Combustion and Flame最新文献

{"title":"Control mechanism of negative-temperature-coefficient phenomenon based on the first temperature jump in two-stage auto-ignition","authors":"Yu Zhang,&nbsp;Xingtong Ma,&nbsp;Cheng Cheng,&nbsp;Yiran Cheng,&nbsp;Taotao Zhou,&nbsp;Tao Wang,&nbsp;Chunmei Wang,&nbsp;Yejian Qian,&nbsp;Yao Xu","doi":"10.1016/j.combustflame.2025.114471","DOIUrl":"10.1016/j.combustflame.2025.114471","url":null,"abstract":"<div><div>Two-stage auto-ignition is often found in homogeneous charge compression ignition (HCCI) engines, which simultaneously achieve high efficiency and low emissions. Two-stage auto-ignition in the intermediate-temperature range causes a negative-temperature-coefficient (NTC) phenomenon, and this work focuses on the relationship between NTC and the first temperature jump in two-stage auto-ignition. Homogeneous models with and without droplet evaporation are applied under different pressures (5–20 bar), temperatures (600–900 K), diameters (0–100 μm), n-heptane molar fractions (0∼100%) and equivalence ratios (0.25–1.0). The results show that the mechanism of NTC control is different for the two models. For the model without evaporation, the NTC phenomenon is closely related to the linear slope of the first temperature jump to the initial temperature. A slope map is divided into NTC, zero-temperature coefficient (ZTC) and non-NTC regions when the slope is less than, equal to or more than the critical slope. For the model with evaporation, the ZTC phenomenon is found when two-stage auto-ignition translates to single-stage auto-ignition. Two- and single-stage auto-ignition are distinguished based on whether the first temperature jump is higher than a critical value. The NTC control helps to improve the heat-release rate because violent heat release limits the application of HCCI engines at high load.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114471"},"PeriodicalIF":6.2,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107627","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":"Soot suppression and radiation enhancement in CO2 diluted laminar inverse diffusion flames","authors":"Wei Lu ,&nbsp;Junjun Guo ,&nbsp;Tai Zhang ,&nbsp;Yongjun Zhang ,&nbsp;Hong G. Im ,&nbsp;Zhaohui Liu","doi":"10.1016/j.combustflame.2025.114477","DOIUrl":"10.1016/j.combustflame.2025.114477","url":null,"abstract":"<div><div>Inverse diffusion flame (IDF) configuration is widely employed in high-temperature industrial processes. While oxy-fuel combustion is considered a promising technology for CO₂ capture, the high CO₂ concentrations involved can significantly suppress soot formation and potentially reduce radiative heat transfer. In this study, ethylene IDFs with varying levels of CO₂ dilution in the oxidizer are investigated through high-fidelity numerical simulations. Detailed soot kinetic models and non-gray radiative property models are employed to ensure close agreement with experimental measurements, including flame temperature, flame height, and soot volume fraction. A fictitious species strategy is employed to isolate the thermal, radiative, transport, and chemical effects of CO₂ on soot formation. Additionally, the individual radiative contributions of CO₂, H₂O, CO, and soot particles are quantitatively evaluated. Results reveal that the thermal and chemical effects of CO₂ are the most significant in suppressing soot formation, primarily by lowering flame temperature and reducing the concentration of soot-forming species. The chemical effect is dominant at a 50% dilution level, while the thermal effect becomes more important at 70%. The transport effect of CO₂ primarily leads to an increase in flame height, but has a negligible impact on peak soot volume fraction. Moreover, the overall radiative capability of CO₂-diluted flames is consistently higher than that of N₂-diluted flames at equivalent dilution levels, with the difference becoming more pronounced at higher dilution levels. In N₂-diluted flames, soot radiation dominates but decreases sharply with increasing dilution. In contrast, CO₂-diluted flames exhibit dominant CO₂ radiation, which remains largely unaffected by further dilution.