| Water storage tank regulating valve of the ultra-supercritical is one of the critical valve in the power plant, whose safety and reliability of is great importance during the operation of the station. In promoting the regulating valve in the process of localization in recent years, its structure design and internal flow field distribution of the pipe system affects its normal work of the valve greatly, which make it the core in the research gradually. Water storage tank regulating valve working environment is relatively poor, usually for high temperature and high pressure, the state of the working medium is also complex, it is in the critical state of gas-liquid two-phase.Cone pressure regulating valve has a stem-seat adjusting structure, when the valve opening is small, the pressure gradient in the adjust clearance(the throat area)changed rapidly. When the medium flows through the area, it will occur serious phenomenon of vaporization, the mixture of gas-liquid two-phase flow makes the medium in the subsequent pipe distribution systems to be very complex, this will seriously affect the safe operation of the valve and its pipe system, so it is necessary to analyze the flow field of this type of valve. This article is aimed at the serious cavitation failure phenomenon of the bottom plate of the pipe distribution system which works under the water storage tank regulating valve in of the ultra-supercritical.Based on the multiphase flow control equations of FLUENT software, the characteristics of its flow field is carried out. The results show that when the cone pressure regulator working under the design conditions, the pressure drop gradient of valve throat area is large, the phenomenon of medium vaporization reached 95%, the speed of the medium increased dramatically and the maximum speed reached 149m/s,which shows that the flow field distribution of valve and its pipe distribution system is very uneven. At the same time, combined with valve design specification on the basis of the results of the analysis, this paper puts forward several structural optimization schemes, the main works are as follows:(1)The original cone pressure regulating valve flow field model is established.Through the HYPERMESH mesh, we get the grid model of the valve under design conditions. According to GB/T4213-2008’pneumatic control valve’, JB/T5296-1991‘the common valve, flow coefficient and flow resistance coefficient test method’ and their relevant standards, the flow characteristics of the valve are verified.(2) The flow field model of the valve is analyzed, and the corresponding velocity field and vaporization field are obtained by collecting the flow field of the key area of the flow field. The results show that the original cone pressure regulating valve and its pipe system does exist the unreasonable structure, also, the phenomenon of turbulence in the flow field is serious, the gas-liquid mixed flow is disordered and complicated,the power of the cavitation bubbles breaking released seriously affects the safe operation of the valve.(3) Combined with the flow field distribution results, the paper optimize the structure of the valve of the original structure by increasing the uniform flow plate or extending its pipe system’s pipe, and the flow field under two kinds of structure are analyzed. Using the same method to collect the key area of the flow field data, the results show that the optimization scheme can solve the problem of cavitation failure of valve.(4) Combined with the boiler pump adjusting structure, we put forward a new kind of hanging structure regulating valve by our independent innovation. Compares the differences of two kinds of valve in structure, we use the same method to analyze the flow field of the new type of regulating valve. The results show that the regulating valve of the structure has a certain inhibiting effect on the vaporization phenomenon at the source, it can effectively solve the problem of valve cavitation failure.(5) In order to further improve the regulating valve of the safety and reliability,the structural stress and strain analysis of the main components of the regulating valve are carried out by using the mode of assembly components, also, we have adopted JB4732 and ASEM standards for the safety evaluation at last.In this paper, the analysis results directly show the forms of gas-liquid two phase flow, and the simulation results for regulating valve and its pipe distribution system design has a strong theoretical guidance, besides, it has some important and positive significance to promote the collectivization and nationalization of this kind of valve. |
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