N. A. Kakutkina

Characteristics of stationary spherical waves of gas combustion in inert porous media

Stationary spherical waves of gas combustion in porous media were studied theoretically and experimentally. It is shown that in spherically convergent and divergent gas flows, the waves differ in the type of stability: they are stable in a divergent flow and unstable in a convergent flow. A mathematical model for standing spherical waves is proposed that establishes the dependences of the coordinate of a standing wave on the gas-flow rate, mixture composition, and parameters of the porous medium and the gas and describes the experiment adequately. It is shown that allowance for heat losses leads to the appearance of limits of existence for standing spherical waves.

Transition Processes in Filtration Gas Combustion

The behavior of gas filtration combustion waves in the low‐velocity regime has been studied experimentally with variation in the parameters of the gas flow and porous medium. It is shown that in transition processes there may be quenching or formation of a stable combustion‐wave structure that does not correspond to the initial or final conditions. A nontrivial type of transition process accompanied by spatial transfer of the combustion zone is found.

Propagation of spherical gas filtration combustion waves in inert porous media

The behavior of spherical combustion waves of gases in inert porous media is described in terms of one- and two-temperature models. Parametric dependences are obtained for the wave velocity and acceleration and for the temperature of the gas and porous medium in the wave. It is shown that in a diverging spherical gas flow, combustion waves initiated at different radii of the sphere converge to the standing wave coordinater*, and in a converging flow, on the other hand, they diverge from it. The experimentally observed propagation behavior of spherical combustion waves is well described by the proposed models.

Ignition of Filtration Gas Combustion Waves by the Flame of the Filtered Gas

Mathematical modeling of ignition of filtration gas combustion waves in a porous medium with external initiation of combustion by the filtered gas is performed. It is shown that the surface temperature of the porous medium at which the flame enters the latter is a function of system parameters. The existence of the lower and upper flammability limits in terms of the gas filtration rate is found. Dependences of the ignition time on parameters of the porous medium are obtained, and their interpretation is given.

SCALE MODELING OF GAS EXPLOSIONS IN CLOSED VESSELS

The effect of geometrical dimensions on combustion of gas mixtures in closed vessels with obstacles has been studied. We show the possibility of considering separately the effects of combustion intensification with allowance for flame self-turbulization and the interaction of flame with obstacles. It has been established that the degree of combustion intensification due to self-turbulization is a universal function of the vessel volume and of the physicochemical characteristics of a gas mixture and is controlled by the Froude and Lewis numbers. Scale modeling of the interaction of flame with obstacles is shown to be possible.