Abstract:

Objective Ring spinning produces a wide range of yarn varieties and yarn fineness with great variety of raw materials, and with simple and easy maintenance of spinning machine. These advantages determine its popular use in producing yarns. However, because of the existence of the twisting triangle area associated to ring spinning, it is difficult to further improve the yarn quality. Also the fact that it integrates twisting and winding together, resulting in the incapability of greatly improving the spinning speed and the reduction in production efficiency. Especially in long fiber spinning, harmful hairiness is an important factor affecting yarn quality. How to reduce harmful hairiness and improve yarn quality is a problem to be solved in spinning. This research was devoted to the reduction of harmful hairiness of long fibers to improve the spinning performance for long fibers.
Method In this research, a three-dimensional model of the agglomeration area was established, and the fluid flow in the agglomeration area was simulated by using the Fluent module of ANSYS software. Computational fluid dynamics (CFD) was adopted to simulate the flow field in the gathering area with different groove structures of compact spinning to analyze and compare the characteristics of different groove shapes of the compact spinning device. Finite element method (FEM) was adopted to simulate the CFD models and mathematical statistics methods were employed in processing the experimental data.
Results 27.78 tex ramie yarn was spun and yarn properties were tested to verify the gathering performance of asymmetric grooves and the influence of gathering airflow on yarn formation. Comparing the final yarn results of asymmetric groove, symmetric groove and ring spinning, the yarn hairiness (77.58%) spun by asymmetric groove gathering device was lower than that of ring spinning, and the yarn strength was 14.32% higher than that of ring spinning. Yarn evenness analysis revealed that the evenness CV values of the two compact spinning devices were not greatly improved compared to ring spinning. The results of this experimental hairiness tests were consistent with the aforementioned theoretical results. The asymmetric groove air flow groove gathering device combine airflow and mechanical action for better fiber gathering and can effectively utilize the gathering air flow. Under the action of the higher gathering air flow, the gathering effect of the fiber whiskers was better and the yarn strength became higher, significantly improving the yarn forming performance.
Conclusion Under the same negative pressure condition, different groove shapes affect the transmission effect of negative pressure. Among the two different groove gathering devices used in this research, the asymmetric gathering device showed the highest speed in the gathering direction of the gathering area. It can gather fibers to a greater extent, hence reduce yarn hairiness and improve yarn strength. The experimental results show that the yarn hairiness of the yarn with different air flow grooves is greatly reduced compared with that of the ring spun yarn, and in the final yarn of the asymmetric groove gathering device, the hairiness above 3 mm decreases the most, and the strength increases, which improves the yarn quality and performance. For the air-flow groove with the groove shape used in the asymmetric condensing device, it needs to be further improved theoretically and experimentally, facilitating the industrialization of the ramie spinning device in the future.

Key words: compact spinning, gathering groove, airflow field, yarn property, airflow velocity