Numerical Analysis of the Geometrical Effects on the Airflow Characteristics of an Air Suction Gun

The yarn suction efficiency of an air suction gun is closely related to the airflow patterns, which are strongly affected by the geometry of the gun. To obtain basic data for the optimum design of a gun, we investigated the airflow patterns in the gun with different geometrical parameters by numerical simulation and discussed the relation between the flow patterns and yarn suction force Fm. Compressed-air inflow angle plays an important role in generating a helical flow by controlling circumferential velocity component vc in a yarn propulsion tube. This helical airflow greatly promotes yarn suction capacity. Fm has a closer relationship to the distribution of air velocity than air pressure, and strongly depends on vc. The airflow patterns are weakly dependent on a passage diverging angle of nozzle and a converging angle of de Laval tube. A reduction in throat diameter of de Laval tube causes a rapid extension of the supersonic flow area near the throat accompanied by increasing axial velocity component in the de Laval tube. However, it leads to decreases in vc in the yarn propulsion tube and air velocity in the yarn inhalation tube, which hinders the promotion of Fm.