Combustion and Flame最新文献

{"title":"Effect of ignition timing on the combustion characteristics of liquid ammonia spray in a lean premixed H2/Air","authors":"Ruihan Ge,&nbsp;Geyuan Yin,&nbsp;Erjiang Hu,&nbsp;Shujie Shen,&nbsp;Haochen Zhan,&nbsp;Chenglong Tang,&nbsp;Zuohua Huang","doi":"10.1016/j.combustflame.2025.114042","DOIUrl":"10.1016/j.combustflame.2025.114042","url":null,"abstract":"<div><div>Combustion of ammonia has recently been emerging as a promising approach for carbon mitigation. However, monitoring ignition of ammonia is a technique challenge due to its low reactivity. This work experimentally investigates the ignition and combustion behaviors of ammonia spray injected into a lean hydrogen air mixture, with emphasis on the ignition timing effect on the ignition and flame evolution behaviors as well as the pressure evolution and heat release. Results show that the ignition timing leads to profound alteration of the ammonia spray ignition and flame evolution due to the mixture status induced by different spray evolution time. Specifically, the flame is the most significantly affected by spray injection at ignition timings close to the start and end of injection and the heat loss is reduced, compared with the premixed fuel due to the lower heat release from evaporation and incomplete combustion. Additionally, for 10 ms pre-ignition timing, at the instant when the spray reaches the flame, the unburned gas assists in the evaporation and diffusion of the liquid ammonia, leading to a sudden increase in flame speed and a higher pressure of combustion. While, finally, for the 10 ms post-ignition timing case, the stratified fuel concentration distribution leads to accelerated heat release rate and a reduced overall combustion duration. The special spray characteristics of liquid ammonia and the high latent heat of evaporation are the main factors leading to the reduction of the combustion efficiency of liquid ammonia spray, which can be effectively solved by precombustion heating or homogeneous mixing. This study is believed to be beneficial for organizing better combustion for this zero-carbon fuel in SI engines.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114042"},"PeriodicalIF":5.8,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387767","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 machine learning based approach for statistical analysis of detonation cells from soot foils","authors":"Vansh Sharma,&nbsp;Michael Ullman,&nbsp;Venkat Raman","doi":"10.1016/j.combustflame.2025.114026","DOIUrl":"10.1016/j.combustflame.2025.114026","url":null,"abstract":"<div><div>This study presents a novel algorithm based on machine learning (ML) for the precise segmentation and measurement of detonation cells from soot foil images, addressing the limitations of manual and primitive edge detection methods prevalent in the field. Using advances in cellular biology segmentation models, the proposed algorithm is designed to accurately extract cellular patterns without a training procedure or dataset, which is a significant challenge in detonation research. The algorithm’s performance was validated using a series of test cases that mimic experimental and numerical detonation studies. The results demonstrated consistent accuracy, with errors remaining within 10%, even in complex cases. The algorithm effectively captured key cell metrics such as cell area and span, revealing trends across different soot foil samples with uniform to highly irregular cellular structures. Although the model proved robust, challenges remain in segmenting and analyzing highly complex or irregular cellular patterns. This work highlights the broad applicability and potential of the algorithm to advance the understanding of detonation wave dynamics.</div><div><strong>Novelty and Significance Statement</strong></div><div>This work, to the best of the authors’ knowledge, is the first to present a generalized algorithm that automatically detects, segments, and precisely measures detonation cells in soot foil images. Existing approaches typically require extensive manual intervention or rely on simplistic edge detection methods, which lack robustness and general applicability across different datasets. The efficacy of the algorithm is demonstrated across a variety of data sets, including regular and highly irregular cellular patterns. This advancement provides a deeper understanding of the detonation wave structures and critical insights into the chemical length scales in shock-compressed gaseous mixtures and their impact on macroscopic detonation behavior. The versatility of the algorithm makes it applicable to a wide range of cellular morphologies, both in experimental setups and in numerical simulations, positioning it as a valuable tool in the study of detonation phenomena.