Proceedings of the Combustion Institute最新文献

{"title":"Towards predicting Deflagration-to-Detonation Transition in smooth channels","authors":"Tom Alexander Alzer,&nbsp;Josué Melguizo-Gavilanes,&nbsp;Irenäus Wlokas,&nbsp;Andreas Markus Kempf","doi":"10.1016/j.proci.2026.106093","DOIUrl":"10.1016/j.proci.2026.106093","url":null,"abstract":"<div><div>Simulations of DDT in smooth channels are presented and compared against experiments. The modelling sensitivities are discussed and the challenging nature of such simulations is highlighted. Flame acceleration is affected by many physical effects of unknown strength. Because of that, detonation onset length and time are very sensitive to the choice of numerical schemes and physical models. This work aims to refine the understanding about certain key parameters (flame resolution and wall friction) which were found to greatly affect the prediction of flame acceleration leading up to DDT. We present a numerical framework which is able to simulate a deflagration which propagates through a channel of rectangular cross-section, accelerates, and eventually transitions to detonation. In contrast to many previous numerical studies of DDT in smooth channels, the results are directly compared against high-quality experimental data for validation. Ultimately, this work is considered to be a step towards building a robust numerical framework that helps to reproduce experimentally measured deflagration histories up to detonation onset.</div><div><em>Novelty and significance statement:</em> There are few attempts to predict Deflagration-to-Detonation Transition (DDT) in smooth channels using 3D simulation, and almost no meaningful comparison to experimental evidence. We attempt to fill this gap and present a modelling strategy that constitutes significant progress in modelling DDT.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106093"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567179","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":"Transient dynamics of extinction and reignition in bluff-body-stabilized premixed flames","authors":"Urbano A. Medina-Martínez,&nbsp;Francisco E. Hernández–Pérez,&nbsp;Takuya Tomidokoro,&nbsp;Hong G. Im","doi":"10.1016/j.proci.2026.106017","DOIUrl":"10.1016/j.proci.2026.106017","url":null,"abstract":"<div><div>The important role of localized extinction and reignition in premixed flames stabilized by a bluff body has extensively been studied. However, a detailed analysis of the transient dynamics is still lacking due to the highly localized and fast timescales in characterizing the phenomena. This study attempts to provide insights into the transient dynamics by applying computational singular perturbation (CSP) and tangential stretching rate (TSR) diagnostic tools to direct numerical simulation data. As a reference, a one-dimensional (1D) unsteady extinction problem in a symmetric counterflow premixed flame configuration was considered, and the CSP and TSR diagnostics were performed during the strain-induced extinction event. The analysis identified important chemical modes and their eigenvalue dynamics during the extinction event, revealing an extinction-associated modal structure. Subsequently, the CSP/TSR analysis was extended to two-dimensional direct numerical simulation cases (Kim et al., 2019). The lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>-air case is selected and studied at the pre-blowoff, stable stage where extinctions are balanced by reignitions. By a joint CSP/TSR analysis, extinction and reignition regions were identified and found to be both preceded by a flame-flame interaction. The temporal evolution of the two events was found to differ significantly: extinction occurs on a faster timescale and is marked by the modal structure identified in the 1D analysis. On the other hand, reignition proceeded through an induction-like phase followed by a thermal runaway, analogous to a zero-dimensional (0D) homogeneous igniting system, marked by an enhanced chemical contribution.</div><div><em>Novelty and significance statement:</em> This study provides new insight into the distinct chemical/transport explosive dynamics underlying the fast transients of local extinction and reignition in premixed flames. A systematic CSP/TSR analysis applied to DNS data reveals the dominant modal mechanisms governing these events without resorting to intuitive hypotheses. In particular, the study identifies a distinct extinction-related eigenstructure, allowing a direct identification of the localized events via a pair of CSP/TSR-based scalars. The results further clarify the different transient pathways associated with extinction and reignition, providing new understanding of the flow-chemistry interactions that precede blowoff.