Experimental Studies of Pressure Pulsations in Draft Tube Diffuser of Pump-Turbine Models for Heads up to 200 m

Abstract

Introduction. Increasing the share of balancing capacities to cover daily peaks in electricity consumption is one of the top priorities of the postwar development of Ukraine’s energy sector.Problem Statement. Today, power plant hydraulic turbines need both to increase effi ciency and to expand their operating range. For example, the new hydraulic units of the Dniester PSP shall operate in turbine mode in the range of 40—100% of rated capacity, while the four previous units operate in the range of 70—100%. This requirement can be met by increasing efficiency and reducing pulsations at low power output.Purpose. Based on studying the infl uence of blade spatial shape of a Francis pump-turbine runners on fl ow parthydrodynamics, to identify the patterns of pressure fluctuations distribution in draft tube diff user of the hydraulic unit model.Materials and Methods. Three options of models (the original and two modifi ed ones) have been studied onthe IMEP ECS-30 hydrodynamic test stand. The runner blades are made of PLA plastic by 3D printing. Pressurepulsations are measured by sensors at two points of draft tube diff user at a distance of 0.2 and 1.5 runner diameters from the runner bottom shroud.Results. Three modifi cations of the pump-turbine runner for heads up to 200 m have been designed and experimentally studied with the use of circumferential lean that diff er from the original version only in relative position of blade profiles. The analysis of obtained energy and pulsation characteristics of the models in turbine modehas shown that the model with the runner having a negative circular blade lean has the best performance. Conclusions. The determined influence of spatial shape of the runner blades on the energy and pulsation characteristics of the Francis pump-turbine model for heads up to 200 m has made it possible to increase its efficiency and to reduce the level of pressure fluctuations in the flow part.