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 0 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.