Abstract The flame propagation behavior and the effect of particle agglomeration are examined by changing the size of PMMA particles in laboratory-scale experiments. PMMA particles having a very narrow size distribution are used. We show that the minimum explosible concentration increases as the particle size decreases. On the other hand, the flame propagation velocity also increases as the particle

Abstract The standard enthalpies of formation of 1,1-bis(methoxy-NNO-azoxy)-3-nitro-3-azabutane and 1,1,8,8-tetrakis (methoxy-NNO-azoxy)-3,6-dinitro-3,6-diazaoctane were experimentally determined to be 87.7 \(\pm\) 3.9 and 283.8 \(\pm\) 6.2 kJ/mol, respectively. Calculations have shown that solid composite propellants containing these two compounds as gasifying components in metal-free compositions

Abstract Thanks to its mesoscopic kinetic nature, the discrete Boltzmann method has a capability of investigating unsteady detonation with essential hydrodynamic and thermodynamic nonequilibrium effects. In this work, an efficient and precise reactive discrete Boltzmann method is employed to investigate the impact of the amplitude and wave length of the initial perturbation, as well as of the chemical

Abstract Transient dynamics of formation and extinction of methane- and ethylene-fueled flames above the flat porous burner in an oxidizing atmosphere is numerically investigated. The simulated scenarios replicate the experimental conditions of the BRE (Flamenco) project of the ACME program focusing on combustion research in microgravity. The 3D unsteady model includes the multi-step and multi-component

Abstract Mathematical modeling of combustion of micron-sized and nanometer boron particles in air with allowance for changes in the heat and mass transfer mechanism and a decreasing particle size is carried out. The Knudsen number is taken as an indicator of a transition from one state to another: a continuous medium assumption is valid for describing the heat and mass transfer mechanisms in the case

Abstract Rapid phase transitions occurring with a sharp increase in a specific volume can be accompanied by explosive gas-dynamic phenomena. A model is presented for calculating shock waves generated in the atmosphere during an explosion of a liquid gas pressure reservoir, based on the assumption of a thermodynamically equilibrium state of a vapor–liquid mixture in which both vapor and liquid have

Abstract Fluorinated ethylene propylene (FEP) wire insulation ignition is investigated in a forced flow field in microgravity and normal gravity with a continuous current. First, FEP insulation melts and decomposes, causing jet bursting in both normal gravity and microgravity. Second, the forced flow and gravity produce minor effects on the core heating and bursting time, while the pyrolysis time increases

Abstract A microwave diagnostics method and radio interferometers with wavelengths of 3.2 and 2.1 mm are used to study the kinematic and electrophysical characteristics of shock-compressed argon plasma, which is initially at atmospheric pressure. This research study is carried out at pressures of 12–56 MPa, shock wave velocities of 3.1–6.2 km/s, temperatures 9000–19 000 K, and densities 0.006–0.012 g/cm3

Abstract This paper deals with the nature of the synergistic effect in flames of methane and formaldehyde mixtures with air. Combustion of mixtures of different fuels is of great practical and fundamental interest. It has been found that the addition of formaldehyde to a rich methane/air flame at a constant concentration of methane first reduces the flame speed and then begins to increase it. The synergism

Abstract This study presents a review of high-velocity projection methods and devices intended for the experimental study of the protection of equipment and structures from a high-velocity impact by compact elements, particularly protecting spacecrafts from collision with natural meteorite particles. Explosive projectors used in experiments to test protective structures at high impact velocities are

Abstract Many industrial combustion devices rely on jet flame combustion in the crossflow to achieve mixing and reaction. Previous research offers a limited predictive capability regarding the coupling effects of the crossflow and jet flow on the flame radiative fraction. In this work, a new theoretical equation is derived to relate the radiative fraction to the fuel flow rate and the crossflow velocity

Abstract Non-combustible solid materials play a major role as inerting agents in explosion prevention. While the importance and application of these materials are well understood, there is still a lack of information about the actual mechanisms responsible for explosion suppression. Especially, the role of inert materials with a large specific surface area and the influence of the moisture content

Abstract If a Li-ion cell fails and the electrolyte leaks out into air, a flammable premixed gas cloud can be formed. The electrolyte combustion energy is 65–70% of the total energy content of the cell. The main objective of this study is to determine the laminar burning velocity and the Markstein length for dimethyl carbonate and propane in a 20-liter explosion sphere with initial conditions at 100 kPa

