Combustion and Flame最新文献

{"title":"Ignition mechanism and laws of explosion-driven thermal field and fuel dispersion flow","authors":"Simin Ren,&nbsp;Zhongqi Wang,&nbsp;Qi Zhang","doi":"10.1016/j.combustflame.2026.114843","DOIUrl":"10.1016/j.combustflame.2026.114843","url":null,"abstract":"<div><div>As an advanced form of conventional explosive energy, fuel mists react with ambient oxygen and can deliver high energy density. In fuel–air explosive (FAE) devices, the central detonation generates high pressure and high temperature: the former drives rapid fuel dispersion, whereas the latter can ignite the evolving fuel–air mixture during dispersion, leading to premature ignition and reduced effective cloud energy utilization. Premature ignition during dispersion involves strongly coupled unsteady processes, including flow, turbulence, heat and mass transfer, droplet-field evolution, and chemical reactions. In this study, numerical simulations together with experimental validation are employed to identify the critical conditions for premature ignition in a typical explosion-driven dispersion configuration and to elucidate the underlying physico-chemical mechanisms. The results show that ignition activity preferentially appears near the upper and lower ends of the device in the early stage, and then migrates toward the ±45° directions relative to the X-axis (defined as 0°) in the middle stage, consistent with the evolving temperature and mixing fields. For a 2 kg propylene-oxide FAE device, no premature-ignition occurs at a central charge ratio of 1.0%, whereas ratios of 2.0% or higher lead to sustained premature ignition. A central charge ratio of 1.5% is identified as the critical condition, with additional cases at 1.25% and 1.75% used to bracket this boundary. This critical boundary can be interpreted by an ignition-in-motion rate-competition criterion, Da = R_A/R_critical≈1; within the present single-step framework, the associated effective critical reaction-rate level is about 0.5 kgmol/m³s. The present results provide a baseline for the studied configuration under controlled ambient conditions. For a 2.0% central charge ratio, premature ignition initiates at the upper edge of the cloud, where the local fuel concentration is about 300 g/m³ and the explosion-driven temperature at the ignition site is about 1146 K.</div><div>Novelty and significance statement</div><div>Significance: Premature-ignition is a critical bottleneck limiting the energy efficiency of fuel-air explosive (FAE) systems. A fundamental understanding of this process is essential for optimizing FAE design to overcome incomplete energy release and maximize performance, providing a basis for developing more advanced energetic systems.</div><div>Novelty: Moving beyond previous work limited to static parameters, this study reveals the fundamental cause of premature-ignition. It is the first to elucidate the dynamic, multi-field coupling between an evolving high-temperature field and a transient fuel cloud, establishing a previously unreported transient ignition mechanism.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114843"},"PeriodicalIF":6.2,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075137","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":"Study on inhibition mechanisms of CO2/ABC gas-solid compound suppressant on propane explosion using experiments and DFT method","authors":"Qiuhong Wang ,&nbsp;He Zhu ,&nbsp;Jun Deng ,&nbsp;Zhenmin Luo ,&nbsp;Wei Gao ,&nbsp;Xiangrong Liu ,&nbsp;Qingfeng Wang ,&nbsp;Yifei Liu ,&nbsp;Siru Wang","doi":"10.1016/j.combustflame.2026.114801","DOIUrl":"10.1016/j.combustflame.2026.114801","url":null,"abstract":"<div><div>Propane can mix with air in storage tanks or pipes during transport and use, causing gas clouds in industrial facilities. At high temperatures or from ignition, gas clouds can explode. Explosion suppressants for propane must be researched for industrial safety. In a 20 L spherical explosion experimental setup, propane explosion pressure and limits under CO₂, ABC powder, and CO₂/ABC gas-solid combination suppressants were examined. Explosion suppression patterns for single-phase and combination suppressants were studied. Linear regression and density functional theory (DFT) calculations revealed the composite suppressant's two components’ major impact on explosive parameters. The results showed that 9% CO₂ with 150 g/m³ ABC powder or 15% CO₂ with 100 g/m³ ABC powder mitigates propane explosions. CO₂ physically diminishes the pressure differential pre- and post-explosion, largely influencing the peak pressure. By sequestering critical free radicals (O₂, H·, OH·, CH₃·), ABC powder disrupts chain reactions and reduces explosion intensity, significantly affecting maximum pressure rise rate. These findings provide a theoretical framework for enhancing the CO₂/ABC powder mass ratio and real-time industrial injection concentration adjustment.