Proceedings of the Combustion Institute最新文献

{"title":"Examining fire spread dynamics in canyon terrain through physics-based modeling: Mechanisms of fire line rotation and non-local fire behavior","authors":"Karl Töpperwien ,&nbsp;Qing Wang ,&nbsp;Yi-Fan Chen ,&nbsp;Cenk Gazen ,&nbsp;John Anderson ,&nbsp;Matthias Ihme","doi":"10.1016/j.proci.2025.105802","DOIUrl":"10.1016/j.proci.2025.105802","url":null,"abstract":"<div><div>Wildfire spread in complex terrain poses a major challenge for predictive modeling, as interactions between topography, wind, and combustion give rise to erratic fire behavior that caused fatalities among fire fighters. This study investigates the spread dynamics of a canyon fire exhibiting a characteristic fire line rotation, wherein the fire front progresses downslope along the canyon side-walls, perpendicular to the nominal wind direction. Using large-eddy simulations with a physics-based mesoscale solver, we model coupled fire–atmosphere–terrain interactions over kilometer-scale domains to resolve the three-dimensional flow and combustion structures governing fire spread. We consider a canyon terrain and compare it against two simpler configurations: a sloped ramp and a flat surface. Analysis of fire arrival times reveals that, despite identical ridge slopes, the canyon induces distinctly different spread behavior, resulting in oblique propagation along the canyon side-walls and intermittent progression in the valley. A detailed examination of flow field quantities attributes these phenomena to terrain-induced wind/slope misalignment and localized vorticity amplification, which persists after fire front passage and promotes extreme fire behavior. Furthermore, we demonstrate that the fire rate of spread in complex terrain is inherently non-local: individual sections of the fire line are influenced by neighboring segments, transient flow structures, and topographic features. Overall, our findings highlight the critical role of topography in modulating fire dynamics and provide physical insights into the mechanisms driving extreme fire behavior in canyon-like environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105802"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144830204","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":"Thermoacoustic instability in two acoustically coupled hydrogen-enriched combustors","authors":"Yu Liao ,&nbsp;Yuxin Lei ,&nbsp;Yongseok Choi ,&nbsp;Peijin Liu ,&nbsp;Kyu Tae Kim ,&nbsp;Yu Guan","doi":"10.1016/j.proci.2025.105914","DOIUrl":"10.1016/j.proci.2025.105914","url":null,"abstract":"<div><div>This study experimentally investigates the potential of tuning acoustic coupling to passively suppress thermoacoustic oscillations in lean-premixed hydrogen-enriched can-annular combustors. Our findings demonstrate that thermoacoustic oscillations in the coupled system can be suppressed by up to 90% compared to the decoupled self-excited baseline, achieved by deliberately mismatching the flame response and chamber acoustics. This mismatch is achieved through hydrogen enrichment and modifications to the acoustic coupling configurations and combustor geometry. As the hydrogen volume fraction increases, the flame preferentially responds to higher frequencies, while the overall “<span><math><mi>Π</mi></math></span>-shaped” acoustic chamber formed by coupling the two identical combustors via cross-talk (XT) sections favors lower acoustic eigenfrequencies, particularly for longer combustors or when XT sections are located further downstream. The amplitude and frequency of the dominant half-wave anti-phase longitudinal mode (i.e., a push-pull mode) are strongly influenced by this mismatch, and a regime of oscillation suppression emerges when the mismatch is maximized, specifically at the highest hydrogen volume fraction and the longest combustor length. The axial location of the most upstream XT defines the total effective length of the “<span><math><mi>Π</mi></math></span>-shaped” acoustic domain, whereas multiple XTs increase the effective acoustic interaction area between the combustors, thereby reducing acoustic resistance and enhancing coupling. This intensified coupling strengthens or triggers the push-pull mode, resulting in pronounced thermoacoustic oscillations and highlighting the importance of accounting for such effects when assessing the stability of individual combustors for integration into can-annular configurations. In summary, this study underscores the critical role of both flame response and acoustic coupling in governing thermoacoustic behavior and demonstrates that careful tailoring of these factors offers a simple yet effective passive strategy to suppress instabilities in hydrogen-enriched can-annular combustion systems, thereby supporting the development of cleaner and more stable heavy-duty gas turbines.