Combustion and Flame最新文献

{"title":"Experimental and kinetic modeling study of cyclopentanone pyrolysis in a jet-stirred reactor","authors":"Hong Wang ,&nbsp;Bingzhi Liu ,&nbsp;Qiang Xu ,&nbsp;Shijun Dong ,&nbsp;Zhandong Wang ,&nbsp;Long Zhu","doi":"10.1016/j.combustflame.2024.113796","DOIUrl":"10.1016/j.combustflame.2024.113796","url":null,"abstract":"<div><div>Cyclopentanone (CPN) is a widely available biofuel with excellent combustion properties, but detailed speciation profiles during its pyrolysis have rarely been studied. This work examines the pyrolysis of CPN in a jet-stirred reactor (JSR) at atmospheric pressure, with residence time of 2 s and a temperature range from 830 K to 1100 K. Dozens of pyrolysis intermediates and products were measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography (GC). Among them, several new species were observed, including water, carbon dioxide, formaldehyde, indene, 1,2-dihydroindene, naphthalene, 1,2-dihydronaphthalene, 1-methylnaphthalene, acenaphthylene, biphenyl, and fluorene. A detailed kinetic model was developed based on the literature, and in general, it predicted the experimental results for most species well. Kinetic analyses indicated that the consumption of CPN was controlled by the bimolecular reactions with H atom. The formation of water, carbon dioxide and formaldehyde could be explained by the reaction pathways of OH radical. The pyrolysis of CPN yielded a significant number of alkenes and alkynes at higher temperatures; the bimolecular addition reactions of these species with resonantly stabilized radicals are important to the formation of polycyclic aromatic hydrocarbons (PAHs). Based on those, this work provides valuable insights into CPN pyrolysis chemistry and it promotes the development of a comprehensive CPN combustion model.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113796"},"PeriodicalIF":5.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441195","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":"Investigation on the dynamics of shock wave generated by detonation reflection","authors":"Zezhong Yang,&nbsp;Bo Zhang","doi":"10.1016/j.combustflame.2024.113791","DOIUrl":"10.1016/j.combustflame.2024.113791","url":null,"abstract":"<div><div>When a detonation wave hits a rigid wall, a reverse shock is created. This occurrence is common in closed pipe detonation experiments. To better comprehend the propagation dynamics of the reverse shock, experiments were performed in a 2.5-meter-long detonation tube. Normal reflection, Mach reflection, and regular reflection of detonation are generated by changing the end-wall profile. Three different mixtures, 2H₂+O₂+40%Ar (with very regular cellular pattern), C₂H₄+3O₂+40%Ar (regular), and CH₄+2O₂ (irregular), are used to examine how detonation stability affects the subsequent reflected shock propagation procedure. The reflection process is visualized by using a high-speed schlieren imaging technique. A one-dimensional simulation with a detailed chemical reaction mechanism was employed to further illustrate the dynamics of the reflected shock, which is generated by detonation normal reflection. Results show that the variation of the reflected shock speed in normal reflection can be categorized into three phases. First, the reflected shock speed rapidly decreases in the detonation reaction zone. It then slowly increases due to the transmitted expansion wave. Finally, the shock wave velocity gradually decreases in the stationary flow. A post-shock blast wave appears in the shocked but unburnt mixture. However, its impact on the reflected shock structure is minimal, as it attenuates drastically. The collision of the detonation and the shock-shock interaction at the tip of the reflectors boosts the reflected shock speed, and the acceleration ratio in the two regular mixtures is 33.7 %–48.7 %, while it is approximately 20 % in the irregular mixture. This study offers a fresh perspective on the complex detonation reflection process through the combined analysis of both experimental and numerical results.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113791"},"PeriodicalIF":5.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142440927","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":"Fuel mobility dynamics and their influence on applied smouldering systems","authors":"Seyed Ziaedin Miry ,&nbsp;Marco A.B. Zanoni ,&nbsp;Tarek L. Rashwan ,&nbsp;Laura Kinsman ,&nbsp;José L. Torero ,&nbsp;Jason I. Gerhard","doi":"10.1016/j.combustflame.2024.113789","DOIUrl":"10.1016/j.combustflame.2024.113789","url":null,"abstract":"<div><div>Many recent environmentally beneficial applications of smouldering treat hazardous organic liquid fuels in inert porous media. In these applications, organic liquid mobilization can affect the treatment process, and the dynamics are poorly understood. Organic liquid mobilization is therefore a key knowledge gap that hinders the optimization of applied smouldering. This is especially the case in large scales where mobilization appears to be more significant. Liquid mobilization inside a porous medium cannot be easily measured directly, therefore numerical modelling is essential to