Multi-objective Optimization Of Anchorage Section Of Submarine Clamping-Pressing Connector And Analysis Of Gas-liquid Parameters On Connection Strength

Submarine pipelines are the main mode of deep-water oil and gas transportation.Due to the harsh working conditions,leaks often occur and cause production accidents.Therefore,the rapid connection between broken pipelines has become a technical problem that must be overcome in the field of underwater pipeline maintenance.Aiming at the problems of the existing submarine pipeline connector's complicated structure and insufficient connection strength of the anchoring section.Taking Submarine Clamping-Pressing connector as research objects,the establishment of anchoring section connection strength criteria,multi-objective optimization of anchoring section structure,influence of gas-liquid parameters on anchoring section connection strength,and experimental tests were carried out.Based on the existing connector,the overall structural scheme of the main and auxiliary seals of the metal and rubber seals of the submarine Clamping-Pressing connector and the inner triangular anchoring teeth was determined.The process of pressing the anchoring teeth into the outer surface of the pipeline is simplified as the plastic flow of the ideal steel-plastic body under load.The maximum anchoring force of the anchoring section after the anchoring teeth are pressed into the pipeline is obtained,which depends on the average pressure at the contact surface.For subsea pipeline systems the requirements for the deformation of the inner diameter of the pipeline after the connection of the code shall not exceed 6% of the wall thickness of the pipeline,and the deformation of the inner diameter of the pipeline is proposed.The connector strength criterion was determined by using the average contact surface pressure and the deformation of the inner diameter of the pipeline as evaluation indicators.The anchoring section is simplified into a combined thick-walled cylinder.A mathematical model for the connection strength of the anchoring section of the submarine Clamping-Pressing connector is established.The mathematical expressions for the stress of the pressure ring,the substrate and the pipeline and the mathematical expressions for the deformation of the inner diameter of the pipeline are obtained.The internal triangular anchoring structure identified 8 optimization variables;the relationship between the optimization variables and the strength of the anchoring section was obtained through the finite element calculation results;and the optimal design variables and parameter sensitivity values of the anchoring section of the connector were obtained through multi-objective optimization.The connection strength of the anchoring section before and after the optimization is compared to verify the rationality of the multi-objective optimization design.For the gas-liquid two-phase state of the transport medium,the gas-liquid parameters were determined by the stratified flow model;the VOF calculation model was used for the transport fluid,and the pressure distribution and the wall pressure distribution of the pipeline at different volumetric gas content rates and fluid transport speeds were calculated.Maximum pressure;the one-way coupling calculation method is used to load the wall pressure of the oil and gas pipeline to the optimized connector,and the relationship curve between the volumetric gas content and the fluid transport speed on the average deformation of the inner diameter and the average pressure on the contact surface is obtained.Provided parameter basis for practical application of the connector.In order to verify the rationality of the submarine Clamping-Pressing connector design.Installation experiments were performed on the connectors before and after optimization,and the maximum loading force was obtained during the connection process.Limit sealing pressure test experiments were performed on the connectors before and after optimization to verify the sealing performance of the connectors before and after optimization.Tensile experiments verified the ultimate axial load that the connector can withstand.The indentation observation experiments were performed on the anchoring section of the connector before and after the optimization to verify the rationality of its connection strength criteria and the credibility of multi-objective optimization.