Combustion and Flame最新文献

{"title":"Reduced chemistry for numerical combustion of NH3/H2 fuel blend","authors":"Giovanni Grassi,&nbsp;Luc Vervisch,&nbsp;Pascale Domingo","doi":"10.1016/j.combustflame.2025.114287","DOIUrl":"10.1016/j.combustflame.2025.114287","url":null,"abstract":"<div><div>Ammonia is increasingly recognized worldwide as a promising carrier for hydrogen and energy. One effective strategy is blending ammonia with hydrogen to achieve combustion characteristics comparable to those of natural gas, including stable flame anchoring, controlled flame length, and sufficient heat release for energy production. The design and optimization of ammonia combustion systems rely heavily on computational fluid dynamics (CFD). Accurate CFD simulations of furnaces and gas turbines require chemical kinetic models that strike a balance between simplicity and fidelity, minimizing computational complexity (typically less than 20 species to be transported with the flow) while effectively capturing the essential thermochemistry of hydrogen-enriched ammonia combustion. This study begins with a detailed ammonia/air combustion mechanism and combines various canonical problems to derive two reduced chemical schemes. The methodology employs automated analyses to identify the most influential chemical species and elementary reactions. Five key reactive scenarios representative of premixed and non-premixed burners with eventual dilution by burnt gases are explored: auto-ignition, chemistry interacting with turbulent micro-mixing, freely propagating laminar premixed flames, strained counterflow diffusion flames, and mixing layers. This comprehensive approach facilitates the development of reduced kinetic models specifically tailored to ammonia/hydrogen–air combustion under a set of given operating conditions.</div><div><strong>Novelty and Significance Statement</strong></div><div>Novel reduced chemical schemes are proposed from a reference detailed mechanism for simulating ammonia–hydrogen-enriched combustion. To ensure their applicability in turbulent flame simulations, the reduction methodology incorporates a specific combination of various canonical test cases, including turbulent micro-mixing, for validation and performance assessment. These schemes achieve a significant reduction in stiffness and the number of degrees of freedom to be solved. To demonstrate their feasibility in computational fluid dynamics, a reactive mixing layer is simulated, and the results obtained with the reduced schemes are compared against those from the reference detailed mechanism.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114287"},"PeriodicalIF":5.8,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502207","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 comprehensive experimental and numerical study on turbulent jet ignition mechanisms of lean hydrogen mixture using a super-rich pre-chamber combustion","authors":"Haoming Gu,&nbsp;Fangsi Ren,&nbsp;Shinji Nakaya,&nbsp;Mitsuhiro Tsue","doi":"10.1016/j.combustflame.2025.114286","DOIUrl":"10.1016/j.combustflame.2025.114286","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In this study, the combustion mechanism of turbulent jet ignition (TJI) with a super-rich hydrogen pre-chamber under globally lean conditions to achieve efficient combustion with low NOx emissions is investigated. Experiments were conducted in a rapid compression machine using a diaphragm-isolated pre-chamber filled with uniformly rich mixtures. Time-resolved measurements of OH* chemiluminescence images, near-infrared emission images from water molecules, and pressure in both chambers were performed to analyze the ignition and subsequent flame propagation. Furthermore, large-eddy simulations (LES) were conducted to investigate the ignition characteristics and flame structures in more detail. Results indicated that peak pressures for TJI were slightly lower than for conventional spark ignition (SI) at the same global equivalence ratio, likely due to additional heat losses. However, TJI significantly increased the pressure rise rate, enabling more efficient combustion in ultra-lean conditions by enhancing the degree of constant-volume heat release. Distinct flame structures were observed experimentally, consisting of a bright core plume surrounded by lower-intensity zones. During the TJI process, a large initial pressure difference between the pre-chamber and main chamber resulted in flame lift-off, characterizing the jet-ignition mode. As the pressure gap decreased, the flame transitioned to the flame-ignition mode, characterized by the attachment of the flame to the nozzle. Statistical analysis concluded that the ignition mode transition duration and lift-off height level during the transition exhibited an inverse correlation with pre-chamber richness and global equivalence ratio. The 2 mm orifice reduced pressure gaps and facilitated a faster mode transition compared to the 1 mm orifice. LES results showed good agreement with the experiments and exhibited the flame mechanism consisting of an outer lean premixed zone and an inner non-premixed core. Although stoichiometric combustion in the non-premixed region was observed H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;O from pre-chamber products likely contributed to dilution, which may have helped limit the temperature rise and reduce NOx formation.