Laval喷管内甲烷-乙烷混合气体低温液化特性

Low temperature liquefaction characteristics of methane-ethane mixed gas in the Laval nozzle

为明确Laval喷管内甲烷-乙烷低温液化特性,获得天然气超声速液化过程中的流动与凝结参数,建立了甲烷-乙烷混合气体超声速凝结流动数学模型,开展了双可凝组分气体凝结相变实验验证,对比分析了凝结流动与等熵流动条件下的流场特性,并重点研究了甲烷-乙烷混合气体低温液化特性,结果表明:凝结相变发生之后,甲烷-乙烷混合气体流动过程中产生了微弱的凝结激波,相比于等熵膨胀过程,Laval喷管出口压力、温度升高,马赫数降低;凝结核数量在很短距离内从0急剧上升至最大值0.879×10^(21)m^(-3)·s^(-1)(约x=0.139m处);Laval喷管可获得的最大液滴半径4.476×10^(-7)kg^(-1),最大液滴数目4.462×10^(14)m^(-3),最大液相质量分数6.089%。

In order to make clear methane-ethane liquefaction characteristics of the Laval nozzle and obtain flow and condensation parameters in the supersonic liquefaction process of natural gas,the mathematical model for the supersonic condensation flow of methane-ethane mixed gas was established,and the experimental verification of gas condensate phase transition of double condensable components was carried out.The flow field characteristics under the condition of condensation flow and isentropic flow were compared,and low temperature liquefaction characteristics of methane-ethane mixed gas in the Laval nozzle were studied.The results showed that when the condensation occurs,a weak condensation shock-wave emerged in the flow of methane-ethane mixed gas,compared with the isentropic expansion process,the pressure and temperature at outlet of the Laval nozzle increased,and the Mach number decreased.In a very short distance,the nucleation rate sharply increased from 0 sharply to a maximum value of 0.879×10^（21）m^（-3）·s^（-1）（approximately at x=0.139m）;the maximum droplet radius in the Laval nozzle was 4.476×10^（-7）m;the maximum droplet number was 4.462×10^（14）m^（-3）;and the maximum liquid mass fraction was 6.089%.