Vol 15, No 2 (2022)

The methods of kinetic processing of experimental data obtained in free piston compressors (ballistic compressors) are analyzed. Among them are various techniques based on the joint solution of a system of equations consisting of the piston motion equation, Poisson’s adiabatic equation, the law of conservation of energy, and the equation of state; techniques based on measuring the deviation from adiabaticity during compression of concentrated mixtures, an approximate technique developed at the A. V. Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences (TIPS RAS) as well as a method for determining kinetic constants during spontaneous ignition of a combustible gas proposed by Babkin and Senachin. It has been shown that at present, for adiabatic compression of gases by a free piston, there is no method for determining the rate of a chemical reaction based on experimental data in the full range of the conversion degrees of the test substance and, consequently, in a wide temperature range. The most promising way to create it is to improve the methodology of the TIPS RAS.

Microexplosive fragmentation is a key phenomenon on which modern methods of secondary atomization of composite fuels are based in industry. The implementation of the corresponding processes makes it possible to reduce the size of secondary droplets by a multiple (from 10–15 to 100–200 times) relative to the initial values of the sizes of the parent droplets formed during spray disintegration. This study presents the results of studying the collective effects in the formation of secondary fragments as a result of microexplosive fragmentation of composite fuels. The characteristics of secondary fragments during microexplosive fragmentation of a group of three droplets of composite fuels are analyzed. Two fuel compositions were used: 90% diesel / 10% water and 10% diesel / 90% water. Using the Shadow Photography method, the typical sizes of secondary fragments, which are formed during the fragmentation of each of the three droplets in a group, are determined. The limiting distances (from 8 to 10 radii) between droplets are established, at which the integral characteristics of the fragmentation of a group of droplets satisfactorily correspond to the similar characteristics of the disintegration of single droplets. At smaller distances between droplets, significant differences in the characteristics of secondary droplets formed as a result of microexplosive fragmentation of composite fuels were registered.

The paper defines the optimal conditions and characteristics of spraying fire extinguishing compositions to reduce the temperature in the combustion zone of typical combustible forest materials. A series of experiments was carried out to establish the conditions and characteristics of the processes occurring during localization and elimination of combustion of typical combustible forest materials (wood, mixed forest combustible materials) under conditions of exposure of different dispersion water drops. The times of thermal decomposition of solid combustible materials after suppression of fiery combustion by fire extinguishing compositions based on water with the addition of a foaming agent and FR-Les 01 were determined. The minimum volume and spraying mode (droplet sizes) of aerosols of different concentrations were established to effectively reduce the temperature in the combustion zone.

The technology of a pulsed-detonation gun for gasification of organic waste with ultrasuperheated steam has been experimentally demonstrated for the first time. The experiments on autothermal natural gas conversion as well as on the allothermal gasification of liquid (waste machine oil) and solid (sawdust) wastes by the products of pulsed detonation of natural gas – oxygen mixture at a pulse frequency of $f=1$ Hz were conducted. At such a frequency, the time-averaged mean temperature and absolute pressure of detonation products in a flow reactor attached to the gun were about 1200 K and 0.1 MPa, respectively. The technology of the pulsed-detonation gun was shown to provide complete (100%) conversion of natural gas in fuel-rich natural gas – oxygen mixture into syngas containing H₂ and CO with an H₂/CO ratio of about 1.25. Gasification of liquid and solid wastes led to the production of syngas containing up to 80 and 65 %(vol.) (dry basis) reactive components (H₂, CO, and CH₄) with H₂/CO ratios of 0.8 and 0.5, respectively. Comparison of syngas compositions obtained in experiments with fuel-rich natural gas – oxygen mixtures and in experiments with gasification of liquid and solid wastes under the same conditions at $f=1$ Hz and 0.1 MPa showed that these compositions almost did not depend on the feedstock type.

The paper briefly analyzes the advantages and prospects for the development of laser-initiated pyrotechnics, the existing developments in this area and their current problems. A structural scheme of a laser initiated pyrocartridge, a scheme for focusing light to initiate a pyrotechnic charge, and a method for implementing control of the pressure pulse generated by it are proposed. Numerical simulation methods have been used to study the behavior of the pyrocartridge design under static high-pressure loading and the possibility of generating various pressure pulses in the working volume of spacecraft pyrounits during the outflow of gases from the pyrocartridge after charge initiation.

Reaction of the surface of individual picric acid crystals to the nanoscale mechanical stimulation was studied to understand the processes responsible for the initiation of energetic materials. Three types of the local mechanical stimulation, i. e., nanoindentation, friction, and impact were performed by atomic force microscopy methods. It was found that the stimulation at a nanoscale leads to the disappearance of the material of crystal surface. Moreover, the response to mechanical stimulation differs with crystal faces. In addition, the observed effect slows down with humidity increase probably due to the interaction of the picric acid surface with atmospheric water.

Examples of the main qualitative manifestations of the rheological effects of thixotropy and superanomalies of viscosity associated with modern chemical technologies are considered: additive technology, thixotropic metallurgy, and self-propagating high-temperature synthesis under conditions of a combination of combustion processes and high-temperature shear deformation.