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Title: Microexplosions and ignition dynamics in engineered aluminum/polymer fuel particles

Journal Article · · Combustion and Flame
 [1];  [1];  [2];  [3];  [4];  [5];  [4];  [1]
  1. Purdue Univ., West Lafayette, IN (United States). School of Mechanical Engineering
  2. South Dakota School of Mines and Technology, Rapid City, SD (United States). Chemical and Biological Engineering
  3. Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering
  4. Purdue Univ., West Lafayette, IN (United States). School of Materials Engineering
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

Aluminum particles are widely used as a metal fuel in solid propellants. However, poor combustion efficiencies and two-phase flow losses result due in part to particle agglomeration. Engineered composite particles of aluminum (Al) with inclusions of polytetrafluoroethylene (PTFE) or low-density polyethylene (LDPE) have been shown to improve ignition and yield smaller agglomerates in solid propellants, recently. Reductions in agglomeration were attributed to internal pressurization and fragmentation (microexplosions) of the composite particles at the propellant surface. We explore the mechanisms responsible for microexplosions in order to better understand the combustion characteristics of composite fuel particles. Single composite particles of Al/PTFE and Al/LDPE with diameters between 100 and 1200 µm are ignited on a substrate to mimic a burning propellant surface in a controlled environment using a CO2 laser in the irradiance range of 78–7700 W/cm2. Furthermore, the effects of particle size, milling time, and inclusion content on the resulting ignition delay, product particle size distributions, and microexplosion tendencies are reported. For example particles with higher PTFE content (30 wt%) had laser flux ignition thresholds as low as 77 W/cm2, exhibiting more burning particle dispersion due to microexplosions compared to the other materials considered. Composite Al/LDPE particles exhibit relatively high ignition thresholds compared to Al/PTFE particles, and microexplosions were observed only with laser fluxes above 5500 W/cm2 due to low LDPE reactivity with Al resulting in negligible particle self-heating. However, results show that microexplosions can occur for Al containing both low and high reactivity inclusions (LDPE and PTFE, respectively) and that polymer inclusions can be used to tailor the ignition threshold. Furthermore, this class of modified metal particles shows significant promise for application in many different energetic materials that use metal fuels.

Research Organization:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1341578
Journal Information:
Combustion and Flame, Vol. 176, Issue C; ISSN 0010-2180
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 34 works
Citation information provided by
Web of Science

References (21)

Nano-aluminum as energetic material for rocket propellants journal September 2007
Metal-based reactive nanomaterials journal April 2009
Correlating Aluminum Burning Times journal September 2005
Experimental data and model predictions of aluminium agglomeration in ammonium perchlorate-based composite propellants including plateau-burning formulations journal January 2013
Ignition of Aluminum Powders Under Different Experimental Conditions journal February 2005
Accumulation of nano-aluminium during combustion of composite solid propellant mixtures journal January 2010
Metal particle combustion and nanotechnology journal January 2009
Microstructure Effects in Aluminized Solid Rocket Propellants journal July 2010
Ignition, combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. I. Theoretical study of the ignition and combustion of aluminum with fluorine-containing coatings journal September 2006
Ignition, combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. II. Experimental studies of agglomeration journal May 2007
Aluminum agglomeration reduction in a composite propellant using tailored Al/PTFE particles journal January 2014
Exploring mechanisms for agglomerate reduction in composite solid propellants with polyethylene inclusion modified aluminum journal March 2015
Laminar Lifted Flame Speed Measurements for Aerosols of Metals and Mechanical Alloys journal July 2004
Altering Reactivity of Aluminum with Selective Inclusion of Polytetrafluoroethylene through Mechanical Activation journal November 2012
Effect of particle size on combustion of aluminum particle dust in air journal January 2009
Heating and Ignition of Metallic Particles by a CO2 Laser journal March 2008
Laser ignition of nanocomposite thermites journal September 2004
Nonuniform laser ignition in energetic materials journal November 2003
Detonation in an aluminum-Teflon mixture journal April 2005
Combustion Behaviors Resulting from Bimodal Aluminum Size Distributions in Thermites journal January 2007
Experimental methodology and heat transfer model for identification of ignition kinetics of powdered fuels journal December 2006

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