Impact of fuel composition on emissions and performance of GTL kerosene blends in a Cessna Citation II

International jet fuel specifications permit up to 50% volume Fischer-Tropsch synthetic paraffinic kerosines (FT-SPKs), such as Gas-to-Liquids (GTL) Kerosine, in Jet A-1. Higher SPK-content fuels could, however, produce desirable fuels: lower density, higher SPK-content fuels may have benefits for Payload range (P/R) performance and their chemistry should improve many engine emissions. Two sets of GTL-containing Jet A-1s, with 0-50% GTL, have been tested both in the laboratory and in a Cessna Citation II, with Pratt & Whitney Canada JT15D-4 turbofan engines. Smoke Point and lower heating values (LHVs) confirm previous work that showed GTL improving performances to above and/or beyond typical Jet A-1 levels. Smoke points are sensitive to the type of aromatics in the fuel while LHVs are more affected by the total aromatics levels. Ground tests (with performance, post test inspections and emissions measurements) have been run. Specifically, one engine has been run according to ICAO power settings with the addition of cruise settings, and probes behind the engine have captured gaseous and particulate emissions. Under all conditions, fuel flow rates are lower than expected; under cruise conditions there is about a 5% reduction for 50% blends. Filters that remove particulates in gaseous emissions lines clearly indicate a progressive improvement with increasing GTL/decreasing total aromatics content. At all engine settings, the particle diameter, emission index in terms of particle number and emission index in terms of particle mass all decrease significantly with GTL content. For gaseous emissions, emissions indices for SO2, NO, NO2, NOx (NO+NO2) and CO have been tracked for each engine setting. SO2 reductions are seen clearly for the higher sulphur base fuel blends, consistent with the reduction in fuel sulphur content. There is a very small reduction of NOx at higher power settings and a 5-10% reduction on CO emissions for 50% GTL at most engine conditions