低温等离子体对甲烷/氧反扩散火焰影响的实验研究

为探究低温等离子体对甲烷/氧反扩散火焰的影响,通过对同轴式喷注器环缝甲烷射流施加介质阻挡放电产生甲烷等离子体,综合采用多种测量手段实验研究了多种工况下该低温等离子体特性及火焰关键参数的变化。结果显示,放电击穿电压随混合比增大而减小,电流脉冲数量和幅值则随混合比增大而先增加后减小;甲烷等离子体呈灰白色,低电压下提高气体流量则放电有所减弱;受等离子体气动效应作用,放电后甲烷射流角有所增大,且电压越高射流角越大,增幅则逐渐减小,过高激励强度下射流发生失稳;等离子体通过改变燃料和氧化剂的掺混而影响甲烷/氧反扩散火焰的形态,使得火焰中心高度总体有所下降,特征长度缩短,释热强度则有所增加,其中小流量、低混合比条件下作用效果更明显;喷注器功率则随混合比上升而先增大后减小。

Experimental Study on the Effect of Low-Temperature Plasma on CH4/O2 Inverse Diffusion Flame

Based on the in-house plasma injector, the effect of dielectric barrier discharge plasma on a CH₄/O₂ inverse diffusion flame was studied. The voltage-current characteristics, photographs, gas dynamic effect of methane plasma, flame shape, heat release, and discharge power were investigated in detail through various measurements. Results showed that the breakdown voltage decreased with the increase of the mixing ratio, while the number of current pulses its amplitude increased first and then decreased. The methane plasma emitted a gray white light and the emission intensity weakened with the flow rate rises. Due to the plasma gas dynamic effect, the CH₄ jet angle expanded notably after discharge. The higher the voltage is, the larger the jet angle is, while the amplitude is decline, and the instability of the jet may occur under the high actuation intensity. The mixing process was altered by the discharge plasma, the inverse diffusive flame showed a different shape compared with its original pattern. Generally, the flame center height and its characteristic length decreased, while the heat release intensity increased. The effect of the plasma on the flame was more obvious under a small flow rate or a low mixing ratio condition. The power of the injector increased and then decreased with the mixing ratio rises.