Artículos de revistas: "Flame extension"

1

Kibrya, M. G. y G. A. Karim. "Blowout Limits of a Jet Diffusion Flame in the Presence of Small Surrounding Jet Pilot Flames". Journal of Energy Resources Technology 118, n.º 2 (1 de junio de 1996): 140–44. http://dx.doi.org/10.1115/1.2792705.

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The blowout limit of a methane jet diffusion flame is examined in the presence of a number of much smaller pilot jet flames of different fuels arranged within an experimental burner assembly in a co-flowing stream of air. It is shown that the blowout limit of the central jet flame can be extended very appreciably by increasing the flow rate through the smaller pilot jets. The basis for this extension to the blowout limit and the role of some changes in the operating parameters are discussed. It is suggested that the extension to the blowout limit observed is due mainly to the thermal contribution of the pilot jet flames.

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2

Yedinak, Kara M., Jack D. Cohen, Jason M. Forthofer y Mark A. Finney. "An examination of flame shape related to convection heat transfer in deep-fuel beds". International Journal of Wildland Fire 19, n.º 2 (2010): 171. http://dx.doi.org/10.1071/wf07143.

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Fire spread through a fuel bed produces an observable curved combustion interface. This shape has been schematically represented largely without consideration for fire spread processes. The shape and dynamics of the flame profile within the fuel bed likely reflect the mechanisms of heat transfer necessary for the pre-heating and ignition of the fuel during fire spread. We developed a simple laminar flame model for examining convection heat transfer as a potentially significant fire spread process. The flame model produced a flame profile qualitatively comparable to experimental flames and similar to the combustion interface of spreading fires. The model comparison to flame experiments revealed that at increasing fuel depths (>0.7 m), lateral flame extension was increased through transition and turbulent flame behaviour. Given previous research indicating that radiation is not sufficient for fire spread, this research suggests that flame turbulence can produce the convection heat transfer (i.e. flame contact) necessary for fire spread particularly in vertically arranged, discontinuous fuels such as shrub and tree canopies.

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3

Obando Vega, Pedro Javier, Axel Coussement, Amsini Sadiki y Alessandro Parente. "Non-Premixed Filtered Tabulated Chemistry: Filtered Flame Modeling of Diffusion Flames". Fuels 2, n.º 2 (25 de marzo de 2021): 87–107. http://dx.doi.org/10.3390/fuels2020006.

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The flame front filtering is a well-known strategy in turbulent premixed combustion. An extension of this approach for the non-premixed combustion context has been proposed by means of directly filtering counterflow diffusion flamelets. Promising results were obtained for the non-premixed filtered tabulated chemistry formalism on 1-D and 2-D unresolved counterflow flame configurations. The present paper demonstrates the soundness of this approach on a 3-D real laminar non-premixed coflow flame. The model results are compared against the direct filtering of the fully resolved laminar diffusion flame showing that the formalism adequately describes the underlying physics. The study reveals the importance of the one-dimensional counterflow flamelet hypothesis, so that the model activation under this condition is ensured by means of a flame sensor. The consistent coupling between the model and the flame sensor adequately retrieves the flame lift-off and satisfactorily predicts the profile extension due to the filtering process.

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4

Albayrak, Alp y Wolfgang Polifke. "An analytical model based on the G-equation for the response of technically premixed flames to perturbations of equivalence ratio". International Journal of Spray and Combustion Dynamics 10, n.º 2 (22 de noviembre de 2017): 103–10. http://dx.doi.org/10.1177/1756827717740776.

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A model for the response of technically premixed flames to equivalence ratio perturbations is proposed. The formulation, which is an extension of an analytical flame tracking model based on the linearized G-equation, considers the flame impulse response to a local, impulsive, infinitesimal perturbation that is transported by convection from the flame base towards the flame surface. It is shown that the contributions of laminar flame speed and heat of reaction to the impulse response exhibit a local behavior, i.e. the flame responds at the moment when and at the location where the equivalence ratio perturbation reaches the flame surface. The time lag of this process is related to a convective time scale, which corresponds to the convective transport of fuel from the base of the flame to the flame surface. On the contrary, the flame surface area contribution exhibits a non-local behavior: albeit fluctuations of the flame shape are generated locally due to a distortion of the kinematic balance between flame speed and the flow velocity, the resulting wrinkles in flame shape are then transported by convection towards the flame tip with the restorative time scale. The impact of radial non-uniformity in equivalence ratio perturbations on the flame impulse response is demonstrated by comparing the impulse responses for uniform and parabolic radial profiles. Considerable deviation in the phase of the flame transfer function, which is important for thermo-acoustic stability, is observed.

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5

Wu, Gang, Jinqing Li, Chunpeng Chai, Zhen Ge, Jialun Lin y Yunjun Luo. "Synthesis and characterization of novel post-chain extension flame retardant waterborne polyurethane". RSC Advances 5, n.º 118 (2015): 97710–19. http://dx.doi.org/10.1039/c5ra12975c.

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6

Cai, Jianan, Alvianto Wirasaputra, Yaming Zhu, Shumei Liu, Yubin Zhou, Chunhua Zhang y Jianqing Zhao. "The flame retardancy and rheological properties of PA6/MCA modified by DOPO-based chain extender". RSC Advances 7, n.º 32 (2017): 19593–603. http://dx.doi.org/10.1039/c6ra28293h.

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7

Haubold, Thorben Sören, Laura Puchot, Antoine Adjaoud, Pierre Verge y Katharina Koschek. "Bio-Based Bisbenzoxazines with Flame Retardant Linker". Polymers 13, n.º 24 (10 de diciembre de 2021): 4330. http://dx.doi.org/10.3390/polym13244330.

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This work explores the strategy of incorporating a highly substituted reactive flame retardant into a benzoxazine moiety. For this purpose, a DOPO-based flame retardant received a chain extension via reaction with ethylene carbonate. It was then reacted with phloretic acid to obtain a diphenol end-capped molecule, and further reacted with furfurylamine and paraformaldehyde to obtain a benzoxazine monomer via a Mannich-like ring closure reaction. This four-step synthesis yielded a partly bio-based halogen-free flame retardant benzoxazine monomer (DOPO-PA-fa). The successful synthesis was proven via NMR, IR and MS analysis. The polymerization behavior was monitored by DSC and rheological analysis both showing the polymerization starts at 200 °C to yield pDOPO-PA-fa. pDOPO-PA-fa has a significant thermal stability with a residual mass of 30% at 800 °C under ambient atmosphere. Furthermore, it reached a V-0 rating against small flames and an OI of 35%. Blended with other benzoxazines, it significantly improves their thermal stability and fire resistance. It emphasizes its potential as flame retardant agent.

