MHD Flow in Curved Pipes Under a Nonuniform Magnetic Field

In fusion reactors, a very hot deuterium–tritium plasma is confined in a toroidal volume by means of a strong magnetic field. In the blanket structure that surrounds the fusion plasma, high-energy neutrons, produced in the D-T fusion reaction, are absorbed by the lithium-containing liquid metal releasing their kinetic energy in the form of volumetric thermal load and breeding the fuel component tritium. The liquid metal flows from the blanket toward external ancillary systems for purification and tritium extraction. When the electrically conducting fluid moves in the strong plasma-confining magnetic field, induced electric currents generate electromagnetic Lorentz forces, which modify velocity distribution and increase pressure losses compared with hydrodynamic flows. These magnetohydrodynamic (MHD) effects have to be investigated to determine their impact on blanket performance. A number of studies on pressure -driven and buoyant MHD flows in geometries related to blanket modules are available, while only few works consider MHD flows in pipelines connecting blanket and ancillary systems. In the present study, we investigate numerically liquid metal MHD flows in the pipes, which cross the shield that protects the superconducting magnets from neutron radiation-induced damages. The geometry features two bends in series that turn the flow from the radial direction perpendicular to the magnetic field into a direction parallel to it and then back to a perpendicular orientation. The correct radial distribution of the magnetic field, as expected along the pipe axis, is taken into account. The flow experiences strong 3-D effects caused by Lorentz forces due to large-scale current loops driven by axial potential differences along the bend axis. In spite of very strong local MHD effects on velocity and pressure distribution, the overall pressure drop does not increase significantly compared with the one in a fully developed flow in a straight pipe of same length

MHD flow in a prototypical manifold of DCLL blankets (KIT Scientific Reports ; 7673)

Critical issues for the feasibility of dual coolant lead lithium blankets are large pressure drop and flow imbalance in parallel ducts due to 3D induced electric currents and 3D magnetohydrodynamic (MHD) phenomena that occur in liquid metal manifolds. In the present work we simulate MHD flows in a manifold where the liquid metal is distributed from a single duct into three parallel channels. The aim is identifying sources of flow imbalance, predicting velocity and pressure distribution

Geometric Optimization of Electrically Coupled Liquid Metal Manifolds for WCLL Blankets

A number of previous theoretical and experimental studies for helium-cooled or water-cooled lead lithium (WCLL) blankets show that the major fraction of magnetohydrodynamic (MHD) pressure drop in the breeder flow originates from manifolds that distribute and collect the liquid metal into and from the breeder units (BUs). Moreover, those studies revealed that without a proper design of the manifolds, the flow partitioning among breeder units would be strongly nonuniform along the poloidal direction. In the present work, MHD flows in electrically coupled liquid metal manifolds are studied by using an efficient hybrid model that has been developed for prediction of MHD pressure drop in such geometries and for determining flow distribution in BUs. The tool combines global mass conservation and pressure drop correlations with detailed 3-D simulations. From the experience gained when applying the model to the geometry of a test blanket module (TBM), it is concluded that the design of the manifolds requires optimization for achieving a balanced flow partitioning among BUs. In the second step, the hybrid model is applied to determine the optimum position of the baffle plates that separate the feeding and collecting ducts in manifolds in order to guarantee comparable flow rates in all BUs