Vol 16, No 3 (2023)

For the first time, detailed kinetic modeling of the behavior of undiluted mixtures of methane with oxygen with СО₂  and Н₂О additives was carried out taking into account the formation of microheterogeneous soot particles in the temperature range 1500–1800 K at a pressure of $P_{50}=1$ bar. The appearance of soot particles was observed for rich mixtures, starting with the equivalence ratio $\varphi =\mathrm{3,33}$. At the lower limit of the studied temperature range $T_{50}=1500$ K, a small amount of soot particles (less than 1 %(mass) of C atoms) is formed, and they do not have a significant effect on the other parameters of the reacting system. A noticeable effect of soot particles at $T_{50}=1500$ K is observed for $\varphi =8.0$. This is most clearly manifested in the fact that the temperature profile of the process changes markedly. When water is added, two maxima are observed on it at times of the order of 0.01 and 0.1 s. In the case of CO₂  additives, the second maximum is almost not pronounced. A complex temperature profile leads to the appearance of a second maximum concentration of hydroxyl OH radicals at $~\mathrm{0,1}$ s.

When designing a new type of power plants operating on pulsed detonations of gaseous or liquid fuels, the concept of fast deflagration-to-detonation transition (FDDT) is used. According to the concept, the flame arising from a weak ignition source must accelerate so fast as to form an intense shock wave at a minimum distance from the ignition source so that the intensity of the shock wave is sufficient for fast shock-to-detonation transition due to some additional arrangements. Hence, the FDDT concept implies the use of special means for flame acceleration and shock wave amplification. In the present work, FDDT has been studied using a standard pulsed detonation tube (SDT) comprising a Shchelkin spiral and a helical tube section with ten coils as the means for flame acceleration and shock amplification (focusing) devices, respectively. To attain the FDDT at the shortest distances for fuels of essentially different detonability, the diameter of the SDT is taken close to the limiting diameter of detonation propagation for air mixtures of regular hydrocarbon fuels (50 mm). The experiments have been conducted with air mixtures of individual gaseous fuels (hydrogen, methane, propane, and ethylene) and binary fuel compositions (methane–hydrogen, propane–hydrogen, and ethylene–hydrogen) at normal pressure and temperature conditions. The use of the helical tube with ten coils is shown to considerably extend the fuel-lean concentration limits of detonation as compared to the straight tube and a tube with a helical section with two coils.

Using the method of mathematical planning of the experiment, the formulation of a foaming polymer composite material based on an ethylene-vinyl acetate thermoplastic binder was optimized. To determine the dependence of the combustibility characteristics (maximum temperature increment and weight loss) of the composite on the content of components in its gas-coke-forming system, a regression model of a full factorial experiment was used using the completed matrix of the orthogonal central-composition plan (OCCP) of the two-factor model of the 2nd order experiment. By adjusting the composition of the gas-coke-forming system, consisting of ammonium phosphate, amine, and carbonate mineral, a slow-burning material with improved thermal insulation ability was obtained. For the studied composition, it was found that the one of the factors causing a decrease in combustibility and an increase in the fire resistance limit (up to 104 min) is the formation of a foamed mechanically strong coke-like structure, stable in a wide temperature range (300–800 C).

The paper presents the results of an experimental study using high-speed video recording of the combustion propagation through inert barriers in Al/CuO nanothermites placed in closed shells (tubes) made of quartz glass. Viscose and air gaps were used as inert barriers. When the luminous front (which the present authors associate with the burning rate) passes through the barrier made of viscose, its propagation velocity drops noticeably but after it enters the nanothermite, its propagation velocity recovers to the original value. As for the air gaps, when the luminous front expands into the air, its speed increases by a factor of 2–3, then the normal mode of propagation is established. The presence of air gaps in a tube with a thermite mixture makes it possible to significantly reduce the mass of this mixture with a slight decrease in the average burning rate compared to a completely filled tube of the same length.

New energy-intensive compounds 4,8-dicyanomethyl-4H,8H-difurazano[3,4-b:3',4'-e]piperazine (DCMFP) and 4,8-ditrazolomethyl-4H,8H-difurazano[3,4-b:3',4'-e]piperazine (DTMFP) have been synthesized for the first time. The synthesis of these compounds is described. Both compounds were studied as possible dispersants of solid fuels for gas generator engines, their densities, enthalpies of combustion and formation, sensitivity to impact and friction were determined (for DCMFP, the sensitivity is very low, at the level of TNT; for DTMFP, at the level of HMX), the ballistic efficiency of solid fuels was estimated based on DCMFP and DTMFP (against 7-amino-7 -difurazano[3,4-b:3',4'-f]furoxano[3'',4''-d]azepine, Az(O)NH₂  the first wins 4%, the second loses ). A comparison was also made with a number of other dispersants developed over the past few years. Preliminary testing of DCMFP and DTMFP for thermal stability was carried out by DTA in a nonisothermal mode, it was shown that these components are very stable, the so-called temperature of the beginning of intensive decomposition is 312 and 270°C, respectively.

The enthalpies of combustion and enthalpies of formation of three trinitromethyl derivatives of 1,3,5-triazine were determined by the calorimetric method. The data obtained can be used for calculating the energy capabilities of related compounds by the method of replacing functional groups. The thermochemical characteristics of trinitromethyl groups from 1,3,5-triazine derivatives are compared with the corresponding properties of these groups in azoles and nitroalkanes.