Numerical study of ammonia/n-dodecane combustion and emission characteristics in a micro gas turbine combustor

• Flow characteristics and recirculation patterns of NH 3 /nC 12 H 26 blends in a micro gas turbine combustor are investigated. • Temperature distribution and combustion efficiency under different ammonia blending ratios are analyzed. • Formation mechanisms and distribution characteristics of NO emissions are studied through reaction pathway analysis. • Effects of ammonia blending on CO emissions and combustion completeness are examined through numerical simulation. In response to global climate change, ammonia (NH 3 ) as a zero-carbon fuel has garnered significant attention for its application in gas turbines. However, its low flame propagation speed and high nitrogen oxide (NOx) emissions pose challenges for practical implementation. This study numerically investigates the combustion characteristics of n-dodecane/ammonia blended fuels in a micro gas turbine combustor. Based on the Aalto75 chemical reaction mechanism, the Reynolds Stress Model and Discrete Ordinates Model were employed to simulate flow field, temperature distribution, and species characteristics under different ammonia blending ratios (0 %-100 %). Results show that as ammonia blending increases, the Primary Recirculation Zone (PRZ) gradually decreases and breaks down into Hub Recirculation Zone (HRZ) and Secondary Recirculation Zones (SRZ). While outlet temperature uniformity remains largely unchanged (Pattern Factor maintains at 1.07–1.12), the average outlet temperature decreases by approximately 50 K (from 1092 K to 1047 K), and combustion efficiency drops by 5 % (from 92.2 % to 87.0 %). Unburned fuel distribution reveals that n-dodecane forms compact high-concentration regions that expand at intermediate ammonia blending ratios, while ammonia exhibits persistent elongated zones extending downstream, indicating slower oxidation kinetics. CO emissions first increase then decrease with ammonia blending, while NO emissions continuously increase. The study demonstrates that ammonia blending can reduce carbon emissions in combustors but requires a optimization of combustion efficiency and NOx emissions. The findings provide critical data for the low-emission design of ammonia/hydrocarbon blends in gas turbines, advancing decarbonization technologies in aviation and energy sectors.