Sustainable aviation fuel blends in aircraft piston engine: Comparative analysis of 30 % vs. 50 % SAF on combustion performance and emission reduction

The integration of Sustainable Aviation Fuel (SAF) blends into heavy-fuel aircraft piston engines (HF-APE) offers a strategic pathway to decarbonizing propulsion systems in general aviation and unmanned aerial vehicles (UAVs). This study presents a comprehensive comparison of combustion behavior and emission characteristics for SAF-biodiesel and SAF-RP-3 blends, utilizing a hybrid experimental-simulation approach. Emissions were measured according to ICAO Annex 16 protocols using precision instrumentation at varying engine speeds. A validated simulation model accurately replicated combustion, gas exchange, and pollutant formation processes. The 50 % SAF +50 % RP-3 blend exhibited the best emission profile, reducing carbon monoxide (CO) by up to 63 % and unburned hydrocarbons (HC) by 75 % compared to biodiesel-dominant blends. In contrast, the 30 % SAF +70 % biodiesel blend resulted in a 19 % increase in nitrogen oxide (NO_x) emissions. Particle size distribution (PSD) analysis showed that RP-3 blends reduced nucleation-mode particles by 30–40 % and total particulate matter (PM) emissions by 38 %. Microscopic examination revealed that RP-3-derived particulates were finer, denser, and less porous, suggesting more complete combustion. A notable strength of this study is the integrated use of differential mobility spectrometer (DMS 500) and environmental scanning electron microscope (eSEM) for comprehensive particulate characterization. Simulations revealed that the 50 % SAF +50 % RP-3 blend achieved superior intake (∼10.7 g/s), exhaust (∼13.8 g/s) mass flow rates, brake power (∼81 kW), fuel efficiency (∼217 g/kWh), and a 28 % reduction in CO₂ emissions. These findings suggest that SAF-enhanced RP-3 fuels offer significant potential for improving HF-APE performance and sustainability.