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8

Li, Linjie, Wuchao Zhang, Zihe Gao y Liangwen Wei. "Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel". Indoor and Built Environment 32, n.º 1 (enero de 2023): 286–95. http://dx.doi.org/10.1177/1420326x221147427.

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The investigation of the fire characteristics and propagation behaviour in the urban utility tunnel is of great practical importance, especially for the conditions with double fire sources. In this work, a 1/8th scaled urban utility tunnel model was built to conduct the experiments to characterize the flame merging and ceiling impingement behaviour of transversely located double fire sources. Two rectangular fire sources with the same dimension were used, and their heat release rate (HRR) and fire source spacings were varied to consider the typical scenarios. Results show that for the smaller HRR, the tunnel ceiling and sidewalls have little influence on the flame merging of double fire sources. With the increase of HRR, the flame gradually impinges on the tunnel ceiling and forms a stable ceiling jet flame extension, and the ceiling and sidewalls of the tunnel can promote the merging of the flames of the double fire sources. Besides, with the increase of the fire source spacings, the flame merging probability P m can be divided into three stages, that is, (i) complete merging stage, (ii) intermittent merging stage and (iii) complete separation stage. On this basis, the predicting relation of P m was obtained by using the piecewise function.

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9

Tornatore, Cinzia y Magnus Sjöberg. "Optical Investigation of a Partial Fuel Stratification Strategy to Stabilize Overall Lean Operation of a DISI Engine Fueled with Gasoline and E30". Energies 14, n.º 2 (12 de enero de 2021): 396. http://dx.doi.org/10.3390/en14020396.

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This paper offers new insights into a partial fuel stratification (PFS) combustion strategy that has proven to be effective at stabilizing overall lean combustion in direct injection spark ignition engines. To this aim, high spatial and temporal resolution optical diagnostics were applied in an optically accessible engine working in PFS mode for two fuels and two different durations of pilot injection at the time of spark: 210 µs and 330 µs for E30 (gasoline blended with ethanol by 30% volume fraction) and gasoline, respectively. In both conditions, early injections during the intake stroke were used to generate a well-mixed lean background. The results were compared to rich, stoichiometric and lean well-mixed combustion with different spark timings. In the PFS combustion process, it was possible to detect a non-spherical and highly wrinkled blue flame, coupled with yellow diffusive flames due to the combustion of rich zones near the spark plug. The initial flame spread for both PFS cases was faster compared to any of the well-mixed cases (lean, stoichiometric and rich), suggesting that the flame propagation for PFS is enhanced by both enrichment and enhanced local turbulence caused by the pilot injection. Different spray evolutions for the two pilot injection durations were found to strongly influence the flame kernel inception and propagation. PFS with pilot durations of 210 µs and 330 µs showed some differences in terms of shapes of the flame front and in terms of extension of diffusive flames. Yet, both cases were highly repeatable.

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10

Huang, Ping, Shengtao Liu, Chunxiang Liu, Fuqiang Yang, Baihan Zhang y Longxing Yu. "Flame extension lengths beneath a double slope roof induced by gaseous fuel jet flame". Fuel 350 (octubre de 2023): 128891. http://dx.doi.org/10.1016/j.fuel.2023.128891.

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11

Majhool, Ahmed Abed Al-Kadhem. "LAMINAR FLAME SPEED MODEL AT THE INITIAL STAGE OF FORMATION DIFFUSION FLAME". Kufa Journal of Engineering 7, n.º 1 (5 de marzo de 2016): 1–14. http://dx.doi.org/10.30572/2018/kje/711220.

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This work paid special attention on the laminar flame speed in a piloted methane-air in jet diffusion flame due to the strong nonlinearity of chemical reaction process where an extension for the unsteady laminar flamelet model is required. The purpose for doing that is set for two folds. The partial differential equations for solving the combustion model required the representation of laminar flame speed in it and the advanced combustion modeling which is promising step. The probability density function required the laminar flame speed to be modelled as a function in terms of the mixture fraction to perform the integration. The laminar flame speed model is discussed, and the results are compared with the experimental database with good accuracy. The model specifies the conditional laminar flame speed and the difference against the gas flow velocity.Â

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12

Liang, Tianxiang, Jianan Cai, Shumei Liu, Hualin Lai y Jianqing Zhao. "Chain Extension and Synergistic Flame-Retardant Effect of Aromatic Schiff Base Diepoxide on Polyamide 6/Aluminum Diethylphosphinate Composites". Materials 12, n.º 14 (10 de julio de 2019): 2217. http://dx.doi.org/10.3390/ma12142217.

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A way to suppress the deterioration in mechanical properties of polyamide 6 (PA6) is required, especially with high loading of flame retardants in the matrix. In this study, a novel aromatic Schiff base diepoxide (DES) was synthesized. It exhibited an efficient chain extension effect on PA6 and a synergistic flame-retardant effect with aluminum diethylphosphinate (AlPi) for PA6. The PA6 composite with 16 wt.% AlPi only passed UL-94 V-0 rating at 1.6 mm thickness, while the combination of 1.5 wt.% DES with 13 wt.% AlPi induced PA6 to achieve a UL-94 V-0 rating at 0.8 mm thickness. The tensile, flexural, and Izod notched impact strengths were increased by 16.2%, 16.5%, and 24.9%, respectively, compared with those of V-0 flame-retarded PA6 composites with 16 wt.% AlPi. The flame-retarded mechanism of PA6/AlPi/DES was investigated by cone calorimetry and infrared characterization of the char residues and pyrolysis products. These results showed that DES had a synergistic effect with AlPi in condensed-phase flame retardation by promoting the production of aluminum phosphorus oxides and polyphosphates in the char residues.

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13

Wang, Aijuan, Brady Manescau, Khaled Chetehouna, Steve Rudz y Ludovic Lamoot. "Experimental study on the flame extension and risk analysis of a diffusion impinging flame in confined compartment". Journal of Fire Sciences 39, n.º 4 (17 de junio de 2021): 285–308. http://dx.doi.org/10.1177/07349041211015766.

