Numerical simulation of the inhomogeneous discharge structure in noble gas MHD generators

Abstract

A numerical calculation has been developed to describe the two-dimensional, time-dependent behavior of an inhomogeneous plasma in nonequilibrium MHD generators. The development of 'streamers' as typical discharge structures is simulated. A cesium-seeded argon plasma is considered. The numerical conditions used in the calculations are set equal to the experimental conditions used in the Eindhoven shock-tube facility. The elliptic part of the equations is solved by the finite-element method and the hyperbolic part by integration along the characteristic lines. It is found that the current concentrations on each electrode edge grow within microseconds into discharge structures which are concentrated in nonstationary streamers transverse to the gas flow. After they are formed, these streamers are frozen in the gas and are convected downstream at the gas velocity. Inside the streamers the cesium is fully ionized and the electron temperature is in range of 4000-6000 K, and outside the streamers the electron density is about 10 to the 19th and the electron temperature is about 2500 K. These calculated results agree quite well with the experimental ones observed in the Eindhoven shock-tube facility.