Variable-velocity MHD induction generator with rotating-machine internal electrical efficiency

A traveling-wave, MHD induction generator with varying fluid velocity between inlet and exit can have the same internal electrical efficiency as a rotating induction generator. The fraction of electric retarding work converted to electric output at each station in the flow channel is (1 + s)^-1, where s is the local slip (U - Us)/Us, between the velocity of the fluid U and the velocity of the zero crossing of the magnetic field wave Us. To produce the rotating-machine efficiency, the product of magnetic field amplitude, wave velocity, and flow channel width is held constant from inlet to exit. The local slip can be freely chosen for maximum electric output from the fluid in the presence of friction, and the inlet magnetic field can be selected for maximum output after winding and end losses. An efficiency of 0.63 is found possible with a 325-kW lithium generator.