输油管道液柱分离模拟

为了研究输油管道在不稳定流动过程中,因轻质组分挥发、气泡聚集而形成的液柱分离现象,建立了水击分析数学方程.基于分相流模型,采用特征线法、有限差分法将偏微分方程数学模型转化为代数方程组,并采用Newton-Raphson法进行求解,给出了分析步骤.最后,采用VC++开发了仿真程序,分析了输油管道中途截断阀突然关闭时,阀后管道拔高点处的水力瞬变工况.同时,还分析了初始油品中的含气率对液柱分离的影响.结果表明,当含气率大于10-6时,初始含气率越大,管道拔高点处低压持续时间越长,压力响应越滞后,液柱弥合压力越大;否则,可以不考虑含气对水力瞬变的影响.

Simulation of the separation of liquid column in oil pipeline

The liquid column in oil pipeline will separate due to the volatilization of light components and the concentration of bubbles.In order to research the phenomenon,the equations for the analysis of water hammer are established.Based on division phase flow model,in which the gas releasing and the oil evaporation are considered when pressure is lower than oil saturated vapor pressure,the partial differential equations are transferred into algebraic equations using characteristic method and finite difference method,and then the equations are solved by Newton-Raphson.Finally,a simulation program is developed in VC++,and the simulation steps are proposed.The transient hydraulic behavior at the high points of the pipeline behind a valve is analyzed when the valve is closed suddenly.The influence of different initial gas fraction(volume ratio of gas to liquid)in oil on the separation of liquid column is studied.It is shown that when the gas fraction is higher than 10-6,the higher the initial gas fraction,the longer the time when low pressure at the high points lasts,the later pressure response and the higher connect pressure of the separated liquid columns.But,when the initial gas fractional is less than 10-6,the effect of the gas in the oil on the transient hydraulic behavior at the high points of the pipeline can be neglected.The study results can be used for guiding the reasonable design and the safe operation of oil pipeline.