Combustion and Flame最新文献

{"title":"On the two-stage auto-ignition of butyl nitrite isomers","authors":"Zhaohan Chu ,&nbsp;Wanxiong Liao ,&nbsp;Zhongkai Liu ,&nbsp;Yiru Wang ,&nbsp;Qifeng Hou ,&nbsp;Feng Zhang ,&nbsp;Chung K. Law ,&nbsp;Bin Yang","doi":"10.1016/j.combustflame.2025.114185","DOIUrl":"10.1016/j.combustflame.2025.114185","url":null,"abstract":"<div><div>In response to the interest in nitrogen-containing compounds as energetic materials, an experimental and kinetic study on the low-temperature oxidation of three butyl nitrites isomers, namely n‑butyl (NBN), isobutyl (IBN), and tert‑butyl (TBN) was performed. By measuring their ignition delays in a rapid compression machine (RCM) under 5–15 bar at temperatures from 550 to 630 K, a two-stage ignition behavior was observed for all the three nitrites, with the first-stage delays of TBN being shorter than those of NBN and IBN. A detailed kinetic mechanism was constructed and validated against the experimental data, and the production rate was analyzed to explain the first-stage ignition behavior. Specifically, the N−O bond dissociation reaction initiated the consumption of butyl nitrites isomers in all cases studied, which produced NO and different butoxy radicals (C₄H₉O). In the case of TBN, the decomposition of TC₄H₉O produces CH₃ in the first-stage ignition. The abundant CH₃ radical reacts with NO₂ to produce CH₃O, which further yields HO₂ and CH₂O through the reaction with O₂. The inert HO₂ radical is converted to OH through the reaction HO₂ + NO = OH + NO₂, resulting in the first-stage ignition. Meanwhile, the decomposition of PC₄H₉O and IC₄H₉O produces n-propyl and i-propyl radicals, respectively, in the cases of NBN and IBN. The reaction sequences of n-propyl and i-propyl radicals produce less HO₂ radicals compared with that in TBN, leading to longer first-stage ignition time.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114185"},"PeriodicalIF":5.8,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851750","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":"Performance prediction of high-energy-density material CL-20 based on FP-CL20 chemical kinetics model","authors":"Teng Zhang ,&nbsp;Lang Chen ,&nbsp;Yao Long ,&nbsp;Bin Zhang ,&nbsp;Tuo Yang ,&nbsp;Kun Yang ,&nbsp;Jianying Lu ,&nbsp;Danyang Liu ,&nbsp;Jun Chen","doi":"10.1016/j.combustflame.2025.114180","DOIUrl":"10.1016/j.combustflame.2025.114180","url":null,"abstract":"<div><div>The instantaneous high-energy release characteristic of high-energy-density materials (HEDMs) renders them an essential component of high-energy propellants or explosives. Hence, the prediction of performance of HEDMs is of paramount significance for its engineering application. In this paper, using first-principle molecular dynamics approach with multi-scale shock technique, the detonation reaction process of CL-20 is studied, and the detailed chemical reaction kinetics are analyzed. Combining quantum chemical calculation, the first chemical kinetics model (FP-CL20 model) which contains 153 species and 412 elementary reactions is constructed. The pyrolysis and detonation performance of the CL-20 explosive under experimental conditions are predicted by using the FP-CL20 model. Within the framework of the approximation, the agreement of predicted key physical quantities of pyrolysis and detonation for CL-20 with the experimental results is satisfactory. FP-CL20 model also reveals that reaction N₂O+NO<img>NO₂+N₂ and CO+NO₂<img>NO+CO₂ play key roles in the formation of N₂ and CO₂ under detonation. While different from detonation, NCO+NO<img>N₂+CO₂ and NCO+NO₂<img>CO₂+N₂O are the main reactions for the formation of N₂ and CO₂ under pyrolysis. Within the detonation reaction zone, the oxidation of small molecular N-heterochains (L-NCNCO+OH<img>NCN+HOCO) and small molecular carbon oxides (HOCO+OH<img>CO₂+H₂O) are key reactions that affect the detonation reaction zone time. Our studies offer a novel insight into understanding the pyrolysis and detonation reaction mechanism of CL-20, also paving the way for the construction of chemical kinetics model and the performance prediction of HEDMs.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114180"},"PeriodicalIF":5.