Comparative Study Of Hydrogen Addition Effects On Flame Stability and Pollutant Emissions In Jet-A1 and Saf/Jet-A1 Lean Lifted Spray Flames

Understanding the combustion characteristics of sustainable aviation fuel (SAF) and conventional fuel spray flames with hydrogen (H₂) mixtures is essential for enabling the transition from fossil fuels to cleaner aircraft propulsion. This study investigates flame stabilization and pollutant emissions in an innovative, fuel-flexible combustor fuelled by Jet-A1, SAF, and H₂ under atmospheric pressure and elevated air inlet temperatures. A new nozzle, based on the "low swirl" lean lifted flame concept, was developed to promote high premixing, significantly reducing NOₓ emissions and minimizing flashback risk compared to conventional swirl-stabilized flames. The design promotes higher flame lift-off heights, enabling stable operation at increased H₂ content. Jet-A1 and SAF/Jet-A1 blend are injected through a centrally mounted hollow-cone atomizer, and H₂ is supplied via injectors arranged circumferentially around the prefilmer. Flame structure, lift-off height, and flame width were characterized using high-speed OH^ chemiluminescence imaging, and pollutant emissions were measured with an exhaust gas analyser. The study compares flame behaviour and pollutant emissions with and without H₂ addition in Jet-A1/air and SAF/Jet-A1/air lean lifted spray flames. The influence of H₂ addition on lean blowout behaviour of the combustor is also assessed for both fuels. Overall, a comprehensive experimental campaign investigates key parameters, such as air inlet temperature and hydrogen blending ratio. The comparison of H₂ addition in Jet-A1 and SAF/Jet-A1 spray flames provides beneficial insights for the design and optimization of next-generation aero-engines.