Numerical Study on Decaying Arcs under Free Recovery Condition in CO2/SF6 Gas Mixture for Various Gas Flow Rates

In the present report, decaying arc behaviors in 80%CO
2
/20%SF
6
gas mixture were numerically studied for various gas flow rates under free recovery condition on the assumption of local thermodynamic equilibrium (LTE) condition. Furthermore, gas flow rates were varied from 100 L/min, 200 L/min and 300 L/min to understand its influence on the arc behaviors. For the preparation of simulation of arc decaying process, first, two-dimensional distributions of gas flow and temperature in arc plasmas in a steady state at an arc current of DC 50 A were calculated. Using these distributions as initial values, transient calculation from 50 A to 0 A was conducted. As a result, an increase in gas flow rate from 100 L/min to 200 L/min causes convection loss to rise. This indicates that the increase in convection loss declines the arc temperature more rapidly, resulting in rapid increase in arc resistance for enhanced recombination of S
⁺
, while convection effect tended to saturate in high gas flow rate.