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Low-frequency AC electric field induced thermoacoustic oscillation of a premixed stagnation flame

机译：低频交流电场引起的预混滞止火焰的热声振荡

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摘要

We present a novel phenomenon of low-frequency AC electric field induced thermoacoustic oscillations by employing a wall jet premixed stagnation flame configuration. A high speed camera and a microphone are used to record the instantaneous flame topographies and the acoustic oscillations, respectively. We find that, under manipulations of the AC electric field, the acoustic oscillation occurs after the flame transits from a 'disc' mode to an 'envelope' mode. The observed correlation between the changing rates of the flame surface area and the pressure fluctuations in the time domain indicates a significant contribution from the unsteady heat release to the acoustic oscillation; meanwhile, the other possible mechanism, i.e. the direct impact of oscillating electric body force on the generated pressure wave, can be ruled out based on a theoretical analysis of a pressure wave equation. The oscillating behaviors of the flame front show that the electric field drives the movement of the flame cusp with a large stretch rate. Assessment of the current density distribution of the weakly-ionized flame plasma is conducted by non-dimensionalizing the convective-diffusive-reactive equation, estimating the electric conductivity, and solving Ohm's Law. This simplified model divulges that the non-uniform current density induces large perturbations at the corner positions of the flame front. The unsteady flame fronts strongly influence the current response of the flame, which indicates a self-looping process among the flame current, the electric body force and the flame reaction rate. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：通过使用壁射流预混滞止火焰配置，我们提出了一种低频交流电场引起的热声振荡的新现象。高速摄像机和麦克风分别用于记录瞬时火焰形貌和声振荡。我们发现，在交流电场的控制下，火焰从“盘”模式转变为“包络”模式后，会发生声波振荡。观察到的火焰表面积变化率与时域压力波动之间的相关性表明，不稳定的热释放对声波振荡起了很大的作用。同时，基于压力波方程的理论分析，可以排除其他可能的机制，即，振荡的电场力对所产生的压力波的直接影响。火焰前沿的振荡行为表明，电场以较大的拉伸速率驱动火焰尖端的运动。通过对流扩散反应方程进行无量纲化，估算电导率并求解欧姆定律，可对弱电离火焰等离子体的电流密度分布进行评估。这个简化的模型揭示了不均匀的电流密度会在火焰前角的位置引起较大的扰动。不稳定的火焰前沿强烈影响火焰的电流响应，这表明火焰电流，电场力和火焰反应速率之间存在自循环过程。 （C）2016年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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  • 来源
    《Combustion and Flame》 |2017年第2期|479-488|共10页
  • 作者

    Ren Yihua; Li Shuiqing; Cui Wei; Zhang Yiyang; Ma Lin;

  • 作者单位

    Tsinghua Univ, Minist Educ, Dept Thermal Engn, Key Lab Thermal Sci & Power Engn, Beijing 100084, Peoples R China;

    Tsinghua Univ, Minist Educ, Dept Thermal Engn, Key Lab Thermal Sci & Power Engn, Beijing 100084, Peoples R China;

    Tsinghua Univ, Minist Educ, Dept Thermal Engn, Key Lab Thermal Sci & Power Engn, Beijing 100084, Peoples R China;

    Tsinghua Univ, Minist Educ, Dept Thermal Engn, Key Lab Thermal Sci & Power Engn, Beijing 100084, Peoples R China|Tsinghua Univ, Minist Educ, Inst Nucl & New Energy Technol, Key Lab Adv Reactor Engn & Safety, Beijing 100084, Peoples R China;

    Virginia Tech, Dept Aerosp & Ocean Engn, Blacksburg, VA 24060 USA;

  • 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

    AC electric field; Premixed stagnation flame; Thermoacoustic oscillation; Electric body force;

    机译：交流电场;预混滞止火焰;热声振荡;电动势;

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