Proceedings of the Combustion Institute最新文献

{"title":"Ozone-initiated low-temperature oxidation of 1,3-dioxane","authors":"Caroline Smith Lewin,&nbsp;Huanhuan Wang,&nbsp;Jiabiao Zou,&nbsp;Alvina Mendy,&nbsp;Olivier Herbinet,&nbsp;Jérémy Bourgalais,&nbsp;Frédérique Battin-Leclerc","doi":"10.1016/j.proci.2026.106385","DOIUrl":"10.1016/j.proci.2026.106385","url":null,"abstract":"<div><div>This study explores the influence of ozone addition on the low-temperature oxidation of 1,3-dioxane, a recently proposed cyclic oxymethylene ether biofuel. Experiments were conducted in a jet-stirred reactor operated slightly above atmospheric pressure over 375–850 K. A new detailed kinetic model was developed, incorporating theoretically calculated rate constants for hydrogen abstraction reactions by atomic oxygen (O), the primary decomposition product of O₃. Experimental results reveal that introducing 1000 ppm of O₃ significantly accelerates fuel reactivity, initiating 1,3-dioxane consumption near 450 K, whereas oxidation without O₃ begins around 550 K. Between 600–700 K, the pronounced negative temperature coefficient (NTC) behavior observed under O₃-free conditions is notably diminished when O₃ is present. Simulations using the new kinetic model successfully reproduce these experimental trends, including fuel conversion and formation of major products. Kinetic analyses demonstrate that O₃-derived O atoms enhance early-stage chain initiation and alter dominant reaction pathways, providing mechanistic insight into O₃-assisted low-temperature oxidation chemistry of oxygenated fuels.</div></div><div><h3>Novelty and significance statement</h3><div>This study is the first to experimentally and computationally investigate the ozone-initiated low-temperature oxidation of 1,3-dioxane. It introduces a new detailed kinetic mechanism that incorporates ab initio–derived rate constants for hydrogen abstraction by O atoms, the primary reactive species generated from ozone decomposition. The study uniquely demonstrates how ozone addition accelerates dioxygenated cyclic ether consumption, lowers the onset temperature of oxidation by ∼100 K, and suppresses negative temperature coefficient (NTC) behavior, providing unprecedented mechanistic insights into O₃-assisted oxidation of oxygenated biofuels.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106385"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A ReaxFF molecular dynamics approach to modeling hardwood hemicellulose pyrolysis","authors":"Shuaihong Liu,&nbsp;Xinru Han,&nbsp;Song Lu,&nbsp;Xiaoyu Ju,&nbsp;Hanfeng Jin","doi":"10.1016/j.proci.2026.106372","DOIUrl":"10.1016/j.proci.2026.106372","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Hemicellulose pyrolysis plays a crucial role in biomass combustion and thermochemical conversion processes. But its kinetic models reported in literature heavily rely on experimental data due to its complex molecular structure. These models thus cannot be widely applied under different combustion conditions. In this study, we proposed a novel \"lumped-simplified\" modeling approach based on ReaxFF molecular dynamics (MD) simulations to well predict the pyrolysis behavior of hardwood hemicellulose. Firstly, we identified the critical intermediates in the reaction system using carbon flux analysis. Then, we quantitatively correlated the concentrations of these critical intermediates, which were later used to formulate the stoichiometric coefficients in the lumped-simplified reaction expression of hemicellulose decomposition. At last, we adopted a double-Gaussian distributed activation energy model (DG-DAEM) to identify two subprocesses with different activation-energy distributions. Two pseudo-components, HCE1 and HCE2, were introduced to describe the early primary decomposition stage and the deep-conversion stage, respectively. Our lumped-simplified model can well reproduce the weight-loss behavior, bimodal DTG characteristics, main product distribution, and typical gaseous product release rate of hardwood hemicellulose pyrolysis across a wide range of heating rates (5 – 100 K/min). The deviations of DTG peak-temperature predictions are below 16 K, and deviations for char, gas, volatiles, and water yields are 1.58%, 1.75%, 2.43%, and 5.51%, respectively. In conclusion, the modeling approach proposed in this study significantly simplifies the development of a kinetic model for complex solid combustibles, which contributes to the advancement of numerical simulations of combustion processes in solid combustibles.