Home – Home – Jornals – Combustion, Explosion and Shock Waves 2021 number 2

Study of the aromatic fraction of Late Devonian oils and organic matter from domanik deposits of the Timan-Pechora petroleum province has revealed compounds whose proportion depends on the degree of OM transformation, namely, 1,1,7,8-tetramethyl-1,2,3,4-tetrahydrophenanthrene (1,1,7,8-TMHP) and 1,2,8-trimethylphenanthrene (1,2,8-TMP). It has been established that 1,1,7,8-TMHP dominates over 1,2,8-TMP in the immature OM; as the thermal maturation of OM increases, 1,2,8-TMP begins to prevail. The same pattern is observed for the Late Devonian oils. An increase in the ratio of 1,2,8-TMP to 1,1,7,8-TMHP with the growing thermal maturation of OM and the transition of one compound into another permit using this ratio as an additional indicator of OM maturity in domanik rocks.

We present research results for the geologic structure of the De Long, Aion, and Pegtymel sedimentary basins of the East Siberian Sea. The materials of geological surveys and drilling in their land area and island surroundings, the data obtained from geophysical surveys conducted by Dal’morneftegeofizika, MAGE, and Sevmorgeologiya, and the seismic and deep drilling data on the U.S. sector of the Chukchi Sea are summarized and analyzed. Pre-Paleozoic strata and the sedimentary cover have been identified throughout the sections of the sedimentary basins, which suggests the existence of a geologic “cover-basement” boundary rather than an arbitrary called “acoustic basement” horizon. The data on the geologic structure and gas saturation of the upper parts of the sedimentary sections were obtained during the study and gas-geochemical testing of core samples and bottom sediments from coastal shallow wells and corers. Gas contained in the rocks and bottom sediments in the study area includes hydrocarbon gases (HCGs) (СН4, С2-С5, and their unsaturated homologues), СО2, Н2, Не, N2, Ar, and, seldom, CO and H2S. The data on gas saturation of bottom sediments and the geochemical parameters of their syngenetic and epigenetic gases are presented. Areas of abnormal saturation of sediments with CO2, СН4, other HCGs, H2, and He (>5, 0.05, 0.001, 0.005, and 0.005 cm3/kg, respectively) have been identified, and maps of the gas saturation patterns in bottom sediments have been compiled. It is established that both gas saturation and distribution are determined mainly by the geologic evolution, tectonics, magmatism, geocryologic conditions, lithologic composition, catagenesis, coal content, bituminosity of sedimentary rocks, and oil and gas potential of the study area.

Based on a comprehensive analysis of the geologic structure, hydrogeology, and hydrogeochemistry, we predict oil and gas occurrence in the Jurassic reservoirs of the zone of junction of the Yenisei-Khatanga and West Siberian basins. We have established the regularities of formation of sandstones of the Sigovaya, Malyshevka, Vym, Nadoyakha, Sharapovka, and Zima reservoirs and examined their poroperm properties. The studied Lower and Middle Jurassic deposits, beginning from the Malyshevka reservoir, are characterized by abnormally high formation pressures with an anomaly ratio of up to 1.92. The Jurassic reservoirs bear weakly alkaline, moderately brackish to slightly saline groundwater of Cl Na, Cl-HCO3 Na, and HCO3-Cl Na compositions with TDS = 3.0-23.3 g/dm3. The low-mineralization connate waters determine an inverse vertical hydrogeochemical zoning in the sedimentary cover of the study region. The research data show favorable conditions for the generation and accumulation of hydrocarbon pools. It is shown that the main criteria for oil and gas occurrence are hydrogeochemical (contents of organic compounds, NH4, B, I, Br, naphthenic acids, and benzene; B/Br and HCO3/Cl coefficients), gas (total gas saturation of formation waters, degree of their gas saturation (Kg), and composition of water-dissolved gases), and hydrodynamic (formation pressures and their anomaly ratio (Ka)) indicators. Also, complex anomalies have been revealed in the Jurassic deposits, which trace the gas fields and revealed oil and gas occurrences. The Jurassic reservoirs are most promising for structure-lithologic traps in the peripheral zones of the basin and on the slopes of large positive structures. The Middle Jurassic deposits in the interior of the Yenisei-Khatanga Basin, poorly studied by deep drilling, might also be of interest as potential hydrocarbon pools.

