Numerical Solution of Three Solid Propellant Combustion Models During a Gun Pressure Transient

Abstract

Abstract : All current gun interior ballistics computer programs rely on, and are sensitive to, the steady state burning rate 'law', r = ap to the n power. It is not clear that this is a valid representation in a highly transient pressure environment. To estimate possible dynamic effects, numerical solutions for three thermal-wave combustion models (KTSS, Levine/Culick, Kooker/Zinn) are obtained for a series of example cases where the imposed pressure variation at the edge of the flame zone is prescribed by an experimental pressure-time history from the 105mm Gun M68. The results obtained with several different numerical solution methods indicate that (1) at low pressure (early time) the instantaneous propellant burning rate can be much greater than ap to the n power; while at high pressure the burning rate returns asymptotically to ap to the n power, and (2) burning rate 'runaway' is a numerical difficulty and is not a solution to the combustion models. The effect of dynamic burning rate on closed-bomb measurements is estimated numerically with a simple model.