Home – Home – Jornals – Combustion, Explosion and Shock Waves 2024 number 4

In a model experiment, the process of interaction of an external artificial disturbance with the leading edge of a straight wing model was investigated. The characteristics and features of the development of boundary layer disturbances, generated as a result of the interaction of external disturbances, and the blunted leading edge of the wing model have been obtained. The research was carried out in a subsonic low-turbulence wind tunnel using a hot-wire anemometry method for detecting disturbances. Localized disturbances generated in the incoming flow were shown to induce longitudinal streaky structures in the boundary layer of the straight wing. High-frequency wave packets (precursors) appeared at the boundaries (fronts) of longitudinal structures. The dynamics of the development of wave packets and localized longitudinal structures in the boundary layer above the wing profile in a gradient flow was studied.

The results of experimental measurements are presented to assess the correlation characteristics of disturbances in the boundary layer of a flat plate with a sharp leading edge and pulsations of the incoming flow in cases of natural pulsations and influence of an N-wave for Mach 2 on the leading edge. The parameters of the cross-correlation of signals from two constant-temperature anemometry (CTA) are obtained digitally. The frequency ranges with apparent correlation between the mass flow rate pulsations measured by the probes are determined.

The gas temperature measurements at the level of the inner wall of Ranque vortex tubes of the square and circular cross sections with variations in the cold mass fractions for both tubes showed the presence of three characteristic zones of temperature growth, which do not change over a wide range of the cold mass fraction. These zones are typical when analyzing the flow in a vortex tube within the framework of the flow crisis concept.

The flow in the vicinity of the source of controlled harmonic non-stationary perturbations of a gas medium, applicable for generating Görtler vortices in a compressible boundary layer, is studied. The source has a flat surface with linearly arranged cylindrical channels, leading alternately to two cavities of variable volume. Various configurations of the source are considered: with separate channel outlet openings and with a slit opening above them. Numerical simulation is performed in the Solid Works Flow Simulation package, and experimental measurement of gas velocity is realized by the PIV method. The developed source is shown to create periodic velocity fluctuations with an amplitude of up to 2 m/s at a frequency of 1 kHz near the surface. The shapes of the profiles of velocity normal to the surface along the source are close to sinusoidal in both time and space.

A method of panoramic temperature measurement based on registering the fluorescence of thin-walled coatings on the inner surface of a flying vehicle model is considered. The method allows investigations in optically polluted flows of high-enthalpy short-duration wind tunnels. The temperature and heat fluxes on the aerodynamic model surface are retrieved by means of combining the results of temperature measurements with the numerical solution of an adjoint problem of the flow around the flying vehicle. Implementation of this method in practice is performed in the flow of a hotshot wind tunnel based at ITAM SB RAS.

Investigation results on the air flow in a convergent channel with a hot bottom wall at a set constant heat flux or a set constant wall temperature are presented. The numerical simulation was carried out in the OpenFOAM software using the k-ω- SST turbulence model. The verification of simulation results demonstrated a good agreement between the calculated data and the experimental velocity profiles and the thermal Stanton number. The study showed that an increase in the temperature of the convergent channel wall leads to the phenomenon of the streamwise velocity overshoot, suppression of turbulence and a decrease in the skin-friction coefficient and thermal Stanton number. In contrast to a zero pressure gradient flow, the type of thermal boundary conditions has a noticeable effect on the skin-friction and heat transfer in the convergent channel.

Numerical simulations of an underexpanded supersonic jet exhausting from a circular nozzle are reported. The study is performed in a three-dimensional formulation using two different approaches: Navier-Stokes equations and Direct Simulation Monte Carlo method. In both cases, a reverse flow zone is formed behind the Mach disk in the first shock cell. Thus, this phenomenon, which was previously observed in axisymmetric simulations, cannot be attributed to inaccuracies of approximation of these equations near the axis of symmetry.

Influence of streamwise slots with the orientation angle φ = 0 and various depths h (corresponding Reynolds number Re_h = 0 -2000) on the stability of the supersonic (M = 2) flat-plate boundary layer with relation to natural disturbances of the first (vorticity) instability mode driving laminar-turbulent transition was investigated experimentally. Experiments shown that such kind of disturbances can be stabilized by small-depth streamwise slots, wherein the maximum stabilization occurs at the Reynolds number (based on the slot depth) of about Re_h ≈ 1000.

