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首页> 外文期刊>Combustion and Flame >Analysis of CH* concentration and flame heat release rate in laminar coflow diffusion flames under microgravity and normal gravity
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Analysis of CH* concentration and flame heat release rate in laminar coflow diffusion flames under microgravity and normal gravity

机译：微重力和法向重力作用下层流共流扩散火焰中CH *浓度和火焰放热率分析

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The chemiluminescence from electronically excited CH (denoted as CH*) is investigated in nitrogen diluted laminar coflow methane diffusion flames under microgravity and normal gravity conditions. In combustion studies, this radical species is of significant interest since its spatial distribution is indicative of the flame front position; moreover, given the relatively simple diagnostic involved with its measurement, several studies have been done to evaluate the ability of CH* chemiluminescence to predict the total and local flame heat release rate. In this work, a subset of the publicly available NASA Structure and Liftoff in Combustion Experiments (SLICE) microgravity and normal gravity nitrogen-diluted methane flames has been considered, and a method to extract quantitative CH* concentration information from the SLICE raw data is demonstrated. The measured CH* concentration is then discussed and compared with numerical simulations to assess the correlation between CH* chemiluminescence and heat release rate. The spectral characterization of the digital single lens reflex (DSLR) color camera used to acquire the flame images allowed the signal collected by the blue channel to be considered representative of the CH* emission of the A(2)Delta -> X-2 Pi transition centered around 431 nm; the analysis of the spectral emission of a reference nitrogen-diluted laminar diffusion methane flame accounted for the contribution of chemiluminescence from emitting species other than CH*. Due to the axisymmetric flame structure, an Abel deconvolution of the line-of-sight chemiluminescence was used to obtain the two-dimensional intensity profile and, thanks to an absolute light intensity calibration, a quantification of the CH* concentration was possible. Comparisons with numerical results display reasonably good agreement between measured and computed flame shapes, and it is shown that the difference in peak CH* concentration, between micro and normal gravity cases, is minimal. Independent of the gravity level, the integrated CH* concentration in a cross section scales proportionally to the integrated computed heat release rate. The two-dimensional CH* and heat release rate spatial profiles match in a satisfactory way, but the gradients and intensity distributions are not comparable. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
机译：在微重力和正常重力条件下，在氮气稀释的层流共流甲烷扩散火焰中研究了电子激发的CH（表示为CH *）的化学发光。在燃烧研究中，这种自由基物质引起人们极大的兴趣，因为其空间分布表明了火焰的前沿位置。此外，鉴于其测量涉及的诊断相对简单，已进行了多项研究以评估CH *化学发光预测总火焰释放率和局部火焰放热率的能力。在这项工作中，已经考虑了可公开获得的NASA燃烧实验中的结构和升空（SLICE）微重力和正常重力下的氮气稀释的甲烷火焰的子集，并展示了一种从SLICE原始数据中提取定量CH *浓度信息的方法。 。然后讨论测量的CH *浓度，并将其与数值模拟进行比较，以评估CH *化学发光与放热速率之间的相关性。用于获取火焰图像的数字单镜反光（DSLR）彩色相机的光谱表征允许将蓝色通道收集的信号视为代表A（2）Delta-> X-2 Pi的CH *发射跃迁集中在431 nm附近;对参考氮稀释层流扩散甲烷火焰的光谱发射进行的分析说明了CH *以外的其他发射物质化学发光的作用。由于轴对称火焰结构，使用了视线化学发光的Abel反卷积来获得二维强度分布图，并且由于进行了绝对光强度校准，因此可以量化CH *浓度。与数值结果的比较表明，在实测火焰形状和计算火焰形状之间有相当好的一致性，并且表明在微重力和正常重力情况下，CH *浓度峰值的差异很小。与重力水平无关，横截面中的积分CH *浓度与积分的计算出的放热率成比例。二维CH *和放热率空间分布以令人满意的方式匹配，但梯度和强度分布不具有可比性。 （C）2016年燃烧研究所。由Elsevier Inc.出版。保留所有权利。

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