Combustion and Flame最新文献

{"title":"A three-dimensional study on premixed flame propagation in narrow channels considering hydrodynamic and thermodiffusive instabilities","authors":"Ziyin Chen , Song Zhao , Bruno Denet , Christophe Almarcha , Pierre Boivin","doi":"10.1016/j.combustflame.2025.114392","DOIUrl":"10.1016/j.combustflame.2025.114392","url":null,"abstract":"<div><div>In numerical studies of quasi-2D problems, such as laminar flame propagation through a slit, the quasi-2D assumption is commonly applied to simplify the problem. However, the impact of the third dimension (in the thickness between walls) can be significant due to strong curvature. The intrinsic Darrieus–Landau instability, the Saffman–Taylor instability, and the thermodiffusive instability lead to curved flame fronts in both the transverse and normal directions and radically change the global flame speed. This study investigates the interaction of these instabilities and their impact on premixed flames freely propagating in narrow channels. Two lean fuel–air mixtures are considered: one with unity Lewis number <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>1</mn></mrow></math></span> and another with <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>. A single-step Arrhenius-type reaction is used for combustion modeling. Joulin Sivashinsky’s model Joulin and Sivashinsky (1994), termed the 2D+ model, is implemented to capture the confinement effect due to walls. By comparing 3D Direct Numerical Simulations (DNS) and 2D simulations at unity <span><math><mrow><mi>L</mi><mi>e</mi></mrow></math></span>, we find that the 2D+ model accurately reproduces confinement effects for channel width <span><math><mi>h</mi></math></span> up to 3.6<span><math><msub><mrow><mi>δ</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span> (<span><math><msub><mrow><mi>δ</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span>: thermal flame thickness), extending the validity of Darcy’s law.</div><div>However, for larger <span><math><mi>h</mi></math></span>, interactions between flame curvatures in two directions result in higher flame surface increment and consumption speed. Besides, for 3D cases with <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>, positive curvature regions on the flame front primarily contribute to the global reaction due to the Lewis effect. Statistical studies on flame dynamics between walls in 3D cases are also conducted, and results show that both the flame surface increment and the Lewis effect on curvature (if <span><math><mrow><mi>L</mi><mi>e</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>) are approximately consistent. 2D simulations for the thickness between walls can predict the acceleration from flame dynamics between walls in the 3D domain for both mixtures.</div><div><strong>Novelty and significance statement</strong></div><div>This study is the first three-dimensional study on premixed flame freely propagating in narrow channels considering both hydrodynamic, including Darrieus–Landau (DL) and Saffman–Taylor (ST) instabilities, and thermodiffusive (TD) instabilities. It is also the first to validate the Joulin–Sivashinsky model’s ability to incorporate wall confinement effects in 2D simulations across various","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114392"},"PeriodicalIF":6.2,"publicationDate":"2025-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144851874","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":"Laminar flame speeds of lean hydrogen-oxygen-helium mixtures under elevated pressures and temperatures","authors":"Hao-Yu Hsieh ,&nbsp;Andrei N. Lipatnikov ,&nbsp;Shenqyang (Steven) Shy","doi":"10.1016/j.combustflame.2025.114412","DOIUrl":"10.1016/j.combustflame.2025.114412","url":null,"abstract":"<div><div>Lean H₂/O₂/He laminar spherical flames expanding after spark ignition in the center of a large cruciform burner are investigated using high-speed Schlieren imaging technique. When processing the images, dependencies of equivalent flame radii &lt;<em>R_f</em>&gt; on time are extracted and unperturbed laminar flame speeds <em>S</em>_L⁰ are evaluated adopting four state-of-the-art flame-speed-correction methods. The experimental conditions cover lean mixtures at three equivalence ratios (<em>ϕ</em> = 0.3, 0.45, and 0.6), three pressures (<em>P</em> = 1, 3, and 5 atm), and two unburned gas temperatures (<em>T</em>_u = 300 and 400 K). Besides, the flame speeds are computed adopting seven state-of-the-art chemical mechanisms. The obtained results show, first, that substitution of nitrogen with helium offers the opportunity to suppress diffusional-thermal instability under the studied conditions and to measure speeds of lean hydrogen laminar flames in wider ranges of equivalence ratios and pressures. Second, substitution of nitrogen with helium results in significantly reducing the influence of non-linear (with respect to flame stretch rate) effects on differences between the observed and unperturbed laminar flame speeds, thus substantially improving accuracy of evaluation of <em>S</em>_L⁰ in lean hydrogen mixtures. Third, none of the tested chemical models predict all the experimental data, with differences between measured and computed <em>S</em>_L⁰ being particularly large in preheated (<em>T</em>_u = 400 K) moderately lean (<em>ϕ</em> = 0.45) flames under elevated pressures (<em>P</em> = 3 and 5 atm). Since chemical kinetic mechanisms of lean hydrogen burning have not yet been tested against experimental data on <em>S</em>_L⁰, obtained at <em>T</em>_u = 400 K, the present results call for further assessment and development of such models for elevated temperature conditions, which occur, e.g., in piston engines. Fourth, differences between the measured and computed flame speeds could in part be attributed to limitations of the adopted transport models, thus calling for further assessment and development of them also.