{"title":"The effects of NH3 pre-cracking and initial temperature on the intrinsic instability and NOx emissions of NH3/bio-syngas/air premixed flames","authors":"","doi":"10.1016/j.joei.2024.101873","DOIUrl":null,"url":null,"abstract":"<div><div>The study of the combustion characteristics of NH₃/bio-syngas/air under NH₃ partial cracking and elevated initial temperatures can enhance its feasibility as a practical fuel. The effects of NH₃ cracking rates (<em>ζ</em>) and initial temperature (<em>T</em><sub><em>0</em></sub>) on the laminar burning velocity (<em>S</em><sub><em>L</em></sub>), instability, and NO emissions of NH₃/bio-syngas/air premixed flames under different equivalence ratios are investigated. The results indicate that increasing <em>ζ</em> and <em>T</em><sub><em>0</em></sub> enhances the <em>S</em><sub><em>L</em></sub> of the premixed flame, with <em>ζ</em> having a more pronounced effect on combustion enhancement. Virtual gas analysis reveals that pre-cracking primarily strengthens combustion through chemical effect. An increase in <em>ζ</em> significantly shifts the peak <em>S</em><sub><em>L</em></sub> towards the fuel-rich region, while at any <em>T</em><sub><em>0</em></sub>, the peak <em>S</em><sub><em>L</em></sub> consistently occurs around Φ = 1.1. Increasing <em>ζ</em> and <em>T</em><sub><em>0</em></sub> reduces the critical radius (<em>r</em><sub><em>c</em></sub>) and the critical Peclet number (<em>Pe</em><sub><em>c</em></sub>) of the premixed fuel, with <em>r</em><sub><em>c</em></sub> decreasing more rapidly when <em>ζ</em> is below 30 %. The dimensionless growth rate (<em>∑</em>) increases with the rise in <em>ζ</em> and <em>T</em><sub><em>0</em></sub>, consistently remaining positive, indicating an unstable state. Additionally, <em>∑</em> varies more significantly with <em>T</em><sub><em>0</em></sub> when <em>T</em><sub><em>0</em></sub> is below 450 K. When <em>ζ</em> is below 60 %, the NO mole fraction increases with the increase in <em>ζ</em>. However, at <em>ζ</em> = 80 %, the NO mole fraction is lower than at <em>ζ</em> = 40 %. Increasing <em>T</em><sub><em>0</em></sub> continually increases the NO mole fraction. Analysis of the NH<sub>3</sub> reaction pathways indicates that NH<sub>i</sub> (i = 0, 1, 2) is closely related to the NO → N<sub>2</sub> reduction reactions.</div></div>","PeriodicalId":17287,"journal":{"name":"Journal of The Energy Institute","volume":null,"pages":null},"PeriodicalIF":5.6000,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of The Energy Institute","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1743967124003519","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
引用次数: 0
Abstract
The study of the combustion characteristics of NH₃/bio-syngas/air under NH₃ partial cracking and elevated initial temperatures can enhance its feasibility as a practical fuel. The effects of NH₃ cracking rates (ζ) and initial temperature (T0) on the laminar burning velocity (SL), instability, and NO emissions of NH₃/bio-syngas/air premixed flames under different equivalence ratios are investigated. The results indicate that increasing ζ and T0 enhances the SL of the premixed flame, with ζ having a more pronounced effect on combustion enhancement. Virtual gas analysis reveals that pre-cracking primarily strengthens combustion through chemical effect. An increase in ζ significantly shifts the peak SL towards the fuel-rich region, while at any T0, the peak SL consistently occurs around Φ = 1.1. Increasing ζ and T0 reduces the critical radius (rc) and the critical Peclet number (Pec) of the premixed fuel, with rc decreasing more rapidly when ζ is below 30 %. The dimensionless growth rate (∑) increases with the rise in ζ and T0, consistently remaining positive, indicating an unstable state. Additionally, ∑ varies more significantly with T0 when T0 is below 450 K. When ζ is below 60 %, the NO mole fraction increases with the increase in ζ. However, at ζ = 80 %, the NO mole fraction is lower than at ζ = 40 %. Increasing T0 continually increases the NO mole fraction. Analysis of the NH3 reaction pathways indicates that NHi (i = 0, 1, 2) is closely related to the NO → N2 reduction reactions.
期刊介绍:
The Journal of the Energy Institute provides peer reviewed coverage of original high quality research on energy, engineering and technology.The coverage is broad and the main areas of interest include:
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