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;The novelty of this study lies in the investigation of lean combustion mechanisms using turbulent jet ignition (TJI) with a super-rich hydrogen pre-chamber as a staged combustion technology with low NOx emissions. A unique combustion mechanism consisting of a non-premixed core diluted by H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;O and surrounding lean flame front was identified. The significance of this work is its potential to stabilize ignition under globally lean conditions while effectively controlling combustion temperatures to reduce NOx emissions. These findings offer valuable insights for the practic","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114286"},"PeriodicalIF":5.8,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144481640","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":"Ignition and combustion characteristics of single Al-Li alloy fuel microparticles in CO2 atmosphere","authors":"Hehui Yao ,&nbsp;Shengji Li ,&nbsp;Yanqi Liu ,&nbsp;Houye Huang ,&nbsp;Fang Wang ,&nbsp;Wei Li ,&nbsp;Xuefeng Huang","doi":"10.1016/j.combustflame.2025.114308","DOIUrl":"10.1016/j.combustflame.2025.114308","url":null,"abstract":"<div><div>Introducing tiny elemental lithium (Li) into aluminum (Al) to form Al-Li alloy has been proved to be a promising potential in substituting for Al in air. However, the ignition and combustion performance of Al-Li in CO₂ atmosphere (as one of main gas products of propellant pyrolysis) has not been investigated. In this work, a comparative study was conducted on the laser-induced ignition and combustion characteristics of individual micron-sized Al-Li alloy (2.5 wt % Li) particles and pure Al fuel particles in CO₂ atmosphere. It was found that the addition of Li prolonged the ignition delay of Al by 116.1 %, which is significantly different with the behavior in air or oxygen atmosphere. The intermediate products during ignition were acquired by accurate quenching technology via controlling the laser operation time to the millisecond level, and its characterization results revealed the presence of Li₂CO₃, indicating that Li in the Al-Li alloy could firstly react with CO₂ to form Li₂CO₃ during ignition, which restricted the expansion of particles and thus prolonged the ignition delay. In comparison to pure Al, the combustion flame propagation of Al-Li in CO₂ atmosphere was constrained, and the micro-explosion performance was mitigated, while there was no significant difference in the combustion temperature on the influence of overall exothermic performance. Finally, the ignition and combustion mechanism of Al-Li alloy in CO₂ was proposed and revealed, through combining with the characteristic analysis of the combustion residues and intermediate products.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114308"},"PeriodicalIF":5.8,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144481639","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":"Identification of instantaneous flame transfer functions","authors":"Justus Florian Radack,&nbsp;Bruno Schuermans,&nbsp;Nicolas Noiray","doi":"10.1016/j.combustflame.2025.114246","DOIUrl":"10.1016/j.combustflame.2025.114246","url":null,"abstract":"<div><div>Most existing system identification methods are designed for time-invariant systems. However, for many practical applications, data collection over a wide range of parameters under stationary conditions is either infeasible or costly. To address this limitation, we propose a time-domain, nonparametric methodology for linear, time-varying (LTV) systems, extending the classical paradigm of impulse response function estimation from broadband data using least-squares regression. We introduce the time-varying impulse response function (TV-IRF), which uniquely characterizes the dynamic behavior of LTV systems, and represent it as a series expansion over an orthonormal basis. The collected nonstationary data is projected onto each basis function, and the TV-IRF is estimated using least-squares regression. To validate and analyze this methodology, we first apply it to data generated from measurements of a swirled, hydrogen-enriched flame. Subsequently, we apply it to identify the TV-IRF and time-varying flame transfer functions (TV-FTF) of a canonical slit flame. Using both stationary and nonstationary direct numerical simulations across a wide range of mean flow velocities in the burner, we demonstrate that the instantaneous flame transfer functions derived from the TV-FTF closely match those identified in a stationary setting. Notably, this accuracy is maintained even when the length of nonstationary time series is equivalent to that used for stationary identification at a single velocity. This methodology promises substantial reductions in computational and experimental costs, paving the way for efficient exploration and identification of dynamical systems across large parameter spaces.