Combustion and Flame最新文献

{"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}

{"title":"Validation and improvement of dimethyl ether kinetic models: Insights from ȮH laser-absorption measurements across a wide pressure range","authors":"Xin Zhang,&nbsp;Zilong Feng,&nbsp;Congjie Hong,&nbsp;Yuyang Zhang,&nbsp;Zuohua Huang,&nbsp;Yingjia Zhang","doi":"10.1016/j.combustflame.2025.114048","DOIUrl":"10.1016/j.combustflame.2025.114048","url":null,"abstract":"<div><div>Aiming to provide stronger constraints on the detailed kinetic models of dimethyl ether (DME) over a wide range of temperatures, pressures, and equivalence ratios, reflected shock waves combined with <em>UV</em> laser absorption were used to quantitatively measure microsecond-resolved ȮH time-histories in the oxidation of highly Ar-diluted DME mixtures with varying equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1188–1823 K. Diagnostic wavelengths near 306.687 nm (1.5 atm) and 306.689 nm (15.5 atm) were selected at the peak of the R₁(5) transition of the ȮH A-X (0,0) rovibronic band. Details on the temperature- and pressure-dependence of the ȮH profiles were revealed by a series of meticulously designed measurements. The first ȮH time-history measurements under high pressures and more fuel-lean conditions provided additional validation targets for the modern reaction models. Comparative evaluation of five recent reaction kinetic models of DME against the new data revealed that none of them perfectly align with all the ȮH time-histories measured in <em>this study</em>. Nevertheless, NUIG Mech1.1 and the Hashemi model demonstrated superior overall predictive performance. Taking into account the predictive performance on the global parameter of ignition delays, NUIG Mech1.1 was chosen to identify key reactions governing the ȮH evolution behavior. A modified NUIG Mech1.1 was proposed by incorporating the recent experimental and literature theoretical work. These new quantitative measurements of ȮH time-histories of DME particularly at 15.5 atm provide a critical contribution to the database needed for further model development at micro-level and combustion organization.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114048"},"PeriodicalIF":5.8,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488795","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":"Shock-induced drop size and distributions","authors":"J.E. Park,&nbsp;T.-W. Lee","doi":"10.1016/j.combustflame.2025.114091","DOIUrl":"10.1016/j.combustflame.2025.114091","url":null,"abstract":"<div><div>We use an integral analysis of conservation equations of mass and energy, to determine the drop size and distributions during shock-induced drop break-up. The result is an updated form for the drop size as a function of its final velocity, from a series of work applied to various atomization geometries. Comparisons with experimental data demonstrate the validity and utility of this method. The shock-induced drop size and distributions can be predicted within reasonable accuracy as a function of the drop velocity ratio and fluid properties. The result also illustrates the dynamical process of kinetic energy deficit transferred to the surface tension energy, and the skewing of the drop size distribution due to the non-linear dependence on velocity ratio.</div></div><div><h3>Novelty and Significance</h3><div>Shock-induced liquid break-up occurs in high-speed combustion devices, and it is an important issue to determine the drop size during this process as it represents the initial condition for evaporation and combustion processes. Yet, due to the length scales at which surface tension acts, numerical simulations of drop formation are computationally quite expensive. <u>Current approach provides an analytical method for determination of the drop size, without modeling or extensive numerics</u>. The derived formula can be used as an atomization algorithm in computational framework, vastly reducing the time and cost of simulating the liquid break-up processes.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114091"},"PeriodicalIF":5.8,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488794","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 describing function of conical laminar premixed flames subjected to parasite-velocity decoupled equivalence ratio oscillation","authors":"Zhixin Zhao,&nbsp;Ze Wang,&nbsp;Mingchen Sun,&nbsp;Hongwei Chen,&nbsp;Dong Yang,&nbsp;Bo Zhou","doi":"10.1016/j.combustflame.2025.114078","DOIUrl":"10.1016/j.combustflame.2025.114078","url":null,"abstract":"<div><div>Thermoacoustic instability presents a prominent challenge widely occurring in combustion systems, with equivalence ratio (ϕ) oscillation plays a vital role. The present work demonstrated a ϕ-modulation system from which the