Combustion and Flame最新文献

{"title":"Dynamic behaviors of burning droplet suspended on NiCr-wire with applied AC electric field","authors":"Seung Hyun Kim ,&nbsp;Jeong Park ,&nbsp;Suk Ho Chung ,&nbsp;Chun Sang Yoo","doi":"10.1016/j.combustflame.2025.114024","DOIUrl":"10.1016/j.combustflame.2025.114024","url":null,"abstract":"<div><div>Effect of applied AC electric field on burning n-decane droplet suspended on NiCr wire (0.5 mm in diameter) was investigated experimentally by varying the AC frequency <em>f</em>_AC (10−1000 Hz) and voltage <em>V</em>_AC (1−5 kV). Three initial diameters of n-decane droplets were tested. Due to the difference in droplet surface temperature between the edge region and the central bottom region of the suspended droplet, caused by the heat transfer through the wire from the flame, an internal circulation is generated inside the droplet during burning, which enhances the evaporation rate, subsequently increases the flame width and height. When an AC is applied, the dynamic behaviors of droplet and flame are significantly influenced. Depending on <em>V</em>_AC and <em>f</em>_AC, six regimes can be classified: dripping (DP) of droplet (Regime I) for large droplets due to decreased surface tension from heat transfer through the wire; vertical oscillation (OS) of the droplet due to a vertical dielectrophoretic force (II); lateral spread (LS) and OS of droplet (III) caused by a horizontal dielectrophoretic force between wire sections with and without the droplet; LS and a flame-spitting (FS) phenomenon due to excessive LS (IV); LS and formation of flame vortex (FV) near flame edges due to induced magnetic field (V); and the simultaneous occurrence of LS, FS, and FV (VI). The behavior of vertical oscillation was examined from the solution of the linearly-perturbed Rayleigh-Plesset equation, where the OS amplitude of the droplet increases with <em>V</em>_AC and decreases with <em>f</em>_AC. The mechanism of lateral spread was investigated by analyzing the onset conditions, specifically in terms of <em>V</em>_AC and <em>f</em>_AC. For burning droplets, it was observed that the vertical oscillatory motion is enhanced due to the imbalance in surface tension between the upper and lower surfaces of the droplet and the internal flow becomes faster due to the reduced droplet viscosity. The internal flow response time decreases with <em>f</em>_AC, leading to an increase in oscillation amplitude with increasing <em>V</em>_AC and/or <em>f</em>_AC. The mechanism of the induced magnetic field was tested through the onset conditions having a constant critical magnetic field intensity. The normalized droplet lifetime is characterized by their related physical parameters, including the gradient of radial electric field intensity at the central surface of droplet, <em>f</em>_AC, droplet diameter, and flame width and height. The droplet lifetime shows a strong correlation with the combination of these parameters in both the OS and LS cases.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114024"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193334","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 adaptive implicit time-integration scheme for stiff chemistry based on Jacobian tabulation method","authors":"Sihang Rao ,&nbsp;Wenyuan Zhou ,&nbsp;Wang Han ,&nbsp;Yihao Tang ,&nbsp;Xu Xu","doi":"10.1016/j.combustflame.2025.113997","DOIUrl":"10.1016/j.combustflame.2025.113997","url":null,"abstract":"<div><div>The use of detailed chemical mechanisms in modeling chemically reacting flows often results in large computational costs. In this study, a stiff ODE solver, combining the backward differentiation formula (BDF) with a novel Jacobian tabulation (JT) method, was developed to significantly reduce the computational cost of solving chemical ordinary differential equations (ODEs) with detailed chemistry. The resulting BDF-JT method offers several key advantages: (a) it accelerates the evaluation and factorization of the Jacobian matrix during the BDF solution process through a two-level dynamic tabulation; (b) a properly selected set of state parameters governs the identification of similar Jacobians and their factorizations within the tabulation system; and (c) efficient look-up and dynamic updates of the tabulation are enabled using hash tables. The accuracy and efficiency of the BDF-JT method were systematically compared against the original BDF and CVODE solvers across a range of scenarios, including homogeneous auto-ignition, laminar flame propagation, and oblique detonation waves (ODW). The results showed that the proposed method had negligible effects on accuracy under the studied tolerances. In terms of computational efficiency, the BDF-JT method achieved significant speedup, reducing the computational cost of solving chemical ODEs by a factor of 173.7 in the auto-ignition case with a 2885-species mechanism and by a factor of 41.3 for ODW combustion with a 1384-species mechanism, with higher efficiency observed for more complex reaction systems. Overall, the BDF-JT method demonstrates strong potential for drastically reducing computational costs while maintaining high accuracy in large-scale combustion simulations, making it a valuable tool for high-fidelity combustion simulation.