Proceedings of the Combustion Institute最新文献

{"title":"Kinetic insight into plasma-assisted oxidation of ethanol based on SVUV-MBMS diagnostic","authors":"Zhaoying Li,&nbsp;Haodong Chen,&nbsp;Chengcheng Liu,&nbsp;Chengyin Tu,&nbsp;Long Zhao,&nbsp;Minggao Xu,&nbsp;Bin Yang","doi":"10.1016/j.proci.2026.106074","DOIUrl":"10.1016/j.proci.2026.106074","url":null,"abstract":"<div><div>The low-temperature oxidation kinetics of ethanol were investigated in an argon-diluted atmosphere using a nanosecond-pulsed dielectric barrier discharge (DBD) in a plasma flow reactor at 340 K and 20 Torr. Species were identified and quantified using photoionization molecular beam mass spectrometry (PI-MBMS). This diagnostic technique effectively minimizes post-sampling reactions and preserves reactive species, enabling the detection of both stable molecules and radicals. Intermediates identified in the experiments include methane (CH₄), water (H₂O), acetylene (C₂H₂), carbon monoxide (CO), ethylene (C₂H₄), formaldehyde (CH₂O), methanol (CH₃OH), ketene (CH₂CO), carbon dioxide (CO₂), acetaldehyde (CH₃CHO), methyl hydroperoxide (CH₄O₂), acetic acid (CH₃COOH), and methyl acetate (CH₃COOCH₃). Furthermore, a kinetic mechanism for plasma-assisted low-temperature ethanol oxidation was developed and validated against the experimental results. Rate-of-production (ROP) analysis revealed that the plasma-induced reaction e/Ar* + C₂H₅OH → e/Ar + C₂H₅O + H serves as an important pathway for ethanol decomposition. The generated alkoxy radicals subsequently undergo the reaction C₂H₅O → CH₃ + CH₂O, which promotes direct oxygen addition CH₃ + O₂ (+M) → CH₃O₂ (+M), leading to peroxide formation. These results demonstrate that DBD plasma effectively activates ethanol oxidation at low temperature of 340 K.</div></div><div><h3>Novelty and significance statement</h3><div>This study employs synchrotron vacuum ultraviolet photoionization molecular beam mass spectrometry (SVUV-MBMS) to diagnose species in the plasma-assisted oxidation of ethanol, enabling the detection of a wide range of intermediates, including both radicals and stable molecules. The present study notably detected peroxides and esters that had not been previously reported in plasma-driven ethanol oxidation. Based on the experimental data, a kinetic mechanism was developed, and the reaction pathways for ethanol consumption, as well as the formation of products and intermediates, were revealed. Given that the kinetics of plasma-assisted alcohol oxidation remain poorly understood and detailed species diagnostics are scarce, this study provides unique species-resolved information essential for elucidating the reaction kinetics in such systems. The results offer critical experimental evidence and kinetic insights into the plasma-assisted oxidation pathways of ethanol, supplying valuable data for mechanism development and modeling.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106074"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567310","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":"Dynamics of flame spread over filter papers in microgravity aboard the ISS","authors":"Yoshinari Kobayashi,&nbsp;Shuhei Takahashi,&nbsp;Hiroyuki Torikai,&nbsp;Masao Kikuchi,&nbsp;Osamu Fujita","doi":"10.1016/j.proci.2026.106032","DOIUrl":"10.1016/j.proci.2026.106032","url":null,"abstract":"<div><div>Flame spread over solid fuels in microgravity is a fundamental phenomenon relevant to fire safety in spacecraft and space habitats. However, experimental data obtained under sustained microgravity conditions are still very limited because access to orbital research platforms is restricted. In the present study, flame spread over filter paper was experimentally investigated through orbital combustion experiments conducted aboard the International Space Station (ISS) using the Solid Combustion Experiment Module (SCEM) installed in the Japanese Experiment Module “Kibo.” Experiments were performed under various combinations of opposed-flow velocity and oxygen concentration to clarify flame spread characteristics in low-flow microgravity environments. Two distinct flame spread modes were observed: conventional two-dimensional (2D) flame spread and a unique spread mode referred to as <em>flamelet spread</em>. The flamelet spread was characterized by a small flame spreading in a zigzag manner along the sample surface and was mainly observed under extremely low-flow conditions near the flammability limit. Notably, flame spread was observed even below the limiting oxygen concentration predicted by a conventional two-dimensional flame spread model, suggesting that the conventional LOC concept may underestimate flammability limits under microgravity conditions. The measured flame spread rates for the 2D flame spread were typically 1.0–1.5 mm/s in the thermal regime, whereas the flamelet spread exhibited significantly lower spread rates. The preheating length decreased with increasing opposed-flow velocity, and the observed trends were reasonably reproduced by theoretical scaling relations. These findings provide new experimental insights into flame spread behavior over thin cellulosic fuels in microgravity and contribute to improving the understanding of solid fuel combustion relevant to fire safety in future space habitats.