Agglomeration and combustion characteristics of composite solid propellants under low-temperature conditions

In this paper, we propose a promising research direction for propellant combustion in low-temperature environments. In the temperature range of -60 to 20 °C, we systematically examine the thermolysis properties, ignition, and combustion characteristics of propellants containing aluminum. A decrease in temperature reduces the recrystallization temperature of ammonium perchlorate and increases the ammonium perchlorate decomposition peak temperature, which is unfavorable for the exothermic reaction of the propellant solid phase. As the initial ambient temperature decreases, the propellant ignition delay time increases (up to a 127.3 % increase), burning rate decreases (up to a 24.8 % reduction), and aggregation degree of aluminum increases, resulting in an increase in the size of the condensed combustion products (up to a 45.0 % increase). Additionally, the propellant combustion efficiency decreases (up to a 20.8 % reduction). We propose physical mechanisms by which low-temperature environments alter the combustion of propellants. Reducing the propellant initial temperature leads to a decrease in the burning surface temperature, thereby reducing radiative heat feedback and lowering the burning rate. A reduced burning rate slows down the escape of aggregates from the burning surface, enhancing the likelihood of additional collisions and fusion among aggregates. This process increases agglomeration size while diminishing combustion efficiency. The results of this study enhance our understanding of the alterations in the combustion traits of propellants in low-temperature settings.