understand the fundamental processes and to clarify the effects and dynamics of the fuel mobilization on the smouldering reaction. Contrasting numerical models with experimental temperature measurements have revealed many aspects of smouldering that cannot be measured. In this study, a previously developed 1D smouldering model was equipped with multiphase flow equations and compared against laboratory column experiments. The combination of model and experiments has served to quantify the dynamics of organic liquid fuel mobility by simulating high (i.e., non-mobile) and low (i.e., mobile) viscous fuels. The findings from this study shed light on the complicated interplay between multiphase flow, heat and mass transfer, and smoulder chemistry common to many applied smouldering systems. Numerical results confirmed that increasing the viscosity results in fuel remaining in the reaction zone and led to an increase in the peak temperature and smouldering front velocities. Lower viscosity fuels mobilized away from the reaction zone, thereby accumulating fuel in the pre-heating zone of the reactor. The fundamental understanding generated from this research will improve the design, implementation, and optimization of smouldering-based technologies for environmentally beneficial applications worldwide.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113789"},"PeriodicalIF":5.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441559","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":"Effect of AP and AN on the combustion and injection performance of Al-H2O gelled propellant","authors":"Songchen Yue ,&nbsp;Zhan Wen ,&nbsp;Qiu Wu ,&nbsp;Yao Shu ,&nbsp;Jian Jiang ,&nbsp;Peijin Liu ,&nbsp;Wen Ao","doi":"10.1016/j.combustflame.2024.113801","DOIUrl":"10.1016/j.combustflame.2024.113801","url":null,"abstract":"<div><div>Aluminum-water propellants (Al-H₂O propellants), representing a novel class of solid propellants, demonstrate the merits of cost efficiency and reduced feature signal characteristics. However, the conventional formulations of Al-H₂O propellants are hampered by the generation of substantial condensed residues. In our investigation, we explored the incorporation of oxidizers into the Al-H₂O propellant grain, aiming to enhance combustion and injection performance. Employing a multifaceted experimental approach, we conducted thermal gravimetric analysis, laser ignition experiments, and ignition tests within a lab-scale solid rocket motor (SRM) firing to systematically examine the effects of varying content of ammonium perchlorate (AP) and ammonium nitrate (AN) on the combustion and injection performance of Al-H₂O propellants. Our findings indicated that integrating AP and AN at a mass fraction of 3 % each notably curtailed ignition delay time by approximately 67 % and 90 %, respectively, and concurrently decreased burning rates by approximately 50 % and 58 %. Significantly, it has been observed that a composition incorporating a 5 % mass fraction of AP enhances the combustion efficiency of the Al-H₂O propellant system by approximately 2 %. Conversely, the integration of a 5 % mass fraction of AN into the same propellant matrix results in an augmentation of the injection efficiency by an estimated 47 %. Empirical evidence validating the augmentative impacts of AP and AN on the performance of Al-H₂O propellants has been substantiated through a series of motor hot firing experiments. Furthermore, the combustion behavior of Al-H₂O propellants has been elucidated through an analysis of the combustion physical mechanism of Al particles. The thermal decomposition of AP yields a substantial volume of oxidizing gases, which effectively accelerates the combustion rate of the Al particles, subsequently leading to an enhancement in the overall combustion efficiency of the propellant. Conversely, the decomposition of AN results in an increased production of nitrogen gas, thereby augmenting the velocity of gas flow and, consequently, elevating the injection efficiency of the propellant. This finding holds promise for guiding the developmental trajectory of Al-H₂O propellants and refining the design parameters of propulsion systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113801"},"PeriodicalIF":5.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441560","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 on 4-methylheptane pyrolysis at atmospheric pressure","authors":"Haikun Lang ,&nbsp;Fangping Bin ,&nbsp;Shuyao Chen ,&nbsp;Xiaoli Zhang ,&nbsp;Jiuzheng Yin ,&nbsp;Jinzeng Pan ,&nbsp;Zhandong Wang ,&nbsp;Lixia Wei","doi":"10.1016/j.combustflame.2024.113790","DOIUrl":"10.1016/j.combustflame.2024.113790","url":null,"abstract":"<div><div>Fischer–Tropsch synthesis is an important route for the productions of cleaner fuels from non-petroleum materials. Monomethylated alkanes are present in large quantities in Fischer–Tropsch synthetic fuels. However, side-chain position may make a difference in the combustion of the fuels. In this work, the 4-methylheptane (MH4) pyrolysis was investigated experimentally by using a jet-stirred reactor at 800–1125 K and at 760 Torr. Major pyrolysis products, including small molecules and aromatic products, were