Model of Convective Burning of Granular Mixtures Used in SHS

Recent publications on the combustion of a granular charge intended for the synthesis of compositions based on titanium carbide have revealed significant changes in the characteristics and combustion rate with an inert gas coflow. The authors of the studies associated these changes with the convective burning regime. This paper presents a theoretical model that makes it possible to analyze the contribution of convective heat transfer during the combustion of a granular charge in a cocurrent gas flow in self-propagating high-temperature synthesis (SHS) processes. It is shown that, depending on the rate of the hot gas flow blown through a granular sample, three combustion regimes are possible. In the absence of gas or a low gas flow rate (up to a level of 1 kg/(m2 s)), the combustion front is predominantly flat and convection does not play a significant role. At moderate flow rates (at the level of 10 kg/(m2 s)), the effect of convection becomes noticeable, the combustion rate doubles, and the combustion front is no longer flat, since the surface layers of the granules heat up faster than the layers in the center. Finally, at high flow rates (at the level of 50 kg/(m2 s)), the contribution of convection becomes predominant, the combustion rate exceeds the base rate (in the absence of gas blowing) by more than an order of magnitude, and the structure of the combustion wave is significantly rearranged.