Search

The influence of an externally applied magnetic field on the characteristics and the transient behavior of the arc in a gas circuit breaker is examined by means of three-dimensional time-dependent numerical simulations. It is assumed that the gas circuit breaker has a ring-shaped permanent magnet and an arc is exposed to the externally applied magnetic field. Numerical results demonstrate that the rotation of arc induced by the Lorentz force produces a three-dimensional spiral structure of the arc. As a consequence of the rotation, the arc shrinks and the arc temperature decreases remarkably just before the time when the arc current is zero, so that applying the magnetic field increases the arc voltage. The numerical results also show that a swirling flow generated by the Lorentz force carries a thermal energy toward the thermal puffer room mainly by the convection during the high arc current phase, and as a result the pressure in the thermal puffer room increases. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Numerical analyses of the experimental-scale scramjet engine driven magnetohydrodynamics generator implemented in the Hypersonic Vehicle Electric Power System project have been carried out to clarify plasma behaviors and power generation characteristics. Three-dimensional numerical analyses have been performed under the two inlet conditions: one is the uniform inlet temperature condition, and the other is the nonuniform inlet temperature condition. Under the nonuniform inlet temperature condition, the generator performance approximately agrees with the experimental result. The tendency of the voltage loss is also reconstructed near the power takeoff electrodes though the voltage loss is smaller than that observed in the experimental result. The electric power output under the nonuniform inlet temperature condition is 40% smaller than that under the uniform inlet temperature condition. This is because the ratio of the Joule dissipation to the work by the Lorentz force increases owing to the decrease of active generator region as the current concentrates in the high-temperature region when the inlet temperature nonuniformity is considered. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]