Research On Structure Of Submarine Jet Trencher And Optimization Of Jet Arm

As an important equipment in the submarine oil and gas transportation project,the submarine jet trencher is used to perform trenching and burying operations to complete the task of protecting the submarine pipeline,so as to ensure the normal transportation of the submarine pipeline.This paper mainly designs a submarine pipeline jet trenching machine and conducts research on the overall mechanism scheme and performance of the jet arm.According to the design index and performance requirements of the jet trencher and the analysis of factors affecting the performance of the trencher,the overall structure of the trencher is determined and the composition of each part is introduced.Combined with the overall structure plan,the working principle and working process of the underwater operation of the trencher are introduced.The structural scheme design of the mud suction backfill system and the jet arm is completed,and a theoretical analysis of ground breaking is carried out on the cone-straight nozzle on the jet arm.According to the physical model of the cone-straight nozzle,the cone-straight nozzle flow field model is established.And the Fluent software is used for CFD simulation analysis,the OSF design sampling method is selected to sample the 3 size parameters in the nozzle structure,and the Kriging approximate model is established through the selected design points.By using the Isight software optimization solution module as the platform,using the NLPQLP algorithm to optimize the nozzle exit velocity target design of the cone-straight nozzle.Finally,the optimization results are analyzed from sensitivity,correlation and response surface.According to the three common jet arm structures,a cone-shaped jet arm is designed by combining the cylindrical jet arm and the trapezoidal jet arm and the internal flow field model is established.ICEM is used to grid the internal flow field model of the trencher jet arm.Divide,the Fluent software is used to perform CFD simulation on the internal flow field model of the jet arm.And the grid independence and calculation step independence analysis are completed.The jet arm is improved by adding a bell mouth structure,and the jet performance of the improved jet arm is compared with that before the improvement,which provides a certain reference for the research of the jet arm structure.By introducing two new types of nozzles,cosine type and arc straight type,to study the influence of nozzle internal streamlines on jet performance,the Fluent software is used to perform CFD simulation analysis on three types of nozzles of cosine type,cone straight type and arc straight type.A comparative study of the jet velocity changes on the central axis and the outlet surface of the external flow field was carried out,and the flow field performance of the three nozzles under different pressures and different sizes were compared and analyzed,which provided usable information for the future research on new nozzles of trenchers.