Proceedings of the Combustion Institute最新文献

{"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":"Hydrogen fluoride emissions from lithium-ion batteries during induced thermal runaway via in situ laser spectroscopy","authors":"Yi Yan,&nbsp;Nicolas S.B. Jaeger,&nbsp;R. Mitchell Spearrin","doi":"10.1016/j.proci.2025.105800","DOIUrl":"10.1016/j.proci.2025.105800","url":null,"abstract":"<div><div>Improved understanding of hydrogen fluoride (HF) emissions from lithium-ion battery fires, including the temporal dynamics, is needed to optimize fire response and protection. Due to the high polarity of HF and its associated surface adsorption and reactivity, most traditional sensing methods are prone to error and slow response due to issues with sampling or surface interactions. To address these limitations, an in situ tunable diode laser absorption spectrometer is developed to achieve real-time measurements of HF emissions during dynamic battery fires with a temporal resolution of milliseconds, and with detection limits of single parts per million along with several orders of magnitude of dynamic range. The laser spectrometer is used in situ to perform measurements near the fire source so that the fire dynamics and the transient behavior of HF emissions can be more accurately characterized. Thermal runaway and fire/explosion conditions of model 18650 lithium-ion batteries are simulated in a conical radiative heater, and HF measurements are performed online via an optical access port in the effluent exhaust. By varying the radiative heating flux of the conical heater and the initial state of charge of the batteries, different characteristics of the safety venting and thermal runaway behavior of lithium-ion batteries and the corresponding emissions of toxic HF gas are measured. These findings provide valuable insights into the dynamics of lithium-ion battery fires and will aid in the development of strategies to mitigate their associated risks.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105800"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860419","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":"Modeling uncertainties in primary zone soot predictions for a rich-quench-lean combustion system","authors":"Shubham Basavaraj Karpe,&nbsp;Suresh Menon","doi":"10.1016/j.proci.2025.105805","DOIUrl":"10.1016/j.proci.2025.105805","url":null,"abstract":"<div><div>A comprehensive uncertainty quantification (UQ) of soot volume fraction (SVF) predictions in the primary zone of a Rich-Quench-Lean (RQL) combustor is presented, with particular emphasis on the modeling uncertainties in the rates of nucleation, growth, oxidation, condensation, and coagulation. Large-eddy simulations (LES) of soot formation in a realistic single-sector RQL combustor are first performed, and the local thermochemical data, along with the volumes of the zones containing the respective finite volume cells, are then used to construct a chemical reactor network (CRN) model. The CRN model, coupled with the UQ tool DAKOTA, is used to conduct forward UQ, sensitivity analysis, and inverse UQ. The forward UQ indicates variability ranging from 28 % to 89% around the mean soot prediction, depending on the location within the combustor. The local and global sensitivity analyses highlight the contributions of nucleation and condensation processes near the fuel injection zone, while growth and oxidation processes predominantly influence soot predictions in the primary zone. Since the baseline model underpredicts soot compared to experimental measurements, a Bayesian inference-based inverse UQ analysis is performed to identify sensitive input rate uncertainties that can improve the quantitative agreement with experimental soot levels. Thus, the overall strategy identifies the most influential aspects of the soot model, their relevant sensitivity to local zones within the combustor, and further refinements to the baseline rates that can provide valuable insights for future model developments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105805"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809685","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":"Systematic temperature error in RCARS diagnostics from improper Raman linewidths","authors":"Jonas I. Hölzer ,&nbsp;Henry Misoi ,&nbsp;Thomas Seeger","doi":"10.1016/j.proci.2025.105842","DOIUrl":"10.1016/j.proci.2025.105842","url":null,"abstract":"<div><div>The coherent anti-Stokes Raman spectroscopy (CARS) stands as the standard for thermometry and major species detection and quantification in gas phase and combustion diagnostics. In recent years the database of empirical S-branch Raman linewidth for a variety of gases, gas mixtures and temperatures for rotational CARS spectroscopy has been significantly expanded. The Raman linewidths are of utmost importance for accurate extraction of thermodynamic information from the spectral information. However, unavailable correct linewidth data for rotational CARS evaluations are regularly substituted by approximated data for example by omission of the proper collisional environment or by using the vibrational Q-branch linewidth instead of the rotational S-branch linewidths. The resulting systematic errors by using incorrect linewidths have only been studied for a few selected cases which hint at a significant temperature error of up to 9 %. In this work we show a clear picture of the temperature and concentration errors resulting from incorrect linewidth data by evaluating the influence of S- vs. Q-branch linewidths in pure oxygen and self-broadening vs. accurate collisional environment in air and nitrogen-water vapor mixtures. The data show that the evaluated temperature is systematically too high by using Q-branch instead of S-branch linewidths in oxygen and nitrogen thermometry and a strong influence of the collisional environment on the temperature and species concentration determination.