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114477"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107502","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":"Three-dimensional morphology and formation mechanism of tongue-shaped oblique detonation waves in elliptical flow channels","authors":"Shuzhen Niu ,&nbsp;Pengfei Yang ,&nbsp;Zijian Zhang ,&nbsp;Honghui Teng","doi":"10.1016/j.combustflame.2025.114468","DOIUrl":"10.1016/j.combustflame.2025.114468","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Oblique detonation waves (ODWs) have been widely studied in nominally two-dimensional rectangular geometries, but it is rarely done in three-dimensional non-rectangular flow channels that are common in realistic hypersonic propulsion systems. In this study, hydrogen–air ODWs in elliptical flow channels with different inlet aspect ratios (&lt;em&gt;AR&lt;/em&gt;) are investigated through numerical simulations. Particular attentions are given to the three-dimensional morphology of ODWs and the relevant formation mechanism. A novel tongue-shaped oblique detonation wave (TSODW) structure, characterized by a quasi-two-dimensional planar of the wavefront in the mid-span region and sweeping backwards near the sidewalls, is identified for the first time. Analysis reveals that its formation follows a two-stage mechanism: firstly, inward flow convergence induced by circumferentially non-uniform compression happens in the upstream, resulting in spanwise variation in ignition distances; and secondly, further amplification of such flow convergence by combustion heat release in the downstream leads to generation of localized kinks and significant flow deflection near the sidewalls, ultimately forming the backswept wavefronts. A parametric study with varying AR demonstrates that a lower &lt;em&gt;AR&lt;/em&gt; promotes earlier onset of wavefront distortion and stronger back sweeping, whereas a higher &lt;em&gt;AR&lt;/em&gt; delays kink formation and results in smoother wavefront transitions. These findings elucidate the role of non-uniform compression induced by three-dimensional geometries in shaping the wave structures of ODWs and provide physical insight into the spatial organization mechanisms of oblique detonative combustion in non-rectangular flow channels.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and Significance Statement&lt;/h3&gt;&lt;div&gt;Oblique detonation engines are attractive in hypersonic air-breathing propulsion, and oblique detonation waves (ODWs) in two-dimensional rectangular configurations have been commonly studied in the past decades. Non-rectangular flow channels are commonly involved in realistic propulsion systems, but the understanding of the combustion flow fields of ODWs under complex three-dimensional geometric confinement remains poor. This study reports the first high-resolution numerical investigation of ODWs in elliptical flow channels, revealing a novel tongue-shaped oblique detonation wave (TSODW) structure that has not been reported in literature. The detailed morphology, relevant formation mechanism, and variation with different flow-channel geometric parameters of this TSODW are revealed, and the important effects of circumferentially non-uniform compression are found as well.&lt;/div&gt;&lt;div&gt;The significance of this work lies in elucidating how geometric confinement induces flow non-uniformity, which is further amplified by combustion heat release to shape the complex three-dimensional detonation front morphology. The findings advance the fundamental understanding of detonatio","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114468"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107499","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 numerical investigation of H2-air lifted flames in swirling fuel injectors","authors":"Brandon W. Li,&nbsp;Benjamin W. Keeton,&nbsp;Keiko K. Nomura,&nbsp;Antonio L. Sánchez,&nbsp;Forman A. Williams","doi":"10.1016/j.combustflame.2025.114461","DOIUrl":"10.1016/j.combustflame.2025.114461","url":null,"abstract":"<div><div>Numerical simulations are conducted to study fundamental aspects of combustion stabilization in hydrogen-fueled gas turbines. The study focuses on laminar lifted flames at moderate Reynolds numbers in axisymmetric configurations, where a swirling hydrogen jet diluted with nitrogen is injected into stagnant, preheated, pre-compressed air. The conservation equations are formulated in the low-Mach-number approximation, employing a mixture-averaged model for molecular transport. Fuel oxidation is modeled using both detailed chemical kinetics and a previously derived explicit one-step reduced mechanism, which assumes steady-state behavior for chemical intermediates—a valid approximation under the high-pressure conditions typical of gas-turbine combustion chambers, and the accuracy of that approximation is ascertained. The investigation explores the interplay between vortex breakdown and flame dynamics, including liftoff and blowoff, as functions of the swirl and Damköhler numbers. The results elucidate the required flow criteria for lifted-flame stabilization and demonstrate the predictive capability and computational cost reduction of the one-step chemistry in connection with hydrogen combustion at high pressures. A regime diagram in a plane of swirl number and Damköhler number is derived, and conditions for the occurrence of steadily pulsating flames are established, along with indications of amplitudes and frequencies of those oscillations. While clearly not directly applicable to practical turbulent-flow conditions, the results can be useful in future analyses and design concepts for combustion chambers of hydrogen-fueled gas turbines.