新型气流牵伸通道结构模型的构建与性能分析

doi:10.13475/j.fzxb.20220701701

摘要/Abstract

摘要：

为提高牵伸比,缩短纺纱工艺流程,提出一种通过气流来实现对棉条牵伸的方法,即气流牵伸方法。建立了气流牵伸通道的结构模型,通过对气流牵伸通道中纤维与气流的双向耦合影响仿真分析,验证该方法的可行性。结果表明:纤维在气流牵伸通道中波动前进,且在接近或流出通道出口时,纤维再次变直;纤维在牵伸通道中加速前进,且在通道不同位置运动速度不同,其结果是纤维在牵伸通道向前运动过程中实现重新分布;弯钩纤维在牵伸通道中受到的气流牵引力大,因此移动得更快,且纤维的弯钩在向前运动过程中逐渐被拉直;在气流牵伸通道中,纤维经历了加速、重新分布和拉直等过程达到牵伸的目的,证实了气流牵伸方法的有效性。

关键词: 气流牵伸方法, 流固耦合, 数值模拟, 流场特性, 纤维运动规律, 纺纱技术

Abstract:

Objective In the spinning process, slivers need to be drafted for several times to achieve a certain fineness. At present, this process is mainly performed through the roller drafting mechanism. Due to the limitation of the deceleration ratio of transmission system, the velocity ratio of front and rear rollers is generally small, hence the slivers need to be drafted for several times to achieve the needed drafting ratio. In the process of drafting, the friction force between fibers changes dynamically and so does the drawing force. In order to solve the above problems, an airflow assisted drafting method is proposed, and the performance of such a system is modeled and simulated.

Method It was proposed that the sliver from the airflow drafting channel goes directly into the twisting channel of the air-jet vortex spinning machine. The drafting ratio was set to 140 according to the drafting ratio of roving frame and spinning frame. The outlet air velocity of airflow drafting channel was set to 420 m/s, according to the air-jet vortex spinning speed. The inlet air velocity of airflow drafting channel was calculated as 3 m/s. The model of the airflow drafting channel was established (Fig. 4). The fluid-solid coupling simulation platform was built based on ANSYS Workbench software, and the fluid-solid coupling effects of single straight fiber, two parallel straight fibers and a single hooked fiber were numerically simulated, respectively.

Results The motion trajectories of a single straight fiber, two parallel straight fibers and a single hooked fiber in the drafting channel were obtained by simulation (Fig. 12-14). The fiber was accelerated forward in the drafting channel, and its motion track was wavy (Fig. 12). Due to the large velocity gradient of the air in the drafting channel, the air velocity at the fiber head was higher than that at the fiber tail. As a result, the fiber straightens again when it flew out of drafting channel. When two straight parallel fibers moved in the drafting channel, they got close and eventually contacted each other (Fig. 13). Because of different air velocities at different positions in the drafting channel, the two fibers stagger with each other in the forward process. Compared with straight fibers, the single hooked fiber moved faster in the drafting channel, and the total moving time was greatly reduced (Fig. 14). At the same time, Because of the influence of the friction force of the air, the hooked fibers gradually extend straight during the forward motion.

Conclusion Through the analysis of the above results, these conclusions can be attained. Firstly, velocity gradient of the air in the drafting channel is large, which makes fibers accelerate forward and straighten again when they exit the drafting channel. Secondly, when multiple fibers move in the drafting channel, different fibers stagger forward by means of different air velocities at different positions. That is, the fibers are redistributed in the advancing process. Thirdly, in the process of movement, the hooked fibers will be gradually straightened due to the friction force of the air. So the purpose of straightening fibers is realized similar to that of roller drafting. Finally, Becaust of the boundary layer effect of the air, the air velocity close to the inner wall of the drafting channel is smaller than that in the center of the drafting channel, and the farther away from the center, the lower the air velocity, suggesting that the fibers tend to move close to the inner wall as they move forward. In summary, in the airflow drafting channel, fibers can be accelerated, redistributed and straightened, that is, the purpose of drafting can be achieved, verifying the effectiveness of the airflow drafting method.

Key words: airflow drafting method, fluid-solid coupling, numerical simulation, flow field characteristic, law of fiber motion, spinning technique

中图分类号:

TS103.2

王青, 梁高翔, 殷俊清, 盛晓超, 吕绪山, 党帅. 新型气流牵伸通道结构模型的构建与性能分析[J]. 纺织学报, 2023, 44(11): 52-60.

WANG Qing, LIANG Gaoxiang, YIN Junqing, SHENG Xiaochao, LÜ Xushan, DANG Shuai. Establishment of novel model and performance analysis of airflow drafting channel[J]. Journal of Textile Research, 2023, 44(11): 52-60.

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试样	密度/ (kg·m^-3)	弹性模量/ Pa	泊松比	直径/ mm	黏度/ (kg·m^-1·s^-1)
纤维	1 540	8×10⁹	0	0.1	—
空气	1.225	—	—	—	1.789 4×10^-5