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In-situ tracking of mixture fraction gradient trajectories and unsteady flamelet analysis in turbulent non-premixed combustion

机译：湍流非预混燃烧中混合分数梯度轨迹的原位跟踪和非稳定小火焰分析

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摘要

Based on in-situ tracking of gradient trajectories in a direct numerical simulation (DNS), this work combines a structural analysis of a turbulent, temporally evolving syngas jet with an extended flamelet model. This flamelet formulation accounts for curvature-induced flame-tangential transport effects and is formulated in a Lagrangian manner. Using the in-situ trajectory tracking algorithm flamelets are tracked in time and space, and for the first time complete unsteady flamelet histories are reconstructed for further analysis. By extracting all relevant flamelet parameters from the DNS, solutions for the flamelet equations in mixture fraction space with and without flame-tangential transport effects are studied and discussed together with budgets of the equations. Although the overall flamelet structure is compliant with laminar flamelet theory, significant departures from classical flamelet realizations are observed for the scalar dissipation rate. Thus, in addition to flamelets in the classical flamelet regime (no significant flame-tangential transport), additional flamelet structures with non-negligible multi-dimensional effects are observed and both types are analyzed in detail. It is shown how the regime classification is influenced by the relative magnitude of scalar dissipation rate and curvature, two quantities related to the topology of mixture fraction isosurfaces. These surfaces exhibit both regions of high curvature and sheet-like structures. The dynamic interplay of compressive and extensive strain, curvature, and scalar dissipation rate is further studied with a formulation of the scalar dissipation rate equation which accounts for variable thermo-chemical properties. The results illustrate how the topological structure of the mixture fraction field interacts with the flamelet structure. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：基于直接数值模拟（DNS）中梯度轨迹的原位跟踪，这项工作将湍流随时间变化的合成气射流的结构分析与扩展的小火焰模型相结合。该小火焰配方解释了由曲率引起的火焰切向传输效应，并以拉格朗日方式配制。使用原位轨迹跟踪算法，可在时间和空间上跟踪小火焰，并首次重建完整的非稳定小火焰历史，以进行进一步分析。通过从DNS中提取所有相关的小火焰参数，研究和讨论了混合分数空间中具有和不具有火焰切向传输效应的小火焰方程的解，并与方程预算一起进行了讨论。尽管总体小火焰结构符合层流小火焰理论，但在标量耗散率方面却观察到与经典小火焰实现的重大偏离。因此，除了经典小火焰状态下的小火焰（没有明显的火焰切向传输）之外，还观察到了具有不可忽略的多维效应的其他小火焰结构，并对这两种类型进行了详细分析。它显示了状态分类如何受到标量耗散率和曲率的相对大小的影响，标量耗散率和曲率是与混合分数等值面拓扑有关的两个量。这些表面既具有高曲率区域又具有片状结构。压缩和广泛的应变，曲率和标量耗散率之间的动态相互作用通过标量耗散率方程的公式进一步研究，该方程考虑了可变的热化学性质。结果说明了混合分数场的拓扑结构如何与小火焰结构相互作用。 （C）2016年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

著录项

  • 来源
    《Combustion and Flame》 |2017年第1期|243-258|共16页
  • 作者

    Scholtissek A.; Dietzsch F.; Gauding M.; Hasse C.;

  • 作者单位

    Tech Univ Bergakad Freiberg, Inst Energy Proc Engn & Chem Engn, Numer Thermofluid Dynam, Freiberg, Germany;

    Tech Univ Bergakad Freiberg, Inst Energy Proc Engn & Chem Engn, Numer Thermofluid Dynam, Freiberg, Germany;

    Tech Univ Bergakad Freiberg, Inst Energy Proc Engn & Chem Engn, Numer Thermofluid Dynam, Freiberg, Germany;

    Tech Univ Bergakad Freiberg, Inst Energy Proc Engn & Chem Engn, Numer Thermofluid Dynam, Freiberg, Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Turbulent combustion; Flamilet analysis; Curvature effects; In-situ trajectory tracking;

    机译：湍流燃烧;火焰分析;曲率效应;原位轨迹跟踪;

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