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The study on the influence of acceleration on the combustion performance of solid rocket motor","authors":"Jinghui Wang ,&nbsp;Junwei Li ,&nbsp;Ye He ,&nbsp;Bingyin Wang ,&nbsp;Xiaodong Wang ,&nbsp;Qiang Li ,&nbsp;Shidi Ai ,&nbsp;Ningfei Wang","doi":"10.1016/j.combustflame.2025.114189","DOIUrl":"10.1016/j.combustflame.2025.114189","url":null,"abstract":"<div><div>Acceleration can cause adverse effects such as abnormal propellant burning rates and irregular interior ballistics in the combustion chamber. To address the issue of solid rocket motors experiencing high accelerations during highly maneuverable flight, this study conducted firing tests on typical solid propellants under acceleration conditions ranging from 0 g to 150 g. A new burning rate model for aluminized propellants in acceleration fields was developed, and the microscopic combustion mechanism of aluminized propellants under these conditions was elucidated. The results indicate that as acceleration increases, the burning rate gain initially increases and then plateaus. The amplitude of burning rate fluctuations significantly exceeds that of pressure fluctuations. Under acceleration conditions of 30 g to 70 g, the interior ballistic curve during the motor's operation phase shows a non-plateau behavior, characterized by an initial pressure increase and subsequent decrease. The retention and agglomeration of aluminum particles on the propellant burning surface were identified as the primary causes of abnormal changes in propellant burning rate and combustion chamber pressure. Simultaneously, the new burning rate model was employed to calculate the burning rate gain ratios under various acceleration conditions, with a maximum value reaching 1.54. The theoretical calculation of the maximum burning rate gain exhibited an error of 4 % compared to the experimental actual values. Additionally, the inner ballistic variation process under different acceleration conditions was predicted, revealing that the theoretically calculated pressure curves were in close agreement with the measured pressure curve trends.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114189"},"PeriodicalIF":5.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848069","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":"Probing the ozone-assisted low-temperature oxidation chemistry of toluene","authors":"Shuyao Chen ,&nbsp;Bingzhi Liu ,&nbsp;Qiang Xu ,&nbsp;Qingbo Zhu ,&nbsp;Long Zhu ,&nbsp;Zhandong Wang","doi":"10.1016/j.combustflame.2025.114176","DOIUrl":"10.1016/j.combustflame.2025.114176","url":null,"abstract":"<div><div>Toluene is the simplest alkylated aromatic and an important component of transportation fuel. The low-temperature oxidation kinetics of toluene is crucial for the development of advanced combustion engines. In this work, we studied the low-temperature oxidation of toluene in a jet-stirred reactor (JSR) with ozone addition, from the temperature range of 350 K to 785 K. Key intermediates such as formaldehyde, benzaldehyde, benzene, phenol, furfural, benzyl alcohol and cresols were measured and quantified using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The hydroperoxides were also detected, such as hydrogen peroxide, methyl hydroperoxide, and benzyl hydroperoxide. The detailed data were used to evaluate the low-temperature oxidation chemistry of toluene by four models, which were developed by Nancy University, Lawrence Livermore National Laboratory, Politecnico di Milano and RWTH Aachen University. Large deviation between experimental measurement and model prediction was observed, especially for the reaction intermediates. We discussed the differences in predictions by these models, and we tentatively improved the low-temperature combustion kinetics of toluene based on the model from Nancy University, with a particular focus on the reaction network of benzyl and phenyl radical. The reaction of benzyl with ozone was considered in this work, and it is important for benzoxyl radical formation. Additionally, two pathways for the formation of benzyl hydroperoxide were considered, which contributes to a better prediction of benzyl hydroperoxide. This work also focuses on discussing the reaction network of the phenoxy radical with O atom, suggesting that the pathway leading to the C₄H₅ radical and CO is the main reaction channel under our experimental conditions. The improved Nancy model yielded a better prediction for the intermediates and products in the low-temperature oxidation of toluene. This work provides a deeper understanding of the low-temperature oxidation chemistry of alkylated aromatics, which are valuable to improve the reaction network and to develop the low-temperature combustion models of alkylated aromatics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114176"},"PeriodicalIF":5.