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114801"},"PeriodicalIF":6.2,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075227","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":"Effects of hydrogen enrichment on the autoignition and lift-off behavior of ammonia jet flames in hot coflows","authors":"Daeyoung Jun ,&nbsp;Seo Hee Cho ,&nbsp;V. Mahendra Reddy ,&nbsp;Bok Jik Lee","doi":"10.1016/j.combustflame.2026.114820","DOIUrl":"10.1016/j.combustflame.2026.114820","url":null,"abstract":"<div><div>Ammonia is a promising carbon-free fuel, but its low reactivity presents a limitation. To mitigate this, hydrogen enrichment can be considered. This experimental study investigates the combustion characteristics and lift-off behaviors of autoignited ammonia–hydrogen flames. A jet in a hot oxidant coflow burner is used to examine the impact of hydrogen enrichment on ammonia jets. The flames exhibit distinct regimes, including attached, lifted, decoupled lifted flames, and blowout, influenced by hydrogen content, jet Reynolds number, and oxygen concentration. As expected, increasing hydrogen content and oxygen concentration stabilized the flame, promoting attachment. Distinctly decoupled lifted flames were observed, characterized by the separation of laminar and turbulent flame branches at the break-up point due to local extinction induced by high strain from developing eddies. Furthermore, flame pocket evolution in lifted flames was analyzed using high-speed imaging, revealing that flame pockets either grew to form new flame bases or were extinguished. During extinction, local turbulent structures cause larger flame pockets to fragment into smaller ones, which are subsequently extinguished rapidly. Regarding the spatial distribution of flame pockets, both decreasing hydrogen content and increasing jet velocity led to a downstream axial shift of the flame pocket locations. In terms of the number of flame pockets, the hydrogen content exhibited a more pronounced effect than the jet velocity. To find the flame stabilization mechanism, several lift-off height models were considered. The large-scale mixing model with autoignition time provided the best prediction, suggesting that flame stabilization is primarily governed by the balance between mixing and autoignition kinetics rather than flame propagation. This was further verified by the blowout correlation.</div><div><strong>Novelty and significance</strong>: The novelty of this study lies in its investigation of ammonia–hydrogen jet flames in hot coflow environments, focusing on the stabilization mechanism of binary fuels with autoignition. Hydrogen enrichment, widely used to compensate for ammonia’s low reactivity, introduces additional complexity due to the large disparity in transport properties, particularly diffusivity. This study examines flame behavior, the transient evolution of flame pockets, and evaluates the applicability of various lift-off correlations. A large-scale mixing model with the autoignition time of a uniform fuel mixture remains effective in predicting lift-off height, despite the pronounced differential diffusion between hydrogen and ammonia. The findings of the present study could provide valuable insights for applications involving ammonia–hydrogen jet combustion.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114820"},"PeriodicalIF":6.2,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075143","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":"Linear stability analysis of laminar premixed planar H2/N2O/N2 flames","authors":"Shumeng Xie ,&nbsp;Christine Mounaïm-Rousselle ,&nbsp;Huangwei Zhang","doi":"10.1016/j.combustflame.2026.114846","DOIUrl":"10.1016/j.combustflame.2026.114846","url":null,"abstract":"<div><div>Hydrogen is a promising energy carrier for power and propulsion systems. While its combustion in air or oxygen has been well studied, hydrogen flames with nitrous oxide as the oxidizer remain less explored. This study presents a systematic numerical investigation of the linear instability characteristics of premixed H₂/N₂O/N₂ flames using detailed numerical simulations. A multi-wavelength