Calculation of the characteristics of the ignition of a metallized composite propellant using various methods for describing its thermophysical properties

The ignition of a metallized composite propellant by a local energy source of limited heat content is studied. The main characteristic of the process (ignition delay time) is calculated over a wide range of initial temperatures of the source (800–1500 K) for the actual inhomogeneous structure of the propellant with consideration of the presence of fine metal particles and for an effective heterogeneous structure with thermophysical properties calculated by formulas based on the rule of additivity of the thermophysical properties of the components. The thermal conductivity of the propellant is also calculated by approximate expressions proposed by Maxwell, Frick, Bruggeman, Meredith, Xiao, Hamilton, Cross, Behrens, Misnar, Peterson, Hermans, and Nielsen for polymeric materials containing finely dispersed inclusions with a higher thermal conductivity as compared to the polymer matrix. It is found that the expressions proposed by these authors yield values of the ignition delay time and the minimum initial temperature of the heat source required to initiate combustion that differ from those predicted by the model with account of the real heterogeneous structure by up to 75 and 15%, respectively.