Proceedings of the Combustion Institute最新文献

{"title":"A combined experimental and numerical investigation focusing on the effects of CH3 substituent on the PAH chemistry in the pyrolysis of cyclopentane and methylcyclopentane","authors":"Qian-Peng Wang ,&nbsp;Du Wang ,&nbsp;Ling-Nan Wu ,&nbsp;Jiu-Jie Kuang ,&nbsp;Qing-Bo Zhu ,&nbsp;Shu-Yao Chen ,&nbsp;Xiang Gao ,&nbsp;Cheng-Yin Ye ,&nbsp;Zhan-Dong Wang ,&nbsp;Marina Braun-Unkhoff ,&nbsp;Zhen-Yu Tian","doi":"10.1016/j.proci.2025.105857","DOIUrl":"10.1016/j.proci.2025.105857","url":null,"abstract":"<div><div>The combustion behavior of cycloalkanes has long fascinated researchers because their cyclic unique structural properties may significantly influence their reactivity and combustion kinetics. In order to achieve a better understanding of the kinetics of cycloalkanes during intermediate to high temperature combustion chemistry, the pyrolysis of cyclopentane (CP) and methylcyclopentane (MCP) was studied in a jet-stirred reactor (869–1210 K, 1 atm) to explore the impact of methyl substituents on polycyclic aromatic hydrocarbon (PAH) formation and combustion kinetics. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) identified monocyclic to polycyclic aromatics, including acenaphthylene, phenanthrene, and pyrene. A newly developed kinetic model, validated against experimental data, revealed distinct decomposition behaviors: MCP exhibited lower initial decomposition temperatures and faster formation of C1–C4 hydrocarbons and aromatics compared to CP. This is attributed to the methyl group’s lower energy barrier, enhancing MCP’s reactivity. While CP pyrolysis generated higher concentrations of 1,3-cyclopentadiene and resonance-stabilized C5 cyclic radicals, these intermediates did not notably elevate PAH levels. In contrast, MCP’s methyl side chain promoted earlier fuel breakdown and accelerated PAH/soot precursor formation via enhanced radical production and alkylation pathways. These findings highlight that methyl substitution in cycloalkanes lowers thermal stability, accelerates decomposition, and amplifies aromatic growth, emphasizing structural effects on combustion chemistry and pollutant formation. The study provides critical insights into fuel design and emission control strategies for cyclic hydrocarbons.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105857"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Examining fire spread dynamics in canyon terrain through physics-based modeling: Mechanisms of fire line rotation and non-local fire behavior","authors":"Karl Töpperwien ,&nbsp;Qing Wang ,&nbsp;Yi-Fan Chen ,&nbsp;Cenk Gazen ,&nbsp;John Anderson ,&nbsp;Matthias Ihme","doi":"10.1016/j.proci.2025.105802","DOIUrl":"10.1016/j.proci.2025.105802","url":null,"abstract":"<div><div>Wildfire spread in complex terrain poses a major challenge for predictive modeling, as interactions between topography, wind, and combustion give rise to erratic fire behavior that caused fatalities among fire fighters. This study investigates the spread dynamics of a canyon fire exhibiting a characteristic fire line rotation, wherein the fire front progresses downslope along the canyon side-walls, perpendicular to the nominal wind direction. Using large-eddy simulations with a physics-based mesoscale solver, we model coupled fire–atmosphere–terrain interactions over kilometer-scale domains to resolve the three-dimensional flow and combustion structures governing fire spread. We consider a canyon terrain and compare it against two simpler configurations: a sloped ramp and a flat surface. Analysis of fire arrival times reveals that, despite identical ridge slopes, the canyon induces distinctly different spread behavior, resulting in oblique propagation along the canyon side-walls and intermittent progression in the valley. A detailed examination of flow field quantities attributes these phenomena to terrain-induced wind/slope misalignment and localized vorticity amplification, which persists after fire front passage and promotes extreme fire behavior. Furthermore, we demonstrate that the fire rate of spread in complex terrain is inherently non-local: individual sections of the fire line are influenced by neighboring segments, transient flow structures, and topographic features. Overall, our findings highlight the critical role of topography in modulating fire dynamics and provide physical insights into the mechanisms driving extreme fire behavior in canyon-like environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105802"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144830204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Propagation limits of cellular detonation in narrow channels","authors":"Brian Devine,&nbsp;Thomas Westenhofer,&nbsp;Xian Shi","doi":"10.1016/j.proci.2025.105819","DOIUrl":"10.1016/j.proci.2025.105819","url":null,"abstract":"<div><div>This study investigates the propagation limits of cellular detonation in narrow channels, aiming to distinguish between two mechanisms that govern these limits: the first associated with detonation cell accommodation