Reaction Mechanism of Aluminum-Particle-Air Detonation

Both in-tube and unconfined experimental evidence showed strong dependence of micrometric aluminum-air detonability on initial pressure and highly nonlinear behavior of abrupt deflagration-to-detonation transition, thus indicating dependence of the aluminum reaction mechanism of the detonation waves on chemical kinetics. On the other hand, the observed aluminum―air detonation manifested itself in a weak transverse wave structure, as revealed by the small-amplitude oscillation that rapidly degenerates behind the shock front in the pressure histories. This suggests a functional dependence that is weaker than the nonlinear Arrhenius kinetic behavior for the later aluminum combustion. Hence, a surface kinetic oxidation and diffusion hybrid reaction model with a degree of condensed detonation products was suggested, and the unsteady two-phase fluid dynamics modeling showed the success of the hybrid reaction model, capable of capturing both the kinetics-limited transient processes of detonation initiation, abrupt deflagration-to-detonation transition and detonation instability, and the diffusion-limited combustion of aluminum in the long reaction zone, supporting the weak transverse wave structure.