Experimental Studies of High-speed Liquid Films on Downward-facing Surfaces for Ife Wet Wall Concepts

The fusion event in inertial fusion energy (IFE) reactors creates neutrons, photons and charged particles that can damage the chamber first walls. The Prometheus design study used a high-speed thin film of molten lead injected tangential to the wall to protect the upper endcap of the reactor chamber from damaging x-rays and target debris (1,2). To assure full chamber coverage, the film must remain attached. Film detachment under the influence of gravity is most likely to occur on the downward facing surfaces over the upper endcap of the reactor chamber. Accurate numerical predictions of detachment length are effectively impossible in this turbulent flow due to difficulties in determining appropriate boundary conditions near the detachment point. As part of the ARIES-IFE study, experimental investigations of high-speed water films injected onto downward-facing planar surfaces at angles of inclination up to 45° below the horizontal were therefore performed. The initial growth and subsequent detachment of films with initial thickness up to 2 mm and injection speeds up to 11 m/s were measured. To our knowledge, these experiments are the first to investigate the detachment of turbulent liquid films on downward facing surfaces. The implications of these initial results on thin liquid protection and the “wet wall” concept are discussed.