Transient response simulation of downstream thermofluid field in a gas circuit breaker during current interruption

A transient response of SF₆ thermofluid field inside the exhaust tube in a Gas Circuit Breaker under high temperature, high pressure and high velocity conditions is analyzed by taking compressible effect and some realistic processes into account related to the available experimental data of GCB test facility. Furthermore, computational simulation is conducted to clarify the effective cooling process of SF₆ hot gas flow inside the exhaust tube for transient time to avoid the SF₆ hot gas breakdown near exhaust tube exit after the arc current interruption. It is found that the SF₆ hot gas flow can be effectively cooled down for the rough inside wall of exhaust tube due to the separation of SF₆ hot gas flow from the inside wall and also active mixing with upstream cold gas. The effect of roughness pattern on the real time thermofluid field of SF₆ hot gas flow and possible breakdown region are also clarified. Finally, the computed temperature in GCB shows the good agreement with the available experimental data for smooth surface of exhaust tube.