Combustion and Flame最新文献

{"title":"Effect of applied AC electric field on flame spread over electrical wire with cross-linked polyethylene insulation","authors":"Zhisheng Li ,&nbsp;Huido Lee ,&nbsp;Jeong Park ,&nbsp;Suk Ho Chung","doi":"10.1016/j.combustflame.2025.114323","DOIUrl":"10.1016/j.combustflame.2025.114323","url":null,"abstract":"<div><div>The effect of applied AC electric field on flame spread over electrical wires with NiCr-core insulated by cross-linked polyethylene (XLPE) is experimentally investigated by varying the AC voltage and frequency. Results are compared with those for low-density polyethylene (LDPE) insulation, commonly studied in fire safety research. For the baseline case without applying electric field, XLPE-insulated case exhibits distinct behaviors such as flame splitting and a unique molten dripping via merging of newly-formed globular molten XLPE, which were not observed in LDPE-insulated one. Under applied electric fields, the flame spread rate (FSR) and molten insulation dynamics differ markedly between XLPE and LDPE. Two regimes of FSR behavior are identified for XLPE and three for LDPE, depending on voltage and frequency. At high voltage and frequency, induced magnetic fields promote flame vortex formation, increasing flame width and FSR, while excessive conditions lead to flame extinction through mass loss via electrospray and dielectrophoresis. Scaling analyses are applied to elucidate the underlying mechanisms. The flame spread rates are phenomenologically characterized depending on these various phenomena in terms of the frequency and voltage, especially emphasizing the electric field intensity on the unburned wire surface. The extinction conditions are correlated with AC voltage and frequency.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114323"},"PeriodicalIF":5.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557295","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":"Effects of NH3 addition on soot particles and gaseous precursors formation in C2H4 pyrolysis","authors":"Kai Zhang ,&nbsp;Yishu Xu ,&nbsp;Ronghao Yu ,&nbsp;Jiahui Wu ,&nbsp;Xiaobei Cheng","doi":"10.1016/j.combustflame.2025.114324","DOIUrl":"10.1016/j.combustflame.2025.114324","url":null,"abstract":"<div><div>The pyrolysis of C₂H₄/NH₃ mixtures was conducted in a plug flow reactor (PFR) in the temperature range of 973 K-1373 K. The pyrolysis products, including C₂H₄, NH₃, C₂H₂, C₆H₆ and HCN, were quantified using gas chromatography (GC) and Fourier transform infrared (FTIR) spectroscopy to elucidate the thermal decomposition behavior of C₂H₄ and NH₃, as well as the effects of NH₃ on the formation of gaseous soot precursors. The results indicate that both C₂H₄ and NH₃ conversion increase during co-pyrolysis compared to their individual pyrolysis. Moreover, C₂H₄ shows a more pronounced promoting effect on NH₃ decomposition. Kinetic analysis reveals that the reactions C₂H₄ + NH₂ and NH₃ + CH₃ are primarily responsible for the increased conversion of C₂H₄ and NH₃, respectively. The effects of NH₃ on soot precursors formation (e.g., C₂H₂ and C₆H₆) exhibit a non-monotonic trend with reaction temperature. Specifically, NH₃ addition promotes soot precursors formation below 1273 K but inhibits it above 1273 K. This trend is determined by the competition between NH₃-induced enhancement of C₂H₄ decomposition and the effects of C<img>N interactions. The former consistently promotes the formation of soot precursors, while the latter becomes significantly effective in inhibiting their formation only above 1273 K by removing C atoms from participating in soot precursors formation. This finding is supported by FTIR measurements with a significant increase of HCN being formed at temperature at 1273 K. It should be noted that as the temperature further increases, the concentration of HCN decreases due to its involvement in the formation of N-containing polycyclic aromatic hydrocarbons (NPAHs). Meaningfully, the molecular structure of NPAHs were identified using gas chromatography-mass spectrometry (GC–MS). Notably, existing kinetic mechanisms are unable to satisfactorily predict the quantitative trends of the experimental results, highlighting the need for further mechanism improvement and refinement.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114324"},"PeriodicalIF":5.