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;Accurate modeling of hemicellulose pyrolysis benefits the prediction of wildfire spread and industrial biomass utilization. Traditional models require extensive experimental data and rigorous parameter optimization across broad combustion conditions. In this study, we proposed a novel \"lumped-simplified\" modeling approach based on ReaxFF MD. Utilizing its rich molecular-level information, we identified critical combustion intermediates by carbon flux analysis, and determined the reaction stoichiometric coefficients by intermediate correlation analysis. This approach simplifies the model development, reduces the experimental data dependence, and enables the prediction of complicated solid fuel combustion across wide conditions. Such a simplified model is specially designed for CFD applications, which contains necessary chemical information but saves computational resources in numerical simulation. It may help to answer those crucial questions in fire science and industrial engineering, such as the fire ignition in wooden architecture, the fire spread in wildfire or wildla","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106372"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153704","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":"Impact of ammonia on hydrogen oxidation near the second explosion limit in a turbulent flow reactor","authors":"Gabriel J. Gotama,&nbsp;Felipe Augusto Ferreira Gomes,&nbsp;Alex Sherwood,&nbsp;Yi Yang,&nbsp;Liang Yu,&nbsp;Xingcai Lu","doi":"10.1016/j.proci.2026.106529","DOIUrl":"10.1016/j.proci.2026.106529","url":null,"abstract":"<div><div>The contrasting combustion properties of ammonia (NH₃) and hydrogen (H₂) offer potential to promote NH₃ oxidation with H₂ and to moderate H₂ reactivity with NH₃. This paper examines the latter in a turbulent flow reactor using mixtures containing 0–20% NH₃ and 0–155 ppm nitric oxide (NO) in H₂ at ϕ = 0.033–0.044. Time-resolved concentrations of H₂, NH₃, NO, NO₂, and N₂O were measured at 926–976 K and at 1.1 bar and 4 bar, corresponding to H₂ oxidation near the second explosion limit where increasing pressure reduces hydrogen oxidation reactivity. At 1.1 bar, NH₃ addition strongly inhibits H₂ oxidation. However, at 4 bar, a small NH₃ addition (H₂:NH₃ = 95:5) promotes H₂ oxidation, which is unexpected given NH₃ is less reactive than H₂. A chemical kinetic model is developed to simulate the experiment. Analysis using the model indicates that at 4 bar, NH₃ promotes H₂ oxidation by generating NO via NH₃ oxidation; NO then converts the less reactive HO₂ to OH through the chain NO + HO₂ → NO₂ + OH and H + NO₂ → NO + OH. In contrast, when NO is present in the reactants, added NH₃ introduces additional OH sinks, which diminishes NO’s promotional effect on H₂ oxidation and reduces the stiffness of the H₂/NO oxidation system at 1.1 bar.</div></div><div><h3>Novelty and significance statement</h3><div>This study reports the first time-resolved species concentrations of H₂/NH₃ and H₂/NH₃/NO oxidations in a turbulent flow reactor. The measurements show that while NH₃ generally slows down H₂ oxidation, conditions exist in which NH₃ addition could promote H₂ oxidation. Such promotion has not been previously observed but potentially affects the use of H₂/NH₃ fuels in practical combustion. By extending the investigation to NO-containing mixtures, it was found that the introduction of NH₃ moderates the steep promotion of NO on H₂ oxidation. This work revealed novel chemistry in H₂/NH₃ and H₂/NH₃/NO combustion and provided new targets to improve ammonia combustion models.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106529"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of aromatics in a 2,5-dimethylfuran-isooctane laminar premixed flame","authors":"Kanika Sood,&nbsp;Sylvie Gosselin,&nbsp;Shunsuke Suzuki,&nbsp;Alessandro Faccinetto,&nbsp;Pascale Desgroux,&nbsp;Laurent Gasnot,&nbsp;Luc-Sy Tran","doi":"10.1016/j.proci.2026.106570","DOIUrl":"10.1016/j.proci.2026.106570","url":null,"abstract":"<div><div>2,5-Dimethylfuran (DMF) has emerged as a promising cellulose-derived biofuel additive and octane booster for gasoline engines. Although prior studies have discussed its combustion chemistry, experimental data quantifying polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) in flames remain limited. In the present work, a premixed low sooting atmospheric flame of DMF blended with isooctane (a gasoline surrogate component) and methane is investigated. The presence of soot particles smaller