Abstract
Ammonia combustion is emerging as a carbon-free energy solution, offering the potential to lower greenhouse gas emissions. Its role as a green hydrogen carrier makes it suitable for use in hard-to-abate sectors as a renewable fuel. However, its combustion produces high NOx emissions due to the nitrogen content in the fuel molecule, especially under lean conditions at elevated air temperatures, as in gas turbine combustors.
In this study, a detailed CFD-based numerical investigation of an optimized 20-kW staged rich–lean ammonia-fueled, non-premixed combustion chamber was carried out to investigate the effects of combustor inlet temperature (CIT) on emissions, combustion efficiency, and overall performance. The CIT was increased from 500 K to 1050 K at a of 0.12. This temperature rise resulted in a 430 K increase in combustor outlet temperature (COT), from 860 K to 1300 K, and a 50 % rise in NOx emissions from 308 to 627 ppm. The higher COT, combined with reductions in unburned NH3 and H2 by 90 % (1094 to 101 ppm) and 27 % (0.03 to 0.02 Vol.%), respectively, contributed to a 5 % improvement in combustion chamber efficiency based on output power.
This CFD-based study also integrates the effects of CIT and different (0.12–1.2) to comprehensively assess the factors influencing combustion efficiency and emissions. The findings provide simulation-driven insights to optimize performance, reduce emissions, and guide the design of future ammonia-fueled micro gas turbines.