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In this work, an experimental investigation on a diffusion impinging flame in a confined compartment was performed. The objective was to study the influence of confinement on the behavior of a flame impinging the ceiling and to deduce the auto-ignition risk of the smoke produced in the confined compartment. For this, configurations with five confinement levels were constructed by the condition of windows and/or door in the compartment and the variation of the heat release rates was made between 0.5 and 18.6 kW. To evaluate the flame morphology and flame extension length, an image processing method based on the direct linear transformation algorithm and the fire segmentation algorithm was adopted. From the experimental data, it was shown that the heat release rate of 4.6 kW presents a critical value for the flame extension in confined configurations, which corresponds to the equivalence ratio of the enclosure greater than 1, highlighting an under-ventilated environment. In addition, an auto-ignition risk analysis of smoke with unburnt gas in the compartment was carried out. The concentration and temperature of these gases were compared to the lower flammability limits and the auto-ignition temperature. It was observed that there was auto-ignition risk of the smoke under the ceiling, especially in the confined compartment of equivalence ratio greater than 1. Under these conditions, it is possible to have a fire spread to another compartment.

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14

Wu, Gang, Jinqing Li y Yunjun Luo. "Flame retardancy and thermal degradation mechanism of a novel post-chain extension flame retardant waterborne polyurethane". Polymer Degradation and Stability 123 (enero de 2016): 36–46. http://dx.doi.org/10.1016/j.polymdegradstab.2015.11.004.

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15

Polifke, W., P. Flohr y M. Brandt. "Modeling of Inhomogeneously Premixed Combustion With an Extended TFC Model". Journal of Engineering for Gas Turbines and Power 124, n.º 1 (1 de febrero de 2000): 58–65. http://dx.doi.org/10.1115/1.1394964.

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In many practical applications, so-called premixed burners do not achieve perfect premixing of fuel and air. Instead, fuel injection pressure is limited, the permissible burner pressure drop is small and mixing lengths are curtailed to reduce the danger of flashback. Furthermore, internal or external piloting is frequently employed to improve combustion stability, while part-load operation often requires burner staging, where neighboring burners operate with unequal fuel/air equivalence ratios. In this report, an extension of the turbulent flame speed closure (TFC) model for highly turbulent premixed combustion is presented, which allows application of the model to the case of inhomogeneously premixed combustion. The extension is quite straightforward, i.e., the dependence of model parameters on mixture fraction is accounted for by providing appropriate lookup tables or functional relationships to the model. The model parameters determined in this way are adiabatic flame temperature, laminar flame speed and critical gradient. The model has been validated against a test case from the open literature and applied to an externally piloted industrial gas turbine burner with good success.

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16

Ghorashi, Seyed Amin, Seyed Mohammad Hashemi, Seyed Abdolmehdi Hashemi y Mahdi Mollamahdi. "Numerical study on the combustion characteristics in a porous-free flame burner for lean mixtures". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 234, n.º 4 (9 de noviembre de 2019): 935–45. http://dx.doi.org/10.1177/0954406219884979.

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The present work implements a numerical simulation to investigate the combustion process in a porous-free flame burner. The non-equilibrium thermal condition is performed, and discretization and solving of the governing equations are conducted in a two-dimensional axisymmetric model. In order to simulate the combustion process, a reduced chemical kinetic mechanism of GRI 3.0, which includes 16 species and 41 reactions, is used. In order to prove the precision of the numerical method, some experimental tests are carried out and the numerical results are in a good agreement with the experimental measurements. The numerical results demonstrate that the porous-free flame burner has a higher flame stability compared to the conventional porous burner and the radiative efficiency of the porous-free flame burner is less than the porous burner. In addition, an increase in thermal conduction of the porous medium leads to an extension in the flame stability. In addition, the results show that with decreasing the pore density of porous medium, the flame stability is extended.

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17

CHAN, Simon Sze Man, Shuichi TORII y Toshiaki YANO. "Extension of Turbulent Jet Diffusion Flame Blowoff Limits by Doublet Flows." Transactions of the Japan Society of Mechanical Engineers Series B 67, n.º 663 (2001): 2841–47. http://dx.doi.org/10.1299/kikaib.67.2841.

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18

Wirasaputra, Alvianto, Lijun Zheng, Shumei Liu, Yanchao Yuan y Jianqing Zhao. "High-Performance Flame-Retarded Polyamide-6 Composite Fabricated by Chain Extension". Macromolecular Materials and Engineering 301, n.º 5 (11 de febrero de 2016): 614–24. http://dx.doi.org/10.1002/mame.201500357.

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19

Kolla, H. y N. Swaminathan. "Influence of Turbulent Scalar Mixing Physics on Premixed Flame Propagation". Journal of Combustion 2011 (2011): 1–8. http://dx.doi.org/10.1155/2011/451351.

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The influence of reactive scalar mixing physics on turbulent premixed flame propagation is studied, within the framework of turbulent flame speed modelling, by comparing predictive ability of two algebraic flame speed models: one that includes all relevant physics and the other ignoring dilatation effects on reactive scalar mixing. This study is an extension of a previous work analysing and validating the former model. The latter is obtained by neglecting modelling terms that include dilatation effects: a direct effect because of density change across the flame front and an indirect effect due to dilatation on turbulence-scalar interaction. An analysis of the limiting behaviour shows that neglecting the indirect effect alters the flame speed scaling considerably when is small and the scaling remains unaffected when is large. This is evident from comparisons of the two models with experimental data which show that the quantitative difference between the two models is as high as 66% at but only 4% at . Furthermore, neglecting the direct effect results in a poor prediction of turbulent flame speed for all values of , and both effects are important for practically relevant values of this velocity ratio.

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20

Resende, Pedro R., Leandro C. Morais, Carlos Pinho y Alexandre M. Afonso. "Combustion Characteristics of Premixed Hydrogen/Air in an Undulate Microchannel". Energies 15, n.º 2 (17 de enero de 2022): 626. http://dx.doi.org/10.3390/en15020626.