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144562940","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 dedicated paper for Pr Sébastien Candel EM2C laboratory, CentraleSupélec","authors":"Christophe Bailly ,&nbsp;Daniel Durox ,&nbsp;Matthew Juniper ,&nbsp;Nicolas Noiray ,&nbsp;Thierry Poinsot ,&nbsp;Thierry Schuller ,&nbsp;Denis Veynante","doi":"10.1016/j.combustflame.2025.114301","DOIUrl":"10.1016/j.combustflame.2025.114301","url":null,"abstract":"<div><div>This dedicated paper presents an overview of six fields of research in combustion in which Pr Sébastien Candel has made remarkable contributions: cryogenic combustion and liquid rocket engine dynamics, turbulent combustion modeling, combustion noise, flame dynamics and combustion instability, flame describing functions in combustion instability analysis, combustion dynamics and instabilities in annular systems. The paper is designed to (1) provide a review of research in each of the six fields, which can be used by all members of our community and (2) show how Pr Candel’s work has oriented and shaped research in these fields over the last few decades.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114301"},"PeriodicalIF":5.8,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144549296","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 theoretical analysis of the reaction H2 + N2O ⇆ H2O + N2","authors":"Clayton R. Mulvihill","doi":"10.1016/j.combustflame.2025.114330","DOIUrl":"10.1016/j.combustflame.2025.114330","url":null,"abstract":"<div><div>The reaction of H₂ and N₂O to directly form H₂O and N₂ has been a matter of some controversy, with reported rate constants spanning nearly five orders of magnitude at 1500 K. This study presents the first theoretical analysis of the title reaction. By coupling an ANL1-QZF potential energy surface with a master equation treatment, the pressure-independent thermal rate constant <span><math><msub><mi>k</mi><mn>1</mn></msub></math></span> was determined between 400 and 3000 K. The best-fit <span><math><msub><mi>k</mi><mn>1</mn></msub></math></span> is given in cm³·mol^–1·s^–1 as <span><math><mrow><msub><mi>k</mi><mn>1</mn></msub><mo>=</mo><mn>5.23</mn><mspace></mspace><mo>×</mo><msup><mrow><mn>10</mn></mrow><mn>4</mn></msup><mspace></mspace><msup><mrow><mi>T</mi></mrow><mrow><mn>2.272</mn></mrow></msup><mrow><mspace></mspace><mtext>exp</mtext></mrow><mi>⁡</mi><mrow><mo>(</mo><mrow><mo>−</mo><mn>21745</mn><mo>/</mo><mi>T</mi></mrow><mo>)</mo></mrow></mrow></math></span>, with <span><math><mi>T</mi></math></span> in K. This rate constant is several orders of magnitude smaller than values utilized in recent kinetics mechanisms.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114330"},"PeriodicalIF":5.8,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144564061","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":"Theoretical elucidation of the hindering effect of oxide-layer growth on the ignition of iron particles","authors":"XiaoCheng Mi","doi":"10.1016/j.combustflame.2025.114310","DOIUrl":"10.1016/j.combustflame.2025.114310","url":null,"abstract":"<div><div>This study investigates the hindering effect of a growing oxide layer on the ignition behavior of fine iron particles, focusing on scenarios where the gas temperature is below the critical ignition temperature (<span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>ign</mi></mrow></msub></math></span>). The analysis is grounded in a thermophysical model integrating solid-phase iron oxidation mechanism and heat and mass transfer between the particle and surrounding gas. The results reveal that the growth of an oxide layer under subcritical temperatures has a hindering effect, significantly raising the <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>ign</mi></mrow></msub></math></span> required for thermal runaway. The effect is more pronounced for smaller particles, with the required <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>ign</mi></mrow></msub></math></span> increasing by 80–250<!--> <!-->K over a residence time of three seconds for particle sizes ranging from 200 to 50<!--> <!-->µm, respectively. These findings provide a theoretical framework linking ignition mechanism to the heating process experienced by an iron particle in a practical combustor, offering insights for improving ignition rates through tailored heating conditions.</div><div><strong>Novelty and significance statement</strong></div><div>This study theoretically identifies the primary reason why a significant number of iron particles fail to ignite in practical combustors—an issue previously reported by developers of iron-powder combustion technologies in industry, yet insufficiently addressed by academic researchers. It elucidates the hindering effect of oxide-layer growth, caused by inadequate heating rates, on the ignition propensity of iron particles—a mechanism suggested in the work of Mi et al. (2022), but still not fully understood within the Metal-enabled Cycle of Renewable Energy (MeCRE) community. By establishing a theoretical framework, this brief communication provides guidance for the design of iron-powder combustors, emphasizing the need for sufficient heating rates to improve ignition reliability and overall combustion efficiency.