Numerical Simulation on Quenching Process of Carbon Dioxide Arcs with Hydrogen Gas Inclusion in Different Nozzle Shapes

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This paper describes the influences of different nozzle shapes on the thermal interruption capability of a CO2 model circuit breaker with H2 inclusion using an fluid dynamic simulation under the assumption of a local thermodynamic equilibrium condition. Six nozzle shape spaces were studied in order to find the effects respectively from differences in the nozzle convergence angle and nozzle throat length. It is proved that the temperature and gas flow velocity around the nozzle inlet position are crucial for the thermal interruption of CO2 arc with H2 gas. Power balance in the whole arc plasma region was also studied to know the dominant power loss during the thermal interruption processes. As a result, convection loss may determine the thermal interruption capability of CO2+H2 arcs, which is also related with a local maximum gas flow velocity on the center axis in the nozzle throat around current zero.