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114026"},"PeriodicalIF":5.8,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387875","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":"Experimental study of ethylene carbonate (EC) pyrolysis and oxidation in jet-stirred reactor by SVUV-PIMS","authors":"Bin Dong ,&nbsp;Yushen Yu ,&nbsp;Qingbo Zhu ,&nbsp;Bingzhi Liu ,&nbsp;Kuiwen Zhang ,&nbsp;Jun Fang ,&nbsp;Longhua Hu ,&nbsp;Zhandong Wang","doi":"10.1016/j.combustflame.2025.114002","DOIUrl":"10.1016/j.combustflame.2025.114002","url":null,"abstract":"<div><div>Ethylene carbonate (EC) is a major component of the widely used lithium-ion battery (LIB) electrolytes, therefore it is of great importance for the risk assessment of LIB fires. In this work, the pyrolysis and oxidation of EC (equivalence ratio of 0.5) was investigated in a jet-stirred reactor (JSR) coupled to synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) and gas chromatography at atmospheric pressure, with initial EC mole fraction of 0.0021 and residence time of 2 s. The mole fraction profiles of reaction products measured in this work, including hydrogen, water, carbon monoxide, carbon dioxide, C_1<img>C₂ hydrocarbons, formaldehyde, acetaldehyde, ketene and etc., were utilized to validate the recently proposed electrolyte surrogate models in the literatures. The results showed that the prediction of ketene yield in EC pyrolysis, as well as the prediction of EC reactivity in EC oxidation, are poor using the previous models. Therefore, based on reaction pathway analysis and sensitivity analysis in JSR, the kinetic model of EC in the literature was improved by updating and tuning the rate constants of some key reactions related to the formation and consumption of formyl methyl radical (ĊH₂CHO) and ketene. The updated model could predict EC consumption and the yield of major species better than those predicted by models in the literatures. In addition, from the oxidation results of EC, we found that the reactivity of EC could be significantly enhanced by hydroxyl radical (ȮH) produced by the reaction of formyl methyl radical with oxygen.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114002"},"PeriodicalIF":5.8,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387873","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 development of low-temperature propane oxidation in a repetitively-pulsed nanosecond discharge","authors":"Zhenyang Li ,&nbsp;Bo Yin ,&nbsp;Qifu Lin ,&nbsp;Yifei Zhu ,&nbsp;Yun Wu","doi":"10.1016/j.combustflame.2025.114023","DOIUrl":"10.1016/j.combustflame.2025.114023","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The kinetics of plasma assisted low temperature oxidation of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;8&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;/&lt;/mo&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;mi&gt;r&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; mixtures have been studied in a wide specific deposited energy with the help of nanosecond repetitively pulsed discharge. Two types of nanosecond pulsed plasma sources, the nanosecond capillary discharge (nCD) and dielectric barrier discharge (DBD) combined with the synchrotron photoionization mass spectrometry are investigated. The electron impact reaction rate of propane dissociation and some combustion chemical reactions rate constants are updated according to the nCD and DBD experiment results, and uncertainty of the reactions are analyzed in detail. Compared to the existing model, the updated model’s prediction accuracy has great improvement in species &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-&lt;span&gt;&lt;math&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;-&lt;span&gt;&lt;math&gt;&lt;mi&gt;P&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;-&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;C&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;7&lt;/mn&gt;","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114023"},"PeriodicalIF":5.8,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379058","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":"Nonlinear dynamics and thermoacoustic intermittency of a hydrogen-powered sequential combustor","authors":"Matteo Impagnatiello,&nbsp;Sergey Shcherbanev,&nbsp;Bayu Dharmaputra,&nbsp;Nicolas Noiray","doi":"10.1016/j.combustflame.2025.114008","DOIUrl":"10.1016/j.combustflame.2025.114008","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study experimentally investigates the coupling between thermoacoustic instabilities and autoignition kernel formation in Constant Pressure Sequential Combustors (CPSCs). Two fuel types are examined: a less reactive methane–hydrogen blend (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) and pure hydrogen (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;). By increasing the thermal power of the first stage, thermoacoustic instabilities arise in both configurations, albeit with distinct behaviors. &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; exhibits a gradual onset of instability, whereas &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; undergoes a subcritical Hopf bifurcation, characterized by abrupt, intermittent transitions between a linearly stable state and limit cycles at intermediate first-stage power. Distinct acoustic pressure spectra are observed during instability: &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; features a single dominant peak around 290 Hz, while &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; displays multiple high-amplitude peaks corresponding to harmonics of the fundamental frequency near 400 Hz. Analysis of acoustic pressure and OH* chemiluminescence during instability reveals a strong coupling between acoustic fluctuations and autoignition kernel formation. With &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, the temporal evolution of the OH* chemiluminescence associated with these