The work is devoted to the study of random statistical processes in two-phase flows. The objective is to obtain new computational and experimental data on the influence of previously undetermined factors on the trajectories of particle motion, their segregation, and the formation of a locally continuous flow field of the dispersed phase in supersonic turbulent two-phase flows. The results of computational and experimental study of the flow features of a two-phase supersonic flow are presented. A new experimental method was applied for analysis of influence of random statistical factors on the particle distribution in a high-speed carrier flow. The physical basis of the proposed method is to indicate the flow rate of the dispersed phase by means of particle adhesion to an obstacle installed in the flow. In order to analyze the segregation of the dispersed phase in the flow, the approach of quasi-continuumization of individual particle trajectories is applied. The method obtains a locally continuous flow stress field for dispersed phase flow. Empirical coefficients resulting from the influence of random statistical factors on the motion of dispersed particles in a two-phase flow are determined. The obtained computational and experimental data clarify the prediction of the distribution and segregation of dispersed phase particles with a size of 15÷40 microns in a supersonic free flow.

Results of a numerical study of supersonic flows formed in channels with a square cross section are reported. Configurations consisting of a constricting entrance section formed by four compression wedges aligned at a right angle to each other and a subsequent channel with a constant cross section are considered. The initial shock waves formed on the nose compression wedges pairwise intersect each other in dihedral corners of the configuration along the swept lines, and a complex system of reflected and subsequent interacting shock waves of the general three-dimensional position is formed further downstream. The data are obtained in a supersonic range of freestream Mach numbers М = 2 - 4 for compression wedge angles of 3° and 8° in flows with both regular and irregular interaction of the initial shock waves in dihedral corners of the configuration.

Measurements of full pressure pulsations in the mixing layer of a supersonic, strongly underexposed jet were performed. The resulting pressure was converted into a longitudinal velocity, which allowed determining the main characteristics of the layer: its growth rate and thickness, longitudinal and transverse dimensions of disturbances, intensity, and spectral composition of turbulence. The layer under consideration was in a state of saturation, with a wide range of disturbances being realized within. The measured growth rate of the layer turned out to be four times higher than that calculated by a statistically generalized method. The intensity of disturbances of the longitudinal velocity component was determined in the considered layer by two groups of disturbances - low-frequency and high-frequency - with approximately equal inputs. From the analysis of the measurement results, it follows that the mass transfer across the layer is inversely proportional to the lengths of the vortices, and in the upper part of the frequency range of intense disturbances it is many times higher. This indicates that intensive mixing generates rapid growth rate of the layer.

It is shown that the vibration transfer and working medium pressure pulsations through vibration-isolating pipeline junctions of various plants may increase by two or three orders of magnitude with an increase in the vibration frequency and in the presence of incompressible working fluid. The results of research of the found physical models that determine this phenomenon are presented. The experimental results for a spatial three-component broadband active vibration-protection system (AVS) for vibration damping beyond the vibration isolation junction with liquid are considered. An experimental plant scheme for studying the simultaneous spatial active damping of dynamic forces, vibrations and pressure pulsations downstream from the junction has been given. Calculated dependences of the maximum efficiency of considered AVS on frequency are obtained. Efficient active damping of forces is shown to be attainable in an open loop without feedback. While damping in an open loop at the experimental plant, the efficiency of active damping of dynamic forces is obtained in three directions up to 10 dB or more in the frequency range from 5 to 800 Hz (more than seven octaves). The analysis of scientific publications reveals the uniqueness of this result. In this case, there are no zones of negative efficiency outside the active damping frequency range, which appear while using other methods of active damping.

An experimental method is proposed for determining the frequency response of a hot-wire and hot-film system using short-pulse laser action on a sensor. The possibility to obtain frequency response by this method is demonstrated. The frequency response is obtained from constant temperature anemometers of two manufacturers with two types of sensors: surface thin-film and wire.

