Characteristics and criteria of ignition of suspensions of aluminum particles in detonation processes

A physicomathematical model of ignition of suspensions of aluminum particles under dynamic conditions including melting, low-temperature oxidation of aluminum, and polymorphic transformation of the oxide film is presented. Model verification is based on experimental data on the limit temperatures and delays of ignition of suspensions of aluminum particles in shock and detonation waves. Applicability of reduced models (without melting and pre-frame oxidation) at an adequate temperature criterion that ensures identical ignition delays is demonstrated, based on the analysis of thermal dynamics of the mixture. Dependences of the ignition temperature on the shock wave parameters, particle size and concentration, and oxidizer concentration are obtained. Formulas for an invariant (with respect to concentrations) criterion are derived, which express the dependence of the ignition temperature on the current temperature of the gas. The governing constants are found for suspensions of particles in air and oxygen.