差速非对称同向双螺杆挤出机内局部停留时间分布测试

Local Residence Time Distributions in a Dual-speed Co-rotating Non-twin Screw Extruder

基于自主研制的可视化差速非对称双螺杆挤出设备,以羧甲基纤维素钠作为模拟挤出流体,采用配置的氯化钠–羧甲基纤维素钠溶液作为脉冲示踪剂,提出了一种与挤出速度同步的拉膜法测试停留时间分布的方法,通过电导率测试完成停留时间分布规律的测量。在全充满的状态下,研究不同螺杆元件单元及不同转速、产量等加工参数下的局部停留时间分布。结果表明,当转速和产量不变时,反向捏合盘平均停留时间最大,停留时间分布曲线最平缓,比其它螺杆元件类型表现出更好的混合效果;不同错列角对停留时间分布影响不大;产量不变时,随着转速的提升,捏合盘单元平均停留时间下降,混合效率提升;相同的转速下,产量的提高导致混合效率下降;停留时间分布对示踪剂的注射位置敏感性强,暗示流道非对称明显。

Based on self-developed visualization extrusion setup with the dual-speed non-twin screw elements using sodium carboxymethyl cellulose as a simulating extrusion fluid and a NaCl–sodium carboxymethyl cellulose solution as a pulse tracer,a pulling film method,where a moving film was adjusted to the same speed of the extrusion,was put forward to measure residence time distributions(RTDs)through the electrical conductivity results.Under the fully-filled conditions,the local RTDs were examined for the units of different screw elements with respect to the operating parameters such as output and screw rotation speed and so on.The experimental results show that the average residence time of the reverse kneading disc is the maximum and the residence time distribution curve is the most gentle when the rotation speed and output are unchanged,and the mixing effect is better than other screw types.Different staggered angles have little effect on residence time distribution.When the output is unchanged,the average residence time of kneading disc unit decreases and the mixing efficiency increases with the increase of rotational speed.At the same rotational speed,the increase of output leads to the decrease of mixing efficiency.The residence time distribution is highly sensitive to the injection location of tracer,suggesting that the flow channel asymmetry is obvious.