Combustion and Flame最新文献

{"title":"The measurement of turbulent burning velocities of methane-hydrogen-air mixtures at elevated pressures in a spherical vessel","authors":"Marwaan Al-Khafaji ,&nbsp;Junfeng Yang ,&nbsp;Alison S. Tomlin ,&nbsp;Harvey M. Thompson ,&nbsp;Gregory de Boer ,&nbsp;Kexin Liu","doi":"10.1016/j.combustflame.2024.113907","DOIUrl":"10.1016/j.combustflame.2024.113907","url":null,"abstract":"<div><div>Few previous experimental studies have focused on pre-mixed turbulent burning velocities (<em>u_t</em>) for hydrogen/air and methane/hydrogen/air mixtures, especially at the high-pressure conditions most relevant to gas turbine applications. This work employed a Schlieren technique to measure flame speeds for such mixtures in a spherical stainless steel combustion vessel, from which turbulent burning velocities were derived. The hydrogen volume fractions in methane were 30, 50, 70 and 100%. The initial pressures were 0.1, 0.5 and 1.0 MPa, and the initial temperatures were 303 and 360 K. The equivalence ratio (ϕ) was varied between 0.5 and 2 for pure hydrogen and from 0.8 to 1.2 for methane/hydrogen mixtures. The root mean square (rms) turbulent velocity (<em>u’</em>) was varied from 2.0 to 10.0 ms⁻¹. The objectives of this study are: (a) to present an extensive experimental database of turbulent burning velocities for these mixtures over a wide range of conditions; (b) to establish a new correlation for <em>u_t</em> for a flame with Lewis numbers, <em>Le,</em> not equal to unity, and (c) to quantify the dependence of turbulent burning velocity on pressure, temperature, stretch rate, laminar flame instability and rms velocity. As the pressure increased, the Taylor length scales decreased, and positive stretch increased, increasing flame wrinkling and <em>u_t</em>. The <em>u_t</em> also increased as the temperature and <em>u’</em> increased. The fuel/air mixture with high laminar flame instability (<em>Le&lt;1</em>) has higher <em>u_t</em> than those with higher <em>Le</em>. However, the normalised <em>u_t</em> peaked in the region of high laminar burning velocity. This study concluded that the increase in <em>u_t</em> resulting from flame reactivity (laminar burning velocity) is more important than that from positive stretch (negative <em>Ma_b</em>) and flame instability.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113907"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102713","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":"Large eddy simulations of turbulent premixed bluff body flames operated with ethanol, n-heptane, and jet fuels","authors":"Arvid Åkerblom,&nbsp;Christer Fureby","doi":"10.1016/j.combustflame.2024.113895","DOIUrl":"10.1016/j.combustflame.2024.113895","url":null,"abstract":"<div><div>Large Eddy Simulations (LES) are carried out targeting an unconfined premixed bluff body burner operated with ethanol, n-heptane, Jet A, and a Sustainable Aviation Fuel (SAF) labeled C1. The purpose is to validate the chosen simulation methodology for these fuels, which have not been simulated in the targeted case before, and to provide new information about how they burn and stabilize. The combustion of each fuel is modeled using Finite Rate Chemistry (FRC) and a pathway-centric chemical reaction mechanism. Subgrid-scale turbulence-chemistry interactions are modeled using a Partially Stirred Reactor (PaSR) approach. In accordance with previous experiments, snapshots of the OH and CH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O distributions, as well as velocity, are extracted from the simulations and subjected to statistical analysis to obtain mean flame progress variable distributions, flame surface density, and CH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O layer thickness. A mesh sensitivity analysis is carried out for all fuels, revealing that a crucial filter width threshold between 0.375 and 0.25 mm must be reached to achieve a stable flame and low mesh sensitivity. Statistically, the simulations show good agreement with previous experimental measurements. The flame sheet diameter is found to be approximately linearly correlated with extinction strain rate and Damköhler number, suggesting that resistance to turbulence is the determining factor for the flame size. The C1 flame is found to experience the weakest fluctuations, and a mechanism based on the relative time scales of flame propagation and the ignition of fuel decomposition products is proposed to explain this effect.</div><div><strong>Novelty and significance statement</strong></div><div>Sustainable aviation fuels are of major importance in reducing the climate impact of aviation, but their combustion is not nearly as well-understood as that of fossil jet fuels. Both experimental and numerical research is needed to map out the relationship between fuel composition and combustion performance, so that blending limits can be increased while guaranteeing safety, operability, and performance in aircraft engines. This work explores the turbulent flame dynamics of one commercial sustainable aviation fuel, C1. It is also the first numerical study to consider ethanol, n-heptane, Jet A, or C1 in the Cambridge bluff body burner, a case which has primarily been studied with methane. The results reveal several trends among the fuels which may be investigated further in future studies. C1 is found to be particularly resistant to outward fluctuations into the reactants, which connects fuel decomposition to flame stability.