Flow-induced Vibration And Noise Characteristics Analysis And Suppression Of Elbow-fluid System In Nuclear Electric Gate Valve

The design and manufacturing of nuclear-powered submarine is an important component of strengthening military and building up a powerful country in marine cause.At present,although China has made great achievements in the construction,welding,outfitting and modernization design of submarine hulls,the technology is relatively lagging behind in submarine damping and noise reduction,especially in the application of new composites.Elbow-fluid system(EFS)in nuclear electric gate valve is an important part of the circuit in nuclear-powered submarine,whose vibration and noise index can directly affect the overall reliability and concealment of liquid-filled pipeline system and nuclear-powered submarine.During the closing of electric gate valve,the unstable steam fluid will occur under the combined action of turbulence caused by flashboard and curvature of elbow,which can lead to vibration of valve and pipe wall,together with direct noise radiation:flow-induced vibration and noise.In addition,vibration of fluid system will spread via supporting seat and magnify in relatively closed metal box of the submarine,thus exciting the housing to generate vibration.And then vibration and noise will radiate from the housing to water,thereby greatly reducing concealment of the submarine.Therefore,with the combination of theoretical analysis,experimental research and numerical simulation,fluid dynamics behavior under fluid-structure interaction and the characteristics of vibration and noise in EFS during the closing of electric gate valve are researched and analyzed in the paper.And structure optimization schemes to suppress vibration and noise in EFS and jam fault and wear of valve are proposed as well.High damping composite supporting seat is designed to reduce the vibration of EFS and block vibration propagation,thereby improving the reliability and concealment of EFS and the submarine.(1)Flow coefficient expression of the elbow is established,and numerical simulation of fluid via the elbow is carried out,obtaining variation regularity of flow coefficient under different Reynolds numbers and ratios of bending and diameter.The hydrodynamic theoretical model for fluid in the elbow is expressed by the Euler numbers,whose scientific nature and rationality has been further verified by the experiment of hydrodynamic distribution inside and outside the elbow.(2)SST k-co simulation method is employed to further study the steady-state dynamic behavior and characteristics of high-temperature and high-pressure steam in EFS under fluid-structure interaction,the result of which has been compared with that of hydrodynamic experiment in flow field.The fluid characteristics including fluid velocity distribution,pressure distribution and turbulent kinetic energy distribution in EFS during the closing process of the electric gate valve are researched in the paper,which can lay foundation for the accurate analysis and prediction of flow-induced vibration and noise characteristics in EFS and the formulation of structure optimization and verification schemes for vibration damping and noise reduction.(3)Based on the real-time dynamic characteristics of steam fluid in EFS and variation regularity of flow parameters during the closing process of electric gate valve,the coupled vibration characteristics of EFS,noise distribution of internal flow field and coupling surface,and the reasons for howling of the system and wear of guide bar are analyzed in the paper.(4)The main reasons for vibration and noise are analyzed,and structural optimization methods are proposed including the increase of transition fillets,the employment of flashboard with flat bottom and the addition of drum-shaped expansion pipes with variable diameters to reduce fluid jet,decrease pressure difference of the valve and pressure pulsation,weaken fluid vortex behind the valve.The purpose is to reduce vibration and noise of EFS,and the preceding optimization methods can be verified by CFD.(5)Secondary topology optimization method is employed in the paper to design a new damping supporting seat which is made of polyimide resin composites,and simulation analysis of static and dynamic performance has been carried out.It can be proved that the new supporting seat has the advantages of strong deformation resistance,high rigidity and light weight.The seat can significantly improve modal of the pipeline system,avoid local and system resonance,reduce fluid pressure pulsation,and inhibit generation and spread of vibration in EFS,thus effectively improving reliability and concealment of the submarine.