Combustion and Flame最新文献

{"title":"On the effect of RDX inclusion in an AP/HTPB composite propellant: A numerical study with detailed kinetics","authors":"Pierre Bernigaud ,&nbsp;Dmitry Davidenko ,&nbsp;Laurent Catoire","doi":"10.1016/j.combustflame.2025.114162","DOIUrl":"10.1016/j.combustflame.2025.114162","url":null,"abstract":"<div><div>In this work, the effect of hexogen (RDX) inclusion in a conventional ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant is investigated. To this end, a detailed gas-phase kinetic mechanism for the ternary system AP/HTPB/RDX is proposed. A revised vapour pressure law is used to model RDX evaporation. The combustion model is able to represent the chemical processes within the flame produced by the combustion of pure AP, homogenized AP/HTPB pseudo-propellants, and pure RDX. With this kinetic model, the combustion of a single RDX particle surrounded by a layer of homogenized AP/HTPB binder is simulated in a 2D axisymmetric configuration. It is shown that RDX inclusion significantly alters the combustion of the propellant. A phenomenological description of the flame structure forming above the heterogeneous propellant is proposed. This flame does not conform to the Beckstead–Derr–Price model, usually valid for conventional AP/HTPB propellants. Ambient pressure and RDX particle size are varied to assess the effect of these key parameters on the combustion. Two combustion regimes are identified: the hot and mild regimes. Conditions for the appearance of each combustion regime are determined in terms of ambient pressure and RDX particle size.</div><div><strong>Novelty and Significance</strong></div><div>Composite propellants could include nitramine ingredients such as hexogen (RDX) in their formulation to improve their performance. The effect of RDX inclusion in a conventional ammonium perchlorate (AP) / hydroxyl-terminated polybutadiene (HTPB) propellant was experimentally studied in the past <span><span>[1]</span></span>, <span><span>[2]</span></span>. However, understanding the fine combustion processes at stake remained out of reach. On the other hand, numerical simulation of the combustion was unachievable, as no gas-phase kinetic mechanism for the ternary system AP/HTPB/RDX was available. This paper first proposes such a kinetic model based on previous work by the authors on pure AP <span><span>[3]</span></span> and AP/HTPB combustion <span><span>[4]</span></span>. In doing so, a revised vapour pressure law is proposed for RDX combustion. With this mechanism, the flame structure obtained above an AP/HTPB/RDX propellant is computed. RDX inclusion significantly alters the combustion of the AP/HTPB propellant via specific processes, which are highlighted.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114162"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828297","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":"Study on the mechanism of polycyclic aromatic hydrocarbons and soot formation in ethylene/hydrogen/ammonia laminar diffusion flames","authors":"Yang Wang ,&nbsp;Ke Liu ,&nbsp;Kun Luo ,&nbsp;Kunzhuo Chang ,&nbsp;Mingyan Gu","doi":"10.1016/j.combustflame.2025.114168","DOIUrl":"10.1016/j.combustflame.2025.114168","url":null,"abstract":"<div><div>Ammonia, as an excellent zero-carbon hydrogen storage energy source, presents a significant research focus in the field of combustion regarding how to achieve efficient and clean combustion. The combustion of hydrocarbon fuels with hydrogen-ammonia addition can enhance ammonia combustion performance, reduce carbon emissions from hydrocarbon fuels, and control soot formation; however, the underlying mechanisms remain unclear. This study uses the CoFlame code to simulate the evolution of soot formation in ethylene/hydrogen/ammonia co-flow laminar diffusion flames and analyzes the mechanisms of polycyclic aromatic hydrocarbons formation and growth influenced by hydrogen-ammonia addition. The study found that the predicted soot volume fraction and average primary particle diameter align well with experimental measurements, indicating that the suppressive effect of hydrogen-ammonia addition increases as the hydrogen/ammonia ratio decreases. The addition of hydrogen-ammonia suppresses the nucleation, surface growth, and agglomeration processes of soot in the ethylene flame. The normalization study indicates that the rates of soot nucleation and surface growth align more closely with the evolution of soot volume fraction, making them the primary contributors to the reduction in soot volume fraction. This is identified as the primary reason for the reduction in soot volume fraction. Reaction pathway analysis indicates that the most significant reaction pathway for the gradual formation of pyrene from A₁ under the influence of small molecular components and free radicals in the ethylene/hydrogen/ammonia flame is as follows: A₁→indene→indenyl→A₂R₅→A₂→A₂⁻→A₃⁻→A₄. Quantitative analysis reveals that the chemical effect of hydrogen-ammonia addition effectively suppresses the hydrogen extraction reaction of A₂ by reducing the concentration of hydrogen radicals, thereby decreasing the formation rate of A₄.