Influence Factor Analysis on Jet Length of Atmospheric Pressure Argon Plasma Jets

Atmospheric pressure Ar plasma jets(APPJs) were designed to research their discharge characteristics with three kinds of different jet configurations,i.e.,double wrapped electrode,single wrapped electrode and center-electrode inside tube.The influences of flow rates,applied voltage amplitudes,and electrode configurations on the length of APPJs were studied.The results show that,as the flow rates increase,the flow status of Ar in tube has a process from the laminar state to the transition state and finally to the turbulent state.Correspondingly,the jet length first increases,then decreases,and finally reaches the maximum length when the Reynolds number is around 2000~3000.Under the same gas flow rate,the length of the single-wrapped electrode jet is slightly longer than double wrapped electrode jet while the center-electrode jet is shortest among three electrode configurations.But the discharge stability of center-electrode jet is superior to that of double-wrapped electrode jet,and the single-wrapped electrode jet is the worst.It is generally believed that the length of the jets is based on the high-energy electron in the ionization head.The electric field of double-wrapped electrode jet and single-wrapped electrode jet is mainly axial component of electric field,which leads to the discharge similar to streamer discharge and prolongs the APPJ length,while the electric field of the center-electrode jet is concentrated at the peak of the center electrode,and the discharge is originated from corona discharge with short jet length.The jet length comparison of different tube sizes shows that under our paper's conditions,the maximum jet length of the double-electrode jet and single-electrode jet first increases with the increment of tube sizes and finally tends to saturation,while the maximum jet length of the centre-electrode jet slightly decreases.