The experimental results on heat transfer when a pulsed multi-nozzle spray flows onto a vertical surface are presented. The behavior of the effective heat transfer coefficient averaged over time and over the entire heat transfer surface has been studied. The experiments were carried out in the regime of evaporative cooling at a constant temperature of the heat transfer surface T_w = 70°C. The duration of pulses for supplying the liquid phase of the spray τ and their repetition frequency F were varied in the experiments within wide limits: τ = 1 ÷10 мс and F = 0,25 ÷ 50 Hz. In addition, the effect of droplet phase flow rate on heat transfer was studied by changing the pressure in front of the nozzles (ΔP_L = 0,05 ÷ 0,6 MPa). Preliminary studies have shown that heat transfer during spray impingement onto a surface can be strongly influenced by the co-supply of air due to turbulization of the wall layer and the return of droplets reflected from the surface. It has been established that the main factor determining the intensity of heat transfer when the spray flows onto the surface is the time-averaged mass velocity of the liquid phase. Using this value, generalization of experimental data on the heat transfer coefficient and the thermal efficiency parameter of a pulsed spray was achieved.

The paper demonstrates a possibility of applying the known class of analytical self-similar solutions in the form of the traveling heat wave for a system of nonlinear integro-differential equations describing radiative transfer for non-stationary, quasi-stationary and regular modes of solution behavior. The solutions are constructed for a kinetic model in the Cartesian geometry under the assumption of local thermodynamic equilibrium with specially chosen absorption and scattering coefficients. A test problem for different solution modes is provided.

In this review paper, using the example of AM-Pb and AM-Bi melts (AM is an alkali metal), modern ideas on the nature of chemical short-range order in liquid metal systems with partial ionic bonding are briefly presented. Generalization and analysis of the experimental data obtained by the authors on the volumetric properties and mutual diffusion in liquid alloys of alkali metals with lead and bismuth have been carried out. The behavior of these properties is shown to generally agree with existing simple models that assume the presence of ionic complexes in melts, which are gradually dissociated with increasing temperature. At the same time, the need to refine the structure of polyanionic complexes in liquid AM-Bi systems is confirmed.

The paper describes an experimental study of the influence of multiple cyclic pressure loading on the service life and sorption performance of a composite sorbent whose granules consist of selectively permeable (to helium) microspheres as a filler and pseudoboehmite as a porous binder. A test bench is specially designed and fabricated for the study, which makes it possible to model various operation regimes of gas-separation plants in the pressure range up to 10 MPa. Cyclic tests of pressure loading of the granulated composite sorbent are performed, and the sorption capacity of the sorbent with respect to helium is measured. It is found that the composite sorbent retains its integrity and sorption performance under cyclic loading of 1000 cycles and more at pressures up to 10 MPa.

The paper presents the experimental results on the disposal of infected medical waste using low-temperature plasma. It is shown that infected medical waste can be processed using plasma technology. During plasma destruction of these materials, their biological disinfection with production of chemically inert, safe slag is guaranteed.

The paper is concerned with an experimental study of heat transfer and boiling crisis development on a biphilic silicon surface made using a set of methods, including chemical vapor deposition and laser texturing. It is shown that the use of a biphilic surface with the proposed configuration of hydrophobic zones on a superhydrophilic base leads simultaneously to an increase in heat transfer by 60% and an increase in the critical heat flux by 76% as compared to an unmodified surface.

Aircraft engines are a source of significant greenhouse gas emissions, in particular CO₂. Due to the tightening of emission standards, ways to reduce CO₂ emissions from aviation are being sought. One of the most promising ways to achieve this goal is the use of fuels from renewable sources, such as plant materials. To simulate the working process of combustion chambers of aircraft engines when burning biofuels and their mixtures with petroleum fuels, knowledge of the physicochemical properties of such fuels is required. This paper provides a review of existing methods for calculating the physicochemical properties of oxygen-containing biofuels, including esters, alcohols and ketones. The presented methods are validated on substances acting as bioadditives to aviation fuel and analyzed in terms of calculation accuracy and ease of use for studying the working process in combustion chambers.

Results of a theoretical study of the reaction of 1-acenaphthylene oxidation by molecular oxygen are presented. The molecular parameters and relative energies are obtained with the use of the G3(MP2,CC)//B3LYP/6-311G(d,p) composite numerical scheme, which ensures chemical accuracy. The values of the rate constants and the relative yields of reaction products are calculated with kinetic accuracy for various conditions within the framework of the RRKM theory with the MESS package. The proposed mechanism includes competing reactions paths, where the channel leading to separation of atomic oxygen dominates at high temperatures and low pressures, while the channel leading to separation of carbon monoxide dominates at low temperatures and pressures.

