三层共挤出吹膜机头流道的流场分析
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摘要
三层共挤吹塑薄膜可将产品的多种特性在挤出过程中进行复合,并能大幅度地降低成本,因而其应用越来越广泛。以LDPE/HDPE/LDPE三层共挤出薄膜为例,确定了三层共挤吹膜机头的流道结构,使用ICEM CFD对机头流道划分全六面体网格,采用POLYFLOW对机头流道内等温流动过程进行求解并分析了压力场、速度场和剪切速率场。机头流道流场的研究结果表明,层分配流道压力降较高,共挤出流道压力降较低;层分配流道存在滞留区,熔体汇入共挤出流道后,相邻层熔体的速度分布向该层速度分布方式不断变化;层分配流道中,沿螺旋槽轴线方向,剪切速率逐渐降低,随着层数的增加,共挤出流道壁面上的剪切速率减小。
The three-layer co-extrusion blown film could combine a variety of different characteristics in the extrusion process and significantly decreased cost,therefore the technology was applied more and more broadly. The flow channel geometry of three-layer co-extrusion blown film die was built and then meshed by ICEM CFD with all-hexahedral elements whose isothermal flow field numerical simulation in the co-extrusion flow channel was solved by POLYFLOW to analysis the pressure field,velocity field and shear rate field for LDPE/HDPE/LDPE three-layer co-extrusion blown film. It shows that pressure drop of the layer distribution channel was relatively high and co-extrusion channel low. Retention regions were found in layer distribution channel. Each layer tended to change the velocity distribution type of adjacent layers to the own,when they met the co-extrusion channel. In the layer distribution channel,the shear rate gradually decreases along the axis of the spiral groove. With the increase of the layers' number,the shear rate on the wall of the co-extrusion channel decreased.
The three-layer co-extrusion blown film could combine a variety of different characteristics in the extrusion process and significantly decreased cost,therefore the technology was applied more and more broadly. The flow channel geometry of three-layer co-extrusion blown film die was built and then meshed by ICEM CFD with all-hexahedral elements whose isothermal flow field numerical simulation in the co-extrusion flow channel was solved by POLYFLOW to analysis the pressure field,velocity field and shear rate field for LDPE/HDPE/LDPE three-layer co-extrusion blown film. It shows that pressure drop of the layer distribution channel was relatively high and co-extrusion channel low. Retention regions were found in layer distribution channel. Each layer tended to change the velocity distribution type of adjacent layers to the own,when they met the co-extrusion channel. In the layer distribution channel,the shear rate gradually decreases along the axis of the spiral groove. With the increase of the layers' number,the shear rate on the wall of the co-extrusion channel decreased.
引文
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[14]邓小珍.塑料异型材气体辅助共挤出成型的实验和理论研究[D].南昌:南昌大学,2014.
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[16] HUANG C C. A systematic approach for the design of a spiral mandrel die[J]. Polymer Engineering and Science,1998,38(4):573-582.
[17]吴卫平.用于管材加工的螺旋机头[J].塑料工业,1991(2):30-34.
[18]张敏.双组分聚合物异型材共挤出过程的数值模拟研究[D].济南:山东大学,2007.
[19]徐玉兴,李国胜.三层复合薄膜共挤机头流场仿真分析[J].CAD/CAM与制造业信息化,2013(10):63-68.
[20] WHITE J L,UFFORD R C,DHAROD K R,et al. Experimental and theoretical study of the extrusion of two-phase molten polymer systems[J]. Journal of Applied Polymer Science,1972,16(6):1313-1330.
[2]苗立荣,张玉霞,薛平.多层共挤出塑料薄膜机头的结构改进与发展[J].中国塑料,2010,24(2):11-20.
[3]武停啟.聚合物共挤出复合流动机理及数值模拟研究[D].北京:北京化工大学,2006.
[4] YU T C,HAN C D. Stratified two-phase flow of molten polymers[J].Journal of Applied Polymer Science,1973,17(4):1203-1225.
[5] HAN C D. Multiphase flow in polymer processing[M]. New York:Academic Press,1981:341-342.
[6] HAN C D,CHIN H B. A study of coextrusion in a circular die[J].Journal of Applied Polymer Science. 1975,19:1875-1883.
[7] HAN C D,SHETTY R. Studies on multilayer film coextrusion I. the rheology of flat film coextrusion[J]. Polymer Engineering and Science,1976,16(10):697-705.
[8] HAN C D,CHIN H B. Theoretical prediction of the pressure gradients in coextrusion of non-newtonian fluids[J]. Polymer Engineering and Science,1979,19(16):1156-1162.
[9] PERDIKOULIAS J,TZOGANAKIS C. Interfacial instability in coextrusion flows of low-density polyethylenes:experimentalstudies[J].Polymer Engineering and Science,2000,40(5):1056-1064.
[10] AHMED R,LIANG R F,MACKLEY M R. The experimental observation and numerical prediction of planar entry flow and die swell for molten polyethylenes[J]. Journal of Non-Newtonian Fluid Mechanics,1995,59(2/3):129-153.
[11] ANDERSON P D,DOOLEY J,MEIJER H E H. Viscoelastic effects in multilayer polymer extrusion[J]. Applied Rheology,2006,16(4):198-205.
[12] MICHAELI W,BLMER P. Flat spiral dies-rheological design with network theory[J]. Journal of Polymer Engineering,2004,24(1/2/3):137-154.
[13]尹华涛,江波.共挤出机头中的聚合物熔体流动分析[J].现代塑料加工应用,2003,15(4):44-47.
[14]邓小珍.塑料异型材气体辅助共挤出成型的实验和理论研究[D].南昌:南昌大学,2014.
[15]解挺,朱元吉,尹延国,等.共挤出的影响因素[J].塑料科技,1996(5):30-33.
[16] HUANG C C. A systematic approach for the design of a spiral mandrel die[J]. Polymer Engineering and Science,1998,38(4):573-582.
[17]吴卫平.用于管材加工的螺旋机头[J].塑料工业,1991(2):30-34.
[18]张敏.双组分聚合物异型材共挤出过程的数值模拟研究[D].济南:山东大学,2007.
[19]徐玉兴,李国胜.三层复合薄膜共挤机头流场仿真分析[J].CAD/CAM与制造业信息化,2013(10):63-68.
[20] WHITE J L,UFFORD R C,DHAROD K R,et al. Experimental and theoretical study of the extrusion of two-phase molten polymer systems[J]. Journal of Applied Polymer Science,1972,16(6):1313-1330.