</div><div><strong>Novelty and significance statement</strong></div><div>This work presents, for the first time, results of computations of nitrogen-diluted hydrogen flame behavior for swirling fuel jets issuing into air that has been heated to temperatures expected at the entrance to gas-turbine combustion chambers. It is novel in that it compares predictions made using both detailed combustion chemistry and one-step systematically derived reduced chemistry. A significant finding is that the results obtained with the reduced chemistry are in general agreement with those of the detailed chemistry, thereby affording substantial reductions in computational cost. Another novel and significant result is the determination of injection and swirl gas-turbine conditions required for stable lifted flames to occur, rather than attached flames or blowoff. The existence and characteristics of pulsating oscillations also are established for the first time. These results will be useful in the design and analysis of hydrogen-fueled gas-turbine combustion chambers.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114461"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107628","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":"Evolution dynamics and instability mechanisms of four-wave collisions in rotating detonation engines","authors":"Yuechen Hou,&nbsp;Peilin Liu,&nbsp;Yixiang Li,&nbsp;Yiting Dang,&nbsp;John Z. Ma,&nbsp;Jianping Wang","doi":"10.1016/j.combustflame.2025.114466","DOIUrl":"10.1016/j.combustflame.2025.114466","url":null,"abstract":"<div><div>This study presents the first systematic investigation of instability mechanisms in four-wave collision regimes of rotating detonation engines (RDEs), within a methane/oxygen-enriched air (<span><math><mrow><mn>30</mn><mtext>%</mtext><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>, <span><math><mrow><mn>50</mn><mtext>%</mtext><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>) annular combustor. Compared to two-wave collisions, four-wave collisions exhibit inherently unstable wave symmetry and heightened sensitivity to inflow variations: elevated oxygen enrichment, equivalence ratio, and mass flow rate induce detonation strength imbalance, driving progressive transitions from symmetric four-wave collisions with stationary collision points to inducing collision-point migration (CPM), asynchronous behaviors (Async 4CR), and eventual single-wave dominance. The Async 4CR regime is uniquely characterized by subharmonic components at half the dominant frequency, originating from temporal offsets between successive wave collisions. Its unstable transitions to single-wave modes involve amplified upstream pressure feedback and elevated wall temperature growth rates. To quantify these instabilities, an analytical framework combining pressure peak-interval calculation and auto-correlation was developed to correlate periodic peak bifurcation and CPM dynamics. A linear model linking pressure peak-interval to angular CPM deviations was established based on near-constant CPM velocities, enabling single-sensor tracking of time-resolved CPM trajectories. The nonlinear and stochastic nature of CPM was revealed, featuring arbitrary migration directions, diverse maximal deviation angles (20–45°), and irregular periods (5–39 ms). The model remains valid under temporally oscillating fuel inflow, capturing transiently amplified CPM angles and reduced detonation stability during fuel flow rise. These findings reveal the complex instabilities and mode evolution patterns of four-wave collision regimes in RDEs, critical for advancing mode control and evaluating RDE performance.</div><div><strong>Novelty and significance</strong></div><div>(1) This study resolved typical CPM patterns during mode evolutions associated with four-wave collision instabilities. Unstable asynchronous collision regimes unique to four-wave collision systems were identified for the first time. (2) The developed linear model enables quantitative reconstruction of time-resolved CPM trajectories through peak bifurcation analysis of easily-accessible single-sensor pressure, offering direct extensibility to two-wave collisions and other high-frequency signals. (3) The stochastic nature of CPM driven by nonlinear detonation dynamics was underscored, while providing the experimental evidence on the destabilizing effects of time-varying oscillating inflow.