Criteria for selecting a magnet for a MHD device

The authors analyze the influence of superconducting (SC) magnets (in air or in iron) on the behavior of the same MHD (magnetohydrodynamic) device for different shapes of duct. The features of the device are evaluated by means of a code which analyzes a 3-D lumped-parameter electrical network equivalent to the fluid flow. It is shown that, for the established operating conditions, if there are no constraints on the dimensions and weight of the device, the best choice is a magnet with a circuit partially in iron. Even though there may be a slight drop in performance, there is an estimated 50% reduction in cost. The reduction in the performance of the devices with SC magnets in iron is considered to be mainly associated with the range of field decays observed in frontal edges. This suggests that it might be possible to further optimize the magnet in iron by varying the dip in field decay according to the frontal edges with reference to the longitudinal dimension of the pump