Research On Dynamic Characteristics Of Multi-section Articulated Pipeline In Deep Sea Mining

The development of deep-sea mineral resources is an important research topic in the field of deep-sea development.As a key component of the mining system,the safety and stability of transportation pipelines need to be solved urgently,otherwise it will greatly restrict the development of deep-sea mineral resources mining..The pipeline in the complex deep-sea environment is prone to form a strong nonlinear coupling with the fluid,which may affect the working efficiency of the deep-sea mining system,and even more seriously may cause accidents and losses.The spherical hinge connection is used to replace the traditional rigid connection deep-sea mining pipeline,and the vibration and mechanical characteristics of the multi-section articulated pipeline for deep-sea mining are studied.The following work has been focused on:(1)According to the flexible multi-body dynamics theory and Hamilton energy principle,the coupled vibration equation of the conveying pipeline is derived.The function method is used to discretize the derived equation,and the dynamic model is established through finite element software for analysis.(2)According to the process of the relay station in the mining process from no-load state to full-load state,the influence of relay stations of different masses on the vibration characteristics of the transmission pipeline was studied,and it was found that the natural frequency of the transmission system decreased with the increase of the relay station's mass.The greater the quality of the pipeline,the smaller the maximum amplitude value in the downstream direction,indicating that the relay station has a certain inhibitory effect on the deformation of the pipeline.(3)Aiming at the internal slurry flow rate that affects the lifting efficiency,the effect of different internal flow speeds on the vibration characteristics of the conveying pipeline is studied.It is found that the natural frequency of the conveying system decreases with the increase of the internal flow velocity,and the amplitude of the pipeline is obtained at the midpoint position.At the maximum value,the asymmetrical amplitude decreases gradually as the position closer to the mining vessel and the relay station is located,and the excessively high internal flow velocity will produce excessively large amplitude.(4)Aiming at the connection mode of the mining ship and the transportation pipeline,the influence of the hinge constraint and the elastic constraint on the vibration characteristics of the transportation pipeline is studied.It is found that the elastic constraint has a larger natural frequency than the hinge constraint.The amplitude of the peaks of the pipeline near the middle part under the two constraints is The largest and the smallest wave peak near the constraint,and the growth trend of the top elastic restraint pipe is less than that of the top hinged restraint.(5)Comparing the effects of rigid connection and spherical hinge connection on the lateral displacement and equivalent stress of the pipeline under the fourth and sixth sea conditions,it is found that although the maximum lateral displacement and offset angle of the rigidly connected pipeline are smaller than those of the hinged pipeline,But the pipeline will endure very large equivalent stress and fatigue damage.Articulated pipelines hardly bear bending moments and torques,which are more suitable for deep-sea mining system operations.