Home – Home – Jornals – Russian Geology and Geophysics 2023 number 2

We present data on the geochronology, geochemistry, and Nd isotope composition of granitoids of the Gremyachikha and North Gremyachikha massifs (Kundusyul pluton) located in the Neoproterozoic metamorphosed island arc calc-alkalic volcanic rocks of the Talanovka-Bogorodka block in northern Kuznetsk Alatau (Martaiga uplift). The granitoids formed 890-880 Ma as a result of the accretion and collision of Neoproterozoic oceanic/island arc complexes with an unknown block formed by continent-marginal metasedimentary strata. The predominance of a metasedimentary source formed during the erosion of the early Precambrian and Neoproterozoic complexes is confirmed by the wide range of the ages of xenogenic zircons in the granitoids (2800 to 930 Ma) and by variations in the ε_Nd values (-7.8 to -1.0) and model Nd age of the granites (2.20-1.64 Ga).

We present the U-Pb (secondary-ion mass spectrometry, SHRIMP-RG) zircon ages and geochemical characteristics of granitoids penetrated by two boreholes at a depth of about 4.5 km in the Bolshezemel zone-the northeasternmost block of the Pechora Basin basement. The age of zircon from granites from the 26-East Khar’yaga borehole is 558 ± 6 Ma. These granites are similar in composition and age to syncollisional granites of the Charkayu granite-granodiorite complex of the Pripechora fault (suture) zone (555-544 Ma). Dating of zircon from granodiorite from the 2-Veyak borehole yielded an age of 607 ± 6 Ma. Potassium-rich granodiorites and granosyenites from this borehole have geochemical features of within-plate granites and are correlated with granites (602-595 Ma) of the southeastern part of the Izhma crustal block of the basement, which is supposed to be a submerged part of the northeastern passive margin of the Baltica paleocontinent.

The Mokrundya alluvial gold placer deposit is located in the Verkhoyansk-Kolyma folded region, within the Tuguchak ore-placer cluster. Using ore and scanning electron microscopy and chemical-analysis methods, we have studied the typomorphic, mineralogical, and geochemical features of gold, minerals of the heavy fraction of the placer, and ore mineralization of the dolerite dike complex stripped in the placer bedrock. The stages of development of the ore-forming system in dolerites have been established. The main productive stages with native gold are associated with the postmagmatic stage: (1) early arsenopyrite-polysulfide stage and (2) gold-bismuth-telluride stage. The gold-bismuth-telluride stage includes bismuth tellurides and sulfotellurides, native gold, bismuth, maldonite AuBi₂, and complex intermetallic compounds of Au and Bi. We hypothesize about the sources of placer gold in alluvial deposits, one of which is the ore mineralization of the dolerite dike complex, and the other is associated with the mineralized zones of the Gematitovoe skarn-hydrothermal ore occurrence localized in the upper reaches of the Mokrundya Brook.

