An Experimental Study of Gas Borne Suspensions of Thermionic Emitters as M.H.D. Working Fluids

The use of gaseous suspensions of thermionically emitting particles as alternatives to alkali metal seeded gases for use as m.h.d. working fluids is discussed briefly. Theoretical relations proposed by Sodha & Bendor (1964) are used to show that suspensions of barium oxide in argon can have significantly higher electrical conductivities than thermally ionized caesium-argon mixtures at temperatures below about 2000 degrees K. This advantage is emphasized at pressures above atmospheric pressure. Experimental studies to check the theoretically predicted conductivities are described. A technique has been developed for the preparation of submicron suspensions of barium oxide and other alkali earth oxides in inert gases. A suspension of barium oxide particles in argon has been shown to have a conductivity of 0$\cdot $1 mho/m at atmospheric pressure and 1600 degrees K. This value is low, because of the relatively large average particle size, 0$\cdot $3 $\mu $m diameter, but is of the same order as the theoretical conductivity for the experimental conditions.