than 7 nm was confirmed by using a nano-SMPS (Scanning Mobility Particle Sizer). &gt;60 species, including 22 aromatic compounds, were quantified using gas chromatography. Using the preconcentration step upstream of the gas chromatography (GC) setup, PAHs and OPAHs, even at concentrations as low as ∼1 ppb were quantified. This constitutes, to the best of our knowledge, the first experimental dataset providing quantitative measurements of both PAHs and OPAHs in a DMF-isooctane-methane flame. Benzene and phenol were found to be the most abundant aromatics, with mole fractions in the order of 100–300 ppm, whereas three-ring PAHs such as phenanthrene were detected at much lower levels (∼20 ppb). Notably, dibenzofuran was observed at concentrations comparable to acenaphthylene (∼300 ppb) and approximately three times higher than its structural analog fluorene. A comparison with an anisole (a lignin-derived biofuel) flame indicated that DMF produces aromatics, particularly OPAHs, at levels approximately 3–20 times lower under similar conditions. Finally, simulations based on existing kinetic models were unable to satisfactorily reproduce the measured PAH/OPAH profiles, highlighting the need for improved chemical mechanisms capable of accurately describing aromatic formation in DMF-containing fuel blends.</div></div><div><h3>Novelty and significance statement</h3><div>This study presents, to the best of our knowledge, the first detailed quantification of aromatics, including polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs), formed in a 2,5-dimethylfuran (DMF)-isooctane-methane flame in a regime where soot becomes measurable. Such data, not previously reported for DMF or for cellulosic-derived oxygenated fuels more broadly, provides a valuable basis for validating and refining kinetic models while highlighting their current limitations in predicting PAH and OPAH formation. Under the investigated conditions, DMF produces approximately 3–20 times lower concentrations of PAHs and OPAHs than anisole, a lignin-derived biofuel. This difference may be attributed to the greater ease of phenoxy radical formation during anisole combustion. Additionally, OPAHs appear to form closer to the burner surface, whereas PAHs develop further downstream. These findings can offer a foundation for improving predictive combustion models for advanced biofuels.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106570"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153707","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":"Understanding co-pyrolysis chemistry of p-cymene/oxymethylene ether-3 blend with concerns on polycyclic aromatic hydrocarbons formation pathways","authors":"Mo Yang,&nbsp;Hairong Ren,&nbsp;Guangda Luo,&nbsp;Sheng Huang,&nbsp;Zhongyue Zhou,&nbsp;Feng Zhang","doi":"10.1016/j.proci.2026.106275","DOIUrl":"10.1016/j.proci.2026.106275","url":null,"abstract":"<div><div>This study investigated, for the first time, the co-pyrolysis chemistry of <em>p</em>-cymene/OME₃ blend in a flow reactor, motivated by the potential of <em>p</em>-cymene as a surrogate for branched aromatic alkyls in biofuels and OME₃ as an additive to reduce carbonaceous particles. The goal is to explore how oxygenated additives affect aromatic mass growth. A photoionization time-of-flight mass spectrometer (PI-TOF-MS) and an atmospheric photoionization high-resolution orbitrap mass spectrometer (APPI-HRMS) were employed to elucidate the formation mechanisms of both monocyclic and polycyclic aromatic hydrocarbons (MAHs/PAHs) over a broad mass range. A detailed kinetic model covering most of the detected MAHs and PAHs up to the size of five rings was developed and validated against the measurements. OME₃ blending was found to promote fuel decomposition while inhibiting PAHs growth. Modeling analysis revealed three key precursor types—fuel-specific MAHs, resonance-stabilized indenyl-like radicals and benzo-fulvenallenyl radicals—governing PAHs formation through distinct progressive reaction pathways. Among them, the chain reactions triggered by combinations of diverse resonance stabilized radicals deserve extensive attention due to their special role in generating the fuel-specific polymethyl-substituted PAHs. The APPI-HRMS analysis further confirms that OME₃ blending leads to the suppressed mass-growth process of highly-condensed PAHs and the promoted formation of high-mass oxygenated PAHs (OPAHs). The regular interval between adjacent peaks observed in APPI-HRMS suggests a stepwise oxidizing-species-addition process, forming OPAHs with hydroxyl or/and ether functional group(s) on the branched chains.