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113895"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103020","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":"Stochastic fields with adaptive mesh refinement for high-speed turbulent combustion","authors":"Tin-Hang Un,&nbsp;Salvador Navarro-Martinez","doi":"10.1016/j.combustflame.2024.113897","DOIUrl":"10.1016/j.combustflame.2024.113897","url":null,"abstract":"<div><div>This paper presents a fully compressible joint velocity-species-energy probability density function (PDF) for modelling turbulent reactive flows across all Mach numbers. By incorporating velocities into the PDF, the approach unifies the treatment of non-linear source and turbulent transport terms with minimal model parameters. The PDF transport is solved using Eulerian stochastic fields, leveraging features from existing grid-based solvers like high-order shock-capturing schemes and adaptive mesh refinement. Validation test cases show that the solver achieves the theoretical convergence rate, maintains accuracy across refinement levels, and demonstrates convergence with a moderate number of fields. Additionally, it outperforms the Smagorinsky model by adding dissipation only when necessary. When applied to a supersonic jet flame, the solver reproduces experimental measurements and results from highly-resolved large eddy simulations, demonstrating robustness in supersonic reacting flows with dynamic flow fields and shocklet structures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113897"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103021","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":"An experimental and modeling study of the auto-ignition of NH3/syngas mixtures in a shock tube","authors":"Shubao Song,&nbsp;Lin Zhang,&nbsp;Qifan Wang,&nbsp;Jiankun Shao","doi":"10.1016/j.combustflame.2024.113918","DOIUrl":"10.1016/j.combustflame.2024.113918","url":null,"abstract":"<div><div>Ammonia (NH₃) holds promise as an ideal zero-carbon fuel for modern energy systems. Co-combustion NH₃ with syngas can enhance the reactivity and improve the combustion efficiency of NH₃. In the current study, the auto-ignition and speciation experiments for NH₃/syngas mixtures were conducted at pressures of 0.86 and 4.0 atm, within a temperature range of 1234–1620 K, and across three equivalence ratios of 0.5, 1.0, and 2.0, with syngas content of 20 %, 30 % and 50 %, respectively. To the best of our knowledge, the experimental study for NH₃/syngas mixtures using shock tubes and laser absorption spectroscopy is the first in the literature. The experimental results show a similar reactivity under fuel-lean and stoichiometric conditions, which is slightly higher than the reactivity observed under fuel-rich conditions. The reactivity of the mixture is enhanced as the syngas content and pressure increase. The sensitivity analyses were conducted based on various kinetic models, and three key elementary reactions were identified that predominantly influence the oxidation of NH₃/syngas mixtures under experimental conditions: R1 (N₂H₂+M&lt;=&gt;NNH+H+M), R2 (NH₃+OH&lt;=&gt;NH₂+H₂O) and R3 (N₂H₂+H&lt;=&gt;NNH+H₂). The rate constants of these three crucial reactions were updated based on literature data, and an updated detailed kinetic model (NH₃-syngas model) was proposed based on our previous work (NH₃-C₂H₄ model). Simulated results by the NH₃-syngas model agree well with experimental data of the ignition delay times and time-histories of ammonia across different equivalence ratios, various syngas contents and pressures, as well as a series of literature data. Rate of production and sensitivity analyses were employed to elucidate the reaction pathways and crucial elementary reactions of NH₃/syngas mixtures. This investigation may contribute to optimizing kinetic models between ammonia and higher carbon number fuels in the future.