Proceedings of the Combustion Institute最新文献

{"title":"Modeling the spatially resolved structural and morphological evolution of nanoparticles in flame spray pyrolysis using a detailed population balance Monte Carlo method","authors":"Song He,&nbsp;Fei Xie,&nbsp;Haibo Zhao","doi":"10.1016/j.proci.2026.106197","DOIUrl":"10.1016/j.proci.2026.106197","url":null,"abstract":"<div><div>Population balance models (PBMs) with high-dimensional particle property spaces offer a more detailed description of nanoparticles undergoing multiple dynamic events. However, these methods are inherently difficult to incorporate with spatial inhomogeneity and particle transport, thus are typically limited to modelling spatially homogeneous or pseudo-one-dimensional systems. In this work, a detailed population balance Monte Carlo (PBMC) model coupled with ballistic cluster-cluster aggregation (BCCA) is developed to investigate the spatially resolved structural evolution of nanoparticles in flame spray pyrolysis (FSP). The model maintains a constant computational volume and a dynamically stable number of stochastic particles through weight adjustment, enabling direct coupling with multi-grid computational fluid dynamics (CFD) simulations. By explicitly resolving the coordinates and connectivity of primary particles, the PBMC-BCCA method provide a full geometrical description of fractal-like particles under nonuniform flame conditions. The proposed method is applied to simulate the generation and growth of ZrO₂ nanoparticles in FSP. The spatially resolved evolution of particle size, morphology, and structure within the flame is discussed in detail. The results demonstrate a marked enhancement in predictive fidelity for aggregate structure and morphology over conventional low-dimensional PBMs.</div></div><div><h3>Novelty and significance statement</h3><div>This study develops a detailed population balance Monte Carlo method coupled with ballistic cluster-cluster aggregation for the spatially resolved simulation of nanoparticle morphology and structure in flame spray pyrolysis. The model maintains a constant computational volume through dynamic weight adjustment, enabling direct coupling with multi-grid CFD simulations while retaining full geometrical description of nanoparticles. By integrating high-dimensional particle modeling with transport and mixing effects in spatially inhomogeneous flame environments, the model captures the spatially resolved structural and morphological evolution of nanoparticles under varying flame conditions, demonstrating significantly improved predictive accuracy over conventional low-dimensional population balance models. To the best of the authors’ knowledge, this study represents the first extension of a particle-resolved, high-dimensional population balance model to multidimensional simulations of reactive flows.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106197"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148415326","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":"Numerical study of inverse H2O2 droplet combustion in methane–nitrogen atmospheres under microgravity","authors":"Alberto Cuoci,&nbsp;Alessio Frassoldati","doi":"10.1016/j.proci.2026.106082","DOIUrl":"10.1016/j.proci.2026.106082","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Inverse droplet combustion, in which the oxidizer evaporates from the liquid phase and the surrounding gas provides the fuel, remains far less understood than classical fuel-droplet burning. In particular, the intrinsic transport–chemistry coupling of &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;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; droplets in hydrocarbon atmospheres is difficult to isolate experimentally because buoyancy alters flame shape, mixing, and heat transfer. In this work, we numerically investigate the inverse combustion of isolated &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;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; droplets in &lt;span&gt;&lt;math&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;mo&gt;/&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;N&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; atmospheres at 1 atm under microgravity conditions using a transient, one-dimensional, spherically symmetric model with detailed chemical kinetics, multicomponent transport, phase equilibrium, and gas-phase radiation. The simulations are carried out for &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;X&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;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;55&lt;/mn&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;00&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and are extended over a range of initial droplet diameters.