We have performed a comprehensive test of the effects of alternative fuels on the trace gas, nonvolatile particulate material (PM), and volatile PM emissions performance of a PW308 aircraft engine. The tests evaluated standard JP-8 jet fuel, a "zero sulfur" and "zero aromatic" synthetic fuel produced from a natural gas feedstock using the Fischer-Tropsch (FT) process, and a 50/50 blend of the FT fuel and JP-8. A Pratt & Whitney PW308 engine was operated under the same thrust and combustion conditions to ensure that the tests captured fuel differences, rather than engine operation differences. Emissions of trace gases, soot particles, and nucleation/growth PM were directly impacted by the sulfur and aromatic content of the fuel. FT fuel combustion greatly reduced SO 2 (>90%), gaseous hydrocarbons (40%), and NO (6-11%) content compared to JP-8 combustion. In general, combustion of the JP-8/FT fuel blend resulted in emissions intermediate to the FT and JP-8 values. FT combustion dramatically reduces soot particle number, mass, and size relative to JP-8, but increases effective soot particle density. In all cases, the drag behavior of the soot particles indicates deviations from spherical shape and effective soot particle densities are consistent with the soot particles being aggregates of primary spherules. As expected, FT combustion plumes support negligible formation of nucleation/growth mode particles (the number of nucleation growth mode particles is <20% the number of soot particles compared to >500% for sulfur containing JP-8). However, particle nucleation/growth for blended fuel combustion is enhanced relative to JP-8, despite the lower sulfur content of the FT/JP-8 fuel blend. A computational model explains the unexpected particle formation result primarily as the effect of much lower soot emissions present in blended fuel combustion exhaust compared to JP-8. Fuel composition, specifically aromatic and sulfur content, affect all aspects of emissions performance and the effect of simultaneously reducing aromatic and sulfur content can lead to surprising behavior.

No abstract

We report evidence that carbon impregnated conductive silicone tubing used in aerosol sampling systems can introduce two types of experimental artifacts: (1) silicon tubing dynamically absorbs carbon dioxide gas, requiring greater than 5 minutes to reach equilibrium and (2) silicone tubing emits organic contaminants containing siloxane that are adsorbed onto particles traveling through it and onto downstream quartz fiber filters. The consequence can be substantial for engine exhaust measurements as both artifacts directly impact calculations of particulate massbased emission indices. The emission of contaminants from the silicone tubing can result in overestimation of organic particle mass concentrations based on real-time aerosol mass spectrometry and the off-line thermal analysis of quartz filters. The adsorption of siloxane contaminants can affect the surface properties of aerosol particles; we observed a marked reduction in the water-affinity • C) or pre-exposure to a solvent (methanol). Further evaluation is warranted to quantify systematically how the contamination responds to variations in system temperature, physicochemical particle properties, exposure to solvent, sample contact time, tubing age, and sample flow rates.

The Aircraft Alternative Fuels Emissions experiment (AAFEX) was conducted at National Aeronautic and Space Administration (NASA) Dryden Flight Research Center (DFRC) Aircraft Operations Facility (DAOF) in Palmdale, California, during January and February 2009. The purpose was to systematically investigate the effect of alternative fuels on both gas-phase and particle emissions from a CFM56-2C1 engine on NASA’s DC-8 aircraft parked on the ground as functions of engine power, fuel composition, and exhaust plume age. Emissions parameters were measured at 6 engine power settings, ranging from idle to maximum thrust, in samples collected at 1, 30, and 145 meters (m) downstream of the exhaust plane as the aircraft burned three pure fuels and two fuel blends. The fuels included JP-8, two fuels produced using the Fischer-Tropsch process and 50/50 blends by volume of the F-T fuels with JP-8. The 1 m sampling rakes contained multiple gas and particle inlet probes and could also be traversed in order to measure the spatial variation of emissions across the engine exhaust plane. The #2 inboard engine on the left side always burned JP-8 while the #3 inboard right side engine was fueled with the various fuels and fuel blends. In addition, emissions from the Auxiliary Power Unit (APU) were also evaluated with both JP-8 and one pure F-T fuel. Both gaseous and particulate emissions are presented. Results show that the synthetic fuels reduced pollutant emissions while having relatively little effect on engine operation or performance.

Lubrication oil was identified in the organic particulate matter (PM) emissions of engine exhaust plumes from in-service commercial aircraft at Chicago Midway Airport (MDW) and O'Hare International Airport (ORD). This is the first field study focused on aircraft lubrication oil emissions, and all of the observed plumes described in this work were due to near-idle engine operations. The identification was carried out with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF AMS) via a collaborative laboratory and field investigation. A characteristic mass marker of lubrication oil, I(85)/I(71), the ratio of ion fragment intensity between m/z = 85 and 71, was used to distinguish lubrication oil from jet engine combustion products. This AMS marker was based on ion fragmentation patterns measured using electron impact ionization for two brands of widely used lubrication oil in a laboratory study. The AMS measurements of exhaust plumes from commercial aircraft in this airport field study reveal that lubrication oil is commonly present in organic PM emissions that are associated with emitted soot particles, unlike the purely oil droplets observed at the lubrication system vent. The characteristic oil marker, I(85)/I(71), was applied to quantitatively determine the contribution from lubrication oil in measured aircraft plumes, which ranges from 5% to 100%.