Combustion and Flame最新文献

{"title":"Ignition characteristics of isolated coal particles under pressurized oxy-fuel combustion conditions","authors":"Qianyun Chen ,&nbsp;Dingyi Qin ,&nbsp;Jing Li ,&nbsp;Zhaohui Liu ,&nbsp;Martin Schiemann","doi":"10.1016/j.combustflame.2025.114276","DOIUrl":"10.1016/j.combustflame.2025.114276","url":null,"abstract":"<div><div>Pressurized oxy-fuel combustion (POC), an advanced iteration of oxy-fuel combustion, is regarded as one of the most promising technologies for CO₂ capture. In this study, the ignition characteristics of Shenhua bituminous and Jincheng anthracite under POC conditions ranging from 0.1 to 0.9 MPa were investigated using an optically-accessible pressurized flat-flame reactor (OPFFR). The ignition process was particle-resolved optical diagnosed by an in-house developed particle-tracking image pyrometer (PTIP) system. The results indicate that multiple ignition modes can coexist under the same conditions. The ratio of heterogeneous ignition is approximately 0.8 at atmospheric pressure, and this ratio decreases with increasing pressure, reaching a minimum of 0.3 at 0.9 MPa with a 30 % O₂/CO₂ atmosphere. As pressure increases, the delay for homogeneous ignition lengthens, while the change in heterogeneous ignition delay remains relatively small. Under atmospheric-pressure O₂/N₂ conditions, the homogeneous ignition delay time for bituminous coal is about 7–10 ms, whereas under the same oxygen concentration and POC conditions, it is 12–15 ms. A heterogeneous ignition model based on Semenov thermal ignition theory was developed to predict the ignition delay times under POC conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114276"},"PeriodicalIF":5.8,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144241594","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 equivalence ratios on the oblique detonation initiation in ammonia/hydrogen/air mixtures","authors":"Yue Sun ,&nbsp;Ruixuan Zhu ,&nbsp;Hongbo Guo ,&nbsp;Baolu Shi ,&nbsp;Majie Zhao ,&nbsp;Zhijun Wei","doi":"10.1016/j.combustflame.2025.114279","DOIUrl":"10.1016/j.combustflame.2025.114279","url":null,"abstract":"<div><div>This paper presents two-dimensional numerical simulations of oblique detonation waves (ODWs), employing Navier-Stokes equations coupled with detailed chemical reaction mechanisms. We explored the effects of equivalence ratio on initiation characteristics, including the transition type from oblique shock waves (OSWs) to ODWs and the induction length in pure ammonia and hydrogen-ammonia blend fuels. Results indicate that, in pure ammonia fuel, a wave structure transition from OSW₁ to OSW₂ and finally to ODW is formed. As the ammonia equivalence ratio increases, the induction length grows linearly and the transition from OSW to ODW becomes more abrupt. Hydrogen addition significantly shortens the induction length in ammonia-based oblique detonation, with low ammonia concentrations resulting in an induction length even shorter than that of pure hydrogen fuel. Chemical explosion mode analysis identifies O, H, OH, NH₂ as key species contributing to detonation process in the induction region, with ammonia playing a more significant role than hydrogen at initial stages. A predictive method for the OSW-ODW transition in hydrogen-ammonia blend fuels is proposed, offering insights into practical applications of ammonia in ODEs.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114279"},"PeriodicalIF":5.8,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144240639","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":"Neural network-augmented eddy viscosity closures for turbulent premixed jet flames","authors":"Priyesh Kakka,&nbsp;Jonathan F. MacArt","doi":"10.1016/j.combustflame.2025.114241","DOIUrl":"10.1016/j.combustflame.2025.114241","url":null,"abstract":"<div><div>Extending gradient-type turbulence closures to turbulent premixed flames is challenging due to the significant influence of combustion heat release. We incorporate a deep neural network (DNN) into Reynolds-averaged Navier–Stokes (RANS) models for the turbulent viscosity and thermal conductivity as nonlinear functions of the local flow state and thermochemical gradients. Our models are optimized over the RANS partial differential equations (PDEs) using an adjoint-based data assimilation procedure. Because we directly target the RANS solution, as opposed to the unclosed terms, successfully trained models are guaranteed to improve the in-sample accuracy of the DNN-augmented RANS