The paper considers the origin of terraces that often complicate the slopes of abnormally deep buried valleys in the northwest of the East European Plain. The Izborsk-Maly valley (Pskov Region, Russia), which is half filled with Quaternary sediments, was chosen as the object of study. Since the upper part of the valley remains unfilled, it is possible to study in detail both geologic and geomorphologic structures of its terraced slopes being of particular interest in the context of the origin of buried valleys and the role of substrate in it. The four denudation-terrace levels that have been identified on the slopes of the Izborsk-Maly valley at absolute elevations of 53, 56-58, 70-72, and 75-77 m formed during the destruction of the preglacial karst landscape under the influence of Pleistocene glaciations. The formation of the terraces was linked probably with several stages of overdeepening of the valley and its expansion by the glacial erosion processes, which corresponded to at least two stages of the ice sheet advance in this area. The last stage may have been the beginning of the Late Valdai (Weichselian) glaciation or the activation of the edge of an ice sheet during its Luga phase (~15.7 cal kyr BP). Results of the study suggest that the Izborsk-Maly valley formed in subglacial conditions. The degree of glacial erosion was determined primarily by the coherence of Devonian carbonate-terrigenous rocks hosting the valley and the degree of the area transformation by karst processes. The cirque shape of slopes is the evidence of karst processes expression in pre-glacial time. Analysis of literature data shows that the origin of denudation terraces in the buried valleys in the northwest of the East European Plain has been paid little attention. The obtained data contribute to the study of this problem and provide insights into the origin of buried valleys.

New isotope-geochemical data on the volcanic complexes of the South Yakut and Martel volcanic depressions in southern Primorye are presented. Their formation in the early Eocene (54.3 Ma) and Late Cretaceous (83.5 Ma), respectively, is evidenced by U-Pb zircon dating (LA-ICP-MS). Based on the geochemical characteristics, it is concluded that the volcanics are typical A -type igneous rocks. Their formation coincides with the sudden change in the vector of motion of the Pacific slab with respect to the continent in the Campanian and Paleocene-Eocene, which caused destruction of the slab with its probable discontinuity and the injection of the subslab asthenosphere. The effect of mantle fluids on the continental lithospheric-rock melting determined the generation of magmas with the specific geochemical features of A -type igneous rocks. The regularities of their composition are due to the deep-seated reduced F-rich fluids that caused the intense differentiation of magmas accumulating fluidized melts enriched in mobile components in the apical part.

The Udina volcanic complex located in the southeastern part of the Klyuchevskoy group of volcanoes in Kamchatka remained dormant for several thousand years, but the magmatic system beneath the area may be awakening judging by seismic unrest. Seismicity in the area is characterized by data from permanent regional seismic stations and campaign local stations, as well as by data of the Kamchatka earthquake catalog. Seismic activity having nucleated at shallow depths in the vicinities of the Udina volcanoes since October 2017 may reflect a beginning cycle of volcanism. The earthquakes are mainly long-period (LP) 0.5-5 Hz events, which are commonly attributed to the movement of viscous magma and resonance phenomena in magma conduits. Such earthquakes may be a response to inputs of new magma batches to the plumbing system that feeds the volcanoes and thus may be precursors of volcanic unrest. Seismic campaigns of May-July 2018 near the Udina complex provided more rigorous constraints on earthquake coordinates and origin depths and showed that most of the earthquakes originated within 5 km beneath the Bolshaya Udina Volcano. Seismic tomographic inversion using the LOTOS code revealed a zone of high P -wave velocities, low S -wave velocities, and a high vP / vS ratio directly beneath the volcano. Such a combination of parameters typically occurs in active volcanic areas and marks intrusion of partially molten magma and/or liquid fluids. The velocity anomaly detected in 2018 is shallower than that recovered in 2014-2015. The seismic evidence, along with the available geological and geophysical data, record the movement of viscous magma related to the Udina feeding system in the middle crust, which is implicit proof for connection between the intermediate crustal and deep mantle magma sources renewed after a long lull.

