A Study of Conventional Fuels for Unconventional Applications

Natural gas (NG) oxidation was studied in a single pulse shock tube at very high pressures (~60 atm and ~240 atm) and with C0-C3 species measured over a temperature range of 1100 K – 1800 K using gas chromatography. The experiments were conducted at different equivalence ratios (φ ~ 0.5 - 3.0) for a reference NG sample. The reference NG experiments showed an unexpected rise in ethane concentration over the temperature range of 1150 – 1300 K, instead of consumption. This phenomenon was observed at lean conditions for the reference natural gas samples. Real NG samples with different compositions sourced from across the United States were studied at stoichiometric conditions. The speciation results for the NG sample experiments showed significant differences as the composition changed suggesting that NG oxidation is sensitive to the composition variation. In addition to the variation, the rise in ethane concentration observed for the reference natural gas was also present for natural gas samples having methane concentration above 95 % by mole. All the experimental data were compared to simulations from four well known chemical kinetic mechanisms and no perfect mechanism was found. The simulations for experiments at ~240 atm were repeated using the changing pressure approach to account for the pressure variation in the experiments. Additionally, since diesel engines will eventually be fueled by both conventional diesel fuels and also by conventional and unconventional jet fuels, the hydrocarbon composition of 11 different jet fuels was obtained from two dimensional gas chromatography coupled with time of flight mass spectrometry and flame ionization detector (GCxGC-TOF-MS/FID) analysis. The molecular weight, carbon and hydrogen content along with the average molecular formula for the 11 jet fuels were estimated and found to be in agreement with the literature. A new tool, S2FG, was developed to convert the hydrocarbon composition of the fuels and mixtures into their functional group composition. The functional group composition of all the fuels analyzed was obtained using S2FG and compared. The functional group composition of the fuels will be useful in development of predictive models for fuel property prediction and surrogate composition selection.