Combustion and Flame最新文献

{"title":"Real-gas effects on explosion limits of hydrogen–oxygen and methane–oxygen mixtures at elevated pressures","authors":"Jianhang Li ,&nbsp;Wenkai Liang ,&nbsp;Wenhu Han ,&nbsp;Minne Du ,&nbsp;Chung K. Law","doi":"10.1016/j.combustflame.2024.113891","DOIUrl":"10.1016/j.combustflame.2024.113891","url":null,"abstract":"<div><div>The explosion limits of hydrogen–oxygen (H₂–O₂) and methane–oxygen (CH₄–O₂) mixtures under high-pressure, supercritical conditions are analyzed computationally. It is shown that the non-ideal effects of the ignition delay time (IDT) occur at pressures above 100 atm, with the extent enhanced with increasing pressure. This causes the third limit for the H₂–O₂ mixture to move towards lower temperatures. Sensitivity analysis then identifies the reaction mechanisms responsible for the observed behavior. It is further shown that the main species, namely fuel and oxidant as well as H₂O₂ radical, affecting the explosion limit of real-gas properties are determined by perturbing the attraction parameter (<span><math><mi>a</mi></math></span>) and repulsive volume correction parameter (<span><math><mi>b</mi></math></span>) of each species in the Redlich–Kwong equation of state. It is shown that fuel and oxidant play essential roles in the triggering the non-ideal effects in the system, and H₂O₂-related reactions are important at high pressures. Furthermore, the parameters <span><math><mi>a</mi></math></span> and <span><math><mi>b</mi></math></span> have different behaviors on the third explosion limit. The latter has a stronger influence on the explosion limit than the former, on account of the temperature of the explosion boundary decreases with increasing pressure. Moreover, the deviation tendency of the explosion limit of H₂–O₂ and CH₄–O₂ mixtures is also applicable to different equivalent ratios and dilutions with the real-gas effects. Results of this study are expected to provide new guidance for future investigations of explosion limits at high pressures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113891"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102617","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":"Advancing the C4 low-temperature oxidation chemistry through species measurements in a rapid compression machine. Part B: n-Butane","authors":"Jesus Caravaca-Vilchez ,&nbsp;Jiaxin Liu ,&nbsp;Pengzhi Wang ,&nbsp;Yuki Murakami ,&nbsp;Yingtao Wu ,&nbsp;Henry J. Curran ,&nbsp;Karl Alexander Heufer","doi":"10.1016/j.combustflame.2024.113861","DOIUrl":"10.1016/j.combustflame.2024.113861","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Studying the oxidation of &lt;em&gt;n&lt;/em&gt;-butane, a major component of LNG, is critical to improve the efficiency of transportation engines. Furthermore, its negative temperature coefficient (NTC) behavior provides insights into the oxidation of larger hydrocarbons. Several studies have investigated &lt;em&gt;n&lt;/em&gt;-butane oxidation at engine-operating pressures using various methods, including ignition delay time (IDT) measurements in rapid compression machines (RCMs) and shock tubes, flame velocities, and species concentrations in flow reactors. While these species measurements provide deeper insights into oxidation networks than IDTs, they are limited to either low-pressure or highly diluted conditions. To address this gap, this study measures species concentrations during &lt;em&gt;n&lt;/em&gt;-butane oxidation at 30 bar in the NTC region (742 K and 855 K, respectively), at stoichiometric and moderate dilution levels in an RCM. A novel two-valve setup allowed gas sample extraction for off-line gas chromatography-mass spectrometry analysis. Complementary IDT data were obtained in the temperature range of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;680&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;910&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; K, at pressures of 15 and 30 bar, and equivalence ratios of 0.5, 1.0, and 2.0. The results suggest that while current &lt;em&gt;n&lt;/em&gt;-butane models reasonably predict its autoignition characteristics, they fall short in predicting the formation of key oxidation intermediates at engine-relevant conditions. In this context, the &lt;em&gt;n&lt;/em&gt;-butane submechanism within the NUIGMech1.3 framework was updated. Modifications involve recently computed thermochemical data for critical intermediates and adjustments to rate constants, using analogies with structurally similar molecules such as &lt;em&gt;n&lt;/em&gt;-propane and &lt;em&gt;n&lt;/em&gt;-pentane. The present model reproduces reasonably well both the measured IDT and species concentrations documented herein and data from the literature. Nevertheless, the model slightly underestimates the reactivity within the NTC domain and the formation of some intermediates at the NTC peak. This study highlights the importance of integrating species concentration and IDT measurements at application-relevant conditions to refine kinetic mechanisms and significantly advances the understanding of C&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; hydrocarbon oxidation chemistry.