Champagne V.K.,U.S. Army |
Helfritch D.J.,Dynamic Science Inc. |
Dinavahi S.P.G.,Lockheed Martin |
Leyman P.F.,Data Matrix Solutions , Inc.
Journal of Thermal Spray Technology
In an effort to corroborate theoretical and experimental techniques used for cold spray particle velocity analysis, two theoretical and one experimental methods were used to analyze the operation of a nozzle accelerating aluminum particles in nitrogen gas. Two-dimensional (2D) axi-symmetric computations of the flow through the nozzle were performed using the Reynolds averaged Navier-Stokes code in a computational fluid dynamics platform. 1D, isentropic, gas-dynamic equations were solved for the same nozzle geometry and initial conditions. Finally, the velocities of particles exiting a nozzle of the same geometry and operated at the same initial conditions were measured by a dual-slit velocimeter. Exit plume particle velocities as determined by the three methods compared reasonably well, and differences could be attributed to frictional and particle distribution effects. © 2010 ASM International. Source
Kellogg F.R.,Data Matrix Solutions , Inc. |
Klotz B.R.,Dynamic Science Inc. |
Nersisyan H.H.,Chungnam National University |
Cho K.C.,U.S. Army
Proceedings of the 8th International Conference on Tungsten, Refractory and Hardmaterials
Salt-assisted combustion synthesis has been used to produce tungsten nanopowders. Tungsten trioxide, zinc, and sodium chloride were dry mixed and heated under argon to promote a combustion reaction. Reaction products were then treated with acid and subjected to hydrogen heat treatment. Samples of the tungsten powders produced were then characterized to determine particle size and purity. Nano-sized particles clustered in larger agglomerates were observed, and samples of the powder produced under different conditions were found to contain varying levels of oxygen. Plasma Pressure Compaction (P2C) was then used to consolidate the powders, and density and grain size of the resulting samples were measured. Bulk samples with nano-sized grains were able to be produced, but high density was not achieved. However, use of tungsten nano powders resulted in consolidated samples with higher density than those achieved with conventional sub-micron tungsten powders under similar processing conditions. Source
Silton S.,U.S. Army |
Howell B.,Data Matrix Solutions , Inc.
26th International Symposium on BALLISTICS
Standard M855 tests shows yaw growth beginning at 400-m, ultimately growing to 4.5 degrees at 600-m. Stability analysis with simulated spin rates can reduce the yaw limit cycle of the M855 by approximately 0.5 degrees. Previous full range shots for M855 do not show evidence of a yaw limit cycle until 600-m. PRODAS simulations of the M855 do not show evidence of a trim angle at 600-m. Gyroscopic and dynamic stability analysis of the M193 show yaw limit cycle is present at 600-m for muzzle spin and adjusted spin cases. Matched spin experiment for the M193 is gyroscopically and dynamically stable at all Mach numbers tested. Source
Rogers J.,Georgia Institute of Technology |
Costello M.,Georgia Institute of Technology |
Harkins T.,U.S. Army |
Hamaoui M.,Data Matrix Solutions , Inc.
Navigation, Journal of the Institute of Navigation
The use of magnetometers for orientation estimation on rapidly-spinning flight bodies is analyzed. Specifically, the effect of spin-induced magnetic field distortion is discussed, with particular attention to its implications for magnetometer-based orientation estimation. First, the nature of spin-induced field distortion is described and it is shown that, if not properly accounted for, distortion can lead to significant estimation errors in artillery projectiles. Then, an orientation estimator is constructed driven by magnetometer, gyroscope, and GPS feedback. A novel feature of this algorithm is its compensation for spin-induced distortion of the Earth's field. The algorithm also incorporates in-flight magnetometer calibration performed simultaneously with projectile orientation estimation. The comprehensive algorithm is built as a coupled set of Extended Kalman filters. Observability of the estimation problem is discussed and unobservable modes are identified. Finally, example results and Monte Carlo simulations compare estimation performance to algorithms which neglect spin-induced distortion effects or do not perform in-flight calibration. These results demonstrate that magnetometer-based systems on-board spinning projectiles should incorporate corrections for field distortion, and that overall accuracy is greatly enhanced by performing in-flight calibration. Source
Levine F.,Data Matrix Solutions , Inc. |
Kayea Iii R.V.,Oak Ridge Institute for Science and Education |
Wexler R.,Oak Ridge Institute for Science and Education |
Sadvary D.J.,Oak Ridge Institute for Science and Education |
And 2 more authors.
JAOCS, Journal of the American Oil Chemists' Society
The military uses JP-8, a kerosene type hydrocarbon, to fuel most of its vehicles and is seeking a renewable alternative fuel that meets strict JP-8 specifications. Biodiesel is typically a mixture of different alkyl esters produced from the transesterification of triglycerides readily available in plant oils and used cooking oil. To date, no traditional biodiesel meets the requirements for heat of combustion, freezing point, viscosity and oxidative stability to be a stand-alone replacement for JP-8. This work is a fundamental survey of the heat of combustion of single fatty acid esters and a predictive model for estimating the heat of combustion given a known molecular structure. The gross heat of combustion of various C6-C18 fatty acids and the methyl, propyl and isopropyl esters of these fatty acids was measured. This study sought to relate the effect of chain length, degree of unsaturation and branching to the critical fuel property of the gross heat of combustion (H c). It was found that H c (kJ/g) increased with chain length. A nearly linear relationship was found between wt% carbon and hydrogen, and H c. Group contribution models previously published for hydrocarbons and polymers were modified to more accurately predict the heat of combustion of the fatty acids and esters. Modification of the molar heat values of carboxylic acid, methyl, and methylene groups improved correlation of the model with the experimental results. © 2013 AOCS. Source