Synthetic Jet Fuel Combustion: Experimental and Kinetic Modeling Study
Résumé
Fischer-Tropsch liquid fuels synthesized from syngas, also called synthetic paraffinic jet fuel (SPK), can be used to replace conventional petroleum-derived fuels in jet engines. Whereas currently syngas is mostly produced from coal of natural gas, its production from biomass has been reported. These synthetic liquid fuels contain a very high fraction of iso-alkanes, while conventional jet fuels contain large fractions of n-alkanes, cycloalkanes (naphtenes), and aromatics. In that contest, a jet-stirred reactor (JSR) was used to study the kinetics of oxidation of a 100% SPK and a 50/50 SPK/Jet A-1mixture over a broad range of experimental conditions (10 atm, 560 to 1030K, equivalence ratios of 0.5 to 2, 1000 ppm of fuel). The temperature was varied step-wise, keeping the mean residence time in the JSR constant and equal to 1s. Three combustion regimes were observed over this temperature range: the cool-flame oxidation regime (560-740K), the negative temperature coefficient (NTC) regime (660-740K), and the high-temperature oxidation regime (>740K). More than 15 species were identified and measured by Fourier transform infrared spectrometry (FTIR), gas chromatography/ mass spectrometry (CG/MS), flame ionization detection (FID), and thermal conductivity detection (TCD). The results consisting of concentration profiles of reactants, stable intermediates and products as a function of temperature showed similar kinetics of oxidation for the fuels considered, although the 100% SPK was more reactive. A surrogate detailed chemical kinetic reaction mechanism was used to model these experiments and ignition experiments taken from the literature. The kinetic modeling showed reasonable agreement between the data and the computations whereas model improvements could be achieved using more appropriate surrogate model fuels. Kinetic computations involving reaction paths analyses and sensitivity analyses were used to interpret the results.