Study On Internal Flow Field Of Nozzle And Fiber Yarn Forming Mechanism Of MVS

Air-jet vortex spinning utilizes vortex produced by jet-stream wind to finish twisting and wrapping the free end fiber accumulating on the top of the hollow spindle.Nozzle is the key component of this technology,the characteristics of its internal airflow field affect the quality and efficiency of air-jet vortex yarn,while the mutual coupling between fiber bundle and air stream is the key to the spinning mechanism.In this paper,the nozzle of air jet vortex spinning was researched.In order to make up for the shortage of previous simulation of nozzle airflow field and to provide a theoretical reference for thoroughly uncovering the spinning mechanism of jet vortex spinning,the relationship between the airflow characteristics of its internal airflow field and the relevant structural parameters(position,angle,number and Jet orifice opening)of the jet hole was studied,and the motion disciplinarian of fiber bundle-airflow two-phase coupling on the situation of air flow field were studied.The conclusions are drawn as follows:1.The influence of the jet hole position on the characteristics of internal airflow field is not obvious.Considering the effects of backflow on the fiber bundle twisting,the best range of H(the distance between the jet hole entrance and the upper face of twisting chamber)is 1 ~ 1.5mm.2.The angle of the jet hole has a great influence on the characteristics of the internal airflow field.With the increase of the jet hole angle,the rotational motion of air flow is gradually enhanced,backflow will occur at the nozzle entrance when the jet hole angle increases to a certain value(70? in this paper).According to the distribution disciplinarian of pressure and velocity of airflow field,the optimal range of the jet hole angle is 50?~ 60?.3.The number of jet holes has a significant influence on the characteristics of internal airflow field.With the increase of the number,the rotational motion of air flow is gradually enhanced,the suction pressure at the nozzle entrance to attract fibers is also increased.4.Jet orifice opening has a great influence on airflow velocity and pressure inside the nozzle,while the increase of the orifice opening,the velocity on the same position increases and the pressure decreases.5.When the fiber bundle moves in the airflow field,bending deformation occurs because of different pressure on both sides,And the displacement of the fiber bundle along the Z direction presents the characteristics of periodic oscillation meanwhile the fiber moves forward in the form of spiral moving with wave characteristics in the whole process.6.The end fiber is separated from the fiber bundle during the fiber bundle rapid swing and add twist to fiber under the action of rotating airflow to complete twisting and wrapping.The shorter exercise period of the end of the fiber bundle and the higher frequency is,the higher strength of the yarn twisting is.Increasing the boundary pressure can effectively improve the yarn strength and the efficiency of twisting and wrapping.