Comparative Study of Hydrogen Addition Effects on Flame Stability and Pollutant Emissions in Jet-A1 and Sustainable Aviation Fuel/Jet-A1 Lean Lifted Spray Flames

Understanding the combustion characteristics of sustainable aviation fuel (SAF) and conventional fuel spray flames with hydrogen (H$_2$) 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 fueled by Jet-A1, SAF, and H$_2$ 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 NO$_x$ emissions and minimizing flashback risk compared to conventional swirl-stabilized flames. The design promotes higher flame lift-off heights (LOH), enabling stable operation at increased H$_2$ content. Jet-A1 and SAF/Jet-A1 blend are injected through a centrally mounted hollow-cone atomizer, and H$_2$ 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 analyzer. The study compares flame behavior and pollutant emissions with and without H$_2$ addition in Jet-A1/air and SAF/Jet-A1/air lean lifted spray flames. ... mehrThe influence of H$_2$ addition on the lean blowout (LBO) behavior 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 H$_2$ addition in Jet-A1 and SAF/Jet-A1 spray flames provides beneficial insights for the design and optimization of next-generation fuel-flexible aero-engines.