Large Eddy Simulation of the evolution of the soot size distribution in turbulent nonpremixed bluff body flames

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-06-18 DOI:10.1016/j.combustflame.2025.114282

Hernando Maldonado Colmán, Michael E. Mueller

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引用次数: 0

Abstract

Large Eddy Simulation (LES) is used to investigate the evolution of the soot size distribution in a series of turbulent nonpremixed bluff body flames, with different bluff body diameters. The new Bivariate Multi-Moment Sectional Method (BMMSM) is employed to characterize the size distribution. BMMSM combines elements of sectional methods and methods of moments and is capable of reproducing fractal aggregate morphology, thanks to its joint volume-surface formulation, all at relatively low computational cost with fewer transported soot scalars compared to traditional sectional methods. LES results show soot volume fraction profiles agreeing correctly with the experimental measurements, exhibiting significant improvement compared to previous work using the Hybrid Method of Moments (HMOM). The evolution of the particle size distribution function (PSDF) was examined across the flame series and shows that the shape of the size distribution is less sensitive to the bluff body diameter than the overall soot volume fraction, which increases with increasing bluff body diameter. The PSDF across the flame exhibit different features compared to turbulent nonpremixed jet flames. The recirculation zone exhibits a nearly bimodal size distribution, which eventually becomes bimodal in the downstream jet-like region. The rather stark differences in the soot volume fraction predicted by HMOM and BMMSM are due to subtle differences in soot oxidation that are amplified in this configuration due to coupling to the flow field via soot radiation. With HMOM, the inner vortex between the central jet and recirculation zone is weaker, leading to significant soot leakage from the recirculation zone nearer the centerline. With BMMSM, the inner vortex is stronger, leading to a longer recirculation zone but with far less soot leakage and nearer the tip of the recirculation zone away from the centerline. The net result is much larger soot nucleation and condensation rates with BMMSM in both the recirculation zone and jet-like region, comparable to surface growth and oxidation, which dominate with HMOM. This work reveals that accounting for the size distribution can be crucial to both predicting global soot quantities accurately and reproducing fundamental mechanisms at least in some flame configurations.

Novelty and Significance Statement

For the first time, the evolution of the soot size distribution in a series of turbulent nonpremixed bluff body flames is investigated, by leveraging the recently developed Bivariate Multi-Moment Sectional Method (BMMSM) and using Large Eddy Simulation (LES). The analysis includes a comprehensive discussion of the evolution of the soot size distribution in the flame series. Finally, BMMSM predicts even the mean soot volume fraction much more accurately than the Hybrid Method of Moments (HMOM), due to amplifications of subtle differences in the models on soot and its feedback on the flow field through radiation, indicating that consideration of the soot size distribution may be required to accurately predict soot global quantities and unravel fundamental mechanisms in some turbulent sooting flames.

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湍流非预混钝体火焰中烟尘粒径分布演变的大涡模拟

采用大涡模拟（LES）方法研究了不同钝体直径的非预混钝体湍流火焰中烟灰粒径分布的演变规律。采用新的二元多矩截面法（BMMSM）来表征尺寸分布。BMMSM结合了截面法和矩量法的元素，由于采用了体积-曲面联合公式，能够再现分形集合体形态，与传统的截面法相比，计算成本相对较低，输运的烟灰标量较少。LES结果表明，烟尘体积分数分布与实验测量结果吻合，与之前使用混合矩量法（HMOM）的工作相比有了显著改善。粒径分布函数（PSDF）在火焰序列上的演化表明，粒径分布的形状对钝体直径的敏感性较低，而总体烟尘体积分数随钝体直径的增加而增加。与湍流非预混射流火焰相比，火焰上的PSDF表现出不同的特征。再环流区大小分布呈近似双峰分布，最终在下游射流区变为双峰分布。HMOM和BMMSM预测的烟尘体积分数的明显差异是由于烟尘氧化的细微差异，在这种配置中，由于烟尘辐射与流场的耦合，这种差异被放大了。采用HMOM时，中心射流与再循环区之间的内涡较弱，导致靠近中心线的再循环区有明显的烟尘泄漏。BMMSM内涡较强，导致再循环区较长，但漏烟少，且离中心线更靠近再循环区顶端。结果表明，在再循环区和射流区，BMMSM的成核速率和凝结速率都要大得多，与HMOM的表面生长和氧化速率相当。这项工作表明，计算尺寸分布对于准确预测全球烟灰数量和至少在某些火焰构型中重现基本机制至关重要。新颖性和意义声明利用新近发展的二元多矩截面法（BMMSM）和大涡模拟（LES），首次研究了一系列湍流非预混钝体火焰中煤烟粒径分布的演变。该分析包括对火焰系列中煤烟尺寸分布的演变进行了全面的讨论。最后，由于烟尘模型及其通过辐射对流场的反馈放大了细微差异，BMMSM预测平均烟尘体积分数的准确性也远高于混合矩量法（HMOM），这表明在某些湍流烟尘火焰中，可能需要考虑烟尘粒径分布来准确预测烟尘的全球数量并揭示其基本机制。

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.