非对称同向双螺杆挤出过程混沌混合动力学机理

The project derives from the scientific problem essentially out of the invention technique attributed to the applicant's own patent (PTC) and aims at establishing the characterization theory of chaotic mixing during the course of the extrusion process by the novel non-twin co-rotating screws we developed. Attempting to develop the experimental extruder with the barrel being clam shell structure, we will investigate the kinematics mechanism of chaotic mixing by means of the combination of the numerical simulation technique and the visualization experiment of passive tracers for pure polymer melt and its compoundings. The periodic velocity field of Non-Newtonian fluid occurring in the extrusion section is computed adopting the finite volume method combined with the fictitious domain method called mesh superposition.The numerical simulations are carried out to show how mixing happens when such objectives are considered as spatial distribution of tracers, deformation of the tracer interfaces, mixing efficiency, Poincaré section mapping, residence time distribution, statistics analysis of mixing index, and so on, which will reveal the scale of chaotic advection and show the effect of the different screw groups on the mixing result. In addition to the visualization experiment for pure polymer and its compoundings, the key factors are investigated which have great impact on mixing and the key regions are searched which have pronounced influence on distributive mixing, dispersive mixing as well as residence time distribution. Based on the result above, the geometry characterization method distinguishing the mixing ability of different screw shapes will be defined, which will provide the theoretical direction for the geometry improvement of screw groups. It is no doubt of great significance in science and reality.

本项目来源于申请人国际发明专利所提升出的科学问题，旨在建立非对称同向双螺杆挤出过程混沌混合动力学表征理论。在研制机筒剖分式实验样机的基础上，我们将计算机数值模拟技术和示踪剂可视化实验相结合，对混沌混合动力学机理进行研究。将有限体积方法与虚拟边界叠加网格技术相结合，求解挤出段非牛顿流体周期性速度场。采用前锋追踪技术开展示踪剂空间构型分布、界面拉伸形变、混合效率、Poincaré截面映射、停留时间分布、分散指数统计等数值模拟计算来表征混合过程，探索不同螺杆组合结构对混合过程的影响规律，揭示混沌场作用尺度。结合聚合物及其填充体系的示踪剂可视化实验结果，以期发现影响分布混合、分散混合、停留时间分布的关键区域，探索影响混合的关键因素，建立表征非对称同向双螺杆混合能力几何表征方法。为优化螺杆结构提供理论指导，具有重要的科学和现实意义。

非对称双螺杆挤出方法源于申请人发明专利，采用两根形状完全不一样的螺杆同向旋转塑化挤出物料。本项目对挤出过程的混沌混合动力学机理开展研究和表征，为双螺杆的理论创新和实践应用提供了指导，主要工作如下：.（1）将商用软件与自编程序代码相结合，利用有限元数值模拟方法，结合叠加网格技术，对非对称同向双螺杆内流动与混合动力学数值模拟模拟与表征。从分散指数分布、分离尺度、界面拉伸及粒子群混合统计数分析等多个方面对非对称流道内的混合动力学进行描述和分析。.（2）在研制成功的机筒剖分式静态可视化及机筒全透明的动态可视化实验样机的基础上，开展了聚合物填充体系及多相体系的混合动力学可视化实验研究。发现左右螺槽的非对称效应，得到了物料输运的拓扑流道，考察了分散相粒子的沿程变化规律，分析了正向输送、捏合块、反向螺纹元件等对混合的影响，为优化螺杆结构和组合提供理论基础。.（3）为引入最新有关宏观拓扑混沌路径触发机制，项目组以远离啮合区的单螺杆模型为切入点，将有限体积方法和有限元叠加网格技术相结合，采用自编程序代码，开展了一系列混合动力学数值模拟研究，从Poincaré映射、周期点分析、粒子群分离尺度等多个角度表征了混合问题，引入摄动理论共振环频率比分析方法，目前已找到了基于摄动理论框架的几何优化路径，催生了带有扰动副螺棱非及螺纹头数渐变对称双螺杆等多项国内外发明专利。. 项目组在《化工学报》、《高分子材料科学与工程》和Chemical Engineering Science, Polymer Engineering Science, Advances in Polymer Technology，Journal of Computational and Nonlinear Dynamics等国内外知名期刊发表有关混沌混合动力学的研究论文41篇，其中，SCI论文12篇，EI论文5篇，国际会议ANTEC报告论文2篇；此外，已接收SCI论文1篇，投稿在审SCI论文2篇；申请国家发明专利10项，PTC国际发明专利3项，申请实用新型专利2项，授权中国发明专利3项；授权美国发明专利1项；获得授权软件成果登记1项。