The Effect of Impurity Gas on the Combustion Mode of Granular Mixtures Ti–C–B

Experimental studies of the combustion of granular mixtures (100 – X)(Ti + C) + X(Ti + 2B), 0 ≤ X ≤ 100 wt %, were carried out. Granules 0.6 and 1.7 mm in size were made using an alcoholic solution of polyvinyl butyral. The combustion velocity dependence on X showed two characteristic areas with a boundary between them near X = 60 wt %. At X > 60 wt %, the combustion velocity increased significantly which allowed us to assume a convective mechanism of combustion due to the release of impurity gas. This assumption was verified by experiments in which the impurity gases were filtered through the side surface of samples to exclude the effect of a convective heat transfer. The necessary conditions for the transition to the convective combustion mode were formulated. Calculations showed that the critical conditions were met for mixture 40%(Ti + C) + 60%(Ti + 2B) with granule size of 1.7 mm. The content of impurity gas (presumably hydrogen) for mixtures burning in convective mode was estimated.