The Central Aldan ore district (CAOD) is unique by the abundance of gold deposits associated with Mesozoic alkaline magmatism. Four types of gold deposits are distinguished here: porphyry gold, gold-sulfide, gold-argillizite-K-feldspar-quartz, and gold-uranium. The available geochronological data on the age of igneous rocks and gold mineralization in the CAOD show that the latter formed in the period 151-120 Ma. These data also agree with the results of U-Pb dating of the El’kon gold-uranium ore-magmatic system (143-125 Ma). Analysis of our geochronological data and previously published ones shows that two stages of magmatism evolution in this region. At the early stage (151-130 Ma), most of alkali syenites, monzonites, and their analogues (sills, stocks, ring intrusions, and volcanic sequences) and ores formed. They are widespread in various deposits and massifs. In the Ryabinovyi massif, this stage is marked by the formation of most of alkaline rocks (Aldan Complex) and ores: aegirine syenites, 151.4 ± 1.9 Ma; pyroxene-K-feldspar pegmatites, 144.8 ± 1.5 Ma; and Au-Cu ores, 137.5 ± 1.7-131.1 ± 16 Ma. The crystallization of amphibole from syenite of the Lunnoe deposit (143.1 ± 2.0 Ma) and clinopyroxenite of the Inagli massif (142.4 ± 2.0 Ma) and the formation of most of the alkaline rocks of its ring framing also took place at this stage. At the Samolazovskoe deposit, this stage is marked by the formation of zircon in pseudoleucite syenite, 135.9 ± 1.9 Ma, and in different syenite porphyry phases, 141.39 ± 0.90-142.4 ± 5.0 and 134.25 ± 0.70-129.9 ± 2.6 Ma, as well as gold-skarn mineralization, 129.9 ± 2.6-134.9 ± 2.8 Ma. The same period included the formation of primary ores at the Kuranakh deposit, 136.2 ± 1.7 Ma, and the deposition of breunnerite mineralization at the Lunnoe deposit, 132.4 ± 1.6 Ma. Early intrusive phases, such as potassic picrites, shonkinites, and lamprophyres, are scarce among the products of this stage of magmatism, which is possibly due to their burial beneath large volumes of later formed alkali syenites and monzanite-syenites. The second stage (128-120 Ma) was distinguished within the Ryabinovyi massif as small intrusions and dikes of olivine lamproites, shonkinite porphyry, minettes, and syenite porphyry. We revealed explosive breccias with an age of 127 Ma at the Samolazovskoe field. Magmatism of this stage was of limited occurrence in the CAOD and did not produce alkali syenites, monzonite-syenites, and ores. At the same time, rocks with an age of 121.1 ± 1.3-115.5 ± 1.6 Ma are widespread in the large (120 km2) Dzheltula ring massif of the Tyrkanda ore district, located east of the Central Aldan region.

The Chudnoe gold-palladium deposit, located within the Central Ural uplift, is confined to the axial zone of an anticlinal structure complicated by faults. Veinlet mineralization is localized in fractured and brecciated Late Riphean-Vendian rhyolites. Native gold and palladium minerals are concentrated mainly in veinlets of Cr-containing muscovite (fuchsite) and, more seldom, at local sites of rhyolite metasomatism, almost free of sulfides. Using a representative material, we studied the composition and structure of native gold and the regularities of their spatial variations. Native gold has composition Au-Ag-Cu and contains Pd and Hg impurities. The element proportion varies significantly: The content of Au ranges from 65.8 to 92.7 wt.%, the content of Ag varies from 0.4 to 33.8 wt.%, the content of Cu reaches 12.7 wt.%, and the content of Pd is up to 2.9 wt.%. Gold formed as a homogeneous Au-Ag-Cu solid solution at temperatures above 220 °C. The presence of copper in native gold is probably due to the absence of sulfide ion from the ore-forming hydrothermal solution. With decreasing temperature, Au-Ag-Cu solid solution containing more than 1.1-2.5 wt.% Cu disintegrates into two or three phases, forming characteristic plate-lattice and tabular exsolution structures. In the case of two-phase exsolution, the final phases are Au3Cu and Au-Ag solid solution or AuCu and Au-Ag solid solution; and in the case of three-phase exsolution, these are Au3Cu, AuCu, and Au-Ag solid solution. In some cases, the exsolution was accompanied by the recrystallization of gold with the formation of grain intergrowths. The composition of native gold in the deposit varies significantly, showing a discrete character at different sites of the ore zones, which is consistent with the veinlet ore mineralization. At the final stages of mineral formation, native gold was partly replaced by secondary high-fineness gold.

A sequence of argillized rocks and hydrothermal clays of the East Pauzhetka thermal field was studied in detail by means of drilling and trenching. We have identified zones composed of unusual mineral associations; their formation conditions are considered. The structure of the base of the hydrothermal-clay mass is shown. The source rocks (brecciated andesites) of the base are altered by hydrothermal-metasomatic processes and are represented by smectite-chlorite-K-feldspar-zeolite-carbonate-siliceous aggregate with sulfides, phosphates, titanium silicates and zircon silicates, and other mineral phases, including rare metals. A conceptual geological and geochemical model for the formation of argillisites and zones with mineral associations has been plotted. It is assumed that modern mineral formation in the East Pauzhetka thermal field inherits an epithermal ore-forming system located in the influence zone of a deep-seated fluid, the derivates of which are outflowing near the surface as alkaline metal-bearing solutions of the Pauzhetka hydrothermal system.

