Numerical Simulation Of Hydraulic Pigging Process Of Multi-product Pipelines Transporting Jet Fuel Successively

The trapped water and solid particle impurities in the multiproduct pipeline where the jet fuel is transported successivly not only affect the quality of oil,but also increase the operation risk of pipelines.It is of great practical significance to carry the trapped water and solid particle impurities out of the pipeline by means of hydraulic pigging method,which can effectively reduce the attenuation of the quality of jet fuel and reduce the operation cost of the pipeline.The essence of hydraulic pigging method is a complex multiphase flow process and the characteristics of local oil-water two-phase flow,and the behavior mechanism of particles in the oil stream are not very understood,especially the research on particle flow is mostly limited to isotropic turbulent flow field at present.There is a difference between the high Reynolds number turbulent field and the anisotropic turbulent field in the industrial pipeline.In view of this,this paper presents a numerical investigation of the flow dynamics of the trapped water and solid particle impurities which are flushed out by flowing oil in the products pipelines.In the study of accumulated water flow dynamics during hydraulic pigging process,firstly,the flow patterns of water displacement in an upward inclined pipeline under the critical oil velocity required for the displacement of the complete accumulated water is analyzed.The result shown that the flow of water displaced by oil stream belongs to oil water two phase stratified wavy flow.The numerical model governing the oil-water stratified wavy flow occurring in trapped water displacement in an upward inclined pipeline is established based on the flow patter aforementioned.The numerical model and algorithm are first validated for simulating the oil-water stratified wavy flow problems through comparison with experimental pressure gradient data from the literature.Then,the flow characteristics of water mobilization are analyzed in detail.Furthermore,the numerical criteria for calculating the critical oil velocity necessary for the onset of the complete water displacement is proposed in this paper.In the study of dynamics of accumulated solid particle impurities migration during hydraulic pigging process,a three-dimensional numerical model governing the tapped particles displacement from the elbow of an inclined oil pipeline is established in the Euler-Lagrangian framework.The simulation is achieved via CFD-DEM coupling solving algorithm.It is observed that the oil stream,carrier phase,in the pipeline can only flused out the solid particle impurities in a certain diameter range under the given operating conditions,and the particle impurities beyond that diameter range will cannot be displaced out of the pipeline.Then,due to the low computational efficiency of the aforementionend numerical model,referring to the “pilling up-collapse” mechanism of sand dunes,the critical oil velocity mechanism model of the particles which can be flushed out the products pipelines is established via using the average force model of particles in the flow field.The mechanism model is validated for predicting the critical velocity through comparison with data from the literature.The effects of pipe diameter,fluid physical properties,particle diameter,particle density and pipe inclination angle on the critical oil velocity are analyzed.It is found that the fluid density alters the critical oil velocity most remarkably.Finally,an Enhanced Hydraulic Pigging Method Based on Multi-physical Field Collaboration(EHPM-MPFC)is also designed to achieve the small-scale particle impurities displacemet in the present work.The multi-physical field hydraulic pigging technic is valided for having high pigging efficiency via the displacement curve of small-scale particles during the EHPM-MPFC process.