Gaseous and Particulate Emissions of an Allison 250-C20B Turboshaft Engine Running on HEFA-SPK and its Jet A-1 Blends

Abstract Aviation is widely recognized as a significant source of air pollutant emissions, encompassing gaseous products such as CO2, CO, NOx, and particulate matter (PM), especially in the form of soot. This study conducted comprehensive emission measurements on an Allison 250 C20B turboshaft engine to investigate sustainable aviation fuel (SAF) impact on emissions. Two conventional Jet A-1 fuel blends with 30% and 50% HEFA-SPK synthesized paraffinic kerosene derived from hydro-processed esters and fatty acids (HEFA-SPK) content together with 100% HEFA-SPK were tested regarding their emissions and compared against neat Jet A-1. The study’s primary focus was quantifying ultrafine particulate matter in terms of number and size. The selection of distinct engine power settings was based on the thrust ratios specified in the International Civil Aviation Organization’s (ICAO) Landing and Take-off-cycle (LTO-cycle). PM emissions were characterized using multiple measurement techniques. These included the application of two distinct electrical mobility analyzers. An additional concentration particle counter (CPC) was utilized to underscore the reliability of the findings. A standard FTIR/O2/FID system was used to assess gaseous emissions, a well-established method for measuring fundamental combustion products such as CO2, CO, unburned hydrocarbons (UHC’s) and NOx. The particle measurement systems revealed a decrease in both the number and size of particles with increasing HEFA-SPK content. This decrease in particle number appeared linear for the 30% and 50% HEFA-SPK blends and was more pronounced for the 100% HEFA-SPK. Furthermore, a more substantial reduction in PM emissions, reaching up to 82%, was observed at lower load settings, such as Ground Idle (GI), compared to higher load settings like Take-Off (TO), where the reduction was up to 40%. Results of the gaseous emissions are also presented in the study.