甲烷燃烧强化实验中电压和频率对火焰的影响

Influence of Voltage and Frequency on Combustion Flame in Experimental Combustion Enhancement of Methane

燃烧强化是在未燃烧的气体燃料或者可燃混合气中进行介质阻挡放电,从而提高燃料的点火性能、燃烧速度和稳定性等燃烧特性的一种技术。为此,利用一种同轴介质阻挡放电结构对甲烷进行放电,然后将处理后的甲烷与空气混合、燃烧。对甲烷气体做了多种频率下的介质阻挡放电处理,观察处理后的燃烧火焰,在电压逐步升高的情况下,研究电压对火焰的影响,以及通过各种频率下的对比得出频率对火焰的影响规律,并做了光谱实验进行分析。结果表明,火焰形态随电压和频率的不同而有区别,其中还发生了甲烷的转化反应,一些在甲烷燃烧过程中重要的光谱波段在放电后有较明显的提高。

It is of great interest in combustion enhancement using dielectric barrier discharges （DBD）. The chemical activity of plasmas, generated in the process of discharging in gaseous fuel or fuel/air mixtures, has an effect on the chemical equilibrium of combustion system so as to improve the ignitability of the fuel, the velocity of combustion and the stability of combustion. Therefore, we employed a coaxial cylindrical configuration to study the influence of DBD on the methane combustion. Methane gas flows out from discharge zone, mixes with air in the mixing zone and finally combusts in the open air. The dependence of combustion properties of methane on the voltage magnitudes and frequencies of power supply is analyzed. Experimental results show that the flame can be affected by voltage magnitude and frequency. A hollow flame caused by the relatively large difference of flow velocity between methane, and air is gradually turned to be a non-hollow flame when the applied voltage magnitude rises. The backward propagation of flame can be observed once the onset voltage is applied. The onset voltage depends on the frequency of the applied voltage. The onset voltage of 50 Hz is much higher than that of high frequencies ranging from 4 kHz to 10 kHz.