Combustion and Flame最新文献

{"title":"Insights into the scalar structures in turbulent diffusion flames with progressive H2 addition using 1D spontaneous Raman scattering and simultaneous PIV-OH PLIF","authors":"Kuppuraj Rajamanickam ,&nbsp;Ariff Magdoom Mahuthannan ,&nbsp;Corine Lacour ,&nbsp;Said Idlahcen ,&nbsp;Armelle Cessou ,&nbsp;David Honoré ,&nbsp;Bertrand Lecordier","doi":"10.1016/j.combustflame.2025.114129","DOIUrl":"10.1016/j.combustflame.2025.114129","url":null,"abstract":"<div><div>This paper examined the effect of H₂ enrichment in a primary fuel (CH₄) on turbulent flame features using 1D spontaneous Raman scattering (SRS) and simultaneous particle Image Velocimetry (PIV), OH-Planar Laser Induced Fluorescence (PLIF) measurements. The experiments are conducted in a canonical non-premixed bluff body burner operating under typical central fuel jet-dominated flow mode. Downstream of the bluff body, the flow exhibits complex patterns, and it can be globally categorized into three successive zones: recirculation, neck, and jet-like zones. The flame undergoes local extinction in the neck zone, where the local flow-induced hydrodynamic strain rate (κ_hyd) is much higher than the flame extinction strain rate (κ_ext). It is well known that H₂ enrichment increases κ_ext and thus modifies the probability of localized flame extinctions in the neck zone. Additionally, recent studies have shown the significance of preferential diffusion effects of H₂ in H₂ + CH₄ bluff body stabilized premixed and turbulent jet diffusion flames. Although 1D SRS measurements in canonical jet and bluff body stabilized non-premixed flames were studied extensively, to the best of our knowledge, differential diffusion has not been reported earlier in the non-premixed bluff body burner fueled with progressive H₂ addition. To better understand this phenomenon, five H₂ enrichment levels are considered: 0 %, 10 %, 30 %, 50 % and 80 % (in vol.). The simultaneous PIV and OH-PLIF measurements revealed the presence of local extinctions in the cases of H₂ enrichment ≤ 30 %, while local extinctions are not witnessed for H₂ = 50, 80 %. The conditional PDFs of the temperature in mixture fraction space obtained from the 1D SRS further confirmed this observation. Furthermore, the local instantaneous hydrogen/methane mass fraction ratio has been estimated to evaluate the differential diffusion effects. The results showed the dominance of the differential diffusion in the burner's near field, while the strong turbulence mixing effect weakens the differential diffusion in the far field.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114129"},"PeriodicalIF":5.8,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714500","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":"Panoramic vision analysis of burning aluminum droplet and oxide cap with 360-degree microscopic photography","authors":"Yu Wang ,&nbsp;Yang Zhang ,&nbsp;Hang Zhang ,&nbsp;Shixi Wu ,&nbsp;Weiqiang Xiong ,&nbsp;Wen Ao ,&nbsp;Dongping Chen ,&nbsp;YingChun Wu ,&nbsp;Xuecheng Wu","doi":"10.1016/j.combustflame.2025.114108","DOIUrl":"10.1016/j.combustflame.2025.114108","url":null,"abstract":"<div><div>The aluminum agglomerate surfaces serve as the essential interfaces for heat and mass transfer processes during combustion, with the attached oxide cap exerting a significant effect on the asymmetrical spatial distribution of agglomerate physical properties. Therefore, understanding the surface characterization and its dynamic evolution during aluminum combustion is important. However, significant challenges exist in visualizing and measuring agglomerate surfaces due to the micrometer-scale size, extremely rapid dynamic evolution, asymmetric three-dimensional morphology, and complex combustion behaviors. Traditional methods are limited in providing three-dimensional, in situ measurements of agglomerate surfaces under the propellant-burning environment. Thus, a panoramic vision analysis method is proposed to achieve 360-degree visualization and measurement of agglomerate surfaces. A high-speed panoramic microscopic imaging system up to 30 kHz is established, composed of two high-speed cameras positioned opposite each other to capture the panoramic view of agglomerates. A data processing pipeline, incorporating an artificial intelligence segmentation algorithm and an ellipsoid geometric model, is developed to reconstruct three-dimensional models of agglomerates with varying diameters over time. The oxide cap distributions and dynamic behaviors, such as rotation and drift on the droplet surface, are visualized. Quantitative measurements of oxide cap and droplet areas are also obtained, with oxide cap area ratios ranging from 10% to 40%. This study provides a method for visualization and quantitative measurement of agglomerate surfaces, offering a tool for further research on the mechanism of oxide cap dynamics on surfaces.