Emissions were measured for four fuels and six combinations of fuels and additives in the exhaust of a T700-GE-700 helicopter engine. The test matrix consisted of three engine power settings: idle, continuous, and maximum continuous. The four fuels were JP-5, F-76, and two synthesized fuels from the Fischer-Troph process, one containing zero sulfur and zero aromatics (synthetic A), and a second containing zero sulfur and 14 vol% aromatics (synthetic B). The JP-5 was also tested with a solvent that increased the aromatic content, and seeded with copper to simulate contamination from shipboard fuel-distribution systems. The JP-5 and F-76 were also tested with an additive commonly used to increase thermal stability. Carbon-monoxide (CO) emission-indices (EIs) for the JP-5 ranged from 53.4 g/kg at idle to 2.3 g/kg at maximum power. The EI of total hydrocarbons (THCs) ranged from 3.9 g/kg to 0.13 g/kg over the same power settings. The effect of the various fuels and additives on the emissions of CO and THCs was negligible (at the 95% confidence level), except at maximum power where CO from the F-76 was about 25% higher, and from the first synthetic, about 16% lower than the JP-5. At all power settings, the CO for JP-5 with the thermal-stabilizer additive were consistently lower by about 12%. Particulate matter was measured and displayed nearly log-normal distributions with a single-mode for all fuels tested. In all cases, count median-diameters (CMDs) ranged from about 20 to 60 nm, and increased with power setting. Mass emissions also increased with power setting. On a number basis, emissions ranged from 1.6 × 1013 to 1.7 × 1015 particles/kg, and increased with power setting for most of the fuels and fuel-additive combinations. The CMD and mass emissions for the JP-5 ranged from 30 to 50 nm and 0.06 to 0.49 g/kg from idle to maximum power. The F-76 produced the largest CMDs and highest particle mass at all conditions, with a CMD of 60 nm and mass emissions of 0.77g/kg occurring at maximum power. Synthetic A fuel produced the smallest particle CMDs and lowest particle mass at all power settings. The thermal-stability additive and variations in aromatic content, and copper particles, did not significantly affect the particle emissions. Particle mass measured with a filter-gravimetric method correlated well with the particle volume calculated from the measured number size-distributions, where the correlation yielded a particle density of 1000 kg/m3.

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