Mixing and Particle Tracking in a Single Screw Extruder (1)

Many single-screw extruders are used in industry to melt polymers and extrude them into a mold to make various pieces, mainly plastic or rubber.  These devices, however, perform very poorly when asked to mix multiple substances together because of their shape and the high viscosity of liquid polymers.  Over the years various attempts have been made to create an extruder that would produce a more evenly mixed outcome, mainly using spatially periodic flow techniques.  Many of these changes increased the cost to produce as well as maintain the specialized extruders because of their more complicated design.  Many of the specializations caused problems by creating pressure changes and other issues which inhibited steady throughput. This issue can be easily overcome by attaching a gear pump to the exit of the extruder.  Much of the happenings inside an extruder are poorly understood, which is why Dr. Campbell and his team are studying chaotic mixing inside the free-helix extruder. The goal of this project is to develop a technique for visualization of the mixing process by using simulations of the process velocities and then using the velocities to predict the position of tracer “particles” in the system.