</div><div><strong>Novelty and significance statement</strong></div><div>The novelty of this work lies in proposing a 360-degree panoramic vision analysis method, which enables three-dimensional surface visualization and quantitative measurement of burning droplets and oxide caps. A high-speed panoramic microscopic imaging system, operating at up to 30 kHz, is established by positioning two high-speed cameras opposite each other to capture the front and back sides of the agglomerates simultaneously. The experimental results demonstrate that the proposed method is competent in reconstructing three-dimensional models of agglomerates with varying diameters over time, allowing for visualizing the evolution of the oxide cap distribution and drift on the droplet surface. Quantitative measurements of the oxide cap and droplet areas are obtained, with the oxide cap area ratio ranging from 10% to 40%. This method provides technical support for deeper insights into the analysis of oxide cap dynamics.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114108"},"PeriodicalIF":5.8,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697464","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":"Boundary layer flashback of H2/Air premixed flames in a swirling flow around a central body","authors":"Justin Bertsch ,&nbsp;Thierry Poinsot ,&nbsp;Nicolas Bertier","doi":"10.1016/j.combustflame.2025.114123","DOIUrl":"10.1016/j.combustflame.2025.114123","url":null,"abstract":"<div><div>Fast and thin premixed hydrogen flames can lead to flashback scenarios which are unusual, especially for swirled configurations. Flashback can occur far from all walls, in the bulk flow, if the flow speed is less than the flame speed: this is a scenario which is usually avoided by increasing flow rates. However, flashback can also occur near walls where the flow speed goes to zero. Injector walls boundary layers always contain a zone where the local flow speed is less than the flame speed, even if the bulk flow velocity is large. The size of this zone is controlled by the velocity gradient at the wall which is the classical parameter used to predict flashbacks in boundary layers.</div><div>In this study, flashback of lean hydrogen–air flames is computed using DNS (Direct Numerical Simulation)(flame resolved). Without swirl, results are compared and validated against experimental measurements and usual flashback criteria based on wall velocity gradient. DNS are also performed with swirl in a sector of an annular chamber, providing maps of flashback occurrence as function of swirl number and wall velocity gradient. Results show that swirl enhances flashback propensity and that thermodiffusive effects must be accounted to build a flashback criteria, indeed very lean H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> flames flashback for flow speeds higher than expected.</div><div><strong>Novelty and significance</strong></div><div>Almost all injection systems designed for hydrogen face a new, key issue in terms of operability: flashback. This study presents for the first time an analysis of the combined effects on flashback of the velocity gradients at the wall and of swirl. DNS of a swirling flow around a central body are performed and flashback maps are produced in a (swirl-velocity gradient) diagram of direct use for systems injecting lean premixed hydrogen–air mixtures.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114123"},"PeriodicalIF":5.8,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143697762","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 comparative study on the effects of NO2 addition on the auto-ignition behavior of n-heptane, iso-octane and toluene at engine relevant conditions","authors":"Shijun Dong ,&nbsp;Da Yao ,&nbsp;A. Abd El-Sabor Mohamed ,&nbsp;Jinhua Li ,&nbsp;Wenxue Gao ,&nbsp;Yang Cao ,&nbsp;Zhaowen Wang ,&nbsp;Jinhu Liang ,&nbsp;Henry J. Curran ,&nbsp;Xiaobei Cheng","doi":"10.1016/j.combustflame.2025.114118","DOIUrl":"10.1016/j.combustflame.2025.114118","url":null,"abstract":"<div><div>It is necessary for gasoline surrogate models to simulate the effect of NOx addition on