Proceedings of the Combustion Institute最新文献

{"title":"A Martian-ready fuel ignition revealed: what the second OH group really changes","authors":"Nurlan Amirov,&nbsp;Zeynep Serinyel,&nbsp;Fabrice Foucher,&nbsp;Guillaume Dayma","doi":"10.1016/j.proci.2026.106159","DOIUrl":"10.1016/j.proci.2026.106159","url":null,"abstract":"<div><div>The combustion mechanism of 2,3-butanediol, a potential Martian rocket propellant, remains unexplored up to date. In this study, the first ever measured ignition delay times of 2,3-butanediol are reported. A single-piston rapid compression machine was used to carry out the measurements at lean, stoichiometric and rich conditions at compressed gas pressures of 10, 15 and 20 bar and at compressed gas temperatures ranging from 815 to 1010 K. In order to be able to make a direct comparison and analyze the effect of the second hydroxy group on the reactivity, experiments under the same conditions were also conducted for 2-butanol. The comparison showed that both fuels overall have very similar ignition behavior, 2,3-butanediol igniting slightly faster than 2-butanol at all conditions. Furthermore, a comprehensive kinetic sub-mechanism for 2,3-butanediol was developed, including high- and low-temperature reactions based on a recent 2-butanol mechanism and validated against the experimental ignition delay times. Overall, successful agreements were achieved by the mechanism for both fuels. Sensitivity analysis on temperature performed for low and high temperatures at stoichiometric ratio and 15 bar compressed gas pressure for both fuels revealed that the main sensitive reactions are H-abstraction reactions by OH and HO₂ radicals along with some reactions from C₀ sub-mechanism. Moreover, reaction pathway analyses revealed that the reactivity of both fuels is mainly driven by their α-radicals, which then follow different pathways: β-scission and direct oxidations leading to reactive intermediates (lactaldehyde, hydroxyacetone and 3-hydroxybutanone) for 2,3-butanediol, on the other hand, reaction with O₂ leading to a relatively less reactive species (butanone) for 2-butanol.</div></div><div><h3>Novelty and significance statement</h3><div>A potential production pathway of 2,3-butanediol on Mars using biotechnology-enabled in situ resource utilization strategy has recently been investigated by Kruyer et al. [1] who proposed the implication of this diol as a Mars relevant rocket propellant. A comprehensive kinetic mechanism developed in this study for 2,3-butanediol, including high- and low-temperature reactivity regimes is an important step as a first attempt to understand its oxidation chemistry. It is validated against the first ever measured ignition delay times of 2,3-butanediol in this work. The study is of its first kind for any diol up to date. Furthermore, 2-butanol, for whose ignition behavior only limited works are available, is also subject to investigation at exactly the same conditions as 2,3-butanediol. This allows to make a direct comparison to reveal the differences in the oxidation nature of these fuels to understand the effects of the second hydroxy group on the global reactivity.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106159"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of lean hydrogen-air premixed flames under high-frequency acoustic forcing: Flame morphology and displacement speed","authors":"Xinyi Chen,&nbsp;Frederick W. Young,&nbsp;Umair Ahmed,&nbsp;Robert Stewart Cant","doi":"10.1016/j.proci.2026.106011","DOIUrl":"10.1016/j.proci.2026.106011","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Fully compressible numerical simulations of two-dimensional laminar lean hydrogen-air premixed flames have been performed, with the flame front subjected to acoustic forcing through the specification of a monopole-type sound source at the inflow. Simulations have been performed for acoustic frequencies ranging from 35 kHz to 500 kHz at two equivalence ratios, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. During the flame-acoustic interaction, the flame evolves from an initially weakly stretched state to exponential perturbation growth, wrinkle interaction, and the formation of non-linear cellular structures, with distinct linear and non-linear stages identified from Fourier mode analysis. The instability dynamics depend strongly on both forcing frequency and equivalence ratio. In the case of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, the flame behaviour is strongly influenced by thermodiffusive instability, with a characteristic sequence of uniform cells, cell splitting, and cell merging. For &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, weaker thermodiffusive effects result in a response more strongly governed by hydrodynamic instability and large-scale wrinkle growth. At low forcing frequencies, flame corrugations remain relatively uniform, whereas at high frequencies the flame front becomes increasingly modulated and develops envelope-like structures, which can be interpreted as the interaction between an intrinsic standing cellular mode and the imposed acoustic disturbance. In the linear growth regime, the density-weighted displacement speed, &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;∗&lt;/mo&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;, shows a linear correlation with total stretch rate, &lt;span&gt;&lt;math&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, for all forcing frequencies. While in the non-linear growth regime, two distinct branches appear, corresponding to weakly stretched flame segments and strongly negatively curved segments associated with flame pinch-off.