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I. Size effects in combustion of isolated methanol droplets II. Autoignition in unstrained, laminar mixing layers.

机译：I.分离的甲醇液滴燃烧中的尺寸效应II。在无应变的层流混合层中自燃。

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摘要

The droplet simulations focus on the effects of droplet size variation on its combustion characteristics. A gradual transition from a kinetically controlled regime of small droplets to a diffusion controlled regime of large droplets is shown. With reduction in the droplet size, the flame-sheet approximation breaks down, and the flame becomes a larger reactive zone relative to the droplet, along with a concomitant reduction in the flame temperature. Fuel vapour accumulation and depletion affects the entire burning history significantly, and combustion characteristics, such as burning rate, and flame stand-off ratio are time dependent, with increasing unsteadiness with reduction in size.;The mixing layer simulations focus on the time evolution of the ignition kernel of different fuels in the oxidizer stream of standard air at 1200 K. Detailed investigations are presented for methanol/air and hydrogen/air mixing layers. Limited investigations for acetylene, ethylene, ethanol, n-heptane, and n-decane are also presented. The volumetric heat release rate during ignition is used to delineate the evolution of the ignition kernel. The results demonstrate a continuous evolution of partially-premixed flame structures into a diffusion flame. For low enough fuel stream temperatures (400 K) ignition is caused by the deflagration travelling from the hot oxidizer stream to the cold fuel stream, as predicted in the literature. With equal fuel and oxidizer stream temperatures (1200 K), for methanol, ethanol, acetylene and ethylene, an additional deflagration is predicted for the first time. Effects on the ignition kernel due to (i) varying fuel stream temperature (400 K to 1200 K), (ii) varying operating pressure (1 bar to 40 bars) and, (iii) varying fuel stream dilution with N2 are also presented.
机译：液滴模拟着重于液滴尺寸变化对其燃烧特性的影响。示出了从小液滴的动力学控制方案到大液滴的扩散控制方案的逐渐过渡。随着液滴尺寸的减小，火焰片近似消失，并且火焰相对于液滴变成更大的反应区，同时伴随着火焰温度的降低。燃料蒸气的积累和消耗会严重影响整个燃烧过程，燃烧特性（如燃烧速率和火焰阻隔率）与时间有关，不稳定程度随尺寸的减小而增加。在1200 K的标准空气氧化剂流中点燃不同燃料的点火核心。详细研究了甲醇/空气和氢气/空气混合层。还介绍了对乙炔，乙烯，乙醇，正庚烷和正癸烷的有限研究。点火期间的体积放热率用于描述点火核的演变。结果表明部分预混的火焰结构不断演变为扩散火焰。如文献中所预测的，对于足够低的燃料流温度（400K），由从热氧化剂流到冷燃料流的爆燃引起点火。在相同的燃料和氧化剂物流温度（1200 K）下，对于甲醇，乙醇，乙炔和乙烯，首次预计会发生额外的爆燃。还提出了由于（i）改变燃料流温度（400 K至1200 K），（ii）改变工作压力（1 bar至40 bar）和（iii）改变燃料流对氮气的稀释而对点火核的影响。

著录项

  • 作者

    Awasthi, Inkant.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Engineering Chemical.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 249 p.
  • 总页数 249
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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