Abstract: Rotor spinning is a widely used new spinning method with the advantages of short process flow and high production efficiency. The fiber strands are directly fed into the carding device and released into a single fiber state, and are transferred to the rotor through negative pressure airflow for condensation and twisting into yarn. The fibers fed into the rotor spinning machine contain various forms of fibers, and are mainly divided into the three categories of straight fibers, front hook fibers, and rear hook fibers. In actual production, it is necessary to avoid the entry of rear hook fibers. If there are many rear hook fibers, the spun rotor yarn may have uneven evenness and easily produce coarse and fine knots. This is the experience summarized in the production process. Therefore, exploring the morphological changes of hook fibers in the rotor spinning machine, as well as the straightening and formation process of hooks, provides reference for improving the spinning mechanism of rotor spinning, and optimizing the rotor structure and process parameters.
We aimed to solve the fiber motion trajectory using the Lagrangian-Euler method, with the airflow as a continuous phase and the fibers as discrete phases. Firstly, we used the 3D modeling software SolidWorks2021 to establish a model of the rotor spinning machine. Then, we coupled and connected Rocky DEM 2022R1 and ANSYS Fluent 2022R1. As for the airflow field, we selected the Standard k-epsilon turbulence model, Standard Wall Function (SWF), and SIMPLE algorithm. The fiber model is of a rod chain structure, and is made of cotton fibers with a length of 28mm. The fiber model established in this article has the size and properties of real cotton fibers, and has been optimized on the fiber model. At the same time, the changes in fiber morphology under different initial forms were considered. The deformation pattern of the hook fibers in the fiber transmission channel under conditions 1-2 is basically consistent, with a small trend of movement towards the main section in the bent section; from the exit of the fiber transport channel to the slip surface, different hooked fibers undergo different morphological differentiation processes; the pattern of morphological changes in the coagulation tank is also roughly the same, with the fibers transitioning from wavy bending to a state close to the inside of the coagulation tank. When the front hook fiber completely enters the condensation groove, the hook part has been straightened and eliminated; after the non-straightened rear hook fibers in the fiber transmission channel enter the condensation tank, it is difficult to fully straighten the hook part. The straightness of the front hook fibers in the condensation groove is significantly higher than that of the rear hook fibers. Therefore, feeding fibers into the rotor spinning machine in the form of hooks can optimize the yarn structure. 
To sum up, numerical simulation is a very good research method. Firstly, computer simulation of the flow field and fiber movement process inside the rotor spinning machine can provide theoretical guidance for production optimization and design solutions, reduce experimental trial and error costs, and improve efficiency. Secondly, by conducting in-depth research on the airflow field and fiber movement process inside the spinner, the mechanism of rotor spinning yarn formation is gradually improved, providing a theoretical basis for the key components such as the fiber conveying channel and rotor in rotor spinning.

Key words: rotor spinning, hook fibers, fiber straightness, changes in fiber morphology, numerical simulation

摘要： 为研究转杯纺纺纱器（输纤通道、滑移面和凝聚槽）中纤维弯曲形态的变化规律，借助数值模拟软件Rocky DEM 2022R1和ANSYS Fluent 2022R1，基于Fluent仿真得到的气流场数据，分别模拟了工况1（朝上后弯钩）和工况2（朝上前弯钩）弯钩纤维在纺纱器内的形态变化过程，对气流特征、纤维弯钩的伸直、弯钩的形成和凝聚槽内纤维伸直度进行分析。结果表明：输纤通道内气流速度梯度随气流流向递增，凝聚槽内气流速度分布不均匀，存在低速和高速气流区；两种工况的弯钩纤维的形态变化规律基本一致，但在输纤通道出口至滑移面处，弯钩纤维呈现出不同形态；前弯钩纤维在完全进入凝聚槽时，弯钩部分会被伸直消除，而后弯钩纤维进入凝聚槽后，其弯钩部分难以完全被伸直；在凝聚槽内，前弯钩纤维的伸直度显著高于后弯钩。该研究通过数值模拟分析探索纤维形态的变化规律，可为生产优化和设计解决方法提供理论指导，对转杯纺输纤通道、转杯等关键部件的设计具有参考意义。

关键词: 转杯纺, 弯钩纤维, 纤维伸直度, 纤维形态变化, 数值模拟