3D particle-in-cell simulations of negative and positive streamers in C4F7N-CO2 mixtures

Abstract

We investigate negative and positive streamers in C4F7N-CO2 mixtures through simulations. These mixtures are considered to be more environmentally friendly than the insulating gas SF6 that is widely used in high voltage technology. Simulations are performed using a 3D particle-in-cell model. Negative streamers can propagate when the background field is close to the critical field. We relate this to their short conductive channels, due to rapid electron attachment, which limits their field enhancement. Positive streamers also require a background field close to the critical field, and in addition a source of free electrons ahead of them. In our simulations these electrons are provided through an artificial stochastic background ionization process as no efficient photoionization process is known for these gases. In 3D, we can only simulate the early inception stage of positive discharges, due to the extremely high electric fields and electron densities that occur. Qualitative 2D Cartesian simulations show that the growth of these discharges is highly irregular, resulting from incoming negative streamers that connect to existing channels. The inclusion of a stochastic background ionization process also has an interesting effect on negative discharges: new streamers can be generated behind previous ones, thereby forming a chain of negative streamers.

References in corpus (8)

• The physics of streamer discharge phenomena
• Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy
• Simulating streamer discharges in 3D with the parallel adaptive Afivo framework
• How pulse polarity and photoionization control streamer discharge development in long air gaps
• A comparison of particle and fluid models for positive streamer discharges in air
• A computational study of steady and stagnating positive streamers in N2-O2 mixtures
• A computational study of accelerating, steady and fading negative streamers in ambient air
• Geometric multigrid method for solving Poisson's equation on octree grids with irregular boundaries

Cited by in corpus (2)

• SF6 streamer breakdown induced by floating linear metal particles: Following streamers and side streamers
• Computational Model for Photoionization in Pure SF6 Streamer at 1-15 atm