Proceedings of the Combustion Institute最新文献

{"title":"Stabilised combustion of lean hydrogen–air mixtures in the presence of silica","authors":"Aki Fujinawa,&nbsp;Ewa J. Marek","doi":"10.1016/j.proci.2025.105841","DOIUrl":"10.1016/j.proci.2025.105841","url":null,"abstract":"<div><div>The urgent need to transition out of our reliance on fossil fuels motivates the development of emission-free combustion technologies. Here we demonstrate a method to burn hydrogen, a fuel that can be produced with green electricity, in a packed bed of silica particles. The presence of silica particles prevents the significant increase in process temperature encountered in gas-flame arrangements, thereby enabling the conversion of hydrogen to heat while mitigating nitrogen oxide emissions. Partial combustion is observed in packed beds of silica particles below the gas-phase ignition temperature, suggesting that a heterogeneous combustion mechanism dominates at low temperatures. Above the gas-phase ignition temperature, silica particles prevent thermal runaway by acting as a heat sink, suppressing the OH<span><math><mo>•</mo></math></span> radical-producing chain branching reactions, and instead promoting the conversion of hydrogen to water vapour by a mechanism involving the hydroperoxyl intermediate. Radical quenching and recombination reactions on surfaces of silica particles further reduce the availability of free radicals during in-bed combustion. The combustion of hydrogen with solid particles of silica can easily be scaled up using a fluidised configuration, owing to the low cost and wide availability of quartz sand. We present a unique opportunity for the stabilised, nitrogen oxides-free conversion of hydrogen to heat, offering an economical and scalable solution for large-scale industrial heat production with important economic and environmental value.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105841"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154440","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 investigation and optimization of ammonia–hydrogen chemical kinetics with ignition delay times from shock tubes","authors":"Torsten Methling ,&nbsp;Michael Pierro ,&nbsp;Nikolas Hulliger ,&nbsp;Justin J. Urso ,&nbsp;Jakob Krämer ,&nbsp;Clemens Naumann ,&nbsp;Markus Köhler ,&nbsp;Subith S. Vasu","doi":"10.1016/j.proci.2025.105835","DOIUrl":"10.1016/j.proci.2025.105835","url":null,"abstract":"<div><div>A combined experimental and numerical approach investigates the ignition delay times of ammonia–hydrogen mixtures in oxygen or synthetic air measured in shock tubes under different dilutions with argon and nitrogen. A series of novel ignition delay time measurements is presented for stoichiometric fuel–air mixtures diluted 1:10 and 1:5 in argon as well as 1:2 in nitrogen at the shock tube facility of the German Aerospace Center (DLR). The initialized gas conditions behind the reflected shock waves range between 940–2200 K and 4–16 bar. Additionally, recent ignition delay time determinations of fuel–air mixtures without subsequent dilution from the shock tube facility of the University of Central Florida (UCF) are reevaluated. Experimental data sets are analyzed with the application of multiple chemical kinetic models. The study reveals deficiencies in the modeling of fuel-oxidizer mixtures with relatively low dilution, representative for real combustion applications. To improve the chemical kinetic modeling capabilities, the reaction model DLR Concise is updated with new insights from literature. Subsequently, the updated model is optimized with the new experimental data and additional data on ignition delay times available from literature. 373 ignition delay times of ammonia and its mixture with hydrogen are targeted for the optimization. The linear transformation model is applied to optimize the most sensitive N-chemistry reactions within their uncertainties. The new experimental data from DLR confirm the observed deviations between the reevaluated experimental data from UCF and established chemical kinetic models. The updated and optimized DLR Concise models are resolve these modeling deficiencies and consistently reproduce the new and reevaluated data from both shock tube facilities. The optimized reaction model consistently reproduces the complete targeted experimental data with a broad range of initial temperature, pressure and mixture boundary conditions. Thus, the model can reliably be applied for numerical investigations of internal combustion engine ignition processes.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105835"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154517","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":"Semi-empirical lumped models of polymer pyrolysis for poly(methyl methacrylate) and polyoxymethylene","authors":"Tim J. Mallo,&nbsp;Adam Dumas,&nbsp;Phillip R. Westmoreland","doi":"10.1016/j.proci.2025.105807","DOIUrl":"10.1016/j.proci.2025.105807","url":null,"abstract":"<div><div>Quantitative lumped-kinetics models are constructed for pyrolysis of poly(methyl methacrylate) (PMMA) and polyoxymethylene (POM) by using known reaction classes to describe mass loss (volatiles loss) by purely 1st-order decomposition rates, averting the need for molar- or number-based concentrations. These semi-empirical models will aid in establishing fundamental kinetics of polymer decomposition for solid rocket fuels and thermal recycling. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) are applied to measure mass-loss and heat-consumption rates and the influences of heating rate, sample size, and end groups as a basis for modeling. This combination of rate data and products is useful for proposing pathways and establishing mechanisms. PMMA and POM homopolymers were selected for base-case pyrolysis studies due to their relatively simple structures and their tendencies to yield primarily monomer. For comparison, kinetics was also measured for POM copolymer, where -CH₂CH₂O- units are interspersed among the -CH₂O- units.