Numerical investigation of the effects of magnetic field and fluid electrical conductivity on the performance of marine magnetohydrodynamic motors

摘要

A magnetohydrodynamic (MHD) thruster is a type of electric motors which does not have mechanical moving parts and directly converts electrical energy into mechanical energy. In this study, the effect of magnetic field intensity and seawater electrical conductivity on the performance of a marine MHD thruster model is investigated using fully three-dimensional numerical simulations. For the first time, all electric, magnetic and fluid flow fields are considered in three dimensions. The effects of seawater electrolysis and end loss are taken into account in all simulations and a simple analytical model is developed to verify the numerical results. It is shown that increasing the magnetic field intensity or the electrical conductivity of the working fluid decreases the electrochemical and ohmic losses of the thruster at a specific velocity. Therefore, a higher efficiency can be achieved at higher magnetic field strengths and higher seawater electrical conductivities. Also, it is revealed the end loss of the channel increases with an increase in the electrical conductivity of the working fluid and decreases with an increase in the magnetic field intensity.