&lt;em&gt;Novelty and significance statement:&lt;/em&gt; This paper reports results from numerical simulations for lean hydrogen-air premixed flames subjected to acoustic oscillations originating from an approximate acoustic monopole. The study addresses the dependence of flame instability patterns on both acoustic forcing frequency and equivalence ratio for the first time. A conceptual framework is proposed to interpret the behaviour of flame evolution. The correlations between density-weighted displacement speed and the total stretch rate are reported for the linear and non-linear growth phases of the flame for the first time in the case of acoustically excited lean hydrogen-air flames. These findings advance the fundamental understanding of acoustically trigg","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106011"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical investigation of differential diffusion and thermal expansion on iron flame propagation at microgravity conditions","authors":"Xu Wen,&nbsp;Fengge Yang,&nbsp;Christian Hasse","doi":"10.1016/j.proci.2026.106156","DOIUrl":"10.1016/j.proci.2026.106156","url":null,"abstract":"<div><div>Microgravity provides ideal conditions for measuring the propagation speed of fuel-lean iron flames with intrinsically low flame speeds, as it suppresses particle sedimentation and buoyancy effects. This work presents a numerical investigation of iron cloud combustion under microgravity conditions, based on the sounding-rocket experiments of Palečka et al. (CNF, 2019). The effects of differential diffusion and thermal expansion on the combustion characteristics of iron particle clouds are quantified. For the <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>/Xe oxidizer mixtures considered here, differential diffusion is expected to be important because Xe has a lower thermal diffusivity than <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. This can affect both the local flame temperature and the flame propagation speed by changing the oxygen mass concentration at the particle surface. Although the particles are nearly stationary under microgravity conditions, thermal expansion can still induce particle motion and thereby alter the local particle concentration. The influence of thermal expansion on the overall combustion behavior of the particle cloud is therefore also quantified. The numerical predictions obtained with differential diffusion and thermal expansion are compared with available experimental data for two oxidizer environments, 20% <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>/80% Xe and 40% <span><math><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>/60% Xe, as well as with corresponding simulations in which these effects are neglected. Overall, the predicted flame structure, flame speed, and flame temperature agree well with the measurements for both oxidizer environments.</div><div><em>Novelty and significance statement</em>: The number of numerical studies for iron combustion at microgravity conditions is limited. In this work, a numerical investigation of fuel-lean iron combustion at microgravity conditions is conducted following the sounding rocket experiment by Palečka et al. (CNF, 2019), in which the effects of differential diffusion and thermal expansion on iron flame propagation are considered for the first time. The simulation results are compared to the unique measurements, including the camera recorded image, flame propagation speed, and the flame temperature, and good overall agreement is achieved. The effects of differential diffusion on the flame propagation speed and the overall flame structure are quantified, and the effects of thermal expansion on the particle motion are investigated in detail. This work is significant since the validated numerical model can aid the design of the new type burner for iron combustion and accelerate the goal of decarbonization combustion.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106156"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582596","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":"On the importance of 2D modeling for quantitative species measurements in burner-stabilized ammonia flames","authors":"A. Cuoci,&nbsp;P. Desgroux,&nbsp;N. El Baba,&nbsp;A. Frassoldati,&nbsp;N. Lamoureux","doi":"10.1016/j.proci.2026.106145","DOIUrl":"10.1016/j.proci.2026.106145","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Ammonia flames stabilized on porous burners are commonly modeled using steady, one-dimensional (1D), isobaric formulations that assume radial uniformity. While this approach is effective for kinetic studies, its validity under low-pressure conditions remains uncertain due to enhanced transport effects. In this work, three low-pressure NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&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;/O&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;/N&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; premixed flames (&lt;span&gt;&lt;math&gt;&lt;mi&gt;Φ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 0.87–1.33, &lt;span&gt;&lt;math&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 10 kPa) were investigated using quantitative laser diagnostics and detailed-chemistry simulations. New absorption-calibrated Laser-Induced Fluorescence measurements of NH, including both axial and radial profiles, are reported together with complementary OH radial profiles, extending previously available datasets for NO and OH. Two-dimensional (2D, axisymmetric) simulations including detailed transport, radiation, and the full burner enclosure were performed and compared with conventional 1D models. While 1D simulations reproduce the general flame structure, they fail to capture the pronounced post-flame decrease of NO (up to 40% over 30 mm) observed in lean and stoichiometric conditions. The 2D simulations reproduce the measured NH and OH distributions and show that the NO decrease originates primarily from transport-induced dilution with burned gases entrained from the surrounding chamber, rather than from additional gas-phase chemical pathways. This effect extends over the axial region typically used for kinetic analysis, indicating that deviations from one-dimensional behavior cannot be neglected under these conditions. These results provide both new experimental datasets and a validated framework to quantify multidimensional transport effects, enabling a more reliable interpretation of low-pressure ammonia flames for the validation and development of detailed kinetic mechanisms.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; The paper presents the first quantitative in-situ measurements (using absorption-calibrated LIF) of NH mole fraction in low-pressure burner-stabilized ammonia flames (BSF). The radial species profiles show important inhomogeneities that call into question the validity of 1D simulations that neglect multidimensional transport effects and entrainment of the surrounding gas. In NH&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&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; flames characterized by low inlet gas velocity, the 2D simulation results agree well with the previously reported experimental NO and OH profiles, as well as with the present NH measurements. This study demonstrates for the first time that 2D effects, such as transport-induced entrainment of the burned gases in the chamber, strongly influence post-flame NO levels under low-pressure conditions. ","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106145"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582610","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A high-pressure jet-stirred reactor study of di-iso-pentyl ether oxidation and detailed kinetic modelling","authors":"Zeynep Serinyel,&nbsp;Guillaume Dayma,&nbsp;Giorgia Cenedese,&nbsp;Philippe Dagaut","doi":"10.1016/j.proci.2026.106169","DOIUrl":"10.1016/j.proci.2026.106169","url":null,"abstract":"<div><div>In this study, the oxidation of di-iso-pentyl ether (DIPEE) is investigated for the first time. Dilute mixtures (DIPEE/O₂/N₂) were oxidized in a jet-stirred reactor at 10 atm, between 450 and 1210 K and at a residence time of 0.7 s. Four mixtures were tested with equivalence ratios of 0.5, 1, 2, and 4. In the low/intermediate temperature region, about 40 species were identified and quantified through FTIR and GC-FID-MS analyses. Given the quantified intermediates, it was observed that alkyl radical intermediates such as iso-pentyl and iso-butyl radicals appear to play an important role as intermediates in DIPEE oxidation. The most abundant oxygenated intermediate species at low temperature include formaldehyde, iso-pentanal, acetaldehyde, and acetone with mole fractions greater than 100 ppm. Besides, species such as iso-butanal, isopentanoic acid, isoamyl formate, and isoamyl alcohol were also identified and quantified. DIPEE has very high reactivity (here, it starts to oxidize at 470 K) and exhibits two distinct zones of negative temperature coefficient before the high-temperature zone, which can also be referred to be as a double-cool flame. This behavior is due to the interactions caused by the low-temperature chemistry of the alkyl radicals within the cool flame regime. A detailed kinetic sub-mechanism for DIPEE oxidation was developed including detailed low-temperature reactions of species like iso-pentanal and iso-butanal, based on our previous studies. While the kinetic mechanism predicts the experimental profiles reasonably well, there is room for improvement especially for the rate constants of the low-temperature reactions of the oxygenated species for which very few theoretically obtained or directly measured values exist.