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106017"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567185","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":"Flame transfer functions and interference analysis under nanosecond repetitively pulsed discharge actuation","authors":"Pablo Kandel,&nbsp;Vikas Yadav,&nbsp;Mario Casel,&nbsp;Abdulla Ghani","doi":"10.1016/j.proci.2026.106013","DOIUrl":"10.1016/j.proci.2026.106013","url":null,"abstract":"<div><div>We present a numerical investigation of how nanosecond repetitively pulsed discharges (NRPDs) modify the linear response of a laminar stagnation flame. We focus on two main discharge parameters, pulse energy deposition <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and pulse repetition frequency (PRF). Compared to the non-actuated flame, NRPDs shift the flame upstream toward the fresh gases, increase the mean and local heat release rate (HRR), enrich the radical pool, and modify the local velocity field. The global response is built from contributions arising from different parts of the flame, and plasma actuation redistributes these contributions along the flame front. We identify the local flame regions that interfere constructively or destructively as a function of the NRPD parameters. These results show that variations of <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> or PRF affect flame dynamics differently at different frequencies, highlighting that NRPDs require well-tuned parameters for successful mitigation of unstable flames.</div><div><em>Novelty and significance statement:</em> NRPDs can be used to alter the thermoacoustic stability of combustors, but the effect of actuation parameters on the linear flame response remains poorly quantified. To the best of our knowledge, this is the first systematic numerical study in which both pulse energy deposition <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and PRF are varied, and FTFs are computed. The results show that NRPDs modify gain and phase mainly through changes in the mean flame shape and position, which affect the effective time delays and the balance between constructive and destructive contributions. NRPD actuation therefore offers a promising route for thermoacoustic control, but it requires a sound understanding of how the NRPD parameters affect the flame response.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106013"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148567572","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":"Demonstration of high-temperature reduction of iron oxide using hydrogen flame: Reduction behavior and microstructural evolution","authors":"Atanu Dolai,&nbsp;Wenjiang Tian,&nbsp;Nicole Stevens,&nbsp;Calvin Wong,&nbsp;Giulia Finotello,&nbsp;XiaoCheng Mi","doi":"10.1016/j.proci.2026.106223","DOIUrl":"10.1016/j.proci.2026.106223","url":null,"abstract":"&lt;div&gt;&lt;div&gt;High-temperature reduction offers a rapid and energy-efficient route for converting iron-oxide fines to iron but requires elevated temperatures and reductants such as hydrogen and carbon monoxide. Fuel-rich hydrogen–air flames offer a simple and scalable solution, as they simultaneously supply both hydrogen (H&lt;sub&gt;2&lt;/sub&gt;) and rapid heating to temperatures (1250K&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;1500 K), enabling a much faster reduction than conventional H&lt;sub&gt;2&lt;/sub&gt;-based reduction processes operating at 700&lt;!--&gt; &lt;!--&gt;K to 1100&lt;!--&gt; &lt;!--&gt;K. In the present work, the reduction of millimeter-sized dense (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;p&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;1.5 mm) and porous (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mtext&gt;p&lt;/mtext&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; 3 mm) iron-oxide particles exposed to the product gases of fuel-rich hydrogen–air flames is experimentally investigated. The product gas composition and temperature are varied by changing the equivalence ratio (&lt;span&gt;&lt;math&gt;&lt;mi&gt;Φ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 2.5 and 3) of the H&lt;sub&gt;2&lt;/sub&gt;-air mixture and tube length (&lt;span&gt;&lt;math&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;). Under all operating conditions, particle temperatures are measured using two-color imaging pyrometry, while the extent of reduction and microstructural evolution are characterized by weight measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Stable particle temperatures and consistent reduction are observed across all operating conditions, confirming that hydrogen–air flames can effectively enable reduction of iron oxide. For dense particles, the reduction proceeds through an initial rapid stage followed by a slower stage associated with densification of the iron layer and pore coalescence that restricts gas transport. Reduction degrees of approximately 0.6 and 0.4 are achieved within 6 min at &lt;span&gt;&lt;math&gt;&lt;mi&gt;Φ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; = 2.5 and 3, respectively, after which the reaction rate significantly decreases. In contrast, porous iron-oxide particles exhibit minimal transport limitations and reach a reduction degree of 0.96 within 15 min.