identified and measured by using the synchrotron ultra-violet photoionization method. Several species were detected and measured, including CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₄, C₃H₆, C₃H₈, C₄H₆, IC₄H₈, C₅H₆, C₅H₈1-3, C₅H₁₀-2, benzene, naphthalene, indene and C₆H₅C₂H, etc. A detailed kinetic model of MH4 pyrolysis was developed and validated against the experimental results in this work. Rate of production analysis of MH4 indicates that the most significant consumption pathways are H-abstractions. The unimolecular decomposition reactions by the breakages of C<img>C bonds are also important pathways in MH4 consumption. The pyrolysis product distributions of 4-methylheptane, 3-methylheptane and 2-methylheptane were compared to demonstrate the effect of the methyl side chain position on the pyrolysis of those fuels. It is noted that the mole fraction distributions of the smaller species, including CH₄, C₂H₂ and C₂H₆, are not sensitive to the position of the methyl side-chain, while those of C3-C5 products, including PC₃H₄, C₃H₆, C₄H₆, IC₄H₈, C₅H₈1-3 and C₅H₁₀-2, are strongly affected.</div></div><div><h3>Novelty and significance statement</h3><div>The products of 4-methylheptane pyrolysis were identified and measured by using the synchrotron ultra-violet photoionization method. A detailed kinetic model of 4-methylheptane pyrolysis at atmospheric was constructed for the first time. The consumption pathways of 4-methylheptane pyrolysis were clarified. The effect of methyl side chain position on fuel pyrolysis was analysed. 4-Methylheptane is one of the important branched alkanes in Fischer–Tropsch synthetic diesel fuel. The present work extends the understanding of pyrolysis of long branched alkanes. The results of the study provide guidance in exploring ideal compositions for diesel alternative fuels.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113790"},"PeriodicalIF":5.8,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423808","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":"Size-resolved ignition temperatures of isolated iron microparticles","authors":"Daoguan Ning,&nbsp;Yuhang Li,&nbsp;Tao Li,&nbsp;Benjamin Böhm,&nbsp;Andreas Dreizler","doi":"10.1016/j.combustflame.2024.113779","DOIUrl":"10.1016/j.combustflame.2024.113779","url":null,"abstract":"<div><div>Ignition temperatures of metal particles play an essential role in not only the fundamental theories of non-volatile dust flames but also the robust operation of practical metal fuel burners. The present paper introduces a novel approach to accurately measure the ignition temperature of an isolated particle. Micron-sized single particles are injected downwards into a quartz tube heated externally by a premixed flame near the bottom end. During free fall, a particle, if sufficiently small, closely follows the gas-phase temperature that increases gradually from top to bottom. By measuring the ignition position of the particles, the ignition temperature is determined from the gas-phase temperature profile that is quantified <em>a priori</em>. Applying the approach together with high-speed imagining and diffuse backlight-illumination techniques, the ignition temperature of approximately 30–60 <span><math><mi>μ</mi></math></span>m iron particles in O₂/N₂ mixtures are comprehensively measured at oxygen mole fractions of 10%–50%. The experimental results reveal that the measured ignition temperatures is in the range of 1030–1130<!--> <!-->K that are independent of the oxygen mole fraction and the particle size. In contrast, the particle size significantly influences the ignition probability. Smaller particles have lower probabilities to ignite. At the oxygen mole fraction of 10%, ignition is only observed for iron particles larger than approximately 45 <span><math><mi>μ</mi></math></span>m. For all other cases, ignition is detected for all particle diameters. Possible mechanisms underlying the experimental observations are discussed.</div><div><strong>Novelty and significance statement</strong></div><div>A novel approach to measure the ignition temperature of an isolated, micron-sized particle is developed. Compared to existing methods, the new approach provides a convenient way to determine the ignition temperature accurately and examine the size dependence of the ignition characteristics. For the first time, size-resolved ignition temperatures of isolated iron particles are reported. For a fixed particle diameter, the existence of an ignition probability is revealed. The quantitative experimental results have a high potential to be widely used to validate models of iron particle ignition.