predictions. We demonstrate the learned closures for in- and out-of-sample <em>a posteriori</em> RANS predictions of compressible, premixed, turbulent jet flames with turbulent Damköhler numbers spanning the gradient- and counter-gradient transport regimes. The DNN-augmented RANS predictions have one to two orders of magnitude lower spatiotemporal mean-squared error than those using a baseline <span><math><mi>k</mi></math></span>–<span><math><mi>ϵ</mi></math></span> model, even for Damköhler numbers far from those used for training. This demonstrates the accuracy, stability, and generalizability of the PDE-constrained modeling approach for turbulent jet flames over this relatively wide Damköhler number range.</div><div><strong>Novelty and Significance Statement</strong></div><div>We develop a deep learning turbulence closure method for RANS calculations of turbulent premixed flames. The closure method embeds an untrained neural network into the RANS equations and then optimizes it over the flow solution using an adjoint-based technique. Novelty: This is the first application of solver-embedded deep learning to turbulent premixed jet flames. Significance: The method is a new, general-purpose closure-modeling framework for turbulent flames. For the present turbulent premixed jet flames, the method significantly reduces the error of <em>a posteriori</em> RANS predictions. The trained models generalize this improved accuracy across a wide range of Damköhler numbers, even in combustion regimes that are far out-of-sample from those used to train a particular model, which is not typical of deep learning closures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114241"},"PeriodicalIF":5.8,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144240638","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":"Extracting global reaction rate and turbulent flame speed from reconstructed 3D spherically expanding flames","authors":"Yutao Zheng ,&nbsp;Pervez Ahmed ,&nbsp;Simone Hochgreb","doi":"10.1016/j.combustflame.2025.114247","DOIUrl":"10.1016/j.combustflame.2025.114247","url":null,"abstract":"<div><div>We analyse a recent set of experiments on turbulent premixed spherically expanding flames (SEFs) using fast 3D scanning measurements of hydrogen and methane/air mixtures. The flame reconstruction using Mie scattering allows for the determination of the volume burned, flame surface location and volume growth rate of mixtures of lean methane and hydrogen at different pressures and temperatures. A balance of progress of reaction unambiguously defines the reaction, convection and accumulation (engulfment) terms within the flame brush. The terms are extracted from 3D and 2D reconstructions of the flame, as a function of the surface location in terms of progress of reaction across the flame brush. We show that the accumulation/engulfment term is of leading order, except at selected locations in the flame, and that it cannot be neglected. Further, we show that measurements of turbulent flame speed in the literature based on the popular approximation <span><math><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>=</mo><mfrac><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>b</mi></mrow></msub></mrow><mrow><msub><mrow><mi>ρ</mi></mrow><mrow><mi>u</mi></mrow></msub></mrow></mfrac><mfrac><mrow><mi>d</mi><msub><mrow><mi>R</mi></mrow><mrow><mi>v</mi></mrow></msub></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac></mrow></math></span> may be in error by a systematic factor of up to 1.5<span><math><mo>∼</mo></math></span>2.0 for the present mixtures. Recommendations are made regarding the analysis of future 3D and 2D measurements, and how one may be able to robustly extract accurate measurements of displacement and reaction speeds from high frequency 2D turbulent SEF interface reconstructions.</div><div><strong>Novelty and significance statement</strong></div><div>The balance of mean progress of reaction is first analysed in an integrated form in spherical expanding flames reconstructed from 3D scanning results. The evolution of the progress of reaction and total volume of burned gas in spherical expanding flames is analysed for the first time in full 3D flame surfaces. Different flame speed terms in the balance equation for the mean progress of reaction are extracted from 3D and 2D reconstructions of the flame surfaces and a new understanding of how to estimate reaction rates and turbulent flame speeds is proposed compared with a popular approximation. Rates of burning, and flame surface density in 2D vs 3D are compared for the first time. The systematic error in the conventional approximation of turbulent flame speeds in spherical expanding flames is quantitatively estimated. A suggested procedure for estimating turbulent flame speeds from the rate of growth of from centreline 2D or full 3D measurements is proposed.