Double ignitions of NI-AL combustion reactions

Double ignitions of Ni-Al combustion reactions have been numerically studied in this research. Due to the lower exothermic heat of the metallic reactions, the propagation of Ni-Al combustion front during combustion synthesis is found to extinguish half way for some reactions. To allow the combustion front to propagate completely, the reaction is always ignited again during the experimental demonstration. In this research, different positions in the combusted region, the reacting region, and the preheating region are chosen to study the effect of the second ignition. The second ignition time and position are found to influence the subsequent temperature profiles. It is noted that the combustion temperature is significantly enhanced or incomplete reaction is occurred as the reaction is ignited again in the combusted region or the preheating region. Stable propagation is observed as the reaction is ignited again in the reacting region. A process map for double ignitions is also generated in this study. From the knowledge of the process map, appropriate double-ignition circumstances can be chosen to acquire stable propagation and homogeneous microstructure.