Combustion and Flame最新文献

{"title":"Numerical investigation on the detonative tangential combustion instability in a rocket combustor","authors":"Bu-Kyeng Sung ,&nbsp;Jiro Kasahara ,&nbsp;Jeong-Yeol Choi","doi":"10.1016/j.combustflame.2025.114092","DOIUrl":"10.1016/j.combustflame.2025.114092","url":null,"abstract":"<div><div>In this study, Large Eddy Simulation (LES) is employed to investigate the self-excited detonative tangential combustion instability in a laboratory-scale rocket combustor with multiple impinging-type injectors. Auto-ignition was initiated with an initial condition of 2000 K in the combustor. It was found that the pressure fluctuations generated by ignition did not dissipate, instead, a pair of rotating waves in CW and CCW direction are steepened, promoting the interaction between the pressure wave-heat release rate. The interaction between these pressure waves and the heat release further developed the rotational motion of the heat release zone. This rotational motion coupled with the rotating pressure waves, ultimately establishing a dominant rotating direction. The coupled rotating wave and heat release eventually lead to resonant behavior, resulting in the development of detonative tangential mode instability. During limit cycle operation, the observation of a detonation cell structure further confirmed that tangential mode combustion instability can evolve into a rotating detonation. Comparing this evolution process with the deflagration-to-detonation transition (DDT), it was found to closely resemble the DDT process.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114092"},"PeriodicalIF":5.8,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519520","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 transfer function measurements in an annular combustor: Comparison with single flame response under hydrogen enrichment","authors":"Abhijat Verma,&nbsp;Nicholas A. Worth","doi":"10.1016/j.combustflame.2025.114051","DOIUrl":"10.1016/j.combustflame.2025.114051","url":null,"abstract":"<div><div>The full heat-release-rate (HRR) field was imaged in an annular combustor to assess the flame response at each injector simultaneously. The combustor geometry was modified to remove optical occlusions from the imaging setup. It was demonstrated that even very minor optical occlusions could lead to significant differences in the measured flame HRR response. When subject to carefully forced azimuthal modes, the sector-integrated HRR response could be decomposed into azimuthal clockwise and anticlockwise components. When decomposed, the HRR response amplitude was shown to be nearly independent of the azimuthal mode direction in the studied configuration. A comparison was made between the response of the same flame in annular and single flame confinement. For some operating conditions, the sector-wise annular flame transfer functions (FTFs) were found to deviate significantly in amplitude from those for a corresponding single flame combustor. This was attributed to inter-flame interactions and differences in confinement. These effects were modulated by studying flames with different hydrogen content and thus different laminar flame speeds. The flames became more compact with increasing hydrogen content, leading to reduced inter-flame and confinement effects. This lead to more similar FTFs in both amplitude and phase, with the phase for shorter flames being partially explained by a convective time delay based on the bulk velocity and flame height. Under azimuthal forcing, preferences to azimuthal mode direction were not significant and were largely unaffected by inter-flame interactions or confinement effects. However, with increasing hydrogen content, there was a larger variability in the thermoacoustic response between different nominally identical injectors, suggesting a sensitivity to small details in the flow.</div><div><strong>Novelty statement</strong></div><div>The symmetry of the azimuthal thermoacoustic response in an annular combustor was assessed in a full view of the annulus, compared to the blocked view from previous studies. It was shown that even a slight blocking of the view leads to a substantially different measurement. The full view revealed that the acoustic wave direction does not affect the flame transfer function (FTF) as much as what was reported in the past, meaning that parameters in models based on direction-dependent FTFs potentially need adjustment. For the first time, the FTF response was compared in an annular combustor and corresponding single flame under a wide range of carefully forced azimuthal modes, and for a wide variety of flame shapes. Though past studies found differences between the annular and single flame combustors, it was shown here that these differences are reduced when inter-flame and confinement interactions are reduced via hydrogen enrichment.