低频和高频交流电场对球形膨胀火焰的影响

Effects of Low-Frequency and High-Frequency Alternating Electric Fields on Spherical Expansion Flame

关键词:  交流电场  频率  贫燃  球形膨胀火焰  火焰传播速度  燃烧压力

Key words:  Alternating electric field  Frequency  Lean combustion  Spherical expansion flame  Flame propagation speed  Combustion pressure

摘要:

为比较不同频率的低频和高频交流电场在辅助燃烧方面的作用，在定容燃烧弹中对交流电场作用下的甲烷/空气预混贫燃火焰的燃烧特性进行了研究，分析了不同频率的低频和高频交流电场对火焰传播速度和燃烧压力的影响。结果表明:交流电场作用下，火焰在水平方向被拉伸，且拉伸幅度随着频率的不同而有所差异。低频交流电场作用下，平均火焰传播速度和燃烧压力均随着频率的减小而增大，而对于高频交流电场，其规律则相反。与未加载电压相比，当过量空气系数[α]=1.6，加载电压有效值U=5kV，频率f=40Hz，60Hz，80Hz，100Hz，10kHz，15kHz，20kHz，25kHz时，平均火焰传播速度分别提高72.41%，55.17%，48.28%，39.66%，62.07%，70.69%，81.03%，87.93%，相对燃烧压力增大率的最大值分别为0.65，0.58，0.48，0.28，0.29，0.51，0.67，0.86。研究表明，高频交流电场在电场助燃方面比低频交流电场更有优势。

Abstract:

The effects of alternating electric fields on premixed lean CH4/air mixtures were studied in a constant volume bomb to compare the roles of different frequencies of low-frequency and high-frequency alternating electric fields in promoting combustion process，and the different effects of low-frequency and high-frequency alternating electric fields on flame propagation speed and combustion pressure were analyzed. The results show that the flame is stretched in the horizontal when alternating electric field is applied to the electrodes and the stretching amplitude varies with frequency. The average flame propagation speed and combustion pressure increase as the frequency decreases under low-frequency alternating electric fields，while the scenario is completely opposite under high-frequency alternating electric fields. Compared with those without the applied voltage，when the voltage virtual value is 5kV and the frequencies are 40Hz，60Hz，80Hz，100Hz，10kHz，15kHz，20kHz and 25kHz，the average flame propagation speed at the excess air ratio of 1.6 increase by 72.41%，55.17%，48.28%，39.66%，62.07%，70.69%，81.03% and 87.93%，the maxima of the increasing rate of relative combustion pressure are 0.65，0.58，0.48，0.28，0.29，0.51，0.67 and 0.86，respectively. These results indicate that high-frequency alternating electric fields perform better than low-frequency alternating electric fields in promoting combustion process.