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114168"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834720","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":"Assessment of the Flamelet Generated Manifold method with preferential diffusion modeling for partially premixed hydrogen flames","authors":"E.J. Pérez-Sánchez,&nbsp;E.M. Fortes,&nbsp;D. Mira","doi":"10.1016/j.combustflame.2025.114141","DOIUrl":"10.1016/j.combustflame.2025.114141","url":null,"abstract":"<div><div>This study presents a systematic analysis of the capabilities of a flamelet model based on Flamelet Generated Manifolds (FGM) to reproduce preferential diffusion effects in partially premixed hydrogen flames. Detailed transport effects are accounted for by including a mixture-averaged transport model when building the flamelet database. This approach adds new terms into the diffusive fluxes of the transport equations of the controlling variables coming from a set of coefficients computed from the data contained in the manifold. The manifold is constructed from the solution of a set of unstretched adiabatic one-dimensional premixed flames within the flammability range using mixture-averaged transport. Special attention is given to the numerical aspects related to the construction of the chemical manifold and how to reduce the numerical errors when evaluating the gradients in composition space required for the fluxes. Finally, a systematic application of the method to simulate laminar hydrogen flames in various canonical configurations is presented from premixed to stratified flames, including the case of a triple flame with different mixing lengths. The results demonstrate that the method describes accurately the flame structure and propagation velocities at a low cost, showing a remarkable agreement with the detailed chemistry solutions for flame structure and propagation speed.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of the paper lies on the presentation of an extended, robust and comprehensive model for tabulated chemistry incorporating mixture-averaged diffusion. The paper demonstrates the suitability of the model to describe stratified flames when preferential diffusion effects are important by simulating a relevant set of canonical flame configurations. The significance of the paper is that it allows to accurately reproduce a complex phenomenon as it is differential diffusion by the application of a tabulated method, without introducing overheads, and allowing to drastically reduce the computational cost of the simulations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114141"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828296","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":"An improved machine learning method for thermochemistry tabulation, with application to LES-PDF simulations of piloted diffusion and swirl-bluff-body stabilised flames with NOx formation","authors":"Tianjie Ding,&nbsp;W.P. Jones,&nbsp;Stelios Rigopoulos","doi":"10.1016/j.combustflame.2025.114130","DOIUrl":"10.1016/j.combustflame.2025.114130","url":null,"abstract":"<div><div>Many turbulent combustion modelling approaches require real-time computation of reaction source terms, which is time-consuming and represents a bottleneck of turbulent combustion simulations. In order to speed up the reaction computation process, an artificial neural network (ANN) thermochemistry tabulation methodology has been proposed and developed in our previous work (Ding et al., 2021). In the present work, this methodology is further developed and applied to thermochemistry that includes NO_x formation, which poses further challenges due to the small concentrations of the N-containing species. In particular, we build on the Multiple Multilayer Perceptrons (MMLP) concept, which aims to improve prediction accuracy by systematically combining multiple ANNs. A new method, MMLP-II, is proposed in this work, which trains different ANNs to predict states with different ranges of initial species concentration, in contrast to the previous MMLP-I method which trains several ANNs with different ranges of output magnitude. Both MMLP methods are applied to tabulate the complete GRI-3.0 mechanism and the resulting ANNs are tested on two different turbulent methane flames: Sandia flame D and Sydney flame SMA2. It is found that MMLP-II method can reduce the ANN error accumulation of minor species, and very accurate results are obtained in both turbulent flames. The successful application to two different turbulent combustion problems is indicative of the capacity for generalisation of the ANN tabulation approach. Finally, the reaction integration step is accelerated by a factor of about 15 with ANNs, thus rendering chemical kinetics no longer the bottleneck of the whole simulation.</div><div><strong>Novelty and significance</strong></div><div>A new ANN thermochemistry tabulation methodology is developed, aimed at providing the higher accuracy needed for predicting species with small concentrations, as encountered in NO_x chemistry. The methodology is applied to two different turbulent flames with NO_x formation: a piloted diffusion flame (Sandia D) and a swirl-bluff-body stabilised flame (Sydney SMA2). The results demonstrate that the method provides both high accuracy and capacity for generalisation. The LES-PDF method is employed here, but the method is applicable to any method that involves real-time calculation of thermochemistry.