Numerical Simulation Of Sand-water Flow And Sediment Wear In The Impulse Turbine Of Jiniu Hydropower Statio

Hydropower bears a heavy responsibility as an important part of renewable energy.When hydroelectric turbines operate on sandy rivers,the problem of sand wear is very serious.Sand wear often leads to the loss of efficiency of hydraulic turbines,especially high-head impact turbines,damage to over-flow components,and frequent maintenance and repair,causing huge economic losses.The Geshizha River,where Jiniu Hydropower Station is located,has frequent mudslides during the flood season,and the upstream water is rich in high hardness sand particles,and the high speed jet of more than 500 meters head is more serious to the Pelton turbine of the station.In this paper,the numerical simulation of sand and water flow inside the Pelton turbine of Jiniu Hydropower Station and the prediction and field-tests of sand abrasion of key overflow components are mainly carried out,and the predicted results are more consistent with the actual measurement results.The main research results are as follows.(1)Numerical simulation of gas-liquid two-phase flow was carried out for the whole flow field model of the Pelton turbine of Jiniu Hydropower station,and the pressure,velocity and water phase distribution of the injector and bucket at each moment were analyzed.It was found that “velocity loss” occurred near the tail of the deflector and the tip of the needle,and the velocity loss gradually decreased along the flow direction;the pressure on the surface of the needle located in the jet domain has the characteristics of first decreasing and then increasing.(2)On the basis of gas-liquid two-phase flow,the sand particle phase is introduced,and the three-phase flow non-constant calculation of the Pelton turbine of Jiniu Hydropower station is carried out to analyze the sand-water flow characteristics and local sand distribution inside the key overflow components.It is found that: sand particles are more concentrated in the middle of the needle and the deflector,some sand is gathered in the transition section of the needle,but the sand particles at the tail of the needle are more dispersed,and some of the sand particles in the jet domain that are sucked by the volume are dispersed around the jet water column;During the torque rise and high torque phase,the sand particles tended to move towards the root of the bucket,and as the particles struck the bucket to produce energy loss,an obvious velocity gradient appeared along the impact position to the trailing edge;the sand particles separated in the tail area of the deflector,and an obvious “velocity loss” phenomenon was observed,which weakened as the flow developed.(3)The Generic wear model was used to predict the abrasive wear of key overflow components of the turbine,and the abrasive wear of the turbine runner was measured in the field.The results show that the wall surface of the needle tail is severely worn due to the centrifugal motion of sand particles with the water flow,and the wear pattern is “dotted” and“flaky”;Due to the impact of sand particles on the head of the deflector and the transition section of the needle,significant abrasive wear occurs;the nozzle opening wear is serious,the wear pattern is “flaky”,and wear along the circumferential distribution is more uniform;Sand particles are more likely to cause wear on the leading face of the bucket near the root,especially on the trailing edge at the root of the bucket,and the wear on the splitter and the notch is greater than the wear on the working surface of the bucket.Based on the multi-year hydrological sand data and operation of Jiniu Hydropower Station,the predicted maximum abrasive wear of key over-flow components after seven years of turbine operation is in better agreement with the actual measurement on site.