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Simulation of reaction initiation in powder compacting from the surface with composite formation in equivalent reaction cell 等效反应池中粉末表面复合压实反应起爆模拟
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-08-02 DOI: 10.1080/13647830.2023.2241421
A. Knyazeva, N. Bukrina
In the present work, we propose a new variant of the model of the composite synthesis under surface heating. We believe that the formation of the composition occurs at the level of reaction cell. The diffusion-controlled process of reduction of one material by another from an oxide is described in the framework of the problem with moving boundaries. It is assumed that the formation of the matrix composition is carried out by the diffusion mechanism. From the position of interfaces, we find the relative volume fractions of oxide phases and the fraction of volume occupied by the matrix. The averaging method of the analysis results at the reaction cell level makes it possible to use these data at the macroscopic level. Volume fractions of phases and average matrix composition (obtained by averaging over the area occupied by the matrix) provide values reflecting the composition of the composite at the macro level. The problem is solved numerically in dimensionless formulation. Dimensionless complexes of physical quantities are distinguished. The estimation of these parameters is performed. The conditions of correctness of the proposed approach are established from comparison of temporal and spatial scales of thermal and diffusion phenomena. A numerical algorithm for the joint solution of macro- and mesolevel problems has been developed. The proposed algorithm makes possible the investigation of the dynamics of composition changes at all points. The model is supplemented by the calculation of stresses and strains from the data on composition and temperature changes in reaction cells. Averaged values of stresses are transferred to macro level.
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引用次数: 0
Updated asymptotic structure of cool diffusion flames 冷扩散火焰的更新渐近结构
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-07-07 DOI: 10.1080/13647830.2023.2232338
F. Williams, V. Nayagam
The influence of adding a seventh important elementary step to a six-step mechanism, previously employed for describing the asymptotic structure of normal-alkane droplet combustion supported by cool-flame chemistry in the negative-temperature-coefficient (NTC) range, is investigated by analytical methods. A development paralleling the classical activation-energy-asymptotic (AEA) analysis of the partial-burning regime, accompanied for the first time by an AEA analysis for a negative activation energy, to account properly for the removal of an important intermediate species, is pursued to make predictions of the combustion process, resulting in a revised asymptotic structure that agrees better with computational predictions based on detailed chemistry.
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引用次数: 0
Coflow filtration combustion waves Coflow过滤燃烧波
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-06-20 DOI: 10.1080/13647830.2023.2226658
A. Bayliss, E. Shafirovich, V. Volpert
Recently, it has been proposed to develop space power systems based on filtration combustion of metal powders with oxygen supplied by a chemical oxygen generator. The experiments with lithium and magnesium powders at natural infiltration of oxygen have shown propagation of both counterflow and coflow combustion waves. However, natural filtration combustion of metal powders at relatively low pressures is not sufficiently understood. In the present paper, we investigate the natural coflow combustion waves propagating through a porous medium. The porous matrix is made of metal particles that react with oxygen flowing from the open end of the sample to the reaction zone where it is consumed forming a condensed product which also has a porous structure. The gas flow is due to the pressure difference between the pressure at the open end and that in the reaction zone (the so-called natural filtration). The open end is where the sample is ignited, so that the gas flows through the reaction products, i.e. in the same direction as the combustion wave propagates (coflow filtration). Our mathematical model involves the conservation of energy equation and gas mass, solid reactant mass, and gas momentum balances, as well as an equation of state, and appropriate boundary and initial conditions. It is studied analytically under the combustion front approximation. When the reaction zone is close to the open end, there is sufficient amount of oxygen in the reaction zone and the reaction is controlled by kinetic factors (the kinetic regime of propagation). As the reaction moves away from the open end, it is gas supply that becomes a limiting factor (filtration regime). Both kinetic and filtration regimes of propagation as well the transition between them are analytically studied in this paper.