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This work reports a numerical investigation of microcombustion in an undulate microchannel, using premixed hydrogen and air to understand the effect of the burner design on the flame in order to obtain stability of the flame. The simulations were performed for a fixed equivalence ratio and a hyperbolic temperature profile imposed at the microchannel walls in order to mimic the heat external losses occurred in experimental setups. Due to the complexity of the flow dynamics combined with the combustion behavior, the present study focuses on understanding the effect of the fuel inlet rate on the flame characteristics, keeping other parameters constant. The results presented stable flame structure regardless of the inlet velocity for this type of design, meaning that a significant reduction in the heat flux losses through the walls occurred, allowing the design of new simpler systems. The increase in inlet velocity increased the flame extension, with the flame being stretched along the microchannel. For higher velocities, flame separation was observed, with two detected different combustion zones, and the temperature profiles along the burner centerline presented a non-monotonic decrease due to the dynamics of the vortices observed in the convex regions of the undulated geometry walls. The geometry effects on the flame structure, flow field, thermal evolution and species distribution for different inlet velocities are reported and discussed.

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21

Yu, Xin, Zhen Cao, JiangBo Peng, Yang Yu, Guang Chang, Yufei Ma, XiaoHui Li, Chaobo Yang y ZhiQiang Wang. "Statistical Analysis of Flame Oscillation Characterization of Oxy-Fuel in Heavy Oil Boiler Using OH Planar Laser-Induced Fluorescence". Journal of Spectroscopy 2019 (2 de julio de 2019): 1–10. http://dx.doi.org/10.1155/2019/7085232.

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The present work investigated the flame structures and oscillations of oxy-fuel combustions in a heavy oil boiler using OH planar laser-induced fluorescence imaging. Combustion instabilities, such as flame oscillation and combustion fluctuation, can assess the performance of an industrial burner in the boiler. The peak position variation in OH concentration was associated with the change of the reaction zone that corresponded with the fluctuation of the heat-release zone in the combustion chamber, which provides a valuable reference for the design of the combustion chamber. The experimental results suggest that the phenomenon of stratified flame combustion is related to the characteristic of flame oscillation. The substitution of N2 with CO2 will not significantly influence the flame oscillation frequency but increases the number of flame surface. As O2 concentration increased in the O2/CO2 atmosphere, the phenomenon of stratified flame combustion disappeared, and the flame presented an island-like structure. The bimodal oscillation of the combustion center was demonstrated by means of the probability density method; CO2 played a role in the extension of the combustion center. The combustion fluctuation of inner regions was quantitatively described; CO2 could maintain interregional stabilization to some extent. Compared with traditional measurement methods, PLIF technology has great advantages in evaluating burner performance and optimizing the design of the combustion chamber.

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22

Sacomano Filho, Fernando Luiz, Louis Dressler, Arash Hosseinzadeh, Amsini Sadiki y Guenther Carlos Krieger Filho. "Investigations of Evaporative Cooling and Turbulence Flame Interaction Modeling in Ethanol Turbulent Spray Combustion Using Tabulated Chemistry". Fluids 4, n.º 4 (31 de octubre de 2019): 187. http://dx.doi.org/10.3390/fluids4040187.

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Evaporative cooling effects and turbulence flame interaction are analyzed in the large eddy simulation (LES) context for an ethanol turbulent spray flame. Investigations are conducted with the artificially thickened flame (ATF) approach coupled with an extension of the mixture adaptive thickening procedure to account for variations of enthalpy. Droplets are tracked in a Euler–Lagrangian framework, in which an evaporation model accounting for the inter-phase non-equilibrium is applied. The chemistry is tabulated following the flamelet generated manifold (FGM) method. Enthalpy variations are incorporated in the resulting FGM database in a universal fashion, which is not limited to the heat losses caused by evaporative cooling effects. The relevance of the evaporative cooling is evaluated with a typically applied setting for a flame surface wrinkling model. Using one of the resulting cases from the evaporative cooling analysis as a reference, the importance of the flame wrinkling modeling is studied. Besides its novelty, the completeness of the proposed modeling strategy allows a significant contribution to the understanding of the most relevant phenomena for the turbulent spray combustion modeling.

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23

Yu, Rixin. "Deep learning of nonlinear flame fronts development due to Darrieus–Landau instability". APL Machine Learning 1, n.º 2 (1 de junio de 2023): 026106. http://dx.doi.org/10.1063/5.0139857.

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The Darrieus–Landau instability is studied using a data-driven, deep neural network approach. The task is set up to learn a time-advancement operator mapping any given flame front to a future time. A recurrent application of such an operator rolls out a long sequence of predicted flame fronts, and a learned operator is required to not only make accurate short-term predictions but also reproduce characteristic nonlinear behavior, such as fractal front structures and detached flame pockets. Using two datasets of flame front solutions obtained from a heavy-duty direct numerical simulation and a light-duty modeling equation, we compare the performance of three state-of-art operator-regression network methods: convolutional neural networks, Fourier neural operator (FNO), and deep operator network. We show that, for learning complicated front evolution, FNO gives the best recurrent predictions in both the short and long term. A consistent extension allowing the operator-regression networks to handle complicated flame front shape is achieved by representing the latter as an implicit curve.

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24

Liu, Yuan Chao, Bao Min Sun y Zhao Yong Ding. "Influence Analysis of Sampling Time for Synthesis of Carbon Nanotubes in the V-Type Pyrolysis Flame". Advanced Materials Research 221 (marzo de 2011): 235–39. http://dx.doi.org/10.4028/www.scientific.net/amr.221.235.

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Synthesis of carbon nanotubes from V-type pyrolysis flame is a kind of novel method. It needs simple laboratory equipments and normal atmosphere pressure. The V-type pyrolysis flame experimental system is introduced. Carbon source is the carbon monoxide and heat source is from acetylene/air premixed flame. Pentacarbonyl iron, served as catalyst, is transported by spray- pyrolysis method into the flame. The carbon nanotubes were characterized by scanning electron microscope and transmission electron microscope. This study aims to find the formation rule of carbon nanotubes from the V-type pyrolysis flame in different sampling times. The carbon nanotubes with less impurity and high yield were captured successfully in the V-type pyrolysis flame. The diameter of carbon nanotubes was approximate between 10nm and 20nm, and its length was dozens of microns. When the sampling time was below 3 minutes, the growth of carbon nanotubes came into the preparation growth period. The length of the carbon nanotubes increased gradually and the diameter had no obvious change with the extension of sampling time. When the sampling time was continued to the 5th minute, the growth of carbon nanotubes came into the exuberant growth period. The carbon nanotubes growth was finished within 5minutes. Longer sampling time was meaningless after the carbon nanotubes formation.

