Том 52, № 6 (2016)

The theory of a strong explosion is used as a basis for the development of an experimental technique for determining the source energy that ensures initiation of the combustible mixture. The technique is tested in experiments aimed at determining the critical energies of spherical detonation initiation E*₃ with the use of an electric discharge for a stoichiometric acetylene–oxygen mixture and also for two-fuel mixtures (acetylene–nitrous oxide–oxygen) possessing bifurcation properties of cellular structures. The critical energy E*₃ for the stoichiometric two-fuel mixture in terms of both fuels with a bifurcation structure is several-fold lower than the value of E*₃ for the monofuel mixture whose cell size at a given pressure is determined by the large scale of bifurcation cells. This result testifies that the value of E*₃ decreases with increasing number of “hot points,” which are numerous regions of collisions of large-scale and small-scale transverse waves in the mixture with bifurcation properties.

The chemical conversion of SO₂ to elemental sulfur in the chain oxidation of hydrogen in a low-temperature flame has been studied. The possible elementary reactions involving atoms and free radicals that may be responsible for the chemical conversion of SO₂ with the formation of sulfur in the conjugate radical chain process are discussed on the basis of thermodynamic and kinetic characteristics.

This paper presents the results of the structure and phase formation in the Ti/Nb/2Al, Ti/Nb/2.5Al and Ti/Nb/3Al systems in the thermal explosion mode of self-propagating hightemperature synthesis. The morphology, phase composition, microstructure, and physical properties have been studied. It has been found that compounds with the highest content of aluminum have the most homogeneous composition and the lowest porosity. The main phase of the synthesis product is a phase based a solid solution of Nb in γ-TiAl.

A possibility of determining the regime of combustion of individual fuel particles on the basis of the dependence of the flame velocity on the fuel and oxidizer concentrations is considered by an example of a dust flame of microsized metal particles with diameters d₁₀ < 15 μm and particle concentrations from ≈10¹⁰ to 10¹¹ m⁻³ in oxygen-containing media at atmospheric pressure. The combustion mode (kinetic or diffusion) is responsible for the qualitative difference in the character of the normal velocity of the flame as a function of the basic parameters of the gas suspension. The analysis of such experimental dependences for fuel-rich mixtures shows that combustion of zirconium particles (d₁₀ = 4 μm) in a laminar dust flame is controlled by oxidizer diffusion toward the particle surface, whereas combustion of iron particles of a similar size is controlled by kinetics of heterogeneous reactions. For aluminum particles with d₁₀ = 5–15 μm, there are no clearly expressed features of either kinetic or diffusion mode of combustion. To obtain more information about the processes responsible for combustion of fine aluminum particles, the flame velocity is studied as a function of the particle size and initial temperature of the gas suspension. It is demonstrated that aluminum particles under the experimental conditions considered in this study burn in the transitional mode.

The solid-state ignition of a metallized composite propellant (ammonium perchlorate + 14% butyl rubber +5% aluminum powder + 6% plasticizer) under local heating by several sources of limited power capacity (dimensions of the hot particle x_p = 4 mm and y_p = 2 mm) was studied by mathematical modeling. For the temperature of the heated steel particles and the distance between them varied in the ranges 700 < T_p < 1500 K and 0.1_xp < Δ_x < 1.5xp, respectively, the values of T_p and Δ_x were determined for which the ignition delay corresponds to the initiation of combustion of the composite propellant by a single particle, by a plate at a constant temperature or by several particles. In the region of low initial temperatures of the local sources (T_p < 1100 K), the limiting values Δ_x → 0.1x_p and Δ_x > 1.5x_p, were identified for which the characteristics and mechanism of ignition of the propellant by a group of heated particles can be studied using the “plate–propellant–gas” model and the “single particle–propellant–gas” model, respectively. Decreasing the distance Δx at T_p < 1100 K decreases the induction period to 50% and reduces the minimum initial temperature of the source required to initiate propellant combustion from 830 to 700 K. At T_p > 1100 K, the ignition of the metallized composite solid propellant by a single or several particles can be studied using relatively simple one-dimensional models of condensed material ignition by a plate at constant temperature. The variation in the ignition delay in this case is less than 5%.

This paper describes the study on the dependence of the critical energy density of the explosive decomposition of PETN on the mass concentration of the additives of ultrafine Al particles (100–120 nm) in the range of 0.025–1% under the influence of the first and second harmonics of a neodymium laser (12 ns, 1064 and 532 nm). It is shown that the critical energy of the explosion initiation by the first and second harmonics of the laser radiation reaches a minimum value at the same absorption rates, but different concentrations of additives. The photoacoustic method is used to show that, as the laser energy radiation is absorbed, the pressure amplitude in the heated layer reaches a maximum value when the concentration of additives corresponds to the minimum value of the critical energy density.

This paper presents the result of a study of the chemical composition, physicotechnical properties, and structure of various types of granulated ammonium nitrate (high-density, porous, and aerated) made in Russia and abroad. It is shown that thermal treatment of high-density ammonium nitrate granules (Russian Standard (GOST) No. 2-2013) leads to changes in the crystal structure (porization) that increase the retention capacity with respect fuel oil. The detonation velocity of ammonium nitrate/fuel oil compositions based on aerated ammonium nitrate was measured.