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The laminar and turbulent flame speed of methanol/ammonia/air, ethyl-acetate/ammonia/air, and dimethoxymethane/ammonia/air under atmospheric and elevated pressures","authors":"Shixing Wang ,&nbsp;Ayman M. Elbaz ,&nbsp;Zhihua Wang ,&nbsp;William L. Roberts","doi":"10.1016/j.combustflame.2025.114187","DOIUrl":"10.1016/j.combustflame.2025.114187","url":null,"abstract":"<div><div>Experiments of the laminar and turbulent flame speed of typical E-fuels blended with ammonia: methanol/ammonia/(CH₃OH/NH₃)/air, ethyl-acetate/ammonia/(EA/NH₃)/air, and dimethoxymethane/ammonia/(DMM/NH₃)/air under atmospheric and elevated pressures (1 and 3 atm) are conducted in a fan-stirred constant volume combustion chamber, with initial temperature of 373 K. The results show that turbulent flame speed (<em>S</em>_T) follow the same ranking order as laminar flame speed (<em>S</em>_L) at fuel-lean side from high to low as: DMM, CH₃OH, and EA; while with ammonia addition, CH₃OH/NH₃ and EA/NH₃ have similar <em>S</em>_L and <em>S</em>_T values; and at fuel-rich side, DMM and EA show increasing <em>S</em>_T and <em>S</em>_T/<em>S</em>_L values than at fuel-lean side Meanwhile, the measured Markstein length (<em>L</em>_b) is decreasing towards the fuel-rich side and even becomes negative for EA. Ammonia addition enhances the turbulent flame wrinkling and deformation from the morphology analyses, and this leads to E-fuel/NH₃ blends always having higher normalized turbulent flame speed (<em>S</em>_T/<em>S</em>_L) than pure E-fuel. Next, we test several different turbulent flame speed correlations composed of (<em>u'</em>/<em>S</em>_L) and (<em>l</em>_T/<em>l</em>_F), it is found that the power exponents of (<em>u'</em>/<em>S</em>_L) and (<em>l</em>_T/<em>l</em>_F) do not necessarily have to be equal; they change as the turbulent regime varies in different zones. <em>S</em>_T/<em>S</em>_L/<em>Ka</em> = <em>a</em>(<em>Da</em>/<em>Le</em>)<em>^b</em> performs best among all correlation types with 0.5 ≤ <em>b</em> ≤ 1 corresponding to the Damköhler's two limits. Comparing three types of Lewis number, it is found that volume based <em>Le</em>_V has the best fitting goodness in the correlation of <em>S</em>_T/<em>S</em>_L/<em>Ka</em> = <em>a</em>(<em>Da</em>/<em>Le</em>)<em>^b</em>. Taking into account the developing flame brush thickness, wrinkling ratio and integral length scale as a function of radius, the flame radius based <em>Da</em>_R correlations are proposed: <em>S</em>_T/<em>S</em>_L/<em>γ</em> = <em>a</em>(<em>Da_R</em>/<em>Le</em>)<em>^b</em> where 0.5 ≤ <em>b</em> ≤ 1 which can unify present experimental data with Lewis number larger than unity and previous data with Lewis number less than unity.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114187"},"PeriodicalIF":5.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848625","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":"Theory of explosion limits of hydrogen/oxygen mixtures","authors":"Jie Liu ,&nbsp;Wenkai Liang ,&nbsp;Chung K. Law","doi":"10.1016/j.combustflame.2025.114186","DOIUrl":"10.1016/j.combustflame.2025.114186","url":null,"abstract":"<div><div>Analytical expressions for the classical Z-shaped pressure-vs-temperature explosion limit curve of hydrogen/oxygen mixtures are expeditiously derived based on the leading-order, algebraically linear reactions between the (H, HO₂, H₂O₂) radicals and the (H₂, O₂) background reactants. The analysis yields a detailed ignition mechanism (DIM) and then a skeletal ignition mechanism (SIM) describing the Z-curve, both of which result in close agreement with those computationally obtained with the original reaction mechanism. The solution leads to the ready identification of the first-second and second-third quadratic limits, the associated lower and upper turning points, and the single first, second, and third limits, with the concomitant demonstration that the conventional second limit, <span><math><mrow><mrow><mo>[</mo><mrow><mi>M</mi></mrow><mo>]</mo></mrow><mo>=</mo><mn>2</mn><msub><mi>k</mi><mn>1</mn></msub><mo>/</mo><msub><mi>k</mi><mn>9</mn></msub></mrow></math></span>, represented by the classical crossover-temperature, is inadequate to describe the transition between the first and third limits. A curvature-reversal, inflection point embedded within the second limit is identified, leading to the precise indication of the controlling transition chemistry between the low- and high-pressure regimes.