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114247"},"PeriodicalIF":5.8,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144222441","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 numerical simulations of head-on quenching of statistically planar turbulent premixed flames on rough walls","authors":"Zhaofan Zhu ,&nbsp;Haiou Wang ,&nbsp;Evatt R. Hawkes ,&nbsp;Kun Luo ,&nbsp;Jianren Fan","doi":"10.1016/j.combustflame.2025.114245","DOIUrl":"10.1016/j.combustflame.2025.114245","url":null,"abstract":"<div><div>Rough walls are common in engineering applications. However, existing understanding of combustion near rough walls is lacking. In the present work, direct numerical simulations (DNS) of head-on quenching of statistically planar turbulent premixed flames on rough walls are reported for the first time. Hydrogen is considered as the fuel because of its importance in a zero-carbon economy. The temporal evolution of premixed flames propagating head-on towards walls with various wall roughnesses are compared. It is observed that rough walls result in incomplete consumption of hydrogen, with a more pronounced effect as the roughness amplitude increases. The impacts of wall roughness on wall heat transfer and local flame quenching are examined. The maximum wall heat flux in the rough-wall cases occurs at the roughness crests, and is significantly higher than that in the smooth-wall cases. The total wall heat loss increases with increasing wall roughness (<em>i.e.</em> increasing amplitude-to-wavelength ratio of roughness). The same trend is also observed in the corresponding laminar cases. A negative correlation between the quenching distance and the quenching wall heat flux exists in both the smooth and rough-wall cases. Moreover, it is found that rough walls lead to reduced quenching distances. The heat release rate on the wall is scrutinized. Remarkably high heat release rates are observed on the wall of the DNS cases, which is not observed in the head-on quenching process of the corresponding laminar flame. The heat release on the wall is dominated by radical recombination reactions. The heat release rate on rough walls is higher than that on smooth wall, which increases with increasing wall roughness. In the rough-wall cases, the heat release rate is the highest in the regions around the roughness crests, which can be explained by the distributions of species concentrations.</div><div><strong>Novelty and significance</strong></div><div>The work presented in this paper is new, original and of interest as it enhances our understanding of combustion near rough walls. For the first time, the interactions between flame and rough walls in turbulent environments are quantitatively examined using DNS. The temporal evolutions of the flow and flame structures during head-on quenching with various wall roughnesses are compared. The effects of wall roughness on wall heat transfer and local flame quenching are analyzed, and the heat release rate at the wall is closely scrutinized. The novel finding that rough walls may lead to incomplete fuel consumption is significant for the safe and efficient operation of industrial burners, and the analysis of wall heat transfer and flame quenching is essential for the design and optimization of advanced combustion devices.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114245"},"PeriodicalIF":5.8,"publicationDate":"2025-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144222440","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 Lagrangian view of flame-vortex interaction during turbulent side-wall quenching using high-speed OH-LIF and PIV","authors":"Alexander Nicolas ,&nbsp;Florian Zentgraf ,&nbsp;Pascal Johe ,&nbsp;Benjamin Böhm ,&nbsp;Andreas Dreizler ,&nbsp;Brian Peterson","doi":"10.1016/j.combustflame.2025.114250","DOIUrl":"10.1016/j.combustflame.2025.114250","url":null,"abstract":"<div><div>Flame-vortex interactions have been suggested to play an important role in flame-wall interactions (FWI). This study presents an experimental investigation of flame-vortex interactions and their influence on flame quenching. Experiments are conducted in a side-wall