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The objective of the present paper is to analyze small-scale experimental facilities of TWDEC (Travelling Wave type Direct Energy Converter) and to propose a modification in regard to a measuring device of the facilities by means of numerical simulation with the axisymmetrical two-dimensional approximation (a PIC method). The numerical simulation has given the following results: (1) tendency of the numerical results agree with the experimental results on the measured deceleration efficiency, (2) the deceleration efficiency measured in the experiment will increase if the radius of Faraday cup installed in the experiment increases and (3) the wave of condensation and rarefaction of measured electric charge density, which is averaged in the r-direction below the radius of Faraday cup, is not formed enough with a small radius of Faraday cup because of the r component of electric field which is induced by the electrode geometry. [Copyright &y& Elsevier]

The separation capability of charged particles is one of the most important requirements for direct energy converters (DEC) of D–3He fusion reactors. An alternative DEC using Helmholtz coils (Helmholtz DEC) is designed to reduce the self-induced electric field and to separate charged particles when the thermal input is large as 10 MW (8.8 MW/m2). Numerical analyses with a two-dimensional approximation have given the following results. (1) When both electrodes (collectors) are grounded, it can separate ions and electrons with 99.4% ion collection efficiency. (2) When the electric potential is applied to both electrodes as nine cases, the highest separation capability of the charged particles is about 95%. (3) When Cusp DEC, Cusp DEC with closer electrodes and Helmholtz DEC are compared, only Helmholtz DEC can separate the charged particles when the electric potential is applied to the anode. [Copyright &y& Elsevier]

The article discusses the effects of electric arc behavior and electrode temperature on the current distribution and the location of arc spots in the boundary layer of magnetohydrodynamic generator. Based on numerical analysis, the potential distribution between electrodes drop dramatically across the boundary layer. If the wall temperature in the arc is high, the heat flux is concentrated on the laminar layer due to the presence of high effective thermal conductivity. The arc spots move in three-dimensional space.

The article discusses the operational characteristics of a power consolidation circuit for Faraday-type magnetohydrodynamic generator. The fundamental characteristics of Christmas tree type and Master/Slave type consolidation circuits are discussed, as well as the electrical nonuniformities caused by slag polarization. A schematic diagram of Christmas tree type power consolidation circuit with electrodes is presented.

The high-temperature ceramic electrode for an open-cycle MHD generator is now under intensive study but it can not be used in practice today. Presently available electrodes are of low-temperature type and made of copper. Currents of such low-temperature electrodes are carried in an arc discharge mode if natural gas or heavy oil is used as fuel. The current and voltage distributions around the electrodes often become very non- linear due to the effect of negative voltages current characteristics of the arc current.

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]