Numerical Simulation Analysis of Flow Field on Repetitive Pellet Injector with Single-Screw Extruder in CFETR

Pellet injection (PI) is the preferred fueling method in the future fusion reactor. It is particularly important to study the flow field characteristics of the frozen fuel extrusion process for the future steady operation of the pellet injector. In order to study the influence of groove depth on extrusion flux and conveying capacity, the flow field characteristics of a repetitive pellet injector with a single-screw extruder in the China Fusion Engineering Test Reactor (CFETR) was numerically simulated with POLYFLOW software. Thus, information about pressure field, viscous heating, and velocity field distribution was obtained. The results indicate that to a certain extent, increasing the groove depth (while maintaining the gaps between the screw and extrusion cylinder) is beneficial for the conveying capacity and pressure building capacity. The results of the numerical simulations show that at a screw speed of 120 rpm, screw outer diameter of 20 mm, screw length of 230 mm, screw groove depth of 6 mm, and screw prism gap of 0.3 mm, solid hydrogen can be stably extruded, and the velocity of the extruded ice at the nozzle is 0.15 m/s, which meets the design requirement of the CFETR PI system. These results also provide good references for structure design and performance optimization of the CFETR pellet injector.