Numerical Investigation On The Flow Field Of Vortex Spinning Nozzle With Fewer Lost-fibers

Air jet vortex spinning uses high-speed airflow to realize fiber bundle separation and twisting.The axial force and centrifugal force of the high-speed airflow in the annular area between the vortex tube and the hollow spindle head make the tail of fiber overcome the restraint during twisting and break free.The bound fibers flow into the exhaust chamber,causing unnecessary fiber loss.The previous work of the researchers verified the effectiveness of the fewer-fibers air-jet vortex spinning nozzle with suction holes on the pipe wall.But the fewer-fibers reduction mechanism of this design has not been revealed yet.This article analyzes the swirling characteristics of the fewer-fibers air-jet vortex spinning nozzle with suction holes,and explores the mechanism of the reduction of the fewer-fibers The specific research work of this paper is as follows:(1)Use Gambit software to model and mesh the fluid area of the nozzle of the low-fiber air-jet vortex spinning.Use Fluent software to perform steady-state numerical calculation of the flow field in the nozzle of the low-noil air-jet vortex spinning.Analyze physical parameters such as the velocity and pressure of the flow field.It is concluded that under the suction action of the negative pressure source,after the airflow in the fiber input channel and the wire guide hole enters the vortex tube,a part of the airflow is entrained by the high-speed rotating airflow and flows between the vortex tube and the hollow spindle head end.Between the annular area.The other part of the airflow is sucked by the negative pressure and flows into the yarn-drawing tube,so there are only two backflows in the vortex tube.The high-speed rotating airflow is not affected by the negative pressure suction and flows into the yarn take-up tube.(2)Analyze the change of nozzle air field velocity to explore the influence of the suction hole parameters on the tow amount and yarn breaking strength.The results show that: the amount of tow is related to the average axial velocity at the entrance of the take-up tube.The increase of the average axial velocity increases the downward force on the fiber head end,which in turn increases the upward pulling force on the fiber tail end,which can make The end fiber resists the pulling action of the high-speed airflow,thereby reducing fiber drop.For example: when the diameter of the suction hole increases from 0.2 mm to 0.3 mm,the average axial velocity increases significantly;when the number of circumferential rows of suction holes increases from 2 to 3,the average axial velocity increases significantly;When the axial distance between holes is reduced from 2 mm to 1 mm,the average axial velocity increases significantly.The average axial velocity at the entrance of the take-up tube is consistent with the experimental results of previous researchers.The breaking strength of the yarn is related to the average radial velocity of the suction hole section and the force-bearing area of the yarn.The greater the average radial velocity means the greater the radial force on the yarn,the lower the cohesion between the fibers,and the lower the breaking strength of the yarn.When the force area of the yarn is reduced,the overall force of the yarn is reduced,which can increase the yarn breaking strength.For example: when the diameter of the suction hole is increased from 0.2 mm to 0.3 mm,the average radial velocity in the yarn-drawing tube increases,and the yarn breaking strength decreases;when the number of circumferential rows increases from 2 to 4,the average radial velocity Increase,the yarn breaking strength decreases.When the axial distance of the suction holes is increased from 1 mm to 2 mm,the average radial velocity of the suction hole section increases,but the force area of the yarn sliver decreases significantly,which reduces the overall force of the yarn,and the interval is 2 mm.The yarn breaking strength is greater than the yarn breaking strength of 1 mm.(3)Analyze the changes in the flow lines of the fiber input channel and the wire guide holes in the nozzle to explore the influence of the suction hole parameters on the core yarn coating quality.The results show that there are two main reasons for the deterioration of the core yarn covering quality.On the one hand,when the suction hole velocity near the inlet of the yarn take-up tube is large,the part of the stream flowing in from the inlet of the yarn take-up tube is drawn from the front row.The outflow from the suction hole causes the yarn sliver to move significantly in the radial direction,which causes the metal wire to sway at the entrance of the yarn-drawing tube,causing uneven fiber winding.On the other hand,when the average axial velocity at the entrance of the yarn-drawing tube is too high,the fiber head end will move rapidly in the downstream direction,and the fiber tail end will be wound on the metal wire without sufficient rotation,resulting in a decrease in the coating quality.The wire shook violently at the entrance,resulting in a decrease in the quality of the coating.For example: when the number of suction holes is 2 rows,the average axial velocity at the inlet of the yarn-drawing tube exceeds twice the axial velocity of the annular area between the vortex tube and the head end of the hollow spindle and is close to the suction aperture direction of the inlet of the yarn-drawing tube.The speed is high,and the sloshing of the metal wire aggravates the unevenness of the fiber winding,making the coating quality of the suction hole with 2 rows poor;when the length of the suction area is reduced from 34 mm to 25 mm,the yarn-drawing tube The average axial velocity at the entrance is similar,but the suction aperture near the entrance of the yarn-drawing tube increases in velocity,and the wire sloshes,resulting in a decrease in the coating quality;when the axial spacing of the suction holes increases from 1 mm to2 mm,the suction hole The average axial speed at the entrance of the bobbin is reduced,the fiber end can be fully rotated and wound on the metal wire,and the coating quality is improved.(4)The Bayesian neural network and particle swarm optimization algorithm are used to establish the multi-objective model of the low-fiber air jet vortex spinning nozzle,and the particle swarm algorithm is used to optimize the weight distribution of the Bayesian neural network,and then the objective function is set to perform iterative optimization.Finally,the optimal parameter combination was obtained as a suction hole diameter of 0.32 mm,a suction hole axial distance of 1 mm,a circumferential arrangement of suction holes of 3,and a suction area length of 30 mm.Under this optimal parameter combination,the average axial velocity at the entrance of the yarn-drawing tube is 164 m/s and the radial velocity is 5.88 m/s.The optimal parameter combination is modeled for fluid simulation,and the error between the simulation result and the algorithm calculation result is within 10%.