喷管内高速流动天然气相变特性数值研究

Study on the phase transition of high-speed natural gas flow in a nozzle by numerical method

在超声速旋流天然气分离器中,气流经过拉伐尔喷管绝热膨胀形成带液滴的超声速低温混合气流,喷管内的相变是实现天然气分离的关键.根据相变理论、气体动力学理论并考虑了实际气体的影响,建立了描述有相变的喷管中天然气高速流动的数学模型.研究了喷管内有相变的天然气的流动特性;计算了不同入口条件下的相变起始点位置和水蒸汽的凝析率;分析了当喷管入口温度一定时,相变起始点、水蒸汽凝析率与入口压力的关系.计算结果表明,随着入口压力的升高,相变起始点位置逐渐前移,水蒸汽凝析率逐渐增大,建立了一种预测超声速旋流分离器正常工作压力范围的方法.

Supersonic swirling natural gas separation is a revolution in natural gas processing technology compared with traditional low-temperature separation technology.In the supersonic swirling separator,the supersonic low-temperature stream with small liquid droplets is formed when the natural gas passes through Laval nozzle and does adiabatic expansion.The phase transition in the nozzle is the key to the separation of natural gas.Based on the theory of phase transition,gas dynamics and the state equation of real gas,the mathematical model of high-speed natural gas flow with phase transition in Laval nozzle is established and the flow characteristics of the natural gas flow are investigated.The starting points of the phase transition and the mass ratio of condensed water to vapor at the outlet of the nozzle are calculated under different inlet conditions;the relations between the starting points of the phase transition and the mass ratio of condensed water to vapor and inlet pressure at constant inlet temperature are also analyzed.The results indicate that,the starting points of the phase transition move forward and the mass ratio of condensed water to vapor increases with the increase of the inlet pressure.The factors of influencing the normal operation of the separator are discussed and a method for predicting the normal operating pressure range of the supersonic swirling natural gas separator is established.