Effects of Positive High-Voltage on Flame Propagation and Combustion Characteristics of Lean Premixed CH4/O2/N2 Flames
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摘要: 在定容燃烧弹上，通过实验研究了正高电压对过量空气系数λ不同的CH4/O2/N2预混稀燃火焰的传播和燃烧特性的影响。结果表明：正高压电场可以显著促进稀燃火焰在电场方向上的传播，且促进效应随着电压幅度的增大而增强。当电压幅度为12 kV时，对于λ为1.6和1.8的CH4/O2/N2预混气体，其平均火焰传播速率为1.38和1.07 m/s，与未加电场时相比，分别增大了133.41%和369.97%；压力峰值分别比未加电场时增大了13.07%和100.81%，压力峰值到达时刻分别提前了35.94%和18.09%。由此可知，正高电压可明显改善CH4/O2/N2稀燃火焰的传播和燃烧特性。Abstract: In this work we carried out an experiment to investigate the effects of positive high-voltage electric fields on the flame propagation and combustion characteristics of lean premixed CH4/O2/N2 flames in a constant-volume combustion chamber when the excess air ratio is respectively 1.6 and 1.8.The results from our experiment show that the flame propagation is significantly improved in the field direction with the application of positive DC electric fields, and this phenomenon is increasingly more obvious with the increase of the electric field.When the voltage input reaches 12 kV, the mean flame propagation velocities for λ=1.6 and 1.8 are 1.38 and 1.07 m/s, respectively, which is an increase by 133.41% and 369.97% compared to the case without an electric field.Moreover, at U=12 kV, the peak pressures for λ=1.6 and 1.8 are increased by 13.07% and 100.81%, and the corresponding time it takes for the peak pressure to occur is advanced by 35.94% and 18.09% respectively.It is therefore concluded that the combustion of lean premixed CH4/O2/N2 can be significantly improved by the positive high-voltage electric fields applied.
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Key words:
- high-voltage electric field /
- lean combustion /
- deformation ratio /
- propagation velocity /
- peak pressure
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图 2 定容燃烧弹和网状电极结构示意图
Figure 2. Structures of constant-volume combustion chamber and mesh electrode
图 4 未加电场与施加电场时的火焰前锋面
Figure 4. Schiliren photos of flame front underthe influence of high-voltage electric fields
图 6 不同过量空气系数和电压时典型火焰扩展纹影图片
Figure 6. Typical flame propagation images with different excess air ratios and applied voltages
图 7 不同加载电压下，规范化火焰变形率随时间的变化
Figure 7. Normalized flame deformation ratio vs. combustion time at various applied voltages
图 8 不同加载电压下，火焰传播速率随火焰半径的变化
Figure 8. Flame propagation speed vs. flame radius at various applied voltages
图 9 不同过量空气系数下，平均火焰传播速率随加载电压的变化
Figure 9. Mean flame propagation speed vs. applied voltage at different excess air ratios
图 10 正高压电场对稀燃火焰燃烧压力的影响
Figure 10. Influence of positive high-voltage electric fields on combustion pressure of lean flame
表 1 当过量空气系数不同时，燃烧特性参数随输入电压的变化情况
Table 1. Combustion Characteristic parameters vs. applied voltage
U/(kV) λ=1.6 λ=1.8 pm/(kPa) tp/(ms) Δpm/(%) Δtp/(%) pm/(kPa) tp/(ms) Δpm/(%) Δtp/(%) 0 393.27 226.90 0 0 173.54 384.10 0 0 2.5 402.04 199.45 2.23 -12.10 199.75 416.00 15.10 8.31 5.0 414.90 186.40 5.50 -17.85 255.88 422.80 47.45 10.08 7.5 421.52 171.30 7.18 -24.50 273.96 412.70 57.87 7.45 10.0 437.69 158.65 11.13 -30.08 330.15 323.20 90.24 -15.86 12.0 444.69 145.35 13.07 -35.94 348.48 314.60 100.81 -18.09 
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