Shock tube measurements of combustion of nano-aluminum

The reaction times and temperatures of nano-aluminum particles burning the reflected shock region of a shock tube was measured experimentally to provide fundamental information on the combustion characteristics of these particles. The particles reacted under temperatures of 1200-2200 K and pressures of 4-32 atm in oxidizers of oxygen and carbon dioxide mixed in varying percentage with nitrogen. An initial bright event was observed where the measured pyrometry temperatures were elevated above the ambient temperature, followed by a decay in light emission to a constant background level where the observed temperature was near the ambient. The timescales of this event varied between 50 to 500 microseconds. Reaction times and temperatures were found to be very dependent on ambient pressure and temperature. In environments where CO₂ was the primary oxidizer, the combustion times and temperatures were found significantly slower and cooler than similar environments with O₂ serving as the primary oxidizer. The light emission consisted primarily of broadband continuum emission, and very little molecular emission was observed. The combustion behavior of nano-aluminum can be explained by a shrinking core flame structure with condensed-phase diffusion or kinetics controlling the combustion process.