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement&lt;/em&gt;: This study provides the first experimental demonstration of hydrogen-flame-based reduction of iron oxide. Unlike conventional reduction methods that are slow and emission-intensive, the proposed approach employs fuel-rich hydrogen flames to simultaneously provide high temperatures and reducing gas, enabling rapid reduction of iron oxide particles. The developed framework provides precise control over flame and particle properties, allowing investigation of single-particle reduction behavior under well-defined combustion conditions. The findings from this study establish a basis for integrating hydrogen combustion with hydrogen-based reduction, offering a clean and efficient reductio","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106223"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582416","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":"Edge-flame dynamics in hydrogen/n-dodecane dual-fuel turbulent mixing layers","authors":"Shibo Gu,&nbsp;Evatt R. Hawkes,&nbsp;Armin Wehrfritz,&nbsp;Haiou Wang","doi":"10.1016/j.proci.2026.106131","DOIUrl":"10.1016/j.proci.2026.106131","url":null,"abstract":"<div><div>This study investigates edge-flame propagation under hydrogen–diesel dual-fuel direct injection (H₂DDI) engine conditions using two-dimensional direct numerical simulations. A single-fuel baseline case (DF00) and two dual-fuel cases (DF01 and DF05) with increasing hydrogen addition are examined. A local Damköhler-number-based indicator is employed to interpret the relative roles of reaction- and transport-driven processes. A statistical framework is developed to quantify the edge-flame speed and its dependence on local scalar dissipation. The results show that ignition behaviour varies systematically with mixture stratification. In cases DF00 and DF01, the edge-flame speed exhibits a non-monotonic dependence on scalar dissipation, accompanied by the presence of both autoignition-like and deflagration-like behaviours across different dissipation levels. With increased hydrogen addition, the edge-flame speed increases monotonically with scalar dissipation and attains higher most-probable values, with a greater prevalence of deflagration-like behaviours.</div><div><em>Novelty and significance statement:</em> To date, the characterisation of edge-flame dynamics in hydrogen–diesel dual-fuel direct injection systems remains limited. This work combines temporal tracking and statistical analysis of edge flame intersection dynamics to elucidate how hydrogen addition modifies edge-flame propagation under engine-relevant conditions. The results demonstrate that hydrogen reshapes the dependence of edge-flame speed on scalar dissipation and alters the dominant ignition mode. A Damköhler-number-based indicator is employed as a physically grounded measure to distinguish autoignition-like and deflagration-like behaviours. These findings clarify how hydrogen modifies edge-flame dynamics in stratified dual-fuel ignition and provide physical insight for combustion modelling and ignition control under engine-relevant conditions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106131"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582499","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":"Flame propagation limit and consumption speed of hydrogen–air flame in narrow channels","authors":"C.C. Mejía-Botero,&nbsp;L. Pratabuy Tran-Quang,&nbsp;Z. Chen,&nbsp;P. Boivin,&nbsp;C. Almarcha","doi":"10.1016/j.proci.2026.106108","DOIUrl":"10.1016/j.proci.2026.106108","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This work presents a combined experimental and numerical methodology to investigate hydrogen–air flame propagation limits and consumption speeds in narrow Hele-Shaw channels. Experiments focus on flame propagation along the channel face, while two-dimensional Lattice Boltzmann simulations are performed within the channel gap, reducing computational cost while resolving transverse flame structure and confinement-induced effects. The results show that increasing the gap size widens the flammability limits and enhances the global consumption speed, primarily due to reduced conductive heat losses to the walls and stronger development of flame instabilities. Confinement plays a dual role: it modifies the balance between heat release and thermal losses, and it alters the growth of flame instabilities. To separate intrinsic burning behavior from geometric amplification associated with flame wrinkling, a normal consumption speed, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;cn&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, based on experimental flame length measurements in face view, is introduced. This quantity provides a physically consistent basis for comparison between experiments and gap-resolved simulations. The numerical approach predicts both propagation limits and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;cn&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; with deviations below 5% for strongly confined configurations. It demonstrates that key deviations of flame propagation velocity to laminar flame speed arise from the physical effects acting within the gap and wrinkling in the face view. For weaker confinement, the local flame curvature is not dominated by curvature within the gap. As a result, discrepancies between the measured experimental &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;s&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;cn&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; and the numerical gap-resolved consumption speed indicate the growing importance of curvature variations induced by face instabilities, thereby defining the validity range of the reduced modeling strategy.