and the second with boundary losses. Hydrogen–oxygen–argon mixtures were tested with and without ozone addition at initial pressures ranging from 5 to 35 kPa in three experimental configurations: (1) a base channel, (2) a half-height channel, and (3) a half-width channel. For each configuration, experiments were conducted at progressively lower pressures until detonation failed. For the base channel with and without ozone addition, and the half-height channel, detonation failure was observed to be governed by the cell limit, i.e., the geometric accommodation of cellular structures by the narrow channel. Specifically, ozone doping extended the detonation limit to lower pressures by reducing cell size, while decreasing channel height constrained cell development, leading to failure at higher pressures. Immediately before their respective limits, all three test sets exhibited the characteristic half-cell, zig-zag pattern. In contrast, results from the half-width channel with enhanced boundary losses revealed that there exists a loss limit: detonation failure started to appear at elevated pressures and became progressively more probable as pressure decreased, eventually reaching absolute failure. Unlike the zig-zag propagation mode, detonation either propagates with a multi-cell structure or fails completely. Ozone addition was ineffective at extending the limit, suggesting that detonation failure is governed by loss mechanisms independent of cell size. We further performed modified ZND calculations that take into account the impact of flow divergence. The models correctly captured the velocity deficit trends and limiting pressures, validating the experimental identification of the loss limit. These findings demonstrate that detonation failure in cellular detonations can be dominated by boundary losses, implying that modifying cellular structures alone may not extend propagation limits in confined systems with significant losses.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105819"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of H2 and Jet-A1 fuel split on flame stability and pollutant emissions from low-swirl burner","authors":"Samarjeet Singh ,&nbsp;Matteo Amerighi ,&nbsp;Nicola Scopolini ,&nbsp;Antonio Andreini ,&nbsp;Stefan R. Harth ,&nbsp;Dimosthenis Trimis","doi":"10.1016/j.proci.2025.105858","DOIUrl":"10.1016/j.proci.2025.105858","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Hydrogen combustion is emerging as a promising solution for future aircraft engines, offering a shift from fossil fuels to sustainable alternatives and the potential for reduced pollutant emissions. While the complete transition to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; presents a significant challenge due to its low volumetric energy density, limited availability, and infrastructure and aircraft redesign constraints, fuel-flexible burner technologies that allow &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; blending with Jet-A1 offer a viable alternative. These technologies provide additional benefits such as an enhanced stability range and can contribute to achieving near-term decarbonization goals. This study explores the capabilities of a novel dual-fuel burner developed as part of the European project FFLECS (Novel Fuel-Flexible ultra-Low Emissions Combustion systems for Sustainable aviation). Flame stabilization in a lean lifted flame combustor operating under atmospheric conditions and fueled by Jet-A1 and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; is experimentally investigated. A new fuel-flexible nozzle, based on the “low swirl” lean lifted flame concept, is developed to enable high premixing, significantly reducing &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;x&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; emissions and minimizing flashback risk compared to conventional swirl-stabilized flames. The &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; injection for the investigated nozzle was optimized for part load conditions, but can still be operated up to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;mtext&gt;%&lt;/mtext&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The flame shape and lift-off height were studied at elevated air inlet temperature and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; blending ratios up to 100% of the total thermal power. Moreover, the lean blowout limits remain similar for &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; blending ratios up to 30% across various air inlet temperatures but change significantly at higher blends. Finally, switching from Jet-A1 to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; lowers &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; emission at low air inlet temperatures and increases it at higher temperatures, with a pronounced rise across all air inlet temperatures at blends above 75% &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; under elevated specific thermal power. In