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Detailed simulations of the DLR auto-igniting pulsed jet experiment

机译：DLR自动点火脉冲喷射试验的详细仿真

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摘要

Numerical simulations of an auto-igniting pulsed jet in a vitiated co-flow experiment by DLR (German Aerospace Center) are conducted by highly-resolved large-eddy simulations using direct chemistry with an augmented reduced mechanism. The experiments consist of two operation modes: continuous injection used for code-verification and pulsed injection utilized for fundamental investigation of auto-ignition dynamics. Initially, reference one-dimensional self-igniting counter-flow flames are investigated. Then, a grid convergence study has been performed. It is shown that even a coarser grid would be sufficient to describe the ignition chemistry since the ignition kernel appears at low velocities and fuel-lean conditions in zones of low scalar dissipation rates. For the statistically steady jet, numerical predictions are in a very good agreement with the experiments, giving confidence in the applied models. For the pulsed jet, all of the predicted ignition delay times and locations are in the range of the experimental observations. Time-resolved statistics reveal that thermochemical properties of the gas in a pulsed jet achieve states that are impossible to reproduce in laminar conditions. For further analysis, hydroxyl and formaldehyde are chosen as a marker for the established flame and for the ignition, respectively. In laminar conditions, these two species are perfectly correlated. However, the unsteady dynamics of the pulsed jet invalidates the correlation between the minor species chemistry prior to ignition. This yields the discrepancy in the auto-ignition delay time and the location of the ignition kernel between different pulses, as the thermochemical state needed for the ignition occurs in a random manner.
机译：DLR（德国航空航天中心）在DLR（德国航天中心）中自动点燃脉冲射流的数值模拟通过使用直接化学的高度分辨的大涡流模拟进行，其具有增强的减少机构。实验包括两种操作模式：用于用于对自动点火动态的基本调查的代码验证和脉冲喷射的连续注射。最初，研究了参考一维自点火反流火焰。然后，已经进行了网格收敛研究。结果表明，即使是较粗的网格也足以描述点火化学，因为点火核在低标量耗散速率的区域中的低速和燃料稀释条件下出现。对于统计上稳定的射流，数值预测与实验非常好，对应用模型提供信心。对于脉冲射流，所有预测的点火延迟时间和位置都在实验观察范围内。时间分辨统计显示，脉冲射流中的气体的热化学性质实现在层状条件下不可能繁殖的状态。对于进一步的分析，分别选择羟基和甲醛作为已建立的火焰和点火的标记物。在层流条件下，这两个物种完全相关。然而，脉冲射流的不稳定动态使得在点火之前使次要物种化学之间的相关性无效。这在不同脉冲之间的自动点火延迟时间和点火核的位置处产生差异，因为点火所需的热化学状态以随机方式发生。

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  • 来源
    《Fuel》 |2021年第15期|118947.1-118947.11|共11页
  • 作者

    Inanc E.; Lipkowicz J. T.; Kempf A. M.;

  • 作者单位

    Univ Duisburg Essen Chair Fluid Dynam Inst Combust & Gasdynam IVG Essen Germany;

    Univ Duisburg Essen Chair Fluid Dynam Inst Combust & Gasdynam IVG Essen Germany;

    Univ Duisburg Essen Chair Fluid Dynam Inst Combust & Gasdynam IVG Essen Germany;

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

    Pulsed jets; Large-eddy simulation; Direct chemistry; Ignition; Scalar dissipation rate;

    机译：脉冲喷射;大涡模拟;直接化学;点火;标量耗散率;

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