parasite velocity oscillation introduced from the mechanical motion ϕ-modulation is eliminated, and the influence of ϕ-modulation on a Bunsen-type premixed CH₄/air laminar flame was systematically investigated for various modulation amplitudes (ɛ), modulation frequencies (<em>f</em>, from 2 Hz to 40 Hz or Strouhal number, St, from 0 to 4) and mean equivalence ratios (ϕ₀=1.2 and ϕ₀=1.0). Synchronized measurements of ϕ, CH* emission, pressure and velocity perturbations were performed. The flame describing functions (FDF) of flame surface area (F_A), surface-integrated burning velocity (<span><math><msub><mi>F</mi><msub><mi>s</mi><mi>L</mi></msub></msub></math></span>) as well as the heat release rate (F_Q) with respect to ϕ-modulation were constructed and compared with analytical small-perturbation (SP) solutions for the first time. It is found that the FDFs (both gain and phase) including F_A, <span><math><msub><mi>F</mi><msub><mi>s</mi><mi>L</mi></msub></msub></math></span> and F_Q show generally a good agreement with the SP solution at a small perturbation amplitude of ɛ=0.05. However, as ɛ increased, the FDFs deviated from the SP solution to varying extents, which is in line with the quasi-steady-state analysis (QSSA) through a necessary fourth-order Taylor expansion of S_L(ϕ), showing a strong nonlinear effect for ϕ-modulation. The QSSA also highlights the FDFs can be highly dependent on ϕ₀. Ultimately, flame-generated acoustic oscillations were detected from the flames subjected to the ϕ-modulation, introducing an additional mechanism that further contributes to the deviation from the SP solution. An improved agreement of the measured FDFs with the SP solution was observed for the introduction of Helmholtz resonators in the burner system.</div><div>In summary, the present experimental platform can be easily applied to turbulent flames, and will allows for future studies on the coupling between equivalence ratio fluctuation with velocity fluctuation as well as the response of entropy waves to equivalence ratio fluctuations, which are important aspects when the flame response goes beyond the linear regime.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114078"},"PeriodicalIF":5.8,"publicationDate":"2025-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143488792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of the blast wave interaction on the flame heat release & droplet dynamics","authors":"Gautham Vadlamudi ,&nbsp;Balasundaram Mohan ,&nbsp;Akhil Aravind ,&nbsp;Saptarshi Basu","doi":"10.1016/j.combustflame.2025.114058","DOIUrl":"10.1016/j.combustflame.2025.114058","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The study comprehensively investigates the response of a combusting droplet during its interaction with high-speed transient flow imposed by a coaxially propagating blast wave. The blast wave is generated using a miniature shock generator which facilitates wide Mach number range (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;01&lt;/mn&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). The interaction of the shock flow occurs in two stages: (1) interaction of the temporally decaying velocity (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) imposed by the blast wave and (2) interaction with the induced flow (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ind&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;). The flame base lifts off due to the imposed flow and the advection of flame base towards flame tip results in flame extinction for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;06&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The timescale of flame extinction is faster (interaction with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The study investigates the effect on droplet regression, flame heat release rate and flame topological evolution during the interaction. The droplet regression rate gets enhanced after the interaction with blast wave for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;06&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, while it slowed down due to complete extinction for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;06&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. A momentary flame heat release rate (HRR) enhancement occurs during the interaction with shock flow, and this HRR enhancement is found to be more than 8 times the nominal unforced flame HRR for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, where rapid flame extinction occurs due to faster interaction with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;v&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). The HRR enhancement has been attributed to the fuel vapor accumulation during the