</div></div><div><h3>Novelty and significance statement</h3><div>This study reports orbital combustion experiments on flame spread over thermally thin filter paper conducted aboard the International Space Station. The results reveal a distinct flame spread mode, termed <em>flamelet spread</em>, which occurs under extremely low-flow conditions near the flammability limit and differs fundamentally from conventional two-dimensional flame spread. The observation that flame spread can occur even below the limiting oxygen concentration predicted by conventional models suggests that existing flammability criteria may underestimate material flammability in microgravity. These findings provide new insights into solid-fuel combustion in low-flow microgravity environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106032"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567401","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":"Radiative heat feedback to the fuel surface in heptane/toluene pool fires","authors":"Jean-Louis Consalvi,&nbsp;Fatiha Nmira,&nbsp;Hussain Najmi","doi":"10.1016/j.proci.2026.106057","DOIUrl":"10.1016/j.proci.2026.106057","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This article provides a detailed analysis of how enhancing the fuel sooting propensity affects the heat feedback to the fuel surface in 30 cm diameter (&lt;span&gt;&lt;math&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) pool fires. It combines specific experiments involving pure heptane (Hept100) and heptane/toluene blends with 5 (Hept95) and 10% (Hept90) toluene in volume and large eddy simulation (LES) based on state-of-the-art turbulent combustion, soot formation, and radiation models. The experiments were designed to isolate the effects of the fuel sooting propensity on the radiative feedback. This was achieved by controlling the addition of toluene to significantly enhance the fuel sooting propensity while preserving the flame structure and the local temperature statistics. In addition, the filtered narrow-band correlated-&lt;span&gt;&lt;math&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; radiative transfer equation is solved during the LES along vertical lines of sight from remote locations within the fire plume towards the fuel surface to provide a detailed spectral representation of the radiative feedback process. The simulations reproduce with fidelity the flame structure as well as the heat feedback towards the flame surface. The experimental and numerical results reveal a very limited impact of the enhancement in fuel sooting propensity on both total and radiative heat feedback. This counterintuitive behavior is explained by analyzing the filtered NB radiative intensity: as the fuel sooting propensity increases, the increasing soot radiative emission for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;z&lt;/mi&gt;&lt;mo&gt;≳&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is counterbalanced by the increase in absorption by relatively cold soot in the fuel rich core of the flame. The results also show that the fuel rich core of flame is mainly dominated by the absorption of soot and radiating gases which attenuates the radiative feedback.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; Although it is known that heat feedback to the fuel surface is dominated by radiation (Hamins et al., 1994; Kim et al., 2019) the effect of increasing fuel sootiness on this process is not fully understood. This article aims to fill this gap through a combined experimental and numerical study of 30 cm diameter heptane/toluene pool fires. The experiments reported here are designed to isolate the effects of the fuel sooting propensity on the radiative feedback while the proposed models allow a deep analysis of the underlying physics. The results highlight the competitive mechanisms that drive this radiative feedback as the fuel’s sooting propensity increases: the enhancement in soot emission is counterbalanced by an increase in absorption by cold soot in the fuel dome. Additionally, the results reveal that the fuel-rich core of these pool fires is mainly dominated by radiative absorption. These findings could represent a significant step towards developing reduced-order models for predicting radiative feedback.