SPONTANEOUS CHANGE IN POROSITY OF A REACTING PRESSED MATERIAL AND NON-ONE-DIMENSIONAL REGIMES OF DIFFUSION COMBUSTION

Essentially non-one-dimensional regimes of synthesis-wave propagation are considered within the framework of a model describing two-dimensio nal diffusion combustion and taking into account a change in porosity of a reacting composition attributed to a change in its physical and c hemical properties. The surface and layer-by-layer burning of a presse d specimen in gas is described qualitatively as well as the interactio n front propagation wherein unreacted material remains in skin layers of the specimen. The conditions of development of a gastight layer on the specimen surface and incomplete material conversion because of pre volume exhaustion have been determined. Dynamics of a number of unsta ble regimes of front propagation is studied. The Pole of diffusion sup ply of a gaseous reagent is analyzed under the conditions of changing porous space in the reacting material. The surface and layer-by-layer burning of pressed specimens, with the reagents interacting in an unst able regime, is considered.