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25

Zheng, Jiaxin, Congxiao Wang, Yuyin Zhao, Menghao Guo, Yadong He y Chunling Xin. "The Synergy of Nanosilica and Zinc Diethyl Hypophosphite Influences the Flame Retardancy and Foaming Performance of Poly(Ethylene Terephthalate)". Advances in Polymer Technology 2023 (28 de abril de 2023): 1–15. http://dx.doi.org/10.1155/2023/4319998.

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In order to improve the flame retardancy of poly(ethylene terephthalate) (PET) and maintain its excellent foamability, nanosilica (nano-SiO2), and zinc diethyl hypophosphite (ZDP) were selected as synergistic flame retardants, and pyromellitic dianhydride (PMDA) was used as a chain extender to carry out flame retardant and chain extension modification of PET simultaneously. The flame retardancy and flame-retardant mechanism of modified PET were characterized by limiting oxygen index, vertical combustion test, thermogravimetric analysis, and SEM. Dynamic rheological test and DSC were used to analyze the rheological and thermal properties. The foaming ability was also studied by batch foaming experiments. The test results indicated that nano-SiO2 and ZDP had a synergistic effect, which could significantly improve flame retardancy of PET. The vertical combustible grade of modified PET reached V-0 grade, and the limiting oxygen index increased from 21% to about 30%. The role of nano-SiO2 on the flame retardancy of PET was mainly to increase compactness and strength of the carbon layer, which could block combustible gas produced by the pyrolysis of PET and resist dripping behavior. At the same time, the addition of nano-SiO2 increased the crystallization temperature and crystallinity of PET. Otherwise, nano-SiO2 could act as a bubble-nucleating agent and improve the foaming ability of modified PET. When the addition amount was 1 wt%, not only did the maximum foaming ratio increase but the foaming temperature zone was also widened from 225°C-235°C to 225°C-250°C. Finally, a flame-retardant PET system with good foaming property was proposed.

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26

Maeder, Xavier, Cees W. Passchier y Rudolph A. J. Trouw. "Flame foliation: Evidence for a schistosity formed normal to the extension direction". Journal of Structural Geology 29, n.º 3 (marzo de 2007): 378–84. http://dx.doi.org/10.1016/j.jsg.2006.10.005.

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27

Zhang, Xiaochun, Haowen Tao, Wenbin Xu, Xiaozhou Liu, Xianda Li, Xiaolei Zhang y Longhua Hu. "Flame extension lengths beneath an inclined ceiling induced by rectangular-source fires". Combustion and Flame 176 (febrero de 2017): 349–57. http://dx.doi.org/10.1016/j.combustflame.2016.11.004.

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28

Li, Jie, Hongtao Li, Chen Chen, Guannan Liu, Yaoyao Ying, Tianjiao Li y Dong Liu. "Edge Effects on Simultaneous Reconstructions of Flame Temperature and Soot Volume Fraction Profiles by a CCD Camera". Sensors 22, n.º 21 (26 de octubre de 2022): 8199. http://dx.doi.org/10.3390/s22218199.

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In this paper, the influence of the edge effect on the simultaneous reconstruction of axisymmetric flame temperature and soot volume fraction profiles by a single CCD camera was investigated in detail. The reconstruction accuracy of the flame temperature profile and soot volume fraction was insensitive to the measurement error of the coefficient matrix. When the signal to ratio (SNR) of the measurement system for both the radiation intensity and coefficient matrix was as low as 46 dB, the reconstruction accuracy for both temperature and soot volume fraction was acceptable and was more influenced by the radiation intensity measurement error. The reconstruction of the flame temperature and soot volume fraction was greatly influenced by the edge effect. When the flame edge with weak radiation signals was ignored during the reconstruction, the relative reconstruction error for the temperature and soot volume fraction increased from the flame center to the edge, and reached an unacceptable value at the reconstruction boundary, especially for the soot volume fraction. The flame image boundary could be chosen as the unified reconstruction boundary to reconstruct the two-dimensional distribution of the temperature and soot volume fraction with satisfactory accuracy. The low soot volume fraction could influence the reconstruction accuracy for both the temperature and soot concentration in non-sooting regions. Moreover, there was no obvious regularity between the reconstruction accuracy of the temperature and soot volume fraction and the extension of the reconstruction boundary.

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29

Peters, N. "A spectral closure for premixed turbulent combustion in the flamelet regime". Journal of Fluid Mechanics 242 (septiembre de 1992): 611–29. http://dx.doi.org/10.1017/s0022112092002519.

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Premixed turbulent combustion in the flamelet regime is analysed on the basis of a field equation. This equation describes the instantaneous flame contour as an isoscalar surface of the scalar field G(x,t). The field equation contains the laminar burning velocity sL as velocity scale and its extension includes the effect of flame stretch involving the Markstein length [Lscr ] as a characteristic lengthscale of the order of the flame thickness. The scalar G(x,t) plays a similar role for premixed flamelet combustion as the mixture fraction Z(x,t) in the theory of non-premixed flamelet combustion.Equations for the mean $\overline{G}$ and variance $\overline{G^{\prime 2}}$ are derived. Additional closure problems arise for the mean source terms in these equations. In order to understand the nature of these terms an ensemble of premixed flamelets with arbitrary initial conditions in constant-density homogeneous isotropic turbulence is considered. An equation for the two-point correlation $\overline{G^{\prime}({\boldmath x},t)G^{\prime}({\boldmath x}+{\boldmath r},t)}$ is derived. When this equation is transformed into spectral space, closure approximations based on the assumption of locality and on dimensional analysis are introduced. This leads to a linear equation for the scalar spectrum function Γ(k,t), which can be solved analytically. The solution Γ(k,t) is analysed by assuming a small-wavenumber cutoff at k0 = lT−1, where lT is the integral lengthscale of turbulence. There exists a $k^{-\frac{5}{3}}$ spectrum between lT and LG, where LG is the Gibson scale. At this scale turbulent fluctuations of the scalar field G(x,t) are kinematically restored by the smoothing effect of laminar flame propagation. A quantity called kinematic restoration ω is introduced, which plays a role similar to the scalar dissipation χ for diffusive scalars.By calculating the appropriate moments of Γ(k,t), an algebraic relation between ω, $\omega,\overline{G^{\prime}({\boldmath x},t)^2}$, the integral lengthscale lT and the viscous dissipation ε is derived. Furthermore, the scalar dissipation χ[Lscr ], based on the Markstein diffusivity [Dscr ][Lscr ] = sL [Lscr ], and the scalar-strain co-variance Σ[Lscr ] are related to ω. Dimensional analysis, again, leads to a closure of the main source term in the equation for the mean scalar $\overline{G}$. For the case of plane normal and oblique turbulent flames the turbulent burning velocity sT and the flame shape is calculated. In the absence of flame stretch the linear relation sT ∼ u′ is recovered. The flame brush thickness is of the order of the integral lengthscale. In the case of a V-shaped flame its increase with downstream position is calculated.