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114310"},"PeriodicalIF":5.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144535837","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":"Enhancing combustion performance of composite propellants through chemical modification to bond nano-aluminum powder and RDX building blocks for energy release coupling","authors":"Hongxia Zhang ,&nbsp;Fei Xiao ,&nbsp;Chongwei An ,&nbsp;Chen Chong ,&nbsp;Yaozhong Ran ,&nbsp;Yongli Zhang ,&nbsp;Ying Li ,&nbsp;Jiawang Shuang ,&nbsp;Jiaru Zhang","doi":"10.1016/j.combustflame.2025.114305","DOIUrl":"10.1016/j.combustflame.2025.114305","url":null,"abstract":"<div><div>Due to the difficulty in establishing organic functional groups on the surface of aluminum powder, the effective combination of aluminum powder with other oxidizing particles is inhibited, thereby limiting its energy characteristics. By introducing effective functional groups on the aluminum powder surface that can form chemical bonds, it is possible to establish links between particles and achieve three-dimensional growth of nano-aluminum powder on various oxidizer particle surfaces. In this study, we propose the creation of two building blocks: nano-aluminum (nAl) modified with 3-mercaptopropyltrimethoxysilane (MPTS) and 1,3,5-trinitro-1,3,5-triazine (RDX) modified with tannic acid (TA). Through the chemical bonding of these two building blocks, three-dimensional growth of nano-aluminum powder on the RDX surface was achieved, resulting in the preparation of RDX@Al. The results demonstrate that RDX@Al effectively reduces the activation energy of RDX, showcasing the energy coupling and synergy between RDX and nAl. Adding RDX@Al to composite propellants significantly improves the combustion performance of the propellants. Due to the shortened mass and heat transfer distances between RDX and nAl, the combustion rate of the propellant increased by 38 %, and the combustion intensity was also enhanced. Additionally, the size of the condensed phase combustion products from the propellant was reduced by 59.8 %. This work provides new insights into the design of composite energetic materials and the elucidation of the combustion mechanisms of composite solid propellants.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114305"},"PeriodicalIF":5.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation on heat exchange of iron particle combustion based on simultaneous multi-physics field measurements","authors":"Yutao Zheng ,&nbsp;Jingruo Chen ,&nbsp;Yuanzhe He ,&nbsp;Minshuo Li ,&nbsp;Xiuxiu Chen ,&nbsp;Shijie Xu ,&nbsp;Xin Wen ,&nbsp;Yingzheng Liu ,&nbsp;Weiwei Cai","doi":"10.1016/j.combustflame.2025.114309","DOIUrl":"10.1016/j.combustflame.2025.114309","url":null,"abstract":"<div><div>A study was conducted using a premixed methane/air/oxygen Bunsen flame laden with iron particles to explore the thermal and fluid dynamic characteristics of iron combustion. An integrated diagnostic system was employed to simultaneously capture the characteristics of both gas and solid phases. The temperature of combusted iron particles was measured using pyrometry in conjunction with an RGB camera, while the gas phase temperature near these particles was determined through Background-Oriented Schlieren Tomography (BOST), calibrated by a B-type thermocouple. Velocities of the iron particles and the surrounding gas phase were quantified using Planar Particle Image Velocimetry (PIV), assisted by image segmentation to distinguish between the iron particles and alumina tracers. Synchronisation of all three measurement techniques was achieved, and calibration ensured that data from each method could be accurately correlated within the same coordinate system. Statistical analysis focused on the behaviour of combusted iron particles downstream of the flame region where the convection and radiation heat loss was fully resolved from in-situ measurement, providing insights beneficial for understanding heat transfer phenomena in two-phase flows. The temperature drop of burnt particles contributed from the inert cooling was estimated and compared with the conditional average of particle temperatures, revealing the significant heat production during the phase of reactive cooling. Overall, this study employed a seamlessly integrated multi-physics measurement technique, offering a comprehensive approach to capture all data on combusted iron particles. This methodology holds potential for extension and application to other reacting flows involving particulates.