Impacts of Fuel Stage Ratio on the Morphological and Nanostructural Characteristics of Soot Emissions from a Twin Annular Premixing Swirler Combustor.

Soot particles emitted from aircraft engines constitute a major anthropogenic source of pollution in the vicinity of airports and at cruising altitudes. This emission poses a significant threat to human health and may alter the global climate. Understanding the characteristics of soot particles, particularly those generated from Twin Annular Premixing Swirler (TAPS) combustors, a mainstream combustor in civil aviation engines, is crucial for aviation environmental protection. In this study, a comprehensive characterization of soot particles emitted from TAPS combustors was conducted using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The morphology and nanostructure of soot particles were examined across three distinct fuel stage ratios (FSR), at 10%, 15%, and 20%. The SEM analysis of soot particle morphology revealed that coated particles constitute over 90% of the total particle sample, with coating content increasing proportionally to the fuel stage ratio. The results obtained from HRTEM indicated that average primary particle sizes increase with the fuel stage ratio. The results of HRTEM and Raman spectroscopy suggest that the nanostructure of soot particles becomes more ordered and graphitized with an increasing fuel stage ratio, resulting in lower oxidation activity. Specifically, soot fringe length increased with the fuel stage ratio, while soot fringe tortuosity and separation distance decreased. In addition, there is a prevalent occurrence of defects in the graphitic lattice structure of soot particles, suggesting a high degree of elemental carbon disorder.

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.