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114186"},"PeriodicalIF":5.8,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843760","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":"Numerical study on the impact of Nanosecond Repetitively Pulsed discharges on the lean blowout limit for a hydrogen/air swirled flame","authors":"Boris Kruljevic,&nbsp;Stéphane Q.E. Wang,&nbsp;Nicolas Vaysse,&nbsp;Jean-Baptiste Perrin-Terrin,&nbsp;Daniel Durox,&nbsp;Antoine Renaud,&nbsp;Christophe O. Laux,&nbsp;Benoît Fiorina","doi":"10.1016/j.combustflame.2025.114149","DOIUrl":"10.1016/j.combustflame.2025.114149","url":null,"abstract":"<div><div>Plasma-assisted combustion (PAC) using Nanosecond Repetitively Pulsed (NRP) discharges is an efficient method to extend the lean blowout limit of flames, as shown in numerous experiments. In this study, the underlying mechanisms by which NRP discharges extend the lean blowout limit in hydrogen-air flames are analyzed numerically for the first time. The computations are performed using Large Eddy Simulations (LES) coupled with a semi-empirical model for the NRP discharges. The blowout is triggered at constant hydrogen mass flow rate (i.e., constant flame thermal power) through a very slow increase of the injected air mass flow rate, resulting in a decrease of the global equivalence ratio. A PAC configuration featuring NRP discharges at a frequency of 15 kHz and a 1.5 mJ deposited energy per pulse is computed, for which the experiments have shown a 20% reduction of the lean blowout equivalence ratio, by using NRP discharges. The case without plasma is also computed. These two configurations are first compared in terms of combustion efficiency. Next, results of blowout simulations are presented. The LES is able to predict the blowout equivalence ratios accurately for both the case without plasma (0.9% error) and with the NRP discharges (2.8% error). In the case without plasma, blowout is triggered through the dilution of burnt gases by fresh gases, which penetrated the inner recirculation zone at sufficiently low global equivalence ratios. Plasma triggers the oxidation of these pockets of fresh gases, resulting in the production of radicals and heat, which stabilizes the flame.</div><div><strong>Novelty and Significance Statement</strong></div><div>This is the first time that simulations are performed of a plasma-assisted combustion (PAC) experiment in pure hydrogen flames. Also, for the first time, a PAC phenomenological model (Castela et al., 2016) is used to predict the lean blowout (LBO) limit of a flame assisted by plasma and the results are evaluated through comparisons with experimental data. The interactions between the flame and the Nanosecond Repetitively Pulsed (NRP) discharges at the LBO limit are studied numerically. The NRP discharges promote the oxidation of pockets of fresh gases, resulting in the production of radicals and heat, which stabilizes the flame and extends the LBO limit.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114149"},"PeriodicalIF":5.8,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843761","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 NO in the post-flame region of laminar premixed ammonia/hydrogen/nitrogen-air flames using laser induced fluorescence","authors":"M. Richter ,&nbsp;J. Lill ,&nbsp;R.S. Barlow ,&nbsp;A. Gruber ,&nbsp;A. Dreizler ,&nbsp;J.R. Dawson ,&nbsp;D. Geyer","doi":"10.1016/j.combustflame.2025.114139","DOIUrl":"10.1016/j.combustflame.2025.114139","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Ammonia-based fuels have been identified as a promising alternative as zero-carbon energy carriers due to their high energy density and simpler logistics compared to hydrogen. As a disadvantage, the presence of fuel-bound nitrogen can lead to order of magnitude higher emissions of undesired nitric oxide (NO), nitrogen dioxide (NO&lt;sub&gt;2&lt;/sub&gt;) and nitrous oxide (N&lt;sub&gt;2&lt;/sub&gt;O) compared to more conventional fuels. Presently, chemical kinetics schemes for the combustion of ammonia and ammonia blends show large variations in the prediction of NO and there is a