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引用次数: 0
Flamelet/transported PDF simulations of ethylene/air jet turbulent non-premixed flame using a three-equation PAH-based soot production model 基于三方程多环芳烃烟尘生成模型的小火焰/传输PDF模拟乙烯/空气射流湍流非预混火焰
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-06-20 DOI: 10.1080/13647830.2023.2224755
F. Nmira, Antoine Bouffard, J. Consalvi
This article reports flamelet/transported PDF (TPDF) simulations of the well-documented ethylene/air turbulent non-premixed jet flame investigated experimentally at Sandia. The transported PDF equation is solved with the Stochastic Eulerian Field method. The soot production is modelled by a validated three equation PAH-based soot model that predicts the mean soot aggregate properties at low computational time and includes a detailed description of the soot production processes. Gas and soot radiation is modelled using the rank-correlated full-spectrum k model. The turbulence/chemistry/soot production/radiation interactions are taken into account by means of the PDF method. Simulations are run by considering or not soot differential mixing. Based on recent conclusions drawn from Direct Numerical Simulations (Zhou et al., Proc. Combsut. Inst. 38 (2021) 2731–2739), soot differential mixing is modelled by neglecting soot mixing owing to sufficiently large mixing timescales. When soot differential mixing is considered, model predictions reproduce reasonably well the exhaustive set of experimental data, including flame structure, soot statistics and radiative outputs without adjusting parameters. In particular, the predictions demonstrate for the first time the capability of RANS/TPDF models to capture the soot intermittency. On the other hand, neglecting the soot differential mixing produces notable reductions in mean and fluctuating soot volume fraction and soot intermittency. Scatter plot analysis shows that the effects of soot differential mixing are more pronounced in regions of the mixture fraction space where soot surface growth and soot oxidation dominate the soot production, affecting these processes in a non-negligible manner. In an opposite way, soot nucleation and PAH condensation are much less significantly affected. Model results show also that disregarding soot differential mixing reduces the mean soot emission as well the soot emission turbulence/radiation interaction.
本文报道了在桑迪亚实验研究的乙烯/空气湍流非预混射流火焰的小火焰/传输PDF(TPDF)模拟。采用随机欧拉场方法求解传输PDF方程。烟尘产生是通过一个经过验证的基于PAH的三方程烟尘模型进行建模的,该模型预测了低计算时间下的平均烟尘聚集特性,并包括烟尘产生过程的详细描述。使用秩相关全谱k模型对气体和烟尘辐射进行建模。湍流/化学/烟尘产生/辐射相互作用通过PDF方法考虑在内。通过考虑或不考虑烟灰差异混合来运行模拟。根据直接数值模拟的最新结论(Zhou et al.,Proc.Combsut.Inst.38(2021)2731–2739),由于混合时间尺度足够大,通过忽略烟灰混合来模拟烟灰差分混合。当考虑烟灰差分混合时,模型预测在不调整参数的情况下合理地再现了详尽的实验数据集,包括火焰结构、烟灰统计和辐射输出。特别是,预测首次证明了RANS/TPDF模型捕捉煤烟间歇性的能力。另一方面,忽略煤烟差异混合会显著降低平均和波动的煤烟体积分数以及煤烟间歇性。散点图分析表明,在混合物分数空间的区域中,烟灰表面生长和烟灰氧化主导了烟灰的产生,烟灰差异混合的影响更为明显,以不可忽略的方式影响这些过程。相反,烟灰成核和PAH冷凝受到的影响要小得多。模型结果还表明,忽略煤烟差异混合会降低平均煤烟排放以及煤烟排放湍流/辐射相互作用。
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引用次数: 0
High-order methods for the simulation of unsteady counterflow flames subject to stochastic forcing of large amplitude 大振幅随机力作用下非定常逆流火焰的高阶模拟方法
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-06-14 DOI: 10.1080/13647830.2023.2218621
F. Bisetti
Unsteady counterflows are employed to understand and model the effect of turbulence on flames. We present a novel numerical approach for the simulation of one-dimensional unsteady counterflow flames with fourth order spatial discretization and up to fourth order time discretization. The approach couples a three-stage Lobatto IIIa formula for boundary value problems and variable-order, variable time step size Backward Differentiation Formulas for time integration. The framework is explained in detail, its computational performance is analysed, and its use is demonstrated for the case of stochastic forcing of premixed counterflow flames, whereby the imposed rate of strain is a multi-scale lognormal discrete random process with exponential autocorrelation. High-order spatial and temporal discretization make the approach well-suited for the accurate and computationally efficient simulation of the effect of turbulence on flames, which are characterised by large amplitude stochastic fluctuations of the local rate of strain.
