Ignition characteristics of a metallized composite solid propellant by a group of hot particles

The solid-state ignition of a metallized composite propellant (ammonium perchlorate + $14\%$ butyl rubber + $5\%$ aluminum powder + $6\%$ plasticizer) under local heating by several sources of limited power capacity (the dimensions of the hot particle $x_p=4$ mm and $y_p=2$ mm) was studied by mathematical modeling. For temperature of the heated steel particles and the distance between them varied in the ranges $700<T_p<1500$ К and $0.1x_p<\Delta_x<1.5x_p$, respectively, the values of $T_p$ and $\Delta_x$ were determined for which the ignition delay corresponds to the initiation of combustion of the composite propellant by a single particle, a plate at a constant temperature or several particles. In the region of low initial temperatures of local sources ($T_p<1100$ K), the limiting values $\Delta_x\to0.1x_p$ and $\Delta_x>1.5x_p$ were identified for which the characteristics and mechanism of ignition of the propellant by a group of heated particles can be studied using the plate-fuel-gas model and the single particle–fuel–gas model, respectively. Reducing the distance $\Delta_x$ at $T_p<1100$ leads to a reduction in the induction period to $50\%$ and a decrease in the minimum initial temperature of the source required for propellant combustion initiation from $830$ to $700$ K. At $T_p>1100$ K, the ignition of the metallized composite solid propellant by a single or several particles can be studied using relatively simple one-dimensional models of condensed matter ignition by a plate at constant temperature. The variation in the ignition delay in this case is less than $5\%$.