Effect of lifting pump position on harmonic response dynamic behavior of deep-sea pipeline
The working environment of lifting system in deep-sea mining is very complicated,so the struc-ture design and parameters of the system still deserve further research.The effect of lifting pump at differ-ent positions on the dynamic behavior of 1 km lifting pipeline is studied.A reasonable dynamic model is established with elastic constraint that is used to replace heave compensation device.The external excita-tion mainly considers the horizontal excitation of wave-flow combination,the longitudinal excitation of wave and the torque excitation generated by the normal operation of the lifting pump.The vibration equation of the pipeline is established by energy integral method and the dynamic response of the lifting pump is ana-lyzed by finite element method when the lifting pump is installed at different positions of the pipeline.The results are as follows:The natural frequency of the system changes from small to large and then from large to small,while the maximum amplitude of the pipeline changes from large to small and then from small to large.Under single load excitation,the amplitude and equivalent stress of the pipeline are increased from small to large respectively:torque excitation,wave longitudinal excitation and wave-flow combined horizon-tal excitation.When the three are combined with the same phase excitation,the harmonic response of the system increases significantly.As the installation position of the lifting pump drops along the pipeline,the maximum amplitude and maximum equivalent stress response of the pipeline show a change rule from large to small and then from small to large.The above results prove that there exists a minimum of amplitude and equivalent stress within the range of a given reasonable installation position,that is,there exists a me-chanically optimal installation position for the lifting pump.On the basis of the model,the minimum equiv-alent stress is taken as the criterion to determine the suboptimal installation position of the lifting pump on the pipeline.The calculation method of installation position of the lifting pump based on harmonic re-sponse analysis that takes equivalent stress as criterion is given in this thesis,and the existence of mechan-ically optimal installation position is proved,which provides an important reference for the structural design of the lifting system.
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