S. V. Kostin

Cellular modes of filtration combustion: Phenomenological features

In conditions of instability, a planar front of infiltration-assisted combustion was found to split into individual hot spots (cells) propagating in an oscillation mode and leaving behind combustion products with the imprints of their periodic motion. Discussed are some subtle details of the phenomenon.

Unsteady infiltration-mediated combustion in conditions of regulated quasi-isobaric flow of gaseous reagent

Unsteady infiltration-mediated combustion of Ti powder in air was explored in conditions of regulated quasi-isobaric flow of gaseous reagent. Variation in the parameters/geometry of air flow was found to affect the structure of reaction zone, burning velocity, composition of combustion products, and extent of conversion.

Combustion of porous solid reagent in quasi-isobaric flow of three-component gaseous reagent

A mathematical model of two-zone infiltration-mediated combustion of a porous solid reagent (Ti) in an isobaric counterflow of three-component gaseous reagent (air) was constructed and numerically analyzed. We explored structural features, stability issues, and also the influence of inert impurity gas on the initiation and structure/stability of two-zone combustion waves. The relevant experimental results are also presented.

Combustion of layered SHS systems: Thermal conditions at the interface

Combustion of two-layer SHS systems was numerically modeled in order to shed new light on the stability of a combustion wave passing through the interface between two reactive heterogeneous systems. Thermal conditions at the interface have been numerically calculated for all stages of a transient process taking place at the interface, with special emphasis on the influence of a gaseous gap between the constituent green pellets.

Irregular and cellular wave structures in the combustion of porous media under conditions of natural gas infiltration

The experimental results on the unsteady propagation of cellular waves during the infiltration-controlled combustion of a titanium powder layer are presented. The modes of frontal combustion of a porous medium with a nonuniform thermal structure that arise because of the loss of stability of the front under conditions of controlled gas transport into the exothermic reaction zone are examined. The conditions of transformation of an irregular combustion front into a cellular combustion wave are determined. The effects of the key thermal parameters of the heterogeneous system on the structure of the irregular and cellular fronts and on the characteristics of the oscillatory dynamics of their propagation are examined.

Infiltration-mediated cellular combustion of Ti powder in an inclined rectangular straight-through air flow reactor: Combustion wave patterning

Explored was infiltration-mediated combustion of Ti powder in an inclined rectangular straight-through air flow reactor in conditions of natural coflow and counter flow convection in the field of gravity forces. In conditions of limited supply of gaseous reagent, a continuous combustion front was found to rearrange into more complicate modes. A distinctive feature of the process under study was the presence of inert gaseous impurities that markedly affected the process of gas exchange within the reaction zone. The results may turn useful in designing reactors and in predicting fire hazards in difficult-to-access sites.

Propagation of Cellular Modes of Combustion of Porous Media under Nonadiabatic Conditions

The formation and propagation of cellular combustion of porous media under near-critical combustion existence conditions were investigated. The sizes and structure of cells in which the condensed component reacted with the gas depended nonlinearly on the heat loss to the environment. With increasing heat loss, the oscillation frequency of the cellular front, its average propagation velocity, and the intensity of the exothermic transformation of the condensed phase increased, and the cell sizes decreased. Cellular combustion was extinguished only when the transformation of the condensed component within a cell was completed.

Passage of SHS wave through a gap: Mathematical modeling

Stability of combustion wave during its passage through a gaseous gap between two reactive layers was studied by mathematical modeling. The character of transient processes in the gap was explored as a function of thermophysical parameters of the layers, kinetic parameters, and gap width at a predominant role of radiative heat transfer. The passage of combustion wave through the gap was found to be accompanied by the attainment of superadiabatic temperatures within the transition zone. A critical temperature for burning failure at the interface was determined.

Infiltration-mediated combustion in porous media: Propagation of cellular structures in conditions of heat losses

Investigated was nonadiabatic propagation of cellular structures in conditions of unsteady infiltration-mediated combustion in porous media. The size and structure of cellular hot spots was found to be a non-linear function of governing parameters, including heat sink into environment. Quasi-stationary dynamics of cell propagation in near-critical conditions was simulated in terms of a quasi-3D mathematical model. The evolution of cellular combustion was investigated as a function of heat losses. Experimental data for cellular combustion of Ti powders in a slit-like reactor were found to agree with predictions of the model.

Cellular combustion of Ti powder in air ducts: Influence of convection currents

Influence of gas convection on cellular combustion of Ti powder in slit-like reactors was studied experimentally. Heterogeneous combustion in inclined and dead-ended reactors was accompanied by diffusional and convective mass exchange between gaseous reactant and metal powder. Free convection of the gases evolved during combustion was found to favor the formation of inclined and cellular combustion fronts.