&lt;/div&gt;&lt;div&gt;The calculations reproduce the main phenomenological features reported by Matsugi et al. (2023) and reveal the intrinsic structure of the inverse flame in the diffusion-controlled limit under microgravity conditions. After a short transient, the droplets evolve toward a quasi-steady regime consistent with the classical &lt;span&gt;&lt;math&gt;&lt;msup&gt;&lt;mrow&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;&lt;/span&gt;-law, showing that diffusion-controlled scaling persists despite the reversal of fuel and oxidizer roles.. The flame exhibits a clear two-layer structure, with an inner region dominated by &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;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; decomposition near the droplet surface and an outer methane-oxidation region sustained by radicals transported from the inner zone. Despite variations in methane concentration and initial droplet diameter, the relative flame position remains nearly constant, indicating that the flame location is primarily controlled by the diffusive balance between outward oxidizer transport and inward methane transport. In contrast, the vaporization rate shows a non-monotonic dependence on the initial droplet size, which arises from the competition between conductive and radiative heat transfer at the droplet surface.&lt;/div&gt;&lt;div&gt;These results provide a detailed kinetic and thermal description of inverse &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msu","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106082"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148409478","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":"Self evolving neural network methodology for chemical kinetics reduction","authors":"Sheharyar Nasir,&nbsp;Cheng Huang","doi":"10.1016/j.proci.2026.106127","DOIUrl":"10.1016/j.proci.2026.106127","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Accurate chemical kinetics are crucial for reacting-flow simulations but detailed mechanisms remain computational prohibitive. To fill this gap, we formulate a self-evolving neural network (SENN) methodology with a species–reaction–species topology, where thermochemical states feed reaction neurons whose outputs represent the collective net species production rates. The SENN undergoes episodic training in which the network is exposed to a subset of data and gradient-based optimization is coupled with stabilized Hebbian plasticity to strengthen persistently co-active connections. After each episode, a stoichiometry-graph guided pruning step removes neurons and edges with consistently low influence. The resulting neural network (NN) constitutes a compact, chemistry-consistent reduced mechanism that faithfully predicts the detailed kinetics over a broad range of thermochemical states. The SENN methodology is demonstrated for 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;/air combustion using a 21-reaction model as the baseline detailed kinetics. First, we demonstrate that the reduced kinetic models from SENN accurately predict net species production rate with negligible mean-squared error (MSE), closely capture ignition delay and flame speed over a wide range of thermochemical states, and provide up to 4.5x computational speedup. Second, we develop a SENN-centered adaptive modeling framework that dynamically adapts the reduced mechanisms on the fly to accurately capture the reaction characteristics while efficiently resolving slower chemical regimes, reproducing the temperature and heat release rate evolution with good agreement with the detailed kinetics and achieving an additional computational speedup of approximately &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;73&lt;/mn&gt;&lt;mo&gt;×&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The SENN methodology offers a new direction in developing an interpretable and scalable scientific machine learning approach for chemical kinetic reduction that balances computational efficiency and modeling accuracy in complex reacting flow simulations.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; This work introduces a self-evolving neural network (SENN) methodology that autonomously evolves its structure to learn a sparse, chemistry-consistent kinetic model. SENN features three key innovations: (1) a species–reaction–species topology enabling adaptive structure evolution; (2) episodic training, which reduces training cost and guides physics-informed adaptation; and (3) stoichiometry-guided graph pruning reinforced by Hebbian consolidation and gradient saliency, yielding reduced kinetic mechanisms that preserve key combustion observables with substantially lower inference cost. SENN provides a generalizable framework for extracting skeletal mechanisms, quantifying reaction-pathway importance, and managing the sparsity–accuracy tradeoff. The approach enables robust mechanism reduction for practical com","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106127"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582377","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":"A mapping-based projection of detailed kinetics uncertainty onto reduced manifolds","authors":"Vansh Sharma,&nbsp;Shuzhi Zhang,&nbsp;Rahul Jain,&nbsp;Venkat Raman","doi":"10.1016/j.proci.2026.106136","DOIUrl":"10.1016/j.proci.2026.106136","url":null,"abstract":"<div><div>Propagating uncertainties introduced by chemical reaction rate parameters to high-fidelity numerical simulations of complex combustion devices is necessary to ascertain impact on computational predictions. However, the high cost of detailed computations combined with the need to conduct multiple simulations to propagate uncertainty makes such an estimation computationally challenging. In order to reduce the computational cost, a two-step framework for quantifying uncertainty introduced by detailed chemical kinetics model parameters using reduced chemistry models is developed here. First, reduced-manifold states are uniquely reconstructed in full-composition space by following trajectories at an unburnt mixing state and