Particulate Matter Emission Comparison of Piston-Engine Aircraft's Full-Rich and Best-Power Operations

The objective of this study was to explore particulate matter (PM) <10 mu m (PM10) emissions of a piston-engine aircraft under different speed points and fuel mixtures. Collected directly from the exhaust duct, PM10 concentrations at the filters reveal different profiles and ranges between 14.1 and 68.7 mgm-3 depending on engine speed and mixture. A new parameter, the accumulation color index (ACI), was developed to scale the tonal change of a polytetrafluoroethylene filter exposed to exhaust gases for a specific period of time and volumetric flow. Being sensitive to mixture type, the highest and lowest ACI scores are generally observed at 2000 and 1000-1250 rpm, respectively. Energy-dispersive X-ray spectroscopy analyses indicate that, regardless of fuel mixture, the main elements that shape the PM10 composition at filters are found to be carbon (C), bromine (Br), lead (Pb), oxygen, aluminum, and, to a lesser extent, chlorine. However, mixture and engine speed significantly affect the size, geometry, and intensity of the particles. Highly significant correlations are obtained, under full-rich mixture, between atomic percentage and fuel flow, engine speed, and ACI. On average, Pb and Br are observed as higher in best-power mixture. The Br/Pb is obtained as 1.2-2.2 for best-power and 1.2-1.9 for full-rich mixtures, depending on speed points.