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113918"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102714","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 kinetics at scramjet-engine-relevant conditions: Role of prompt dissociation of weakly-bound radicals","authors":"Amelia Kokernak ,&nbsp;Joel Mathew ,&nbsp;Raghu Sivaramakrishnan ,&nbsp;Stephen J. Klippenstein ,&nbsp;Jagannath Jayachandran","doi":"10.1016/j.combustflame.2024.113834","DOIUrl":"10.1016/j.combustflame.2024.113834","url":null,"abstract":"<div><div>Combustion in high-speed ram-based propulsion engines occurs under distinct thermodynamic conditions of high reactant temperatures (greater than 1000 K) and relatively low pressures (&lt;5 atm). There is a lack of fundamental flame measurements at such conditions that result in adiabatic flame temperatures (<em>T</em>_ad) exceeding 2500 K. In this work, we have measured laminar flame speeds of oxygen-enriched CH₄/oxidizer mixtures at sub-atmospheric conditions to probe kinetics at high <em>T</em>_ad using the isobaric spherically expanding flame approach. Simulations with recent kinetic models revealed increasing differences between data and model predictions with increasing <em>T</em>_ad, reaching up to 25 %. Kinetic analyses reveal that at the thermodynamic conditions in these O₂-enriched flames, i.e., lower pressures and higher <em>T</em>_ad, the effects of HCO prompt dissociation are accentuated. In addition to HCO, the prompt dissociations of CH₂OH and C₂H₅ are also considered. The prompt dissociations of all three radicals were evaluated and their effects considered in flame speed simulations. Reaction path analysis for the present flames revealed that approximately half of the reaction flux for HCO formation undergoes prompt dissociation to H + CO. Furthermore, these analyses also revealed that the pathways and sensitive reactions are similar between oxygen-enriched fuel/oxidizer mixtures and preheated fuel/air mixtures, if both have similar <em>T</em>_ad. Thus, flames of oxygen-enriched mixtures could be a surrogate to probe the flame chemistry of highly preheated mixtures at relatively low pressures that are often encountered in ram-based propulsion engine combustors.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113834"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103014","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 kinetic modeling study of the ignition of methane/n-decane blends","authors":"Jiaxin Liu ,&nbsp;Shangkun Zhou ,&nbsp;Pengzhi Wang ,&nbsp;Yuki Murakami ,&nbsp;Ahmed Abd El-Sabor Mohamed ,&nbsp;Mohsin Raza ,&nbsp;Adrian Nolte ,&nbsp;Karl Alexander Heufer ,&nbsp;Peter K. Senecal ,&nbsp;Henry J. Curran","doi":"10.1016/j.combustflame.2024.113884","DOIUrl":"10.1016/j.combustflame.2024.113884","url":null,"abstract":"<div><div>An experimental and kinetic modeling study of the combustion of methane/<em>n</em>-decane blends is performed. Ignition delay times (IDTs) of the pure fuels in addition to their blends are measured using both a shock tube and a rapid compression machine at three different methane/<em>n</em>-decane (mol%) compositions of 99/1 (M99D1), 95/5 (M95D5), and 80/20 (M80D20) in ‘air’, over the temperature range of 610–1495 K, at a pressure of 30 bar. A new chemical kinetic mechanism, GalwayMech1.0, is proposed to describe the combustion of these blends and is validated against the new IDT data including 1st-stage and total IDTs as well as existing experimental <em>n</em>-decane data available in the literature. Sensitivity analyses reveal that H-atom abstraction from <em>n</em>-decane by methyl peroxy radicals (CH₃Ȯ₂) play an important role in promoting blend reactivity at intermediate temperatures, which is not observed for pure <em>n</em>-decane. By investigating the effect of the <em>n</em>-decane concentration on the ignition characteristics, we found that the low ignition temperature limit is extended with increasing <em>n</em>-decane content with a non-linear reactivity-promoting effect. Flux analyses reveal that CH₄ oxidation in the blends is initiated via CH₄ + ȮH = ĊH₃ + H₂O, driven by the ȮH radicals produced from the early oxidation of <em>n</em>-decane and the CH₃Ȯ₂ radicals formed from CH₄ oxidation which subsequently accelerates <em>n</em>C₁₀H₂₂ consumption via H-atom abstraction. Comparisons of CH₄/<em>n</em>C₁₀H₂₂ and H₂/<em>n</em>C₁₀H₂₂ blends from a previous study demonstrate consistently higher reactivity for hydrogen blending compared to methane and that the magnitude of this increase diminishes with increasing <em>n</em>-decane content. Finally, we also compare our current model predictions of our new data with other <em>n</em>-decane models available in the literature.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113884"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A global evolution of the downward jet flame behavior: From the laminar to the turbulent","authors":"Xiepeng Sun,&nbsp;Jiang Lv,&nbsp;Yu Han,&nbsp;Xiaolei Zhang,&nbsp;Fei Tang,&nbsp;Longhua Hu","doi":"10.1016/j.combustflame.2024.113906","DOIUrl":"10.1016/j.combustflame.2024.113906","url":null,"abstract":"<div><div>The diffusion jet flame is a high-speed flow gas ignited at the outlet, a common combustion behavior in fundamental science of combustion, including applications in the industrial exhaust gas treatment torches and engines. This paper investigates experimentally the downward jet flame characteristics from the laminar to the turbulent, which has not been reported comprehensively yet. The overall jet flame length, jet flame downward distance, temperature and flame radiation heat flux profile are studied, as important characteristic parameters determining the flame boundary in vertical direction, the farthest distance that the flame could travel, as well as the thermal effect on the surrounding, respectively. Experiments were conducted to explore the global evolutionary process of downward jet flame with increasing initial fuel jet velocity for various circle nozzle diameters (3 mm, 4 mm and 5 mm), fuel types (pure fuel and blended fuel), and Reynolds numbers widely ranging from 65 to 97,209 involving laminar, transition and turbulent combustion regimes before reaching the flame blowout limit. The downward jet flame length and the downward distance show a non-monotonic evolution with the Reynolds number or heat release rate, <em>i.e.