双螺杆挤出机内非牛顿粘性流场计算及其挤出行为研究

In this dissertation, the twin screw intermeshing geometry is systematically analyzed according to the rolative motion principle. The relations among the geometric parameters of screw and the analytic of screw sections are derived, the formulas of calculating the aroa and volume of characteristic screw regions are deduced, and the relations between them and the geometric parameters of screw are discussed. Based on the results above, the principles of designing the geometric parameters of scrow are put forward from the gemotric point of view. To verify the validity of theory, the theoretical and experimontal results of intermeshing geometry are compared.

   Countering the special flow characters of the fluid and the complex of the flow field in twin screw extruder, the penalty finite element method (PFEM) and the boundary element method (BEM) are first adopted in this dissertation to solve the flow field in twin screw extruder after analyzing the defects of the traditional pressure-velocity finite element method in solving the similar flow field and a now method is proposed to handle the nonlinearity. It is proved by practical calculation that new methods above have many advantages (such as economy, convenience, high efficiency, high generality and reliability etc. ) in solving the complicated flow field.

   Based on analyzing the work done by predecssors, the physical and mathomatical models which are most close to practice up to now are established for the flow fields in the metering zone and venting zone of the intermeshing corotating twin screw extruder. By means of PFEM and BEM, the viscous flow fields in the metering zone and venting zone which are nonnewtonian, nonisothermal and include three directional velocities are solved in IBM-PC computer, according to the results of flow field calculation, the operating charaeteristic parameters are colculated, analyzed and discussed. After this, the Principles of selecting the technological parameters and designing the geometric parameters of screw are raised on the basis of the achievement above, in addition, the ways of solving the problems occuring in practice (such as how to restrain melt flooding from vent, improve the venting effect, restrain the fluctuation of operating characteristic parameters and so on) are pointed out.

   In this dissertation, the principles of scaling corotating twin screw extruder up and down are proposed on the basis of analyzing the similar conditions of the flow field in metering zone.

   The experimental results obtained in the laberatory and factories are compared with the theoretical results, it is proved that in this dissertation the models are resonable, the calculating methods are advanced and the conclusions are reliable, therefore, the theory established in this dissortation can be used to direct practice.