Autoignition behavior of synthetic alternative jet fuels: An examination of chemical composition effects on ignition delays at low to intermediate temperatures

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 review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines

“…Low-temperature ignition studies show that HRJ fuels ignite more readily than the Jet A fuels due to their higher cetane numbers [308,328], and higher levels of branching in the fuel lead to reduced low-temperature reactivity as does inclusion of cycloalkanes [329]. Under high-temperature ignition conditions, FT fuels collapse onto results for Jet A [328,330], consistent with the observed lack of sensitivity of high-temperature ignition of long-chain alkanes to the hydrocarbon chain length [239,331] and the collapse of the high-temperature flame speeds [307,[315][316][317][318][319][320][321].…”

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

“…Meanwhile, jet fuels can more easily decompose/oxidize during the compression stroke, before the desired test conditions are reached, and this is especially true if the t50 of the machine is longer than 4 to 5 ms. As such, the 'compression' limit identified in Fig. 28 is more easily reached so leaner/more dilute mixtures, lower temperature and/or lower pressures must be used to avoid this [31,160,161]. A summary of studies performed on jet fuel and its surrogates is provided in Table 9.…”

“…Gas turbines must balance the propensity for autoignition, flashback and instabilities, whilst still being operable for a variety of fuels, typically natural gas, with a wide range of minor gas compositions (mainly H2 and higher hydrocarbons in methane, as highlighted in Section 6), but also synthesis gases, biogases, and new synthetic and modified liquid fuels and biofuels. Synthetic fuels vary widely in composition and corresponding propensities for autoignition [31], so it is challenging to design premixed or direct injection systems that work well with a wide variety of fuels using a fixed geometry. Fuel chemistry and interactions with the turbulent flows can influence burning rates and important combustor parameters, such as the lean blowout limit [32,33].…”

Theoretical Prediction of the Effect of Blending JP-8 With Syngas on the Ignition Delay Time and Laminar Burning Speed

“…Allen et al [10] compared the ignition delay time of JP-8 with a hydrotreated renewable jet (HRJ) fuel at low temperature by using rapid compression machine and the direct test chamber charge preparation approach and found faster ignition of HRJ fuels than JP-8. Later, Valco et al [11] compared JP-8 and HRJ fuel together with other conventional jet fuels and got the same result. Moghaddas et al [12] measured the laminar burning speed of Jet-A and different types of JP-8 using a constant volume spherical chamber.…”