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Modeling of pneumatic melt spinning processes

机译：气动熔纺工艺建模

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Computer simulation of the pneumatic processes of fiber formation from the polymer melts is discussed. The dynamics of air-drawing of thin polymer streams in supersonic air jets formed in the Laval nozzle is presented versus the melt blowing process. In the Laval nozzle process, the air flow takes place with high Reynolds number and the k-ω model is used which considers kinetic energy of the air flow and the specific dissipation rate of the kinetic energy. For melt blowing, the air fields are simulated with the use of the k-ε turbulent model. The air velocity, temperature, and pressure distributions along the centerline of the air jets are considered in the modeling of both pneumatic processes. The air fields are predetermined at the absence of the polymer streams for several air compression values in the Laval nozzle inlet and several initial air velocities in the melt blowing process. Each polymer stream in a usual configuration of a single row of the filaments in the process is considered as non-interacting aerodynamically with other streams, and the air jet is assumed to be undisturbed by the polymer streams. Air-drawing of the polymer filaments is simulated as controlled by the distribution of air velocity, temperature, and pressure on the air jet centerline with the use of a stationary model of melt spinning in a single-, thin-filament approximation. Effects of non-linear viscoelasticity of the polymer melt subjected to fast uniaxial elongation are accounted for in the modeling. Strong influence of the air jet velocity, the melt viscosity which controls response of the polymer melt on the air-drawing forces, and the die-to-collector distance has been predicted. Influence of initial air temperature, geometry of the air die, initial velocity and temperature of the melt, extrusion orifice diameter can be also predicted from the model. The example computations concern air-drawing of isotactic polypropylene with the use of the Laval nozzle are compared with the predictions for the melt blowing process.
机译：讨论了由聚合物熔体形成纤维的气动过程的计算机模拟。给出了拉瓦尔喷嘴中形成的超音速气流中稀聚合物流的吸气动力学与熔喷工艺的关系。在拉瓦尔喷嘴过程中，气流以高雷诺数发生，并使用k-ω模型，该模型考虑了气流的动能和动能的比耗散率。对于熔喷，使用k-ε湍流模型模拟空气场。在两个气动过程的模型中都考虑了沿空气射流中心线的空气速度，温度和压力分布。在不存在聚合物流的情况下，对于拉瓦尔喷嘴入口中的几个空气压缩值和熔喷过程中的几个初始空气速度，预先确定了空气场。在该方法中，以单排长丝的通常构型的每种聚合物流被认为与其他流在空气动力学上是不相互作用的，并且假定空气流不受聚合物流的干扰。聚合物细丝的空气拉伸模拟为通过使用单丝，细丝近似的熔融纺丝固定模型，通过在喷气中心线上的空气速度，温度和压力的分布来控制。在建模中考虑了经受快速单轴伸长的聚合物熔体的非线性粘弹性的影响。已经预测到空气喷射速度，控制聚合物熔体对吸气力响应的熔体粘度以及管芯到收集器距离的强烈影响。初始空气温度，空气模具的几何形状，熔体的初始速度和温度，挤出孔直径的影响也可以从模型中预测。该示例计算涉及使用Laval喷嘴吸取全同立构聚丙烯的空气，并与熔喷工艺的预测值进行了比较。

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