Sealing Design And Working Characteristics Of Deep Sea Piston Pressure Level

The special high pressure environment in deep sea brings unprecedented challenges to the application of traditional sealing components.As an important deep-sea sealing scheme,pressure balance sealing technology provides a new solution to deep-sea sealing problems.The piston pressure balancer can reduce the pressure difference between inside and outside of deep-sea seals and improve the working conditions of traditional seals by introducing deep-sea pressure into the sealing object.The piston pressure balancer requires the piston assembly to seal reliably under deep sea pressure and respond rapidly to the change of deep sea pressure,which puts forward higher requirements for the existing piston sealing technology.This paper has carried out relevant research from the following aspects:(1)A new type of deep-sea piston seal structure was designed,i.e.star-shaped seal with PTFE sliding ring as the main seal,labyrinth seal as the pre-auxiliary seal,and related design parameters are worked out.The contact stress model of the main seal was established,and the sealing judgment conditions are put forward to prepare for the subsequent verification of the main seal performance and the study of the working characteristics of the piston pressure balancer.(2)The finite element model is established according to the structure of the main seal and the actual working conditions,and the effects of compression ratio,internal and external pressure difference,slip ring thickness and star ring diameter on the contact stress and Von-Mises stress of the main seal are obtained by simulation calculation;the stress values of contact line nodes are extracted to study the contact width and contact stress variation law of the sealing interface;the compression ratio and star ring ruler are analyzed by orthogonal test.The influence of inch and slip ring thickness on sealing performance.(3)CFD(Fluid Computational Dynamics)is used to simulate and analyze thelabyrinth auxiliary seal structure under the sealing boundary conditions.The effects of seal clearance,comb thickness and seal chamber depth on the performance of the auxiliary seal are studied.The rules of the influence of labyrinth seal parameters on the sealing performance are summarized,which provides a reference for the design of the piston auxiliary seal.(4)Based on the design of the main seal,a two-degree-of-freedom mass-spring-damper system is established to describe the mechanism of piston crawling and calculate the conditions of crawling phenomenon from the dynamic point of view;the static equilibrium equation of the piston pressure balancer is established to study the influence of the parameters of the main seal on the start-up pressure;the dynamic equilibrium equation of the pressure balancer varying with the depth of sea water is established to study the initial state.The variation of displacement,velocity and internal and external pressure of the lower piston.