</div></div><div><h3>Novelty and significance statement</h3><div>This study provides the first comprehensive characterization of <em>p</em>-cymene/OME₃ co-pyrolysis chemistry with explicit emphasis on aromatic mass-growth pathways. Its novelty lies in combining the complementary PI-TOF-MS and APPI-HRMS diagnostics with detailed kinetic modeling to bridge fuel decomposition, fuel-specific MAHs formation, and PAHs evolution up to five-ring species while extending analysis to highly-condensed oxygenated aromatics over a broad mass range. The work reveals how an oxygenated additive modifies PAHs yield, and how the dominant precursor classes and radical-chain growth routes control aromatics formation with high abundance. These findings advance mechanistic understanding of aromatic mass-growth chemistry in bio-derived fuel components and provide new guidance for designing oxygenated blending strategies to suppress soot and carbonaceous deposits.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106275"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148634406","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":"From PAH to fullerenes: Closing a nano bowl with a nano lid","authors":"Lotefa Binta Tuli,&nbsp;Ralf I. Kaiser,&nbsp;Alexander M. Mebel","doi":"10.1016/j.proci.2026.106155","DOIUrl":"10.1016/j.proci.2026.106155","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Quantum chemical DLPNO-CCSD(T)/cc-pVDZ//B3LYP/6–31G(d) calculations have been performed to unravel the formation mechanism of buckminsterfullerene (C&lt;sub&gt;60&lt;/sub&gt;) via the reaction of the C40 nano bowl (C&lt;sub&gt;40&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;) and corannulene (C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;). The generated potential energy surfaces and molecular properties were further utilized to evaluate equilibrium constants and rate constants of elementary chemical reactions involved in the C&lt;sub&gt;60&lt;/sub&gt; synthesis. The overall C&lt;sub&gt;40&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt; + C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt; → C&lt;sub&gt;60&lt;/sub&gt; + 10H&lt;sub&gt;2&lt;/sub&gt; reaction is shown to be highly exoergic and hence thermodynamically favorable at temperatures above 700 K and a kinetically feasible pathway under high-temperature conditions was revealed. This route involves hydrogen atom abstraction steps to activate closed-shell reactants/intermediates alternating with cyclodehydrogenation reactions eventually zipping the edges between the reacting C40 and C20 units by consecutive closures of six- and five-membered rings between them. The reaction is driven/catalyzed by hydrogen atoms which carry out the hydrogen abstractions from C&lt;sub&gt;60&lt;/sub&gt;H&lt;em&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/em&gt; and are later recovered on the cyclodehydrogenation stages. The initial association reaction, C&lt;sub&gt;40&lt;/sub&gt;H&lt;sub&gt;9&lt;/sub&gt; + C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt; → C&lt;sub&gt;60&lt;/sub&gt;H&lt;sub&gt;18&lt;/sub&gt; + H, linking the two units by a covalent C-C bond appears to represent the kinetic bottleneck of the whole multistep process. This reaction is fast at low temperatures but slows down and has its equilibrium shifted toward the reactants at high temperatures. The feasibility of the proposed mechanism corroborates the hypothesis that C&lt;sub&gt;60&lt;/sub&gt; can be produced through a series of elementary reactions typical for the PAH growth.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;Development of new technologies to produce hydrogen and carbon materials, e.g., thermal or plasma-assisted pyrolysis of natural gas and the gas-phase production of carbon black and nanotubes, requires detailed understanding of the formation of carbonaceous particles from hydrocarbons. While PAHs are firmly established as molecular precursors of carbonaceous particles and their growth mechanisms at the pyrolysis/combustion conditions have been revealed in recent years, the physico-chemical processes leading from small PAHs to fullerenes and nanotubes remain poorly understood. Here, we demonstrate that the formation of C&lt;sub&gt;60&lt;/sub&gt; can be accounted for in terms of PAH growth mechanisms proceeding in a particular order. Our theoretical study reveals a novel thermodynamically favorable and kinetically feasible route for the gas-phase synthesis of C&lt;sub&gt;60&lt;/sub&gt; through