Combustion and Flame最新文献

{"title":"Probing the reactivity of ammonia/C1 mixtures using shock tube coupled with laser absorption spectroscopy","authors":"Nafi Farzana ,&nbsp;Henrique Karas ,&nbsp;Denghao Zhu ,&nbsp;Mengdi Li ,&nbsp;Sumit Agarwal ,&nbsp;Hariprasad Parambath ,&nbsp;Ravi Fernandes ,&nbsp;Bo Shu","doi":"10.1016/j.combustflame.2025.114278","DOIUrl":"10.1016/j.combustflame.2025.114278","url":null,"abstract":"<div><div>Ignition delay times (IDT) and speciation profiles (NH₃, NO, and CO) were measured for NH₃/C₁ fuel blends (NH₃/CO, NH₃/CH₄, NH₃/CH₃OH) in a shock tube using laser absorption spectroscopy. Experiments spanned equivalence ratios of 0.5–1.5, 5–20 % C₁ additives, and temperatures of 1477–2236 K at around 2.5 bar. The experimental data were validated against the simulation results from the PTB-NH₃/C₂ 1.1 mechanism, which demonstrated robust performance across all mixtures. Methanol significantly enhances ignition reactivity, resulting in the shortest IDTs among the three C₁ additives. Combining the findings from our prior studies, the IDT reduction order by different hydrocarbons at high temperatures is: C₂H₅OH ≈ C₂H₆ &gt; CH₃OH &gt; CH₄ &gt; CO, indicating that high temperature favors C₂ compounds. While at intermediate temperatures and high pressures, where the functional groups dominate, the reactivity order is: C₂H₅OH &gt; CH₃OH &gt; C₂H₆ &gt; CH₄, as alcohols enhance reactivity stronger than alkanes. Kinetic modeling analysis identified NH₂ as a key intermediate in NH₃ oxidation, following the primary pathway NH₃ → NH₂ → NH → N → NO. For NH₃/CO, CO contributed to secondary branching intermediates like HNCO through reactions like NH₂ + CO ≤&gt; HNCO + <em>H</em>, influencing nitrogen-carbon interactions. In NH₃/CH₄, hydrocarbon oxidation promoted CO and CH₂O formation, with limited C<img>N cross-reactions. NH₃/CH₃OH pathways exhibited unique CH₃O and CH₂OH radical dynamics, facilitating prolonged CO formation and unique broader CO peaks under fuel-rich conditions. While the PTB-NH₃/C₂ 1.1 mechanism captured most trends, discrepancies emerged at lower temperatures and fuel-rich conditions, underscoring the need for further improvement in future. Measuring more intermediate species such as N₂O, NO₂, and CH₂O would also benefit model validation.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114278"},"PeriodicalIF":5.8,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144205000","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 combustion properties of ultrasonically levitated single nano-Aluminum-based slurry droplets with various liquid oxygenated fuels and solid contents","authors":"Daolun Liang ,&nbsp;Tianhua Xue ,&nbsp;Lixiang Li,&nbsp;Yiwen Qian,&nbsp;Wangzi Xu,&nbsp;Richen Lin,&nbsp;Dekui Shen","doi":"10.1016/j.combustflame.2025.114275","DOIUrl":"10.1016/j.combustflame.2025.114275","url":null,"abstract":"<div><div>Nano-aluminum (nAl)/oxygenated slurry is a promising fuel for aerospace and internal combustion engines. This study investigated the ignition and combustion of single nAl-based slurry droplets containing various oxygenated fuels (dimethyl carbonate (DMC) and triglyceride triacetate (TA)) and varying solid contents (1 wt. %, 5 wt.%, 10 wt.%, 15 wt.%, and 20 wt.%). Droplets were levitated using an ultrasonic levitator, and their deformation and flame evolution were recorded using a digital high-speed camera. A fiber-optic spectrometer was employed to measure the optical signals from the droplets, and a dual-color infrared thermometer was used to measure the surface temperatures of both the droplets and nAl particles (nAls). The experimental results indicate that the ignition and combustion processes can be categorized into three consecutive stages: a stable endothermic stage, an oscillation and micro-explosion stage, and an aerosol combustion stage. The expansion, deformation, and breakup of the bubbles within the droplet resulted in micro-explosions. The burning solid nAls appeared bright orange, and the aerosol flame of the droplet exhibited distinct signs of heterogeneous combustion. Among the two oxygenated fuels, the sample with TA (Al/TA) exhibited a longer ignition delay and higher temperature integral during the ignition process. During combustion, it also demonstrated higher flame brightness and overall spectral integrated intensity at 900 nm, with the spectral integrated intensity approximately 77.6% higher than that of Al/DMC, indicating superior combustion performance. As the solid content increased from 1 wt. % to 20 wt.