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Large Eddy Simulations (LES) are performed to study the vortex characteristics in a rotating rotor cup of rotor spinning. The instantaneous evolution process of vortex in the cup is analyzed, and the effects of rotor speed, slip surface angle, and rotor diameter on the airflow field in the rotor cup are examined. The numerical results show that vortices mainly concentrate at the outlet of the transfer channel, which may be due to the collision between the high-speed air stream from the transfer channel and the rotating wall. The strengths of these vortices gradually decrease as they are transported downstream due to the rotating of the cup. To analyze the impact of the parameters on the airflow field and yarn formation, a vortex area ratio ( S ) is defined which characterizes how much the rotor cup is occupied by vortices. A larger  S  value usually means a more chaotic and less structured flow field, thus is undesired for the spinning as it may adversely affect the slip and assemble of fibers in the rotor cup. Our parametric study indicates that the largest  S  value is found at 80,000 rpm for a 50 mm-rotor with a slip surface angle ofA rotor speed close to this thus may be unfavorable in spinning according to our criterion. For a rotor speed of 100,000 rpm and a diameter of 50 mm, the optimal slip surface angle is found to be aboutwhich brings a smallest  S  value. For a rotor speed of 100,000 rpm and a slip surface angle ofthe  S  value is observed to drop dramatically when the rotor diameter reaches 60 mm, a large enough rotor cup thus can efficiently alleviate the chaotic level of the airflow field. The numerical results may provide a preliminary guideline for the choice of spinning conditions that would be better for rotor spinning.

Vortex characteristics in rotating rotor cup of rotor spinning based on large eddy simulation