@article{639e3c7a-64de-473f-b527-7eb44b7746e2,
  abstract     = {{Aluminum combustion in steam offers a promising route for recyclable, zero-carbon cogeneration of heat and hydrogen. However, the development and validation of mechanisms and models for micron-sized Al droplet combustion is limited by the scarcity of quantitative, high spatiotemporal resolution experimental data. We combine high-speed microscopy with laser absorption imaging tomography to quantitatively investigate the spatiotemporal evolution of the key intermediate species, aluminum monoxide (AlO), during the combustion of Al droplets of different radii in both O<sub>2</sub>-containing and O<sub>2</sub>-free water-vapor-rich environments. After correcting for the non-resonant laser extinction interference caused by the condensed-phase products, the resolved characteristic AlO absorption images reveal that AlO molar concentration is negligible near the droplet surface, peaks within the condensed layer, and extends beyond it. The O<sub>2</sub>-containing environments yield faster Al consumption rates and roughly triple the peak AlO concentration (up to 2.2% for larger droplets), with the peak located further from the condensed layer. Two dynamic features are identified: droplet coalescence between the parent Al and the product alumina droplets associated with asymmetric combustion, alongside radius and AlO oscillation for large droplets in symmetric combustion mode. During the coalescence, the alumina droplet heats the Al droplet, increasing the AlO level by a factor of approximately 1.5, but no violent phase change or localized AlO-producing reaction is observed. The high-frequency AlO oscillation, decoupled from the droplet oscillation, may indicate the presence of nonlinear kinetic mechanisms. The spatiotemporal evolution of AlO under different conditions provide experimental reference for developing and validating Al combustion mechanisms and models, while the transient dynamics reveal instabilities that inspire new insights into Al droplet combustion.}},
  author       = {{Wang, Weitian and Wu, Zhiyong and Song, Zihao and Chao, Xing and Alden, Marcus and Li, Zhongshan}},
  issn         = {{1540-7489}},
  keywords     = {{Aluminum combustion; Al-water combustion; Aluminum monoxide evolution; Droplet coalescence; Laser absorption imaging}},
  language     = {{eng}},
  month        = {{07}},
  publisher    = {{Elsevier}},
  series       = {{Proceedings of the Combustion Institute}},
  title        = {{AlO evolution and dynamics around aluminum droplets burning in water-vapor-rich environments}},
  url          = {{http://dx.doi.org/10.1016/j.proci.2026.106171}},
  doi          = {{10.1016/j.proci.2026.106171}},
  volume       = {{42}},
  year         = {{2026}},
}