采用非定常逆流来理解和模拟湍流对火焰的影响。本文提出了一种具有四阶空间离散和高达四阶时间离散的一维非定常逆流火焰数值模拟方法。该方法结合了边值问题的三阶段Lobatto IIIa公式和时间积分的变阶、变时间步长后向微分公式。详细解释了该框架,分析了其计算性能,并演示了其在预混合逆流火焰随机强迫情况下的应用,其中施加的应变速率是一个多尺度对数正态离散随机过程,具有指数自相关。高阶空间和时间离散化使得该方法非常适合于湍流对火焰的影响的精确和计算效率的模拟,其特征是局部应变率的大幅度随机波动。
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引用次数: 1
Structure and similarity properties of the laminar counterflow spray flame 层流逆流喷雾火焰的结构与相似特性
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-05-18 DOI: 10.1080/13647830.2023.2212637
Qun Hu, Lipo Wang
The spray flame in a laminar counterflow is influenced by various setup conditions, for instance the strain rate and liquid droplet parameters, including the initial temperature, size distribution, hydrodynamics and the vaporisation history. With some reasonable simplification, the two phase governing equations can be reformulated as equations in the single gas phase with reconstructed spray-related source terms. Numerical solutions assume interesting similarity features, such as the (almost) independence of the evaporation path after mapping onto a newly defined quantity R, constructed from sensible enthalpy and mixture fraction. In this regard, the dimensionality of free parameters describing the structure of the spray flame can be hopefully reduced, which then provides a different scenario to understand the spray combustion physics. The flame regime diagram is also elaborated in the present framework.
层流逆流中的喷射火焰受到各种设置条件的影响,例如应变速率和液滴参数,包括初始温度、尺寸分布、流体力学和汽化历史。通过合理的简化,两相控制方程可以重新表述为单个气相的方程,其中重构了与喷雾相关的源项。数值解具有有趣的相似性特征,例如在映射到新定义的由显焓和混合物分数构建的量R后,蒸发路径(几乎)独立。在这方面,描述喷雾火焰结构的自由参数的维数有望降低,从而为理解喷雾燃烧物理提供不同的场景。在本框架中还详细阐述了火焰状态图。
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引用次数: 1
Conditional space evaluation of progress variable definitions for Cambridge/Sandia swirl flames 剑桥/桑迪亚漩涡火焰进展变量定义的条件空间评价
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-05-12 DOI: 10.1080/13647830.2023.2211537
N. Sekularac, X. Fang, W. Bushe, M. Davy
Data from all spatial locations of nine turbulent flames in the Cambridge/Sandia swirl database are combined to study how the choice of scalar variables in conditional moment closure (CMC) type approaches affect the conditional spatial fluctuations of reactive scalars. In order to investigate the influence of swirl and stratification, two additional data-sets have been constructed. Principal component analysis (PCA) is applied to help identify the number of scalar variables and the most appropriate choices to describe the composition space. Two PCA scaling methods have been adopted, namely Pareto and Auto-scaling. Regardless of the data-set investigated and the scaling method used, the results suggest that a single principal component correlated with temperature accounted for the largest variance. For the first moment hypothesis, four progress variable, c, definitions identified by PCA are selected as conditioning variables to investigate the conditional fluctuations and normalised RMS of various species and temperature from all three databases at all axial locations. The results indicate that two control variables based on mixture fraction, Z, and progress variable significantly reduce the conditional fluctuations of scalars compared to a single variable. The selection of progress variables had minimal effects on the RMS of conditional fluctuations for all tested conditions, although a slight reduction of conditional fluctuations was found for the temperature-based progress variable, which can potentially help the further extension of CMC-based models in different flame configurations. The present study also shows that using Z and c (regardless of its definition) as two conditioning scalars enables the detachment of the thermo-chemical state from space, swirl and stratification effects. This suggests that adopting a doubly conditioned source term estimation (DCSE) approach might successfully predict the considered set of flames, assuming that ensembles are divided along the axial direction.
