Transient Behavior of Magnetohydrodynamic Power-Generating Plasma

Abstract

We present the structure of a nonequilibrium cesium-seeded argon (Ar-Cs) plasma in a closed-cycle magnetohydrodynamic (MHD) electrical power generator driven by a shock-tunnel facility. The transitional behavior from an inflow phase to an MHD phase is visualized. In the inflow phase, the high-temperature Ar-Cs gas produced by shock-wave heating flows in a supersonic channel. In the MHD phase, the plasma is self-organized by MHD effects. At the same time, the enthalpy of a flow is extracted in the form of electricity via the MHD effects. Index Terms-Magnetohydrodynamic power generation, plasma waves.(CCMHD) electrical power generator, which is one of the most efficient energy-conversion devices, directly converts the enthalpy of a flow into electrical energy using a nonequilibrium plasma without rotating high-temperature parts. Therefore, the CCMHD generator has several advantages, namely, high upper limits to the temperature it can tolerate, a rapid response, and the ability to achieve high thermal efficiency and high power density.A shock tunnel supplies a high-enthalpy gas flow to a diskshaped supersonic MHD channel with a total gas temperature of 2200 K and a total gas pressure of 0.2 MPa. An inert gas, argon, seeded with a small amount of alkali-metal vapor, cesium (10-1000 ppm), is used as the working medium (a cesium-seeded argon (Ar-Cs) plasma). The Ar-Cs gas expands from a highly pressurized stagnation state to a supersonic state through the MHD channel (the gas flows in the radial (r) direction in a narrow gap between parallel disks), where an external magnet applies a steady magnetic flux in the height (z) direction. The motion of the conducting gas through the magnetic field gives rise to an electromotive force and a flow of current in accordance with the Faraday law of induction. An electromotive force of u × B induces a Faraday current in the azimuthal (θ) direction, and a radial Hall electric field is induced by the Hall effect (u is the flow velocity vector, and B is the magnetic flux density vector). During the MHD interaction, the electron temperature differs from the heavyparticle temperature so that the plasma is in a nonequilibrium Manuscript