Effect of nanosecond pulse discharge on emission spectral behavior in CH4-air diffusion flame

A nanosecond pulsed dielectric barrier discharge (ns-DBD) setup is built to preliminarily analyze effect of different discharge repetition (600Hz ~ 1800Hz) and voltage (6.0kV ~ 10.4kV) on CH4-air diffusion flame. Emission spectral is used to understand temperature and relative change of components’ concentrations in diffusion flame, such as O radical (777nm band), OH radical (308nm band). Plasma induced consumption process of repetitive pulsed nanosecond discharges on O radical has been directly observed at 900Hz discharge repetition. Based on time resolved emission spectral, significant changes of OH radical distribution at early discharge stage can be observed, which can be due to air-discharge plasma, and rapidly recover in microsecond scale due to rapidly consumption of generated OH radical. Besides, great differences in reaction time scale of OH radical (half-value period of OH radical consumption ~81.8μs) and O atom (half-value period of O atom consumption ~3.6min) is observed, corresponding to different chemical reaction mechanism of O atom and OH radical. A model based on rate equation is built to describe generation and consumption process of O atom and OH radical, which can also well predict voltage behavior of 777nm band at steady state (6.0kV ~ 10.4kV).