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114412"},"PeriodicalIF":6.2,"publicationDate":"2025-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144851875","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":"An experimental and chemical kinetic modelling study of toluene oxidation with nitrous oxide","authors":"Atmadeep Bhattacharya ,&nbsp;Mohsin Raza ,&nbsp;Shangkun Zhou ,&nbsp;Claire M. Grégoire ,&nbsp;Sumit Agarwal ,&nbsp;Denghao Zhu ,&nbsp;Ravi Fernandes ,&nbsp;Bo Shu ,&nbsp;Ossi Kaario ,&nbsp;Chong-Wen Zhou ,&nbsp;Olivier Mathieu ,&nbsp;Eric L. Petersen ,&nbsp;Henry J. Curran","doi":"10.1016/j.combustflame.2025.114349","DOIUrl":"10.1016/j.combustflame.2025.114349","url":null,"abstract":"<div><div>The oxidation of toluene in the presence of nitrous oxide (N₂O) is investigated experimentally using shock tubes, and the results are simulated using an improved chemical kinetic model. The improved model is based on GalwayMech1.0 with updated rate constants for the reactions Ċ₆H₅ + <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span> (+M) ↔ C₆H₆ (+M), N₂O (+M) ↔ N₂ + Ö (+M), N₂O + <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span> ↔ N₂ + <span><math><mover><mi>O</mi><mo>˙</mo></mover></math></span>H, N₂O + Ö ↔ NO + NO, and N₂O + Ö ↔ N₂ + O₂. Additionally, the current model includes HNNO and NHNO intermediate chemistry. The proposed mechanism is validated over a wide range of temperatures and equivalence ratios, with validation targets including experimental data for toluene, H₂/N₂O, and newly generated toluene/N₂O blend data from shock tubes. High-pressure shock tube experiments reveal that the toluene/N₂O mixture is highly susceptible to pre-ignition at low temperatures. The chemical kinetic analysis indicates that the ignition of the toluene/N₂O mixtures is highly sensitive to the N₂O (+M) ↔ N₂ + Ö (+M) reaction. The heat released, along with the Ö atoms generated during the decomposition of N₂O, causes the rapid depletion of toluene at a substantially faster rate than N₂O. Similarly, <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span> atoms, mostly produced from toluene chemistry, e.g., through benzyl radical breakup C₆H₅ĊH₂ ↔ Ċ₇H₆ + <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span>, help the decomposition of N₂O molecules via N₂O + <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span> ↔ NO + <span><math><mover><mi>N</mi><mo>¨</mo></mover></math></span>H. Moreover, other major nitric oxide (NO) producing reactions are identified, including N₂O + Ö ↔ NO + NO and <span><math><mover><mi>N</mi><mo>¨</mo></mover></math></span>H + Ö ↔ NO + <span><math><mover><mi>H</mi><mo>˙</mo></mover></math></span>. Due to the rapid depletion of toluene, direct chemical interactions between N₂O and the aromatic ring have little influence on overall combustion chemistry. However, the enthalpy of formation of toluene and benzyl radical do influence N₂O decomposition significantly.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114349"},"PeriodicalIF":6.2,"publicationDate":"2025-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842729","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":"The transition from CJ-deflagration to detonation in a square channel","authors":"Maddy Moran,&nbsp;Gaby Ciccarelli","doi":"10.1016/j.combustflame.2025.114407","DOIUrl":"10.1016/j.combustflame.2025.114407","url":null,"abstract":"<div><div>Experiments were performed in a 7.6 cm square channel to study the transition of a Chapman-Jouguet (CJ) deflagration to detonation in stoichiometric propane-oxygen, hydrogen-oxygen, and acetylene-oxygen with and without argon dilution. The subcritical transmission of a CJ detonation wave through a perforated plate produced a CJ deflagration. High-speed side-view schlieren, end view chemiluminescence visualization, and soot foils were used to identify the location and nature of the deflagration-to-detonation transition (DDT) process. Detonation initiation was categorized as prompt or delayed depending on the effect of the compressible-turbulent flow immediately downstream of the perforated plate. For prompt initiation the transverse waves generated by the decoupled detonation were directly responsible for detonation initiation. The mixture detonation cell structure irregularity played no role in prompt initiation but played a significant role for delayed initiation. For undiluted propane-oxygen progressive strengthening of the transverse waves ultimately led to detonation initiation at the channel walls because of lateral transverse wave collisions. For the argon diluted mixtures that have regular detonation cell structures, detonation initiation typically occurred in the corners, most likely due to flame boundary layer interaction due to the absence of transverse wave collisions at the DDT location. The mechanism for transverse wave amplification was not present for the regular cell structure mixture.