A comprehensive parametric study on NO and N2O formation in ammonia-methane cofired premixed flames: Spatially resolved measurements and kinetic analysis
Qing Li , Liuhao Ma , Jiwei Zhou , Jintao Li , Fuwu Yan , Jianguo Du , Yu Wang
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引用次数: 0
Abstract
Understanding the mechanism of NOx formation and destruction is a prerequisite for the development of effective NOx mitigation techniques in ammonia flames. Laboratory-scale laminar ammonia (NH3) flames are well suited for such fundamental kinetic studies as the complex interaction between chemistry and fluid flow can be largely decoupled. However, quantitative and spatially resolved NO/N2O concentration data in canonical laminar ammonia flames are surprisingly scarce. Such data is, on the other hand, crucial for developing and validating kinetic models for NH3 combustion. In this regard, we developed a novel NO/N2O measurement method combining microprobe sampling and calibration-free mid-infrared laser absorption spectroscopy and realized spatially-resolved detection with high accuracy and large dynamic ratio. The fidelity of the method has been rigorously tested before being applied to perform a comprehensive parametric study on NO and N2O formation in NH3-CH4 co-fired burner-stabilized premixed flames. The effects of NH3 fuel ratio, equivalence ratio and flame temperature on NO/N2O formation have been experimentally determined. Corresponding numerical modelling was also performed using literature-based mechanisms to provide kinetic insights into the experimental observations. It is found that existing mechanisms generally have satisfactory predictions in fuel-lean flames; however, under fuel-rich conditions, these mechanisms overpredict NO formation but underestimate its destruction, leading to significant over-prediction. Such discrepancies were further investigated through sensitivity and reaction pathway analysis. The present study not only provides extensive spatially-resolved NO/N2O data in ammonia flames that are urgently needed for the development and validation of NH3 combustion mechanisms, the comparison between neat CH4 and NH3-cofired flames also points to the fact that traditional NOx mitigation techniques that are popular in combustion of hydrocarbon fuels may not be appropriate in NH3 flames. Perhaps most interestingly, the present experimental results show an oxygen-enriched oxidizer can in some cases reduce NO emission from NH3 flames.
期刊介绍：
The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on:
Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including:
Conventional, alternative and surrogate fuels;
Pollutants;
Particulate and aerosol formation and abatement;
Heterogeneous processes.
Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including:
Premixed and non-premixed flames;
Ignition and extinction phenomena;
Flame propagation;
Flame structure;
Instabilities and swirl;
Flame spread;
Multi-phase reactants.
Advances in diagnostic and computational methods in combustion, including:
Measurement and simulation of scalar and vector properties;
Novel techniques;
State-of-the art applications.
Fundamental investigations of combustion technologies and systems, including:
Internal combustion engines;
Gas turbines;
Small- and large-scale stationary combustion and power generation;
Catalytic combustion;
Combustion synthesis;
Combustion under extreme conditions;
New concepts.
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