%, the ignition delay and maximum temperature during the ignition process of Al/TA initially increased and subsequently decreased, reaching a maximum at 15 wt.%. The 15 wt.% Al/TA sample also exhibited bright flame and highest integrated intensity at 900 nm, indicating the best combustion performance. This study provides valuable insights for the application of nAl/oxygenated slurries.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114275"},"PeriodicalIF":5.8,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204393","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 instabilities in annular systems: Evidence that liquid fuels with similar characteristics can lead to notably different behaviors","authors":"Véranika Latour,&nbsp;Daniel Durox,&nbsp;Antoine Renaud,&nbsp;Sébastien Candel","doi":"10.1016/j.combustflame.2025.114235","DOIUrl":"10.1016/j.combustflame.2025.114235","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The transition towards the use of sustainable aviation fuels (SAFs) requires the understanding of the effects of fuel composition on combustion properties in order to ensure the safe operability of the existing or new aircraft engines. Among the many concerns and challenges raised by the use of SAFs, the question of the dynamical behavior of the combustion systems requires specific attention. It is known that combustion dynamics phenomena depend on the flames’ response to incoming disturbances and on the possible coupling of combustion with the acoustic modes of the system. This work proposes to shed light on the effects of chemical characteristics on this issue by comparing the dynamical properties of heptane and iso-octane, two fuels featuring close physical and thermochemical properties, but presenting different chemical kinetics characteristics. This is tentatively linked to the cetane numbers of heptane and iso-octane which are notably different. These numbers are generally used to characterize the auto-ignition delay and auto-ignition temperature. It is here suggested that they might also be used as an index to categorize different fuels with respect to their dynamical behavior. Using the laboratory-scale annular combustor MICCA, it is shown that these two fuels induce significantly different combustion dynamics, with a broader unstable region and higher limit cycle oscillation amplitudes for heptane than iso-octane. Experimental observations are interpreted by gathering flame dynamics data in the single-sector configuration SICCA and from simultaneous pressure and photomultiplier recordings in MICCA operating at limit cycle. Experimental data show that the two fuels differ mainly by their FDF phase values and iso-octane presents a significant decrease in the FDF phase with the oscillation amplitude. The collected data, combined with an analytical framework, are used to determine growth rates and trajectories towards limit cycle. This enables the interpretation of the experimental observations and indicates that the unstable points in MICCA operated with iso-octane are exclusively of nonlinear nature, highlighting the importance of a phase evolution with amplitude on the thermoacoustic behavior of a combustion system.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This study shows the effects of chemical reactivity on azimuthal combustion instabilities by comparing two fuels (heptane and iso-octane) featuring close physical properties but different chemical characteristics. It is here inferred that the cetane numbers (which are significantly different for heptane and iso-octane) might be used as an index to distinguish different fuels with respect to their dynamical behaviors. The experimental data collected in two different test rigs (an annular combustor and a single-sector setup) are used to compare the dynamical behavior of the two fuels and interpret the differences observed. Flame dynamics data are t","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114235"},"PeriodicalIF":5.8,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204394","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":"Towards efficient/low emission NH3 swirl combustion under axially staged regime through oxygen enrichment","authors":"Zundi Liu,&nbsp;Sibo Han,&nbsp;Soroush Sheykhbaglou,&nbsp;Wei Li,&nbsp;Tianyou Lian,&nbsp;Yichen Cao,&nbsp;Xiaoyuan Yang,&nbsp;Yi Zhang,&nbsp;Xiaoxiang Shi,&nbsp;Yuyang Li","doi":"10.1016/j.combustflame.2025.114254","DOIUrl":"10.1016/j.combustflame.2025.114254","url":null,"abstract":"<div><div>Aimed at controlling emissions and increasing efficiency in a gas turbine combustor, this work conducts the experimental and kinetic modelling investigation