&lt;/div&gt;&lt;/d","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106057"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567402","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":"Prediction of limit cycle amplitudes over an operating domain and direct comparison with thermoacoustic instability experiments","authors":"Pierre-Alexandre Barré,&nbsp;Sébastien Candel,&nbsp;Daniel Durox,&nbsp;Antoine Renaud","doi":"10.1016/j.proci.2026.106002","DOIUrl":"10.1016/j.proci.2026.106002","url":null,"abstract":"&lt;div&gt;&lt;div&gt;One central challenge in combustion instability analysis is to reconcile experimental data and model predictions. In most cases, experimental observations are carried out at the limit cycle, i.e. when the regime of oscillation is established, while modeling generally provides growth rates which are used to infer whether the system is stable or unstable. A considerable effort has been made to develop models that describe linear and nonlinear features of the unstable process. However, there are not many contributions that are trying to obtain the layout of the unstable domain as a function of operating parameters. This article is aimed at showing that it is possible to calculate amplitudes at the limit cycle over a wide domain of operation with a reduced-order model, thus distinguishing stable and unstable regions and compare the calculated levels of oscillations to the amplitudes determined experimentally in a laboratory scale annular combustor (the MICCA facility). Calculations are carried out by projecting the wave equation onto acoustic modes to derive coupled evolution equations, which are then solved using slow-flow variables and time averaging. This model enables the determination at low computational cost of both limit-cycle amplitudes and effective growth rates, relying on velocity-based Flame Describing Function (FDF) data measured in a single-sector combustor equipped with the same injection unit, converted to pressure-based FDF and extended to actual oscillation conditions. The flame response (gain and phase of the FDF) is updated during integration to match with the observed frequency drift which is continuously monitored. The model successfully reproduces the experimental instability domain layout, as well as a frequency drift, highlighting its predictive capability for nonlinear dynamics in realistic annular combustor geometries.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This work extends a reduced-order model for thermoacoustic instability prediction in a multi-burner annular combustor &lt;span&gt;&lt;span&gt;[1]&lt;/span&gt;&lt;/span&gt; to a wide operating domain. The model includes several novel elements: an extension to annular conditions of velocity-based Flame Describing Functions using single-sector measurements; a frequency monitoring scheme based on dynamical equations to ensure consistent flame response; and a method to constrain admissible frequency shift using experimental knowledge and an extended Rayleigh criterion accounting for damping effects. This approach demonstrates, for the first time, that single-sector flame response data can be used to predict nonlinear instability behavior and limit-cycle amplitudes in multi-injector annular geometries across a broad operating range. The model captures experimental trends and stability boundaries with low computational cost and provides a practical framework for stability analysis and design optimization in future low-emission engines, offering a simple yet ","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106002"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567571","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":"Interplay of strain and thermodiffusive instabilities in lean premixed hydrogen flames","authors":"V. Schuh,&nbsp;M. Glushko,&nbsp;C. Hasse,&nbsp;H. Nicolai","doi":"10.1016/j.proci.2026.106092","DOIUrl":"10.1016/j.proci.2026.106092","url":null,"abstract":"<div><div>Lean premixed hydrogen combustion is a promising route toward low-NOx carbon-free energy systems, but its high sensitivity to thermodiffusive instabilities (TDI) and flow-induced strain presents major design challenges. While both effects enhance burning rates, their mutual interaction and formation remain insufficiently understood. This study investigates the interplay between strain and TDI in a well-defined 2D Tsuji burner configuration through detailed chemistry simulations spanning a range of global strain rates and operating conditions, while independently varying the Markstein number <span><math><mi>M</mi></math></span> and the mixture’s instability factor <span><math><msub><mrow><mi>ω</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. The flames consistently transition from strain-dominated to TDI-dominated regimes, with increasing global strain pushing the onset of instability further downstream from the high-strain zone. A detailed local stretch analysis shows that TDI formation is triggered only once the local strain rate falls below a small, nearly constant critical value — significantly lower than the globally imposed strain — highlighting a consistent onset condition across all cases. A budget analysis of differential transport elucidates this mechanism: strain-induced tangential fuel transport stabilizes the flame by suppressing local mixture-leaning; once this transport weakens, differential diffusion promotes the emergence of TDI cells. Comparisons across operating points with identical instability susceptibility demonstrate a pronounced sensitivity to the Markstein number, establishing a clear link between mixture-dependent strain response and the suppression of TDI formation.