Study on effects of structural parameters on untwisting performance in pneumatic yarn splicing

The internal airflow of an untwisting chamber clearly affects the untwisting performance as determined by the appearance of the untwisted yarn end. This study established a geometric model of an untwisting chamber comprising an intake tube and untwisting tube, and adopted the renormalization-group k-ɛ turbulence model to simulate the airflow patterns inside chamber structures having three varying parameters. These were the chamfer angle of the intake nozzle, rotation angle of the intake nozzle, and eccentric distance between the intake nozzle and untwisting tube. The chamber angle of the intake nozzle mainly induces a radial flow from the axial flow in the intake nozzle. The strength of the circumferential airflow in the untwisting tube, which is converted from the radial flow, is affected by the combined effects of the rotation angle of the intake nozzle and the eccentric distance between the intake nozzle and untwisting tube. An experimental bench that employed a high-speed camera to capture yarn movement was designed to verify the numerical results. Comparisons between simulation and experimental data show that the structural parameters of the untwisting chamber affect the airflow patterns and consequently the performance of untwisting the yarn end.