Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Sonar & Radar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Influence of Aluminum Passivation on the Reaction Mechanism: Flame Propagation Studies

Abstract: Currently, two main known mechanisms of aluminum (Al) nanoparticle reaction are discussed in the literature, namely those based on diffusion through an oxide shell and melt-dispersion. The two mechanisms lead to opposite predictions in nanoparticle design. The diffusion mechanism suggests that the reduction or complete elimination of the oxide shell will increase Al reactivity, whereas the meltdispersionmechanismsuggestsanincreaseininitialoxidethicknessuptoanoptimalvalue.Thegoalofthis study is to perform critical experiments in a confined flame tube apparatus to compare these two predictions. Specifically, the flame propagation rates of perfluoroalkyl carboxylic acid (C13F27COOH)treatedAlnanoparticleswithandwithoutanaluminashellweremeasured.Resultsshowthatwhenthereis no alumina passivation shell encasing the Al core, the flame rate decreases by a factor of 22-95 and peak pressure deceases by 3 orders of magnitude, in comparison with the Al particles with an oxide shell. These results imply that the melt-dispersion reaction mechanism is responsible for high flame propagation rates observed in these confined tube experiments.

Magnetostriction of Stress-annealed Fe-Ga and Fe-Ga-Al Alloys under Compressive and Tensile Stress:

Abstract: The addition of Al and Ga to b.c.c. Fe increases the magnetostriction of Fe in the [100] direction (a factor of 12 for Fe81Ga19). The Fe-based magnetostrictive materials are machineable, mechanically tough, and saturate in fields of only a few hundred Oersteds, even under compressive loads up to 97 MPa. The effect of annealing single crystal Fe86.9Ga4.1Al9.0 and Fe86.9Ga8.7Al4.4 and polycrystalline Fe81.6Ga18.4 rods under compressive stress of 100MPa for 10 min at temperatures between 625 and 750 C were examined. After annealing, all samples showed nearly full performance at near-zero stresses and tensile stresses up to 20 MPa, allowing tough wide-bandwidth magnetomechanical devices.

Maintenance of chaos in a computational model of a thermal pulse combustor.

Abstract: The dynamics of a thermal pulse combustor model are examined It is found that, as a parameter related to the fuel flow rate is varied, the combustor will undergo a transition from periodic pulsing to chaotic pulsing to a chaotic transient leading to flameout Results from the numerical model are compared to those obtained from a laboratory-scale thermal pulse combustor Finally the technique of maintenance (or anticontrol) of chaos is successfully applied to the model, with the result that the operation of the combustor can be continued well into the flameout regime