Abstract To measure the temperature of shaped-charge jets, we fabricated three-layer copper–copper–Constantan liners consisting of a solid copper conical shell with a cone angle of 45° and a wall 1.5 mm thick and a shell pressed into it and rolled from a 1.0 mm thick copper sheet clad on the inside with a Constantan layer 0.5 mm thick by explosive welding. Then, the Constantan layer was partially removed

Abstract The heat of combustion and enthalpy of formation of bis(4\(''\)-nitro[3,3\('\):4\('\),3\(''\)]terfurazan-4-yl)-diazene (DNFNF) and (bis(4\(''\)-azido-[3,3\('\):4\('\),3\(''\)]terfurazan-4-yl)-diazene (DAzFNF) were first experimentally determined. It is found that the energy increment for replacing the nitro group with an azide group in the furazan cycle averages 290 kJ/mol and is close to

Abstract Combustion and ignition processes are considered from the standpoint of the theory of thermal ignition and reaction kinetics. An analytical solution to the problem of thermal hotspot ignition is obtained to describe the ignition of reactive gas mixtures. As a result of this solution, the critical ignition conditions and induction time were determined. A solution to the problem of ignition

Abstract The change in the structure of welds made with a new welding wire and subjected to high-velocity impact was investigated by optical and scanning electron microscopy and X-ray diffraction analysis. It is shown that after welding, a structure consisting of martensite, \(\delta\)-ferrite, and metastable austenite is formed in the weld metal. The subsequent severe impact leads to hardening of

Abstract The spread of crown forest fires in the presence of fire breaks and barriers of finite sizes was studied by mathematical modeling. Mathematically, this problem reduces to solving the Reynolds equations for turbulent flow taking into account chemical reactions. The control volume method was used to obtain a discrete analog. The fields of temperature, concentrations of oxygen and volatile pyrolysis

Abstract Synthesis is carried out in a Ti + Al mixture prepared by two methods, namely preliminary mechanical activation (MA) or preheating. Synthesis occurs in the cases of layer-by-layer combustion (SHS) and thermal explosion. The dependences of burning rates of activated Ti + Al mixtures on the MA duration are investigated. The relationships between the initial temperature and the rates and maximum

Abstract The initiation and stabilization of detonation combustion of kerosene vapor in a supersonic air flow entering an expanding axisymmetric nozzle with a coaxial central body is numerically studied. Calculations are based on a reduced kinetic model of combustion, which includes 68 reactions for 44 components. Enthalpy and entropy of components are determined using approximating polynomials from

Abstract Combustion and the formation of structures and phases in a 2Co–Ti–Al system during self-propagating high-temperature synthesis in a thermal explosion are under study. It is determined that a single-phase product (a Co2TiAl Geissler compound) can be obtained in this system. Morphology, microstructure, and physical-magnetic properties of combustion products of the system are investigated.

Abstract The work presents a simplified algebraic model for calculating the OH*, CH*, and CO\(_{2}^*\) concentrations within the context of reduced propane flame oxidation treatment. Excited and precursor species are obtained through post-processing of the basic simulation results, employing well-established quasi-steady state expressions produced from the detailed chemiluminescence kinetics. Inaccuracies

Abstract Gas detonation in ethylene– and propylene–oxygen explosive mixtures was studied over a wide range of equivalence ratio. Detonation parameters were calculated using the DETON code. The experiments were performed on an improved detonation facility in which the flow feed of the components of the explosive mixture and the intensification of deflagration-to-detonation transition (DDT) due to charge

Abstract In order to ensure the safety and reliability of weapons, it is very important to grasp the influence of the inside and outside diameters of the shell on the delay time. In this paper, a fluid–solid coupling model is established for a metal baffle-type delay element with a silicon-based delay composition. The combustion flow field of the delay element with the inside diameter of 3, 4, and

Abstract Evaporation of a water–methanol solution droplet is experimentally studied. This process is mathematically modeled. Based on the results of a comparative analysis of the results of physical and numerical studies, the parameters of the evaporation of a water–methanol solution droplet are determined for the purpose of using its combustion in mathematical modeling. The results of numerical studies

