基于二维微流控模型的多孔介质渗透特性

Permeability characteristics of porous media based on 2D microfluidic chips

多孔介质材料内部孔隙通道复杂,为了在孔隙层面上研究多孔介质材料的渗透特性,利用微纳加工技术制作的不同孔隙结构的PDMS微流控芯片,芯片内部规则排列的圆形微柱构成二维通道网络。首先,在微流控芯片的一端使用精密注射泵施加一定流量梯度的无气水;其次,使用压力传感器测量芯片两端的压力响应;最后,利用达西定律计算出不同结构的微流控芯片的渗透系数。研究结果表明:多孔介质的内部孔隙通道结构对其渗透特性有决定性的影响;多孔介质中微柱正方形排列时的渗透能力强于微柱正三角形排列的渗透能力;多孔介质中孔隙喉道越小,渗透能力则越弱;二维微流控芯片测得的渗透系数与使用经典的Kozeny-Carman公式计算的渗透系数更接近,可以使用该公式更准确地估算均匀多孔介质的渗透系数。

In order to study permeability characteristics of porous media materials at pore scale,micro−nano processing technology was used to fabricate PDMS microfluidic chips with different pore structures,and two dimensional pore networks were composed of regularly arranged micropillars.Firstly,a precise syringe pump was used to apply a certain flow gradient of airless water at one end of microfluidic chip.Secondly,pressure sensors were used to measure pressure response at both ends of the chip.Finally,Darcy's law was used to calculate permeability coefficients of various microfluidic chips.The results show that internal pore networks of porous media have a decisive influence on its permeability.Permeability of square micropillars in porous media is stronger than that of triangular micropillars.The smaller the pore throat of porous media,the weaker its permeability.Permeability coefficients measured by two-dimensional microfluidic chips are closer to permeability coefficients calculated by classic Kozeny-Carman equation,which can be used to more accurately estimate permeability coefficient of uniform porous media.