perturbation method is employed to extract the dispersion relations, providing insights into the linear stability characteristics of the flame front. The effects of equivalence ratio and N₂O concentration are quantified. The equivalence ratio primarily affects the Lewis number, and thus thermo-diffusive instability, with lean mixtures exhibiting greater instability. The N₂O concentration has opposing effects on lean and rich flames: higher N₂O content reduces instability for lean mixtures but exerts little effect on rich mixtures. In addition, the flame stability is also strongly influenced by the thermodynamic state: higher unburned temperatures stabilize the flame by reducing the thermal expansion ratio, whereas elevated pressures destabilize it by influencing both the thermal expansion ratio and Zeldovich number. At the end, correlations between the numerical dispersion relations and asymptotic theory are quantified, and empirical fits are derived to capture the dependence of growth rates and cutoff wavenumbers on mixture composition, providing practical tools for reduced-order stability modeling. Collectively, these findings advance the fundamental understanding of hydrogen–nitrous oxide combustion.</div><div><strong>Novelty and Significance Statement</strong></div><div>Flames involving H₂ and N₂O exhibit a high susceptibility to instabilities due to the high diffusivity of H₂ and the exothermic decomposition of N₂O. This study presents the first systematic analysis of the linear instability characteristics of premixed planar H₂/N₂O/N₂ flames using high-fidelity detailed numerical simulations. Quantitative dispersion relations are obtained over a wide range of temperatures, pressures, and mixture compositions, which are absent in the existing literature. Another key novelty of this work lies in the systematic evaluation of fundamental non-dimensional parameters, including the thermal expansion ratio, Zeldovich number, and effective Lewis number, and in the examination of correlations between theoretical and numerical dispersion relations. Together, these analyses elucidate how thermodynamic and compositional variations govern the instability growth rate and cutoff wavenumber in H₂/N₂O/N₂ flames.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114846"},"PeriodicalIF":6.2,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075138","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":"Is the NH3 + N2O = H3NO + N2 reaction important in ammonia oxidation by nitrous oxide or oxygen?","authors":"Xiaoyang Lei ,&nbsp;Xiao Liu ,&nbsp;Bin Yang ,&nbsp;Shuiqing Li","doi":"10.1016/j.combustflame.2026.114824","DOIUrl":"10.1016/j.combustflame.2026.114824","url":null,"abstract":"<div><div>Nitrous oxide (N₂O) is an important intermediate/pollutant in combustion, particularly in the case of ammonia. Meanwhile, it can also be used as oxidizer or additive in the oxidation of fuels or propellants. Many studies have been performed for ammonia oxidation by N₂O or O₂. Whereas, the answers for the two basic questions “what are the main consumption pathways of N₂O in ammonia oxidation by N₂O or O₂?” and “why adding N₂O can improve the reactivity of ammonia for combustion?” are still unknown. In this work, the direct reactions between NH₃ and N₂O are investigated by quantum-chemical and kinetic calculations. The computations indicate that the dominant pathway of the NH₃ + N₂O reaction is to directly produce a zwitterionic intermediate, H₃NO, and N₂ molecule via the O-attack mechanism. The H₃NO intermediate is a metastable tautomer of hydroxylamine (NH₂OH), and its detection and characterization in the gas phase is still a challenge for experimentalists. To evaluate the importance of the NH₃ + N₂O reaction in ammonia oxidation by N₂O or O₂, twelve combustion models of ammonia in literatures are modified by the computed reaction parameters. The simulations show that the NH₃ + N₂O = H₃NO + N₂ reaction plays an important role in the consumption of N₂O during ammonia oxidation by N₂O and O₂. Therefore, this reaction should be much more considered in the development of ammonia combustion model.