带有扰动副螺棱的单螺杆挤出机内混沌混合

提出一种采用副螺棱轴向往复运动来提高单螺杆挤出机混合的结构,探讨不同扰动幅度对螺槽内混合的影响。建立扰动副螺棱作用下三维周期性物理模型和相应的数学模型,对挤出机内牛顿流体三维周期性流动和混合过程进行计算。采用有限体积方法,变量分布采用交错网格,副螺棱的周期性运动边界通过叠加网格方式实现。采用4阶Runge-Kutta方法实现流体运动前锋追踪计算,对比Poincaré截面,得到示踪剂空间构型演变及界面增长。结果表明,副螺棱往复运动将导致螺槽内部的混沌混合区域围绕内部KAM管,并被外部准周期运动区域包围。处于混沌区域的流体界面呈现指数增长规律,而处于准周期运动的区域界面随时间仍然保持线性增长。副螺棱扰动幅度越大,内部准周期混合区域越小,混沌场覆盖的尺度越大。

Chaotic Mixing in Single Screw Extruders with Reciprocating Baffle

A geometry in which the mixing of single screw extruder is enhanced by a reciprocating baffle is proposed and the effect of baffle amplitude on mixing in the screw channel is investigated.The corresponding physical and mathematical models are developed.The periodic flow and mixing of Newtonian fluid in such an extruder are investigated.Finite volume method is used and flow domain is meshed by staggered grids with the periodic boundary conditions of the baffle motion being imposed by the mesh supposition technique.Fluid particles tracking is carried out by fourth order Runge-Kutta scheme and the Poincaré section mappings are used in order to show the scale of chaotic mixing.The evolution of mixing patterns of the tracers and their growth of interface stretch with time are obtained which are released from different initial positions.The results reveal that the reciprocating motion of the baffle can lead to chaotic mixing region surrounded by the pseudo-periodic regions with two KAM tubes inside.The tracers will experience the exponent growth with time when captured by the chaotic mixing zones with the linear growth when trapped in the pseudo-periodic zones.The larger the baffle amplitude is,the smaller the inner pseudo-periodic region is,the larger the chaotic mixing region is.