Numerical investigation of soot formation in sustainable aviation fuels*

The increasing demand in the aviation sector motivates the study of soot formation and alternative fuels to minimize the environmental impact on climate change. The formation of condensation trails (contrails) by aircraft engines corresponds to approximately 4-5 % of the total net effective radiative forcing causing global warming. The contrails are composed of ice crystals formed primarily from the interaction of soot particles and water vapor emitted by the engine. The objective of this work is to analyze the processes related to soot formation for the commercially available Jet-A, and the C1 fuel representative of a Sustainable Aviation Fuel with low aromatic content and low ignition propensity. First, a reduced chemical mechanism is developed for both fuels using experimental measurements in counter-flow configurations and predictions using the state-of-the-art detailed chemical mechanism from Lawrence Livermore National Laboratory. Soot predictions with the reduced mechanisms are obtained with the DNS code, PeleLMeX, and a state-of-the-art soot model (Hybrid Method of Moments). The predictions revealed that Jet-A and C1 have a reduction in soot volume fraction with the increase in fluid dynamic strain. However, the interaction between the soot nucleation, surface growth, condensation and oxidation, and their response to strain is different. The findings of this research provide us a better understanding on the fundamental aspects of soot emissions in sustainable aviation fuels.