</div><div>Two-, three-, and four-lumped-reaction parameterized models are presented for pyrolysis rates and yields from POM homopolymer, POM copolymer, and PMMA, respectively. The lumped reactions correspond to temperature regions that are dominated by a single type of first-order reaction, each with a mass fractional yield of volatiles, an Arrhenius pre-exponential factor, and an activation energy. The first, lowest-temperature lump may be pericyclic reactions to molecular intermediates, or the main chain or weakly bound end groups or side groups may homolytically scission. Polymer-radical fragments could be trapped by recombination and be too large to be volatile. If enough polymeric radicals are formed, beta-scission into monomers can be rate-limiting for volatiles formation, and at higher temperatures, homolytic scission would be rate-limiting. At highest temperatures, stages can be rate-limited by internal H-abstraction or termination via exothermic reactions to make strongly bound char residues.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105807"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144830202","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":"NOx production in a canonical Micromix hydrogen flame","authors":"Zisen Li ,&nbsp;Philippe Versailles ,&nbsp;Martin Vabre ,&nbsp;Evatt R. Hawkes ,&nbsp;Bruno Savard","doi":"10.1016/j.proci.2025.105793","DOIUrl":"10.1016/j.proci.2025.105793","url":null,"abstract":"<div><div>A direct numerical simulation (DNS) of two reactive hydrogen jets in an air crossflow at representative gas turbine conditions is performed. The thermochemical state nominally corresponds to a non-autoignitive, partially premixed turbulent flame. The analysis focuses on the instantaneous and conditional mean flame structures, and the NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> production mechanism. The results show that the flame along the jet centerline plane features two branches, one stabilized on the leeward side and a second lifted above the jet trajectory. The former is located close to the jet exit where the advective velocity is low due to the recirculation zone and the boundary layer. The hot products of the leeward flame are transported downstream and interact with the windward non-premixed flame branch. An analysis of the flame index indicates that both, non-premixed and premixed, flames coexist and undergo strong interactions. Through reaction pathway analyses, it is demonstrated that the production of NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> over the whole domain proceeds mainly through the thermal (Zel’dovich) route; this is the primary pathway in near-stoichiometric regions, while the N₂O and NNH routes are locally dominant in lean and rich premixed regions, respectively. Moreover, a post-flame (<span><math><mrow><mi>T</mi><mo>&gt;</mo><mn>1850</mn></mrow></math></span> K) residence time is used to track the time spent by fluid parcels in regions where thermal-NO prevails. This reveals that large quantities of NO produced through the thermal route near stoichiometry are transported in rich zones, resulting in a strong departure from 1D laminar reference cases.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105793"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144864681","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-priori and a-posteriori studies of finite-rate chemistry based combustion models for turbulent spherical lean premixed hydrogen/air flames","authors":"Yiqing Wang,&nbsp;Chao Xu,&nbsp;Riccardo Scarcelli","doi":"10.1016/j.proci.2025.105815","DOIUrl":"10.1016/j.proci.2025.105815","url":null,"abstract":"<div><div>Lean hydrogen combustion has emerged as a promising pathway to achieve high efficiency and low emissions in various energy and propulsion systems. However, the development of accurate turbulent combustion models for lean premixed hydrogen flames remains a significant challenge due to the complicated interplay between thermodiffusive instabilities and turbulence. In this study, the spherically expanding flame of a lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>/air mixture is simulated in a homogeneous isotropic turbulence environment at engine-relevant conditions using both direct numerical simulation (DNS) and large-eddy simulation (LES). These simulations enable both <em>a-priori</em> and <em>a-posteriori</em> evaluations of finite-rate chemistry (FRC) based turbulent combustion models within the LES framework, with the focus on their abilities to predict turbulent burning velocity (<span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span>). Two combustion models are investigated in particular: the well-stirred reactor (WSR) model and the thickened flame model (TFM). <em>A-priori</em> evaluation is first carried out for the WSR model based on DNS results. It is found that WSR tends to over-predict <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span>, which can be reproduced from a 1-D twin-premixed stretched laminar flame at high stretch rates. This indicates that such over-prediction is resulted from the response of local reaction rates to the LES filtering operation, rather than turbulence. In contrast, the <em>a-posteriori</em> test through LES shows that <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span> is significantly under-predicted by the WSR model. This is because the interactions between flame instabilities and turbulence are not sufficiently captured in LES/WSR, which leads to reduced flame wrinkling and stretching factors. The performance of the TFM model is also evaluated <em>a-posteriori</em> in LES. Results show that with flame thickening, the local flame reactivity is enhanced, while the flame wrinkling is reduced, resulting in limited improvement on the prediction of <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span> by LES/TFM. By introducing a proper correction factor to the efficiency function, the prediction by TFM can be largely improved, but the instantaneous <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>T</mi></mrow></msub></math></span> is still not well reproduced. These findings highlight that caution needs to be taken when interpreting the <em>a-priori</em> analysis results for FRC-based turbulent combustion models. Results from this study further provide novel insights into potential pathways to improve turbulent combustion models such as TFM, especially in the context of turbulent lean premixed hydrogen flames.