Transient AlH distribution around a burning micron-sized Al droplet quantified by laser absorption imaging

This study presents the first direct measurement of aluminum monohydride (AlH) distribution and dynamics during aluminum combustion. Single micron-sized aluminum droplets were burned in a controlled H₂O/N₂/O₂ environment to ensure repeatable conditions. A dual-wavelength laser absorption imaging system is used to quantify the AlH concentration with high temporal and spatial resolution. The results show that AlH concentration peaks near the droplet surface and decreases from about 1.2% to a negligible level within the condensation layer. As combustion proceeds, AlH extends outward from the droplet surface, and its distribution area stabilizes approximately 12 ms after ignition. This work demonstrates a robust technique for AlH quantification and provides novel data which is critical to understand the aluminum combustion mechanism.