On the Nature of Concentration Limits of Combustion Wave Propagation in Powdered and Pelletized Ti + C + xAl2O3 Mixtures

Abstract

The applicability of the percolation theory to describe the combustion of powdered and pelletized Ti + C mixtures in the vicinity of the concentration limits of the combustion wave propagation using different methods of dilution with an inert material—fine and coarse Al₂O₃ particles—has been studied. It has been shown that the pelletized mixtures diluted with coarse inert particles by more than 50% undergo incomplete combustion; at the combustion limit, the incompleteness achieves 50%; this finding is in qualitative agreement with the percolation theory. It has been found that the obtained concentration limit of combustion (75 wt %) and the ratio of the combustion velocities of the undiluted mixture and the mixture at the propagation limit (2.6) correspond to the predictions of the percolation theory. The possibility of flame propagation at the calculated combustion temperature of the mixture below the melting point of titanium is attributed to the presence of a percolation cluster. Necessary conditions for the applicability of the percolation theory to describe the combustion processes in condensed gasless systems have been formulated.