Home – Home – Jornals – Advanced Search

A model of nonequilibrium gas dynamics is proposed to describe ignition and combustion of a mixture of silane, hydrogen, oxygen, and an inert gas (nitrogen or argon). The model is based on detailed chemical kinetics of nonequilibrium chemical reactions. The model adequately describes the behavior of experimental data on the ignition delay time for this mixture versus the temperature behind the reflected shock wave in accordance with three criteria of ignition. The detonation wave velocity and equilibrium parameters of the mixture (pressure and temperature) are calculated as functions of the fuel-oxidizer equivalence ratio. Based on the dependences of the ignition delay time on the temperature behind the reflected shock wave calculated by this model, an approximation formula for the silane-oxygen-nitrogen/argon is derived.

The combustion and chemical transformation of a Fe₂O₃/Al/Zr mixture has been studied. From the results of thermodynamic calculations and experiments, it has been found that the ratio of Al and Zr affects the phenomenology and features of the combustion and the composition of cast combustion products. The range of obtaining oxide materials (Al₂O₃ and ZrO₂) is determined. A qualitative model for the combustion of thermite systems with two parallel reactions is proposed.

The coagulation dynamics of condensed products of vapor-phase or gas-phase combustion of gas mixtures of microdispersed metal particles in dust laminar flame considered taking into account the ionization of the combustion zone due to additives of electronegative and electropositive atoms and due to thermionic emission. The influence of the degree of ionization of a monodisperse coagulating aerosol and the charge of the particles on the coagulation rate constant is studied. It is shown that the rate of coagulation of the aerosol is most significantly affected by the Coulomb interaction of like-charged condensed-phase particles, which, under certain conditions, leads to an early stop of this stage in the condensation of combustion products. Ionization of the coagulating particles gives rise to a dependence of the size of primary particles of combustion products on the environmental parameters affecting their electric charge, and can be used for targeted control of the degree of dispersion of the combustion products.

It has been shown that Ti-Al-N ternary compounds, belonging to MAX phases (ceramic materials that can be processed as metals) can be produced by combustion of a granular powder of T65Yu35 (TiAl) alloy in nitrogen flow at a pressure close to atmospheric pressure. Combustion is accompanied by transfer of part of the aluminum through the gas phase. The propagation velocity of the combustion zone and the maximum temperature increase with increasing flow rate.

Burning rates of hydrazine borane at a pressure of 20-100 atm have been measured. Spectroscopic and electron microscopic studies have demonstrated that the condensed combustion product is a fine powder of boron nitride. Thermal decomposition of hydrazine borane has been studied. The obtained kinetic data and physicochemical properties of the materials and the foam combustion model have been used to calculate the pressure dependence of the burning rate of hydrazine borane, which agrees with the experimental one. The obtained degree of conversion of the material to boron nitride indicates the possibility of using hydrazine borane and similar compounds in high-performance systems.

The effect of the activation time of the Ti + 2B mixture on the burning rate of cylindrical samples and thin foils is studied. For cylindrical samples, combustion of samples activated in argon is compared with combustion of samples activated in air. The burning rates are almost identical in these two cases. It is demonstrated that the burning rate of cylindrical samples continuously increases with increasing activation time. The burning rate of thin foils remains almost unchanged as the activation time increases up to 4 min and then drastically increases and reaches a value twice greater than the burning rate of cylindrical samples. For the titanium and boron powders used in this study, the time needed to reach the maximum burning rate is 7 min in the case of activation in air and 5 min in the case of activation in argon; if the activation time is longer, then the product of combustion is formed. The features of combustion observed in this study can be explained from the viewpoint of convective-conductive model of combustion wave propagation.

We investigated the probability of explosion of tetranitropentaerythrite (ρ = 1.73 g/cm³) containing 0.1% (by weight) ultrafine nickel particles of size 270-300 and 140-175 nm at the distribution maxima depending on the energy density of the initiating laser pulse (1064 nm, 14 ns). In the first case, the critical energy density corresponding to a 50% the probability of explosion was 1.4 J/cm², and in the second case, 0.7 J/cm². Dependences of the light absorption cross section and the absorption coefficient on the inclusions particle size were calculated using the microhotspot theory of laser ignition. The calculation results are consistent with the microhotspot model of the initiation of thermal explosion.

The stability of detonation waves in nitromethane and FEFO was studied in experiments using a VISAR laser interferometer and an SFR high-speed photorecorder. It is shown that the relationship between various types of instability of the detonation front in liquid explosives is not strictly deterministic. Waves of reaction failure exist in the case of a stable detonation front (no cellular structure) and are absent in the case of an unstable detonation front.

The normalized electrical resistance R/R₀ of tin for different pressures of shock compression p is measured. The resultant dependence R/R₀(p) differs significantly from the known dependences for static and quasi-isentropic compression and demonstrates the growth of the electrical resistance with increasing pressure. The dependence has an inflection testifying to a phase transition. The inflection corresponds to pressures of 4.7-5.3 GPa in the dielectric embracing a thin sample and to pressures of 8.4-9.6 GPa in the first shock wave. The latter parameters qualitatively agree with the characteristics of the phase transition β-n → γ-n. The first shock wave in tin determines the final electrical resistance of the sample after wave reverberation. The experimental data obtained in this study are indicative of the kinetic behavior of the electrical resistance in the transition β-n → γ-n, which is accompanied by generation of crystalline structure defects with a characteristic time greater than 1 μs. A drastic increase in the electrical resistance of the sample in the expansion wave is observed. This increase is attributed to tin melting.

An explosive mixture of cyclotrimethylenetrinitramine (RDX) and titanium hydride (TiH₂) is introduced. To investigate the explosion characteristics of the composite explosive, charges with various contents of the TiH₂ powder are prepared and tested in air explosion experiments. Results show that the peak overpressure, positive duration, and positive specific impulse increase as the content of TiH₂ increases from 10 to 20%, as compared to passivated RDX. The peak overpressure, duration, and specific impulse have the largest increase of 6, 9, and 23%, respectively, as compared to passivated RDX, when the TiH₂ content is 20%. The effect of the TiH₂ particle size is also considered. The charge containing the TiH₂ powder with a mean particle size of 4.6 mm shows higher values of the three parameters than that containing 45-mm TiH₂ particles under the condition of the same content of TiH₂. However, the relationship between the detonation velocity and TiH₂ content is a linear inverse proportion, and the particle size of TiH₂ has a minor effect on it. Solid explosion products of the TiH₂/RDX composite explosive are analyzed by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDX). TiO₂ is found in explosion products, which is believed to form due to TiH₂ oxidation.