Multidimensional, Multiphase Flow Analysis of Flamespreading in a Stick Propellant Charge

Abstract : The interior ballistic performance of propelling charges employing stick propellant often cannot be simulated using either lumped-parameter or two- phase flow models. Much of this disparity is usually attributed to enhanced burning within the long perforations, perhaps accompanied by splitting or fracture of the stick to yield additional burning surface. During developmental testing of a stick propellant charge for the 155-mm howitzer, unusually low (or even reversed) sensitivity of performance to propellant conditioning temperature has been noted, a factor that, if controllable, may have significant impact on the acceptability of new stick propellant charges. Moreover, the mechanisms responsible for all the above behavior may well be exploitable as high- progressivity, high-density (HPD) propelling charge concepts. In this work, a state-of-the-art version of TDNOVA, a two-dimensional, two-phase flow interior ballistic code, is employed to probe the ignition and flamespreading processes in stick propellant charges. Calculations of flame propagation on exterior and interior surfaces, as well as pressurization profiles both within the perforations and in the interstices, are described for typical and simplified stick charge configurations. Reconciliation of predicted behavior with experimental observation is discussed, and further specific studies using TDNOVA are identified in order to verify a postulated explanation for stick charge ballistic data exhibiting an anomalous temperature sensitivity.