interaction. Furthermore, for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, compressible vortex interaction occurs with the droplet resulting in droplet atomization. The ","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114058"},"PeriodicalIF":5.8,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479208","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":"Physical and chemical effects of steam dilution on premixed NH3/O2/H2O flames","authors":"Yu Zhang,&nbsp;Bo Han,&nbsp;Jinqi Zhu,&nbsp;Wenda Zhang,&nbsp;Linyao Zhang,&nbsp;Yijun Zhao,&nbsp;Shaozeng Sun","doi":"10.1016/j.combustflame.2025.114074","DOIUrl":"10.1016/j.combustflame.2025.114074","url":null,"abstract":"&lt;div&gt;&lt;div&gt;NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2/&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt;O combustion combines oxygen-rich enhanced combustion with steam to control flame temperature and NO&lt;sub&gt;x&lt;/sub&gt; emissions, and it is a promising ammonia combustion technology for future clean and efficient power generation. For investigating the regulation mechanisms of steam dilution in NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O flames, this study employed premixed free flame and counterflow flame models to investigate the impact of steam dilution on laminar flame characteristics, including flame speed (&lt;em&gt;S&lt;/em&gt;&lt;sub&gt;L&lt;/sub&gt;), temperature (&lt;em&gt;T&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt;), NO emissions (&lt;em&gt;E&lt;/em&gt;&lt;sub&gt;NO&lt;/sub&gt;), and extinction strain rate (&lt;em&gt;κ&lt;/em&gt;&lt;sub&gt;ext&lt;/sub&gt;). The effects of steam dilution are decoupled into physical (dilution effect, thermal effect, transport effect, radiation effect) and chemical effects (direct reaction effect and third-body effect) to investigate the competitive and synergistic mechanisms between these effects on the kinetic scale. Results indicate that the NH&lt;sub&gt;3&lt;/sub&gt; primary decomposition and the H/O radical pools determine NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O flame speed. H/O radical formation and NH&lt;sub&gt;3&lt;/sub&gt; staged dehydrogenation dominate the heat release and consumption, respectively. NO is mainly produced from HNO and NH radicals, and the reduction reactions of NH&lt;sub&gt;i(i=0–2)&lt;/sub&gt; and NNH-N&lt;sub&gt;2&lt;/sub&gt;O mechanism dominate NO consumption in NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O flame. The dilution effect strongly inhibits &lt;em&gt;S&lt;/em&gt;&lt;sub&gt;L&lt;/sub&gt;, &lt;em&gt;T&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt;, &lt;em&gt;E&lt;/em&gt;&lt;sub&gt;NO&lt;/sub&gt;, and &lt;em&gt;κ&lt;/em&gt;&lt;sub&gt;ext&lt;/sub&gt; of NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O flames, as it reduces fuel concentration and leads to low active radicals. The thermal and radiation effects increase the reaction heat loss to decrease &lt;em&gt;S&lt;/em&gt;&lt;sub&gt;L&lt;/sub&gt;, &lt;em&gt;T&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt;, and &lt;em&gt;κ&lt;/em&gt;&lt;sub&gt;ext&lt;/sub&gt;, while the transport effect helps the rapid reactant diffusion with contrast results. The thermal/radiation/transport effects extend the heat release and OH/HNO accumulation region to increase &lt;em&gt;E&lt;/em&gt;&lt;sub&gt;NO&lt;/sub&gt; at fuel-lean conditions. For chemical effects, the direct reaction and third-body effect synergistically suppress &lt;em&gt;T&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt; and promote &lt;em&gt;E&lt;/em&gt;&lt;sub&gt;NO&lt;/sub&gt;, exhibiting competition on &lt;em&gt;S&lt;/em&gt;&lt;sub&gt;L&lt;/sub&gt;. Under most conditions, the direct reaction effect dominates the chemical effects, which are reversed at a high dilution ratio (&lt;em&gt;Z&lt;/em&gt;&lt;sub&gt;H2O&lt;/sub&gt;). For the extinction strain rate, the direct reaction effect and three-body effect transition from competitive to synergistic with increased &lt;em&gt;Z&lt;/em&gt;&lt;sub&gt;H2O&lt;/sub&gt;. To balance the NH&lt;sub&gt;3&lt;/sub&gt;/O&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O combustion efficiency, combustor thermal resistance, emissions, and flame stability, future strategies may involve adopting steam staged injection and RQL (Rich-Quench-Lean) combustion organization, as well as combining with plasma-assisted/porous media c","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114074"},"PeriodicalIF":5.8,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474055","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":"Quantification of detonation regularity","authors":"Rachel Hytovick,&nbsp;Liliana Berson,&nbsp;Robyn Cideme,&nbsp;Kareem Ahmed","doi":"10.1016/j.combustflame.2025.114043","DOIUrl":"10.1016/j.combustflame.2025.114043","url":null,"abstract":"<div><div>Physical parameters as indicators for detonation regularity have been previously identified; however, a metric for the degree of regularity has yet to be defined. Quantifying the degree of regularity in cellular detonations offers valuable insight into their stability and potential failure. An experimentally derived regularity parameter, the coefficient of variation of velocity ((<em>σ</em>/<em>μ</em>)_V/DCJ), is defined. This regularity parameter forms the finite boundaries relative to the effective activation energy using statistically significant and temporally resolved experiments.