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114051"},"PeriodicalIF":5.8,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation of transcritical multiphase combustion using real-fluid thermochemical and transport properties","authors":"Mohamad Fathi,&nbsp;Dirk Roekaerts,&nbsp;Stefan Hickel","doi":"10.1016/j.combustflame.2025.114055","DOIUrl":"10.1016/j.combustflame.2025.114055","url":null,"abstract":"<div><div>We scrutinize high-fidelity physical and numerical models for mixing and combustion in high-pressure thermal propulsion systems, where the operating pressure is typically above the critical pressures of the pure fuel and oxidizer, but lower than the cricondenbar values of the mixture. At such transcritical operating conditions, the fluid’s state and transport properties strongly deviate from ideal-gas or ideal-liquid models. The possible coexistence of vapor and liquid phases, governed by the local composition of the fluid mixture, further complicates the physical and numerical modeling. To this end, we present a comprehensive framework for the simulation of combustion at transcritical pressures using multiphase thermodynamics. The Navier–Stokes equations are solved for a multi-component working fluid with thermodynamic properties computed by solving suitable volumetric and caloric state equations combined with phase-splitting equations. The transport properties of the working fluid are modeled using high-pressure correction methods with appropriate structural mixing rules in the co-existence regime. Real-fluid effects on the diffusion driving force are quantified via the thermodynamic correction factor with a proposed extension to the multiphase transcritical regime. The finite-rate chemistry model includes real-fluid high-pressure effects in reaction source terms via the fugacity of the species. Computational results demonstrate the need for accurate models of thermochemical and transport properties and their impact on the predicted ignition behavior of transcritical flames.</div><div><strong>Novelty and Significance statement:</strong> This paper tackles the complexities of simulating transcritical multiphase combustion, highlighting the non-ideal behavior of fluid mixtures under high pressure and the potential coexistence of vapor and liquid phases dictated by local composition. Its significance extends beyond the pure usage of multiphase thermodynamics (MT), which couples the equation of state with vapor–liquid equilibrium calculations to accurately predict the thermodynamic properties of the mixture within the two-phase region. This work generalizes and extends the MT approach to transport properties and the diffusion driving force for real-fluid mixtures at transcritical pressures. Additionally, it introduces a finite-rate chemistry model that comprehensively addresses the real-fluid effects in high-pressure combustion based on species fugacity. The integration of these innovations provides a predictive model of unprecedented accuracy.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114055"},"PeriodicalIF":5.8,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flamelet modelling of turbulent reactive flows with non-premixed reactants and multiple inlets","authors":"Uday Chikkabikkodu ,&nbsp;Germain Boyer ,&nbsp;Franck Richard ,&nbsp;Arnaud Mura","doi":"10.1016/j.combustflame.2025.114052","DOIUrl":"10.1016/j.combustflame.2025.114052","url":null,"abstract":"<div><div>The present work describes an extension of the standard (i.e., two-inlet) mixture-fraction-based flamelet model, that is aimed at accommodating an arbitrary number of inlets. The corresponding framework relies on the consideration of inlet tracers, which allow to retrieve the fresh mixture composition, used in conjunction with a single mixture fraction variable that discriminates oxidizer inlets from fuel inlets contributions. This mixture fraction variable is also retained as a mapping variable to parameterize a chemical manifold generated from diluted one-dimensional non-premixed flamelets, with corresponding levels of dilution set from the knowledge of inlet tracers values. The resulting turbulent combustion model is presented in detail and subsequently applied to the Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation of an experimental benchmark featuring three distinct inlets. The detailed comparisons between computational results and experimental data together with ternary plots in the inlet tracers space confirm the relevance of the proposed modelling framework.</div><div><strong>Novelty and significance statements</strong></div><div>A modelling framework is introduced to describe turbulent non-premixed flames in situations featuring an arbitrary number of feeding inlet streams. It makes use of inlet tracers together with a single mixture fraction variable — used as a marker — to discriminate oxidizer inlets from fuel inlets contributions. By embedding an inlet tracer description within the tabulated flamelet framework, this original strategy can accommodate an arbitrary number of inlets and, as such, provides a significant generalization — as well as a strong mathematical background — to previous research efforts devoted to three-inlet flamelet models.