The results of Hg content determination in the water of the Angara River source are considered in relationship with the seismic processes proceeding at different levels of the lithosphere in the Baikal Rift Zone (BRZ), the geodynamic rejuvenation of the South Baikal rifting attractor structure (RAS), and the time distribution of M ≥ 7 earthquakes which occurred at a significant distance from the water sampling station. The correlation coefficients calculated between the pairs Hg content-earthquake numbers n and Hg-logarithm of summary seismic energy lgΣ E _S are most often low, thus indicating the absence of a statistically meaningful relationship between the remote seismic process and the dynamics of mercury release. However, the correlation coefficients in the vicinity of the Angara River source are high, thus proving the relationship of the mercury release with the deformation of this territory. The statistical validity of the «deformation-mercury release» cause-and-effect relationship is verified by the fact that strong geodynamic impacts precede all meaningful Hg release maxima. In the period 1997-1998, the South Baikal RAS produced the highest impact, being in the phase of the maximum geodynamic activity. The combined impact of the RAS and the South Baikal earthquake of 1999 resulted in a series of the maximum mercury contents within 1999-2000. The subsequent gradual relaxation of the RAS activity led to a reduction in the average annual Hg content. Remote M ≥ 7 earthquakes and close strong earthquakes of the BRZ are responsible for the significant Hg release maxima. The predicted trend of the average annual Hg contents is their considerable increase in the fields of fluid discharge of faults under the powerful geodynamic impact of the RAS or strong earthquake. We assume that in the study lithosphere area, the powerful geodynamic impact caused an opening of fault zones leading to decompression with boiling and degassing of mercury and its rapid rise to the surface.

The study focuses on detection of geomagnetic secular variation and the respective correction of tectonomagnetic data. A new technique is proposed for picking the secular variation component in the Earth’s main magnetic field recorded by precise measurements at 100 to 500 km sites on the surface. Long-period field variations presumably arise from fluid motions in the liquid core, at depths of about 3000 km, whereas the sizes of observation networks are within 500 km. The sources of secular variation, irrespective of their configuration, are much deeper than those of tectonomagnetic anomalies located above the Curie surface depths of ~10 to 20 km. Therefore, the surfaces that represent the space distribution of secular variation must be smoother than the respective surfaces for tectonomagnetic anomalies. The problem is thus to separate the regional and local signals from the two types of sources located at different depths. The new method is tested using data of yearly geomagnetic measurements at more than 30 repeat stations of a ~120 km long geodynamic network in Gorny Altai spanning the period from 2004 through 2018. The secular variation pattern is reconstructed by quadratic interpolation. The precise data corrected for secular variation of the main field reveal previously hidden tectonomagnetic anomalies up to 12 nT. The 3 nT positive anomaly falls within the zone of surface deformation caused by the Mw = 7.3 Chuya earthquake of 27 September 2003.

An algorithm for combined estimation of the frequency and its change rate by increasing chirp signal sampling is proposed. The algorithm allows sequential calculation of the frequency estimates taking into account the time correlation of errors of the initial phase difference measurements. The proposed method is computationally efficient, and the results tend to the minimum variance unbiased estimator as the input signal-to-noise ratio increases.