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114407"},"PeriodicalIF":6.2,"publicationDate":"2025-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study of instability mechanisms and scaling relation in boundary layer flame","authors":"Yue Zhang,&nbsp;Yuji Nakamura","doi":"10.1016/j.combustflame.2025.114405","DOIUrl":"10.1016/j.combustflame.2025.114405","url":null,"abstract":"<div><div>Streaklike coherent structures observed in boundary-layer flames, particularly in wildland fires, have drawn increasing attention to these instability phenomena. In this study, a simplified Fire Dynamics Simulator (FDS) model was employed to investigate the underlying mechanisms responsible for the formation of these streaklike structures. The simulation setup consisted of an open wind tunnel measuring 1.0 m (length) × 0.5 m (width) × 0.5 m (height). Methane (CH₄) was used as the fuel source, and streaklike structures were induced by incorporating a non-slip surface segment upstream of the CH₄ burner under wind-driven conditions. In this work, the non-slip segment length was varied from 0 to 20 cm, and wind velocities ranged from 0.5 to 3.0 m/s. The results indicated that streaklike instabilities originated from disturbances in the incoming flow, specifically triggered by baroclinic vorticity generation. These coherent structures emerged when the baroclinic torque exceeded a critical threshold of approximately 10⁴ s^-2 in this work. To further explore the ensemble effects of flow instabilities on boundary layer flames, simulation, experimental, and real fire results were collected to establish a dimensionless correlation among the Strouhal number (<em>St</em>), Reynolds number (<em>Re</em>), and velocity instability (<em>I</em>) as <em>St</em>∼<em>Re</em>^-0.5<em>I</em>^-1.5. This relationship offers a framework for studying real-scale fire scenarios using bench-scale experiments and highlights the critical influence of initial laminar instabilities on flame dynamics even under turbulent conditions. This relationship also indicates that convection is the primary heat transfer mechanism in wildfire spread. The insights gained from this work enhance the understanding of boundary-layer combustion and contribute to advancing fire modeling and safety research.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114405"},"PeriodicalIF":6.2,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144840773","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":"An ignition delay time and automated chemical kinetic modeling study of three heptene isomers","authors":"Jiaxin Liu ,&nbsp;Yichen Gao ,&nbsp;Pengzhi Wang ,&nbsp;Hossein S. Saraee ,&nbsp;Sirio Brunialti ,&nbsp;S. Mani Sarathy ,&nbsp;Peter K. Senecal ,&nbsp;Jin-Tao Chen ,&nbsp;Shuai Huang ,&nbsp;Qingmiao Ding ,&nbsp;Shijun Dong ,&nbsp;Henry J. Curran","doi":"10.1016/j.combustflame.2025.114409","DOIUrl":"10.1016/j.combustflame.2025.114409","url":null,"abstract":"<div><div>An experimental and kinetic modeling study of the ignition of 1-heptene (C₇H₁₄-1), <em>trans</em>-2-heptene (C₇H₁₄-2), and <em>trans</em>-3-heptene (C₇H₁₄-3) is performed. Ignition delay times (IDTs) of these three isomers are measured using both a high-pressure shock tube and a rapid compression machine over the temperature range of 613–1257 K, at pressures of 15 and 30 bar diluted in air. An automated kinetic model development procedure is utilized in this study. We extended the capabilities of the MAMOX++ program, originally designed for alkane mechanism generation, to generate alkene reaction mechanisms. Using this enhanced framework, we systematically construct a detailed kinetic model for C₅–C₇ linear alkenes involving 52 reaction classes based on the core C₀–C₄ GalwayMech1.0 chemistry. The rate constants of each reaction class of the initial model are systematically optimized within their predefined uncertainty limits by comparing simulations with the new IDT data including 1^st-stage and total IDTs as well as existing experimental data in the literature. Sensitivity and flux analyses reveal that HȮ₂ addition to alkenes, forming <em>β</em>-Q̇OOH radicals, significantly enhances reactivity at low and intermediate temperatures by converting HȮ₂ radicals into more reactive ȮH radicals. Furthermore, by comparing the IDTs of the three heptene isomers with those of <em>n</em>-heptane, it is observed that reactivity is inhibited and is more pronounced as the C<img>C bond shifts toward the center of the molecular structure. Notably, C₇H₁₄-1 and C₇H₁₄-2 display similar reactivities due to their comparable levels of <em>γ</em>-hydroperoxyl alkenyl radical formation. Additionally, by comparing the IDTs of C₅–C₇ 1-alkenes and 2-alkenes, it is observed that, at