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114043"},"PeriodicalIF":5.8,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474056","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":"SkeleCHy: A skeletal mechanism for low hydrocarbon content blends with hydrogen","authors":"Christoph D.K. Schumann ,&nbsp;Quentin Cazères ,&nbsp;James C. Massey ,&nbsp;Caleb J. Li ,&nbsp;Yusuke Tanaka ,&nbsp;Nedunchezhian Swaminathan","doi":"10.1016/j.combustflame.2025.114036","DOIUrl":"10.1016/j.combustflame.2025.114036","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In order to achieve short-term reductions in carbon dioxide emissions, combustion systems may be retrofitted to operate with blends of methane and hydrogen. However, the volume fuel fraction of hydrogen must be at least 70% to achieve significant reductions in carbon dioxide emissions. Comprehensive chemical kinetic mechanisms can be used to simulate these high hydrogen content hydrogen/methane blends but such mechanisms are computationally demanding, especially when nitrogen chemistry is included. However, formation of nitrogen oxides (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NO&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;x&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) is one of the major factors to consider for the transition towards hydrogen-fuelled carbon neutrality. This motivates development of a skeletal mechanism that can capture the key attributes of laminar combustion, which are the burning velocity, ignition delay time, distribution of major species and emissions, and the extinction strain rate. To identify the best available base mechanism for the chemical mechanism reduction process, an extensive experimental database of approximately 2000 data points is considered explicitly for volume fuel fractions of hydrogen of 70% or greater and the performances of several commonly employed mechanisms are reviewed. State-of-the-art chemiluminescence kinetics as well as nitrogen chemistry are added to the best available comprehensive mechanism. A skeletal mechanism, SkeleCHy, is derived with quasi-steady state assumptions, the directed relation graph with error propagation method and isomer lumping. The reduction is validated with approximately 2200 data points and the skeletal mechanism is further validated with a subset of approximately 330 experimental data points of high interest. It is demonstrated that the key attributes of laminar combustion for hydrogen/methane–air mixtures with high hydrogen content with unburnt mixture temperatures of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;300&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;700&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and operating pressures of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; to &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mi&gt;bar&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; are captured while the computational cost of the SkeleCHy mechanism is comparable to the commonly used GRI 3.0 mechanism. &lt;strong&gt;Novelty and significance statement:&lt;/strong&gt; The fuel volume fraction of hydrogen in hydrogen/methane fuel blends targeting decarbonisation is at least 70%. Emissions of NO are a concern in this blending regime and chemiluminescence is frequently used for validation of simulations. It is therefore of high interest to find the best available chemical kinetic mechanism for this fuel blending regime. This work is the first to assess chemical kinetic mechanisms explicitly in this fuel blending regime using an extensive database of experimental measurements. A ","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114036"},"PeriodicalIF":5.8,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463757","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":"Optimizing iron powder combustion: Influence of particle size on flame stability, nanoparticle formation, and nitric oxide emission","authors":"Willie Prasidha ,&nbsp;Mohammadreza Baigmohammadi ,&nbsp;Yuriy Shoshin ,&nbsp;Philip de Goey","doi":"10.1016/j.combustflame.2025.114068","DOIUrl":"10.1016/j.combustflame.2025.114068","url":null,"abstract":"<div><div>This study utilizes a