Combustion and Flame最新文献

{"title":"Large Eddy Simulation of the evolution of the soot size distribution in turbulent nonpremixed bluff body flames","authors":"Hernando Maldonado Colmán, Michael E. Mueller","doi":"10.1016/j.combustflame.2025.114282","DOIUrl":"10.1016/j.combustflame.2025.114282","url":null,"abstract":"<div><div>Large Eddy Simulation (LES) is used to investigate the evolution of the soot size distribution in a series of turbulent nonpremixed bluff body flames, with different bluff body diameters. The new Bivariate Multi-Moment Sectional Method (BMMSM) is employed to characterize the size distribution. BMMSM combines elements of sectional methods and methods of moments and is capable of reproducing fractal aggregate morphology, thanks to its joint volume-surface formulation, all at relatively low computational cost with fewer transported soot scalars compared to traditional sectional methods. LES results show soot volume fraction profiles agreeing correctly with the experimental measurements, exhibiting significant improvement compared to previous work using the Hybrid Method of Moments (HMOM). The evolution of the particle size distribution function (PSDF) was examined across the flame series and shows that the shape of the size distribution is less sensitive to the bluff body diameter than the overall soot volume fraction, which increases with increasing bluff body diameter. The PSDF across the flame exhibit different features compared to turbulent nonpremixed jet flames. The recirculation zone exhibits a nearly bimodal size distribution, which eventually becomes bimodal in the downstream jet-like region. The rather stark differences in the soot volume fraction predicted by HMOM and BMMSM are due to subtle differences in soot oxidation that are amplified in this configuration due to coupling to the flow field via soot radiation. With HMOM, the inner vortex between the central jet and recirculation zone is weaker, leading to significant soot leakage from the recirculation zone nearer the centerline. With BMMSM, the inner vortex is stronger, leading to a longer recirculation zone but with far less soot leakage and nearer the tip of the recirculation zone away from the centerline. The net result is much larger soot nucleation and condensation rates with BMMSM in both the recirculation zone and jet-like region, comparable to surface growth and oxidation, which dominate with HMOM. This work reveals that accounting for the size distribution can be crucial to both predicting global soot quantities accurately and reproducing fundamental mechanisms at least in some flame configurations.</div><div><strong>Novelty and Significance Statement</strong></div><div>For the first time, the evolution of the soot size distribution in a series of turbulent nonpremixed bluff body flames is investigated, by leveraging the recently developed Bivariate Multi-Moment Sectional Method (BMMSM) and using Large Eddy Simulation (LES). The analysis includes a comprehensive discussion of the evolution of the soot size distribution in the flame series. Finally, BMMSM predicts even the mean soot volume fraction much more accurately than the Hybrid Method of Moments (HMOM), due to amplifications of subtle differences in the models on soot and its feedback on the flow field throug","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114282"},"PeriodicalIF":5.8,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144306680","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":"Publication / Copyright Information","authors":"","doi":"10.1016/S0010-2180(25)00329-3","DOIUrl":"10.1016/S0010-2180(25)00329-3","url":null,"abstract":"","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"278 ","pages":"Article 114291"},"PeriodicalIF":5.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297588","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":"Multi-regime turbulent spray combustion modeling by similarity mapping","authors":"Junyi He,&nbsp;Qun Hu,&nbsp;Lipo Wang","doi":"10.1016/j.combustflame.2025.114271","DOIUrl":"10.1016/j.combustflame.2025.114271","url":null,"abstract":"<div><div>In turbulent spray combustion modeling, the primary challenge comes from the involvement of multiple physical parameters in the flamelet framework. Benefiting from the recently developed similarity mapping for the spray flamelet-progress variable model (SMFPV), the tabulation parameters can be much reduced. In general, spray combustion is characterized by multiple combustion regimes under different working conditions, for instance, the non-premixed flame at the oxidizer side and the premixed flame after complete evaporation of initially small droplets. In the present study, a unified multi-SMFPV model is proposed to account for such a multi-regime issue, by adjusting the spatial range of the evaporation source and adopting the scalar dissipation rate of mixture fraction as an additional entry parameter. Validated against three typical laminar spray counterflow flame cases, multi-SMFPV performs better than other models and aligns closely with the direct integration of the finite-rate chemistry (DIC) results. With regard to the turbulent combustion case, multi-SMFPV is also implemented to simulate the Sydney turbulent spray flame and shows reasonable accuracy.