The single-component propellants hydrazine and hydrogen peroxide are widely used in rocketry. Their use is associated with the development of catalysts that initiate ignition and combustion of propellants upon simple contact with the catalyst without prior heating. It is obvious that the initial step of ignition is the liquid-phase decomposition of a single-component fuel on a catalyst. Otherwise, the propellants simply could not ignite. Physicochemical and mathematical models of the liquid-phase catalytic decomposition and subsequent ignition of a single-component propellant in a granular catalyst layer are proposed.

Results of a theoretical study of the methine radical (CH) with acetonitrile (CH₃CN), which is a potentially important step in the formation of heterocyclic nitrogen-containing molecules in the interstellar space and planetary atmospheres, are presented. A profile of the potential energy surface is constructed, which describes the mechanism of the formation of both linear and cyclic products. The geometry, frequency of oscillations, and relative energy of the resultant structures are determined with the use of the explicitly correlated coupled cluster method and the density functional theory CCSD(T)-F12/cc-pVTZ-f12//ωB97xd/cc-pVTZ. Within the framework of the Rice-Ramsperger-Kassel-Marcus theory, rate constants and branching coefficients of reaction products are calculated under the conditions of deep space corresponding to the limit of zero pressure for various impact energies. It is found that the relative yields of reaction products depend on the initial adduct of the reaction.

The formation of nitrogen oxides during combustion of coal or biofuel containing fuel-coupled nitrogen is an important environmental problem. As the simplest model system used to describe coal combustion, one can use a pyridyl molecule, which, on the one hand, has an aromatic structure and, on the other hand, contains a nitrogen atom in its structure. This paper describes a theoretical study of the reaction of para-pyridyl interaction with molecular oxygen. A surface of potential energy interaction of para-pyridyl interaction with molecular oxygen is constructed. The para-pyridyl radical barrierlessly attaches an oxygen molecule with formation of the PyOO radical, and then the reaction can follow one of three paths, leading to four possible products: 3H-pyrrole, HCO + HCN, 1λ²-pyrrole, and 1λ³,4-oxazine.

The paper presents an experimental study of the lean and ultra-lean combustion modes of a multicomponent hydrogen-containing fuel in swirling flow under aerodynamic counterflow conditions. A counterflow burner unit was used to implement diffusion-kinetic combustion of a mixture of methane and a multicomponent hydrogen-containing gas in different concentration ratios. The experiments show that the addition of the multicomponent fuel to methane extends the range of stable combustion of lean mixtures and provides a reduction in the emission of polluting components in combustion products. These results can be used to increase the efficiency, safety, and service life of combustion chambers of gas turbine engines and power plants.

Subsonic turbulent combustion in a premixed methane--air mixture in a model channel with a backward step is considered (P. Magre et al., ONERA, 1975-1989). The main physical mechanisms characteristic of combustion in gas turbine combustors are reproduced in experiments. A brief overview of previous numerical simulations of these experiments is given. New results from a numerical study of the stabilized combustion regime in this combustor are described. Several partially stirred reactor (PaSR) models for describing turbulent combustion are compared with a quasi-laminar approach. A model of variable turbulent Prandtl and Schmidt numbers is presented, and its influence on the reproduction of this flow in calculations is considered.

A method of modeling turbulent combustion is implemented by an example of the diffusion flame of propane. A grid is generated, and tests are performed to verify that the grid element size is sufficient to satisfy criteria of the turbulence scale needed for large eddy simulation (LES). Results of numerical modeling of the temperature distribution during combustion of a diffusion flame of propane obtained by using the Reynolds-averaged Navier-Stokes (RANS) and LES approaches in a three-dimensional formulation are presented, and the numerical model is validated in terms of the main and intermediate combustion products. LES results for the temperature distribution in the combustion zone agree much better with experimental data than RANS predictions, and model validation based on the LES approach is confirmed by the analysis of numerical and experimental data on the main and intermediate combustion products. The averaged numerical parameters of turbulent combustion of the diffusion flame of propane can be used for determining the most complicated products of incomplete combustion of the fuel, e.g., polycyclic aromatic hydrocarbons by means of kinetic modeling with detailed chemical kinetics.

A review of the literature on the topic of soot formation during combustion of fuels from biocomponents is presented. The review contains brief information on the mechanisms of soot formation, the stages of its formation and the factors influencing this process. An analysis of representatives of various groups of oxygenated biofuels is carried out in terms of their influence on the level of soot formation. Generally accepted characteristics of the level of soot emissions for hydrocarbon fuels are given, their advantages and disadvantages are presented.

