Detailed and simplified chemical kinetics of aviation fuels and surrogates

Abstract

The chemistries of aviation fuels are invariably complex due to large hydrocarbon molecules. There are also large variations for a given fuel type. Furthermore, flow timescales encountered in high performance propulsion devices increasingly lead to difficulties associated with kinetically controlled or influenced phenomena such as flame stability, extinction and re-light. Current indications also suggest that fuel sources will become significantly more diverse in the future and may, for example, encompass Fischer-Tropsch and/or bio-derived components. The combustion properties of such fuels can vary significantly from those in current use and this work outlines a route towards surrogate fuel mechanisms of sufficient accuracy and generality to support the development of practical devices. A reaction class based route to the derivation of detailed chemical kinetic mechanisms for alkyl-substituted aromatics is outlined and applied to the cyclopentadiene/indene, benzene/naphthalene, toluene/1-methyl naphthalene systems. Work has also been extended to the n-propyl benzene system as well. These reaction classes were applied to model the oxidation of the above fuels with encouraging results. Important reaction channels during oxidation were identified and specifically, the methyl groups on aromatic rings have been identified as important in the context of radical scavenging. Furthermore, 1-methyl naphthalene may also be used to modulate sooting tendencies in aviation and Diesel surrogates. Results obtained from chemical kinetic modelling of cyclopentadiene, toluene, npropyl benzene, naphthalene and 1-methyl naphthalene oxidation in shock tubes, jet-stirred and plug-flow reactors at various sets of representative stoichiometries and temperatures are reported.