| In the heat absorption,heat transfer and heat storage process section of solar thermal power generation,the high temperature molten salt regulating valve is one of the core equipment,and its main function is to precisely adjust the pressure and flow rate of the molten salt under high temperature conditions,due to high temperature melting.The salt has strong chemical corrosion characteristics and physical erosion characteristics,and the molten salt causes severe erosion on the valve core of the core of the regulating valve,thereby causing problems such as a decrease in the regulating performance of the regulating valve,a failure in the sealing performance of the valve seat,and a decrease in the service life.Therefore,researching and improving the flushing resistance of the high-temperature molten salt regulating valve and prolonging the service life of the valve have important value and significance for improving the technical reliability and economic economy of the solar thermal power plant.In order to solve the problem of valve core erosion corrosion of high temperature molten salt regulating valve in solar thermal power plant,a series of researches have been carried out by valve manufacturers at home and abroad.The main direction to study and solve this problem is to use various metal surface hardness techniques,such as spraying or surfacing hard alloy to improve the material hardness of the surface of the valve core,and the other is to reduce the fluid to valve by reducing the process parameters.The erosion and erosion effects of the core sealing surface.The former solution has many manufacturers.The advantage of this solution is that it does not need to change the basic design structure of the valve and the valve core.The disadvantage is that the valve core manufacturing process is complicated,involving welding and heat treatment processes,and the material cost and process cost are very high.However,too high hardness causes great difficulty in precision machining,and because the heat treatment technology does not cause uneven surface hardness,it causes stress corrosion.The latter solution is applied to a relatively small number of manufacturers,because it involves the design change of solar thermal power plants and the reduction of operational efficiency.Although the use effect and life of the valve are improved,the overall integrated operation effect of the power plant is not improved.In this paper,the main reason for the "erosion" phenomenon of the valve disc is that the high-temperature molten salt medium flowing quickly near the valve disc and seat causes the surface of the valve disc to be washed.Therefore,this paper applies the conventional plug type valve disc to be optimized,a two-stage pressure-reducing valve disc structure is designed to reduce the flushing action of each stage spool by reducing the flow rate of the medium through each stage of the spool,so that the sealing performance and regulating performance of the valve are improved as well as a longer serve life.In this paper,the high-temperature working condition(565℃ molten salt)in a pilot power plant of a solar power generation enterprise and the control valve of the diameter DN80 and the nominal pressure PN100 with a working pressure of 1.58 MPa to 5.78 MPa are used as example to be researched,and the CFDesign software is used for modeling for the control valves with the conventional plug type valve disc and the new two-stage pressure-reducing valve disc,and then the flow rate and pressure of the fluid near the valve disc at different opening degrees are numerically simulated.Finally,the actual flow test is used to verify the numerical simulation and the accuracy of the results.The main contents of this paper are as follows:Introducing the working conditions,existing problems and research and application status of the high temperature molten salt control valve.Introducing the basic theory and formula of numerical simulation,the commonly used fluid analysis software,and related processes of pre-processing and post-processing.Comparing the structural characteristics of the two valve core design structures(conventional plug type valve disc and two-stage pressure-reducing valve disc)and its product’s structural characteristics used for simulation in detail.For the two valve disc models,the flow field simulation under different opening degrees is performed in three working conditions,such as small opening degree,medium opening degree and large opening degree,and the corresponding flow rate and pressure data are extracted as well as the flow rate curve of the fluid,and then calculate the valve flow capacity Cv value.Install the valves with the two valve disc models on the flow testing system,perform the actual flow performance testing,obtain the actual pressure and flow data,and compare and analyze the testing results with the simulation results to verify the software numerical simulation.The results are accurate and reliable.The simulation and experimental comparison results show that the new two-stage pressure-reducing valve disc design can effectively reduce the flow velocity of the fluid near the sealing surface of the valve disc compared with the conventional plug valve disc design,at a small opening(5%to 30%)range,flow rate decreased by 33%to 45%,in the range of medium opening(40%to 70%),the flow rate decreased by 27%to 36%,and in the range of large opening(80%to 100%),the flow rate decreased by about 12%.The flow rate is reduced,so that the erosion resistance of the valve core is greatly improved,the service life of the valve is prolonged,and the sealing reliability of the valve is improved.Compared with the traditional high-temperature molten salt regulating valve,the new valve core structure design can effectively improve the anti-scour performance of the valve core,and will not cause too much increase in product cost,nor will it reduce the process parameters of the solar thermal power plant,and improve operational effectiveness as a whole. |
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