</div><div><strong>Novelty and Significance Statement</strong></div><div>There is an urgent need to incorporate more realistic chemical mechanisms in modeling chemical reacting flows. Due to the large computational cost of using detailed chemical kinetics, operator-splitting schemes along with several stiff ODE solvers have been studied and demonstrated performance. Unfortunately, most stiff ODE solvers are likely developed trading off accuracy for performance. The present study provides a dynamic tabulation method for chemical Jacobian in the implicit ODE solvers. As such, it helps to accelerate the computations in combustion simulations without sacrificing accuracy.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 113997"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193338","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":"Computational diagnostics and characterization of combustion recession in diesel sprays","authors":"F.J. Arguelles ,&nbsp;M.D. Fagade ,&nbsp;J. Mehra ,&nbsp;C. Xu ,&nbsp;N. Sekularac ,&nbsp;X.H. Fang","doi":"10.1016/j.combustflame.2025.113993","DOIUrl":"10.1016/j.combustflame.2025.113993","url":null,"abstract":"&lt;div&gt;&lt;div&gt;While low-temperature combustion (LTC) strategies have been found to mitigate nitrogen oxides and particulate matter emissions in diesel engines, studies have also associated LTC with an increase in unburnt hydrocarbons. With more recent studies on diesel after end-of-injection (AEOI), combustion recession is identified as a phenomenon where at near nozzle region, high-temperature ignition (HTI) combustion can propagate back to the nozzle tip consuming the unburnt hydrocarbons AEOI. Current literature has suggested that combustion recession is controlled by auto-ignition. However, high-fidelity simulations and detailed analysis of such a mechanism are missing. In this study, comprehensive Large Eddy Simulations of a reacting spray at “Spray A” conditions are performed, where detailed analysis of combustion recession concerning flame morphology and propagation modes are included. In particular, this study demonstrated for the first time that while combustion recession is mainly auto-ignition dominated (consistent with the literature), a cool flame was found to deflagrate towards the richer regions of the mixture, promoting mixing and increasing the mixture temperature. This leads to HTI kernels, which then grow and develop as deflagrative waves, therefore sustaining the combustion recession process. The study also detailed the extinction mechanism of combustion: the entrainment wave will overlean the near-nozzle mixtures, rendering it unable to support HTI, which leads to the extinction of the upstream flame AEOI in lower reactivity mixtures. Combustion recession is also observed to be contingent on the chemical and diffusion processes, even at low scalar dissipation rates. Finally, a new criterion for combustion recession based on chemical explosive mode is proposed and validated with previous combustion recession index to quantify the extent of HTI in near-nozzle mixtures AEOI. The newly developed metric combined with a previous experimentally-based metric can provide simple but valuable measurements of the degree and propensity of the upstream flame AEOI.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This work covers the literature gap in detailing the spray after end-of-injection combustion recession mechanisms. The study is significant, suggesting that while combustion recession is auto-ignition-dominated, deflagration modes were found, for the first time, to exist within the kernels via a cool flame at the end of injection. With further analysis, the deflagration modes were found to promote mixing at the end of injection which is deemed critical in sustaining combustion recession. The extinction mechanisms on the other hand were associated with the significant role of entrainment waves after end-of-injection. To generalize the findings of our study, a novel combustion recession metric based on the chemical explosive mode is proposed where agreement is found with the experimental observations. The new metri","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 113993"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193359","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":"Theoretical investigation on unimolecular decomposition network of n-propylamine with advanced kinetic methods","authors":"Zhenpeng Zhang ,&nbsp;Chong Li ,&nbsp;Yanlei Shang ,&nbsp;Haiyong Zhao ,&nbsp;Sheng-Nian Luo","doi":"10.1016/j.combustflame.2025.113996","DOIUrl":"10.1016/j.combustflame.2025.113996","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Unimolecular decomposition network of &lt;span&gt;&lt;math&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-propylamine (NPA) is theoretically investigated. Twenty intramolecular H-shift/H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; elimination reactions and three bond dissociation reactions are identified, including some new reactions producing singlet species. Among these reactions, only one intramolecular H-shift reaction that yields C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; + NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and three bond dissociation reactions are dominant. The M06-2X/jun-cc-pVTZ and M06-L/jun-cc-pVTZ methods are adopted for kinetic calculations given their well-balanced accuracy and computational costs. The reaction-path variational transition state theory