on oxygen-enriched ammonia swirl combustion under axially staged regime. Combustion and emission characteristics of ammonia/oxygen/nitrogen mixtures are explored using direct flame imaging, planar laser-induced fluorescence, and Fourier Transform Infrared spectroscopy. The results reveal that oxygen enrichment strengthens combustion intensity and flame stabilization, thus contributing to the expanded stability limit. Furthermore, oxygen enrichment can effectively widen the low NOx/NH₃ emission window which can reach six times in the primary stage from 21 %O₂ to 40 %O₂. Kinetic modelling is performed using the freely propagating laminar flame model and a hybrid chemical reactor network model. According to kinetic analysis, thermal effects play a dominant role due to the nearly 500 K increment in adiabatic flame temperature, which enhances self-promoted ammonia pyrolysis into nitrogen and hydrogen under rich conditions in the primary stage. The low NOx/NH₃ emission window is thus broadened and H₂ rather than NH₃ is released. Under axially staged regime, nearly 100 % combustion efficiency and zero H₂ emissions can be achieved under all conditions. Oxygen enrichment from 21 % to 40 % shifts the optimized primary equivalence ratio (<em>ϕ</em>_opt) from 1.05 to 1.32 at an overall equivalence ratio (<em>ϕ</em>_overall) of 0.6. Shifting the oxygen content and primary equivalence ratio from 21 % and 1.05 to 40 % and 1.32 can also halve the NOx emissions from 144 ppmv to 72 ppmv at <em>ϕ</em>_overall = 0.8. At 21 %O₂, the optimized NOx emissions can only be achieved through the thermal deNOx mechanism under near-stoichiometric conditions. This can be attributed to the narrow low NOx/NH₃ emission window in the primary stage leading to lean NH₃/H₂ combustion and NH₃-to-NO penalty in the secondary stage. Under oxygen enrichment, residual hydrogen rather than residual ammonia enters the ultra-lean secondary stage, avoiding the NH₃-to-NO penalty. This leads to a shift of <em>ϕ</em>_opt to richer conditions and a halving of the optimized NOx emissions. This study suggests that oxygen-enriched ammonia combustion under axially staged regime is a promising and efficient clean combustion technology for ammonia.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114254"},"PeriodicalIF":5.8,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144189563","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":"ȮH insights into the interaction of hydrogen-rich methane and water: Laser absorption experiments and chemical kinetics","authors":"Xin Zhang,&nbsp;Zilong Feng,&nbsp;Congjie Hong,&nbsp;Wuchuan Sun,&nbsp;Zuohua Huang,&nbsp;Yingjia Zhang","doi":"10.1016/j.combustflame.2025.114251","DOIUrl":"10.1016/j.combustflame.2025.114251","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Flue gas recirculation and steam injection are employed in hydrogen-rich gas turbines to stabilize fuel reactivity and improve cycle efficiency, introducing high water vapor content into the combustion chamber and thereby necessitating an investigation of water-fuel interactions at elevated temperatures. &lt;em&gt;This study&lt;/em&gt; employed &lt;em&gt;UV&lt;/em&gt; laser absorption diagnostics behind reflected shock waves to conduct in situ measurements of the ȮH concentration time-histories during the oxidation of CH&lt;sub&gt;4&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;O/O&lt;sub&gt;2&lt;/sub&gt;/Ar mixtures at pressures of approximately 1.3, 5.0, and 15.2 atm and temperatures ranging from 1225 to 1888 K with varying hydrogen blending and water addition ratios. The absorption lineshapes of the ȮH R&lt;sub&gt;1&lt;/sub&gt;(5) transition in the A-X(0,0) vibronic band were characterized after broadening and shifting in Ar at different pressures, with diagnostic center wavelengths set at 306.6868 nm (1.3 atm), 306.6874 nm (5.0 atm), and 306.6886 nm (15.2 atm), respectively. The obtained ȮH concentration time-history data were compared in detail with predictions from eight representative reaction kinetic models, and the predictive capability of the models for ȮH behavior was quantitatively assessed using the error function method. NUIGMech1.1 exhibited superior performance in predicting ȮH behavior and was subsequently selected for kinetic analysis to elucidate stage-specific micro-mechanisms and identify key reactions driving the concentration evolution. The activating effect of H&lt;sub&gt;2&lt;/sub&gt; on ȮH behavior during CH&lt;sub&gt;4&lt;/sub&gt; oxidation was investigated. Results indicate that higher hydrogen levels intensify hydrogen-related reaction