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114824"},"PeriodicalIF":6.2,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075184","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":"Flame morphology boundaries and fundamental combustion properties in unobstructed channels","authors":"Cristian C. Mejía-Botero ,&nbsp;Florent Virot ,&nbsp;Luis Fernando Figueira da Silva ,&nbsp;Josué Melguizo-Gavilanes","doi":"10.1016/j.combustflame.2026.114806","DOIUrl":"10.1016/j.combustflame.2026.114806","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We investigated the effect of fundamental combustion properties (FCP) on the 3D morphology and dynamics of flames and shocks during acceleration and transition to detonation in unobstructed channels. To achieve this, an extensive experimental campaign was conducted using a simultaneous schlieren visualization setup. The effect of selected FCP was assessed by evaluating nine different mixtures of hydrogen, methane, and hydrogen/methane blends, using oxygen with and without dilution by nitrogen, helium, or argon. The experimental results revealed two characteristic flame evolution behaviors during flame acceleration (FA), depending on the mixtures: (i) a symmetric flame inversion (tulip flame) during the early stages of FA, followed by a short, symmetric flame in the later stages, with the formation of a precursor compression wave located relatively far from the flame, and (ii) an asymmetric, wrinkled flame during the early stages, which develops into a longer flame with the tip inclined toward a corner of the channel, accompanied by the formation of multiple precursor compression waves ahead of the flame in the later stages of FA. For a more robust statistical analysis, a morphology database was compiled from literature sources reporting similar flame morphologies to those observed in our experiments. This database was analyzed using the Feature Elimination Technique in conjunction with the Logistic Regression Model, which enabled the identification of FCP boundaries between the observed flame morphologies. The analysis showed that the pairs of properties most influencing flame morphology are the expansion ratio and the ratio of the laminar flame speed to the sound speed in the combustion products, i.e., &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, as well as the latter ratio with the heat capacity ratio, i.e., &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mi&gt;σ&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;b&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Additionally, this methodology helped to identify experimental conditions where little or no data is available in the literature, such as for mixtures with Lewis numbers smaller than unity, which are expected to be affected by thermodiffusive instabilities. These boundaries can, therefore, serve as guidelines for selecting experimental conditions that develop specific flame and shock morphologies and dynamics.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This study establishes, for the first time, a direct link between fundamental combustion properties (FCP) and the observed flame and shock morphologies during flame acceleration in unobstructed channels from ignition to detonation onset. The results offer predictive in","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114806"},"PeriodicalIF":6.2,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075185","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":"Low-order modeling of thermoacoustic instability: Modal competition induced by fluid–structure interaction","authors":"Dario Passato ,&nbsp;Berksu Erkal ,&nbsp;Claire Bourquard ,&nbsp;Jim B.W. Kok ,&nbsp;Ines Lopez Arteaga","doi":"10.1016/j.combustflame.2026.114841","DOIUrl":"10.1016/j.combustflame.2026.114841","url":null,"abstract":"<div><div>This work presents an experimental and theoretical investigation into the influence of a passive, off-resonance flexible plate on a dual-mode thermoacoustic instability. Simultaneous measurements of acoustic pressure, heat release, and plate velocity (via Laser Doppler Vibrometry) are used to characterize the coupled fluid–structure dynamics. In the rigid-wall baseline, the combustor exhibits a limit cycle dominated by a single acoustic mode. Introducing the flexible plate fundamentally alters this behavior, inducing modal competition in which the dominance intermittently shifts between two closely spaced acoustic modes. A low-order model, consisting of two coupled delayed oscillators, is developed and calibrated against the experimental data to probe the underlying mechanism. The analysis shows that, although the plate acts as an energy sink, this additional damping alone cannot account for the emergence of the secondary mode. Instead, the model indicates that modal competition arises from an alteration of the thermoacoustic feedback loop, driven by an induced frequency shift and a modification of the effective flame driving strengths. This demonstrates that the compliant boundary does not merely introduce damping but reshapes the competitive stability balance between modes, revealing a non-intuitive mechanism with direct relevance for passive control strategies.