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The macrokinetic laws of combustion and the kinetics of thermal decomposition of energetic condensed compositions containing high-enthalpy polynitrogen compounds based on the system of furazan, furoxan, and azepine rings and poly-2-methyl-5-vinyltetrazole as an active binder. The linear rates of high-temperature transformations (combustion) of compositions with different ratios of components were determined in the nitrogen pressure range 1 ÷ 6 MPa. It was found that the burning rate of compositions of polycyclic compounds and poly-2-methyl-5-vinyltetrazole exceeds the burning rate of individual components, with the synergistic effect increasing with decreasing nitrogen pressure in the system. Kinetic studies of heat release during thermal decomposition of energetic compositions in the temperature range 50 ÷ 350 °С under isothermal and nonisothermal conditions have shown that in pressed compositions, reactants interact, leading to a significant increase in the rate thermal decomposition of the mixture relative to the rate of decomposition of individual components. The data obtained indicate that one of the reasons for an increase in the burning rate upon mixing of components may be a change in the leading combustion reactions as a result of the chemical interaction of components of the binary composition.

Combustion of high-energy condensed systems may include the formation of an intermediate structure (skeleton layer, which significantly affects the combustion process. The influence of binder solidification on the formation of such a structure is studied experimentally. It is demonstrated that the laws of the skeleton layer formation during binder solidification depend to a large extent on the polymer structure. A specific role of the substance acting as a binder is determined. The basic features of modeling phenomena in the surface layer with and without the skeleton layer are presented. The possibility of predicting a number of characteristics of the combustion process is demonstrated.

Distribution of plutonium and americium compounds in the combustion products of radioactive graphite in water vapor or air is analyzed. The study is carried out via thermodynamic analysis using the TERRA software package in a temperature range of 400÷3200 K. It is revealed that all carbon in water vapor passes into gas at temperatures above 900 K, and its transition temperature in air is 1000 K. Condensed plutonium compounds transform into vapor compounds in water vapor at temperatures above 1800 K and in air at 1700 K. Condensed americium compounds begin transforming into a vapor state at temperatures above 2000 K, and their transition temperature in air is 2200 K.

Powders of various metals and boron are widely used in mixed fuel compositions to increase the combustion temperature and specific impulse of rocket engines. The article presents the results of an experimental study of the oxidation and ignition in air of ultrafine aluminum powders Alex, amorphous boron and microsized aluminum powders μAl, aluminum borides AlB₂ and AlB₁₂. Metal and boron powders were heated and ignited by a cw CO₂ laser in the heat flux density range 65 ÷ 190 W/cm². Based on thermal analysis data, it was found that the powder reactivity parameters are arranged in the following sequence (in descending order of activity): Alex ® B ® AlB₁₂ ® AlB₂ ® μAl. During the oxidation of amorphous boron and aluminum dodecaboride AlB₁₂, the total specific heat release and the rate of mass change have maximum values. Alex, boron and AlB₁₂ powders ignite more easily in air under the action of an external radiant source. Power exponent n as a function of the ignition delay time t_ign on the heat flux density t_ign ( q ) = Aq ^{- n} for μAl powders, AlB₂ and AlB₁₂ are approximately the same and equal to »2.0, for ultrafine Alex and boron powders it is lower and amounts to n = 1.5 and 1.0, respectively.

Effect of furan (C₄H₄O) and tetrahydrofuran (C₄H₈O) additives in a mixture of ethylene (C₂H₄) with argon on soot formation during pyrolysis behind reflected shock waves in a pressure range p ₅ = 2.1 ÷ 4.4 atm and a temperature range T ₅ = 1 600 ÷ 2 580 K is studied. Temperature dependences for the volume fraction of the condensed phase and the sizes of forming carbon nanoparticles in the studied mixtures are obtained by laser extinction and laser-induced incandescence. It is revealed that adding these furans increases the volume fraction of soot and expands the temperature range of its formation. The effect of furan turns out to be more pronounced than that of tetrahydrofuran. It is shown by the kinetic modeling of ethylene pyrolysis processes with the selected additives that alternative pathways for the production of C₃H₃ propargyl are formed in the presence of C₄H₄O and C₄H₈O, which is the reason why soot formation improves.