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114466"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107503","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 micron-sized Al-Mg alloy particles in water vapour atmosphere","authors":"Ronggang Wei ,&nbsp;Kai Ma ,&nbsp;Yu Fu ,&nbsp;Chunbo Hu","doi":"10.1016/j.combustflame.2025.114482","DOIUrl":"10.1016/j.combustflame.2025.114482","url":null,"abstract":"<div><div>This paper addresses ignition start-up challenges and low combustion efficiency in aluminum-water reactions by proposing the use of Al-Mg alloy particles to enhance ignition and combustion through microexplosion phenomena. Experiments were conducted in a high-temperature furnace with adjustable temperature and pressure in a water vapor environment, varying magnesium content, particle size, ambient conditions to study their impact on ignition delay time (<span><math><msub><mi>t</mi><mtext>ig</mtext></msub></math></span>), microexplosion generation time (<span><math><msub><mi>t</mi><mtext>expl</mtext></msub></math></span>), combustion time (<span><math><msub><mi>t</mi><mtext>com</mtext></msub></math></span>), and ignition temperature (<span><math><msub><mi>T</mi><mtext>ig</mtext></msub></math></span>). Key findings include: <span><math><msub><mi>t</mi><mtext>ig</mtext></msub></math></span> for Al-Mg particles fluctuates between 50 ms to 200 ms, secondary particles from microexplosion reduce combustion particle size significantly, and <span><math><msub><mi>t</mi><mtext>com</mtext></msub></math></span> ranges from 3 ms to 10 ms. The study shows consistency with theoretical expectations in the pre-microexplosion stage, while post-microexplosion reveals opposing effects of ambient temperature and pressure on <span><math><msub><mi>t</mi><mtext>com</mtext></msub></math></span>. Empirical equations for Al-Mg particle ignition and combustion characteristics in a water vapor atmosphere were derived, aiding in predicting effects by adjusting variable parameters. These results support the development of an (Al-Mg)/H₂O microexplosion model and engine combustion design.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114482"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107629","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":"Modelling thermodiffusive instabilities in hydrogen flames and their impact on the combustion process in a direct-injection hydrogen engine","authors":"Andrea Scalambro,&nbsp;Andrea Piano,&nbsp;Federico Millo","doi":"10.1016/j.combustflame.2025.114457","DOIUrl":"10.1016/j.combustflame.2025.114457","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Hydrogen-fueled Internal Combustion Engines (H&lt;sub&gt;2&lt;/sub&gt;-ICEs) are typically operated with lean mixtures to minimize NOx emissions and reduce the risk of abnormal combustion events. Due to hydrogen’s low Lewis number, premixed hydrogen-air flames in lean conditions exhibit strong thermodiffusive instabilities, which make the numerical simulation of the combustion process particularly challenging. Indeed, the intensity of these instabilities is significantly influenced by thermodynamic parameters – such as mixture temperature, pressure, and dilution rate – resulting in substantial variations in combustion behaviour across different operating conditions. Therefore, they have to be properly considered not only to ensure model robustness, but also to improve model accuracy over a wider range of operations. In this study, the combustion process in a Direct Injection H&lt;sub&gt;2&lt;/sub&gt;-ICE was analyzed using 3D-CFD simulations, relying on a flamelet-based combustion model. Two sets of lookup flame speed maps were defined: laminar flame speed (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) maps derived from standard 1D-CFD simulations in homogeneous reactor, and freely propagating flame speed (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) maps which account for the effects of thermodiffusive instabilities. The model that uses &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; maps required the recalibration of some combustion model parameters when changing the dilution rate to ensure consistency with experimental data. Instead, the model relying on &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; maps featured a noticeable accuracy across different air-to-fuel ratios without the need for recalibration any combustion model parameter, highlighting the key role of thermodiffusive flame instabilities on the combustion process. Based on these findings, the impact of such instabilities was evaluated throughout the entire combustion process from both global and local perspectives. The relevance of thermodiffusive instabilities was observed to increase with the air-to-fuel ratio, thereby enhancing combustion speed in leaner mixtures. Additionally, the implementation of thermodiffusive instabilities was found to affect also preferred direction of flame propagation, as stronger instabilities were identified in the leanest and low-temperature portions of the flame front.