</div><div><strong>Novelty and significance statement</strong> This work provides new insight into the complex dynamics of a multi-mode unstable thermoacoustic system interacting with a compliant boundary. The study combines simultaneous acoustic, heat release and vibrometry measurements to characterize such an interaction in-situ. We experimentally investigate a phenomenon of modal competition triggered by this passive, off-resonance structural element, which alters the dynamics of the thermoacoustic modes. The findings provide a valuable benchmark for the development and validation of descriptive low-order models.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114841"},"PeriodicalIF":6.2,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075142","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":"Cumene pyrolysis: a combined experimental and Ab initio modeling approach","authors":"Boris Roux ,&nbsp;Yves Simon ,&nbsp;Sandra Poeuf ,&nbsp;Marc Bouchez ,&nbsp;Maxime Lechevallier ,&nbsp;Pierre-Alexandre Glaude ,&nbsp;Baptiste Sirjean ,&nbsp;René Fournet","doi":"10.1016/j.combustflame.2026.114840","DOIUrl":"10.1016/j.combustflame.2026.114840","url":null,"abstract":"<div><div>An experimental study of the pyrolysis of cumene was performed at atmospheric pressure, in a jet-stirred reactor (JSR) with 2% fuel diluted in helium, a residence time of 1 s, and for temperatures ranging from 863 to 1023 K. Fifty-four species were identified from light compounds to C₂₀, by gas chromatography coupled with mass spectrometry (GC–MS) and quantified by GC-FID (flame ionization detector) and GC-PDHID (pulsed discharged helium ionization detector). Among these products, several aromatic species (C₉+) were detected for the first time. In addition, a comprehensive kinetic model, including a growth sub-mechanism to bicycle compounds with sizes up to C₁₄, has been developed, based on electronic structure calculations, performed at the QCISD(T)/CBS//B2PLYP-D3/6–311+<em>G</em>(d,p) level of theory. Calculations were used to derive kinetic parameters and thermodynamic data. Comparisons between experiments and simulations showed good agreement for thirty-six species, including the most important products and a marked improvement from previous modeling studies reported in the literature. The allylic H-atom and tertiary carbon atom allows cumene to readily decompose to form styrene, benzene and α-methylstyrene, the main primary aromatic compounds. These species are less reactive than cumene, and our study clearly shows the importance of addition reactions on their side chain or aromatic ring, leading to the formation of bicyclic structures that are key intermediates in the formation of heavier PAHs. In particular, our mechanism models the formation of mono- and bi-aromatic products that had not previously been reported during cumene pyrolysis, such as trimethylbenzene, butenylbenzene, an important precursor of 3-methylindene, as well as diphenylethylene and diphenylstyrene, which are PAH precursors. In addition, a detailed investigation of the potential energy surfaces has clarified the elementary steps involved in the formation pathways of all modeled species, including various isomers, such as methylnaphthalene and methylindene. In particular, the involvement of sigmatropic rearrangements accounts for the formation of 2-methylindene and 2-methylnaphthalene.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114840"},"PeriodicalIF":6.2,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075182","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":"Unravelling the unique kinetic interactions between N2O and unsaturated hydrocarbons","authors":"Hongqing Wu ,&nbsp;Guojie Liang ,&nbsp;Tianzhou Jiang ,&nbsp;Fan Li ,&nbsp;Yang Li ,&nbsp;Rongpei Jiang ,&nbsp;Ruoyue Tang ,&nbsp;Song Cheng","doi":"10.1016/j.combustflame.2026.114817","DOIUrl":"10.1016/j.combustflame.2026.114817","url":null,"abstract":"<div><div>The interaction between unsaturated hydrocarbons and N₂O has attracted considerable attention in recent years due to their important role as potential propellants for advanced propulsion systems (e.g. Nitrous oxide fuel blend (NOFBX)) and key combustion intermediates in exhaust gas recirculation systems. Although experimental studies