AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Chemical Characterization of Aircraft Engine Soot from JP-8, Fischer-Tropsch and Alternative Fuel Surrogates by Micro-FTIR Spectroscopy
JEREMY CAIN, Alexander Laskin, Edwin Corporan, David Blunck, Paul Gassman, William Roquemore, Air Force Research Laboratory/Propulsion Directorate
Abstract Number: 406 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Aircraft are the major source of black carbon in the upper troposphere and lower stratosphere. These non-refractory particles impact the Earth’s climate and atmospheric environment through absorption of solar radiation and modification of cloud forming processes. As alternative fuels are explored to supplement the current jet fuel feedstock, it is important to assess the environmental impact of particulate matter (PM) emissions relevant to these fuels. PM emissions from an Allison T63-A-700 turboshaft engine are chemically characterized in this work. Six fuels were tested: a JP-8, Fischer-Tropsch (F-T) and four alternative fuel surrogates (n-dodecane blends). Soot samples were deposited on silicon frame windows inside an inertial cascade impactor and subsequently analyzed by micro-FTIR spectroscopy. The chemical group functionalities present in the PM samples, i.e., aliphatic C-H, acetylene C-H, C-O and C=O, were quantified. Results show similar ordering of the relative (to aromatic C-H) functionalities for JP-8 and the F-T fuel spanning the particle size and engine power ranges: aliphatic C-H (0.3-7.0) ≈ C-O (0.2-5.0) > acetylene C-H (0.07-0.7) > C=O (0.01-1.0). This trend was slightly different for the alternative fuel surrogates: [aliphatic C-H] > [C-O] > [C=O] > [acetylene C-H]. No trends in engine power or particle size were consistently observed with the relative abundances of these groups for all fuels tested. However, relative concentrations of most functionalities increased with particle size and engine power. Comparisons of particle emission rate and composition of soot from JP-8 and F-T fuels suggest that the F-T fuel might have less environmental impact, primarily due to lower emission rates. However, spectroscopy results reveal that both JP-8 and F-T produced soot particles may have ample aliphatic hydrocarbon bonds to serve as surface sites for heterogeneous reactions at cruise altitudes.