Laser-induced breakdown spectroscopy measurements of mean mixture fraction in turbulent methane flames with a novel calibration scheme
Laser-induced breakdown spectroscopy measurements of mean mixture fraction in turbulent methane flames with a novel calibration scheme
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DOI：
10.1016/j.combustflame.2016.02.025
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发表时间：
2016-05
影响因子：
4.4
通讯作者：
M. Kotzagianni;R. Yuan;E. Mastorakos;S. Couris
中科院分区：
文献类型：
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作者：
M. Kotzagianni;R. Yuan;E. Mastorakos;S. Couris
将激光诱导击穿光谱技术(LIBS)应用于从纯空气到纯燃料的多种组成的甲烷-空气均相混合物，建立了一种新的激光诱导击穿光谱测量湍流非预混火焰中混合气分数的标定方案。采用便携式低分辨率光谱仪和单色仪对等离子体发射进行了监测。两种检测系统得到的结果完全一致，这表明LIBS可以成功地与更适合工业应用的CCD探测器一起使用。光谱分析表明，Hα(656.3 nm)与O(777.3 nm)(Hα/Ο)和C2(ΔυΠ=0 0，d3Πg-#x03B1；3Δυu)在CN(Β=0，Σ+-Χ2Σ+)(C2/CN)上的强度比分别在0.0-0.3和0.3-1.0范围内与甲烷摩尔分数呈单调关系，从而为整个当量比范围内非预混体系混合分数的测量提供了一种新的方案.该技术还被应用于旋转循环预混火焰，发现在反应物和产物中都成功地测量了当量比。在此基础上，在轴对称非反应射流和反应射流中进行了LIBS实验，由上述标定曲线确定的平均混合分数与经验关联式吻合较好，而RMS测量结果显示了预期的趋势，从而证明了该技术的有效性。
Laser Induced Breakdown Spectroscopy (LIBS) was applied to homogenous methane–air mixtures of a wide range of compositions ranging from only air to only fuel in order to establish a new calibration scheme suitable for LIBS measurement of mixture fraction in turbulent non-premixed flames. Both a portable low resolution spectrometer equipped with a CCD detector with wide temporal detection window and a monochromator with a fast gated ICCD camera were employed to monitor the plasma emission. The results obtained using the two detection systems were fully consistent, suggesting that LIBS can be used successfully with the CCD detector that is more suitable for industrial applications. From the spectroscopic analysis, it was shown that the ratio of the intensities of Hα(656.3 nm) over O (777.3 nm) (Hα/Ο) and of C2(Δυ = 0,d3Πg–#x03B1;3Πu) over CN (Δυ= 0,Β2Σ+–Χ2Σ+) (C2/CN) depend monotonically on the mole fraction of methane in the ranges of 0.0–0.3 and 0.3–1.0 respectively, therefore providing a new scheme for measurement of mixture fraction in non-premixed systems spanning the complete range of equivalence ratios. The technique was also applied to a swirling recirculating premixed flame and it was found that the equivalence ratio is successfully measured in both reactants and products. Based on the above, LIBS experiments were then carried out in turbulent axisymmetric non-reacting and reacting jets, and the mean mixture fraction determined by the aforementioned calibration curves was in good agreement with empirical correlations, while the rms measurement showed the expected trends, demonstrating hence the usefulness of the technique.