| The butterfly valve is wildly used as a control device for the pipe. Its reliability, energy efficiency, manufacturing and operating costs for the national economy are of great significance. It has been the difficulties in butterfly design on reducing and calculating flow resistance, calculating water torque, analyzing load conditions and strength under several opening degree of the valve, calculating sealing performance, and so on. In traditional design, designers usually designed butterfly valve by testing and inspection manual, which not only takes longer, and also increased cost. In this dissertation, the main difficulties are investigated in designing the soft rubber seal butterfly valve by the finite element method (FEM). It is expounded as follow:Firstly, it introduces structure, main performances and features, application fields and significance of butterfly valve. Then the main methods for butterfly valve design and main problems in the methods are reviewed, and then the research background and meaning are discussed. Also related fluent theory is introduced.Secondly, a parameter geometry model and a structural static finite element model of the butterfly valve are built. Then the stress and deformation of the valve are analyzed in fully closed state. Afterwards, optimize the structure of the butterfly valve and achieve better performance.Thirdly, in order to analyze the fluid flow through the butterfly valve, the dissertation built a finite element model for calculating the flow resistance coefficient, and calculated the pressure loss of the pipe using Cosmosflow. Then it calculated the flow resistance coefficient of several opening degrees. Compared with experiment result data, the analysis result of flow resistance coefficient is valid. Afterward, optimize the butterfly plate, which can reduce the flow resistance coefficient. Also, a finite element model was built for analyzing valve flow, and the pressure, flow rate and streamlines of several opening degrees were analyzed.Fourthly, it built a fluid-structure interaction (FSI) finite elements model of butterfly valve working on pump station. And it analyzed the model on several opening degrees conditions. The analysis results show that the valve fully closed when the stress and strain is the largest. Hydraulic torque of the valve was analyzed using the FSI finite elements model on several opening degrees. Compared the hydraulic torque with the result calculated by theory, the opening degree is acquired when the hydraulic torque is the largest. The dissertation analyzed the cavitations erosion under constant flow and variable flow. The cavitations erosion coefficient of several opening degree and conditions which prone to cavitations erosion are acquired by compare the analyzed results. And it point out that butterfly valve should avoid excessive pressure difference between two sides of the valve plate so that control the cavitations erosion. Also it provides several methods to prevent the cavitations erosion.Lastly, the dissertation built and analyzed a finite elements model for analyzing sealing performance. And obtain the curve between compressed displacement and radial dimension of sealing ring. Then the progress of valve plate's rotation was analyzed, and the best degree when the plate and bottom started to contact is acquired. Also, it proposes several programs to improve sealing the surface.The dissertation analyzed the strength, stiffness, flow resistance coefficient, flow status and sealing performance in the butterfly valve design using finite element technique. It helps to realize the transition from traditional design to modern design.
|
PDF Full Text Request