fuel auto-ignition behavior, as NOx can affect engine combustion via exhaust gas recirculation (EGR). Toluene is often used as a representative aromatic component in gasoline surrogate models, and hence it is important to investigate the effect of NOx addition on its auto-ignition behavior and to fully understand the interaction chemistry between toluene and NOx. In this paper, high-pressure shock tubes and a rapid compression machine are used to measure the ignition delay times (IDTs) of toluene in ‘air’ mixtures with and without the addition of nitrogen dioxide (NO₂), at a pressure of 20 atm and at temperatures in the range 600–1400 K. The IDTs of <em>n</em>-heptane, <em>iso-</em>octane and a mixture of toluene/<em>n</em>-heptane/<em>iso-</em>octane are measured at the same conditions for comparison. The experimental results show that the auto-ignition behavior of toluene exhibits significantly different sensitivity to NO₂ addition compared to <em>n</em>-heptane and <em>iso-</em>octane. NO₂ significantly promotes the reactivity of toluene at low temperatures (600–1000 K), in which the IDTs decreased by two orders of magnitude when 1000 ppm of NO₂ is added, whereas there is an order of magnitude decrease with the addition of 200 ppm NO₂. The promoting effect of NO₂ on toluene oxidation reduces significantly at temperatures above 1000 K. The experimental results also show that NO₂ addition exhibits a slight promoting effect on the reactivity of <em>n</em>-heptane and <em>iso-</em>octane at temperatures above 750 K at the conditions studied. A kinetic model is proposed based on C3MechV3.3 in which the interaction chemistry between these gasoline surrogates and NOx is updated. The proposed kinetic model can simulate well the effect of NO₂ addition on the auto-ignition behavior of these surrogates. Flux and sensitivity analyses are performed to highlight the important interaction reaction pathways.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114118"},"PeriodicalIF":5.8,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684403","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":"Two dimensional flame structure of oscillating burner-stabilized methane-air flames","authors":"Ningyi Li ,&nbsp;Viatcheslav Bykov ,&nbsp;Anastasia Moroshkina ,&nbsp;Evgeniy Sereshchenko ,&nbsp;Vladimir Gubernov","doi":"10.1016/j.combustflame.2025.114115","DOIUrl":"10.1016/j.combustflame.2025.114115","url":null,"abstract":"<div><div>The highly transient relaxational diffusive-thermal oscillations of flat burner-stabilized flames can be very attractive to probe the performance of detailed reaction mechanisms in the regimes close to ignition/extinction. In such regimes, certain reaction zones can travel over distances of the order of 10 mm and this raises an important question if one dimensional numerical models can be accurate in describing them. The question of quantitative comparison of modeling and experiments becomes crucial to study, to understand these regimes and to utilize them for validation. In this work, we experimentally investigate relaxational oscillations of methane-air flames on a flat porous burner with a surrounding nitrogen co-flow and perform fully resolved 2D numerical simulations of the same burner configuration, using a detailed reaction mechanism and molecular diffusion model, buoyancy and radiation, alongside corresponding experiments. The focus is on the effect of the nitrogen co-flow on the flame oscillations, which can only be studied numerically in 2D simulations due to the mutual effect of the complex flow field and flame dynamics. The results of both numerical and experimental approaches are found to be in quantitative agreement. They show that there is an optimal co-flow velocity that removes the secondary diffusion flame and extinguishes the edge flame settled in the stagnation flow region. This optimal regime makes the flame flatter and closer to a one-dimensional configuration and this is a most favorable condition for validation of kinetic mechanisms. The detailed data from the simulations will guide the design of the next generation of the burner configurations to study the kinetics and dynamics of complex fuels required for a sustainable energy transition.