</em>, first increase at the laminar combustion regime, change a little at the transition regime, and finally increase significantly after reaching fully turbulent combustion regime. The vertical temperature profile along the centerline of the downward jet flame is associated with the downward jet flame morphologic characteristic parameters, it decreases significantly with the non-dimensional height at the intermittent region compared to the upward jet flame. The flame radiation fraction of the downward jet flame based on the measured flame radiation heat fluxes first changes a little and then decreases with the Reynolds number as a power function. The flame length could be well correlated by the non-dimensional heat release rate, the flame Froude number as well as the non-dimensional volumetric flow rate based on the air entrainment dynamics. The jet flame downward distance could be well correlated by the momentum-buoyancy length scale at the turbulent combustion regime. A non-dimensional global model involving the momentum-buoyancy length, flow rate length scale and the stoichiometric air-fuel ratio is developed to describe the global jet flame downward distance evolution. This work provides essential and fundamental knowledge about the dynamic evolution of downward jet flame in designing rocket propulsion/combustor structures, combustion and evolution characteristics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113906"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103024","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 influence of spatial dispersion on the steady-state characteristics and thermodynamic instability fluctuations of one-dimensional iron particle flames","authors":"Chengcheng Shan ,&nbsp;Haogang Wei ,&nbsp;Jiefeng Wan ,&nbsp;Zijian Zhang ,&nbsp;Philip De Goey ,&nbsp;Lei Zhou","doi":"10.1016/j.combustflame.2024.113889","DOIUrl":"10.1016/j.combustflame.2024.113889","url":null,"abstract":"<div><div>This study utilizes a simplified one-dimensional discrete model to analyze the characteristic parameters involved in the flame propagation of iron particles. It focuses on the influence of dispersive \"micro flames\" within these flames on propagation dynamics, investigating stable and unstable scenarios. The model adopts the form of particle suspension delineating alternant reaction intervals and inert intervals. The spatial dispersion rate (Γ) which describes the spatial extent of the \"micro flames\" is introduced, with Γ = 1 for the continuum model and Γ &gt; 1 for the discrete model. Theoretical equations, combining kinetic and diffusion equations, are solved with the finite difference method. The solution is evaluated preliminarily to distinguish numerical instability and thermodynamic instability. Additionally, in the preset time and space range, conditions for different equivalence ratios, particle radius and spatial dispersion rates are analyzed emphatically, with a comparison of typical simulation results and experimental data. As shown in the numerical simulation, the flame maintains stable propagation when <em>ϕ</em>≥0.7. The flame front, where the particle temperature rises above the gas temperature, extends backward with the increase of particle radius. The increase of Γ tends to extend the flame front of the fuel-lean flame and constringe that of the fuel-rich flame. Thermodynamic instability occurs in fuel-lean suspension with its manifestation preliminarily classified to distinct fluctuation, faint fluctuation and the final cessation. The increase of Γ also extends the flame propagation time under the dominance of thermodynamic instability, indicating different temperature structure evolution from the continuum model.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113889"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine learned compact kinetic model for liquid fuel combustion","authors":"Mark Kelly ,&nbsp;G. Bourque ,&nbsp;M. Hase ,&nbsp;S. Dooley","doi":"10.1016/j.combustflame.2024.113876","DOIUrl":"10.1016/j.combustflame.2024.113876","url":null,"abstract":"<div><div>A novel data-intensive methodology to produce a high fidelity, extremely-reduced “compact” kinetic model for a high boiling point complex liquid fuel is proposed and demonstrated. A five-component surrogate definition for the liquid fuel is developed that displays a high accuracy to the experimentally-derived combustion property targets. The calculations of the Lawrence Livermore National Lab diesel surrogate model containing 6476 species are used to serve as gas turbine industry-defined performance targets for this surrogate.