喷气涡流纺旋转气流场及纱体运动的数值模拟

Numerical Simulation of Swirling Airflow Field and Yarn Motion in Vortex Spinning

对喷气涡流纺喷嘴内的高速旋转气流场进行分析研究,并在此基础上研究纱体在该气流场中的运动。对喷气涡流纺喷嘴及纱体分别进行三维建模,采用Realizable κ-ε模型求解高速旋转气流的湍动特征,采用壁面函数法对近壁区域的流动进行求解,采用三角形插值法对纱体运动进行求解。实现对喷嘴内高速旋转气流的动力学特性及纱体运动的三维数值模拟分析,揭示喷气涡流纺纱过程中喷嘴内高速旋转气流的流动规律、湍动现象及纱体的运动情况。模拟结果表明:气流速度在喷孔出口处最大,且气流区域各截面的径向速度均为正值,这有助于自由端纤维的形成和纱强力的提高;喷嘴内气流区域各截面有不同程度的不规则湍流涡存在;温度在喷气孔的出口处最小;喷嘴内气流的静压值大部分为负压且小于外界大气压强;喷气孔气流流线进行较为规律的旋转运动,而喷嘴入口气流流线较为复杂,并有回流现象;纱体在喷嘴高速旋转气流场中运动时会产生较大的位移和弯曲,而产生的扭转相对较小,几乎没有伸长。

High-speed swirling airflow field in the vortex spinning nozzle was studied. On the basis of the airflow field, the single yarn motion is further studied. Three dimensional numerical simulation models of vortex spinning nozzle and a single yarn were established, respectively. Realizable κ-ε model was used to solve the turbulent characteristics of high speed rotating flow, and the wall function method was used to solve the flow in the near wall region. The displacement of a single yarn under the action of the airflow force was solved by the interpolation function method. Thus, the three-dimensional numerical simulation of high-speed swirling airflow dynamic characteristics and the single yarn movement in the nozzle were obtained and analyzed. The research further reveals the principle of the high-speed swirling airflow, the turbulent phenomenon, and the movement of a single yarn in the vortex spinning nozzle. The simulation results show that the airflow velocity is maximum at the exit of jet orifices, and the radial velocity of each cross section of the airflow area is positive, which is conducive to the formation of free end fibers and to improve the yarn strength. Irregular turbulence vortices exist in the various cross sections of the airflow area in the nozzle. The temperature is minimal at the exit of jet orifices. The static pressure of the airflow in the nozzle is mostly negative and less than the external atmospheric pressure. The streamlines of jet orifices rotate regularly, however, the streamlines of nozzle inlet is complex which has reflux phenomenon. When the yarn body moves in the high-speed rotating airflow field of the nozzle, it produces greater displacement and bending, the torsion is relatively small, and there is almost no elongation.