Effect of atomizing gas type on kerosene spray combustion using gas-blast atomizer: A comparative numerical study

Abstract

In order to attain optimal combustion efficiency, minimal pollutant emissions, and reliable stability in gas turbines, a computational model was developed to study the combustion and atomization characteristics of liquid fuel (Kerosene). Seven different atomizing gases were considered, namely, air, ammonia, hydrogen, natural gas, superheated steam, oxygen, and nitrogen. The work aims to investigate the potential of hydrogen in contrast to the other atomizing gases, in minimizing pollutant concentrations in the combustion exhaust considering the associated cost implications. A 3D cylindrical combustor with a gas blast atomizer was employed while maintaining a constant air swirl number. The total thermal load across all tests was kept constant by varying the liquid kerosene flow rate. The simulations analyzed various parameters in order to address the combustion characteristics, such as reverse flow zone (RFZ), recirculated flow mass ratio, flow pathlines, temperature maps, centreline axial temperatures, outlet temperatures, species concentrations, and droplets characteristics. The results showed that the flame temperature reached its peak when hydrogen was utilized. When using combustible atomizing gases, the CO and CO2 concentrations at the exit of the combustor tube were generally lower. However, the CO concentration is notably higher when air is employed, unlike other gases such as nitrogen, oxygen, and natural gas, which showed decreased CO levels. Remarkably, the CO concentration experiences a significant decline of about 98% when natural gas is utilized. The average concentration of NOx is highest when oxygen and hydrogen are used as atomizing gases, but it experiences a significant decrease of approximately 75% when air is employed instead. It can be deduced that different gases such as hydrogen gas have a possibility as an option and sustainable atomizing gases on spray performance.