Discharge Behaviors of Supercritical N2under Direct-current Electric Field

Key words:  SCN₂, discharge  behavior, avalanche, streamer, Charged particle clusters

Abstract:

The precise mathematical method was adopted to simulation the breakdown process of the 5mm gap of the rod-plate electrode system being filled supercritical nitrogen at the condition of 127K, 4MPa and seed electron density1×10₆^m_-3 under 29kV DC voltage. The results showed that the discharge process was completed in 11.8 ns from seed electron triggering, avalanche bulking to streamer extending until gap eventually breakdown. The entire gap breakdown process was divided into three discharge stages, namely, the initial discharge triggered in 0~4ns, 4ns~7ns avalanche and 7ns~11.8ns streamer phase. At the same time, the facts were also revealed that the discharge evolution, electric field distribution, and electron density had different values, and also showed different temporal and spatial distribution characteristics along the axis of discharge gap. Specifically, the discharge characteristics of SCN2 under 1, 2, 3, 4, 4.5, and 5 MPa at 127 K were theoretically analyzed respectively, and the microscopic mechanisms of the breakdown process were also detailed. The results indicate that the gas discharge law remained applicable within the 1-3 MPa range. However, the discharge characteristics of supercritical nitrogen at 3.4-5 MPa differed significantly from those at lower pressures, likely attributable to the unique state of matter exhibited by supercritical nitrogen. This study contributes to understanding the discharge mechanism of supercritical nitrogen and offers theoretical guidance for its practical application in the power industry.