Home – Home – Jornals – Combustion, Explosion and Shock Waves 2026 number 5

Due to the high risks associated with explosive experiments, modern research typically focuses on small-scale models that determine parameters such as pressure and momentum using the distance reduction principle. Due to the complexity of the physical picture of an explosion, numerical modeling in combination with experimental methods is becoming a reliable tool for studying the parameters of detonation and shock wave propagation. In this paper, a small-scale explosive experiment was calculated using CFD modeling, the effect of the computational grid size was studied, and the effectiveness of protective devices placed above the blast barrier was assessed. Additionally, the TNT equivalent was estimated and an approach to its determination based on the Chapman-Jouguet relations was proposed. The results show that the calculation accuracy can correlate with both the grid size and the reduced distance. Modeling of protective devices revealed their noticeable effect on the shock wave distribution in the air. The proposed method for estimating the TNT equivalent showed promising results for the studied explosives; However, further research is recommended to expand its scope of application, particularly for aluminized compounds and other types of explosives.

The interaction of a shock wave with a Mach number of up to 2.5 with a quasi-elliptical lean laminar flame front was studied in a vertically positioned shock tube with a square cross-section of 138 × 138 mm. The low-pressure chamber of the shock tube was filled with a combustible mixture of 8% H₂, 18.4% O₂, and 73.6% Ar to a pressure of 20 kPa, and the high-pressure chamber was filled with air or helium to a pressure of 100 or 400 kPa. Pulsed laser radiation, focused onto a point near the axis of the low-pressure chamber, ignited the combustible mixture, resulting in the formation of an isolated, slowly growing flame source-a bubble. This quasi-elliptical shape represented the contact boundary between media of different densities-light combustion products in a heavy unburned mixture. After the membrane separating the high- and low-pressure chambers was forced to rupture, a shock wave formed in the latter. Upon interaction with the flame source, it caused the development of a Richtmyer-Meshkov instability at its boundary. The unstable flow-a quasi-elliptical flame evolving into a toroidal vortex-was recorded through a pair of optical windows in opposite walls of the tube using high-speed schlieren videography at a frame rate of 50 kHz.

A study was conducted on the flammability characteristics of 0.35 and 1 mm thick glass fiber-reinforced epoxy resin plates with additives of the phosphorus-containing flame retardant DOPO-THPO, graphene, and graphene oxide. The fire resistance of the plates was determined using the oxygen index test and the UL-94 HB test. The tests revealed no significant effect of flame retardant additives on fire resistance. The mechanism of action of the flame retardants was further investigated in experiments on horizontal flame propagation towards the oxidizer flow with different oxygen concentrations. It was found that the addition of 2 wt. % graphene + 4 wt. % DOPO-THPO leads to a decrease in the flame propagation velocity of 0.35 mm thick samples. However, an increase in the concentration of DOPO-THPO additive to 6 ÷ 8 wt. % had the opposite effect. The effect of the addition of 8 wt. % graphene oxide was higher than that of the addition of a mixture of graphene and DOPO-THPO. No effect of flame retardants on flame propagation velocity was detected for 1 mm thick specimens. This is presumably due to the specimen thickness, which corresponds to the thermal limit of thickness. Furthermore, temperature profiles in the condensed and gas phases during flame propagation were determined.

The evaporation and combustion of fuel droplets have been studied since the middle of the last century. Existing spray combustion modeling is based on a simplified one-dimensional model. This model, as well as recently developed three-dimensional combustion models for single droplets, do not describe the conditions under which various droplet combustion regimes exist. In this paper, droplet evaporation and combustion are studied using hydrodynamic and experimental methods. The hydrodynamic section considers a two-dimensional axisymmetric evaporating and burning droplet. The equations of motion are solved using an integral method similar to the Karman-Pohlhausen method for calculating the boundary layer in the presence of a pressure gradient. The resulting solution yields a local evaporation rate and flame radius consistent with known experimental data. In the experimental section, the influence of relative gas velocity, pressure, and gas temperature on droplet evaporation and combustion processes is determined. Various droplet combustion regimes at different relative velocities are experimentally revealed, explaining the change in the evaporation constant with increasing relative velocity. The theoretical results are confirmed by experimental studies of suspended droplet evaporation.

A method for automating the determination of dispersed phase parameters in materials is proposed, based on digital holographic recording and deep machine learning. Numerical and field experiments were conducted on holographic recording of a cloud of particles with sizes on the order of 10 µm, and the resulting holograms were reconstructed layer-by-layer. It was demonstrated that a neural network is capable of recognizing particles in reconstructed holograms with accuracy metrics exceeding 75%, which is more than twice the accuracy of binarization and the Hough, Sobel, and Canny algorithms.

The effect of potassium, calcium, magnesium, and iron chloride inclusions on the critical energy density of laser radiation sufficient for igniting pre-demineralized grade 2B brown coal using millisecond laser pulses with a wavelength of 1070 nm and an intensity in the range of 6.4-52 kW/cm² was studied. For minimum radiation intensities, additional calcium and magnesium concentrations of 5-7% increase the critical ignition energy density by 2-4 times. Potassium increases the critical energy density by less than 20%, while iron reduces it by approximately 2 times, with a tendency to saturate as the inclusion concentration increases to 7%. The effect of the inclusions used decreases with increasing radiation intensity and virtually ceases at a radiation intensity of 52 kW/cm².