kernels follows a quasi-sinusoidal profile at the instability frequency, whereas with &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, it consists of sharp pulses synchronized with the fundamental acoustic mode. Although existing Low-Order Models (LOMs) successfully capture the experimental behavior in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;CH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;4&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, they fail to replicate the complex dynamics of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;F&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;. To address this, a novel LOM incorporating a strongly nonlinear Heat Release Rate (HRR) feedback term is developed, specifically tailored for configurations with significant coupling between autoignition and thermoacousti","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114008"},"PeriodicalIF":5.8,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143376547","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":"Direct numerical simulations of laboratory-scale NH3/air jet flames: Analysis of flame structure, flame stabilization and NO emission characteristics","authors":"Tingquan Tian ,&nbsp;Haiou Wang ,&nbsp;Jacqueline H. Chen ,&nbsp;Zhongshan Li ,&nbsp;Marcus Aldén ,&nbsp;Kun Luo ,&nbsp;Jianren Fan","doi":"10.1016/j.combustflame.2025.114007","DOIUrl":"10.1016/j.combustflame.2025.114007","url":null,"abstract":"<div><div>In the present study, three-dimensional direct numerical simulations (DNS) of experimental ammonia/air premixed jet flames with different turbulent intensities were performed. The DNS results were first compared to the measurements with good agreements. Based on the DNS data, the turbulent flame structure, stabilization mechanism and NO emission characteristics of the flames were investigated. It was found that the flame with higher turbulent intensity exhibits a higher degree of wrinkling and an increased flame surface area. In addition, turbulent eddies can enter into the reaction zone and disrupt the distributions of NH and temperature more strongly for the flame with higher turbulent intensity. It was shown that the heat release rate of the turbulent flame can be approximated by the results of strained laminar flames to some extent. Enhanced heat release rates were observed in the regions of negative curvature near the reactant side and in the regions of positive curvature near the product side, which is due to the local enhancement of radicals such as NH and NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> that contribute significantly to the heat release. To understand the flame stabilization mechanism of the turbulent flames, corresponding one-dimensional unstrained and strained unsteady laminar flames were simulated. It was found that auto-ignition initially occurs and the reaction front transitions into a propagating front following the ignition process for both the unstrained and strained laminar flames. The ignition characteristics of the turbulent flames are largely consistent with those of the laminar flames. The study also revealed the NO formation characteristics. NO is consumed in the reaction zone and produced in the product side. The maximum NO mass fraction increases with increasing axial distance. Analysis of NO pathway suggests that this phenomenon is due to the enhanced NO production in the downstream regions, which is related to the accumulation of radicals such as OH, O and H.</div><div><strong>Novelty and significance</strong></div><div>This research reports the first direct numerical simulations of laboratory-scale ammonia/air turbulent premixed jet flames with varying turbulent intensities. The novelty of this research is that the flame structure, flame stabilization and NO emission characteristics of ammonia/air jet flames are explored using detailed DNS data, which are crucial for improved understanding of ammonia combustion. Furthermore, the present work provides high-fidelity DNS data of turbulent ammonia combustion for the development of combustion models.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114007"},"PeriodicalIF":5.8,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349904","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":"Simultaneous PLIF imaging of NH2, NH, and NH3 in ammonia-hydrogen-nitrogen flames using a single dye laser","authors":"Hongchao Dai ,&nbsp;Santiago Cardona ,&nbsp;Shixing Wang ,&nbsp;Xiao Cai ,&nbsp;Jinhua Wang ,&nbsp;Zuohua Huang ,&nbsp;Thibault F. Guiberti","doi":"10.1016/j.combustflame.2025.114031","DOIUrl":"10.1016/j.combustflame.2025.114031","url":null,"abstract":"<div><div>The amidogen radical (NH₂) is a crucial species in ammonia decomposition and de-NOx processes within ammonia flames. Accurate <em>in situ</em> measurements of NH₂ radicals, particularly to determine their spatial distribution in turbulent flames, are scarce. This is mainly due to the lack of methods capable of imaging NH₂ with a sufficiently high signal-to-noise ratio and in a time-resolved fashion. This study proposes a novel multi-species imaging method based on planar laser-induced fluorescence (PLIF) capable of simultaneously imaging, in single-shot, NH₂, NH, and NH₃ in flames with a single dye laser. Effective NH₂-PLIF is achieved by probing the A²A₁(0,12,0) ← X²B₁(0,2,0) transitions with a laser beam at ∼609 