微尺度下基于对流混合的充填不平衡影响因素数值模拟分析

Numerical simulation analysis of factors affecting filling unbalance based on convective mixing at microscale

针对流道中采用对流混合的充填不平衡新的调控方法,通过数值模拟研究了微尺度聚合物熔体流动因素对流道熔体温度分布调控特性的影响。以“H”型流道作为研究对象,在流道中布局了对流混合装置。采用单因素的实验方法研究熔体温度、对流换热系数、流道系统对熔体充填不平衡的影响。数值模拟结果表明:绝热边界条件时,升高熔体温度伴随着熔体自身黏度的下降,对称点之间的温差减小,改善了充填不平衡,对流换热边界时,升高熔体温度加大了熔体通过壁面散失的热量,对称点之间的温差加大,充填不平衡越明显;对流换热系数越小,熔体与壁面之间的导热效率越低,熔体平均温度较高,增加了对称点之间的温差,加剧了充填不平衡;随着流道系统的减小,微尺度效应减弱,可以降低对称点间的温差,充填不平衡的现象得到了较好的改善。其中对流换热系数对充填不平衡的影响最大,其次是流道系统,最后是熔体温度。

Aiming at the new control method of filling unbalance in the flow channel by using convection mixing,the influence of micro-scale polymer melt flow factors on the control characteristics of melt temperature distribution in the flow channel was studied by numerical simulation.Taking the"H"flow channel as the research object,the convection mixing device was arranged in the flow channel.The effects of melt temperature,convective heat transfer coefficient and flow channel size on melt filling unbalance were studied by single factor experiment.The numerical simulation results show that,the increase in melt temperature is accompanied by the decrease of melt self-viscosity under adiabatic boundary conditions.The temperature difference between symmetric points decreases,which improves the filling imbalance.Under the convective heat transfer boundary,the increase of melt temperature increases the heat loss of melt through the wall,and the increase of temperature difference between symmetric points leads to the more obvious filling imbalance.The lower the convective heat transfer coefficient,the lower the thermal conductivity efficiency between melt and wall,and the higher the average melt temperature,which increases the temperature difference between symmetric points and intensifies the filling imbalance.With the decrease in the size of the flow path,the micro-scale effect is weakened,the temperature difference between symmetric points can be reduced,and the phenomenon of filling imbalance is better improved.The convective heat transfer coefficient has the greatest influence on the filling unbalance,followed by the flow channel size,and finally the melt temperature.