a series of elementary chemical reactions typical for the high-temperature PAH growth. While corannulene (C&lt;sub&gt;20&lt;/sub&gt;H&lt;sub&gt;10&lt;/sub&gt;) can form from benzene and naphthalene via phenyl addition and cyclization (PAC)","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106155"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148634407","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":"Toward reliable high-temperature NH3-NO interaction kinetics: Oxygen-free measurements and evaluation of the NH2+NO branching ratio","authors":"Songlin Liu,&nbsp;Jianguo Zhang,&nbsp;Qiying Zhang,&nbsp;Yi Zhang,&nbsp;Xiaoxiang Shi,&nbsp;Wei Li,&nbsp;Yuyang Li","doi":"10.1016/j.proci.2026.106272","DOIUrl":"10.1016/j.proci.2026.106272","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The interaction between NH&lt;sub&gt;3&lt;/sub&gt; and NO plays a crucial role in controlling NOx formation during ammonia combustion. However, experimental data and mechanistic understanding under practical combustion temperatures and pressures remain limited. In this study, laminar burning velocities (LBVs) and ignition delay times (IDTs) of NH&lt;sub&gt;3&lt;/sub&gt;/NO mixtures under oxygen-free conditions were systematically investigated. Experiments were conducted using a combustion vessel and a shock tube, covering a broad range of temperatures (1500–2800 K), pressures (1.5–10 atm), and equivalence ratios (&lt;em&gt;ϕ&lt;/em&gt; = 1.0–2.0). Key findings reveal that LBVs peak at 31 cm/s (&lt;em&gt;ϕ&lt;/em&gt; = 1.4, 373 K, 1 atm) but decrease significantly with pressure (24 cm/s at 5 atm). IDTs shorten abruptly above 1630 K at 10 atm (&lt;100 μs). Kinetic analyses demonstrate that the reactions NH&lt;sub&gt;2&lt;/sub&gt; + NO → Products plays a dominant role in both flame propagation and ignition over the studied temperature range, due to their natures of chain branching and chain termination, with an even more pronounced influence during ignition. The pressure-dependent reaction NNH + M = N&lt;sub&gt;2&lt;/sub&gt; + H + M exhibits a significant pressure-dependent effect on flame propagation but has almost no influence on ignition. Through a careful evaluation of the branching ratio between NH&lt;sub&gt;2&lt;/sub&gt; + NO = NNH + OH and NH&lt;sub&gt;2&lt;/sub&gt; + NO = N&lt;sub&gt;2&lt;/sub&gt; + H&lt;sub&gt;2&lt;/sub&gt;O, the kinetic mechanism was optimized using the rate constants recommended by Klippenstein [Proc. Combust. Inst. 36 (2017) 77–111], enabling the developed kinetic model to reasonably predict the newly obtained experimental data. These findings reveal the reaction mechanism governing the interactions between NH&lt;sub&gt;3&lt;/sub&gt; and NO, providing a solid theoretical foundation for achieving low-NOx ammonia combustion under practical operating conditions.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; Understanding the interaction between NH&lt;sub&gt;3&lt;/sub&gt; and NO is essential for advancing low-NOx ammonia combustion technologies, especially under fuel-rich conditions where NH&lt;sub&gt;3&lt;/sub&gt;–NO reactions play a crucial role in NOx reduction. This work systematically investigates the interaction between NH&lt;sub&gt;3&lt;/sub&gt; and NO during ignition and flame propagation across a wide range of temperatures and pressures, achieving the first implementation of oxygen-free NH&lt;sub&gt;3&lt;/sub&gt;/NO ignition experiments in a shock tube. The results demonstrate the dominant role of the two competing reactions NH&lt;sub&gt;2&lt;/sub&gt; + NO = NNH + OH and NH&lt;sub&gt;2&lt;/sub&gt; + NO = N&lt;sub&gt;2&lt;/sub&gt; + H&lt;sub&gt;2&lt;/sub&gt;O in both ignition and flame propagation characteristics due to their roles as chain branching and chain termination reactions, respectively. These measurements establish highly sensitive validation targets for its kinetic chemistry. The updated kinetic model exhibits outstanding predictive performance across broad combustion regimes, offering critical insights into NO","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106272"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148656946","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":"Kinetics of the reaction between propan-2-yl radical and molecular oxygen: Experiments and master-equation simulations","authors":"Arkke J. Eskola,&nbsp;Jukka S. Ruotsalainen,&nbsp;Timo T. Pekkanen,&nbsp;Akshat Shirish Zalte,&nbsp;Matti P. Rissanen,&nbsp;William H. Green","doi":"10.1016/j.proci.2026.106445","DOIUrl":"10.1016/j.proci.2026.106445","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We