Design and numerical validation of a pump turbine considering hydraulic and abrasion performance

Reversible pump turbines have been widely used in pumped storage plants in recent years. The base loads rapidly respond to the power grid demands by switching operations. Thus, the great contribution can be grained to significantly integrate the new energy sources into the grid. This study aims to design to the pump turbine with the high energy efficiency, structural function and operational stability. The hydraulic performance and sediment abrasion were evaluated from the medium to high head of pump turbine (power generation head H_T=315 m, and pumping head H_P=310 m). The inverse method was utilized to control the load distribution on the blade crown and band streamlines. The initial pump turbine was formulated to determine the meridional shape of flow passage through curve interpolation. The equal velocity moment approach was applied to define the variation in the cross-sectional areas of the volute. While the equirectangular helix projection was used to design the profiles of guide vane. The preliminary design of pump turbine was optimized using the Latin hypercube sampling with the NSGA-II non-dominated sorting genetic algorithm. A Pareto front of optimal solution was generated within the design space. The SST k-ω turbulence and the Tabak off abrasion models were adopted to investigate the hydraulic and abrasion performance of various pump turbine after numerical simulation. The results show that the optimal design was achieved in the hydraulic efficiencies of 91.8% and 93.19% in the pumping and generating modes, respectively. In the interval of 0.8Q_BEP-1.2Q_BEP, the hydraulic efficiency exceeded 85% in both modes. In the pumping mode of the optimal pump-turbine model, the blade inlet edge near the upper crown and lower ring were offset towards the suction and pressure sides by θ₁=6.93°, respectively. Conversely, the blade outlet edge near the upper crown and lower ring were offset towards the pressure and suction side by θ=8.62°. This inclination was reduced the average blade abrasion rate by 9.26% and 9.71% in the pumping and generating modes, respectively. There were the great correlations between flow capacity and sediment erosion under diverse operation. There were the polynomial relationships between the flow rate and the average volume fraction of sediment on the blade surfaces, the mean sediment velocity near blade walls, and the average rates of blade erosion, including a fifth-degree function for volume fraction, a quadratic function for velocity, and a cubic function for erosion rate.