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Research Papers: Combustion and Reactive Flows

Enhanced Convective Heat Transfer in Nongas Generating Nanoparticle Thermites

[+] Author and Article Information
S. W. Dean, S. C. Stacy

Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79401

M. L. Pantoya1

Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79401michelle.pantoya@ttu.edu

A. E. Gash

 Lawrence Livermore National Laboratory, Livermore, CA 94550

L. J. Hope-Weeks

Department of Chemistry, Texas Tech University, Lubbock, TX 79401

1

Corresponding author.

J. Heat Transfer 132(11), 111201 (Aug 10, 2010) (7 pages) doi:10.1115/1.4001933 History: Received March 03, 2009; Revised March 26, 2010; Published August 10, 2010; Online August 10, 2010

Flame propagation and peak pressure measurements were taken of two nanoscaled thermites using aluminum (Al) fuel and copper oxide (CuO) or nickel oxide (NiO) oxidizers in a confined flame tube apparatus. Thermal equilibrium simulations predict that the Al+CuO reaction exhibits high gas generation and, thus, high convective flame propagation rates while the Al+NiO reaction produces little to no gas and, therefore, should exhibit much lower flame propagation rates. Results show flame propagation rates ranged between 200 m/s and 600 m/s and peak pressures ranged between 1.7 MPa and 3.7 MPa for both composites. These results were significantly higher than expected for the Al+NiO, which generates virtually no gas. For nanometric Al particles, oxidation has recently been described by a melt-dispersion oxidation mechanism that involves a dispersion of high velocity alumina shell fragments and molten Al droplets that promote a pressure build-up by inducing a bulk movement of fluid. This mechanism unique to nanoparticle reaction may promote convection without the need for additional gas generation.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

REAL code thermochemical simulation for Al+CuO and Al+NiO

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Figure 2

SEM of (a) Al+CuO reactant composite and (b) Al+NiO reactant composite

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Figure 3

Schematic showing high speed camera and data acquisition systems

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Figure 4

Still frame images from an Al+CuO test

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Figure 5

Flame propagation results for Al+CuO and Al+NiO composites

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Figure 6

Peak pressure results for Al+CuO and Al+NiO composites

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Figure 7

Heat flow and mass loss curves from the DSC/TGA for Al+NiO at an equivalence ratio of 1.6

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Figure 8

Heat flow and mass loss curves from the DSC/TGA for Al+CuO at an equivalence ratio of 1.6

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Figure 9

XRD graph of intensity versus 2θ for the sol-gel synthesized NiO powder

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Figure 10

Schematic of combustion regimes

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