It is shown that the “new methodologies” of processing and using results calculated for rotating detonation engines, as well as those of recent measurement of forces acting on the models of ramjet (rotorless) models in “hot” and “cold” runs in supersonic test benches, which are developed and promoted by S.M. Frolov and V.I Zvegintsev with their colleagues, are incorrect.

The traditional approach to measuring the thrust of air-breathing jet engines (ABJEs) was proposed by B.S. Stechkin in 1929. In this approach, the thrust is determined as the difference between the momenta of the gas flows at the engine inlet and outlet. The approach involves some methodological and terminological problems. Based on a critical analysis of available concepts, the present article proposes a new approach to determining the ABJE thrust in the form of the decrease of the initial drag of the aircraft + ABJE system when the power plant operates with fuel supply and energy release. For the thrust thus obtained, we propose using the term “real thrust”. It is shown that the proposed approach eliminates terminological problems and simplifies the technique for measuring the thrust characteristics of the ABJE. The paper considers various options for applying the proposed approach to the determination of the “real thrust” for different cases of using and modeling ABJEs, including the calculation of flight trajectories of the aircraft with ABJE.

We present the experimental results on the thermal efficiency in a wall gas screen injected through inclined cylindrical holes along a smooth surface, and when a secondary flow is blown through cylindrical holes into a transverse trench. The thermal efficiency fields of the wall screen were measured using an infrared camera. In the case of blowing into a trench, the experimental data are characterized by an insignificant influence of the injection parameter on the thermal efficiency of the wall screen for all the trenches under study. It has been established that an increase in the trench depth leads to an increase in the thermal efficiency of the wall gas screen. The maximum increase in thermal efficiency is achieved for a trench with relative depth h/d = 0.94 . The data of the measurements presented are compared with the experimental and numerical results of other authors for the cases of injecting through the holes into a transverse trench.

Results of experimental and numerical studies of the properties of a turbulent boundary layer modified with a control action in the form of distributed air blowing through a high-technology perforated wall are presented. The wall is part of the surface of an elongated axisymmetric body in a low-velocity gas flow. The Reynolds number Re^** based on the momentum thickness δ^** ahead of the perforated region formed by holes 0.14 mm in diameter with microchannels with a small aspect ratio is 2660. The area-averaged blowing coefficient C_b varies in the interval 0 - 0.00885. As the streamwise coordinate increases up to the distance 550δ^** from the blowing region, the local friction is seen to decrease consistently; the greatest value of the local friction is 64% directly in the blowing region in the case of the maximum blowing intensity.

The thermal conductivity of the R-32/R-125 (15/85) mixture was investigated in the temperature range of 305 - 411 K and pressures of 0.1 - 1.8 MPa. Measurements were carried out by the stationary method of coaxial cylinders. The error of the experimental data on thermal conductivity was 1.5 - 2.5%, and the measurement errors of temperature and pressure did not exceed 0.05 K and 4 kPa, respectively. A generalizing equation for calculating the thermal conductivity as a function of pressure and temperature was obtained. The thermal conductivity on the condensation line and in the ideal gas state was determined.

Using the previously established dependence of the excess viscosity on the internal energy density, a simple low-parameter equation was obtained to describe the krypton viscosity coefficient in a wide range of state parameters. It was shown that the proposed low-parameter equation for calculating the viscosity coefficient of liquid and gas allows for reliable extrapolation beyond the limits of the studied area.

The paper presents results of numerical simulation for development of localized disturbances emerging from a single source or double synchronous sources in a laminar boundary disturbances at the plate with the flow with the Mach number М = 2 (variants for different distances between sources). Simulation was performed using the FlowVision software complex at the parameters typical for T-324 wind tunnel (developed by ITAM SB RAS). The problem was studied in the range of linear development of disturbance. The study demonstrates that, depending on the distance between the sources, the generated disturbances might either enhance or decay in the downstream flow. The frequency-wavelet analysis of disturbance structure was performed. Two distanced local synchronous sources generate the disturbances with wavelet spectra: these spectra exhibits nodes and crests; their positions depend on the distances between two sources.

