Research On The Harmonic Response Dynamic Behavior And Characteristics Of Deep-Sea Mining System

In the 21 st century,with the consumption of land resources,the deep-sea mineral resources have been paid more and more attention by human beings.At present,the deep-sea mining system,which elevates the deep-sea mineral resources from the seabed to the surface of the sea,is the research hotspot of various ocean powers.The deep-sea ore raising system working environment is extremely complex,because the lifting pipeline is excited by wave,sea currents and pump vibration loads,lifting pipeline under multiple load excitation at the same time,bending,stretching,torsion deformation and vibration influence the deep-sea mining system working stability and structural safety,so at present in the deep-sea mining system structure design and parameters depend on further research.At present,when studying the dynamic behavior of the ore raising pipeline,most of the lifting pump is ignored,and the lifting pump weighs several tons in real and the different installation position changes the spatial distribution of the mass of the ore raising system,which will affect the dynamic characteristics of the ore raising system.In order to study the effect of lifting pump at different positions on the dynamic behavior of lifting pipeline with different lengths,elastic restraint was used to replace heave compensation device.The external excitation 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 mine lift pump;Vibration equation of pipeline is established by energy integration method and dynamic analysis is carried out by finite element method.The main work and conclusions are as follows:(1)The finite element discrete method is used to study the deformation of lifting pipe element under multi-load excitation,and the vibration equation of lifting pipe is established by energy integration method.(2)With 1000 meters length of pipeline as an example,experience in lifting pump installation position within the scope of 6 different installation position for the young mine pump,lifting pipe is obtained by using the finite element method of wet modal,found that as the lifting pump installation location along the pipeline to drop,present the natural frequency of the system from small to large,from big to small again,while the maximum inverse bending point amplitude of the pipeline shows a change rule from large to small,and then from small to large,that is,there are extreme values of the natural frequency and maximum inverse bending point amplitude of the pipeline within the empirical range of the installation position of the lifting pump.In view of the influence of different installation positions of the lifting pump on mechanical properties of specific length the lifting pipeline,the harmonic response of the lifting system under the combined action of single load excitation and multi-load synchronous phase excitation is calculated by using finite element method.It is found that the maximum amplitude and maximum equivalent stress of pipeline monitoring point are as follows: The harmonic response of the system increases significantly when the torque excitation,wave longitudinal excitation and wave-flow combined horizontal excitation are combined with the same phase excitation.Under combined and with phase excitation,the lifting pipeline maximum amplitude response and the maximum equivalent stress response as the lifting pump installation position down,presents the regularity of changes from big to small,from small to large,to maximize the amplitude response and the maximum equivalent stress is minimum as the criterion,in the given the lifting pump installation location time discrete model of the optimal installation location.(3)Considering that deep-sea mineral resources are usually found at depths of 1000m-6000 m,the pipeline lengths of deep-sea mining systems will vary within this range.On the basis of the previous research,similar research is done on the ore raising system of 2000 m,3000m,4000 m,5000m and 6000 m.The results show that the dynamic behaviors of these pipelines with different lengths are similar to those of 1000 m pipelines.(4)According to the sub-optimal installation position data of lifting pump of different lengths of pipelines,it is found that there is a linear relationship between the sub-optimal installation position and pipeline length,and an empirical formula for the sub-optimal installation position of lifting pump of different lengths of pipelines is established through linear fitting.This paper studies the multiple incentive under the action of different length of the lifting pump installation position of the deep-sea mining system of the influence of the structural dynamic behavior and its mechanism,it proposes a criterion for equivalent stress of the lifting pump time calculating method of the optimal installation location for the deep-sea mining system structure design and safety analysis provides quantitative method and reference,has good engineering application value.