Combustion and Flame最新文献

{"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":"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}

{"title":"Large-eddy simulation of air-propane premixed combustion affected by centrifugal acceleration","authors":"Ghasem Moshir,&nbsp;Alireza Mostofizadeh,&nbsp;Mehrdad Bazazzadeh","doi":"10.1016/j.combustflame.2025.114299","DOIUrl":"10.1016/j.combustflame.2025.114299","url":null,"abstract":"<div><div>Lewis's experimental investigation of the impact of centrifugal acceleration on flame propagation speed posed a novel concept that could shorten combustion chamber length and improve the thrust-to-weight ratio. This work implemented the large-eddy simulation (LES) of air-propane premixed combustion in a closed pipe under centrifugal acceleration on the OpenFOAM software platform. First, using the moving reference frame (MRF) method, the cold flow mixture in the rotating tube was investigated. Then, the combustion of the resulting air-propane mixture at specific centrifugal accelerations (expressed in g) is simulated. Five different cases were considered, including one case without rotation and four cases with centrifugal accelerations of 395 g, 1000 g, 3000 g, and 4000 g. The flame surface wrinkling, a key parameter in premixed combustion, was studied along the longitudinal axis and in the radial direction. For centrifugal acceleration up to 3000 g, the flame surface wrinkling and flame propagation speed raised, but with increasing centrifugal acceleration, these parameters decreased. By investigating the temperature gradient along the longitudinal axis of the pipe, the maximum value occurred in the 4000 g case. The produced pressure wave in the tube was also studied by investigating the instantaneous pressure gradient contour and concluding that the reflected pressure wave does not collide with the flame surface between the flame speed measurement locations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114299"},"PeriodicalIF":5.8,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144511045","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":"Unraveling non-equilibrium kinetics in plasma-driven methanol ignition: A combined experimental and global modelling study","authors":"Nan Liu ,&nbsp;Qi Chen ,&nbsp;Shuang Yu ,&nbsp;Zhiyuan Qian ,&nbsp;Jie Chen ,&nbsp;Xianwu Jiang","doi":"10.1016/j.combustflame.2025.114321","DOIUrl":"10.1016/j.combustflame.2025.114321","url":null,"abstract":"<div><div>Methanol holds promise as a fuel for spark ignition engines in achieving carbon neutrality, though its cold-starting remains a key challenge. Non-equilibrium plasma excitation emerges as a transformative solution, where a mechanistic understanding of reaction kinetics, particularly electron-fuel interactions governing radical generation and chain branching, is pivotal to advancing the efficiency of plasma-assisted methanol ignition. This study investigates the kinetic interplay between non-equilibrium plasma excitation and methanol oxidation through combined experiments and modelling. A detailed kinetic mechanism for plasma-driven methanol ignition is developed, incorporating electron scattering cross-sections of CH₃OH calculated via the <em>R</em>-matrix method. For the first time, wall quenching of electronically excited species is integrated into the model. Experimental validation using GC confirms the modelling accuracy in predicting species evolution. Key findings reveal that non-thermal plasma reduces ignition delay time by 1–3 orders of magnitude compared to auto-ignition, with 89 % of discharge energy allocated to non-equilibrium excitation and &lt;10 % to thermal effects. Path flux analysis reveals that there are distinct dissociation pathways for methanol under plasma conditions. Combustion reactions predominantly produce CH₂OH via H-atom abstraction, while plasma reactions primarily generate CH₃O through e + CH₃OH → e + CH₃O + H and CH₃OH + X^⁎(N(²D), O(¹D)) → CH₃O + XH. The difference is due to the fact that excited CH₃OH is dissociated into CH₃O and H, demonstrated via Quantum chemical calculations. Notably, electronically excited methanol undergoes two competing processes: the wall quenching reactions (CH₃OH(e) + Wall → CH₃OH + Wall) and the dehydrogenation reactions (CH₃OH(e) + OH/HO₂ → CH₂OH + H₂O/H₂O₂). The former quenches excited species, while the latter increases fuel radicals, thereby accelerating the chain reaction. These insights bridge plasma physics and combustion chemistry, offering a predictive framework for optimizing plasma-assisted methanol ignition under cold-starting conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114321"},"PeriodicalIF":5.8,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502206","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":"Effect of annulus width on combustion characteristics of liquid oxygen/methane swirl coaxial injectors","authors":"Pengjin Cao,&nbsp;Xiao Bai,&nbsp;Qinglian Li,&nbsp;Peng Cheng","doi":"10.1016/j.combustflame.2025.114217","DOIUrl":"10.1016/j.combustflame.2025.114217","url":null,"abstract":"<div><div>A parametric investigation was conducted based on an experimental approach to evaluate the effect of annulus width on spray and flame dynamics in liquid oxygen/methane swirl coaxial injectors. By employing dual-camera laser background light imaging and visualization of a rectangular combustor, a comprehensive range of combustion characteristics were captured, including spray morphology, flame structure, and combustion stability. The results demonstrate that the combustion process of the liquid oxygen/methane engine can be classified into two distinct categories: quasi-steady (QS) combustion and quasi-steady converting to unstable (QSCU) combustion, as the annulus width increases. The spray and flame of QS combustion exhibits a conical shape, whose spray length, spray cone angle, and flame spreading angle are rise with increasing the annulus width. During QSCU combustion, a portion of the liquid oxygen inside the injector vaporizes, leading to oscillations in both the spray and the flame. These oscillations, in turn, induce combustion instabilities within the frequency range of 43.3 to 48.3 Hz. The flame morphology undergoes a series of transformations, beginning with a stable cone, then evolving into a “double cone”, and ultimately manifesting as a “tadpole”. Subsequently, the flame exhibits periodic flashback and filling motion. During shutdown, the spray cone angle and flame spreading angle gradually increase. This is followed by the emergence of combustion oscillation, with an oscillation frequency distributes between 337.4 and 356.0 Hz. This oscillation is independent of the supply system and is primarily attributed to flame oscillates within the outer recirculation zone.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114217"},"PeriodicalIF":5.8,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144489716","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}