Modeling the steady-state combustion of solid propellant ingredients with detailed kinetics

The steady-state combustion of the monopropellants glycidyl azide polymer (GAP) and butane triol trinitrate (BTTN), and the pseudo-propellants GAP/RDX and RDX/GAP/BTTN have been modeled using a 1-dimensional three-phase numerical model, with detailed kinetics in the gas phase. Global decomposition reactions and kinetic parameters for GAP and BTTN in the condensed phase have been developed, based on experimental data. The evaporation of BTTN has been included. Detailed gas phase kinetic mechanisms have been used, with as many as 488 reactions and 76 species. The combustion has been modeled over as wide a range of conditions as 1–100 atm and 298 ± 50 K. The calculated combustion characteristics include the burning rate, pressure exponent, temperature sensitivity, surface and flame temperatures, temperature and species profiles, and condensed and gas phase heat released.; Combustion characteristics of four formulations of cured GAP with varying amounts of the curing agent hexamethylene di-isocyanate (HMDI) have been modeled. The calculated GAP burning rates were ∼1.05–1.93 cm/sec at 70 atm, increasing with the GAP content of the formulation. The calculated pressure exponents were ∼0.4 and the calculated temperature sensitivities were ∼0.01–0.014K −1. The BTTN combustion model predicted a burning rate of ∼1.15 cm/sec at 70 atm, with a pressure exponent of ∼0.87 and a temperature sensitivity of ∼0.005 K−1. The gas phase heat release dominates the combustion process for BTTN, while the condensed phase plays a significant role for GAP combustion.; Based on the monopropellant models of GAP and BTTN, and using the monopropellant RDX model of Davidson et al., the pseudo-propellant combustion of RDX/GAP and RDX/GAP/BTTN have been modeled. Three formulations of RDX/GAP, i.e., 90/10, 80/20 and 70/30 RDX/GAP have been modeled. The calculated burning rate decreased with increasing GAP content (∼0.25–0.87 cm/sec at 70 atm). Blind predictions of the burning rate of a 70/9/21 RDX/GAP/BTTN pseudo-propellant (∼0.84 cm/sec at 70 atm) matched the experimental data typically within 1%. The calculated pressure exponent was 0.8 and temperature sensitivity was ∼0.0012–0.0014 K−1. The calculated values for the monopropellants and pseudo-propellants have been compared with available experimental data. Overall, model calculations and their trends agree well with experimental data.