Abstract A reaction model is proposed for calculating the process of ignition of diborane mixtures with air. The model summarizes the previously developed kinetic models of oxidation of diborane, boron, as well as lower oxides and hydroxides of boron. A distinctive feature of the model is the use of physically grounded rate constants of the most important reaction channels, which were either computed

Abstract The formation and dynamics of a spherical gas bubble (from \(\approx1\)nm to 1 \(\mu\)m) in the liquid gasification zone of a solid high-energy material at high pressures is theoretically investigated. A simple model is proposed in which all thermodynamic parameters with the exception of fluid pressure and fluid velocity are independent of spatial variables. The stationary radius of bubbles

Abstract 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

Abstract The PIV and PLIF OH techniques were used to experimentally study the structure of a jet impinging on a flat obstacle with swirling and combustion of a propane–air mixture with an equivalence ratio of 0.7 for a nozzle–obstacle distance H/d = 1 and 3 and in the absence of the obstacle. The swirl ratio was 0.41 and 1.0, and the Reynolds number was 5 000. It is concluded that for both values of

Abstract Combustion of FTi70 industrial ferrotitanium containing 65.9% Ti and a model alloy of iron with 30.6% 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

Abstract This paper describes an experimental study pertaining to laser ignition of igniters of liquid rocket engines operating on such propellants as O\(_{2g}\) + kerosene, O\(_{2g}\) + ethanol, and O\(_{2g}\) + H\(_{2g}\), and to how they ignite the propellant of a model combustion chamber. A quartz fiber based optical device is described, which allows for multiple ignition of the igniter and the

Abstract 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

Abstract The 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 with dispersion of the pressed pellet material in the unloading wave was investigated. From the results of pyrometric measurements, the maximum

The transition of the combustion wave of a titanium powder layer in air through an inert shaped obstacle has been experimentally studied. It has been shown that an inhomogeneous wave-like structure of the combustion front can form due to the limited supply of gaseous reagents and the thermal instability of combustion of the titanium powder layer. Conditions of the optimal transient combustion mode

The ignition of a filtration gas combustion wave by a heated region of an inert porous medium is studied by numerical simulation. The mechanism of formation of the combustion wave is described. Dependences of the time of wave formation on the velocity of the gas mixture, the temperature of the heated region of the porous medium, and its length were obtained. The existence of ignition limits of the

The objective of the present analysis is to investigate the effect of gaseous hydrocarbon fuels, such as Octane C8H18, Hexane C6H14, and Pentane C5H12 on the cyclic combustion process in an obstructed channel of the pulse detonation engine. Three-dimensional reactive Navier-Stokes equations are used to simulate the combustion mechanism of stoichiometric hydrocarbon fuels along with a one-step reaction

The results of diagnostics of thermal conditions of an electric thermal explosion (ETE) of a mixture of titanium and soot powders under quasistatic compression are presented. The effect of quasistatic compression pressure on the thermal and electrical parameters of an ETE is studied. It is shown that nonuniform heating occurs at low pressure, while uniform heating occurs at high pressure. A criterion

The conditions of occurrence, nature, size, and shape of combustion hotspots of energetic condensed systems and the spatial dynamics of the hotspot combustion wave are discussed. A model for the propagation of hotspot combustion waves in condensed systems is briefly described based on the cellular automata method. A possible explanation for the occurrence of unsteady effects in the combustion of solid

An intense effect of acoustic waves on the structure and shape of the burner flame was discovered by Rayleigh. The present paper deals with acoustic waves in the case of flame propagation in a tube. The flame emits acoustic waves generating the flow in the tube. Being actually a wave beam, the flow bounded by the walls experiences friction and also diffraction divergence, resulting in the emergence

A method for calculating the optimal ratio of the fuel and solid propellant in the gas generator of a high-velocity flying vehicle is proposed. A thermodynamic approach is used to describe the processes in the gas generator. The ratio of the solid propellant and fuel in the gas generator is determined by their physical and chemical properties. An increase in the density and heat of combustion of the

The laws and mechanism of combustion of TiO2 based thermite systems with a complex reducing agent (Al and Ca) under the influence of overload are revealed. The thermite system includes a basic composition whose combustion products are target elements (Ti, Al, Nb, and Cr) and a high-energy additive (CaO2, Al, and Ca) for ensuring high-temperature combustion. With the introduction of an energy additive