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105815"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912911","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":"Interaction and ignition process of multiple injections of oxygenated fuels in an optical, heavy-duty diesel engine","authors":"Kaylyn Buchanan ,&nbsp;Akash Dhotre ,&nbsp;Daipayan Sen ,&nbsp;Ales Srna ,&nbsp;Rajavasanth Rajasegar","doi":"10.1016/j.proci.2025.105820","DOIUrl":"10.1016/j.proci.2025.105820","url":null,"abstract":"<div><div>Poly-oxymethylene ethers (OMEs) are a class of highly oxygenated synthetic fuels that offer promising pathways for decarbonizing transportation and enhancing energy security. Their favorable ignition properties, high cetane number, and soot-free combustion characteristics make them attractive alternatives to conventional diesel. However, their lower energy density, weaker negative temperature coefficient (NTC) behavior, and rapid mixing due to fuel-bound oxygen introduce complex interactions during combustion, particularly under multiple-injection strategies common in modern diesel engines. This study investigates the ignition and combustion behavior of OMEs compared to a conventional non-oxygenated surrogate fuel (n-dodecane) under various pilot-main injection configurations using a heavy-duty, optical single-cylinder engine. A suite of diagnostics, including apparent heat release rate (AHRR) analysis and simultaneous planar laser-induced fluorescence (PLIF) imaging of formaldehyde (HCHO) and hydroxyl (OH), was employed to capture the low- and high-temperature combustion phases. Experiments were conducted across a matrix of pilot injection durations, dwell times, and EGR dilution levels to evaluate their influence on ignition delay (ID), flame structure, and heat release dynamics. Results show that OME requires longer pilot injections to overcome rapid lean-out and achieve comparable ignition assistance due to its low stoichiometric air–fuel ratio (AFR_ST) and reduced LTHR contribution. A critical minimum injection duration was identified for OME below which the pilot fails to ignite, a behavior not observed with n-dodecane. Despite this, OME displays rapid, volumetric ignition once combustion initiates, owing to favorable mixture stratification from fuel-bound oxygen. A conceptual model is proposed to distinguish ignition regimes based on pilot duration and fuel oxygenation level, explaining the interplay between entrainment-driven mixing, HTHR suppression, and reactive zone formation. The findings enhance understanding of the underlying physics governing multiple injections and provide guidance for optimizing pilot strategies when adapting diesel engines to oxygenated fuels like OME.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105820"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145007767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of water vapor on nitriding of stainless steel walls induced by ammonia flames","authors":"Yujian Xing,&nbsp;Minhyeok Lee,&nbsp;Yuji Suzuki","doi":"10.1016/j.proci.2025.105831","DOIUrl":"10.1016/j.proci.2025.105831","url":null,"abstract":"<div><div>Ammonia is a promising candidate fuel for future carbon-free energy systems. However, significant interactions between ammonia flames and metal walls in combustors result in “unwanted” nitriding, compromising safe operation and shortening the lifespan of combustion systems. The substantial water vapor generated during ammonia combustion further influences this flame-wall interaction. This study examines the effect of water vapor on two interconnected processes: the heterogeneous decomposition of ammonia and the nitriding of stainless steel induced by ammonia flames. Ammonia conversion ratios due to heterogeneous decomposition on stainless steel surfaces were measured in a flow reactor under varying water vapor concentrations, and the mechanisms underlying the impact of water vapor on both surface reactivity and surface nitriding were examined. Additionally, the effect of water vapor on nitriding induced by ammonia flames was investigated. The findings confirm that the oxidation effect of water vapor reduces surface reactivity for heterogeneous ammonia decomposition, making it the primary factor behind the hindering effect on nitriding during ammonia combustion.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105831"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the performance of the joint velocity-scalar PDF method near walls","authors":"Tin-Hang Un ,&nbsp;Salvador Navarro-Martinez","doi":"10.1016/j.proci.2025.105838","DOIUrl":"10.1016/j.proci.2025.105838","url":null,"abstract":"<div><div>Wall modelling of turbulent reacting flows is crucial for applications such as aero-engine simulations. The velocity-scalar probability density function (PDF) method has proven effective for modelling flames in complex combustion regimes, but its application near walls is computationally expensive due to the need for wall-resolving grids, even with the aid of adaptive mesh refinement. This study aims to reduce computational cost by employing a modern wall model in large eddy simulations (LES). We demonstrate that a simple subgrid model is sufficient for a wide range of wall distances, though modification to the stochastic forcing is needed to prevent spurious pressure formation near walls. The proposed wall-modelled stochastic fields framework significantly