Analysis Of Vibration And Lifting Performance Of Lifting Pipe Under The Action Of Coupled Internal And External Flow Field

Lifting pipe is a device that uses compressed air to lift liquids and solid-liquid mixtures.Because of its simple structure,low cost,corrosion resistance,easy operation,safety and environmental protection,it plays an important role in the mining of mineral nodules under the sea,the transportation of toxic and corrosive liquids in the chemical industry,and the removal of mud and weight reduction from sunken ships in salvage projects.The main body of the lifting pipe is a vertical riser,which often has to complete long-distance transport in the marine environment of tens to thousands of meters,so it also tends to have a large L/D ratio.The multiphase flow inside the lifting pipe has a complex flow pattern,while the external marine environment in which the lifting pipe is located is also complex and variable,so the lifting pipe will vibrate during the lifting process under the coupling of the internal and external flow fields,and the long time vibration will not only affect the fatigue life of the lifting pipe,but also affect the lifting performance of the lifting pipe.In addition,due to the intermittent gas inside the lifting pipe will also produce the surge effect,the effect will not only aggravate the vibration of the lifting pipe,but also have an impact on the lifting performance of the lifting pipe.Therefore,the vibration and lifting performance of the lifting pipe under the action of coupled internal and external flow fields should be studied.In this thesis,the vibration and lifting performance of the lifting pipe is studied by a combination of numerical simulation and experiment.Firstly,this thesis establishes a computational model of the lifting pipe in hydrostatic water under the coupling effect of gasliquid two-phase flow internal flow field by referring to the empirical model,and numerically simulates the vibration and liquid lifting of lifting pipes with different pipe diameters under the coupling effect of internal flow field with different inlet gas flow rates,and analyzes the influence law of inlet gas flow rate and pipe diameter on the vibration and lifting performance of lifting pipes.Secondly,on the basis of the completed work,a computational model of the lifting pipe under the coupling effect of internal and external flow fields is established,and the vibration and liquid lifting of lifting pipes of different diameters under the coupling effect of external flow fields with different Reynolds numbers and internal flow fields with different gas holding rates are numerically simulated,and the influence law of the Reynolds number of external flow fields on the vibration of pipes in different positions and directions is analyzed,and the eddy-excited vibration effect of external flow fields and the lifting performance of lifting pipes by different internal flow field parameters and pipe structure parameters are further analyzed.Finally,combining with numerical simulation and actual conditions,experiments are designed and completed for lifting pipes in hydrostatic water with the same conditions under the coupling effect of gas-liquid two-phase flow internal flow field,and the vibration and liquid lifting of lifting pipes with different pipe diameters under the action of internal flow field with different inlet gas flow rates are obtained,which are compared and analyzed with the numerical simulation results to verify the accuracy of the law.And in the further analysis,the influence law of surge effect on the vibration and lifting performance of the lifting pipe is discussed.Numerical simulation and experimental results show that: with the increase of the inlet gas flow rate,the amplitude of the lifting pipe increases,the lifting flow rate increases and the lifting efficiency decreases;with the increase of the pipe diameter,the amplitude of the lifting pipe decreases,and the lifting performance improves as a whole.With the increase of Reynolds number of external flow field,the amplitude and frequency of eddy vibration of lifting pipe increase,and the lifting performance decreases as a whole;with the increase of gas holding rate of internal flow field,the amplitude of lifting pipe increases,the frequency decreases,and the lifting performance decreases as a whole;with the increase of pipe diameter,the amplitude and frequency of lifting pipe decreases,and the lifting performance improves as a whole.In practical engineering applications,the inlet gas flow rate and pipe diameter are the most important power source parameters and structural parameters of the lifting pipe,while the external flow field conditions will also have an important impact on the lifting pipe,so the research content of this thesis can provide theoretical reference for the selection of parameters to meet the requirements of both vibration control and guaranteeing lifting performance of lifting pipes in engineering applications,and inspire researchers to conduct more research on the impact of the surge effect of lifting pipes.