Transient Analysis of the Gas-Liquid Two Phase Flow in Long-Distance Water Pipelines

摘要

In a long distance pipeline,the trapped air is usually resided at the dead ends and the segments of pipes with the high elevations because the air can not exhaust smoothly.When the pump shuts off or the valve is closed suddenly,the water hammer with gas-liquid two phase flow will occur.The pressure resulted from the gas-liquid two phase transient flow will be much bigger than that from the general water hammer.It is one of the major factors to result in pipe burst.The objective of this paper is to study the gas-liquid two phase transient flow in the pressure pipeline.The research achievement is applied in an actual engineering project.Firstly,the control equations of the gas-liquid two phase transient flow in pressure pipelines are presented based on the gas-liquid two phase flow theory and computational fluid dynamics.Then,by means of volume of fluid (VOF) model,the flow field around the trapped air in pipelines is numerical simulated and analyzed on the stages of water filling and pump failure.The pressure fluctuation around the trapped air is obtained.Finally,the research achievement is applied to an actual long distance pipeline.The results show that the VOF model could effectively simulate the flow fields of the gas-liquid two phase transient flow.On the stage of water filling,the maximum pressure head decreases with the increase of the valve opening duration.When the pump shuts off suddenly,the maximum pressure head rises up with the increase of the pipe slope in which the trapped air exists.