Comparative Analysis Of Flow Characteristics In "S" Zone Of Pump Turbine With Or Without Splitter Blades

In recent years,in order to meet the requirements of energy saving and environmental protection in production and life and ensure the stable operation of the power grid,pumped storage power stations are developing rapidly.The key component is the reversible pump turbine,because of its inherent hydraulic instability "S" characteristics,it is easy to cause safety hazards during operation.In this paper,the model of a pump-turbine with splitter blades of a pumped storage power station in China is taken as the research object.Based on the experimental model,the model of the pump-turbine with splitter blades and without splitter blades is constructed.The SST k-? turbulence model is used to numerically calculate the hydraulic turbine operating conditions,brake operating conditions and reverse pump operating conditions with guide vane opening degrees of 6.4 degrees and 23 degrees.Analyze and compare its internal flow characteristics,and study the characteristics of the pressure pulsation of the turbine in its small opening degree and obtain the effect of the splitter blade on the hydraulic performance of the "S" area of the pump turbine.The main research contents are as follows:The experimental condition point is simulated by steady calculation,and the characteristic curve of "S" is compared with the experimental results.The feasibility and error range of the numerical simulation are discussed.The results of steady calculation of pump turbine design conditions are analyzed.The results show that the numerical calculation can accurately simulate the internal flow characteristics of the pump turbine.Under the working condition of the turbine,the flow characteristics of the pump turbine with or without splitter blades are good.The flow field with a large guide blade opening is more smooth,and the splitter blade is conducive to improving the efficiency of the pump turbine.Scheme design with or without splitter blades runner: On the basis of the original splitter blades runner,through preliminary theoretical analysis and calculation,referring to the model of similar specific speed,and in order to enhance comparability,the long blade profile line and the long blade profile line of the splitter blades runner are exactly the same,9 long blade runner are designed.The steady simulation analysis shows that the "S" curve of pump turbine without splitter blades is more obvious,and the hydraulic efficiency is lower than that of pump turbine with splitter blades.The steady-state calculation results of the two transition conditions of the pump turbine are analyzed to explore the influence of the splitter blades on the internal flow characteristics of the pump turbine under the two transition conditions with different opening of the guide blade.The results show that the internal flow state of the pump turbine under braking condition is very bad,especially under small opening,transverse flow and vortex structure are easy to appear in the flow passage.The flow separation in the guide vane area is obvious and the rectification effect is poor.Backflow phenomenon appeared in the draft tube;The presence of splitter blades reduces the generation of vortex structure in the flow passage of volute and guide blade,reduces the size of runner vortex and blade load,and is more obvious under large opening,and weakens the backflow degree of the draft tube.Under the reverse pump condition,the runner has a large range of negative pressure area,and the negative pressure value is lower under the large opening.The internal flow of the volute is relatively smooth,the water flow is thrown out,and the overall load of the blade changes little.The existence of splitter blades is beneficial to reduce the number of vortices in the runner's passage.According to the analysis of the steady-state calculation results,the "S" characteristic is obvious at a small opening.The efficiency of pump turbine with splitter blades is high under the working condition.Therefore,the unsteady calculation is carried out for the turbine condition of the pump turbine with or without splitter blades with the guide blade opening of 6.4 degrees.The pressure pulsation monitoring points were set for each component and the influence law of the splitter blade on the pressure pulsation of each component was explored.The results show that the pressure pulsation in the volute is mainly affected by the internal flow characteristics.The pressure pulsation in the guide vane passage is affected by its own flow pattern and rotor-stator interference of the runner blade,and the closer it is to the runner,the more it is affected by rotor-stator interference of the runner.The pressure pulsation in the bladeless region is the largest,which is greatly affected by the runner.Within one rotation cycle,the number of pressure changes with time is the same as the number of blades.The pressure pulsation in the runner is mainly affected by the rotor-stator interference of the guide vane.The pressure pulsation in the draft tube is mainly affected by the vortex zone in the flow passage.The pressure pulsation of the pump turbine with splitter blades is lower than that of the pump turbine without splitter blades.