Feasibility study on frozen inert gas plasma MHD generator

The feasibility of a magnetohydrodynamics (MHD) generator with frozen inert gas plasma (FIP) is examined numerically. The FIP is produced by pre-ionizing helium of inert gas without alkali metal seed at the generator inlet. Because the three-body recombination coefficient of helium ions is low at the electron temperature more than 5000 K, the ionization degree of inert gas is kept almost constant in the entire region of the generator channel and the relation between the electron temperature and the electron number density deviates from the Saha equilibrium. In a small-scale disk-shaped generator, the enthalpy extraction ratio of 22.7% and the isentropic efficiency of 54.8% are obtainable for the load resistance of 3.0 /spl Omega/ and magnetic flux density of 4 T under the pre-ionization degree of 4.79/spl times/10/sup -5/. The auxiliary power to sustain the pre-ionized plasma corresponds to about 2% of the thermal input. For high-magnetic flux density, the generator performance can be improved as well as a conventional-seeded plasma MHD generator.