low and intermediate temperatures, the reactivity increases with increasing chain length, whereas similar reactivities of all C₅–C₇ alkenes are observed at high temperatures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114409"},"PeriodicalIF":6.2,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144840770","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 boron particles with multilayer oxide structures considering knudsen transition effects","authors":"Guangyi Li ,&nbsp;Te Sun ,&nbsp;Baolu Shi ,&nbsp;Qiang Li ,&nbsp;Majie Zhao ,&nbsp;Ningfei Wang","doi":"10.1016/j.combustflame.2025.114397","DOIUrl":"10.1016/j.combustflame.2025.114397","url":null,"abstract":"<div><div>Boron powder is a promising fuel candidate for powder-fueled scramjet engines due to its high energy density. In this study, a semi-empirical model is developed to describe the ignition and combustion behavior of boron particles by accounting for a multilayer oxide structures and Knudsen transition effects. Ignition characteristics are investigated under constant ambient temperature and oxidizer concentration, with emphasis on the effects of pressure (0.1–10 atm) and particle size (1–40 μm). The ignition delay increases exponentially with decreasing pressure. The pressure exponent exhibits a non-monotonic dependence on the Knudsen number (<em>Kn</em>), attributed to the competition among dominant reaction pathways over varying pressure regimes. For combustion, the mode transition diameter (<em>D</em>_tr), defined via the Damköhler number (<em>Da</em>), decreases with increasing pressure and temperature. This trend reflects a shift in the controlling mechanism between kinetic and diffusive processes, influenced by particle size, ambient temperature, and Langmuir-layer temperature.</div><div><strong>Novelty and significance statement:</strong> This study presents a novel semi-empirical model that integrates multilayer oxide structures and Knudsen transition effects to capture the ignition and combustion behavior of boron particles under various conditions. Unlike existing models, it includes bidirectional diffusion across oxide layers and the shift between heat transfer regimes. The model explains the non-monotonic pressure dependence of ignition characteristics based on mechanistic analysis. A transition diameter (<em>D</em>ₜᵣ) based on the Damköhler number serves as a new criterion to classify combustion modes. The model achieves high predictive accuracy across a wide range of particle sizes and ambient conditions. These results enhance the understanding of boron combustion mechanisms and support the design and optimization of powder-fueled scramjet propulsion systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114397"},"PeriodicalIF":6.2,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828611","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":"Flamelet modeling of aluminum particle combustion","authors":"Jiarui Zhang,&nbsp;Liya Huang,&nbsp;Likun Ma,&nbsp;Zhixun Xia","doi":"10.1016/j.combustflame.2025.114389","DOIUrl":"10.1016/j.combustflame.2025.114389","url":null,"abstract":"&lt;div&gt;&lt;div&gt;To facilitate comprehensive numerical studies on metal fuel combustion within large-scale burners, a novel flamelet model is formulated for aluminum (Al) particle combustion using Flamelet Generated Manifold (FGM). The new FGM model for Al particle combustion is referred as Al-FGM model. The model introduces an oxidizer depletion parameter &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; that quantitatively captures oxygen consumption mechanisms through both heterogeneous surface reactions and alumina deposition processes. This key advancement complements three fundamental combustion descriptors: fuel-oriented mixture fraction &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Al&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, reaction progress variable &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Y&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, and normalized enthalpy deficit &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. The resulting four-variable manifold (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;Al&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Y&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;ˆ&lt;/mo&gt;&lt;/mrow&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;t&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) establishes a thermochemical state space for efficient flamelet tabulation. The flamelet library is constructed by solving a series of one-dimensional (1D) gaseous counterflow flames. To accurately represent the significant gas-phase enthalpy changes due to intense interphase and radiative heat transfer within Al particle cloud combustion, the temperature boundary conditions of the 1D counterflow flames and the proportion of energy released by chemical reactions in the gas-phase energy equation are synergistically adjusted during the solution process. The proposed Al-FGM model undergoes validation using a dust counterflow flame setup. Using solutions derived from detailed chemistry as reference data, the Al-FGM model is validated across various dust