nm. This beam is available as the residual of a frequency-doubling unit required to yield another beam at ∼304.5 nm and that is used to excite both NH (A³Π-X³Σ⁻ (1,0) band) and NH₃ (NH₃ C'-X (2,0) band). According to the excitation scans, two wavelength couples, 609.474/304.737 nm and 609.726/304.863 nm, are suggested to simultaneously excite NH₂, NH, and NH₃. This method is used to visualize the 2D structure of premixed laminar and turbulent ammonia-hydrogen-nitrogen flames with different equivalence ratios and fuel compositions. Consistent with expectations built from 1D simulations, results show that the NH₂ layer partially overlaps with that of NH and primarily sits on the reactants’ side of the NH layer. An SNR near 4 is achieved for NH₂-PLIF with an NH₂ concentration of around 800 ppm. The fluorescence signals of NH₂ and NH₃ exhibit partial spectral overlap, but they are spatially separated in premixed flames. Tests whereby NH₂- and NH₃-PLIF signals are captured simultaneously on the same camera show that this method may be used to mark the location of the preheat zone in premixed ammonia flames with only one camera and one dye laser.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114031"},"PeriodicalIF":5.8,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193336","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 reduced order numerical model for high-pressure hydrogen leak self-ignition","authors":"Marc Le Boursicaud ,&nbsp;Song Zhao ,&nbsp;Jean-Louis Consalvi ,&nbsp;Pierre Boivin","doi":"10.1016/j.combustflame.2025.114003","DOIUrl":"10.1016/j.combustflame.2025.114003","url":null,"abstract":"<div><div>The numerical study of ignition risk in the event of high-pressure hydrogen leakage presents numerous challenges. The first is to properly simulate the complex multi-dimensional flow (hemispherical expanding shock and contact discontinuity). The second is to properly resolve the diffusion/reaction interface, which has a very small length scale compared to the jet radius. We propose a low-order numerical model for such flows by first decoupling the flow and the diffusion/reaction interface into one cold flow and one reaction interface problem. The flow can be further simplified by assuming a “pseudo” 1D model with corrective source terms to account for axisymmetric (for a 2D test case) or spherical effects. Meanwhile, the diffusion interface is solved with a different space variable to optimize the mesh while using the results of flow simulation. The interface problem is further simplified by using the passive scalar approach recently developed for hydrogen ignition prediction (Le Boursicaud et al., 2023). Validation of the flow and interface solver is achieved through simple test cases, and the full configuration results are compared to the state-of-the-art model of the literature (Maxwell and Radulescu, 2011).</div><div><strong>Novelty and Significance Statement</strong>: In order to study the risk of shock-induced self-ignition of high-pressure hydrogen leakage, a new approach is developed by considering the flow to be pseudo-1D. This pseudo-1D model uses a specific source term in the governing equations, allowing for a drastic computational cost reduction compared to 2D-axisymmetrical or 3D simulations while being more general than partial models found in the literature. This source term is found to be independent of the hydrogen storage pressure and leakage radius. Moreover, a recently developed passive scalar approach was introduced for the first time to predict ignition within a dynamic diffusion layer.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 114003"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193353","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":"Interactions of preferential diffusion and mixture inhomogeneities in hydrogen and iso-octane flame kernels under engine conditions","authors":"Hongchao Chu,&nbsp;Lukas Berger,&nbsp;Michael Gauding,&nbsp;Sebastian Pieper,&nbsp;Heinz Pitsch","doi":"10.1016/j.combustflame.2025.113991","DOIUrl":"10.1016/j.combustflame.2025.113991","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In direct-injection spark-ignition engines, the in-cylinder fuel-air equivalence ratio field at the time of ignition is often inhomogeneous, which can significantly influence the flame kernel development and thus the entire combustion stroke. This can be particularly important for ultra-lean combustion concepts applied for increasing thermal efficiencies. For mixtures of species with different diffusivities, the flame kernel development can be significantly influenced by preferential diffusion. Both the inhomogeneous fuel distribution in the unburned gas and preferential diffusion alter the equivalence ratio in the reaction zone, thus influencing the combustion process. In this study, direct numerical simulations of lean hydrogen and iso-octane flame kernels have been performed to investigate the interactions between the mixture inhomogeneity in the unburned gas and the preferential diffusion under realistic engine conditions. For this purpose, a passive scalar is transported in the simulation to distinguish the variations of the local equivalence ratio caused by preferential diffusion from those caused by the mixture inhomogeneity in the unburned gas. While inhomogeneities are found to have a strong impact on flame kernel development for iso-octane