THERMAL SCIENCE

International Scientific Journal

Thermal Science - Online First

Authors of this Paper

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Shijia Liu

,

Zhicong Li

online first only

Assessing the potential of chemiluminescence to characterize no formation in ammonia-methane premixed flat flames

ABSTRACT
The NO formation characteristics in laminar NH3-CH4 premixed flat flames and their relationship with chemiluminescence are numerically investigated across different ammonia blending ratios (XNH3, 0-1.0) and equivalence ratios (φ, 0.7-1.3). The applicability of the reaction mechanism and flame model in predicting the formation of NO and OH*/NH*/CH*/CO2*/NH2* radicals is verified. The results show that the peak flame temperature gradually increases with increasing XNH3, while it first increases and then decreases with increasing φ. For NO mole fraction, increasing XNH3 affects the competition among reactions R763 (HNO + H = NO + H2), R765 (HNO + OH = NO + H2O), and R842 (NH + NO = N2O + H) by altering the HNO and NH mole fractions, causing NO to first increase and then decrease. Moreover, increasing φ continuously reduces the formation rate of NO via R765. For OH*/NH*/CH*/CO2*/NH2* mole fractions, as XNH3 increases, NH* and CH* peak at XNH3 = 0.3 and 0.6, respectively; OH* and NH2* increase monotonically, while CO2* decreases. With increasing φ, the peaks of OH*/NH*/CH*/CO2* appear at φ = 1.0/1.0/1.0/0.8, while NH2* continues to rise. Regarding the relationship between NO and chemiluminescence, a nearly monotonic relationship is observed between the peak mole fraction of NO and CO2*. With varying XNH3, similar relationships exist between NO and the ratios of CO2*/OH*, CO2*/NH*, and CO2*/CH*, but these relationships break down at high XNH3. Over a wide φ range, the NH2*/CO2* ratio shows good potential for predicting NO formation and emission. This study facilitates accurate monitoring and emission control of NOx in NH3-blended combustion systems.
KEYWORDS
ammonia, NO, chemiluminescence, premixed flat flame, kinetic analysis
PAPER SUBMITTED: 2025-05-16
PAPER REVISED: 2025-08-08
PAPER ACCEPTED: 2025-08-14
PUBLISHED ONLINE: 2025-09-13
DOI REFERENCE: https://doi.org/10.2298/TSCI250516156L
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Assessing the potential of chemiluminescence to characterize no formation in ammonia-methane premixed flat flames