Discharge mode transformations and reactive species generations of sliding arc reactor with ball-helix electrodes regulated by gas flow speeds and applied frequencies

Discharge mode would be affected by both of the gas flow state and applied electrical parameter. In this study, a sliding arc discharge reactor was established by a pair of ball-helix electrodes, and the discharge modes and the reactive species generations were investigated under different gas flow speeds and applied frequencies. The results show that the discharge modes transformed from pure arc to arc-spark transition and pure spark discharge with 9.0 kHz when the gas flow speeds are less than 3.2 m/s, 3.2-5.6 m/s and greater than 7.2 m/s, respectively. Meanwhile, with the gas flow speed as 4.8 m/s, the discharge modes transformed from arc, arc-spark transition and spark when the applied frequencies are 5.0 kHz, 6.0 ~ 10.0 kHz, and 11.0 kHz, respectively. Moreover, the discharge modes affected reactive species. Fixed the applied frequency as 9.0 kHz, the gas flow speeds changed at 1.6 m/s, 4.0 m/s, and 7.2 m/s (the corresponding discharge modes are arc, arc-spark transition and spark). The energy conversion efficiencies of NO
2
, NO
2
, and NO
x
are maintained each constant as 12 mg/kJ, 18 mg/kJ, and 48 mg/kJ, respectively. However, that of O
3
are increased from 32 mg/kJ to 54 mg/kJ, and then decreased to 30 mg/kJ. Additionally, the total applied energy and the gas flow speed was fixed as 93 J and 4.8 m/s, the applied frequencies employed as 5.0 kHz, 7.0 kHz, 9.0 kHz, and 11.0 kHz. The concentrations of NO
2
NO
2
, NO
x
, and O
3
are decreased. This work can provide experimental support for the application of plasma in the fields of medicine, nitrogen fixation, energy and environmental protection.