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Autoignited lifted flames of dimethyl ether in heated coflow air

机译：在加热的气流中自动点燃二甲醚的火焰

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摘要

Autoignited lifted flames of dimethyl ether (DME) in laminar nonpremixed jets with high-temperature coflow air have been studied experimentally. When the initial temperature was elevated to over 860 K, an autoignition occurred without requiring an external ignition source. A planar laser-induced fluorescence (PLIF) technique for formaldehyde (CH2O) visualized qualitatively the zone of low temperature kinetics in a premixed flame. Two flame configurations were investigated; (1) autoignited lifted flames with tribrachial edge having three distinct branches of a lean and a rich premixed flame wings with a trailing diffusion flame and (2) autoignited lifted flames with mild combustion when the fuel was highly diluted. For the autoignited tribrachial edge flames at critical autoignition conditions, exhibiting repetitive extinction and re-ignition phenomena near a blowout condition, the characteristic flow time (liftoff height scaled with jet velocity) was correlated with the square of the ignition delay time of the stoichiometric mixture. The liftoff heights were also correlated as a function of jet velocity times the square of ignition delay time. Formaldehydes were observed between the fuel nozzle and the lifted flame edge, emphasizing a low-temperature kinetics for autoignited lifted flames, while for a non-autoignited lifted flame, formaldehydes were observed near a thin luminous flame zone.For the autoignited lifted flames with mild combustion, especially at a high temperature, a unique non-monotonic liftoff height behavior was observed; decreasing and then increasing liftoff height with jet velocity. This behavior was similar to the binary mixture fuels of CH4/H2and CO/H2observed previously. A transient homogeneous autoignition analysis suggested that such decreasing behavior with jet velocity can be attributed to partial oxidation characteristics of DME in producing appreciable amounts of CH4/CO/H2ahead of the edge flame region.
机译：实验研究了层状非预混射流中带有高温同流空气的二甲醚（DME）的自燃火焰。当初始温度升高到860 K以上时，不需要外部点火源即可进行自燃。用于甲醛（CH2O）的平面激光诱导荧光（PLIF）技术定性地可视化了预混火焰中的低温动力学区域。研究了两种火焰形态； （1）具有三臂边缘的自动点燃的提升火焰，具有三个明显的稀薄分支和浓的预混火焰翅片，并带有尾随扩散火焰；（2）当燃料高度稀释时，在轻度燃烧下自动点燃的火焰。对于临界自燃条件下的自燃三臂边缘火焰，在井喷条件下表现出反复的熄灭和再燃现象，特征流动时间（升空高度与射流速度成比例）与化学计量混合物的点火延迟时间的平方相关。升空高度也与射流速度乘以点火延迟时间的平方有关。在燃料喷嘴和火焰上升边缘之间观察到甲醛，强调了自燃火焰的低温动力学特性，而对于非自燃火焰，则在较薄的发光火焰区域观察到了甲醛。燃烧，特别是在高温下，观察到独特的非单调升空高度行为；然后随着射流速度降低升空高度，然后升高。这种行为类似于先前观察到的CH4 / H2和CO / H2的二元混合燃料。瞬态均质自燃分析表明，这种随射流速度降低的行为可归因于DME在边缘火焰区域前方产生大量CH4 / CO / H2时产生的部分氧化特征。

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  • 来源
    《Combustion and Flame》 |2018年第9期|75-83|共9页
  • 作者

    Saeed M. Al-Noman; Byung Chul Choi; Suk Ho Chung;

  • 作者单位

    Research and Development Department, Saudi Electricity Company;

    Research and Development Center, Korean Register of Shipping;

    Clean Combustion Research Center, King Abdullah University of Science and Technology;

  • 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

    Autoignition; Tribrachial flame; DME;

    机译：自燃;三臂火焰;DME;

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