pathways, expanding the radical pools (H, ȮH, and Ö), thereby promoting fuel consumption through Ḣ-atom abstraction reactions. Additionally, by introducing weak collision H&lt;sub&gt;2&lt;/sub&gt;O* and inert H&lt;sub&gt;2&lt;/sub&gt;O**, the thermodynamic and kinetic effects of water were distinguished. The results show that under the current conditions, H&lt;sub&gt;2&lt;/sub&gt;O primarily affects ȮH behavior through direct participation in reactions rather than through third-body collisions or thermal effects. Further selectively activating the water-containing pathways revealed that the reactions CH&lt;sub&gt;4&lt;/sub&gt; + ȮH = ĊH&lt;sub&gt;3&lt;/sub&gt; + H&lt;sub&gt;2&lt;/sub&gt;O, Ö + H&lt;sub&gt;2&lt;/sub&gt;O = 2ȮH and H&lt;sub&gt;2&lt;/sub&gt; + ȮH = Ḣ + H&lt;sub&gt;2&lt;/sub&gt;O are key channels for water participation in hydrogen-rich methane combustion chemistry.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;&lt;em&gt;This study&lt;/em&gt; presents a first high-fidelity investigation of methane oxidation at the ȮH radical level, elucidating the effects of hydrogen blending and steam addition, thereby addressing a significant knowledge gap in high-temperature water-fuel interaction mechanisms. We have established an unprecedented high-resolution experimental database documenting ȮH time-histories in blended environments, which serves to rigorously val","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114251"},"PeriodicalIF":5.8,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144178613","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":"Kinetic modeling and experimental study of laminar burning velocities of CH4/NH3/N2O/Ar premixed flames","authors":"Yun Ge,&nbsp;Hong-Hao Ma,&nbsp;Lu-Qing Wang","doi":"10.1016/j.combustflame.2025.114253","DOIUrl":"10.1016/j.combustflame.2025.114253","url":null,"abstract":"<div><div>Ammonia (NH₃) is regarded as a carbon-free alternative fuel in modern energy systems. Co-firing NH₃ with CH₄ and/or using N₂O as an oxidizer are promising strategies for overcoming the low reactivity of NH₃. An experimental and kinetic modeling study of laminar burning velocities of CH₄/NH₃/N₂O/Ar flames was first reported in this study. Experiments were performed using the spherical flame method, and the measured conditions covered a full range of CH₄ fractions and a large range of equivalence ratios at 1 atm and 298 K. Several literature mechanisms were tested, but none of them could accurately predict the laminar burning velocities for all the experimental conditions. A new mechanism with 72 species and 521 elementary reactions was proposed and validated. The new model performed well in predicting laminar burning velocity, ignition delay time, and species mole fraction profile (measured not only in this work but in the literature) for CH₄/NH₃/N₂O/Ar relevant flames, and the performance was better than the existing mechanisms. Detailed kinetic analyses using the present model were carried out to reveal the major reaction pathways based on N-atom and C-atom, the dominant elementary reactions, and the thermal and chemical kinetic effects. It was found that the dominant reactions with the two largest positive sensitivity coefficients, N₂O(+M)=N₂+O(+M) and N₂O+H=N₂+OH, were directly relevant to N₂O. Besides, most of the dominant elementary reactions influencing laminar burning velocities were relevant to the N-family, while few involved the C-family. The positive effect of CH₄ addition was mainly attributed to the enhancement of thermal and chemical kinetic effects. The present model provides insights into the chemical kinetics for CH₄/NH₃/N₂O/Ar flames, and can be considered as the foundation for developing larger fuel molecule mechanisms.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114253"},"PeriodicalIF":5.8,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144178552","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":"Impact of ethanol addition on the autoignition characteristics of a certification gasoline","authors":"Khalid Aljohani ,&nbsp;Ahmed Abd El-Sabor Mohamed ,&nbsp;Haitao Lu ,&nbsp;Henry J. Curran ,&nbsp;Jihad Badra ,&nbsp;Aamir Farooq","doi":"10.1016/j.combustflame.2025.114252","DOIUrl":"10.1016/j.combustflame.2025.114252","url":null,"abstract":"<div><div>As the world grapples with climate change, decarbonizing the transportation sector remains an immense challenge. Ethanol-containing gasolines offer a promising pathway that aligns with global initiatives to transition towards low-carbon transportation fuels. This study investigates ignition delay times (IDTs) of a