The BRISK, AKAZE, and ORB feature detectors are compared in a series of experiments on a set of 10,000 images. Several characteristics of the efficiency of these detectors are estimated: the proportion of correctly found positions of features, the proportion of correctly established correspondences, and the number of correspondences in comparisons of two randomly chosen images. The dependence between the average number of false correspondences and the value of proximity of descriptors is estimated. Distributions of the number of correct and false correspondences are plotted.

Convolutional neural networks (CNNs) allow reaching the highest accuracy for the task of object detection in images. The major challenges in further development of object detectors are false-positive detections. In some applications, it is of interest to detect only moving objects: face of a person approaching the intercom or car in overall traffic. In this paper, we propose an approach to object detection, which makes it possible to reduce the number of false-positive detections by processing only moving objects. The proposed approach is a modification of CNNs already trained for the object detection task and can be used to improve the accuracy of an existing system by applying minor changes to the algorithm. The efficiency of the proposed approach is demonstrated on the open dataset "CDNet2014 pedestrian."

Issues of anomaly detection in nonstationary process signals are considered because anomalies could be an early indication of defects and equipment failure. An approach to detection of anomalies utilizing the Hilbert-Huang transformation and statistical model is presented. The main idea of the proposed approach is to analyze the statistical parameters of the components of the Hilbert-Huang transformation, which has high adaptive properties for nonstationary signals and provides precise resolution in the time-frequency domain. The paper describes the principal scheme and algorithm of the approach, detailed definition of the statistical model, numeric experiments on real and augmented data, and comparative analysis with similar anomaly detection methods.

The results of the indication of the vaccinia virus by using nanowire biosensors made on the silicon-on-insulator basis are presented. In the experiments, we used the vaccinia virus, the strain of LIVP from the collection of the Federal State Scientific Research Center of Virology and Biotechnology "Vector" of Rospotrebnadzor, and the rabbit blood serum containing specific polyclonal antibodies to the vaccinia virus. The results show that the polyvalent blood serum at the interface between the biosensor surface and the viral suspension is electrically neutral, the vaccinia virus is positively charged, and the complex of the polyvalent blood serum and vaccinia virus is negatively charged.

The analysis of nucleic acids remains an important trend in the development of medical diagnostics. Modern ultrasensitive diagnostic systems make it possible to convert a specific interaction during the analysis into a hardware-recorded signal. An example of such diagnostic devices is biosensors based on silicon-on-insulator (SOI) field-effect transistors (FET). In this work, we use glass surfaces (as a Si/SiO₂ surface of a SOI biosensor) to optimize and test all stages of the analysis. Efficient immobilization of electrically neutral analogs of oligonucleotides on the Si/SiO₂ surface after activation of Si-OH groups with 3-glycidoxypropyltrimethoxysilane or carbonyldiimidazole is demonstrated. The possibility of detecting an RNA target on model glass surfaces in the parallel analysis mode under conditions of a low or zero salt concentration is provided. The regeneration of the Si/SiO₂ surface of the sensors for the repeated analysis and the stability of the sensors during long-term storage are demonstrated.

An analytical review of optical-acoustic receivers (OARs) based on the Golay cells in the infrared and terahertz radiation ranges is presented. The history of the OAR emergence and development from the first works of Bell, Hayes, Golay, up to the present time is considered. The OAR advantages, namely, the constant and high sensitivity in a wide range of the spectrum and the highest detection ability among thermal receivers, are noted. The main characteristics of membranes, which are the main elements of OARs, are considered, and the physical properties of graphene, as the most preferred material for membranes, are analyzed. Three OAR design groups are considered: single cells with optical information reading and a condenser microphone, selective receivers with gas-filled chambers, and matrix receivers. Estimates are presented, which show that the use of single layer graphene membranes makes it possible to create IR and THZ radiation receivers with cells of the order of tens of microns with extremely high sensitivity. A new design scheme of matrix terahertz opto-acoustic receivers with the use of hexatrigraphene (C)₆₃₍₆₎ membranes with record-breaking characteristics is proposed.

