MILD combustion in diffusion-controlled regimes of Hot Diluted Fuel
MILD combustion in diffusion-controlled regimes of Hot Diluted Fuel
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DOI：
10.1016/j.combustflame.2012.01.013
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发表时间：
2012-05-01
影响因子：
4.4
通讯作者：
Cavaliere, A.
中科院分区：
文献类型：
--
作者：
de Joannon, M.;Sorrentino, G.;Cavaliere, A.
在中等或强烈的低氧稀释(温和)燃烧条件下，在热燃料和稀释燃料的中等或强烈的低氧(温和)燃烧条件下，在密集的参数网格上的稳定的层流、一维混合层中的反应结构已经被表征。用标准程序和标准动力学模式研究了不同拉伸速率范围和两个参考压力(1和10bar)下混合分数空间中的温度和放热分布。在反应结构分析中，前人的工作指出了三个综合特征来区分不同燃烧状态的发生。这些特征包括氧化结构的厚度，热解区域的存在/不存在，以及最大放热区域与混合物化学计量比区域之间的相关/不相关。在相同的准则下，建立了固定拉伸率和不同压力下进气燃料温升平面上的区域图。指出在热稀释燃料的扩散控制区域中，温和的燃烧条件具有火焰增厚和热解抑制的特征，这也是典型的无焰燃烧。此外，最大放热区域与化学计量区域通常具有很高的相关性。因此，温和燃烧模式不同于在其他扩散控制模式中发现的温和燃烧模式，在这些扩散控制模式中，最大放热区域通常与化学计量比区域无关。在本文提出的情况下，只有第二个解，对应于在很宽的拉伸速率范围内发生的很低的转化率，表明放热与化学计量混合分数之间没有相关性。这种行为归因于甲烷的氧化热解。在常压下，如果燃料被稀释，这种无名特征延伸到低水平的预热，从而导致低水平的温度升高，从而证实了温和和无焰状态并不是在所有可能的进料条件下都是一致的。总的来说，在这些热燃料-稀释燃料条件下获得的结果与文献中报道的热氧化物-稀释燃料、热氧化物和稀释燃料条件下的结果一致并扩展，支持了这些入口参数是定义温和燃烧的合适选择的断言。(C)2012年，燃烧研究所。爱思唯尔公司出版，版权所有。
Reactive structures have been characterized in a steady laminar, unidimensional mixing layer on a dense grid of parameters in moderate or intense low-oxygen dilution (MILD) combustion conditions with hot and diluted fuel. The structures have been studied in terms of temperature and heat release profiles in a mixture fraction space for various ranges of stretch rates and for two reference pressures (1 and 10 bar) using a standard code and standard kinetic scheme.In the analysis of reactive structure three synthetic characteristics have been pointed out in previous works as discriminative for the occurrence of different combustion regimes. Such characteristics are the thickness of the oxidation structures, the presence/absence of a pyrolysis region and the correlation/no correlation of the regions of maximum heat release with those at which the mixture is stoichiometric. Following the same criteria, maps of regimes have been built up on a inlet fuel temperature - temperature increase plane for fixed stretch rates and different pressures.It has been pointed out that in diffusion controlled regimes of Hot Diluted Fuel, analysed in this paper, MILD combustion conditions are characterized by flame thickening and pyrolysis depression, which are also typical of flameless combustion. In addition, the region of maximum heat release has a generally high level of correlation with the stoichiometric regions. Thus, MILD combustion regime differs from MILD combustion regime found in other diffusion controlled regimes where the region of maximum heat release is generally not correlated with the stoichiometric regions. In the case presented in this paper, only a second solution, corresponding to a very low conversion occurring in a very wide stretch-rate range, shows no correlation between heat release and stoichiometric mixture fraction. This behavior has been attributed to the oxidative pyrolysis of methane.At atmospheric pressure, the nameless characteristics extend to a low level of preheating, provided that the fuel is diluted, with a consequently low level of temperature increase, thus confirming that MILD and flameless regimes are not coincident in all possible feeding conditions.In general, the results obtained in these Hot-Fuel-Diluted-Fuel conditions are consistent with and extend those reported in the literature for Hot-Oxidant-Diluted-Fuel, Hot-Oxidant and Diluted-Fuel conditions, supporting the assertion that these inlet parameters are a suitable choice for the definition of MILD combustion. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.