背压对湿天然气超声速凝结特性影响的数值模拟  

Numerical simulation on effects of back pressure on supersonic condensation propertites of wet natural gas

作　　者：边江[1] 杨健 李玉星[1] 刘杨[1] 褚奇 杨文 曹学文[1] BIAN Jiang;YANG Jian;LI Yuxing;LIU Yang;CHU Qi;YANG Wen;CAO Xuewen(College of Pipeline and Civil Engineering,China University of Petroleum(East China)//Shandong Key Laboratory of Oil&Gas Storage and Transportation Safety;PipeChina South China Company)

机构地区：[1]中国石油大学(华东)储运与建筑工程学院·山东省油气储运安全重点实验室 [2]国家管网集团华南分公司

出　　处：《油气储运》2022年第8期980-986,共7页Oil & Gas Storage and Transportation

基　　金：国家自然科学基金资助项目“基于超声速膨胀的重烃结晶促进天然气凝结液化机理”,52104071;国家自然科学基金资助项目“基于超声速膨胀的天然气非均质凝结机理”,52074341。

摘　　要：超声速旋流分离器出口背压会导致Laval喷管内产生气动激波,而超声速流动、激波与相变的相互作用十分复杂。为探究激波作用下湿天然气超声速流动特性,以甲烷-水蒸气双组分混合气体为研究对象,建立湿天然气超声速凝结和流动数学模型,分析出口背压和入口压力对湿天然气超声速凝结流动特性的影响,以评估激波作用下超声速旋流分离器的工作性能。模拟结果表明:激波的存在导致水蒸气压力和温度在短时间内急剧升高,使已凝结的液滴重新蒸发,出口液相质量分数大幅减小;随着入口压力的增大,成核发生位置逐渐靠近Laval喷管喉部,相应的极限成核率与液滴数目随之减小,但由于液滴生长速率和液滴半径的增大,液相质量分数随之增大;当背压高于25 kPa(即压比高于0.58)时,喷管已失去液化性能,无法正常工作。因此,需要合理控制压比以保障背压存在情况下超声速旋流分离器的脱水效率。The back pressure at the outlet of supersonic cyclone separator usually causes aerodynamic shock wave in Laval nozzle,and the interaction of supersonic flow,shock wave and phase transition is very complicated.In order to explore the supersonic flow properties of wet gas under the action of shock wave,study was performed on the methane-water vapor mixtures.Then,a mathematical model for the supersonic condensation and flow of wet natural gas was established.Meanwhile,the effect of the outlet back pressure and inlet pressure on the supersonic condensation property of wet natural gas was analyzed to evaluate the performance of the supersonic cyclone separator under the action of shock waves.The simulation results show that the shock waves can cause the rapid increase in pressure and temperature of water vapor in a short time,leading to the condensed droplets re-evaporate and the liquid mass fraction at outlet reduces sharply.Besides,as the inlet pressure increases,the location of nucleation approaches the throat of Laval nozzle gradually,and the limit nucleation rate and the droplet number decrease accordingly.However,the liquid mass fraction increases due to the increasing of growth rate and sizes of droplets.Moreover,the nozzle loses its function of liquefaction when the back pressure is higher than 25 kPa(i.e.,the pressure ratio is higher than 0.58),and then the nozzle cannot operate normally.Therefore,it is necessary to control the reasonable pressure ratio to ensure the dehydration efficiency of the supersonic separator with back pressure.

关 键 词：天然气 水蒸气 Laval喷管 超声速 凝结 背压 激波 数值模拟 

分 类 号：TE86[石油与天然气工程—油气储运工程]