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Browsing by Subject "Measuring the Accommodation Coefficient"

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    Heat Transfer and Combustion Characteristics of Nano-Sized Aluminum and Aluminum Oxide Utilizing Advanced Laser and Optical Diagnostics
    (2024-01) Jeong, Hayoug
    The present study uses advanced optical diagnostics to explore the heat transfer and combustion characteristics of nano-sized aluminum and alumina (aluminum oxide) particles. The study employs a two-prong approach, conducting two distinct experiments utilizing nano-aluminum and nano-alumina. Alumina forms an oxide coating on aluminum, requiring an understanding of the associated heat transfer characteristics. The first part of this study focuses on determining the accommodation coefficient of nano-alumina particles. The accommodation coefficient represents the efficiency of a gas in removing heat from a surface, expressed as the ratio of the actual heat loss to the ideal loss. A comprehensive mathematical framework has been developed for calculating the accommodation coefficient utilizing a two-colored time-resolved Laser-Induced Incandescence technique (TiRe-LII). The model’s validity was confirmed by comparing it with data from existing literature. This model serves as a reliable foundation for measuring the accommodation coefficient in future studies involving particles other than alumina. The second part of the study utilizes Laser-induced Air Shock from Energetic Material (LASEM) to assess the energetic behavior of nano-aluminum. LASEM is employed to measure and compare the shockwave velocity generated by laser-induced combustion of both nano-aluminum and nano-alumina particles. The observed shockwave velocity from aluminum surpasses that from alumina, indicating higher energy content in aluminum. LASEM proves to be an effective lab-scale technique, capable of characterizing energetic behavior with minimal sample material (~ milligram). Intermediate species (e.g., AlO, Al, O, etc.) emissions from laser-induced plasma and combustion signals affirm exothermic reactions in the early stages, supporting the hypothesis that these reactions contribute to the increased shockwave velocity of aluminum particles. These findings significantly enhance our understanding of nanoparticle combustion phenomena.