A technique is described and the results of an experimental study of the aerodynamic structure of a turbulent streamlining, velocity fluctuations and pressure fields on the surface of a single trench hole located on the wall of a flat rectangular channel are presented. The trench hole cross-section is a cylindrical segment with hemispheres at its edges. The measurements were carried out with a two-component laser-Doppler velocity meter at two angles of hole inclination relative to the flow direction φ=0 и 45°. The development of the flow in the direction transverse to the trench, as well as along its span, was studied. The fundamental difference between the velocity fields and their fluctuations in a trench located normally and at an angle to the flow is shown.

The paper is the study of electric resistance of a graphene layer washed by a liquid with different flow rate parameters. Experiments demonstrate that if the fabricated composite (graphene upon a PET/EVA polymeric substrate) is submerged into distilled water, the sample resistance increases by 120 %. Meanwhile, the flow of liquid near the graphene layer decreases this gain in the electric conductivity. The effect offers a general design of a flow rate sensor based on the graphene layer, taken as a sensitive matrix. The study demonstrates that this design of graphene flow sensor (taken for distilled water) exhibits a linear dependency of the sensor resistance on flow rate.

Results of an experimental study and direct numerical modeling of the steady flow in a channel branching region simulating the proximal anastomosis of the femoral artery, are reported. The Reynolds number was Re = 1500, which value corresponds to the maximum blood flow during the period of heart contractions. The ratio of the rates of the liquid flows through the branch and the main channel was a varied parameter. Regularities in the development of the flow structure in the primary channel and in the branch region are revealed, with much attention having been paid to flow separation regions. The occurrence of secondary flows localized within the separation regions has been established. The ranges of the ratio of the flow rates at which flow turbulence signs appear in the mixing layer at the interface between these regions are determined.

The paper studies the segmented flow modes of immiscible liquids in microchannels with T- and X-shaped inputs for 3D printing technologies. On the basis of the flow visualization results, mode maps with a distinguished area of stable plug flow are constructed. A fair coincidence of the maps built on the basis on the superficial flow velocities is revealed, and the influence of the channel input on the boundaries of flow modes is shown to be insignificant. When using a less viscous carrier phase, the region of a stable plug mode is demonstrated to expand towards higher superficial flow velocities. The separation of microdrops from the trailing edges of plugs is investigated. It has been found that the transition to the separation of microdrops is described in terms of the capillarity number, constructed from the bulk velocity of the phases, and the ratio of phase flow rates. Thus, a range of dimensionless parameters of microchannel devices, suitable for 3D printing of composite materials with specified properties has been determined.

The paper deals with simulation study of aerodynamics and heat transfer for a case of a four-vortex furnace chamber designed for jet fire of brown coal from Eastern coal deposits. The combustion modeling is achieved by a set of linked submodels: they describe turbulent gas flow? Thermal and radiative heat transfer, the processes of degradation and burning of coal particles, NO_x generation. Simulation demonstrated that using of these types of brown coal in a specific-design furnace chamber creates a steady four-vortex flow structure that provides a uniform temperature field in the volume and admissible generation of NO_x .

Laser water jet processing is a new hybrid method developed on the basis of traditional laser processing technology. It combines high laser processing efficiency with the impact and cooling effects of water jets. Laser water jet processing can effectively process hard and brittle materials such as silicon. In-depth study of the processing technology has important practical significance. For this reason, the controlled variable method is used to study the influence of different processing parameters on groove depth. The research results show that with the increase of current and laser pulse width , the groove depth gradually increases; with the increase of laser repetition frequency and water jet velocity, the groove depth increases first and then decreases. The experiment of laser water jet processing silicon can provide guidance for processing other difficult-to-process materials in the future.

Laser radiation is a leading tool in the field of materials processing and design. Recently, the prob-lem of controlled changes in the wetting properties of metals realized by the micro- and nanostructuring of surfaces has been actively investigated. In the pre-sent paper, the influence of the conditions of nano-second laser treatment on the wetting properties of a copper surface in the mode of formation of a ran-domly distributed hierarchical structure is investigat-ed. Special attention is paid to the evolution of the contact angle of wetting over time. The mechanisms of changing the wetting properties over time are con-sidered. It is shown that the overlap of laser spots is more important than the fluence in the beam from the point of view of hydrophobization of the copper surface.

