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 as a fuel, would be a key enabler in the transition to hydrogen operation but have received limited attention in research and development. Therefore, 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 the 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 broad range of geometry variations, the Reynolds-Averaged Navier-Stokes (RANS) approach is employed for simulations, while Large Eddy Simulations (LES) are performed on selected geometries to validate emission trends. Prior to optimizing the injector, the CFD setup is validated against available measurements for conceptual injector geometries, confirming its capability to accurately predict emission levels. This study demonstrates 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 identified optimal geometric features, achieving reduction of emissions for both fuels during Landing-Take-Off (LTO) cycle for the proposed injector configuration. Emissions are evaluated in accordance with ICAO-prescribed legislation. In the future, the optimized injector will undergo further evaluation through experimental testing to confirm the predicted performance and set the next step towards dual-fuel capable combustion systems.