No abstract

Tonghun, "Ignition behavior and surrogate modeling of JP-8 and of camelina and tallow hydrotreated renewable jet fuels at low temperatures" (2012 b s t r a c tThe autoignition characteristics of the conventional jet fuel, JP-8, and the alternative jet fuels, camelina and tallow hydrotreated renewable jet (HRJ) fuels, are investigated using a rapid compression machine and the direct test chamber charge preparation approach. Ignition delay measurements are made at low compressed temperatures (625 K 6 T c 6 730 K), compressed pressures of p c = 5, 10, and 20 bar, and equivalence ratios of / = 0.25, 0.5 and 1.0 in air. The HRJ fuels ignite more readily than JP-8 for all tested conditions, consistent with derived cetane number data in the literature. The camelina and tallow HRJ fuels exhibit similar autoignition characteristics, but the two fuels can be distinguished under stoichiometric conditions. Kinetic modeling is conducted with a 2-component surrogate (10% n-dodecane/90% 2-methylundecane) and a single component surrogate (2-methylnonane) to evaluate the potential to predict ignition behavior of the HRJ fuels. Modeling results indicate that the surrogate fuels can only provide useful predictions at a limited set of conditions (p c = 5 bar and / = 1.0), and that the agreement of the model and experimental data improves with decreasing compressed pressure. Under most conditions, the 2-component surrogate provides better prediction of ignition behavior, but the single component surrogate is superior at low pressures near the negative temperature coefficient region.

No abstract

The autoignition characteristics of military aviation fuels (JP-5 and JP-8), proposed camelina-derived hydroprocessed renewable jet fuel replacements (HRJ-8 and HRJ-5), Fischer-Tropsch fuels (Shell and Sasol), three Sasol isoparaffinic solvents, as well as 50/50 volumetric blends of the alternative fuels with the conventional fuels are examined. Experiments were conducted in a rapid compression machine and shock tube at compressed temperatures of 625 K 6 T c 6 1000 K, a compressed pressure of 20 bar, and under stoichiometric and lean conditions. Several implicit properties of the alternative fuels prompted a study of the influence of chemical composition on autoignition, including the influence of isoparaffinic, cycloparaffinic, and aromatic structures. In addition, interesting combustion phenomena at low-temperature conditions are investigated under lean conditions, specifically concerning jet fuel blend reactivity, where a convergence in blend reactivity to the reactivity of either a conventional or alternative fuel is observed.

A heated rapid compression machine has been used to investigate the autoignition behavior of JP-5 and camelina-based hydrotreated renewable jet (HRJ-5) fuels. Testing was conducted at low temperatures (T c = 627–733 K), low-to-moderate pressures (p c = 5, 10, and 20 bar), and lean (ϕ = 0.25 and 0.50) and stoichiometric mixtures in air. The HRJ-5 fuel, which is 99% paraffinic, exhibited greater reactivity than the JP-5 fuel in the form of shorter ignition delays. The HRJ-5 fuel also exhibited transition into the negative temperature coefficient region at a lower compressed temperature (T c = 675 K) than the JP-5 fuel (T c = 700 K). Two surrogate fuel blends and kinetic models intended for Jet-A and kerosene-type fuels are evaluated for their ability to predict JP-5 ignition delay times because JP-5 and Jet-A ignition delay times showed close resemblance. The models reproduced the qualitative trend in the data, including an accurate representation of when the negative temperature coefficient behavior appears. The best agreement between the data and predictions was obtained at p c = 5 bar and ϕ = 1.0, but outside of this region, the disparity was often 2-fold or greater.