and kinetic models have been developed to investigate its fuel chemistry, discrepancies remain between modeled and measured ignition delay times at low temperatures. In this work, we characterize previously unreported direct interaction pathways between N₂O and unsaturated hydrocarbons (C₂H₄, C₃H₆, C₂H₂, C₃H₄-A, and C₃H₄-P) through quantum chemistry calculations, comprehensive kinetic modeling, and experimental validation. These reactions proceed via O-atom addition from N₂O to unsaturated hydrocarbons, forming five-membered ring intermediates that decompose into N₂ and hydrocarbon-specific products. Distinct differences are identified between alkenes and dienes and alkynes, arising from the disparity in N–C bond lengths within the intermediates (∼1.480 Å for alkenes and 1.429 Å for dienes vs. ∼1.381 Å for alkynes), which governs their decomposition pathways. The corresponding rate coefficients are determined and implemented into multiple kinetic models, with autoignition simulations showing a pronounced promoting effect on model reactivity and improved agreement with experiments, especially at low temperatures. Comprehensive uncertainty analyses of the potential energy surfaces, rate coefficients, and ignition delay times are conducted to ensure the robustness and reliability of the findings. Flux analysis further reveals that the new pathways suppress conventional inhibiting channels while enabling aldehyde- and ketone-forming pathways that enhance overall reactivity, with JSR simulations further confirming the feasibility of validating these pathways through experiments. This work provides a more complete description of N₂O–hydrocarbon interactions and reveals other important N₂O–hydrocarbon interaction chemistries that need to be further studied via both theoretical and experimental investigations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114817"},"PeriodicalIF":6.2,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075181","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":"Spray flamelet structures in a theoretical tubular counterflow configuration","authors":"Francisco Rivadeneira ,&nbsp;Felipe Huenchuguala ,&nbsp;Arne Scholtissek ,&nbsp;Christian Hasse ,&nbsp;Eva Gutheil ,&nbsp;Hernan Olguin","doi":"10.1016/j.combustflame.2026.114839","DOIUrl":"10.1016/j.combustflame.2026.114839","url":null,"abstract":"<div><div>In this work, spray flamelet structures subject to curvature are systematically studied, emphasizing the ways in which this quantity modifies the budgets of the corresponding flamelet equations and their stretch-induced extinction limit. More specifically, a theoretical extension of the tubular counterflow configuration is first proposed, which allows the injection of droplets from the inner cylinder. After appropriate mathematical descriptions for this new configuration in physical and composition space are introduced, several ethanol/air tubular counterflow flames are studied. It is found that increasing curvature leads to major modifications of the resulting flamelet structures, which is attributable to its influence on the evaporation profiles. Further, it is found that increasing curvature considerably reduces the stretch-induced extinction limit, which can be directly related to a corresponding reduction of the maximum mixture fraction within the flamelet. Finally, it is concluded that extinction in tubular counterflow spray flames occurs through a mechanism significantly different from what has been previously observed for gas flamelets.</div><div><strong>Novelty and Significance Statement</strong></div><div>A theoretical extension of the classical gas tubular counterflow configuration is proposed, which allowed systematically studying curvature effects on spray flamelet structures for the first time. Mathematical models currently available in the literature, both in physical and mixture fraction space, are extended accordingly and used to analyze different flamelet structures. It was found that spray flamelet structures are considerably more sensitive to curvature than their gaseous counterpart, which can be attributed to the explicit effect of this quantity on the evaporation profiles. Additionally, a new extinction mechanism is identified, which considerably differs from what has been previously observed for gas flamelets.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"286 ","pages":"Article 114839"},"PeriodicalIF":6.2,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146075139","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}