Influence of wall heat loss on the emission characteristics of premixed ammonia-air swirling flames interacting with the combustor wall

Stability limits and NO emissions of premixed swirl ammonia-air flames enriched with hydrogen or methane at elevated pressures

“…While stabilization of turbulent ammonia-air flames has been achieved in a few instances, e.g. in [9][10][11][12][13][14], many other experiments, e.g. [7,[15][16][17], showed that stabilizing premixed ammonia-air flames is much more challenging than premixed methane-air flames.…”

“…For example, early experiments of [7] showed that the ammonia-hydrogen-nitrogen fuel blend obtained by cracking 28% of the ammonia features the same flame-stability performance as typical hydrocarbons. More recently, the benefits of enriching ammonia have been verified for a range of different configurations [9][10][11][12][15][16][17][18][19][20][21][22][23][24][25][26]. Franco et al [18] developed a novel swirl combustor and found a reasonably wide stable range when only a small addition of hydrogen is added in the ammoniahydrogen fuel blend.…”

“…As a consequence, reducing flame temperature by operating lean, to penalize thermal NOx pathways, is insufficient with ammoniaair flames to abate NO emissions below acceptable limits [29]. This strategy has been the topic of many experimental and numerical studies that examined NO formation in ammonia flames as a function of equivalence ratio [10,12,18,25,26], ammonia fuel fraction [9,17,19,30], or pressure [11,21,22,31]. In many of these studies, the OH radical was identified as one of the main drivers for NO formation.…”

“…While rich burning benefits NO performance, a globally-rich operation must be avoided to avoid harmful unburned NH3 emissions and efficiency penalties. Therefore, two-stage combustors have been successfully developed, in which a first locally-rich stage precedes a second locally-lean stage, yielding globally-lean operation [10,12,14,22,26].…”

Recent Combustion Strategies in Gas Turbines for Propulsion and Power Generation toward a Zero-Emissions Future: Fuels, Burners, and Combustion Techniques

“…For these reasons, lean ammonia-hydrogenair blends are promising candidates for gas turbines since elevated pressure is expected to reduce NO emissions even further. The main limitation of lean ammonia-hydrogen-air flames is the elevated production of N 2 O under certain operating conditions [26]. N 2 O is a dangerous greenhouse gas, around 250 times more effective than CO 2 , and thus, it could potentially cancel the benefits associated with a carbon-free combustion.…”