Macrokinetic analysis of the combustion patterns in the transition from powder to granulated mixtures by the example of 5Ti + 3Si and Ti + C compositions

摘要

In self-propagating high temperature synthesis processes, even a slight change in the amount of impurity gases adsorbed in initial components can lead to a change in the combustion mode and characteristics of the desired products. The influence of both impurity gas release and particle size of the initial components on the combustion velocity of 5Ti + 3Si and Ti + C mixtures is considered. Experimental results are analysed using a convective-conductive combustion model, which explains the strong effect of impurity gas release on combustion velocity. The usage of the mixtures with a crystalline non-metallic component (Si, C) allowed to reveal for the first time the suppressing effect of gases released during heating of titanium particles of different sizes on the velocity of the combustion wave in the mixtures. The conditions of warming up of initial components in the preheating zone of the combustion wave in powder mixtures were formulated in the work. These allowed predicting whether the combustion velocity (Rev.3) of 5Ti + 3Si and Ti + C mixtures increases or decreases during the transition from powder to granulated mixtures. Unlike powder mixtures, a monotonous decrease in the velocity of combustion of granulated mixtures with an increase in the total particle size of the initial components is associated with a significant decrease in the effect of impurity gas release on the combustion process. The values of combustion velocities of granulated mixtures are approximated by similar power dependence on the total particle size of the initial components for both compositions; it corresponds to the linear law of interaction of the initial components in the theory of flame front propagation in a condensed heterogeneous medium. (c) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.