Spatial distribution of propane laminar pre-mixed flame temperature and equivalence ratio based on LIBS
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摘要:
激光诱导击穿光谱（LIBS）是监测燃烧过程关键参数的重要手段之一。为此搭建了LIBS三维可移动实验测量平台，结合等离子体能量和光谱研究了丙烷层流预混火焰的空间结构，得到了不同当量比和不同高度的温度趋势和当量比空间分布。结果表明：本生灯火焰预混燃烧区厚度随高度增加而增加；H、N、O的谱线强度和等离子体能量变化趋势一致，说明粒子体积分数是影响等离子体能量的主因。通过标定H656和N746的谱线强度比值与当量比的关系得到了局部当量比的空间分布。
Abstract:Laser induced breakdown spectroscopy （LIBS） is one of the important means to monitor the key parameters of combustion process. A three-dimensional movable experimental measurement platform of LIBS was built, then the spatial structure of propane laminar premixed flame was studied by combining plasma energy and spectroscopy, and the temperature trends and equivalence ratio spatial distributions with different equivalence ratios and heights were obtained. The results showed that the thickness of premixed combustion zone of Bunsen flame increased with the increase of height, and the spectral line intensity of H, N and O was consistent with the change trend of plasma energy, indicating that the particle volume fraction is the main factor affecting plasma energy. Then the spatial distribution of local equivalent ratio was obtained by calibrating the relationship between H656/N746 and equivalence ratio.
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Key words:
- propane /
- Bunsen burner /
- premixed flame /
- laser induced breakdown spectroscopy /
- temperature /
- equivalence ratio
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图 3 不同谱线强度比随φ变化情况（H=6.5 mm）
Figure 3. Variation of different line intensities ratio with φ （H=6.5 mm）
图 4 火焰不同高度上μ H656/N746随φ变化曲线和线性拟合
Figure 4. Variation of μ H656/N746 with φ for different heights and linear fitting
图 6 Ethreshold与Eplasma的径向分布曲线（φ=1.1, H=4.0 mm）
Figure 6. Radial distribution of Ethreshold and Eplasma （ φ=1.1, H=4.0 mm）
图 8 Eplasma在H=6.5 mm处不同φ的径向分布
Figure 8. Radial distribution of Eplasma at H=6.5 mm with different φ
图 9 Eplasma在当量比φ=0.9不同高度上的径向分布
Figure 9. Radial distribution of Eplasma at φ=0.9 with different heights
图 10 不同高度不同φ下的击穿光谱图
Figure 10. Breakdown spectra with different heights and different φ
图 11 不同高度上H656谱线强度径向分布（φ =0.9）
Figure 11. Radial distribution of line intensities of H656 withdifferent heights （φ=0.9）
图 12 各元素谱线强度径向分布（φ=0.9）
Figure 12. Radial distribution of lines intensities of different elments （φ=0.9）
表 1 实验工况表
Table 1. Experimental conditions
流量/（L/min） 高度H/mm 当量比φ 4 4.0, 6.5, 9.0 0.9, 1.0, 1.45 
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表 2 谱线强度比值与φ线性拟合参数
Table 2. Linear fitting parameters of line intensities ratio with φ
H/mm R2 μ H656/N742 μ H656/N744 μ H656/N746 μ H656/O778 4.0 0.96119 0.96891 0.98113 0.96934 6.5 0.99486 0.98832 0.99459 0.96742 9.0 0.97017 0.98799 0.98261 0.82648
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表 3 μ H656/N746与φ线性拟合参数表
Table 3. Linear fitting parameters of μ H656/N746 with φ
H/mm R2 b a 4.0 0.98113 2.18485 2.56087 6.5 0.99459 2.22861 2.57575 9.0 0.98261 2.67172 2.03759 注：表中a、b分别为方程y=a+bx的截距和斜率。
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