An analytical solution of the problem of deflection of a deformable mirror with a thin circular plate with a free edge under the action of a concentrated load generated by one of the actuators acting on the plate with the other end resting on an infinitely rigid base is derived. The solution is based on the application of integral transforms and takes into consideration the kinematic pairs between the plate and each actuator, which is deformed according to Hooke’s law. The analytical solution is compared to the finite element solution obtained by using the ANSYS software. The results of the study can be used to optimize the actuator positions and to control the circular deformable mirrors in adaptive optics problems.

A method for measuring displacements based on a logometric method using a branched fiber-optic collector is analyzed. An analytical model of an optical-electronic probe of small axial displacements has been developed, and significant factors influencing the character of the calibration characteristic have been determined. The light-energy analysis of the optical scheme of the measuring optoelectronic probe is carried out, and the optical loss along the optical path length is estimated.

A method for the formation and transmission of 3D holographic images is proposed, based on the formation of a 2D holographic signal by subtracting the carrier spatial frequency from the signal, thereby, compressing the holographic information for the purpose of fast transmission over a standard radio channel in real time. The information about the3D structure of the holographic object is recorded with the use of coherent and incoherent radiation, in which an analog of the object's hologram is obtained by structured light methods, suitable for transmission to a distance in the form of a 2D frame equivalent to a hologram with eliminated redundancy. This way of transmission of 3D holographic information is similar to the transmission known in radio engineering on one sideband with subtraction of the carrier frequency and the possibility of subsequent introduction of this frequency or any other carrier frequency at a distance from the holographic object. This method of transmission of 3D holographic information is applicable for problems of holographic TV and 3D augmented reality. Examples of the implementation of this technology in creating holographic images of a real 3D portrait of a person and transmitting it over WiFi are given. 3D images synthesized in the IR range are shown. This technology is easily adaptable to the tasks of integrating images of different parts of the spectrum of electromagnetic radiation. Possible applications of the method in 3D instrumentation are proposed.

The method of laser pulsed location as applied to the problem of detecting retroreflective objects, including optical and optoelectronic observation devices, is studied. By using the created specialized mobile hardware and software stand, the retroreflection indices of typical video recording devices under real conditions are experimentally determined. The effectiveness of using periodic illumination, frame accumulation, and formation of difference images for object detection under conditions of intense sunlight is demonstrated.

The result of scribing of silicon very large-scale integrated (VLSI) circuits in hybrid infrared photodetectors by laser radiation in an aqueous medium is studied. The width of the material damage around the scribe groove (approximately 47 microns) and the occurrence of a water hammer when water boils during scribing (exerting the pressure on the material equal to 1.5 x 10^-6 kg/ μm² or more) are determined.

A method of focused delivery of ultrasonic energy to a specified point inside a biological object using an annular antenna array is presented. A functional diagram of a multi-element annular array with alternating radiating and receiving elements is described. The channels of the radiating elements have controlled phase shifters, and all the receiving elements are connected to the adder. The possibility of focusing the ultrasonic energy with allowance for the wave propagation in two media is demonstrated by means of simulations of the annular antenna array operation. The result of focusing with considering the interface between the two media is estimated. It is assumed that the two media have different speeds of ultrasonic wave propagation. The presence of two media on the ultrasonic wave path leads to defocusing and shifting of the focus position.

In this paper, we investigate the existence of solutions for a second-order differential inclusion with nonlocal boundary conditions. To establish the existence results for the given problem, first we apply Schaefer's fixed point theorem combined with a selection theorem due to Bressan and Colombo. Second, our result is based on the fixed point theorem for multivalued maps due to Covitz and Nadler. An example is given to illustrate the obtained results.

