Influence of Fuel Hydrogen Content and Atomisation Quality on Ultrafine Non-volatile Particulate Matter Emissions in RQL Gas Turbine Technology

Aircraft engines are a source of harmful non-volatile Particulate Matter (nvPM) emissions, negatively affecting human health and the global environment. To mitigate this, new sources of fuel are being assessed for the commercial aviation sector. Sustainable Aviation Fuels (SAF) show significant promise as replacements to conventional aviation fuels, with the potential to reduce lifecycle CO₂ and nvPM emissions because of lower aromatic contents and higher hydrogen content. Towards better understanding of the nvPM emissions from aircraft combustors operating with SAF, this work outlines results from the RAPTOR experimental test campaigns performed at Cardiff University’s Gas Turbine Research Centre (GTRC). Several aviation fuels of varying physiochemical properties were burned in a non-proprietary Rich- Quench-Lean (RQL) combustor rig. The nvPM emissions were measured using the European nvPM reference system, with data corrected for particle loss in the sampling and measurement system using additional particle size measurement. nvPM emission reductions were achieved for fuels of higher hydrogen content, and system loss correction was required to accurately quantify those reductions. Additionally, independent control of the air supply to the combustor rig allowed the impact of fuel spray quality to be decoupled from AFR, demonstrating that small improvements in spray droplet atomisation predicted from benchmarking fuel spray experiments (~5% reduction in SMD) consistently yielded significant reductions in nvPM emissions, ranging from 5-72% for nvPM EI_mass, 11-89% for nvPM EI_number, and 1-7% for GMD.