Effects of inclined transversal magnetic fields on magnetohydrodynamic coupling duct flow states in liquid metal blankets: Under uniform magnetic fields

Abstract

Investigations of magnetohydrodynamic (MHD) coupling duct flows are important for liquid metal blankets of fusion reactors. In this study, numerical simulations are performed to systematically clarify the influence of the inclined transversal magnetic fields on the MHD flow states such as pressure gradients and velocity distributions through two coupling ducts with conducting walls. It is found that the MHD coupling effect in the co-flow case is much weaker than that in the counter-flow case. The inclined transversal magnetic fields have an obvious influence on the velocity distributions in the MHD coupling duct flows especially for the counter-flow case, which will induce large reversal flow regions. The inclined transversal magnetic fields will also have a significant impact on the pressure gradients in the two coupling ducts in the counter-flow case, for instance, the MHD coupling effect is so strong that the pressure gradients in the coupling ducts are several even dozens of times bigger than that in a single duct. The aspect ratio of the coupling ducts affects the MHD coupling effect significantly in the counter-flow case, and the coupling effect will be strengthen as the aspect ratio decreases. A special MHD coupling effect is firstly found, because of this effect the pressure gradients in the coupling ducts of the counter-flow case decrease with the increase of the coupling Hartmann wall thickness.

MHD effects of liquid metal flows through multiple electrically coupling ducts with U-turn bends in fusion blankets

“…It is clear that the peak values of velocity jets decrease with the increases of the wall conductance ratios. This trend is opposite to that of a single conductive duct case because of the special MHD coupling effects (Zhang X et al [29]). It is worth noting that the reversal flow in the core fluid region will disappear with the increase of C w .…”

“…The short-circuit currents flow across the coupling wall and form the current loops between two adjacent ducts. In this study, C w is increased by increasing the wall thickness (t w ), as a result, it will lead to an increase of the electrical resistance of the coupling wall due to the currents direction according to the special MHD coupling effects (Zhang X et al [29]), which will result in the reduction of induced currents and the MHD coupling effects. Effects of the wall conductance ratios (C w ) on the velocity distribution in duct 2 is shown in figure 12.…”

Computational MHD analyses in support of the design of the WCLL TBM breeding zone

“…Counter-flowing channels from nearby BUs could potentially further reduce ∆p 2D compared with the simple case considered in Section 5.3, as well as coupling via Hartmann wall with the neighboring BU stack. For this last case, the flow in coflowing square channels has been theoretically investigated by Bluck et al [44] and numerically by Zhang et al [45]. In particular, the latter investigated this effect alongside an inclined magnetic field and observed ≈15% pressure gradient decrease for α ≈ 22°, c w = 0.1 and Ha =1 × 10 3 compared with the purely toroidal field case [45].…”

“…For this last case, the flow in coflowing square channels has been theoretically investigated by Bluck et al [44] and numerically by Zhang et al [45]. In particular, the latter investigated this effect alongside an inclined magnetic field and observed ≈15% pressure gradient decrease for α ≈ 22°, c w = 0.1 and Ha =1 × 10 3 compared with the purely toroidal field case [45].…”

MHD R&D Activities for Liquid Metal Blankets

“…[4]. Analytical solutions exist only for very special electrical boundary conditions [28] so that for applications in complex blanket geometries only coupled 2D or 3D simulations can provide the relevant friction coefficients when general scaling laws do not exist [29][30][31]. The problem becomes even more complex for flows in multiple coupled bends, where the coupling can be responsible for strongly increased flow in external ducts, while the flow in the central channels is significantly reduced, as predicted by Madarame et al [32] and shown in experiments by Stieglitz et al [33].…”