</div></div><div><h3>Novelty and significance statement</h3><div>This is the first time di-iso-pentyl ether is studied for its combustion kinetics (detailed speciation and kinetic mechanism). Our ether oxidation mechanism is updated with this new sub-mechanism and used to explain the “unconventional” double cool-flame behavior exhibited by this fuel. This is a rather recent and hence under-studied area of low-temperature oxidation. This study on di-iso-pentyl ether reveals similarities and differences between the trends observed with dialkyl ethers previously studied in the same experimental set-up under same thermodynamic conditions. With &gt;30 products identified, it helps constraining the kinetic mechanism while pointing out sources of inaccuracies commonly encountered but not necessarily addressed. Some of these ethers have the potential to be a biofuel, but they also contribute to the understanding the fundamentals of low-temperature chemistry dealing with the double cool-flames.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106169"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study and kinetic modeling on the effects of HBr on CO and NO emissions during CO/NH3 co-combustion","authors":"Jing Zhao,&nbsp;Qingqing Chen,&nbsp;Yang Wang,&nbsp;Sen Li,&nbsp;Xiaolin Wei","doi":"10.1016/j.proci.2026.106285","DOIUrl":"10.1016/j.proci.2026.106285","url":null,"abstract":"<div><div>Bromine released from fossil fuel combustion, particularly in the form of HBr, is a significant atmospheric pollutant and a well-known inhibitor in combustion systems. However, its precise reaction mechanism during CO/NH₃ co-combustion remains unclear and highly sensitive to reaction conditions. To address this research gap, this work conducts an experimental and kinetic modeling study to investigate the effect of HBr on CO and NO emissions under simplified combustion conditions. Using an entrained flow reactor and detailed kinetic analysis, we examined HBr’s influence across a range of temperatures and concentrations. The results show that HBr strongly inhibits CO oxidation and NO formation at lower temperatures (1023–1123 K) by scavenging H radicals via reaction R272 (HBr + H = Br + H₂). This effect, however, is highly temperature-dependent: at higher temperatures (up to 1223 K), the influence shifts to NO promotion, attributed to the kinetically favored Br-species reaction R302 (Br + HNO = HBr + NO). This study provides critical insights into the competing radical mechanisms governing halogen-pollutant interactions, thereby advancing the mechanistic understanding of HBr’s temperature-dependent effects on pollutant emissions during CO/NH₃ co-combustion.</div></div><div><h3>Novelty and Significance Statement</h3><div>This work focuses on the industrially relevant CO/NH₃ co-combustion system, a research niche less explored in halogen combustion chemistry, and combines entrained flow reactor experiments with multi-dimensional kinetic analyses (ROP, sensitivity, radical profiling) to uncover the distinct temperature-dependent dual effects of HBr: potent inhibition of CO oxidation and NO formation at 1023–1123 K via H-radical scavenging (R272: (H + HBr = H2 + Br)), and a shift to NO promotion above 1173 K driven by kinetically dominant R302: Br + HNO = NO + HBr. It clarifies the radical competition mechanism of bromine-containing species in halogen-nitrogen-carbon coupling reactions, furnishing novel kinetic insights into HBr’s regulatory role in denitration-related combustion processes. The findings further provide a targeted theoretical basis for optimizing pollutant control strategies in bromine-containing combustion systems, supplementing the current understanding of halogen-involved combustion chemistry.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106285"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148656884","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":"Dynamics of flame initiation, propagation, and transition to detonation","authors":"Zheng Chen,&nbsp;Wang Han,&nbsp;Tianhan Zhang","doi":"10.1016/j.proci.2026.106299","DOIUrl":"10.1016/j.proci.2026.106299","url":null,"abstract":"<div><div>Understanding of flame initiation, propagation, and transition to detonation is vital for both fundamental combustion science and practical applications, including the development of high-performance engines and the enhancement of explosion safety. This paper reviews recent progress in the flame dynamics and critical physical conditions governing these interconnected processes, focusing on <em>laminar, premixed, gaseous</em> mixtures. First, recent advances in forced ignition of premixed flames are reviewed, with an emphasis on theoretical analysis of critical ignition radius and minimum ignition energy. The effects of low-temperature chemistry and imposed flow on forced ignition of premixed flames are also discussed. Subsequently, flame propagation into autoigniting mixtures is addressed. Under engine-relevant high-temperature and high-pressure conditions, the ignition delay of the end-gas can become comparable to the flame transit time, leading to end-gas autoignition, autoignition-assisted flames, and cool flame development and transition to hot flame. Finally, the dynamics of autoignition-induced transition to detonation are analyzed, with a focus on the mechanism for detonation development in autoigniting mixtures. Throughout the paper, the continuous physical chain—from ignition kernel initiation to flame propagation and ultimately to detonation transition—is emphasized.