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;The novelty of this research lies in the measurement of species concentrations during the ignition delay of &lt;em&gt;n&lt;/em&gt;-butane mixtures in an RCM at high pressures near the NTC minimum and maximum using a novel two-valve gas sampling setup. This, in combination with new thermochemical data and rate rules based on analogies with propane and &lt;em&gt;n&lt;/em&gt;-pentane, allowed the refinement of the &lt;em&gt;n&lt;/em&gt;-butane sub-mechanism within the NUIGMech1.3 framework.&lt;/div&gt;&lt;div&gt;By combining species concentration measurements w","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113861"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103015","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":"Shock activation theory for aluminum nano-particles outside high explosives","authors":"Zhandong Wang,&nbsp;Fang Chen,&nbsp;Peng Liu,&nbsp;Yang Zhou,&nbsp;Chuan Xiao","doi":"10.1016/j.combustflame.2024.113882","DOIUrl":"10.1016/j.combustflame.2024.113882","url":null,"abstract":"<div><div>Recent research has revealed that aluminum nanoparticles (ANPs) can also be activated by shock waves when positioned outside high explosives. To explore the shock activation of the ANPs in the composite explosive (where ANPs are placed outside high explosives), the shock activation theory for ANPs is proposed. According to this theory, ANPs heat up from initial state to a critical reaction state due to both shock work and plastic work. To verify this theory, we conducted four rounds of explosion experiments in an enclosed space, varying ANP layer thicknesses and measuring quasi-static pressure to estimate the activation efficiency of the ANPs. The experimental results show that, as the ANP layer thickness increases from 0.44 mm to 0.94 mm and 1.90 mm, the activation degree of ANPs decreases from 59.4% to 44.8% and 46.5%, respectively. This indicates that thicker ANP layers result in lower activation efficiencies. Notably, all experimental results fall within the range of theoretical predictions, confirming the reliability of the shock activation theory for ANPs. Further research indicates that the activation efficiency of ANPs can be regulated by increasing the detonation velocity of the inner explosive and adjusting the fill ratio of the ANP layer, thereby enhancing the total energy of the composite charge. Our study provides a new perspective on the activation mechanism of ANPs outside high explosives and offers theoretical references for regulating energy output in explosive charges.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113882"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103135","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":"High-pressure conversion of ammonia additivated with dimethyl ether in a flow reactor","authors":"Pedro García-Ruiz,&nbsp;Pablo Ferrando,&nbsp;María Abián,&nbsp;María U. Alzueta","doi":"10.1016/j.combustflame.2024.113875","DOIUrl":"10.1016/j.combustflame.2024.113875","url":null,"abstract":"<div><div>The oxidation of ammonia (NH₃) mixed with dimethyl ether (DME) was investigated from experimental and modeling points of view using a quartz flow reactor with argon as bath gas from 350 K to 1225 K, for two different DME/NH₃ ratios (0.05 and 0.3), three oxygen excess ratios (λ = 0.7, 1 and 3) and various pressures (1, 10, 20 and 40 bar).</div><div>The effect of pressure, oxygen stoichiometry, temperature, and DME/NH₃ ratio has been analyzed on DME, NH₃, NO, NO₂, N₂O, N₂, O₂, H₂, HCN, CH₄, CO, and CO₂ concentrations.</div><div>The present study indicates that oxygen availability, DME/NH₃ ratio, and pressure are important variables that shift NH₃ and DME conversion to lower temperatures as their values increase. Under certain conditions, the pressure effect can avoid NO and HCN production, which would represent a benefit for pressure applications.</div><div>The main products of ammonia/dimethyl ether oxidation are N₂, N₂O, CO, and CO₂, and under certain conditions, NO, H₂, CH_4, and HCN are also produced. NO₂ is always detected below 5 ppm for all the conditions considered. The N₂O formation is favored by increasing the O₂ stoichiometry, pressure, and/or DME/NH₃ ratio.