</div><div><strong>Novelty and significance</strong></div><div>A new version of the similarity mapping spray flamelet progress variable model, named multi-SMFPV, has been proposed to correctly capture multiple combustion regimes encountered in spray combustion. The modeling principles include adjusting the spatial range of the evaporation source and adopting the scalar dissipation rate of mixture fraction as an additional entry parameter to distinguish different combustion regimes. Predicted results of three typical laminar spray counterflow flame cases show significant improvements compared to the former version. Results of the Sydney turbulent spray flame simulation show that multi-SMFPV is also feasible in turbulent situations.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114271"},"PeriodicalIF":5.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298656","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 multi-tier auto-ignition detection applied to dual-fuel combustion simulations","authors":"Jorge S. Salinas ,&nbsp;Hemanth Kolla ,&nbsp;Martin Rieth ,&nbsp;Ki Sung Jung ,&nbsp;Jacqueline Chen ,&nbsp;Janine Bennett ,&nbsp;Marco Arienti ,&nbsp;Lucas Esclapez ,&nbsp;Marc Day ,&nbsp;Nicole Marsaglia ,&nbsp;Cyrus Harrison ,&nbsp;Terece L. Turton ,&nbsp;James Ahrens","doi":"10.1016/j.combustflame.2025.114273","DOIUrl":"10.1016/j.combustflame.2025.114273","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Here we use an anomaly detection methodology that is centered on analyzing fourth-order joint moments (co-kurtosis), particularly focusing on its application in auto-ignition of combustion problems with large numbers of species. Unsupervised anomaly detection is challenging to generalize across problem types and domains. A recent technique, centered on analyzing information in the fourth-order joint moment co-kurtosis, has shown promise, especially for high-dimensional scientific data. In this work we present developments to the co-kurtosis based anomaly detection method needed to make it effective and scalable for large-scale distributed scientific data, such as those generated by massively parallel simulations. An in situ co-kurtosis algorithm is employed as the anomaly detection method for identifying ignition kernels in simulations of turbulent combustion. We extend an existing methodology which identifies regions of the domain where anomalies are present, and add another tier of anomaly detection where the individual samples contributing to the anomaly are identified. We apply this algorithm on-the-fly to a variety of turbulent reacting flow problems and compare it to the widely used (but significantly more expensive) chemical explosive mode analysis (CEMA). We demonstrate the ability of the method to detect and identify the onset of low and high temperature ignition which can be used for computational steering, as chemical and combustion anomalies occur intermittently at spatio-temporal locations unknown a priori. Finally, we apply our lightweight in situ algorithm to an exascale high-fidelity simulation with a total of 2.4 Trillion degrees of freedom, performed using an adaptive mesh refinement solver. Furthermore, through a scalability analysis, we show that the relative computational cost of this in-situ anomaly detection algorithm compared to an iteration of the reacting flow solver is negligible.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;Techniques to identify occurrence of auto-ignition have hitherto relied on the specifics of the chemical kinetics, and criteria have been based on ad-hoc thresholds. The novelty of this work lies in adopting a purely statistical viewpoint of auto-ignition, as one signified by higher-order joint moments, instead of a chemical kinetic viewpoint which does not generalize from one fuel to another or under different conditions. While previous work has demonstrated the accuracy and generalizability of the higher-order joint moments (co-kurtosis) approach in identifying regions of auto-ignition, this work builds on the concept and presents additional tiers of identifying auto-ignition, specifically individual samples within regions. Such multi-tiered detection is demonstrated to be accurate in simulations with spatio-temporally complex ignition behavior. Moreover, the technique is shown to be significantly more computationally efficient and scalable when deployed in sit","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114273"},"PeriodicalIF":5.