| High-temperature molten salt pump is a vertical liquid centrifugal pump,which is mainly used for high-temperature molten salt transportation.In solar thermal power generation system,it is the core power equipment.It works in a high temperature environment for a long time.Once it stops operating due to a fault,it will have a serious impact on the entire power generation system.Therefore,there is a higher requirement for the design of high-temperature molten salt pumps.This type of high-temperature molten salt pump has a medium temperature of 300°C-565°C.Its unique structure leads to the complexity of internal flow.There is an interaction between the internal flow field and the structure.The hydraulic vibration can induce the vibration of the pump body,under the joint action of thermal load,the structure will produce greater stress and deformation.In this paper,under the support of the Jiangsu Provincial Achievement Transformation Project(BA2016167)and the Jiangsu Provincial Key R&D Project(BE2015146),a study was conducted on the high-temperature molten salt pumps for solar thermal power generation systems.The inflow characteristics of molten salt pumps under different temperature conditions were analyzed.Based on the fluid-solid multi-field coupling method,the temperature,stress and deformation of the molten salt pump impeller were simulated and analyzed,which provided technical support for the development of the high-temperature molten salt pump.The main work and research results of this paper are as follows:(1)According to the design requirements for the high-temperature molten salt pump of Demingha 50 MW tower solar thermal power plant demonstration project in Qinghai,a multi-plan hydraulic design was carried out for the impeller and space guide vane,and numerical simulation and performance prediction were performed by CFD method.The performance and internal flow characteristics of high-temperature molten salt pumps of different schemes were compared and analyzed to determine the final hydraulic optimization scheme.(2)According to the characteristics of high-temperature molten salt medium,the real-life operation conditions were simulated,and the full flow field numerical calculation was performed for the internal flow of the high-temperature molten salt pump,and analyzed the hydraulic performance of molten salt pump under different temperature medium Numerical simulation results show that the simulation results of the head and efficiency of the molten salt pump are all higher than the experimental values,and the flow condition in the pump is gradually stable with the increase of the flow rate.In molten salt medium,as the temperature increases,the density and viscosity of the medium gradually decrease,and the head and efficiency decrease gradually.According to the analysis of the internal flow field,the surface pressure of the impeller blade increases from the inlet to the outlet,the pressure at the working surface is higher than the back surface,and the pressure at each part gradually decreases with the increase of the flow rate.Under the molten salt condition,the temperature is higher.The surface pressure is lower but the whole is higher than the clear water medium.(3)Based on the internal flow analysis of high-temperature molten salt pump under different working conditions,the axial force,radial force and load distribution characteristics of the impeller under high temperature conditions were systematically analyzed.N umerical simulation results show that the axial force of the impeller is much greater than the radial force.Under the same working conditions,the axial force under the molten salt medium is higher than that of the clear water medium.The higher the molten salt temperature is,the smaller the axial force is.With the increase of the flow rate,the impeller The radial force gradually increases and the axial force gradually decreases,which is proportional to the head.Under the condition of various temperature conditions,the maximum position of the blade surface load is at the rim,the load from the rim to the hub surface gradually decreases,and the surface load of the blade is gradually reduced with the increase of temperature in the molten salt medium.(4)Based on fluid-solid-heat coupling technology,the impeller is calculated and analyzed.The impeller temperature is symmetrically distributed.The highest temperature point is located at the front cover mouth ring and the blade outlet,the lowest temperature area is located in the vicinity of the intersection of the hub and the blade inlet,and the maximum temperature of the impeller decreases as the flow increases.Under the combined action of various loads on the impeller,there is a strong correlation between the gradient distribution of the stress of the front and rear cover plates and the position of the blades between them.The stress concentration mainly occurs at the connection of the blade outlet and the front and back cover plates,and the fluid pressure and inertial force load play a leading role in each load action.The deformation of the impeller shows a clear symmetry distribution.In the contact position between the front and rear cover plates and the blades,it can be seen that the deformation of the area is small,and there is obvious stress concentration.Temperature load is a major factor in the deformation of the impeller.After the strength check,it is proved that the original structure strength meets the requirements,and the impeller will not be damaged due to strength problems during normal operation.(5)In order to ensure the stable and reliable operation of the rotor system of the high-temperature molten salt pump,based on the finite element analysis method,the modal analysis of the molten salt pump multistage impeller rotor structure The numerical results show that under the influence of external loads,the natural frequency rises to some extent,and the amplitude does not change significantly.By analyzing the critical speed of the rotor system,it is shown that the rotor will not be resonant when it is running,ensure the operating reliability of high-temperature molten salt pumps. |
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