Simulation And Numerical Modeling Research On Stress Characteristics Of Steam Pipes ＆ Valves

Steam pipes are applied widely in industrial fields and they are important parts of the power system.The stability and safety in the process of running are the research hotspots.This paper firstly uses CAESAR II to simulate the overall stress distribution under different working conditons of the steam pipe system,and then uses ANSYS Workbench to carry out the FSI analysis on the reducing pipes,T-branch pipes and the valves of the system.With loading the hydraulic,heating and restrain boundary conditions,the computed results contain the stress distribution of the pipe components,and the analysis also focus on the influence of different temperature,pressure and structure conditions on the components’ stress distribution.Based on a certain steam pipe system,this paper firstly use CAESAR II to establish the geometric model,load the boundary conditions,and then run the static analysis.The simulation results contain primary stress of all nodes under the sustaining loads such as pressure,weight and the effect of the spring hangers,secondary stress under displacement loads of temperature and restraint,and the nodes over the allowable stress.Geometric models and mesh of the pipe system are established in Workbench,and hydraulic calculation is carried out in Fluent,then the static analysis is executed for the pipe solid region with the loading of hydraulic and heating boudary conditions,and finally the stress distributions of these components are calculated under oprating mode.The calculation shows that stress concentration mainly locate in joint of reducer,flange,T-branch pipes’ intersection as well as constraint positon.Reasons for the concentration include the piping local structure,space layout and the constraint category.The numerical modeling results indicate that the axis and hoop stress concentrate on the inner and outer walls of major and minor diameter of the reducer.The effects of restraint against inflation caused by temperature and pressure,as well as stretch and extrusion in major and minor diameter caused the trapezoid structure are the main reason for axis stress concentrate,and the V structure in major and minor diameter for hoop stress concentrate.The axis and hoop stress both increase as the temperature rises,while the variation of pressure has a non-significant influence.The models of reducer also impact the stress distribution notably,and the219-380 mm pattern has the maximum stress as a result of the most discontinuous structure.The T-branch pipes’ stress concentrate in the intersecting line between the major and branch pipes,and the results according the 3rd strength theory of material and the equivalent stress both increase as the temperature rises,and variation of pressure has a non-significant impact as the reducer.Stress analysis on sluice valves mainly focus on the axis stress,and the concentration positons locate in the two points of the interfaces between flashboard and the valve body.The maximum tensile stress locates in the flashboard facing the incoming flow,and the reseaon for the concentration is the axis inflation and deformation under temperature and pressure loads and the restraint in continuous structure as well as the push effect of pressure difference between the two faces of the flashboard and the restraint from the valve body result in the axis defromation.The variation of temperature and flashboard opening impact the stress distribution observably,and the change of flashboard’s rigidity and flexibility result from its length variation also impacts a lot,while the stress distribution has an insensitivity to pressure change.