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114052"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation on ignition characteristic of NH3/O2/N2 mixtures: High pressure effects and model comparison","authors":"Yueying Liang ,&nbsp;Zimu Wang ,&nbsp;Gabriel J. Gotama ,&nbsp;Wei Zhou ,&nbsp;Yongxiang Zhang ,&nbsp;Liang Yu ,&nbsp;Xingcai Lu","doi":"10.1016/j.combustflame.2025.114079","DOIUrl":"10.1016/j.combustflame.2025.114079","url":null,"abstract":"<div><div>To gain a deep insight into ammonia combustion under real powertrain operating conditions, the oxidation of NH₃/O₂/N₂ mixtures is measured using a rapid compression machine at high pressures of 40−100 bar, temperature of 1000−1200 K, equivalence ratios of 0.25−1.0, and dilution ratio N₂/O₂ of 3.76−8.52. Four representative ammonia oxidation mechanisms, including Glarborg−2024, POLIMI−2023, NUIG−2024, and KAUST−2023, are validated against the new high-pressure auto-ignition data and the results reveal that the performance of these mechanisms varies depending on the experimental conditions where POLIMI−2023 shows a relatively better prediction on the current data. Twelve high sensitivity coefficient reactions in four mechanisms are selected to compare the rate constant, indicating the necessity to unify the rate coefficients of important reactions and update old values. Rate coefficients even differ by an order of magnitude or more, including NH₂+HO₂=OH+H₂NO, H₂NO+NH₂=HNO+NH₃, and H₂NO+HO₂=HNO+H₂O₂. The kinetic analysis indicates that the reduced sensitivity coefficients of inhibiting reactions NH₃+O₂=NH₂+HO₂, NH₂+NO=N₂+H₂O and NH₂+NO₂ =N₂O+H₂O contribute to the high reactivity of ammonia mixtures at high pressures. The NH₂ radicals also participate less in the oxidation of species including NO, N₂H₂, N₂H₄ and H₂NO as the pressure rises. The experimental data qualitatively reveals the temperature effect on the pre-ignition phenomenon. The measured pressure profiles under different temperatures show that pre-ignition diminishes gradually as the temperature rises. A large amount of heat accumulation from exothermic reactions including NH₂+NO=N₂+H₂O, NH₃+OH=H₂O+NH_2, and NH₂+NO₂ =N₂O+H₂O contribute to slow pressure rise during the pre-ignition. One possible reason for the pre-ignition should be facility-related factors such as little lubricating oil attached to the wall.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114079"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation of NH3-H2 jet flames adopting multi-scalar imaging: Comparison of turbulent burning velocities obtained using different flame-front markers","authors":"Ze Wang ,&nbsp;Xun Li ,&nbsp;Tao Li ,&nbsp;Andreas Dreizler ,&nbsp;Seyed M. Mousavi ,&nbsp;Andrei N. Lipatnikov ,&nbsp;Bo Zhou","doi":"10.1016/j.combustflame.2025.114054","DOIUrl":"10.1016/j.combustflame.2025.114054","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A series of lean NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/N&lt;sub&gt;2&lt;/sub&gt; pilot jet flames is investigated using simultaneous planar laser-induced fluorescence (PLIF) imaging of NH&lt;sub&gt;3&lt;/sub&gt;/NH/OH species. Turbulent rms velocity &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msup&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/msup&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and Karlovitz number &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; are varied in a wide range by changing the inlet bulk flow velocity. The Lewis number &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is varied by changing the hydrogen volume fraction in the fuel blends. Laminar flame speed &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, flame thickness &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, and Zel'dovich number &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; are varied by enriching air with oxygen. Turbulent burning velocities &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; are evaluated by measuring the inlet mass flow rates and mean flame front areas associated with different flame markers, i.e., NH&lt;sub&gt;3&lt;/sub&gt;, NH, and OH. The obtained results show the following trends. First, there are significant quantitative differences between burning velocities measured using different flame front markers. Second, while &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mtext&gt;NH&lt;/mtext&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, which is associated with an isosurface within flame preheat zones, is weakly affected by variations in &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; or &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, the three other burning velocities, which are associated with isosurfaces within flame reaction zones, are significantly higher in flames characterized by smaller &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; or &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. Third, for NH and OH marked flame fronts, the increase in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; with decreasing &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is attributed to differential diffusion effects, which are more pronounced for NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/air mixtures characterized by a higher &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Z&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; when compared to the counterpart mixtures enriched with oxygen. Fourth, the data measured at the highest &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/msup&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;234&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1670&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; do not show any sign of levelling-off of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;U&lt;/mi&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;m","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114054"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143509895","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":"Characterizing acoustic modes in a hollow rotating detonation combustor","authors":"Tyler Pritschau,&nbsp;Aatresh Karnam ,&nbsp;Ephraim Gutmark","doi":"10.1016/j.combustflame.2025.114057","DOIUrl":"10.1016/j.combustflame.2025.114057","url":null,"abstract":"<div><div>A multifaceted approach to studying the acoustics in a center-bodiless, Rotating Detonation Combustor (RDC) is conducted. Initially, a fundamental eigenmode study of the combustor volume is performed in COMSOL across a range of gas properties. These are computed via NASA CEA Detonation models to represent varying fueling conditions. The resulting values are compared against calculated fundamental modes for closed/open cylinder based on linearized wave equations. These two findings are then compared to experimental data across a range of bulk flow rates and equivalence ratios. While some modes showed good agreement with the computed results, others were left unexplained. Further direct analysis of the experimental data is then conducted to characterize these modes. Cross-spectral phase analysis is performed on high-frequency pressure transducers spaced azimuthally around the combustion chamber to identify the structural nature of each acoustic mode in the 2D plane. Bi-spectral Mode Decomposition (BMD) is conducted on high-speed video captured looking into the exit plane of the combustor. Good agreement is observed between these tools and the image analysis allows further characterization of the structures associated with each mode. Furthermore, BMD extracts the role of triadic interactions in the formation of an acoustic mode. This shows how the coupling of a few primary acoustic modes then form many of the additional modes observed in experimental results. The combination of these results begins to shed some light on the complex processes through which classical acoustic modes in a combustor interact to set up conditions which allow for rotating detonations to form.</div><div><strong>Novelty and significance statement</strong></div><div>Rotating detonation combustors (RDCs) are a rapidly expanding topic in combustion research. Presently, no clear guidelines or methodologies have been developed for designing RDC geometries; and most recorded RDC experiments are derivatives of the originally studied annular RDC. Recently, various non-traditional RDC geometries have demonstrated detonative operation and are being further studied. In traditional deflagrative combustors, one of the primary design challenges is ensuring that there are no thermoacoustic modes which are readily excited during normal operation; this challenge is no different in RDCs. Furthermore, thermoacoustic oscillations play a critical role in the transition from a deflagrative mode of combustion into detonations. If a practical RDC is to be realized, it is critical that the interactions between rotating detonation waves and traditional combustion acoustics are studied further across a range of unique geometries.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114057"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143511990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study of heat release rate indicators in 1D and 2D atmospheric and high pressure premixed ammonia-air and ammonia-hydrogen-air tubular flames","authors":"Frances C. Brown,&nbsp;Robert W. Pitz","doi":"10.1016/j.combustflame.2025.114066","DOIUrl":"10.1016/j.combustflame.2025.114066","url":null,"abstract":"<div><div>Heat release rate (HRR) is an important flame characteristic, providing information about thermoacoustic instabilities and flame front location in practical combustion applications. HRR indicators are essential to determining heat release rate profiles because HRR cannot be measured experimentally. Several indicators have been proposed for NH₃/air and NH₃/H₂/air flames, but no study has looked at how stretch rate or curvature might affect the performance of these suggested indicators. The numerically predicted species concentration profiles of measurable proposed tracers are compared to the calculated heat release rate profiles to qualitatively and quantitatively determine the best heat release rate markers in stretched premixed 1D tubular flames for a range of equivalence ratios and pressures as well as in atmospheric 2D cellular dual tubular NH₃/H₂/air flames. [O][NH₂] was found to be a well performing indicator for a wide range of pressures and equivalence ratios in the stretched and curved 1D NH₃/air and NH₃/H₂/air tubular flames. [OH][NH₃] was the best performing marker when the flames were in the stoichiometric regime. If a single species indicator is desired to reduce complexity of simultaneous multi-species measurements, [NH] performed well for all the 1D flames investigated but it was consistently outperformed by the species combinations. In the 2D cellular dual tubular flames, [NH] outperformed all the species combinations considered.</div></div><div><h3>Novelty and significance statement</h3><div>To characterize ammonia combustion accurately, heat release rate indicators need to be defined for a wide array of flame conditions and burner configurations. Several studies have defined potential heat release rate indicators for different equivalence ratios and burners. The present study identifies an HRR indicator for an array of flame conditions that are experiencing stretch and curvature. These conditions include high pressure and atmospheric pressure flames, lean and rich flames, and 1D non-cellular and 2D cellular flames. The identified indicator is of use to experimentalists because it utilizes a single species allowing for a less complex measurement procedure compared to simultaneous multi-species measurement.