TY - JOUR
T1 - Flame propagation in nano-aluminum–water (nAl–H2O) mixtures
T2 - The role of thermal interface resistance
AU - Muraleedharan, Murali Gopal
AU - Unnikrishnan, Umesh
AU - Henry, Asegun
AU - Yang, Vigor
N1 - Funding Information:
This work was sponsored by the Air force Office of Scientific Research under contract no. FA-9550-13-1-0004 . The support and encouragement provided by Dr. Mitat A. Birkan is gratefully acknowledged.
PY - 2019/3
Y1 - 2019/3
N2 - A detailed numerical analysis of flame propagation in nano-aluminum–water (nAl–H2O) mixture is performed. Emphasis is placed on investigating the role of particle thermal conductivity in the prediction of the burning properties of the mixture. Flame structure and burning characteristics are obtained by solving the energy equation using finite difference discretization and the Gauss–Seidel iteration method. Particle thermal conductivity is modeled using the temperature-dependent thermal conductivities of the aluminum core and oxide layer, as well as their interface resistance. The effective thermal conductivity of the mixture is modeled as a function of temperature, spatial coordinate, and local mixture composition, by means of the unified Maxwell–Eucken–Bruggeman model, accounting for random particle distribution and inter-particle interaction. Results indicate that the combined thermal resistance offered by the oxide layer and the interface constitute 95% of the total resistance of the particle. The calculated particle-size dependent linear burning rates show good agreement with experimental data, with only 5% error. Error in burning rate prediction increases, however, to 20% when interface resistance is excluded from the particle thermal conductivity model. It was also observed that burning rate varies as the inverse of particle size. Finally, an analysis of the sensitivity of burning rate to the individual components of the particle thermal conductivity model is also performed. Results suggest a 30% decrease in burning rate for two orders of magnitude reduction in both interface conductance and oxide thermal conductivity. The burning rate drops by only 15%, however, for a similar reduction in aluminum thermal conductivity. A heat conduction perspective on flame propagation in nanocomposites is presented, identifying the highest and the lowest conductive pathways for energy transport.
AB - A detailed numerical analysis of flame propagation in nano-aluminum–water (nAl–H2O) mixture is performed. Emphasis is placed on investigating the role of particle thermal conductivity in the prediction of the burning properties of the mixture. Flame structure and burning characteristics are obtained by solving the energy equation using finite difference discretization and the Gauss–Seidel iteration method. Particle thermal conductivity is modeled using the temperature-dependent thermal conductivities of the aluminum core and oxide layer, as well as their interface resistance. The effective thermal conductivity of the mixture is modeled as a function of temperature, spatial coordinate, and local mixture composition, by means of the unified Maxwell–Eucken–Bruggeman model, accounting for random particle distribution and inter-particle interaction. Results indicate that the combined thermal resistance offered by the oxide layer and the interface constitute 95% of the total resistance of the particle. The calculated particle-size dependent linear burning rates show good agreement with experimental data, with only 5% error. Error in burning rate prediction increases, however, to 20% when interface resistance is excluded from the particle thermal conductivity model. It was also observed that burning rate varies as the inverse of particle size. Finally, an analysis of the sensitivity of burning rate to the individual components of the particle thermal conductivity model is also performed. Results suggest a 30% decrease in burning rate for two orders of magnitude reduction in both interface conductance and oxide thermal conductivity. The burning rate drops by only 15%, however, for a similar reduction in aluminum thermal conductivity. A heat conduction perspective on flame propagation in nanocomposites is presented, identifying the highest and the lowest conductive pathways for energy transport.
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U2 - 10.1016/j.combustflame.2018.12.022
DO - 10.1016/j.combustflame.2018.12.022
M3 - Article
AN - SCOPUS:85059269688
VL - 201
SP - 160
EP - 169
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
ER -