On the numerical accuracy of homogeneous solid propellant combustion models

Abstract

Most theoretical treatments of solid propellant combustion assume a highly idealized mechanism: an exothermic surface decomposition reaction followed by a single exothermic gas phase reaction. Despite its conceptual simplicity this mechanism does not permit an exact solution to the conservation equations. Published combustion models addressing the stated idealization rely on various approximation schemes which have never been tested for accuracy. This report examines the numerical reliability of a number of these schemes by direct comparison of model results with accurate numerical integrations of the conservation equations. Four propellant data sets which span a wide range of kinetics parameters were utilized. None of the approximations proved accurate for all the data sets, but some models are quite accurate in certain limiting cases. The calculations provide a benchmark against which future models might be tested.