Fundamentals of metal combustion in composite explosives revealed by high speed microphotography.

摘要

High-speed and high resolution microphotography has been used to examine the ignition and combustion of small 25--76 (mu)m diameter and 23 mm long aluminum wires in water, rapidly heated by a capacitor discharge system. Streak photographs were obtained over periods of 30--500 (mu)s with a spatial resolution of 2 (mu)m. The wire temperature was determined as a function of time by integrating the circuit equation together with the energy equation for an adiabatic wire and known aluminum electrical resistivity and temperature functions of energy density. We discovered a transition in the ignition and combustion of the aluminum from mild to rapid sustained chemical reaction with the water when the wire is heated above a critical temperature within 1 (mu)s. The triggering mechanism for this rapid reaction appears to be the collapse of a vapor blanket during its first oscillation.