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114130"},"PeriodicalIF":5.8,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143829666","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":"Direct measurement of the NH3+OH reaction rate behind incident and reflected shock waves","authors":"Luke T. Zaczek,&nbsp;Sean Clees,&nbsp;Ronald K. Hanson","doi":"10.1016/j.combustflame.2025.114174","DOIUrl":"10.1016/j.combustflame.2025.114174","url":null,"abstract":"<div><div>A novel method was used to directly measure the reaction rate, <em>k₁</em>, of NH₃+OH&lt;=&gt;NH₂+H₂O in shock tube experiments behind incident and reflected shock waves from 910–2474 K and 0.23–3.59 atm. NH₃ concentration of test gases was measured prior to each shock with a scanned laser absorption NH₃ diagnostic near 10.36 µm. OH was produced via thermal decomposition of <em>tert</em>‑butyl hydroperoxide behind incident and reflected shock waves, and post-shock OH time-histories were measured via laser absorption at 308.6 nm. Measured OH profiles were fit with a detailed chemical kinetic model to find best-fit values for <em>k₁</em> at each experimental condition, and results are compared to previous data, calculations, and recommendations for the NH₃+OH reaction rate. To the authors’ knowledge, this is the first direct measurement of the NH₃+OH reaction rate above 1425 K and significantly reduces the uncertainty of <em>k₁</em> compared to previous indirect determinations at high temperatures. A recommendation is made for continued use of the NH₃+OH rate expression <em>k₁</em> = 10^6.31 T[K]^2.04 exp(-285/T[K]) cm³/ mol/s suggested by Salimian et al. from 230 &lt; <em>T</em> &lt; 2474 K, which agrees well with the current data and prior low-temperature measurements. The technique used in this work also provides a new strategy for direct measurement of +OH reaction rates at reflected-shock temperatures above ∼1450 K, which has previously been a practical high-temperature limit when using <em>tert</em>‑butyl hydroperoxide as a source of OH radicals.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114174"},"PeriodicalIF":5.8,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A computational fluid dynamics model of combustion of nanoaluminum–water propellant strands","authors":"Prasanna Kulkarni,&nbsp;Ganeshkumar Venukumar,&nbsp;Dilip Sundaram","doi":"10.1016/j.combustflame.2025.114143","DOIUrl":"10.1016/j.combustflame.2025.114143","url":null,"abstract":"<div><div>A computational fluid dynamics model of combustion of nanoaluminum–water propellants is developed. An unsteady and axisymmetric model of strand combustion is developed to mimic the experimental setup and conditions. The entire time evolution of strand combustion from ignition until steady-state flame propagation through the strand is simulated. A multiphase Eulerian modeling approach is adopted to handle multiple phases and the associated transport processes. The mass, momentum, species, and energy conservation equations are discretized using the Finite Volume Method. A rigorous computational framework with superior accuracy and stability characteristics is developed and implemented. The theoretical and computational framework is first verified and validated by running standard test cases such as Stefan problem, fluidized bed, and constant-volume reactor. Upon verification and validation, the framework is applied to simulate combustion of stoichiometric nanoaluminum–water propellant strands. The particle size is chosen to be 80 nm and pressure range is taken as 1–10 MPa. The temporal evolutions of flow, temperature, and species composition fields are computed and insights into the underlying physicochemical processes are provided. Measurable quantities such as the burning rate and pressure exponent are computed. Both fixed bed and moving bed combustion scenarios are simulated and the effects of particle retainment in the propellant bed and particle agglomeration are studied. It is found that the multiphase flow dynamics strongly affect the burning rate and its pressure exponent. The present study suggests that the combustion of nano-aluminum and water propellants is diffusion-controlled due to agglomeration of particles.</div><div><strong>Novelty and significance statement</strong></div><div>A novel theoretical and computational framework is developed to simulate nano-aluminum and water propellant strand combustion. In a paradigm shift in the modeling and simulation approach, a Computational Fluid Dynamics (CFD) approach is adopted to simulate strand burning experiments as closely as possible. A comprehensive multiphase model is developed to resolve all underlying physiochemical processes including boiling of liquid water, multiphase flow dynamics, chemical reactions, and thermal transport. The entire time evolution from ignition until steady-state flame propagation is simulated for an axisymmetric propellant strand. The study provides new insights on the underlying processes that occur during the entire time history of propellant combustion. The simulations demonstrate the importance of multiphase flow dynamics and its impact on propellant combustion. It is discovered that the pressure dependence of burning rate of nano-aluminum and water propellant is primarily due to multiphase flow dynamics and that the combustion of nano-aluminum and water propellants is diffusion-controlled due to agglomeration of particles.