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30

Boyde, Jan M., Patrick C. Le Clercq, Massimiliano Di Domenico y Manfred Aigner. "Extension of the turbulent flame speed closure model to ignition in multiphase flows". Combustion and Flame 160, n.º 2 (febrero de 2013): 351–65. http://dx.doi.org/10.1016/j.combustflame.2012.10.006.

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31

Kamal, MM. "Combustion via multiple pairs of opposing premixed flames with a cross-flow". Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, n.º 1 (7 de octubre de 2016): 39–58. http://dx.doi.org/10.1177/0957650916673256.

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A cylindrical burner accommodating stoichiometric fuel–air mixture combustion via multiple pairs of opposing jets and a cross-flow provided heat intensification and duplication of the stagnation impact for extending the firing limits and maximizing the power density. Six pairs of circumferentially opposing stoichiometric mixture jets sustained bulk injection velocities as high as 21.8 m/s and were associated with NOx emissions of 22 ppm, while emissions of 10 ppm were recorded upon reaching a lean limit equivalence ratio of 0.59. A stoichiometric mixture jet issuing perpendicular to the opposing jets at a momentum flux ratio of 0.3 increased the turbulence production rates to the extent that increased the maximum bulk injection velocity to 28.3 m/s and reduced the NOx emissions to 17 ppm. Since the recirculation zones between the two stagnation centers got compressed by increasing the momentum flux ratio to 0.8, the corresponding residence time reduction decreased the NOx emissions to 12 ppm. As the cross-flow mixture was made fuel–lean, dilution of the stoichiometric mixture by the fuel–lean mixture combustion products made it possible to get NOx emissions of single digit ppm. Emissions of 9 ppm resulted from using the cross-flow fuel–lean mixture jet due to compromising the flame stability limit extension and the temperature reduction in the post flame region. Such emissions, in turn, decreased to 4 ppm as the momentum flux ratio increased to 1.7 at which the stoichiometric mixture flames shrank into their ports. A minimum NOx emission index of 0.27 g/kg fuel was thus obtained at a volumetric heat release of 50.4 MW/m3. The momentum flux ratio corresponding to merging the two stagnation zones was correlated with Reynolds and Froude numbers, the jets’ separation as well as the density and viscosity values pertaining to the lean and stoichiometric mixtures’ flame temperatures.

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32

Zhao, Wenbin, Fangshun Liu, Bo Liu, Yang Liu, Huaisheng Cao, Qing Tan y Jinfeng Wang. "Study on Permeability and Flame Retardancy of Coal Aerosol Atomized by Ultrasonic Wave". Atmosphere 13, n.º 9 (1 de septiembre de 2022): 1415. http://dx.doi.org/10.3390/atmos13091415.

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In order to analyze the permeability and particle size distribution of atomized aerosol in different coal particle sizes and to explore the inhibition performance of an atomized inhibitor in different atomization times and positions, the following conclusions are obtained by ultrasonic atomization device: The results of permeability experiment show that the particle size of aerosol decreases with the increase of atomization frequency. In addition, with the particle size of the coal sample decreasing from 5 cm to 0.6 cm, the penetration ratio of aerosol in coal decreases from 64.2% to 15.5% due to the interception of large particle size water mist by dense coal. The aerosol with a particle size of 2~4 μm has better permeability in crushed coal. The flame retardant experiment shows that compared with the raw coal, the aliphatic hydrocarbon of the atomized coal decreases by 75.9%, the aromatic hydrocarbon decreases by 57.5%, and the flame retardant effect is good. Meanwhile, the extension of solution atomization time will further enhance the flame retardant ability of ultrasonic atomized aerosol.

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33

Nicolai, H., L. Dressler, J. Janicka y C. Hasse. "Assessing the importance of differential diffusion in stratified hydrogen–methane flames using extended flamelet tabulation approaches". Physics of Fluids 34, n.º 8 (agosto de 2022): 085118. http://dx.doi.org/10.1063/5.0102675.

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Taking into account detailed chemical kinetics and therefore allowing for a detailed representation of the flame's microstructure at reduced computational cost make flamelet-based tabulation approaches such as the flamelet-generated manifold (FGM) a commonly used method for turbulent combustion simulations. However, there has been little focus on analyzing such models for fuel blends, including hydrogen. One reason for that is the challenging inclusion of differential diffusion effects into FGM, which may become crucial for highly diffusive fuels such as hydrogen. This paper presents an extension of the FGM approach that takes into account differential diffusion to assess the importance of differential diffusion for methane hydrogen blends. To this end, an extended model containing five controlling variables can be derived. However, the high correlation of certain controlling variables and the number of control variables could be reduced to three controlling variables in this study. These models are coupled to the artificially thickened flame (ATF) approach to facilitate large-eddy simulations (LESs). To ensure the consistency of the coupling between FGM and ATF when differential diffusion is considered, the model is thoroughly verified and validated using freely propagating and stratified laminar one-dimensional flames. Finally, simulations of the turbulent premixed stratified burner operated with a hydrogen methane blend are performed. The validation of the modeling framework is performed by comparing the simulation results to extensive experimental data, allowing an in-depth analysis of the macro- and microstructure of the flame.

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34

Kim, Gyeong Taek, Gyeong Taek Kim, Hyun Seok You, Chun Sang Yoo, Jeong Park y Suk Ho Chung. "Extension of Lean Operation and Extinction Limit of Premixed Flame Applying Non-Thermal Plasma". Journal of The Korean Society of Combustion 24, n.º 1 (31 de marzo de 2019): 46–50. http://dx.doi.org/10.15231/jksc.2019.24.1.046.

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35

Torii, Shuichi. "Effect of Collar Length on Extension of Subsonic Hydrogen Jet Diffusion Flame Blowout Limits". International Journal of Green Energy 4, n.º 4 (31 de julio de 2007): 367–75. http://dx.doi.org/10.1080/15435070701332070.

