一种折流板双螺杆构型挤出压力脉动响应

Fluctuation Response of Extrusion Pressure in a Baffled Co-Rotating Non-Twin Screw Channel

文中提出了一种带有折流板的双螺杆结构,旨在混炼过程中引入对称破缺机理并降低挤出过程的压力波动。为探索折流板双螺杆的挤出特性,自行研制了全程可视化的实验样机。以常温黏弹流体羧甲基纤维素钠(CMC-Na)为实验流体,测量了传统及折流板双螺杆流道机头处的压力响应。首次通过傅里叶变换方法分析了压力脉动的产生机理,探究了螺杆构型、转速及喂料量对压力脉动的影响。结果表明,在较低螺杆转速和喂料量条件下,全充满状态下挤出压力的脉动周期与螺杆转动的周期一致,压力波动幅度随着螺杆转速的增加而增加;压力随喂料量增加而增加,但波动随着喂料量的增加而减小;螺杆旋转1周,传统双螺杆压力呈现双峰曲线,而折流板双螺杆为单峰分布,且峰值更小。粒子图像测速(PIV)显示,折流板双螺杆内啮合区存在物料相互交汇现象,保持啮合的同时实现横向和纵向开放连通,因而导致了压力脉动幅度较小。

A new type of non-twin screw with an internal baffle is proposed to introduce symmetry break into the mixing process and to reduce the pressure fluctuation in the extrusion process.In order to explore the extrusion characteristics of such a baffle non-twin screw extruder(BNTSE),a visualization extruder with a transparent barrel was developed.Sodium carboxymethyl cellulose(CMC-Na),a viscoelastic fluid at room temperature,was selected as experimental fluid.The response of extrusion pressure of the traditional twin-screw extruders(TSE)and BNTSE were measured.For the first time,Fourier transform was applied to examine the generation mechanism of pressure fluctuation.The influence of screw configuration,screw speed and feed rate on the extrusion pressure was investigated.The experimental results show that under the fully-filled condition of lower screw speed and lower feed rate,the pulsation period of the pressure is equal to the screw periodicity,and the pressure fluctuation increases with the increase of screw speed,and decreases with the increase of feed rate.The extrusion pressure increases with the increase of feed rate.Within one rotation cycle,the pressure curve of the TSE shows a bimodal distribution,while the BNTSE has a single peak distribution with a smaller amplitude.Particle image velocimetry(PIV)shows that there is confluence of materials in the intermeshing regions of BNTSE.BNTSE provides the opening channel in the transverse and longitudinal directions of the screw grooves while keeping their intermeshing rotation,resulting in less pressure fluctuation when compared to TSE.