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Title:Optical combustion measurements of novel energetic materials in a heterogeneous shock tube
Author(s):Allen, David
Advisor(s):Glumac, Nick G.; Krier, Herman
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Mechanical Alloys
Optical Combustion Diagnostic
Emission Spectroscopy
Abstract:Metal additives are commonly added to explosives to increase the potential heat release and cause longer blast overpressures. However, the theoretically achievable benefits of the metal additives are not fully realized due to the relatively long ignition delays and slow combustion rates of the system. Mechanically alloyed energetic systems have potential to improve combustion behavior as compared to their pure metal counterparts. The alloys can also be tailored for specific applications by varying the compound constituents. Ti-B and Al-I2 mechanically alloyed compounds are of specific interest due to their potential use in explosives designed for the defeat of biological weaponry. The Ti-B system is a highly energetic compound as energy can be released due to the oxidation of either metal constituent or the intermetallic reaction producing TiB2. It is capable of generating long lasting high temperature fireballs after the initial blast, which is ideal for defeating biological weapons. The Al-I2 system is similarly suited for the defeat of biological weapons due to high combustion temperatures and the addition of iodine which has known biocidal capabilities. This study looks at the behavior of small (10 micron and smaller) particles of Ti-B and Al-I2 mechanical alloys and compares the performance of each to baseline samples of aluminum and titanium boride (TiB2) using a heterogeneous shock tube. The dispersed cloud of individually burning particles is analyzed using photometry, pyrometry, and emission spectroscopy to determine important quantifiable combustion characteristics such as temperature, burning time, ignition delay, and reaction intermediate species. The heterogeneous shock tube is a highly controlled experiment that provides explosive loading conditions during which measurements can be made on small scale samples in well known ambient conditions. This allows the determination of fundamental combustion parameters that cannot be determined in larger scale testing environments where many factors can affect performance. The resulting data provides insight into the combustion mechanisms that can be scaled and used in modeling efforts. The results found that the mechanical alloys showed improved ignition characteristics with respect to the base line test samples. The burning times, temperatures, and intermediate species, previously unknown for the mechanical alloys, were quantified and found to be similar to the baseline cases. The emission spectroscopy provided knowledge of potential key combustion diagnostic species. The pyrometry measurements give insight into the condensed phase temperatures present during the combustion process, and the burning time measurements give valuable spatially resolved high speed imaging of the entire event.
Issue Date:2012-09-18
Rights Information:Copyright 2012 David Allen
Date Available in IDEALS:2012-09-18
Date Deposited:2012-08

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