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36

Mahmoud, Rihab, Mehdi Jangi, Florian Ries, Benoit Fiorina, Johannes Janicka y Amsini Sadiki. "Combustion Characteristics of a Non-Premixed Oxy-Flame Applying a Hybrid Filtered Eulerian Stochastic Field/Flamelet Progress Variable Approach". Applied Sciences 9, n.º 7 (29 de marzo de 2019): 1320. http://dx.doi.org/10.3390/app9071320.

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The oxidation of methane under oxy-fuel combustion conditions with carbon capture is attractive and deserves huge interest towards reducing CO2 and NOx emissions. The current paper reports on the predictions and analysis of combustion characteristics of a turbulent oxy-methane non-premixed flame operating under highly diluted conditions of CO2 and H2 in oxidizer and fuel streams, respectively. These are achieved by applying a novel, well-designed numerical combustion model. The latter consists of a large eddy simulation (LES) extension of a recently suggested hybrid model in Reynolds averaging-based numerical simulation (RANS) context by the authors. It combines a transported joint scalar probability density function (T-PDF) following the Eulerian Stochastic Field methodology (ESF) on the one hand, and a flamelet progress variable (FPV) turbulent combustion model under consideration of detailed chemical reaction mechanism on the other hand. This novel hybrid ESF/FPV approach removes the weaknesses of the presumed-probability density function (P-PDF)-based FPV modeling, along with the solving of associated additional modeled transport equations while rendering the T-PDF computationally less affordable. First, the prediction capability of the LES hybrid ESF/FPV was appraised on the well-known air-piloted methane jet flame (Sandia Flame D). Then, it was assessed in analyzing the combustion properties of a non-premixed oxy-flame and in capturing the CO2 dilution effect on the oxy-fuel flame behavior. To this end, the so-called oxy-flame B3, already numerically investigated in a RANS context, was analyzed. Comparisons with experimental data in terms of temperature, scalar distributions, and scatter plots agree satisfactorily. Finally, the impact of generating the FPV chemistry table under condition of unity Lewis number, even with CO2 dilution, was investigated on the general prediction of the oxy-fuel flame structure, stability and emissions. In particular, it turns out that 68% molar percentage of CO2 leads to 0.39% of CO formation near the burner fuel nozzle and 0.62% at 10 dfuel above the nozzle.

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37

Liu, Peng, Jiandi Ling, Taoyan Mao, Feng Liu, Wenzhi Zhou, Guojie Zhang y Fengwei Xie. "Adhesive and Flame-Retardant Properties of Starch/Ca2+ Gels with Different Amylose Contents". Molecules 28, n.º 11 (4 de junio de 2023): 4543. http://dx.doi.org/10.3390/molecules28114543.

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Starch, being renewable and biodegradable, is a viable resource for developing sustainable and environmentally friendly materials. The potential of starch/Ca2+ gels based on waxy corn starch (WCS), normal corn starch (NCS), and two high-amylose corn starches, G50 (55% amylose content) and G70 (68% amylose content) as flame-retardant adhesives has been explored. Being stored at 57% relative humidity (RH) for up to 30 days, the G50/Ca2+ and G70/Ca2+ gels were stable without water absorption or retrogradation. The starch gels with increasing amylose content displayed increased cohesion, as reflected by significantly higher tensile strength and fracture energy. All the four starch-based gels showed good adhesive properties on corrugated paper. For wooden boards, because of the slow diffusion of the gels, the adhesive abilities are weak initially but improve with storage extension. After storage, the adhesive abilities of the starch-based gels are essentially unchanged except for G70/Ca2+, which peels from a wood surface. Moreover, all the starch/Ca2+ gels exhibited excellent flame retardancy with limiting oxygen index (LOI) values all around 60. A facile method for the preparation of starch-based flame-retardant adhesives simply by gelating starch with a CaCl2 solution, which can be used in paper or wood products, has been demonstrated.

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38

Yun-yun, Chen, Li Zhen-hua, Song Yang y He An-zhi. "Extension of the Gladstone-Dale equation for flame flow field diagnosis by optical computerized tomography". Applied Optics 48, n.º 13 (24 de abril de 2009): 2485. http://dx.doi.org/10.1364/ao.48.002485.

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39

Wang, Zhenhua, Kuibin Zhou, Le Zhang, Xuan Nie, Yueqiong Wu, Juncheng Jiang, Anne Simone Dederichs y Lu He. "Flame extension area and temperature profile of horizontal jet fire impinging on a vertical plate". Process Safety and Environmental Protection 147 (marzo de 2021): 547–58. http://dx.doi.org/10.1016/j.psep.2020.11.028.

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40

UCHIDA, Tetsuo, Hirofumi ISOYAMA, Mariko TATEMATSU, Isao KOJIMA, Chuzo IIDA, Keisuke GOTO y Michio MATSUBARA. "Application of absolute amount measurement in flame AAS; Extension of linear range of calibration curve." Bunseki kagaku 37, n.º 12 (1988): T232—T237. http://dx.doi.org/10.2116/bunsekikagaku.37.12_t232.

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41

Heidari, Mohammad, Panagiotis Kotsovinos y Guillermo Rein. "Flame extension and the near field under the ceiling for travelling fires inside large compartments". Fire and Materials 44, n.º 3 (13 de diciembre de 2019): 423–36. http://dx.doi.org/10.1002/fam.2773.

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42

Zhang, Xiaochun, Haowen Tao, Zijian Zhang, Jingyong Liu, Aihua Liu, Wenbin Xu y Xiaozhou Liu. "Flame extension area of unconfined thermal ceiling jets induced by rectangular-source jet fire impingement". Applied Thermal Engineering 132 (marzo de 2018): 801–7. http://dx.doi.org/10.1016/j.applthermaleng.2017.12.096.

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43

Vilmart, Gautier, Nelly Dorval, Robin Devillers, Yves Fabignon, Brigitte Attal-Trétout y Alexandre Bresson. "Imaging Aluminum Particles in Solid-Propellant Flames Using 5 kHz LIF of Al Atoms". Materials 12, n.º 15 (29 de julio de 2019): 2421. http://dx.doi.org/10.3390/ma12152421.