</div><div><strong>Novelty and Significance Statement</strong></div><div>The novelty of this research lies in the synergy of these modeling, computations with experimental measurements, allowing both parametric studies of the oscillation regime and deeper insights into the flame structure. These results are significant because they allow to develop more accurate burner configurations for studying flames near extinction and ignition conditions, which will be an important task for more complex fuels from renewable sources required for a sustainable energy transition. Ultimately, our understanding of the interplay between chemistry and diffusion controlled combustion regimes under transient conditions can be approved and validation data for e.g. chemical reaction mechanisms can be generated. The latter becomes extremely important since efficiency and pollutant mitigation issues require lean and chemistry controlled combustion processes used in the combustion facilities. Thus understanding, optimization and control of such regimes has become a crucial point for further development of the sustainable combustion.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114115"},"PeriodicalIF":5.8,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684407","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":"Analysis of combustion behavior and regression rate of hypergolic solid fuels in counterflow spray experiment","authors":"Wei-Che Lin ,&nbsp;Ray Peterson ,&nbsp;Michael J. Bortner ,&nbsp;Gregory Young","doi":"10.1016/j.combustflame.2025.114132","DOIUrl":"10.1016/j.combustflame.2025.114132","url":null,"abstract":"<div><div>Recent studies have shown the advantages of hypergolic solid fuels in hybrid rockets, particularly their short ignition delays and simplified designs. However, research on their combustion behavior and regression rates remains limited. This study attempts to address some of these gaps using low-density polyethylene-based fuels embedded with sodium borohydride and 90 wt% hydrogen peroxide as the oxidizer. A modified counterflow spray experiment was employed, revealing unique combustion features and surface structures, such as char spots and bulges. A novel technique was developed to measure the fuel regression rate under an oxidizer spray, yielding averages between 0.39 to 0.52 mm/s at oxidizer mass flow rates of 0.38 to 0.43 g/s, significantly higher than those obtained with oxygen counterflow burners. Regression rates increased with higher flow rates and additive concentrations, primarily due to enhanced surface reactions. The measured combustion delay times were considerably longer than the ignition delay times observed in droplet tests, highlighting the importance of evaluating ignition performance under spray conditions. Reignition tests revealed longer ignition and combustion delay times compared to the first ignition, with averages increasing from 23 to 162 ms and 158 to 342 ms, respectively. Thermochemical analysis and Fourier transform infrared spectroscopy (FTIR) identified the char layer as primarily sodium metaborate tetrahydrate, which is identified as a cause for its reduced reactivity with the oxidizer during reignition.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114132"},"PeriodicalIF":5.8,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684401","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 and validation: A comprehensive and robust surrogate kinetic model for oxidation of various biodiesels","authors":"Lalit Y. Attarde,&nbsp;Krithika Narayanaswamy","doi":"10.1016/j.combustflame.2025.114109","DOIUrl":"10.1016/j.combustflame.2025.114109","url":null,"abstract":"<div><div>In recent years, there has been a notable surge in experimental and kinetic modeling efforts concerning various biodiesels, their surrogates, and relevant molecules. This work culminates these research efforts to construct a comprehensive and robust surrogate kinetic model for various biodiesel fuels. This model has incorporated accurate chemistry and undergone extensive validation against a broad range of experimental data available for biodiesel. In order to accurately reproduce the combustion characteristics of biodiesel, methyl butanoate, methyl crotonate, 3-hexene, and n-dodecane are chosen as surrogate components. These molecules have been chosen to replicate the functional groups found in biodiesel methyl esters. Each surrogate component is firstly validated thoroughly against a wide array of experimental studies. The kinetics of each component are improved through careful rate assignments derived from various theoretical investigations. Subsequently, a surrogate mixture comprising these selected components is formulated by matching the functional groups of target fuels. This surrogate mechanism is used to validate the experimental data associated with various biodiesel fuels, their constituents, and methyl esters exhibiting similar functional groups to those present in actual biodiesel. The current kinetic model has demonstrated good agreement for various biodiesel fuels and their commonly used surrogates for a range of experimental studies, encompassing ignition delay times measured in shock tubes and rapid compression machines, laminar flame speeds, as well as species mole fractions measured in jet stirred reactors and laminar flow reactors.