The standard enthalpy of formation of 1,4-diethynylbenzene experimentally to be 500.6 ± 6.7 kJ/mol. Calculations show that 1,4-diethynylbenzene has a relatively high adiabatic combustion temperature (about 1970 K at a pressure of 5 atm) and very high heat of combustion in oxygen (42 MJ/kg); therefore, 1,4-diethynylbenzene can be used as the basis to develop an effective dispersing agent of solid fuel

Effect of carbon content in a Ni–Al–C system and preliminary mechanical activation on a burning rate, sample elongation, and mixture yield after mechanical activation, as well as on the structural features of combustion products is under study. Combustion in pressed samples from a mechanically preactivated Ni + Al mixture at room temperature could not be activated. The addition of carbon [2, 4, and

An experimental study of the effect of pulverization on the thermal destruction of coal is carried out. Artificial neural networks are used to develop a model that allows predicting the degree of burnout of pulverized coals with high accuracy (an average relative error of 3% and a determination coefficient of 96%).

This paper presents a study of direct conversion of chemical energy into electrical energy during the combustion of a (80Zr + 20CuO)–(LiF + CaF2 + MgF2)–(15Zr + 85CuO) thin three-layer condensed energy system, which is a high-temperature galvanic cell. It is determined that this cell during combustion generates an electric signal with an amplitude of 1.6 V and a half-width of 15 s. Its formation mechanism

The results of studying the laser induced explosive decomposition thresholds of PETN-aluminum composites depending on the concentration of inclusions at various sample densities are presented. An increase in the density of the samples reduces the minimum critical energy density of explosive decomposition and the concentration of inclusions at which explosions are observed.

Sound velocity variation behind a shock wave front is measured in pressed samples of micro- and nanodispersed mixtures of nickel and aluminum powders at pressures of 10, 30, and 60 GPa in order to verify the possibility of a reaction with the formation of nickel aluminide in a submicrosecond time range. It is shown that, in a pressure range of up to 60 GPa, the sound velocity in the samples from a

The breach of a steel column target (Steel 45, 120 mm in diameter) by an inward-cutting circular shaped charge is considered. The jet penetration process is simulated by a 3D model run in the ANSYS/LS-DYNA program. The results are compared with actual tests, where photographs of the jet penetration process allowed observation of detonation forms, timing of the jets arising at the cross section of the

This paper presents a computational comparison of the penetration capability of two shaped charges—with conical and hemispherical (degressive thickness) liners. It is shown that close values of the penetration capability of the charges are provided only in the ideal case of strictly axisymmetric motion of shaped-charge jets.

It is a key problem to design and prepare metallized explosives of high energy and low sensitivity. In order to study the effect of the content of the boron/aluminum (B/Al) compound powder on the energy output property of metallized explosives in the air blast, three HMX-based explosives containing B/Al were designed and prepared. Air blast tests of cylindrical samples are performed, accompanied by

Shock loading is an effective method of bulk hardening of materials. This study of the structure and mechanical properties of 110G13L steel before and after explosion loading showed that the mechanical characteristics reached maximum values at the surface of the explosively treated material: Vickers hardness HV =480, yield strength of 850 MPa, and tensile strength of 1240 MPa. The thickness of the

The structures of three laminar premixed stoichiometric flames at low pressure (6.7 kPa): a pure methane flame, a pure ethanol flame and a methane flame doped by 30% of ethanol, have been investigated and compared. The results consist of concentration profiles of methane, ethanol, O2, Ar, CO, CO2, H2O, H2, C2H6, C2H4, C2H2, C3H8, C3H6, p-C3H4, a-C3H4, CH2O, CH3HCO, measured as a function of the height

This paper describes the influence of mechanical activation of coals on ignition and thermal-oxidative degradation using two independent methods: thermogravimetric analysis and ignition of a coal suspension in a vertical pipe furnace. It is determined that the ignition temperature of mechanically activated coals decreases and that mechanical activation affects the further process of thermal-oxidative

The kinetic parameters of thermal decomposition of furazano-1,2,3,4-tetrazine-1,3-dioxide (FTDO) and the (75/25) FTDO/dinitrazapentane (DNP) system were experimentally investigated by differential scanning calorimetry. Kissinger kinetic analysis was performed using differential scanning calorimetry data obtained at heating rates of 0.1–5.0 K/min. The thermal decomposition of FTDO and the FTDO/DNP system