</div><div>The experimental results are interpreted and discussed in terms of an updated detailed chemical kinetic mechanism, which captures, with a general good agreement, the main trends of NH₃ and DME conversion under the considered conditions. Despite this, some calculated species present discrepancies with the experimental results. The main challenge is the consideration of the C-N interactions that can be present in the combustion of DME/NH₃ mixtures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113875"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103016","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":"Understanding key interactions between NOx and C2-C5 alkanes and alkenes: The ab initio kinetics and influences of H-atom abstractions by NO2","authors":"Hongqing Wu ,&nbsp;Ruoyue Tang ,&nbsp;Xinrui Ren ,&nbsp;Mingrui Wang ,&nbsp;Guojie Liang ,&nbsp;Haolong Li ,&nbsp;Song Cheng","doi":"10.1016/j.combustflame.2024.113885","DOIUrl":"10.1016/j.combustflame.2024.113885","url":null,"abstract":"<div><div>This study aims to reveal the important role and the respective rate rules of H-atom abstractions by NO₂ for better understanding NO_X/hydrocarbon interactions. To this end, H-atom abstractions from C₂-C₅ alkanes and alkenes (15 species) by NO₂, leading to the formation of three HNO₂ isomers (<em>trans</em>-HONO, HNO₂, and <em>cis</em>-HONO) and their respective products (45 reactions), are first characterized through quantum chemistry computation, where electronic structures, single point energies, C-H bond dissociation energies and 1-D hindered rotor potentials are determined at DLPNO-CCSD(T)/cc-pVDZ//M06–2X/6−311++g(d,p). The rate coefficients for all studied reactions, over a temperature range from 298.15 to 2000 K, are computed using transition state theory with the Master Equation System Solver program. Comprehensive analysis of branching ratios elucidates the diversity and similarities between different species, HNO₂ isomers, and abstraction sites, from which accurate rate rules are determined. With the rate rules, the rate coefficients at various reaction sites on heavier hydrocarbons (e.g., &gt; C₅) can be reliably estimated by analogy. Incorporating the updated rate parameters into a detailed chemical kinetic model reveals the significant influences of this type of reaction on model prediction results, where the simulated ignition delay times are either prolonged or reduced, depending on the original rate parameters presented in the selected model. Sensitivity and flux analysis further highlight the critical role of this type of reaction in affecting system reactivity and reaction pathways, emphasizing the need for adequately representing these kinetics in existing chemistry models. This can now be sufficiently achieved for alkanes and alkenes based on the results from this study.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113885"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and fuel-surrogates modeling study of the oxidation of specialty cetane number fuels","authors":"Mohammed Abdulrahman ,&nbsp;Subharaj Hossain ,&nbsp;P.T. Lynch ,&nbsp;Eric K. Mayhew ,&nbsp;K. Brezinsky","doi":"10.1016/j.combustflame.2024.113910","DOIUrl":"10.1016/j.combustflame.2024.113910","url":null,"abstract":"<div><div>Single pulse shock tube experiments were performed at 50 atm nominal pressure and 4 milliseconds nominal reaction time over a temperature range of 900–1800 K, to study the oxidation speciation of a multicomponent jet fuel, F-24, and six cetane number (CN) specialty fuels - CN30, CN35, CN40, CN45, CN50, and CN55. The oxidation experiments were carried out at an equivalence ratio of approximately 1.0. Gas chromatography (GC) was used to quantitatively and qualitatively analyze the post shock gases. The correlation between the formation of critical oxidation species and the chemically controlled combustion propensity as reflected by the cetane number of each fuel was investigated. The species were simulated using a surrogate-based mechanism from the CRECK Modelling Group. The species produced from the oxidation of the CN fuels were initially modeled using optimized chemical composition surrogates, but with less than satisfactory agreement. Efforts to enhance the agreement of experiment with model results by increasing the iso-paraffinic content in the surrogates did not yield significant improvements. Subsequently, the aromatic content of the surrogates was adjusted, resulting in surrogates whose model predicted oxidation species better matched the experimental data. Rate of production, sensitivity and reaction path analyses using the surrogate model were performed to obtain the important reactions responsible for the formation of key species and to examine the chemistry of complex multicomponent fuel systems. The primary reactions responsible for driving the oxidation chemistry were largely influenced by the chemical functional groups present in the fuels. In addition, the study highlights the effectiveness of the fuel-surrogate approach where surrogates representing the chemical functional group composition of the parent fuel serve as a valuable tool for predicting the combustion chemistry of unknown fuels.