</div><div><strong>Novelty and significance statement</strong></div><div>This study introduces novel surrogate mixtures consisting of methyl butanoate, methyl crotonate, 3-hexene, and n-dodecane, formulated to predict the combustion characteristics of biodiesel. While several surrogate formulations for biodiesel exist in the literature, the novelty of this work lies in its extensive validation and reliable kinetic of the surrogate mixtures, which is leveraged from well-validated chemistry of each of these individual components. The study investigates whether selected small methyl esters and alkene can sufficiently capture combustion characteristics of molecules with similar functional groups. Currently, there are only two comprehensive biodiesel kinetic models in the literature, both developed over a decade ago, which have been widely used in subsequent studies for optimization and reduction. The new model presented in this study offers a more reliable chemistry while being relatively more compact, owing to its use of well validated small molecule surrogate components.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114109"},"PeriodicalIF":5.8,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684404","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":"Combustion characteristics and primary particle size of soot in ethylene/propylene-air coflow flames under dynamic pressure rise environment","authors":"Jingru Zheng ,&nbsp;Xiaolei Zhang ,&nbsp;Suk Ho Chung ,&nbsp;Longhua Hu","doi":"10.1016/j.combustflame.2025.114113","DOIUrl":"10.1016/j.combustflame.2025.114113","url":null,"abstract":"<div><div>The effect of dynamic pressure rise rate on the burning characteristics and soot particle size in laminar coflow flames of ethylene and propylene is studied. Flame characteristics are observed at constant fuel flow rates under five pressure rise rates. Soot particles are collected using a thermophoretic sampling method at a pressure of 65 kPa during the pressure increase, and the primary soot particle diameters in ethylene flames are measured using a transmission electron microscope (TEM). The results show that the flame height increases with chamber pressure until 65 kPa, then slightly decreases. The flame becomes shorter with a higher pressure rise rate, influenced by both diffusion and buoyancy effects. As pressure increases, the transverse diffusion of fuel molecules diminishes, causing the flame to become slender. Simultaneously, the buoyancy effect enhances air entrainment, contributing to a reduction in flame height. A relationship between the flame height, pressure and dynamic pressure rise rate is derived based on the Burke-Schumann theory by assuming the pressure as a function of time. The proposed model can successfully predict the experimental data. The length of the soot-free main reaction zone (exhibiting a blue color) decreases with increasing pressure and is longer at smaller pressure rise rates. The relationship between the blue flame zone length and the dynamic pressure rise rate, which is characterized by soot formation time, correlates well with experimental results. The measured soot particle sizes range from 25 to 35 nm. The soot particle sizes are larger at lower pressure rise rates. The fractal dimension decreases with increasing pressure rise rates, while the pre-factor increases as the pressure rise rates become higher.