Mechanisms of energy conversion in induction magnetohydrodynamic pumps for transporting conducting liquids

Abstract

Efficiency of energy conversion in magnetohydrodynamic (MHD) pumps is relatively lower compared with conventional mechanical pumps. The processes of energy conversion in an induction MHD pump are identified and the energy efficiencies of the processes are evaluated based on the numerical simulations. Two numerical models with different geometrical dimensions are built to simulate all involved processes. The results illustrate that vortices suddenly occur in the pump channel when the flow rate reduces below a critical value. The size and scale of the vortices are dependent on the modeling dimension. By analyzing the energy conversion among different forms of energy, it is demonstrated that the energy conversion is strongly correlated with the vortex flow. The appearing vortices at low flow rates result in both large Ohmic dissipation and negative power of Lorentz force, which are the main obstructions for energy transfer from the input power to the fluid pressure energy. In addition, the overall efficiency of this machine is estimated using the model containing external components (e.g., coils, stators and ducts). It is found that the energy dissipation in the external components plays an increasing role of reducing the energy efficiency with the increasing flow rate.