lack of quantitative experimental data to validate and optimize these reaction mechanisms. This paper presents measurements of NO in the product gases of laminar premixed NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/N&lt;sub&gt;2&lt;/sub&gt; air flames on a flat-flame burner for 4 different ammonia decomposition ratios and over a range of equivalence ratios using laser-induced fluorescence in the NO A-X (0,1) system. A linear calibration approach based on the addition of NO to a lean premixed CH&lt;sub&gt;4&lt;/sub&gt; flame is presented. Initial signal treatment includes the correction of laser absorption, fluorescence absorption (signal trapping) and fluctuations in laser energy. The LIF signals are corrected for changes in the Boltzmann fraction, line overlap, number density, and quenching between calibration and measurement, which requires knowledge of the local temperature and mole fractions of the main species. Temperature measurements using N&lt;sub&gt;2&lt;/sub&gt; thermometry, where a theoretical N&lt;sub&gt;2&lt;/sub&gt; Raman spectrum is fitted to an experimental N&lt;sub&gt;2&lt;/sub&gt; Raman signal, excited by a 532 nm cw laser, allow characterization of the local near-adiabatic flame conditions as a function of operating conditions and adjustment of the signal corrections to the local temperature. Major species are extracted from 1-D simulations. The measured NO mole fractions are compared with five recent chemical kinetic schemes, which show good agreement for rich mixtures, however, a systematic underprediction of NO is found for stoichiometric and lean mixtures.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;Emissions of NO are a major challenge for advancement of ammonia as a carbon-free fuel, yet very few measurements of NO levels in ammonia flames exist in the literature. In this paper, we present much needed quantitative experimental data on NO emissions from premixed NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/N&lt;sub&gt;2&lt;/sub&gt;-air flames using laser-induced fluorescence (LIF). Our diagnostic approach employs a linear calibration method based on the addition of NO to a lean CH&lt;sub&gt;4&lt;/sub&gt; flame. Post-flame temperatures are measured by Raman spectroscopy to ensure accuracy of the local thermochemical states used in converting LIF signals to quantitative NO concentrations, accounting for variations in number density, electronic quenching, Boltzmann fraction, and the line overlap integral. Additionally, laser absorption and signal trapping ar","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114139"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834718","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":"Volumetric heat release, fuel-air mixing and turbulent dissipation of vertically-downward turbulent nonpremixed jet flames under sub-atmospheric pressures","authors":"Hongyu Lu ,&nbsp;Jiang Lv ,&nbsp;Xiaolei Zhang ,&nbsp;Jong Moon Lee ,&nbsp;Chun Sang Yoo ,&nbsp;Suk Ho Chung ,&nbsp;Longhua Hu","doi":"10.1016/j.combustflame.2025.114161","DOIUrl":"10.1016/j.combustflame.2025.114161","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In this study, volumetric heat release rate (related to flame radiation characteristics), fuel-air mixing, and turbulent dissipation rate of vertically-downward nonpremixed jet flames under standard- and various sub-atmospheric pressures are investigated, which have not been quantified yet. The interaction of downward jet momentum and upward buoyancy influences flow turbulence and fuel-air mixing. Experiments are conducted in a reduced-pressure chamber with controlled ambient pressures from 40 to 101 kPa. The flame volume and volumetric heat release rate are experimentally determined through image processing. Three-dimensional large eddy simulations are performed to further understand fuel-air mixing and flame behaviors. A quantitative agreement is obtained between the measured and calculated flame volumes. Results show that the turbulent dissipation rate &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ε&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; of vertically-downward jet flame is stronger and distributes more broadly than that of the upward jet flame because of the rapid deceleration of jet momentum by the buoyancy. As the pressure decreases, more intense turbulent kinetic energy and turbulence dissipation rate are observed. The flame volume &lt;em&gt;V&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt; for the vertically-downward jet flame is found to increase as heat release rate &lt;span&gt;&lt;math&gt;&lt;mover&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt;&lt;/math&gt;&lt;/span&gt; increases and decreases with the increase of ambient pressure. The flame volume has a power relation as &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;V&lt;/mi&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/msub&gt;&lt;mrow&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;/mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and on ambient pressure &lt;em&gt;P&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; as &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;V&lt;/mi&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;msubsup&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. Moreover, the volumetric heat release rate scales satisfactorily with &lt;em&gt;P&lt;/em&gt;&lt;sub&gt;c&lt;/sub&gt; as &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt;&lt;mrow&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;″&lt;/mo&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/mrow&gt;&lt;msubsup&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;mrow&gt;&lt;mi&gt;c&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The differences of &lt;em&gt;V&lt;/em&gt;&lt;sub&gt;f&lt;/sub&gt; (or &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mover&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;mo&gt;˙&lt;/mo&gt;&lt;/mover&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;″&lt;/mo&gt;&lt;mo&gt;′&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) among pool-type flame (purely buoyancy driven), upward jet flame and downward jet flame are revealed and explained by turbulent dissipation rate and fuel-air mixing characteristics. A general global dimensionless model for flame volume of downward jet flame is proposed by taking into account the initial jet momentum, flame buoyancy, and ambient air pressure, in which a new dimensionless heat release rate is defined based on two derived length scales (momentum-buoyancy competitio","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114161"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143835315","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 modeling investigation of nitrogen-containing product formation during N,N-dimethylformamide (DMF) oxidation in a jet-stirred reactor (JSR)","authors":"Su Zhang,&nbsp;Fuheng Xia,&nbsp;Meijun Fan,&nbsp;Yixiang Zhang,&nbsp;Guan Wang,&nbsp;Bin Liu,&nbsp;Yongqiang Chen,&nbsp;Yili Zhang,&nbsp;Renhui Ruan,&nbsp;Xuebin Wang","doi":"10.1016/j.combustflame.2025.114188","DOIUrl":"10.1016/j.combustflame.2025.114188","url":null,"abstract":"<div><div>The oxidation of N, N-dimethylformamide (DMF) was investigated both experimentally and numerically. Experiments were carried out in a fused silica jet-stirred reactor (JSR) under atmospheric pressure covering a temperature range of <em>T</em> = 500–900 °C with different equivalence ratio (φ=0.5, 0.7, 0.9 and 1.2). A detailed analysis of the main nitrogen-containing products and intermediates was performed, and the results were interpreted with an improved kinetic model, describing the oxidation mechanism of DMF and the nitrogen conversion path. The measurements suggest that the primary nitrogen-containing products of DMF oxidation are HCN, NO, and N₂O, with HCN identified as a key intermediate. Kinetic analysis shows that higher temperatures promote H₂CN decomposition to stimulates the production of HCN, while increased O₂ levels enhance OH radical production, which facilitates the conversion of HCN to NO and N₂O. At 750 °C, flux analysis elucidated the main conversion pathways for NO and N₂O, providing valuable information for optimizing combustion and emissions control processes. The main conversion pathway of NO is Fuel-N→CH₃N(CH₂)CHO→CH₃NCH₂→CH₂NCH₂→H₂CN→HCN→NCO→HNCO→NH₂→H₂NO→HNO→NO, while the main conversion pathway of N₂O is Fuel-N→CH₃N(CH₂)CHO→CH₃NCH₂→CH₂NCH₂→H₂CN→HCN→NCO→N₂O. The findings offer important implications for reducing nitrogen-based pollutants in industrial applications, contributing to a more sustainable approach to DMF oxidation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114188"},"PeriodicalIF":5.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143839445","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}