Proceedings of the Combustion Institute最新文献

{"title":"Influence of magnetic field on flame dynamics in hydrogen flames: A numerical study","authors":"Vaibhav Mysore Natesh,&nbsp;Ivan Langella","doi":"10.1016/j.proci.2025.105892","DOIUrl":"10.1016/j.proci.2025.105892","url":null,"abstract":"<div><div>Electromagnetic fields influence flame behavior by altering the transport of paramagnetic species such as oxygen and OH radicals in hydrogen flames, affecting reaction pathways and combustion dynamics. This study presents a numerical investigation of the effects of magnetic fields on a premixed swirl-stabilized hydrogen flame using a modified combustion solver in OpenFOAM. Additional body force and diffusion terms were incorporated into the governing equations to model interactions with paramagnetic species, and the solver was validated against experimental data and simulations from the literature. The study focuses on analyzing flame structure, species redistribution, and mixture fraction variations under magnetic conditioning. Large Eddy Simulations (LES) with the Eulerian Stochastic Fields (ESF) method were employed to capture turbulence-chemistry interactions. The results indicate that the presence of a magnetic field induces an upstream-directed force on oxygen, leading to localized changes in mixture fraction and combustion characteristics. A reduction in temperature, heat release rate, and OH concentration was observed, with peak reductions of approximately 2%, 5%, and 6%, respectively. These effects are attributed to the redistribution of oxygen, which makes the flame locally leaner. This study extends the understanding of hydrogen combustion under electromagnetic influence and demonstrates the potential of magnetic fields for controlling the flame behavior. The findings provide new insights into magnetic field-assisted combustion strategies, offering a framework for further research in advanced propulsion and energy applications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105892"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262549","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":"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}

{"title":"Meta-learning innovates chemical kinetics: An efficient approach for surrogate model construction","authors":"Chenyue Tao,&nbsp;Chengcheng Liu,&nbsp;Yiru Wang,&nbsp;Bin Yang","doi":"10.1016/j.proci.2025.105860","DOIUrl":"10.1016/j.proci.2025.105860","url":null,"abstract":"<div><div>The construction of surrogate models is an essential step in the uncertainty quantification of combustion reaction kinetics. These models create a mapping between inputs and outputs of combustion kinetics simulations, thereby replacing the time-consuming numerical simulations of reaction kinetics and significantly lowering the computational costs for uncertainty quantification. However, in applications such as experimental design that require repeated construction of surrogate models under multiple operating conditions, the associated computational burden becomes substantial and can even limit the feasibility of the entire task. It is therefore essential to investigate cost-efficient surrogate model construction methods. Drawing inspiration from image classification in computer vision, this work introduces a meta-learning-assisted approach to efficiently construct surrogate models by leveraging the intrinsic shared features among them. By learning from a limited set of training tasks, the approach facilitates rapid creating surrogate models for new conditions with fewer samples. This is particularly beneficial for reducing computational costs since the most significant expense comes from the generation of original samples. The method has been tested in ammonia-hydrogen combustion targeting ignition delay time and laminar burning velocity. Results show that the efficiency of the surrogate model construction can be improved by a factor of eight for individual new conditions, and the total computational costs across the entire condition range can be reduced to 29 % and 37 % of the original values for the two prediction targets, respectively. Notably, dual pretraining across both prediction targets further enhances model performance. The meta-learning-assisted surrogate model construction approach is applicable across a broad range of operating conditions, requiring only minimal additional pretraining costs while offering flexible precision control based on task-specific requirements.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105860"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154444","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":"Recombination of NH2 with alkyl radicals: VRC-TST rate constants from neural network potentials","authors":"Simone Vari,&nbsp;Carlo Cavallotti","doi":"10.1016/j.proci.2025.105829","DOIUrl":"10.1016/j.proci.2025.105829","url":null,"abstract":"<div><div>The recombination between CH₃ and NH₂ is an important reference reaction for describing the formation of chemical bonds between hydrocarbons and nitrogen compounds in combustion. This is for example the case when ammonia is burned together with hydrocarbon mixtures. Despite the important role played by this reaction in combustion processes, the theoretical studies on the accurate determination of its rate constant, or on the pressure dependence, are limited. At present, most existing kinetic mechanism use experimental measures performed at room temperatures, or detailed balance and the rate constants measured for the reverse process at high temperatures, thus in conditions in which the reaction rate is pressure dependent. This places some limits on the ability to accurately describe the reactivity of two key radical species: methyl and NH₂, in particular when this reaction pathway is in competition with others. The present work aims at filling this gap, providing ab-initio rate constant estimations for the recombination pathway of the reaction family C_nH_2n+1 + NH₂, with <em>n</em> = 1, 2, 3. Rate constants are estimated using Variable Reaction Coordinate – Transition State Theory (VRC-TST) and machine learning. VRC-TST is the golden standard for kinetic studies of barrierless reactions, which do not have a well-defined transition state. The rate constants estimated with VRC-TST approach the experimental accuracy, at the cost of a computationally demanding Monte Carlo sampling of the reactive Potential Energy Surface (PES). In this work we use Artificial Neural Network (ANN) to learn the portion of the multidimensional PES relevant to the reaction of interest as a function of the degrees of freedom describing the relative orientation of the two reacting fragments. The physics-informed ANN architecture significantly reduces the number of explicit electronic structure calculations needed by VRC-TST, thus gaining significant time savings without compromising accuracy. The calculated rate constants are in good agreement with the available experimental data and are thus expected to provide a useful reference for the kinetic modelling of the co-combustion of nitrogen compounds and hydrocarbons.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105829"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154518","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":"In-Situ Adaptive Manifolds for soot evolution in non-adiabatic turbulent reacting flows","authors":"Matthew X. Yao,&nbsp;Israel J. Bonilla,&nbsp;S. Trevor Fush,&nbsp;Michael E. Mueller","doi":"10.1016/j.proci.2025.105824","DOIUrl":"10.1016/j.proci.2025.105824","url":null,"abstract":"<div><div>To reduce the computational cost of simulations of turbulent reacting flows, manifold-based combustion models are often employed. In these models, the thermochemical state is projected onto a low-dimensional manifold, which can be computed separately from the flow solver. Traditionally, the model involves the pretabulation of solutions to a set of manifold equations, which are obtained a priori. The inclusion of soot and emissions introduces additional physics due to the importance of radiation heat losses. To account for the effects of heat loss, the number of table dimensions necessarily increases. Consequently, these tables can become very memory intensive and include many thermochemical states that may not even be accessed during the simulation. To reduce this memory burden, the concept of In-Situ Adaptive Manifolds (ISAM) has recently been proposed. Within this framework, necessary manifold solutions are computed on-the-fly and stored for lookup using In-Situ Adaptive Tabulation (ISAT). In this work, ISAM is coupled to a soot model based on the Hybrid Method of Moments (HMOM) model. To incorporate heat losses, the manifold equations are augmented with an equation for the heat loss parameter <span><math><mi>H</mi></math></span>, which is also evolved in the LES flow solver. The manifold equations are formulated based on a quasi-steady assumption, and a model heat loss source term is multiplied by a constant <span><math><mi>Ω</mi></math></span> to account for varying magnitudes of radiation heat losses from the gas-phase and soot. During runtime, the <span><math><mi>H</mi></math></span> field from the LES must be matched by ISAM to produce the correct thermochemical state. An iterative procedure is developed to obtain the correct value of <span><math><mi>Ω</mi></math></span> to ensure consistency of the heat loss parameter between LES and ISAM. The model is demonstrated on the Sandia Sooting Flame. Compared to traditional precomputed tables, ISAM is shown to provide significant memory savings at a minor increase in the computational cost, which is sensitive to the initial guesses for the iterative approach for matching <span><math><mi>H</mi></math></span>.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105824"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154519","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":"Exploring discrepancies among theoretical and experimental data for NH2 + CH4 ⇌ NH3 + CH3","authors":"Ella C. Kane ,&nbsp;Joe Lee ,&nbsp;Jonathan M. Pankauski ,&nbsp;Rodger E. Cornell ,&nbsp;Michael P. Burke","doi":"10.1016/j.proci.2025.105809","DOIUrl":"10.1016/j.proci.2025.105809","url":null,"abstract":"<div><div>Ammonia has been of great recent interest as a carbon-free fuel amidst growing concern around greenhouse gas emissions. Ammonia’s poor combustion characteristics have motivated exploration of co-combustion of ammonia and various co-fuels to yield more favorable combustion behavior. When the co-fuel is a hydrocarbon, the co-combustion kinetics can involve a host of reactions between nitrogen-containing species and carbon-containing species that are not otherwise important during combustion of either fuel when pure. Recent studies have highlighted hydrogen abstraction from hydrocarbons by NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> as an important class of such C-N interaction mechanisms. However, even for NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> + CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> <span><math><mi>⇌</mi></math></span> NH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> + CH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span>, which is among the simplest and most studied reactions of this reaction class, there is significant disagreement among rate constants from various theoretical and experimental studies. Of particular note, two shock tube studies at high temperatures reported rate constant determinations that differ by a factor of <span><math><mo>∼</mo></math></span>4. Interestingly, both studies use thermal decomposition of a precursor following the shock wave to form NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> and then monitor NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> time profiles, but they use different precursors—raising the possibility that secondary reactions unique to each precursor (methylamine or hydrazine) may contribute to the discrepancies. The disagreement between these experimental studies, along with similar disagreement among theoretical studies, makes this an interesting system for analysis using MultiScale Informatics (MSI), which has previously identified consistent explanations of apparently inconsistent data for other reactions. We find, however, that the data reported in one of the shock tube studies are not internally consistent. An MSI model based on the other experimental and theoretical data is found to be consistent with all other data (including for the methylamine precursor) and essentially upholds the other experimental determinations despite significant revisions to the secondary chemistry since the original analysis, including further insights into methylamine chemistry described herein.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105809"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154520","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":"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}