Dynamical Instability of Non-Equilibrium MHD Generator with Fully Ionized Seed Plasma

摘要

The time-dependent characteristics of a non-equilibrium Faraday-type MHD generator operating under the condition of "fully ionized seed regime" are analyzed, to examine the practical applicability of this regime. Potassium-seeded argon plasma is adopted as the working gas. High electrical efficiencies are known to be realizable with this fully ionized seed regime, but such a regime severely narrows down the range of operating conditions that ensure maintenance of stable plasma, and this introduces the risk of incurring dynamical instabilities like fluctuations of output power occasioned by minor derangements of the plasma state such as small changes affecting the seed density, gas pressure or load current of the generator. Moreover, for a given load resistance, the generator has two operating points-one in the stable region free from ionization instability, and the other in the partially-ionized region of argon. When the operating point is shifted from the former to the latter point, the generator output power diminishes sharply. Some technique for suppressing the dynamical instability would require to be established.