Key points are not available for this paper at this time.
Emissions from small gas turbine engines pose environmental and health risks and they are, dependent of engine type and manufacture date, not regulated or only subject to smoke emission standards resulting in a lack of detailed emission characterization. This study examines the emission behavior of an Allison 250-C20B turboshaft engine when powered by different blends (30, 50, and 100%) of Hydroprocessed Esters and Fatty Acids (HEFA) based Sustainable Aviation Fuel (SAF). The change in engine power is linked to differences in gaseous and particulate matter (PM) emissions. Emission indices (EI) for gas phase constituents are reduced at higher power settings due to a higher combustion chamber efficiency resulting from better fuel atomization, fuel-air mixing behavior, and higher flame temperatures. Differences in gaseous EI at the same power setting between the fuels investigated are negligible for all regulated gaseous compounds (UHC, CO, NOx). However, there are variations in the gaseous volatile organic compounds (VOC) and in polycyclic aromatic hydrocarbons (PAH). Significantly more pronounced changes can be seen in the particulate phase. The non-volatile particulate matter (nvPM) number concentrations were reduced by up to 81% using 100% SAF compared to Jet A-1 fuel. In addition, using SAF shifts the mode of the particle number size distribution (PNSD) to smaller sizes, that is, from the maximum at 55 nm (Jet A-1) to a maximum at 25 nm (100% SAF). This reduces the emitted particle mass up to 76%. The reduction can be explained by the chemical composition of the fuels and the subsequent PAH and soot formation during combustion.
Rohkamp et al. (Thu,) studied this question.