</div><div><em>Novelty and significance statement:</em> This review uniquely connects forced ignition, flame propagation into autoigniting mixtures, and transition to detonation. It presents recent theoretical advances in premixed flame ignition, end-gas autoignition, and detonation development. The role of low-temperature chemistry in reducing ignition energy, enabling flame propagation, and promoting detonation development is highlighted. The paper also discusses flow-facilitated ignition, autoignition-assisted flame speed scaling, and practical implications for detonation development in engines, thereby offering a systematic foundation for controlling extreme combustion events.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106299"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148656923","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 Review of interactive smoldering-flaming fires at the wildland-urban interface","authors":"Xinyan Huang,&nbsp;Shaorun Lin,&nbsp;Yuying Chen,&nbsp;Yunzhu Qin,&nbsp;Yichao Zhang,&nbsp;Yifei Ding","doi":"10.1016/j.proci.2026.106298","DOIUrl":"10.1016/j.proci.2026.106298","url":null,"abstract":"<div><div>Wildland–urban interface (WUI) fires show complex interactions among multi-fuel burning, the built environment, and extreme atmospheric conditions, posing a growing global hazard. Although flaming has traditionally dominated the combustion research for wildfires and their mitigation frameworks, increasing evidence indicates that smoldering combustion plays a critical and often underrecognized role in fire ignition, spread, and persistence. Smoldering of WUI fuels often coexists with flaming, and their dynamical interactions through different ignition and extinction processes control the spread of WUI fires. This work first synthesizes distinctive WUI fire phenomena, including firebrand showers, cascading vegetation-structure interactions, and structure-to-structure fire spread. The fundamentals of smoldering and flaming fire behaviors are reviewed to highlight their similarities and differences in the initiation and development of large outdoor fires. Then, we present a detailed analysis of bi-directional smoldering-flaming transition and symbiotic co-existence as unifying mechanisms linking diverse fire behaviors. Finally, we highlight challenges and future research directions in understanding WUI fire dynamics, including innovative modeling methods, data-driven and AI-assisted fire forecasting, characterization of coupled and derived fire hazards, and the integration of combustion fundamentals into performance-based community fire protection codes and mitigation frameworks.</div><div>Novelty and significance statement</div><div>This review has examined wildland–urban interface fires through a progressive synthesis of unique fire phenomena, underlying combustion fundamentals, and their interactions. This work first synthesizes distinctive WUI fire phenomena, including firebrand showers, cascading vegetation-structure interactions, and structure-to-structure fire spread. Then, we present a detailed analysis of bi-directional smoldering-flaming transition and symbiotic co-existence as unifying mechanisms linking diverse fire behaviors. Finally, the review highlights challenges and future research directions in understanding WUI fire dynamics and the integration of combustion fundamentals into performance-based community fire protection strategies.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106298"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148737772","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":"Tracing oxygen incorporation in flame-formed soot from oxygenated fuels","authors":"Mariano Sirignano,&nbsp;Vincenzo Esposito,&nbsp;Barbara Apicella,&nbsp;Carmela Russo","doi":"10.1016/j.proci.2026.106624","DOIUrl":"10.1016/j.proci.2026.106624","url":null,"abstract":"<div><div>The influence of oxygenated fuels on soot oxidation chemistry was investigated to clarify the role of acetaldehyde (CH₃CHO) in oxygen incorporation onto soot particles. Premixed fuel-rich flames of ethylene (C₂H₄) and six oxygenated blends – ethanol (EtOH), oxymethylene ether-3 (OME₃), and four butanol isomers – were studied under identical conditions (<strong>Φ</strong> = 2.46). Soot samples were characterized using infrared spectroscopy (FTIR), UV–visible (UV–vis) spectroscopy, and thermogravimetric analysis (TGA), while CH₃CHO concentrations were measured in the exhaust. Specifically, to quantify oxygen in the collected particles, TGA in an inert environment was combined with UV–vis spectroscopy. UV–vis measurements were used to estimate the volatile organic fraction, enabling attribution of the remaining TGA mass loss to oxygen-containing surface groups. A consistent correlation between soot oxygen content and CH₃CHO concentration was observed across all fuels, identifying CH₃CHO as a key oxidizing intermediate in particle growth. Building on this evidence, a surface reaction model inspired by analogous gas-phase kinetics was developed and implemented within a sectional framework that accounts for particle-size-dependent reactivity. Using a single effective rate constant, the model accurately reproduced the experimentally measured oxygen content within 15 wt.