Morphological and nanostructure characteristics of soot particles emitted from a jet-stirred reactor burning aviation fuel

Aircraft engine soot emissions have been a growing concern because of their adverse impacts on global climate and human health. In this study, soot emissions from a Jet-Stirred Reactor (JSR) which could be considered as a basic aero-engine combustor were investigated under different combustion conditions including varying combustion pressures, fuel flow rates, and inlet air temperatures. The emitted soot particles were collected onto quartz fiber filters and then examined using high-resolution transmission electron microscopic (HRTEM) and Raman techniques. The HRTEM images and Raman spectra of the filter-laden soot samples were analyzed to determine the morphology and the nanostructure characteristics of the soot particles. It turned out that compared to the reference point, both high combustion pressure and high flow rate led to an increase in primary particle size. The HRTEM and Raman studies showed that there was no amorphous carbon present in the soot particles generated under high combustion pressure. Inlet air temperature exhibited a significant influence on the size and the morphology of soot particles; a large quantity of amorphous carbon with a lower degree of graphitization was generated under the low inlet temperature condition presumably due to poor fuel spray breakup and atomization in the JSR. In addition, we found that nanostructure parameters, such as soot fringe length and fringe tortuosity could be strongly dependent upon the residence time and the inlet air temperature.