Numerical study of 3D MHD flow of Pb-Li liquid metal in a rectangular U-bend

Abstract

The eutectic Pb-Li alloy has been chosen as a candidate material for the liquid breeder blanket, as it offers a unique combination of tritium breeding neutron absorbing and neutron multiplying capabilities. In fusion blanket, molten Pb-Li moves under plasma confining toroidal magnetic field, producing an induced electric current inside the liquid metal due to the interaction of the moving fluid with the magnetic field. The coupling of induced electric current and magnetic field generates a Lorentz force opposite to the flow direction, and this in turn, modifies the flow profile. The experimental and numerical flow studies of liquid Pb-Li under transverse magnetic field are of great importance, as it directly impacts the blanket performance. A liquid Lead Lithium MHD loop is being developed at Institute for Plasma Research (IPR), Gujarat, India for isothermal and thermo-fluid MHD studies in blanket relevant flow geometries such as sudden expansion/contraction, coupled channels and multiple bends. A test mockup with rectangular flow cross-section and having bends perpendicular to the magnetic field has been fabricated. A 3D MHD flow analysis has been performed numerically for the test mock up at a magnetic field of 1.4T (Hartmann number of order of 1500). The fabrication details of test mockup and the results of the Pb-Li flow analysis are presented and discussed. The flow field and pressure distribution in the presence and absence of the magnetic field are also compared. The existence of recirculation zones and their redistribution in the presence of magnetic field are discussed.