摘要
液化是天然气利用的一种重要形式,在天然气消费中占有重要地位,天然气超音速液化技术是一种新型的天然气液化手段。为研究低温条件下天然气超音速凝结过程,特设计用于天然气超音速液化的Laval喷管,采用内部一致经典成核理论及Gyarmathy模型计算成核率及液滴生长率,在入口压力6 MPa、温度273.15 K的工况下,通过Fluent软件数值模拟了天然气超音速液化过程中主要参数在Laval喷管内的分布情况。结果表明:天然气进入Laval喷管后压力、温度不断降低(最低压力0.796 MPa,最低温度191 K),与等熵(无凝结)流动相比,天然气在Laval喷管喉部之后的一段距离饱和度增大到一定值时,由于释放潜热对气流的加热作用,压力开始升高,天然气产生凝结冲波现象,极限成核率为2.60×10^21/(kg·s);随着凝结潜热的释放,成核率急剧变为0;凝结核生成后伴随着液滴的继续生长,在Laval喷管出口处天然气凝结的液滴半径为3.90×10^-7 m,液滴数目为7.42×10^14/m^3,液相质量分数达0.232,取得了良好效果。
Liquefied natural gas(LNG)is an important form of natural gas utilization,which occupies an important proportion in natural gas consumption.Supersonic liquefaction of natural gas is a new method of natural gas liquefaction.In order to study the supersonic condensation process of natural gas,the Laval nozzle for the liquefaction of natural gas was designed,internally consistent classical theory and Gyarmathy models were used to calculate droplet nucleation rate and growth rate,respectively.Under the condition that the inlet pressure was 6 MPa,the inlet temperature was 273.15 K,Fluent numerical simulation software was used to investigate the distribution of main parameters in the Laval nozzle in the supersonic condensation process.The results show that the pressure and temperature decrease when the gas enters the Laval nozzle(the minimum pressure is 0.796 MPa,and the lowest temperature is 191 K).Compared with isentropic(non-condensing)flow,when the gas through the throat into the expansion section,with the increasing of supersaturation,natural gas starts to condense,the maximum nucleation rate is 2.60×10^21/(kg·s).With the release of latent heat of condensation,the nucleation rate sharply changes to 0.When the condensation nucleus is formed,the droplets continue to grow.At the outlet of Laval nozzle,the droplet radius is 3.90×10^-7 m,the droplet number is 7.42×10^14/m^3,and the liquid mass fraction is 0.232.
作者
王梓来
余芬
袁时雨
俞壹凡
Wang Zilai;Yu Fen;Yuan Shiyu;Yu Yifan(Hubei Province Natural Gas Development Co.,Ltd.,Wuhan 430205,China;Zhejiang Energy Group Co Ltd.,Hangzhou 310000,China)
出处
《低温与超导》
CAS
北大核心
2019年第10期15-19,共5页
Cryogenics and Superconductivity