In the present discussion, we analyze the semilocal convergence of a class of modified Chebyshev-Halley methods under two different sets of assumptions. In the first set, we just assumed the bound of the second order Frèchet derivative in lieu of the third order. In the second set of hypotheses, the bound of the norm of the third order Frèchet derivative is assumed at initial iterate preferably supposed it earlier on the domain of the given operator along with fulfillment of the local ω-continuity in order to prove the convergence, existence and uniqueness followed by a priori error bound. Two numerical experiments strongly support the theory included in this paper.

In this paper, we discuss a priori error estimates and superconvergence of P ₀²- P ₁ mixed finite element methods for elliptic boundary control problems. The state variables and co-state variables are approximated by a P ₀²- P ₁ (velocity-pressure) pair and the control variable is approximated by piecewise constant functions. First, we derive a priori error estimates for the control variable, the state variables and the co-state variables. Then we obtain a superconvergence result for the control variable by using postprocessing projection operator.

Layer-resolving grids remain an important element of comprehensive software codes when solving real-life problems with layers of singularities as they can substantially enhance the efficiency of computer-resource utilization. This paper describes an explicit approach to generating layer-resolving grids which is aimed at application of difference schemes of an arbitrary order. The approach proposed is based on estimates of derivatives of solutions to singularly-perturbed problems and is a generalization of the approach developed for the first order schemes. The layer-resolving grids proposed are suitable to tackle problems with exponential-, power-, logarithmic-, and mixed-type boundary and interior layers. Theoretical results have been confirmed by the numerical experiments on a number of test problems with such layers; the results were compared to those obtained with difference schemes of different orders of accuracy.

Usually, the ocean depth is measured by the echo sounder in the course of a vessel cruise. However, there are a lot of areas in the World Ocean which are free of navigation. This means that by now there are no direct bathymetry measurements. For the numerical modeling of the trans-oceanic tsunami we need the digital bathymetry of the whole water area. The thus arising problem is to restore (at least, approximately) the depth values in the areas without reliable bathymetric data. This can be done in the process of the propagation of a real tsunami with the help of detectors used. Two algorithms for the depth restoration based on the tsunami arrival times are proposed. The algorithm has been tested on the depth restoration problem in the area with a sloping bottom, where the tsunami arrival times are known at the nodes of a rectangular grid.

In this paper, the Lie-Trotter splitting method (LSM) is used to solve the generalized Burgers-Huxley equation (GBHE) numerically. We first establish the local error bounds of approximate solutions of the GBHE with the help of the theory of differential operators in a Banach space. Then we prove the global convergence by using a telescoping identity. At the end, the accuracy of the method is provided by numerical results which are compared with earlier studies.

Ignition and combustion of a homogeneous stoichiometric methane-air mixture under simultaneous local thermal and photochemical actions, resulting in the formation of either O₂(a¹\Δ_g ) molecules or O atoms, are numerically simulated. A two-dimensional unsteady multicomponent approach with the use of the known detailed kinetic mechanism of methane oxidation, which takes into account reactions with participation of electronically excited oxygen molecules O₂(a¹\Δ_g ) and O₂(b¹\ _{), is applied. It is shown that an additional photochemical action ensures ignition of the mixture in situations where the thermal action alone is insufficient. Moreover, for identical energy inputs, a higher burning rate at the initial stage is observed in the case of generation of oxygen atoms. This method of the photochemical action seems to be more effective from the viewpoint of combustion initiation. The computed results on propagation of turbulent combustion are in reasonable agreement with available experimental data.}

The ignition of a methane-air mixture with additives of ClF₅, ClF₃, OF₂, and H₂O₂ (additive content in the mixture ≤ 1%) is studied by numerical simulation. The ignition temperature of the mixture is determined as a function of the initial pressure and additive content. It is shown that the introduction of additives into the mixture leads to a significant decrease in the ignition temperature due to the acceleration of the formation of active particles and intensification of the chain mechanism of the process. Of the additives considered, chlorine pentafluoride is the most effective additive, and hydrogen peroxide is the least effective one.

