高压气体在微圆管中的流动特性

摘要

The flow characteristics of nitrogen in microtubes with diameters of 14. 9, 10. 1, 5. 03 and 2. 05 μm were investigated experimentally under high pressure condition. Based on capillary bundle model, the gaseous seepage properties in low-permeability porous media influenced by high pressure microscale flow characteristics were researched. The results show that the flow characteristics of high pressure nitrogen in microtube with the diameter of 14. 9μm are in accordance with the classical fluid mechanics theory. However, with the decrease of the inner diameter of microtube, gas flow shows an apparent microscale effect and the experimental results depart from the theoretical predictions of the classical fluid mechanics theory, moreover , the smaller the diameter, the more obvious the microscale effect. Besides, the high pressure microscale effect can not be characterized by the Knudsen number, which is proposed for studying rarefaction effect. The gas seepage in low-permeability porous media has an obvious characteristic of non-Darcy's flow, and the real permeability is larger than absolute permeability calculated by classical H-P equation or Darcy's equation.%在高压条件下,试验研究氮气在直径为14 9、10.1、5.03、2.05 μm微圆管中的流动特性.结合毛管束模型,研究气体的高压微尺度流动特性对气体在低渗多孔介质中渗流特性的影响.结果表明:气体在14.9 μm微圆管中的高压流动特性与经典流体力学规律相符；随着管径的减小,气体的流动出现了明显的微尺度效应,表现为实测流量偏离经典流体力学理论预测流量,且管径越小,这种微尺度流动效应越显著;研究稀薄气体效应时提出的Kn数不能用来表征高压条件下气体的微尺度效应；气体在微小孔喉中的高压微尺度流动效应导致气体在低渗多孔介质中的渗流具有非达西渗流特征,表现为实际渗透率大于由经典H-P方程和达西公式计算的绝对渗透率.