and variable reaction coordinate variational transition state theory are applied to determine the high-pressure limit rate constants of the intramolecular H-shift reaction and bond dissociation reactions, respectively, and the multi-structure torsional anharmonicity and small-curvature tunneling correction are considered. The pressure-dependent rate constants are also determined using the system-specific quantum Rice–Ramsperger–Kassel theory at 700–2000 K and 0.001–100 atm. The C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;–C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; bond dissociation reaction that produces CH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;CH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and CH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; radicals is the most important with a branching ratio larger than 0.85 over the investigated temperature range. Our calculated rate constants agree well with the literature data and effectively capture the effect of pressure on the rate constants within the uncertainty in energy determination. With our calculations, a literature combustion model is updated and performs better in predicting the speciation data during the NPA pyrolysis and ignition delay times of NPA.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This work theoretically investigates the unimolecular decomposition network of &lt;span&gt;&lt;math&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-propylamine (NPA) by using the advanced reaction-path variational transition state theory and the variable reaction coordinate variational transition state theory for reactions with tight and loose transition states, respectively, with the consideration of multi-structure torsional anharmonicity and small-curvature tunneling correction. Some novel unimolecular decomposition reactions producing singlet specie","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 113996"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193337","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":"Quantitative studies of instabilities of confined spherically expanding flames: Application to flame propagation and autoignition of natural gas blends with hydrogen at engine-relevant conditions","authors":"Kyuho Van ,&nbsp;Anguo Hu ,&nbsp;Jung Z. Fang ,&nbsp;Tushar K. Bera ,&nbsp;Allen A. Aradi ,&nbsp;Sandeep K. Jain ,&nbsp;Fokion N. Egolfopoulos","doi":"10.1016/j.combustflame.2025.114009","DOIUrl":"10.1016/j.combustflame.2025.114009","url":null,"abstract":"<div><div>The availability of accurate fundamental combustion properties at engine-relevant conditions is of paramount importance in testing kinetic and transport models so that they can be used in large-scale simulations of practical devices. However, a literature search reveals that flame data can be scarce at engine-relevant conditions, and those that are available may be of limited value due to large uncertainties associated with experiments at high temperatures and pressures that can render the flames unstable. The main contribution of this study was the introduction of one-dimensional and multi-dimensional direct numerical simulations to quantify the onset of flame instabilities at conditions used in measuring laminar flame speeds. This is a deviation from the traditional approaches that use theoretical predictions and/or circumstantial evidence to vet and interpret experimental data. To that end, the confined spherically expanding flame method was used to measure laminar flame speeds for reacting mixtures of hydrogen-natural gas blends, for pressures ranging from 8 to 30 atm, and for unburned mixture temperatures ranging from 420 to 530 K. This approach proved to be successful as the predicted and experimental results were consistent with each other, and the reported data herein were measured for conditions that the direct numerical simulations revealed that they resulted in stable flames throughout all stages of propagation. As expected, the laminar flame speed increases with hydrogen addition, and this increase was found to be slightly more notable compared to recently published data under similar conditions for hydrogen-methane flames. Additionally, under suitably chosen conditions, autoignition in the end gas was induced during the compression stage of stable flame propagation, and ignition delay times with remarkably low repeatability scatter were measured through the rapid changes in the pressure-time derivatives. The autoignition studies included <em>n</em>-pentane as an additive to achieve autoignition within the available times in the existing constant-volume spherical facility. For blends of hydrogen with natural gas and <em>n</em>-pentane, a two-stage ignition behavior was observed, and the hydrogen addition resulted in the reduction of ignition delay times. All reported data were modeled, offering insights into the mechanisms governing flame propagation and autoignition. The results of the present study are expected to contribute to ongoing endeavors related to hydrogen utilization and decarbonization in the transportation sector.