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; This work presents, for the first time, a direct comparison between experimental flame propagation measured on the channel face of Hele-Shaw cells and two-dimensional gap-resolved simulations performed exclusively within the sub-millimetric and millimetric channel gap. This reduced-order strategy decouples transverse flame dynamics from large-scale face instabilities, enabling accurate prediction of propagation limits and consumption speeds without simulating the full channel geometry. By introducing an average normal consumption speed based on the experimentally measured total flame length, a physically consistent bridge between face measurements and gap simulations is established. The study demonstrates that, under strong confinement, flame propagation is primarily governed by the transverse structure within the gap, thereby providing a computationally efficient and ","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106108"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582478","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":"Theoretical investigation on the combustion kinetics of nitroalkanes/ammonia: hydrogen abstraction reactions from C1–C5 nitroalkanes by ṄH2 radicals","authors":"Mingxia Liu,&nbsp;Ruiyang Fan,&nbsp;Chong-Wen Zhou,&nbsp;Zhen-Yu Tian","doi":"10.1016/j.proci.2026.106180","DOIUrl":"10.1016/j.proci.2026.106180","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Nitroalkanes found application as fuel initiators/additives and propellants, being commonly utilized in transportation or propulsion systems. Recently, it has attracted widespread attention in ammonia/reactive fuel co-combustion as a high-performance additive to improve ammonia combustion. Thus, C&lt;img&gt;N interactions play a pivotal role during the nitroalkane/ammonia blending process, especially for the hydrogen atom abstraction reaction by ṄH&lt;sub&gt;2&lt;/sub&gt; radicals. The present study thus concentrates on a systematic kinetic investigation of the hydrogen abstraction reactions between C1-C5 nitroalkanes and ṄH&lt;sub&gt;2&lt;/sub&gt; radicals. Geometry optimization and frequency calculations, as well as intrinsic reaction coordinate and one-dimensional hindered rotor calculations, were performed at the M06-2X/6-311++G(d,p) level of theory. High-level single-point energies were ultimately calculated at the QCISD(T)/CBS level of theory, incorporating zero-point energies. The high-pressure limit rate constants for 38 reactions of 12 nitroalkanes with ṄH&lt;sub&gt;2&lt;/sub&gt; radicals were computed over the temperature range of 500 K to 2000 K utilizing transition state theory. Rate constants for each nitroalkane and the average rate constant rules for ten reaction classes, including abstraction from primary, secondary, and tertiary carbons at the &lt;em&gt;α, β, γ&lt;/em&gt;, and &lt;em&gt;δ&lt;/em&gt; sites, are provided in this work. Results indicate that the nitro functional group exerts a marginal effect on lowering the &lt;em&gt;α&lt;/em&gt; site energy barrier, and the rate constants follow the order: primary &lt; secondary &lt; tertiary. Concurrently, a comprehensive comparison of the average rate constants for analogous structures between nitroalkanes, alkanes, alcohols, and primary amines was performed to elucidate the impact of disparate functional groups on the kinetic parameters. The rate rules exhibited the following trend: nitroalkanes &lt; alkanes &lt; alcohols &lt; primary amines at the &lt;em&gt;α&lt;/em&gt; site. The updated kinetic parameters were incorporated into the nitroalkane/NH&lt;sub&gt;3&lt;/sub&gt; mechanism to assess their impact on predictions for nitrogen-containing species. These calculated kinetic parameters support a better understanding of the combustion chemistry of nitroalkane/NH&lt;sub&gt;3&lt;/sub&gt; blends.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;Nitroalkanes, particularly nitromethane, have been used as fuel additives to enhance the low-temperature combustion performance of NH&lt;sub&gt;3&lt;/sub&gt;/methanol blends. As such, nitromethane serves as an effective NO precursor, facilitating the investigation of high-temperature NH&lt;sub&gt;3&lt;/sub&gt;/NO interactions. C&lt;img&gt;N cross-reactions play an important role during the nitroalkane/NH&lt;sub&gt;3&lt;/sub&gt; blending process. This work is the first kinetic investigation on the H-atom abstraction reactions between nitroalkanes and amino radicals. A total of 38 reactions were identified, which were subsequently categorized into 10 distinct reaction cla","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106180"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582649","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":"Quantum chemical kinetic modeling of condensed phase guanidinium nitrate: a detailed mechanism validated by laser pyrolysis/FTIR","authors":"Jay