Influence of gas free stream layer on charge accumulation and hydroxyl radical production in the atmospheric pressure plasma jets

This study investigates the influence of gas free stream layer on the charge accumulation and hydroxyl radical (OH) production in the atmospheric pressure plasma jet. It is hypothesized that the inertial force of the gas free stream layer influences plasma interactions, including wall charge accumulation and air entrainment. Electrical measurements revealed that increased gas flow rate led to higher breakdown voltage, indicating reduced charge accumulation on the wall. Schlieren imaging and OH-planar laser-induced fluorescence diagnostics showed that OH generation occurs primarily at the boundary between the plasma jet and ambient air. Notably, a linear correlation was observed between the simulated free stream layer and the OH emission boundary gap, suggesting that the gas free stream layer critically affects air entrainment for OH production. These findings provide insight into optimizing gas flow conditions for enhanced OH production and discharge in atmospheric plasma jets.