Aromatic Selection for Surrogate Jet Fuel

The aromatic component of jet fuel is limited to 25% by volume in the current aviation specification for commercial flight. Aromatic hydrocrabons present in petroleum
fuels are acknowledged to contribute to the formation of polycyclic aromatic hydrocarbons (PAH) and subsequently high levels of soot. Non-volatile particulate matter
in the form of soot, or black carbon, contributes significantly to global warming, contrail formation, the degradation of combustion liner walls and has an adverse effect
on human health. There is significant interest in minimising the emission levels
of non-volatile particulate matter and smoke by varying the source and chemical
composition of Jet fuel. While the overall volumetric proportion of aromatics is currently regulated, there is no indication as to the effect of the molecular composition
of the aromatic component. The composition of conventional and surrogate fuels
with specific focus on the variation of aromatic type and composition is investigated
in this work with the goal of reducing the emission of nVPM in the aviation sector. In this report, a metadata analysis of the correlation between aromatic and
naphthalene content and the smoke point of fuel samples finds a week correlation
between the two variables as determined by the Jet fuel specification. The composition of Jet fuel is then discussed as is the contemporary understanding of the various
formation mechanisms of non-volatile particulate matter. A literature review of the
effect of molecular composition of the aromatic component on soot formation found
a correlation with total aromatic volume, naphthalene volume, hydrogen mass proportion and the proportion of ring carbon present, although no individual factor
agreed consistently with experimental results. A knowledge gap was identified as to
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the effect of varying individual aromatic species in an aviation context. This report
presents experimental data collected using a Rolls Royce Tay single can combustor
using extractive laser induced incandescence to measure the mass concentration of
black carbon emitted by thirteen different aromatic species in four blend proportions
(7.5%, 12.5%, 17.5%, 22.5% vol/vol) in an alkene paraffinic surrogate for Jet-A. Data
for the same configuration is also presented using a differential mobility analyser to
determine the size distribution and total number concentration when combusting
sixteen aromatics in three blend proportions (8%, 13%, 18% vol/vol). Fuel global
density and the aggregate Unified YSI were found to be of statistical significance
and regression models were developed to estimate black carbon mass and number
exhaust concentrations with high accuracy.