Pressure distribution in MHD flows in an experimental test-section for a HCLL blanket

Abstract

Liquid metal magnetohydrodynamic (MHD) flows in a scaled mock-up of a Helium cooled lead lithium blanket have been investigated experimentally in the MEKKA laboratory at the Karlsruhe Institute of Technology. The test section consists of 8 breeder units (BUs) connected two by two at the first wall (FW) through a series of small openings. The large boxes are fed and drained by poloidal manifolds formed by two parallel channels separated by a step-shaped wall, which is electrically conducting. The complexity of the geometry and the strong 3D MHD effects that characterize the flow in the mock-up are at the present time still very challenging for numerical simulations. Therefore, experiments are required to obtain an overview of pressure and velocity distributions in such geometry and to derive scaling laws to extrapolate the results to realistic ITER operating conditions. Pressure differences between several points on the test section have been measured. The influence of magnetic field strength and flow rate on pressure losses in the mock-up has been studied. The largest pressure drops occur along the manifolds. Another significant part of the entire pressure drop comes from flow near the FW, where the liquid metal passes through small gaps into the adjacent BU. This pressure drop between external pairs of BUs is at least 4–5 times larger than that in the internal ones. This suggests an inhomogeneous partitioning of the liquid metal flow among the BUs, which is related to the geometry of the manifold.