Oxidation of a Coal-to-Liquid Synthetic Jet Fuel: Experimental and Chemical Kinetic Modeling Study

The kinetics of oxidation of a Coal-to-Liquid (CtL) Fully
Synthetic
Jet Fuel (FSJF) was studied using three complementary experiments
operating over a wide range of conditions: a jet stirred reactor (p = 10 bar), constant mean residence time of 1 s, over the
temperature range 570–1070 K, and for equivalence ratios φ
= 0.5, 1.0, and 2.0; a shock-tube (p ∼ 16
bar, temperature range between 900 and 1400 K, φ = 0.5 and φ
= 1), and a conical flame burner (preheat temperature T0 = 473 K, and for two pressure regimes, p = 1 bar for equivalence ratios ranging from 0.95 to 1.4, and p = 3 bar for equivalence ratios ranging from 0.95 to 1.3).
Concentration profiles of reactants, stable intermediates, and final
products in the jet stirred reactor were obtained by probe sampling
followed by online and off-line gas chromatography analyses and online
Fourier transform infrared spectrometry. Ignition delay times were
determined behind reflected shock waves by measuring time-dependent
CH* emission at 431 nm. Flame speeds were determined by applying the
cone angle method. Comparison with corresponding results for Jet A-1
was performed showing similar combustion properties. The oxidation
of the CtL-fuel under these conditions was modeled using a detailed
kinetic reaction mechanism consisting of 8217 reactions and 2185 species
and a 4-component surrogate fuel mixture (n-decane, iso-octane, n-propylcyclohexane, and n-propylbenzene). A reasonable representation of the kinetics
of oxidation of this FSJF was obtained. The model showed good agreement
with concentration profiles measured in a jet stirred reactor at 10
bar over a range of temperatures (550–1150 K) and equivalence
ratios (0.5–2). Acceptable agreement between measured and predicted
ignition delay times was found for the investigated fuel air mixtures,
with significantly longer ignition delay times predicted. Also, the
ignition behavior of the surrogate is mainly influenced by the n-alkane and not by the addition of iso-alkanes, naphthenes, and aromatics. In general, a reasonable agreement
between predicted and measured burning velocity data exists, with
larger deviations at higher pressure. No deviation is to be seen between
burning velocity data for Jet A-1 and CtL, within the uncertainty
range. Within the parameter range studied, the measured data of burning
velocity and ignition delay time agree with data obtained earlier
for petrol-derived kerosene. Our findings support the potential of
the CtL investigated to serve as an alternative aviation fuel.