Study on Airflow Field of Condensing Zone in Compact Spinning System with Perforated Drum

Negative pressure plays a very important role in compact spinning system.To know airflow field and its distribution is helpful to look into the condensing principle of fiber bundle.Therefore,computational fluid dynamics(CFD)software was used to simulate airflow field in this paper.Airflow velocity distributions both in different fiber layers and under different negative pressures were discussed.The results indicate that airflow velocity in upper layer of the fiber bundle is greater than that in lower layer.Airflow velocities in both X and Y axis directions have a positive correlation with negative pressure.It can provide a theoretical base to make high quality compact yarns in productive practice.

Additional Twists of Yarn Produced by System of Compact Spinning with Lattice Apron

Based on the flow simulation in the condensing zone of compact spinning with lattice apron and a bead-elastic rod dynamic model of the flexible fiber,trajectories of fibers with different negative pressure are simulated by specially designed Matlab procedure.Then displacement components of fibers at YZ profile under different negative pressure conditions are extracted and compared.The results show that the fibers of different initial positions gradually converge,and are interlaced for position change in yarn cross-section,caused by the airflow in the condensing zone.Finally,compact-spun yarn with different negative pressure and conventional ring spun yarn are produced and their twists are tested.Both the results of simulation and experiments illustrate the existence of additional twists.Also the relationship between additional twists and negative pressure is verified.

Motion Analysis of Fiber Band in Compact Field of Compact Spinning

The technological process of compact spinning and the compact procedure of fiber band in compact field are briefly illustrated. The motions of fiber band in compact field are discussed theoretically from which tilting angle of suction slot in profile tube, additional twists created by fiber band’s rotating around its own axis and ultimate twists in compact yarn are deduced accordingly. The existence of additional twists is also verified through experiments.

Simulation and Analysis of Fiber Motion in Condensing Zone of Compact Spinning with Lattice Apron

To get fiber motion in condensing zone of compact spinning,velocity of this area is achieved by simulation,and then a bead-elastic rod fiber model is established.Based on simulation and dynamic analysis on this zone,governing equations are constructed and Runge-Kutta approach is used.Lastly,trajectories of fibers are calculated by specially designed Matlab procedure according to the principles mentioned above.Results show that fiber motions at different initial positions are different;X-axis velocity component makes fibers gathering on sides of suction slot;Y-axis airflow gets fibers gradually close and then stick to the surface of lattice apron.Fiber motions also reflect that the compact spinning process in condensing zone can be divided into three parts:fast convergence zone,adjustment convergence zone,and steady convergence zone.

Numerical Computation in Airflow Field of Compact Spinning with Pneumatic Groove

In compact spinning with pneumatic groove,the computational fluid dynamic model,computed with parallel technologies & Fluent 6.3,is developed to simulate the flow field in condensing zone with 3D computational fluid dynamic (CFD) technology.Flowing state,distribution rules of static pressure,and velocity in condensing zone are characterized and analyzed.The results show that the fiber bundle in compact spinning with pneumatic groove is compacted by airflow and the shape of the pneumatic groove,and the static pressure in condensing zone is negative,as well as the velocity of airflow in condensing zone is not zero.The fluctuation frequencies of the static pressure and velocity near the bottom of the pneumatic groove are relatively higher,and the number of the fluctuation is equal to that of the round holes in condensing zone.

Modeling Additional Twists of Yarn Spun by Lateral Compact Spinning with Pneumatic Groove

Compact spinning with pneumatic grooves is a spinning process to gather fibers by blended actions of airflow and mechanical forces.Modified from the ring spinning system,the lateral compact spinning with pneumatic grooves can improve yarn appearance and properties due to generated additional twists.In this study,we investigated additional twists of the lateral compact spinning with pneumatic grooves via a finite element(FE)method.An elastic thin rod was used to model a fiber to simulate its dynamic deformation in the three-dimensional space,and the space bar unit was used to simplify the fiber model for the dynamic analysis.The stiffness equation of the elastic rod element and the dynamic equation of the rigid body mass element were derived from the differential equation of the elastic thin rod.In the analysis of the nonlinear geometric displacement of the space elastic thin rod unit,the large deformation problem was solved with the stepwise loading successive approximation.The simulation results explained the mechanism of generating additional twists,and the experiment results proved the existence of additional twists.The study demonstrated that the FE model is effective for predicting additional twists of fiber bundles in the agglomeration zone,and for simulating the fiber motion in the compact spinning with pneumatic grooves.

Modeling and analysis of the compact spinning yam structure by interference

The fiber stress and elongation after the yam twisting has been analyzed in this paper. A method has been proposed to improve the strength of compact spinning yam. A structure model of the interference compact spinning yarn was established. It theoretically proves that interference compact spinning yarn has higher strength than that of traditional compact spinning yarn.

Numerical Study on Effect of Suction Slot Geometric Parameters on Airflow Field in Compact Spinning

The airflow field in the condensing zone is crucial as it affects the fiber condensing,additional twists,and consequently yarn properties.Parameters of spinning and suction slot geometric were found to be key factors influencing the airflow characteristics.To develop a better understanding of the complex airflow field within the pneumatic compact spinning system with lattice apron,a 3D numerical simulation model was built and the influence of negative pressure and geometric of suction slot was investigated.The results reveal that the accelerating air from the top of the suction slot generates transverse condensing force and downward pressure on the fiber strand.The inclination angle has a small effect on airflow velocity.The absolute z-velocity and c-velocity in the positive a-axis were both increased with increasing the slot width from 1.0mm to 1.5 mm.An arc suction slot increased the absolute z-velocity and a-velocity compared with a linear one,thus benefiting fiber condensing.By decreasing the outlet negative pressure to-3kPa,the airflow velocity increased significantly.