Experimental and modeling study of the effects of adding oxygenated fuels to premixed n-heptane flames
Experimental and modeling study of the effects of adding oxygenated fuels to premixed n-heptane flames
复制标题
添加含氧燃料对预混正庚烷火焰影响的实验和模型研究
DOI：
10.1016/j.combustflame.2012.02.020
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发表时间：
2012-07-01
影响因子：
4.4
通讯作者：
Qi, Fei
中科院分区：
文献类型：
--
作者：
Chen, Gen;Yu, Wu;Qi, Fei
采用同步辐射光电离和分子束质谱（PI-MBMS）技术研究了甲醇、二甲氧基甲烷（DMM）和碳酸二甲酯（DMC）对低压正庚烷层流预混火焰的影响。总的C/O比保持恒定（0.507），并且对于所有测试的火焰，当量比保持在1.6左右。调整未燃烧混合物的组成，使得对于所有测试条件，火焰后温度几乎相等。摩尔分数配置文件的主要和中间物种的推导和火焰之间的比较。并行计算进行了修改后的模型的基础上，预测的火焰物种的浓度与测量结果相当吻合。在DMC掺杂的火焰中观察到CO2的早期产生。反应通量分析表明，这是由CH 3 OC =O自由基、DMC分子和CH 3 OC =OO自由基的分解引起的。随着含氧燃料的加入，大部分C1 ~ C5烃类中间产物的浓度降低，苯（C6 H6）的浓度也明显降低，且苯的降低程度在含氧燃料火焰中差异不大。反应通量分析表明，在所有火焰中，小分子化合物生成C6 H6的主要途径是C3 + C3反应，包括炔丙基自由基（C3 H3）的自复合反应和C3 H3与烯丙基自由基（a-C3 H5）的交叉反应。考虑到所测试的火焰的温度几乎是相等的，当掺杂含氧燃料时，C6 H6浓度的降低应该是由于其前体物浓度的降低。此外，还检查了某些含氧中间体的浓度。甲醛（CH_2 O）的浓度被发现增加时，火焰中掺杂含氧燃料，而乙醛（CH_3CHO）和乙烯醇（C_2 H_3OH）的浓度几乎相等的所有火焰。甲酸甲酯（CH 3 OCHO）仅在DMM掺杂的火焰中被检测到，这归因于CH 3 OCHOCH 3自由基在火焰中分解形成CH 3 OCHO的有效途径。(C)2012燃烧研究所爱思唯尔公司出版All rights reserved.
The effects of methanol, dimethoxymethane (DMM), and dimethylcarbonate (DMC) on laminar premixed low pressure (30 Torr) n-heptane flames were investigated by using synchrotron photoionization and molecular-beam mass spectrometry (PI-MBMS) techniques. The overall C/O ratio was maintained constant (0.507) and the equivalence ratio was kept around 1.6 for all the tested flames. The composition of unburned mixtures was adjusted such that the post-flame temperatures were nearly equivalent for all the test conditions. Mole fraction profiles of major and intermediate species were derived and compared among the flames. Parallel computations were performed based on a modified model, and the predicted concentrations of flame species agree reasonably well with the measured results. Early production of CO2 was observed in the DMC-doped flame. Reaction flux analysis suggested that it was caused by the decomposition of CH3OC=O radical, DMC molecule and CH3OC=OO radical. As oxygenated fuels were added, the concentrations of most C-1-C-5 hydrocarbon intermediates were reduced while that of benzene (C6H6) also decreased apparently, and the extent of benzene reduction showed little difference among the oxygenate-doped flames. Reaction flux analysis indicated that, in all the tested flames, the primary pathway leading from small aliphatics to C6H6 was through C-3 + C-3 reactions, including the self-recombination reaction of propargyl radical (C3H3) and the cross reaction between C3H3 and allyl radical (a-C3H5). Considering that the temperatures of the tested flames were almost equivalent, the reduction of C6H6 concentration when doped with oxygenated fuels should be resulted from the reduced concentrations of its precursors. Furthermore, concentrations of certain oxygenated intermediates were also examined. The concentration of formaldehyde (CH2O) was found to increase when flames were doped with oxygenated fuels, while those of acetaldehyde (CH3CHO) and vinyl alcohol (C2H3OH) were nearly equivalent for all the flames. Methyl formate (CH3OCHO) was detected only in the DMM-doped flame, which was attributed to the efficient CH3OCHO formation pathway through the decomposition of CH3OCHOCH3 radical in the flame. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.