Numerical simulation of airflow characteristics in the spinning zone at starting time of air-jet spinning machine

To clarify the formation mechanism of a source of yarn and to discuss the effects of supplied air pressure and exhaust air pressure on the fiber suction force and twist torque at the starting time of the spinning process in an air-jet spinning machine, we simulated, numerically, the three-dimensional airflow pattern without fibers in the spinning zone. Results obtained are as follows: High-speed air jetted through the starting nozzles into the yarn duct in the circumferential direction causes a swirl flow in the yarn duct and a negative pressure region near the center axis of the yarn duct. Hence, air and fibers at the fiber inlet are sucked through the processing duct into the yarn duct. A fiber bundle sucked into the yarn duct rotates, owing to the action of the swirl airflow, and twists the fiber bundle in the processing duct, hence generating a source of yarn. The fiber suction force takes a distribution with a peak against the supplied air pressure and is independent of the exhaust air pressure. The fiber twist torque increases monotonously with supplied air pressure.