An economical calculation method for self-excitation of gas oscillations in low-emission combustion chambers of gas turbine units has been developed. The method is based on the SST SAS turbulence model and the turbulent combustion model with a modified equation for a variable degree of combustion completion. A multiplier associated with gas pressure oscillations is introduced into the source term of this equation. The tendency of the combustion chamber to excite gas oscillations is estimated by two parameters: the exponent of this multiplier (interaction index) and the logarithmic decrement of oscillation damping. When solving the problem of self-excitation of oscillations in the case of specifying a homogeneous methane-air mixture at the combustion chamber inlet, the first radial oscillation mode with a frequency of 2700 Hz appeared. In the case of separate air and fuel supply to the combustion chamber, the first longitudinal oscillation mode with a frequency of 300 Hz was excited. The use of resonant absorbers (small anti-vibration screens) made it possible to completely suppress radial oscillations.

This paper presents an analysis of trends in the development of combustion chambers for high- and medium-power gas turbine power units of advanced manufacturers pursuing a significant increase in the efficiency of the plants and fuel flexibility while maintaining environmental requirements. The experience in developing low-emission combustion chamber (LECC) in the All-Russian Thermal Engineering Institute is presented. The results of tests of the GT-16P LECC in a single-burner compartment with full parameters are presented. Its modification to a dual-zone configuration is shown, which made it possible to significantly extend the range of stable low-emission combustion over a wide temperature range of outside air. For acceptable values of NO_x , it was possible to reach a combustor exhaust gas temperature of 1700 °C. An analysis is made of the designs of gas turbine LECC burners allowing to avoid the main problems arising when burning fuel with a high content of hydrogen: flame breakthrough into the premixing zone, high pressure losses on burners, and combustion instability. It is shown that these designs do not contain a blade swirler and a pronounced premixing zone.

The annual dynamics of (1) chloroform-extractable substances (CES) and petroleum hydrocarbons (PH) in riverside fluvial sediments, in the bottom sediments of the mixing zone of river and sea waters, and in the bottom sediments of the marine area, and (2) the abundance of hydrocarbon-oxidizing (HOB) and heterotrophic (HB) bacterial groups in the bottom sediments of the marine area and riverside sediments is analysed. The maximal content of CES was found in the marine area (450±17.5 mg/100 g), and the minimal one - in the river part (127.6±10.9 mg/100 g), in the mixing zone of river and sea waters - 370±37.9 mg/100 g. The average concentrations of PH are distributed similarly to the concentrations of CES: the maximal values (127.5±10.9 mg/100 g) are detected in marine ground, the values for the sediments of the mixing zone are slightly lower (103.1±9.4 mg/100 g), and the minimal values (54.8±23.9 mg/100 g) are detected in river sediments. The physicochemical characteristics of bottom and coastal sediments are presented. The abundance of HB in the bottom sediments of the marine area varied from 7.5∙10³ to 2.5∙10⁶ cells/g, respectively, and from 9.5∙10³ to 9.5∙10⁸ cells/g in the river area. There was no seasonal variability in the abundance of HB at both areas. Hydrocarbon-oxidizing bacteria were registered in 100 % of the samples of bottom and riverside sediments of the designated water areas. The abundance of HOB varied from 25 to 2.5∙10⁴ cells/g in the marine zone and from 25 to 4.5∙10³ cells/g in the river zone. The maximal values of HOB abundance in the riverside sediments were recorded during the flood period (February-April).

The acidity of NH-groups of a number of sulphonamides and glycine derivatives in a dimethyl sulphoxide medium has been investigated using the potentiometric method. Dissociation constants of these compounds are determined from titration curves. It is shown that the acidity of NH groups in the studied sulphonamides is controlled by the polar effect of substituents. The possibility of quantitative potentiometric analysis of glycine derivatives has been established for the first time. Biological activity has been predicted with the help of PASS software. The correlation of NH group acidity with the biological potential of the compounds has been established.

