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Computational simulation of air flow in the rotor spinning unit

A three-dimensional computational model is established to simulate the air flow patterns in the rotor spinning unit of a rotor spinning machine. The effects of rotor speed, rotor diameter and rotor slide wall angle on air flow characteristics and hence yarn properties are investigated. The airstream accelerates from the transfer channel inlet to the outlet. There are velocity differences in both the cross-section and along the transfer channel, causing hooked fibers to straighten. The airstream swirls around the rotor at a high speed. However, vortices that can cause fiber curving and buckling are formed inside the rotor. The effect of rotor speed is significant. There are more vortices near the wall at a lower rotor speed, while too large a rotor speed can lead to an excessive centrifugal force, thus increasing yarn breakages. The rotor diameter affects the flow characteristics in a way similar to that of rotor speed. As a smaller slide wall angle generates higher velocities in the transfer channel and more stable velocities in the rotor groove, a small angle is preferable. Computational modeling has provided a useful insight into the rotor spinning flow pattern, thus it can be used to optimize the rotor design to produce better rotor spun yarn.