The flow-type microreactors, being designed for small-scale production of pharmaceutical substances, have a moderate volume and ensure steady synthesis for pharmaceutical production while using noninva-sive methods for mixing of ingredients. The paper describes experimental and simulation study of the efficiency for natural convection mechanisms for so-lutions mixing in a Y-type symmetric microreactor. The mixing zone is arranged for discovery of con-vection potential. We consider both variants of chemically inert and chemically active systems. A model reaction is represented by a rapid acid-base neutralization reaction. The theoretical model com-prises the 3D Navier-Stokes equation and the reac-tants transfer equation (written with account for non-linear diffusion). Experimental and numerical results have been compared. The dependency for the effec-tive mixing length on the instability type and sol-vents flow rates was found.

The article presents the results of an experimental study of the cavitation flow around the NACA 0012 series foil in a narrow slit channel with a width of 1.2 mm. The aspect ratio of the streamlined body was 0.02. To identify the main features of the two-phase flow, high-speed visualization was performed using the Photron FASTCAM NOVA S12 camera with a sampling frequency of 20 kHz. The internal structure of cavities was detected. The main frequencies of cavities formation in the flow were determined using digital processing of visualization data. The close location of the channel walls was shown to significantly affect the return flow propagation under the cavity and its separation.

The study is focused on the process of bubble growth inside a intensively evaporating liquid droplet placed on a hot structured surface made of black silicon. Experiments are carried out with volatile fluids FС-72, HFE 7100, ethanol and water. The method using the Schliren-system was developed for study of bubble growth inside a droplet. The contact line speed was measured during microdroplet evaporation, including the case of a growing bubble inside the droplet. The speeds of the contact for droplet evaporation with/without bubble were compared. The contact line instability was found, emerging due to a developed structure of substrate; it facilitates the enlargement of local flows in microregions. This facilitates the heat transfer enhancement.

Microchannel cooling systems are widespread due to their efficiency. In this work boiling of dielectric liquid FC-72 in a flat microchannel with a height of 66 μm and a width of 10 mm was studied. Heating was carried out by a thin-film ITO heater in direct contact with the working liquid. The flow regimes at boiling in a wide range of liquid flow rates were investigated. It is shown that boiling regimes in a flat microchannel differ significantly from the flow regimes in circular and rectangular mini- and microchannels. The dependences of heat flux on the temperature head have been plotted. The dependence of the heat transfer coefficient on the heat flux was investigated for different regimes of the two-phase flow.

This paper presents calculation results on plasma ignition and combustion of coal in the furnace of the PK-39-II boiler at Reftinskaya SDPP. For mathematical modeling of coal combustion in the boiler furnace, a three-dimensional mathematical model Cinar ICE and a software package for physical modeling and calculation of hydro-dynamics, heat and mass transfer and combustion of fuels in the volume of furnace devices were applied used. Cal-culations were performed for two regimes of pulverized coal combustion: the traditional one and using plasma activa-tion of coal combustion. It is shown that the use of plasma-fuel systems (PFS) allows optimization of the coal com-bustion process in the combustion chamber. Three-dimensional modeling of a pulverized coal furnace equipped with a PFS allows one to determine the optimal PFS layout on boilers of thermal power plants.

An experimental study of the specific heat capacity of gadolinium-scandium-gallium and calcium-niobium-gallium garnets widely used in laser technology and microelectronics was carried out by the method of differential scanning calorimetry. New experimental results on the specific isobaric heat capacity in the temperature range of 300 -1270 K were obtained; approximation equations and a table of recommended values for scientific and practical use were developed on their basis. The comparison with the known literature data was carried out. The estimated error of the data obtained was 2-4%.

