Fischer-Tropsch synthetic paraffinic kerosines (FT-SPKs), such as Gas-to- Liquids (GTL) Kerosine, are now accepted as suitable blend components for Jet fuel production, via ASTM D7566. This sets limitations on distillation profiles for the final fuel and neat SPK, and the cycloparaffin content of the neat SPK. SPKs, from FT and other production routes, can be envisaged that would fall outside these limits yet produce perfectly acceptable, even desirable fuels. They are not generally available yet but one can define their compositions in terms of key components (normal paraffins, iso-paraffins and cycloparaffins) and carbon number distributions, derived from 2-dimensional gas chromatography. Surrogate blends approximating to these compositions have been produced with existing FT kerosines and commercial solvents.

The methodology used to blend these surrogate fuels will be presented as well as the results of the first experimental campaign at Rolls-Royce Derby on 5 real and surrogate SPKs in Technology Readiness Level 3 (TRL 3) altitude relight tests, with a baseline crude-derived Jet A-1. SPK choices permitted the impact of several main compositional variables on laboratory and performance measures to be determined from the small fuel set. Standard specification tests and altitude relight tests were performed. Not only were engine/combustor performances assessed but also combustion processes were captured with high speed flame imaging subject to a poster by DLR (Mosbach et al). Laboratory tests showed some sensitivity to SPK composition (e.g. viscosity increasing and lower heating value decreasing with increased cycloparaffin content) but these were less evident with ignition relight test results. All SPKs ignited, suggesting that the distillation criteria could be relaxed from current values. There may be a positive impact of lower iso/normal content on ignition performance, but this needs testing in more advanced (higher TRL) equipment.


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