Numerical simulation of breakdown properties and streamer development processes in SF6/CO2 mixed gas

Abstract

In this paper, the dielectric breakdown properties in SF6/CO2 mixed gas, the development of the streamer in SF6/CO2 mixed gas, and the distribution of each component with time were studied. First, the electron transport parameters (mean energy, longitudinal diffusion coefficients, Townsend coefficient, critical reduced electric field coefficients, and electron energy distribution function) in SF6/CO2 mixtures with different ratios in the E/N range of over 50–1000 Td were obtained by two-term Boltzmann equation analysis. Then, coupled with the Boltzmann drift–diffusion equation and Poisson equation, the hydrodynamic model of discharge of SF6/CO2 mixtures in a strongly non-uniform electric field was established. Many different influence factors are considered, such as the gas mixture ratio, applied voltage, space temperature, space pressure, and electrode structures. The results indicate that the increase in SF6 content in the mixed gas will reduce the ionization rate of the total mixed gas, and therefore, it takes a longer time for breakdown. The higher the pressure, the more concentrated the form of the streamer. As the temperature increases, the shape of the streamer head becomes more scattered, and it loses its contoured shape at about 3000 K; in addition, the existence of the maximum electron number density value appears at the tip of the rod electrode rather than at the streamer head. The simulation also revealed that the dielectric strength of SF6/CO2 mixtures is stronger than that of SF6/N2 mixtures and reached a turning point at an SF6 ratio of 60% under extremely non-uniform electric fields, which agreed well with experiments.

Robust approximation rules for critical electric field of dielectric gas mixtures

“…This computational sieve approach to rapidly explore, trial, and assess potential scenarios then informs the design of targeted and efficient experiments and solution prototypes. For example, insight through large simulations of breakdown scenarios in often complex geometries [9] or detailed kinetic calculations of electron energy distribution functions (EEDFs) in gas mixtures over density or pressure windows [10] are now capable with advances in computing. This being said, these non-trivial computational tasks can also present their own challenges and barriers to entry, such as advanced computational domain knowledge or access to sufficient computing power or time.…”

Simulation on the effect of oxygen concentration on the positive secondary streamer generated in oxygen-rich nitrogen–oxygen mixtures under atmospheric pressure

“…Furthermore, as the discharge process before the arc discharge, the secondary streamer can be converted into arc discharge under certain conditions [24]. Thus, the characteristics of the secondary streamer have an important influence on the breakdown characteristics of the gap [25,26] and are required to be understood for the design of the gap insulation.…”

Electronic transport study for SF6 Plasma

“…Several experiments [ 9 ] and numerical simulations [10,11] have been devoted to the determination of EEDF in dusty plasmas, and in most theoretical studies, the local approximation is used [12,13,14]. Here, we assumed a kinetic model (self-consistent) of dusty SF 6 -glow discharge plasmas ,which is SF6 is a high electric strength gas, [15,16], by a solution of the Boltzmann Transport Equation ( BTE ) in case of a pristine and dusty plasma at low pressure weakly ionized which include the interaction between electron with dusty particle, and the dust charging balance relation [17], using currently cross-section data [18,19] Our results contained a determination of electron transport parameters (mean electron energy (  ), drift velocity ( d V ), diffusion coefficient (D) ,mobility (  ) and ionization coefficient( N…”