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114009"},"PeriodicalIF":5.8,"publicationDate":"2025-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193352","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":"Simplified radiation and soot models for buoyant diffusion flames: Quantitative investigation of fuel mixing effects","authors":"Wenbin Yao,&nbsp;Haidong Liu,&nbsp;Zehua Yang,&nbsp;Xiao Chen,&nbsp;Shouxiang Lu","doi":"10.1016/j.combustflame.2024.113904","DOIUrl":"10.1016/j.combustflame.2024.113904","url":null,"abstract":"<div><div>Simplified radiation and soot models were proposed to provide a simple yet effective method predicting flame radiation and soot characteristics for buoyant diffusion flames. To explore the quantitative effects of fuel mixing and validate the proposed models, LII measurement of soot distribution and multi-point measurement of radiation flux were conducted for different fuel mixtures and different mixing ratios. Characteristic length scales, including the height of soot inception, the height of maximum soot volume fraction and the height of soot oxidation in the soot distributions, were determined by the fuel type and mixing ratio, and resulted in different maximum soot volume fractions. The axial distribution of soot volume fraction, maximum soot volume fraction, soot volume and soot yield can be predicted by the simplified soot model based on the critical mixture fractions. The probability density function of axial soot volume fraction can be described by an exponential function related to the non-sooty probability and maximum soot volume fraction. In addition, flame radiation power presents a linear correlation with soot volume, and flame radiation fraction of buoyant diffusion flame of fuel mixtures presents a linear relationship with the maximum soot volume fraction, which is in agreement with the simplified radiation model proposed in this work.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113904"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102433","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 modeling study on indene oxidation: Emphasizing the competing kinetics between PAH oxidative decomposition and mass growth","authors":"Yuwen Deng ,&nbsp;Zaili Xiong ,&nbsp;Jijun Guo ,&nbsp;Chen Huang ,&nbsp;Long Zhao ,&nbsp;Meirong Zeng ,&nbsp;Zhongyue Zhou ,&nbsp;Wenhao Yuan ,&nbsp;Fei Qi","doi":"10.1016/j.combustflame.2024.113912","DOIUrl":"10.1016/j.combustflame.2024.113912","url":null,"abstract":"<div><div>Fundamental knowledge about the production and oxidation chemistry of polycyclic aromatic hydrocarbons (PAHs) is essential for developing predictive soot models. In contrast to the significant progress in understanding the formation/growth kinetics of PAHs, the detailed oxidation kinetics of PAHs remains to be fully established. This study investigates the oxidation kinetics of indene, the simplest PAH, as a foundational step for examining larger PAHs. Experiments were conducted in a flow reactor at temperatures from 850 to 1350 K, under a pressure of 0.04 atm and an equivalence ratio of 0.5. Characteristic products were quantified using synchrotron vacuum ultraviolet photoionization mass spectrometry, including large resonance-stabilized PAH radicals with 3–4 aromatic rings. Results indicate that even under highly oxidative conditions, the mass growth pathways of indene remain competitive, leading to the production of various large PAHs. This phenomenon is unique to indene oxidation and has not been observed in other bicyclic aromatics. A detailed kinetic model was developed to interpret these findings, revealing that PAH formation is predominantly driven by the indenyl radical. This study further calculates the rate coefficients for the dominant mass growth pathway of indenyl, specifically its self-recombination reaction, to enhance predictions of indenyl and bi-indene. Notably, while spiran and bridging mechanisms are comparably important in cyclopentadienyl mass growth, the spiran mechanism is favored for indenyl, suggesting that the addition of a benzenoid ring significantly alters the reactivity of cyclopenta-like radicals. Comparative analysis with indene pyrolysis experiments reveals that under oxidative conditions, the indenyl radical preferentially decomposes into smaller species, e.g., cyclopentadienyl or cyclopentadiene, thereby enhancing the yields of PAHs that depend on C₅ species as precursors. In the early reaction stage (&lt;1220 K), oxidation reactions promote indenyl formation, thus increasing the proportion of mass growth products. However, at higher temperatures (&gt;1220 K), enhanced oxidation reactions of indenyl lead to its decomposition, outcompeting mass growth reactions and sharply reducing the proportion of mass growth products.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113912"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102618","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":"Role of hydrogen enrichment in ammonia forced ignition at elevated pressures","authors":"Lei Wang,&nbsp;Xingqian Mao,&nbsp;Jinguang Li,&nbsp;Haiqiao Wei,&nbsp;Gequn Shu,&nbsp;Jiaying Pan","doi":"10.1016/j.combustflame.2024.113908","DOIUrl":"10.1016/j.combustflame.2024.113908","url":null,"abstract":"<div><div>Numerous studies have demonstrated that hydrogen enrichment can improve ammonia reactivity, leading to enhanced ignition and combustion performance. However, the role of hydrogen enrichment in forced ignition of ammonia, especially at elevated pressures, remains not fully understood. This study employed a localized energy deposition technique to initiate the forced ignition of