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113910"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103022","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":"Synchrotron vacuum ultraviolet photoionization mass spectrometry to examine low temperature oxidation chemistry of n-heptane under different fuel concentrations and pressures","authors":"Weiye Chen ,&nbsp;Bingzhi Liu ,&nbsp;Hao Lou ,&nbsp;Bin Dong ,&nbsp;Cheng Xie ,&nbsp;Jiuzhong Yang ,&nbsp;Long Zhu ,&nbsp;Zhandong Wang","doi":"10.1016/j.combustflame.2024.113898","DOIUrl":"10.1016/j.combustflame.2024.113898","url":null,"abstract":"<div><div>The study of low temperature oxidation provides valuable insight into the development of low temperature combustion (LTC) engines. Fuel concentration and pressure are the keys to controlling reaction activities, significantly influencing low temperature oxidation behavior. Understanding the effects of these parameters is important to develop and improve the kinetic models, however, the impact of fuel concentration and pressure is rarely examined in the low temperature oxidation process of hydrocarbons. In this work, <em>n</em>-heptane oxidation, with initial fuel mole fractions of 0.1 %, 0.25 % and 0.5 % and pressures of one, five and ten bar, was examined at 440–800 K. The goal was to investigate the influence of these key parameters on <em>n</em>-heptane low temperature oxidation. First, reactivity and formation of products was promoted by increasing the initial fuel concentration; there was a threshold for the initial fuel concentration, and reactions occurred only when it was higher than the threshold at a fixed pressure and residence time. However, the model in the literature was unable to capture this phenomenon. Species profiles were compared with the prediction of the kinetic model in the literature at three initial fuel concentrations and pressures; simulation results were verified, and the different pressure effects on product formation were observed. A preliminary analysis of the reaction mechanism was conducted using the kinetic model for clarification of the pressure effects. Finally, the selectivity of products under one and ten bar was revealed. In general, hydroperoxides and carboxylic acids, etc., displayed positive selectivity, while olefins and cyclic ethers, etc., showed negative selectivity at high pressures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113898"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143103026","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 novel method of efficiently using the experimental data for mechanism optimization: Theory and application to NH3/H2 combustion","authors":"Kexiang Guo ,&nbsp;Rui Fu ,&nbsp;Chun Zou ,&nbsp;Wenyu Li ,&nbsp;Weijia Shen","doi":"10.1016/j.combustflame.2024.113886","DOIUrl":"10.1016/j.combustflame.2024.113886","url":null,"abstract":"<div><div>In this work, a novel method of efficiently using the experimental data (EUED) is proposed to reduce the computational cost of evaluating the objective function. The EUED method involves splitting the full experimental dataset into several subsets that retain the essential features of the full dataset's effects on the influential reactions, with these subsets used in rotation during the iterations. The constraint probability density function (PDF) of the constraint frequency distribution spectrum of the influential reactions reflects the essential features of the experimental data's effects. Thus, the subsets should meet 2 criteria: first, the union of all subsets must equal the full dataset; second, the PDF of the frequency spectrum of the influential reactions in any subset should align with that of the full dataset. A strategy for allocating data into several subsets is proposed. An optimized NH₃ combustion model was developed using the EUED method. The prediction errors are 1.22 for species concentrations during pyrolysis, 1.67 for ST-IDT, 1.45 for species concentrations during oxidation, 1.84 for LBV, and 4.29 for RCM-IDT measurements, respectively. The 200 ST-IDT measurements, 911 LBV measurements and 172 RCM-IDT measurements are split into 4, 10 and 4 subsets, respectively. This approach reduces the computational costs of evaluating the objective function at each iteration by about 80 % during the NH₃ model optimization. The roles of the unimolecular decomposition reactions of NH₃, 2 H-abstraction reactions of NH_i by H and 4 reactions involving NH_i in NH₃ pyrolysis were discussed in detail. The optimization automatically weighs the rate constants of the 7 important reactions in an extraordinarily tangled and complicated reaction network, leading to satisfactory predictions of the NH₃, NH₂ and NH profiles.</div></div><div><h3>Novelty and Significance Statement</h3><div>In this work, a novel method of efficiently using the experimental data (EUED) is proposed to reduce the computational cost of evaluating the objective function. The idea of the EUED method is that the full experimental dataset is split into several subsets which remain the essential feature of the effects of full experimental data on the influential reactions, and the several subsets are used in rotation in the iteration. An optimized NH₃ combustion model was obtained using the EUED method with reducing 80 % computational costs of evaluating the objective function. The optimized NH₃ model outperforms the initial one and the models considered in this work.