交流电场对高压下甲烷/空气预混稀燃火焰的影响

Effects of Alternating Electric Fields on CH_4/O_2 Lean Combustion Flame under High Pressure

为了改善天然气燃烧速率慢、稀燃条件下着火延迟以及火焰稳定性差等不足,在常温、初始压力为3×97kPa下,研究分析了定容燃烧弹中低频交流电场对甲烷/空气预混稀燃火焰形状、火焰传播速度、燃烧压力相关特性参数等的影响。结果表明:与未加载交流电压相比,加载10~100Hz交流电压的火焰在水平方向均发生拉伸变形,电压频率越小,拉伸变形越明显,在15 Hz附近时变化最明显;加载电压后火焰传播速度增大,且随电压频率的减小先增大后减小,在接近15 Hz时最大;交流电场作用下燃烧压力峰值增大,压力峰值到达时间、初始燃烧期和主燃烧期均缩短;随着电压频率的减小,燃烧压力峰值与火焰传播速度变化相一致,而压力峰值到达时间的变化则相反,但均在15Hz附近其绝对值出现最大值,比未加载电压时分别增加了19.90%、-42.23%。

To improve the combustion speed,ignition delay and flame stabilization of the nature gas under lean combustion conditions,an experiment was conducted to investigate the effects of low-frequency alternating electric fields on the flame shape,propagation speed,combustion pressure and other characteristic parameters of premixed methane/air mixtures in a constant volume combustion bomb at room temperature and under high initial pressure of 3 local atmospheric pressure.The results show that the flame is stretched in the horizontal,and the average flame propagation speed increases when low-frequency alternating electric field of 10-100 Hz is applied to the electrodes.With the decreasing frequency the flame stretch deformation degree and flame propagation speed increase firstly then decrease and reach the maximum near 15 Hz.The peak combustion pressure increases,and the peak pressure arrival time,the initial combustion period and the main combustion period are shortened under alternating electric fields.As the frequency decreases,the changes of peak combustion pressure and flame propagation speed tend identically,but the change of peak combustion pressure arrival time tends oppositely,however both the peak combustion pressure and the peak arrival time get their maximum valuesnear of 15 Hz,and increase by 19.90% and-42.23% respectively compared with the case without electric field.