Dynamics and combustion of single aluminium agglomerate in solid propellant environment

Aluminized composite propellant used in solid rocket motors contain a lot of aluminium particles because high combustion energy is generated and propulsion efficiency increases by burning aluminium particles. The combustion of aluminum occurs in a significant portion of the combustion chamber and produces aluminum oxide smokes and residues that are carried into the flowfield. Agglomerates have non-spherical shape, and consist of aluminium droplet and oxide particle (oxide cap) attached to the droplet. Unlike the liquid droplet ignition, the solid oxide film blocks the liquid aluminum from the penetration of the oxidizer hence prevents the particle from its ignition. Development of robust models of aluminum particle dynamics is essential in the design of advanced propulsion systems. The mathematical model of two-phase flow around a single aluminum droplet with oxide cap is developed. The model solves the continuity, momentum, energy and species continuity equations simultaneously to obtain the species and temperature profiles and the burning time of droplet. The results of numerical simulations are compared with predictions from semi-empirical correlations and computational data. •The model of aluminum droplet dynamics and combustion is developed.•The flowfield over aluminum droplet with oxide cap is computed.•The burning time is evaluated and compared with empirical correlations.•A better understanding of mechanism of droplet combustion is achieved.