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298649","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 modal decomposition-based partially stirred reactor (mPaSR) model for turbulent combustion closure: Implementation details and a posteriori validation","authors":"Arthur Péquin ,&nbsp;Erica Quadarella ,&nbsp;Riccardo Malpica Galassi ,&nbsp;Salvatore Iavarone ,&nbsp;Hong G. Im ,&nbsp;Alessandro Parente","doi":"10.1016/j.combustflame.2025.114269","DOIUrl":"10.1016/j.combustflame.2025.114269","url":null,"abstract":"<div><div>This paper investigates a turbulence-chemistry interaction model based on the Partially Stirred Reactor (PaSR) paradigm where the hypothesis of relying on an individual chemical timescale is relaxed to deal with multiscale problems. The modal Partially Stirred Reactor (mPaSR) model relies on the Computational Singular Perturbation (CSP) theory and performs an eigen-decomposition of the Jacobian matrix of the chemical source terms. The CSP manifold is then corrected by modal fractions that, similarly to the cell reacting fraction of the original PaSR model, account for the individual mode timescales. The vector of the chemical source terms, to be returned to the computational fluid dynamics solver, acts as an aggregated contribution of the corrected CSP modes. The predictive capabilities of the mPaSR model are demonstrated <em>a posteriori</em> through a series of Unsteady Reynolds-Averaged Navier–Stokes simulations of the well-documented Sandia flames. Promising results are observed at different turbulence levels making the mPaSR approach a valuable alternative to existing turbulence-chemistry interaction models. Particular attention is given to the formation of pollutants, and accurate predictions of nitric oxide NO are obtained.</div><div><strong>Novelty and significance statement</strong> The novelty of this work lies in the code development, integration and <em>a posteriori</em> testing of an innovative combustion model accounting for several timescales of dynamical chemical systems. This represents an important step towards well-suited approaches for the modelling of multiscale processes such as pollutant formation in turbulent flames. The model shows promising prediction capabilities with desirable computational efficiency on the investigated cases, motivating follow-up investigations in a larger range of combustion scenarios.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114269"},"PeriodicalIF":5.8,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298650","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":"Eco-friendly and high-efficiency Halon replacement fire suppressant: Mechanistic and application insights into the synergistic effects of 2-bromo-3,3,3-trifluoropropene and perfluoro-2-methyl-3-pentanone","authors":"Yitao Liu,&nbsp;Jun Wang,&nbsp;Huiming Sun,&nbsp;Ruiyu Chen ,&nbsp;Ying Xu,&nbsp;Renming Pan","doi":"10.1016/j.combustflame.2025.114295","DOIUrl":"10.1016/j.combustflame.2025.114295","url":null,"abstract":"<div><div>To develop an efficient, eco-friendly Halon replacement, this study investigates a composite fire suppressant of perfluoro-2-methyl-3-pentanone (C₆F₁₂O) and 2-bromo-3,3,3-trifluoropropene (2-BTP). Molecular dynamics simulations confirmed the components’ compatibility, and a 72-h static test validated their combined physicochemical stability. Experimental trials using a custom cup burner platform evaluated fire suppression performance by measuring minimum extinguishing concentration (MEC), flame temperature and morphology at varying 2-BTP concentrations. Synergistic factors were calculated to quantify the components' synergistic effects. Combustion products were analyzed with Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS) and electron paramagnetic resonance (EPR) to examine chemical interactions during combustion inhibition. Results showed that the composite suppressant maintains excellent thermodynamic stability and compatibility across temperature ranges. Increasing the 2-BTP fraction from 0 to 50 % decreased the boiling point from 49.0°C to 34.6°C and the MEC from 4.6 % to 2.98 %, while reducing flame temperature, height, and initially decreasing flame area. Product analysis suggested that physical and chemical synergy between C₆F₁₂O and 2-BTP effectively disrupts the combustion chain reaction, improving fire suppression efficiency. At a 50 % 2-BTP to C₆F₁₂O ratio, the suppressant achieved optimal physical and chemical inhibition effects, representing the most cost-effective composition.