TY - JOUR
T1 - Stability and characteristics of NH3/CH4/air flames in a combustor fired by a double swirl stabilized burner
AU - Elbaz, Ayman M.
AU - Albalawi, Alfaisal M.
AU - Wang, Shixing
AU - Roberts, William L.
N1 - Funding Information:
This work was supported by King Abdullah University of Science and Technology . The authors would like to thank Youssef Elhagrasy for his effort in editing and reviewing the paper linguistically. Authors would like to thank Mohammed Almomtan, Khalid Mojallid, and Felipe Campuzano Diosa for their discussion and consultations.
Funding Information:
This work was supported by King Abdullah University of Science and Technology. The authors would like to thank Youssef Elhagrasy for his effort in editing and reviewing the paper linguistically. Authors would like to thank Mohammed Almomtan, Khalid Mojallid, and Felipe Campuzano Diosa for their discussion and consultations.
Publisher Copyright:
© 2022
PY - 2023/1
Y1 - 2023/1
N2 - Compared to hydrocarbons, ammonia's low reactivity and higher NOx emissions limit its practical application. Consequently, its implementation in combustion systems requires a different combustor geometry, by adapting existing systems or developing new ones. This study investigates the flame stability, NO emissions, and flame structure of NH3/CH4/air premixed flames in a novel combustor comprising a double swirl burner. A lean premixed CH4/air mixture of equivalence ratio, Φout, was supplied to the outer swirl, while a NH3/CH4/Air mixture fed the inner swirl. The molar fraction of NH3 in the inner fuel blend, xNH3, was varied from 0 (pure CH4) to 1 (pure NH3) over far-lean to far-rich inner stream equivalence ratio, Φin. This new burner's stability map was established in terms of Φin versus xNH3 for different Φout. Then, NO emissions were measured versus Φin for various xNH3 and Φout. Finally, based on the NO emissions, eight flames were down-selected for in-flame measurements, which included temperature and OH-PLIF. The stability measurements revealed that increasing xNH3 modifies the stability map by increasing the lean blowout limits and narrowing the flashback region. At Φout ≥ 0.6, a stable flame was achieved for a pure inner NH3/air mixture. Low NO emissions were achieved in this burner configuration at xNH3=1 by either enriching or far-leaning Φin. Enriching Φin led to a steep decrease in NO concentrations. However, to achieve low NO concentrations, precise control of Φout was needed. At Φin=1.4, 220 ppm NO at Φout=0.7 versus 690 at Φout=0.6 was measured. Moreover, substantially enriching Φin>1.2 led to a slight decrease in measured NO. Generally, the OH-PLIF images revealed a conical OH-layer at the burner exit. Certain flame conditions created OH-pockets inside the conical structure or formed a V-shaped OH-layer far downstream. This change in flame structure was found to impact NO emissions strongly.
AB - Compared to hydrocarbons, ammonia's low reactivity and higher NOx emissions limit its practical application. Consequently, its implementation in combustion systems requires a different combustor geometry, by adapting existing systems or developing new ones. This study investigates the flame stability, NO emissions, and flame structure of NH3/CH4/air premixed flames in a novel combustor comprising a double swirl burner. A lean premixed CH4/air mixture of equivalence ratio, Φout, was supplied to the outer swirl, while a NH3/CH4/Air mixture fed the inner swirl. The molar fraction of NH3 in the inner fuel blend, xNH3, was varied from 0 (pure CH4) to 1 (pure NH3) over far-lean to far-rich inner stream equivalence ratio, Φin. This new burner's stability map was established in terms of Φin versus xNH3 for different Φout. Then, NO emissions were measured versus Φin for various xNH3 and Φout. Finally, based on the NO emissions, eight flames were down-selected for in-flame measurements, which included temperature and OH-PLIF. The stability measurements revealed that increasing xNH3 modifies the stability map by increasing the lean blowout limits and narrowing the flashback region. At Φout ≥ 0.6, a stable flame was achieved for a pure inner NH3/air mixture. Low NO emissions were achieved in this burner configuration at xNH3=1 by either enriching or far-leaning Φin. Enriching Φin led to a steep decrease in NO concentrations. However, to achieve low NO concentrations, precise control of Φout was needed. At Φin=1.4, 220 ppm NO at Φout=0.7 versus 690 at Φout=0.6 was measured. Moreover, substantially enriching Φin>1.2 led to a slight decrease in measured NO. Generally, the OH-PLIF images revealed a conical OH-layer at the burner exit. Certain flame conditions created OH-pockets inside the conical structure or formed a V-shaped OH-layer far downstream. This change in flame structure was found to impact NO emissions strongly.
KW - Ammonia/methane swirling flames
KW - Double swirls
KW - Low NO combustion
UR - http://www.scopus.com/inward/record.url?scp=85133553496&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2022.06.004
DO - 10.1016/j.proci.2022.06.004
M3 - Article
AN - SCOPUS:85133553496
SN - 1540-7489
VL - 39
SP - 4205
EP - 4213
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 4
ER -