Analysis of Hydrogen-fuelled Combustor Design for Micro Gas Turbine Applications: Performance, Emissions, and Stability Considerations

To address global CO2 emissions and the intermittency of renewables, hydrogen is emerging as a promising carbon-free fuel for micro gas turbines (MGTs), offering potential for grid stability and decarbonization. However, its high flame speed and adiabatic temperature present challenges, including flashback and elevated NOx emissions. Conventional combustors often lack the compactness and NOx control needed for MGT-scale systems. This study numerically investigates pure hydrogen combustion in a compact MGT combustor using a secondary air dilution strategy. Based on the experimental setup of Tanneberger et al., simulations were conducted in ANSYS Fluent using steady-state RANS equations, a CRECK-based chemical mechanism, and the Flamelet Generated Manifold (FGM) model. The parametric study explores three design variables, swirler blockage (B), central fuel tube length (C), and fuel injection split (S), along with five secondary air configurations (T1–T5). Results show that the secondary air hole pattern significantly affects flow structure and temperature uniformity. Configuration T1 provided the most uniform exhaust and lowest NOx emissions due to better air penetration and earlier dilution. Higher B and S increased local flame temperature, intensifying thermal NOx via the Zeldovich mechanism. The findings offer design guidance for stable, low-emission hydrogen combustors suitable for compact MGT applications.