present here an experimental and master-equation-modeling investigation of the reaction between propan-2-yl (iso-propyl) and molecular oxygen (&lt;span&gt;&lt;math&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;C&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;3&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;7&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;•&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;2&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). Experiments were performed over a wide temperature range (200–755 K) and moderate pressure range (0.2–12 Torr) using laser photolysis for radical production and photoionization mass spectrometry for detection. Both He and N&lt;sub&gt;2&lt;/sub&gt; bath gases were utilized. A master-equation model was constructed using the stationary-point energies calculated at high-level of theory by of Lahm et al. (2023), and key parameters in the model were optimized by minimizing differences between experimental and simulated kinetic traces. Excellent agreement between experiments and simulations was obtained with this fitting procedure. The model was further refined by “combining” different reaction channels together to reduce the number of phenomenological rate coefficients output by the model. We found the results produced by the reduced model to be effectively identical to those of the full model. The reduced model was then used to model the title reaction over a wide range of conditions relevant to combustion, and the phenomenological rate coefficients produced by these simulations were parameterized in Chemkin and Cantera compatible formats to facilitate their use in combustion modeling. A comparison between the current results and the few existing experimental results is provided. Possible uncertainties and shortcomings in previous experimental and computational works are discussed. The current work confirms that the title reaction mostly forms propene and hydroperoxyl under combustion conditions and is thus chain terminating.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; The current investigation is the first-ever kinetic study of the &lt;span&gt;&lt;math&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;C&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;3&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;7&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;•&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;O&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;2&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; reaction in which the reaction’s rate coefficient has been directly measured over wide temperature and moderate pressure ranges. Past studies were only performed at room temperature in a limited pressure range (1–4 Torr) or relied on indirect techniques. Lahm et al. (2023) have calculated the energetics of the title reaction at a very high-level of theory (i.e., with CCSD(T) energies, geometries, and various post-CCSD(T) corrections), and by utilizing their results, we constructed a master-equation model. After using the ex","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106445"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148995093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laminar flame speed of shock-heated cyclohexane/O2/Ar mixtures over 492–849 K and 5–11 bar within pre-autoignition regime","authors":"Jiabiao Zou,&nbsp;Xin Zhang,&nbsp;Mengxin Wang,&nbsp;Touqeer Anwar Kashif,&nbsp;Janardhanraj Subburaj,&nbsp;Xiang Gao,&nbsp;Aamir Farooq","doi":"10.1016/j.proci.2026.106391","DOIUrl":"10.1016/j.proci.2026.106391","url":null,"abstract":"<div><div>Laminar flame speeds (LFS) of cyclohexane/airgon (21%O₂/79%Ar) mixtures were measured under engine-relevant conditions using a shock tube based spherical flame method. Experiments covered temperatures ranging 492–849 K, pressures of 5–11 bar, and equivalence ratios of 0.8, 1.0, and 1.2. Flame front evolution was recorded via high-speed imaging in the visible region, and LFS values were derived using a nonlinear extrapolation approach based on spherical flame theory. The results show a pronounced positive temperature dependence across all equivalence ratios, providing the first benchmark dataset of cyclohexane flame propagation under elevated-temperature and elevated-pressure pre-autoignition conditions. The updated-JetSurF 2.0 and JetSurF 2.0 both reproduce the measurements well at 5 bar, while JetSurF 2.0 underpredicts flame speeds at 11 bar. Scaled