Research On Flow-field Of Large Diameter Butterfly Valve Based On Fluent Software

The butterfly valve is widely used as a control device in the large pipeline system. Its control and reliability, safety, manufacturing and operating costs, high life are of great significance for the national economy. The traditional design methods of butterfly valve are mainly based on semi-empirical formulas and engineering design manuals and diagrams, and so on, in which the kinds of experience constants, correction coefficients are obtained through a large number of experiments, which often requires a lot of experiment data, not only needs high investment, takes longer time, and increases the design and manufacturing costs.In this dissertation, a new way of design butterfly valve is provided by applying the computational fluid dynamics method. Through the numerical simulation, we can not only get the necessary flow characteristic parameters of product design, but also grasp the details of the internal flow field, such as pressure distribution, velocity distribution, flow separation, cavitation location and the changes of various parameters during unsteady processes, meanwhile, it is possible to calculate the flow resistance coefficient and hydrodynamic torque of butterfly valve by using the method of numerical simulation. It is concluded that the computational fluid dynamics method can be used to guide the design of butterfly valve effectively.The main content of the thesis includes:(1) It briefly introduces the current state and the development of the study on valve. Then the development overview and the application fields and significance and the basic characteristics of butterfly valve are described, and the main design methods for butterfly valve and the main problems in the methods are pointed out, and then the research background, research significance and research method are discussed. Also related theory of numerical sumulation is introduced.(2) Three-dimensional numerical simulation and analysis of the flow characteristics of butterfly valve are carried out. Then it calculates the flow coefficient and the hydrodynamic torque coefficient of butterfly valve. Comparing the simulation data with its experimental date, the applicability of the building calculation model for numerical simulation of flow field of butterfly valve is verified. Also, it analyses the flow structure of butterfly valve at various opening degrees, which contains the pressure, flow rate and pathlines of several opening degrees.(3) The numerical simulation and analysis of butterfly valve in a particular working environment is conducted for flow resistance coefficient and hydrodynamic torque of butterfly valve under several opening degrees. Comparing the hydrodynamic torque with the result calculated by theory, the opening degree range of butterfly valve is acquired when the hydrodynamic torque is the largest. The cavitation coefficients of butterfly valve under constant flow and variable flow are compared and analyzed, the reasons that prone to cavitation are analyzed and the view for avoiding cavitation is pointed out.(4) The numerical simulation and analysis of hydraulic cavitation of butterfly valve is carried out. Combining with actural engineering, the reseach of the impacts of different inlet pressures and different pipeline structures on cavitation flow are finised, and then it provides several methods to reduce cavitation.(5) The unsteady state numerical simulation and analysis of butterfly valve is conducted. The changes of flow rate and the drag coefficient, the lift coefficient and the hydrodynamic torque coefficient of the valve disk under dieffernt opening and closing time of butterfly valve can be aquired, and the internal flow field distribution, the cavitation are also analyzed simultaneously. Finally the conclusion and suggestion that are beneficial to the engineering design and operation management have been drawn.