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114113"},"PeriodicalIF":5.8,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A fundamental investigation of the pyrolysis chemistry of Oxymethylene Ethers. Part I: Quantum chemical calculations and kinetic model development","authors":"Kevin De Ras ,&nbsp;Olivier Herbinet ,&nbsp;Frédérique Battin-Leclerc ,&nbsp;Yann Fenard ,&nbsp;Luc-Sy Tran ,&nbsp;Guillaume Vanhove ,&nbsp;Joris W. Thybaut ,&nbsp;Kevin M. Van Geem","doi":"10.1016/j.combustflame.2025.114121","DOIUrl":"10.1016/j.combustflame.2025.114121","url":null,"abstract":"<div><div>Oxymethylene ethers (OMEs) have emerged as a promising and sustainable alternative for fossil-based fuels in recent years. This class of synthetic fuels can be produced from captured CO₂ with renewable electricity, so-called e-fuels, using carbon capture and utilization technology resulting in environmentally cleaner combustion. However, before OMEs can be used globally, it is essential to have a thorough understanding of their radical decomposition chemistry. In this study, combined experimental and kinetic modeling work is conducted to unravel the pyrolysis chemistry of oxymethylene ether-3 (OME-3), oxymethylene ether-4 (OME-4), and oxymethylene ether-5 (OME-5). A detailed kinetic model for pyrolysis of these long-chain OMEs with elementary reaction steps is developed based on first principles with the automatic kinetic model generation tool ‘Genesys’. The unimolecular decomposition pathways are explored by constructing potential energy surfaces, which highlight the importance of formaldehyde elimination reactions. In addition, rate rules are regressed for the unimolecular decomposition reactions of radicals, based on the quantum chemical results, to enable extrapolation of the kinetic data. The developed kinetic model is validated using experimental datasets from the literature, and benchmarking against other pyrolysis models demonstrates better predictive performance. The experimental observations are accurately predicted, on average within the uncertainty margin (∼10 mol% relative) for major compounds, without fitting model parameters. Part II of this study presents six newly acquired experimental datasets from jet-stirred and tubular reactors, additional kinetic model validation, and a comprehensive model analysis through rate of production and sensitivity analyses.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"275 ","pages":"Article 114121"},"PeriodicalIF":5.8,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-phase hypergolic ignition model","authors":"David A. Castaneda ,&nbsp;Joseph K. Lefkowitz ,&nbsp;Benveniste Natan","doi":"10.1016/j.combustflame.2025.114114","DOIUrl":"10.1016/j.combustflame.2025.114114","url":null,"abstract":"<div><div>A novel approach for modeling hypergolic ignition is presented, validated, and used to successfully predict ignition delay times for a hybrid rocket propellant configuration. This configuration employs a hypergolic additive (sodium borohydride) that allows two non-hypergolic reactants (polyethylene and hydrogen peroxide) to gain hypergolic capabilities. The model considers multiple phases and multiple species, heterogeneous and homogeneous chemical reactions, mass transfer between phases, and heat transfer. The transient behavior of the various chemical and thermal properties involved in hypergolic ignition is studied. In addition, a parametric investigation is conducted to predict ignition delay times as functions of multiple variables such as additive loading, oxidizer concentration, and initial propellant temperatures, among others. The results are presented in the form of ignition delay time contour maps. The heat release rate is shown to be controlled mostly by hypergolic chemical reactions. Gas homogeneous reactions only take place during the last portion of the ignition process and are the ones responsible for ultimately leading to a gas thermal runaway. The proper inclusion of the vaporization and pyrolysis of the propellants is found to be crucial since these determine the formation of a gas phase, where ignition is achieved. It is found that the vaporization of the liquid oxidizer is the controlling mass transfer mechanism for the hybrid rocket configuration considered. The model successfully predicts the minimum hypergolic additive loading and the range of oxidizer-to-fuel ratios required for ignition. It is found that the optimal oxidizer-to-fuel ratio leading to the shortest ignition delay time is mostly a function of additive loading. In addition, it is found that pressure, propellant initial temperature, and oxidizer concentration, have a major influence on ignition delay times and that they barely affect the optimal oxidizer-to-fuel ratio. The presented model, although evaluated for the hybrid rocket configuration, is considered to be applicable for any hypergolic propellant configuration.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"276 ","pages":"Article 114114"},"PeriodicalIF":5.8,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143684400","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}