Effect of vortex tube structure on yarn quality in vortex spinning machine

In order to study the effect of the structure of vortex tube on the yarn performance in jet vortex spinning, 8 groups of vortex tube structure were designed, and the corresponding 3D computational fluid dynamic models were established to numerically simulate the airflow in the nozzle. Through analysis of the characteristics of air flow inside the different nozzles, such as pressure distribution and velocity vectors, the motion of drafted fibers and performances of yarns were discussed. Simulation results show that when the structure of vortex tube has a transition region between the cylindrical and conical cavity (CCT) and the outlet of jet orifice is located at the junction of cylindrical and transition cavity, the airflow state within the nozzle has a large negative pressure with appropriate axial and tangential velocity, which is conducive to the formation of the open-ends of fibers and twisting, and the yarn quality turns out to be better. Spinning experiment results prove that the yarn strength reaches the maximum value, while the unevenness of breaking strength meets the minimum, and the other yarn properties are superior, which shows a good agreement with the simulation results. Thus, the numerical simulation can provide the theoretical as well as quantitative reference for the vortex tube design in the coming future.