Patel,&nbsp;Arindrajit Chowdhury,&nbsp;Neeraj Kumbhakarna","doi":"10.1016/j.proci.2026.106250","DOIUrl":"10.1016/j.proci.2026.106250","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The aim of this work is the development and validation of a detailed chemical kinetic mechanism describing the condensed phase thermal decomposition of guanidinium nitrate (GN&lt;img&gt;C(NH₂)₃NO₃). As a key compound in energetic materials, GN requires a comprehensive understanding of its condensed phase decomposition pathways to support safety evaluation and performance prediction across diverse applications. The mechanism is constructed through quantum chemical identification of elementary reactions and intermediates using calculations at the B3LYP/6–311++G(d,p) level of theory, with the polarizable continuum model (PCM) employed to represent condensed phase solvation effects. Reaction thermochemistry is evaluated using the CBS-QB3 composite method, and temperature dependent kinetic parameters are determined using conventional transition state theory. The developed mechanism establishes condensed phase reaction pathways leading to major experimentally observed products, including NH₃, N₂O, H₂O, CO₂, HNCO, and HNO₃. Validation is performed against laser pyrolysis coupled with FTIR measurements reported at isothermal temperatures of 350 °C, 360 °C, and 370 °C. A zero-dimensional species conservation framework is developed to simulate the laser pyrolysis configuration, incorporating the detailed reaction set to predict time dependent mass loss and gas phase mole fraction profiles. The predicted mass loss behavior and species evolution show good agreement with experimental observations across all investigated conditions, demonstrating the predictive capability of the mechanism. The resulting condensed phase kinetic mechanism provides combustion relevant kinetics for solid propellant combustion models and heterogeneous combustion simulations, offering a practical, mechanistically grounded framework for simulating GN decomposition under varied thermal environments and guiding GN containing energetic formulation design.&lt;/div&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Novelty and significance statement&lt;/h3&gt;&lt;div&gt;This study presents the first detailed, validated condensed phase chemical kinetic mechanism for guanidinium nitrate (GN), developed through quantum chemical analysis and validated using laser pyrolysis/FTIR under rapid heating (∼2 × 10⁴ °C s⁻¹). The mechanism provides thermodynamic and rate parameters and captures condensed phase pathways, including proton transfer, nitration, and dimerization/trimerization, leading to major products such as NH₃, N₂O, H₂O, CO₂, HNCO, and melamine, while quantitatively reproducing experimental mass loss and time resolved species profiles. By addressing the often-overlooked condensed phase reaction network controlling early decomposition and gas release in solid propellant combustion, this work advances molecular level understanding of heterogeneous energetic material decomposition. The quantum chemical experiment framework provides prediction of GN decomposition under combustion relevant conditions, supports safety and performance asse","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106250"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148582703","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":"Third-body effects of N2 and Ar in ammonia pyrolysis: Shock tube experiments and modeling insights","authors":"Timoteo Dinelli,&nbsp;Belal Y. Belal,&nbsp;Ali Elkhazraji,&nbsp;Sulaiman A. Alturaifi,&nbsp;Alessandro Stagni","doi":"10.1016/j.proci.2026.106431","DOIUrl":"10.1016/j.proci.2026.106431","url":null,"abstract":"&lt;div&gt;&lt;div&gt;A physically-grounded description of the ammonia (NH&lt;sub&gt;3&lt;/sub&gt;) pyrolysis is essential to set up predictive kinetic models of NH&lt;sub&gt;3&lt;/sub&gt; combustion. However, most reference experiments employed for model development and validation are conducted in argon-diluted conditions. When these experiments are applied directly to conventional combustion environments, they may introduce systematic biases due to bath-gas dependencies. To address these effects, ammonia pyrolysis was investigated in a shock tube at near-atmospheric pressure, using Ar, N&lt;sub&gt;2&lt;/sub&gt; and their equimolar mixture as bath gases. At the same time, a recently developed kinetic framework, including an accurate description of collider-specific effects in pressure-dependent reactions, was leveraged to analyze the experimental measurements. It was found that the progressive replacement of Ar with N&lt;sub&gt;2&lt;/sub&gt; significantly accelerated the ammonia decomposition rate by up to a factor of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;∼&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The kinetic model showed a satisfactory agreement with experimental data, in terms of both NH&lt;sub&gt;3&lt;/sub&gt; time histories and half-life times under all the investigated conditions. Moreover, kinetic analysis showed that such acceleration in the decomposition rate was almost exclusively due to the change in the NH&lt;sub&gt;3&lt;/sub&gt; decomposition reaction &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mi&gt;(+M)&lt;/mi&gt;&lt;mo&gt;→&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;NH&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mi&gt;(+M)&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, because of the enhanced N&lt;sub&gt;2&lt;/sub&gt; collider efficiency relative to Ar. These results provide direct experimental evidence of the recent theoretical findings on third-body effects in NH&lt;sub&gt;3&lt;/sub&gt; chemistry, and highlight the importance of accounting for bath-gas effects when developing kinetic models.