MIXING IN LIQUID METAL BATTERIES BY ELECTRO-VORTEX FLOWS
Résumé
MIXING IN LIQUID METAL BATTERIES BY ELECTRO-VORTEX FLOWs
Caroline Nore (LISN, Orsay, France) in collaboration with Wietze Herreman (FAST, Orsay, France), Sabrina Benard (LISN, Orsay, France), Paolo Personnettaz (HZDR, Dresden, Germany), Loic Cappanera (Univ. Houston, Houston, USA), and Jean-Luc Guermond (Texas A&M University, College Station, USA)
Liquid Metal Batteries (LMB) are composed of three layers of fluids (liquid metal electrode--electrolyte--liquid metal alloy electrode) of different densities lying over each other and stabilized by gravity. The composition of the positive/bottom electrode of an LMB may become very inhomogeneous over charge/discharge cycles, which limits the battery efficiency. Yet rotational flows in electrically conducting fluids can be generated by the Electro-Vortex-Flow (EVF) phenomenon, i.e. the interaction of a non-uniform current with the magnetic field it generates (Herreman et al., PRF, 4:113702, 2019). This non-swirling EVF has been shown to be non-efficient in mixing the bottom layer alloy because, during discharge, it is dominated by stable stratification and, during charge, it is overwhelmed by solutal convection (Herreman et al. PRF, 5(7), 074501, 2020). When a vertical magnetic field is present, the resulting flow is a swirling EVF. Using axisymmetric and fully three-dimensional numerical simulations with the multiphase magnetohydrodynamic code SFEMaNS (Cappanera et al., IJNMF, 86(8):541–563, 2018), we show that swirling electrovortex flows significantly enhance the mixing of the bottom layer alloy in liquid metal batteries during discharge. By varying the parameters, we identify a novel scaling law for the intensity of these swirling electrovortex flows leading to estimates of the minimal intensity of the external magnetic field needed to efficiently mix the alloys in the bottom electrode of arbitrary liquid metal batteries (Herreman et al. JFM, 915, A17, 2021).