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114246"},"PeriodicalIF":5.8,"publicationDate":"2025-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144481629","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":"Eigenvalue detonation: Particle size effects in aluminized explosives","authors":"Vincent R. Schuetz,&nbsp;D. Scott Stewart","doi":"10.1016/j.combustflame.2025.114256","DOIUrl":"10.1016/j.combustflame.2025.114256","url":null,"abstract":"<div><div>Experiments demonstrate that incorporating aluminum into high explosives like HMX can significantly influence their detonation characteristics. Specifically, aluminum particle sizes of 150, 15, 7, and <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> in diameter result in variation to detonation velocity, and pressure within the detonation reaction zone. Pressure histories recorded at the explosive-indicator interface show an initial peak corresponding to the detonation shock pressure, followed by a pressure drop and a subsequent rise to a second peak within <span><math><mrow><mn>1</mn><mspace></mspace><mi>μ</mi><mi>s</mi></mrow></math></span> of the shock front. The presence of double pressure peak profiles are dependent on the aluminum particle size. To replicate the experimental results numerically, we employ eigenvalue detonation theory consisting of two reactions: a bulk <em>exothermic</em> step followed by a bulk <em>endothermic</em> step. The explosives are characterized by JWL equations of state, and reaction rates that account for the melting temperature of aluminum. We find that the experimental results can be matched for the four aluminum particle sizes by varying only two equation of state parameters, and three rate parameters. Double peak pressure profiles arise from Rate Limited Weak Detonation (RLWD), where aluminum particles rapidly absorb energy during HMX decomposition, leading to a sign change in thermicity. Additionally we explore the potential for strong detonations in aluminized explosives through flyer impact simulations, informing experiments on inducing and sustaining strong detonation in aluminized explosives.</div><div><strong>Novelty and Significance Statement</strong></div><div>This is a follow-on paper to “On the structure and dynamics of strong and weak eigenvalue detonation in condensed explosives”, V. R. Schuetz and D. S. Stewart, Combustion and Flame 263, (2024) 113414. This paper specializes our 3-component model to aluminized explosives, and predicts experimental results for mixtures of explosive and aluminum particles with varying particle sizes. The model shows that both weak and strong eigenvalue detonation exist and shows the dramatic differences afforded by confinement in the case of strong detonation, which has not received much (or no) attention in the literature. Hence the work is novel and open new doors to principles that can be used to improve explosives and understand the effects of aluminum particle additives.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114256"},"PeriodicalIF":5.8,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471636","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":"Detonation cellular regularity: A data analysis","authors":"Xian Shi","doi":"10.1016/j.combustflame.2025.114296","DOIUrl":"10.1016/j.combustflame.2025.114296","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Detonation cellular regularity describes the spatial organization of the cellular patterns that emerge from the unsteady shock interactions within a propagating detonation. This study introduces the regularity index (RI), a quantitative metric derived from the spatial distribution of triple-point collision locations recorded on soot foils. The RI provides a robust and accessible approach for characterizing cellular regularity and leverages the extensive archive of soot foil measurements in the literature. Over 100 soot foils were analyzed to calculate RI values, enabling a systematic evaluation of the relationship between cellular regularity and key detonation properties. Among the properties considered, the effective activation energy (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ɛ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) emerged as the most effective predictor of regularity, with higher &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ɛ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; correlating with high RI values, indicating increasingly irregular cellular structures. In contrast, the stability parameter (&lt;span&gt;&lt;math&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;), traditionally used to describe detonation instability, exhibited limited applicability across the broader dataset. The discrepancies originate from large uncertainties in calculating &lt;span&gt;&lt;math&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and related properties when different chemical kinetic modes were used, underscoring the need for improved chemical kinetic knowledge under detonation-relevant conditions. New soot foil measurements were performed for acetylene–oxygen, acetylene–oxygen–argon, and hydrogen–oxygen mixtures, where &lt;span&gt;&lt;math&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; had previously been proposed as an effective measure for regularity. The derived RI values as well as the visual inspection of the new soot foils confirmed the strong correlation between &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ɛ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and cellular regularity. Overall, the regularity index concept was shown to effectively capture cellular regularity, and offers opportunities for future quantitative analyses of detonation dynamics involving regularity.