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114143"},"PeriodicalIF":5.8,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143823206","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":"Radiative characterization detection and mechanism analysis of soot generation and oxidation during coal combustion based on hyperspectral and mid-wave infrared imaging techniques","authors":"Ke Chang,&nbsp;Meng Liu,&nbsp;Zixue Luo,&nbsp;Qiang Cheng","doi":"10.1016/j.combustflame.2025.114177","DOIUrl":"10.1016/j.combustflame.2025.114177","url":null,"abstract":"<div><div>The generation of soot during coal combustion is closely related to tar, and the incomplete combustion product soot competes with the complete oxidation product CO₂ during the combustion process. In this study, the light volatiles of coal particles are experimentally precipitated to obtain tar coal, and the simultaneous measurement of soot and CO₂ radiation characteristics is achieved by combining hyperspectral (HSI) and mid-wave infrared (MWIR) imaging technologies. Furthermore, the inherent competitive mechanism between the generation and oxidation of polycyclic aromatic hydrocarbons (PAHs) is revealed through mechanistic analysis. As the core structure of soot, PAHs have complex and diverse generation pathways. A1 is formed through both the C3 pathway involving odd-carbon atoms and the C2+C4 pathway involving even-carbon atoms. The generation of A2 to A4 is closely related to direct addition reactions on the benzene ring, and tar coal combustion corresponds to a higher generation rate of PAHs. The generation of soot and CO₂ during coal combustion is not sequential, but exists as a competitive relationship throughout the whole process. The experimental validation results show that the soot volume fraction from coal combustion ranges from 5 ppm to 20 ppm, and the CO₂ concentration ranges from 10 % to 25 %, with tar coal combustion corresponding to a higher content of soot and CO₂. Although the mole fraction of soot is much smaller than that of CO₂, solid soot particles have a more significant radiative capacity in terms of emission and absorption, with the spectral radiative intensity of soot being an order of magnitude higher than that of CO₂ during the stable combustion stage.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114177"},"PeriodicalIF":5.8,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816677","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":"Macrostructure and ultraviolet chemiluminescence of NH3/H2/Air swirling micromix flames","authors":"Can Cao ,&nbsp;Linyao Zhang ,&nbsp;Chang Xing ,&nbsp;Li Liu ,&nbsp;Penghua Qiu ,&nbsp;Shaozeng Sun","doi":"10.1016/j.combustflame.2025.114170","DOIUrl":"10.1016/j.combustflame.2025.114170","url":null,"abstract":"<div><div>This study investigates the macrostructure and ultraviolet chemiluminescence of NH₃/H₂/Air flames using a novel single-nozzle micromix swirl burner at relatively wide ranges of hydrogen mixing ratio (30 %≤<em>X</em>_H2≤70 %) and equivalence ratio (0.4≤<em>φ</em>≤1.3). The transition of flame macrostructure and its relationship with the ultraviolet spectrum is revealed in detail. The flame macrostructure transition was observed as the equivalence ratio increased at different hydrogen mixing ratio studied in this work. The chemiluminescence intensity and intensity ratios of selected emission peaks within the wavelength range of 200∼400 nm showed that the <em>Overlap</em> part (275–302 nm) is important for indicating the characteristics of NH₃/H₂/Air micromix flames. The normalized peak height at wavelength of 296 nm in the <em>Overlap</em> part is quite sensitive to the NH₃/H₂ mixing fraction and insensitive to the equivalence ratio, making it a useful indicator for predicting the hydrogen ratio in the NH₃/H₂ mixed fuels. The NO*/<em>Overlap</em> and NH*/<em>Overlap</em> ratios can be used to predict the equivalence ratio of NH₃/H₂/Air micromix flames when the hydrogen ratio is known. Additionally, turning points were found along the chemiluminescence intensity ratio curves (as a function of equivalence ratio), which could well match the critical equivalence ratio for the macrostructure transition from “V” to “M” at different hydrogen ratios.