Combustion and Flame最新文献

{"title":"Detailed validation of LES for H2/CH4/Air deflagrations in an obstructed tube using PIV measurements","authors":"Loïc De Nardi ,&nbsp;Francis Adrian Meziat Ramirez ,&nbsp;Yecine Djebien ,&nbsp;Quentin Douasbin ,&nbsp;Omar Dounia ,&nbsp;Olivier Vermorel ,&nbsp;Thierry Poinsot","doi":"10.1016/j.combustflame.2024.113879","DOIUrl":"10.1016/j.combustflame.2024.113879","url":null,"abstract":"<div><div>This study offers a detailed validation of Large Eddy Simulation (LES) for lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>/Air deflagrations in an obstructed tube. An exhaustive validation is conducted against detailed measurements from Li et al. (2019), which include pressure traces, flame speeds, and especially, Particle Image Velocimetry measurements of the deflagration-induced flow field. The exercise is performed without adjusting any model parameters, so that all simulations are executed using a unique numerical setup across all test cases. This approach provides a robust and unbiased assessment of LES capabilities in capturing the complex interactions between flame propagation, turbulence, and obstacles in explosion scenarios. Results demonstrate that LES accurately predicts the detailed evolution of the flow field in the recirculation zone behind the second obstacle, and the resulting over-pressure as well as flame speed and flame qualitative shape for various deflagration severities. Such results highlight the potential of LES for improving Safety Computational Fluid Dynamics predictive capabilities in industrial applications involving explosive environments. Once validated, LES is analyzed to unravel flame propagation dynamics: It is demonstrated that the flame remains laminar-like up to the second obstacle and then transitions to the turbulent combustion regime. Independently from the mixture blend, the maximum over-pressure is correlated to flame-turbulence interactions occurring in the wake of the second obstacle. While LES effectively captures these dynamics, it is noted that usual methods to quantify flows in pipes are inadequate for fully characterizing the transition to turbulence: Developing more refined indicators to detect this transition are required.</div><div><strong>Novelty and significance statement</strong></div><div>This study presents a significant advancement in the validation of Large Eddy Simulation (LES) for complex deflagration scenarios within obstructed geometries. Unlike previous works that typically rely on pressure data, flame speeds, and basic visualizations, this research integrates comparisons to Particle Image Velocimetry measurements for a quantitative validation of LES deflagrations in obstructed channels. By leveraging the detailed experimental dataset from Li et al. (2019), this paper establishes a new benchmark for simulation accuracy, demonstrating LES ability to capture complex flame-turbulence interactions in confined spaces. This work not only addresses the critical gap in the literature but also opens the way for advancements in Safety Computational Dynamics, setting a higher standard for future simulation studies.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113879"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102424","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 study of ammonia combustion induced by high reactivity fuel based on optical diagnostics and chemical kinetic analyses","authors":"Mingsheng Wen ,&nbsp;Haifeng Liu ,&nbsp;Shouzhen Zhang ,&nbsp;Zongyu Yue ,&nbsp;Yanqing Cui ,&nbsp;Zhenyang Ming ,&nbsp;Lei Feng ,&nbsp;Mingfa Yao","doi":"10.1016/j.combustflame.2024.113896","DOIUrl":"10.1016/j.combustflame.2024.113896","url":null,"abstract":"<div><div>Ammonia is considered an optimal alternative fuel due to its non-emission of CO₂. However, the use of pure ammonia presents significant challenges. A dual fuel approach utilizing ammonia and high reactivity fuel (HRF) is expected to address these challenges. Nevertheless, the interaction mechanism between ammonia and HRF remains unclear. In the current study, various direct injection (DI) fuels such as n-heptane, n-dodecane, and n-dodecane mixed with 3%_vol 2-ethylhexyl nitrate (EHN) were selected. Optical diagnostic methods and kinetic analyses were employed to investigate the effects of DI fuel reactivity and DI energy ratio on the dual fuel method adopting HRF and ammonia. Experimental results reveal that DI fuel reactivity and DI energy ratio determine the ability to ignite ammonia and influence flame development mode, respectively. Notably, the n-dodecane/EHN blend can operate at a 4% DI energy ratio, with a flame speed of less than 5 m/s, while at a 40% DI energy ratio, the flame speed increases to 10–15 m/s. Emissions at the 40% DI energy ratio include 4373 ppm of NO, 41.4 ppm of N₂O, 71.2 ppm of NO₂, and 6391 ppm of unburned NH₃. Reducing the DI energy ratio from 40% to 20% decreases NO and NO₂ emissions by 14.6% and 7.3%, respectively, while N₂O and unburned NH₃ emissions increase by 129.7% and 105%, respectively. Chemical kinetic analyses suggest that the active atmosphere produced by HRF has a certain impact on reducing ammonia ignition delay in the initial phase of combustion. As combustion progresses, the impacts of the HRF-induced thermal atmosphere on reducing the ammonia ignition delay become more pronounced, with ambient temperature playing a critical role. Furthermore, as the combustion process develops, the influence of ambient pressure on reducing ammonia ignition delay becomes increasingly significant.