research-grade oxygenated gasoline (Euro 6 E10) containing a substantial proportion (20–40 %, by vol.) of ethanol. Experiments were conducted across three domains: (a) a cooperative fuel research (CFR) engine, (b) two high-pressure shock tubes (HPSTs), and (c) two rapid compression machines (RCMs). IDTs were investigated over a broad range of temperatures (655–1470 K), pressures (20 and 40 bar), and equivalence ratios (<em>φ</em> = 0.5, 1, 1.5). The CFR engine results indicated that blending ethanol with Euro 6 E10 gasoline led to a synergistic increase in octane ratings across the two ethanol-blended gasoline mixtures. IDTs results showed a pronounced reactivity-inhibiting effect of ethanol at temperatures below ≈ 830 K across the entire range of conditions investigated. In contrast, intermediate- and high-temperature ignition delays of gasoline-ethanol blends exhibited close similarities regardless of the blend octane numbers, compositions, or ethanol content. A reactivity-promoting effect of ethanol was observed solely in fuel-rich scenarios (<em>φ</em> = 1.5) and at temperatures greater than ≈ 950 K. A recently published gasoline model by the authors was updated with the latest kinetic knowledge to evaluate the effects of ethanol blending and was subsequently used to validate the measured IDTs. The revised model demonstrated reasonable accuracy with both the 4-component and 8-multicomponent ethanol-containing surrogates developed in this study, with the 4-component surrogate demonstrating better performance. Finally, sensitivity analyses were performed to identify key reactions contributing to the reactivity perturbative effects of ethanol blending on Euro 6 reactivity characteristics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114252"},"PeriodicalIF":5.8,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167782","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":"Nanostructured oxidizer of ammonium fluoroferrates with high gas yield and F release capacity to improve the combustion behavior of Al powder","authors":"Xiandie Zhang,&nbsp;Haozhe Li,&nbsp;Xuxu Cui,&nbsp;Xinwen Ma,&nbsp;Jiaming Liu,&nbsp;Xiaode Guo,&nbsp;Xiang Zhou","doi":"10.1016/j.combustflame.2025.114255","DOIUrl":"10.1016/j.combustflame.2025.114255","url":null,"abstract":"<div><div>The passivation layer of Al powder hinders the mass transfer during Al combustion. Fluorinated oxidants, such as metal fluorides and fluoropolymers, substantially improve the combustion behaviour of Al powder. Herein, a simple solvothermal method is employed to produce a high-entropy acicular accumulational fluorine-containing oxidiser based on ammonium fluoroferrates. The characterization results indicate that heating the fluorine-containing oxidiser can release gaseous products of HF and NH₃. HF etches the passivation layer, and NH₃ provides kinetic energy to the fuel, resulting in multiple hot spots and secondary combustion as well as prevention of reaction sintering. Compared with traditional FeF₃, this novel fluorine-containing oxidiser considerably improves the combustion of Al powder by reducing its onset temperature as well as increasing its exothermic enthalpy, flame area and F release ability.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114255"},"PeriodicalIF":5.8,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167781","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 simulation of methanol combustion in dry air with a spark-plug electric discharge ignition","authors":"Marcelo Gomes da Silva ,&nbsp;Lucas Wilman da Silva Crispim ,&nbsp;Maria Uxue Alzueta ,&nbsp;Maikel Yusat Ballester","doi":"10.1016/j.combustflame.2025.114179","DOIUrl":"10.1016/j.combustflame.2025.114179","url":null,"abstract":"<div><div>This study explores the complexities of plasma-assisted methanol combustion, at the molecular level. A methanol–air mixture is considered, assuming that species <span><math><msub><mrow><mi>N</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and <span><math><mrow><msub><mrow><mi>CH</mi></mrow><mrow><mn>3</mn></mrow></msub><mi>OH</mi></mrow></math></span> are initially in thermodynamic equilibrium, with initial densities of 77%, 18%, and 5% (molecular ratio 1525:381:100), respectively. The original mixture is homogeneously distributed in a 2D axial symmetric domain, concentric with the bottom spark-plug electrode and <span><math><mrow><mi>r</mi><mo>=</mo><mn>20</mn><mspace></mspace><mi>mm</mi></mrow></math></span>. The plasmo-chemical kinetic model comprises 112 species interconnected by 1081 physical and chemical processes, including cross-sections resulting