A comprehensive model for AP-based composite propellant ignition
A comprehensive model and numerical solutions for ignition of AP-based composite solid propellants are presented. The analysis simulates the ignition process of a propellant sample, located in a stagnation region, under rapid pressure loading conditions. Specific features considered in the model include: 1) detailed chemical kinetics information for the ignition of AP-based composite propellants, 2) two-dimensional (axisymmetric) geometry for the composite propellant, and 3) rapid pressurization of the gas phase. An implicit finite difference scheme is used to solve the set of transient, second-order, coupled, inhomogeneous, nonlinear, governing partial differential equations. Numerical solutions reveal a number of important events occurring during the ignition sequence, including: igniter gas penetration to the region near the sample surface, combustion of unburned species upon arrival of compression waves, heat transfer to the propellant, pyrolysis of the oxidizer and fuel, and gas-phase reactions leading to ignition. The model correctly predicts the experimental observation that the ignition delay time decreases as the pressurization rate is increased. The various ignition criteria considered show the same trend as that measured experimentally.