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Combustion of Nanoaluminum and Water Propellants: Effect of Equivalence Ratio and Safety/Aging Characterization
Author(s) -
Sippel Travis R.,
Pourpoint Timothée L.,
Son Steven F.
Publication year - 2013
Publication title -
propellants, explosives, pyrotechnics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.56
H-Index - 65
eISSN - 1521-4087
pISSN - 0721-3115
DOI - 10.1002/prep.201200143
Subject(s) - propellant , combustion , ignition system , deflagration , materials science , analytical chemistry (journal) , equivalence ratio , particle size , composite material , chemistry , thermodynamics , detonation , chromatography , explosive material , organic chemistry , physics , combustor
The deflagration and combustion efficiency of 80 nm aluminum/ice (ALICE) mixtures with equivalence ratios of ϕ =1.0, 0.75, and 0.67 were experimentally investigated. We find that pressure exponent and burning rate vary little between these three mixtures, with the exponent varying only from 0.42 to 0.50 and burning rate at 6.9 MPa varying from 2.05 to 2.10 cm s −1 . However, reducing the equivalence ratio from 1.0 to 0.67 surprisingly increases combustion efficiency from 70 % to 95 % with unburned aluminum agglomerates visible in electron microscopy photographs of 70 % combustion efficiency ( ϕ =1.0) products. Our findings suggest that nanoaluminum/water combustion is diffusionally limited for all conditions considered. Aging tests on the propellant show that storage at −30 °C essentially stops the Al/H 2 O reaction such that little nanoaluminum degradation occurs after 200 days. Electrostatic discharge (ESD), shock initiation, and impact sensitivity tests indicate that the propellant is insensitive to ignition by these stimuli. Specifically, while neat nanoaluminum powders are highly ESD sensitive (ignition threshold 0.3–14 mJ), nAl/H 2 O mixtures are insensitive to ESD and have ignition thresholds in excess of 400 mJ. Likewise, nAl/H 2 O mixtures are insensitive to impact ignition, having an ignition threshold in excess of 2.2 m. Propellants containing 80 nm or larger average particle size aluminum were also found to be insensitive to shock initiation.