactingmixture with a stoichiometric composition equal to 300 torr. The numerical kinetic analysis of the mechanism is consistent with experimental data.

The present paper describes the development of two reduced kinetic schemes suitable for multidimensional turbulent flame simulations in high-temperature oxidation of methane. Formal reduction of the USC Mech II C1-C4 detailed kinetic model by using the directed relations graph mechanism results in a 31-species derivative scheme for lean to near-stoichiometric conditions. To deduce a still shorter, simpler, and less stiff kinetic model, further species elimination is based on combined sensitivity and chemical time scale information to arrive at a 22-species scheme. The kinetic rates of lumped reactions are here expressed as simple Arrhenius rates, avoiding nonlinear algebraic combinations of excluded elementary steps or species. The accuracy is maintained by tuning pre-exponential constants in the global Arrhenius rate expressions and computing a range of target data. A more compact, quasi-global 14-species scheme is subsequently formulated by modeling fuel decomposition to a methyl radical pool, followed by CH3 oxidation with O and OH toward CH2 and CO, and retaining a full CO/H2/O2 subset. The C2-chain with recombination of CH3 into C2H6 and production of C2H2 is also represented in both schemes. Equilibrium 0D and 1D propagating premixed flames and axisymmetric co-flowing lifted laminar jet flames are computed through an iterative validation process. Accompanying computations with the USC Mech II mechanism, as well as available experimental results, are exploited for optimization. The comparisons demonstrate that the derived schemes ensure satisfactory agreement with data over the investigated parameter space.

The heat of combustion and standard the formation enthalpy of 3,4-bis (4-azidofurazan-3-yl) furoxan (DAzFF) and 4-azido-4'$-nitro-3,3':4','3'-terfurazan (AzNTF) were experimentally determined. Thermodynamic analysis was performed to investigate the efficiency of these compounds as potential components of metal-free composite solid propellants based on an active binder with the possibility of introducing an additional small additive oxidant with a high oxygen content, such as ammonium perchlorate.

A negative erosive effect arises in the simulation of combustion due to a generated turbulent motion in the gasification zone of a solid energy material. A thermal energy in the gasification zone comprises the heat of chemical sources in it and the heat coming up to the gasification surface from the flame zone in a gaseous phase. Some of this energy returns to the gaseous phase in the form of the mechanical energy of turbulent motion, and this turbulence cools down the gasification zone. This model is used to explain the weakening of the negative erosive effect, observed in the experiments, with increasing pressure and decreasing initial temperature.

This paper presents the results of study of combustion processes in the Cu(NO3)2-Al(NO3)3-H2O - PVA system, the composition and characteristics of the phases formed, the influence of heat treatment conditions on phase formation and particle size of the powders. It is shown that the combustion of organic-inorganic mixtures can be used to obtain CuO/Al2O3 catalysts or precursors of CuO/Al2O3catalysts and copper-matrix composites for electrical contacts.

The burning rate and limits of ribbons rolled from mixtures of titanium with boron were determined as a function of the concentration of boron. The combustion of single ribbons near the lower limit is unsteady and has a two-zone structure across the width of the ribbons, due to the difference in burning and cooling rates between the edges of the ribbons and its middle. With increasing boron concentration in the mixture, the combustion becomes steady-state and the front becomes more even. Maximum burning rate of the ribbons is achieved at a boron concentration of 21-25% in the mixture.

To optimize the reactant synthesis and improve the pressure property of Al/Bi2O3, the influencing factors in the dynamic pressure discharge of nanothermite reactions are investigated, including the oxide type, Bi2O3 particle size, and fuel-to-oxidant mole ratio. All samples are prepared by the ultrasonic mixing method. The synthesized Al/Bi2O3 composites are characterized by X-ray diffraction analysis and scanning electron microscopy. By using a closed bomb, the pressure discharge characteristics, including the peak pressure, ignition delay time, and pressurization rate, are obtained. Among the as-prepared nanothermites Al/CuO, Al/Fe2O3, and Al/Bi2O3, the latter shows the best pressure discharge performance. For the Al (100 nm)/Bi2O3 (47 nm) composite with an optimal stoichiometric ratio, the maximum peak pressure, the pressurization rate, and the shortest ignition delay time are 4559 kPa, 11.398 GPa/s, and 27.20 ms respectively. The results indicate that the nano-Bi2O3 particle size also produces a significant effect on the pressure output.

