Combustion characteristics of premixed ammonia-hydrogen/air flames in a swirl model combustor

Ammonia (NH3)-hydrogen (H2) blends based on the thermal cracking of NH3 are considered as a prominent carbon-free fuel. This study aims to provide the combustion characteristics of premixed NH3-H2(-N2)/air swirl flames under various conditions of fuel-equivalence ratio (0) and H2 content in the fuel blend (xh,f). Results show four representative types of premixed NH3-H2(-N2)/air flames depending on 0. Combustion stability limits are extended with increasing xh,f and through the transition from laminar to turbulent combustion condition. With increasing xh,f, NOx emissions are enhanced and their peak values are observed to fuel-leaner condition. The deNOx effect of NH3 is enhanced with increasing xh,f, and different main pathways for the oxidation of NH3 to NO are found depending on 0. Flame visualization including the distributions of OH(*) and NO radicals indicates that OH promotes NO production. No remarkable discrepancies of the combustion characteristics between the premixed NH3-H2/air and NH3-H2-N2/air flames are found. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.