Combustion of liquid hydrocarbons sprayed with a jet of superheated steam is experimentally studied using n-heptane as an example as a promising method for efficient and environmentally safe combustion. with forced air supply to the gas generation chamber. It is a modernized design of an atmospheric burner with a natural air inflow, studied by the authors earlier, and it allows obtaining additional information about the effect of changing the excess air ratio inside the device on the process of burning liquid fuel in the presence of superheated steam. New data on the environmental and energy characteristics of the burner under study were obtained based on thermocouple measurements, gas analysis of intermediate flame components, measurements of combustion efficiency and harmful emissions in the final combustion products. They were compared with characteristics of the burner with natural air inflow. It was found that formation of carbon monoxide during the combustion of heptane is reduced by 25%, and formation of nitrogen is reduced oxides by 15% with a decrease in the excess air ratio in the combustion chamber from 0.7 to 0.16. At the same time, a burner with a natural air inflow is characterized by a higher flame temperature and a shorter flame length. At that, the level of CO and NO_x emissions in all regimes corresponds to the European standard EN 267. It was determined that the forced air flow does not have a noticeable effect on the heat generated for the studied regimes, and the calorific value of fuel combustion in all cases is close to the higher calorific value of heptane, which indicates the high efficiency of the combustion method under study.

The experimental results on the turbulent flow structure in a lattice matrix cell, which is a region between intersecting ribs on the opposite walls of a flat channel, are presented. The angle between the ribs was 2β = 60º, 90º and 120º; the Reynolds number calculated from the average velocity and hydraulic diameter of the channel was varied in the range Re = (1 - 7)×10⁴. The aerodynamic characteristics of the flow inside a lattice matrix cell placed in a rectangular channel with a cross-section of 20 × 150 mm and a length of 400 mm were measured using a two-component laser Doppler anemometer (LDA). The flow structure was studied in individual cells of 15 × 15 mm, formed by crossing ribs on the opposite channel walls. The complex three-dimensional structure of the flow in the matrix cells and strong turbulence of the flow in the near-wall regions are shown. The installation of ribs leads to a significant increase in hydraulic losses, especially at large crossing angles.

This paper presents a mathematical model of combustion of a coal dust particle-gas suspension in a methane-air mixture, which takes into account the inhomogeneity of temperature distribution in the particles. The particle-gas suspension state parameters are determined by the model of the dynamics of a two-phase two-velocity reacting gas-dispersed medium. The combustion of coal dust particles is simulated using a local mathematical model of a heterogeneous reaction on the particle surface and particle heating. A solution to local problems of coal dust particle combustion is used determine the heat release rate of the entire set of particles in the heterogeneous reaction of coal dust with oxygen and the heat exchange with gas. Dependences between the combustion front propagation velocity and the mass concentration of coal dust and the volumetric concentration of methane are determined. The estimated combustion front velocity in a methane-air mixture with no coal dust is in good agreement with experimental data. The comparison of calculating the flame velocity in a coal-methane-air mixture using two models (with and with no account for the inhomogeneity of the temperature distribution in the particles) is given. This comparison shows a significant difference in the values of the estimated combustion front velocity of rapidly burning gas-particle suspensions. For slowly burning particle-gas suspensions, this difference decreases. The developed model explains the shift of the maximum flame propagation velocity in the coal-methane-air mixture toward the excess of fuel in air.

Flame propagation over a thin film of various liquid fuels with an ignition point below the ambient temperature was experimentally studyied. The study was carried out on thin copper and thick glass substrates in media with different oxygen concentrations. It is shown that with an increase in the oxygen concentration, the flame speed increases faster than the normal speed of the corresponding homogeneous stoichiometric mixture. When the proportion of oxygen in the mixture with nitrogen changes from 0.21 (air) to 1, the flame speed range is 0.02 ÷ 2.4 m/s. At flame propagation speeds above 0.3 m/s, the condition of thermal thinness is not satisfied even for thin copper substrates. The flame speed ceases to depend on the properties of the substrate and the fuel layer thickness and becomes dependent only on the properties of the fuel. In this speed range, the flame propagation speed increases linearly with an increase in the thermal effect of a unit volume of a stoichiometric mixture of fuel vapor with oxidizer and decreases with an increase in the difference between the temperature T_st at which the stoichiometric composition is formed under equilibrium conditions and the ambient temperature T₀.

