Particulate and Gaseous Emissions of An Allison 250-C20B Turboshaft Engine Using Ft-Spk

Abstract Aviation remains a major contributor to air pollutant emissions. While full decarbonization through electrification or carbon-free fuels is not feasible in the near term, Sustainable Aviation Fuels (SAF) offer a promising interim alternative. This study examines the emission behavior of a synthetic paraffinic kerosene (FT-SPK), produced via the Fischer-Tropsch process, and compares it to both conventional Jet A-1 and previously tested HEFA-SPK. Experiments were conducted on an Allison 250-C20B turboshaft engine using Jet A-1, a 50% FT-SPK and HEFA-SPK blend, and 100% FT-SPK and HEFA-SPK. Engine power settings were selected based on the ICAO LTO-cycle. Non-volatile particulate matter (nvPM) was analyzed with a condensation particle counter (CPC) and a scanning mobility particle sizer (SMPS), while gaseous emissions (CO2, NOx, CO, UHC) were measured using a FTIR/O2/FID combi-system. A resonance-enhanced multiphoton ionization time-of-flight mass spectrometer (REMPI ToF-MS) provided insight into polycyclic aromatic hydrocarbons (PAH) in the exhaust. Both 100% FT-SPK and HEFA-SPK demonstrated similarly strong reductions in nvPM at low power settings compared to conventional Jet A-1, though differences became apparent at higher power settings. Further, the 50% FT-SPK blend consistently showed greater nvPM reductions than the 50% HEFA-SPK blend across all power settings. Compared to HEFA-SPK, FT-SPK showed similar gaseous emission behavior at high power settings but indicated more complete combustion at low power, with higher CO2 and lower CO and UHC emissions.