| With the rapid development of industry,land mineral resources have been increasingly depleted,and countries all over the world have raised the development of seabed mineral resources as a national strategic goal.At present,pipeline hydraulic lifting technology is the most likely to be commercialized,but the complex liquid-solid two-phase flow characteristics of this technology are still lack of complete theoretical guidance,which directly affects the improvement of transportation efficiency and the guarantee of transportation safety.Therefore,this dissertation takes the non-spherical ore particles as the research object,and combines the theoretical analysis,experimental research and CFD-DEM numerical simulation method to study the swirling hydraulic lifting process of non-spherical ore particles in the swirl field with the goal of achieving safe and efficient hydraulic lifting process.So as to provide theoretical guidance for the industrial application of swirling lifting device,broaden the application field of hydraulic lifting technology and swirling conveying technology.The main research contents and conclusions are as follows:Based on the fluid-solid coupling theory and Newton's law of motion,the force composition of ore particles is clarified.Based on Hertz-Mindlin contact theory and the introduction of virtual pipe wall assumption method,the particle-pipe wall collision motion and force equation are obtained and the dynamic characteristics of ore particles in the axial flow and swirling flow are analysed.The non-spherical drag coefficient formula is corrected,and the correction and call of the formula model are realized based on the custom API interface of EDEM.Based on the numerical calculation of non-spherical ore swirling conveying system in this thesis,the matching built-in model is selected to determine the liquid-solid two-phase calculation method and parameters.The numerical simulation of horizontal pipeline mortar transportation test was carried out to verify the accuracy of the selected built-in model by comparing with the test data.The spherical and non-spherical drag models were used for numerical simulation,respectively.The accuracy of the modified non-spherical drag model was verified by comparing with the data of hydrostatic settlement test of single-particle circular pipe and non-spherical particle pneumatic spouted bed test.The results show that the built-in model selected in this thesis is reasonable,and the accuracy of the modified non-spherical drag model is higher and closer to the test value than that of the spherical model.The characteristics of the existing swirling generator are analyzed,and a new pipeline lifting system is proposed.The CFD-DEM coupling method was used to calculate the liquid swirling flow field and the carrier flow process.The results show that the axial and tangential velocities of swirling flow and the particle number concentration are significantly higher than those of straight pipe.With the increase of tangential proportion,the swirl number and vorticity increase,the vortex core is broken more quickly,and the particle number concentration increases.The retention effect and axial drag of each shape particle in the straight pipe are quite different,while in the swirling pipe,each shape particle is uniformly mixed and promoted by swirling flow.According to the mechanism of swirling generation,attenuation and loading,a multifunctional swirling device with variable strength is designed.In the process of vertical hydraulic transportation,high intensity swirling generated by reasonable energy consumption is mixed with the mainstream,so as to speed up the start velocity of particle,reduce the risk of siltation and improve the efficiency of long-distance transportation. |
PDF Full Text Request