Abstract:

Objective In order to optimize the airflow state in the converging zone of the compact spinning system, improve the utilization rate of negative pressure, and reduce the energy consumption of production, this research aims to modify the flow field distribution by installing an airflow-guiding device in the converging zone to enhance the effect of airflow. Through numerical simulations and spinning experiments, the performance of the airflow-guiding device was explored under various yarn densities to assess its enhancement of yarn properties.

Method A three-dimensional (3-D) geometrical model of the converging zone was developed, and numerical simulations of the flow field were performed using ANSYS Fluent software. A lattice-apron was innovatively added to the model to obtain a more accurate airflow distribution pattern in the converging zone. At the end of the simulation, the effective airflow area in the converging zone was compared, and the influence of negative pressure and the airflow-guiding device on airflow distribution in the converging zone was analyzed. Finally, spinning experiments were conducted to verify the accuracy of the numerical simulation.

Results A comparison of the enhancement of the effective convergence area by increasing negative pressure and installing the airflow-guiding device showed that the enhancement achieved by installing the airflow-guiding device was significantly more remarkable than that achieved by increasing negative pressure. Numerical simulations demonstrated that the airflow-guiding device was efficient and energy-saving, improving the airflow field in the converging zone without increasing production energy consumption thus enabling better fiber convergence. The number of hairiness (≥3 mm) was reduced across all yarn densities after the installation of the airflow-guiding device. For the yarn linear densities (14.6, 19.4, and 29.2 tex), the greater was the yarn linear density, the more effective was the hairiness reduction. In particular, the hairiness for the three yarns was reduced by 2.88%, 22.7%, and 28.9%, respectively. For the 9.7, 7.3, and 6.5 tex yarns, hairiness was reduced, but the reduction rate was smaller, only 3.57%, 1.02%, and 3.05%, respectively. The combination of numerical simulation and the results of the installation of the airflow guiding device showed that the fiber bundles passing through the convergence zone were subjected to greater transverse airflow forces, resulting in narrower fiber bundle widths and smaller twisted triangles, thus reducing yarn hairiness. In terms of breaking strength, for yarns with the linear density in the range of 6.5-29.2 tex, the breaking strength increased by 2.81%, 3.77%, 2.89%, 3.08%, 7.62%, and 2.24% following the installation of the airflow-guiding device. After installation, the fiber bundle in the converging zone became narrower, fibers were more tightly packed, and friction between the fibers increased, making it more difficult for them to slip, which enhanced the yarn strength and elongation. Regarding yarn evenness, the installation of the airflow-guiding device improved the evenness of all yarns to a certain extent. The increased airflow speed caused fibers to shift from the yarn edges and be distributed more uniformly within the yarn, improving the yarn evenness.

Conclusion An airflow-guiding device was designed for four-roller compact spinning with the lattice-apron, and the influence of the airflow-guiding device on the airflow field was investigated through numerical simulation and spinning tests. The numerical simulation results show that both the increase of negative pressure and the installation of the airflow-guiding device can enhance the effect of airflow in the converging zone. The airflow-guiding device directs more transverse airflow into the converging zone, which facilitates fiber bundle convergence. Yarn performance tests confirm that the airflow-guiding device improves yarn hairiness, elongation, and evenness across six different yarn densities, proving the device's effectiveness and broad applicability. In conclusion, the positive effects of the airflow-guiding device were confirmed in high and low-count yarns through numerical simulation and spinning tests.

Key words: compact spinning, numerical simulation, airflow-guiding device, airflow analysis, yarn quality