Combustion and Flame最新文献

{"title":"Synergistic shock-enhancing mixing and multi-wave driven heat release in a locally dual-channel combustor","authors":"Yu Zeng,&nbsp;Hongbo Wang,&nbsp;Haoyang Peng,&nbsp;Shijie Liu,&nbsp;Jiangfei Yu,&nbsp;Mingbo Sun,&nbsp;Weidong Liu","doi":"10.1016/j.combustflame.2026.114778","DOIUrl":"10.1016/j.combustflame.2026.114778","url":null,"abstract":"<div><div>Addressing the challenges of inadequate mixing efficiency and difficulty in organizing detonation combustion in high-speed inflow of an air-breathing cylindrical combustor, this study constructs a locally dual-channel configuration by integrating a circular strut. Three-dimensional numerical simulations of non-premixed ethylene-air combustion demonstrate the superior capability of this configuration in enhancing mixing and promoting heat release. The circular strut facilitates intense interactions between the shocks and the fuel-jet mixing layer. This enhances fuel cross-diffusion and prolongs the residence time. The mixing efficiency is improved by up to 22.86% compared to the no-strut configuration at the end of the combustor cavity. The axial length required for full mixing is reduced by 27.92%. The leading shock and the reflected shock waves together enhance heat release. The leading shock contributes predominantly to this enhancement by triggering detonation combustion, while the reflected shock waves induce premature auto-ignition of the freshly fuel and the parasitic combustion at the burned/unburned interface at the pre-wave. Under the synergy of multi-wave structures, the overall energy release efficiency is substantially improved. The stably self-sustaining detonation wave drives the upward rotating shock wave to stir the mixing fuel. Local flow reversal and tangential motion induced by shocks improve the uniformity of mixture. A positive feedback process is achieved, where shock-enhanced mixing promotes more vigorous combustion, which in turn reinforces the mixing quantity. This provides a new approach for the design of efficient and compact air-breathing rotating detonation engines.</div><div><strong>Novelty and significance statement:</strong> This study explores a locally dual-channel (LDC) combustor with a concentric strut, demonstrating its synergistic enhancement mechanism on mixing and combustion. The tight coupling relation between mixing and combustion redefines the understanding of the stability criteria for rotating detonation waves (RDWs) in air-breathing engines. The enhancement on mixing quantity is related with the intense shock-jet interactions. This local configuration also facilitates detonation wave initiation. Reflected shock waves (RSWs) collectively intensify combustion along the burned/unburned interface. The RDW drives upward-rotating shock waves (URSWs) to repeatedly sweep through the jet-mixing layer. This induces local reverse flow and tangential motion, increasing fuel residence time and improving mixing homogeneity. This LDC design offers a compact, stable, and efficient propulsion strategy, providing valuable approach for rotating detonation systems. The study reveals a closed-loop coupling mechanism involving shock-enhanced mixing, shock-induced combustion, and combustion-facilitated mixing.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114778"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combustion characteristics of ammonia/air flames assisted by microwave plasma in a two-staged swirl burner","authors":"Kuanyu Wang ,&nbsp;Zixu Nian ,&nbsp;Xiangnan Chen ,&nbsp;Yong Tang ,&nbsp;Bangdou Huang ,&nbsp;Baolu Shi","doi":"10.1016/j.combustflame.2026.114783","DOIUrl":"10.1016/j.combustflame.2026.114783","url":null,"abstract":"<div><div>As a zero-carbon fuel, ammonia (NH₃) has represented a promising candidate to replace fossil fuels for reducing greenhouse gas emissions. In this work, microwave-generated plasma torch was employed to assist two-staged swirl combustion of NH₃/air. Comprehensive experiments were conducted to elucidate the effects of plasma activation, primary equivalence ratio (Φ_p), and global equivalence ratio (Φ_g) on combustion characteristics. The plasma achieves simultaneous extension of lean blow-off (LBO) limit and reduction of both NOx and N₂O. OH planar laser-induced fluorescence (OH-PLIF) and NH₂* chemiluminescence diagnostics revealed that microwave discharge generates substantial concentrations of OH and NH₂* radicals, which markedly accelerate ammonia pyrolysis and oxidation, yielding a more compact flame and significantly widening the operable range of Φ_p. By integrating plasma assistance with staged combustion, the LBO limit of NH₃/air flames was extended from 0.55 ∼ 0.63 (without plasma) to 0.40 ∼ 0.56 within the range 2 ≤ Φ_p ≤ 6. At the same time, NO emissions were simultaneously reduced from ∼2600 ppm to ∼1000 ppm when Φ_g was fixed at 0.7. Spatial distributions of OH and NH₂*, combined with mechanistic analyses of NOx formation and consumption pathways, indicate that NOx emissions in the absence of plasma are governed primarily by OH-controlled formation processes, whereas DeNOx process dominates NO consumption under plasma activation. Meanwhile, N₂O emissions can be maintained below 50 ppm by appropriately increasing Φ_p.