quenching (SWQ) burner with V-flame configuration. Simultaneous high-resolution particle image velocimetry and OH laser induced fluorescence are conducted to study the flame-flow-wall dynamics under turbulent FWI conditions. Reynolds decomposition is used to provide a Lagrangian reference frame relative to the ensemble-mean velocity field to visualize the evolution of coherent turbulent vortical structures. These vortical flow structures are correlated with regions of elevated swirling strength in the instantaneous velocity field. Three classifications of flame-vortex interaction are identified. One of these classifications emulates a flame-vortex interaction mechanism recently proposed in the literature. This particular flame-vortex interaction reveals a vortex that emanates from the burnt gas and moves quickly towards the wall. The vortex impacts the wall, where local flame quenching occurs and the flame transitions from a head-on quenching (HOQ) to a SWQ flame topology. After quenching, the vortex remains next to the wall and directly above the flame tip as the flame progresses downstream. Each flame quenching event observed in the data exhibits this flame-vortex interaction. This work evaluates the kinematic attributes of the vortex and reveals the tendency of the vortex to push the flame closer to the wall, where the flame experiences flame quenching. Alongside previous DNS studies, this work shows that flame-vortex interactions are phenomenological features that influence flame quenching, as well as heat and mass transport near the wall.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114250"},"PeriodicalIF":5.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144212908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic and experimental study of multimodal PM generation in coal char combustion","authors":"Yimin Shang ,&nbsp;Chen Wang ,&nbsp;Haiyu Huang ,&nbsp;Ying Yu ,&nbsp;Xuan Yang ,&nbsp;Guangyao Wang ,&nbsp;Lei Chen ,&nbsp;Yanqing Niu","doi":"10.1016/j.combustflame.2025.114272","DOIUrl":"10.1016/j.combustflame.2025.114272","url":null,"abstract":"<div><div>A char burning and particulate matter kinetics (CBPMK) model has been further developed within a spherical coordinates system. It considers the mechanisms of volatilization, nucleation, condensation, coagulation-coalescence, char fragmentation, and mineral melt polymerization. In this model, char is simplified to a three-dimensional discrete spherical shell filled with carbon, ash, and macropore. To effectively simulate char fragmentation and mineral melt polymerization, an \"effective connection\" assumption is proposed, which facilitates the accurate modeling of fine/coarse particulate matter (PM) generation. The simulation results demonstrate a high degree of accuracy, with errors consistently below 10%. During char combustion, the mineral volatilization rate drops sharply due to the rapid decrease in particle temperature, resulting in the total mineral volatilization reaching the maximum within 0.01 -0.03 seconds. The number density of ultra-fine PM exhibits a bell-shaped curve, initially rising before dropping. Meanwhile, fine PM begins to generate in the early stage of combustion with a smooth process. In contrast, coarse PM generation is relatively delayed but then increases rapidly. Furthermore, an increase in ambient combustion temperature promotes the generation of ultra-fine PM and coarse PM. Based on the mass generation at 1100°C, ultra-fine PM increases by 8% (1300°C) and 107% (1500°C), while coarse PM increases by 32% (1300°C) and 51% (1500°C). The change of fine PM is related to ash melting, increasing when the ambient combustion temperature is below the ash flow temperature and decreasing when it's above, with the ratio of increase for fine PM is 45% (1300°C) and 26% (1500°C). Additionally, an increase in char particle size results in increasing generation of coarse PM while decreasing the generation of ultra-fine PM and fine PM. From 45-75 μm to 90-125 μm, ultra-fine PM and fine PM decreases by 66% and 17%, while coarse PM increases by 48%.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114272"},"PeriodicalIF":5.