A comparison of two approaches to describing a stretching spherical flame is made. Processing of a large amount of experimental data shows that the approach in which a parameter proportional to the strain rate is used as a small parameter gives a lower accuracy of approximation than the approach based on the use of the ratio of the flame thickness to the radius of curvature.

Methyl methacrylate (MMA) is the main pyrolysis product of the widely used polymer polymethyl methacrylate; therefore, the compact mechanism of MMA oxidation is of interest for CFD modeling of the spread of a fire over this polymer. A reduced mechanism for MMA combustion consisting of 263 elementary reactions involving 66 species was developed for a detailed chemical-kinetic mechanism of MMA oxidation in flames using Chemical Workbench software. The developed mechanism was validated against experimental data on the speed of premixed MMA/air flame at an equivalence ratio 0.9 < f < 1.3 and against literature data on the structure of an MMA/O₂/Ar (f = 1) flame stabilized on a flat burner at a pressure of 1 atm. The proposed reduced kinetic model for MMA describes the experimental data with satisfactory accuracy, and simulation results for the full and reduced mechanisms MMA oxidation are in good agreement with each other in terms of the concentrations of the main species of the flame and the concentration of most combustion intermediates, including hydrogen, methane, ethylene, acetylene, propane, acetaldehyde, methyl acrylate, etc.

A general model of combustion of mixed gases is proposed, taking into account the chemical work, in which one chemical reaction is assumed. An energy equation is written for an arbitrary mixture of fuel/oxidizer/combustion product. The combustion of a H₂/O₂ mixture is considered on the basis of the model. Modeling is carried out for two options: with and without account for a temperature dependence between the heat capacity of the components of the mixture H₂, O₂, and H₂O. The chemical work has a positive sign, and its relative contribution to the main characteristics of the process (temperature and burning rate) is estimated at 3.9 and 19 %.

A computational and experimental study of the passage of a gasless combustion wave through a wedge-shaped inert barrier was performed. The stability of the transient combustion process to a change in the thermophysical, geometric parameters of the barrier and the energy-kinetic parameters of chemically active layers was studied. By the region of stable transient combustion process is meant the range of parameters in which the passage of the combustion wave through the contact boundary ends with the establishment of a steady-state mode of its propagation along the ignited composition. The dynamics of transient combustion under near-critical conditions of its existence was investigated.

Effect of K₂CO₃ and KCl additives on the process of high-temperature oxidation and ignition of conglomerates of powdered boron and aluminum particles and on the critical conditions for the ignition of air-gas mixtures of these metals is studied experimentally. It is revealed that the mixtures of boron and aluminum particles covered (encapsulated) with salts ignite at temperatures lower than the ignition temperatures of mechanical mixtures of metals with these salts in appropriate proportions and significantly lower ignition temperatures of pure boron and aluminum. This indicates the active role of salts in the process of heterogeneous ignition. It is established that, for boron conglomerates, the accelerating effect of salt additives on the oxidation of conglomerates is noticeable at all investigated concentrations and compositions starting from 1 % (by weight). For aluminum, an increase in the reaction rate is noticeable only for KCl additives at concentrations of 3 % and above.

A Ni-Al-C based composite material is synthesized by the method of electric thermal explosion under a pressure of 96 MPa. During an electrothermal explosion in a powder reaction medium (Ni + Al + C), a Ni and Al based melt is formed, in which carbon dissolves. It is shown that in the process of crystallization of the final product, carbon, due to low solubility in NiAl, is located on the surface of intermetallic grains of NiAl in the form of multilayer graphite nanofilms with a thickness of 50 ÷ 80 nm, filling the intergranular space. The microhardness of the synthesized material is 3.084 MPa.

