Simulation And Thermal Stress Analysis Of LNG Low Temperature Ball Valve

In recent years,with the adjustment of energy structure,LNG energy use has increased dramatically,so the liquefaction of natural gas and liquefied natural gas transportation and storage of cryogenic valves demand has increased dramatically.But in the transportation and storage of liquefied natural gas will need large cryogenic valves,therefore,with the rapid development of LNG industry,the demand for LNG cryogenic valves will be more and more,so the LNG low temperature valve will be an unprecedented development in our country.The design and safety of traditional LNG cryogenic valves have many shortcomings,such as too long stem cover,unsafety relief,and over-critical design problems.Aiming at the problems of traditional LNG cryogenic valves,first of all,from the analysis of heat transfer angle,this paper uses cold fin technology to solve the problem of too long valve cover,valve stem.Install a set of cooling fin on the long neck LNG cryogenic valve bonnet to increase the heat exchange area between the neck of the cover and the environment,strengthen the convective heat transfer between the neck of the cover and the environment,slow down and stop the cooling capacity transferring upwards,in order to reduce the cover and stem height,reduce the torque of valve stem when open and close and extend the use of the valve.Secondly,according to the self-pressurized principle and the matching of clamp load and the delivery pressure,it can solve safety relief and critical design problems.Install LNG pressure regulator on the valve ball to export LNG in blind area when the ball valve open and close and achieve safety relief,so as to improve the efficiency of LNG process control and the safety of the valve.In addition,LNG pressure regulating valve relieves pressure in time,reducing the design pressure of valve and system and improving the security and reliability of valve and system operation.Finally,according to the cryogenic valve design manual and related principles,make the LNG ball valve and LNG pressure regulating valve structure design reasonably.Based on heat transfer theory combined with the numerical simulation,make some following researches on the designed long neck bonnet with scattered finned and LNG pressure regulating valve:(1)A physical model is established for the structural components of the long-necked bonnet with finned fins.Firstly,according to the theory of heat transfer,the theoretical calculates and numerical simulates calculates of the thickness of cold-keeping layer of the low temperature ball valve of LNG,and then compares the two results to the optimal thickness of cold-keeping layer.Secondly,the temperature field distribution of the structure of the long-neck valve cover is simulated by using the Simulation plug-in the Solidworks software,and then the best model and the best number of the fins are obtained.And finally determine the best model of long neck valve cover structure and the actual height of the neck after the installation of cooling fins.(2)According to the theory of fluid mechanics,the flow field of LNG pressure regulating valve is simulated by using Flow Simulation plug-in in Solidworks software,and the flow field,temperature,pressure,velocity and density distribution are obtained.(3)According to the theory of heat transfer and thermodynamics related theory,the thermal-structure coupling model of long neck cover structure components in the thermal stress analysis,it is concluded that the stress,displacement,strain change rule,In addition,the thermal stress analysis of the pretension spring of the LNG pressure regulator is analyzed,and the change of shear stress and axial displacement is obtained,and the theoretical verification is carried out.This article is based on the method of theoretical calculation and simulation analysis for LNG cryogenic ball valve as the research object,on how to reduce the height of the long neck valve cover,analyzes the key problems such as how to safety relief and research,and draws some useful conclusions for,provide reference for the development of LNG cryogenic valves.