Errors in using balance relations in the theory of combustion of condensed systems

Due to the total lack of reliable experimental data on the kinetics of solid-phase transformations at high temperatures, adequate estimates of the ignition and combustion characteristics of real energetic materials are currently unavailable. In combustion theory, balance relations in the form of ignition criteria and in the form of the equivalence principle of the increase in burning rate under the action of a radiation flux corresponding to an increase in initial temperature are used in most cases without sufficient theoretical justification, what can lead to incorrect results. Numerical simulation of the ignition and combustion of model energetic materials can provide the basis to determine the conditions for the correct use of balance relations. In this work, ignition and combustion under the action of a radiant flux have been numerically studied using a model of unsteady combustion of melting energetic materials and the matching coefficients in the balance relations were obtained. It is shown that the values of these coefficients depend on the kinetic parameters of solid-phase transformations and the intensity of the external heating source. It is concluded that it is necessary to continue the theoretical research aimed at developing valid approaches to determining the parameters of global reactions in the condensed phase using data on ignition delay by heat flux and to determining the correct matching coefficients when using the equivalence principle.