异向双螺杆S型元件混炼效果的数值研究

Numerical Study on the Mixing Performance of Different S Screw Elements of Counter-rotating Twin Screw Extruder

使用Polyfl ow软件,数值模拟了高密度聚乙烯(PE-HD)/炭黑熔体在异向双螺杆挤出机流道内的流动,数值计算了不同S型元件流道内熔体的三维等温流场,采用粒子示踪分析法(PTA)分析了不同S型元件流道内粒子的拉伸效果、分离尺度和停留时间,考察了啮合方式和两螺杆装配方式对S型元件混炼效果的影响。研究结果表明,啮合方式主要影响螺杆的输送能力、剪切能力和分布混合能力,非啮合元件的输送能力约为部分啮合元件的1.14倍,停留时间约为部分啮合元件的2.5倍,但是其剪切能力仅为部分啮合元件0.86倍;而螺杆的装配方式则影响其输送能力、拉伸能力和分布混合能力,并列式装配元件的输送能力约为错列式装配元件的1.11倍,停留时间约为错列式装配元件的1.2倍,但是其拉伸能力不如错列式装配的元件。三种元件中,部分啮合元件的分散混合性能最佳。

The flow of high density polyethylene（PE-HD） / carbon black in channel of screw element of counter-rotating twin screw extruder was simulated by using the Polyflow software. A three dimensional isothermal flow field of melt in channel of different kinds of S-element was calculated. The logarithm stretching, segregation scale and resident time of particles in channel of different kinds of S-element was analyzed. The effect of screw meshing method and assembling method on mixing performance were studied. The mixing performance was compared with particle tracking analysis（PTA）. The results show that the meshing method effects on the conveying capacity, shearing ability and distribution mixing of screw. The conveying capacity of non-intermeshing element was 1.14 times as much as part-intermeshing element, the residence time of non-intermeshing element is 2.5 times as much as part-intermeshing element, but the shearing ability of non-intermeshing element is only 0.86 times as much as part-intermeshing element. The assembling method effects on the stretching ability, distribution and dispersive mixing of screw. The conveying capacity of matched elements is 1.11 times as much as staggered elements, the residence time of matched elements is 1.2 times as much as staggered elements, but the stretching ability of matched elements is weaker than staggered elements. The dispersive mixing performance of part-intermeshing element is the best in all the three S-screw elements.