结合剑桥/桑迪亚涡流数据库中9个湍流火焰的所有空间位置数据,研究了条件矩闭(CMC)型方法中标量变量的选择如何影响反应标量的条件空间波动。为了研究旋流和分层的影响,我们构建了两个额外的数据集。应用主成分分析(PCA)来帮助确定标量变量的数量和描述组合空间的最合适选择。采用了两种PCA尺度变换方法,即Pareto和Auto-scaling。无论调查的数据集和使用的标度方法如何,结果表明,与温度相关的单一主成分占最大的方差。在第一矩假设中,选取由主成分分析(PCA)确定的四个进程变量c作为条件变量,研究三个数据库在所有轴向位置上不同物种和温度的条件波动和归一化均方根。结果表明,与单一变量相比,基于混合分数的两个控制变量Z和进度变量显著降低了标量的条件波动。在所有测试条件下,进度变量的选择对条件波动的均方根影响最小,尽管基于温度的进度变量的条件波动略有减少,这可能有助于进一步扩展基于cmc的模型在不同火焰配置下的应用。本研究还表明,使用Z和c(无论其定义如何)作为两个调节标量,可以使热化学状态脱离空间、旋流和分层效应。这表明,采用双条件源项估计(DCSE)方法可能成功地预测考虑的火焰集,假设集合沿轴向划分。
{"title":"Conditional space evaluation of progress variable definitions for Cambridge/Sandia swirl flames","authors":"N. Sekularac, X. Fang, W. Bushe, M. Davy","doi":"10.1080/13647830.2023.2211537","DOIUrl":"https://doi.org/10.1080/13647830.2023.2211537","url":null,"abstract":"Data from all spatial locations of nine turbulent flames in the Cambridge/Sandia swirl database are combined to study how the choice of scalar variables in conditional moment closure (CMC) type approaches affect the conditional spatial fluctuations of reactive scalars. In order to investigate the influence of swirl and stratification, two additional data-sets have been constructed. Principal component analysis (PCA) is applied to help identify the number of scalar variables and the most appropriate choices to describe the composition space. Two PCA scaling methods have been adopted, namely Pareto and Auto-scaling. Regardless of the data-set investigated and the scaling method used, the results suggest that a single principal component correlated with temperature accounted for the largest variance. For the first moment hypothesis, four progress variable, c, definitions identified by PCA are selected as conditioning variables to investigate the conditional fluctuations and normalised RMS of various species and temperature from all three databases at all axial locations. The results indicate that two control variables based on mixture fraction, Z, and progress variable significantly reduce the conditional fluctuations of scalars compared to a single variable. The selection of progress variables had minimal effects on the RMS of conditional fluctuations for all tested conditions, although a slight reduction of conditional fluctuations was found for the temperature-based progress variable, which can potentially help the further extension of CMC-based models in different flame configurations. The present study also shows that using Z and c (regardless of its definition) as two conditioning scalars enables the detachment of the thermo-chemical state from space, swirl and stratification effects. This suggests that adopting a doubly conditioned source term estimation (DCSE) approach might successfully predict the considered set of flames, assuming that ensembles are divided along the axial direction.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"27 1","pages":"736 - 767"},"PeriodicalIF":1.3,"publicationDate":"2023-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48205184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Quenching modes of local flame–wall interaction for turbulent premixed methane combustion in a constant volume vessel 定容容器中紊流预混甲烷燃烧局部火焰-壁面相互作用的猝灭模式
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-05-11 DOI: 10.1080/13647830.2023.2209047
Ye Wang, Y. Minamoto, M. Shimura, M. Tanahashi
The quenching mode of local flame–wall interaction (FWI) is investigated for its response to different levels of turbulence intensity as well as its effect on quenching distance, wall heat flux, and near-wall reaction. For that, direct numerical simulations of turbulent premixed methane combustion in a constant volume vessel are carried with initial Karlovitz numbers (Ka) of 1.0, 10.0, and 30.0. Local flame–wall quenching positions are identified based on the local fuel consumption speed during the turbulent combustion process, and the local FWI events have been classified into four quenching modes according to the flame–wall geometric relationships of quenching positions, namely head-on quenching (HOQ), oblique-wall quenching, side-wall quenching (SWQ), and back-on quenching (BOQ). The results show that in the case with higher initial Ka, the flame surface shows a more complicated wrinkled structure due to the flame–turbulence interaction. Meanwhile, the local quenching distance defined based on the identified quenching position is strongly influenced by the near-wall flow, and the range of the local quenching mode extends further to BOQ. However, for all three cases, HOQ and near-HOQ modes account for the majority of local FWI. Wall heat flux and heat release rate (HRR) of near-wall reaction yield high values for the FWI under HOQ or BOQ and are low for SWQ. In addition, there is a discrepancy in the near-wall transportation of some species under different quenching modes, which further leads to the difference in FWI-induced near-wall reaction regarding its total and elementary HRR.