contrast, the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;NO&lt;/mtext","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105858"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145117637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Premixing effects on NOx scaling in high-pressure, lean methane-air axial stage combustion","authors":"Penelope Torres Serrano,&nbsp;Michael Tonarely,&nbsp;Anthony Morales,&nbsp;Max Fortin,&nbsp;Khaoula Chougag,&nbsp;Charles Clark,&nbsp;Kareem Ahmed","doi":"10.1016/j.proci.2025.105810","DOIUrl":"10.1016/j.proci.2025.105810","url":null,"abstract":"<div><div>Reducing pollutant emissions continues to be a primary concern for the development and operation of power generation systems to minimize environmental impacts. Operating combustors under fuel-lean conditions with enhanced premixing is a proven strategy for reducing NO_x emissions, but a deeper understanding of NO_x formation mechanisms across a range of engine-relevant conditions is vital. Recent studies have shown that the dominant NO_x formation mechanism shifts from prompt to thermal when increasing pressure from atmospheric to high pressure conditions, emphasizing the need for system relevant data. This study presents emissions measurements of a high-pressure, lean axially staged combustion experiment designed to quantify changes in NO_x production relative to equivalence ratio and fuel-air premixing. For each test case, constant vitiated crossflow conditions are supplied to the secondary combustion zone which consists of a lean methane-air reacting jet in crossflow. Results show that NO_x emissions increase with increased jet equivalence ratio and with reduced fuel-air premixing, as less premixed jets create locally rich regions that promote NO_x-forming hotspots. To collapse the measured NO_x trends, two scaling strategies are applied. First, flame and post-flame NO_x contributions are quantified through detailed chemical kinetics across a spread of equivalence ratio. Second, the effects of premixing are captured using mixture fraction distributions in the axial jet injector, defined by CFD simulations of the injector mixing at each tested equivalence ratio. When experimental data are first scaled using only the individual NO_x production rates, results converge well for highly premixed conditions, effectively collapsing equivalence ratio effects, but show scatter at lower premixing levels. Incorporating the CFD-derived mixture fraction distributions further collapses the data, eliminating observable trends with premixing and indicating successful normalization of mixing effects. This approach resulted in a mean scaled emissions value of 0.34 with a standard deviation of about 25 %. The result of the current study is an effective collapse of experimental NO_x emissions across both global (equivalence ratio) and local (jet premixing) fuel-air variations in lean, premixed, axially staged flames - an operating regime not previously characterized in this manner.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105810"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hybrid physics-machine learning model for multispecies and temperature inference from FTIR spectra: Application to ammonia flames","authors":"Zituo Chen,&nbsp;Nicolas Tricard,&nbsp;Sili Deng","doi":"10.1016/j.proci.2025.105811","DOIUrl":"10.1016/j.proci.2025.105811","url":null,"abstract":"<div><div>Fourier-transform infrared (FTIR) spectroscopy offers a powerful, non-intrusive diagnostic tool for <em>in-situ</em> measurements of temperature and species concentrations in combustion systems. However, in practical applications, FTIR spectra often suffer from low spectral resolution, strong band overlap, and significant variation in species concentration levels, making quantitative interpretation a challenging inverse problem. In this work, we present a hybrid physics-machine learning framework for inferring temperature, path length, and species mole fractions from FTIR emission spectra of ammonia flames. The model is trained on high-fidelity synthetic spectra generated via line-by-line radiative transfer using HITEMP/HITRAN spectroscopic databases. To address challenges of spectral overlap, minor-species detectability, and measurement noise, the architecture incorporates physics-based regularization and a self-supervised spectrum reconstruction module that enforces consistency with the radiative transfer equation. Our hybrid approach enables robust multi-target inference across species spanning several orders of magnitude in concentration. Compared to standard partial least squares (PLS) regression and ablated models, the proposed framework achieves superior accuracy and noise robustness while remaining compact and interpretable. Additionally, the co-trained reconstruction module exhibits effective denoising capabilities, highlighting the physical relevance of the learned spectral representation. This framework provides a foundation for practical, generalizable FTIR diagnostics and opens pathways toward spatially resolved inference in complex combustion environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105811"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scientific