Overview on the Aircraft Particle Emissions Experiment
Conducted at the NASA Dryden Flight Research Center during April 2004, the Aircraft Particle Emissions Experiment systematically investigated the gas-phase and particle emissions from a CFM56-2C1 engine on NASA's DC-8 aircraft as functions of engine power, fuel composition, and exhaust-plume age. Emissions parameters were measured at 11 engine power settings ranging from idle to maximum thrust, in samples collected 1, 10, and 30 m downstream of the exhaust plane as the aircraft burned three fuels with different aromatic and sulfur contents. The 1- and 10-m sampling rakes contained multiple gas and particle inlet probes to facilitate a study of the spatial variation of emissions across the engine exhaust plane. Gas-phase emission indices measured at 1 m were in good agreement with the engine certification data as well as with predictions provided by the engine company. However, at low power settings, trace-species emissions were observed to be highly dependent on ambient conditions and engine temperature. Nonvolatile particles emitted by the engine exhibited a log-normal size distribution that peaked between 15 and 40 nm, depending on engine power. Samples collected 30 m downstream of the engine exit plane exhibited a prominent nucleation mode, indicating that secondary aerosols composed of sulfuric acid and lowvolatility organic species formed rapidly within the plume as it expanded and cooled. Black carbon emissions were a minimum at approach and a maximum at climb and takeoff engine power settings. Black carbon dominated total mass emissions at high thrust, whereas volatile particles contributed an equal or perhaps greater fraction at low- to midpower settings. Although variations in fuel aromatic content had no discernible impact on particle emissions, volatile particle number and mass concentrations in aged exhaust plumes were highly sensitive to the fuel sulfur content.
C. C. Wey et al., "Overview on the Aircraft Particle Emissions Experiment," Journal of Propulsion and Power, American Institute of Aeronautics and Astronautics (AIAA), Jan 2007.
The definitive version is available at http://dx.doi.org/10.2514/1.26406
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