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114783"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973687","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":"Numerical simulation of microwave-enhanced low swirl methane-air flames","authors":"K. Nordin-Bates ,&nbsp;T. Hurtig ,&nbsp;N. Zettervall ,&nbsp;R. Robertsson ,&nbsp;E. Nilsson ,&nbsp;D. Lörstad ,&nbsp;A. Ehn ,&nbsp;C. Fureby","doi":"10.1016/j.combustflame.2026.114764","DOIUrl":"10.1016/j.combustflame.2026.114764","url":null,"abstract":"<div><div>Efficient and clean production of electrical and mechanical energy for use in industry, transportation and propulsion is currently a concern. The transition from fossil fuels to biofuels involves challenges related to the fuel composition and combustion, as well as methods to increase engine fuel flexibility. One potentially useful tool under development is Plasma Assisted Combustion (PAC), where a small amount of electrical energy is supplied to the combustion process to increase the chemical reactivity of a fuel-air mixture to promote faster ignition and flame propagation. Ability to control the ignition delay time and the laminar flame speed also provides ways to suppress thermoacoustic instabilities which is another challenge in the transition to sustainable fuels. Microwave irradiation is especially advantageous for direct flame stimulation since there is no need to insert electrodes into the combustion zone, and here we focus on microwave assisted combustion. Most prior studies of microwave assisted combustion have been performed experimentally for laminar flames but now there is a need to study also turbulent flames. Numerical simulations have proven useful in analyzing turbulent flames after the introduction of the Large Eddy Simulation (LES) method. Here, we perform on LES of microwave assisted turbulent combustion in a turbulent low-swirl flame previously studied by Ehn et al. (Proc. Comb. Inst. 36, 2017, p 4121). We here use a newly developed reaction mechanism for combustion and plasma chemistry including also ambipolar diffusion and explicit calculation of the self-induced electric field. Comparison with experimental data shows improved results compared to previous LES and increased understanding.</div><div>Novelty and significance statement: This study pioneers the numerical simulation of microwave-assisted turbulent combustion, extending prior experimental research beyond laminar flames. By incorporating a newly developed reaction mechanism with plasma chemistry, ambipolar diffusion, and self-induced electric fields, it enhances predictive accuracy and understanding, addressing critical challenges in fuel flexibility, ignition control, and thermoacoustic stability for sustainable combustion technologies.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114764"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973690","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":"Non-compact heat release rate oscillations in high-frequency combustion instabilities coupled to transverse modes","authors":"Hyebin Kang ,&nbsp;Hugo Paniez ,&nbsp;Thierry Schuller","doi":"10.1016/j.combustflame.2026.114785","DOIUrl":"10.1016/j.combustflame.2026.114785","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Hydrogen combustion systems are highly susceptible to high-frequency thermoacoustic instabilities coupled with transverse acoustic modes, whose prediction and physical understanding remain challenging due to the breakdown of the classical compact flame assumption. This study develops a framework for the determination of non-compact heat release rate (HRR) oscillations based on the description of disturbances &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̃&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; of the absolute flame boundary displacement with respect to the steady mean HRR distribution. The formulation separates unsteady HRR disturbances into two distinct mechanisms, (I) oscillations of flame displacement normal to the mean flame boundary &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̃&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;⋅&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and (II) oscillations of flame deformation corresponding to the divergence of the perturbed displacement field &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∇&lt;/mo&gt;&lt;mi&gt;⋅&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;̃&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Unlike earlier acoustic pressure-based approaches, the proposed framework naturally includes both acoustic and hydrodynamic pathways to flame displacement and extends the deformation term beyond isentropic compression to include non-isentropic flame dilatation effects. The framework is validated in a dual-swirl hydrogen combustor exhibiting a self-excited spinning combustion instability at &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; kHz, coupled to the first transverse acoustic mode of the combustion chamber. The phase-averaged velocity field and flame boundaries are deduced from PIV–OH PLIF measurements synchronized with acoustic pressure signals, while high-speed OH&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;∗&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; chemiluminescence, post-processed via Radon transform, is used to reconstruct the three-dimensional unsteady flame