| Since the tri-eccentric metal sealing butterfly valve was invented in 1970's abroad, it has been widely used in high pressure fluid power system in the different industry areas. By using oblique cone surface as sealing face, it has good seal and fine wearability and long service life, and smaller moment of force than the other valves during opening and closing. This kind of butterfly valve was introduced from oversea in 1980's, however, the tri-eccentric metal sealing butterfly valve could be manufactured only by a few factories in our country so far, and some key technologies are not griped .For example, the design of sealing pair's surfaces is rather difficult as the sealing surface is complex 3-dimensional surface. If the design is not reasonable, it will be interfered during the opening and closing, so it could not achieve the requests of "zero" friction, "zero" discharge and fast closure by far. Until now, the design method of sealing pair in this kind of butterfly valve is mainly based on experience parameters. It would change the mechanical behavior and structure of butterfly plate as the pressure, temperature and velocity of fluid medium under practical operating conditions. On the other hand, structural parameters of butterfly valve is decided not only its kinematics and static mechanical characteristic, but also dynamic mechanical characteristic on opening and shutting in fluid system. So it is important to systematically analyses mechanical characteristic of the tri-eccentric metal sealing butterfly valve in the optimizing design in order to enhance the reliability.To combine with practical engineering, a tri-eccentric metal sealing butterfly valve equipped in vacuum Pressure Swing Adsorption (VPSA) hydrogen purification equipments was taken as an example. To analyze the mechanics characteristic in the practical operating condition of a tri-eccentric metal sealing butterfly valve, the pipeline network model of adsorption process of tri-eccentric metal sealing butterfly valve in hydrogen production plant with VPSA was established; FLOWMASTER software was adopted to calculate the fluid dynamic characteristics of tri-eccentric butterfly valve under both opened and closed during processing of absorption.; The forces on valve brought from fluid inside the pipeline network in the closing process of the butterfly plate were analyzed and the result was taken as load of the butterfly plate. ANSYS? software was used to constitute three-dimensional geometric model of butterfly plate, and to perform structural mechanics characteristic analysis of fluid medium under effects both of static load and dynamic load in Hydrogen production plant with variable pressure and vacuum adsorption. The analysis showed that the butterfly plate appeared 0.08mm distortion under force of fluid. In order to optimize the structure design of butterfly valve, three-dimensional mathematical model of sealing surface of butterfly plate was constituted based on the sealing structure design of butterfly valve, mechanics kinematics and computational analysis of structural dynamics. MATLAB(?) was adopted to develop a computer program for calculating the opened and closed angles of each point when butterfly plate mechanism was opening and to verify whether the butterfly plate interfered with valve's body. The simulating result showed that the original design of the butterfly valve didn't interfere, but it would interfere on the sealing surface nearby rotating axis when opening and closing as the unfit structure parameter of the butterfly plate. Moreover, the parameters of butterfly plate sealing surface were optimized to decrease the possibility of causing interference from butterfly plate sealing surface. This optimization not only improves fast dynamic response characteristic of tri-eccentric butterfly valve but also increases its reliability.
|
PDF Full Text Request