concentrations through both &lt;em&gt;a priori&lt;/em&gt; and &lt;em&gt;a posteriori&lt;/em&gt; analysis. In the &lt;em&gt;a priori&lt;/em&gt; studies, the proposed Al-FGM model is first validated on a pure gas Al counterflow flame setup, demonstrating perfect agreement. At a low Al particle concentrations (&lt;span&gt;&lt;math&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 300 &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;g/m&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;), Al-FGM results match perfectly with ","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114389"},"PeriodicalIF":6.2,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study on the propagation characteristics of detonation waves in a semi-confined channel affected by different inert gases","authors":"Ruijie Mao,&nbsp;Chenwei Si,&nbsp;Runze Li,&nbsp;Xingyi Li,&nbsp;Yuejin Zhu","doi":"10.1016/j.combustflame.2025.114400","DOIUrl":"10.1016/j.combustflame.2025.114400","url":null,"abstract":"<div><div>In rotating detonation engines, the lateral expansion of detonation waves within a semi-confined channel often leads to a velocity deficit in the wave and a reduction in combustion efficiency. Based on the OpenFOAM open-source computational platform, this paper numerically investigates the impact of different inert gases on the propagation characteristics of detonation waves in a semi-confined channel. The results show that: for gases with a large acoustic impedance ratio, such as Ar, CO₂ and N₂, the lateral expansion of the detonation wave forms an oblique shock wave - incident shock wave - detonation wave complex structure. The reflected wave formed at the inert gas boundary interacts with the existing transverse waves on the detonation wave front, the wave wrinkles, and the lower solid wall. As a result, the pressure ratio both behind and ahead of the reflected wave continuously increases, gradually enhancing its intensity until it eventually evolves into a new transverse wave. This process contributes to maintaining the stability of the detonation wave for a certain period. However, because the transverse waves continuously transmit into the inert gas, the intensity of the detonation wave still gradually decreases until it leads to detonation quenching. Owing to the physical properties of the inert gases affecting the intensity of the oblique shock waves (Ma_Ar &gt; Ma_CO2 &gt; Ma_N2), which in turn affects the propagation of the detonation wave, the propagation distance of the detonation wave is the shortest when the inert gas is N₂. For gases with a lower acoustic impedance ratio, such as He, the propagation of the detonation wave results in a complex structure of detached shock - transmitted shock wave - incident shock wave - detonation wave. In addition, the interaction between transverse waves and the compressed reaction zone can promote the formation of new transverse waves. The wave front maintains a large number of triple points, and the pressure ratio behind and ahead of the transverse waves remains at a high level, indicating that the wave intensity does not significantly decay. This sustained wave intensity contributes to the stability of the detonation wave. As a result, the detonation wave propagates farther in inert gases with a lower acoustic impedance ratio (He) compared to those with larger impedance ratios (Ar, CO₂, N₂).</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114400"},"PeriodicalIF":6.2,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810174","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":"Theoretical investigation of dual flame coupling in the centrally-staged combustor","authors":"Ziyu Qin ,&nbsp;Yuzhen Lin ,&nbsp;Xiao Han","doi":"10.1016/j.combustflame.2025.114391","DOIUrl":"10.1016/j.combustflame.2025.114391","url":null,"abstract":"<div><div>The communication theoretically investigates the coupling between the pilot and main stage flames, which is an essential issue in the centrally-staged combustor. First, an explicit solution to the mixture fraction equation is formulated, followed by a disturbance analysis to this basic solution. The mixture fraction response to the small bulk flow disturbance is derived. The corresponding linearized transfer function is then defined. Further, the flame sensitivity and coupling-induced oscillation suppression and enhancement are quantified. Finally, a dimensionless number is proposed to distinguish the strong and weak flame coupling based on the fuel transport.</div><div><strong>Novelty and significance statement</strong></div><div>We demonstrate a novel method to quantify the dual flame coupling characteristics and distinguish the strong and weak coupling effects. The analytical formulation visualizes the coupling intuitively. This conceptual investigation is of practical significance because it is helpful in understanding the dual-flame and multi-flame combustion systems, such as the centrally-staged stratificated flame and mesoscale hydrogen array flame.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114391"},"PeriodicalIF":6.2,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810177","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}