关键词: 分离, 多孔介质, 界面, 丝网膜, 液滴撞击, 水锤压力, 渗漏, 临界准则

Abstract:

When impact velocity of liquid droplets reaches to a critical breakthrough condition, subdroplets will be generated and passed through mesh screen membrane in droplet-capturing devices of gas-liquid separators, which could cause severe performance and safety concern of downstream processes. Critical breakthrough velocity was measured on various mesh screens by visualization experiment and was studied for its dependence on factors including diameter and wettability of liquid droplets as well as structure parameters and inclination angle of mesh screen. Critical breakthrough was governed by normal dynamic pressure together with water hammer pressure in competing with capillary pressure. The normal dynamic pressure was a dynamic pressure component with regards to inclination angle of mesh screen. Water hammer pressure was created by significant water compression within a very short time of droplet impact on mesh screen membrane, and was related to the number of mesh pores in droplet projection area. The capillary pressure was related to location of liquid-gas interface in mesh pore and wettability of mesh screen. Both water hammer pressure and capillary pressure were affected by structure parameters of mesh screen. A non-dimensional critical criterion for liquid droplet breakthrough was established from force analysis of liquid-gas interface in mesh pore in combination with consideration of all influential factors. The critical criterion was matched well to experimental results and would be useful for designing gas-liquid separator with mesh screen membrane. The increase of inclination angle, decrease of droplet diameter, and increase of mesh screen hydrophobicity could increase critical impacting velocity and avoid occurrence of breakthrough condition.

Key words: separation, porous media, interface, mesh screen membrane, droplet impact, water hammer pressure, breakthrough, critical criterion