双螺杆挤出的非充满熔融理论的研究

【作者】 任冬云；

【导师】 朱复华；

【作者基本信息】 北京化工大学 ， 化工过程机械， 1997， 博士

【摘要】 北京化工大学塑料机械及塑料工程研究所研制的全程三向可视双螺杆挤出机对观察物料在双螺杆挤出机中真实的物态变化及运动状态、研究物料的挤出机理、建立切合实际的物理模型和数学模型、探索合理的物料加工工艺及配方有着极其重要的意义和深远的影响。目前，研究双螺杆挤出机中混炼和熔体输送方面的资料文献较多，但鲜能见到有关物料熔融方面的文章。显而易见，只讨论熔体输送而不讨论物料熔融，对全面研究双螺杆挤出理论是很不够的。熔融直接影响到产品质量。因此，本文作者在全程三向可视双螺杆挤出机上做了大量的实验，并查阅了刘廷华博士所做实验的录相资料。在此基础上建立了塑料双螺杆挤出机中非充满熔融理论的圆柱团物理模型和相应的数学模型，并求出相应的近似解析解。针对实验所选操作工况条件及实验数据进行理论计算。依据所建的物理模型，利用有限元法进行数值计算并模拟熔融过程。最后用实验数据验证了本文所建物理模型、数学模型及理论计算的正确性及合理性。作者所做的主要工作如下： 1．根据实验观察结果，分析了物料在双螺杆挤出过程中的熔融机理和运动状态，提出非充满固相熔融两相圆柱团的物理模型。依据建立物理模型中的几点假设，由能量方程的一般形式、液相运动的N-S方程和自由边界上的能量平衡条件，建立双螺杆挤出非充满熔融问题的数学模型。 2．参考文献[46]、[49]作者对凝固过程中自由边界问题的求解思路，结合两相圆柱团熔融问题的复杂情况，引入了传热学中的对流传热概念。求出两相圆柱团熔融过程中固液界面s(自由边界)与时间t的解析表达式，它对分析研究影响物料团熔融的相关因素起着重要作用。由于实际双螺杆螺槽截面形状与圆柱团物理模型之间存在着差异，因而引入圆柱团当量直径和当量长度的概念，简化了计算。将两个算例的计算结果(物料团熔融时间t_a、熔融区总长度Z_r)与相应的实验结果比较，得出本文所建双螺杆挤出非充满熔融两相圆柱团物理模型、数更多还原

【Abstract】 The trasparent twin screw extruder with glass windows, developed by Institute of Plastic Machinery and Engineering of Beijing University of Chemical Technology (EPME of BUCT), is of important significance and profound influence. By the extruder, the real material change in the twin screw extruder can be boserved, the extrusion mechanism is more easily studied, the applicable physical and mathematical models can be established, and the reasonable processing technology and composition can be explored. At present, there are a lot of literatures on the intermixing and melt handling in a twin screw extruder, but there are few articles on the material melting. It is obviously that only taking account of melt handling without considering material melting is not suitable to study twin screw extrusion theory thoroughly. The meltintg is a very important factor to affect the quality of products. After doing a lot of experiments on the transparent twin screw extruder and looking up the video tapes recorded by Dr. Liu Tinghua, a physical model of cylinder group of filled partially melting theory in the twin screw extruder and a mathematical model corresponding to the physical model are established. An approximately analytical solution of the problem is found out. In accordance with the operation conditions of the experiments done by the auther and the experimental data, the theoretical calculation has been carried out. The numerical results of the physical model are obtained by the finite element method, and the melting process of the cylinder group is simulated. Finally, the correctness and the reasonableness of the physical model, the mathematical model and the theoretical calculation are tested and verified with the experimental data. The following are the main aspects of this paper:1. In accordance with the oberserved results in experiments, the melting mechanism and the moving state of material in the twin screw extruding process are analysed, and the physical model of two phase cylinder group about the filled partially melting is proposed. In the light of some pypotheses in building the physical model, the mathematical model of the filled partially melting problem in the two screw extruding更多还原