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114170"},"PeriodicalIF":5.8,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807807","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":"Catalytic and gas-phase combustion of SOFC off-gases over platinum surfaces: an experimental and numerical investigation at pressures up to 8 bar","authors":"Vinoth K. Arumugam ,&nbsp;Ulrich Doll ,&nbsp;John Mantzaras","doi":"10.1016/j.combustflame.2025.114167","DOIUrl":"10.1016/j.combustflame.2025.114167","url":null,"abstract":"<div><div>The combustion of low calorific value Solid Oxide Fuel Cell (SOFC) off-gases was investigated in a platinum-coated channel-flow reactor, at pressures 1–8 bar and surface temperatures 700–1060 K. H₂/CO/H₂O/CO₂/Air mixtures were used at a global equivalence ratio <em>φ</em> = 0.90, with compositions relevant to either high- or low-FUR (Fuel Utilization Rate) operation of the SOFC. Spatially resolved, in situ Raman measurements of main gas-phase species concentrations evaluated the catalytic (heterogeneous) reactivity, while Planar Laser Induced Fluorescence of the OH radical monitored gas-phase (homogeneous) combustion. Two-dimensional numerical simulations were carried out with detailed heterogeneous and homogeneous chemical reaction mechanisms. Under high-FUR operation, the lower contents of H₂ and CO favored catalytic ignition as they diminished the chemical self-inhibition that both fuels exhibited on Pt. High pressures were beneficial due to the positive pressure dependence of both H₂ and CO reactivities on Pt. For the typically high temperatures of the SOFC off-gases (&gt; 700 K), catalytic ignition was readily achieved, whereas gaseous chemistry was negligible in all high-FUR cases. For the low-FUR cases with much higher H₂ contents, the H₂ preferential diffusion rendered O₂ locally the deficient surface reactant, despite the globally fuel-lean stoichiometry, resulting in reduced H₂ and CO conversions. By increasing the surface temperatures in the low-FUR cases to ∼1100 K, homogeneous combustion was ignited for pressures <em>p</em> ≥ 3 bar. Upon homogeneous ignition, the flames did not stabilize inside the reactor but propagated upstream and anchored at the channel entry. This resulted in an inverse catalytically stabilized hybrid combustion concept, wherein a downstream catalytic section served as an igniter and stabilizer for an upstream homogeneous combustion zone. This concept was advantageous, as it permitted complete consumption of H₂ and CO via homogeneous reactions at appreciably shorter reactor lengths.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114167"},"PeriodicalIF":5.8,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816676","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":"Morphing flames and localized hot spots: Unlocking the dynamics of deflagration-to-detonation transition in curved channels","authors":"Suwei Sun,&nbsp;Zhenhua Pan","doi":"10.1016/j.combustflame.2025.114169","DOIUrl":"10.1016/j.combustflame.2025.114169","url":null,"abstract":"<div><div>This study presents a systematic experimental investigation into the flame propagation and deflagration-to-detonation transition (DDT) processes within curved channels, with a particular focus on the influence of initial pressure and geometric parameters (inner and outer radii). The experimental setup, featuring a 270° curved channel and utilizing stoichiometric ethylene-oxygen mixtures as the fuel, employed high-speed camera to capture flame dynamics and pressure transducers to monitor pressure wave distributions. The results demonstrate that the geometric characteristics of the curved channel significantly modulate flame acceleration, with smaller outer radii and larger inner radii markedly enhancing flame acceleration and reducing the time required for DDT (<em>t</em>_DDT). The initial pressure emerges as a key parameter governing the spatial distribution of hot spots and the onset of detonation. Higher initial pressures drive hot spots toward the flame front, accelerate energy accumulation, and significantly improve DDT efficiency. The experimental findings demonstrate that hot spots exclusively form near the outer wall of the channel, a phenomenon attributed to localized high-temperature and high-pressure regions induced by the interaction between the leading shock wave and the outer wall. Under varying initial pressures, hot spots exhibit three distinct spatial distribution patterns: (1) at the root of the tongue-shaped flame, (2) at the tip of the tongue-shaped flame, and (3) simultaneously at both the root and tip. Notably, the presence of flame front wrinkles at the tip of the tongue-shaped flame is identified as a key feature in the latter two patterns, playing a dominant role in hot spot formation. Quantitative analysis further reveals a positive correlation between the characteristic length of the tongue-shaped flame at the moment of the hot spot formation and <em>t</em>_DDT. This finding highlights the synergistic interplay between the geometric properties of the curved channel and initial conditions in determining the efficiency and characteristics of the DDT process. Collectively, this study provides critical experimental insights and theoretical support for understanding the complex physical mechanisms underlying flame propagation and detonation transition in curved channels, offering valuable implications for optimizing combustion dynamics in geometrically complex systems.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114169"},"PeriodicalIF":5.8,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143807808","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}