Design And Optimization Of A Francis Turbine Runner With Low Head

Our country built a large number of low head hydropower station based on Francis units in the 1980s,those head are in the range of 20~45m and turbine runner type is HL240.However,until 1992,turbine runner type spectrum JB/T 6310-1992 published,Francis turbine runner for the head is still HL240 which should be replaced by high performance Francis turbine runner.In recent years,along with many power plant operation problems have become increasingly prominent,a large number of synergistic expansion project for domestic low head hydropower plants have been put on the agenda.Major hydropower equipment manufacturers are developing suitable new Francis runner section for the head,and have available high performance runners.However,due to technical confidentiality,these runners have not been widely used.Meanwhile,the specific circumstances of each station is different,different power plants should be analyzed differently.Therefore,The thesis aims to researching and developing a new kind of low head Francis turbine runner through the transformation project of a hydropower station in Southwest China.Through the usage of the new one which be test by the computational fluid dynamics(Computational Fluid Dynamics,called CFD)numerical simulation and optimization,replacing the original turbine of the hydropower station,the target of capacity synergistic expansion transformation of the station has been realized.In the traditional R&D process of hydraulic turbine runner,it's must to be test the performance parameters of hydraulic turbine by model test,which will extend the R&D cycle and increase the R&D cost.In recent years,CFD technology has developed rapidly,and its reliability,accuracy,computational efficiency and visualization degree has been greatly improved.those advantages make the technology has been applied widely in the research and design of hydraulic turbine.It provides a software platform for predicting the hydraulic turbine performance that using CFD-3D steady turbulent flow calculation to simulate hydraulic turbine,and makes it possible that the numerical model test replace model test.For the capacity expansion transformation of the hydropower station,the technology facilitates retrofit design of the flow passage components,and has the advantages of less investment,short cycle and high economic efficiency.In order to verify the reliability and accuracy of the CFD technology,the author carries out numerical simulation of HL240-46 which is the original model turbine of the hydropower plant,the result shows that the calculated values of the turbine performance parameters are in good agreement with the actual value in the model composite performance curve.The work in this study will be implemented based on the specific situation of synergistic expansion project of the power station.The total installed capacity of the power station is4×3200kW,and the turbine runner type is HL240.The transformation goal of the power station is to make full use of the water resources and make the original unit capacity increasing from 3200kW to 4000kW under condition of keeping the unit embedded parts unmodified.In this paper,through the study,the author determines passageway structure shapes and sizes of the new turbine runner and design new runner blade.The runner diameter increase from 1.4m to 1.415m,guide vanes relative height increase from 0.365 to 0.367,and the linear crown type-line is optimized to be the curvilinear one.After the crown type-line is optimized,according to the flow field analysis,the author gets the correction value trend curve of the blade outlet angle by drawing the blade outlet velocity triangle,and then modifies the runner blade.Eventually the optimal efficiency of the new turbine runner reaches 91.95%,and it increases by 0.95%than the original HL240 runner optimal efficiency;the optimal unit flow is 1.293m~3/s and it increases by 0.193m~3/s;the maximum unit flow is 1.568m~3/s and it increases by 0.382m~3/s.According to the design and optimization results of the new runner,the rated condition point of the power station ultimately is determined to that rated head is 30.5m,rated speed is300r/min,rated flow rate is 15.56m~3/s,rated output is 4000kW.The goal of power plant synergism expansion is achieved.