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290457","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":"Shock-induced auto-ignition of partially dissociated ammonia mixtures","authors":"Shubao Song ,&nbsp;Ding Guo ,&nbsp;Cheng Wang ,&nbsp;Jiankun Shao","doi":"10.1016/j.combustflame.2025.114280","DOIUrl":"10.1016/j.combustflame.2025.114280","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Ammonia (NH₃) is emerging as a promising zero-carbon fuel, offering vital support for the transition to sustainable energy systems. Among various applications, partially dissociated ammonia mixtures have exhibited great potential in internal combustion engines and gas turbines due to their enhanced reactivity and improved combustion performance. In this study, comprehensive ignition delay times (IDTs) and NH₃ time-history measurements of partially dissociated ammonia mixtures (NH₃/H₂/N₂) were conducted over a wide range of temperatures (1115—1611 K), pressures (1.0—4.0 atm), dissociation proportions, and oxygen concentrations (3.33 %, 7.5 %, and 13.33 %). The results revealed that the reactivity of dissociated ammonia mixtures increases significantly with higher pressures, dissociation degrees, and oxygen contents, while the elevated oxygen concentrations may lead to excessive NO&lt;sub&gt;x&lt;/sub&gt; emissions. A recently developed NH₃-syngas chemical kinetic model proposed by our group was systematically validated against the experimental data from this work, including IDTs and NH₃ time-histories, as well as laminar flame speeds, speciation data, and NO&lt;sub&gt;x&lt;/sub&gt; emissions from literature. The model exhibited remarkable predictive accuracy under high-pressure and fuel-lean conditions, filling the gap in current kinetic models for dissociated ammonia combustion. Further rate of production and sensitivity analyses were carried out to unveil the dominant oxidation pathways and identify key elementary reactions controlling the reactivity of dissociated ammonia mixtures. Moreover, the generation and consumption pathways of NO&lt;sub&gt;x&lt;/sub&gt; were thoroughly elucidated, providing valuable insights into NO&lt;sub&gt;x&lt;/sub&gt; formation mechanisms under varying dissociation proportions and oxygen contents. This study may enhance the kinetic understanding of partially dissociated ammonia combustion and provides theoretical foundation for the development of two-stage ammonia combustors with optimized performance and reduced NO&lt;sub&gt;x&lt;/sub&gt; emissions.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;Ammonia is a highly promising zero-carbon fuel with considerable potential to support the transition to sustainable energy. However, its inherently low reactivity poses significant challenges to widespread application. Recent studies suggest that two-stage combustors, leveraging partially decomposed ammonia products, can enhance combustion reactivity. In this work, ignition delay times and key species profiles of NH₃/H₂/N₂ mixtures were systematically measured using a shock tube coupled with laser absorption spectroscopy — to the best of our knowledge, this represents the first dataset of its kind in the literature. The NH₃-syngas kinetic model developed by our group was validated against both our experimental results and extensive literature data, demonstrating improved predictive accuracy. Furthermore, rate of production and sensitivity analyses were per","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114280"},"PeriodicalIF":5.8,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144262617","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":"Publication / Copyright Information","authors":"","doi":"10.1016/S0010-2180(25)00299-8","DOIUrl":"10.1016/S0010-2180(25)00299-8","url":null,"abstract":"","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"277 ","pages":"Article 114261"},"PeriodicalIF":5.8,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144261740","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":"Elucidation of the interaction between ammonium perchlorate and hydroxyl-terminated polyether during co-pyrolysis","authors":"Jingjing Wang ,&nbsp;Zhandong Wang ,&nbsp;Yan Zhang ,&nbsp;Wanyun Shao ,&nbsp;Heng Li ,&nbsp;Sihai Ni ,&nbsp;Siyu Xu ,&nbsp;Liangyuan Jia","doi":"10.1016/j.combustflame.2025.114281","DOIUrl":"10.1016/j.combustflame.2025.114281","url":null,"abstract":"<div><div>Oxidizers and binders are indispensable constituents of propellants, but the chemistry of their thermal decomposition remains ambiguous. This study elucidates the cross-interactions between ammonium perchlorate (AP, as an oxidizer) and hydroxyl‑terminated polyether (HTPE, as a binder) in their co-pyrolysis processes by using online single photoionization mass spectrometry and thermogravimetry-Fourier transform infrared methods. The results show that AP significantly promotes the thermal decomposition of HTPE and the formation of products such as light olefins (e.g., propylene and 1,3-butadiene), esters (e.g., ethyl formate), and especially ethers (e.g., tetrahydrofuran and 1,4-dioxane). In addition, the differences in the decomposition temperature ranges and product distributions during the whole thermal decomposition stage between the pure components (pure AP or HTPE) and the AP/HTPE composite components were compared in detail. Two reaction regimes related to the co-pyrolysis of AP and HTPE were proposed at the molecular level (i.e., the reactions between the polyether chain of the HTPE binder and the decomposition products HClO₄ and O₂ of AP). This work provides a theoretical basis for further understanding insensitive propellants.