Nitrogen Oxides Emission Measurement and Numerical Validation for Cracked Ammonia Combustion in a Semi Industrial Burner Design

Abstract Ammonia cracking is a promising solution for the abatement of the nitrogen oxides (NOx) emissions since it allows to partially avoid the fuel bound formation pathway. Rising with the cracking percentage, the benefit of the emission reduction is partially mitigated by a higher complexity of the auxiliary system, especially when such strategy means to be coupled with an existing gas turbine plant. With regard to the numerical models, the growing interest in ammonia combustion highlights the need for methods that are able to predict the intricate NOx emissions production. In the present paper, the experimental measurements of a semi-industrial burner operated in nonpremixed mode and fed with a mixture corresponding to 99% of cracked ammonia will be presented. The experimental measures aim to characterize both the flame morphology, and the pollutant emissions. Different operating pressures will be explored with the thermal power of the rig remaining constant. From the numerical point of view, three test conditions will be simulated by large-eddy simulation (LES) relying on a pretabulated approach for turbulence-chemistry interaction. The main goal of the numerical campaign is the prediction of the flame shape at the different operating conditions. Conversely, LES won't be used for the assessment of the pollutant emissions, but they will support a chemical reactor network (CRN) built at this scope. The time averaged fields coming from the computational fluid dynamic model will be leveraged to setup the network and retrieve the trend of the main pollutant emissions. The flexibility of this methodology allows for detailed sensitivity to the chemical mechanism, with a focus on rate of production (ROP) analysis of the main NOx-forming reactions. This will allow for in-depth investigation of the dominant pathways of NOx formation.