Numerical Simulation Of Gas-liquid Two-phase Flow In Gas Lift Pump

The air lift pump is a kind of fluid mechanical device which can lift the liquid by injecting compressed gas into the vertical riser,resulting in the pressure difference between the inside and outside of the riser.Compared with the traditional mechanical pump,it has simple structure,no mechanical transmission parts and no system wear.It has the advantages of easy implementation of lifting technology,low energy consumption and wide source of driving energy.It can be used in high temperature,high pressure,vacuum,radioactive and corrosive environment,or in irregular channels.Due to the low maintenance cost and high reliability of air lift pump.It has wide application prospects in many fields,such as sewage treatment,sea water pumping,port dredging,oil field production,liquid metal cooled reactor and liquid metal MHD converter.Therefore,the research of air lift pump has important scientific value and engineering significance.In this paper,based on fluent simulation software,Eulerian model and k-omega SST Turbulence model are used to study the gas-liquid two-phase flow in the air lift pump under the conditions of liquid temperature,medium density and variable air volume inflation.The variation laws of gas volume fraction,liquid flow rate,lifting efficiency and liquid radial velocity at riser outlet are analyzed when the system is stable.The main results of this paper are as follows:(1)The hydraulic characteristics of gas-liquid two-phase flow of air-water air lift pump at different liquid temperatures(20?,60?,90?)were simulated.The results show that:The lifting flow rate of liquid increases with the increase of temperature at the same gas volume,and the lifting flow rate tends to fluctuate periodically with time.The influence of temperature on the void fraction is small at low gas volume rate,then as the air volume rate increases,the higher the temperature,the larger the void fraction.When the air volume rate is near 2.5m3/h,the lifting efficiency of air lift pump reaches the peak value,and the higher the temperature,the greater the peak value.(2)The flow behaviors of gas-liquid two-phase flow in nitrogen-water,nitrogen-kerosene,nitrogen-mercury and air-water,argon-water,nitrogen-underwater air lift pump were simulated.The results show that:In the nitrogen-water,nitrogen-kerosene and nitrogen-mercury systems,the higher the density of liquid medium,the smaller the gas volume fraction in the lifting pipe,the greater the flow rate of lifting liquid and the higher the promoting efficiency.In the air-water,argon-water and nitrogen-water systems,the higher the density of gas medium,the smaller the gas volume fraction in the lifting pipe,the larger the flow rate of lifting liquid,and the smaller the peak value of promoting efficiency.With the increase of gas flow rate,the liquid radial velocity at the lifting pipe outlet increases with overall fluctuation.Finally,the liquid velocity near the center of pipe axis is large,near the pipe wall is small.The research provide the scientific theoretical basis for the optimization of gas lifting technology in applications such as sewage treatment,deep well oil recovery,liquid metal cooled reactor and magneto hydrodynamic power converters.(3)The hydraulic characteristics of the air-water air lift pump are simulated under the conditions of air flow linear opening,air flow linear closing and air flow stepwise intake.The results show that:Compared with the fast opening mode,it takes longer for the liquid to lift to the outlet of the pipeline in the slow opening mode,and the fluctuation of the lifting flow is more uniform and smaller in the linear opening mode of gas flow.Compared with the fast closing mode,the time required to lift the liquid flow to zero at the outlet of the pipeline is longer,and the change of the flow pattern in the pipeline is more uniform and the fluctuation range is smaller.In the air stepped staged charging mode,the period of the air flow determines the period of the lifting liquid flow,and the periods of the two are approximately the same.The shorter the period is,the shorter the lifting time is and the larger the fluctuation range is.The longer the period is,the longer the lifting time is,and the smaller the fluctuation amplitude is.The research results of this paper will lay a scientific theoretical foundation for the application of air lift technology in river dredging,sewage treatment,gas lift,liquid heavy metal cooled nuclear reactor and MHD converter.