On the transition boundary from steady to pulsating combustion in shs flames

The self-propagating high-temperature synthesis (SHS) transition boundary that separates steady combustion from pulsating combustion has been studied for the practical relevance that materials synthesized in the pulsating combustion mode are of a laminated structure and consequently are of little use as a bulk. The essential heterogeneous nature of the SHS flame propagation is described, and the effects of the particle size on the combustion behavior are captured. It is shown that steady combustion proceeds when the product of the mass burning rate and the heat of combustion is smaller than a critical value determined by the material strength and flame instability. Furthermore, the analysis has succeeded in identifying the transition boundary as function of the system parameters, such as the mixture ratio, the degree of dilution, the particle size, and the initial temperature. Related to this identification, the system parameters when steady combustion proceeds even at the adiabatic condition have been obtained. The boundary thus determined turns out to represent well that for the SHS process with small particles less than a few micrometers in diameter. In addition, effects of transverse wave number on the boundary between steady combustion and pulsating combustion have been examined in order to evaluate effects of heat loss on the side surface. Appropriateness of the boundary has further been demonstrated by comparing the predicted results with the experimental results in the literature.