The solution to the problems of ecological safety when cleaning water objects from organic pollutants is indissolubly related to developing new sorbents and improving the technologies of their synthesis. Various materials in dispersed and granulated forms are successfully used in the production of sorbents. This article deals with the development and improvement of the technologies for producing the sorbents of petroleum and petroleum products. As a basis for the development of new sorbents, the properties of the granular foamed silicate obtained from the siftings of waste products from mining and processing plants were studied. The trial batches of oleophilic sorbents were obtained through thermochemical modification of hydrocarbons in the gas-vapour phase. It has been established that foamed silicate does not change its porous structure and amorphous state after thermo-chemical modification, retaining the high sorption activity. The nature of the porous structure of sorbents and the influence of porosity on their key properties, such as oil capacity, water absorption, and buoyancy, are investigated. The studies of the fractions of modified foamed silicate revealed low water-absorption capacity of the coarse- and middle-sized fractions. The minimum water absorption was determined for the fine fraction of the modified material, which is related to the absence of pores in these samples. Determination of oil capacity characteristics provides evidence of high oil receptivity and sorption capacity of the modified foamed silicate with respect to petroleum products. The results of experiments on sorbent regeneration after the end of its service life are presented. The developed semi-production experimental plant for the modification and regeneration of porous loose materials in the fixed bed is presented. The technological scheme of regeneration is proposed, allowing for regeneration and repeated modification of the used sorbent during one processing stage without any decrease in its sorption properties. The advantage of the developed technology of sorbent properties recovery is in the implementation simplicity and economic rationality. The repeatedly modified sorbent retains its characteristics and, first of all, sorption properties with respect to petroleum products. The practicability of developing new sorbents of petroleum products based on granular foamed silicate is demonstrated.

A fuel processor for autothermal reforming of diesel fuel into synthesis gas is developed and tested. The developed reactor is demonstrated to possess a fast start-up and high efficiency. During the tests, complete conversion of diesel fuel and the composition of reaction products close to equilibrium values were achieved. The thermal circuit of a power plant based on a solid oxide fuel cell (SOFC) with the electrical power of 1 kW was optimized. The results obtained are the basis for the further development of a real prototype of a power plant based on planar SOFC with an integrated diesel fuel processor, opening up the prospects in the area of making low-power electrochemical generators.

The binary systems of deep eutectic solvents (DESs) have been synthesised and investigated: tetraxydroxy alcohol - a salt of a quaternary ammonium base (DES₁), tetrahydroxy alcohol - carbamide (DES₂), a salt of a quaternary ammonium base - carbamide (DES₃), and the ternary system tetrahydroxy alcohol - a salt of a quaternary ammonium base - carbamide (DES₄). Eutectic compositions of binary systems DES₁, DES₂ and DES₃ are characterised by significantly lower pour/melting points than those of the initial components. The lowest pour point among the binary mixtures is that of eutectic composition DES₃. The ternary system is characterised by an even lower melting point (-14 °C), which is associated with the formation of intermolecular donor-acceptor hydrogen bonds within the system. An aqueous solution of DES₄ with the concentration of 26 wt% was prepared, and its pH value was determined depending on temperature during preparation. At room temperature, pH of three-component DES is 6.6-7.1, but after thermostating for 6 h at 150 °C pH increases to 9.2 due to carbamide hydrolysis. It is assumed that further on, using DES₄ as the basis for an alkaline oil-displacing composition directly in the reservoir, under the influence of the temperature of injected heat carrier, CO₂ is formed, along with the ammonia buffer system with the maximal buffer capacity within the pH range 9-10. Resulting carbon dioxide, dissolving predominantly in oil, will cause a decrease in its viscosity, on the one hand, while the formed alkaline medium, being most favourable for surfactant performance due to a decrease in interfacial tension, liquefaction of high-viscosity layers or films at the oil-water-rock boundaries, on the other hand, will ensure efficient use of this system for oil displacement. In addition, the oil-displacing composition based on DES₄ will be low-solidifying, which opens the possibility of its transportation and use in the northern regions and the Arctic zone.

Samples of primary low-sulphide gold-quartz ore and oxidised host rock containing up to 10 wt% sulphides and 5 wt% their oxidation products were investigated to reveal the relationship between the migration of elements during the hypergenic transformation of ores and rocks and their mineral composition. Mineralogical studies employed optical and electron microscopy to identify the shapes and sizes of mineral individuals and aggregates and to determine their chemical composition. It is determined for major element content that the oxidised host rocks contain significantly more iron, sulphur, aluminium, potassium and phosphorus than primary low-sulphide quartz gold ores, while silicon and calcium content is lower. This is due to the removal of sulphur and iron into the near-vein rocks with the formation of primarily pyrite and arsenopyrite, and the presence of aluminosilicates (feldspars and layered silicates) in them. The same applies to arsenic and antimony, as their concentrations are higher in the host rocks than in the ores. The rates of lithophile elements recovery from primary gold-quartz ores are much higher than those from oxidised host rocks. Сhalcophile elements, on the contrary, are more intensively transferred to the solution from host rocks. Thus, the complex of elements extracted from ore suspensions is directly determined by their mineral composition. The main carrier of gold is native gold and its tellurides. Silver is associated with low-grade gold, copper and silver sulphosalts, and also tellurides.