integrating forward to a prescribed progress variable constraint. Second, parametric uncertainty is propagated by sampling perturbed rate coefficients from mechanism covariance matrices and integrating each realization to the target state, yielding uncertainty maps for reduced-space quantities. The method is applied in two configurations: a subsonic multi-tube combustor with interacting jet flames and recirculation, and a three-dimensional reacting high-speed flowpath. Uncertainty-instrumented estimated are reported for a trajectory time (time for the reconstructed unreacted mixture to reach the local target state) and for the time to equilibrium, revealing order-of-magnitude spatial variations driven by mixing, stratification, and residence-time effects. The largest relative variability occurs in low-to-intermediate temperature regimes associated with induction and the onset of heat release, where branching-related chemistry amplifies sensitivity, particularly away from stoichiometric conditions. The method provides a scalable route to spatially resolved, physically interpretable chemistry-UQ for practical reacting-flow simulations.</div><div><em>Novelty and significance statement:</em> Only recently, detailed chemistry models with estimated uncertainty have started to be formulated. There still remains a challenge in using these uncertainty estimates in practical flame simulations due to the high computational cost of sampling from distributions. In this work, we propose a new approach to recover uncertainty maps, where (a) simulations conducted using simpler chemistry models (and hence relatively inexpensive) can be mapped to detailed chemistry models, and (b) uncertainty estimates from the detailed models can be applied to the simpler chemistry model based simulations. The mapping approach is flexible and can be formulated for specific flame processes, in a manner similar to flamelet or flame-generated manifold approaches. The results quantify variability in key processes modulated due to mixing-interaction and geometry-induced residence times, emphasizing the importance of mechanism-consistent UQ within modeling and design workflows.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106136"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582378","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":"High-temperature NO-LIF measurements in laminar premixed NH3/H2/N2–air counterflow flames","authors":"Martin Richter,&nbsp;Robert S. Barlow,&nbsp;James R. Dawson,&nbsp;Andreas Dreizler,&nbsp;Dirk Geyer","doi":"10.1016/j.proci.2026.106091","DOIUrl":"10.1016/j.proci.2026.106091","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The presence of fuel-bound nitrogen in ammonia-based fuels leads to increased emissions of nitric oxide (NO) and its derivatives. Quantitative datasets for model validation of premixed flames under atmospheric conditions remain limited, especially for systematic variations in strain rate and fuel composition. This study presents spatially resolved NO profiles in premixed 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 counterflow flames with H&lt;sub&gt;2&lt;/sub&gt; fractions between 27–45 % and global strain rates from 400–800 s&lt;sup&gt;-1&lt;/sup&gt; for lean (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0.8&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and rich (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;ϕ&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1.1&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) mixtures, measured by laser-induced fluorescence (LIF). Excitation in the A–X(0,1) system near 236 nm confines the evaluation to the high-temperature regime (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;≥&lt;/mo&gt;&lt;mn&gt;1200&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mstyle&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mstyle&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). Quantification combined calibrated NO-LIF with 532&lt;!--&gt; &lt;!--&gt;nm Rayleigh scattering and one-dimensional simulations to determine the local thermochemical states to account for state-dependent effects on the LIF signal between calibration and measurement conditions. Results show a pronounced strain rate dependence of NO in fuel-rich, low-H&lt;sub&gt;2&lt;/sub&gt; flames, which weakens as the H&lt;sub&gt;2&lt;/sub&gt; fraction increases. Across all tested conditions, measured NO profiles agree well with predictions from three chemical kinetic mechanisms in lean flames, whereas substantial deviations occur in fuel-rich, low-H&lt;sub&gt;2&lt;/sub&gt; flames. To interpret these trends, the 27 % H&lt;sub&gt;2&lt;/sub&gt; flames were analyzed using simulation-based indicators for the O/H/OH and &lt;figure&gt;&lt;img&gt;&lt;/figure&gt; (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1,2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) radical pools, addressing strain response and mechanism agreement. The strain response of rich flames is consistent with a strong decrease in O/H/OH radicals with increasing strain rate, while both radical pools respond only weakly to strain in lean flames, resulting in no significant NO response. Across the mechanisms, the &lt;figure&gt;&lt;img&gt;&lt;/figure&gt; pools differ substantially in both lean and rich flames, whereas the O/H/OH pool is consistent in lean flames but differs strongly in rich flames, suggesting that it is a key contributor to the observed NO deviations. The present dataset provides a basis for validating and improving chemical kinetic mechanisms over a broad range of operating conditions.