Decarbonizing Gas Turbines: Multi-Physics Modeling of Lean Hydrogen Combustion and NOx Formation

Abstract

Decarbonization of gas turbines requires stabilizing highly reactive hydrogen-air flames while suppressing nitrogen oxide (NOx) emissions. This study presents a 3D numerical validation of a co-swirling lean hydrogen-air combustor (equivalence ratio of 0.66) using a steady-state RANS framework in ANSYS Fluent, coupling Menter’s SST k-omega Curvature Correction model, non-adiabatic Equilibrium PDF chemistry, and a multi-pathway NOx transport model. Grid convergence is demonstrated on three mesh levels with a fine-grid axial velocity GCI of 0.58% and a net mass flow imbalance of -0.55%, resolving the stagnation points and reverse flow velocities of the central recirculation zone. The predicted peak time-averaged flame temperature is 1943.74 K, differing from DLR CARS measurements by 0.32%, while emissions calculations yield an exit NOx concentration of 0.135 ppm. The results indicate that coupling non-adiabatic equilibrium chemistry with radiation and intermediate NOx pathways provides a computationally efficient method to predict emissions and thermal fields in hydrogen swirl burners.