【摘要】 为明确喷气涡流纺纺纱过程中加捻腔内的气流变化和纤维运动规律，对引纱过程和稳定纺纱过程中的气流和纤维运动进行模拟研究。结果表明：高速旋转气流的卷吸作用使得喷嘴入口形成负压气流吸入纤维，还导致加捻腔出现向上运动的气流，在纤维输入通道内形成回流区域。引纱纺纱过程中喷嘴加捻腔内的气流场分布规律与纺纱阶段下的分布规律相似，但是受到空心管内的气流影响，越靠近空心锭口，负压值和气流速度就越大，越靠近导引针，梯度越不明显，在引纱通道内有明显的压力、速度梯度分布。在纺纱过程中纤维在喷嘴内的运动分为4个阶段，分别对应纤维输入通道进出口、加捻腔进出口、空心锭表面停留和引纱管进出口。从纤维输入通道进口到出口纤维速度逐渐增大，进入加捻腔后加速度进一步增大，速度更快，继续向前接触空心锭表面在进入引纱管前，纤维速度逐渐降低，进入引纱管后速度提高并在引纱管出口达到最大；在引纱过程纤维速度变化与此类似。更多还原

【Abstract】 Objective The quality of yarn produced by airjet spinning is highly dependent on the airflow field characteristics inside the nozzle. However, the nozzle′s complex structure and small internal space make direct experimental measurement of the airflow field challenging. In oder to clarify the airflow variation and fiber motion rules in the twisting chamber during spinning, finite element simulation was employed to investigate the airflow and fiber motion during both initial and staple spinning stages.Method First, a three-dimensional geometric model of the air-jet vortex spinning nozzle was established, followed by mesh division and boundary condition configuration. Numerical simulation of the flow field in the standard nozzle model was then performed, with in-depth analysis of the flow patterns inside the twisting chamber. Second, a discretized flexible fiber model was developed to characterize the fiber′s physical and mechanical properties. Finally, coupled simulations were conducted using Rocky DEM 2022R1 and ANSYS Fluent 2022R1 to simulate the fiber′s dynamic behavior during the yarn piecing and twisting processes of air-jet vortex spinning, and systematic spinning experiments were carried out accordingly.Results The results indicate that the rotational suction effect of the high-speed swirling airflow induces negative pressure at the nozzle inlet to draw in fibers. Meanwhile, it drives the airflow in the twisting chamber to move upward and forms a backflow region in the fiber feeding channel. The opposite directions of radial and axial airflow at different radial positions are crucial for ensuring the smooth convergence of fibers into the twisting chamber for entanglement and twisting, thereby forming a core-sheath yarn structure(outer fibers wrapping core fibers). The distribution pattern of the airflow field in the nozzle twisting chamber during the initial spinning stage is similar to that in the steady spinning state. However, affected by the airflow in the hollow tube, the negative pressure and airflow velocity increase as the position approaches the hollow spindle orifice, while the gradient becomes less significant near the guide needle. A distinct pressure and velocity gradient distribution is observed in the guide channel.Fiber motion within the nozzle in the spinning stage can be divided into four stages, corresponding to the following periods: fiber passage through the inlet and outlet of the fiber feeding channel, the inlet and outlet of the twisting chamber, fiber residence on the hollow spindle surface, and passage through the inlet and outlet of the guide tube. Fiber velocity increases gradually in the fiber feeding channel. Upon entering the twisting chamber, the acceleration increases further, leading to a higher speed. As the fiber moves forward and contacts the hollow spindle surface, its speed decreases gradually before entering the guide tube. After entering the guide tube, the speed increases again and peaks at the guide tube outlet. The fiber velocity variation in the yarn piecing stage follows the same trend.Conclusion This study conducts an in-depth investigation into the airflow characteristics within the twisting chamber, analyzes the motion characteristics of fibers during both the yarn piecing stage and the spinning stage, and reveals the coupled motion mechanism between the airflow and fibers inside the nozzle. The findings are of great significance for optimizing the spinning process and designing key structural components. Currently, fiber simulations are limited to motion pattern variations. Future research could extend to simulating fiber aggregation, twisting, and yarn piecing processes, which would facilitate a more comprehensive understanding of the laws governing fiber motion and morphological evolution. Owing to computational resource limitations, the current simulations are constrained by the number of fibers and time steps. Future work should focus on expanding the simulation scale(i.e., increasing the number of fibers and prolonging the simulation duration) and simulating continuous fiber feeding to better replicate actual production scenarios.更多还原