Spray ignition is widely encountered in energy and power engineering and is an important characteristic in combustor operation and design. Droplet ignition is an important part of spray ignition. Most present studies of droplet and spray ignition use numerical simulation, which sometimes cannot explicitly indicate the mechanism of ignition and is inconvenient for engineering applications. This paper reports experimental and analytical studies on ignition of a single droplet and spray under different flow conditions. Analytical results based on a one-dimensional model are compared with experimental results. The results reveal that the droplet ignition temperature decreases with an increase in the droplet size and increases with an increase in the relative gas velocity. The temperature of kerosene spray ignition by propane combustion products increases with an increase in the excess air and decreases with an increase in the droplet size. The obtained research results are useful for liquid-fueled combustor design and operation.

The thermal decomposition of bis-R-substituted gem-dinitroethyl-N-nitramines in diphenyl ether solution was studied by a manometric method in combination with mass spectrometry and photoelectric colorimetry. The reaction proceeds according to the first order equation and is not complicated by chain and heterogeneous processes. The rate-determining step of the process is the homolysis of the C-NO₂ bond in the gem-dinitro group. The kinetic parameters of the rate-determining step were determined. The influence of the structure on the reactivity of the investigated compounds was analyzed. Linear relationships were found between the rate constant, the activation energy of thermal decomposition, and the steric constants of the α-substituent of the reaction center.

Phase composition of thermal explosion products in compacts made of Ti-C-Al powder mixtures with an equiatomic ratio of titanium and carbon (soot) and with an aluminum content of 10 ÷ 40 % (wt.) is studied. The compacts are heated at a rate of 40 ± 5 °C /min in an argon atmosphere. Self-ignition temperature of all compositions was close to the melting point of aluminum (660 °C). Peak temperatures and the maximum rate at which temperature elevation becomes higher as the aluminum powder content in the mixtures increases. Synthesis products contain titanium carbide and Al₃Ti titanium trialuminide, whose ratio depends on the aluminum content in the mixture. Pretreatment of reaction mixtures in a planetary mill flattens aluminum particles, thereby preventing the formation of a melt. The spreading of a melt over the titanium surface with subsequent reaction diffusion and the formation of Al₃Ti increases the temperature in compacts made of nonactivated mixtures.

This paper describes experimental studies and a mathematical model of mechanical activation and high-temperature synthesis during the Nb-2Si combustion. The model is constructed in the macroscopic approximation. Synthesis regimes are determined depending on the duration of joint mechanical activation of the reagents. The kinetic parameters of pulverization of the initial powder mixture and the mechanochemical synthesis of the reaction product are obtained on the basis of experimental data by the inverse problem method.

Alloys based on the Ti-Al-Mn ternary system are among the most important in the development of doped titanium alloys for various purposes. In this work, an alloy made of 42.9 % of Ti, 24.3 % of Al, and 32.8 % of Mn (by wt.) is obtained via self-propagating high-temperature synthesis (SHS) during a thermal explosion. X-ray diffraction analysis shows that the final synthesis product containsa cubic TiMn_0.32Al_2.68 phase, a hexagonal TiMn_0.755Al_1.246 phase, and a binary Mn₃Al₂ phase. The porosity of synthesized samples is rather high ≈41 %), and they contain many pores (up to 300 ÷ 400 μm). Phase formation may be due to the fact that the maximum temperature reached during the combustion of this system in the SHS process is insufficient for complete interaction with the formation of a Mn₂Ti intermetallic phase and the dissolution of aluminum Al in it with the formation of a solid solution (Mn, Al)₂Ti. This promotes the formation of intermediate intermetallic phases, which can be in equilibrium with the liquid phase up to a melting point of titanium.

This paper presents an analysis of approaches to ensuring the performance of a ramjet combustor using an unconventional method of measuring the axial force in testing a liquid-fuel combustor model under flight conditions simulated by a fired heater. The thrust and drag of the combustor model were measured in fire tests on an attached air duct using an axial force meter. Thrust is a parameter that characterizes the energy potential of any engine. In the conventional method, lengthy multi-parameter studies and calculations of performance are required to get an idea of the thrust and economic characteristics of a heat engine. The new method allows one to determine the effect of any parameter or structural element on the physical process in a combustor in units of the thrust force and evaluate the change in any parameter by the thrust level directly in fire tests. Using the proposed thrust measurement system at an initial stage of testing, one can clarify the direction of the search for the organization of the workflow and reduce the amount of intermediate calculations, saving a huge amount of time and money. This, combined with measurements of static pressure along the length of the combustor, allows a guaranteed prediction of the direction of search for improving the workflow efficiency. The ways to improve the workflow efficiency in a ramjet combustor using a thrust meter to evaluate the overall engine performance under conditions of limited technical and methodical possibilities in fire tests of the combustor are discussed.

