Filtration Combustion Theory

In contrast with the theory for gasless reactions (Sections IV,A and IV,B). which was adapted from classical combustion theory, filtration combustion (FC) theory was developed specifically to describe gas-solid reactions in CS (Merzhanov eta/., 1972 Aldushin ef a/., 1974). 

Depending on reaction and permeation conditions, two modes of FC can be defined natural and forced filtration. In the first case, infiltration flow is a consequence of the natural pressure gradient between the atmosphere (typically constant) and the reaction zone. In the second case, forced gas flow is induced by 

For natural permeation combustion, the reactant gas may flow in either the same (cocurrent flow, Fig. 27a) or opposite (countercurrent flow. Fig. 27b) direction as that of combustion wave propagation, and in some cases even in both directions Fig. 27c). One-dimensional flow regimes can be achieved by placing the sample in a quartz tube, which in turn can be closed at one end (Pityulin et al, 1979). In the general case (see Fig. 26), the reactant gas also enters from the side surface, and the process can be described by two- or three-dimensional numerical simulations (cf Ivleva and Shkadinskii, 1981 Dandekar et al., 1990, 1993). In this section, results for the simpler one-dimensional case are analyzed and features of the higher dimensional studies are briefly discussed. 

Let us consider the reaction front propagation for a binary system AIsl-Fi BIgl Cfs, ). 

In addition to equations for heat conduction and chemical kinetics used for gasless systems [cf Eq. (6)], gas-solid reactions require equations describing the 

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Aldushin, A. P., and Merzhanov, A. G., Filtration combustion theory General approaches and results. In Thermal Wave Propagation in Heterogeneous Media (Russ.). Nauka, Novosibirsk, 1988, p. 9. 

Aldushin, A. P., New results in the theory of filtration combustion. Combust. Flame, 94,308 (1993). 

Aldushin, A. R, Merzhanov, A. G., and Sepliarskii, B. S., Theory of filtration combustion of metals. Combust. Explos. Shock Waves, 12,285 (1976b). 

Aldushin, A.P., Sepliarskii, B.S., and Shkadinskii, K.G. (1980) Theory of filtration combustion. Combust Explos. Shock Waves, 16, 33. 

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