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; This work advances the quantitative understanding of NO formation in premixed 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 counterflow flames by providing quantitative, non-intrusive NO measurements using linear LIF at 236 nm and extending prior saturated-LIF studies &lt;span&gt;&lt;span&gt;[1]&lt;/span&gt;&lt;/span&gt; through systematic variation of strain rate and fuel composition. A previously unobserved strain depen","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106091"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582564","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":"Synchronous CH*/OH* chemiluminescence imaging of detonation dynamics in a methane-fueled rotating detonation engine","authors":"Ashley James,&nbsp;Ajay K. Agrawal","doi":"10.1016/j.proci.2026.106110","DOIUrl":"10.1016/j.proci.2026.106110","url":null,"abstract":"<div><div>Rotating detonation engines (RDEs) offer advantages over conventional propulsion systems, but near-complete fuel consumption via detonation is required to realize these benefits. This work presents the first spatially and temporally synchronous CH* and OH* chemiluminescence imaging within an RDE annulus, revealing detailed detonation wave dynamics. A novel optical system enables direct pixel-to-pixel comparison of fuel decomposition and fuel oxidation zones without introducing parallax or path-length errors. Methane and oxygen-enriched air combustion at varying equivalence ratios reveals three distinct phases: (1) presence of CH* in the refill zone indicating fuel breakdown before wave arrival, (2) spatially separated CH* and OH* regions in the detonation zone, and (3) reappearance of OH* post-detonation indicating fuel leakage through the detonation zone. Results provide experimental evidence of fuel breakdown in the refill zone and fuel leakage from the detonation zone that can contribute to deflagration, even in case of RDE operation at lean and stoichiometric equivalence ratios. The spatial separation between centroids of CH* and OH* emissions exhibit a systematic equivalence ratio dependence, with a minimum at stoichiometric conditions and increasing spatial separation towards fuel-lean and fuel-rich bounds. The trend of CH* to OH* spatial separation with mixture composition is shown to correlate with CH<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>-O<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> detonation cell width data available in the literature.</div><div><em>Novelty and significance statement:</em> This work presents the first spatially and temporally synchronous CH* and OH* chemiluminescence imaging in a hydrocarbon-fueled rotating detonation engine (RDE), simultaneously resolving fuel decomposition and oxidation regimes throughout the detonation cycle—a feature invisible to conventional single-species OH* diagnostics. Existing multi-species chemiluminescence approaches using independent optical paths introduce parallax errors, path-length differences, and temporal misalignment that prevent accurate spatial mapping of reaction zone structure. The optical configuration in this study eliminates these limitations, enabling characterization of detonation wave structure with equivalence ratio in a methane-fueled RDE.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106110"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582565","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":"Self-excited thermoacoustic instabilities and flame dynamics in an H2-fueled trapped vortex combustor","authors":"Qian Wang,&nbsp;Aksel Ånestad,&nbsp;Kai Wang,&nbsp;Dong Yang,&nbsp;Nicholas A. Worth","doi":"10.1016/j.proci.2026.106014","DOIUrl":"10.1016/j.proci.2026.106014","url":null,"abstract":"<div><div>Self-excited thermoacoustic instabilities are investigated in a laboratory-scale staged trapped vortex combustor operated with pure hydrogen. The main stage equivalence ratio and power split ratio between the pilot and main stages are varied while maintaining a constant total thermal power of 35 kW. Two different instability modes are observed. Low-order network model analysis and consideration of the flame Strouhal numbers indicate that the low and high-frequency modes are dominated by the main and pilot flame, respectively. Image analysis is used to separate heat release rate oscillations from the pilot and main stage, allowing their phase relationship and the Rayleigh index to be assessed. Changing the power split ratio is shown to modify the phase of the heat release rate oscillations in the two stages such that global cancellation occurs, allowing instabilities to be mitigated while maintaining the overall thermal power. Quantifying driving/damping through the Rayleigh Index shows some evidence of heat release rate cancellation between the stages. The findings demonstrate how instabilities can be controlled through staging, which can inform practical approaches to stabilizing combustion systems.</div><div><em>Novelty and significance statement:</em> Mitigating thermoacoustic instabilities remains a critical challenge in gas turbine design, particularly for pure hydrogen flames in next-generation combustion systems. Recent studies have sought to leverage the operational flexibility of fuel staging to mitigate instabilities; however, its potential in systems with interacting flames remains unexplored.