Simulation and Structural Optimization of an Eccentric Rotor Extruder Feeding Section

The eccentric rotor extruder (ERE) is polymer processing equipment that exhibits excellent processing capabilities for materials with extremely high viscosity, which are difficult to plastically deform and transport efficiently. However, the mass transfer mechanism in the solid conveying section of this new device is fundamentally different from that of traditional extruders, and no related research has been reported. This study uses discrete element method (DEM) simulation technology to model the solid conveying process of the ERE. By visualizing the positive displacement conveying process, and with an analysis of the output parameters, the study clarifies the mass transfer principles and quantifies the conveying capacity, providing guidance for optimizing the extruder design. The simulation results show that the ERE exhibits positive displacement conveying characteristics, with the conveying process achieved by the forward movement of the cavities (closed cavities between the rotor and stator) in a helical manner. However, differences in the dual-cavity (two types of cavities) feeding process and low fill level can lead to significant fluctuations in extrusion output and reduced conveying capacity. To address these issues, an improvement scheme for the dual-cavity feed opening is proposed, with feed openings designed with different opening lengths. Then, by analyzing the particle coordinate data from the simulation output, the conveying capacities of different feed opening structures are quantified and optimized. Finally, experimental and simulation verification results indicate that the optimized structure significantly improves the issues of uneven filling and low fill level, with good correspondence between the simulation and experimental results. Simulation results show that, compared with the original structure, the optimized dual-feed opening structure increases the feed capacity from 3953 particles per cavity to 5132 particles per cavity, an improvement of 29.8%, and it achieves balanced filling between the two cavities. Experimental validation indicates that the UPE4040 output can be increased from 165.3 g/min with structure op-00 to 231.7 g/min with the optimized structure op-05.