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113896"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102612","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 computational investigation of pressure effects on soot formation in counterflow diffusion flames of methane in MILD conditions","authors":"Subrat Garnayak ,&nbsp;Prabhu Selvaraj ,&nbsp;Bok Jik Lee ,&nbsp;V. Mahendra Reddy","doi":"10.1016/j.combustflame.2024.113863","DOIUrl":"10.1016/j.combustflame.2024.113863","url":null,"abstract":"<div><div>Moderate or Intense Low-oxygen Dilution (MILD) combustion has been extensively studied as a promising technology to achieve high efficiency and low-emission power generation. The present study numerically investigates the soot formation in non-premixed methane-air flames in MILD conditions at elevated pressures of up to 20 atm. The soot formations under MILD conditions are compared with their conventional counterparts to elucidate the underlying physical and chemical pathways affecting the sooting features. The gas-phase kinetic mechanism is a reduced version of KAUST Aramco PAH Mech 1.0, which has been validated for C₁ and C₂ fuels for the prediction of PAHs (polycyclic aromatic hydrocarbons) species up to coronene (C₂₄H₁₂). A sectional method is used for the soot-aerosol model. The soot formation (SF) flame, with a high strain rate under conventional and MILD combustion conditions, is employed for the investigation. An improved consistent soot model comprising a broad range of precursors from A₂ (naphthalene) to A₇ (coronene) is used for the analysis. The results show that MILD combustion produces an extremely low soot compared to its conventional counterparts at high pressures. The inception rate has a larger contribution towards the overall soot mass growth rate when compared with the HACA rate and condensation rate in MILD conditions. Conversely, the HACA rate is higher than the inception and condensation rates in conventional conditions, suggesting that the soot mass growth rate is HACA rate-oriented. The soot volume fraction and particle number density increase with pressure, and their peak values are positioned near the oxidizer side of the stagnation plane for both conventional and MILD conditions. A rise in pressure increases the major precursors for soot formation, such as benzene (A₁), naphthalene (A₂), pyrene (A₄), and coronene (A₇) in both conventional and MILD conditions. It also enhances the inception, HACA, condensation, and oxidation rates for soot.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113863"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102613","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":"Investigating NO emissions, stability, and flame structure in co-fired premixed NH3/CH4/air swirling flames","authors":"Ayman M. Elbaz ,&nbsp;Zubayr O. Hassan ,&nbsp;Alfaisal M. Albalawi ,&nbsp;Mahmoud MA. Ahmed ,&nbsp;Marwan Abdullah ,&nbsp;Emre Cenker ,&nbsp;William L. Roberts","doi":"10.1016/j.combustflame.2024.113892","DOIUrl":"10.1016/j.combustflame.2024.113892","url":null,"abstract":"<div><div>Ammonia combustion poses challenges due to low reactivity and high NO_x emissions, requiring optimization of combustor designs and fueling strategies. This study examines NO emissions, flame stability, and structure in co-fired premixed NH₃/CH₄/air flames using a double-swirl burner. The inner swirl stream consists of NH₃/CH₄/air mixtures with varying ammonia mole fractions (<em>x</em>_NH3: 0 to 1) and equivalence ratios (Φ_in: 0.4 to 1.4), while the outer stream contains CH₄/air mixtures with Φ_out ranging from 0.5 to 0.8 and Reynolds numbers (Re_out) of 4350, 5250, and 6000. NO emissions varied significantly with Re_out, Φ_in, and Φ_out, prompting further investigation of flame structure using OH-NO PLIF and PIV diagnostics for three flame sets: FA (Φ_in=0.4), FB (Φ_in=0.8), and FC (Φ_in =1.4). Far-rich (FC) and far-lean (FA) flames exhibited an early conical OH layer followed by a V-shaped OH layer, while NO dispersed across the flame, forming a thin layer at the OH boundary with a V-shaped distribution downstream. Higher Re_out facilitated V-OH/NO formation through enhanced mixing, increased recirculation, and more effective ammonia cracking in rich mixtures. At Re_out=4350, the absence of a V-OH layer in FA resulted in reduced NO emissions. Flame FB showed a broader, positively correlated NO and OH structure along the central region of the flame, indicating enhanced NH_i oxidation to NO. Overall, co-firing ammonia with methane in the outer stream was crucial for improving flame stability. To minimize NO emissions, it is important to lower Re_out, increase Φ_out, and avoid premixing NH₃/CH₄ in the inner stream. At high Re_out, limiting rich Φ_in to 1.2 or leaning it out, combined with increasing Φ_out, was the most effective strategy for reducing NO emissions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113892"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102428","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":"Combustion fundamentals on the melt layer of metalized propellants with surface stress evolution","authors":"Hong-Suk Choi,&nbsp;Jack J. Yoh","doi":"10.1016/j.combustflame.2024.113893","DOIUrl":"10.1016/j.combustflame.2024.113893","url":null,"abstract":"<div><div>While progress has been made in the modeling of burning surface of solid propellants, the intricate interactions within the melt layer involving three distinct phases and multi-materials remain unresolved and present a formidable challenge. This study aims to present a comprehensive analysis on the combustion characteristics of metal-added propellants that considers reactive metal particles of random size. Three pivotal techniques are developed for 1) tracking the dynamics of two-phase interface with deforming material boundaries between reactive particle and binder, 2) incorporating the full stress field evolution within each particle, and 3) introducing the phase and composition identifiers to monitor the process of reaction via oxide cap formation, heat transfer between multi-materials, and agglomeration of metal oxide. To address the stability constraint on an explicit time integrator, both normal-size and scale-up simulations of heterogeneous particle packing models are developed using dimensionless numbers. The contours depicting pressure, temperature, stress, and material phase reveal the emergence and expansion of the melt layer, which includes isolated solid reactants with a multi-phase oxide cap and vaporized binder separated from the unburnt region. The quantitative weight fraction analysis delineates and provides insights on the three distinct sections, demarcated by predominant shifts in material phases. The results of the homogeneous model are compared to the reference data as well as heterogeneous model to validate the accuracy. The simulation successfully replicates the visual images taken from experiments without the need for complex mathematical models.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"272 ","pages":"Article 113893"},"PeriodicalIF":5.8,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143102430","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":"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}