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105914"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262472","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":"Unique phase change behaviors of ammonia droplets under varying ambient water vapor concentrations and pressures: A molecular dynamics simulation study","authors":"Feilong Chen,&nbsp;Yanzhi Zhang,&nbsp;Xuehao Zhang,&nbsp;Ming Jia","doi":"10.1016/j.proci.2025.105897","DOIUrl":"10.1016/j.proci.2025.105897","url":null,"abstract":"<div><div>This study employs molecular dynamics (MD) simulations to study the effect of polar water vapor on the phase change characteristics of ammonia droplets under varying ambient pressures. First, a new flexible potential model for ammonia was developed based on first-principles calculations. Then, the accuracy of this model in predicting the thermodynamic and transport properties of ammonia was extensively validated. Consequently, MD simulations using the new potential model were conducted to explore phase change behaviors of ammonia droplets under different ambient environments. The results reveal that both elevated ambient pressures and increased water vapor concentrations can promote the ammonia droplet evaporation. A unique phase change behavior of ammonia droplets in nitrogen/water environments was observed. Specifically, the polar water vapor dissolves and subsequently condenses within the ammonia droplet, thereby facilitating a transition from the ammonia-dominated evaporation to the water-dominated evaporation. Moreover, the dissolution and condensation become more intense at higher initial water vapor concentrations or pressures. Finally, the specific mechanisms by which water vapor enhances ammonia droplet evaporation were explored. During the dissolution and condensation process, water vapor releases latent heat and increases thermal conductivity, raising the droplet temperature. Additionally, water weakens the hydrogen bonding among ammonia molecules, thereby lowering the evaporation energy barrier. These findings provide essential insights into the phase change mechanisms of liquid ammonia and their dependence on ambient conditions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105897"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262474","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":"Propagation limits of cellular detonation in narrow channels","authors":"Brian Devine,&nbsp;Thomas Westenhofer,&nbsp;Xian Shi","doi":"10.1016/j.proci.2025.105819","DOIUrl":"10.1016/j.proci.2025.105819","url":null,"abstract":"<div><div>This study investigates the propagation limits of cellular detonation in narrow channels, aiming to distinguish between two mechanisms that govern these limits: the first associated with detonation cell accommodation and the second with boundary losses. Hydrogen–oxygen–argon mixtures were tested with and without ozone addition at initial pressures ranging from 5 to 35 kPa in three experimental configurations: (1) a base channel, (2) a half-height channel, and (3) a half-width channel. For each configuration, experiments were conducted at progressively lower pressures until detonation failed. For the base channel with and without ozone addition, and the half-height channel, detonation failure was observed to be governed by the cell limit, i.e., the geometric accommodation of cellular structures by the narrow channel. Specifically, ozone doping extended the detonation limit to lower pressures by reducing cell size, while decreasing channel height constrained cell development, leading to failure at higher pressures. Immediately before their respective limits, all three test sets exhibited the characteristic half-cell, zig-zag pattern. In contrast, results from the half-width channel with enhanced boundary losses revealed that there exists a loss limit: detonation failure started to appear at elevated pressures and became progressively more probable as pressure decreased, eventually reaching absolute failure. Unlike the zig-zag propagation mode, detonation either propagates with a multi-cell structure or fails completely. Ozone addition was ineffective at extending the limit, suggesting that detonation failure is governed by loss mechanisms independent of cell size. We further performed modified ZND calculations that take into account the impact of flow divergence. The models correctly captured the velocity deficit trends and limiting pressures, validating the experimental identification of the loss limit. These findings demonstrate that detonation failure in cellular detonations can be dominated by boundary losses, implying that modifying cellular structures alone may not extend propagation limits in confined systems with significant losses.