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113886"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102429","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":"Ignition and flame development of high-pressure liquid ammonia spray combustion with simultaneous high-speed OH* and NH2* chemiluminescence imaging","authors":"Haoqing Wu,&nbsp;Yong Qian,&nbsp;Tianhao Zhang,&nbsp;Jizhen Zhu,&nbsp;Xingcai Lu","doi":"10.1016/j.combustflame.2024.113899","DOIUrl":"10.1016/j.combustflame.2024.113899","url":null,"abstract":"<div><div>Liquid ammonia, benefiting from its convenient storage and high hydrogen content, has gained widespread attention as a carbon-free fuel for combustion devices to achieve carbon emission reduction. In this study, the ignition and flame development characteristics of liquid ammonia spray flame are analyzed with simultaneous high-speed OH*, NH₂* chemiluminescence and flame luminosity imaging. The test is conducted at the ambient pressure of 3 MPa, the ambient temperature of 950 K, and the injection pressure of 40 MPa. The results revealed that liquid ammonia spray flame can be divided into four stages: 1) the ignition process with the appearance of auto-ignition kernels at the jet front; 2) the flame propagation process with auto-ignition kernels expanding to the central spray region; 3) the fully-developed combustion process with the flame filling the core region; 4) the post-combustion process with the flame area decreasing rapidly. OH* signals were first observed at the jet front, and NH₂* signals were observed after OH* signals appeared in aggregated form. Throughout the combustion process, OH* had a wide distribution and a long duration, while the NH₂* not only appeared later but dissipated earlier, and the distribution was smaller than the OH*. Chemical kinetic analysis showed that the primary elementary reactions to produce OH at the ignition moment were O+H₂O=2OH, H+O₂=OH+O, and H₂+O=H+OH, while NH₂ was mainly formed through NH₃+OH=NH₂+H₂O. It was worth noting that after the combustion end, sporadic flames and NH₂* signals can still be observed in the jet region.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113899"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102432","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 speciation study of DME, OME1, and OME2 in a single-pulse shock tube at high pressures","authors":"Fabian Lindner ,&nbsp;Marina Braun-Unkhoff ,&nbsp;Clemens Naumann ,&nbsp;Torsten Methling ,&nbsp;Markus Köhler ,&nbsp;Uwe Riedel","doi":"10.1016/j.combustflame.2024.113883","DOIUrl":"10.1016/j.combustflame.2024.113883","url":null,"abstract":"<div><div>The pyrolysis of dimethyl ether (DME), oxymethylene ether-1 (OME₁), and oxymethylene ether-2 (OME₂) and their oxidation with oxygen under three different equivalence ratios (<em>φ</em> = 0.5, 1.0, and 2.0) have been studied experimentally in a customized single-pulse shock tube. The measurements were carried out highly diluted in argon over a wide temperature range between 975 K and 1400 K at initial pressures behind reflected shock waves <em>p</em>₅(<em>t</em> = 0) of about 16 bar. The classical single-pulse mode involving a dump tank was not employed. Instead, post-shock gas samples were extracted through a fast-acting solenoid valve located inside the end flange of the driven section of the shock tube, to reduce measurement errors from thermal boundary layers. Thirteen stable species were identified and quantified by three different gas chromatographs simultaneously, in detail, DME, OME₁, OME₂, methane, ethane, ethene, acetylene, carbon monoxide, carbon dioxide, molecular hydrogen, formaldehyde, methanol, and methyl formate. The temperature dependent, measured, and normalized species concentration profiles were compared with the predicted species profiles obtained by using two different chemical kinetic reaction mechanisms from the literature and an updated version of the in-house reaction model DLR Concise. In addition, speciation data of 1,1,1-trifluoroethane and nitrous oxide at elevated pressures are presented, which were used as external chemical thermometers to validate the calculated temperature behind the reflected shock wave of the single-pulse shock tube.</div></div><div><h3>Novelty and Significance</h3><div>In this work, a series of more than 300 single-pulse shock tube experiments have been performed, to investigate the decomposition products of oxygenated fuels at pressures around 16 bar. To the best of our knowledge, no speciation data is yet available for this pressure regime. By comparing the data with chemical-kinetic reaction mechanisms from the literature, opportunities for model improvement have been identified, particularly regarding methanol formation, which could be further developed in the future.</div><div>The presented high-pressure validation data contributes to the development of chemical-kinetic reaction models for new oxygenated fuels derived from renewable sources. By incorporating these reaction mechanisms into CFD codes, advancements in combustors and engine technology are facilitated, promoting cleaner combustion processes.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113883"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102425","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}