2009 Annual Report - NASA Airborne Science Program

mass; black carbon morphology, composition and
total mass; volatile aerosol speciation and mass; and
particle mixing state. In addition to NASA, test
participants included DOD, FAA, EPA, Boeing,
General Electric, Pratt & Whitney, Carnegie Mellon
University, Harvard, MSU, UCSD, and UTRC.
During AAFEX, the aircraft was parked outdoors
in the DAOF open-air engine run-up facility
and complete sets of gas and particle emission
measurements were made as a function of thrust
as the engine alternately burned JP-8 or one of the
alternative fuels. Two fuels were procured for the
tests: a Fischer/Tropsch (FT) fuel prepared from
natural gas and an FT fuel made from coal. The
test series consisted of five fuel configurations: (1)
Standard JP-8, (2) Shell Fischer-Tropsch fuel from
natural gas (FT1), (3) 50/50 JP-8/FT1 blend, (4)
Sasol Fischer-Tropsch fuel from coal (FT2) and, (5)
50/50 JP-8/FT2 blend.
To delineate fuel-matrix related changes in emissions
from those caused by changes in ambient conditions,
samples were alternately drawn from the exhaust
of an engine on the opposite wing, which was
simultaneously burning JP-8. To examine plume
chemistry and particle evolution in time, samples
were drawn from inlet probes positioned 1, and 30
m downstream of the aircraft’s inboard engines;
instruments were also placed in a trailer parked
~200 meters behind the aircraft to measure aerosol
and gaseous properties in the more aged plume.
In addition, the 1 m rake included multiple gas
and aerosol inlet tips so that during initial tests,
emissions could be mapped across the breadth of
the engine exhaust plane to establish the extent of
the core-flow region within the near-field plume.
Taking advantage of the broad diurnal variation in
air temperature in the Mojave Desert, tests were
conducted in the early morning and at mid-day to
examine the effect of ambient conditions on gas
phase and volatile aerosol emissions.
Preliminary results have shown that: (1) Alternative
fuels do not affect engine performance but may
cause fuel system seal leaks. (2) Engine black
carbon emissions are substantially reduced when
burning Fischer-Tropsch fuels. (3) The aircraft
engine consumes ambient methane at most power
settings. (4) A great deal was learned regarding the
temperature dependence of engine emissions which
will be used to influence local air quality modeling.
For more information, visit:
http://www.nasa.gov/topics/aeronautics/features/
aafex.html
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