Large Eddy Simulation of Ammonia Combustion in a Lean Premixed Swirl Burner for Flame Structure and Emissions Investigation

Environmental problems caused by excessive use of fossil fuels are amongst the top governmental, research and industrial agendas. Under this situation, requirements for new environmentally friendly fuel systems to replace fossil fuel technologies are critical. Ammonia, as a carbon-free fuel, has the potential to be the fuel for future energy systems. Ammonia has a high hydrogen content, which is 17% and yields only water and nitrogen as combustion products when completely burned. Although research has been undertaken on operational flame limits, chemical models, flame speed and internal combustion engines, gas turbines have played a minor role in using this fuel. Research that has shown some development in understanding these systems is limited. Results showed a series of challenges when using this fuel. Hence, this study aimed to in investigate the flame structure and the properties of ammonia combustion in a lean premixed swirl burner. Through the simulation, the capabilities of premixed flames to stabilize in the swirl burner and the effect of the NOx emission also become a target outcome. The simulation of premixed ammonia combustion is performed using ANSYS fluent software. Ammonia and hydrogen were used as substances of combustion fuel and five composition ratios of mol percentage between ammonia and hydrogen fuels were set. A large eddy simulation (LES) was used and the sub-grid scale Smagorinsky model was considered for this simulation setup. The findings revealed that combustion with 30% hydrogen and 70% ammonia fuel gives a high stability to the flame structure due to low flame speed and high ignition energy. The NOx emissions for this fuel composition show the lowest distribution due to the low combustion flame temperature of ammonia fuel. The simulation combustion of 70% hydrogen and 30% ammonia fuel composition shows high combustion efficiency and NOx emissions but low flame structure stability. Results show the model can provide detailed information on flow field, flame structure, emissions, etc. It can be used to optimize the procedure of utilizing ammonia as a fuel in future equipment design.