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113779"},"PeriodicalIF":5.8,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423854","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":"The improved performance of plasma assisted combustion (PAC) simulations using the fully analytical Jacobian","authors":"Yangyang Ban ,&nbsp;Fan Zhang ,&nbsp;Naiyuan Zhang ,&nbsp;Shenghui Zhong ,&nbsp;Jiajian Zhu ,&nbsp;Yiqiang Pei","doi":"10.1016/j.combustflame.2024.113788","DOIUrl":"10.1016/j.combustflame.2024.113788","url":null,"abstract":"<div><div>The open-source package ZDPlasKin is integrated into OpenFOAM to develop the ZDP-OF platform, facilitating simultaneous computations of plasma discharge and chemical reactions for plasma assisted combustion (PAC) simulations. To address the computational challenges arising from the disparity between plasma and chemical kinetics, a chemical model program providing a novel fully analytic molar concentration-based Jacobian, CKJac, is introduced, which incorporates computation cost minimization (CCM) strategies and a revised third-body reactions treatment to enhance the efficiency of solving Ordinary Differential Equations (ODE). Then, the efficiency, accuracy, and applicability of CKJac in handling stiff reactions are evaluated by comparing it with other chemistry models, such as pyJac and Standard (a native chemical model in OpenFOAM). The KLU sparse linear algebra library and LAPACK dense linear algebra library are integrated into CVODE and seulex. The effectiveness and robustness of CKJac with stiff ODE solvers, CVODE, and seulex are rigorously validated and demonstrated on four academic configurations: the zero-dimensional (0D) autoignition and PAC under adiabatic homogeneous constant-pressure systems, a two-dimensional (2D) turbulent reacting shear layer case, the three-dimensional (3D) Sandia Flame D, and 2D plasma assisted flame propagation configuration. It is found that CVODE exhibits a requirement for tighter tolerances to achieve high accuracy, and when using the internally generated numerical Jacobian, CVODE demonstrates high robustness. Seulex consistently presents high efficiency and comparable accuracy to CVODE. The low efficiency of CVODE is ascribed to the inefficient linear algebraic equation solving brought by the inherent reinitialization problem in CVODE. CKJac+seulex showcases a notable up to twofold speedup, delivering high accuracy under loose tolerances compared to Standard+seulex. Moreover, CKJac exhibits superior performance compared to pyJac in diverse combustion scenarios due to its low time costs associated with omega and Jacobian formulation evaluations. When combing with linear algebra libraries, pyJac+seulex_LAPACK shows high robustness and CKJac+seulex_KLU shows orders of magnitude speedup for large mechanisms tested in this work.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113788"},"PeriodicalIF":5.8,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423855","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 Thickened Flame Model adaptation to weakly stretched flames for non-unity Lewis number mixtures","authors":"S. Poncet,&nbsp;C. Mehl,&nbsp;K. Truffin,&nbsp;O. Colin","doi":"10.1016/j.combustflame.2024.113758","DOIUrl":"10.1016/j.combustflame.2024.113758","url":null,"abstract":"&lt;div&gt;&lt;div&gt;For the study and design of industrial scale combustion systems, the Thickened Flame Model (TFM) is a widely used turbulent combustion model. It allows for the direct resolution of the flame front on Large Eddy Simulation (LES) meshes by artificially thickening the flame front by a factor &lt;span&gt;&lt;math&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, i.e. &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, while the unstretched adiabatic flame speed &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; is preserved. However, when considering differential diffusion effects, the modification of flame reactivity induced by strain rate and curvature is enhanced by the flame thickening process. Especially, at low stretch rates, the derivative of the flame speed with stretch, i.e. the Markstein length &lt;span&gt;&lt;math&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, is multiplied by &lt;span&gt;&lt;math&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;. This induces large errors on the stretched flame speed estimation for mixtures with Lewis numbers &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; far from unity, such as for lean hydrogen/air combustion. The present work proposes a methodology to recover the exact Markstein length of thickened flames, called &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-TFM. This easy-to-implement method relies on a 2-parameters evaluation, which monitors &lt;span&gt;&lt;math&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;. Various Markstein length definitions from literature are considered and estimated using two laminar stretched flame configurations: (i) reactants-to-products counter-flow and (ii) spherical flames. &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-TFM is evaluated for (i) lean 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;/air (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and (ii) stoichiometric C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;8&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;H&lt;sub&gt;18&lt;/sub&gt;/air (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) mixtures at ambient conditions. &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-TFM accurately recovers the targeted Markstein lengths for both mixtures, enabling precise estimation of either consumption or displacement flame speed at low stretch rates. &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-TFM remains fairly accurate even at large strain rates for the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; flame, while on the contrary for the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;mo&gt;&lt;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; flame, the consumption","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113758"},"PeriodicalIF":5.