&lt;/div&gt;&lt;div&gt;&lt;em&gt;Novelty and significance statement:&lt;/em&gt; By designing ad-hoc shock-tube experiments, this work advances the fundamental understanding of the collider-dependent decomposition rate of ammonia. To the authors’ knowledge, this is the first study providing time-resolved measurements of NH&lt;sub&gt;3&lt;/sub&gt; mole fractions during pyrolysis including pure N&lt;sub&gt;2&lt;/sub&gt; as a bath gas, assessing its role as a third-body collider. Most reference data for tuning and validating NH&lt;sub&gt;3&lt;/sub&gt; decomposition rates have indeed been obtained in Ar-diluted systems, and only recent studies have considered N&lt;sub&gt;2&lt;/sub&gt;-containing mixtures at high temperatures. These results provide a novel and unique benchmark for assessing kinetic models, and consolidate recent theoretical findings on third-body collision efficiencies, bridging fundamental theory with experiments. Moreover, this work establishes an experimental protocol that can be systematically extended to investigate a wider range of colliders, supporting future improvement of NH&lt;sub&gt;3&lt;/sub&gt; pyrolysis and combustion mechanisms.&lt;/di","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106431"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148995090","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 Study on the Soot Formation Mechanism in a Methane Microwave Plasma","authors":"Maristella Di Teodoro,&nbsp;Carlo Cavallotti","doi":"10.1016/j.proci.2026.106579","DOIUrl":"10.1016/j.proci.2026.106579","url":null,"abstract":"<div><div>The conversion of methane to carbon and hydrogen through plasmas is one of the most promising technologies for the generation of turquoise hydrogen. Its efficient implementation requires the availability of models that can properly describe the main processes taking place both in plasma as well as in the afterglow. In this work, a model suitable to describe both the gas phase chemical kinetics as well as the soot nucleation and growth in a microwave plasma was developed. The model was then used to study the reactivity in the plasma region and in the subsequent gas cooling stage as a function of the microwave input power. The plasma was initially simulated as a homogeneous discharge under adiabatic conditions using a detailed kinetic mechanism that includes H, H₂, and C₁-C₃ non oxygenated hydrocarbons. The possibility of a feed-gas bypass was considered in estimating the adiabatic plasma temperature and methane conversion, while the post-discharge reactivity was examined assuming different cooling rates, describing soot nucleation and growth through an extensively validated literature discrete sectional model. This analysis allowed to identify the threshold conditions for soot inception, which affect notably the particle size distribution, soot yield, and overall methane conversion. It was found that the acetylene and atomic hydrogen formed in the plasma affect significantly soot nucleation. Subsequently, isothermal simulations of plasma at the adiabatic temperature were performed with an extended mechanism suitable to describe PAHs formation and soot nucleation and growth. Results show that, within a limited range of operating conditions, large polycyclic aromatic species can be formed in relevant quantities in the plasma. The inclusion of a more comprehensive plasma chemistry is shown to have a substantial impact on the predictions of the reactivity in the successive cooling stage, thus indicating the relevance of including soot nucleation models in methane plasma kinetic mechanisms.</div></div><div><h3>Novelty and significance statement</h3><div>The present work is the first to model soot nucleation and growth in methane microwave plasma systems through the application of an extensive detailed kinetic model inclusive of plasma chemistry, gas phase chemistry, particles inception and growth both in plasma and in the successive cooling stage. Simulations allowed to evaluate the impact of operating conditions (power absorbed, feed gas bypass, gas cooling rate) on process efficiency and generated soot. The finding that soot inception can take place within the plasma will have significant impact on future literature studies, as it implies the likely formation of charged nuclei, whose reactivity is presently unknown and requires investigation.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"42 ","pages":"Article 106579"},"PeriodicalIF":4.6,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149050885","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}