</div><div><strong>Novelty and significance statement</strong></div><div>Understanding the interplay of strain and thermodiffusive instabilities in lean hydrogen flames is crucial since both effects have been shown to dominate flame propagation and stabilization under various conditions. This study examines the interplay between flow strain and thermodiffusive instabilities in the non-linear regime in a well-defined steady-state configuration where regions governed by strain and by thermodiffusive instabilities coexist. In particular, the study reveals how strain suppresses the formation of thermodiffusive instability (TDI) structures, a key mechanism that has not been fully understood so far, and subsequently characterizes the transition between strain-dominated and TDI-dominated regions. The findings advance the community’s understanding of flame physics and provide essential insight for model development by identifying the conditions under which TDI can emerge in strained flame configurations, while linking these results to well-established quantities such as the Markstein number and the instability factor.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106092"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567576","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":"High pressure and temperature H2 laminar flame speeds: bridging experiments and kinetic models","authors":"Seif Zitouni,&nbsp;Patrick J. Singal,&nbsp;Nicolas Villenave,&nbsp;Olfa Mechergui,&nbsp;Joachim Beeckmann,&nbsp;Fabien Halter,&nbsp;Michael P. Burke,&nbsp;Guillaume Dayma","doi":"10.1016/j.proci.2026.106035","DOIUrl":"10.1016/j.proci.2026.106035","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Laminar flame speeds of hydrogen–air mixtures were measured under isochoric conditions using a spherical constant-volume chamber, providing reference data for model validation under conditions relevant to advanced combustion systems. Measurements were performed for equivalence ratios &lt;em&gt;φ&lt;/em&gt; = 1.4–5 and initial pressures between 0.5–2 bar, corresponding to unburned gas pressures and temperatures up to 8.8 bar and 460 K. Three state-of-the-art kinetic mechanisms, namely Konnov, CRECK, and ThInK, were assessed, with and without inclusion of recently proposed chemically termolecular reactions (H + O&lt;sub&gt;2&lt;/sub&gt; + R; R = H, O, OH). Additionally, reduced-pressure-based linear mixture rules (LMR-R) were implemented for key pressure-dependent reactions to better capture mixture dependence of complex-forming reactions, and to incorporate &lt;em&gt;ab initio&lt;/em&gt; determined temperature-dependent third-body efficiencies. At pressures below 3 bar, all mechanisms reproduce the measured laminar flame speeds within experimental uncertainty. However, at higher pressures and fuel-rich conditions, models including chemically termolecular reactions tend to underestimate laminar flame speeds due to enhanced radical termination, while their exclusion leads to systematic large overprediction. Incorporation of LMR-R with recent &lt;em&gt;ab initio&lt;/em&gt; data mitigates these deviations, improving agreement by balancing termination and chain-branching kinetics. Sensitivity analyses reveal that H + O&lt;sub&gt;2&lt;/sub&gt; ⇄ O + OH and competing HO&lt;sub&gt;2&lt;/sub&gt; formation pathways dominate under these conditions, while HO&lt;sub&gt;2&lt;/sub&gt; + H pathways and H recombination also have a significant influence on flame speed. Collider-resolved sensitivity analysis further shows that bath-gas effects are concentrated primarily in the HO&lt;sub&gt;2&lt;/sub&gt;-forming channel from H + O&lt;sub&gt;2&lt;/sub&gt; recombination, with H&lt;sub&gt;2&lt;/sub&gt;O emerging as the most influential collider, whereas collider dependence is much weaker for H + OH + M ⇄ H&lt;sub&gt;2&lt;/sub&gt;O + M and 2 OH + M ⇄ H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; + M. The results demonstrate that accurate simulation of hydrogen flames at elevated pressures and rich equivalence ratios requires not only chemically termolecular reactions, but also temperature-, pressure-, and collider-dependent treatment of pressure-dependent kinetics.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This study reports new isochoric laminar flame speed measurements of hydrogen–air mixtures under fuel-rich, high-pressure conditions up to 8.8 bar and 460 K, where experimental data remain scarce. The experiments are combined with detailed kinetic modeling to evaluate three state-of-the-art hydrogen combustion mechanisms, with and without chemically termolecular reactions, and to implement a reduced-pressure-based linear mixture rule (LMR-R) for key pressure-dependent reactions using recent &lt;em&gt;ab initio&lt;/em&gt; evaluations. The analysis isolates the competing roles of radical ter","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106035"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567186","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":"Assessment of ammonia chemical kinetics using NH2 time histories in NH3 and N2O mixtures","authors":"Matthew Abulail,&nbsp;Matthew G. Sandberg,&nbsp;Olivier Mathieu,&nbsp;Eric L. Petersen","doi":"10.1016/j.proci.2026.106487","DOIUrl":"10.1016/j.proci.2026.106487","url":null,"abstract":"<div><div>Ammonia oxidation with N₂O was studied through NH₂ laser