螺距变化对异向双螺杆挤出机流场影响的仿真分析

Simulation analysis of influence of pitch variation on flow field of twin screw extruder with different direction

目的:以聚乳酸(PLA)为例,研究螺距变化下的异向双螺杆挤出流道的分布规律。方法:在Solidworks中根据理论端面曲线方程并修正,绘制变螺距与不变螺距两种三维模型,使用Workbench软件对两种螺杆构型使用扫略网格方法生成所需要的分析模型,再使用Polyflow流体仿真软件进行实际情况的模拟得到后处理结果,使用FieldView软件进行最终结果分析;研究聚乳酸流体在模拟条件下的压力、剪切速率以及黏度。同时使用Polystat统计模块对停留时间分布曲线RTD进行分析。结果:在其他条件相同的情况下,相比于不变螺杆,变螺距螺杆的压力变大,剪切速率和黏度波动增加,轴向混合性能提高,但自清洁能力降低。结论:螺距变化对聚乳酸来说存在一定的影响,但过大的螺距变化往往产生不利的影响,因此,需要结合实际情况具体设计合适的变螺距螺杆以提高产量和质量。

Objective:Taking polylactic acid(PLA)as an example,the flow channel distribution of twin-screw extrusion under different pitch was studied.Methods:In Solidworks,two 3D models with variable pitch and constant pitch were drawn according to the theoretical end curve equation and modified.Workbench software was used to generate the required analysis models with the swept mesh method for the two screw configurations,and then Polyflow fluid simulation software was used to simulate the actual situation.After obtaining the post-processing results,FieldView software was used to analyze the final results.The pressure,shear rate and viscosity of polylactic acid fluid under simulated conditions were studied.Meanwhile,the residence time distribution curve RTD was analyzed by Polystat statistical module.Results:Under the same conditions,the pressure,shear rate and viscosity fluctuation of the screw with variable pitch increased,and the axial mixing performance improved,but the self-cleaning ability decreased.Conclusion:The change of pitch has a certain effect on polylactic acid,but too large change of pitch often produces adverse effects.Therefore,it is necessary to design suitable variable pitch screw according to the actual situation to improve the yield and quality.