Numerical Analysis of Factors Affecting NOx Emissions in Hydrogen-Fueled Micromix Combustors

Micromix combustion is a promising approach to addressing issues such as flashback, combustion instability, and nitrogen oxide (NOx) emissions in hydrogen-fueled gas turbines. In this study, a numerical analysis was conducted to investigate key factors influencing NOx emissions in a lab-scale micromix combustor under atmospheric pressure and room temperature. The effects of air flow rate, equivalence ratio, and combustor component surface temperature on NOx formation were systematically evaluated. The results show that increasing the air and hydrogen flow rates at a constant equivalence ratio reduced NOx emissions due to shorter residence times. In addition, higher surface temperatures of combustor components increased flame temperatures and NOx production. Lastly, high equivalence ratios led to partial flame merging, increasing NOx emissions. These findings highlight that the efficient cooling of combustor components and proper selection of air flow rate and equivalence ratio are critical to minimizing NOx emissions in micromix combustors. The study provides design and operational guidelines for the future development of hydrogen-fueled gas turbines.