</div><div><strong>Novelty and significance statement</strong></div><div>A multi-physical measurement was <em>first</em> conducted to capture all thermal characteristics of iron combustion where the heat exchange between the iron combustion and its surrounding environment can be estimated from <em>direct</em> measurement. The temperature evolution of iron particles and their corresponding heat loss was estimated <em>statistically</em> as a function of their residence time, which was started from when they left the flame front of the assisted flame. A good consistency between the modelled and measured iron temperature revealed the reliability of such a measurement technique.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114309"},"PeriodicalIF":5.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524303","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 studies on intrinsically unstable H2/CO2 flames: Effect of CO2 dilution, equivalence ratio, temperature and pressure","authors":"Mayank Pandey,&nbsp;Krishnakant Agrawal,&nbsp;Anjan Ray","doi":"10.1016/j.combustflame.2025.114307","DOIUrl":"10.1016/j.combustflame.2025.114307","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Direct combustion of H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; gas mixtures obtained from the gasification and steam reforming processes can help avoid CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; separation costs and safety concerns associated with the fast combustion of pure hydrogen as a fuel. This work studies the effect of varying CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; concentrations in hydrogen-air flames through detailed numerical simulations (DNS) as well as canonical flame calculations. The species transport budget calculated using one-dimensional freely propagating flames shows dominance of diffusion against convection with increase in CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; percentage. Similarly, an increase in reaction rate and negative Markstein length is observed for flames under strain, suggesting enhanced thermodiffusive response. Quantification of thermodiffusive instability in linear and non-linear flame propagation regimes has been performed for CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;-rich hydrogen-air mixtures using two-dimensional freely propagating flames in a classical inflow, outflow and periodic domain for a range of equivalence ratios (0.8–1.1), unburned temperatures (300 K–700 K) and pressures (1 atm–8 atm). The growth rate of perturbation amplitude increases with decreasing the equivalence ratio and temperature, and increases with CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; dilution and pressure, enhancing intrinsic instability. The flame propagates with a finger-like structure with increasing propensity of subadiabatic and superadiabatic regions for mixtures corresponding to higher growth rates. These findings will further the understanding of burning characteristics of H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/air mixtures when used in practical combustion devices.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;Direct combustion of H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; fuel mixtures can provide different low-cost pathways for grey hydrogen utilization. Such mixtures are known to exhibit intrinsic flame instabilities, especially of a thermodiffusive nature. This work presents a one-dimensional assessment of the convective, diffusive, reactive balance of H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/CO&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; fuel-air flames and their response to flow-stretch, which confir","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114307"},"PeriodicalIF":5.8,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524301","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":"Effects of hydrogen addition on flame structures in counterflow n-dodecane/air spray flames","authors":"Jianyi Jiang,&nbsp;Xiaoxu Zhang,&nbsp;Jian Zhang,&nbsp;Hua Zhou,&nbsp;Zhuyin Ren","doi":"10.1016/j.combustflame.2025.114322","DOIUrl":"10.1016/j.combustflame.2025.114322","url":null,"abstract":"<div><div>On the path to a carbon-neutral aviation industry, hydrogen drop-in technology could be a viable transition solution that could take advantage of existing infrastructure. The effect of hydrogen addition on the surrogate n-dodecane spray flame dynamics is investigated in a counterflow flame configuration under engine-related operating conditions, with the H₂ASp-A configuration representing the concept of premixed H₂/air mixture with n-dodecane droplets opposing an air flow, and ASp-H₂A representing the droplets introduced in an air flow opposing premixed H₂/air mixture. Results indicate that the n-dodecane/air spray flame with varying pressure can lead to significant differences in the behavior of multiple solutions, with some single solution behavior transitioning into multiple solutions due to the competition between endothermic evaporation and exothermic chemical reactions. Hydrogen addition on the spray side in H₂ASp-A