ammonia/hydrogen mixtures. The role of hydrogen ratio and ignition energy in ignition and flame kernel initiation was numerically investigated, and the critical ignition conditions were identified by assessing the correlations between heat release and thermal diffusion. The results show that the forced ignition at low pressures involves four traditional stages, whereas only two stages are present at high pressures, i.e., ignition assisted flame kernel propagation and normal laminar flame propagation. The weakening stretching responses at high pressures cause the flame kernel to propagate outward without additional ignition energy. Then deposited ignition energy mainly heats ignition kernels and increases the local temperature, thereby reducing ignition delay time and accelerating ignition initiation. Hydrogen enrichment enhancing ignition performance is mainly due to the changed fuel property and reduced ignition delay time. Kinetic analysis suggests that this enhancement is primarily attributed to the increased sensitivity of H+O₂=O+OH and the substantial H generation from the reverse of NH₃+H=NH₂+H₂, both of which promote the chain branching of H+O₂=O+OH. Besides, successful ignition also depends on the competition between chemical heat release and thermal diffusion. Chemical heat release dominates within a timescale of ∼0.1 ms, while thermal diffusion prevails beyond the threshold. Hydrogen enrichment can significantly reduce minimum ignition energy, but this tendency becomes less pronounced when hydrogen ratio exceeds 20 %.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113908"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102619","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":"Publication / Copyright Information","authors":"","doi":"10.1016/S0010-2180(24)00645-X","DOIUrl":"10.1016/S0010-2180(24)00645-X","url":null,"abstract":"","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113936"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103013","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":"Tabulated chemistry approach for detonation simulations","authors":"Alexandra Baumgart,&nbsp;Matthew X. Yao,&nbsp;Guillaume Blanquart","doi":"10.1016/j.combustflame.2024.113878","DOIUrl":"10.1016/j.combustflame.2024.113878","url":null,"abstract":"<div><div>Chemistry modeling in detonations typically relies on two broad approaches: simplified models with one- or two-step chemistry, and detailed chemistry. These approaches require choosing between computational efficiency or physical accuracy. To reduce the cost of chemistry while maintaining accurate physics, tabulated chemistry has been used extensively for flames/deflagrations in the low Mach number framework. In the simplest tabulated chemistry model for premixed flames, a progress variable, describing the progress of reactions in the system, is transported in the simulation. This progress variable is then used to look up all other species, transport properties, and thermodynamic variables from a pre-computed table. The present work extends the tabulated chemistry method to detonations. Even in non-reacting compressible flow simulations, the enthalpy and specific heat capacity are required; to describe these thermodynamic variables, the temperature is selected as a second table coordinate. The two table coordinates are able to capture virtually all variations in the progress variable source term. The Zel’dovich–von Neumann–Döring (ZND) model is found to be the most appropriate one-dimensional problem for generation of the table. The ZND tabulation approach is validated for both one-dimensional stable and pulsating and two-dimensional regular and irregular detonations in various <span><math><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>-<span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> mixtures. The tabulated chemistry simulations are able to reproduce the detailed chemistry results in terms of propagation speed, cellular structures, and source term statistics. For hydrogen detonations, the computational cost of scalar transport is reduced by a factor of 9 and the cost of the chemistry is reduced by a factor of 17. More substantial computational savings are expected for hydrocarbon fuels.</div><div><strong>Novelty and significance statement</strong></div><div>Detonations are often challenging to simulate due to the significant cost of integrating accurate chemical models. In deflagrations, this cost has been reduced by pre-computing the chemistry and collecting the information into a lookup table to be used at runtime. Although chemistry tabulation has been adapted recently for supersonic combustion, such as in scramjets, the typical assumptions of these approaches do not apply to detonations. We propose a new tabulated chemistry approach, valid for detonations and reproducing critical parameters such as induction zone length and detonation velocity. The key novelty lies in (1) the use of progress variable and temperature as the coordinates for tabulation, and (2) the selection of one-dimensional Zel’dovich–von Neumann–Döring detonations as the relevant physical problem to be tabulated. The new model significantly reduces the cost of simulations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113878"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103025","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}