流道截面形状对微流体流动性能的影响

微尺度条件下流体的流动特性是微纳零件制造与微机械装置控制系统设计中需考虑的重要因素.采用基于Navier-stokes运动方程开发的Moldflow MPI软件,以PMMA（聚甲基丙烯酸甲酯）材料为对象,研究圆形、半圆形、梯形、矩形和正三角形5种微流道截面形状对非等温非牛顿流体流动性能的影响.研究结果表明：微流体在截面形态不同,长度均为50 mm微流道中的流动长度与流道截面的比表面积（截面周长与截面面积的比值）呈反比关系,比表面积越小,流动长度越大;当微流道的比表面积较小时,熔体温度与注射压力对流动长度的影响较大;当比表面积较大时,熔体温度与注射压力对流动长度的影响较小,且不论比表面积如何变化,注射压力对流动长度的影响比熔体温度对流动长度的影响显著.

Influence of section shape of micro channels on microfluid flowability

The flow character of microfluid in micro channel is the significant factor in micro injection molding and microfluid control system design.The rule of micro channel section shape,such as circle,semicircle,trapezia,rectangle,regular triangle,influencing non-Newton and non-isothermal fluid flow capability was investigated with Moldflow MPI software based on Navier-stokes momentum equation for PMMA material.The results show that the flow length of micro fluid in micro channels that have different section shapes but the same length(50 mm) is in inverse proportion to sections' RPA(RPA means the ratio of the section's perimeter to its area),and the smaller the RPA,the longer the flow length.In the range of small RPA,the effect of melt temperature and injection pressure on flow length is strong while in the range of large RPA the effect is week.Furthermore,the effect of injection pressure on flow length is stronger than that of melt temperature whatever the value of RPA is.