configuration can induce some single solution behavior transitioning into multiple solutions, whereas the addition on the non-spray side in H₂ASp-A has little impact on multiple solution behavior. In addition, Hydrogen addition under both configurations increases flame speed and temperature, but H₂ASp-A and ASp-H₂A exhibit different flame dynamics. In ASp-H₂A, a lean hydrogen/air premixed reaction zone could be formed at low strain rate that significantly enhance the temperature on the non-spray side, while in H₂ASp-A, it causes non-monotonic speed variation based on autoignition-assisted flame propagation and the balance between hydrogen’s inhibition on low temperature chemistry and enhancing effects on reactions. At the same time, the increased droplet diameter can mitigate the rise in flame speed due to hydrogen addition in both ASp-H₂A and H₂ASp-A, and hydrogen addition in the ASp-H₂A configuration has a better effect on increasing the flame temperature compared to the H₂ASp-A. In terms of extinction, hydrogen addition and reduced initial droplet diameter enhance the spray flame resistance to strain rate in both configurations, with H₂ASp-A performing better at lower hydrogen levels and ASp-H₂A at higher levels.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114322"},"PeriodicalIF":5.8,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524300","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":"Characterizing the influence of thermodiffusive effects on turbulent burning velocity of lean hydrogen/air mixtures using critically stretched laminar flames","authors":"Yiqing Wang ,&nbsp;Andrei N. Lipatnikov ,&nbsp;Zheng Chen","doi":"10.1016/j.combustflame.2025.114306","DOIUrl":"10.1016/j.combustflame.2025.114306","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This work focuses on characterizing the influence of thermodiffusive effects on turbulent burning velocity (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) of lean hydrogen/air mixtures, employing the so-called leading point concept. To this end, the flame characteristics of 1-D critically stretched laminar flames, including the flame consumption velocity and flame thickness, are extracted from two flame configurations: counter-flow twin premixed flames and spherically expanding flames. The former configuration is solely subject to strain-related stretch, whereas the latter configuration is subject to both strain-related and curvature-related stretches. Lean hydrogen/air mixtures are considered at a wide range of temperatures and pressures, addressed in recent direct numerical simulations (DNS) of turbulent, premixed, lean hydrogen/air flames (Wang et al., 2024). It is found that the critically stretched flame consumption velocities obtained from these two configurations are closely aligned, while the flame thickness obtained from the spherically expanding flames is substantially greater than that from the counter-flow twin premixed flames. Capabilities of these flame characteristics for capturing the thermodiffusive effects on &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; are demonstrated by incorporating these characteristics into fits to &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; dataset obtained from the aforementioned DNS study. Various definitions of flame thickness are also examined, with the thickness of fuel consumption zone showing the best performance. These findings support the leading point concept and imply that both critically strained planar flames and highly curved spherically expanding flames could be used to characterize the local burning state at the leading edges of turbulent lean premixed hydrogen flames.&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 consists of comparing characteristics of critically stretched laminar flames, extracted from two flame configurations, i.e., twin planar counterflow flames and highly curved spherical flames. The results show that flame consumption velocities are approximately equal in these two extreme cases if complex chemistry of lean hydrogen burning is taken into account. Furthermore, for the first time to the authors’ knowledge, the results (i) validate the leading point concept under conditions of fixed Karlovitz and Damköhler numbers, but different pressures and temperatures, (ii) indicate utility of characteristics of highly curved spherically expanding flames within the framework of this concept, and (iii) imply that the width of fuel consumption zone is better suited for evaluating thicknesses of critically stretched laminar flames (again within the framework of this concept). It is significant becaus","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114306"},"PeriodicalIF":5.8,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144518204","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}