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114066"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143511863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational identification and Stuart-Landau modeling of collective dynamical behaviors of octuple laminar diffusion flame oscillators","authors":"Tao Yang ,&nbsp;Yuan Ma ,&nbsp;Peng Zhang","doi":"10.1016/j.combustflame.2025.114090","DOIUrl":"10.1016/j.combustflame.2025.114090","url":null,"abstract":"<div><div>Annular combustion chambers, consisting of multiple flame nozzles, are commonly used in gas turbine engines, particularly in aircraft engines and industrial power generation systems. In the study, we proposed a novel approach to the problem of annular combustion with emphasis on the collective dynamical behaviours that its individuals do not have. A series of circular arrays of octuple flickering laminar buoyant diffusion flames were investigated computationally and theoretically. Five distinct dynamical modes, such as the merged, in-phase, rotation, flickering death, partially flickering death, and anti-phase modes, were computationally identified and interpreted from the perspective of vortex dynamics. These modes were classified into three regimes. A unified regime diagram was obtained in terms of the normalized flame frequency <span><math><mrow><mi>f</mi><mo>/</mo><msub><mi>f</mi><mn>0</mn></msub></mrow></math></span> and the combined parameter <span><math><mrow><mrow><mo>(</mo><mi>α</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow><mi>G</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math></span>, where <span><math><mrow><mi>α</mi><mo>=</mo><mi>l</mi><mo>/</mo><mi>D</mi></mrow></math></span> is the ratio of the flame separation distance <span><math><mi>l</mi></math></span> to the flame nozzle size <span><math><mi>D</mi></math></span> and <span><math><mrow><mi>G</mi><mi>r</mi></mrow></math></span> is the Grashof number. The bifurcation transition between the in-phase and anti-phase regimes occurs at <span><math><mrow><mrow><mo>(</mo><mi>α</mi><mo>−</mo><mn>1</mn><mo>)</mo></mrow><mi>G</mi><msup><mrow><mi>r</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mo>=</mo><mn>655</mn><mo>±</mo><mn>55</mn></mrow></math></span>, where flames present the totally or partially flickering death. In addition, a Stuart-Landau model with a nearest neighbor time-delay coupling was utilized to reproduce the general features and collective modes of the octuple oscillator flame systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114090"},"PeriodicalIF":5.8,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143511989","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":"Comparing the low-temperature oxidation chemistry of butane isomers with ozone addition: An experimental and modeling study","authors":"Long Zhu,&nbsp;Qiang Xu,&nbsp;Cheng Xie,&nbsp;Bingzhi Liu,&nbsp;Hong Wang,&nbsp;Qingbo Zhu,&nbsp;Zhandong Wang","doi":"10.1016/j.combustflame.2025.114056","DOIUrl":"10.1016/j.combustflame.2025.114056","url":null,"abstract":"<div><div>Butane is the simplest alkane with isomers of linear and branched structures. The low-temperature oxidation kinetics of the butane isomers is essential in constructing a comprehensive combustion model for hydrocarbon and oxygenated fuels. This paper studies the low-temperature oxidation of <em>n</em>-butane and isobutane in an atmospheric pressure jet-stirred reactor (JSR) with ozone addition. The experiments were conducted within a temperature range of 350 to 800 K, maintaining a consistent initial molar fraction, equivalence ratio, and residence time. Over thirty species were measured and quantified using the synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography (GC). The NUIGMech1.3 and the Princeton ozone submechanism were modified to predict the reactivity of the two butane isomers from 350 to 750 K, with particular emphasis on bimolecular reactions of peroxy radicals, alkyl radical-ozone reactions, and hydrogen peroxide thermal decomposition. The experimental results suggest that while butane isomers exhibit similar reactivity from 350 to 575 K, significant differences emerge from 575 to 750 K. The experiments show that the low-temperature oxidation of <em>n</em>-butane primarily yields C₂ products (C₂H₄, CH₂CO, CH₃CHO, C₂H₃OH, C₂H₅OH, CH₃COOH, and C₂H₅O₂H), whereas isobutane favors the production of C₃ products, particularly CH₃COCH₃ and C₃H₆. A comprehensive analysis of experimental data and model simulations reveals that these differences can be attributed to the distinct reaction pathways of butyl peroxy radicals and the thermal decomposition reactions of C₄-ketohydroperoxides and C_1–4 alkyl hydroperoxides. Compared to <em>n</em>-butane, ozone significantly promotes the low-temperature reactivity of isobutane. Furthermore, ozone strongly promotes the peak mole fraction of C₂H₅OH, C₂H₅O₂H, PC₄H₉OH, NC₃H₇CHO, PC₄H₉O₂H and C₄-KHP during the low-temperature oxidation of <em>n</em>-butane. These promotions highlight the role of hydroperoxides and peroxy radicals in the ozone-assisted combustion system.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114056"},"PeriodicalIF":5.8,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488793","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}