</div><div>This work presents the first detailed analysis of self-excited instabilities in a fully optically accessible trapped vortex burner that captures key features of the practical FlameSheet^TM combustor, demonstrating that strategic staging can suppress instabilities even amid interacting flames. The burner introduces both axial and radial staging with separate pilot and main inlets. A low-order network model with side branches is developed to predict system’s acoustic modes. Furthermore, a region-based approach is proposed to separate heat release rates in two stages, quantifying their contributions and showing how thermoacoustic modes couple to different inlet, offering general insight into multi-inlet combustion systems, and staged systems with interacting flames.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106014"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582608","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":"Kinetic model development and experimental study of high-pressure ignition of nitropropane","authors":"Mirko Bardin,&nbsp;Jesus Caravaca-Vilchez,&nbsp;Julien Glorian,&nbsp;Barbara Baschung,&nbsp;Karl Alexander Heufer","doi":"10.1016/j.proci.2026.106163","DOIUrl":"10.1016/j.proci.2026.106163","url":null,"abstract":"<div><div>Nitropropane (NP) is a promising candidate for advanced propulsion systems as a propellant or fuel additive. While some studies of its ignition have been conducted in the past, they focused on highly diluted conditions, and only one high-pressure dataset is available. This study extends the high-pressure dataset with ignition delay time (IDT) measurements conducted in a shock tube (ST) and a rapid compression machine (RCM) at pressures ranging from 20<!--> <!-->bar to 30<!--> <!-->bar, temperatures ranging from 730<!--> <!-->K to 980<!--> <!-->K, and air-like conditions. These measurements were supplemented by species concentration profiles obtained during the IDT in the RCM using a rapid sampling system coupled with gas chromatography and mass spectrometry (GC–MS) techniques. In addition, a detailed kinetic model was developed. New rate parameters for unimolecular decomposition reactions were estimated by analogy to nitroethane (NE) and alkane-like low temperature pathways were added. The model also includes interactions between alkanes and nitrogen dioxide to better reflect the experimentally observed fuel behavior. Sensitivity and rate-of-production (ROP) analyses revealed that competition among C-N bond fission, H-migration, and H-atom abstraction (HAA) dominates NP reactivity. Previously absent NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> cycling reactions and alkane-like low temperature pathways have a significant influence on the reaction network, particularly at low temperatures. The new model outperforms the literature model over a wider range of conditions. It can predict air-like dilution experiments and the most abundant species formed during ignition.</div><div><em>Novelty and significance statement:</em> This work presents a new experimental dataset that includes non-diluted IDT measurements and simultaneous species measurements in the RCM at previously unexplored low-temperature and high-pressure conditions. These measurements extend the range of experimental data on high temperatures and high levels of dilution available in the literature (He et al., 2022). The model while partially based on literature has been reworked and new reaction rates are used for the main decomposition reactions to better predict the fuel behavior. The newly added reaction pathways help to understand the complex competition of decomposition, NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> cycling and conventional low temperature pathways that are critical at low levels of dilution and medium-to-low temperatures. This understanding will support the modeling of other nitrogenated compounds in future studies.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106163"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582707","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":"Ultra-lean methane as a kinetic promoter of early oxidation in Fe-based oxygen carriers","authors":"Xinjiang Dong,&nbsp;Jilong Li,&nbsp;Fang Liu,&nbsp;Li Yang","doi":"10.1016/j.proci.2026.106154","DOIUrl":"10.1016/j.proci.2026.106154","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Methane is a potent greenhouse gas, and large volumes of ultra-lean methane are continuously emitted through coal mine ventilation systems. Although the methane concentration is typically below 1 vol%, the enormous gas flow rates result in significant cumulative emissions. Chemical looping oxidation offers a promising pathway for the safe and efficient mitigation of such dilute methane streams, yet the influence of methane on the oxidation behavior of oxygen carriers remains insufficiently understood. In this work, the effect of ultra-lean methane on the early oxidation behavior of Fe-based oxygen carriers was investigated by combining thermogravimetric analysis with reactive molecular dynamics simulations. The experiments reveal a non-monotonic kinetic response: a trace amount of methane (0.5 vol%) accelerates the initial oxidation rate, whereas higher methane concentrations suppress oxygen uptake. Atomic-scale simulations demonstrate that