Analysis of kinetic models for rich to ultra-rich premixed CH4/air weak flames using a micro flow reactor with a controlled temperature profile
Analysis of kinetic models for rich to ultra-rich premixed CH4/air weak flames using a micro flow reactor with a controlled temperature profile
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DOI：
10.1016/j.combustflame.2019.04.041
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发表时间：
2019-08
影响因子：
4.4
通讯作者：
A. Dubey;T. Tezuka;S. Hasegawa;H. Nakamura;K. Maruta
中科院分区：
文献类型：
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作者：
A. Dubey;T. Tezuka;S. Hasegawa;H. Nakamura;K. Maruta
甲烷燃烧中芳香族化合物的形成仍不清楚。建立芳烃形成动力学模型的第一步是了解富燃料氧化以及在不同温度和当量比条件下乙炔和乙烯等芳烃前体的形成。这种理解对于优化富含燃料条件下的甲烷部分氧化也很有用。基于这一观点，当前的工作采用微流反应器对当量比在 1.7 至 6.0 之间的富含燃料但无烟尘的预混合甲烷/空气火焰进行研究，规定温度梯度从 300K 到最高温度 1200K，并研究了代表燃料点火行为的弱火焰。使用带有热导检测器的气相色谱仪 (GC-TCD) 测量主要稳定物质 CH4、CO、CO2、C2H6、C2H4 和 C2H2 的浓度。使用现有动力学模型、GRI 3.0、SD 2016 (San Diego mech)、KAUST (USC II) 和 ARAMCO 1.3 进行一维反应流模型计算。研究了弱火焰结构随当量比变化的变化。 KAUST (USC II) 很好地预测了当量比为 2.0 和 6.0 时的弱火焰位置，但物种摩尔分数的预测不太好。研究发现，CH3+O2 <=> CH2O+OH (SD 2016) 和 CH3+HO2 <=> CH3O+OH (GRI 3.0) 比率较高的模型可预测上游弱火焰位置，从而预测较高的反应性。然而，SD 2016 和 GRI 3.0 更好地预测了物质摩尔分数，特别是在较高当量比的情况下。当前工作中使用的所有机制在此处讨论的所有当量比下都低估了 C2H2 的摩尔分数四到五倍。反应路径分析显示动力学模型之间存在显着差异。特别是，CH3的消耗途径在不同的动力学模型中差异很大，导致不同的反应性。讨论了现有机制预测当前富燃料到超富燃料甲烷燃烧的灵活性和适用性。 HO2自由基在高压下通常很重要，但在当前燃料丰富的条件下也很重要。
Aromatic formation in methane combustion is still not well understood. The first step to build kinetic models for aromatic formation is to understand fuel-rich oxidation and formation of aromatic precursors like acetylene and ethylene in varied temperature and equivalence ratio conditions. This understanding is also useful to optimize partial oxidation of methane in fuel-rich conditions. With this view, the current work presents investigation of fuel-rich but non-sooting premixed methane/air flames for equivalence ratios between 1.7 and 6.0 using a micro flow reactor with a prescribed temperature gradient from 300 K up to maximum temperature of 1200 K. Weak flames which represent the ignition behavior of fuel were studied. Concentrations of major stable species, CH4, CO, CO2, C2H6, C2H4and C2H2were measured using a gas chromatograph with a thermal conductivity detector (GC-TCD). Computations with 1-D reactive flow model using existing kinetic models, GRI 3.0, SD 2016 (San Diego mech), KAUST (USC II) and ARAMCO 1.3 were performed. Change in weak flame structure with change in equivalence ratio was studied. KAUST (USC II) predicted the weak flame positions very well at both equivalence ratios of 2.0 and 6.0, but species mole fractions were not so well predicted. It was found that models with higher rates of CH3+O2<=> CH2O+OH (SD 2016) and CH3+HO2<=> CH3O+OH (GRI 3.0) predicted upstream weak flame positions and thus higher reactivity. However, SD 2016 and GRI 3.0 predicted species mole fractions better, particularly at higher equivalence ratios. All the mechanisms used in the current work underpredicted the mole fractions of C2H2by factors of four to five at all equivalence ratios addressed here. Reaction path analysis showed significant differences among kinetic models. Particularly, consumption pathways of CH3vary greatly among kinetic models leading to different reactivity. Flexibility and applicability of existing mechanisms to predict the current fuel-rich to ultra-fuel-rich CH4combustion was discussed. HO2radicals, which are generally important at high pressures are found to be significant in current fuel-rich conditions.