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423987","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":"Kinetic investigations on the β-scission reactions of hydroperoxy methyl-ester radicals and the concerted HO2 elimination reactions of methyl-ester peroxy radicals: Implication for low-temperature combustion modeling of methyl esters","authors":"Tao Li ,&nbsp;Siyu Chen ,&nbsp;Juanqin Li ,&nbsp;Quan Zhu ,&nbsp;Zerong Li","doi":"10.1016/j.combustflame.2024.113787","DOIUrl":"10.1016/j.combustflame.2024.113787","url":null,"abstract":"<div><div>The β-scission reactions of hydroperoxy methyl-ester radicals (•QOOH radicals in methyl esters) and the concerted HO₂• elimination reactions of methyl-ester peroxy radicals (ROO• in methyl esters) are two reaction classes that play a crucial role in terminating the chain reaction during the low-temperature combustion of methyl esters. These reactions are also key contributors to the negative temperature coefficient behavior and ignition inhibition observed in biodiesel. Although limited rate constants for these classes in small methyl esters have been calculated, those in larger methyl ester models are frequently approximated based on analogous alkyl reactions in alkanes. In this study, the isodesmic reaction method is utilized to correct the energy barriers and high-pressure-limit rate constants calculated at the low-level B3LYP method. The objective is to approximate the results obtained with the high-level G4 method. The β-scission class is further categorized into 6 subclasses based on the position of the newly formed C<img>C bond in the olefin ester product and the location of the radical on the reactant and the concerted elimination class is divided into 4 subclasses based on the position of the newly formed C<img>C bond in the olefin ester product and the carbon sites where the -OOH group and the eliminated H atom are situated. High-pressure-limit and pressure-dependent rate rules for subclasses are established by averaging rate constants within each subclass. Notably, substantial disparities are observed between our rate constants and those reported in models for large methyl esters, where rate constants are approximated from analogous alkyl reactions in alkanes. This underscores the significant uncertainty associated with the direct application of alkyl reaction rate constants in biodiesel models. Consequently, a low-temperature oxidation model of methyl octanoate/ethanol is developed through the incorporation of the rate rules derived in this study, resulting in a model that effectively reproduces experimental data within the conditions of a jet-stirred reactor.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113787"},"PeriodicalIF":5.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423806","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 tube experiments and numerical study on ignition delay times of ammonia/oxymethylene ether-2 (OME2) mixtures","authors":"Lingfeng Dai,&nbsp;Jiacheng Liu,&nbsp;Chun Zou,&nbsp;Qianjin Lin,&nbsp;Tong Jiang,&nbsp;Chao Peng","doi":"10.1016/j.combustflame.2024.113783","DOIUrl":"10.1016/j.combustflame.2024.113783","url":null,"abstract":"<div><div>Recently, ammonia (NH₃) becomes an attractive alternative fuel to reduce CO₂ emissions. The combustion of NH₃ mixed with reactive fuels is a feasible solution to the issue of low reactivity. In the present study, the ignition delay times (IDTs) of NH₃/OME₂ were measured in a shock tube at an equivalence ratio of 0.5, two pressures of 1.75 and 10 bar, and a temperature range of 1245–1797 K with OME₂ mole fractions of 0.05, 0.1, and 0.2. The OME₂<img>NH₃ model was proposed including the OME₂ model updated in this work, the NH₃ model optimized in our previous work, and some cross-reactions between nitrogen-containing species and C₁<img>C₄ species. The OME₂<img>NH₃ model well predicts the IDTs and species profiles of NH₃/OME₂ and IDTs and laminar flame speeds of NH₃/OME₁, as well as the IDTs, laminar flame speeds, and species profiles of OME₁ and OME₂. The cross-reactions considered in this work significantly improve the model prediction. The effects of cross-reactions on the high and low-temperature reactivity of NH₃/OME₂ were analyzed in detail. The comparison between the OME₂<img>NH₃ model and the Li-Shrestha model illustrated that the OME₂ model updated in this work significantly improves the model prediction. This research provides archival experimental data for the NH₃/OME₂ ignition and provides insights into the interactions between OME₂ and NH₃ by the detailed numerical simulations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"270 ","pages":"Article 113783"},"PeriodicalIF":5.8,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423809","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}