dynamics and infer the distribution of HRR within the flame boundaries. Quantitative comparisons show good agreement between model predictions and experiments. The analysis reveals a clear hierarchy among the driving mechanisms of HRR oscillations in the swirling hydrogen flame. Flame deformation dominates the HRR oscillations, governed primarily by density fluctuations associated with non-isentropic processes rather than by isentropic compression and expansion due to transverse acoustic waves. In contrast, flame displacement plays a secondary role and is governed mainly by hydrodynamic vortex-induced motion rather than by direct impact of transverse acoustic velocity perturbations. This framework provides new physical insight and establishes a foundation for modeling non-compact high-frequency combustion instabilities coupled to transverse acou","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114785"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973689","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":"Nanoscale insights into morphological and structural characteristics of soot particles emitted from general aviation engines burning sustainable aviation fuel","authors":"Yang Cao ,&nbsp;Longfei Chen ,&nbsp;Xuehuan Hu ,&nbsp;Sow Chorng Haur ,&nbsp;Xiaoyang Chen","doi":"10.1016/j.combustflame.2026.114787","DOIUrl":"10.1016/j.combustflame.2026.114787","url":null,"abstract":"<div><div>With the aviation industry committed to achieving net-zero emissions by 2050, sustainable aviation fuels (SAFs)—notably hydroprocessed esters and fatty acids (HEFA)—have emerged as a pivotal decarburization pathway due to their drop-in capability. However, limited understanding of morphological and nanostructure characteristics of soot particles derived from SAF hinders a comprehensive assessment of its environmental and health impacts. This study investigates the microscopic characteristics of soot particles emitted from two general aviation engines operated under low (7%), medium (50% or 60%), and high (100%) loads burning 100% HEFA-SAF and RP-3 fuels. The results indicate that the <span><math><msub><mi>D</mi><mover><mi>p</mi><mo>¯</mo></mover></msub></math></span> of HEFA-SAF soot particles remain smaller than RP-3 across all loads, and HEFA-SAF soot particles feature the morphology of smaller \"core\" part (amorphous carbon) and thicker \"shell\" part (concentric graphite layers). Additionally, the findings reveal a close correlation between the elemental ratio of carbon-to-oxygen, internal nanostructures, and the degree of graphitization of soot particles and engine load, while the influence of fuel composition on these parameters demonstrated non-monotonic characteristics, which can be attributed to the kinetic time scales competition between fuel-air mixing and fuel pyrolysis kinetics. Therefore, this study highlights that morphological and nanostructure of soot particles are influenced by coupled effects of fuel composition and operational load. Importantly, while HEFA-SAF effectively reduces soot particle emission concentrations, its derived soot particles microscopic characteristics remain statistically indistinguishable from those of soot particles derived from RP-3. This finding implies that HEFA-SAF implementation can mitigate aviation’s particulate climate forcing without enhancing per-particle radiative efficiency, thereby decoupling emission reduction from amplified climate impacts and accelerating aviation industry decarbonization.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114787"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973691","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":"High-temperature pyrolysis and oxidation of nitromethane: laser diagnostics and model development for C–N–O combustion chemistry","authors":"Shubao Song ,&nbsp;Lin Zhang ,&nbsp;Jinghua Wu ,&nbsp;Meishuai Zou ,&nbsp;Jiankun Shao","doi":"10.1016/j.combustflame.2026.114782","DOIUrl":"10.1016/j.combustflame.2026.114782","url":null,"abstract":"<div><div>A detailed experimental and modeling study was conducted to investigate the high-temperature decomposition and ignition behavior of nitromethane (CH₃NO₂) and its relevance to the development of a comprehensive C–N–O kinetic model. Shock tube experiments coupled with high temporal resolution and low detection limit laser absorption diagnostics were employed to measure time-resolved species profiles of NO, CO, and CH₄ during CH₃NO₂ pyrolysis under argon-diluted conditions (1.0 % and 1.3 % CH₃NO₂ in Ar). In addition, ignition delay times (IDTs) of CH₃NO₂/O₂/Ar mixtures were measured over a wide range of equivalence ratios (<em>φ</em> = 0.5, 1.0, and 2.0) at near-atmospheric pressure. To further constrain the kinetics, the rate constant for the unimolecular decomposition reaction R1 (CH₃NO₂ (+M)=&gt; CH₃ + NO₂ (+M)) was experimentally determined at high temperatures, the resulting rate constant data can be represented by the Arrhenius equation <em>k</em>_R1(1043–1350 K, 1.5 atm) = 4.98 <span><math><mo>×</mo></math></span> 10¹² exp(-44,990 cal/mol/<em>RT</em>)<em>s</em>^-1. A refined kinetic model for CH₃NO₂ combustion was developed by integrating the newly obtained rate constant data of R1 and updating the CH₃NO₂ sub-mechanism within a previously established NH₃–syngas model. Rate of production and sensitivity analyses