Development and Assessment of Dual-Fuel Capabilities in Next-Generation Aero-Engine Injectors for Hydrogen and Liquid Fuels

Dual-fuel aero-engines, capable of using hydrogen alongside SAF or kerosene, are key enablers in the transition to hydrogen operation but have received limited research attention. This study explores the potential of retrofitting the kerosene injector in a Rolls-Royce Pearl RQL combustor for dual-fuel operation. Adapting the existing injector for combined use with hydrogen poses a significant challenge due to elevated NOx emissions. To address this, an automated Computational Fluid Dynamics (CFD) workflow is used to optimize the injector geometry for emission performance, enabling rapid evaluation under realistic engine conditions. To explore a wide range of geometry variations, the Reynolds-Averaged Navier-Stokes (RANS) approach is employed for simulations, while Large Eddy Simulations (LES) validate emission trends for selected geometries. The CFD setup is validated against measurements for conceptual injector geometries, confirming its accuracy in predicting emissions. This study shows that dual-fuel capability can be incorporated into an existing combustion system while preserving flame stability and emission levels comparable to standard kerosene injectors. The CFD-based workflow successfully identifies optimal geometric features, achieving reduced emissions for both fuels during the Landing-Take-Off (LTO) cycle. Emissions are evaluated per ICAO legislation. The optimized injector will undergo further evaluation through experimental testing to confirm predicted performance and advance development toward dual-fuel combustion systems.