Numerical investigation on the flow field of a modified vortex spinning system for producing core-spun yarns

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained.