The Design And Simulation Of An Air Pre-twister Based On Air-jet Vortex Field

The pre-twisted ring spinning is raised by the research of the twisting and winding principle of ring spinning in this thesis.The fiber strand is twisted by the vortex field and ring twisting separately in this spinning system.Through this process,the spinning speed will be improved greatly.The main content of this thesis is the design of an air-twister in the pre-twist ring spinning system based on the jet-vortex field.And the computational fluid simulation is used to study the airflow motion in the pre-twister.The important structure parameters are also researched to be optimized,meeting the requirement of air pre-twisting.Through the research,the main achievements can be divided into the following three aspects:(a)The study of the airflow motion simulation in the air pre-twisterWith the numerical simulation by the fluid dynamics software-FLUENT,the airflow motion in the pre-twister is studied.The air vortex field in the air twisting cavity is generated by the eompressed air from the nozzles.And a low pressure zone is generated in the twisting eavity because of the significant airflow's centrifugai effect.Thus the air is sueked into the twisting cavity from the feeding channel and the exporting channel At last the air is exhausted through the air outlets to the atmosphere.(b)The design of airflow pre-twisterAccording to the structure of ring spinning and twisting device of the existing air jet vortex field theory,carries on the design to the airflow pre twisting device based on.The first generation of pre-twister had some wrapped twisting effect.But fake twist phenomenon of the fiber strand is serious because of the large holding distance and the large feeding channel.And the false twisting is eliminated with the arch feeding channel and arch exporting channel in the second generation of pre-twister.But the airflow blocking in the nozzle is caused by the 3D print,reducing the airflow twisting.The size of the third generation of pre-twister is further reduced,shortening the fiber clamping distance.And the distance of heave is shortened as well to enhance the airflow effect.(c)The study of the key structure parameters of air pre-twisterThrough the single variable numerical simulation,it is clear that the effect of the conical angle of the twisting cavity and the diameter of nozzle is significant,while the influence of nozzle axial angular and radial angle is not obvious.With the cavity conical angle increasing,the radial velocity decreases,as well as nthe tangential velocity increases.So the small conical degree makes the insufficiency diffusion of the fiber,but decreases the twisting effect The big diameter of nozzle enhances the airflow motion in the cavity directly.With the increasing nozzle diameter,radial velocity and tangential velocity of airflow in the cavity are improved,enhancing the diffusing and twisting effect But the nozzle diameter increasing will cause the energy consumption.The tangential angle of nozzle should not be too large to avoid airflow direct impact to the fiber strand directly.And the axial angle also should not be too large,preventing the increase of pre air-twister's axial size.