Journal
PROCEEDINGS OF THE COMBUSTION INSTITUTE
Volume 36, Issue 2, Pages 2325-2332Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.proci.2016.06.144
Keywords
Agglomerates; Al nanoparticles; Microexplosion; Melt/vapor dispersion mechanism
Funding
- National Natural Science Foundation of China [51176094, 51206089]
- National Key Basic Research and Development Program [2013CB228506]
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While the nano-sized energetic materials are featured with ultra-high energy density, the ubiquitous agglomeration in their combustion is still unexplored. In this paper, the combustion characteristics of aluminum nanoparticle agglomerates in the size range of 4-20 mu m are investigated on a modified Hencken burner with different temperature (800-1800 K) and oxygen concentration (0.5-5.5 mol/m(3)). Due to the heat accumulation effect of the designed porous structures, the nanoparticle agglomerates even maintain the advantages of combustion process of single nanoparticle in terms of a low ignition temperature (similar to 800 K) and a fast energy release rate. Further, the combustion of agglomerates is numerically studied by a newly-developed model, which accurately predicts both burn time and temperature of agglomerate of the mild combustion process. The microexplosion phenomenon occurs when the oxygen concentration exceeds 3.5 mol/m(3). Mea-surements of particle temperature, burn time, emission spectra and morphologies indicate that this explosion is driven by the vaporization of unreacted aluminum core, which results in huge stresses to tear the Al/Al2O3 particle into many smaller, dispersed clusters. Thus a melt/vapor dispersion mechanism (MVDM) based on melt dispersion mechanism is proposed to cover the microexplosion and subsequent accelerated oxidation reactions. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.
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