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105819"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903029","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":"Effect of H2 and Jet-A1 fuel split on flame stability and pollutant emissions from low-swirl burner","authors":"Samarjeet Singh ,&nbsp;Matteo Amerighi ,&nbsp;Nicola Scopolini ,&nbsp;Antonio Andreini ,&nbsp;Stefan R. Harth ,&nbsp;Dimosthenis Trimis","doi":"10.1016/j.proci.2025.105858","DOIUrl":"10.1016/j.proci.2025.105858","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Hydrogen combustion is emerging as a promising solution for future aircraft engines, offering a shift from fossil fuels to sustainable alternatives and the potential for reduced pollutant emissions. While the complete transition to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; presents a significant challenge due to its low volumetric energy density, limited availability, and infrastructure and aircraft redesign constraints, fuel-flexible burner technologies that allow &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; blending with Jet-A1 offer a viable alternative. These technologies provide additional benefits such as an enhanced stability range and can contribute to achieving near-term decarbonization goals. This study explores the capabilities of a novel dual-fuel burner developed as part of the European project FFLECS (Novel Fuel-Flexible ultra-Low Emissions Combustion systems for Sustainable aviation). Flame stabilization in a lean lifted flame combustor operating under atmospheric conditions and fueled by Jet-A1 and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; is experimentally investigated. A new fuel-flexible nozzle, based on the “low swirl” lean lifted flame concept, is developed to enable high premixing, significantly reducing &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;NO&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;x&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; emissions and minimizing flashback risk compared to conventional swirl-stabilized flames. The &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; injection for the investigated nozzle was optimized for part load conditions, but can still be operated up to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;mtext&gt;%&lt;/mtext&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The flame shape and lift-off height were studied at elevated air inlet temperature and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; blending ratios up to 100% of the total thermal power. Moreover, the lean blowout limits remain similar for &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; blending ratios up to 30% across various air inlet temperatures but change significantly at higher blends. Finally, switching from Jet-A1 to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; lowers &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; emission at low air inlet temperatures and increases it at higher temperatures, with a pronounced rise across all air inlet temperatures at blends above 75% &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;H&lt;/mtext&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; under elevated specific thermal power. In contrast, the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mtext&gt;NO&lt;/mtext","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105858"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145117637","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":"Premixing effects on NOx scaling in high-pressure, lean methane-air axial stage combustion","authors":"Penelope Torres Serrano,&nbsp;Michael Tonarely,&nbsp;Anthony Morales,&nbsp;Max Fortin,&nbsp;Khaoula Chougag,&nbsp;Charles Clark,&nbsp;Kareem Ahmed","doi":"10.1016/j.proci.2025.105810","DOIUrl":"10.1016/j.proci.2025.105810","url":null,"abstract":"<div><div>Reducing pollutant emissions continues to be a primary concern for the development and operation of power generation systems to minimize environmental impacts. Operating combustors under fuel-lean conditions with enhanced premixing is a proven strategy for reducing NO_x emissions, but a deeper understanding of NO_x formation mechanisms across a range of engine-relevant conditions is vital. Recent studies have shown that the dominant NO_x formation mechanism shifts from prompt to thermal when increasing pressure from atmospheric to high pressure conditions, emphasizing the need for system relevant data. This study presents emissions measurements of a high-pressure, lean axially staged combustion experiment designed to quantify changes in NO_x production relative to equivalence ratio and fuel-air premixing. For each test case, constant vitiated crossflow conditions are supplied to the secondary combustion zone which consists of a lean methane-air reacting jet in crossflow. Results show that NO_x emissions increase with increased jet equivalence ratio and with reduced fuel-air premixing, as less premixed jets create locally rich regions that promote NO_x-forming hotspots. To collapse the measured NO_x trends, two scaling strategies are applied. First, flame