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This study addresses a critical knowledge gap regarding the role of thermodiffusive flame instabilities in accurately replicating the combustion process of a direct-injection internal combustion engine within a RANS simulation framework. Indeed, while these instabilities have been shown to significantly enhance the mixture consumption rate in quiescent environments at low to moderate pressures and temperatures, particularly in lean mixtures, their impact on the burn rate under engi","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114457"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107498","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":"Studies of real-fluid supercritical simulation using the 3rd virial equation of state based on Boltzmann-weighted Full-dimensional potential","authors":"Xin Zhang,&nbsp;Junfeng Bai,&nbsp;Hao Zhao","doi":"10.1016/j.combustflame.2025.114465","DOIUrl":"10.1016/j.combustflame.2025.114465","url":null,"abstract":"<div><div>Under extreme conditions such as supercritical combustion, real-fluid effects become significant, necessitating accurate and robust simulation methodologies for high-pressure environments. In this study, we propose a real-fluid simulation method, the BWF-Virial method, which integrates the Boltzmann-weighted Full-dimensional (BWF) potential into the virial equation of state (EoS) for physical properties and combustion characteristics simulations under high to ultra-high pressures. Based on the BWF potential model, the second and third virial coefficients, along with their corresponding thermodynamic and transport properties, are rigorously derived. These methods are subsequently integrated into the Cantera software package, establishing a comprehensive real-fluid simulation platform. The BWF-Virial method attains the accuracy of the third-order virial EoS, thereby offering a precise description of real-fluid behavior for various fuels. Its effectiveness has been validated through thermodynamic and transport property calculations across various species, with relative errors of 0.1%–10%. We further investigate zero-dimensional and one-dimensional combustion characteristics of supercritical methane and n-heptane. The BWF-Virial method demonstrates strong robustness and predictive accuracy in modeling combustion phenomena across a wide range of extreme operating conditions. Compared to the LJ-Virial method, it exhibits a 5%–20% difference, aligning more closely with experimental data and reinforcing its potential for high-fidelity supercritical combustion simulations.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of this research lies in the development of the BWF-Virial method for real-fluid supercritical simulations. Real-fluid effects are significantly amplified in non-ideal flows, such as supercritical fluids and plasmas. These flows are highly relevant to propulsion and energy conversion processes. Unfortunately, the real-fluid intermolecular interactions in the literature are mainly based on the Lennard-Jones potential, which reveals significant errors for physical properties and combustion simulations at high to ultra-high pressures, especially for polar and long-chain molecules. The BWF-Virial method can effectively overcome these limitations. It provides comprehensive and robust support in (i) the thermodynamic and transport property library establishment for polar and long-chain molecules, (ii) the reactive real-fluid combustion simulations, and (iii) the physical investigations of real-fluid impact on reactive flow simulations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114465"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107630","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":"Quenching and pollutant emissions in side-wall and head-on NH3/H2/N2 premixed laminar flames","authors":"Olivier Chabot,&nbsp;Bruno Savard","doi":"10.1016/j.combustflame.2025.114463","DOIUrl":"10.1016/j.combustflame.2025.114463","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We present quenching distance, wall heat loss, and pollutant emission results from a series of simulations of NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/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;/N&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; premixed laminar flames in side-wall and head-on quenching configurations. Conditions cover lean to rich mixtures (equivalence ratio from 0.3 to 1.2) at both atmospheric and moderate (10 atm) pressures. For each set of conditions, two-dimensional “V”-flame simulations with side-wall quenching (SWQ) and with symmetric boundary conditions are compared to isolate wall heat loss from curvature effects. Simulations of one-dimensional head-on quenched (HOQ) flames covering the same range of conditions are also included for further comparison. First, a non-monotonic relationship between quenching Peclet