Coupling Numerical Simulation And Experimental Study On Hydraulic Characteristics Of Long Diversion Hydropower Station

In order to overcome the shortcomings of hydropower station pure one-dimensional calculation can not accurately describe the dynamic characteristics of key components and the waste of computational resources in full three-dimensional calculation,it is necessary to carry out one-dimensional three-dimensional coupled simulation calculation of hydropower system.Based on a hydropower station in Yalong River,this paper first tests the internal pressure of the turbine at the site,and then based on the data of the research group on the water level fluctuation of the hydropower station:(1)Through Visual Basic 6.0,the secondary development of FLUENT is realized,and a one-dimensional three-dimensional coupled simulation model is established to realize automatic operations such as opening and reading case and date files,changing boundary conditions,calculating and outputting coupling surface data.(2)The coupling model and the traditional one-dimensional model were used to calculate the single-machine load shedding process for the diversion tunnel and surge tank system of a hydropower station in Yalong River.Compared with the measured data,it is found that the water level amplitudes of the large chamber,riser 1,and riser 2 are 56.84 m,57.95 m,and 57.95 m,and the difference from the measured data is-0.23 m,1.71 m,0.58 m.The calculated amplitude of the model is 57.20 m,55.50 m,57.69 m,and the difference from the measured data is 0.13 m,-0.74 m,0.32 m.In describing the water level difference of each part,the maximum error of the one-dimensional model is 4.16 m,and the maximum error of the coupling model is 1.06 m.The coupling model can better simulate the water level difference of each part and the oscillation characteristics of the water flow in the pressure regulating room.Analysis of the 2# unit volute inlet pressure frequency is 0.002 Hz and the same as the surge chamber,the water level fluctuation of the surge chamber will have an impact on the unit.The effects of overflow weir height,riser area,and impedance hole area at the bottom of the chamber on the hydraulic characteristics of the surge tank were studied.The results show that the higher the weir height,the smaller the riser area,and the lower the impedance hole at the bottom of the chamber.Small,the fluctuation period and amplitude are smaller.(3)Prototype test was carried out at a hydropower station in Yalong River,and the pulsation pressure data of the turbine volute inlet and the draft tube outlet were tested.The turbine model was established to calculate the steady state.The calculated inlet pressure,end pressure and draft tube inlet pressure of the volute were compared with the measured data.The errors were 3.70%,4.58% and 7.18%,respectively.The true frequency of the volute inlet pressure pulsation at full load is 0.38 Hz;the inlet pressure of the draft tube is mainly 0.3-0.9 Hz,and the numerical calculation frequency is 0.73 Hz and 0.38-0.76 Hz.The coupling model was used to calculate the flyover transition process of the water turbine system of a hydropower station on the Yalong River.The calculation results show that the pressure of the turbine volute and the pressure of the vane rise during the transition period,and the pressure drop gradient decreases.The flow direction of the runner deteriorates and develops into the impact turbine blade.The pulse pressure frequencies at the entrance of the volute and the draft tube at the end of the calculation are calculated to be 0.78 Hz and 0.78-1.56 Hz,respectively.The vortex inlet pulsation is caused by the tail water vortex,so the frequency of the tail water vortex increases,which is not conducive to the turbine operation.