</div><div>Acknowledging that the retention of a multi-component surrogate definition is a limitation on the size of the model, the surrogate fuel is consolidated into a single virtual molecule. Subsequently, the reaction mechanism is simplified by replacing high carbon number chemistry with a virtual scheme. This scheme links the virtual fuel molecule to low carbon number chemistry using four virtual species and forty-four virtual reactions, resulting in a reduction to 429 species in the model.</div><div>The Machine Learned Optimisation of Chemical Kinetics (MLOCK) algorithm is adapted to “compact” this model. Compaction is the over-reduction and optimisation of a kinetic model. Path flux analysis generates an overly-reduced model with 31 species that has a poor replication of the detailed model calculations. To address this, virtual reaction rate constants of important virtual reactions are numerically optimized to detailed model high temperature calculations. MLOCK systematically perturbs all three virtual Arrhenius reaction rate constant parameters to generate and evaluate numerous model candidates, refining the search space based on prior results, finding better models. A low temperature virtual reaction network, comprising one new virtual species and three new virtual reactions, is appended to the high temperature compact model. MLOCK is employed to reoptimize the model to calculations at low and intermediate temperatures.</div><div>The application of this methodology results in a 32-species compact model in ChemKin/Cantera format, which retains fidelities in the range of 76 to 92 % across a comprehensive range of gas-turbine relevant performance calculations for low, intermediate and high temperatures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113876"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102427","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":"Adjoint-based mean-flow uncertainty and feedback-forcing analyses of a thermoacoustic model system","authors":"Jiasen Wei,&nbsp;Alessandro Bottaro,&nbsp;Jan O. Pralits","doi":"10.1016/j.combustflame.2024.113901","DOIUrl":"10.1016/j.combustflame.2024.113901","url":null,"abstract":"<div><div>Clean combustion, particularly premixed hydrogen combustion aimed at reducing NOx emissions, is prone to thermoacoustic instabilities that can cause structural vibrations and equipment failures. This study focuses on a low-order model for a thermoacoustic prototype, a simple quasi-one-dimensional combustor comprising a plenum, premixing duct, and combustion chamber. Resonant modes of the combustor are identified by solving a nonlinear eigenvalue problem. Using an adjoint-based sensitivity analysis, the impact of uncertainties in base flow parameters on resonant frequencies and linear growth rates is assessed. The results obtained highlight the significant influence of variations in cold gas density within the plenum and premixing duct on the linear growth rates, potentially explaining discrepancies with literature data. Additionally, structural sensitivities in both the base and the perturbation flow are examined to evaluate the effects of a generic feedback mechanism on the eigenvalues. Structural sensitivities at the base-flow level are evaluated as a function of the flame position, identifying effective stabilizing mechanisms such as heat addition and mass flow rate reduction at duct intersections. The most stabilizing feedback mechanism is identified as mass fluctuations proportional to pressure perturbation at the end of the plenum, an effect achievable with Helmholtz resonators. Adjoint analyses permit uncertainty quantification of base-state parameters and gradient information for optimization strategies aimed at mitigating thermoacoustic instabilities through efficient and low-cost calculations.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of this research lies in its development of a comprehensive adjoint analysis framework for three types of sensitivity analyses within a thermoacoustic premixed combustor model. This paper uses base-state sensitivity to quantify the significant effect of base flow uncertainties, such as cold gas properties in the premixer, on the unstable resonant mode growth rates. In addition to structural perturbation sensitivity analysis, it uniquely applies structural sensitivity to base flow modifications, uncovering effective steady control mechanisms like mass suction and heating. The findings identify efficient approaches to mitigate thermoacoustic instabilities in premixed combustion systems and broaden the scope of potential control strategies.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113901"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102611","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}