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105842"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104547","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":"Full-spectrum fitting method applied to YAG:Dy : Impact of oxygen content and laser fluence on wall-temperature phosphor thermometry for combustion","authors":"Tobias Guivarch ,&nbsp;Hugo Samson ,&nbsp;Jérôme Bonnety ,&nbsp;Jessy Elias ,&nbsp;Sébastien Ducruix ,&nbsp;Clément Mirat ,&nbsp;Christopher Betrancourt ,&nbsp;Guilhem Dezanneau ,&nbsp;Ronan Vicquelin","doi":"10.1016/j.proci.2025.105845","DOIUrl":"10.1016/j.proci.2025.105845","url":null,"abstract":"<div><div>Achieving the European net-zero greenhouse gas emissions target requires the development of sustainable combustion processes across various industrial sectors. These promising alternatives introduce new challenges, such as modifying wall heat transfer. Accurate surface temperature measurements are essential for understanding these effects. Laser-Induced Phosphorescence (LIP) provides a semi-invasive method that exploits the temperature-dependent phosphorescence spectra of thermographic phosphors. YAG:Dy is a thermographic phosphor that emits a phosphorescence signal over the range of 300 K to 2000 K. However, its poor sensitivity with the intensity ratio method and its low sensitivity at lower temperatures with the lifetime method limit its use to high-temperature combustion applications. Additionally, its sensitivity to ambient oxygen reduces the accuracy of those methods. This study evaluates the performance of the Full-Spectrum Fitting (FSF) method, developed by the EM2C Laboratory in Lechner et al. (2022), when applied to YAG:Dy. The method leverages the phosphor’s spectral temperature dependence over a wide range (303 to 1773 K), achieving an accuracy of 0.3 K and a precision of 8.4 K under given experimental conditions. It is observed that there is a laser fluence threshold above which temperature determination using the FSF method becomes independent of laser fluence. The impact of YAG:Dy’s sensitivity to oxygen concentration on temperature measurement is quantified. In the worst case, uncertainty in oxygen concentration can introduce a temperature error ranging from 7 to 19 K. Guidelines are provided to help mitigate these sensitivities in combustion applications.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105845"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154442","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":"Influence of discrete injection on asymptotic and transient dynamics of rotating detonation engines","authors":"Trevor Kickliter ,&nbsp;Eli Young ,&nbsp;Vishal Acharya ,&nbsp;Tim Lieuwen","doi":"10.1016/j.proci.2025.105814","DOIUrl":"10.1016/j.proci.2025.105814","url":null,"abstract":"<div><div>Rotating detonation engines (RDEs) promise improved thermodynamic efficiency over traditional combustion engines, improved energy density, mechanical simplicity, and continuous operation. Nevertheless, several questions remain on how to optimize these devices. The injection system governs the dynamics of these systems through several, crucial mechanisms. These include the creation of a spatially varying reactant field and wave scattering off injectors. However, how these dynamics influence the number of detonations, presence of counter-propagating detonations, or other wave features is not well understood. This lack of understanding prevents the creation of general guidelines for designing the injection system. To address these obstacles, we studied a 2-dimensional “unwrapped” computational model of an RDE with simplified reaction kinetics and injector physics. The inlet consisted of equally spaced zones of constant mass flux (“injectors”) separated by isothermal walls. The number and area ratio of these injectors were varied over several individual simulations, and the impacts of these parameters were assessed. Results revealed that discrete injection introduces multiple physical processes – such as variable acoustic impedance, promotion of hot spots between injectors, and periodic de- and re-coupling of detonations – that increase the propensity for multiple detonations. Higher injector numbers and decreased area ratio tend to promote more detonations. Nevertheless, this relationship was non-monotonic, and further testing showed that additional wave modes besides those observed were stable. These wave modes appear to have definite, albeit topologically complex, basins of attraction — i.e., the system favors certain modes over others, but their link to the initial conditions is difficult to characterize. We therefore hypothesize that wave number is governed by the interplay between transient chaos during the initial transient and the new physics introduced by the injection system.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105814"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912912","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":"Nanosecond pulsed discharges for reliable ignition of ultra-lean hydrogen-air mixtures","authors":"Galia Faingold,&nbsp;Leander Krieg,&nbsp;Francis Pagaud,&nbsp;Quentin Malé,&nbsp;Nicolas Noiray","doi":"10.1016/j.proci.2025.105840","DOIUrl":"10.1016/j.proci.2025.105840","url":null,"abstract":"<div><div>The safe ignition and stabilization of ultra-lean hydrogen-air mixtures remain a critical challenge for enabling low-emission hydrogen combustion in gas turbines. This study investigates nanosecond repetitively pulsed discharges for reliable ignition under conditions relevant to lean-premixed hydrogen operation. Experiments were conducted in a modular combustion rig, where the influence of plasma parameters – including pulse energy, pulse repetition frequency, and pulse number – on ignition and flame kernel development was systematically explored. High-speed OH<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> chemiluminescence imaging tracked ignition kernel formation and propagation, while optical emission spectroscopy provided characterization of the plasma properties. For equivalence ratios of <span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>15</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>, successful ignition is mostly a function of pulse energy, more than pulse number, with a clear transition from non-ignition to reliable ignition observed above a critical energy threshold. This transition coincides with the change from glow to spark regime. Rather than showing a probabilistic ignition behavior, ignition occurs reliably in the spark regime, and fails at the transition to glow. Optical emission spectroscopy measurements of gas and vibrational temperatures indicate that this shift coincides with an increased production of radicals rather than vibrational excitation, which are more effective in enhancing ignition. For equivalence ratios of <span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>086</mn></mrow></math></span> and 0.1, kernels were created but did not expand in the flowing mixture, and the interaction between pulses — pulse number and repetition frequency became critical. At these ultra-lean conditions, these interactions enable the formation of larger ignition kernels that are less prone to extinction. These findings demonstrate that nanosecond repetitively pulsed based plasma-assisted ignition can significantly extend the ignition limits of lean hydrogen mixtures, offering a promising pathway for stabilizing ultra-lean hydrogen combustion with minimized NO<span><math><msub><mrow></mrow><mrow><mi>x</mi></mrow></msub></math></span> emissions. Moreover, the ability to reliably ignite ultra-lean mixtures is highly relevant for hydrogen internal combustion engines, where consistent ignition at low equivalence ratios is crucial to reducing cycle-to-cycle variability and improving efficiency.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105840"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104439","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}