TY - JOUR
T1 - Effects of ammonia in-situ partial cracking on the structure of bluff-body non-premixed flames
AU - Alfazazi, Adamu
AU - Es-sebbar, Et touhami
AU - Kumar, Sonu
AU - Abdelwahid, Suliman
AU - Asiri, Abdulrahman H.
AU - Zhao, Wanxia
AU - Im, Hong G.
AU - Dally, Bassam
N1 - Publisher Copyright:
© 2024 The Combustion Institute
PY - 2024/1
Y1 - 2024/1
N2 - Direct utilization of ammonia for energy generation saves the cost of the endothermic cracking process that consumes 15% of the total specific energy in ammonia. This combined experimental and computational study focuses on the direct use of ammonia and enhancing its burning rate through in-situ partial conversion into H2 and N2 within the recirculation zone. In this paper, an axisymmetric bluff-body burner, is employed to establish a self-sustained pure ammonia flame at jet Reynolds number, 9000, enabling stable turbulent non-premixed flames. Various diagnostic techniques, including planar laser-induced fluorescence (PLIF) of NH, NO & OH, Fourier-transformed infrared (FTIR), and gas chromatography (GC), are used to explore flame features, and concentrations of NO, N2O, H2, O2, and NH3 within the flame and at the exhaust. The RANS flamelet/progress variable (FPV) approach is utilized to qualitatively capture the flame features. The flame exhibits a broad and luminous recirculation region, followed by a narrower zone downstream, where the reaction continues in flameless mode. In the flameless region, reactant temperatures rise despite the absence of a visible flame. The flammable region is marked by high concentrations of NO, OH, NH, and the post-flame region witnesses rapid consumption of H2, NO, and N2O. Approximately 20% of NH3 dissociates in the first zone, while more than 60% of NH3 dissociated by the flame's maximum height. At the flame tip, most H2 and NO are consumed, leaving around 30% NH3 and 100 ppm of N2O slip. Ammonia cracking is greater radially across the bluff-body surface, over 70% dissociating into H2 and intermediates. Overall, this study provides insights into the concept of in-situ partial cracking at the flame base as a method to establish self-sustained ammonia combustion, allowing for on-site and direct ammonia fuel combustion and yielding low NO emissions and a promising optimization potential of ammonia utilization.
AB - Direct utilization of ammonia for energy generation saves the cost of the endothermic cracking process that consumes 15% of the total specific energy in ammonia. This combined experimental and computational study focuses on the direct use of ammonia and enhancing its burning rate through in-situ partial conversion into H2 and N2 within the recirculation zone. In this paper, an axisymmetric bluff-body burner, is employed to establish a self-sustained pure ammonia flame at jet Reynolds number, 9000, enabling stable turbulent non-premixed flames. Various diagnostic techniques, including planar laser-induced fluorescence (PLIF) of NH, NO & OH, Fourier-transformed infrared (FTIR), and gas chromatography (GC), are used to explore flame features, and concentrations of NO, N2O, H2, O2, and NH3 within the flame and at the exhaust. The RANS flamelet/progress variable (FPV) approach is utilized to qualitatively capture the flame features. The flame exhibits a broad and luminous recirculation region, followed by a narrower zone downstream, where the reaction continues in flameless mode. In the flameless region, reactant temperatures rise despite the absence of a visible flame. The flammable region is marked by high concentrations of NO, OH, NH, and the post-flame region witnesses rapid consumption of H2, NO, and N2O. Approximately 20% of NH3 dissociates in the first zone, while more than 60% of NH3 dissociated by the flame's maximum height. At the flame tip, most H2 and NO are consumed, leaving around 30% NH3 and 100 ppm of N2O slip. Ammonia cracking is greater radially across the bluff-body surface, over 70% dissociating into H2 and intermediates. Overall, this study provides insights into the concept of in-situ partial cracking at the flame base as a method to establish self-sustained ammonia combustion, allowing for on-site and direct ammonia fuel combustion and yielding low NO emissions and a promising optimization potential of ammonia utilization.
KW - Bluff-body burners
KW - In situ—cracking of ammonia
KW - Non-premixed turbulent flames
KW - Turbulent flames
UR - http://www.scopus.com/inward/record.url?scp=85201270060&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2024.105697
DO - 10.1016/j.proci.2024.105697
M3 - Article
AN - SCOPUS:85201270060
SN - 1540-7489
VL - 40
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1-4
M1 - 105697
ER -