small-scale semi-practical burner “Metal Cyclonic Combustor (MC²)” to investigate the combustion behavior of iron powder as a potential clean energy carrier, focusing on varying powder sieve ranges and input equivalence ratios. The iron aerosol burner, used previously, can stabilize iron-air flames without a pilot flame or external heat supply. Experimental results demonstrate that smaller iron powder sizes produce stable and steady iron flames with higher degrees of oxidation. The critical powder sieve size for achieving steady iron flames in the current small-scale semi-practical burner (MC²) was found to be below 75 µm, ensuring adequate residence time for combustion. Additionally, nanoparticle formation and nitric oxide (NO) emissions are significantly influenced by the size of the iron particles and combustion conditions, with smaller sizes and leaner conditions producing higher nanoparticles and NO emissions. A critical parameter identified is the average distance between particles being less than 1 mm for studied powder sizes to sustain a steady and stable iron flame without external heat support. These findings provide valuable data for developing commercial iron powder-firing burners and advancing iron powder as a sustainable energy carrier, offering practical guidance for efficient and environmentally friendly combustion processes.</div><div>Novelty and Significance Statement</div><div>This study provides an investigation into the combustion behavior of micron-sized iron powder using a practical burner, exploring its potential as a clean energy carrier. The novelty of this research lies in the detailed analysis of iron flame characteristics, nanoparticle formation, and NO formation under varying powder sieve ranges and combustion conditions. Unlike previous studies that focused much more on single-particle characteristics, this study examines larger-scale continuous combustion, highlighting critical parameters needed to achieve stable and steady iron flames without external heat support. The findings indicate that specific particle spacing is essential for sustaining stable and steady iron flames for practical particle size ranges employed in this study. These insights are pivotal for optimizing iron powder combustion processes, advancing the development of commercial iron powder burners, and promoting iron powder as a viable, sustainable alternative to fossil fuels. This research offers practical guidance for achieving efficient and environmentally friendly combustion, contributing significantly to the iron energy carrier cycle.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114068"},"PeriodicalIF":5.8,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453674","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":"Role of anions in the electrochemical modulation of flammability of ionic liquids","authors":"Afrida Anis,&nbsp;Keren Shi,&nbsp;Erik Hagen,&nbsp;Yujie Wang,&nbsp;Prithwish Biswas,&nbsp;Michael R. Zachariah","doi":"10.1016/j.combustflame.2025.113994","DOIUrl":"10.1016/j.combustflame.2025.113994","url":null,"abstract":"<div><div>The flammability and combustion of liquid fuels is very dependent on volatility. Although room temperature ionic liquids (RTILs) without metastable anions possess high energy density, they are often considered non-flammable due to their low vapor pressure. We have demonstrated that these thermally stable and seemingly non-flammable imidazole cation based RTILs without metastable anions can be made flammable by applying a voltage bias which generates volatile flammable gaseous species. Conversely removing the voltage bias terminates the generation of these gaseous species, rendering the liquid non-flammable again. Utilizing this concept, we extend our study to investigate the effect of different anions BF₄⁻, ClO₄⁻, NO₃⁻, PF₆⁻ and CH₃COO⁻, paired with the same 1-butyl-3-methylimidazolium cation. We find that the rate of gaseous species generation largely depends on the conductivity of the RTILs. RTIL with higher conductivity produces more gaseous species. However, we also found that despite generating reactive gaseous species, some RTILs can still remain non-flammable. Mass spectrometric analysis of the gaseous species generated during the electrochemical decomposition shows that if the species generated from anodic oxidation possess flame inhibition properties, they can interfere with the combustion of the flammable species generated at the cathode, making them non-flammable. Flammability of other RTILs that do not have inhibiting species generated at the anode can be modulated electrochemically.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 113994"},"PeriodicalIF":5.8,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143463756","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}