Experimental investigation and simulation of the performance of a pre-twister based on the jet vortex field used for the ring spinning frame

Abstract

The ring spun technique has always held a domain position in yarn spinning, thanks to its simple and robust structure, ease of maintenance and good quality in the product. A pre-twist device is arranged between the front rollers and an additional pair of rollers, which are named the holding rollers. In this paper, the simulation and characterization of the airflow field, as well as the fiber movement and deformation, in this pre-twisting zone are carried out by computational fluid dynamics software. The airflow simulation results show that there is a core region formed around the roving in the pre-twister, with a radius of about 1.55 mm. In the core region, the tangential speed is the major velocity component ranging from 0–70 m/s and the axial velocity is the minor one ranging from –13 to about 4.1 m/s. The air velocity inside the whole tube is from 462 to 0 m/s. The two-way coupled simulation verified that the airflow can drive the fibers to wind on the roving. The experiments on the surface morphology verified the wrapping phenomena in the simulation. Due to the employment of the pre-twister, the yarn properties got a little worse, with declines of 6% in strength and 10% in evenness, respectively. Comparing with the Uster Statistics for 2018, these declines are acceptable. Furthermore, it is shown that with this kind of pre-twister, the spinning speed can increase by 27.13% with an acceptable decrease in cotton yarn property (decreases of 13% in strength and 8% in evenness).