Reduced Chemical-Kinetic Mechanisms for the Dark Zones of Double-Base andNitramine Gun Propellants

摘要

Simplified chemical-kinetic mechanisms were employed to calculate the structureof the dark zones of burning double-base and nitramine propellants. These reduced mechanisms are expected to be useful in interior ballistic calculations. First, skeletal mechanisms comprised of 22 elementary reactions among 15 species and 23 elementary reactions among 17 species were used to calculate dark zone structures for double-base and nitramine propellants, respectively. Ignition delay times tau sub ig were calculated for homogeneous mixtures in which the initial concentrations of reactants were similar to those found at the beginning of propellent dark zones. The tau sub ig calculations were performed for various initial pressures and temperatures. The tau sub ig calculated using the skeletal and detailed mechanisms agreed well. Reduced mechanisms were derived from the skeletal mechanisms by introducing steady-state approximations for a number of species. For double-base propellants, a reduced mechanism of three global reactions was obtained. Reduced mechanisms utilizing six and four global reactions were deduced for nitramine propellants. The tau sub ig and structures of the dark zones calculated using the reduced three-step mechanism for double-base propellants and six-step mechanism for nitramine propellants were in agreement with calculations made using the skeletal mechanisms. Agreement using the four-step reduced mechanism for nitramine propellants was not good; however, it might still be useful for some applications.