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204396","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":"Low-frequency streaky structures in turbulent hydrogen jet flames","authors":"Jakob G.R. von Saldern ,&nbsp;Jan Paul Beuth ,&nbsp;Johann Moritz Reumschüssel ,&nbsp;Alexander Jaeschke ,&nbsp;Christian Oliver Paschereit ,&nbsp;Kilian Oberleithner","doi":"10.1016/j.combustflame.2025.114231","DOIUrl":"10.1016/j.combustflame.2025.114231","url":null,"abstract":"<div><div>This study investigates the dynamics of a lean technically premixed, turbulent, hydrogen jet flame at a Reynolds number of 10’000 in a multi-jet combustor configuration. The focus is on the natural, unforced dynamics observed in line-of-sight integrated OH* and mono-PIV measurements. Long time series are recorded in order to analyze the dynamics in a broad spectrum that extends down to very low frequencies. The discussion of the experimental results is supported by a resolvent model based on linearized Navier–Stokes equations and the experimental mean velocity field. The model allows to investigate the underlying mechanisms of the dominant dynamics observed in the flow. It is found that the dynamics of the investigated hydrogen jet flame are mainly driven by two mechanisms. At intermediate frequencies, the Kelvin–Helmholtz mechanism dominates the dynamics and generates axis-symmetric oscillations in the OH* data. In the low Strouhal number regime, large-scale structures of coherent axial velocity fluctuation generated by the lift-up mechanism are observed. These energetic structures are known as streaks in boundary layer flows and non-reacting jets. Here, the streaks are found to play a significant role in the low-frequency dynamics of the turbulent hydrogen jet flames. Most notably, the OH* signal, which is indicative of heat release, is also significantly influenced by the large-scale structures. It is therefore to be expected that streaks are of high technical relevance. Since streaks are associated with strong fluctuations in the axial velocity component, it can be assumed that they are of particular importance for triggering flashback events.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114231"},"PeriodicalIF":5.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144212909","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":"Comprehensive particle behaviors in an impinging entrained-flow gasifier: from atomization to deposition","authors":"Yan Gong ,&nbsp;Hantao Lu ,&nbsp;Qinghua Guo ,&nbsp;Xudong Song ,&nbsp;Lu Ding ,&nbsp;Guangsuo Yu","doi":"10.1016/j.combustflame.2025.114277","DOIUrl":"10.1016/j.combustflame.2025.114277","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The behavior of coal particles in an entrained-flow gasifier is critically linked to the stable operation of the gasifier. However, observing these particles has been a significant challenge due to the high temperatures and complex atmosphere within the gasifier. In this study, utilizing a bench-scale opposed multi-burner (OMB) coal-water slurry (CWS) entrained-flow gasifier and a visualization system equipped with high-temperature endoscopes and high-speed cameras of varying specifications, the comprehensive behaviors of particles within the gasifier are thoroughly investigated. The imaging region of the visualization system spans all axial areas of the gasifier, from the dome above the burner plane to 300 mm below it. Detailed discussions are provided on CWS atomization, particle fragmentation, conversion, and deposition behaviors. The findings reveal that as the relative velocity between oxygen and CWS increases, the primary atomization mode transitions from a Rayleigh-type breakup to a superpulsating atomization mode. A synergistic atomization mode, accounting for 30.1 % of the secondary atomization mode, is identified for impinging entrained-flow gasification. The probability of particle fragmentation peaks at 16.84 %, influenced by the combined forces of the upward impinging-flow from the burner plane and the reverse flow from the dome at approximately 400 mm (4/3 height-diameter ratio of the gasification chamber) above the burner plane. The study concludes with an integrated analysis of the thermal behavior and conversion characteristics of particles across different reaction stages. Deposition behaviors in the gasifier are categorized into three droplet deposition modes and four particle deposition modes. Ultimately, a comprehensive particle evolution model corresponding to the droplet/particle deposition stage is established. Additionally, it is noted that within the gasifier, the char oxidation process typically has the longest duration, ranging from 200 to 2000 ms.