Characteristic evaluation of electromagnetic flow couplers using a liquid metal MHD analysis code

It is known that electromagnetic flow couplers have high efficiency. In fact, an experiment using a small-scale annulus model shows that it has the maximum efficiency of 60%. However, another experiment using a middle-scale sector model exhibits that the maximum efficiency is less than 20%. In order to analyze this discrepancy, a computer code for solving magnetohydrodynamic flows is developed and is applied to the evaluation of these experiments. The obtained results show that the efficiency of the small-scale annulus model is high as observed in the experiment and the low efficiency observed in the middle-scale sector model is ascribed to the energy loss due to the eddy current arising in the ends of the magnetic region and the electric contact resistance between the stainless steel duct and the copper bus bar.