flames, interestingly, turbulent hydrogen flame kernels possess increased resistance to the impact of mixture inhomogeneity. This is an important finding for the application of ultra-lean combustion concepts in hydrogen engines and is attributed to the enhanced flame propagation for hydrogen facilitated by thermodiffusive instability. Mixture inhomogeneity was found to trigger an earlier onset of cellular instabilities in the laminar hydrogen flame kernel. However, under the investigated conditions, no enhancement of the established thermodiffusive instabilities by the mixture inhomogeneity can be observed. This is demonstrated by the unchanged preferential diffusion-induced fluctuations of the fuel-air equivalence ratio and the linear scaling of its conditional mean with the mixture inhomogeneity. Further, the mixture inhomogeneity does not show a significant influence on the tangential strain rate, which is a key factor in flame kernel interactions with turbulence. For the investigated flames in the thin reaction zones regime, the same scaling of the tangential strain rate with the Kolmogorov time is observed for flame kernels with and without mixture inhomogeneity.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;Despite extensive studies that have separately examined the effects of mixture inhomogeneity and preferential diffusion, their interactions remain unexplored but are of significant practical importance, particularly for hydrogen engines with direct injection. This study is the first to investigate these interactions in flame kernels under engine-relevant conditions. It provides novel and fundamental insights into such interactions, including how mixture inh","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 113991"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193360","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":"Extension of the dynamic Thickened Flame model for partially-premixed multi-fuel multi-injection combustion and application to an ammonia–hydrogen swirled flame","authors":"H.J. Vargas Ruiz ,&nbsp;D. Laera ,&nbsp;G. Lartigue ,&nbsp;S. Mashruk ,&nbsp;A. Valera-Medina ,&nbsp;L. Gicquel","doi":"10.1016/j.combustflame.2025.113992","DOIUrl":"10.1016/j.combustflame.2025.113992","url":null,"abstract":"&lt;div&gt;&lt;div&gt;An extension of the widely-used Thickened Flame model for Large Eddy Simulations (TFLES) is proposed to take into account multi-fuel multi-injection combustion processes. Indeed, in such systems the local variations of the fuel composition and the local evolution of the equivalence ratio issued by differential diffusion effects inferred by the potential different nature of the used fuels need to be addressed for a proper use of the standard TFLES model. To do so, the extended model relies on a description of the differentiated fuel injections mixing that is computed from a transported mixture fraction tracing the spatial evolution of each fuel stream. This allows to both incorporate local fuel composition inhomogeneities into the combustion model and a proper parameterization of the flame sensor or turbulent combustion model. The proposed modeling is then used to predict the ammonia–air swirling flame stabilized by multiple hydrogen injection holes and operated at Cardiff University. To perform this specific simulations, a dedicated and novel analytically reduced chemical kinetics model for NH&lt;sub&gt;3&lt;/sub&gt;-H&lt;sub&gt;2&lt;/sub&gt;-N&lt;sub&gt;2&lt;/sub&gt;/air combustion is also derived and validated at gas turbine operating conditions and for multiple ammonia–hydrogen binary fuel blends as well as ternary fuel blends derived from ammonia decomposition. The results obtained by the use of the novel Multi-Fuel TFLES model (MF-TFLES) are compared against the conventional TFLES predictions and assessed via OH* chemiluminescence and NO Planar Laser Induced Fluorescence (NO-PLIF) experimental data. As shown, the proposed modeling improves the flame shape and structure prediction by assuring the correct local application of the artificial flame thickening coherently, taking into consideration the multi-fuel complex mixing process, a feature that the standard TFLES model cannot consider hindering the quality of the prediction.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;The novelty of this research can be summarized in two statements: 1. Extension of the widely used TFLES turbulent combustion model to consider flames where differential diffusion is present, as well as, partially-premixed multi-fuel multi-injection problems. 2. A novel 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;-H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;-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; analytically reduced chemistry suited for reactive LES. This work is significant because it allows to simulate unconventional burner setups which are being explored for decarbonized fuels, such as 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; and the highly diffusive H&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, in an effort to reduce the impact of power generation on climate change. Furthermore, high-fidelity modeling,","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"274 ","pages":"Article 113992"},"PeriodicalIF":5.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143193335","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}