number and equivalence ratio is found at 10 atm for both SWQ and HOQ, attributed to a significant change in flame structure at lean conditions, with the Jiang chemical kinetics mechanism. Second, wall heat loss normalized by laminar flame power is lower for HOQ flames, compared to SWQ, at lean conditions and higher at rich conditions, which is attributed to the effect of flame curvature on heat release rate in SWQ flames. Yet, normalized wall heat loss shows a similar correlation with quenching Peclet number for both pressures and quenching configurations. Third, similar to previously reported experimental results, we find that ammonia slip increases due to wall heat loss and curvature effects, while hydrogen slip departs negligibly from that of unstretched laminar flames. The contrast with ammonia slip is striking at low equivalence ratio and is attributed to the strongly diverging flux of hydrogen near the quenching point, promoting its consumption. Fourth, both wall heat loss and negative flame curvature at the wall significantly reduce NO emissions as the rates of NO forming reaction pathways are diminished. In the SWQ cases, NO consuming pathways are comparatively less inhibited, being in part fed by NO diffusing towards the wall from non-quenched regions. Finally, both negative curvature at the wall and wall heat loss increase N&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 emissions. A non-monotonic relationship between N&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 emissions and equivalence ratio is observed at elevated pressure, as the rate of the N&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 consuming reaction &lt;figure&gt;&lt;img&gt;&lt;/figure&gt; increases for equivalence ratios below 0.6.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;We present the first flame-resolved simulations at elevated pressure of side-wall quenching (SWQ) and head-on quenching (HOQ) in NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;m","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114463"},"PeriodicalIF":6.2,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107631","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":"Measurements of NO in the post-flame region of laminar premixed ammonia/methane-air flames using laser-induced fluorescence","authors":"M. Richter ,&nbsp;J. Lill ,&nbsp;R.S. Barlow ,&nbsp;A. Dreizler ,&nbsp;J.R. Dawson ,&nbsp;D. Geyer","doi":"10.1016/j.combustflame.2025.114450","DOIUrl":"10.1016/j.combustflame.2025.114450","url":null,"abstract":"<div><div>Cofiring of ammonia (NH₃) with methane (CH₄) offers a promising route to enhance the combustion characteristics of pure ammonia while partially decarbonizing methane-based energy systems. However, the presence of fuel-bound nitrogen in ammonia leads to elevated NOx emissions. Although NO measurements in NH₃-containing flames have been reported, there is a notable lack of validation datasets for NH₃/CH₄ cofiring based on non-intrusive diagnostics. In this communication, a laser-induced fluorescence (LIF) approach recently developed for post-flame NO measurements is applied to NH₃/CH₄-air flames with CH₄ contents ranging from 50 vol.-% to 80 vol.-% in the fuel mixture. The LIF signal processing includes corrections for laser absorption, signal trapping, and pulse energy fluctuations. Thermochemical differences between calibration and target flames are addressed through corrections for number density, Boltzmann fraction, spectral line overlap, and electronic quenching. The results show good agreement with recent chemical kinetic models over a broad range of conditions. Within the tested range, increasing the NH₃ content results in a notable reduction of NO emissions under fuel-rich conditions, while the opposite trend is observed under fuel-lean conditions. The observed NO trends are interpreted using normalized radical pool indicators for <figure><img></figure> and O/H/OH species.</div><div><strong>Novelty and Significance</strong></div><div>Quantitative data on NO emissions from ammonia-based fuels remain limited, especially those obtained using non-intrusive diagnostics. In this paper, we extend a previously presented laser-induced fluorescence (LIF) method to measure post-flame NO concentrations in NH₃/CH₄-air flames across a broad range of equivalence ratios and fuel compositions. The dataset covers CH₄ contents from 50 to 80 vol.%. By introducing normalized radical pool indicators for <figure><img></figure> and O/H/OH species, the work helps to interpret observed NO trends. The results provide a basis for refining chemical kinetic models with respect to NO formation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"282 ","pages":"Article 114450"},"PeriodicalIF":6.2,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145061356","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}