ultra-lean methane promotes oxygen activation and leads to more uniform lattice oxygen incorporation, accompanied by smoother strain evolution and faster Fe redox conversion. However, increasing methane concentration enhances oxygen diversion toward methane-involved pathways, forming intermediates such as OH and products including H&lt;sub&gt;2&lt;/sub&gt;O, CO, and CO&lt;sub&gt;2&lt;/sub&gt;. This competitive oxygen consumption reduces the fraction of oxygen incorporated into the lattice. These results reveal a dual regulatory mechanism governed by the balance between synergistic oxygen activation and competitive oxygen diversion. The findings provide new insight into gas–solid coupled oxidation mechanisms under ultra-lean fuel conditions and offer guidance for the design of chemical looping systems for methane mitigation.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance statement:&lt;/strong&gt; The novelty of this study lies in the detailed investigation of the regulatory effect of ultra-lean methane on the oxidation behavior of Fe-based oxygen carriers through a combined thermogravimetric and reactive molecular dynamics approach. By integrating macroscopic kinetic measurements with atomic-scale simulations, this work elucidates how trace methane influences oxygen activation, lattice oxygen incorporation, and the evolution of reaction intermediates. Furthermore, the underlying mechanism governing the transition from oxidation promotion to inhibition with increasing methane concentration is systematically clarified.&lt;/div&gt;&lt;div&gt;This research is significant because ultra-lean methane emitted from coal mine ventilation systems represents a major source of fugitive greenhouse gas emissions, yet its efficient mitigation remains a technological challenge due to the extremely low fuel concentration. Chemical looping oxidation offers a promising strategy for the safe and efficient treatment of such dilute methane streams. However, the interaction between methane and oxygen carriers under ultra-lean conditions remains insufficiently understood","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106154"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148587489","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":"The role of detailed kinetics in the double flame structure of nitromethane droplet combustion","authors":"Alessio Frassoldati,&nbsp;Alberto Cuoci,&nbsp;Alessandro Stagni","doi":"10.1016/j.proci.2026.106103","DOIUrl":"10.1016/j.proci.2026.106103","url":null,"abstract":"<div><div>Although nitromethane (NM) kinetics has been long examined, either as a fuel or as an intermediate in the carbon-nitrogen interaction, the coupling between its gas-phase chemistry and liquid droplet evaporation still needs further fundamental investigation. To address this, this work performs the first detailed numerical comparison of existing nitromethane kinetic mechanisms applied to single-droplet combustion, providing quantitative assessment against available experimental data. The numerical model accounts for transient heat and mass transfer, vapor-liquid equilibrium, radiative effects, and the influence of the supporting rod. It was observed that existing literature kinetic mechanisms for NM often contain inaccurate parameters for NM transport properties, which strongly affect droplet evaporation predictions, particularly through overestimated thermal conductivity values. Comparisons with experimental data show that the CRECK mechanism has the best trade-off in reproducing both droplet burning rates and flame propagation when corrected transport properties are applied, although the predicted flame speeds are slightly overestimated. All models capture the characteristic double-flame structure typical of hybrid monopropellant combustion, with an inner decomposition zone and an outer oxidation layer. Only the Caltech mechanism exhibits an endothermic peak within the inner flame region. These results provide insight into droplet combustion behavior and the performance of different kinetic mechanisms.</div></div><div><h3>Novelty and significance statement</h3><div>This study presents the first simulation of nitromethane (NM) droplet combustion in air with variable oxygen concentration, using transient one-dimensional modeling with six detailed kinetic mechanisms. Unlike earlier studies focused on gaseous flames or simplified droplet models, the approach couples detailed chemistry with accurate transport and thermodynamic properties, including a correction to the previously overestimated NM thermal conductivity. Radiation and buoyancy-driven convection under normal gravity are also considered. Comparison with two experimental datasets identifies mechanisms capable of reproducing both droplet burning rates and flame speeds. Analysis of the characteristic double-flame structure provides new insight into hybrid combustion behavior and kinetic-mechanism validation for green propulsion applications. A comparison with a methanol droplet flame under identical conditions is also included. Overall, the work improves understanding of NM droplet combustion, highlights the influence of uncertainties in transport data, and provides a validated framework for modeling energetic monopropellants and related combustion systems.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106103"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148587495","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}