Design Analysis of Migration Nozzles Using CFD.

This paper presents a design analysis approach for migration nozzles used in the spinning process of synthetic fibers. A migration nozzle system consists of a yarn channel, air orifices, and a yarn loading slit. The entire system was analyzed in detail using computational fluid dynamics (CFD). The design parameters considered include the cross-sectional shape of the yarn channel, as well as the diameter and number of air orifices. Two different cross-sectional shapes, square and circle, were examined. The diameter of the air orifice varied from 0.6 mm to 2.0 mm, and both single and double orifice configurations were studied. A square cross-section resulted in the formation of a secondary vortex above the main vortex, making the circular cross-section preferable. The diameter of the air orifice significantly affects the vortex flow within the yarn channel. Vortex flow characteristics were quantified in two ways: the vorticity averaged across the cross-section in the direction of the yarn channel and the vorticity at the centerline. The highest vorticity at the centerline was observed at a diameter of 1.3 mm for single air orifice and 0.9 mm for double air orifices. These CFD results were validated through comparison with corresponding experimental data. A statistical analysis confirms that the centerline vorticity, particularly in the area of the air orifice, is a key and reliable parameter for evaluating the design of migration nozzles.