&lt;/div&gt;&lt;div&gt;Novelty and significance statement&lt;/div&gt;&lt;div&gt;This work introduces a new metric, the regularity index (RI), for quantitatively characterizing detonation cellular regularity. By analyzing a comprehensive dataset of over 100 soot foils and conducting new experiments, the study establishes the effective activation energy (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;ɛ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) as the most reliable predictor of cellular regularity. Moreover, the broader applicability of the stability parameter (&lt;span&gt;&lt;math&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) to cellular regularity was evaluated, and only a weak correlation, if any, was observed. The previously reported trends were shown to result from chemical kinetic models with significant uncertainties under detonation-","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114296"},"PeriodicalIF":5.8,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471638","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":"Velocity-forced nonlinear heat release response of transverse reacting jet in an axial fuel-staged combustion system","authors":"Yongseok Choi,&nbsp;Heeyoung Kim,&nbsp;Kyu Tae Kim","doi":"10.1016/j.combustflame.2025.114316","DOIUrl":"10.1016/j.combustflame.2025.114316","url":null,"abstract":"<div><div>Heavy-duty gas turbines integrated with axial fuel staging functionality outperform conventional non-staged systems in terms of controlling nitrogen oxides emissions under high turbine inlet temperature conditions, while maintaining reliable part load operations. Substantial developments have been achieved in the understanding of nitrogen oxide reaction pathways and autoignition-related stabilization mechanisms, whereas limited attention has been paid to thermoacoustic interactions driven by coupled primary-secondary flame dynamics. In particular, flame describing functions (FDF) and underlying mechanisms of a second-stage transverse reacting jet in high-temperature vitiated crossflow remain unknown. To address these problems, here we perform velocity-forced nonlinear heat release response measurements in the absence and presence of crossflow velocity modulations, in conjunction with phase-resolved flame surface density (FSD) characterization and dynamic mode decomposition (DMD)-based representation of complex modal dynamics. Experimentally, we show that high-amplitude velocity perturbations cause the FDF gain to be reduced to some degree with no sign of strong saturation; the transverse reacting jet’s nonlinear response is dictated by non-axisymmetric vortex-flame interactions. The coexistence of two different sources of upstream velocity disturbances – including the primary flame dynamics-induced mono-frequency crossflow modulations and the preexisting velocity fluctuations propagating normally from the secondary injector’s inlet plenum – is observed to promote the secondary flame’s FDF gain reduction, as well as to reduce the characteristic response time. Taken together, these results provide previously unidentified nonlinearity-relevant information, pivotal to improving our understanding of acoustically-constrained interactions between two axially staged flames.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114316"},"PeriodicalIF":5.8,"publicationDate":"2025-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471637","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":"Machine learning tabulation of thermochemistry for the PAH mechanism and applications to laminar and turbulent sooting flames","authors":"Anxiong Liu ,&nbsp;Tianjie Ding ,&nbsp;Kun Luo","doi":"10.1016/j.combustflame.2025.114148","DOIUrl":"10.1016/j.combustflame.2025.114148","url":null,"abstract":"<div><div>This work proposes a novel machine learning tabulation methodology to accelerate the computation of a large polycyclic aromatic hydrocarbon (PAH) mechanism for soot formation in combustion. This methodology combines the directed relation graph error propagation (DRGEP) analysis with previous hybrid flamelet/random data and multiple multilayer perceptrons (HFRD-MMLP) method (Ding et al., 2021), to select target species and determine connected species list for each target. By this means, the number and size of artificial neural networks (ANNs) are substantially reduced. The HFRD method utilises the random process to expand data from laminar flamelets with the full BPP mechanism to cover reactive compositions in practical turbulent sooting combustion. The MMLP approach trains separate ANNs for composition states of different magnitudes, aiming to improve the prediction accuracy. The ANNs are tested on 1-D laminar flame simulations with varying strain rates, demonstrating higher prediction accuracy compared to using the direct integration with the simplified PAH mechanism. Validation is further conducted on simulations of laminar co-flow (Santoro) and