and post-flame NO_x contributions are quantified through detailed chemical kinetics across a spread of equivalence ratio. Second, the effects of premixing are captured using mixture fraction distributions in the axial jet injector, defined by CFD simulations of the injector mixing at each tested equivalence ratio. When experimental data are first scaled using only the individual NO_x production rates, results converge well for highly premixed conditions, effectively collapsing equivalence ratio effects, but show scatter at lower premixing levels. Incorporating the CFD-derived mixture fraction distributions further collapses the data, eliminating observable trends with premixing and indicating successful normalization of mixing effects. This approach resulted in a mean scaled emissions value of 0.34 with a standard deviation of about 25 %. The result of the current study is an effective collapse of experimental NO_x emissions across both global (equivalence ratio) and local (jet premixing) fuel-air variations in lean, premixed, axially staged flames - an operating regime not previously characterized in this manner.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105810"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864591","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":"Hybrid physics-machine learning model for multispecies and temperature inference from FTIR spectra: Application to ammonia flames","authors":"Zituo Chen,&nbsp;Nicolas Tricard,&nbsp;Sili Deng","doi":"10.1016/j.proci.2025.105811","DOIUrl":"10.1016/j.proci.2025.105811","url":null,"abstract":"<div><div>Fourier-transform infrared (FTIR) spectroscopy offers a powerful, non-intrusive diagnostic tool for <em>in-situ</em> measurements of temperature and species concentrations in combustion systems. However, in practical applications, FTIR spectra often suffer from low spectral resolution, strong band overlap, and significant variation in species concentration levels, making quantitative interpretation a challenging inverse problem. In this work, we present a hybrid physics-machine learning framework for inferring temperature, path length, and species mole fractions from FTIR emission spectra of ammonia flames. The model is trained on high-fidelity synthetic spectra generated via line-by-line radiative transfer using HITEMP/HITRAN spectroscopic databases. To address challenges of spectral overlap, minor-species detectability, and measurement noise, the architecture incorporates physics-based regularization and a self-supervised spectrum reconstruction module that enforces consistency with the radiative transfer equation. Our hybrid approach enables robust multi-target inference across species spanning several orders of magnitude in concentration. Compared to standard partial least squares (PLS) regression and ablated models, the proposed framework achieves superior accuracy and noise robustness while remaining compact and interpretable. Additionally, the co-trained reconstruction module exhibits effective denoising capabilities, highlighting the physical relevance of the learned spectral representation. This framework provides a foundation for practical, generalizable FTIR diagnostics and opens pathways toward spatially resolved inference in complex combustion environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105811"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864680","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":"Scientific machine learning in combustion for discovery, simulation, and control","authors":"Sili Deng,&nbsp;Linzheng Wang,&nbsp;Suyong Kim,&nbsp;Benjamin C. Koenig","doi":"10.1016/j.proci.2025.105796","DOIUrl":"10.1016/j.proci.2025.105796","url":null,"abstract":"<div><div>Combustion science is undergoing a transformation, driven by the need to model increasingly complex, multi-scale systems and accelerate progress toward cleaner, more efficient energy technologies. While traditional modeling approaches remain foundational, they face growing limitations under modern demands such as alternative fuels, stringent emission standards, and extreme operating environments. This review explores how scientific machine learning (SciML), which integrates data-driven models with physical constraints, is reshaping combustion research across three central fronts: model discovery, simulation acceleration, and system state reconstruction. We highlight recent advances in parameter estimation, reaction mechanism generation, and interpretable model discovery using tools such as physics-informed neural networks, chemical reaction neural networks, symbolic regression, and governing equation-constrained parameter optimization. For simulation, we examine neural surrogates, operator learning, and physics-inspired architectures that enable fast and accurate predictions while preserving physical fidelity. Finally, we review emerging methods for reconstructing full-field combustion states from sparse data, enabling mutual inference across physical quantities and advancing digital twin development through multi-modal data fusion. Together, these developments demonstrate how SciML is enabling new capabilities for combustion modeling, diagnostics, and control. As the field evolves, continued progress will depend on integrating domain knowledge with scalable algorithms, rigorous uncertainty quantification, and cross-disciplinary collaboration, paving the way for next-generation combustion systems that are intelligent, adaptive, and physically grounded.