% of relative error for all cases. These results establish a quantitative link between gas-phase oxidation intermediates and soot surface functionalization, providing a framework to integrate oxygen-addition chemistry into predictive soot models and flame synthesis applications.</div><div><strong>Novelty and significance statement</strong></div><div>Despite the recognized potential of oxygenated fuels to lower soot emissions, the mechanism by which oxygen becomes incorporated into soot has remained unresolved. This work identifies acetaldehyde (CH₃CHO) as a key gas-phase driver of soot oxygenation and establishes, for the first time, a quantitative correlation between CH₃CHO concentration and soot oxygen content across a broad set of oxygenated-fuel flames. By combining complementary diagnostics, soot oxygenation was independently assessed and linked to gas-phase chemistry. A lumped kinetic scheme, inspired by the analogous gas-phase C₆H₅• + CH₃CHO reaction and implemented in a sectional soot model, reproduced the measured oxygen content using a single effective rate constant. These results move soot oxygenation from a qualitative observation to a predictive framework, enabling integration of oxygen-functionalization pathways into combustion and flame-synthesis models. Beyond emission control, the study opens a route to tailoring the surface chemistry of flame-formed carbon nanostructures through fuel-dependent oxidation chemistry.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106624"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149050872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Propanal oxidation at engine-relevant conditions: Autoignition and species evolution in an RCM","authors":"Jesus Caravaca-Vilchez,&nbsp;Karl Alexander Heufer","doi":"10.1016/j.proci.2026.106627","DOIUrl":"10.1016/j.proci.2026.106627","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Understanding the oxidation of propanal, a toxic carbonyl compound formed during the oxidation of bio-derived fuels and hydrocarbons, is critical for emission control in combustion engines. Prior low-temperature jet-stirred reactor (JSR) studies were limited to either low-pressure conditions with moderate fuel loadings, or higher pressures at highly diluted conditions. To bridge the gap between JSR and engine operation, ignition delay times (IDTs) were measured in a rapid compression machine (RCM) over a wide range of conditions (10-40 bar, 609-957 K, and &lt;span&gt;&lt;math&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 0.5-1.5), alongside simultaneous measurements of species concentrations using a single-valve gas sampling system and Gas Chromatography-Mass Spectrometry techniques. The propanal subset of the C3MechV4.0.1 model was revised using rate analogies to propane and our recent acetaldehyde mechanism. The latter contains fuel-specific radical reactions that were absent in the original model. The revision also incorporated literature-based rate refinements and thermochemistry updates. Our kinetic analysis indicates that, at low-temperature RCM conditions, propanal oxidation is governed by fuel-specific peroxyl pathways and alkylperoxyl reactions. At higher temperatures or lower oxygen concentrations, the former channels are disfavored, while alkylperoxyl pathways compete with concerted elimination steps and reactions with hydroperoxyl radicals. Literature models significantly underpredict low-temperature reactivity at RCM conditions, including those performing reasonably well against JSR targets. These discrepancies arise from missing fuel-specific peroxyl pathways or an underestimation of alkylperoxyl chemistry. The updated mechanism reproduces most measured targets and generally outperforms the original model against literature data. Remaining discrepancies in the medium-temperature RCM regime and at low-temperature, highly-diluted JSR conditions highlight fundamental knowledge gaps in alkylperoxyl and fuel radical chemistry. This work provides a basis for understanding propanal oxidation at engine-relevant conditions.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; This work presents the first investigation of low-temperature propanal oxidation at both high pressure and high reactant concentrations using a rapid compression machine, providing IDTs and simultaneous species measurements at engine-relevant conditions. These data extend prior low-temperature targets that were limited to either low pressures (Zhang et al., 2019) or low fuel loadings (Veloo et al., 2013). A systematic reassessment of propanal oxidation chemistry using rate analogies to propane and our recently developed acetaldehyde mechanism (Caravaca-Vilchez et al., 2025), together with refinements constrained by the new data, resulted in a mechanism with improved predictive performance compared to existing models.&lt;/div&gt;&lt;div&gt;This study contributes to the advancement of the mechanisti","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106627"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149153648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}