turbulent lifted (DLR) sooting flames, showing overall agreement with direct integration methods in terms of temperature, soot volume fraction and species mole fractions, except errors are observed at flame downstream regions for some minor species and PAHs. The proposed HFRD-MMLP-DRGEP method for the PAH mechanism achieves significant speed improvement compared to traditional integration algorithms. In the laminar co-flow case, the method achieves speed-up factors of 59 and 22 for the reaction step and total computation time, respectively, when compared to the DVODE algorithm. In the LES-PDF-PBE simulation of the turbulent flame, speed-up factors are 4.0 and 2.3, compared to the Euler backward algorithm. If compared to the DVODE, the speed-up ratios should be 50 and 27. These speed-up factors are much higher than those achieved with small-size mechanisms, like GRI-1.2 (Ding et al., 2022) and DME (Liu et al., 2024) mechanisms, indicating the high efficacy of the HRFD-MMLP-DRGEP method in reducing computational costs for large mechanisms.</div><div><strong>Novelty and significance</strong></div><div>This study presents a novel methodology for accelerating the real-time computation of a complete polycyclic aromatic hydrocarbon (PAH) mechanism (Blanquart et al., 2009) in soot formation modelling. This new methodology combines the DRGEP analysis with the HFRD-MMLP approach (Ding et al., 2021, 2022) to reduce the number and size of trained artificial neural networks (ANNs). This is the first application of the ANN method to accelerate a complete PAH mechanism in laminar and turbulent sooting flame simulations</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114148"},"PeriodicalIF":5.8,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471639","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 modeling studies of quenching diameters of laminar premixed flames of NH3/air mixtures","authors":"Xiaofei Yao,&nbsp;Hongnan Wang,&nbsp;Weijian Zhou,&nbsp;Jian Gao","doi":"10.1016/j.combustflame.2025.114312","DOIUrl":"10.1016/j.combustflame.2025.114312","url":null,"abstract":"<div><div>The quenching diameters of laminar premixed flames of NH₃/air mixtures under ambient temperature and pressure were investigated via experimentation and kinetic modeling. In the experiments, a premixed Busen flame was at first established on the exit of a cylindrical quartz tube, and then the gas flow was suddenly stopped to test whether it incurs quasi-steady state flame propagation or flame quenching in the tube. The tube diameter was progressively decreased from 15.0 to 8.0 mm and the quenching diameter is the diameter that just prevents flame propagation (flashback) and incurs flame quenching. Quenching diameters were measured at varied equivalence ratios of 0.6 - 1.4. A transient two-dimensional axisymmetric numerical model was applied to simulate the flame structure and the propagation and quenching processes. Heat exchange between the flame and the conductive wall was considered. Three detailed reaction mechanisms were employed for chemical kinetics, namely, the Glarborg et al., Okafor et al., and Zhang et al. mechanisms. The Glarborg et al. mechanism shows a better agreement with the experimental results in predicting the quenching diameters, while all three mechanisms over predicted the quenching diameter at the lean limit. Kinetic analysis suggests that the H involved reactions, H + O₂ = O + OH and H + NO (+M) = HNO (+M), are the most contributive exothermic reactions. The H₂NN related reactions that included in the Glarborg et al. mechanism shows a minor impact on the prediction of the quenching diameter, while influences the NO_x formation significantly.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114312"},"PeriodicalIF":5.8,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144365772","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":"Ignition of micron amorphous boron particles in CO2 with shock tube","authors":"Shengyu Pang ,&nbsp;Kai Pang ,&nbsp;Long Miao ,&nbsp;Yugan Liao ,&nbsp;Xiao Hou ,&nbsp;Baolu Shi","doi":"10.1016/j.combustflame.2025.114311","DOIUrl":"10.1016/j.combustflame.2025.114311","url":null,"abstract":"<div><div>This study successfully ignited 11 μm amorphous boron (B) powder in a pure carbon dioxide (CO₂) atmosphere using a shock tube ignition platform, providing important insights for CO₂-B reaction which was generally neglected in propulsion system. The experiments were conducted at temperatures ranging from 2100 to 2900 K and 3.5 atm, focusing on the effects of temperature and CO₂ concentration on the ignition characteristics. The results show that the ignition delay time decreases with increasing temperature. And the critical ignition temperature of boron was found to beyond 2100 K. The effects of CO₂ concentration on the ignition delay time and critical ignition temperature were much complex. These findings provide new data on boron ignition characteristics in CO₂ environments, offering valuable reference information for CO₂ propulsion technologies in space exploration.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114311"},"PeriodicalIF":5.8,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144364923","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}