machine learning in combustion for discovery, simulation, and control","authors":"Sili Deng,&nbsp;Linzheng Wang,&nbsp;Suyong Kim,&nbsp;Benjamin C. Koenig","doi":"10.1016/j.proci.2025.105796","DOIUrl":"10.1016/j.proci.2025.105796","url":null,"abstract":"<div><div>Combustion science is undergoing a transformation, driven by the need to model increasingly complex, multi-scale systems and accelerate progress toward cleaner, more efficient energy technologies. While traditional modeling approaches remain foundational, they face growing limitations under modern demands such as alternative fuels, stringent emission standards, and extreme operating environments. This review explores how scientific machine learning (SciML), which integrates data-driven models with physical constraints, is reshaping combustion research across three central fronts: model discovery, simulation acceleration, and system state reconstruction. We highlight recent advances in parameter estimation, reaction mechanism generation, and interpretable model discovery using tools such as physics-informed neural networks, chemical reaction neural networks, symbolic regression, and governing equation-constrained parameter optimization. For simulation, we examine neural surrogates, operator learning, and physics-inspired architectures that enable fast and accurate predictions while preserving physical fidelity. Finally, we review emerging methods for reconstructing full-field combustion states from sparse data, enabling mutual inference across physical quantities and advancing digital twin development through multi-modal data fusion. Together, these developments demonstrate how SciML is enabling new capabilities for combustion modeling, diagnostics, and control. As the field evolves, continued progress will depend on integrating domain knowledge with scalable algorithms, rigorous uncertainty quantification, and cross-disciplinary collaboration, paving the way for next-generation combustion systems that are intelligent, adaptive, and physically grounded.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105796"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simultaneous NH/NO PLIF measurements in plasma-assisted ammonia and ammonia/hydrogen swirling flames","authors":"Hao Tang,&nbsp;Evangelos Chatziandreou,&nbsp;Griffin Rahn,&nbsp;Bo Peng,&nbsp;Wenting Sun","doi":"10.1016/j.proci.2025.105789","DOIUrl":"10.1016/j.proci.2025.105789","url":null,"abstract":"<div><div>This study investigates simultaneous NH/NO planar laser-induced fluorescence (PLIF) measurements in plasma-assisted NH₃/air and NH₃/H₂ (9:1 volume ratio)/air flames at equivalence ratios of <span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>75</mn></mrow></math></span>, <span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>94</mn></mrow></math></span>, and 1.1. A single dye laser system, equipped with frequency-doubling and mixing units, was employed to simultaneously generate excitation wavelengths near <span><math><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mtext>NO</mtext></mrow></msub><mo>=</mo><mn>236</mn><mo>.</mo><mn>214</mn></mrow></math></span> <!--> <!-->nm and <span><math><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mtext>NH</mtext></mrow></msub><mo>=</mo><mn>303</mn><mo>.</mo><mn>545</mn></mrow></math></span> <!--> <!-->nm, enabling optimized excitation of NO and NH fluorescence, respectively. Across all equivalence ratios, plasma was found to enhance NO and NH concentrations in both NH₃/air and NH₃/H₂/air flames in the near field, although NH enhancement was less pronounced in the NH₃/H₂/air cases. In NH₃/air flames, NO concentrations decreased faster downstream with plasma activation, whereas in NH₃/H₂/air flames, NO levels remained relatively unchanged regardless of plasma activation. For NH₃/air flames, plasma could enhance atomic O production therefore acceleration of NH₃/NH₂/NH and form OH at the same time. The enhanced OH levels further promote NH production via NH₂ <span><math><mo>+</mo></math></span> OH <span><math><mo>→</mo></math></span> NH <span><math><mo>+</mo></math></span> H₂O in NH₃/air flames, though this effect is less significant in NH₃/H₂/air flames owing to the contribution of H₂ on radical pool buildup and less NH₃ availability in NH₃/H₂/air mixtures. In the downstream region, the reaction NH <span><math><mo>+</mo></math></span> NO <span><math><mo>→</mo></math></span> N₂H₂ <span><math><mo>+</mo></math></span> H plays a key role in reducing NO emissions in NH₃/air flames with plasma activation. These findings provide new insights into plasma-enhanced NH₃ flame chemistry and pollutant formation pathways, contributing to the development of cleaner and more efficient NH₃-based combustion technologies.