absorption spectroscopy behind reflected shock waves. An NH₃ laser absorption diagnostic was used to verify the initial ammonia concentration in each experiment, while a new NH₂ laser diagnostic measured the NH₂ concentrations. Three equivalence ratios of 0.31, 0.82, and 1.71 were studied in 99 % Ar between 1297 and 2155 K at near-atmospheric pressures. The measured NH₂ time histories were compared with prominent ammonia oxidation models to compare performance over the range of temperatures studied. Three key reactions, namely NH₃ + O ⇆ NH₂ + OH (R1), NH₃ + OH ⇆ NH₂ + H₂O (R2), and N₂O + M ⇆ N₂ + O + M (R3) were identified across the models as most sensitive to NH₂ concentrations. This study also provides new experimental traces of NH₂ for use in ammonia chemical kinetics validation.</div></div><div><h3>Novelty and significance statement</h3><div>The novelty of this study is the measurement of an ammonia-related radical, NH₂, in a shock tube. Intermediate reactions often rely almost exclusively on theoretical calculations as few have been verified directly through experimental work. As ammonia continues to become an increasingly important alternative fuel candidate due to the carbon-free nature of ammonia for power and transportation, measurements of intermediates such as NH₂ provide key insights into further refinement of NH₃ chemical kinetics models and thus a better understanding of ammonia chemical kinetics in general.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106487"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153697","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":"Refining the low-temperature oxidation chemistry of butanone via ozone addition: A combined synchrotron VUV-PIMS and kinetic model study","authors":"Jiacheng Shi,&nbsp;Shuyao Chen,&nbsp;Cheng Xie,&nbsp;Qingbo Zhu,&nbsp;Zhandong Wang,&nbsp;Long Zhu","doi":"10.1016/j.proci.2026.106543","DOIUrl":"10.1016/j.proci.2026.106543","url":null,"abstract":"<div><div>Butanone, a promising biomass-derived fuel, exhibits low reactivity at low temperatures, making its detailed mechanistic understanding challenging. To address this, we investigated the ozone-assisted low-temperature oxidation of butanone in an atmospheric jet-stirred reactor (JSR) over a temperature range of 335–825 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) enabled the observation of key intermediates, including CH₂O, C₂H₃COCH₃, C₂H₄, CH₃CHO, CH₃OH, CH₃O₂H, ROOH and KHP. A kinetic model was developed and validated against the experimental data, providing reliable predictions for fuel consumption and intermediate formation. Reaction pathway analysis at 545 K reveals that the reaction network is dominated by conversions among fuel radicals, alkoxy radicals (RO), and peroxyl radicals (RO₂). Crucially, the carbonyl group within butanone significantly inhibits classical chain-branching pathways, particularly the RO₂ ↔ QOOH isomerization. This shifts the overall mechanism towards propagation-dominated reactions, primarily governed by RO radical chemistry, thereby accounting for butanone's low reactivity. This combined experimental and modeling study provides fundamental insights into the low-temperature oxidation kinetics of butanone.</div></div><div><h3>Novelty and significance statement</h3><div>The novelty of this research is as follows: We present the ozone-assisted low-temperature oxidation study of butanone in a JSR with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS), enabling detection of various intermediates, including ROOH and KHP. Guided by these data, we update PCFCv3 by integrating a C0-C4 base and revising key radical reactions, achieving good agreement for fuel reactivity and intermediate speciation. ROP analysis at 545 K reveals a carbonyl driven suppression of O₂ addition and RO₂ ↔ QOOH isomerization, shifting reactivity to RO dominated chain propagation. The results contrast with alkanes, establishing new constraints for oxygenated fuels.</div><div>Butanone is a key biomass-derived fuel, but existing kinetic models fail to capture its low-temperature behavior, hindering the design of advanced combustion strategies. This work provides the combustion community with a critical missing piece: an experimentally validated mechanism that accurately predicts inhibited butanone reactivity. The elucidation of the carbonyl-induced shift from chain-branching to chain-propagation has broad relevance for other oxygenated fuels. The refined kinetic model enhances mechanistic understanding of ozone‑assisted oxidation, providing quantitative insights for validating combustion models and designing efficient low-temperature oxidation strategies for emerging oxygenated and partially oxidized biofuels.