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105796"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912910","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":"Premixed flame quenching distance between cold walls: Effects of flow and Lewis number","authors":"Aiden Kelly ,&nbsp;Rémi Daou ,&nbsp;Joel Daou ,&nbsp;Vadim N. Kurdyumov ,&nbsp;Prabakaran Rajamanickam","doi":"10.1016/j.proci.2025.105836","DOIUrl":"10.1016/j.proci.2025.105836","url":null,"abstract":"<div><div>This study investigates the critical conditions for flame propagation in channels with cold walls. We analyse the impact of the Lewis number and flow amplitude (<span><math><mi>A</mi></math></span>) on the minimum channel width required to sustain a premixed flame. Our results span a wide range of Lewis numbers, encompassing both aiding and opposing flow conditions. Results are presented for both variable and constant density models. A combined numerical approach, involving stationary and time-dependent simulations, is employed to determine quenching distances and solution stability. We find that smaller Lewis numbers and aiding flows (<span><math><mrow><mi>A</mi><mo>&lt;</mo><mn>0</mn></mrow></math></span>) facilitate flame propagation in narrower channels, while opposing flows (<span><math><mrow><mi>A</mi><mo>&gt;</mo><mn>0</mn></mrow></math></span>) tend to destabilise the flame, promoting asymmetric solutions. For sufficiently large positive values of <span><math><mi>A</mi></math></span>, the quenching distance is determined by asymmetric solutions, rather than the typical symmetric ones.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105836"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flame Propagation of refrigerant R-1234yf (CF3CFCH2) in humid air: A DNS study","authors":"Zezheng Li ,&nbsp;Hongchao Chu ,&nbsp;Gregory T. Linteris ,&nbsp;Roman Glaznev ,&nbsp;Joachim Beeckmann ,&nbsp;Michael Gauding ,&nbsp;Heinz Pitsch","doi":"10.1016/j.proci.2025.105883","DOIUrl":"10.1016/j.proci.2025.105883","url":null,"abstract":"<div><div>The next-generation refrigerant R-1234yf (<span><math><mrow><msub><mrow><mtext>CF</mtext></mrow><mrow><mn>3</mn></mrow></msub><msub><mrow><mtext>CFCH</mtext></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>) is expected to be widely used but is mildly flammable, requiring new fire-safety considerations. Water vapor can significantly facilitate the combustion of R-1234yf, increasing the flame speed by a factor of up to three. This study employs direct numerical simulations (DNS) to investigate the flame dynamics and assess the flame propagation behavior of humid R-1234yf-air mixtures. Effects of gravity, radiation, differential diffusion, and air humidity are taken into account in the DNS for a comprehensive assessment. It is found that although air humidity significantly increases the unstretched flame speed for lean mixtures at ambient conditions, radiation and strong Markstein effects inhibit combustion, ultimately resulting in complete extinction. This underscores the influence of the Markstein effects and highlights a potentially underestimated hazard under rich conditions when relying solely on the unstretched flame speed of refrigerants. In addition, this work provides a holistic analysis of buoyant R-1234yf flames in humid air, focusing on flame evolution, flame structures, and the Markstein effects. In particular, the Markstein numbers are separately determined for positive and negative components of curvature and strain rate. In this study, positive curvature indicates a flame front convex toward the reactants. It is found that Markstein effects due to positive curvature are the dominant factor, leading to inhibited flame propagation, particularly in lean conditions, while Markstein effects due to strain rate have a minor influence. The Markstein numbers in lean and rich flames in response to air humidity vary notably. In rich conditions, higher humidity reduces the Markstein number for positive curvatures, which promotes flame propagation. Conversely, under lean conditions, no significant effects of humidity levels on the Markstein numbers can be observed.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105883"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216304","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}