Nonequilibrium ionization in magnetoplasmadynamic power generation - theory and experiment

Abstract

Test results from a closed-loop magnetoplasmadynamic (MPD) generator experiment at gas temperatures in the range of 1000°-1100 °F are examined in the light of the theory of magnetoplasmadynamic electrical power generation with nonequilibrium ionization. The effective electrical conductivities measured under virtual short-circuit electrical load conditions in a segmented-electrodes constant-area-duct experiment when the magnetic field is applied, are compared with the thermal equilibrium ionization conductivities, which are calculated using electron densities derived from Saha's equation with the corresponding gas temperatures inserted. This comparison gives a verification of the presence of magnetically-induced nonequilibrium ionization in the MPD generator duct. Next, the energy balance equation is used to derive the electron temperature. The electron temperature is in turn used to calculate the resultant nonequilibrium electron density. This is done using two approaches. One approach uses an ion balance equation, which balances the rate of generation of ions by the hot electrons with the rate of loss of ions by recombination. The other approach derives the electron density from Saha's thermal equilibrium equation using the electron temperature instead of the gas temperature. The calculated nonequilibrium conductivities resulting from the use of these two approaches are compared with those obtained by experiment.