Effects of dielectric-barrier-discharge plasma on soot and NOx in diffusion flame

In this study, we experimentally investigated soot and NOx in a diffusion flame on a coaxial burner. By applying a dielectric-barrier-discharge (DBD) plasma, we tried to reduce these emissions. When the DBD plasma was exposed to the air flow, the height of the luminous flame slightly decreased. By considering the fact that the flame height without the DBD plasma is proportional to the fuel flow rate, the DBD plasma surely affects the soot concentration of the luminous flame. Based on the LII image, the soot region identified by the LII signal corresponds to the luminous flame zone. This soot distribution is similar even when the DBD plasma is activated, but the soot concentration of the luminous flame zone is reduced. As the air flow rate increases, the reduction of the integrated LII signal by the DBD plasma is smaller. This could be because the plasma is only active at the exit of the air flow, and the effect of the plasma is relatively weaker when the air flow rate increases. As for NOx emission, it is confirmed that the EINOx without plasma increases by increasing the air flow rate, showing that the thermal NOx could increase. Overall, when the plasma is activated, the EINOx always increases at any air flow rate. That is, the simultaneous reduction of soot and NOx cannot be achieved.