comparisons with literature data confirm good consistency with previous studies at lower temperatures and pressures. A revised non-Arrhenius correlation was also established to represent the current and literature data. For cyclohexane oxidation under engine-relevant conditions, the formation and oxidation of vinyl and 1,3-butadiene enhance the H-radical pool and promote flame propagation, whereas chain-termination pathways involving methyl and allyl radicals inhibit the overall reactivity, particularly at elevated pressures. These findings advance the kinetic understanding of cyclic hydrocarbon combustion and offer guidance for the design of efficient, low-emission cycloalkane-based fuels for next-generation propulsion systems.</div><div><strong>Novelty and significance statement:</strong> This work provides the first laminar flame speed data for cyclohexane under engine-relevant elevated-temperature and elevated-pressure conditions. The present results establish a new experimental database for cyclohexane flame propagation in the pre-autoignition regime, providing critical validation benchmarks for the development and refinement of kinetic model. The derived non-Arrhenius correlation substantially enhances predictive capability over a broad range of operating conditions and advances the fundamental understanding of cyclic hydrocarbon combustion relevant to carbon-neutral energy applications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106391"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148958414","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":"Combined effects of heat losses and curvature in hydrogen–air flame propagation below the lean flammability limit","authors":"Rubén Palomeque-Santiago,&nbsp;Anne Dejoan,&nbsp;Daniel Fernández-Galisteo,&nbsp;Mariano Rubio-Rubio,&nbsp;Mario Sánchez-Sanz","doi":"10.1016/j.proci.2026.106100","DOIUrl":"10.1016/j.proci.2026.106100","url":null,"abstract":"<div><div>Recent experiments have shown that, below the flammability limit, ultra-lean hydrogen flame fronts can fragment into isolated flame cells when propagating within narrow channels. To further elucidate the underlying mechanisms of this behavior, three-dimensional (3D) numerical simulations are performed, systematically varying the heat losses through the confining walls. Under adiabatic conditions, a continuous flame front embedded with small cellular structures is sustained. When heat losses are introduced, this front fragments, forming isolated flame cells. The characteristic size of these cells is found to be comparable to the dominant wavelength of the corrugated front obtained under adiabatic conditions. The results indicate that heat losses have a pronounced impact on the flame curvature between the wall plates, which transitions from a highly asymmetric configuration to a nearly circular shape as the heat losses increase, while the curvature in the mid-channel plane is barely affected. The size and propagation velocity of the isolated flame cells exhibit a moderate dependence on the magnitude of the heat losses. Sufficiently large heat losses induce a bifurcation of the isolated fronts from a circular to a double-cell flame shape</div><div><em>Novelty and significance statement</em></div><div>This work presents fully three-dimensional numerical simulations to investigate the mechanisms governing the fragmentation of ultra-lean hydrogen–air flame fronts in narrow channels under the influence of varying wall heat losses. The main novelty is the quantification of the heat-loss effect on flame curvature, both across and along the confining plates. A direct correspondence is established between the characteristic size of the isolated cells and the dominant wavelength of flame corrugation under adiabatic conditions, revealing how increasing heat losses promote the transition from a non-symmetric flame to stable, symmetric isolated flame cells below the lean flammability limit of the adiabatic planar deflagration. This study explains that heat losses, typically associated with quenching, can instead stabilize discrete flame cells by reshaping the flame’s three-dimensional curvature and propagation dynamics. These findings clarify the mechanisms behind stable ultra-lean hydrogen combustion, with direct implications for hydrogen safety and the design of efficient, low-emission micro-combustion systems.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106100"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148587491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}