were performed to identify the dominant reaction pathways governing species formation, with particular emphasis on the role of R1 and its competition with secondary reactions. This work advances the understanding of nitroalkane combustion, offering a robust and transferable kinetic framework for future simulations of energetic materials in propulsion and energy systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114782"},"PeriodicalIF":6.2,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973688","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":"Experimental and kinetic study of pyridine pyrolysis with tunable synchrotron VUV photoionization and molecular beam mass spectrometry","authors":"Cheng-Yin Ye ,&nbsp;Ling-Nan Wu ,&nbsp;Dong-Xu Tian ,&nbsp;Jiu-Zhong Yang ,&nbsp;Long Zhao ,&nbsp;Zhen-Yu Tian","doi":"10.1016/j.combustflame.2025.114742","DOIUrl":"10.1016/j.combustflame.2025.114742","url":null,"abstract":"<div><div>The pyrolysis of pyridine, a model compound for fuel-nitrogen in coal, biomass, and tar, was investigated in a flow reactor at a pressure of 30 Torr and a temperature range from 773 to 1473 K. Twenty-seven species, including three radicals, three sets of isomers, nine hydrocarbons and nine nitrogenous species, were identified and quantified by synchrotron vacuum ultraviolet photoionization mass spectrometry. Several intermediates were newly detected compared with previous pyridine pyrolysis studies based on the photoionization efficiency spectra including cyanides, a benzene isomer, and resonance-stabilized radicals (propargyl and benzyl radicals). A new kinetic model for pyridine pyrolysis was developed and validated against the measured data. Kinetic modeling, rate-of-production and sensitivity analysis were performed to reveal the pyrolysis kinetics of pyridine and the formation of the key products. The results indicate that the decomposition of pyridine is dominated by the H-abstraction reactions. Hydrocarbon radicals, alkenes and alkynes are mainly produced by the elimination of HCN from nitrogenous intermediates. The formation of nitrogenous products relates to the removal of acetylene from pyridine. A new growth route from C₃HN to C₅HN and C₇HN was observed and analyzed, which has not been reported previously regarding the pyrolysis studies of fuel-N. By comparing the pyridine pyrolysis with pyrrole pyrolysis experiments, the influence of different C-N bond structures on reaction mechanisms and product distributions was revealed. Results of this work are helpful in deepening the understanding of pyridine conversion behaviors related to coal and biomass combustion and conversion processes.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114742"},"PeriodicalIF":6.2,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973684","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":"A statistical framework for modeling and simulation of direct initiation","authors":"Jacob Leff,&nbsp;Sebastian Perna,&nbsp;James Braun","doi":"10.1016/j.combustflame.2026.114773","DOIUrl":"10.1016/j.combustflame.2026.114773","url":null,"abstract":"<div><div>Prediction of direct initiation (DI) of detonation in a fuel-air mixture is hindered by the probabilistic nature of the outcome, which is a function of many variables including composition, temperature, pressure, and ignition energy. This paper presents a statistical surrogate model of the probability of direct initiation as a function of the latter three variables for stoichiometric mixtures of ethylene and air. An idealized 2D piston-driven detonation tube was simulated at different conditions and diaphragm burst pressures and the database of DI outcomes was used to train a radial basis function neural network (RBFNN). The surrogate model identified the manifold of 50% DI probability and expressed the fundamental outcome variability near the threshold. The necessary ignition pressure showed a negative exponential dependence on temperature and a complex dependence on pressure. The reaction speed and detonation cell size were also obtained at every case for validation and verification, and a variation of the Cellpose-SAM neural network was used to automatically identify the detonation cells in 355 numerical soot foils. The corresponding detonation cell sizes were several times smaller than predicted by empirical correlations, indicating that numerical underprediction of cell size also results in underprediction of critical energy. The results also show that critical energy does not correlate with detonation cell size when compared at different pressures. The framework used in this study is generalizable to other variables that influence DI and can be used to study and optimize variations in composition and configuration of the ignition system.</div></div><div><h3>Novelty and significance statement</h3><div>This paper presents the first effort to use numerical simulation and machine learning to predict the probability of detonation in a complex configuration. The probabilistic forecast reflects the intrinsic variability of detonation and offers a more repeatable prediction than simulations of individual events. The rigorous data-driven approach also enables identification of trends and quantification of accuracy.