Impacts of Alternative Fuels on Morphological and Nanostructural Characteristics of Soot Emissions from an Aviation Piston Engine

Soot emissions from aviation piston engines (APEs) are a major source of environment pollution in airport vicinity, stratosphere, and troposphere, and their nanostructure and surface chemistry play a critical role in determining the impact on human health and environment. In this work, the morphology and nanostructure of soot emitted from an aviation piston engine burning five different fuels including blends of promising alternative jet and biofuels were investigated via high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The graphitic structures were observed by analyzing primary particles in the HRTEM images. Morphological analysis demonstrated that the separation distance of the graphene layers of soot particles from the kerosene-pentanol blend combustion was larger than that from kerosene-Fischer-Tropsch blend combustion, indicating that adding pentanol tended to generate particles with more loosely stacked layers and higher oxidation tendency. Raman results were in agreement with primary particle nanostructure analysis based on the HRTEM images. Furthermore, soot particles from different fuels exhibited different concentrations of amorphous carbon and structural defects.