This paper examines the problems of describing conductive and radiative heat transfer in models of aluminum nanoparticle combustion. The agreement between theoretical models of classical electrodynamics and experimental data on absorption cross sections in the IR region is analyzed. It is shown that in both the far- and near-IR regions, the models underestimate the absorption cross section of aluminum nanoparticles compared to experimental data. Models that assume a small nanoparticle size compared to the skin depth differ from experiment not only quantitatively but also qualitatively in the near-IR region. This indicates that the skin depth in the near-IR region is no greater than the size of the nanoparticles, and therefore, the dissipation of wave energy within the nanoparticles should be considered taking into account partial shielding of the wave field. A semiempirical formula for calculating the thermal radiation of nanoparticles is proposed, taking into account the partial shielding of the wave field within the nanoparticle volume.

The results of an experimental study of the detonation characteristics of the C25A model explosive composition manufactured at the V.V. Bakhirev State Research Institute of Machine Building (GosNIIMash) are presented. The following detonation parameters were determined: density, detonation velocity, pressure, and chemical spike duration; pressure, temperature, density, mass velocity, speed of sound, and the adiabatic index at the Chapman-Jouguet point. The onset time of the aluminum oxidation reaction after the passage of the detonation wave and the response time during the expansion of the explosion products in the detonation flow were estimated, and an adiabatic curve for the unloading of the detonation products was constructed. Equipment from the Lavrentyev Institute of Hydrodynamics and the Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences was used in the study.

The combustion behavior of granulated mixtures (100 - X )(Ti + C) + X(Co---Cr---Ni) at X = 0 ÷ 40 wt. %, used for the synthesis of metal ceramics, was studied for the first time. The mixture composition at which the release of impurity gases leads to a transition from the conductive to the convective combustion mode ( X = 20%) was determined by calculation, which made it possible to estimate the impurity hydrogen content in the studied mixtures. For granules of 1.7 mm in size, the filtration of impurity gases through the sample leads to the convective combustion mode at X < 20% and to the conductive one at X > 20%. The conductive combustion mode is realized in all mixtures with granules of 0.6 mm in size. The phase composition of the obtained composite samples is represented by TiC and the fcc phase of the medium-entropy CoCrNi alloy. The interphase heat transfer coefficient in granulated SHS mixtures, calculated using experimental data, is an order of magnitude higher than the theoretical values for the heat transfer coefficient in a porous medium. The proposed synthesis method from granulated mixtures in a flow reactor holds promise for the production of TiC-CoCrNi composite powders used for applying hardening coatings.

The influence of the Fe + Co + Cr + Ni + Al metallic binder content, mechanical activation and compression of the samples on the maximum combustion temperature and rate, sample elongation during synthesis, mixture yield after mechanical activation, morphology and phase composition of the combustion products in the 5Ti + 3Si + x(Fe + Co + Cr + Ni + Al) system was studied. A composite material consisting of ceramics and a high-entropy silicide was obtained using self-propagating high-temperature synthesis. A two-phase high-entropy alloy consisting of solid solutions with an fcc and bcc lattice is formed during a 5-minute activation of 5Ti + 3Si + x(Fe + Co + Cr + Ni + Al) mixtures. With an increase in the metallic binder content in the mixtures, the grain size of the ceramics in the products, the maximum combustion temperature and the mixture yield after mechanical activation decrease. Compression of the samples from the initial mixtures expanded the concentration limits of combustion for the metallic binder content. The dependence of the combustion rate on the metallic binder content shows a maximum at x = 10% by weight. Activation of the mixtures increased the combustion rate and expanded the combustion concentration range depending on the binder content.

The results of a study examining the effect of dimethyl ether additives on sooty ethylene/air flat flames are presented. The study was conducted using quadrupole mass spectrometry. The experimental data are compared with kinetic modeling results. It is shown that the studied dimethyl ether additives do not significantly affect the formation of the aromatic compound C₆H₆. However, with increasing dimethyl ether content, the intensity of signals from aliphatic structures increases. The impact of this effect on soot formation is analyzed.

The problem of linear modal stability of a cylindrical Chapman-Jouguet deflagration combustion front in a radially diverging subsonic flow with a low Mach number is formulated and solved, taking into account vortex velocity disturbances. Unstable oscillation modes and waves with amplitudes increasing over time are detected for the considered types of small disturbances of the main combustible mixture flow and flame front. Quasi-natural frequencies and spatial modes of oscillations and disturbance waves of the combustion front are obtained. The presence of rotating circumferential disturbance waves of the combustion front in the annular combustion chamber channel is demonstrated, and their rotation velocities are determined. The main features of accounting for vortex disturbances are presented.

Experimental data on hydrogen propagation in a room with forced ventilation are presented. The dependence of the maximum volume fraction of hydrogen on the volumetric gas flow rate for ventilation of an 8 m³ room is determined. Experiments on the ignition of a hydrogen-air mixture formed after the discharge of a jet from a high-pressure cylinder at up to 14 MPa are also conducted. The effect of the total area of the blowout windows on the magnitude of the baric loads exerted on the room walls during combustion of the hydrogen-air mixture is assessed.

The results of an experimental study of combustion and detonation wave diffraction in a poorly understood class of dual-fuel systems (using the methane/hydrogen fuel system as an example) are presented. A characteristic feature of the studied systems is the significant difference in the kinetic parameters of the individual fuel components. New data are obtained on the dynamics of combustion wave propagation, detonation cell sizes, diffracting wave velocities, critical initiation conditions, and their optimization.