SC-CO2及工艺条件对高固含量发射药CA/CaCO3体系挤出停留时间的影响

Effect of SC-CO2 and Process Conditions on Residence Time of High Solid Content Propellant Substitute in Extrusion

为了研究挤出过程中超临界二氧化碳(SC-CO2)对高固含量发射药停留时间分布的影响,采用示踪粒子轨迹跟踪技术研究了醋酸纤维素(CA)/碳酸钙(CaCO3)/SC-CO2代料停留时间的影响因素,结合反应器流动模型确定了CA/CaCO3/SC-CO2在机筒中的流动情况。数值模拟结果显示,注入体积流量为0.1 mL/min的SC-CO2后,平均停留时间缩短了35%,Pe减小了196.4;螺杆转速由6 r/min增加到14 r/min时,平均停留时间缩短了54.5%,Pe减小了210.8;当机筒温度从40℃升高至60℃,平均停留时间减少了19%,Pe减小了75.0。反应器流动模型拟合结果显示,螺杆转速由6 r/min增加到14 r/min时,CA/CaCO3/SC-CO2的体积分数从0.65降低到0.62。由此可知,SC-CO2的加入、螺杆转速的增加以及机筒温度的升高都显著缩短了物料的停留时间,并促进了轴向混合,CA/CaCO3/SC-CO2在螺杆内的主要流型为活塞流。

In order to study the effect of supercritical carbon dioxide(SC-CO2)on the residence time distribution of high solid propellant in extrusion process,numerical simulation of CA/CaCO3/SC-CO2 substitutes was performed to analyze the influencing factors of residence time by particle tracing method.Combined with reactor flow pattern,the main flow patterns of CA/CaCO3/SC-CO2 in the barrel were determined.The results show that after injection of SC-CO2 with a volume flow of 0.1 mL/min,the mean residence time reduces by 35%,and the Pe number reduces by 196.4.When the screw speed increases from 6 r/min to 14 r/min,the mean residence time reduces by 54.5%,and the Pe number decreases 210.8.The mean residence time reduces by 19%and the Pe number reduces by 75.0 when the cylinder temperature increases from 40℃to 60℃.The fitting results show that the volume fraction of CA/CaCO3/SC-CO2 decreases from 0.65 to 0.62 as the screw speed increases from 6 r/min to 14 r/min.The residence time of the material is significantly shortened,the axial mixing is enhanced by the addition of SC-CO2,and the acceleration of screw speed and the increase in barrel temperature.Plug flow is the dominant flow pattern of CA/CaCO3/SC-CO2 in the screw.