A comprehensive parametric study on NO and N2O formation in ammonia-methane cofired premixed flames: Spatially resolved measurements and kinetic analysis

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2024-11-16 DOI:10.1016/j.combustflame.2024.113851

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.

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氨-甲烷共燃预混合火焰中 NO 和 N2O 形成的综合参数研究：空间分辨测量和动力学分析

了解氮氧化物的形成和破坏机理是开发有效的氨火焰氮氧化物减排技术的先决条件。实验室规模的层状氨（NH3）火焰非常适合进行此类基础动力学研究，因为化学与流体流动之间复杂的相互作用在很大程度上可以被分离。然而，典型层状氨火焰中的定量和空间分辨 NO/N2O 浓度数据却少得令人吃惊。另一方面，这些数据对于开发和验证 NH3 燃烧动力学模型至关重要。为此，我们开发了一种新型 NO/N2O 测量方法，该方法结合了微探针采样和免校准中红外激光吸收光谱技术，实现了高精度和大动态比的空间分辨检测。在应用该方法对 NH3-CH4 共烧燃烧器稳定预混合火焰中 NO 和 N2O 的形成进行综合参数研究之前，已经对该方法的准确性进行了严格测试。实验确定了 NH3 燃料比、当量比和火焰温度对 NO/N2O 形成的影响。还利用基于文献的机制进行了相应的数值建模，以便为实验观察提供动力学见解。研究发现，现有的机理通常对燃料贫乏火焰的预测令人满意；然而，在燃料丰富的条件下，这些机理高估了 NO 的形成，却低估了其破坏，导致严重的预测过度。通过灵敏度和反应途径分析，对这种差异进行了进一步研究。本研究不仅提供了开发和验证 NH3 燃烧机制所急需的氨火焰中广泛的空间分辨 NO/N2O 数据，而且对纯 CH4 和 NH3 燃烧火焰的比较还表明，在碳氢化合物燃料燃烧中流行的传统 NOx 减缓技术可能并不适用于 NH3 火焰。也许最有趣的是，本实验结果表明富氧氧化剂在某些情况下可以减少 NH3 火焰的氮氧化物排放。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

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.