A discussion is given of the basic physical processes occurring in magnetohydrodynamic (MHD) generators. In designing a generator two parameters are of importance, namely, the power output per unit volume and the isentropic efficiency ñs which is a measure of the departure of the generation processes from the ideal. It is shown that the maximum electrical output per unit volume of gas is
ñs(1-ñs)θu2B2
where θ is the electrical conductivity, u the flow speed down the duct, and B the magnetic field strength.
The paper describes how the isentropic efficiency depends on the load characteristics, how to calculate the electrical conductivity, the effect of a strong magnetic field on the electrical conductivity and the optimum shape of an MHD duct.
A brief account is given of the progress in the development of experimental generators and of the practical problems still to be solved.
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