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105789"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combustion kinetics of amines: Exploring hydrogen atom abstraction reactions from primary amines by ṄH2 radicals","authors":"Mingxia Liu ,&nbsp;Minxing Chen ,&nbsp;Ruiyang Fan ,&nbsp;Yansen Liao ,&nbsp;Jingbo Wang ,&nbsp;Chong-Wen Zhou ,&nbsp;Zhen-Yu Tian","doi":"10.1016/j.proci.2025.105832","DOIUrl":"10.1016/j.proci.2025.105832","url":null,"abstract":"<div><div>Amines are often used as model compounds to investigate the combustion chemistry of the nitrogen-containing compounds in biomass. The amino radical (ṄH₂) plays a pivotal role in the initial stages of biomass pyrolysis and oxidation. To gain insight into nitrogen conversion chemistry, it is necessary to understand the cross-reactions between amine-bearing molecules and ṄH₂ radicals. In this study, a comprehensive investigation was performed on the chemical kinetics of hydrogen atom abstraction reactions of twelve C₁ – C₅ amines by ṄH₂ radicals. Geometry optimizations and frequency analyses were conducted for all species involved in fifty reaction channels at the M06–2X/6–311++<em>G</em>(d,p) level of theory. Single-point energies were calculated at the QCISD(T)/CBS level of theory, and subsequently corrected by zero-point energy. Conventional transition state theory with asymmetric Eckart tunneling corrections and the one-dimensional hindered rotor approximation was used to calculate the high-pressure limit rate constants for these targeted reactions over a temperature range of 500 – 2000 K. The average rate constants for hydrogen atom abstraction from primary, secondary, and tertiary carbons at different positions relative to the amino functional group, labelled as α, β, γ, and δ, were provided, following the order: primary &lt; secondary &lt; tertiary. The hyperconjugation effect of the amino group on the <em>α</em> C–H bond lowers the electronic energy barrier; therefore, rate constants for abstraction from the <em>α</em> C–H site largely dominate. A comparison of the average rate constants for amines and the previous studies on alkanes, alcohols, ethers, and esters was performed to reveal the influence of different functional groups on kinetic parameters. The updated rate constants were then employed in the target fuel mechanism to investigate their effect on the prediction of species concentrations associated with H-atom abstraction reactions in a jet-stirred reactor.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105832"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145007768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fuel blend and secondary air injection effects on the stability, morphology, and dynamics of two-stage NH3-CH4/H2 swirl flames","authors":"Cristian D. Avila Jimenez ,&nbsp;Andrew Macfarlane ,&nbsp;Felipe Campuzano ,&nbsp;Santiago Cardona ,&nbsp;Matthew Dunn ,&nbsp;Thibault F. Guiberti ,&nbsp;Assaad R. Masri ,&nbsp;William L. Roberts","doi":"10.1016/j.proci.2025.105817","DOIUrl":"10.1016/j.proci.2025.105817","url":null,"abstract":"<div><div>Ammonia (NH₃) has been identified as a potential carbon-free fuel to decarbonize power generation by gas turbines. However, challenges associated with flame stabilization and emissions must be solved. Two-stage, rich-lean combustion is a promising strategy that requires fine control of the secondary stage parameters, where air is injected to oxidize the remaining unburned fuel from the rich primary stage. This study investigates the effects of the fuel blend composition (NH₃-CH₄ and NH₃-H₂), NH₃vol fraction (X_NH3), primary (<em>ϕ_primary</em>) and global (<em>ϕ_global</em>) equivalence ratios, and geometry of the secondary air injection (number and diameter of holes) on the morphology of the lean secondary and rich-premixed primary flames, and primary flame stability and dynamics. Experiments are conducted with a lab-scale piloted burner inspired by the AE-T100’s micro gas turbine burner. By increasing the secondary air flow rate (<em>Q_sec</em>), <em>ϕ_global</em> varied from 0.91 down to a value that produces primary flame morphology changes (<em>ϕ_global,FC</em>), and then to a minimum value that eventually led to flame instability followed by blowout (<em>ϕ_global,BO</em>). These thresholds were found to depend on fuel composition and air injection geometry. High-speed chemiluminescence imaging of NH₂* combined with Dynamic Mode Decomposition (DMD) revealed distinct instability mechanisms: CH₄-blended flames exhibited longitudinal pulsations, while H₂-blended flames showed a rotating inner core that reignites upstream reactants. These instabilities are linked with a combustion regime transition for the secondary combustion zone, from diffusion-like to premixed-like (or partially premixed), indicative of an optimum <em>ϕ_global</em> for each geometry. Finally, increasing the number of secondary air holes (while keeping diameter constant) extended flame stability to leaner <em>ϕ_global</em>. Data showed that the geometry of the secondary air injection is more important for stability than other varied parameters, a valuable finding for the design of future two-stage, rich-lean NH₃ burners.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105817"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144886775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}