The fraction of methane in gas hydrates is approximately 12 wt. %. Theoretically, the temperature of combustion of such a composition is rather low. Nevertheless, the measurements show that an appropriate organization of the process may ensure a much higher flame temperature. For this purpose, it is necessary to separate the regions of dissociation and combustion (i.e., eliminate water heating). On the other hand, for combustion to be stable, some part of the combustion heat should be returned to the hydrate region to maintain the dissociation rate at a needed level. Stability of methane hydrate combustion is naturally determined by the ratio of heat release and heat transfer. The present paper described experiments on methane combustion above a layer of a dissociating gas hydrate, and a simple mathematical model is proposed for estimating diffusion combustion stability. A comparison of the modeling results with experimental data allows one to determine the water vapor concentration and to find the thermal balance of hydrate combustion.

Combustion of ethylene and kerosene in flows with Mach numbers M ≤ 2 is numerically studied. Flow throttling with the use of a side jet of compressed air is provided for igniting the fuel injected through an axial injector and for supporting its combustion. The Reynolds-averaged Navier - Stokes equations closed with the k-ε turbulence model are solved. Fuel combustion is modeled by one reaction. The possibility of formation of a transonic flow is considered. The gas-dynamic structure of the flow in the channel in the case of kerosene combustion is investigated for the Mach number M = 1.7 and stagnation temperatures of 1 400 and 1 500 K. The computations are performed for various values of the limiter of turbulent kinetic energy generation.

We give the substantiation of the choice of methods and devices for physical laboratory modeling of the process of freezing and heaving of soils in order to study their heaving properties, as well as the parameters of the freezing process to verify the developed mathematical methods of the process modeling. The methods under consideration make it possible in freezing soils to set and control in automated mode the dynamics of the temperature state, the heat and water flows, the sheaving and shrinkage deformations, the moisture and density, the pore hydraulic pressure and the segregation ice release through the use of time-lapse video recording, the simulation of external mechanical and hydraulic loads.

Aufeis fields (or icings) are widespread in the North-East of Russia, and have a substantial impact on many components of landscapes. The public availability of Landsat and Sentinel-2 satellite data has opened up new opportunities for aufeis mapping. Based on satellite images, we have compiled an up-to-date GIS dataset of aufeis fields in the North-East of Russia, and also have analyzed the long-term and seasonal variability of the largest aufeis. Based on the synthesis of historical (obtained in the middle of the 20th century using aerial photography) and satellite data on aufeis, we have prepared a new cartographic product - the Atlas of giant aufeis-taryn of the North-East of Russia. The Atlas had been published in 2021. In this paper, we have considered the approaches to aufeis mapping used in creating the Atlas, and have presented the main characteristics of the aufeis fields based on historical and satellite data. In total, according to Landsat images obtained in 2013-2020, we have found and delineated 9306 aufeis with a total area of 4854.5 km². According to satellite images, 1146 are giant aufeis, i.e. they cover an area of over 1 km². For these giant aufeis, we have analyzed long-term and seasonal dynamics of their area based on satellite images obtained for the period from the 1970s to the present. On this basis, a series of image-based maps have been created, which are also included in the content of the Atlas. We have not found a substantial reduction in their area between 1970s and the present for most of the giant aufeis. We also have found that the largest aufeis in the north-east of Russia is located in the basin of the Syuryuktyah river. Its area immediately after snowmelt period is on average 14.4 km² larger than the area of the Bolshaya Momskaya aufeis, which had been previously considered as the largest aufeis in Russia.

This paper presents the developed analytical model of the functioning of the system of temperature stabilization of soils of the "HET" type, based on the integral method. The paper presents the solutions of numerical and analytical models for temperature stabilization systems of soils of the "HET" type with different lengths of the evaporating part, as well as for the Arctic cities with different climates - Salekhard, Varandey, Igarka. By comparing the results obtained within the framework of numerical and analytical solutions, it has been concluded that the developed analytical model can be used for an express assessment of the functioning of the system of temperature stabilization of soils of the "HET" type for various design solutions and climatic characteristics.