improves upon existing methods without wall modelling. It also highlights the potential for cost savings by using wall-modelled LES-PDF. For this purpose, the Eulerian stochastic fields framework is particularly suited as it can integrate with most existing LES wall models with minimal modifications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105838"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145117636","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":"Transported PDF and MMC modelling of local extinction in turbulent piloted NH3/H2/N2-air jet flames","authors":"Lu Tian ,&nbsp;Andrew P. Wandel ,&nbsp;R.P. Lindstedt","doi":"10.1016/j.proci.2025.105843","DOIUrl":"10.1016/j.proci.2025.105843","url":null,"abstract":"<div><div>Ammonia is a potential alternative fuel for decarbonising hard-to-abate sectors. Practical utilisation is hindered by unfavourable combustion properties that include slow chemical kinetics, low flame speeds and high nitrogen oxide emissions. These challenges are further exacerbated by local extinction in turbulent flames driven by turbulence–chemistry interactions. This study uses the joint-scalar transported probability density function (JPDF) and Multiple Mapping Conditioning (MMC) frameworks, both of which inherently provide a closed chemical source term treatment, to investigate such interactions in two turbulent ammonia–hydrogen–nitrogen–air flames exhibiting local extinction. The flames have been experimentally characterised and correspond to 59.2% (Flame D) and 88.9% (Flame F) of the blow-off velocity. The performance of JPDF methods, featuring Modified Curl’s (JPDF-MC) and Euclidean Minimum Spanning Tree (JPDF-EMST) closures for transport in scalar space, is evaluated alongside the MMC-based MMC-MC and MMC-IEM models for predicting local extinction. All four models provide generally good predictions for Flame D, but show noticeable differences for Flame F, particularly where local extinction is extensive. The JPDF-EMST closure predicts the least amount of local extinction, followed by MMC-IEM, with JPDF-MC and MMC-MC providing closer agreement with experimental data. The presence of NH₃ containing fluid in fuel lean regions for Flame F is related to local extinction events with computed results found to be sensitive to very minor changes (<span><math><mrow><mo>≃</mo><mn>1</mn><mtext>%</mtext></mrow></math></span>) in the fuel jet exit velocity. The MMC-MC formulation improves predictions of temperature PDFs in fuel-rich regions and OH PDFs in fuel-lean regions due to the enforced localness of transport in scalar space.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105843"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145117638","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":"Role of hydrodynamic instabilities in high-frequency transverse thermoacoustic instabilities in a dual-swirl H2 burner","authors":"Hyebin Kang ,&nbsp;Hugo Paniez ,&nbsp;Thierry Schuller","doi":"10.1016/j.proci.2025.105837","DOIUrl":"10.1016/j.proci.2025.105837","url":null,"abstract":"&lt;div&gt;&lt;div&gt;High-frequency thermoacoustic instabilities pose a significant challenge to the development of new generations of combustion systems. This study investigates the interplay between helical hydrodynamic instabilities in a dual-swirl hydrogen-air burner, featuring a spinning thermoacoustic instability coupled to the first transverse acoustic mode of the combustion chamber in the absence of injector coupling. Particle image velocimetry coupled with OH planar laser-induced fluorescence, high-speed OH&lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;∗&lt;/mo&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt; imaging, and pressure measurements are used to explore how varying the swirl level &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; imparted to the hydrogen stream influences the flow and flame dynamics during self-sustained oscillations for a fixed swirl level &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;e&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; of the air stream. A dramatic shift in flame response is revealed. At low swirl &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, elongated flames with low-frequency self-sustained oscillations are observed, while compact flames dominated by high-frequency transverse instabilities are triggered at higher swirl levels &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and 1.0. In the latter case, the flow dynamics in the internal recirculation zone of the swirling flow is dominated by a transverse bulk oscillation due to acoustic displacement, while the shear layers are influenced by large-scale helical hydrodynamic structures. It is demonstrated that the amplitude of the high-frequency combustion instability depends on the synchronization between hydrodynamic &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;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and acoustic &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;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; frequencies. When synchronization occurs (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≃&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), large vortical structures synchronized with the transverse acoustic wave are formed. These structures strongly dominate flame deformation compared to the direct displacement caused by the transverse spinning acoustic wave, thereby substantially enhancing the amplitude of thermoacoustic instability. Conversely, when the frequencies are misaligned (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;≠&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), transverse oscillations are weaker but persist, indicating that the helical hydrodynamic instability primarily a","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105837"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154431","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}