Abstract
Vortex spinning, which adopts high speed airflow to insert twist into the yarn, is one of the most promising technological innovations in the textile industry. In vortex spinning, the dynamic behavior of the fiber inside the nozzle, which involves fiber-airflow interaction and fiber-wall contact, plays an important role in the twist insertion process. This paper investigates the airflow characteristics and the fiber dynamic behavior inside the vortex spinning nozzle via a two-dimensional numerical model with the fiber-airflow interaction and fiber-wall contact included. The fiber is assumed to be isotropic, elastic material. The airflow inside the nozzle is assumed to be turbulent, viscous and incompressible. The numerical results show that two vortices with momentarily changed sizes are created upstream of the jet orifice outlets. The imbalance of the pressure around the fiber causes the fiber to move and deform. The trailing end of the fiber rotates with wave shape within the nozzle chamber for several periods to insert twist into the yarn. Based on the model, the effects of three nozzle structure parameters – the jet orifice angle, jet orifice diameter, distance between the nozzle inlet and the hollow spindle, on the dynamic behavior of the fiber, and in turn, the yarn structure and tensile property are investigated. The results show that the appropriate jet orifice angle for obtaining the best yarn tenacity is 70°. The optimal jet orifice diameter is 0.4 mm. The spun yarn has the highest tenacity when the distance between the nozzle inlet and the hollow spindle is 14 mm.