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114281"},"PeriodicalIF":5.8,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144262676","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 extinction and burning limits of stretched premixed ammonia flames at elevated pressures","authors":"Shumeng Xie ,&nbsp;Huangwei Zhang","doi":"10.1016/j.combustflame.2025.114248","DOIUrl":"10.1016/j.combustflame.2025.114248","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In this study, one-dimensional detailed simulations of stretched premixed counterflow flames are conducted to investigate the flame extinction, bifurcations, and burning limits of NH&lt;sub&gt;3&lt;/sub&gt;/air and NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/air mixtures at elevated pressures up to 25 atm. For the NH&lt;sub&gt;3&lt;/sub&gt;/air mixtures, the incorporation of radiative heat loss results in a left weak flame branch at low strain rates, which exists only within a narrow strain rate range. A regime diagram is proposed to illustrate sustainable strain rate ranges of normal and weak flames at different equivalence ratios. Kinetic analyses show that the ammonia oxidation in the weak flames is governed by H&lt;sub&gt;2&lt;/sub&gt;NO at the lean side and N&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;x&lt;/sub&gt; at the rich side. Nonetheless, for the normal flames, the H&lt;sub&gt;2&lt;/sub&gt;NO, NH&lt;sub&gt;i&lt;/sub&gt;, and N&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;x&lt;/sub&gt; pathways are significant under lean, near stoichiometric, and rich conditions, respectively. Furthermore, the influence of hydrogen additions on ammonia flames is investigated. The results show that hydrogen addition, e.g., &lt;span&gt;&lt;math&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;/math&gt;&lt;/span&gt; 0.1 by volume, leads to the formation of a stable right weak flame branch, with the H&lt;sub&gt;2&lt;/sub&gt;NO sub-chemistry being the dominant oxidization mechanism. Then, the flame bifurcation and extinction behaviors at different equivalence ratios are summarized in a regime diagram with five critical strain rates. It is shown that the low-temperature H&lt;sub&gt;2&lt;/sub&gt;NO route extends the rich burning limit from 3.45 to 5.68 for the NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/air mixture at a hydrogen mole fraction of 0.1. In the end, the burning limits are determined as a function of hydrogen molar fraction and pressure, and the hydrogen addition significantly expands the burning limits both on the lean and rich side. These findings provide valuable insights into the flammability of ammonia/hydrogen flames and the underlying oxidation mechanisms subject to elevated pressure conditions.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and Significance Statement&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This study fills a noticeable gap in the literature by providing a comprehensive regime diagram of extinction and burning limits for NH&lt;sub&gt;3&lt;/sub&gt;/air and NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt;/air flames under varying mixture composition conditions. A key novelty lies in exploring NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt; combustion behaviors under elevated pressures up to 25 atm, revealing distinct flame bifurcations and weak flame branches induced by radiative heat loss—phenomena not captured for NH&lt;sub&gt;3&lt;/sub&gt;/H&lt;sub&gt;2&lt;/sub&gt; mixtures previously. The work also highlights those most relevant ammonia oxidation paths under different temperature and composition conditions, which is beneficial for future mechanism development. It further clarifies the influence of hydrogen enrichment and pressure on the burning limits and discusses their relationship with fundamental flammability limits derived from unstretched planar flames","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"279 ","pages":"Article 114248"},"PeriodicalIF":5.8,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144262675","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}