Three-dimensional numerical simulation of a detonation wave propagating in a circular tube filled with a gas suspension of aluminum particles in oxygen is performed with the use of the HyCFS-R code developed by the authors for modeling on hybrid computational systems. The regime of propagation with a single-head spin is reproduced. It is shown that combustion occurs in a certain localized front zone rotating during front propagation, which is typical for spin detonation in both purely gaseous mixtures and heterogeneous media. Data on the basic parameters of detonation wave propagation in a gas suspension of aluminum particles in the spin detonation mode are obtained. Comparisons with theoretical predictions and with numerical and experimental results of other researchers are performed.

Industrial micron-size hexahydro-1,3,5-trinitro-1,3,5-triazine (m-RDX) has been widely used in RDX-based polymer-bonded explosives (PBX). However, m-RDX results in poor mechanical properties and adhesive properties of RDX-based PBX m-RDX-PBX). Nano-RDX (n-RDX) has a small particle size and a large specific surface area, which provides a larger contact area with the polymer system. Thus, the porosity and compressive properties of PBX are improved if n-RDX is used in RDX-based PBX (RDX-PBX). In this study, m-RDX and n-RDX are used in RDX-PBX. The microstructure, component content, compressive properties, sensitivity properties, and detonation properties of RDX-PBX are investigated. The results show that n-RDX can make RDX-PBX more compact than m-RDX. The strain of n-RDX-based PBX (n-RDX-PBX) is increased by 39.7 % as compared to that of m-RDX-PBX. Meanwhile, the content of each component in n-RDX-PBX is consistent with that of the formula. The sensitivity of n-RDX-PBX is lower as compared to that of m-RDX-PBX, whereas the detonation velocity, detonation pressure, and detonation heat of n-RDX-PBX are equivalent to those of m-RDX-PBX.

Explosives are often exposed to war environments at different temperatures. The shock initiation characteristics of explosives are related to their properties and the ambient temperature in which they are located. In the present work, the parameters of the Ignition and Growth model of the LX-04 explosive at different temperatures are determined, based on the shock initiation experiments at different temperatures. Furthermore, the impact sensitivity simulation of LX-04 at initial temperatures of 25, 60, 100, 150, and 170 °C is carried out, and the critical impact velocity at these initial temperatures is found to be 325, 280, 233, 201, and 194 m/s, respectively. Based on the present simulation data, a new model for the relationship between the critical impact velocity and initial temperature is proposed. In addition, the initial temperature of the explosive has an important effect on the detonation performance: the higher the initial temperature, the higher the impact sensitivity of LX-04, and the higher the peak temperature of detonation.

Experimental data on the electrical resistance of aluminum under shock compression are analyzed. The electrical resistance of two types of aluminum foil located in dielectrics with different shock impedances is measured by the electrical contact method. The resultant dependences of the electrical resistance of aluminum on the shock wave pressure are monotonically increasing functions of pressure. However, the dependence of the specific electrical resistance of aluminum on the shock wave pressure can be monotonic (foil in Plexiglas) or nonmonotonic (foil in fluoroplastic). In the latter cased, the specific electrical resistance first slightly decreases with an increase in pressure and then increases. This behavior can be explained by the competing effects of compression and temperature heating on the specific electrical resistance. Due to shock compression of metal foil in the dielectric with a smaller shock impedance (Plexiglas), the measured electrical resistance is greater than that in the dielectric with a greater shock impedance (fluoroplastic). This result is caused by the greater temperature heating of metal foil in Plexiglas. The reasons for the qualitative difference in the behavior of the specific electrical resistance of metal under static and dynamic compression are discussed.