Ignition 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 (dimensions of the hot particle x _p = 4 mm and y _p = 2 mm) was studied by mathematical modeling. For the temperature of the heated steel particles and the distance between them varied in the ranges 700 < T _p < 1500 K and 0.1_{x p} < Δ_x < 1.5xp, respectively, the values of T _p and Δ_x were determined for which the ignition delay corresponds to the initiation of combustion of the composite propellant by a single particle, by a plate at a constant temperature or by several particles. In the region of low initial temperatures of the local sources (T _p < 1100 K), the limiting values Δ_x → 0.1x _p and Δ_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–propellant–gas” model and the “single particle–propellant–gas” model, respectively. Decreasing the distance Δx at T _p < 1100 K decreases the induction period to 50% and reduces the minimum initial temperature of the source required to initiate propellant combustion 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 material ignition by a plate at constant temperature. The variation in the ignition delay in this case is less than 5%.