Influence of surface dielectric barrier discharge on diffusion flame combustion characteristics
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摘要:
针对表面介质阻挡放电（SDBD）在激发等离子体时具有显著的气动效应和化学活化效应，为分析表面介质阻挡放电对空气/甲烷同轴剪切扩散燃烧的助燃效果，实验使用高频交流电源，基于等离子体诱导射流逆向激励对火焰施加控制。根据获取的射流流场纹影图像、火焰图像和CH*自发辐射，研究了等离子体对不同燃烧条件下火焰燃烧特性的影响。结果表明：受等离子体气动激励作用，火焰上游细长剪切层的空气/甲烷掺混得到增强，从而扩大了剪切层燃烧宽度，同时燃烧释热速率会明显提高，这主要与等离子体活化效应有关，并且该效应显著增强了位于喷嘴出口火焰基的燃烧强度。在空气流量较低时，等离子体气动激励可有效增大火焰下游湍流度和射流角，使火焰高度降低、宽度增大，且作用效果随放电电压提高逐渐增强。
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关键词:
- 表面介质阻挡放电(SDBD) /
- 等离子体 /
- 甲烷 /
- 扩散火焰 /
- 燃烧特性
Abstract:The plasma excited by Surface Dielectric Barrier Discharge (SDBD) owns both significant aerodynamic effect and chemical activation effect. In order to analyze the combustion-assisted effect of surface dielectric barrier discharge on shear-coaxial air/methane diffusion flame, the reverse excitation of plasma induced jet is applied to the flame through the use of high-frequency AC power supply in the experiment, and the influence of plasma on the flame combustion characteristics under different combustion conditions is investigated according to the obtained jet flow field schlieren photograph, flame image and CH* spontaneous emission. The results show that the air/methane mixing of elongated shear layer in the upstream of flame is enhanced under the plasma aerodynamic excitation, which enlarges the combustion width of the shear layer. And the combustion heat release rate is also significantly increased, which is mainly related to the plasma activation effect, and the activation effect significantly enhances the combustion intensity of base flame at nozzle outlet. Both the turbulence intensity and jet angle of the flame downstream can be effectively increased with plasma aerodynamic excitation at a reasonably low air flow rate, making the flame height reduced and the flame width enlarged, and the effect tends to be more obvious with a higher discharge voltage.
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图 2 不同当量比下火焰图像随激励电压的变化(
Figure 2. Variation of flame images with excitation voltage under different equivalence ratios (
图 3 不同当量比下射流纹影图随激励电压的变化(
Figure 3. Variation of schlieren images of jet flow with excitation voltage under different equivalence ratios (
图 4 不同空气流量下放电对火焰图像的影响(Upp=20 kV)
Figure 4. Influence of discharge on flame images at different air flow rates (Upp=20 kV)
图 5 不同空气流量下放电对射流纹影图的影响(Upp=20 kV)
Figure 5. Influence of discharge on schlieren images of jet flow at different air flow rates (Upp=20 kV)
图 6 不同当量比下CH*自发辐射图像随激励电压的变化
Figure 6. Variation of CH* chemiluminescence images with excitation voltage under different equivalence ratios
图 7 不同空气流量下放电对CH*自发辐射图像的影响
Figure 7. Influence of discharge on CH* chemiluminescence images at different air flow rates
图 8 不同空气流量下放电对CH*自发辐射强度径向分布曲线的影响
Figure 8. Influence of discharge on CH* chemiluminescence radiation intensity radial distribution profiles at different air flow rates
表 1 实验不同燃烧条件
Table 1. Different combustion conditions inexperiment
Φoverall 
uair/(m·s-1) uCH4/(m·s-1) Reair ReCH4 (O/F)mon 10 0.6 0.6 0.77 0.06 298 53 410 10 1.0 1.0 0.77 0.10 298 88 148 10 1.4 1.4 0.77 0.13 298 123 75 15 0.6 0.9 1.16 0.09 449 79 410 15 1.0 1.5 1.16 0.14 449 132 148 15 1.4 2.1 1.16 0.20 449 185 75 20 0.6 1.2 1.54 0.11 596 106 410 20 1.0 2.0 1.54 0.19 596 176 148 20 1.4 2.8 1.54 0.27 596 246 75 25 0.6 1.5 1.93 0.14 747 132 410 25 1.0 2.5 1.93 0.24 747 220 148 25 1.4 3.5 1.93 0.33 747 308 75 
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