| In petrochemical industry,natural gas is transmitted through pipelines,yet the fluid in the pipelines is not single-phased.Natural gas,as the main-phase fluid extracted from gas wells,are also accompanied by trace solid grains,which may cause serious erosive wear of the typical pipe fittings in natural gas pipelines.This paper conducted a research on the erosion and wear phenomenon of natural gas pipeline elbows based on fluid dynamics and erosion theory,as well as the actual situation of production field of YB natural gas filed.Erosive wear has a complex mechanism behind it,therefore,the study of erosion and wear of elbows in natural gas pipeline is of great significance to the optimization of field operation.Based on the actual flow situation of the fluid in the field,the model algorithms are selected for the simulation which include RNG k-?model,discrete phase model,erosion rate equation and SIMPLE algorithm,etc.according to the natural gas flow in the elbow of pipeline.Secondly,an elbow model of 89~°elbow,which is frequently used in YB natural gas filed,is established.A numerical simulation is carried out with this model as an example,and the simulation results are compared with the actual erosion situation,which proves that the simulation is reasonable and reproducible.Thirdly,the effects of actual flow conditions(flow field characteristics,flow velocity,pressure),gas quality conditions(particle diameter,particle mass flow rate)and structural conditions(elbow diameter,elbow angle)on elbow erosion are simulated by FLUENT.By comparing different operating conditions through analysis with control variate method,it was found that:(1)Elbows placed at different trends are eroded to different degrees,yet the outer wall of them is the most seriously eroded area.(2)The erosion rate increases when the flow rate increases,yet the erosion position basically remains.(3)Gas pressure doesn't affect the erosion rate obviously.(4)The larger the diameter of sand particles,the greater the erosion rate of elbow,and the position of the maximum erosion rate will move in the opposite direction of the velocity.(5)When mass and flow of sand grains increase,the erosion rate will also increase.(6)When grain density changes within the designed scope,the erosion rate will change yet not fluctuate a lot.(7)With the increase of pipe diameter,the erosion rate will become smaller.(8)The maximum erosion rate of 89~°elbow is the highest,while the maximum erosion rate of 44~°and 180~°elbow is almost the same,the erosion rate of 58~°is smaller than that of the first three elbows.Finally,through the mutual verification between the actual erosion situation and the simulation results,it is proved that the simulation results are consistent with the actual situation.At the same time,a series of preventive measures were also proposed as suggestions according to the simulation results. |
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