Radiative properties of micron-sized Al/air premixed flames described by an effective medium core-shell formulation

• Published in: International journal of heat and mass transfer 2023-04, Vol.203, p.123815, Article 123815
• Main Authors: González de Arrieta, I., Blanchard, C., Laboureur, P., Chauveau, C., Genevois, C., Rozenbaum, O., Halter, F.
• Format: Article
• Language: English
• Subjects: Alumina nanoparticles; Aluminum combustion; Effective medium approximations; Emissivity; Engineering Sciences; Lorenz-Mie scattering; Optics; Physics; Reactive fluid environment
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.123815

•A premixed Al/air flame was investigated by experiment and numerical simulations.•Each micron-sized Al/Al2O3 flame can be modeled using Lorenz-Mie core-shell theory.•Optical indices of homogenized Al2O3 nanoparticle shells were fitted from a model.•This basic model can reproduce the radiometric results of a small burner prototype.•A power law for the emissivity was obtained, with exponents close to -0.5. The goal of this article is to contribute to the knowledge of the phenomenology of the poorly understood micron-sized Al/air flames, with the intention of assessing the viability of an energy carrier based on aluminum powders. To this end, the combustion efficiency, temperature, radiative profile, and solid combustion products of a flame prototype have been studied in depth. These fundamental parameters are required to explore the possibilities of recovering the energy released by these flames. In addition, a theoretical model has been established to analyze the radiative properties of the flame, derived for an optically thin collection of independent burning Al particles, each modeled by a core-shell geometry. The structure of the shell, made up of a cloud of alumina nanoparticles, has been modeled with an effective medium following the Maxwell-Garnett relation. This approach can reproduce the experimental results and is thus suggested as a starting point for modeling experiments characterized by strong emission by the nanoparticle cloud.