Design of the nozzle of a yarn suction gun for fully drawn yarn

Abstract

The yarn suction gun is a kind of fluid machinery using compressed air as power. Airflow geometry in the gun has a significant influence on the airflow distribution, which decides the yarn suction performance. To clarify the effect of the nozzle structure on the yarn suction performance, we designed 16 nozzles, determined yarn suction force F, mass flow rate of compressed air G and analyzed yarn suction efficiency , which is defined as the ratio of F to G. The rational geometrical parameters are obtained as follows: the number of jet orifices N ¼ 3, jet orifice diameter d ¼ 1.6 mm, jet orifice angle f ¼ 75 and passage diverging angle of the nozzle ¼ 60 . A smaller N reduces the conflict between jet streams and then increases . Decreasing d contributes to greater but smaller F. In the range of f 75, increasing f causes both F and to increase. An appropriate promotes the yarn suction performance by helping the injected air to go forward smoothly and reducing backflow. It is more rational to use to evaluate the yarn suction performance.

Numerical Simulation Analysis of Influence of Jet Orifice Structure on Fluid Field in Yarn Suction Gun for Fully Drawn Yarn

“…N>3), the mutual conflict of sprayed airflow was enlarged, and the kinetic energy loss was increased, which led to decrease of airflow velocity and vortex intensity. This may be one of main reasons why the yarn suction force F was highest when N=3 [12]. As shown in Figure 4, when N≥2, v z and v c near tube wall of Laval tube and straight tube were all much larger than those in center part, so the stronger swirling flow was formed.…”

“…As v c increased, screw pitch of yarn in helical motion was reduced, L was enlarged. Near the tube wall, v c reached to the largest value when N=3, this is one of the main reasons why F achieved the largest value when N=3 [12].…”

“…Figure 2 shows the three-dimensional computational domain of yarn suction gun. Because 0.6 MPa (absolute pressure, the following contents all using absolute pressure) of supply pressure was employed in literature [12], to facilitate comparison, the supply pressure of compressed air and the kelvin temperature in this work are P 0 =0.6013 MPa and T 0 =293 K, respectively.…”

“…Hence, when N=1, the swirling flow was very weak, the zone of negative pressure inside Laval tube was small, which cannot produced enough suction force. This is the main reason why the yarn suction gun cannot achieve suction of yarn reported in literature [12].…”

“…Li etc. further designed the structure of yarn suction gun [11][12][13], achieving more reasonable nozzle structure [12]. However, the mechanism of the effect of jet orifice structure parameters in nozzles on the properties of yarn suction guns is still not clarified.…”