The milestones of the development of X-ray diffraction and crystal chemical studies in the Laboratory of Crystal Chemistry of the Nikolaev Institute of Inorganic Chemistry SB RAS for 1958-2024 are highlighted.

The targeted screening of 11 phenolic toxicants (phenol, chlorophenols, 2,4-dichlorophenoxyacetic acid, octylphenol, nonylphenol, bisphenol A) has been carried out over river water and bottom sediments (BS) in the middle reaches of the Don river within the boundaries of the Voronezh Region. Three sampling points were selected for quantitative chemical analysis: in the zone affected by the discharge of sewage treatment plants of a large city (Voronezh), in the district centre (the city of Liski), and in an area with insignificant anthropogenic influence. The concentrations of phenolic compounds were determined using gas chromatography - mass spectrometry (GC-MS), the analytes were preconcentrated on a magnetic sorbent functionalised with aminated hypercrosslinked polystyrene. Sampling was carried out four times a year, taking into account seasonal climatic fluctuations and precipitation. The maximum concentrations were established in the spring for 2,4-dichlorophenoxyacetic acid (1022 ng/L) and 2,4-dichlorophenol (557 ng/L). In bottom sediments, the highest concentrations are achieved for alkylphenols: 1.99 and 7.84 μg/g for octylphenol and nonylphenol, respectively. Bisphenol A has not been found in detectable amounts in waters, however, a significant concentration of this compound has been found in bottom sediments: 3.18 μg/kg. The bottom sediments were also determined to contain 2,4,5-trichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol. The maximum concentrations of phenolic pollutants in river water are usually observed in spring during high water and after heavy rainfall. Phenol concentrations in bottom sediments are less susceptible to seasonal fluctuations. The hydrophobicity of substances and an increase in their stability against degradation significantly affect their accumulation in BS.

In order to develop a catalytic technology for processing coal mine methane into hydrogen-containing gas, thermodynamic analysis of methane tri-reforming (TRM) was carried out, and the influence of temperature (600-850 °C), contact time (0.04-0.15 s), linear feed rate (80-240 cm/min) and composition (CH₄ / CO₂ / H₂O / O₂ / He = 1: (0.3-0.5) : (0.2-0.5) : (0.1-0.3) : (2.9-3.2)) of the reaction mixture on the conversion of the initial reagents and target products in the TRM process in the presence of a supported Ni catalyst was studied. It has been shown that with an increase in the temperature of the TRM reaction from 600 to 800 °C the process performance improves (methane conversion: 36 → 94 %, carbon dioxide conversion: 57 → 97 %, hydrogen yield: 37→ 91 %, carbon monoxide yield: 44→ 94 %, molar ratio H₂/CO: 1.5 → 1.7), and at a reaction temperature of 850 °C the process indicators are close to equilibrium values. It has been established that varying the O/C value and the composition of oxidants makes it possible to regulate the performance of TRM process. The optimal conditions for the TRM process were identified to achieve maximum efficiency of the catalytic processing of coal mine methane into hydrogen-containing gas: temperature - in the range of 800-850 °C, contact time - 0.15 s, linear feed rate - 160 cm/min and molar ratio of reagents in the initial feed - CH₄ / CO₂ / H₂O / O₂ = 1: 0.5 : 0.2 : 0.25.

A mathematical model of the flow of hydrogen from gas mixtures through the walls of capillary tubes made of metallic nickel has been developed, taking into account the inhomogeneity of the partial pressure of hydrogen along a long tube, as well as temperature nonuniformity in different regions of the tube. Using the model and relying on experimental data, the kinetic parameters of hydrogen transport were calculated within the temperature range of 600-850 ºС and the hydrogen partial pressure range of 0.3-0.8 atm. The model can be used in the design of membrane modules for hydrogen separation from gas mixtures to calculate the length of individual membranes, their number, and the optimal flow rate of the hydrogen-containing gas mixture through the membrane.