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and Significance Statement&lt;/h3&gt;&lt;div&gt;The thermal behaviors of coal particles in entrained-flow gasifiers are critical for stable operation but challenging to observe due to extreme high-temperature and complex atmospheric conditions. This study addresses this gap by developing an advanced in-situ visualization system, enabling multi-angle observation of particle dynamics—including atomization, fragmentation, conversion, and deposition—in a bench-scale OMB CWS gasifier. By integrating high-speed imaging and advanced image processing algorithms, a comprehensive particle evolution model was established, providing a theoretical foundation for optimizing gasification processes. Furthermore, the scalable visualization technology, validated on an OMB CWS gasifier, is adaptable to other industrial reactors, particularly complex entrained-flow systems, marking a significant advancement in characterizing multiphase thermal processes and supporting ","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114277"},"PeriodicalIF":5.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204397","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 simple sensor for kHz-rate simultaneous measurement of OH and temperature in combustion based on UV broadband absorption spectroscopy","authors":"Baojian Qian ,&nbsp;Haitao Chang ,&nbsp;Yanjun Du ,&nbsp;Jian Zhao ,&nbsp;Jing Cai ,&nbsp;Yongjun Yang ,&nbsp;Xinyu Yang","doi":"10.1016/j.combustflame.2025.114243","DOIUrl":"10.1016/j.combustflame.2025.114243","url":null,"abstract":"<div><div>Temperature and hydroxyl (OH) radical concentration are critical parameters in combustion processes. However, current measurement techniques often rely on ultraviolet (UV) lasers, which involve complex optical setups and high costs, thereby limiting their applicability in harsh industrial conditions. This study introduces a simple and cost-effective sensor based on UV broadband absorption spectroscopy (BAS) using a 308 nm light-emitting diode (LED) and a portable spectrometer, capable of performing kHz-rate dynamic measurements of temperature and OH concentration. To reduce the processing time of BAS multi-line spectra, two methods are presented: a polynomial method (accuracy 10⁻⁷, 35 ms computation time) and a neural network method (accuracy 10⁻³, <span><math><mrow><mn>15</mn><mspace></mspace><mi>μ</mi><mi>s</mi></mrow></math></span> computation time). The developed BAS sensor was evaluated in methane/air premixed flat flames with varying equivalence ratios (0.8 to 1.2) and in a thermal wind tunnel with different total temperatures (1373 K to 1873 K). Time-averaged results in flat flames at different heights showed good agreement with computational fluid dynamics (CFD) simulations. Under stable fuel-lean conditions, kHz-rate measurements exhibited high precision, with repeatability errors (1<span><math><mi>σ</mi></math></span>) of 29 K (1.7%) and 49 ppm (2.5%). In unstable fuel-rich conditions, fast Fourier transform (FFT) analysis revealed distinct frequency characteristics. In the thermal wind tunnel, time-averaged temperature results closely matched thermocouple data in the stabilization section. The precision of kHz-rate temperature measurements remained comparable to that of laboratory flat flame experiments, with a temperature repeatability error (1<span><math><mi>σ</mi></math></span>) of 52 K (2.8%) at 1900 K. FFT analysis also clearly demonstrated the frequency characteristics. Experiments conducted in both laboratory and thermal wind tunnel environments validated the sensor’s accuracy and high-rate dynamic measurement capability, affirming its potential for diverse applications and providing a new technical reference for industrial measurement of temperature and OH concentration.</div><div><strong>Novelty and significance</strong></div><div>This study proposes a novel temperature and OH concentration sensor, which offers the advantages of simplicity, low cost, and robust environmental adaptability. Additionally, two fast data processing methods with ms-level and <span><math><mi>μ</mi></math></span>s-level computational times were developed. High-precision (2.8%) simultaneous kHz-rate dynamic measurements of temperature and OH concentration were achieved in the harsh industrial environment of the thermal wind tunnel using the proposed sensor. In summary, this study provides a new approach for dynamic measurement of temperature and OH concentration in harsh environments.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114243"},"PeriodicalIF":5.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204395","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}