Magnetohydrodynamic effects on liquid metal film flowing along an inclined plate relating to plasma facing components

Abstract

The liquid metal film plasma facing component (PFC) is considered to be one of the most promising ways to realize a PFC capbable of operating for long periods. However, in the presence of a magnetic field, magnetohydrodynamic effects appearing in the liquid metal film flow directly influence the reliability of the flowing liquid metal limiter or divertor. In the present study, we consider the influence of flow rate, transverse magnetic field, and inclination angle, and conduct experiments on a liquid metal film flowing along an inclined conducting stainless steel plate. A laser profilometer (LP) and a high-speed camera are respectively adopted to obtain the local film thickness quantitatively, and its free surface structures qualitatively. We observe the magnetohydrodynamic effects of liquid metal film flow, such as the nonmonotonic change of film thickness, the reduction of film flow velocity, and the weakening of free surface waves in the direction of magnetic lines. Moreover, the film thickness increases with an increasing flow rate, whereas it decreases with an increasing inclination angle at a constant value of the magnetic field. When plotting the relative film thickening δ en, and the reduction of flow velocity against the Stuart number N, we find that there is a critical N, N cr ≈ 0.1, at which δ en begins to increase dramatically. The δ en sinβ with 1 • ≤ β ≤ 5 • , based on all of the experimental data, collapses into one line, which can be scaled as δ en sinβ ∼ N. The present experimental data and its scaling law may prove useful for estimating magnetohydrodynamic effects on liquid metal film flows when considering the design of liquid metal film PFCs.

Magnetohydrodynamics in free surface liquid metal flow relevant to plasma-facing components

“…Appling 0.3 T magnetic field led the surface more reflective and waves aligned along the magnetic field emerged as the red arrows indicated in figure 12(b). This is consistent with theory prediction [53] and other experiments [26]. Due to the anisotropy of MHD drag, which acts to hinder flow across magnetic field lines, vorticity perpendicular to the magnetic field is greatly subdued, and turbulent eddies are elongated along magnetic field lines.…”

“…Results of experiments on LM flow under the influence of magnetic fields are presented in past studies [26,31,32,[34][35][36]. The experimentally achieved Hartmann numbers (formally defined in section 2.1) <∼100 were relatively low, and the relatively high Reynolds number led to turbulent flow.…”

“…Yet another candidate is the use of vertically oriented LM jets [25]. The considerable Magnetohydrodynamic (MHD) drag that conducting liquids experience in magnetic fields is of significant interest [25][26][27][28][29]. While these effects have been evaluated for fusion blankets, the applications considered for divertor PFCs, and possible distortions to the flow channels, represent a complex design challenge for free surface flow concepts.…”

Magnetic field control of three‐dimensional self‐driven multi‐physical thermoelectric system in metal energy storage

“…As reported by Morely et al, 6 the flow pattern of the liquid metal film is closely relative to the magnetic magnitude and geometric parameters. Yang et al 7 investigated the film flow of liquid metal GaInSn in a transverse magnetic field. MHD effect on liquid metal, such as reduction of flow velocity, decay of free surface waves along magnetic lines, is observed in their experiments.…”