Numerical Demonstration of No Emissions Reduction by Steam Injection in the Aero Engine Combustor Iaev 2500

Reducing nitrogen oxides (NOx) emissions is a key objective in developing novel aero engines. The climate effect of NOx at high altitudes is significant despite regulations during the Landing and Takeoff (LTO) cycle. Various methods to reduce NOx formation in combustion chambers are under active research. This study examines the Water Enhanced Turbofan (WET) concept by MTU Aero Engines AG, which involves injecting steam into the combustion chamber. Steam injection can mitigate local temperature peaks, thereby reducing NOx formation. To investigate these effects under real aero engine conditions, the IAE V2500 combustor is analyzed using Large Eddy Simulations (LES) and the Flamelet-Generated Manifold (FGM) combustion model. Given that the chemical time scale of nitric oxide (NO) is much longer than that of major combustion species, an additional NO transport equation is solved, improving prediction accuracy. Three levels of steam injection are analyzed, with steam introduced into the diffuser before entering the combustor. The outlet temperature and thermal power remain constant, resulting in an increased global equivalence ratio with higher steam injection. The potential for NO reduction is demonstrated under cruise conditions. A higher steam content in the oxidizer effectively reduces temperature peaks and gradients, particularly in the rich combustion zone, leading to a notable decrease in NO emissions. While dominant NO formation occurs in the dilution zone for all cases, absolute NO values are considerably lower compared to the reference dry case, illustrating the potential to mitigate climate impact.