Abstract
In order to clarify the working mechanism of an air suction gun, yarn motion in the air suction gun was captured with a high-speed video camera, then characteristics of the yarn motion in the air suction gun and the geometrical effects on the yarn motion were investigated. A yarn moves forward with a high-speed rotation in a yarn propulsion tube, and performs a helical motion more regularly in a de Laval tube than in a straight tube. The motion path is different from the yarn posture. The yarn motion is unsteady and considerably affected by the friction from the tube wall, which causes a large reduction in the yarn circumferential velocity component vyc. The changes in the geometrical parameters mainly produce changes in vyc with a negligible effect on the yarn axial velocity component. vyc increases with an increase in the compressed-air inflow angle and with a decrease in the throat diameter of de Laval tube. An increase in the convergence angle of de Laval tube causes vyc to increase in the de Laval tube. Yarn motion is almost independent of the passage divergence angle of nozzle. It is mainly determined by the circumferential component of air velocity vac and bears less relationship to the axial one. Yarn suction force Fm is associated with various effects, and depends on vyc in particular. For achieving a high Fm, the swirl intensity of helical airflow, namely vac, needs to be controlled at an appropriate level because an increment of vac increases both air drag on the yarn and friction between the yarn and the tube wall.