We have studied the effect of preload and the delay in application of pressure to the product of high-temperature synthesis under conditions of thermal explosion of a powder mixture of stoichiometric composition on the grain size in the synthesized Ni3Al compound, on the nature of its fracture, strength, and ductility.

The effect of the kinetic model of the thermal decomposition of wood on the results of prognostic modeling of the ignition of wood particles was analyzed. The results of mathematical modeling were verified by experimental studies of the ignition of wood particles in a high-temperature environment. Comparative analysis of the delays of ignition obtained theoretically and experimentally showed their good agreement. The prognostic potential of three substantially different kinetic models of wood pyrolysis was analyzed. It was established that the model of one-step pyrolysis with the formation of gaseous reaction products provides a good description of the thermal decomposition during thermal preparation (deviation from the times obtained using the three-stage pyrolysis model does not exceed 5%) in the whole range of heating conditions. Numerical simulation results show that consideration of thermal decomposition reactions of the second and third levels with the formation of intermediate pyrolysis products (liquid and solid) does not have a significant influence on the characteristics and conditions of ignition of wood particles in a high-temperature gas environment.

In this study, millimeter-sized magnesium particles are ignited using a CO2 laser. The flame structure, particle temperature, heat release region, and spectral information of the burning magnesium particle are determined. The experimental results show that the developing process of the particle temperature can be divided into five stages: gradually rising stage, steady stage, sharply rising stage, high-temperature stage, and descent stage. Through a series of ignition experiments, the ignition temperature of a magnesium particle ≈3 mm in air is estimated to be 900-940 K. During steady combustion, the maximum diameters of the flame and of the heat release region are found to be greater than the particle diameter approximately by a factor of 1.9 and 3-3.5, respectively. The experimental results also suggest that the combustion of magnesium in air should be controlled by vapor diffusion from the particle surface.

This paper describes the effect of the composition of energy condensed systems, containing glycerol trinitrate, aluminum powder, ammonium perchlorate, and HMX, on their ignition in an electric field with a frequency of 50 Hz. Conditions under which energy condensed systems ignite in an alternating electric field with a frequency of 50 Hz are determined experimentally. Temperature changes of their dielectric characteristics in a frequency range from 20 Hz to 1 MHz are established. The possibilities of an electric breakdown and heating of the samples are theoretically estimated. It is revealed that electrical luminescence is observed in a polymer binder based on glycerol trinitrate and polyetherurethane.

Physicomathematical modeling of interaction of detonation waves in silane/hydrogen composite mixtures with clouds of inert micro- and nanoparticles ranging from 10 nm to 100 μm is performed. The normalized detonation velocity is calculated as a function of the volume concentration of particles. It is found that the efficiency of detonation suppression increases only as the particle diameter decreases to 1 μm. The influence of the thermodynamic parameters of particles on the detonation suppression efficiency is identified. The concentration limits of detonation are determined. It is demonstrated that a certain equilibrium asymptotic level of the concentration limits of detonation is reached as the particle diameter decreases below 1 μm. An approximation of the concentration limits of detonation is obtained in the form of an analytical dependence of the limiting volume concentration of particles on their diameter and fuel concentration in a composite two-fuel mixture of silane, hydrogen, and air.

This paper describes the experimental measurement of thresholds of explosive decomposition of PETN with inclusions of aluminum nanoparticles (an average particle diameter of 100 nm) with a static pressure of 0-0.288 GPa applied to the samples under the action of the first harmonic of pulsed (14 ns) neodymium laser. Amplitudes of optoacoustic signals as a function of concentration of inclusions in the samples with a fixed density of laser initiation energy are measured. There is a significant decrease in the initiation threshold, which is due to the fact that a gas-dynamic load is blocked and the sample density increases.