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114773"},"PeriodicalIF":6.2,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973267","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":"Structure and stability analysis of the ultra-rich H2CO2O2 premixed flames at various CO2 concentrations","authors":"Yulong Chen,&nbsp;Wenquan Yang,&nbsp;Jianlong Wan","doi":"10.1016/j.combustflame.2026.114770","DOIUrl":"10.1016/j.combustflame.2026.114770","url":null,"abstract":"<div><div>A novel high-temperature hydrogen reduction method based on the hydrogen-oxygen ultra-rich premixed combustion technology is proposed to achieve nearly zero CO₂ emission when reducing the limestone or metallic mineral in our previous work. As the first step of the aforementioned study, the dynamics of the self-sustaining ultra-rich H₂_<img>CO₂_<img>O₂ premixed flame needs to be revealed in detail. In this study, the structure and stability of ultra-rich H₂_<img>CO₂_<img>O₂ premixed flame in a micro tube-burner with a backward step at three volume percentages of CO₂ (73%H₂–10%O₂–15%CO₂, 68%H₂–10%O₂–20%CO₂, and 63%H₂–10%O₂–25%CO₂) are investigated for the first time by employing experiment and simulation. It is found that the flame tip is brighter than its root primarily owing to a larger combustion intensity at the former. The CO sensitivity is also analyzed based on identifying ten sensitive reactions, including five inhibitory and five facilitatory reactions in the fast production region of CO. The CO is primarily generated by the reaction of CO₂ with H and OH radicals. Hydrogen is partially consumed by the combustion reaction first just before the flame front, and then it reacts with CO₂ to form CO via the RWGS (Reverse Water-gas Shift) reaction in the downstream high-temperature zone. Unexpectedly, the heat release rate and the corresponding reaction rate at the flame tip in the case of the volume percentage of CO₂ X_CO2=20% are larger than those in the case of X_CO2=15% and X_CO2=25%. This is primarily because the equivalent equivalence ratio of H₂_<img>O₂ in the fresh mixture is closer to the stoichiometric ratio and the negative CO₂ dilution effect is smaller in the case of X_CO2=20%. The flame displacement speed along the flame front is smaller at a larger X_CO2 value primarily due to a more remarkable negative CO₂ dilution effect. It is found that the thermal interaction of flame-wall effect contributes to anchoring the flame root rather than the flame tip. The relative fuel-rich region at the flame root reduces its stability. To the best of our knowledge, the present ultra-rich H₂_<img>CO₂_<img>O₂ premixed flame structure and stability analysis have not been reported yet. This study expands our understanding of the ultra-rich premixed flame dynamics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114770"},"PeriodicalIF":6.2,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973685","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":"A theoretical study of the chemistry of the pentane isomers with the amino radical: Rate constants, branching ratios, and kinetic modeling","authors":"Myriam Belmekki ,&nbsp;Manuel Monge-Palacios ,&nbsp;Qi Wang,&nbsp;S. Mani Sarathy","doi":"10.1016/j.combustflame.2026.114775","DOIUrl":"10.1016/j.combustflame.2026.114775","url":null,"abstract":"<div><div>Hydrogen atom abstraction reactions from hydrocarbons by the amino radical (NH₂) is a key pathway governing the reactivity of ammonia/alkane blends in both combustion and atmospheric chemistry. Despite their relevance, kinetic data for reactions between NH₂ and large alkanes such as the C₅ isomers remain scarce. In this work, we present a comprehensive theoretical kinetic study for the hydrogen abstraction reactions from n-pentane, isopentane, and neopentane by NH₂ radicals over the 200–3000 K temperature range. Site-specific rate constants were calculated using canonical variational transition state theory with small curvature tunneling and multistructural torsional anharmonicity corrections. Potential energy surfaces were characterized at the CCSD(T)/aug-cc-pVTZ//M06–2X/aug-cc-pVTZ level of theory, and extensive conformational sampling was performed for both the C₅ reactant and saddle point of each reaction. The results reveal a strong dependence of reactivity on both molecular branching and torsional flexibility, with multistructural torsional anharmonicity effects notably enhancing or suppressing specific reaction pathways. Comparisons with existing theoretical and experimental data highlight the necessity of incorporating multistructural torsional anharmonicity and variational effects to accurately model the kinetics of such reactions. Moreover, our results point out the good performance of the M06–2X functional, when used in conjunction with a large basis set, at predicting barrier heights and multistructural torsional anharmonicity effects, which would facilitate the modeling of reactions involving large hydrocarbons. Our refined kinetic parameters and mechanistic insights that are essential for developing kinetic models for the combustion of NH₃-alkane blends as well as for modeling NH₂-alkane interactions in atmospheric chemistry applications.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"285 ","pages":"Article 114775"},"PeriodicalIF":6.2,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922225","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}