Composite propellants are tested using the quench particle collection bomb (QPCB) for the pressure ranging from 2 to 8 MPa to estimate the particle size distribution of aluminum agglomerates from quenched combustion residues emerged out from the burning surface. The major ingredients included in the propellants are ammonium perchlorate (AP), aluminum (Al), hydroxyl-terminated polybutadiene (HTPB), and toluene diisocyanate (TDI). Five propellant compositions are considered in this study; two of them are mixed with catalysts. Propellant formulation variables like the coarse AP/fine AP ratio, total solid loadings, catalyst percentage, and aluminum content are varied to assess their effects on the aluminum agglomeration process at different pressures. Unburnt aluminum in agglomerates is continuously getting combusted as they move out from the propellant burning surface. Large agglomerates comprise both Al₂O₃ and unburnt aluminum. The majority of agglomerates are spherical in shape, and the sizes vary from 31 to 115 µ m for non-catalyzed propellants and from 28 to 136 µ m for catalyzed propellants over the tested pressure conditions. These results can give further insight into the aluminum agglomeration process of catalyzed and non-catalyzed propellants and also affect the choice of the propellant ingredient percentage aimed at reducing aluminum agglomeration, which causes two-phase flow losses of thrust and slag accumulation in full-scale solid rocket motors.

The dependence of the diameter of a porous carbon particle on stationary temperature at various pressures of the gas mixture is analyzed. Cases of self-ignition of a particle in a heated nitrogen-oxygen mixture and forced ignition in a cold nitrogen-oxygen mixture leading to quasi-stationary combustion, followed by spontaneous extinction, are considered. It is shown that the combustion temperature of small particles with a diameter d < 200  m, which are characterized by a transient regime of chemical reactions, increases with increasing pressure of the gas mixture. An analytical dependence that qualitatively describes this dynamics is obtained. The greatest growth falls on a pressure interval of 0.1 ÷ 0.3 MPa. A similar analysis for particles of various coals is presented. The dependence of the critical oxygen concentrations corresponding to ignition and extinction on the diameter of a carbon particle was obtained analytically taking into account the internal reaction. It is shown that an increase in the pressure in the mixture leads to a decrease in the critical concentrations of oxygen.

In this paper, confined explosions of HMX-based aluminized explosives in a spherical chamber are studied. The effects of aluminum particles on the afterburning reaction and explosive performance are obtained by changing the size of the particles and the gas environment. The results show that the concentration of oxygen in air is not sufficient to support complete combustion of aluminum particles. The estimated oxidation rate of aluminum particles is 87 ÷ 93 %, and it tends to decrease with increasing particle size. Part of aluminum particles oxidize with detonation products, and the reaction can last for hundreds of microseconds. However, the degree of oxidation between the large-sized aluminum particles and detonation products is small. A new method is used to estimate the initial energy of detonation by observing the time difference between sensing the initial light and the pressure wave. This method leads to a conclusion that some of the aluminum particles are oxidized during detonation and provide additional energy to the primary blast wave. Small micron-sized aluminum particles in the range of 48.9 nm ÷ 46.7 m extend the duration of the fireball.

A method of obtaining detonation nanodiamonds from tetryl by means of blasting the latter in a water shell with the explosive/water mass ratio of 1/(10 ÷ 14) is developed. The proposed process ensures the yield of the target product in the amount of 6 ÷ 7 wt. % of the initial mass of the reagent with the content of nanodiamonds in the resultant batch mixture equal to 57 ± 6 %. It is demonstrated that the use of individual explosives offers some advantages over the known multicomponent mixtures in terms of cost efficiency and safety of the charge preparation process.

It is revealed by scanning electron microscopy that the formation of filamentous structures up to 10 μm in length long can be induced in spheroplastics based on organosilicon elastomer by a shock-wave pulse of microsecond duration. Threaded structures are formed on the surface of fractured microspheres. Their formation is facilitated by the metallization of the surface of glass spheres. The results of an experimental study of changes in the dielectric and mechanical characteristics of metallized spheroplastics, caused by impact-wave action, are presented. Possible reasons for the formation of threaded structures upon a shock-wave impact on spheroplasics are discussed.