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Laser-induced fluorescence imaging of aluminum atoms (Al-PLIF) is used to analyze the spatio-temporal behavior of aluminized solid propellant combustion. Using alternating LIF and chemiluminescence emission images of the particles in the gaseous and liquid phase evolving close to and far above the dynamically varying propellant surface, sequences of images were recorded and analyzed. The good sensitivity achieved enabled us to track the dynamics of the flame in the vicinity of particles detected all along the flame extension and up to 1.5 MPa. Analysis of wide-field images enabled droplet velocity measurements due to the high LIF sampling rate (5 kHz). The observed typical plume structures were in good agreement with alumina-formation prediction and previous shadowgraphy visualization. High-resolution sequences of images showed gaseous distribution behavior around the molten particles. The Al vapor phase was thus found to extend between 3 and 6.5 radii around the particles. Particle detachment dynamics were captured just above the propellant surface.

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44

Larsson, I. A. Sofia. "The Aerodynamics of an Iron Ore Pelletizing Rotary Kiln". Fluids 7, n.º 5 (5 de mayo de 2022): 160. http://dx.doi.org/10.3390/fluids7050160.

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This paper summarizes more than a decade of systematic studies of the flow field in an iron ore pelletizing rotary kiln using computational fluid dynamics (CFD) on simplified models of a real kiln. Physical, laser-based experiments have been performed to validate part of the numerical results. The objective is a better understanding of the kiln aerodynamics and, by extension, its effect on the combustion process. Despite all of the simplifications regarding the models studied in this project, the results show the importance of correctly predicting the flow field in order to optimize the combustion process. Combustion simulations revealed that the heat release from the flame does not affect or change the flow field in any significant way; the flow field, however, governs the flame propagation and affects the combustion process by controlling the mixing rates of fuel and air. Using down-scaled isothermal water models for investigating kiln aerodynamics in general and mixing properties in particular is therefore justified. Although the heat release from the flame cannot be accounted for in isothermal models, valuable implications regarding the real process can still be gained. To better model the actual process numerically, more advanced submodels for both the combustion and especially the flow field are needed. The complex flow field in this type of rotary kiln requires a careful choice of turbulence model to obtain accurate simulation results.

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45

Liu, Zheng Qin, Wei Guo Liu, Xiu Li Qiu, Yu Qing Zhang y Fan Dong Kong. "Study on Properties of Blended Fabrics Containing Phenolic Fiber". Advanced Materials Research 709 (junio de 2013): 242–45. http://dx.doi.org/10.4028/www.scientific.net/amr.709.242.

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Phenolic fiber is a new fiber and has excellent flame retardant properties. In order to investigate the textile possibility of phenolic fiber and to develop protective clothing and decorative fabrics containing phenolic fiber, the mechanical properties of phenolic fiber were studied firstly, then the polyester fiber was chosen to blend with different portion of phenolic fiber to enhance the strength of the blended yarn and finally the fabrics were knitted with different blended yarns. The strength and wear resistance of different blending ratio of phenolic/polyester blended yarn, and the bursting strength, abrasion resistance and flame retardant properties of the blended fabrics were analyzed and compared. The experimental results shows that the breaking tenacity and elongation at break are low, only 1.3 cN/dtex and 9.4%, respectively, which is not suitable for 100% phenolic fiber to be processed in yarn. The strength and wear resistance of the phenolic/polyester blend yarns and their knitted fabrics increase while the contents of polyester are increased. The flame retardant of phenolic/polyester blend fabrics is improved greatly due to phenolic fiber. Therefore, it is necessary for phenolic fiber to modify its strength and extension in order to be able to get the 100% phenolic yarn and products and in order to give full play to the excellent characteristics of the phenolic fiber.

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46

Marques, Ana C., Helena Dias, Sandro Matos, Bruno Sargaço, Ricardo Simoes, Aster De Schrijver y João C. Bordado. "Polyurethane one-component foam formulation optimization for low free isocianate monomer content". Journal of Cellular Plastics 53, n.º 2 (28 de julio de 2016): 167–79. http://dx.doi.org/10.1177/0021955x16639230.

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Recent changes in legislation have forced one-component foam producers to drop the amount of free monomeric isocyanate in their polyurethane systems. Also, it is required that commercial polyurethane aerosol cans exhibit at least one year of shelf life and polyurethane foams must be classified as B2 on the fire testing following DIN 4102. This paper reports on a systematic optimization study of polyurethane formulations dedicated to address these current industry requirements. A one-component foam system exhibiting simultaneously all of these parameters was achieved by reacting conventional diols, a relatively low-molecular weight monol (2-ethylhexanol), a flame retardant high-molecular weight monol (tris(bromoneopentyl)alcohol), a methylene diphenyl diisocyanate-based prepolymer (GreenAdduct 13), and a small amount of 2,4′-toluene diisocyanate. The use of monols allows producing prepolymers with low free methylene diphenyl diisocyanate by preventing chain extension and, therefore, avoiding extreme viscosity build-up. Toluene diisocyanate also promotes a lower viscosity inside the aerosol can, which enables the use of high enough quantities of high-molecular weight flame retardant monol to achieve a B2 fire test classification.

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47

Kazmouz, Samuel J., Daniel C. Haworth, Peter Lillo y Volker Sick. "Extension of a thickened flame model to highly stratified combustion—Application to a spark-ignition engine". Combustion and Flame 236 (febrero de 2022): 111798. http://dx.doi.org/10.1016/j.combustflame.2021.111798.

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48

Wang, Zhirong, Kewei Jiang, Kun Zhao y Pinkun Guo. "Macroscopic characteristics and prediction model of horizontal extension length for syngas jet flame under inclined conditions". International Journal of Hydrogen Energy 46, n.º 44 (junio de 2021): 23091–99. http://dx.doi.org/10.1016/j.ijhydene.2021.04.118.

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49

Wu, Hao, Mourad Krifa y Joseph H. Koo. "Rubber (SEBS-g-MA) Toughened Flame-Retardant Polyamide 6: Microstructure, Combustion, Extension, and Izod Impact Behavior". Polymer-Plastics Technology and Engineering 57, n.º 8 (28 de septiembre de 2017): 727–39. http://dx.doi.org/10.1080/03602559.2017.1344856.

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50

Lu, K. H., S. H. Mao, J. Wang y L. H. Hu. "Flame extension length beneath a horizontal eave in fire-induced thermal plume ejected from a compartment". Applied Thermal Engineering 127 (diciembre de 2017): 729–35. http://dx.doi.org/10.1016/j.applthermaleng.2017.07.175.

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