Dynamic Simulation And Reliability Analysis For Hydraulic System Of Emergency Cut-off Valve

Steam turbine is the key equipment in the thermal and nuclear power plants, whether it is safe in operating will affect the safety of the power plants. With the development of power industry, steam turbine becomes larger in size and gets gigantic in unit capacity, so the requirement of its protection and safety system is getting higher and higher. As Emergency Cut-off Valve is one of core parts in the protection and safety system of steam turbine, the response speed and reliability of Emergency Cut-off Valve are very important to the safe operation of steam turbine. The traditional design methods for controlling system of Emergency Cut-off Valve was based on trial-error, which prolongs the cycle of its R&D and manufacture and increases the cost of its' research and design. So the design method can't meet the modern design of Emergent Cut-off Valve system.With the developments of relevant subjects such as fluid mechanics, modern control theory, numerical arithmetic, reliability theory, especially computer technology, the technology of computer simulation is gradually applied to the hydraulic systematical design of Emergency Cut-off Valve. It can optimize the systematical design and ensure the systematical reliability of it by simulating dynamic performance and analyzing the reliability of the system.Recently, the tri-eccentric butterfly valve is applied to the protection and safety system of steam turbine. To analyze the response speed and reliability of thetri-eccentric butterfly valve system, the main structural features of Emergency Cut-off Valve (the tri-eccentric butterfly valve) is presented in this dissertation, and the hydraulic systematical schemes have been worked out, the optimized hydraulic systematical scheme of Emergency Cut-off Valve is selected by comparison of the hydraulic systematical schemes respectively. At the same time, the structural features of some of components such as the main body of the valve, mechanical actuator, pilot valve, are clarified. During setting up the systematical simulation model, the simulation models of the mechanical actuator and the pilot valve are designed by the author because they are for a special purpose. During the closure and open of the valve, the magnitude of force on mechanical actuator, which is caused by the valve plate gravity, is changeable as the central position of valve plate gravity is varying, so the simulation will be time-dependent and dynamic. After the simulation model for hydraulic system of Emergency Cut-off Valve is set up with AMEsim software in the light of its work principle, the dynamic simulation of the closure and open processes of the valve is carried out. Simulation curves are acquired and simulation results are presented, which are in good accordance with the experimental results tested by the cooperative team. Finally, the systematical reliability based on reliability theory and failure ratio is analyzed in regard to the basis of dynamic simulation resultsIt has proved that Dynamic simulation and reliability analysis for hydraulic system of Emergency Cut-off Valve on the base of computer simulation technology and reliability theory can reduce the cycle of research and manufacture, decrease the cost of development in the practical engineering. An important theoretic and practical engineering significance has also been shown.