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106543"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153706","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":"Nonlinear interactions in counterflow flames under dual-frequency excitations","authors":"Jose G. Rivera Lizarralde,&nbsp;Abhishek Saha","doi":"10.1016/j.proci.2026.106111","DOIUrl":"10.1016/j.proci.2026.106111","url":null,"abstract":"<div><div>While multi-frequency perturbations are common in combustors, the dynamics of laminar flames under multi-frequency strain rates remain less explored. Here, we investigate unsteady counterflow flames subjected to dual-frequency excitation using high-speed Mie-scattering imaging and Particle Image Velocimetry. The measurements reveal a complex flame response that differs fundamentally from that under single-frequency forcing. Nonlinear interactions among the imposed forcing modes generate additional child modes that strongly influence flame dynamics, particularly in the outer shear layer. Bispectral Mode Decomposition (BMD) is used to identify both strong and weak modal interactions and to quantify the emergence of these new frequencies. Together, the measurements and BMD analysis provide interesting physical insight into the nonlinear dynamics of unsteady strained flames and establish a framework for interpreting multi-frequency flame behavior in practical combustors.</div><div><em>Novelty and significance statement:</em> This study provides the first detailed investigation of premixed counterflow flames under dual-frequency excitation, examining the dynamic response not only along the centerline but also at off-center locations where the flame behavior is fundamentally different. The results reveal that nonlinear interactions between the imposed excitation modes generate distinctive flame dynamics that are absent under single-frequency forcing, including the emergence of new coupled modes and a clear spatial segregation of the response into regions with markedly different spectral characteristics. A further novelty of this work lies in the use of Bispectral Mode Decomposition in this context, which enables direct identification of the nonlinear triadic coupling mechanisms governing the observed flame behavior. Beyond advancing the fundamental understanding of strained-flame dynamics, the study establishes a physics-based framework for interpreting nonlinear flame responses under multi-frequency forcing, with direct relevance to the complex unsteadiness encountered in practical combustion systems.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106111"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148409500","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":"Validation of leading-point-concept-based approach to predicting an increase in turbulent burning rate due to diffusional-thermal effects","authors":"Yiqing Wang,&nbsp;Van Tinh Mai,&nbsp;Zheng Chen,&nbsp;Shenqyang (Steven) Shy,&nbsp;Andrei N. Lipatnikov","doi":"10.1016/j.proci.2026.106134","DOIUrl":"10.1016/j.proci.2026.106134","url":null,"abstract":"<div><div>A promising approach to predicting a significant increase in turbulent burning rate due to diffusional-thermal phenomena in lean H₂-containing mixtures is based on the leading point concept and consists in substituting characteristics of unstretched laminar flames with the counterpart characteristics of highly strained, twin, counterflow laminar flames. In the present work, the predictive capabilities of this approach are validated by processing two experimental databases obtained recently by independent research groups from (i) piloted, statistically stationary, Bunsen-type lean CH₄/H₂/air weakly turbulent (<span><math><mrow><mi>R</mi><msub><mi>e</mi><mi>T</mi></msub><mo>=</mo><mn>64</mn></mrow></math></span>) flames at Karlovitz numbers ranging from 0.5 to 100 and (ii) statistically spherical turbulent flames expanding in various mixtures (stoichiometric CH₄/O₂/N₂, lean H₂/O₂/N₂, H₂/O₂/He, and H₂/O₂/Ar) under different pressures and temperatures. In each set of experiments, an increase in the burning velocity, <em>U_T</em>, due to diffusional-thermal effects is well pronounced and the use of standard characteristics of laminar flames to fit the data yields a significant scatter. On the contrary, when adopting the consumption velocities and thicknesses of highly strained laminar counterflow twin flames, computed using detailed chemistry, both databases on <em>U_T</em> are well parameterized.</div></div><div><h3>Novelty and significance statement</h3><div>Analyses of two recent advanced experimental databases on turbulent burning velocities of lean H₂-containing mixtures demonstrate the capabilities of the leading point concept for predicting a significant increase in turbulent burning rate due to diffusional-thermal effects. These capabilities are demonstrated for two very different flame configurations under a wide range of conditions, including elevated pressures and temperatures. The validation of the leading point concept is significant for modeling turbulent burning of lean mixtures that contain H₂. The concept can be adapted in both Reynolds-Averaged Navier-Stokes and Large Eddy Simulations of turbulent combustion of various lean mixtures, e.g., blends of hydrogen with ammonia, carbon oxide, or methane, in various engines such as piston engines, stationary gas turbines, or aeroengine afterburners.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106134"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567183","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}