from electron impact, covering excitation, ionization, dissociation, recombination, attachment, and detachment. Heat and mass transfers are also considered, along with fluid dynamics. By comparing simulations and analyzing reaction rates, the research sheds light on the contribution of reactive oxygen and nitrogen species (RONS) and key reagents such as H, OH, and <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mn>2</mn></mrow></msub><mi>O</mi></mrow></math></span> in methanol decomposition. Additionally, it highlights the role of the duty cycle in producing atmospheric pollutants (<span><math><msub><mrow><mi>NO</mi></mrow><mrow><mi>x</mi></mrow></msub></math></span>, CO, <span><math><msub><mrow><mi>CO</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, and <span><math><mrow><msub><mrow><mi>CH</mi></mrow><mrow><mn>2</mn></mrow></msub><mi>O</mi></mrow></math></span>). Through detailed analysis of reaction pathways, the study reveals crucial plasma-chemical processes and their implications for combustion and environmental pollution.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114179"},"PeriodicalIF":5.8,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139398","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":"Deep learning based combustion chemistry acceleration method for widely applicable NH3/H2 turbulent combustion simulations","authors":"Sipei Wu ,&nbsp;Wenkai Liang ,&nbsp;Kai Hong Luo","doi":"10.1016/j.combustflame.2025.114218","DOIUrl":"10.1016/j.combustflame.2025.114218","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Simulating reacting flows with detailed chemistry is often prohibitively expensive due to the complexity of reaction mechanisms and the numerical stiffness arising from disparate chemical time scales. While recent advancements in neural networks offer potential for efficiently capturing the dynamics of stiff chemistry, its application to dual-fuels with drastic differences in reactivity such as ammonia (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) and hydrogen (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&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;) remains challenging. In this study, we present a neural network model with variable time steps aimed at enhancing the efficiency of combustion chemistry simulations focusing on the complex dual-fuel &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; under premixed combustion. We improved the ”sampling-training” workflow based on previous HFRD method to overcome the challenge of generalizing neural network models to fuel blends under premixed combustion. This workflow involves three improvements: defining the base manifold using unity Lewis number laminar flames, introducing continuously controllable randomization, and employing a training process with mass conservation and heat release rate similarity constraints. Our approach is validated against simulations of planar turbulent premixed flames and temporally-evolving jet flames across various conditions. The model demonstrates high accuracy and consistency, achieving a chemical calculation acceleration of 7 times and an overall simulation acceleration of 5 times using a model with 4 hidden layers and 800 neurons on the same CPU device. When a GPU is adopted, the chemical calculation acceleration increases to 30 times, and the overall simulation acceleration reaches 10 times.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;Utilizing detailed chemistry in reacting flow simulations drastically increases computational cost due to numerical stiffness and disparate time scales. A promising approach is to replace the time-consuming ODE solvers with compact neural networks. Despite the rapid development of the neural network approach for accelerating combustion kinetics calculations, the application of this concept to fuel blends with varying mixing ratios and reactivities remains insufficient, particularly in turbulent premixed flames. In this study, we improved the neural network framework that could predict the kinetics of fuel blends of low-reactivity fuel &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and high-reactivity fuel &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&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;, highlighting the applications to binary fuel with large reactivity differences. Specifically, the unity Lewis number","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114218"},"PeriodicalIF":5.8,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144139397","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}