Research On Characteristics Of Lifting Pipe Conveying System Under The Influence Of Inflow In Deep-sea Mining

Deep-ocean mining is a vital important branch of marine industry,which has strategic significance in national energy development.Implementing lifting pipe as the system scheme to hoist and transport mine has high working efficiency,and meet the mining requirement at present,which is one of the most comprehensive system scheme in related research field in China.Bearing both inner and outer current load in practical working environment,the force condition of lifting pipe is quite complicated,which makes it the most critical part of the mining system research.Therefore,the working performance research of lifting pipe is very meaningful.Through the physical model of lifting pipe analysis,environment load analysis and linear wave theory,the motion equation under different sea state was induced.By analyzing amplitude loss between mining ship and wave water particle,the heave law of mining ship was summarized.Using Morison theory,the variation law of hydrodynamic load along the water depth under the combined action of wave and current on the side of the mining pipe under different sea conditions was obtained.According to the Hamilton energy principle,the kinetic energy,potential energy and non-conservative work of the pipeline system were analyzed.Using the idea of finite element plane beam element,the finite element discretization of the differential equation of the lifting pipe was carried out,and the mass,damping and stiffness matrix of the node load matrix and the tube beam element were analyzed one by one,and by exploring the combination regulation of matrix from unit to whole,the overall vibration equilibrium equation of the mining pipe conveying system was carried out under the combined action of wave and current,considering the influence of internal flow.The variation regulation of elongation with water depth of lifting pipe was obtained by static analysis of the lifting pipe.Introduced the Newmark method,on which induced the calculation method of dynamic equilibrium equation based.The FEA model of the lifting pipe was established in ADINA.According to the results of the simulation,it was found that the net elongation of the lifting pipe gradually decreased with the increasing of the water depth.The maximum stress of the lifting pipe is applied to the top of the lifting pipe under different working conditions.The maximum shift position occurs at the bottom of the pipe.Compared with the launch and recovery possess,the maximum stress of the lifting pipe system is 0.4%larger,and the maximum lateral shift is 2%larger.When the system carries out mining operations,that is,when the lifting pipe considers the inflow,the inflow velocity increases from 1 m/s to 3 m/s.The maximum stress at the top of the pipe increases by about 80%,the maximum lateral displacement at the bottom end of the pipe is increased by approximately 87.5%.The maximum internal stress from the 3m/s to 5m/s pipe increases by about 87%,and the maximum lateral displacement at the bottom of the pipe increases by about 90%.In conclusion,study on characteristics of deep sea mining pipe system considering the influence of inflow has certain guiding value and reference significance for the vibration absorbing of the lifting pipe,the optimization design of the elevating pump and the selection of lifting speed.