Evaluation of methods for characterizing the fine particulate matter emissions from aircraft and other diffusion flame combustion aerosol sources

Characterizing and Predicting nvPM Size Distributions for Aviation Emission Inventories and Environmental Impact

“…The decreasing average nvPM density with increasing (N/M) SL (i.e., decreasing thrust) contrasts with previous studies that calculated the average particle effective density using integrated PSD and size-dependent effective densities. Previous investigations of a large turbofan engine and a small turbojet reported average densities between 0.6 and 1.0 g/cm 3 , slightly decreasing with increasing thrust. , The differences may lay in the inherently different definition of the average nvPM density used here (including the log-normality assumption). The average nvPM density used here depends on the optical properties of soot, which vary with the thrust.…”

“…48 The EC fraction of aircraft engine soot has been found to increase with thrust, with a maximum value of ∼90%, 49 which was also confirmed visually where particles collected at idle were brown whereas high-thrust particles were black. 50 Consequently, the optical nvPM mass measurement may significantly underreport the total PM mass obtained from integrated PSD and size-dependent density distributions, as reported by Giannelli et al 47 Nevertheless, the methodology for determining the average nvPM density adopted in this study, along with the reported values, is appropriate in the context of regulatory nvPM measurements and the relationship between the regulatory nvPM mass and number.…”

“…Previous investigations of a large turbofan engine and a small turbojet reported average densities between 0.6 and 1.0 g/cm 3 , slightly decreasing with increasing thrust. 46,47 The differences may lay in the inherently different definition of the average nvPM density used here (including the log-normality assumption). The average nvPM density used here depends on the optical properties of soot, which vary with the thrust.…”