研究了局部火焰-壁面相互作用(FWI)的猝灭方式对不同湍流强度的响应,以及对猝灭距离、壁面热流密度和近壁面反应的影响。为此,在初始Karlovitz数(Ka)分别为1.0、10.0和30.0的条件下,对定容容器内的湍流预混甲烷燃烧进行了直接数值模拟。根据湍流燃烧过程中局部燃油消耗速度确定局部火焰壁淬火位置,并根据淬火位置的火焰壁几何关系将局部火焰wi事件划分为4种淬火模式,即正淬(HOQ)、斜壁淬火(斜壁淬火)、侧壁淬火(SWQ)和反向淬火(BOQ)。结果表明,在初始Ka较高的情况下,由于火焰-湍流相互作用,火焰表面呈现出更为复杂的褶皱结构。同时,根据确定的淬火位置确定的局部淬火距离受近壁流的影响较大,局部淬火方式的范围进一步扩展到物料清单。然而,在这三种情况下,居屋和近居屋模式占本地wi的大部分。近壁反应的壁面热流密度和热释放率(HRR)在总质量和总排水量条件下高,在总排水量条件下低。此外,在不同的淬火模式下,一些物质的近壁输运存在差异,这进一步导致了fwi诱导的近壁反应在总HRR和基本HRR上的差异。
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引用次数: 0
Hydrodynamic instability of premixed tubular flame stabilized in stretched rotating flow 预混管状火焰在拉伸旋转流中稳定的流体力学不稳定性
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-05-02 DOI: 10.1080/13647830.2023.2204065
S. Minaev, E. Dats, K. Shtym
The paper analyzes the hydrodynamic instability of a cylindrical flame stabilized in a converging rotating gas flow simulating the flow in a cyclone combustion chamber. The analysis was carried out within the framework of a two-dimensional model describing the gas flow with radial and tangential supply of combustible gas through the walls of a cylindrical chamber. In the stationary case, the gas flow in combustion products and the combustible mixture is described by the solution for a rotating tornado-shaped vortex. The rotation of the gas creates a centrifugal force, which has a stabilizing effect on the flame perturbations. The dependences of the perturbations growth rate on the wave vector of perturbations, the radial and tangential inlet gas velocities, and other parameters of the problem are obtained. The analytical criterion of neutral stability separating regions of stable flame with respect of any perturbations and flame instability in the plane of radial and tangential velocities is obtained. In the absence of rotation and at the large flame radii, the model converts into the Landau- Darrieus model of flame hydrodynamic instability.
本文分析了圆柱形火焰在收敛旋转气流中稳定的流体动力学不稳定性,模拟了旋流燃烧室中的流动。分析是在二维模型的框架内进行的,该模型描述了通过圆柱形腔室壁径向和切向供应可燃气体的气流。在静止情况下,燃烧产物和可燃混合物中的气体流动由旋转龙卷风形涡流的解描述。气体的旋转产生离心力,对火焰扰动具有稳定作用。得到了扰动增长率与扰动波矢量、径向和切向进气速度以及问题的其他参数的关系。得到了在径向和切向速度平面上,稳定火焰在任何扰动和火焰不稳定性下的中性稳定分离区的解析准则。在没有旋转和火焰半径较大的情况下,该模型转化为火焰流体动力学不稳定性的Landau-Darrieus模型。
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引用次数: 0
How random fluctuations can generate and suppress complex oscillatory regimes in continuous stirred tank reactors 随机波动如何在连续搅拌槽式反应器中产生和抑制复杂的振荡状态
IF 1.3 4区 工程技术 Q4 ENERGY & FUELS Pub Date : 2023-04-27 DOI: 10.1080/13647830.2023.2206379
I. Bashkirtseva, L. Ryashko
Motivated by important chemical engineering applications, we study probabilistic mechanisms of stochastic effects in a randomly forced model of the continuous stirred tank reactor. The bifurcation analysis of the deterministic model reveals the parameter zone of bistability with coexistence of the equilibrium and oscillatory regimes. It is shown that the boundary between basins of these regimes is moving as the bifurcation parameter changes. We study noise-induced transitions across this boundary leading to the stochastic generation of spiking oscillations and backward effect of the noise-induced suppression of large-amplitude spiking. In the study of these stochastic effects, we use statistics extracted from the direct numerical simulation, and an analytical approach using confidence ellipses method. An important probabilistic phenomenon of coherence resonance is revealed and discussed.
受重要化学工程应用的启发,我们研究了连续搅拌釜反应器随机强迫模型中随机效应的概率机制。确定性模型的分岔分析揭示了平衡态和振荡态共存的双稳态参数区。结果表明,随着分叉参数的变化,这些区域盆地之间的边界是移动的。我们研究了噪声引起的跨越该边界的跃迁,该跃迁导致尖峰振荡的随机产生以及噪声引起的大幅度尖峰抑制的反向效应。在研究这些随机效应时,我们使用了从直接数值模拟中提取的统计数据,以及使用置信椭圆法的分析方法。揭示并讨论了相干共振的一个重要概率现象。
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引用次数: 0
期刊
Combustion Theory and Modelling
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