关键词: 喷丝板, 不停丝, 自动化铲板, 流体仿真, 螺旋流场, 集排丝技术, 倒漏斗状集丝装置

Abstract:

Objective Regular shoveling on the spinneret surface is necessary to ensure spinning quality. Automated shoveling under non-stop-spinning conditions can ensure stable spinning quality without stopping the pump. However, the technical solution of rotating the filament collecting bobbin and the shovel assembly together requires high rotation speeds to ensure successful collection of the waste filament, which to some extent negatively affects the shoveling results. In order to eliminate the negative effects of waste filament collecting operation on the shoveling effect when non-stop-spinning automated shoveling, a method was proposed for the design of a non-stop automated shoveling system with the filament collecting device stationary at the center and the offset shovel assembly for continuous rotation, so that board shoveling and filament collection could operate simultaneously without any mutual influence on the operating effect.
Method By applying mechanical design and gearing technology, the inverted collecting funnel was located directly below the spinneret to collect filament and the shovel assembly was driven by a motor to rotate around the spinneret axis to do shove movement. Based on hydrodynamics, the airflow field was designed by combining upper positive pressure blowing with lower negative pressure pumping to form a spiral downward flow of air. In such a way, the waste filament was blown away from the funnel wall and gathered inwards to wind down and discharge. The structural and airflow parameters of the filament collecting assembly were designed in detail by applying fluid simulation analysis methods, and an experimental equipment was developed for test verification.
Results Firstly, the layout and inclination of the air guide holes were designed to form a spiral cohesive airflow field inside the funnel. A spiral-blowing pipeline with multiple spaced through holes was arranged on the outer wall of the collection funnel to guide the external air with positive pressure into a spiral airflow inside the funnel (Fig. 2). The simulated flow field domain model of the filament collection system was built (Fig. 4). After setting the relevant flow parameters, the flow field simulation was carried out for the cases with different number of air guide holes 5, 6 and 7, whose inclination angle was between 25° and 55°, and through the simulation analysis the number of holes was determined to be 6 and the inclination angle to be 40° (Fig. 5). Then, setting the design targets as the peak temperature fluctuation of the spinneret surface at no more than 3 ℃ and the temperature drop of the surface at no more than 18 ℃, simulation of the internal flow field of the collection system was carried out for working conditions with blowing flow rates of 20, 35, 40 and 45 m/s. By observing the temperature cloud of the spinneret surface and measuring the flow velocity in the shielding zone, the relationship between the relevant temperature and flow parameters and the blowing rate was obtained (Tab. 1), and it was found that the design specifications could be satisfied when the blowing rate was valued less than 25 m/s. Finally, the negative pressure parameter at the end of the filament discharge pipeline was adjusted to achieve effective contact between negative pressure pumping and positive pressure blowing at the lower end of the funnel, and thus the flow distribution of the filament collection system was further optimized to form a spiral cohesive downward airflow field. Setting the blowing rate at 15 and 20 m/s, a steady-state analysis of the flow field of the filament collection system was carried out (Fig. 6), and it was found that the trend of uneven flow distribution in the circumferential direction inside the funnel increased as the end vacuum increased. Further combined with transient analysis of the flow field, it was found that at a blowing rate of 15 m/s and an end pressure of -85 Pa, the filament collection system was able to quickly generate a spiral downward flow field within 2.5 s (Fig. 7). As a result, the flow parameters of the blowing rate and end negative pressure were determined.
Conclusion After completing the design of the main parameters of the non-stop automated shoveling system, the design correctness was further tested through fluid simulation and actual experiments. It was found that the traces presented a curved and oblique inward shape, and closer to the center of the pipeline, the pitch of the trace decreased until it became straight, so the airflow field of the collecting system could achieve spiral cohesive downward flow. The simulated filaments converged inwards and intertwined within the positive and negative pressure flow field, thus also verifying the correctness of the system design above. The research reported in this paper has achieved the independence of the board shoveling and wire collection in terms of design parameters, and effectively solved the adverse effects of waste filament collecting operation on the shoveling effect, and thus provided a new technical solution for automated board shoveling under non-stop-spinning condition.

Key words: spinneret, non-stop-spinning, automated board shoveling, fluid simulation, spiral flow field, filament collection and discharge, inverted-funnel shaped filament collecting device