Nonlinear response functions of the burning rate of ballistite powders

Second-order nonlinear response functions to pressure oscillations are calculated for a group of ballistite powders with additives, based on results of microthermocouple measurements. A unified law of gasification of ballistite powders is refined. A classification of nonlinear response functions is proposed: viscous, normal, and critical response functions are identified. More than half of the burning regimes of these powders are demonstrated to have a viscous response type with a weak dependence on frequency and with a weakly expressed maximum in the case of a resonance. The effect of the powder composition on the nonlinear response functions is analyzed. Specific features of the nonlinear response as a function of a new parameter (phase shift between the interacting modes) are considered. It is shown that the errors in determining the nonlinear response functions depend on the response type and have low values for the majority of the burning regimes. Arguments in favor of the process one-dimensionality in the reactive layer of the condensed phase are given. A hypothesis of the near-critical state of some products of decomposition in this layer is proposed.