| As an unconventional new clean energy,shale gas has attracted great attention all over the world in recent years.As the most commonly used and effective technical method in the process of shale gas development,hydraulic fracturing technology has become an important technical means for large-scale production of many enterprises.In the process of long-term continuous mining operation,the fracturing unit should have the characteristics of high pressure resistance,large displacement and long service life.Elbow is one of the important pipe fittings in the process of fracturing fluid transmission.Due to the complexity of pipeline layout and harsh working environment,the fracturing fluid containing solid particle proppant turns at the elbow,resulting in serious erosion and wear problems.The average life of elbow is far lower than that of other conventional fracturing components,which seriously restricts the reliability of the whole fracturing unit and has a serious impact on the development efficiency and economic benefits of shale gas.In recent years,scholars at home and abroad mostly take 90 ° single elbow as the main research object,and have made many achievements in its erosion wear law.However,in the actual process of engineering,the pipeline system is mainly continuous,multi-stage and spatial pipeline layout,and the understanding of the erosion law of type elbow is not sufficient at present.Taking the spatial z-bend as the research object,this paper aims to reveal the erosion wear law of spatial z-bend pipeline and accurately predict the maximum erosion wear position through the analysis of erosion wear characteristics and anti erosion optimization of spatial z-bend,which is of great significance to improve the service life and design level of bend and enhance the safety of fracturing operation.This paper is mainly divided into the following parts:Firstly,through the analysis and induction of elbow erosion mechanism,erosion influencing factors and erosion calculation model,this paper summarizes the applicable scope and condition limitations of each theoretical model,selects the erosion wear model suitable for this paper,and further verifies the effectiveness of the erosion model proposed in this paper through the comparative analysis of numerical and experimental results of typical 90 ° elbow die.Secondly,the numerical model of erosion wear is established based on the structure of spatial z-bend.The causes of the maximum erosion wear position are explained by analyzing the trajectory of solid particles in the liquid phase.Then,by analyzing the different flow velocity,particle size,mass flow,viscosity,gravity direction,bend diameter ratio,bend angle,bend space angle,pipe diameter The influence law of the distance between two bends and the change of material surface hardness on the maximum erosion rate is obtained,and the correlation degree of each parameter on the erosion rate is obtained.The simulation results show that among the fluid parameters,the mass flow has the greatest influence on the erosion wear of bends;Among the structural parameters,the included angle of elbow has the greatest influence on erosion wear.Finally,by analyzing the maximum erosion position and erosion wear law of spatial zbend,several typical anti erosion optimization models are compared and analyzed,and a corrugated anti erosion structure based on bionic structure is further proposed.Through the comparative analysis of three anti erosion models,it is found that from the numerical value of erosion rate,the anti erosion performance of T-type blind long head pipe is better,while from the erosion cloud diagram,the anti erosion performance of corrugated structure is better.This provides technical support for the anti erosion structure design and practical application of space pipeline system in the future. |
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